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 ■A'^-;^^'. 
 
 JOHN LOUDON MACADAM 
 
 The Road-Maker 
 Sept. 21, 1756— Nov. 26, 1836 
 
THE ART OF 
 
 ROADMAKING 
 
 TREATING OF THE VARIOUS PROBLEMS AND OPERATIONS IN 
 THE CONSTRUCTION AND MAINTENANCE OF 
 
 ROADS, STREETS, AND PAVEMENTS 
 
 WRITTEN IN NON-TECHNICAL LANGUAGE, SUITABLE FOR THE 
 
 GENERAL READER; WITH AN EXTENSIVE BIBLIOGRAPHY 
 
 AND A DESCRIPTIVE LIST OF RELIABLE CURRENT 
 
 BOOKS AND PAMPHLETS ON THESE SUBJECTS 
 
 BY 
 
 HARWOOD FROST, B.A.Sc. 
 
 Member American Society of Mechanical Engineers 
 Member Society for the Promotion of Engineering Education 
 
 NEW YORK 
 
 PUBLISHED BY THE AUTHOR 
 
 London: CONSTABLE AND COMPANY, Ltd, 
 1910 
 

 Copyright, 1910 
 
 BT 
 
 HARWOOD FROST 
 
 Entered at Stationers' Hall, London, E.C., 1910 
 
 THE SCIENTIFIC PRESS 
 
 aOaERT ORUMMOND AND CofuPANY 
 
 BROOKLYN, N. V. 
 
TO 
 
 Evelyn Lynas Frost 
 
 WHOSE ENCOURAGEMENT LED TO THE PREPARATION 
 
 OF THIS MATERIAL, AND TO WHOM I AM GREATLY 
 
 INDEBTED FOB ASSISTANCE IN ITS COMPILATION 
 
 THIS BOOK IS AFFECTIONATELY DEDICATED 
 
PREFACE 
 
 RoADMAKiNG is an art, based on a science. Although it 
 forms one of the most common and most important engineer- 
 ing works that engage the attention of man, the use of roads 
 is so much a part of our daily life that we almost cease to 
 consider their construction and upkeep as problems in en- 
 gineering. Yet Roads may be said to be the backbone of the 
 national life of a country and the most important element in 
 the progress of civilization from the very earliest times. 
 
 This book is intended to give an outline of the history of 
 road building; of the problems that confront the engineer in 
 the location, construction and maintenance of roads; of the 
 properties of the various road-making materials, and of many 
 other features of the subject, and an effort has been made to 
 present this information in a style suitable for the intelligent 
 reader with or without previous technical experience. 
 
 No claim is made for originality in the contents, or for 
 the presentation of new ideas or methods; in fact, since 
 the days of Telford and Macadam little advance was 
 made in the science of roadmaking, until the comparatively 
 recent inventions of the modem mechanical methods of 
 quarrying, stone crushing, grading, etc., and the various 
 improved methods of dust prevention, street cleaning, and 
 road maintenance. In the compilation of the material the 
 columns of "Engineering News" and other technical period- 
 icals have been drawn upon, government reports and a few 
 trade pubhcations devoted to the making of roads have been 
 freely quoted, and a large number of treatises have been 
 referred to. Foremost among these may be mentioned 
 Byrne's "Highway Construction," Baker's "Roads and Pave- 
 ments," Tillson's "Pavements and Paving Materials," Aitkin's 
 "Road Making and Maintenance," Judson's "City Roads and 
 Pavements," and " Road Preservation and Dust Proven- 
 
PREFACE vu 
 
 tion/' Soper's "Modern Methods of Street Cleaning/' Spald- 
 ing's *' Roads and Pavements/' and Coane's "Australasian 
 Roads." 
 
 The majority of these publications so specialize in one or 
 more features of the subject^ or cover the entire subject in 
 such encyclopedic detail, that they do not appeal to the 
 average non-technical general reader. On the other hand, 
 in spite, of the modern specialization of the engineering pro- 
 fession, even the most specialized engineer is often called on 
 to make use' of information regarding some form of road work, 
 and although he may be a specialist, and well informed on the 
 subject of drainage, or of automobiles, he may be decidedly 
 ignorant of the methods of roadbuilding and maintenance, 
 which are outside of, but closely allied to, his specialty. 
 
 The present book has been written for both of these men. 
 The object has been to condense into the comparatively small 
 space of a single volume, the fundamental and essential prin- 
 ciples of the roadmaker's art as presented by the most re- 
 liable authorities. It gives to the reader unacquainted with 
 the subject a good general knowledge, and to the technical 
 man, an outline of the main facts and an indication where 
 further reliable and specialized information can be obtained. 
 
 To do this, all involved mathematical tables and formulas, 
 records of tests and analyses, tables of statistics and the 
 higher technical features of the subject have been omitted; 
 information that covers pages in some treatises has been 
 reduced to conclusions and tabulated, and such illustrations 
 have been selected that will emphasize the popular features 
 of the subject. 
 
 H. F. 
 
 220 Broadway, New Yokk, 
 March, 1910 
 
CONTENTS 
 
 PAGE 
 
 PREFACE vi 
 
 POEM— "THE ROAD."— Anonymous xiv 
 
 INTRODUCTION: HISTORICAL SKETCH OF ROAD DE- 
 VELOPMENT 1 
 
 PART I 
 
 PRELIMINARY COXSIDERATIOXS 
 
 CHAPTER I. RESISTANCES TO TRACTION 
 
 Object of a road — Causes of tractive resistance — Power required 
 to move vehicles — Recent experiments in tractive resistance 
 — Calculation of tractive force — Rolling friction — Effect of size 
 of wheels — Effect of springs — General results of experiments 
 in tractive resistance — Gradient — Loss of power on inclinations 
 — Necessity of easy gradients — Hauling power of horses — Power 
 of teams — Calculation of load on gradient — Load drawn by 
 horses on grades — Steep grades objectionable — Methods of 
 expressing grade ." 10 
 
 CHAPTER II. ROAD AND PAVEMENT ECONOMICS 
 
 Value of good roads — Advantages of paved city streets — Eco- 
 nomic value of road improvements — Ultimate economy of road 
 improvements — Questions affecting design of city pavements 
 — Methods of payment for city pavements — Administration of 
 highways — European systems of management — American sys- 
 tems — The labor-tax — Maintenance of city pavements — Opening 
 of pavements 19 
 
 CHAPTER III. PRINCIPLES UNDERLYING THE SELECTION 
 OF PAVEMENTS FOR DIFFERENT PURPOSES 
 
 Road and pavement definitions — Requirements of a good pave- 
 ment — Properties of an ideal pavement — Relative values of 
 qualities of different pavements — Use of tables in selection of 
 pavements — Adaptability — Desirability — Serviceability — Com- 
 parative safety of pavements — Durability — Cost 28 
 
CONTENTS ix 
 
 PART II 
 
 COUNTRY AND SUBURBAN ROADS 
 
 CHAPTER IV. LOCATION OF COUNTRY ROADS 
 
 PAGE 
 
 Length of straight and curved roads — Comparative advantages of 
 straight and curved roads — Economy the basis of location — 
 Value of scientific road location — Methods employed in location 
 — Characteristics of country noted — Instruments used — Contour 
 lines — Topographical map — Levels and bench marks — Value of 
 saving distance — Grades — Methods of overcoming grades — Deter- 
 mination of maximum grade — Most suitable maximum grades — 
 Most advantageous grade — Establishment of maximum grade — 
 Establishing the final grade — Curves — Curves on an ascent — 
 Width of roadway — Selection of bridge sites — Principles to be 
 observed in final selection — Method of final location 37 
 
 CHAPTER V. CONSTRUCTION AND PROTECTIVE WORKS 
 
 Earthwork: Classification of earthwork — Equalizing earthwork — 
 Transverse balancing — Natural slope of embankments — Shrink- 
 age of earthwork — Making embankments — Cost of earthwork . . 53 
 
 Foundations and Drainage: The importance of drainage — Systems 
 of drainage — Object of side ditches — Surface drainage — Trans- 
 verse contour 62 
 
 Highway Bridges: Location — Classification — Bridge trusses — Types 
 of trusses and bridges — Short-span bridges — Low-truss bridges 
 High-truss bridges — Plate-girder bridges — Use of timber in 
 bridges — Masonry and concrete bridges — Culverts — Size of open- 
 ing — Floorbeams and floors — Substructures — Abutments — Most 
 economic bridge 69 
 
 Retaining Walls: Where retaining walls are built — Drainage — Sea 
 
 walls 87 
 
 CHAPTER VI. MATERIALS USED IN ROAD CONSTRUCTION 
 
 Most suitable material — Selection of material — Agencies causing 
 destruction of roads — Physical agencies — Mechanical agencies 
 — Chemical agencies — Organic agencies — Essential qualities 
 of roadmaking stone — Hardness — Toughness — Durability — 
 Cementing value — Classification of rocks — Igneous rocks^-Sedi- 
 mentary rocks — Metamorphic rocks — Primary mineral constit- 
 uents — Physical properties of rocks — Conclusions regarding pav- 
 ing stones — Principal varieties of roadmaking rocks — Granite — 
 Basalt — Sandstone — Limestones — Sand and clay — Gravel — Free 
 government tests 91 
 
X CONTENTS 
 
 CHAPTER VII. EARTH, GRAVEL, SAND, AND CLAY ROADS 
 
 PAGE 
 
 Earth Roads: The first step in construction — Preparation of road- 
 bed — Preparation of road surface — Drainage — Culverts — Main- 
 tenance and repair 117 
 
 Gravel Roads: Gravel — First course — Second course 123 
 
 Sandy Roads: 126 
 
 Clay Roads: 126 
 
 Sand-clay Roads: Essentials to success — Causes of failure — Cost of 
 
 sand-clay construction 127 
 
 Bumt-clay Roads: Fuel — Preparation of the roadbed — Firing — Cost 
 
 of burnt-clay constrution 133 
 
 Tools Used in Construction of Country Roads: Tools for clearing 
 and grubbing — Tools for grading — Scrapers — Road graders — 
 Elevating grader — Carts — Dump-cars — Dump wagons — Surface 
 
 grader — Road leveler — Draining tools 137 
 
 The Earth-road Drag: Requisites for success — Description of drag 
 — Object of road dragging — Theory of road dragging — Effect 
 of dragging roads — Instructions for dragging — Conclusion 145 
 
 CHAPTER VIII— BROKEN-STONE ROADS 
 
 Difference between methods of Telford and Macadam — John Loudon 
 Macadam — Thomas Telford — Tresaguet's method — Telford's 
 method — Macadam's method — Modern telford and macadam 
 — Defects of telford system — Defects of macadam system 
 — Advantages and defects of broken-stone pavements — Diffi- 
 culties in construction — Essentials for successful construction — 
 Errors in construction — Materials — Dimensions of the macadam 
 surface — Subgrade — First course — Second course — Third course 
 — Trimming — RolUng — What holds macadam roads together — 
 Steam rollers — Breaking stone — Stone crushers — Stone crushing 
 plant — Stone distributing carts — Scarifiers — Straight-edge — 
 Water carts — Cost of macadam surfaces 154 
 
 CHAPTER IX— ROADS IN MOUNTAINOUS DISTRICTS 
 
 Evolution of mountain roads — Grade — Importance of location 
 — Object of drainage — Necessity for proper side slope — Width 
 — Curves — Slide rock — Corduroy — Dressing 189 
 
 CHAPTER X. IMPROVEMENT AND MAINTENANCE OF 
 COUNTRY ROADS 
 
 Reconstruction and Improvement: Defects of existing roads — 
 
 Benefits of improvements — Clay roads — Sand roads 203 
 
CONTENTS XI 
 
 PAQE 
 
 Maintenance and Repairs; Necessity for maintenance — Systems 
 of maintenance — Maintenance of country roads — Errors in 
 maintenance — Cost of maintenance — Causes which make re- 
 pairs necessary — Repair — Instructions to roadmen — Season for 
 repairs ; . . . . 205 
 
 CHAPTER XL CONTROL AND PREVENTION OF ROAD 
 
 DUST 
 
 Importance of dust prevention — Value and effects of road dust 
 — Effects of automobile traffic — Necessity for dust prevention 
 — General results of experiments — Methods of dust prevention — 
 Moisture — Salt water — Calcium chloride — Oil emulsions — Oils — 
 Inexperience in handling road oils — General rules for oiling roads 
 — Coal-tar preparations — Success of "tarviating" — Tar-spraying 
 machines — Tests of coal-tar — Tar-macadam — Mixing tar-mac- 
 adam — The " Gladwell" system — Use of tar-macadam in America 
 — Rock asphalt macadam — Bitulithic pavement 218 
 
 CHAPTER XII. STATE AID LAWS 
 
 Distribution of State-aid funds — Supervision of construction — 
 
 Form of commission 248 
 
 Digest of State- Aid Laws: 
 
 State Highway Department — State Aid Highways — State Aid 
 Fund — Powers and Duties of Counties — County or District 
 Highway Engineers — How Localities get State Aid — Construction 
 of State Aid Highways — Payment for State Aid Highways — Main- 
 tenance of State Aid Highways 252 
 
 Convict Labor on Roads 271 
 
 Excerpts from Specifications used in Constructing State-aid Roads in 
 Massachusetts, New Jersey, New York, Connecticut, Pennsylvania 
 and Maryland ." 272 
 
 PART III 
 
 CITY STREETS AND PAVEMENTS 
 
 CHAPTER XIII. THE DESIGN OF CITY STREETS 
 
 Objects in planning city streets — Size of blocks — Location of 
 streets — General plans for location of streets — Width of streets 
 Area of streets — Width of pavement — Driving in middle of road 
 destruetive — Center walks instead of sidewalks 296 
 
xii CONTENTS 
 
 CHAPTER XIV. STONE BLOCK PAVEMENTS 
 
 PAGE 
 
 Roman roads — Cobblestone pavement — Belgian block pavement — 
 Granite block pavement — Advantages and defects — Quality 
 of the stone — Size and shape of the blocks — Manner of laying 
 the blocks — Foundation — Laying the blocks — Joint fiUing — 
 Pavements on steep grades — Durability of granite blocks 311 
 
 CHAPTER XV. BRICK PAVEMENTS 
 
 Advantages and defects — Quality of brick — Brick-clay — Region of 
 production — Manufacture of paving bricks — Size and shape 
 of bricks — Testing bricks — Construction of pavement — Manner of 
 laying bricks — Durability 323 
 
 CHAPTER XVI. AVOOD BLOCK PAVEMENTS 
 
 Progress of wood paving — Woods used for paving — Qualities of 
 treated wood pavement — Cost — Service — Durability — Tractive 
 resistance — Quality of wood used for paving — Wood preserving 
 methods — Creosoting — Impregnation of timber — Kreodone-creo- 
 sote process — Creo-resinate process — Foundation and cushion — 
 Blocks — Angle of courses — Expansion joints — Filler — Top dress- 
 ing — Repairs and maintenance 335 
 
 CHAPTER XVII. ASPHALT PAVEMENTS 
 
 Nomenclature — Bitumen — Asphalt — Historical — European and 
 American pavements — Artificial sheet asphalt pavement — Dur- 
 ability ' 357 
 
 Construction of the Pavement: Foundation — Binder course — Com- 
 position of wearing surface — Mixing and spreading wearing 
 surface — Failures of asphalt pavements — Repairs 365 
 
 Asphalt Block Pavement: Manufacture — Advantages and defects. . . 376 
 
 Coal-tar Pavements: Coal-tar and asphalt — Advantages — Defects. . . 377 
 
 CHAPTER XVIII. CONCRETE PAVEMENTS 
 
 Advantages of concrete — First cost — Cost of maintenance — 
 Ease of traction — Foothold — Noiselessness — Cleanhness and 
 healthfulness — Acceptability — Construction — Hassam pavement 
 — Materials — Method of Work — Proportioning materials — Mix- 
 ing — Topping and finishing — Road surface of concrete cubes — 
 Concrete block trackway 380 
 
 Concrete Foundations 399 
 
CONTENTS xui 
 
 CHAPTER XIX. THE CLEANING AND SANITATION OF CITY 
 
 STREETS 
 
 PAGE 
 
 Early history of street cleaning — Municipal growth in America 
 — Uses of city streets — Sources of street dirt — Reasons for un- 
 clean streets — Aim of sanitation — Cooperation required — Varie- 
 ties of city waste — Comparative cleanUness of pavements — - 
 Orderlies — Machinery employed in street cleaning — Street clean- 
 ing authority — Organization of forces — Flushing — Disposal of 
 street dirt — Removal of household refuse — Summary 401 
 
 CHAPTER XX. SIDEWALKS, CURBS, AND GUTTERS 
 
 Width — Slope — Foundation — Requirements of a good walk — 
 Materials used — Sandstone — Granite — Wood — Brick — Artificial 
 stone — Gravel — Cement and concrete — Sub-foundation and drain- 
 age — Upheaval by tree roots — Foundation — Concrete base — Top 
 Coat— Joints 424 
 
 Standard Specifications for Portland Cement Concrete Sidewalks of the 
 
 National Association of Cement Users 441 
 
 Curbs and Gutters: 444 
 
 CHAPTER XXI. MISCELLANEOUS ROADS AND PAVEMENTS 
 
 Stone trackways — Steel trackways — Concrete-block trackways — 
 Artificial granite blocks — Plank roads — Corduroy roads — Char- 
 coal — Slag roads — Coal-slack roads — Clinkers — Destructor con- 
 crete — Shell roads — Cork — Copper slag — India rubber — Artificial 
 paving stones — " Durax '' roads 450 
 
 CHAPTER XXII. THE ROADSIDE 
 
 Hedges and fences — Trees — Selection of trees — Planting — Tree- 
 planting Association 463 
 
 APPENDIX 
 
 I. Specifications and Contracts 473 
 
 II. Pavement Guarantees 4S7 
 
 III. Concerning the Wear of Roads by Automobiles 491 
 
 IV. Statistics of American Roads 499 
 
 V. Bibliography of Roads, Streets, and Pavements 505 
 
 Index , 535 
 
THE ROAD* 
 
 Soon as I knew you gathered from all lands, 
 
 And that my cause was in your skilful hands, 
 
 My pulses gave one throb and, with a bound, 
 
 To be with you I quitted all my ground, 
 
 City and village, forest, hill and plain. 
 
 And, Phryne at the judgment once again, 
 
 My veil of dust hiding the fears you gave me, 
 
 Behold me at your feet, my masters! Save, oh save me! 
 
 Oh save me, when I wander o'er the plains 
 
 Or, 'twixt the hedges of the country lanes, 
 
 I stretch my arms beneath some leafy glade, 
 
 Heavy with sleep and flecked with sun and shade; 
 
 When like a serpent undulate I glide, 
 
 Trailing my white robe up the mountain's side; 
 
 When, drunk with light, for breezes fresh I look 
 
 And wind along some chattering brook; 
 
 When I plunge into chasms, sound the deeps, 
 
 Climb to the plateaux, mount the dizzy steeps; 
 
 Or when above the mountains, near the skies, 
 
 I spread new worlds before men's dazzled eyes 
 
 For all the gifts on you I have bestowed, 
 
 Be my good doctor — save, oh save the Road! 
 
 My case is grave and needs swift remedy; 
 Never has greater peril threatened me — 
 True, as in France, so in all other climes. 
 Much have I suffered from most ancient times. 
 In days when, sometimes subject, sometimes free, 
 People met people in fierce enmity, 
 I bore the shock of many a battle train 
 Rushing to doubtful death or doubtful gain; 
 And, like some avalanche of myriad tons. 
 The murd'rous passage of the heavy guns. 
 
 * Translation of an anonymous poem recited by Mme. Bartet at the GaJa Per- 
 formance given at the Com^die Francaise on Oct. 14, 1908, in honor of the First 
 International Road Congress, Paris. Reprinted from "The First International Road 
 Congress, Paris, 1908." By G. M. Harris and H. T. Wakelam. 
 
 xiv 
 
THE ROAD XV 
 
 Chanting the Marseillaise, thirsting for war 
 A nation shod with sabots passed me o'er, 
 And the great Emperor, to spread his fame 
 Over a world which trembled at his name, 
 Compelled me to his will and, spurring fast, 
 Triumphant o'er my prostrate body passed. 
 Glory I've borne — a heavy load to bear! 
 And others too as heavy and less fair; 
 The clumsy cart, rumbling with jolt and jar 
 Has crushed my bosom, leaving many a scar; 
 Coach, post-chaise, and postilions in full cry, 
 Flayed^my back sorely, as they galloped by. 
 
 The lumber wagon laid my sinews bare! 
 Yet I stood firm, defying wear and tear, 
 Even I thought to breathe with greater ease; 
 My toil, less burdensome, began to please. 
 No longer coach or post-chaise o'er me whirled, 
 I was forgot, abandoned by the world. 
 Rarely some cart with tranquil pace would creep 
 Me by, the lazy driver half asleep — 
 Nought else by day or night disturbed my rest, 
 Thus, by sweet dolce far niente blessed, 
 Thinking my woes forever passed away, 
 In a false calm I lived until one day — 
 
 A terrible monster burst into sight, 
 God knows from out of what hell 'twas cast. 
 Sheathed all in iron, a thing of might, 
 Swiftly it passes — it has passed! 
 
 It has passed, with a fearsome hooting, 
 Trail of smoke and a sudden glare, 
 Like to some dazzling meteor shooting 
 Over the highways of the air. 
 
 Fast and furious, onward dashing 
 Tow'rds an horizon which e'er shrinks back; 
 Fiery bolts of lightning flashing 
 Over an echoing thunder track! 
 
 v 
 
 And ah! for me it means a wound indeed, 
 
 My face is crushed, my sides their binding bleed, 
 
 Car after car make ever fresh attacks, 
 
 Till my macadam's nought but ruts and cracks. 
 
XVI THE KOAD 
 
 My body thus commences to decay 
 And, into dust dissolving, floats away! 
 Must I then die? 
 
 No, no! For you are here; 
 With you to aid me I have nought to fear. 
 Science and genius are in you alhed ! 
 In your great wisdom I can well confide. 
 Quitting the beaten paths, you'll seek new ways 
 Towards the cure for which your suppliant prays, 
 Thresh out fresh doctrines, find the golden mean 
 And, to preserve the route avoid routine! 
 
 Your patient's at your feet, apply your skill, 
 
 Probe, sound, investigate me as you will. 
 
 And, to prevent the tortures of the past. 
 
 Perfect a work, my masters, that will last! 
 
 Do this, and grateful evermore will be 
 
 All travelers — nay, all humanity; 
 
 For 'tis the road that is the fertile way, 
 
 Where Life and Progress must forever stray; 
 
 Where, seeking space and beauty far and wide, 
 
 The tourist flings unnumbered miles aside. 
 
 And over hills and valleys sows the seed 
 
 Which shall bring forth abundance in our need! 
 
 And when at length you have achieved your aim, 
 
 Restored my health and strengthened all my frame; 
 
 When by your work you've made me proof to shock, 
 
 Fearless, invulnerable, firm as rock; 
 
 My youth renewed, and more than ever fair, 
 
 I'll sing your praise here, there and everyv/here; 
 
 Beneath all skies, telling the joyful story. 
 
 At every cross-roads I'll proclaim your glory 
 
 On Touring Club sign-posts for all to see! 
 
 The surest road to Immortality! 
 
ADDENDA. 
 
 Page 23. It should be added to the last paragraph that some of the 
 States have created and financed Highway Commissions, as is detailed 
 on Page 252. 
 
 It should also be added that New York State has classified its roads 
 as follows: 
 
 2,800 miles of main roads across the State from N. to S. and E. to W., 
 known as " State " Roads, to be built and maintained at cost of State 
 and by the State. 
 
 7,500 miles of main " County " roads, being the most important roads 
 in the 47 Counties to be improved by the State, which pays 50%, the 
 County paying 35% and the Town 15%. 
 
 70,000 miles of " Town " roads to be improved as eurth roads under 
 State supervision, at the expense of the Towns, plus an equal sum to be 
 donated by the State as *' State Aid." 
 
 Page 24. In reference to the last paragraph, while the Massachusetts 
 State Highway Commission is one of the most important, at the 
 present time the most important highway undertaking is probably 
 that of the New York State Highway Commission, which is charged with 
 the expenditure of the proceeds of fifty million dollars* worth of bonds, 
 having taken from the State Engineering Department the charge of High- 
 ways in February, 1909. 
 
 Until about 1902 the Massachusetts Highway Commission was the 
 most important State organization, the other States (including New 
 York) learning much from the experience and good work in Massachusetts 
 and meantime exceeding them in mileage. The mileage of New York was 
 about 520 miles in 1909, while the Massachusetts Commission reports 
 show their annual new mileage as: 47 miles finished in 1907, 38 miles 
 built in 1908, and about 45 miles in 1909. 
 
THE ART OF ROADMAKING 
 
 INTRODUCTION 
 HISTORICAL SKETCH OF ROAD DEVELOPMENT* 
 
 The word "Road" (Anglo-Saxon radj a riding, and ridan, 
 to ride) is commonly used to mean a public highway, but 
 custom has applied it to any kind of a path open to foot or 
 vehicular traffic. In the most ancient times there were 
 no roads. The wants of man were few and were easily 
 satisfied by nature and his knowledge and intercourse were 
 limited to his immediate vicinity. But as the population of 
 the various communities multiplied, and with it the neces- 
 sities of life, man was led further afield to supply them. He 
 formed rough pathways, which, in time, came to be the 
 recognized routes from one locality to another, by means 
 of which he satisfied his desire for investigation and inter- 
 course with his neighbors, for the products of other localities, 
 and for conquest. 
 
 ''Countries inhabited by the least civilized people, whose 
 wants can be supplied in the immediate vicinity of their 
 dwellings, are almost destitute of roads; hence it has come 
 to be said that roads are the physical symbol by which to 
 measure the progress of any age or people. ' If the community 
 is stagnant, the condition of the roads will indicate the fact; 
 if they have no roads, they are savages.' " f 
 
 * The majority of current books on the subject of roads open with 
 an introductory historical chapter, but the most comprehensive general 
 histories may be found in Bj'^rne's "Treatise on Highway Construction," 
 and Tillson's "Street Pavements and Paving Materials," and the best 
 as applied to British Roads in Aitkin's "Road Making and Maintenance." 
 
 t Byrne: "Highway Construction." 
 
 1 
 
2 THE ART OF ROADMAKING 
 
 Roads are not only the offspring of civilization, but they 
 are also the greatest contributors to it and the greatest factors 
 in its advancement. 
 
 Without them the arts that are so beneficial and necessary 
 to the welfare of man could not develop; the interchange of 
 ideas and the advantages that result therefrom could not 
 be maintained; in fact, the civilization of to-day with its 
 large cities and towns, its commerce, newspapers, and its 
 highly developed moral, physical, and intellectual life, could 
 not exist at all. 
 
 One of the very first steps in the opening up of a new 
 country is the location and building of roads for the accom- 
 modation of travelers, the carriage of commodities, and for 
 the development of the natural resources and manufactures 
 of the country. Smiles, in his '^ Lives of the Engineers/' says: 
 "The road is so necessary an instrument of social well-being, 
 that in every new colony it is one of the first things thought 
 of. . . . The new country, as well as the old, can only be 
 effectually opened up, as the common phrase is, by roads, 
 and until these are made it is virtually closed." 
 
 Of the early history of road building as' of other works 
 done in the early life of the human race, little is known; 
 while no authentic records exist, it is known that the import- 
 ance of good roads was recognized in very ancient times. 
 We are told by Herodotus of a stone roadway built by King 
 Cheops about 4000 b.c, over which were conveyed the heavy 
 materials for the construction of the great Eg5^ptian pyramid 
 that bears his name. We are also told of a broad roadway 
 connecting the ancient city of Memphis with the pyramids 
 and lined on both sides with temples, mausoleums, porticos, 
 monuments, etc. Later historians tell us of the pavements 
 of Babylon, of many paved roadways diverging from that 
 city and of a highway connecting Babylon and Memphis and 
 passing through the great commercial cities of Nineveh, 
 Palmyra, Damascus, Tyre, and Antioch. It is to the Carthe- 
 genians, however, that credit must be given for the earliest 
 systematic and scientific efforts at road building, for as early 
 as the fifth century B.C. they had developed a system of 
 
INTRODUCTION 3 
 
 communication and military power that enabled them to 
 maintain their integrity against Greece and the Roman 
 Empire for four hundred years. The Romans learned the 
 art of road building from the Carthagenians, and so fully did 
 they appreciate the military advantages of improved high- 
 ways that they soon became the greatest road builders of 
 history. 
 
 The first Roman road of which we have historical evidence 
 was built in 312 B.C. by Appius Claudius, the censor, and 
 was named after him — the Appian Way. Some years later, 
 the Flaminian Way was built, and under Augustus and Julius 
 Csesar and succeeding emperors, Rome was made the center 
 of a wonderful system of paved roadways stretching out to 
 all parts of its great empire. These reached through Italy, 
 Gaul, and Spain; through Germany, Hungary, Macedonia; 
 to the islands of Sicily, Corsica, Sardinia, England, and to 
 Africa and Asia Minor and the East; in all, a system of 372 
 roads, which, according to Antoninus, amount to a total 
 length of 52,964 Roman miles. 
 
 It is said that for a distance of fifty miles from Rome many 
 of these roads were decorated with temples and other superb 
 edifices; lodging houses for the accommodation of couriers 
 and mansions for soldiers were erected at regular intervals 
 at the public expense. The width of these military roads 
 was from 36 to 40 Roman feet, the middle portion being for 
 the infantry, and the margins for horses and carriages. Many 
 miles of these roads still remain as great monuments to the 
 energy and skill of the Romans, and show the truth of the 
 familiar saying that "All roads led to Rome.'' 
 
 Not far behind the Romans in the art of road building were 
 the ancient Incas of Peru, who built some thousands of 
 miles of good roads in the face of great difficulties. In his 
 "History of Peru," Prescott says of the mountain road from 
 Quito to Cuzco: "It was conducted over sierras covered with 
 snow; galleries were cut through the living rock; rivers were 
 crossed by means of bridges swung suspended in the air; 
 precipices were scaled by stairways hewn out of the native 
 bed, and ravines of hideous depth were filled up with solid 
 
4 THE ART OF ROADMAKING 
 
 masonry." Most of this roadway was built at an elevation 
 of 12,000 feet above the sea; it was more than 1500 miles 
 long and 20 feet wide; paved with stones 10 feet square and 
 had a running stream and a row of shade trees on each side. 
 
 After the decline of the Roman Empire, the roads fell into 
 disuse and during the succeeding dark ages they were used 
 more as aids to plunder and violence than for purposes of 
 legitimate intercourse. Later they became practicable for 
 pack horses and rude vehicles, but no effort was made to 
 restore them until the middle of the eighteenth century when 
 a revival of road building arose simultaneously in England 
 and France. The highways of England at that time were 
 wretched beyond description and an effort was made to improve 
 this condition by the establishment of a system of turnpikes. 
 Many thousands of miles of these roads were built, but they 
 were little or no improvement over the old roads, and no 
 further advance was made until the time of Macadam and 
 Telford, to whom England is indebted for her present admir- 
 able system of roads. 
 
 In the United States the highways are much inferior to 
 those of European countries, the reason for which Byrne * 
 states may be attributed to (1) the excellence of the railroad 
 systems and waterways; (2) the indifference of those in 
 charge of highway maintenance; (3) the want of appreciation 
 of the benefits of good roads and the fear of increased taxation 
 on the part of the rural population; (4) the dispersion of 
 the people over large areas in their search for desirable 
 localities for residences, and (5) the ill-effects of the system 
 requiring the personal services of the rural population on the 
 highways. 
 
 The first inhabitants of this country were too fulty occupied 
 in subduing the wilderness, establishing homes, opening 
 farms to provide the necessaries of life, and setting up the 
 framework of a government, to give much attention to the 
 conveniences and comforts of transportation; and hence 
 their wagon roads were of the crudest and poorest sort. 
 
 * "Highway Construction. "p. xxxviii. 
 
i 
 
 CO 
 
INTRODUCTION 5 
 
 Later, just as an extension of the population to the West 
 necessitated the development of better means of transporta- 
 tion, the introduction of the railroad made less important 
 the wagon roads and engrossed the attention of the popu- 
 lation of the new territory. In a large part of the United 
 States the railroad has been the pioneer and has rendered 
 unnecessary long lines of wagon transportation. At present 
 the country is so well supplied with excellently managed 
 railroads that the chief function of the wagon road is to 
 afford easy communication and transportation between 
 neighboring farms, and between the farm and the nearest 
 railroad station. Thus the problem of good roads had become 
 a local question, both with respect to the community the 
 road serves and to the materials and methods most suitable 
 for use in the construction. 
 
 These facts relate to roads as distinguished from pavements, 
 or road surfaces. The date of the introduction of pavements 
 is very indefinite. In his "History of Inventions and Dis- 
 coveries," John Beekmann, professor in the University of 
 Gottingen, devotes a chapter to the paving of streets, and 
 from his historical sketch the following more interesting 
 points are taken: 
 
 "While Roman writers of early date often refer to paved 
 highways and especially describe the famous Appian Way, 
 of 3 1 2 B . c . , there is comparatively little reference to the 
 paving of streets in cities. The streets of Thebes were 
 regularly cleaned under the inspection of Telsarchs, and it 
 is to be assumed that they were paved; and the Talmud 
 says that the streets of Jerusalem were swept ever}' day, 
 which undoubtedly implies a hard and solid pavement. There 
 is no record of the first street pavement in Rome; but Livy 
 mentions that certain streets were ordered to be paved in 
 169 B.C., and as early as 530 b.c. the Emperor Heliogabulus 
 paved the streets around the palace with foreign marble. 
 The streets of Pompeii and Herculaneum still show their 
 paving blocks of lava, cut into deep ruts by the wheels of 
 passing chariots. 
 
 "Passing to later times, we find the streets of Cordova, 
 
6 THE ART OF ROADMAKING 
 
 in Spain, paved as early as a.d. 850, by order of the Caliph, 
 Abderrahman II. The first record of any street paving in 
 Paris is dated in the year 1184, when the name of the city 
 was changed from 'Lutetia,' the dirty, to 'Paris/ This 
 innovation is said to have arisen from the fact that the 
 King, Philip II, was annoyed by the offensive odors produced 
 by the agitation of the mud in front of his palace by passing 
 vehicles. He resolved to remedy the intolerable nuisance by 
 ordering the streets paved, and succeeded in having this done, 
 in part, at least, notwithstanding the heavy cost, which had 
 deterred his predecessors. 
 
 ''In 1090 the streets of London were soft earth only; but 
 when the first pavement was introduced is not known. 
 Holborn was paved for the first time, by royal command, 
 in 1417; Henry VIII ordered other streets paved, and the 
 great market square of Smithfield was first paved in 1614. 
 Augsburg, in Germany, seems to have been the first city 
 in that country to introduce footways and street pavement, 
 in 1415, but the extension of the improvement to other 
 towns was slow, and the streets of Berlin were not all paved 
 even in 1679.'' 
 
 In the United States, Boston was the first place to pave 
 its streets — pebbles, cobblestones, and flagging being used 
 during the seventeenth century. In New York city the first 
 stone pavement was laid about 1657 on what is known to-day 
 as Stone Street, and the first sidewalks were laid in 1790, 
 on the west side of Broadwa}^ 
 
 Toll roads were first constructed in England in 1346, and 
 were built until 1878, when they were entirely abolished. 
 In 1792 a toll road company was incorporated in Pennsylvania 
 to construct and maintain an artificial road from Philadelphia 
 to Lancaster. In 1834, the Albany and Schenectady turn- 
 pike was laid with stone wheel-tracks for a distance of fourteen 
 or sixteen miles. The turnpike itself was made in 1805, 
 of gravel, at a cost of $8400 per mile. Ten years later a 
 "sunken pavement" of cobblestones was built on the dry 
 and sandy parts of the road, and broken quarrystone, to the 
 depth of twelve inches, was bedded in the wet and clayey 
 
INTRODUCTION 7 
 
 parts, the edges bonded by lines of small boulders imbedded 
 in the earth along each side. 
 
 In 1831 protests were made by the stockholders of this 
 turnpike company against the effect of the charter granted 
 to the Mohawk & Hudson Railroad Company, on the ground 
 that 
 
 "Should the railroad company succeed, their operations 
 will necessarily diminish materially the tolls of the turnpike 
 company, and thus sap the consideration upon the faith of 
 which the latter have constructed their road." 
 
 Referring to the application of the railroad company for 
 leave to run a side-track into the heart of Albany, Chancellor 
 Kent wrote: 
 
 "If that would not be an interference with the rights 
 of the turnpike company, then nothing would be an inter- 
 ference short of plowing up the turnpike road." 
 
 It was feared that the railroad might eventually displace 
 the stages, the tolls from which formed a large portion of the 
 revenues of the previously chartered turnpike company, but 
 the steam railroad was built, and was opened to operation 
 on September 12, 1831, as the first exclusively passenger 
 railroad in the world. The handhng of freight by the rail- 
 road was not begun until December 6, 1832, when three 
 cords of wood, making two carloads, were taken to Albany, 
 and were the first freight carried on what is now the New 
 York Central Railroad. In order to compete with the rail- 
 road, the turnpike company then made many efforts to 
 arrange to build another railroad of their own aloiig the 
 side of the turnpike, and the failure of these efforts resulted 
 in deciding, in 1832, to lay the " stone rails," of which twenty 
 thousand linear feet were laid in 1833 and 1834, at a cost, 
 including the cobble paving between the tracks and the 
 forming of the roadbed, of $3300 per mile. Sections of this 
 stone wheel-track, in some cases half a mile or more in length, 
 are still in good condition and in daily use, as shown in the 
 photograph on next page, made in 1901. 
 
 About 1862, a system of similar wheel-track roads was 
 built in Ulster County, N. Y., as a toll-road from Kingston, 
 
THE ART OF ROADMAKING 
 
 B ft. of Urge cobble pavement 
 
 Road from Albany west to Schenectady, N. Y., 1901. 
 Bnilt by Turnpike Company in 1834. 
 
 ; -r- ■ 
 
 "'NtjBjftic-i"- — --—' ■^^^nrCll^B^ 
 
 > 
 
 
 I ' - 
 
 ^/^^r^'" :'|ii' ""^tHf^ 
 
 
 ■^ 
 
 k -"\a V' 
 
 ife^^ii'-^' 'B 
 
 
 P!IK 
 
 ^fe. -^nitaMffiH 
 
 
 
 HGbeRRII^^^^^BS^^^I^S^^^^^^*' — 
 
 
 -f^ 
 
 BJ^^HJ^^j^raffl^^SpSBpr ^P' ^^ *Ki£^^" 
 
 
 
 Road west from Kingston, Ulster Co., N, Y., 1902, 
 
 Built bj' Turnpike Company in 1862. 
 
 STONE WHEEL-TRACKS. 
 
 (From JudsorVs " City Roads and Pavements,") 
 
INTRODUCTION 9 
 
 eight miles up the Delaware and Ulster Valley, to the blue- 
 stone quarries in the Catskill mountains. This proved to 
 be so successful that branches, and other roads of the same 
 sort, were soon built and are still in decreasing use.* 
 
 The ease of traction on these smooth slabs led to an increase 
 of the loads drawn upon them, until eight tons has been 
 and is an ordinary load for two horses to bring from the 
 quarries to the wharves at Kingston and Rondout, while 
 loads of twelve to fourteen tons are drawn by three horses, 
 and loads of seventeen tons actual weight have sometimes 
 been drawn by four horses. These great loads were formerly 
 carried upon narrow tires of one and one-half to two inches, 
 which speedily cut furrows in the hard stones, so that slabs 
 six to eight inches thick were cut through in three or four 
 years. 
 
 * Judson's "City Roads and Pavements." 
 
PART I 
 PRELIMINARY CONSIDERATIONS 
 
 CHAPTER I 
 RESISTANCE TO TRACTION 
 
 Before taking up the study of the location and construc- 
 tion of roads, it is necessary for the reader to understand 
 something of the problems connected with the theory of road- 
 making — ^the obstructions and resistances to motion to be 
 overcome by the traffic using the road, the financial considera- 
 tions involved in the construction to insure its greatest econ- 
 omy, and the questions that confront the engineer in making 
 roads to suit the many different uses to which they are pat. 
 These problems are outlined in this and the two following 
 chapters. 
 
 The object of a road is to provide means of transporta- 
 tion of persons and goods with the least possible expenditure 
 of time and money. This economy depends upon 
 ^^'\ ° the amount of resistance to easy motion offered 
 by the road, the causes and effects of which are 
 matters of great importance in determining the ruling gradient 
 to be adopted on a proposed road, according to its situation 
 and the class of traffic that will use it. 
 
 Resistance to traction is made up of: 
 Causes of -^ ^^^^ friction, which is nearly constant at all 
 
 tractive , ■ ■ , . . , \ . ,. 
 
 resistance velocities, and is mdependent of the con- 
 
 dition of the surface of the road. 
 
 10 
 
RESISTANCE TO TRACTION 
 
 11 
 
 2. Rolling resistance, due to collisions with irregularities 
 
 of the surface, and to the penetration or sinking of 
 the tire in the roadway. 
 
 3. Gravity, or resistance due to gradient. 
 
 4. Air resistance, varying according to the velocity of the 
 
 wind, the area of the surface acted upon, the velocity 
 of the vehicle, and the angle or direction at which it 
 impinges against the plane of the surface. 
 The tractive force, or the power required to move vehicles 
 along a road, is variable, depending upon the conditions of the 
 road and the power of the horse. The power of p^^gj. 
 the horse varies in turn, according to its strength, required to 
 weight and special training, the speed at which °ioye 
 it travels and the hours of work, but it may be 
 taken as an average of -gV of the load on a level macadamized 
 road in good repair, varying from -^ of the load on the best 
 roads to -^ on roads with a badly maintained surface. 
 
 Reliable tests have been made to determine the force re- 
 quired to overcome the combined resistances of the vehicle 
 and the road, resulting in the accompanying table: 
 
 Table I 
 
 STANDARD TRACTIVE RESISTANCE OF DIFFERENT ROADS 
 
 AND PAVEMENTS * 
 
 Kind of Road Surface. 
 
 Tractive Resistance. 
 
 Lbs. per Ton. In Terms of Load. 
 
 Asphalt, artificial sheet 
 
 Brick 
 
 Cobble stones 
 
 Earth roads, ordinary condition 
 
 Gravel roads 
 
 Macadam 
 
 Plank road 
 
 Sand, ordinary condition 
 
 Stone block 
 
 Steel wheelway 
 
 Wood block: Rectangular 
 
 Cylindrical 
 
 30 to 70 
 15 to 40 
 50 to 100 
 50 to 200 
 50 to 100 
 20 to 100 
 30 to 50 
 100 to 200 
 30 to 80 
 15 to 40 
 30 to 50 
 40 to 80 
 
 1/67 
 
 1/133 
 
 1/40 
 
 1/40 
 
 1/40 
 
 1/100 
 
 1/67 
 
 1/20 
 
 1/67 
 
 1/133 
 
 1/67 
 
 1/50 
 
 to 1/30 
 to 1/50 
 
 to 1/20 
 to 1/10 
 to 1/20 
 to 1/20 
 to 1/40 
 to 1/10 
 to 1/25 
 to 1/50 
 to 1/40 
 to 1/25 
 
 * Baker: "Roads and Pavements," p. 31. 
 
12 THE ART OF ROADMAKING 
 
 The resistance of pavements to tractive effort has recently 
 been investigated in the city of Toronto^ Ont., and reported 
 to the Canadian Society of Civil Engineers in a 
 Recent ex- paper by Mr. A. C. D. Blanchard. All experi- 
 ^^tr^T ^ i^ents were made with a good, steady team of 
 resistance, horses, weighing 2940 pounds, and drawing a 
 truck weighing 2710 pounds, with a load of 8570 
 pounds. Between the horses and the truck there was placed 
 a standard dynamometer which was read by an observer on 
 the truck, at stated distances paced and called out by the 
 notekeeper walking alongside. Observations were made on 
 wet and dry streets of varying grade and paved with asphalt, 
 bitulithic, brick, cedar block, granite block, and treated wood 
 block. From the figures so determined curves have been 
 plotted on grade of street as an abscissa and tractive resistance 
 as an ordinate. For dry streets these curves, which are 
 straight lines, show the brick paving to have the least resist- 
 ance, the others following in the order: treated block, bitulithic, 
 cedar block, granite block, asphalt. These lines all show a 
 fairty uniform rate of increase of resistance with grade, except 
 that the granite block seems to increase its resistance with 
 grade somewhat more sharply than the others. 
 
 On wet streets, the order of tractive resistances, beginning 
 with the lowest and going up is: bitulithic, asphalt, treated 
 block and cedar block. Wet brick pavements were not 
 tested. The wetness of the streets seems to show small 
 effect on the resistive powers of the pavement. The high 
 place of the asphalt in the H^t of dry weather records is 
 due to, no doubt, the fact that dry weather is hot weather 
 and the asphalt pavement then is rather a soft mass into 
 which the wheels of a wagon sink. On wet, and therefore 
 cold and hard, asphalt pavements, the asphalt shows a very low 
 resistance. 
 
 The tractive force required to overcome obstacles is equal 
 
 to the horizontal force required to raise the wheel 
 
 Calculation ^^g height of the obstruction when applied 
 
 force directly to the axle, and may be calculated as 
 
 follows : 
 
RESISTANCE TO TRACTION 
 
 J3 
 
 In Fig. 1; let P = power required to overcome obstacle 
 
 B, acting in direction AP, with the 
 leverage x. 
 
 W= Weight; or Gravity, resisting in 
 direction WA, with leverage y. 
 
 This makes an equation of equilibrium 
 
 Px=Wy, or P=WXy/x 
 or in terms or radius R, where s^height of obstruction 
 
 P=WVr^-j^/{R-z). 
 
 Example. Let radius of wheel be 26 inches; height of obstruction be 
 4 inches; and the weight of wheel and load on axle be 500 pounds. 
 
 -4); 
 
 Then P = 500^676- 484/ (26- 
 
 = 500X^192/22; 
 
 = 500X13.86/22 =314.9 pounds. 
 The pressure at point 5 = TFXi2/a; = 500X26/22 = 591 pounds. 
 
 Rolling friction is affected largely by the width of the tires 
 and can be materially decreased by increasing their width, 
 a tire of 2^ inches wide causing fully double the 
 wear of one 4J inches wide. The only exceptions to 
 this are in cases of 
 
 1. Hard and incompressible surfaces, where width makes 
 
 little difference in traction, the advantage being 
 in favor of the narrow tire. 
 
 2. Sticky and dusty surfaces, where the large quantity 
 
 of mud and dust raised by the wide tires increases 
 the draft. 
 A solid rubber tire offers slightly less resistance than an 
 
 Rolling 
 friction 
 
14 THE ART OF ROADMAKING 
 
 iron one if the road is wet and heavy, but more if the surface 
 is hard and sniooxh. Pneumatic tires reduce tractive re- 
 sistance from 25 to 50 per cent^ in increasing proportion as 
 the road grows worse. 
 
 The size of the wheel also has much to do with tractive re- 
 sistance. Acting on the principle of a lever, small wheels in- 
 crease, and large wheels decrease, resistance, pro- 
 Effect of vided the diameter of the wheels is not so great 
 wheels ^^^^ ^^^ ^^^^ ^^ traction will be downward and 
 
 consume part of the power of the horse by pressing 
 the wheel against the ground. The most economical size of 
 wheels is considered to be about six feet in diameter. 
 
 The effect of springs on vehicles is to diminish the wear 
 
 on roads, especially at speeds beyond a walking pace. Going 
 
 at a trot, they cause no more wear than vehicles 
 
 ?*^ ° without springs at a walk, all other conditions 
 springs ^ ° ' 
 
 being equal. 
 
 The following are the general results of experiments made 
 
 by M. Morin upon the resistance to traction of 
 General re- , . , , ^ 
 
 suits of vehicles on common roads i"^ 
 
 fn tolTive^^ 1. The resistance to traction is directly pro- 
 resistance portional to the load, and inversely proportional 
 to the diameter of the wheel. 
 
 2. Upon a paved or a hard macadamized road the resistance 
 is independent of the width of the tire, when this exceeds 
 from 3 to 4 inches. 
 
 3. At a walking pace, the resistance to traction is the same, 
 under the same circumstances, for carriages with springs 
 and for carriages without springs. 
 
 4. Upon hard macadamized roads and upon paved roads, 
 the resistance to traction increases with velocity — the incre- 
 
 * Of the many experiments made by the English, German, and French 
 engineers on the force necessary to pull different vehicles at various speeds 
 over various surfaces, those made by M. Morin in 1838-41, seem to 
 have been the most extensive series, and were made with much care and 
 a high degree of accuracy. They were first described by him in his 
 *' Experience sur le tirage des Voitures," Paris, 1842, and have been 
 leferred to by nearly all modem writers. 
 
RESISTANCE TO TRACTION 
 
 15 
 
 ments of traction being directly proportional to the increments 
 of velocity above the velocity of 3.28 feet per second^ or about 
 2^ miles per hour. The equal increments of traction thus 
 due to equal increments of velocity are less as the road is 
 smoother, and as the carriage is less rigid or better hung. 
 
 5. Upon soft roads of earth, sand, turf, or roads fresh and 
 thickly graveled, the resistance to traction is independent 
 of the velocity. 
 
 6. Upon a well-made and compact pavement of hewn stones, 
 the resistance to traction at a walking pace is not more than 
 three-fourths of the resistance upon the best macadamized 
 roads, under similar conditions. At a trotting pace the re- 
 sistance is equal. 
 
 7. The destruction of the road is, in all cases, greater as the 
 diameters of the wheels are less, and it is greater in carriages 
 without than in those with springs. 
 
 Gradient 
 
 The grade of the road is the quantity by which it differs from 
 the level. Theoretically, all roads should be level, and where 
 they are not so, a large portion of the tractive force of the ve- 
 hicles traveling over them will necessarily be expended 
 in raising the load up the ascent. This resistance 
 of the force of gravity, or weight to be overcome, is the same 
 on all roads in any condition, and is in all cases approximately 
 equal to the load divided by the rate of grade. That is, the 
 grade resistance on any incline in pounds per ton is 2240 /Rate 
 of Grade, from which the following table has been computed: 
 
 Table II 
 RESISTANCE DUE TO GRAVITY ON DIFFERENT INCLINATIONS 
 
 Grade, 1 in 
 
 Rise in feet per mile . 
 
 Resistance in pounds 
 
 per ton 
 
 20 
 
 30 
 
 40 
 
 50 
 
 60 
 
 70 
 
 80 
 
 90 
 
 100 
 
 200 
 
 300 
 
 264 
 
 176 
 
 132 
 
 105 
 
 88 
 
 75 
 
 66 
 
 58 
 
 52 
 
 26 
 
 17 
 
 112 
 
 m 
 
 56 
 
 45 
 
 38 
 
 32 
 
 28 
 
 25 
 
 22 
 
 Hi 
 
 7i 
 
 400 
 13 
 
 5^ 
 
 On account of this loss of power on inclinations, it is im- 
 portant not to allow a road to ascend or descend a single foot 
 more than is absolutely unavoidable. In case of ascending 
 a hill, the road should be so located and have such cuttings 
 
16 THE ART OF ROADMAKING 
 
 and fillings as will secure a gradual and uninterrupted ascent 
 
 the whole way, as the slightest fall would make 
 
 Loss of ^^ additional, and probably a steeper, incline. 
 
 power on . . ^ 
 
 inclinations ^ ^^ necessity 01 easy gradients is dependent upon 
 
 the power of the horse to overcome the total of 
 the four elements of resistance to motion. On a level, smooth 
 
 road, the pull which a good average horse, weighing 
 Necessity ^qqq ^^ -^200 pounds, can exert at a walking pace, 
 gradients is about 100 pounds, or one-tenth his weight. 
 
 A 1650-pound horse can develop the conven- 
 tional horse-power of 550 foot-pounds per second and 16,500,000 
 
 foot-pounds per day of eight and one-third hours, 
 
 Hauhng which, however, may be considered as the limit 
 
 power of . 
 
 horses ^^ endurance. If the time of effort is decreased, 
 
 the draft ma}^ be proportionately increased, and vice 
 versa. The maximum draft for a horse is about half his weight, 
 and under certain conditions, this may be two-thirds, but 
 the working tractive power may be safely taken as one- 
 tenth, with an average maximum of one-quarter the weight, 
 which may, in great emergencies, be increased to one-half. 
 
 Increasing the number of horses does not increase 
 teams ^^^ power proportionately. With teams, the trac- 
 
 tive power is about as follows: 
 
 1 horse 1 
 
 2 horses 0.95X2 = 1.90 
 
 3 horses 0.85X3-2.55 
 
 4 horses 0.80X4 = 3.20 
 
 The gross load that can be drawn by a horse on any grade 
 
 Calculation 
 of load on 
 a gradient. 
 
 A- 
 
 can be approximately calculated by the formula: 
 L={t-WIR) ^ {T + 224:0/ R) ; 
 
RESISTANCE TO TRACTION 17 
 
 where L = load in tons, inclusive of vehicle, 
 i = tractive pull of horse in pounds, 
 T'7 = weight of horse in pounds, 
 retractive force required to haul one ton on a level 
 
 (See Table I), 
 i2 = rate of grade, or horizontal distances in which the 
 rise is unity; BC:AB, (See Table II). 
 Example. What load can a good horse, weighing 1500 pounds, haul 
 on un ordinary country earth road (7' = 150) on a gradient of 1 in 20, 
 when exerting a pull of 200 pounds? 
 
 L = (200 - 1500/20) -^ (150 + 2240/20) ; 
 = (200-75)^(150 + 112); 
 = 125/262 = .477, or about i ton. 
 
 Actual experience has shown that a good average horse can 
 draw on a level earth road in best condition a load of about 
 3600 pounds, which is reduced on grades as follows: 
 
 
 Pounds. 
 
 
 Pounds 
 
 1 per cent grade. . . 
 
 . ... 2880 
 
 5 per cent grade . 
 
 .. 1476 
 
 cy li a ii 
 
 ....2376 
 
 10 '' '' " .. 
 
 ... 936 
 
 q a ii ii 
 
 . . . . 1980 
 
 15 '' 
 
 ... 360 
 
 4 " '^ '* . . . 
 
 . ... 1692 
 
 20 '' '' " . . 
 
 ... 144 
 
 In ascending inclines a horse's power diminishes rapidly. A 
 large portion of his strength is expended in over- 
 coming the resistance of gravity due to his own Load drawn 
 weight as well as that of the load; also by fatigue J^ grades 
 on a long ascent owing to his anatomical formation 
 and great weight, while the amount of foot-hold afforded by 
 the road surface seriously affects the size of the load he can draw. 
 
 Assuming a wagon weighing 1200 pounds, with a load of 1800 
 pounds, amounting to 3000 pounds, the force of gravity on a 
 1 per cent grade would be approximately 30 pounds, 
 
 5 '' " '' " " " 150 " 
 
 10 '^ '' " '' '' " 300 '' 
 
 and so on, being always constant, regardless of the condition 
 
 of the road. „^ , 
 
 steep grades 
 
 Steep grades are thus seen to be objectionable, objection- 
 and they are particularly so when a single one occurs ^-ble. 
 
18 
 
 THE ART OF ROADMAKING 
 
 in an otherwise comparatively level road, in which ease the 
 load carried over the less inclined portions must be reduced 
 to what can be hauled up the steeper portion. 
 
 Their bad effects are especially felt in winter, when ice covers 
 the road, for the shppery condition of the surface causes 
 danger in descending, as well as increased labor on ascending. 
 Rain water runs down the road and gullies it out, destroying 
 its surface and causing a constant expense for repairs, while 
 the inclined portions are subject to greater wear from the feet 
 of horses ascending and require thicker covering than the 
 more level portions, thus increasing the cost of construction. 
 
 The correct determination of grade is of the utmost im- 
 portance in road building. It is expressed in different ways, 
 generally by percentage. A 1 per cent grade means 
 Methods of ^ j.jgg Qf I fQ(3|. f^Y each 100 feet of horizontal 
 grade. distance traveled. There are 5280 feet in a mile; 
 
 hence, a 1 per cent grade means a rise of 52. s 
 feet in that distance, a 2 per cent grade a rise of 105.6 feet, 
 and a 10 per cent grade a rise of 528 feet. 
 
 The proper grade in each case must be determined by the 
 conditions and requirements. This selection of grade is further 
 discussed, in its relation to the location of roads, on p. 45. 
 
 Table Ila 
 VARIOUS METHODS OF INDICATIXG GRADE 
 
 American 
 Method. 
 Feet per 
 100 Feet. 
 
 Enghsh 
 Method. 
 
 Feet 
 per Mile. 
 
 Angle with 
 
 the 
 
 Horizon. 
 
 American 
 Method. 
 Feet per 
 100 Feet. 
 
 English 
 Method. 
 
 1 
 Feet 
 per Mile., 
 
 Angle with 
 
 the 
 Horizon. 
 
 2° 0' 16" 
 
 i 
 
 1:400 
 
 13.2 
 
 0° 8' 36" 
 
 3^ 
 
 
 28^ 
 
 184.8 
 
 i 
 
 
 200 
 
 26.4 
 
 17 11 
 
 H 
 
 
 26! 
 
 198 I 2 8 51 
 
 3. 
 4 
 
 
 150 
 
 39.6 
 
 22 So 
 
 4 
 
 
 25 
 
 211.2 1 17 26 
 
 1 
 
 
 100 
 
 52.8 
 
 34 23 
 
 ^ 
 
 
 23.V 
 
 224.4 1^2 26 10 
 
 H 
 
 
 80 
 
 66 
 
 42 58 
 
 H 
 
 
 22i 
 
 237.6 ,^2 34 36 
 
 1^ 
 
 
 66f 
 
 79.2 
 
 51 28 
 
 4| 
 
 
 21 
 
 2.30.8 
 
 2 43 35 
 
 n 
 
 
 57i 
 
 ^92.4 
 
 1 51 
 
 5 
 
 
 20 
 
 264 
 
 2 51 44 
 
 2 
 
 
 50 
 
 105.6 
 
 1 8 6 
 
 6 
 
 
 13i 
 
 316.8 
 
 3 26 12 
 
 21 
 
 
 44i 
 
 118.8 
 
 1 17 39 
 
 7 
 
 
 14t 
 
 369 . 6 
 
 1 15 
 
 2* 
 
 
 40 
 
 132 
 
 1 25 57 
 
 8 
 
 
 12.V 
 
 422.4 
 
 4 34 26 
 
 21 
 
 
 36^ 
 
 145.2 
 
 1 34 22 
 
 9 
 
 
 lU 
 
 475.2 
 
 5 8 31 
 
 3 
 
 
 33} 
 
 158.4 
 
 1 43 08 
 
 10 
 
 
 10 
 
 528 
 
 5 42 37 
 
 3i 
 
 
 30f 
 
 171.6 
 
 1 51 42 
 
 
 
 
 
 
CHAPTER II 
 ROAD AND PAVEMENT ECONOMICS 
 
 Good country roads and city streets possess a considerable 
 value; as on them depend largely the development of the 
 financial, social and educational well-being of the 
 community. In cities and towns, smooth and p^fod^j-oads 
 comparatively dustless roads are regarded as es- 
 sential to the comfort and health of the inhabitants. In the 
 rural districts, the conditions of life being so different and 
 ways and means entering so largely into consideration, the 
 same arguments do not apply, but the monetary advantages 
 of good roads are none the less apparent. 
 
 No enumeration of the advantages of good country roads 
 could include all the benefits, but a few of the most evident of 
 these may be mentioned, as follows: 
 
 1. Decrease in cost of haulage. 
 
 2. Better facilities in the marketing of crops, thus permitting 
 
 the cultivation of crops not otherwise marketable — an 
 especially valuable feature to farmers located in the 
 vicinity of a large city. 
 
 3. The marketing of produce at the most favorable times — 
 
 an important consideration in connection with perishable 
 products. 
 
 4. A wider choice of market. 
 
 5. The equahzing of railway traffic and mercantile business 
 
 between different seasons of the year. 
 
 6. The promotion of social and intellectual intercourse 
 
 between members of rural communities and also be- 
 tween rural and urban populations. 
 
 7. Consolidation of rural schools and the increase in their 
 
 economy and efficiency. 
 
 8. Facilitation of the rural mail dehvery. 
 
 19 
 
20 THE ART OF ROADMAKING 
 
 9. Increase in value of rural property by maldng it more 
 
 accessible to cities. 
 Highway improvements in rural districts should be con- 
 sidered for both their financial and intellectual benefits, and 
 are to be urged principally because they increase 
 Advantages ^}^q intelligence and value of the citizen to society, 
 city streets '^^^ effects of pavements on city life are also far- 
 reaching and important, but should be studied 
 more particularly in connection with their cost, healthfulness 
 and appearance. Among their principal advantages may be 
 mentioned the following: 
 
 1. Decrease in cost of transportation. 
 
 2. Increase in fire protection. 
 
 3. Establishment of a permanent grade — an important 
 
 feature in connection with all street improvements. 
 
 4. Improvement in general appearance of streets. 
 
 5. Improvements in standards of sanitation and health, 
 
 by decreasing dust and mud and facilitating the clean- 
 ing of streets. 
 
 6. Facilitation of social intercourse and pleasure driving. 
 These and the many other advantages of a well-paved street, 
 
 naturally enhance the value of abutting property, so that this 
 must also be included in any list of the benefits derived. 
 
 The chief financial advantage of good roads and pavements 
 is the lowering of the cost of transportation, by permitting 
 faster traveling and the hauling of heavier loads, 
 value of ^^^ ^^y reducing the wear and tear on horses and 
 road im- vehicles. Just what the economic value of road 
 prove- improvements may be depends on location, cost 
 
 of improvements, maintenance charges, class of 
 traffic, and other considerations, and is always a difficult 
 problem to solve. A distinction must be made between traffic 
 carried on regularly by an organized transportation department, 
 such as an express company, and occasional traffic carried on 
 by farmers ; also between the transportation of perishable 
 and non-perishable products, the marketing of the former 
 being compulsory under any conditions, while the latter can 
 wait for comparatively favorable conditions. 
 
ROAD AND PAVEMENT ECONOMICS 21 
 
 The cost of transportation to the average farmer producing 
 non-perishable products depends chiefly upon the condition 
 of the road surface, and upon the demands of general farm 
 work. Loam or clay roads, which form the most common 
 variety in this country are reasonably good when dry, while 
 sand roads are at their worst when dry and are therefore in 
 their worst condition during the greater part of the year, and 
 especially so during the crop season. In a busy season, the 
 cost of haulage on a fairly level loam or clay road is probably 
 not over 10 or 12 cents per ton-mile, and where farm work is not 
 so pressing, this may be reduced to 8 or 10 cents per ton-mile/'' 
 
 There is no method of ascertaining definitely the value of 
 improvements or the saving in cost of transportation or the 
 loss occasioned by bad roads; the only way of arriving at such 
 conclusions being either by (1) mere guess work; (2) a rough 
 estimate based upon the estimated annual saving per horse, 
 multiplied by the number of horses given in the census report; 
 (3) statistical results pubhshed by the United States Depart- 
 ment of Agriculture; (4) making an estimate of present cost 
 per ton-mile and an estimate of cost after the improvement. 
 
 While the actual value can with difficulty be established, it 
 cannot be denied that such improvements are beneficial, 
 but before deciding upon their design^ the question 
 of ultimate economy should be fully gone into. economy 
 This includes: of road 
 
 1. Interest on first cost. improve- 
 
 meiits 
 
 2. Annual payments to a sinking fund for the 
 
 extinction of the debt at the end of some time correspond- 
 ing to the life of the structure, or with a fixed period 
 within which payment must be made. 
 
 3. Maintenance and cleaning charges. 
 
 4. Equal annual payments to a depreciation or renewal fund 
 
 which, properly invested for a number of years corre- 
 sponding with the life of the structure, will provide at 
 the end of the term the amount required for rebuilding. 
 
 *The subject of "Cost of Wagon Transportation" was discussed very 
 fully by Prof. I. O. Baker, in the Proc. of 111. Soc. of Engineers, vol. 16; 
 abstracted in Engineering News, of Jan. 31, 1901. 
 
22 THE ART OF ROADMAKING 
 
 In the designing of city pavements the questions of comfort 
 and luxury as affected by freedom from dust; noise, and shp- 
 perinesSj enter very largely. GranitC; for instance, 
 affecting makes a durable and, in the long run, an economical 
 design of pavement, but its use in cities is Umited, if not 
 *^**y precluded altogether, on the grounds that it is 
 
 noisy, slippery, and destructive to horses' feet. 
 It will be seen, therefore, when attempting to adjust the 
 economical value of pavements, how local conditions and 
 necessities must be given full weight. It may be said, how- 
 ever, that vveil-paved sidewalks and roadways form an eco- 
 nomic and social necessity to any community that wishes to 
 preserve its existence . Without them it cannot compete 
 with other places thus properly equipped. The lack of 
 pavements or the presence of bad pavements impedes the 
 moving of people and materials, prevents proper street 
 cleaning, endangers the comfort and health, and retards the 
 character, education, and success of the people. 
 
 The question of cost of city pavements is a relative one, but 
 
 in the matter of payment for them, there is always some 
 
 discussion. The three most common methods of 
 Methods of , . , r . 
 
 payment apportionment ot cost are: 
 
 for city 1. Muncipality to pay entire cost. 
 
 P^"^^~ 2. Municipality and abutting property to pay 
 
 50 per cent each. 
 3. Abutting property to pay entire cost. 
 There are arguments both for and against each of these 
 systems. It is claimed that (1) the residents who do not 
 own a horse or vehicle or make actual use of the pavement 
 should not be required to pay for it, ignoring the other ad- 
 vantages conferred upon them by the pavement; (2) as the 
 pavement is for the benefit of the general public, the cost 
 should be divided, which overlooks the distinct benefits secured 
 by abutting property, but tends to discourage an extravagent 
 demand for improvements; (3) the benefits accrue only to the 
 abutting property, which should, therefore, bear the entire ex- 
 pense, disregarding the fact that the pavement is for the use of 
 the general pubhc and benefits all the people of the community. 
 
ROAD AND PAVEMENT ECONOMICS 23 
 
 In a paper on "Theory and Practice of Special Assess- 
 ments/'* J. L. Van Ornum gives a table showing the apportion- 
 ment of cost of pavements in fifty American cities, which shows, 
 for original paving, in 11 cases the city pays all, in 7 the cost is 
 divided and in 32 the property pays all; for re-paving, in 20 
 cases city pays all, in 8 cost is divided and in 22 property 
 pays all; for grading, in 16 cases city pays all, in 6 cost is 
 divided and in 28 property pays all. This table also shows 
 that as a rule the Eastern and Southern cities pay a larger 
 proportion of the cost than do the Western, which is probably 
 due to the hmited revenues of new cities and to the many de- 
 mands upon the general tax fund. It seems to be equitable 
 and just that the cost should be borne jointly l>y the private 
 property and the city at large, since then the cost falls upon 
 both interests which directly profit by the improvement, and 
 neither receives a substantial benefit without sharing in its 
 cost. 
 
 The administration of highways is a feature of road economics 
 that has had much attention. Roads should not be con- 
 sidered merely as local facilities for traffic; it is 
 possible to develop them into great trunk fines ^^^^l^^"^^' 
 with many branches, just as a railroad may have highways 
 many branches connecting the main fine with 
 fertile agricultural districts and great commercial centers. 
 One of the greatest values of the road is in reaching where the 
 railroad cannot. There is no other means of traveling or haul- 
 ing which possesses the advantages of through communication 
 from farm and garden to market, from house to office, from 
 dairy to factory or shop, or for pleasure travel, that are offered 
 by a complete and consistent system of roads. 
 
 The management of roads in this country rests almost 
 entirely upon local township or county authorities, and 
 this makes it difficult to secure either good country roads" 
 or an efficient road administration. As a remedy it has 
 been urged that roads be classified according to their im- 
 portance into State, Count}', and Township roads, each class 
 
 * Trans. Am. Soc. C. E., Vol. 38. 
 
24 THE ART OF ROADMAKING 
 
 to be under a corresponding administrative board. Similar 
 European classifications are made in many European coun- 
 systems tries, and their systems of administration, which 
 of man- have been in force for many years, have produced 
 agemen . ^^^ magnificent roads seen in Europe to-day. In 
 France, where the road system has been brought to the highest 
 state of efficiency, there are five great classifications: 
 
 1 . Routes Nationales, or national highways, government 
 roads, managed by government engineers of the Department 
 of Bridges and Roads (Fonts et Chaussees) . 
 
 2. Routes Departmentales, or department highways, main- 
 tained at the joint cost of the government and the communes. 
 
 3. Chemins Vecivaux de Grande Communication, or main 
 feeder roads. 
 
 4. Chemins Vecivaux d'Interet Commune, or district roads. 
 These two classes are made at the cost of the communal 
 
 funds, with departmental or government subsidies, and are 
 maintained largely by the Department, partly by the com- 
 munes, and partly by individual labor. 
 
 5. Chemins Vecivaux Ordinaires, or small local or parish 
 roads, made by the communes with governmem. subsidies, and 
 maintained by communal tax and a part of the days of "presta- 
 tion." 
 
 In Germany the control of the public roads belongs to the 
 several states, and the standard of maintenance in some is 
 very high. There are usually two divisions : the Staats- 
 Strassen^ or state roads, and the Lands-Strassen, or local 
 roads. In Italy and Spain there are three classes of roads: 
 National, Provincial, and Communal. In Austria there are 
 Provincial, Subventioned or Competition, and Community 
 roadSj under the authority of provincial committees, dis- 
 trict road boards and the communities. In Denmark there 
 are four classes of roads, classed according to the number of 
 vehicles that pass over them. 
 
 In the United States the most important highway undertak- 
 ing is that of the Massachusetts State Highway 
 American Commission, appointed in 1893 by an Act of the 
 Legislature for improving, making, and encouraging 
 the making of roads. In several other states there are high- 
 
ROAD AND PAVEMENT ECONOMICS 25 
 
 way departments, or commissioners; some of which are em- 
 powered to give financial and other help for country and 
 local roads. But neither a general system of road classifica- 
 tion nor of state aid for road building and maintenance has 
 as yet been established. 
 
 For the maintenance of country roads there are three forms 
 of tax: 
 
 1. A tax upon the traveler, by a system of toll roads, con- 
 ducted on the theory that the travelers over a road are the 
 recipients of its benefits and should pay for it. The disad- 
 vantages and the many evils of this system have caused it to 
 be almost entirely abolished both in Europe and in the United 
 States. 
 
 2. A capitation tax, or poll-tax, which is levied in nearly 
 all states. This is usually paid in labor and in many parts 
 of the country is nearly the sole support of the roads. 
 
 3. A property tax, either by a special assessment on all 
 property within a certain distance of the improvement, or by a 
 general tax on all property within stated districts. 
 
 The labor tax system, as regularly employed in many states, 
 was brought from England, and is a survival of the feudal 
 method of requiring all able-bodied men to render 
 public service. It is still in operation in some of ® ^ 
 
 the European countries, but upon a much less ex- 
 tensive scale than in this country. The system has many 
 defects, but these are owing rather to poor administration 
 than to the actual working of the system, and may be classified 
 as follows: 
 
 1. Indifferent and inefficient work. 
 
 2. Impossibility of getting the work done at themo&t suit- 
 able times. 
 
 3. No selection of the laborer. 
 
 All of these are important considerations, but they are partly 
 counterbalanced by the facts: (1) that the farmer is willing 
 to pay more in labor than in money; (2) that in rural districts 
 it is impossible to secure anyone to do road work at reasonable 
 wages at the most suitable times, and (3) that if the tax were 
 paid in money there would be no certainty that the labor 
 
26 THE ART OF ROADMAKING 
 
 would be any more efficient. The labor-tax system is not 
 necessarily the cause of inferior roads nor the cash-tax in itself 
 the cause of improved roads. The one thing necessary for 
 successful road management is effective supervision of the 
 work. Without it neither system will accomplish much, and 
 with it either system will do well. 
 
 The methods of payment for the maintenance of city pave- 
 ments have already been briefly mentioned;* the system of 
 Mainten- maintenance is usually either by a contractor's- 
 ance of guaranteef for a specified time, or by the munici- 
 city pave- pality, depending upon local conditions. 
 
 In the course of an address before the Civic 
 Association of Morristown, N. J., in 1908, Col. J. W. Howard 
 spoke of the difficulties experienced by municipalities in the 
 methods of pavement construction and maintenance, and 
 said: 
 
 " The best pavements are obtained and maintained by 
 employing experienced, efficient and honest men and by elimi- 
 nating so-called practical politicians, whether office holders, 
 party managers or others. Paving contractors and the men 
 who supply paving materials not only must include in their 
 charges against a city or taxpayer the cost of construction or 
 materials and labor, but also any amounts they expend for 
 bribery (called ''graft" by many), and political contributions, 
 thus either increasing the cost of pavements or making their 
 quality bad. If full printed forms of contracts and complete 
 specifications are prepared by a competent paving expert not 
 under local influences, the community receives the benefit of 
 the experience of many other places, and if the specifications 
 enumerate the preliminary laboratory tests which the paving 
 materials must meet, and fully describe the materials, methods, 
 and processes, then with honest inspection, good and durable 
 pavements will be the result." 
 
 A serious cause of the destruction of pavements in the 
 United States and a difficulty in the way of proper maintenance, 
 
 * The subject of the apportionment of expenses and the system em- 
 ployed in building, maintaining, and grading roads and pavements is 
 an important one and is discussed very fully in Baker's "Roads and 
 Pavements" and in Byrne's "Highway Construction." 
 
 fThe subject of *' Guarantees" is discussed briefly in Appendix II. 
 
ROAD AND PAVEMENT ECONOMICS 27 
 
 is the frequency with which they are torn up for the intro- 
 duction and replacing of underground pipes. As 
 
 the pavement should be impervious to water, it *^P^°^°g ^^ 
 
 ^ pave- 
 
 should also be impervious to the destroying pick ments. 
 
 and shovel of the ignorant workman, to whom this 
 work is usually assigned. A pavement once torn up in this 
 way is never properly repaired, and will always be a source of 
 expense. In most European countries, neither corporations 
 nor individuals are permitted to disurb the pavements^ all 
 removals and restorations being done by the city's own em- 
 ployees, upon the deposit^ by the parties who required the open- 
 ing of the street, of a sufficient sum to cover the expense of each 
 piece of paving done, at a fixed price per yard, according to 
 the kind of pavement. The only way to entirely avoid this 
 disturbance is by the introduction of a series of subways under 
 the pavements for wires, pipes, etc.; a costly, but, in the end, 
 an economical remedy. 
 
CHAPTER III 
 
 PRINCIPLES UNDERLYING THE SELECTION OF 
 PAVEMENTS FOR DIFFERENT PURPOSES 
 
 A Road may be defined as a highway or thoroughfare for 
 the use of foot travelers or veliicles; a Pavement (from the 
 
 Latin Pavimentum, ^'a floor rammed or beaten 
 Road and down") as the artificial surface or covering of the 
 definitions, ^'o^*^!- I^s purpose is not, as may be commonly 
 
 supposed, to support the vehicles passing over it, 
 the weight of which, together with that of the covering itself, 
 must be actually borne by the natural soil, but it is (1) to 
 distribute the pressure of the traffic over a sufficient area of 
 sub-soil ; (2) to facilitate travel by reducing the resistance to 
 traction to the lowest practicable limit, at the least cost for 
 construction and maintenance, and (3) to secure a water- 
 tight covering that will preserve the natural soil from the 
 effects of moisture. 
 
 P . The pavement, or road covering, is composed of 
 
 ments of a suitable materials laid upon a firm bed, or upon an 
 good pave- artificial foundation from which water is excluded 
 
 by suitable drainage, and should be: 
 
 1. Cheap — that is, low as to first cost. 
 
 2. Hard and durable, to resist wear and disintegration. 
 
 3. Easily cleaned. 
 
 4. Adaptable to every grade with little resistance to traction. 
 
 5. Non-shppery, affording a good foothold for horses. 
 
 6. Cheaply maintained. 
 
 7. Suitable for every class of traffic. 
 
 8. Impervious to water, yielding neither dust nor mud, and 
 noiseless. 
 
 Of these requirements (1), (2) and (6) affect the taxpayers, 
 both as to the serviceable life of the pavement and as to the 
 
 28 
 
PAVEMENTS FOR DIFFERENT PURPOSES 29 
 
 amount of annual repairs; (3) and (8) affect the occupiers of 
 adjacent premises, who suffer physically, and the owners of 
 the premises, whose income from rents is diminished by these 
 disadvantages; (4), (5) and (7) affect the traffic and determine 
 the cost of haulage and hmitations of loads, speed, wear and 
 tear of horses and vehicles. 
 
 Assuming an ideal pavement possessing these different 
 properties in perfection, and giving it a value of . 
 
 100, Tillson* assigns to each its proportional value of an ideal 
 of the whole as follows: pavement 
 
 Cheapness. . 14 
 
 DurabiUty 21 
 
 lipase of cleaning 
 
 Light resistance to traffic 
 
 Non-slipperiness 
 
 Ease of maintenance .... 
 Favorableness to travel. . 
 Sanitariness 
 
 15 
 15 
 
 7 
 10 
 
 5 
 13 
 
 100 
 
 Baker t divides the properties of the ideal pavement into 
 Economic and Sanitary Qualities and Acceptability, and gives 
 a table showing the following relative values of the different 
 qualities : 
 
 Economic Qualities: 
 
 Low first cost 15 
 
 Low cost of maintenance 20 
 
 Ease of traction 10 
 
 Good foothold 5 
 
 Ease of cleaning 10 
 
 — 60 
 Sanitary Qualities: 
 
 Noiselessness 15 
 
 Healthfulness 10 
 
 — 25 
 
 * "Street Pavements and Paving Materials," p. 147. 
 f "Roads and Pavements," p. 583. 
 
30 THE ART OF ROADMAKING 
 
 Acceptability: 
 
 Freedom from dust and mud 10 
 
 Comfortable to use 3 
 
 Xon-absorbent of heat 2 
 
 — 15 100 
 
 Cheapness is placed first as the first cost of a material is a 
 question of vital importance in deciding upon its availability. 
 No matter how desirable or how economical a material may 
 be, if the property owners cannot pay for it, the question is 
 settled at once and a committee's recommendation is often 
 rejected when its wisdom is not questioned, simply on this 
 account. 
 
 Durability is also an economic question, upon which de- 
 pends ultimate cost, and it must, therefore, be considered in 
 connection with first cost. A pavement may be cheap, and 
 also fill several other requirements but it cannot be a complete 
 success unless it has durability. This is affected by many and 
 various conditions and is measured by the amount of traffic 
 tonnage it will bear before it becomes so worn that the cost 
 of replacing it is less than the expense incurred by its use. 
 
 Ease of Cleaning. The experience of many cities has demon- 
 strated the importance of this quality. Street cleaning is 
 an expensive process and considerable attention is given to 
 devices and sj^stems of construction that will effect economies 
 in this direction. 
 
 Resistance to Traction is an important item, as one of the 
 objects in the building of a pavement is to effect its greatest 
 possible reduction. 
 
 NoU'slipperiness is necessary in a pavement, as on it de- 
 pends the efficiency of a draft horse or other motive power. 
 
 Ease of Maintenance is closely allied to first cost. There 
 is not a pavement, just as there is no other work of man, 
 however perfect originally, that will not require constant at- 
 tention to keep it in its original condition, and the construc- 
 tion that requires the least attention to keep in good repair, 
 and allows that to be done at the least expense, is the best. 
 
 Suitability for Traffic means the ease and comfort obtained 
 
PAVEMENTS FOR DIFFERENT PURPOSES 
 
 31 
 
 by the user of the road and the wear and tear on the horses 
 and vehicles used. 
 
 Sanitariness. To be sanitary a pavement must be im- 
 pervious to water in order to prevent the accumulation of 
 decaying organic matter, garbage, droppings, and various 
 kinds of filth from collecting in joints or soaking through the 
 surface to the underlying soil, out of reach of the street cleaners. 
 It should be of material that will not decay, or otherwise 
 yield dust or mud. Under this head should also 
 be classed noise, which is an important factor yaiues of 
 affecting the comfort of the persons living adjacent qualities of 
 to or otherwise using the street. 
 
 Tillson"^ makes a comparison of the various 
 pavements in connection with these properties, as shown in 
 the accompanying table : 
 
 Table III 
 
 SHOWING HOW EACH MATERIAL STANDS RELATIVELY TO 
 OTHERS AND ALSO WHAT PROPORTION OF THE PROP- 
 ERTIES OF A PERFECT PAVEMENT IS POSSESSED BY 
 EACH PAVEMENT UNDER CONSIDERATION 
 
 different 
 pavements 
 
 Pavement Qualities. 
 
 Cheapness 
 
 Durability 
 
 Ease of cleaning 
 
 Light resistance to traffic . 
 
 Non-slipperiness 
 
 Ease of maintenance . . . . 
 J'avorableness to travel . . 
 Sanitariness 
 
 14 
 21 
 15 
 15 
 
 7 
 10 
 
 5 
 13 
 
 2 
 
 21 
 11 
 7 
 6 
 10 
 3 
 9 
 
 4 
 17 
 8 
 6 
 5 
 7 
 
 4 
 
 15 
 
 15 
 
 15 
 
 3 
 
 6 
 
 5 
 
 13 
 
 3 
 
 13 
 12 
 12 
 
 4 
 11 
 
 5 
 17 
 
 7 
 6 
 3 
 
 7 
 
 14 
 15 
 2 
 4 
 5 
 2 
 
 
 
 2 
 
 Total 100 
 
 I 
 
 69 
 
 56 
 
 76 
 
 67 
 
 45 
 
 44 
 
 Making Asphalt the standard at 100, the values of the others 
 will be: Granite A, 91; Brick, 88; Granite B, 74; Belgian, 68; 
 Macadam, 59; Cobblestone, 5S. 
 
 * "Street Pavements and Paving Materials," p. 167. 
 
32 
 
 THE ART OF ROADMAKING 
 
 The United States Forestry Service recently made an 
 Investigation in order to obtain opinions from engineers of 
 a number of American cities who have had experience with 
 the modern creosoted wood block pavement as to the com- 
 parative qualities of different kinds of pavements. This 
 was made in a form slightly modified from the one presented 
 above, by Tillson, and resulted in the percentages given in 
 Table IV^ in which the figures given are the averages of ten 
 replies to the inquiry. In this table the pavement ranking first 
 under any given quality is given the full quality percentage, 
 the rest grading down from this value in proper proportion. 
 
 Table IV 
 COMPARATIVE VALUE OF DIFFERENT PAVEMENTS* 
 
 Pavement Qualities. 
 
 Cheapness (first cost) . 
 
 Durability 
 
 Ease of maintenance. . 
 
 Ease of cleaning 
 
 Low tractive resistance 
 
 Non-slip periness 
 
 Favorableness to travel 
 
 Acceptability 
 
 Sanitary quality .... 
 
 Total 
 
 Average cost per square 
 yard (1905) 
 
 14 
 
 20 
 
 10 
 
 14 
 
 14 
 
 7 
 
 4 
 
 4 
 
 13 
 
 100 
 
 o 
 
 4.0 
 20.0 
 9.5 
 10.0 
 8.5 
 5.5 
 2.5 
 2.0 
 9.0 
 
 71.0 
 $3.26 
 
 4.0 
 
 17.5 
 
 10.0 
 
 11.0 
 
 9.5 
 
 7.0 
 
 3.5 
 
 2.5 
 
 8.5 
 
 73.5 
 $3.50 
 
 6.5 
 
 10.0 
 
 7.5 
 
 14.0 
 
 14.0 
 
 3.5 
 
 4.0 
 
 3.5 
 
 13.0 
 
 76.0 
 $2.36 
 
 
 6.5 
 
 14.0 
 
 8.0 
 
 14.0 
 
 13.5 
 
 4.5 
 
 3.5 
 
 3.5 
 
 12.0 
 
 79.5 
 
 $2 . 29 
 
 7.0 
 
 12.5 
 
 8.5 
 
 12.5 
 
 12.5 
 
 5.5 
 
 3.0 
 
 2.5 
 
 10.5 
 
 74.5 
 $2.06 
 
 14.0 
 6.0 
 4.5 
 6.0 
 8.0 
 6.5 
 3.0 
 2.5 
 4.5 
 
 55.0 
 $0.99 
 
 m O 
 
 4.5 
 
 14.0 
 
 9.5 
 
 14.0 
 
 14.0 
 
 4.0 
 
 3.5 
 
 4.0 
 
 -12.5 
 
 80.0 
 $3.10 
 
 Acceptability includes noise, reflection of light, radiation of heat, emission of un- 
 pleasant odors, etc., and chiefly concerns the pedestrian and the adjoining resident. 
 
 Cost per square yard includes concrete, but not excavation, curbing, etc.; except for 
 macadam which is not usually laid on concrete. 
 
 As in Table III, giving Asphalt (sheet) the value of 100, 
 the values of the others will be, approximately: Granite, 
 95.0; Sandstone, 98.; Asphalt (block), 104; Brick, 99; Mac- 
 adam, 72; Creosoted wood, 104. 
 
 * From Circular 141, Forest Service, U. S. Department of Agriculture. 
 
PAVEMENTS FOR DIFFERENT PURPOSES 
 
 33 
 
 Use of 
 tables in 
 selection 
 of pave- 
 ments. 
 
 By a proper understanding and use of these tables, the prin- 
 ciples used in their construction can be easily applied to any 
 particular case. One or two examples will suffice 
 to make this clear. Assume a street over which 
 the traffic must be heavy and continuous; ulti- 
 mate cost is of so great importance that it over- 
 rules first cost. Light resistance to traffic and 
 foothold for horses are ruling elements, so that a given power 
 may move its maximum load. The items first to be studied 
 are, then: durability, maintenance, traction, and non-slipper- 
 iness. Consulting Table IV and combining the values for 
 these items. Granite has a value of 43.5; Sandstone, 44.0; 
 Asphalt (sheet), 35; Asphalt (block), 40; Brick, 39; Mac- 
 adam, 25, and Creosoted wood, 41.5. Granite and sandstone 
 have almost equal advantages and a selection must be made 
 between them, according to local conditions. 
 
 In a residence district built up with homes, there is quite 
 a different problem. Cost, durability, and maintenance are 
 secondary considerations. Ease of cleanliness, non-slipperiness, 
 favorableness to travel, acceptability, and sanitariness are the 
 governing characteristics, and we find that Granite has a value 
 of 29; Sandstone, 32; Asphalt (sheet), 38; Asphalt (block), 
 37.5; Brick, 34; Macadam, 22.5, and Creosoted wood, 38. 
 Asphalt or creosoted wood, either of which possesses all the 
 desirable qualities in so high a degree, should be selected 
 without question. 
 
 The following table shows the comparative rank of pave- 
 ments in the order of their merit, as given by Byrne: * 
 
 Table V 
 
 COMPARATIVE ] 
 
 RANK OF PAVEMENTS, 
 ORDER OF THEIR MERIT 
 
 NAMED 
 
 IN THE 
 
 
 Durability. 
 
 Service- 
 ability. 
 
 Hygienic 
 Pitness. 
 
 Service on 
 Grades. 
 
 Gross An- 
 nual Cost. 
 
 Facility for 
 Cleansing. 
 
 1 
 2 
 3 
 
 4 
 
 Granite 
 Asphalt 
 Brick 
 Wood 
 
 Asphalt 
 Brick 
 Wood 
 Granite 
 
 Asphalt 
 Brick 
 Granite 
 Wood 
 
 Granite 
 Brick 
 
 Wood 
 Asphalt 
 
 Asphalt 
 Brick 
 Wood 
 Granite 
 
 Asphalt 
 Brick 
 Granite 
 Wood 
 
 * "Highway Construction," p. 21. 
 
34 THE ART OF ROADMAKING 
 
 In general, the selection of a suitable pavement to meet any 
 
 local conditions of traffic is a problem involving questions of 
 
 adaptability, desirability, serviceability, durability, and cost; 
 
 but, apart from strictly local considerations, appearance, 
 
 cleanliness, healthfulness, and noise should be con- 
 Adapta- ■ -, j 
 
 bilit?. ^^^^^^^• 
 
 In regard to adaptability, the materials most 
 
 commonly employed are: 
 
 1. For country roads — earth, sand, clay, gravel, and broken 
 
 stone. 
 
 2. For suburban streets, parks and pleasure drives, and 
 
 main country roads — broken stone (macadam), tar- 
 macadam, gravel, vitrified brick. 
 
 3. For city streets having heavy and constant traffic — 
 
 recta'ngular blocks of stone laid upon a concrete founda- 
 tion with the joints filled with bituminous or Portland 
 cement grout. 
 
 4. For city streets devoted to lighter traffic, and where 
 
 comparative noiselessness is essential — sheet asphalt, 
 
 asphalt block, vitrified brick, creosoted wood block, 
 
 concrete. 
 
 The desirability of any pavement depends partly upon 
 
 its fitness for service, but is dependent principall}' on the 
 
 personal prejudices of the persons using or seeing 
 Desirability. ^ -n / ^ . ri ■ 
 
 it. Between two or more pavements alike m 
 
 cost and durability, there will always be a diversity of 
 
 opinion as to desirability according as each possesses qualities 
 
 that make it satisfactory for the individual purposes of 
 
 each person. The economic desirability is governed b}- the 
 
 ease of movement over a pavement, and is measured b}^ 
 
 the tractive power required to move a given weight over 
 
 it. 
 
 The serviceability of a pavement is its quality of fitness for 
 
 use, as measured by the expense caused to the 
 Serviceability ' . . , , 
 
 traffic using it, such as the wear and tear on 
 
 horses, vehicles, loss of time, etc. This is estimated to be as 
 
 follows : 
 
PAVEMENTS FOR DIFFERENT PURPOSES 35 
 
 Cents per Mile Traveled. 
 
 On Cobblestones 5 
 
 Belgian block 4 
 
 Granite block 3 
 
 Wood 2.5 
 
 Broken stone in first-class condition. . . 1.2 
 
 Asphalt 1 
 
 Serviceability also largely depends on the amount of foot- 
 hold it offers to horses, provided, however, that the surface 
 friction does not absorb too large a percentage of the tractive 
 force required to move a given load over it. Cobblestones 
 afford an excellent foothold, and for that reason were largely 
 employed between the tracks of the early stone-track roads, 
 and later by horse-car companies for paving between the rails. 
 The resistance of their surface to motion, however, requires 
 the expenditure of about 280 pounds tractive force to move 
 a load of one ton, which makes it unserviceable for many 
 purposes, as compared with asphalt, which affords the least 
 foothold, but requires a tractive force of only 
 
 about 30 pounds per ton to overcome the resist- ^*l°2^^^i*^^ 
 
 ^ ^ . safety of 
 
 ance it offers to motion. pavements. 
 
 The materials affording the best foothold for 
 
 horses, are stated as follows in the order of their merit. "^ 
 
 1. Earth, dry and compact. 
 
 2. Gravel. 
 
 3. Broken stone (macadcim). 
 
 4. Wood. 
 
 5. Sandstone and brick. 
 
 6. Asphalt. 
 
 7. Granite blocks. 
 
 Observations on the comparative safety of different pave- 
 ments show that: 
 
 1. Asphalt is most sUppery when merely damp, and safest 
 when perfectly dry. 
 
 2. Granite is most slippery when dry and safest when wet. 
 
 ♦Byrne: ^'Highway Construction,'' p. 7. 
 
36 THE ART OF ROADMAKING 
 
 3. Wood is most slippery when damp and safest when 
 dry. 
 
 Granite is, therefore, least safe and wood and asphalt most 
 
 safe when clean. Slipperiness can be prevented by the sprink- 
 
 hng of sand on asphalt, and gravel on wood, but both make 
 
 dirt. While the sand tends to wear and damage to the asphalt, 
 
 the gravel tends to the preservation of the wood. 
 
 The durability or life of the different pavements 
 Durability. . . 
 
 IS given as: 
 
 Granite block 12 to 30 years 
 
 Sandstone 6 to 12 years 
 
 Asphalt 10 to 14 years 
 
 Wood 3 to 7 years 
 
 Limestone 1 to 3 years 
 
 Brick 5 to ? years 
 
 Macadam ? years 
 
 Cost is always an important question, and while cheapness 
 is placed as the first requirement of an ideal pavement it must 
 be considered in connection with the returns on the 
 investment. The most expensive pavement is not 
 always the best, nor is the cheapest the most economical. 
 The most economical is the one which gives the most profitable 
 returns in proportion to the expenses incurred in its con- 
 struction and maintenance. 
 
 ''Cheapness'* in road-building, as in nearly every other mat- 
 ter, may be false economy. If the first cost is to be charged 
 against the abutting property, the average property owner 
 will look for cheapness without reaUzing the early destruction 
 of the pavement and the annoyance and expense of endless 
 repairs. A good pavement costs more than a poor one, but 
 it is easier and cheaper to keep in repair, and will last many 
 years longer, while its other economic benefits, comprising 
 greater and easier facilities for traveling, less cost for repair 
 to vehicles, less wear on horses, saving of time, and the ease 
 and comfort of those using it, will much more than compensate 
 for the extra expense involved in building it. 
 
PART II 
 
 COUNTRY, SUBURBAN, AND MISCELLANEOUS 
 ROADS 
 
 CHAPTER IV 
 
 LOCATION OF COUNTRY ROADS 
 
 The problems involved in the construction of country roads 
 are quite different from those connected with similar opera- 
 tions on city pavements, and may in general, be divided into 
 three periods: 
 
 1. Locating, or laying out, the route; 
 
 2. Making the roadbed; 
 
 3. Making the road surface. 
 
 The location of country roads is the scientific determination 
 of the most suitable route and gradients for the proposed 
 line of communication. In the earUest days or in the early 
 days of new settlements, routes were made according to the 
 Hne of least resistance, and without regard to any considera- 
 tions other than the easiest method of traveling, or of convey- 
 ing goods, from one place to another. 
 
 The Romans, at very great expense, built their roads up- 
 hill and down hill, through swamps and forests, t +>, * 
 and over all obstacles, in perfectly straight lines, straight 
 in the belief that this was the shortest distance be- ^^^ curved 
 tween two points and constituted the best location. ^°^^^' 
 
 Theoretically they were right, but practically they were cor- 
 rect to a very limited degree, for a straight road over a hill is 
 not necessarily any shorter than a curved road around it. Both 
 
 37 
 
a. Before Improvement. 
 
 b. In Process of Construction. 
 
 c. The Finished Road. 
 Fig. 3.— The Evolution of a Country Road. 38 
 
LOCATION OF COUNTRY ROADS 39 
 
 are curved, one in its vertical and the other in its horizontal 
 plane, and they may be precisely the same length, but the one 
 over the hill is said to be straight, only because its vertical 
 curvature is less apparent to the eye. 
 
 Of the two roads of equal length, the route over the hill 
 has the disadvantages of greater first cost, greater mainten- 
 ance expense, greater damage from rains and other causes, 
 greater wear on horses and vehicles in the haulage 
 of goods over it, and consequently greater cost to ^^^P^*"^" 
 those using it. But even if the level, curved road tages of 
 were much Ion ger than the straight and steep straight 
 one, the former would, as a rule, be the more ^^ c^^^ 
 economical on account of the ease of travel over it. 
 '^ Straightness " in a country road is frequently overrated, and 
 efforts to obtain it involve in many cases injury to the beauty 
 of the road and of the landscape, with no compensating 
 economic advantages. 
 
 Economy forms the true basis of proper location; that is, 
 ultimate economy in making the route as direct ^ 
 and, subject to drainage requirements, as level as the basis 
 practicable, in achieving the best results at the o* loca- 
 least present and future expense. ^°^' 
 
 Too much *' economy '^ should not, however, be urged in the 
 work of location. There is an old saying: " Nothing pays like 
 first cost in road-building," meaning simply that money 
 expended in intelligent study of the location is the most 
 economical expenditure in the construction of a road. The 
 importance of the selection of the best route cannot be too 
 strongly urged, because an error made in this first stage of 
 roadmaking will cause a heavy expense for rectification, and, 
 until rectified, imposes a perpetual tax upon the pubhc for 
 maintenance. 
 
 Gillespie in his book on roads (1847) gives a forcible instance 
 of the value of road improvement by scientific loca- ^ 
 tion. An old road in Anglesea, Noi-th Wales, rose scientific 
 and fell between its two extremities, a distance of road loca- 
 24 miles, a total perpendicular amount of 3540 feet, **°°' 
 while a new road, laid out by Telford between the same 
 
40 
 
 THE ART OF ROADMAKING 
 
 Fig. 4. — Pocket T'ompass, with foldin.i; eights. 
 
 Ftg. 7. — Pedometer. 
 
 Fig. 5. — Aneroid Barometer. 
 
 bic. 8. — Odometer. 
 
 Fig. 6. — Hand Leveh 
 
 Instruments used in Location. 
 
LOCATION OF COUNTRY ROADS 41 
 
 points, not only reduced the road distance to 22 miles, but 
 also reduced the rise and fall to only 2257 feet. Thus, 1283 
 feet of perpendicular height was done away with which every 
 horse passing over the road had previously been obliged to 
 ascend and descend with its load. 
 
 The principles observed and the methods employed in the 
 location of a road are substantially the same as used in the 
 location of a railroad. Hard and fast rules cannot m th d 
 be laid down, for each road must be designed for employed 
 the place it is to occupy and the service it is to i^ loca- 
 render, and is dependent upon many local conditions, ^°^' 
 as well as upon the topographical features and the nature and 
 extent of the traffic that it may develop. The problem in- 
 volves considerations of distance, grades, curves, width, and 
 the estabUshment of controUing points, and always presents 
 an opportunity for the exercise of the most careful judgment. 
 
 To obtain the requisite data regarding these points upon 
 which to form his judgment, the engineer must study maps 
 of the district and must make a personal reconnoissance, or 
 examination, of the tract to be traversed, by either riding or 
 walking over it, and carefully noting its principal physical 
 contours and natural features, the immediate object being to 
 select one or more trial lines, from which the final route may 
 be ultimately determined. 
 
 In making this reconnoissance, a knowledge of physical 
 geography is essential. Among the characteristics of the 
 country noted are: 
 
 1. Inclinations of the strata and their nature and istics of 
 
 conditions as to dryness. country 
 
 2. Extent to which the surface of the road will ^°^^^- 
 
 be exposed to the action of the air and the rays of the 
 sun. 
 
 3. Location of crossings of valleys, rivers, and passes. 
 
 4. Condition of river beds, with a view to secure stable 
 
 foundations for bridges, etc. 
 
 5. Sources, accesses, and distances of the supply of material 
 
 for structural works, such as retaining walls, etc., and 
 for stones suitable for road covering. 
 
42 
 
 THE AKT OF ROADMAKING 
 
 Fig. 9. — Contour Lines. 
 
LOCATION OF COUNTRY ROADS 43 
 
 6. Levels of all existing lines of communication, such as 
 
 railways, roads, canals, and of rivers and streams. 
 The instruments used in the reconnoissance are: 
 
 1. Compass, for ascertaining the direction. 
 
 2. Aneroid Barometer, for fixing approximate ^^ f""°^®^ ^ 
 
 elevation of summits. 
 
 3. Hand-level, for measuring slopes, 
 
 4. Odometer, or Pedometer, to determine the distance, the 
 
 former for use with a vehicle and the latter for use in 
 walking, but if these instruments cannot be used, the 
 distance can be approximated closely enough foi pre- 
 liminary work by various other means. 
 The irregularities of the surface of the ground are laid out on 
 paper by means of "contour lines" — fine lines traced through 
 the points of equal level over the surface surveyed, 
 denoting that the level of the ground throughout ,?^ ^"^ 
 the whole of their course is identical; that is to say, 
 that each part of the ground over which the line passes is at 
 a certain height above a known fixed point, this height being 
 indicated by the figures written against the line. These lines, 
 by their greater or less distance apart, have the effect of 
 shading, and make apparent to the eye, the undulations and 
 irregularities in the surface of the country. 
 
 A map is then made showing the topography of the district 
 — the length and directions of the proposed line; the rivers, 
 watercourses, roads and railroads; town, county and 
 property boundary lines, and any other matters of . ^'P^S'^^P 
 interest. The nature of the soil; character of 
 excavations; width, depth and velocity of rivers; character 
 of banks and bottom, and other features and figures that 
 cannot be shown on a map or profile, are given in an accom- 
 panying '' memoir." 
 
 Levels are taken along different lines, at regular intervals, 
 and heights of all objects that may affect location Levels and 
 are noted, and "bench-marks"* are established, bench 
 From these levels, a profile, or longitudinal section ™^ks. 
 
 * Reference marks made on fixed objects, such as gate posts, houses, 
 trees, etc. 
 
Fig. 10. — Topographical Map. 
 
LOCATION OF COUNTRY ROADS 45 
 
 of the proposed route is made, on such a scale that it will 
 show with distinctness the inequalities of the ground. 
 
 In regard to the saving of distance, the value is quite evi- 
 dent where the road is so situated that it would enable teams 
 to make an additional trip per day in the hauling 
 
 of freiaiht. But where the traffic is of a more in- Value of 
 
 saving dis- 
 definite nature, or the saving proposed is insufficient tance. 
 
 to admit of additional trips, this value depends 
 
 upon the value to other work of the small portion of time of 
 
 men and teams which may be saved by the shorter route — a 
 
 value which exists, but is difficult to estimate. 
 
 There are other points of value in the saving of distance, 
 
 which may be summed up as follows: 
 
 1. The advantage to the community of bringing various 
 points closer together, such as bringing two towns into 
 closer relations or bringing country property nearer to 
 markets. 
 
 2. Variation due to the character of the road surface: as 
 the cost of transportation is less over a smooth than over rough 
 surface, the value of reducing distance is also less on the smooth 
 surface. 
 
 3. Variation due to gradient: on a road where the ruling 
 gradients are steep the value is greater than upon one with 
 light gradients, because of the greater number of loads neces- 
 sary to move traffic. 
 
 4. The cost of maintenance of a road may be considered, 
 like the costs of transportation, to be directly proportional to 
 the length of road, and a saving of distance involves a saving 
 in cost of maintenance. 
 
 There are two kinds of grades: Maximum and Minimum. 
 The *' Maximum Grade " is the steepest which is 
 permissable and the " Minimum Grade " is the 
 least allowable for good drainage. 
 
 A level road is desirable and preferable, but as it can seldom 
 be obtained, the roadbuilder must investigate the effects of 
 grades upon the cost of construction and maintenance, and 
 also determine the most suitable grade under the special 
 conditions. 
 
46 THE ART OF ROADMAKING 
 
 Where there is a grade to be overcome, it can be reduced by 
 
 (1) going around the hill; (2) zig-zagging up the 
 
 Methods of slope- (3) cutting through the hill. In the case of 
 
 overcoming ^ -, i n ^ ■, i i 
 
 grades. ^ ^*^^&" slope, the first or second must be employed, 
 
 but if the grade is short, the third method is usually 
 the cheapest. 
 
 Fig. 11. — A poorly located road; by turning to the right a gentle grade 
 could have been secured and the two bad hills avoided. 
 
 The determination of the proper maximum, or ruling, grade 
 is important and is governed by two considerations; one 
 Determina- ^^^^^i^S to the power expended in ascending, and 
 tion of the other to the acceleration in descending, the 
 maximum inchne. As an ascent, it concerns the draft of 
 ^^^ ®* heavy loads; as a descent, it mainly concerns the 
 
 safety of rapid traveling. 
 
 Men and animals can ascend steeper slopes than they can 
 descend. A man walks slowly up-hill and quickly down-hill. 
 A horse does the reverse; the steeper the ascent, the faster he 
 attempts to travel, while in descending he moves at a slow- 
 trot which gradually subsides into a walk. Consequently the 
 inclination which admits of high speed in descending practically 
 controls the maximum grade. 
 
 This will depend upon (1) the class of traffic that will 
 
LOCATION OF COUNTRY ROADS 47 
 
 use it, whether fast or slow, heavy or light; (2) the character 
 of the pavement adopted; (3) the cost of construction. It is 
 evident, therefore, that no fixed maximum gradient can be 
 adopted to suit all conditions. Experience has shown that for 
 fast and light traffic, the maximum should not exceed 2 per 
 cent, or 1 in 50; for mixed traffic, 3 per cent, or 1 in 30, may be 
 adopted; for slow traffic, combined with economy, 5 per cent, 
 or 1 in 20, should not be exceeded. 
 
 For bicycle travel a 2 per cent grade can be ascended with 
 comparative ease and descended with little effort. Heavier 
 grades, up to 5 per cent, can be ascended by the average 
 bicycle rider without extremely arduous effort and descended 
 without serious danger^ but grades above 5 per cent are too 
 steep for ascent with comfort or descent with assured safety. 
 
 For pleasure driving the grade, when practicable, should not 
 exceed 4 per cent. A good horse with a light carriage and two 
 persons will trot easily up a 4 per cent grade and as easily down 
 without a brake. With a higher gradient the strain in either 
 direction becomes increasingly apparent. For freight 
 traffic the maximum grade admissible is 12 per Most suit- 
 cent. ^**^^ '^^^- 
 
 mum 
 
 The maximum grades estabUshed by experience grades. 
 for various paving materials are approximately: 
 
 For stone blocks All grades 
 
 " wood and brick 5 per cent, or 1 in 20 
 
 " broken stone 3 per cent, or 1 in 30 
 
 ^ ' asphalt 2^- per cent, or 1 in 40. 
 
 The maximum adopted by the French engineers is 1 
 in 20, while that adopted in England by Telford was 
 1 in 30. 
 
 It does not follow, however, that the maximum grade is the 
 most advantageous grade. To determine the latter, every 
 element that affects the cost of transportation must 
 be considered. It is dependent upon the amount ^°^* ^^~ 
 of traffic, and the cost of construction and main- ^^^. geous 
 tenance of the highway, and has been found by 
 experiment to be approximately: 
 
48 THE ART OF ROADMAKING 
 
 For mountainous country^ between 1/20 and 1/30 
 " hilly country, between 1/30 and 1/40 
 
 *' level country, between 1/40 and 1/50. 
 
 The establishment of a minimum grade is also necessary, 
 as well as economical, in cost of maintenance. All roads 
 Establish- should be higher in the center than at the sides in 
 ment of order to shed the rain into the side ditches, but 
 minimum even on the best roads longitudinal ruts are liable to 
 gra e. form from excessive use or neglect of proper main- 
 
 tenance, and these seriously interfere with the surface drainage. 
 If the road were perfectly level, every rut would hold water, 
 which would soon soak into and damage the road, whereas 
 with even a slight grade, every rut and wheel track becomes 
 a channel to carry off the rain water. 
 
 The minimum grade established in England is 1 in 80, or 
 li per cent; in France it is 1 in 125, or .8 per cent, which may 
 be adopted as a minimum, and in a flat country, the roads 
 should be artificially formed into gentle undulations approxi- 
 mating this minimum limit. In the United States it is 1 in 
 200, or .5 per cent. 
 
 When the profile has been made a grade line is drawn upon 
 it in such a manner as to follow its general slope, but to average 
 its irregular elevations and depressions. If the 
 Establishing j-a^^io between the whole distance and the height of 
 grade ^^^ ^^^^ ^^ ^^^^ than the maximum grade intended 
 
 to be used, this line will be satisfactory; but if it 
 is steeper, the cuttings or the length of the line will 
 have to be increased — preferably the latter, by means of 
 curves. 
 
 As regards curves in roads, no fixed rules can be laid down. 
 The greatest radius possible should be employed, depending 
 upon the width and location of the roadway and 
 the character of the traffic, but it should not be 
 less than 100 feet for a 12-foot road, 75 feet for a 16-foot road, 
 of 66 feet for an 18-foot road. In France, country roads of 
 20 feet width have a radius of 50 feet; in Germany, it is 
 40 feet. 
 
LOCATION OF COUNTRY ROADS 
 
 49 
 
 When the curve occurs on an ascent, the grade at that place 
 must be diminished in order to compensate for the additional 
 resistance of the curve. Curves may be built 
 circular or parabohc, the latter preferable when 
 possible, and the width of the wheelway should 
 be increased to permit the swinging of teams and to prevent 
 accidents. 
 
 Curves on 
 an ascent. 
 
 a. Simple Curve. 
 
 h. Compound Curve. 
 
 c. Reverse Curve. 
 
 d. Double Reverse Curve. 
 
 Fig. 12. — Types of Curves. 
 
 Excessive crookedness should be avoided on account of 
 expense of construction and maintenance and of the extra 
 time and labor necessary in traveling over the road. Partly 
 on these grounds and partly on the grounds of its dangers and 
 its inconvenience as regards drainage, etc., a zig-zag method 
 of surmounting a hill should be avoided. 
 
 The width of a road depends upon the amount and nature 
 of the traffic to be accommodated, and cannot be standardized. 
 Wide roads are best as they expose a larger surface 
 to the drying action of the sun and wind and require 
 less supervision than narrow ones, but the first cost 
 is greater and in country districts they are not necessary. In 
 many places a rordway just wide enough for a single team 
 is all that is required. In cases of more frequently used 
 roads, the minimum width should allow two teams to 
 pass with safety, but in all cases the width of land ap- 
 propriated for highway purposes — the " right of way " — - 
 
 Width of 
 roadway. 
 
50 
 
 THE ART OF ROADMAKING 
 
 should be sufficient to provide for future increase in 
 traffic. On main country highways, this width should 
 allow for a double roadway — a paved center and a natural 
 earth road at the side. 
 
 Some of the most common widths of roadways and rights 
 of way are: 
 
 Right of way. Roadway. 
 
 United States 49i to 66 16 
 
 England 66 20 to 22 
 
 Holland 38 14 
 
 France: National roads 66 22 
 
 Departmental roads . 40 20 
 
 Provincial roads ... 33 20 
 
 Neighborhood roads . 26 16 
 
 One of the most important points in location is the selection 
 of suitable bridge sites. These are sometimes restricted to a 
 certain point, but if not, the best possible site is 
 determined and the location of the road is made 
 subordinate to it. In this selection consideration 
 must be given to 
 
 Selection of 
 bridge sites. 
 
 Tep Tt^Jf/?— >- 
 
 1 f- 
 
 FiG. 13. — Showing three bridges, A, B, C, where if a road were put in as 
 shown by the dotted lines only the bridge at A would be needed, and 
 the public convenience would be served just as well as with the 
 present arrangement. 
 
 1. The character of the river bed, in order to obtain the best 
 foundation. 
 
 2. Stability of the river banks. 
 
 3. Straightness or curvature of the river, so that the bridge 
 may be at right angles to the stream-flow and if possible, over 
 a straight stretch of the stream. 
 
LOCATION OF COUNTRY ROADS 
 
 51 
 
 Principlen to 
 be observed 
 
 In malving the final selection of a route; some of the basic 
 principles to be observed are:* 
 
 1. To follow the route which affords the easiest 
 grade. 
 
 2. To connect the places by the shortest and in final 
 most direct route commensurate with easy grades. 
 
 3. To avoid all unnecessary ascents and descents. 
 
 4. To give the center hue such a position with reference to 
 the natural surface of the ground that the cost of construction 
 shall be reduced to the smallest possible amount. 
 
 5. To cross all obstacles, where structures are necessary, as 
 nearly as possible at right angles. 
 
 6. To cross ridges through the lowest pass which occurs. 
 
 7. To cross either under or over railroads and to avoid grade 
 crossings. 
 
 Stakes are placed at intervals along the route, indicating 
 
 STATION J^UHBERb 
 
 175 170 165 +25 
 
 Fig. 14. — Construction Profile. 
 
 158 
 
 curves and their tangent points and careful notes are taken 
 
 of the location of the stakes, so that they can be 
 
 replaced if disturbed. Levels and cross levels are ^^t^o^ of 
 ^ , , . r-i ■ 1 final loca- 
 
 taken and a construction, or workmg profile, is then ^j^^^ 
 
 drawn, indicating all elevations, cuttings, fillings, 
 
 embankments, bridges and other features necessary to permit 
 
 making an estimate of the work. 
 
 * Byrne: "Highway Construction," p. 460. 
 
52 
 
 THE AKT OF ROADMAKING 
 
 Fig, 15.— a Costly Piece of Grading, 
 
CHAPTER V 
 
 CONSTRUCTION AND PROTECTIVE WORKS 
 
 Under this head may be included such works connected 
 with the construction of the roadbed, as earthwork, founda- 
 tions, bridges, culverts and retaining walls. 
 
 EARTHWORK 
 
 The term "Earthwork'' embraces all operations performed 
 in the making of the excavations and embankments to pre- 
 pare them for the road covering, such as the reduction of 
 gradient upon steep inclinations, by cutting and filling, and 
 the making of better drainage by raising the road across low 
 ground. In its broadest sense and as generally 
 understood, "earthwork" includes work in rock Classifica- 
 as well as in the looser materials of the earth's earthwork 
 crust, and for purposes of comparison, may be 
 classified with regard to the ease or difficulty with which it 
 can be excavated, as follows : 
 
 1 . Earth, including loam, clay, sand, and loose gravel. 
 
 This may be further classified approximately as: 
 a. Easy ground, h. Average ground, c. Hard ground. 
 
 2. Hardpan, including cemented gravel, slate, cobbles and 
 
 small boulders, and other materials of a compact 
 earthy nature. 
 
 3. Loose rock, including shale, decomposed rock, boulders 
 
 and detached masses of rock, and other material of a 
 rock nature that may be loosened with a pick. 
 
 4. Solid rock, including all rock found in place in ledges 
 
 and masses, and large boulders which can be removed 
 only by blasting. 
 
 53 
 
54 THE ART OF ROADMAKING 
 
 In selecting the final location and gradient of the road, the 
 engineer must take into consideration the ''equalizing" or 
 
 "balancing" of the earthwork, so that the material 
 e^^hwork ^^^^^ from a cutting may, as nearly as possible, 
 
 and consistent with the distance and cost of haulage, 
 be sufficient to form an embankment. This redistribution of 
 the earthwork along the line of the road is in many cases 
 essential to economy in the cost of the work, as a surplus of 
 cutting or filling involves either waste or borrowing, both 
 of which cause additional expense for labor and land. If there 
 is a surplus of cutting, the waste earth is disposed of in con- 
 venient banks adjoining the work, termed "spoil-banks." 
 If, on the other hand, there is an excess of embankment 
 requirements over the supply from cuttings, the deficiency 
 is obtained either by widening the excavations or from 
 an excavation termed a "borrow-pit," made in the vicinity 
 of the embankment. Sometimes, however, the location 
 of cuts and fills makes it more economical to either waste 
 the earth or to borrow it, than to haul it any considerable 
 distance. 
 
 When the road lies along the side of a hill, this balancing, 
 termed in this case, "transverse balancing" is accomplished 
 
 by locating the center line of the road so that 
 
 ransverse ^j^^ cuttine; from one side will form the embankment 
 balancing. ° 
 
 on the other, unless the side slopes are very steep, 
 
 when it is better to make the road mostly in cuts on account 
 
 of the difficulty of forming stable embankments on steep 
 
 slopes. 
 
 The problem of balancing earthwork is a very important 
 one in practice, for upon its mode of solution depends a large 
 portion of the cost of the work. The most economical use 
 of the material depends on the machinery used in moving the 
 earth; the character of the earth; the road over which it is to 
 be transported; the cost of labor and land, and other conditions, 
 all of which must be taken into consideration by the engineer 
 in deciding what is best for each particular case. 
 
 In making excavations or forming side slopes, it is necessary 
 to insure stability and prevent slipping or sliding of its parts 
 
CONSTRUCTION AND PROTECTIVE WORKS 55 
 
 on each other by giving proper consideration to the ''natural 
 slope" of the material used. This is the slope assumed by 
 the face of a mass of earth after considerable exposure to the 
 elements, at which the earth, by friction alone, will have per- 
 fect stability. The angle made by this slope with 
 the horizontal is the "angle of repose," or the ^^*"^^1 
 "angle of internal friction." Loose earth will re- bankments. 
 main in equilibrium with its face at this slope; 
 if piled at a greater slope, cohesion will hold the face at this 
 greater slope for a time, but the earth will soon crumble and 
 slide down until the angle of repose is attained. This angle 
 depends on the nature of the soil, the action of the atmosphere 
 and of internal moisture, being approximately as follows: 
 
 Compact earth 50° J : 1 
 
 Rubble 45° 1:1 
 
 Clay (well drained) 45° 1:1 
 
 Gravel 40° H:I 
 
 Shingle. 39° 11-:1 
 
 Dry sand 3S° U:! 
 
 Vegetable earth (Loam) ... 28° If : 1 
 
 Wet sand 22° 2^:1 
 
 Clay (wet) 16° 3:1 
 
 For all practical purposes it may be said that in both 
 excavation and embankment, earth, sand and gravel stand 
 at a slope of H:l, or 33° 41'' 
 
 The natural and strongest form of earth slopes is a concave 
 curve, with the flattest portion at the bottom, but this form 
 is seldom given to the slopes in construction, as straight or 
 convex forms save excavation by the contractor, and will 
 continue to slip until the natural form is attained. Figs. 16 
 and 17 show the contours of embankment and excavation 
 which have met with the most general approval of the engineer- 
 ing profession. While it is not usual to employ artificial means 
 to protect the surface from the action of the weather, it will 
 be an ultimate economy in keeping the roadways in order, 
 if the side-slopes are sown with grass-seed, as the roots 
 
66 
 
 THE ART OF ROADMAKING 
 
 of the grass bind the earth together and prevent slipping, 
 which is usually caused by the saturation of the earth with 
 water. 
 
 When the earth is first thrown up by a shovel, without break- 
 ing down the clods, or artificial consolidation of any sort, it 
 occupies more space than it did in place, but after 
 
 rth ^^k° ^^^^S placjed in embankment, it subsides or shrinks, 
 until it occupies less space than in the pit from 
 which it was taken, the amount of this shrinkage depending 
 on the method of compacting. 
 
 When it is considered that the earth in embankment is not 
 so hard and firm as in its original position, and that it will 
 settle still further after the embankment is finished, this 
 
 Fig. 16. — Cross-section for Embankment. 
 
 OT/Ie OTile 
 
 Fig. 17. — Cross-section for Excavation. 
 
 "shrinkage of earthwork" may seem strange, but may be 
 accounted for by the following facts:* 
 
 1. The continued action of frost has made the soil in its 
 
 natural position more or less porous. 
 
 2. Earth which has been lying in situ for centuries becomes 
 
 more or less porous through the slow solution of their 
 soluble constituents by percolating water. 
 
 3. The surface soil in rendered more or less porous by the 
 
 penetration of vegetable roots which subsequently 
 decay. 
 
 *" Roads and Pavements," I. O. Baker, page 91. 
 
CONSTRUCTION AND PROTECTIVE WORKS 57 
 
 4. There is ordinarily more or less soil lost or wasted in 
 transporting it from the excavation to the embankment. 
 
 From the many experiments made to obtain exact data 
 regarding this shrinkage, the following general rules or prin- 
 ciples have been deduced: * 
 
 1. Taking extreme cases, earth swells when first loosened 
 with a shovel, so that after loosening it occupies 1-^ to IJ 
 times as much space as it did before loosening; in other words, 
 loose earth is 14 per cent to 50 per cent more bulky than nat- 
 ural bank earth. 
 
 2. As an average we may say that clean sand and gravel 
 swell -\, or 14 to 15 per cent; loam, loamy sand or gravel swell 
 ^, or 20 per cent; dense clay, dense mixtures of gravel and 
 clay swell ^ to ^, or 33 to 50 per cent, ordinarily about 35 
 per cent, while unusually dense gravel and clay banks swell 
 50 per cent, 
 
 3. That this loose earth is compacted by several means; 
 (a) the puddling action of water, (b) the pounding of hoofs 
 and wheels, (c) the jarring and compressive action of rolling 
 artificially. 
 
 4. If the puddling action of rains is the only factor, a loose 
 mass of earth will shrink slowly back to its original volume, 
 but an embankment of loose earth will at the end of a year be 
 still about -j^Y, or 8 per cent greater than the cut it came from. 
 
 5. If the embankment is made with small one-horse carts, 
 or wheel scrapers, at the end of the work it will occup}'' 5 to 
 10 per cent less space than the cut from which the earth was 
 taken, and in subsequent years will shrink about 2 per cent 
 more, often less than 2 per cent. 
 
 6. If the embankment is made with wagons or dump cars, 
 and made rapidly in dry weather without water, it will shrink 
 about 3 per cent to 10 per cent in the year following the 
 completion of the work, and very little in subsequent years. 
 
 7. The height of the embankment appears to have little 
 effect on its subsequent shrinkage. 
 
 8. By the proper mixing of clay or loam and gravel, followed 
 by sprinkling and rolling in thin layers, a bank can be made 
 weighing If times as much as loose earth, or 133 pounds per 
 cubic foot. 
 
 9. The bottom lands of certain river valleys and banks of 
 
 * "Earthwork and Its Cost," by H. P. GUlette, page 17. 
 
58 
 
 THE ART OF ROADMAKING 
 
 cemented gravel or hardpan are more than ordinarily dense 
 and will occupy more space in the fill than in the cut unless 
 rolled. 
 
 The natural shrinkage of the ordinary soils is in the following 
 order, beginning with the least: (1) sand and sandy gravel, 
 
 (2) clay and clayey soils, (3) loams; and according to the 
 method of handling: (1) dragscrapers, (2) wheelscrapers, 
 
 (3) wagons, (4) cars, (5) wheelbarrows. 
 
 Fig. 18 shows an embankment made in the customary manner by dump- 
 ing material mainly in the center of the roadway and sloping it to the 
 right and left by the usual means, leaving it always higher in the 
 center and with a tendency to slide off at both sides. 
 
 In making embankments, materials are used which have 
 the greatest frictional stability, Such as rock, shingle, gravel 
 and clean sand; wet clay and mud are entirely unsuitable. 
 The cheapest and quickest method of building the embank- 
 ment is by making it of a single layer, but in- certain 
 a ing em- gpggjg^i cases, such as filling in behind a retaining 
 wall and bridge abutments, the embankment is 
 
 Fig. 19 shows the method in which the material has been deposited 
 properly and the surface kept hollowed until finished. 
 
 made in thin horizontal layers, 9 to 18 inches deep, each 
 rolled and rammed down so as to make it compact and firm 
 before laying down the next layer. 
 
 Specifications usually require that "all matter of vegetable 
 nature be carefully excluded from the embankment," but 
 this is sometimes impracticable. It is desirable that all 
 stumps, weeds, brush, etc., are removed from the space to be 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 59 
 
 occupied by the embankment as well as all deposits of soft 
 compressible matter, in order to give it a firm base and to 
 permit it to bond with the earth below. To overcome the 
 tendency to spread, a small trench is sometimes excavated 
 
 Fig. 20. — Method of Construction on Slopes by Embankment. 
 
 along the foot of the embankment, or it may be buttressed 
 with a low stone wall. 
 
 When a roadway is built on the side slope of a hill, partly 
 by excavating and partly by embanking, the most common 
 method is to build the embankment out gradually along the 
 whole line of the excavation. This, however, is insecure, 
 
 Fig. 21. — Method of Construction on Slopes by Stepped Embankment. 
 
 as the excavated material, if simply deposited on the natural 
 slope, is Hable to slip. It should be given a secure hold, 
 particularly at the foot of the slope, by cutting the natural 
 surface into steps perpendicular to the axis of greatest pressure. 
 
60 
 
 THE ART OF KOADMAKING 
 
 But on side hills of great inclination, retaining walls must be 
 substituted for the side slopes of both the excavations and 
 the embankments (see page 88). 
 
 On rock slopes where the inclination of the natural surface 
 is not greater than 1:2 the road may be constructed partly 
 in excavation and partly in embankment in the usual manner 
 
 Pig. 
 
 using Retaininor Walls. 
 
 as outlined, but when the rock slope has a greater inclination 
 than 1 : 2 the whole of the roadway should be in excavation as 
 ishown in Fig. 24. Roads on rock slopes may also be built 
 in the form of a platform on timber frameworks supported by 
 beams and struts. 
 
 Fig. 23. Fig. 24. 
 
 Method of Construction on Rock Slopes. 
 
 In constructing embankments across wet and unstable 
 ground it is frequently necessary to form an artificial founda- 
 tion upon which to place the earth embankment. This may 
 be accomplished in some cases by excavating a little of the 
 soft material and substituting sand or gravel, or in other 
 €ases it may be advisable to employ layers of brushwood or 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 61 
 
 fascines as a support for the embankment. Sometimes it 
 may be possible to drain the soft material by deep ditches, 
 so as to render it capable of sustaining the road, and in all 
 cases drainage should be provided in so far as possible to make 
 the embankment more secure. 
 
 (From Coane's "Australasian Roads ") 
 Fig. 25. — Road entirely in Rock Cut. Hawk's Crag, Buller Gorge, 
 New Zealand. 
 
 Earthwork is paid for by the cubic yard, usually measured 
 '^in place," that is, in the natural bank, cut, or 
 pit, before loosening, the cost being based on the °^, ° , 
 daily wages of a common unskilled laborer. This 
 cost may be divided into three parts: 
 
62 THE ART OF ROADMAKING 
 
 1. Cost of loosening the earth, depending on the kind of 
 
 earth to be handled. 
 
 2. Cost of transport, depending on the quantity of material 
 
 to be moved, the distance of haulage and the kinds of 
 roads over which it must be hauled. 
 
 3 . Cost of transforming the transported earth into the 
 
 desired shape. 
 
 It is necessary, therefore, to study the various methods of 
 loosening and handling the various kinds of materials and 
 their costs, and the relative economy of moving earth with 
 a shovel, or transporting it by wheelbarrow or horse cart, which 
 involve more questions than could be taken up satisfactorily 
 within the limits of a few pages. 
 
 The calculation of earthwork forms a large part of the 
 necessary labor of the engineer, and to relieve him of the 
 tediousness of this work, as well as to facilitate its operation, 
 many tables, diagrams, and approximate formula) have 
 been devised, no one of which has, however, met with general 
 favor by engineers. Several publications dealing with these 
 methods of calculations are listed in the bibliography in 
 Appendix V. 
 
 Foundation and Drainage 
 
 In building any roadway, whether for the city or the country, 
 for light or heavy traffic, two of the most important points to 
 be considered are drainage and foundation. 
 
 Theoretically, the foundation should last forever, and the 
 sole cost of maintenance should be borne by the wearing 
 surface, but this, for economical reasons, is difficult of realiza- 
 tion. The light traffic roadway of to-day, requiring for 
 foundation only four inches of broken stone, may be the heavy 
 traffic street of to-morrow, requiring six inches of Portland 
 cement concrete. The advent of the pleasure and the industrial 
 automobile is bringing upon the macadam roads of the country 
 far greater weight than was imagined by the original builders 
 of these roads, and it is only a question of time when it may 
 be necessary to reconstruct many of these roadways from the 
 bottom up with a firm concrete foundation. 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 63 
 
 In building new roads, future traffic should be taken into 
 account, and a foundation sufficient for all reasonable develop- 
 ment should be provided. The stability of the road surface 
 depends upon the foundation and this in turn largely depends 
 upon the facilities provided for drainage. While proper 
 
 u. Country Highway. 
 
 
 b. Road in Embankment, 
 
 :^STONt 
 
 .^O s>^_5" FLA GGING 
 
 ■ 3"TILE DRAIN 
 ^ lO'O"- 
 
 c. Suburban Street. 
 Fig. 26. — Methods of Drainage. 
 
 attention may be given to surface drainage by providing 
 sufficient crown to shed the water and ditches to 
 carry it away, the importance of subdrainage is ^^^ impor- 
 often overlooked. Its necessity must be realized, drainaee 
 as a permanent foundation can be secured only by 
 keeping the subsoil dry; unless this is done, and water is 
 kept out of the foundation, sooner or later it will destroy the 
 superstructure. Most earths, when kept dry, form a strong 
 foundation, but when the ground is naturally wet a good road 
 cannot be constructed without proper subdrainage, as the 
 earth loses its sustaining power and the formation goes to 
 pieces. Where the soil, however, is sandy or calcareous, or 
 
64 
 
 THE ART OF ROADMAKING 
 
 
 
 '^^^^^m^^^Ty- 
 
 FiG. 27. — Types of Drains. 
 
 Pole Drain Blind Drain 
 
 Silt Basin Tile Drain 
 
 Outlet 
 
 Stone Drain 
 Silt Basin 
 
CONSTRUCTION AND PROTECTIVE WORKS 65 
 
 where the subsoil consists of fairly open gravel, underdrains 
 are seldom, if ever, required. 
 
 Drainage is especially important upon earth roads, because 
 the material of the road surface is more susceptible to the 
 action of the water, and more easily destroyed by it than are 
 the materials used in the construction of the better class of 
 roads. When water is allowed to stand upon the road in 
 ruts and hollows, the earth is softened and readily penetrated 
 by the wheels, which continually deepen and enlarge the 
 ruts until the whole crust of the road and the subsoil beneath 
 is weakened. The action of frost is also apt to be more 
 disastrous upon the more permeable surface of the earth road, 
 having an effect to swell and heave the roadway and throw its 
 surface out of shape. It may, in fact, be said that the whole 
 problem of the improvement and maintenance of ordinary 
 country roads is one of mere drainage. A road on a wet 
 undrained bottom will always be troublesome and expensive 
 to maintain, and it will be economical in the long run to go to 
 considerable expense in making the drainage of the subsoil as 
 perfect as possible. 
 
 There are three systems of drainage: underdrainage, side 
 ditches, and surface drainage: 
 
 The objects of underdrainage are: 
 
 1. To lower the water level in the soil and get it ^ystems of 
 
 ^ drainage. 
 
 away from the foundations. The action of 
 sun and wind will dry the surface of the road, but if the 
 foundation is soft and spongy the road will soon become 
 a mass of mud. 
 
 2. To dry the ground quickly after a freeze. When the 
 
 frost comes out of the ground in the spring, it thaws 
 quite as much from the bottom as from the top and with 
 proper underdrainage the water, when released by 
 thawing from below, will be immediately carried 
 away. 
 
 3. To remove the "underflow." In some places when the 
 
 ground is comparatively dry when it freezes in the fall, it 
 will be very wet in the spring when the frost comes out. 
 The reason is that after the ground freezes, water rises 
 
66 
 
 THE ART OF ROADMAKING 
 
 slowly in the soil by hydrostatic pressure of the water 
 in higher places; and if it is not drawn off by under- 
 drainage it saturates the subsoil and rises as the frost 
 goes out. The underdrainage not only removes the 
 
 i^p^?!lflpfp!^^ 
 
 
 
 Fig. 28. — Methods of Drainage of Surface Water from Country Roads. 
 
 On roads where there are no sidewalks, gutters are formed between the 
 roadway and the pathway, and the water is conducted from these gutters 
 into the side ditches by pipes laid under the walk at intervals. 
 
 water, but prevents, or reduces, the destructive effects 
 of frost. 
 The object of side ditches or gutters is to receive the water 
 from the surface of the traveled roadway, and they should 
 
CONSTRUCTION AND PROTECTIVE WORKS 67 
 
 carry it rapidly and entirely away from the roadside. Th^y 
 also intercept and carry off the water that would 
 otherwise flow from the side hills upon the road. -J^^^u 
 The side ditch need not be deep, and should have 
 a broad flaring side toward the roadway, while the outside 
 bank should be flat enough to prevent caving. It should 
 have a good fall and a free outlet into some stream so as to 
 keep the water moving and to carry it entirely away from the 
 road. 
 
 Surface drainage of the traveled portion of the road affects 
 mainly the maintenance of the road and is fully as 
 important as the underdrainage. It is provided for i^^^ce 
 by crowning the surface. The slope from the center 
 to the side should be enough to carry the water freely and 
 quickly to the side ditch. 
 
 3 4 & 8 10 Q 14 16 18 ^ ^ ^ 
 
 Fig. 29.-— Profile of Road Section. 
 
 There has been much discussion as to the exact crown and 
 
 slope to be given to the surface of the roadway. Some claim 
 
 that the shape should be the arc of a circle, others 
 
 that it should be a parabolic arch started at the '^'^a^sverse 
 
 contour. 
 curb line or at the edge of the gutter, and still 
 
 others that it should consist of two planes meeting at the 
 center and having their junction rounded off with a short 
 curve. The last two forms are probably better than the first, 
 but great refinement in this matter is neither possible nor 
 important. 
 
 The proper crown varies with the nature of the roadway; 
 when a good surface is maintained a very moderate rise is 
 sufficient, but in all cases this rise should bear a certain propor- 
 tion to the width of the roadway, as shown approximately in 
 the accompanying table: 
 
68 
 
 THE ART OF ROADMAKING 
 
 Table VI 
 
 AMOUNT OF TRANSVERSE RISE REQUIRED FOR DIFFERENT 
 
 PAVEMENTS, 
 
 Surface. 
 
 Proportion of the 
 ■width of roadway 
 
 Earth, Rise at center 
 
 ■^/40 
 
 Gravel, ' ' 
 
 . - • V50 
 
 Broken stone, " 
 
 Veo 
 
 Stone Block, ' ' 
 
 -^/so 
 
 Wood, 
 
 /lOO 
 
 Brick, 
 
 "^/so 
 
 Asphalt, ^' 
 
 -^/so 
 
 Although the cui^ved profile is universally used, no set 
 practice in respect to the crown exists. In some places asphalt 
 
 I 
 
 
 Fig. 30. — Arrangements of Transverse Grade in Cases of Streets in which 
 the Opposite Sides are at Different Levels. 
 
 is given the smallest crown of any pavement, while in others, 
 notably in Omaha, it has the largest, both methods seeming 
 to be based on good judgment, the former on the smoothness 
 of the surface and the latter on the fact that asphalt rots when 
 continuously wet. 
 
CONSTRUCTION AND PROTECTIVE WORKS 69 
 
 Highway Bridges 
 
 Of the money spent in many parts of the country on the 
 maintenance of a highway system, nearly one-half is expended 
 in the construction and repair of culverts and bridges. Espe- 
 cially in well-watered areas the problem of keeping these 
 works in good repair is one of considerable difficulty. In 
 fact, it is sometimes more necessary to spend money for good 
 bridges than for good roads. Rarely is the condition of a 
 road so bad that it stops travel entirely or becomes actually 
 dangerous to life or property, as happens in case of the destruc- 
 tion of an important bridge. 
 
 To secure the safety of a bridge a good foundation for the 
 substructure is of the highest importance; a bridge on a poor 
 foundation cannot be maintained. If the stream bed be 
 too soft to support the substructure, piles should be driven; 
 if it is subject to wash such as to endanger the fourdations, 
 special pains should be taken to protect the foundations. 
 
 In building a permanent structure the first thing to be con- 
 sidered is the site upon which it is to be erected, which should, 
 if possible, be in a location where the bridge will 
 be exposed as little as possible to the various in- 
 fluences tending to cause its destruction. It should be so 
 located that the cost of construction will be as low as is con- 
 sistent with good service to the public, and care should be 
 observed to avoid placing the bridge at a point where a stream 
 is apt to change its bed. For the safety of the public the 
 approaches should be in line with the bridge for as great a dis- 
 tance as possible at each end, especially if the road is on a 
 grade. 
 
 By a judicious change in the location of a road, bridges can 
 sometimes be avoided without inconvenience to the public. 
 Fig. 13 (page 50) shows a case in which there are three 
 bridges of 60-feet span over a stream where one would be 
 sufficient for the public convenience. 
 
 Highway bridges may be classed according to the materials 
 of which the superstructures are built, as follows: 
 
70 
 
 THE ART OF ROADMAKING 
 
 Fig. 31. — Clariton-Clifton Two-hinged Arch Highway Bridge Over 
 Niagara River. 
 
 Fig. 32. — Suspension Highway Bridge Over Niagara River. 
 iFrom "Design of Highway Bridges," by M. S. Ketchum) 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 71 
 
 1. Steel or iron. 
 
 a. Short span; b. High truss; c. Plate girder. 
 
 2. Steel or iron in combination with timber. 
 
 3. Timber. 
 
 4. Masonry or concrete. 
 
 a. Arches; h. Beam; c. Culverts. 
 
 5. Reinforced concrete. 
 
 There are locations for which each type is adapted. In the 
 past, the cheapness of good lumber, the ease with which tim- 
 
 Classifica- 
 tion of 
 highway 
 bridges. 
 
 (From Wis. Geological Survey Bulletin) 
 Fig. 33.— The Old Style Highway Bridge. 
 
 ber bridges could be built and repaired, and the high price 
 of other materials were the causes for the wide use of such a 
 perishable material as timber, but in recent years conditions 
 have changed; lumber has increased in price while the prices 
 of steel and Portland cement have decreased. Steel is the 
 material most widely used and is used for bridges of all 
 spans. 
 
 A bridge truss is a framework composed of individual mem- 
 bers so fastened together that loads applied at the 
 joints produce onty direct tension or compression. "dge 
 
 In its simplest form every truss is a triangle or a 
 combination of triangles, this being the only geometrical figure 
 
72 
 
 THE ART OF ROADMAKING 
 
 in which the form is changed only by changing the length of the 
 sides. The members of the truss are either fastened together 
 with pins, termed "pin-connected/' or with plates and rivets^ 
 termed '^riveted." 
 
 Fig. 34 represents a bridge consisting of two vertical 
 trusses which carry the floor and the load; two horizontal 
 
 f-T^y^ 
 
 Top 10^ " 
 
 For/a/ — 
 
 ,. L&°''"' 
 
 
 (From "Design of Highway Bridges " by jl/. 5. 
 ,^yi Ketchum) 
 
 ^-^ ^ r '^ 
 
 Fig. 34.^Diagrammatic Sketch of a Through Pratt Truss Highway 
 
 Bridge. 
 
 trusses in the planes of the top and bottom chords, respectively,, 
 which carry the horizontal wind load along the bridge; and 
 cross-bracing in the plane of the end-posts, called "portals,'' 
 and in the plane of the intermediate posts, called '' sway 
 bracing:" The floor is carried on joists placed parallel to the 
 length of the bridge, and which are supported in turn by the 
 floorbeams. The main ties, hip verticals, counters and inter- 
 mediate posts are together called "webs." The bridge shown 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 73 
 
 in Fig. 34 is a ''through pin-connected" bridge of the "Pratt" 
 type, the traffic passing through the bridge. Short-span 
 highway bridges have low trusses and no top lateral system 
 or portals. 
 
 The simplest type of bridge is the "beam" bridge (a) Fig. 
 
 /^^ZEZSZX. 
 
 (a) beam Brldqe* 
 
 /"c/j L o\A^ Warren Truss. 
 
 m 
 
 ^ 
 
 (b) Beam L egdrfcfge, (e) LowPrafi Truss. Half Hip. 
 
 i^i^^i^ 
 
 ^::^^ax 
 
 (f) Low Praft Truss.Full Slope. 
 
 (c) Truss Leg" dridqe. 
 
 (From " Dcftign of Highway Bridges," by M. S. Ketchum) 
 
 Fig. 35. — Types of Short Span Highway Bridges. 
 
 35. This commonly consists of I-beams which spa.n the 
 
 opening, and are placed near enough together to 
 
 carry the floor of the bridge. Where foundations Types of 
 
 • a trim^f*^ f) Tin 
 
 are relatively expensive the beams may be carried bj-i^e-es 
 on posts as in (6). A "Truss Leg" bridge is shown 
 in (c) . A " Warren " truss is a combination of isosceles 
 triangles as shown in {d). The "Pratt'' truss has its vertical 
 web members in compression while its diagonal web members 
 
74 
 
 THE ART OF ROADMAKING 
 
 are in tension, as shown in (e) and (/). The "Warren'' truss 
 is commonly built with riveted joints while the "Pratt" truss 
 is usually built with pin-connected joints. The "Warren" 
 
 / 
 
 /// 
 
 
 / 
 
 
 / 
 
 5 
 
 / 
 
 \) 
 
 i 
 
 N 
 
 \ 
 
 J . iL. _ 
 
 . . _i 
 
 Zl_ 
 
 . — - — --^ — . — . 
 
 -^ — 1.^ — 
 
 
 \-t 
 
 Fig. 36.~Through Howe Truss. 
 
 low truss with riveted joints as shown in (d) is generally 
 preferable to the low "Pratt" truss in either (e) or (/). 
 The "Howe" truss has its vertical web members in tension, 
 
 Fig. 37.— Baltimore Truss. 
 
 and its inclined web members in compression, as in Fig. 36. 
 The upper and lower chords and the inclined members of a 
 " Howe " truss are commonly made of timber, while the 
 vertical tension members are iron or steel rods. 
 
 Fig. 38.— Petit Truss. 
 
 The "Whipple" truss is a double intersection "Pratt" truss. 
 This was designed to give short panels in long spans which 
 have a considerable depth. 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 75 
 
 The "Baltimore" truss is a "Pratt'' truss with parallel 
 chords in which the main panels have been subdivided by an 
 auxiliary framework as in Fig. 37. The "Baltimore" truss 
 with inclined upper chords, is called a "Petit" truss. 
 
 Fig. 39.— Typical Leg Bridge. 
 
 Short span highway bridges include beam^ leg and low- 
 truss bridges. 
 
 Beam bridges are made by placing steel beams side by side 
 
 Fig. 40. (a) and (h). — Illustrating Deflection of Supports of Leg Bridge. 
 
 Fig. 40 (a), a shows the position of the top of the upright leg at time of erection 
 with fall of temperature, the floor joists shorten and the legs assume the new position b- 
 With increase in temperature the tops of the legs are forced back towards their original 
 positions, and the bank is compelled to yield to their pressure, but mainly at the top. 
 The legs will then assume the curved position c in Fig. 40 (b). The tendency of the 
 curved beam to straighten throws the foot out and the leg takes a step into the stream 
 the final position being shown at d. This process is repeated with every recurring change 
 of temperature. 
 
 with the ends resting in the abutments. The roadway floor 
 
 is usually made of planks laid transversely on top 
 
 of the beams. The spacing of the beams depends ^^.^""t-span 
 
 on the load to be carried and upon the thickness 
 
 of the floor planks, for which a common rule is that the plank 
 
76 
 
 THE ART OF ROADMAKING 
 
 Fig. 41. — ^A Warren Low Truss Highway Bridge. 
 
 Fig. 42.— a Pratt Low Truss Highway Bridge; Seven 100-It. Spans, 
 
CONSTRUCTION AND PROTECTIVE WORKS 77 
 
 shall have at least one inch in thickness for each foot of spacing 
 of the joists or stringers. The outside beams carry a smaller 
 load than the intermediate beams and are usually steel channels, 
 while the intermediate beams are steel I-beams having a depth 
 of about -^ of the span. 
 
 Beam and truss bridges are sometimes supported on steel 
 legs in the place of abutments, and should be designed to 
 carry the thrust of the filling in addition to the live and dead 
 load on one-half of the span. Unless very carefully designed 
 and constructed, leg bridges are inferior structures and are not 
 to be recommended. 
 
 Pig. 43.— a Pratt Low Truss Bridge 40-ft. Span with Concrete Floor. 
 
 Low-truss bridges are used for spans of from 30 to 80 feet, 
 and special designs to about 100 feet. ' The trusses may 
 have either pin-connected or riveted joints; they 
 may have either half-hips, or full slopes, and may J-o^-^russ 
 be either of the "Warren" or the "Pratt'' type. 
 
 High-truss bridges with spans of from 80 to 170 feet are 
 built with parallel chords and with either pin-connected or 
 riveted joints; with spans of from 160 to 220 feet, 
 they are usually built of the "Pratt" type with ^jf^^f"^^ 
 inclined upper chords trusses; with spans above 
 220 feet, bridges are usually built with the "Petit" type of 
 
78 
 
 THE ART OF ROADMAKING 
 
 Fig. 44. — Cantilever Highway Bridge. 
 
 Fig. 45. — Plate Girder Highway Bridge. 
 
 (From " Design of Highway Bridges," by M. S. Ketchum,) 
 
CONSTRUCTION AND PROTECTIVE WORKS 79 
 
 truss. High-truss pin-connected bridges should never be 
 built with less than five panels. 
 
 A "plate girder" consists of a vertical steel or iron web 
 plate to whose top and bottom edges are riveted horizoiiital 
 pairs of angles to form .flanges, and to whose ends ; 
 
 are attached vertical angles which ti^ansmit the , ^^'^^ ^^ 
 load to the supports. 
 
 A plate-girder highway bridge consists of two or more, 
 usually two, plate girders fastened together by lateral bracing. 
 The roadway is carried on a floor system supported near the 
 bottoms of the plate girders. Short spans up to 70 or 80 
 feet have one end fixed while the other end is allowed to move 
 on a sliding plate. For greater lengths of span the expansion 
 end is supported on nests of rollers. The ordinary limit of 
 plate-girder spans is about 100 feet. 
 
 Timber was formerly quite generally used in the construction 
 of highway bridges, and is still used for temporary structures 
 in locations where timber is cheap and iron and 
 steel are relatively expensive. It is used in (1) Useoftim- 
 timber trestles, (2) timber bridges and (3) badges 
 combination bridges, in which the top chords 
 and intermediate parts are made of timber while the tension 
 members are made or iron or steel. 
 
 Wooden bridges are expensive to maintain, and, where 
 built strong enough to carry heavy loads their first cost is 
 high. They are dangerous, since they will often give way 
 without showing any signs of weakness. 
 
 When properly constructed, masonry and concrete bridges 
 are permanent, and this type of structure should be given 
 the preference when conditions are favorable for 
 its construction. Masonry and 
 
 Stone arches have been built from time im- bridc^e^s ^ 
 memorial, and while many existing arches are 
 standing after hundreds of years it is equally certain that many 
 have fallen down. Rightly built they are permanent, since 
 there is nothing to decay, and to break them down it is neces- 
 sary to crush the rock of which they are built. 
 
 Reinforced concrete beam bridges for short spans up to 15 
 
80 
 
 THE ART OF ROADMAKING 
 
 Fig. 46. — Reinforced Concrete Bridge, 20-ft. Span. 
 
 . 47.— Timber Box Culvert. 
 
 Fig 
 
 
 ^--- 6'0'---M 
 
 >r 
 
 
 
 's^ 
 
 *N 
 
 ^W 
 
 
 ' 
 
 ""i 
 
 
 , 1 
 
 
 Fig. 4S.- -Timber Culvert. 
 
 -^,/4^ 
 
 *«\^><^>^^ 
 
 m^^^^ 
 
 ^^^^^^^ 
 
 FiG. 49. — Endwalls for Pipe Culverts. 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 81 
 
 to 20 feet are commonly made of a single slab of uniform 
 thickness spanning the opening. For longer spans the floor 
 system is made of deeper horizontal girders supporting a 
 relatively thin floor slab. 
 
 Fig. 50.— a Well Built Concrete Culvert. 
 
 Fig. 51. — A concrete culvert cracked a few days after being built, due to 
 the concrete not being thoroughly mixed and tamped. 
 
 Culverts are made of timber, vitrified clay brick, cast iron 
 pipe, brick, stone, concrete, and reinforced concrete. For 
 temporary culverts the timber box may be used, 
 the bottom being paved to prevent scour. Care 
 should be used to tamp the filling to prevent water flowing 
 
82 THE ART OF ROADMAKING 
 
 along the sides. Timber culverts are very unsatisfactory and 
 in the long run are very expensive. Pipe culverts should be 
 laid on a firm foundation and to a careful grade. The center 
 should be raised so that there will be no hollows in the pipe. 
 Head walls, preferably of masonry or concrete, should ex- 
 tend high enough to carry the fill, and should be carried 
 down far enough to prevent the water from following along 
 the outside of the pipe, which should preferably be laid in 
 concrete. 
 
 The location of culverts should also have careful considera- 
 tion; often they are built and maintained where they are 
 unnecessary. It is of no benefit to carry water across a road 
 in a culvert unless it can be carried away from the road at that 
 point; it should be carried along a road as long as its volume 
 does not become so great as to cause serious washing. Culverts 
 should, of course, be built with a view to permanency, and 
 they should be protected. 
 
 An important feature in the planning of a bridge or culvert 
 
 is the making of a careful estimate of the amount of water 
 
 for the passage of which it is necessary to provide. 
 
 ize o rpj^-g ^g always done by railroad companies in planning 
 
 opening. , *' -^ ^ r- o 
 
 their structures and should be done for every 
 
 highway structure as well. 
 
 The amount of water that -^ill come from a certain drainage 
 
 area and flow through any culvert or under any bridge in a 
 
 given amount of time can be determined only in a general way 
 
 and rarely with any "high degree of accuracy, as it depends 
 
 upon too many factors. These are: 
 
 1. Area of drainage basin. 
 
 2. Maximum rainfall per hour. 
 
 3. Slope of the surface, 
 
 4. Character of the soil — porous or compact. 
 
 Some of the more important of these factors are practically 
 unknown, as even the most carefully kept weather records 
 seldom give the rainfall for each shower, which is the point of 
 importance in determining the amount of water to be provided 
 for. The amount of water which the soil will absorb may 
 vary from a small percentage to almost the whole amount of the 
 
CONSTRUCTION AND PROTECTIVE WORKS 83 
 
 rainfall, depending on its conditions at the time of the shower. 
 
 Floorbeams for highway bridges are made of rolled I-beams 
 
 or riveted plate girders, and may be riveted to the posts or 
 
 hung from the lower chord pins. Joists or stringers 
 
 are made either of rolled I-beams or of timber. ^^P^ ^^™^ 
 
 and floors. 
 
 The floors are made of timber, remforced concrete, 
 
 bent steel or iron plates or bars, or angles and plates filled 
 
 with concrete. 
 
 In the past steel bridges have generally been built with 
 plank floors, but the increase in the price of lumber has re- 
 sulted in the use of the more substantial materials which will 
 endure as long as the bridge. 
 
 In any type of bridge it is of the utmost importance that 
 
 the superstructure be well supported. If this is not done the 
 
 best bridge that can be constructed will fail. When 
 
 an arch fails it is generally because the foundation " "^ 
 
 ^ "^ structures, 
 
 has settled. In the case of steel structures, failures 
 
 are often the result of failures in the substructure. These 
 bridges are designed to withstand certain forces applied in 
 certain ways. So long as the bridge rests securely upon the 
 substructure, the conditions expected in the design are ful- 
 filled, but if the structure settles to any great extent, strains 
 which are entirely unexpected and consequently not provided 
 for in the design are introduced, and though the bridge may 
 not fail all at once its joints become loose, the trusses get out 
 of line, the bars begin to rattle badly when any considerable 
 load crosses, and the structure weakens much more rapidly 
 than under ordinary conditions. The forms of substructures 
 ordinarily employed are abutments and piers of stone or 
 concrete, and steel piling. 
 
 An abutment is a structure, commonly made of masonry, 
 that supports the ends of the bridge and acts as a retaining 
 wall to hold back the earth fill. A pier is a 
 structure that supports the ends of the bridge where 
 there is no filling to support. Abutments and piers are gen- 
 erally at right angles with the center line of the bridge. A 
 bridge in which the abutments are not at right angles to the 
 center line is called a "skew" bridge. 
 
84 
 
 THE ART OF ROADMAKING 
 
 Transverse Section. 
 
 Fig. 52, — Beam Bridge with Solid Floor. 
 
 Fig. 53. — Details of Concrete Floor. 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 85 
 
 Fig. 54. — A Substructure of Five Light I-beams with a, Backing or 
 "Abutment" of Planks which will have to be Renewed Every Few 
 Years. 
 
 {From " Design of Highway Bridges," by M. S. Ketckum) 
 Fig. 55.— Concrete Abutments for 111' 6" Span Steel Riveted Highway 
 Bridge Across Illinois and Mississippi Canal. 
 
86 THE ART OF ROADMAKING 
 
 Abutments are made with 
 
 1. A straight main section without wings. 
 
 2. AVings making an angle of from 30 to 45° with the axis 
 
 of the stream. 
 
 3. A T-section^ the stem of the T running back into the fill. 
 
 4. A U-section where the wings make an angle of 90° with 
 
 the axis of the stream. 
 Highwa}^ bridge abutments are usually made with wing 
 wallsj the wings making an angle of 30 to 45° with the face of 
 the abutment. The abutment with wing walls holds the filling 
 and gives a freer channel than any of the other types. 
 
 (From Wis. Geological Survey Bulletin) 
 Fig. 56. — The Result of Flimsy Construction. 
 
 While abutments of stone or concrete are practically unaf- 
 fected by decay they may be destroyed by undermining. The 
 foundation should always be at such a depth that there will 
 be no danger of wash, and if in soft ground, piles should be 
 driven. One great advantage of stone or concrete abutments 
 over all other structures is that they serve as retaining walls 
 and permit embankments to be made right up to the end of 
 the bridge. When built with suitable wing walls the embank- 
 ments are well protected against washing. 
 
CONSTRUCTION AND PROTECTIVE WORKS 87 
 
 The most economic bridge is the one which in the long run 
 will give the best service and cost the least money, taking as 
 a measure of the cost the amount of money which 
 it will be necessary to capitalize in order that ^**^* 
 the interest may pay for (1) the maintenance and bridge, 
 repairs, (2) the interest on the first cost, and (3) a 
 sinking fund for depreciation so that the bridge may be re- 
 placed when it is no longer fit for the service demanded. 
 
 The possible life of any particular bridge is difficult to 
 estimate. Steel bridges, if properly constructed, should last 
 from 25 to 40 years; combination bridges, from 10 to 15 years, 
 while masonry and reinforced concrete bridges are ordinarily 
 considered as permanent structures. Timber floors must be 
 replaced in 3 to 5 years, and steel bridgeb should be painted 
 every 3 to 4 years. Hence the first cost of a bridge is not a 
 safe criterion upon which to base economy. Much morfey is 
 wasted in putting in cheap, flimsy, bridges which are short- 
 lived, unsatisfactory and are continually in need of repairs. 
 
 Retaining Walls 
 
 A retaining wall is a structure that retains the lateral 
 pressure of the earth on hillsides. The pressure of the material 
 supported varies considerably, depending upon the material, the 
 manner of depositing it in place, and upon the amount of 
 moisture. If dry clay is loosely deposited behind the wall 
 it will exert the full pressure due to this condition. In time 
 the earth becomes consolidated and cohesion and moisture 
 make a solid clay, which often causes the bank to shrink 
 away from the wall, and there will be no pressure exerted. 
 On the othsr hand, if a considerable amount of water is added, 
 the normal pressure rapidly increases and approaches that 
 due to a liquid having the same specific gravity. 
 
 Retaining walls should be built on steep hillsides and moun- 
 tain roads — 
 
 1. At all re-entering curves. Where re- 
 
 2. At all culverts and bridges. ^^ehaih^ 
 
 3. On the edge of all precipitous places. 
 
 4. When the bank slope and the ground slope are nearly or 
 
 quite parallel to each other. 
 
ss 
 
 THE ART OF ROADMAKING 
 
 5. Where a bank would be of excessive length owing to 
 
 the angle of the natural ground slope. 
 
 6. Where a wall would be cheaper than a bank. 
 
 On the edges of dangerous precipices, when there is a heavy 
 
 Fig. 57. — Road Construction on Hillside, with Retaining Walls. 
 
 Fig. 58. — Surcharged Wall. 
 
 A wall is said to be " surcharged " when the bank it retains slopes back- 
 wards to a higher level than top of the wall. 
 
 load to support, the walls should be built of masonry, but 
 where the pressure is not too great they may be built of large 
 stones laid dry. They should be carried up as high as the 
 natural surface of the ground or to the surface of the roadway 
 
CONSTRUCTION AND PROTECTIVE WORKS 
 
 89 
 
 and a parapet wall or fence raised upon it, to protect pedes- 
 trians against accident. 
 
 Dry stone retaining walls are best suited for roads on account 
 of their self-draining properties and their cheapness. 
 
 The filling back of the wall should be entirely of stone if 
 it is available. Where earth is used it should be deposited 
 and tamped in approximately horizontal layers or 
 in layers sloping back from the wall; and a layer 
 of sand, gravel, or other porous material should be deposited 
 between the fill and the wall to drain the fill downwards. In 
 case of masonry retaining walls, to insure drainage of the 
 filling, drains should be provided back of the footing and 
 ^'weep-holes'' should be provided in the body of the wall 
 
 Concrete -X , "-VL-,. ^r'--^ 
 
 w. Stepped Profile. 
 
 h. Ogee Profile. c. Vertical Profile. 
 
 Fig. 59.— Sea Walls. 
 
 at frequent intervals to allow the water to pass through. 
 The filling in front of the wall should also be carefully 
 drained. 
 
 Roads along the seashore are protected b}^ sea walls, which 
 resist the wave action and support the embanked roadways. 
 The principal weakness of most sea structures, 
 especially those directly opposed to the action \ 
 
 of the waves, lies in the liability of the foundation 
 to wash out. To provide against this the footings should be 
 carried well' down, and the profile of the wall should be such 
 as to break up the waves with the minimum effect on the foun- 
 dations. 
 
 The stepped profile is believed to accomplish this object 
 better than any other form, as the steps break up the waves, 
 
90 THE ART OF ROADMAKING 
 
 and reduce the volume of water likely to be thrown on to the 
 roadway. The ogee profile looks well but is less effective 
 in breaking up the waves, is more troublesome to construct, 
 and is not as strong as the other forms. The vertical, or 
 nearly vertical, profile is used in locations open to really heavy 
 seas. 
 
CHAPTER VI 
 
 MATERIALS USED IN ROAD CONSTRUCTION 
 
 A GREAT variety of material enters into the construction of 
 present-day roads on account of the widely varying climatic, 
 geologic and topographic conditions which exist in this country 
 as a whole and almost equally so of any particular state or 
 locality. Materials which might be used with economy in 
 one locality may be entirely unserviceable elsewhere because 
 of excessive cost of haulage. This forms so large a part of 
 the cost that an inferior material may often be useful econom- 
 ically on account of the expense of securing a superior material. 
 In general it may be stated that for country roads, materials 
 from local sources must be employed. 
 
 The best material available should be chosen, and if not 
 very strong, it will suffice where the- traffic is moderate, a 
 greater quantity making up for want of durability, 
 but more labor will be required to keep the surface ^*J®* ^"^*" 
 of the road in proper order than with a better material. 
 material. With heavier traffic the use of a better 
 material, even at a higher price, becomes more advantageous, 
 and in or near large towns the best material at almost any 
 price is generally the most economical in the end. This is 
 especially the case when the dirt arising from wear must not 
 only be scraped off constantly, but be removed altogether from 
 the road. Sometimes a stronger and more costly material 
 may be used for the surface only, the body of the road being 
 made of inferior local stone. For repairs, the better material 
 may be laid only on the middle of the road, where the wear 
 is the greatest. 
 
 In the making of new roads, and to a greater extent in the 
 selection of the most suitable spots for opening the necessar\^ 
 quarries for supplying road-making materials, geology, chem- 
 
 91 
 
■92 THE AKT OF ROADMAKING 
 
 istry, and petrology all contribute to the knowledge necessary 
 for the proper scientific study of the materials. While observa- 
 tion of the behavior of the stones in a road may be more con- 
 vincing than theoretical knowledge^ time is necessary for such 
 -a trial, and the material may, after all, turn out to be defi- 
 'cient in durability. Experience has shown that even in the 
 same quarry, remarkable differences exist in the quality of 
 the rock which, to all appearance, is of a similar nature, and 
 it is only by a microscopical examination of the rock that 
 these peculiarities and the diverse wearing properties of 
 different rock-types can be detected. To the science of 
 petrology, therefore, must the road engineer look for that 
 assurance, which, combined with a study of the physical tests 
 and his own knowledge of the actual use of some reliable types 
 of road-stone, will insure the most suitable and durable ma- 
 terial being selected for any particular road. 
 
 The materials most commonly used for roads and pave- 
 ments are: 
 
 1. Stone, in the form of blocks and broken fragments. 
 
 2. Wood, in the form of blocks and planks. 
 
 3. Asphalt in two forms: sheet and block. 
 
 4. Concrete. 
 
 5. Sand. 
 
 6. Clay. 
 
 7. Gravel. 
 
 8. Bituminous materials (other than sheet and block asphalt). 
 
 In order to determine the fitness of the different 
 
 Selection of . • i i • j*,* £ - •, 
 
 . , materials under any given conditions of service, it 
 
 is necessary to know: 
 
 1. The agencies causing their destruction. 
 
 2. The extent and character of the traffic. 
 
 3. The topographic and climatic conditions under which 
 they are to be used. 
 
 4. The properties which the materials must possess in order 
 to resist the destroying agencies. 
 
 5. The most reliable method of ascertaining experimentally 
 the extent to which the materials possess the required properties. 
 
 Other things being equal, the endurance of a roadbed 
 
MATERIALS USED IN ROAD CONSTRUCTION 93 
 
 depends upon the qualities of the materials used; assuming 
 the road to be properly constructed and adequately ^ 
 drained. A road is subject to attack and conse- causing de- 
 quent loss of material in part by reason of the struction of 
 composition of that material. The other forces ^^^ ^' 
 operating upon the surface to destroy the road or pavement 
 are: (1) physical, (2) mechanical or dynamical, (3) chemical, 
 (4) organic. It is estimated that the mechanical agencies 
 cause SO per cent of the destruction and the others 20 per 
 cent. 
 The physical agencies are: 
 
 1. The disrupting effects of frost and ice, both 
 
 on the intee:rity of the road bed as a whole and ^^*^^ 
 
 o -^ agencies. 
 
 on the individual rock fragments and minerals. 
 
 2. The transporting power of water. 
 
 3. The transporting power of the winds. 
 
 4. Heat due to changes of temperature. 
 
 5. The attrition and effect of falling rain. 
 
 6. Gravity. 
 
 It has been the object of the highway engineer ever since 
 the days of Macadam to construct a road in such a manner that 
 frost action above subgrade may be reduced to a minimum. 
 Macadam contended strenuously for a dry foundation. The 
 evils resulting from the disrupting effects of water alternately 
 freezing and thawing in the foundation of a road are apparent 
 and are well known. Freezing action not only disrupts a 
 road as a whole, but its presence in stones is promotive of 
 weakness and more rapid crumbling. The presence of frost in 
 fragments of broken stone operates to increase their brittleness 
 to a considerable degree, and for this reason gives rise to a more 
 rapid disintegration of the screenings and the upper portion 
 of the road. In the formation of ice, 100 volumes of water 
 expands to 109 volumes of ice, and the pressure exerted on 
 cooling the water one degree below the normal freezing-point 
 is 144 tons per square foot. Its most destructive effect, 
 therefore, is produced in the structure of the pavement and 
 its foundation; if the construction is defective and the main- 
 tenance poor, water accumulates in the body of the roadway. 
 
94 THE ART OF ROADMAKING 
 
 and on freezing either destroys the bond or weakens it mate- 
 TisAly. 
 
 The ability of water as a medium of transportation of 
 material depends upon the specific gravity, the size and the 
 form of the fragments, and upon the velocity of the water, or, 
 what amounts to the same thing, the grade of the roadbed. 
 The gullying of roadbeds during heavy rains or melting snows 
 by washing particles of sand and clay to the side drains 
 and ditches is the most conspicuous work done by flowing 
 water, but the sorting process it exercises even on gentle 
 slopes, where the grains of the least weight and specific gravity 
 are forced to the surface of the road to be blown away by the 
 wind, is also important. This sorting action arises from 
 the fact that the sand grains will arrange themselves in water 
 in the order of their specific gravities, the heaviest at the 
 bottom. 
 
 The combined operation of wind and water play a con- 
 siderable part in the destruction of the roadway. Measure- 
 ments made by French engineers show that about seven 
 cubic yards of material per mile per annum are removed by 
 these agencies. Considered from the point of view of wind 
 action alone, the ability of wind to carry away grains of any 
 rock depends on: 
 
 1. The form of the particles subjected to the wind's influence. 
 
 2. The specific gravity and size of the individual grains. 
 
 3. The accessibility of the grains to the action of the wind. 
 Heat, through changes of temperature, causes expansions 
 
 and contractions which produce a slight movement among the 
 component particles of the material, thus breaking their 
 cohesion and leaving them more susceptible to the destroying 
 effect of the other agents. 
 
 The impact of falling rainwater, while relatively unimportant 
 as a source of injury, causes a certain amount of attrition and 
 loosening of those grains which it is able to move about, and 
 a certain breaking of the coherency of the surface as far down 
 as the water is able to penetrate. 
 
 Gravity also plays its part, as seen by the work done in 
 running water and falling rain, but through its operation alone 
 
MATERIALS USED IN ROAD CONSTRUCTION 95 
 
 there is always a tendency for grains and fragments of rock 
 to work down the slopes towards the sides of the road, which 
 may in time completely destroy a roadbed. 
 The mechanical, or dynamical, agencies are: 
 
 1. Friction, resulting from the grinding action of 
 
 one fragment of rock against another, due to traffic, ^^ amca 
 ° o ; J agencies. 
 
 as, 
 
 a. Impact produced by the action of horses' feet. 
 
 b. Percussive and abrading action of moving wheels. 
 
 c. Crushing due to the weight of the load on the wheels. 
 
 2, The disrupting effect of roots. 
 
 The gradual destruction of a roadbed by the ordinary 
 processes of friction and impact is always to be expected, and 
 if these forces are applied in the presence of water, thus pro- 
 ducing attrition in the presence of a solvent, their destroying 
 effects are most energetic. 
 
 The chemical agencies are: 
 
 1. Decomposition, shown, for example, by the 
 
 disintegration of the feldspar-bearing rocks whereby emica 
 
 ° . ^ . *^ agencies. 
 
 the feldspars and other minerals are converted into 
 
 clay, quartz, calcite, etc. 
 
 2. Solution, or the power possessed by surface waters im- 
 pregnated with acids to dissolve most rocks and to carry 
 them away. 
 
 The action of the chemical agencies is very slow, and their 
 effect may be ignored except in the case of rocks already in 
 a state of decon;position or containing readily soluble mineral 
 matter. The rocks that are most susceptible to the solvent 
 action of water impregnated with acids are the limestones, 
 calcareous sandstones, and the granites containing feldspar. 
 
 The softening or partial decomposition of a road-stone by 
 these chemical changes has generally been regarded as a 
 destructive element in road maintenance, but although it 
 appears from recent investigations, that the chemical decom- 
 position is not so destructive as it was formerly imagined to 
 be, it can hardly be doubted that the weathering properties 
 of a stone are determined by resistance to chemical action. 
 And although this may be, in some instances, slow and not 
 
96 THE ART OF ROADMAKING 
 
 appreciable on the surface of a road which is renewed from 
 time to time, the internal structure, by the solvent action of 
 surface waters percolating through the coating under abnormal 
 conditions of weather, must be adversely affected. 
 
 The organic agencies are vegetable or fungus growths that 
 
 thrive in damp, shady places. 
 rganic rpj^^ essential qualities of a good roadmaking stone 
 
 may be stated as follows: 
 
 Paving Blocks: Hardness, toughness, durability, uniformity 
 of wear, retention of a rough surface under traffic in all con- 
 ditions of weather. 
 
 Macadam : Hardness , toughness , durability, retention of 
 
 ^ . , rough surface (though this does not apply to the 
 
 qualities of extent as in paving blocks) , and the property of 
 
 roadmaking binding necessary to maintain cohesion under 
 
 varying conditions. 
 
 These qualifications are rarely found together in any high 
 degree. Thus flint, though hard, is often brittle, and some 
 schistose or slaty rocks, although hard and tough when 
 quarried, often disintegrate when exposed to the weather. 
 The quality of cohesion is rarely found in combination with 
 extreme hardness and toughness. Material well consolidated 
 and united in a mass, resists crushing much better than when 
 loose, and good binding property enables a stone comparatively 
 weak to wear better than a harder stone which does not bind. 
 
 Hardness is an essential quality and may be described as 
 that resisting property which a solid offers against any dis- 
 placement of its parts or abrasion of its surface, 
 ar ness. rpj^^ definition adopted by the U. S. Road Material 
 Laboratory is "the resistance which a material offers to the 
 displacement of its particles by friction.'' When applied to 
 materials used for paving it signifies the resistance offered by 
 the material to wear by abrasion under the action of wheels. 
 
 Hardness varies inversely as the loss in weight by grinding 
 with a standard abrasive agent.- A test piece in the form of a 
 cylinder about three inches in length by one inch in diameter 
 is placed in the grinding machine in such a manner that the 
 base of the cylinder rests on the upper surface of a circular 
 
MATERIALS USED IN ROAD CONSTRUCTION 
 
 97 
 
 grinding disk of cast iron, which is rotated in a horizontal 
 plane by a crank movement. The specimen is weighted so as 
 to exert a pressure of 250 grams per square centimeter against 
 the disk, which is fed from a funnel with sand of about 
 1-^ mm. in diameter. After 1000 revolutions the loss in weight 
 of the sample is determined and the coefficient of wear obtained 
 by deducting one-third of this loss from 20. 
 Toughness is also essential quality, and is that property 
 
 /i I [ I !L I P I 
 
 Fig. 60. — Dorrey Machine for Testing Hardness. 
 
 Toughness. 
 
 which admits of the constituent minerals yielding to a small 
 extent without separation of the parts, and enabling 
 the stone to resist fracture by impact. As applied 
 to a paving material it may be defined as that propert}- which 
 enables it to resist fracture under the blows and concussions 
 produced by traffic. The determination of toughness is 
 obtained by the use of a test piece similar to that used in 
 determining hardness, and the test is made with an impact 
 machine constructed on the principle of a pile driver. The 
 
98 
 
 THE ART OF ROADMAKING 
 
 _Uiini 1 rmijumintmmfni! ill 
 
 H 
 
 n, =^™ 
 
 i Af" ■ lilr 
 
 Fig. 61.— Page Machine 
 for Determining Toughness, 
 
 Fig. 62. — Page Impact 
 Machine. 
 
MATERIALS USED IN KOAD CONSTRUCTION 99 
 
 blow is delivered by a hammer weighing 2 kg., falling 1 cm. 
 for the first blow, which is increased by 1 cm. for each succeed- 
 ing blow until failure of the test piece occurs. The number 
 of blows required to cause this failure represents the tough- 
 ness. 
 
 Durability depends on the hardness and cohesion of the 
 material, and also on the chemical stability of the con- 
 stituent minerals. Not onl}^ is the tendency to 
 decompose present in most stones when brought "^^ ^ 
 under the oxidizing influence of air and water, but nearly all 
 paving and road materials are further subjected to the solvent 
 action of impure surface water, hence the question of the 
 resistance of a road material to chemical agents is, as might 
 be supposed, of great importance. 
 
 Percentage of wear, representing durability, is the amount of 
 material under 0.16 cm. in diameter lost by abrasion from a 
 
 Fig. 63.— Deval Machine for Testing Resistance to Abrasion and 
 
 Impact. 
 
 weighed quantity of rock fragments of definite size. The 
 rock sample is broken into pieces that will pass through a 
 2.4-inch ring but not through a 1.2-inch ring, and after being 
 thoroughly cleansed, dried, and cooled, 5 kg. are weighed and 
 placed in a cast iron cylinder (34 cm. deep by 20 cm. in diameter) 
 closed at one end and having a tight-fitting iron cover at the 
 other. This cylinder is one of four attached to a shaft so that 
 the axis of each is inclined at an angle of 30° with that of 
 the shaft. These cylinders are revolved for five hours at the 
 rate of 2000 revolutions per hour, during which the stone 
 fragments are thrown from one end of the cylinder to the 
 other twice in each revolution. At the end of five hours the 
 
100 
 
 THE ART OF ROADMAKING 
 
 machine is stopped, the cylinders opened, and their contents 
 poured into a basin, in which every stone is carefully washed to 
 remove any adherent detritus. This abraded material is 
 then thoroughly dried, and from the amount lost below 0.16 
 cm. the per cent of wear is estimated. 
 
 The cementing value, or binding power, of a road material, 
 
 is the property possessed by a rock dust to act as a cement 
 
 on the coarser fragments comprising crushed stone 
 
 val^e^ ^°^ ^^ gravel roads. This property is a very important 
 
 one and is determined approximately as follows: 
 
 One kg. of the rock to be tested is broken sufficiently small to 
 
 UXCTIOWLATTICHHEHT Ffit 
 
 CPENIHG JtHD CiOSiNB 
 
 T>IH£C-W«rC3CK. 
 
 Fig. 64. — Briquette Machine. 
 
 pass through a 6 mm. but not a 1 mm. screen. It is then 
 moistened with a sufficient amount of water and placed in an 
 iron ball mill containing two chilled iron balls weighing 25 
 pounds each and revolved at the rate of 2000 revolutions per 
 hour for two hours and a half, or until all the material has been 
 reduced to a thick dough, the particles of which are not above 
 0.25 mm. in diameter. About 25 grams of this dough is then 
 placed in a cylindrical metal die, 25 mm. in diameter, and by 
 means of a specially designed hydraulic press, known as a 
 briquette machine, is subjected to momentarj'- pressure of 
 
MATEKIALS USED IN ROAD CONSTRUCTION 101 
 
 100 kg. per square centimeter. Five of the resultant briquettes, 
 measuring exactly 25 mm. in height, are taken out and allowed 
 to dry for 12 hours in air and 12 hours in a hot oven at 100° C. 
 After cooling in a desiccator they are tested by impact in a 
 machine especially constructed for the purpose. The standard 
 fall of the hammer for a test is 1 cm., and the average number 
 of blows required to destroy the bond of cementation in the 
 five briquettes determines the cementing value. 
 
 The rocks from which stone for paving purposes is obtained 
 vary in quality within wide limits, according to their geo- 
 logical position, physical structure, and chemical composition. 
 Several varieties of structure are met with the same chemical 
 constituents, this being due to the degree of crystallization of 
 the mineral elements. These differences fit the various rocks 
 for special purposes. 
 
 The choice of suitable words to describe the different stones 
 which are used in road-building is not an easy matter. When 
 petrological terms are used they are often applied ciassifica- 
 incorrectly, one of the difficulties of this way of tion of 
 naming stones being due to the fact that the dif- ^o^^s. 
 ferent minerals forming the important constituents of these 
 stones are combined in such varying proportions that the 
 different kinds of stone shade into one another, and many may 
 properly be called by any one of several names. 
 
 A systematic arrangement of rocks (Table VII) has been 
 adopted by the Office of Public Roads of the U. S. Department 
 of Agriculture. This has been made more from the standpoint 
 of the road-builder and engineer than from that of the 
 geologist, although attention has been given as far as possible 
 to the origin of the materials as well as to their mineral com- 
 position. In this arrangement all rocks used as road materials 
 have been separated into three general groups or classes, 
 according to their geologic character, these groups being again 
 divided into types and families. 
 
102 
 
 THE ART OF ROADMAKING 
 
 Table VII 
 GENERAL CLASSIFICATION OF ROCKS 
 
 Class. 
 
 I. Igneous. 
 
 II. Sedimentary 
 
 ...f 
 
 III. Metamorphic . 
 
 Type. 
 
 Family. 
 
 
 
 r a. 
 
 Granite 
 
 
 
 b. 
 
 Syenite 
 
 f 1. 
 
 Intrusive (plutonic) . . ■ 
 
 c. 
 
 Diorite 
 
 
 
 d. 
 
 Gabbro 
 
 
 
 [e. 
 
 Peridotite 
 
 
 
 I a. 
 
 Rhyolite 
 
 ■ 2. 
 
 Extrusive (volcanic) J "• 
 c. 
 
 Trachyte 
 Andesite 
 
 
 
 [d. 
 
 Basalt and diabase 
 
 
 
 fa. 
 lb. 
 
 Limestone 
 
 1. 
 
 Calcareous 'i 
 
 Dalomite 
 
 
 
 ra. 
 
 Shale 
 
 ■ 2. 
 
 Siliceous ■ 
 
 b. 
 
 Sandstone 
 
 
 
 [c. 
 
 Chert (flint) 
 
 
 
 ra. 
 
 Gneiss 
 
 ■ 1. 
 
 Foliated \ b. 
 
 Schist 
 
 
 [c. 
 
 Amphibolite 
 
 
 
 ' a. 
 b. 
 
 Slate 
 
 2 
 
 Non-foliated 
 
 Quartzite 
 
 L 
 
 
 Eclogite 
 
 
 
 [d. 
 
 Marble 
 
 With the exception of rocks of the second class, where 
 chemical distinctions prevail, structural features indicating 
 mode of origin define the type, and mineral composition the 
 family. Photomicrographs, illustrating the structure and 
 mineral composition of the principal rocks are given in Figs. 
 65 to 78, inclusive. 
 
 All rocks of the igneous class are presumed to have solidified 
 from a molten state, either upon reaching the earth's surface or 
 at varying depths beneath it. They vary in color 
 from the light gray, pink, and brown of the acid 
 granites and syenites to the dark steel gray or black 
 of the basic gabbro, peridotite, diabase and basalt. The darker 
 varieties are commonly called "trap." This term is in very 
 general use and is derived from trappUj Swedish for stair, 
 because rocks of this kind on cooling frequently break into 
 large tabular masses, rising one above the other like steps. 
 
 Igneous 
 rocks. 
 
MATERIALS USED IN ROAD CONSTRUCTION 
 
 103 
 
 The sedimentary rocks as a class, represent the consoli- 
 dated products of former rock disintegration, as in case 
 
 Fig. 65. — Granite. 
 
 of sandstone, conglomerate, shale, etc., or the}^ have been 
 formed from an accumulation of oi'ganic remains chiefly 
 
 Fig. 66. — Andesite. 
 
 of a calcareous nature, as in true limestone and dolomite 
 (Fig. 72). Loose or unconsolidated rock debris of a pre- 
 
104 
 
 THE ART OF ROADMAKING 
 
 Fig. 67.— Syenite. 
 
 Fig. 68.— Gabbro. 
 
 Fig. 69.— Peridotite. 
 
MATERIALS USED IN ROAD CONSTRUCTION 105 
 
 vailing silicious nature comprise the sands, gravels, finer silts, 
 and clays. Shell sands and marls, on the other 
 hand, are mainly calcareous and are formed ^y^Q^.^^^^^^ 
 an accumulation of the marine shells and of lime- 
 secreting animals. 
 
 Such terms as flagstone, freestone, brownstone, bluestone, 
 graystone, etc., are given generally to sandstones of various 
 color and composition, while puddingstone, conglomerate, 
 buccia, etc., apply to consolidated gravels and coarse feldspathic 
 sands. 
 
 The calcareous rocks are of many colors, according to the 
 amount and character of the impurities present. 
 
 Metamorphic rocks are such as have been produced by the 
 prolonged action of physical and chemical forces (heat, pressure, 
 moisture, etc.) on both sedimentary and igneous 
 rocks alike. The foliated types (gneiss, schist, etc.) ^. ^°^°?" 
 represent an advanced stage of metamorphism on 
 a large scale and the peculiar schistose or foliated structure 
 is due to the more or less parallel arrangement of their 
 mineral components (Figs. 73, 74, 75). The nonfoliated types 
 (quartzite, marble, slate, etc.) have resulted from the altera- 
 tion of sedimentary rocks without materially affecting the 
 structure and chemical composition of the original material. 
 (Fig. 78). 
 
 The color of metamorphic rocks varies between gray and 
 white of the purer marbles and quartzites to dark gra}- and 
 green of the gneisses, schists, and amphibolites. The green 
 varieties are commonly known as greenstones or greenstone 
 schists. 
 
 The family groups given in Table VII may be further 
 subdivided into many subfamilies or varieties — 
 as, for instance, biotite-granite, hornblende-schist. Primary 
 etc., according to characteristic primary ^iiieral ^.^j^g^-^^^^^g 
 constituents, a list of which is given in Table 
 VIII, together with their approximate chemical composi- 
 tion. 
 
106 
 
 THE ART OF ROADMAKING 
 
 Fig. 70.— Rhyulite 
 
 J 
 
 p««^^^ 
 
 Fig. 72, — C'ry.-.tal'niL' Linie^tune 
 
MATERIALS USED IN ROAD CONSTRUCTION 
 
 107 
 
 Table VIII 
 
 PRIMARY MINERAL CONSTITUENTS OF ROCKS 
 
 USED FOR ROADMAKING 
 Name. Chemical Composition. 
 
 Quartz Silica 
 
 Orthoclase (micro- 
 
 cline) Silicate of alumina and potash 
 
 Plagioclase Silicate of alumina, lime, and soda 
 
 Augite Silicate of lime^ magnesia, iron, and alumina 
 
 Hornblende Silicate of lime, magnesia, iron, and alumina 
 
 Calcite Carbonate of lime 
 
 Dolomite Carbonate of lime and magnesia 
 
 Biotite Hydrous silicate of alumina, iron, magnesia, and potash 
 
 Muscovite Hydrous silicate of alumina and potash 
 
 Magnetite Magnetic oxide of iron 
 
 Rock glass Variable 
 
 Garnet Silicate of iron, alumina, and lime 
 
 Olivine Silicate of magnesia and iron 
 
 Pyrite Disulphide of iron 
 
 Hematite Oxide of iron 
 
 Hypersthene .... Siliacte of iron and magnesia 
 
 Titanite Titano-silicate of lime 
 
 Apatite Phosphate of lime 
 
 Zircon Silicate of zirconia 
 
 The physical properties of the principal road-making rocks 
 are given in Table IX, in which they are arranged physical 
 according to the classification given in Table properties 
 VII, with their more important varieties. °^ rocks. 
 
 Table IX 
 PHYSICAL PROPERTIES OF ROCKS FOR ROADMAKING* 
 
 
 Physical Properties. 
 
 Rock Varietiea. 
 
 Per Cent 
 AVear.i 
 
 Tough- 
 ness.^ 
 
 Hardness.' 
 
 Cement- 
 ing Value. I 
 
 Specific 
 Gravity. 2 
 
 Granite 
 
 3.5 
 4.4 
 2.6 
 2.6 
 2.9 
 2.8 
 2.8 
 4.0 
 
 15 
 10 
 21 
 10 
 21 
 19 
 16 
 12 
 
 IS.l 
 16.8 
 
 18.3 
 
 18.4 
 18.1 
 17.7 
 17.9 
 15.2 
 
 20 
 
 17 
 
 30 
 24 
 41 
 
 55 
 29 
 28 
 
 2.65 
 
 Biotite eranite . . 
 
 2.64 
 
 Hornblende granite 
 
 Augite syenite 
 
 2.76 
 2.80 
 
 Diorite 
 
 2.90 
 
 Augite diorite 
 
 2.9S 
 
 Gabbro 
 
 3.00 
 
 Peridotite 
 
 3.40 
 
 
 
 (Table IX continued on p. 109.) 
 
108 
 
 THE ART OF ROADMAIONG 
 
 Fig. 73. — Granite-gneiss. 
 
 Fig. 74. — Chlorite-schist. 
 
 Fig. 75. — Mica-schist. 
 
MATERIALS USED IN ROAD CONSTRUCTION 
 Table IX* — Continued. 
 
 109 
 
 Rock Varieties. 
 
 Rhyolite 
 
 Andesite 
 
 Fresh basalt 
 
 Altered basalt 
 
 Fresh diabase 
 
 Altered diabase 
 
 Limestone 
 
 Dolomite 
 
 Sandstone 
 
 Feldspathic sandstone. 
 Calcareous sandstone . 
 Chert 
 
 Granite gneiss 
 
 Hornblende gneiss. . . . 
 
 Biotite gneiss 
 
 Mica schist 
 
 Biotite schist 
 
 Chlorite schist 
 
 Hornblende schist 
 
 Amphibolite 
 
 Slate 
 
 Quartzite 
 
 Feldspathic quartzite . 
 Pyroxene quartzite . . . 
 
 Eclogite 
 
 Epidosite 
 
 Physical Properties. 
 
 Per ^ 
 
 Wea 
 
 Cent 
 
 3.7 
 
 4.7 
 3.3 
 5.3 
 
 2.0 
 2.5 
 
 5.6 
 5.7 
 6.9 
 3.3 
 7.4 
 10.8 
 
 3.8 
 3.7 
 3.2 
 
 4.4 
 
 1 
 
 Tough- 
 ness ^ 
 
 20 
 11 
 23 
 17 
 30 
 24 
 
 10 
 10 
 26 
 17 
 15 
 15 
 
 12 
 
 10 
 19 
 10 
 
 21 
 10 
 
 12 
 19 
 17 
 27 
 31 
 16 
 
 Hardness. 
 
 17.8 
 13.7 
 17.1 
 15.6 
 18.2 
 17.5 
 
 12.7 
 14.8 
 17.4 
 15.3 
 
 19 
 
 17.7 
 17.1 
 17.5 
 17.3 
 
 16.5 
 19.0 
 
 11.5 
 
 18.4 
 18.3 
 18.6 
 17.4 
 16.0 
 
 Cement 
 ing Val 
 
 lue. 
 
 48 
 189 
 111 
 239 
 
 49 
 156 
 
 60 
 42 
 90 
 119 
 60 
 27 
 
 26 
 30 
 41 
 30 
 16 
 24 
 53 
 29 
 
 102 
 17 
 21 
 17 
 21 
 47 
 
 Specific 
 Gravity.^ 
 
 2.60 
 2.50 
 2.90 
 2.75 
 3.00 
 2.95 
 
 2.70 
 2.70 
 2.55 
 2.70 
 2.66 
 2.50 
 
 2.68 
 3.02 
 2.76 
 2.80 
 2.70 
 2.90 
 3.00 
 3.00 
 
 2.80 
 2.70 
 2.70 
 3.00 
 3.30 
 3.03 
 
 * Condensed from an extensive table of the mineral composition of 
 rocks compiled by the Bureau of Chemistry of the U. IS. Dept. of Agri- 
 culture. 
 
 l.The tests for obtaining these values were outlined in pages 97- 
 100. 
 
 2. The specific gravity is the weight of the material compared with that 
 of an equal volume of water, and is obtained by dividing the weight in 
 air of a rock fragment by the difference of its weight in air and water. 
 Given the specific gravity, the weight per cubic foot of a rock is found 
 by multiplying this value by 62.5 pounds,- the weight of a cubic foot 
 of water. 
 
110 
 
 THE ART OF KOADMAKING 
 
 Fig. 78. — Quartzite. 
 
MATERIALS USED IN KOAD CONSTRUCTION 111 
 
 From the results of the extensive series of tests of road 
 
 materials made by various methods by the Office of Public 
 
 Roads, the followine; conclusions have been reached :* « , . 
 
 ' ° . Conclusions 
 
 1. Igneous and metamoz'phic rocks, owmg to a regarding 
 higher degree of crystallization and a prepon- paving 
 derance of silicate minerals, offer a greater resistance ^ °^^^' 
 to abrasion than nearl}^ all varieties of sedimentar}'- rocks. 
 
 2. The coarse-grained intrusive rocks of the igneous class 
 are harder, but break mox*e readily under impact than the 
 finer-grained volcanic varieties of like mineral composition. 
 
 3. The deleterious effect of atmospheric weathering on the 
 wearing qualities of rocks has been demonstrated. 
 
 4. The cementing value of rocks is, to a certain degree, 
 measured by the abundance of secondary minerals resulting 
 from rock decay. 
 
 5. Metamorphic rocks have, as a rule, a low binding power, 
 owing to a regeneration of secondary minerals and to the 
 effects of heat and pressure. The foliated types part readily 
 along planes of schistosity, and therefore are not well adapted 
 to road construction. 
 
 6. The quantitative mineral analysis of rocks serves to a 
 certain extent as a measure of their useful properties for road 
 construction. 
 
 The principal varieties of rock employed for paving-blocks 
 are the granites, basalts, sandstones, and limestones, because 
 of the facility with which they split into the p • ■ j 
 desired shapes; for broken-stone pavements all varieties of 
 varieties of rock are used, including the flints roadmaking 
 and gravels. ^^^ ^' 
 
 Granite is an unstratified igneous rock, consisting of quartz, 
 feldspar, and some form of mica, or hornblende, in addition 
 to which essential constituents one or more acces- 
 sory minerals may be present. The character of 
 the granite is determined principally by its essentials, but 
 the accessories have much to do with its qualities. 
 
 * U. S. Department of Agriculture, Office of Public Roads, Bulletin 
 No. 31. 
 
112 THE ART OF ROADMaKING 
 
 The colors of granite are white, gray, various shades of red, 
 and green, the color being generally fixed by the feldspar, but 
 the mica is often a governing characteristic, the presence of 
 muscovite (potash mica), making a granite light, while biotite 
 (iron-magnesia mica) has the opposite effect. 
 
 The durability of granite depends to a great extent upon the 
 character of the feldspar present, too much of it rendering the 
 granite soft and tough, but liable to decomposition, while a 
 large amount of quartz will make it hard and brittle. The 
 susceptibility to polish and its ability to resist the action of 
 the elements depend greatly upon the accessory components; 
 hornblende permits it to take a high polish, while pyroxene, 
 being very brittle, often gives a pitted appearance to an other- 
 wise smooth surface. 
 
 The structure of granite varies considerably from coarse to 
 fine and is termed the holocrystalline, which implies that it is 
 made up exclusively of crystalline particles having clear, well- 
 defined boundaries. A fine-grained stone, of small and evenly 
 distributed grains, is compact in texture, excluding air and 
 moisture, both of which are destructive agencies to all minerals, 
 and may be more easily cut and polished than a coarse-grained 
 stone. On account of its peculiar structure, granite can 
 easily be broken into blocks of any desired shape or size. It 
 is specially adapted in roadwork for paving blocks, curbing, 
 flagging, basin-heads, crossing stones, and gutter stones; it is 
 also crushed and used for manufacture of concrete and arti- 
 ficial stone. 
 
 The term "granite," which should in a strict sense not be 
 applied to any stone not containing mica, is often applied 
 commercial^ and popularly to what are known as the gneisses 
 (foliated and bedded granites), syenite, diorite, gabbro, and 
 other crystalline rocks whose uses are similar. 
 
 Syenite (so named because it was first found in Syene, 
 Egypt) consists of feldspar and hornblende, with or without 
 quartz. It is massive and furnishes excellent material for 
 paving blocks, but is seldom found or used in this country, 
 
 Diorite is composed of a crystalline mixture of oligoclase 
 (soda and lime feldspar) and hornblende with magnetic iron 
 
MATERIALS USED IN ROAD CONSTRUCTION 113 
 
 and apatite, and occurs under conditions similar to syenite. 
 When the component minerals are fine-grained and compact 
 they make a very satisfactory material for broken-stone roads. 
 
 Basalt is one of the names given to a large group of un- 
 stratified eruptive rocks, commonly called trap-rock (See 
 page 102). The trap-rocks are generally close- 
 grained and compact in texture; they are hard 
 and tough and break irregularly and are usually difficult to 
 work. In color the}^ are dark gray, dark green, or grayish 
 black, the dark color being due to a larger proportion of 
 magnetite, which also contributes to the high specific gravity 
 of these rocks. The trap-rock of the Palisades on the west 
 shore of the Hudson river split easily into blocks, and has 
 been extensively and satisfactoril}^ used for paving in the 
 cities of New York and New Jersey. 
 
 Sandstone is formed by the decomposition on disintegra- 
 tion of rocks. The pockets of sand often found in beds of 
 earth or limestone are the results of boulders being 
 surrounded when these deposits of clay or stone 
 were first made, and which long afterwards decayed, leaving 
 in their places these pockets of sand, whose composition 
 depends upon the minerals contained in the original rocks. 
 
 Sandstone is formed by grains of sand being deposited in 
 beds by some agency and afterwards compacted. The sand 
 proper is almost all quartz, as this mineral is indestructible 
 from the ordinary action of the elements, while the cementing 
 portion of the original rock has generally been decomposed 
 and a new substance formed. The solidification of the stone 
 is caused by great pressure, partial solution, fusion of some 
 of its own parts, or by the infiltration of some cementing 
 material, such as silica lime, or the oxides of iron. It is 
 generally found in layers of variable thickness separated from 
 each other by some softer material, the thickness of these layers 
 probably depending upon the time one force acted continu- 
 ously upon the sand, the softer deposits being made during the 
 intervening period. 
 
 The texture of the stone varies according to the sizes of the 
 sand grains. 
 
114 THE ART OF ROADMAKING 
 
 Sandstones are of many colors, the most common, however, 
 being gray, yellow, and red. These colors are determined by 
 the different combinations of iron; the red being due to 
 peroxides, and the yellow to hydrous peroxides. Some 
 varieties will change color upon exposure to the air or the 
 application to heat, on account of the oxidation of the iron. 
 
 In street construction sandstones are used for curbing, 
 cross-walks, flagging and for paving the roadway. 
 
 Limestone, like sandstone, is a sedimentary rock, but 
 differs from it very much in its foz*mation. 
 
 Water flowing down from a rough mountainous 
 country carries with it a large amount of matter both in solu- 
 tion and in suspension. As the stream reaches any larger 
 body of still water its velocity gradually decreases and that 
 portion is suspension is deposited, the coarser and heavier 
 near the shore and the finer farther out. Calcareous matter, 
 as a rule, being soft, is generally fine, and is borne from a 
 distance and finally deposited as silt. 
 
 All these flowing streams contain a considerable quantity of 
 lime in solution which, being in part precipitated, serves to 
 consolidate the silt. From this same source certain marine 
 animals derive their supply for their shells. Upon the death 
 and decomposition of the animal life the shells and corals are 
 left and, breaking up, in time form calcareous banks which 
 later on become beds of limestones of more or less fragmental 
 nature. 
 
 These formations are generally in well-defined beds nearly 
 level when not disturbed by any subsequent force, but when 
 they have been acted upon by some of the forces so frequent 
 during the formation of the earth's crust, the strata are found 
 at all angles with the horizontal. 
 
 Limestones differ greatly in structure, from the variety 
 highly charged with fossils to the hard compact rocks denser 
 and heavier than granite. They also vary in color according 
 to the iron and carbonaceous compounds that may be present. 
 
 Silica and clay are often found in composition, and when 
 they exist in quantities exceeding ten per cent the stone is 
 said to be "hydraulic." That is, upon being burned and ground 
 
MATERIALS USED IN ROAD CONSTRUCTION 115 
 
 it can be made into mortar that will harden under water, a 
 property not belonging to ordinary limestones. 
 
 Marble is a crystalline limestone of such a character as to 
 be capable of receiving a high polish. 
 
 Of the other materials used in road making, wood is treated 
 in Chapter XVI; asphalt, in Chapter XVII, and concrete in 
 Chapter XVIII. 
 
 Sand is an aggregation of loose incoherent grains, crystal- 
 line in structure and angular in shape, of silicious, argillaceous, 
 calcareous, or other material, derived from the 
 disintegration of rocks or other mineral matter, .^^ ^^ 
 and unmixed with earth or organic matter. 
 
 Clay consists of a hydrated silicate of alumina in combina- 
 tion with other substances derived from the feldspathic rocks, 
 which by their disintegration and decomposition have formed 
 the clay. Pure clay is soft, white and opaque; has a char- 
 acteristic odor, is infusible, and insoluble either by water, 
 nitric or hydrochloric acids. It may be converted by water 
 into a doughy, tenacious, plastic paste; it absorbs water, 
 but when burned at a sufficiently high temperature it becomes 
 hard and gritty, and loses almost wholly this property of 
 combining with water. 
 
 With the single exception of ordinary earth or loam, sand 
 and clay in combination form probably the lowest type of 
 material available for road purposes. 
 
 Sand of itself, while at its best in winter and spring, does 
 not ever have sufficient stability to sustain traffic over it, 
 and cla}', of itself, is open to the same or greater objection 
 than loam. It is possible, however, to combine sand with 
 clay in such a manner that under moderate traffic and favorable 
 climatic conditions a fairly serviceable road may be obtained. 
 (See Chapter VII.) 
 
 The principal use of sand is as a foundation for broken stone, 
 a cushion and bed for stone paving-blocks, and as a joint 
 filling. For these purposes it is most suitable, because when 
 confined so that it cannot escape or spread, it possesses the 
 valuable property of incompressibility, and mobility, or the 
 
116 THE ART OF ROADMAKING 
 
 property of assuming a new position when any portion of 
 it is disturbed. 
 
 Sharp sand, with angular grains, is much better than sand 
 with rounded grains, although it is often difficult to obtain. 
 The sharpness of sand can be determined by rubbing a few 
 grains in the hand or b}^ crushing it near the ear and noting 
 if a grating sound is produced. 
 
 The sand for bedding rocks and for jointing should be free 
 from loam or clay. The clearness may be tested by rubbing 
 a little of the dry sand in the palm of the hand and, after 
 throwing it out, noticing the amount of dust left in the hand. 
 The cleanness of sand may also be judged by pressing it to- 
 gether between the fingers while it is damp; if the sand is 
 clean, it will not stick together, but will immediately fall 
 apart when the pressure is removed. 
 
 Gravel is an accumulation of fragments of stone, or small 
 
 stones, varying in size from a pea up to an egg. It is often 
 
 _ , intermixed with other substances, such as sand, 
 
 Gravel. . . . 
 
 clay, loam, etc., from each of which it derives 
 
 a distinctive name. 
 
 As a rule, gravel is unserviceable for roadmaking, mainly 
 
 due to the smoothness of the surface of the pebbles, preventing 
 
 their binding together in the manner of broken stone. There 
 
 is also an absence of dust or other cementing material, and even 
 
 if such binder is furnished it is difficult to effectively hold the 
 
 rounded and polished surfaces of the pebbles together. 
 
 At the present time there should be no difficulty in de- 
 termining the relative values of stones for road 
 
 Free purposes in any locality. The Office of Public 
 
 ment tests ^^ads, of the United States Department of Agri- 
 culture, undertakes to make tests and analyses of 
 
 samples of stones, without charge, and to give advice as to 
 
 their value for roadbuilding purposes. 
 
CHAPTER VII 
 EARTH, GRAVEL, SAND AND CLAY ROADS 
 
 Earth Roads 
 
 The term "Earth Roads" includes all those constructed of 
 natural soil, whether loam, clay or sand, without a crust or 
 other road covering. The earth road is the cheapest form 
 of road as regards first cost, and is generally the pioneer in 
 any new country. In its simplest form it consists of dirt 
 from the sides, simply thrown up into the center, with little 
 or no regard for the formation of a crown for the lateral 
 shedding of rain-water. The bulk of the country roads of 
 America are made of earth alone, and as a well-made earth 
 road forms an excellent foundation for a graveled or a broken- 
 stone road, and its construction is in many cases preparatory 
 to a more permanent improvement, the importance of scien- 
 tific design and construction will be easily seen. 
 
 Fig. 79. — Earth Road With Flat Surface, as ordinarily constructed. 
 
 If, as is often done, the loose earth be thrown into the 
 middle of the road to be compacted by the wheels of the traffic, 
 the action of the wheels will be to cut it, or at least to pack 
 it in a very uneven manner, producing a surface uneven and 
 full of ruts, which will hold water and ultimately cause the 
 destruction of the road. In case, however, the surface be 
 properly rolled, it may usually be made sufficiently firm to 
 hold up the wheels and retain its form under the traffic, and 
 if kept free from ruts until thoroughly compacted will thus 
 be rendered much more capable of resisting the penetration 
 of water and shedding it into the side gutters. 
 
 117 
 
118 
 
 THE ART OF ROADMAKING 
 
 The first step in the construction of a new earth road in 
 most localities is to clear the surface over the entire width 
 
 of all stumps, brush, vegetable matter^ rocks, and 
 The first boulders. These should be removed and the 
 struction resulting holes filled in with suitable materials 
 
 thoroughly tamped or rolled, before the road 
 embankment is commenced. No perishable material should 
 be used in forming the permanent embankment. 
 
 Fig. 80. — Proper Cross-section for Road in Loamy Soil. Crown 1 inch 
 
 per foot. 
 
 Fig. 81. — Proper Cross-section for a Clay Road. Crown 1^ inches per 
 
 foot. 
 
 Fig. 82. — Cross-section of Road as usually left by the grader, with the 
 last cut of the blade at 2. It should have been left as in Fig. 81, 
 with the last cut of the grader blade in position 1. 
 
 ht- Travel ---Ol^ Mo Trdvcl 
 
 Fig. S3. — Cross-section of Road Graded Too Wide, with a pile of loose 
 dirt and sods in the center. The travel naturally takes the sides 
 where the earth has been scraped off by the grader. 
 
 In a wet district or where the soil is naturally damp the 
 trees and scrub should be cleared the full width of the right- 
 of-way to allow of proper evaporation, but in hot and dry 
 districts, where the comfort of travelers must be considered, 
 it is well to leave growing trees on each side of the roadway. 
 
 Whenever the subgrade soil is found unsuitable it should 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 119 
 
 be removed and replaced with good material rolled to a 
 bearing. The roadbed having been brought to the 
 required grade and crown, should be rolled several f^^^Jh h° 
 times to compact the surface and all irrequalities 
 leveled up and re-rolled. On this prepared subgrade the 
 earth should be spread, harrowed, if necessary, and then 
 rolled to a bearing by passing the road roller a number of 
 times over every portion of the surface. 
 
 In level countries and with narrow roads enough material 
 can generally be excavated in forming the side ditches to raise 
 the roadway above the subgrade. If not, the re- 
 quired earth may be obtained by Avidening the Preparation 
 side excavations, or from cuttings on the line gm-face 
 of the new roadway, or from borrow-pits close 
 by. When the earth is brought up to the final height it is 
 again harrowed, then trimmed by means of road levelers or 
 road machines, and ultimately rolled to a smooth and solid 
 surface, the cross-section of the roadway being maintained 
 during the last rolling stage by the addition of earth as needed. 
 Before the earth road is opened to traffic, the side ditches 
 should be cleaned and left with the drain tiling in good working 
 order. 
 
 On account of the loose character of the material, earth 
 roads require most careful design in order that the road may 
 be kept dry. Water is the great destroyer of earth 
 roads, and drainage is especially important in their ^^ ^ ' 
 proper making and maintenance because the material of the 
 roadway is more susceptible to the action of the water and 
 more easily destroyed than any other material used in the 
 construction of roads. If not properly drained the rain and 
 snow soften it and it soon becomes impassable mud. If, on 
 the other hand, water is allowed to run on the road surface, 
 it will soon wash away the earth and form gullies. 
 
 As stated in Chapter V, the prime necessity of every road is 
 thorough drainage; without it, the road cannot long remain 
 intact. In the construction of earth roads it is, in fact, the 
 most important matter to be considered; drainage alone will 
 often change a bad earth road to a good one, and the best 
 
120 THE ART OF ROADMAKING 
 
 road may be quickly destroyed by the absence of proper 
 drainage. 
 
 Side ditches are provided for country roads in most cases; 
 but these are often imperfectly made, and even the best 
 side drahis are usually inadequate to relieve the road from 
 its soggy, impassable condition. Nothing brings relief except 
 the slow process of evaporation, and even when a road is 
 dried by the sun and wind it is generally left in a rough, 
 rutty condition. 
 
 With wet or claye}^ roadways surface drainage alone 
 is not sufficient. Without underdrainage the crown of such 
 roadways will dry only by the action of the sun, during which 
 time the topping becomes more and more rutted by the passing 
 traffic. A subdrain in such soils will not prove efficient for 
 more than about 12 feet on each side; hence, two lines of 
 longitudinal subdrains are needed on those roads that pass 
 through wet places, low-lying lands, or clayey soils. They 
 should have an average fall of about 1 in 100, with a minimum 
 of 1 in 1000. At short intervals of about 36 to 100 feet 
 apart, are placed cross drains to discharge the water into the 
 side ditches, which may have a fall up to 1 in 30. It is 
 advantageous to bed these tiles in well-rammed brick frag- 
 ments and to cover them with stone, taking care that nothing 
 interferes with their free discharge. The bottom of the tiles 
 should be laid both to the proper grade and below the frost 
 line, after which the tile trench is filled up to subgrade with 
 clean gravel, small stones, or broken stone or bricks. The 
 cross drains should be made of unglazed tiles, with outlet 
 sections of vitrified culvert pipes. Regular branch pipes 
 should connect the longitudinal and cross tiles. On level 
 reaches the lateral roadway slopes for surface drainage should 
 not be less than 1 in 24, and side ditches should be provided, 
 when necessary. A rapid discharge of the side ditches is of the 
 utmost importance to roadway preservation. 
 
 Too many trees should not be allowed on the sides of dirt 
 roads, because they impede the drying action of the sun and 
 wind, and their water-seeking roots are apt to creep into 
 the drains and thus obstruct or prevent the junction of the tiles. 
 
EARTH. GRAVEL, SAND AND CLAY ROADS 121 
 
 The water having been taken from under the road and off 
 the road it is next necessary to carry it across and away from 
 the road by proper culverts. These should be put 
 in at every point that water can be carried away 
 from the road by natural channels, and their location will be 
 regulated by the position of these channels. Probably in no 
 way is more money wasted in road work than in the building 
 of cheap and temporary culverts. Nothing but the best 
 should be built even if something else must be sacrificed. 
 (See Chapter V.) 
 
 The great point in having good roads is the care of them 
 
 after they are made. It is absolutely necessary in order to 
 
 have good roads that it must be the constant 
 
 duty of someone to look after them after the road ^!° enance 
 
 ... . . £ina repair. 
 
 is built; especially durmg and foUowmg a rain, 
 
 that water may be kept off as far as possible. 
 
 Dirt roads are readily repaired by a judicious use of road 
 machines and road rollers. Ploughs and scoop scrapers should 
 should not be used for this purpose, as they would loosen the 
 portion of the road that was already consolidated by the 
 traffic. Repairs should be attended to, particularly in the 
 spring of the year, and whenever the roadway becomes rutted. 
 
 Any small breaks in the surface must be immediately 
 repaired and ruts filled and smoothed before they become 
 serious. 
 
 The work required to keep a road in repair depends upon 
 the nature of the surface and the efficiency of the drainage. 
 A well-constructed road of good material will be much easier 
 and less expensive to keep in repair than one in which the 
 surface is not firm enough to resist the cutting action of the 
 traffic, or which has a surface of material readily softened by 
 the action of water which may fall upon it. 
 
 Earth roads under the most favorable conditions are expen- 
 sive to maintain, and especially so under the common system 
 of repairing once or twice a year, or at long intervals. This 
 system is not only costly in the work required, which usually 
 amounts to a practical reconstruction of the road each time 
 repairs are undertaken, but it is ineffectual in that the road 
 
122 THE ART OF ROABMAKING 
 
 for the larger portion of the thne is out of repair and in bad 
 condition, even if the work of construction has been well 
 done, which is not usually the case where this method obtains. 
 
 The only way to keep an earth road in good condition is 
 by the employment of men whose business it shall be to con- 
 tinually watch the road, and make such small repairs as may 
 be necessary from time to time. The small washes that may 
 occur during heavy storms, ruts formed by wagons traveling 
 in the same tracks, or in passing over soft spots when the 
 road is wet, or any small breaks in the surface of the road, 
 should be at once attended to and carefully filled with new 
 material. 
 
 When there are long-continued rains, or when the ice and 
 snow of winter are melting in the spring, an earth-road surface 
 will necessarily be more or less softened and cut by passing 
 vehicles; and at such time a road of this character cannot be 
 maintained in the same condition as in dry weather, or in the 
 condition which would be possible with a less permeable 
 surface, but if at the beginning of the wet period it be in 
 proper form and if the drainage be efficient^ the injury to the 
 road, as well as the duration of the bad condition, wiU be 
 reduced to a minimum. As soon as possible after such a wet 
 period, the roads should be gone over with the scraper, or a 
 "split-log drag." This should be done before the ground 
 becomes thoroughly hard and dry, as it will work more freely, 
 and may be compacted much closer than afterward. 
 
 The difficulty in the cost of maintaining the road will of 
 course vary with the nature of the traffic that passes over it. 
 A road for light driving will be much easier to keep in repair 
 than one used for heavy loads, and as the amount of heavy 
 traffic becomes greater, the economy of the earth surface is 
 lessened, and the desirability of the substitution of a more 
 durable wearing surface increases. 
 
 The width of the wheel tires upon which the loads are 
 carried is also important in its effect upon the cost of keeping 
 a road in repair. Narrow tires cut and rut the surface of a 
 road, while those of sufficient width act as rollers to compact 
 the material. 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 123 
 
 Gravel Roads 
 
 Gravel furnishes a very acceptable substitute for stone as a 
 material for the construction of roads with a moderate 
 amount of travel, and, when well constructed, a gravel 
 road is a satisfactory one. It has to commend it its ease 
 of laying and ease of repair, but it has not the durable 
 qualities of a good broken-stone road when subjected to heavy 
 travel. 
 
 Gravel roads may be roughly subdivided into two classes: 
 
 1. Those made of gravel which has been crushed and screened 
 in the same manner as stone. This class of road is con- 
 structed exactly like a stone road under the same condi- 
 tions, as described in Chapter VIII. 
 
 2. Those made of gravel which is used practically as it 
 comes from the pit. 
 
 Gravel roads can be constructed, as they most often are, 
 by simply dumping the unscreened gravel on the road and 
 letting the traffic do the rest, but this is a poor and expensive 
 method. They can be made by spreading the gravel in one 
 course only, but so made are not satisfactory or lasting. To 
 make a really satisfactory and economic gravel road, the 
 gravel should be much the same size as is the stone used for 
 stone roads, and should be spread in two courses of not over 
 6 inches each, and rolled with a 7- or 10-ton roller. 
 
 Gravel to be used on roads should be sharp and compara- 
 tively clean. If it runs very unevenly in the pit it should 
 be screened; the material not going through the 
 
 • . Gr3.vfil 
 
 1^-mch screen bemg used for the first course and 
 that going through for the second. Even if the gravel runs 
 evenly there will always be some large stones and these should 
 be thrown out. No stone larger than 3 or 4 inches should be 
 allowed in the road even in the first course. 
 
 After screening, the sand or clay left in the gravel should 
 be no more than just enough to fill the voids in the stone, 
 and the less it takes to do this the better the gravel is for 
 road purposes. After spreading, the gravel should be gone 
 over once or twice with a harrow to mix it thoroughly and 
 
124 
 
 THE ART OF ROADMAKING 
 
 to get rid of small pockets of sand or dirt, which, however, 
 can often be prevented by careful selection in the pit. 
 
 Fig. 84. — Gravel Road in Ohio; Dries Quickly After a Rain. 
 
 There are a few pits from which very satisfactory gravel 
 roads can be built by using the gravel just as it occurs without 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 
 
 125 
 
 screening or crushing. A community that has such material 
 is blessed above all others. Even the best of material, how- 
 ever, must be properly laid and rolled if permanent and 
 economical results are to be secured. It does not pay to 
 throw gravel or stone on the road in the old slipshod way. 
 The subgrade should be prepared in the same way as for 
 
 Fig. 85. — A Gravel Road under Construction in the Old Way. The 
 gravel is spread but no shoulders have been made to hold it, and no 
 attempt is made to get gravel of an even quality. Such a road soon 
 wears into holes which must be filled before the road is in good 
 condition for travel. 
 
 First 
 course. 
 
 crushed stone. Material for the first course should consist 
 
 of gravel of 1^- inch to 3^ inches diameter and not 
 
 more than 30 per cent of material less than IJ 
 
 inches in size. This should be spread evenly and 
 
 rolled and finished in the same manner as the first course of 
 
 stone. If it does not consolidate add more clay and roll 
 
 again until it is firm and hard with an even cross slope. 
 
 The second course of gravel should consist of the gravel 
 and sand passing the 1-^-inch screen, and should contain not 
 
126 THE ART OF ROADMAKING 
 
 over 20 per cent of sand or clay. This should be spread 
 
 evenly to 1^ times the depth required, and harrowed 
 
 ^^^^ and raked until uniformity in the mixture is secured ; 
 
 course. . *^ . ' 
 
 then rolled until the whole is firm and hard, clay 
 being added when necessary to make the gravel compact. 
 
 Uncrushed gravel needs no third or binder course, and when 
 the second course is rolled thoroughly and is smooth and hard 
 it is ready for travel. 
 
 Sandy Roads 
 
 There are many miles of sandy roads in different parts of 
 the country, and the remarks as to drainage, shaping, etc., 
 do not apply to them in their natural condition. The wetter 
 they are kept the better they are. Sand; when confined, will 
 support almost any weight, the objection' to sand alone; as a 
 road material lying in the total absence of any binding or 
 cementing qualities. Sandy roads are good only when damp. 
 It is useless to form or crown sand roads, as they do not 
 require drainage. They should be made either flat, or lower 
 in the center than at the sides, and trees and undergrowth 
 should be allowed to grow as near the road as possible, as 
 they help to retain the moisture. For temporary improve- 
 ment of sandy roads a layer of cut straw, leaves, shavings, 
 hay, bark, sawdust or any material that will accumulate and 
 retain moisture and offer some resistance to the wheels, is of 
 benefit, but for a semi-permanent improvement clay should 
 be mixed with the sand in proper proportions, making a sand- 
 clay road. 
 
 Clay Roads 
 
 The clay road in contrast to the sandy one, needs all the 
 drainage and crown possible. Care should be taken to give 
 a clay road a steeper cross slope, to make the ditches wide, 
 to keep them open and clean, and to underdrain spots where 
 the road is especially bad. These are the first essentials, but 
 even with these precautions a clay road will never be a good 
 road at all times unless it is treated with sand or dragged 
 with a split-log drag. 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 127 
 
 Sand-Clay Roads 
 
 In some sections of the country sand and clay are the only 
 road materials available, and while neither of these materials 
 alone makes satisfactory roads, a proper combination of the 
 two, with thorough drainage and suitable crown, will produce 
 satisfactory results. Natural sand-clay roads may frequently 
 be found in localities -where the soil contains the right pro- 
 portions of sand and clay. In sections of the country where 
 the prevailing subsoil is composed entirely of clay, or, on the 
 other hand, is of an extremely sandy character, these materials 
 may be mixed in such proportions so as to overcome the most 
 objectionable features of each. The mixing of sand and clay 
 as a form of road construction has received careful study 
 and is of great importance, especially to the Atlantic and 
 Gulf States, Avhere throughout large areas sand and clay 
 are practically the only materials available for road build- 
 ing. 
 
 The essentials to success in this form of road ^ ssentia s 
 
 to success. 
 are puddling and saturation. ' The clay must be 
 
 rendered homogeneous by adding water until it is plastic 
 like dough; and to this plastic 
 clay, sand must be added to 
 the point of saturation, but 
 not beyond. What is meant 
 by saturation may be clearly 
 understood by reference to 
 Fig. 86, which shows a mag- 
 nified cross-section of sand- 
 clay composition as found 
 in a substantial sand-clay 
 road. 
 
 No sand-clay road can sat- 
 isfactorily withstand the Fig. 86. — Clay Mixed with Sand to 
 severity of public travel with- the Point of Saturation, the angular 
 out having first been reduced ^^^^^ ^'^^' ^^^^ ^^ *=^^^^«^- 
 to a compact homogeneous mass of sand and clay, in which 
 each grain of sand should be in touch with other grains on 
 
128 
 
 THE ART OF ROADMAKING 
 
 all sides. Such a condition is secured only by a thorough 
 
 mixing of the wet clay and 
 sand, and rolling as the mix- 
 ture dries. This forces the 
 particles of sand together, and 
 any excess of clay tends to 
 rise to the surface, which must 
 in turn be sanded and the 
 operations repeated until the 
 surface has become hard and 
 compact, and free from clay- 
 stickiness. 
 
 Sand-clay roads fail for 
 various reasons. Imperfect 
 drainage is the first cause. 
 The imperfections may be in 
 
 the cross-sectional drainage, the side ditches, or the drain- 
 age of the subgrade or roadbed. It is cus- 
 tomary to give to a sand-clay road a little greater 
 crown than is usually given to a macadam road, 
 
 Fig. 87. — Sand-clay Mixture with 
 not enough Sand, the grains not 
 being in contact. 
 
 Causes of 
 failure. 
 
 especially where the grade 
 subject of side ditches should 
 have more careful considera- 
 tion than is usually given in 
 case of macadam roads. 
 
 If the subsoil is clay, the 
 bottom of the side ditches 
 should be 18 inches or more 
 below the crown, but if the 
 land is rolling and the subsoil 
 is sand of considerable depth, 
 there is natural drainage and 
 little or no side ditch will be 
 required. Perhaps the most 
 common error in drainage 
 is the failure to drain 
 
 above 
 
 cent. The 
 
 Fig. 88. — Unsatisfactory Sand-clay 
 Mixture, the sand grains being 
 worn round. 
 
 properly and thoroughly all places where there are wet- 
 weather springs. If necessary, the roadbed must be changed 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 129 
 
 SO as to locate it upon dry gound, as even the deepest side 
 ditches practicable may fail to give relief where such springs 
 exist. It is important to avoid deep cuts and to carefully 
 consider all probable sources of trouble. Water, beyond a 
 very limited amount, adds nothing of value to the sand-clay 
 road after it is completed. If water is always present, sand 
 should be used without clay^ as sand and water make a better 
 road than sand and clay and water. 
 
 ,.--^SoC%^O^SC)^"StE^~>^^ 
 
 Fig. 89. — Cross-section of Road, showing lumps of clay placed on a sand 
 subsoil and covered with sand. 
 
 Another cause of failure is the want of thorough mixing 
 of even the proper proportions of sand and clay. Clay in 
 lumps is useless; it should be uniformly saturated with sand 
 to a depth of 10 inches. When ridges and holes appear, the high 
 places should be leveled down and the holes filled in with sand. 
 
 In northern sections frost is another cause of failure and a 
 
 ^'-^^^^s##^-~... 
 
 Fig. 90.— Cross-section of Road, showing displacement of lumps of clay 
 when subjected to travel. 
 
 difficult one to deal with. It is temporarily destructive and 
 for that reason the mixture must extend below the frost-Hne 
 if the road is built on a clay foundation. Freezing disinte- 
 grates the sand-clay composition and makes of it a soft, slushy 
 mud, which, however, repacks again after each heavy rain, 
 although, as a rule, leaving the road surface somewhat rough. 
 
 Failure is sometimes due to the kind of sand selected. None 
 except sand made up of angular grains is adapted to sand-clay 
 road making. Sand with grains which are worn off round, 
 or sand which has been ground up by the action of wheels 
 or water until very fine, is unsatisfactory and often worthless. 
 The use of such material should be avoided, as a perfect bond 
 can not be effected (Fig. 88), and the road can not resist the 
 
a. Typical Clay Road Before Improvement. 
 
 b. Sand-clay Road in Process of Construction, Gamesville, Fla. 
 
 c. Finished Sand-clay Road, Columbia, S. C. 
 
 Fig. 91. Sand-clay Roads. 130 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 131 
 
 rolling action of wheels, the tendency being much the same as 
 when pressure is applied to a mass of marbles. 
 
 Other causes of failure are the improper selection of clay 
 and the improper treatment of the clay used. Ferruginous 
 clays are the best, and chalky clays are the worst for road- 
 building purposes. Some clays have a large percentage of 
 sand to begin with and require less sand, while as a rule the 
 chalky (sedimentary) clays have very little or very fine 
 sand, and are more difficult to get fully saturated with 
 sharp sand so as to become unyielding and homogeneous. 
 
 Another cause of failure in the use of this particular clay is 
 the fact that it rarely has iron enough to cement or bind the 
 material together; hence it is easily broken up and washed 
 away or blown away as dust. There are many localities, 
 especially in the South, where sand predominates, and the 
 only clays to be found are sedimentary, often carrying a 
 large percentage of very fine sand and scarcely any iron at 
 all. It is difficult to build a first-class road of this material; 
 but the first step should be to make the roadbed at least 20 
 inches above standing water in the ditches. 
 
 Lack of perseverance by the road builder is another cause 
 of failure, and probably more failures result from this than 
 from any other cause. The building of a sand-clay road is 
 a process, not an instantaneous operation, and the builder 
 may fail when well within view of success. 
 
 The building of sand-clay roads has passed the experimental 
 stage, and it is no longer a question of doubtful procedure. 
 The important things to be borne in mind are as stated, thorough 
 mixing to the saturation point, and then properly shaping 
 and rolling the road. This mixing might be done by the use 
 of plows and harrows when the clay is wet; but it is customary 
 to let the teams and vehicles of the traveling public accomplish 
 it. This is the critical period in the construction of a sand- 
 clay road, because care must be taken to secure an even 
 amount of puddling, so that all the lumps of clay shall be broken 
 and saturated with sand to a depth of 8 to 10 inches. If this 
 can be done and the road is properly crowned as it dries, the 
 result will be satisfactory. 
 
132 THE ART OF ROADMAKING 
 
 It is, of course, impossible to state definitely the cost of this 
 form of construction, as it will be found to vary with the 
 Cost of price of labor, the length of haul, the width of 
 
 sand- roadway, and depth and nature of material. If 
 
 clay con- however, the clay can be procured within a mile of 
 the road which is to be improved, and the cost of 
 labor is about $1 per day and teams $3 per day, the cost of 
 constructing a 12-foot sand-clay road on a sand foundation, 
 covered with clay to an average depth of 6 inches, would be 
 approximately as follows for a distance of 1 mile: * 
 
 Crowning and shaping road with road machine, using 2 teams at 
 
 $3 and 1 operator at SI. 50 per day for 1 day S7.50 
 
 Loosening, 1173^ cubic yards of clay with pick and shoveling into 
 
 wagons, at 15 cents per cubic yard 176 . 00 
 
 Hauling 1173^ cubic yards of clay, at 23 cents per cubic yard. . . . 269.86 
 Spreading clay with road machine, using 2 teams at $3 and expert 
 
 operator at $1.50 per day for 3 days 22 . 50 
 
 Shoveling sand on clay, estimated at I cent per square yard 35 . 20 
 
 Plowing, using 1 team at $3 per day for 4 days 12 . 00 
 
 Harrowing, using 1 team at $3 per day for 2 days 6 . 00 
 
 Shaping and dressing with road machine, using 2 teams at $3 and 
 
 expert operator at $1.50 per day for 2 days 15.00 
 
 Rolling, estimated at I cent per square yard 35 . 20 
 
 Total .$579.26 
 
 The estimated cost per square yard of road surface, therefore, 
 when computed on the basis of this table, would be about 
 8 cents, or at the rate of $579.26 per mile. 
 
 The cost of building a sand-clay road on a clay foundation 
 would not vary much from the figures given. The latter form 
 of construction would probably be slightly cheaper, by reason 
 of the fact that sand can be handled more economically than 
 clay. 
 
 According to the experience of the Office of Public Roads, the 
 cost of sand-clay construction in the South has been found to 
 range from $200 to $1200 per mile, in most cases running from 
 $300 to $800. In case changes of grade have to be made 
 with consequent cuts and fills, the cost would be proportionately 
 greater than the figures given above, but there can be no 
 
 * Office of Public Roads Bulletin, No. 27. 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 133 
 
 question, that under all circumstances this form of construction 
 is cheaper than macadam. 
 
 Burnt-Clay Roads 
 
 In some sections of the country the only material available 
 from which roads can be constructed is clay. This is especially 
 the case in large areas in the South, where there is little or no 
 sand and the clays are of a particularly plastic and sticky 
 variety, locally known as ''gumbo'' and ''buckshot." In such 
 localities traffic is absolutely impossible during the wet 
 season, as the wheels of heavy vehicles will sink to the hub. 
 To meet this condition the U. S. Office of PubHc Roads made 
 an experiment in the district of the lower Mississippi Valley, of 
 burning the clay along the entire length of the road. By 
 burning clay, even at a moderate heat, its sticky or plastic 
 quality is destroyed, so that even in the wettest weather 
 it will bear traffic. It was found by laboratory experiments 
 that the clinkering point of the clay was sufficiently low to 
 indicate that simple burning of the lumpy clays upon the 
 road surface by means of open wood fires would accomplish the 
 desired result. This permits the firing of the clay along the 
 entire length of the road, thus avoiding the cost of hauling 
 it, and at the same time gaining the advantage of burning the 
 foundation of the road as well as the material to be placed 
 upon it. 
 
 Gumbo clay is black, owing to the high percentage of organic 
 or vegetable matter it contains. It is particularly sticky 
 in its nature, and is almost wholly free from sand and grit. 
 After it has been burned, however, the plasticity is entirely 
 destroyed,, and a light clinker is formed which, though not 
 particularly hard, whQii pulverized forms a smooth surface 
 and seems to wear well. It is not necessary that all of the 
 clay out of which the road is to be constructed should be 
 clinkered, but only a sufficient amount should be rendered 
 nonplastic to neutralize the too sticky character of the native 
 clay. 
 
 Good sound wood, as dry and well seasoned as it is possible 
 
134 
 
 THE ART OF ROADMAKING 
 
 a. Pile of Wood and Clay Completed and Firing Begun. 
 
 h. Section of Road Burned. 
 Fig. 92. — Burnt-cla.y Roads. 
 
EAKTH, GRAVEL, SAND AND CLAY ROADS 
 
 135 
 
 c. Partial View of Finished Road. 
 Fig, 92. — Bttrnt-clay Roads. 
 
 Fuel. 
 
 to procure^ is stacked at convenient intervals along the side of 
 the road before the work is commenced. About 
 one cord of wood is necessary for 8 linear feet of 
 roadbed 12 feet wide. Brushwood, if it is dry, as well as chips, 
 bark, old fence rails and railroad ties, coal slack — in fact any 
 sort of fuel that can be easily and economically obtained, 
 may be used to advantage with the cord wood. 
 
 After grading the road to an even width between ditches, 
 it is plowed up as deeply as practicable. Furrows are then 
 dug across the road from ditch to ditch, extending 
 through and beyond the width to be burned; if Preparation 
 it is intended to burn 12 feet of roadway, the trans- j-oadbed 
 verse furrows should be 16 feet long, so as to extend 
 2 feet on each side beyond the width of the final roadway. 
 Across the ridges formed between these furrows, which should 
 be about 4 feet apart, the first course of cordwood is laid 
 longitudinally so as to form a series of flues in which the firing 
 is started — from 15 to 20 of these flues are fired at one time. 
 
 The best and soundest cordwood is selected for this course 
 and should be laid so that the pieces will touch, thus forming 
 
136 THE ART OF ROADMAKING 
 
 a floor. Another layer of wood is thrown irregularly across 
 this floor, in crib formation, with spaces left between in which 
 the lumps of clay are piled in such a way as to allow a draft 
 for easy combustion. 
 
 After the lumps of clay have been heaped upon this floor, 
 another course of wood is laid parallel to the first. The third 
 layer is laid in exactly the same manner as the first, and each 
 opening and crack should be filled with brush, chips, bark,, 
 small sticks, or any other combustible material. The top 
 layer of clay is placed over all and the finer portions of the 
 material are heaped over the whole structure. ' 
 
 The deep covering of clay which is thrown over all should be 
 taken from the side ditches, and may be in lumps of all sizes, 
 including the very finest material. It is spread as evenly as 
 possible over the top in a layer of not less than 6 to 8 inches. 
 Finally the whole is tamped and rounded off so that the heat 
 will be held within the flues as long as possible. 
 
 It is necessary to get the fires well under way in the flues 
 before the first layer of wood is burned through. The first 
 action of the fire is to drive out the water contained in the 
 clay before the actual burning and clinkering can begin. In 
 burning the gumbo clays a great advantage is gained from 
 the organic and vegetable matter which is contained in the 
 clay, as that in itself aids combustion. 
 
 The best results are obtained by firing all the flues of a section 
 
 simultaneously and maintaining the combustion as evenly as 
 
 possible. A supply of light, dry, kindling wood, 
 
 or any easily inflammable material, should be at 
 
 hand to prevent the fire from dying down in any one 
 
 place. 
 
 After the firing is completed not only the portion of clay 
 which forms the top of the kiln, but the ridges between the 
 flues should be burned thoroughly, so as to form a covering of 
 burnt clay 10 to 12 inches in depth, which, when rolled down 
 and compacted, forms a road surface of from 6 to 8 inches in 
 thickness. If properly burned, the material should be entirely 
 changed in character, and when it is wet it will have no tendency 
 to form mud. 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 137 
 
 When the material is sufficiently cooled the roadbed should 
 be brought to a high crown with a road grader in order to 
 allow for the compacting of the material. After this the rolling 
 should be begun and continued until the roadbed is smooth 
 and hard. The finished crown should have a slope of at least 
 one-half inch to the foot. 
 
 The main advantages of this method of burning a road over 
 its entire length are, first, that the cost of transporting the clay 
 is avoided; second, that the subgrade of the road is burned as 
 well as the material above. 
 
 Although this form of construction in the South up to the 
 present time has been successful, it cannot as yet be said to 
 have passed the experimental stage, so that the cost ^ . r 
 figures which will apply to the same work in all burnt-clay 
 sections of the country cannot be given. The construc- 
 items of cost of the experimental road 300 feet ^°^' 
 long, as constructed at Clarksdale, Miss., are as follows: 
 
 30^ cords of wood at $1.30 per cord $39.65 
 
 20 loads of bark, chips, etc 6 . 00 
 
 Labor at $1.25 per day and teams at $3 per day 38 . 30 
 
 Total cost of 300 feet 83.95 
 
 Total cost per mile at this rate 1478 .40 
 
 TOOLS USED IN CONSTRUCTION OF COUNTRY ROADS 
 
 Tools for Clearing and Grubbing 
 Bush hooks (Fig. 93). 
 Axes. 
 Grub hoes. 
 
 Mattocks (Fig. 94 and 95). 
 Stump-pulling machine. 
 Gross-cut saws. 
 
 Tools for Grading 
 
 Picks. 
 
 Grading pick (Fig. 96). 
 
 Clay pick (Fig. 97). 
 
 Shovels. 
 
 Ploughs (Fig. 98). 
 
138 
 
 THE ART OF ROADMAKING 
 
 Fig. 113. — Bush-hooks. 
 
 Fk;. !I4.— Axo Mattock. 
 
 Fig. 9.3.— Pick Mattock. 
 
 Fig. 1)0. — ( JraJing-pick. 
 
 Fig. 97. — Ckiy-pick. 
 
 Fig. 9s. ^Hard-pan Plough. 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 139 
 
 There are many forms of ploughs, known as '^ grading 
 ploughs," "road ploughs/' ''breaking ploughs," ''hardpan 
 ploughs/' "township ploughs/' etc., varying in construction 
 
 Fig. 99. — Roadscraper. 
 
 according to the kind of work they are intended for, such as 
 loosening earth, gravel, hardpan, etc. 
 
 Wheelbarrows (Fig. 100). 
 Scrapers (Fig. 101-103). 
 
 These are made of wood or pressed steel and are employed 
 in moving earth short distances, in maintenance and street- 
 
 FiG. 100.— Dirt Wheelbarrow. 
 
 cleaning work. The maximum distance to which earth can 
 be wheeled economically in barrows is about 200 feet. 
 
140 
 
 THE ART OF ROADMAKING 
 
 Scrapers 
 
 Scrapers are generally used for moving material after it 
 has been loosened by ploughing. The two principal varieties 
 are the drag and the wheel scraper. 
 
 Drag Scraper. — The scoop (Fig. 101) is made in three sizes, 
 3 and 7 cubic feet capacity. Some have metal runners on 
 
 Fig. 101. — Drag-scraper. 
 
 the bottom, others have a double bottom, which decreases 
 draft and increases durability. Used for moving earth short 
 distances, but unsuitable for building a bank of uniform 
 
 Fig. 102. — Drag-scraper -with. Runners. 
 
 solidity or for finishing an embankment, as each scraperful 
 is deposited in a compact mass and the surface made with 
 it is a succession of lumps and hollows. Sometimes used for 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 
 
 141 
 
 loading wagonS; by means of an elevated platform and an 
 excavated runway.. 
 
 Flat-bottomed Pole or Tongue Scraper. — Made in two 
 sizes, 36 and 48 inches wide. Used for leveling up the road 
 surface in excavations, and in preparing the subgrade for 
 pavements. 
 
 Buck Scraper. — Made in three sizes, 3^, 4, and 5 feet 
 wide, with capacity of 8, 10, and 12 cubic feet, respect- 
 ively. An improvement over the common scoop scraper, 
 
 Fig. 103.— Wheel Scraper. 
 
 having the advantages of being more readily loaded to its 
 full capacity, a better and more uniform distribution of the 
 of the earth, more durable and more easily loaded. 
 
 Wheel Scrapers (Fig. 103) consist of a steel box mounted 
 on wheels and furnished with levers for raising, lowering, and 
 dumping, all movements being made without stopping the team. 
 Made in three sizes, with capacities of 9, 12, and 16 cubic feet. 
 
 Road Graders. — This is one of the various forms of road 
 machines. It is also known as the "scraping grader" (Fig. 99), 
 to distinguish it from the "elevating grader," and is a very 
 important factor in the construction and maintenance of earth 
 roads. It consists of a frame carried on four wheels, support- 
 
142 THE ART OF ROADMAKING 
 
 ing an adjustable scraper-blade, the front end of which ploughs 
 a furrow while the rear end pushes the earth toward the center 
 of the road or distributes it uniformly to form a smooth surface. 
 The blade is adjustable backward and forward and to any angle 
 or height. It will work in almost any soil. It is hauled by 
 horses and makes successive rounds or cuts until the desired 
 depth of ditch and crown of road is obtained. There are 
 several forms of the machine, differing in minor details, but 
 all are intended for practically the same purposes. 
 
 Elevating Grader, consists of a frame carried on four 
 wheels, from which is suspended a plough and a frame carry- 
 ing a wide traveling inclined belt. The plough loosens 
 the soil and throws it upon the belt, which delivers it upon 
 the embankment or into wagons. The machine is adjustable 
 and is made in two sizes, delivering earth from 7 to 8 feet ver- 
 tically and 14 to 22 feet horizontally. 
 
 It is a very effective machine for building open ditches, 
 earth embankments, filling of wagons, and for highway work. 
 By proper adjustment the machine will build broad and 
 low or narrow and high embankments or will excavate a deep 
 and narrow or a shallow ditch. 
 
 The larger machine will place 1000 cubic yards of earth in 
 an embankment in ten hours, or will load 600 cubic yards 
 into wagons in the same time. It is propelled by twelve 
 horses, eight in front and four behind, or by a traction engine, 
 and is operated usually by three men. 
 
 The smaller machine will grade a quarter of a mile of 
 ordinary unbroken road per day, with a width of 25 to 30 
 feet and a crown of 12 inches at the center. It is drawn by 
 eight horses and operated by two men. 
 
 These machines are specially adapted to building earth roads 
 in a prairie country, for which purpose they are very largely used. 
 
 Carts. — These carts are furnished with wide tires and the 
 body is so balanced that the load is evenly divided above the 
 axle. The average capacity is 22 cubic feet and the average 
 weight, about 800 pounds. 
 
 Dump Cars. — Made to dump on one or both sides or ends, 
 and at the bottom. They are used singly or in trains, according 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 143 
 
144 
 
 THE ART OF ROADMAKING 
 
 to the magnitude of the work, and are drawn by horses or 
 tractors. 
 
 Dump Wagons. — The use of these wagons for moving 
 excavated earth, etc., and for transporting sandj gravel, and 
 other materials, materially shortens the time required for 
 
 NoJ. 
 
 No.7> 
 
 Fig. 105. — Draining-tools. 
 
 No3. 3, 4, and 5, used for digging the ditch; Nos. 6 and 7 for cleaning and rounding 
 the bottom of the ditch for round tile. No. 2 for shoveling out loose earth and leveling 
 the bottom of the ditch; No. 1 for the same purpose when the ditch is intended for 
 "sole" tile. 
 
 unloading over that required by the ordinary form of con- 
 tractor's wagon. They are operated by the driver and have 
 a capacity of from 35 to 45 cubic feet. 
 
 Surface Grader. — Is operated by one horse and is used for 
 removing earth previously loosened by the plough. It is also 
 used to level off and trim the surface after scrapers. 
 
 Road Leveler. — Is used for trimming and smoothing 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 145 
 
 the surface of earth roads and is largely employed in the 
 spring when the frost leaves the ground. 
 
 Draining Tools. — These are used for digging the ditches 
 and sloping the bottom to fit the drain-tiles. 
 
 The Earth-road Drag * 
 
 During the last few years a great deal has been written on the 
 subject of the earth-road drag and its uses. Great changes 
 in the general condition of many roads have been produced 
 by the use of this simple tool, and several states have passed 
 special laws allowing towns to make provisions for dragging 
 all their clay roads after each rain. 
 
 The drag is not a cure for all evil roads, but if it is used at 
 the proper time and on proper soils it will produce a road good 
 for travel at times when the road, if undragged, would be an 
 impassable mud hole. 
 
 The question as to. whether to shape up a road before drag- 
 ging is one that can only be decided by the character of the 
 present road surface. If this is badly out of shape, narrow, 
 with no ditches, or much higher on one side than Requisites 
 on the other, it is best to plough it a furrow at a time for success, 
 and form it up with the road machine to shape approximately 
 as shown in Fig. 80, which is the proper shape for a dragged 
 road. Not quite as great a cross slope should be given in 
 order to allow for material being pulled to the center by 
 the drag. If the road is fairly well shaped and of the proper 
 width it is ready for dragging at any time after the drainage 
 has been attended to. 
 
 The road must have proper surface drainage or it is use- 
 less to drag it. Wherever the road is continually soft and 
 spongy from underground water tile under-drain should be 
 put in. Ditches should be kept clean and open at all times 
 and proper culverts and bridges provided where necessary. 
 The drag will smooth the surface so that water is quickly 
 
 * Condensed from Road Pamphlet, No. 2, "The Earth Road Drag," 
 by Arthur R. Hirst, Highway Engineer, issued by the Wisconsin Geo- 
 logical and Natural History Survey. 
 
146 
 
 THE ART OF ROADMAKING 
 
 carried to the ditches, but in order that dragging may be 
 fully effective it is necessary that the water should be quickly 
 carried away by the ditches and culverts. 
 
 (From Technical World Magazine) 
 Fig. 106. — A Country Road Dragged with the King Split-log Drag. 
 
 The exact form or style of drag to be used is not the most 
 
 essential part or road dragging. Almost any device will prove 
 
 effective which will move a small amount of earth 
 
 Description ^^^^rds the middle of the road and at the same 
 of drag. 
 
 time smooth the surface. As the whole theory 
 
 and effectiveness of road dragging depends on the moving 
 
 of but a small amount of earth at a time, it is important that 
 
 no road drag be used which is heavy. In fact, the lighter and 
 
 more simple the drag the more effective it usually is. 
 
 A simple stick of timber or piece or railroad iron has proved 
 
 useful for this work. V-shaped drags have also been used, 
 
 but seem to be objectionable, on account of their heavy 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 147 
 
 draft. Perhaps the most effective form of drag is that 
 known as the "split-log drag/' which may also be made of 
 two stout planks in place of the split log. Oak or other heavy 
 wood should not be used where it is possible to get a log of 
 lighter wood. 
 
 Figures 107 and 108 show two varieties of split-log drags 
 which are so simple in construction that they can be made on 
 every farm. The log should be from 8 to 12 inches in diameter 
 and from 7 to 9 feet long. The holes in the front half of the 
 log should be bored so that a slight slant forward is given to 
 the lower part of the front face of the split log. The holes 
 in the rear log are bored so that its flat face will be perpendicular 
 to the sticks forming the connecting braces, which should be 
 tapered at the ends so that they will fit snugly into the holes 
 bored into the logs. The holes should not be less than 2 inches 
 in diameter. The ends of the cross sticks should be split 
 and wedges driven so as to secure the cross-braces in place. 
 The wedges should be driven crosswise of the^grain of the log 
 or plank so as not to split it. A diagonal cross-brace is placed 
 between the logs at the leading end to stiffen the frame of the 
 drag. The distance from the face of the back log to the face 
 of the front log should be about 2J or 3 feet. The lower front 
 edge or toe of the drag should be protected by a strip of old 
 wagon tire, or other piece of iron about a quarter of an inch 
 thick, 3 or 4 inches wide and about 4 feet long. This strip 
 of iron should be bolted to the front log and the heads of the 
 bolts countersunk. The strip of iron should not be carried 
 the entire length of the front log. 
 
 Chains should be provided with which to haul the drag, 
 arranged with a short and long hitch as shown in the sketch, 
 so that the drag will travel at an angle of about forty-five 
 degrees with the direction of the road. 
 
 Before giving instructions for operating a drag, it is well 
 to keep in mind the objects to be attained by this method 
 of road maintenance, which are to smooth the object of 
 surface of the road when it is soft and muddy, to road drag- 
 move a small amount of moist earth to the center, ^^°^' 
 and to maintain the crown or oval shape of the road. 
 
148 
 
 THE ART OF ROADMAKING 
 
 Fig. 107. — Split-log Drag Recommended by the Wisconsin Geological 
 and Natural History Survey. 
 
 (From Technical WorM Magazine) 
 FiQ. 108, — The D. W. King Split-log Drag used extensively in Missouri. 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 149 
 
 The drag is not an implement to use to move large quan- 
 tities or earth, nor does the maintenance of an earth road re- 
 quire the use of such an implement. A consideration of the 
 theory of road dragging will help to make the use of the drag 
 more fully understood. 
 
 If a sample of moist earth is taken from the traveled por- 
 tion of a road over a clay soil, it will be found 
 practically impervious to water. Theory of 
 
 Earth in this condition is what the clay workers draeeine 
 call ''puddled." It has been worked and reworked 
 by the carriage wheels and animals' hoofs until nearly all the 
 traveled portion of a sticky, muddy road is covered with a 
 layer of this impervious, puddled eai'th. 
 
 As usually found on most of the roads, this puddled earth 
 is full of holes and ruts, which are filled with water that can- 
 not escape through the impervious soil. As long as the water 
 remains the soil cannot dry out and the road is kept in a most 
 uncomfortable if not impassable condition. 
 
 It is also a matter of observation that this puddled earth 
 when compressed and dried becomes extremely hard . On 
 these two facts, the imperviousness of puddled earth and its 
 hardness when dried, rests the theory of road dragging. 
 
 When the road drag is properly used it spreads out the 
 layer of impervious soil over the surface of the road, filling 
 up the ruts and hollows until a smooth surface is 
 secured. As a small amount of material is always '^^^ effect 
 to be pushed to the center, a slightly rounded roads^^^*^^ 
 effect will be given to the road, which may be 
 increased or decreased as desired by subsequent dra,gging. 
 By forcing the mud into the hollows and ruts it is evident 
 that the water must go out, which it does by running off to the 
 side of the road. The drying out of the road is thus much 
 facilitated and the road is made immediately firmer. 
 
 The effect of traffic over the road tends to press down and 
 thoroughly compact each thin layer of puddled earth which 
 the drag spreads over the surface every time it is used. After 
 the first few draggings the road becomes constantly smoother 
 and harder so that the effect of a rain is scarcely noticeable, 
 
150 
 
 THE ART OF ROADMAKING 
 
 Fig. 109. — Where Brooks flow in the Wagon Ruts, showing how a danger- 
 ous quagmire gets its start. 
 
 
 a ^^.^ 
 
 
 
 
 k^-'^ 
 
 ^H^H - -s^ 
 
 
 ? ""' '^^ 
 
 
 fl^f 
 
 M 1^^ ■',j 
 
 ii 
 
 
 prji 
 
 
 
 Fig. 110. — Part of same stretch of Road after Dragging. 
 {From Technical World Magazine) 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 151 
 
 the water running off the surface, which is so smooth and hard 
 -as to absorb but Uttle of it. 
 
 The following points are to be borne in mind in dragging 
 a road. 
 
 Make a light drag, which is hauled over the 
 road at an anffle so that a small amount of ,°^ ,^^ ^^!^^ 
 
 ° tor dragging. 
 
 earth is pushed to the center of the road. 
 
 Drive the team at a walk. 
 
 Ride on the drag; do not walk. 
 
 Begin at one side of the road, returning on the opposite 
 side. 
 
 Drag the road as soon after every rain as possible, but not 
 when the mud is in such a condition as to stick to the drag. 
 
 Do not drag a dry road. 
 
 Drag whenever possible at all seasons of the year. If a 
 road is dragged immediately before a cold spell it will freeze 
 in a smooth condition. 
 
 The width of traveled way to be maintained by the drag 
 should be from 18 to 20 feet; first drag a little more than the 
 width of a single wheel track, then gradually increase until 
 the desired width is obtained. 
 
 Always drag a little earth towards the center of the road 
 until it is raised from 10 to 12 inches above the edge of the 
 traveled way. 
 
 If the drag cuts in too much, shorten the hitch. 
 
 The amount of earth that the drag will carry along can 
 be very considerably controlled by the driver, according as 
 he stands near the cutting end or away from it. 
 
 When the roads are first dragged after a very muddy spell 
 the wagons should drive if possible to one side until the road- 
 way has a chance to freeze or partially dry out. 
 
 The best results from dragging are obtained only by re- 
 peated applications. 
 
 The following suggestions for using the drag are taken from 
 the monthly bulletin of the Missouri Board of Agriculture 
 for April, 1906. 
 
 1. "The length of the chain, which is regulated by slipping 
 it backward or forward through the hole in ditch end of drag. 
 
152 THE ART OF ROADMAKING 
 
 regulates the hold taken on the earth. To make the chain 
 longer is equivalent to putting weight on the drag. If the 
 drag is too heavy shorten the chain." 
 
 2. "The position of the snatch hook, which attaches the 
 double-trees. To move much dirt or cut small weeds hitch 
 the hook close to the ditch end of the drag and stand as nearly 
 on the end of the front slab as is safe. Drive very slowly 
 when thus hitched. This one hitch seems to be the hardest 
 to learn. The others suggest themselves." 
 
 3. "Position of the driver on the drag. To move dirt see 
 above. In a soft spot stand on rear slab. On a hard spot 
 stand on front slab and drive slowly. If the drag clogs with 
 straw, weeds, sod or mud, step to a point as far as possible 
 from ditch end of the drag. To drop dirt in a low place step 
 quickly from ditch end to other extreme. To fill a low place 
 or mud hole nicely is the severest test of skill with a drag." 
 
 4. '* Presence or absence and sharpness or dullness of the 
 steel. The steel may project half an inch below the wood 
 at the ditch end of the steel, but should come up flush with 
 the wood at other end of the steel. After a clay or gumbo 
 road has been dragged four or five }'ears the soil becomes so 
 tough and putty-like that one must study it closely to know 
 what to do. Sometimes the sharp edge of steel is used; some- 
 times the dull edge (holes are bored in both edges of steel so 
 that it can be turned upside down and same bolt holes used) , 
 and sometimes the plain wood. This can be learned only 
 by experience." 
 
 To one unacquainted with the results obtained by the use 
 of the drag it seems unbelievable that so much 
 good can be done with so simple an instrument. 
 
 Xo definite rule can be laid down as to the best time to 
 drag. If traffic amounts to practically nothing the wetter 
 the road is the better. Ordinarily however, it is useless to 
 drag a road when it is so wet the mud flows or so dry that it 
 pulverizes. The best time is when the mud passes along 
 the front edge of the drag without balling or sticking and 
 packs easily into ruts and holes under pressure from the rear 
 log and subsequent travel. The best time may be as soon 
 
EARTH, GRAVEL, SAND AND CLAY ROADS 153 
 
 as the rain stops on some roads and hours afterward on others. 
 Each man must find out for himself, by experience on his 
 own piece of road, the proper time to drag it. In general, 
 it will be found best to start right after the rain, especially 
 when first starting to drag a road into shape, as throwing clay 
 into the ruts drives the water out and the road dries much 
 quicker. It is a good thing, however, to drag a road at almost 
 ■any time with almost any kind of drag. 
 
CHAPTER VIII 
 BROKEN-STONE ROADS 
 
 A BROKEN-STONE road is one built of small fragments of 
 stone laid on a suitable earth foundation and compacted 
 together into a solid mass. It is uncertain just when this 
 system of road construction was invented, but as near as can 
 be ascertained, the first systematic construction of broken- 
 stone pavements was carried on in France in 1764 by M. 
 Tresaguet, who built many miles of such pavements in the 
 latter part of the eighteenth century. In the early part of the 
 nineteenth century two systems were introduced into England^ 
 the first by Telford, the second by Macadam, From these two 
 pioneers of good roads, modern engineers have drawn the 
 principles upon which all present-day broken-stone roads are 
 built. Such roads are generally known as ''macadam'* roads; 
 the material itself is often called ''macadam," and the work 
 of construction, "macadamizing.'' These roads are also 
 sometimes called " telford '' roads, but this term is more 
 appropriately restricted to a particular form of rough stone 
 foundation for a broken-stone road. Neither is the term 
 "macadam" altogether appropriate as a synonym for a broken- 
 stone road, but should strictly be used only to designate the 
 foundation or lower course of a stone road composed entirely 
 of small fragments. 
 
 The difference between the methods of Telford and Macadam 
 is mainly on one point and has been more dwelt upon than the 
 similarity of their systems on many other points 
 between ^^ which they both differed so widely from the 
 methods of practice of their predecessors. Both insisted on 
 Telford and ^-^e necessity for the thorough drainage of the road- 
 bed, a thing then utterly neglected; both made use 
 of materials broken to gauge to form a solid hard surface of 
 
 154 
 
BROKEN-STONE ROADS 
 
 155 
 
 uniform cross-section, and of a surf ace curvature just sufficient 
 to throw the rain water off freely to the sides. The distinc- 
 tion usually drawn between the Telford system and that of 
 Macadam is in the foundation of large stones upon which 
 Telford generally laid the broken stone or gravel. 
 
 To Macadam is due the credit of having been the first to 
 direct public attention to the necessity of the proper breaking 
 and preparation of road materials, and to the possibility of 
 forming with them a compact road surface nearly impenetrable 
 to water, which can be laid so flat as to allow vehicles to pass 
 freely over all parts of the road, and at the same time throw 
 off the water. 
 
 ^roAo JC'fawj 
 
 ^^^i^^ ^t^fts^i^^ 
 
 Fig. 111.- 
 
 -Cross-section of Typical European Roads before the time of 
 Macadam. 
 
 What the process of roadmaking and road-mending was in 
 the early part of the nineteenth century is thus described by 
 Macadam: 
 
 '^The practice common in England, and universal in Scotland, 
 on the formation of a new road, is to dig a trench below the 
 surface of the ground adjoining, and in this trench to deposit 
 a quantity of large stones; after this a second quantity of stone, 
 broken smaller, generally to about seven or eight pounds weight; 
 
 Fig. 112. — Cross-section of a Typical English Road a Hundred Years Ago, 
 showing method of making repairs. 
 
 these previous beds of stone are called the bottoming of the 
 road, and are of various thicknesses, according to the caprice 
 of the maker and generally in proportion to the sum of money 
 placed at his disposal. On some new roads made in Scotland 
 in the summer of 1819, the thickness exceeded three feet. 
 
156 THE ART OF ROADMAKING 
 
 ''That which is properly called the road is then placed on 
 the bottoming, by putting a large quantity of broken stone or 
 gravel, generally a foot or eighteen inches thick, at once upon 
 it, and from the careless way in which it is done the road is as 
 open as a sieve to receive the water^ which is retained in the 
 trench/' * 
 
 AYith respect to repairs, he says that there seemed to be 
 '' no other idea of mending a road than bringing a great quan- 
 tity of material and shooting it on the ground. '^ 
 
 John Loudon Macadam was born on September 21, 1756, 
 in Ayr, Scotland^ where his father was a landed proprietor 
 and founder of the first bank in the town. He was 
 John educated in the parish school, and is said to have 
 
 Macadam shown an early inclination towards road construction 
 by making a model of a road in the district. On the 
 death of his father in 1770, he was sent to his uncle, William 
 Macadam, a merchant in the city of New York, from whom he 
 received his business training. During the American Revolu- 
 tionary War he acted as an agent for the sale of prizes taken in 
 battle, and on the declaration of peace, in 1783, he returned to 
 Scotland, having remained loyal to the King of England. 
 
 After his return to Scotland he was for thirteen years a 
 member of the Commission of Peace, and Deputy Lieutenant of 
 the County. During the Napoleonic wars he raised a volunteer 
 corps of artillery for the defense of the coast and was com- 
 missioned as a major. 
 
 During this period, as trustee on certain highways, he carried 
 on experiments at his own expense, and in the face of great 
 opposition he succeeded in improving the roads under his 
 jurisdiction. The Highland Rebellion of 1745 had given an 
 impetus to road building in Scotland, though these roads were 
 chiefly for military purposes. Between 1760 and 1780 more 
 than 600 Turnpike Acts were passed, but the roads actually 
 built under this authorit}^ were constructed, as a rule, with- 
 out system or technical knowledge. 
 
 * ''Remarks on the Present System of Road Making," etc., by John 
 Loudon Macadam, 1820. 
 
BROKEN-STONE ROADS 157 
 
 In 1798, Macadam moved to Bristol, England, and engaged 
 in business connected with the victualing of the navy, but he 
 spent much time in private travel about the kingdom in the 
 investigation of roads and the various methods of construction 
 and repair then in operation. By August, 1814, he had 
 traveled 30,000 miles and had expended from his private purse 
 over $25,000, but had gained experience that made him a 
 recognized authority on road building and made his advice 
 eagerly sought for by those having charge of roads, while his 
 views were boldly expressed in print and before several parlia- 
 mentary committees. The first recorded practical application 
 of his knowledge, on a large scale, followed his election as a 
 trustee of the Bristol Turnpike Trust. He found the roads of 
 that district in a very bad condition, and on Jan. 16, 1816, 
 he was appointed surveyor for the trust, in direct charge of 
 construction and repairs. His salary was at first $2000 per 
 year, and later $2500, and out of this sum he had to pay his 
 traveling and other expenses, amounting to about $1000 per 
 annum. The roads under his management aggregated 149 
 miles in length, but this was later increased to 178 miles. 
 In June, 1817, he was enabled to report that none of the roads 
 in the Bristol District were in bad condition; the cost of 
 maintenance had largely decreased; the income had increased 
 in proportion; a floating debt of $7000 had been paid off, and 
 the principal debt had been reduced by $3650. 
 
 His work as surveyor to the Bristol Trust did not engage 
 his whole time, and by 1819 he had been consulted by thirt^^-four 
 different bodies of road commissioners, representing thirteen 
 counties. In 1823 he had reported to seventy sets of com- 
 missioners in twenty-eight counties; and of these the roads in 
 thirty-two trusts were being managed by Mr. Macadam and 
 his sons according to the system devised by him, and the work 
 done by men trained under him. Macadam received no 
 compensation for this extra work other than his traveling 
 expenses, and in the cases where the road trusts were very poor 
 he did not receive his expenses. 
 
 The opposition to the Macadam system of road building was 
 formidable at first, the chief objection being that the ramming 
 
15S THE ART OF ROADMAKING 
 
 of the bed was unnatural and ineffective, and was damaging 
 to the wheels of vehicles and to the feet of the horses, but the 
 critics failed to remember that previous to the improve- 
 ment of roads on the Macadam system the average life of a 
 coach-horse was only three years. 
 
 In 1817 Macadam put down the first piece of macadamized 
 road in London, by improving the approaches to Blackfriars 
 and Westminster bridges. George IV. took a strong personal 
 interest in the improvement ^of London streets, which fact 
 induced Macadam to leave Bristol in 1823 and take up his 
 residence within a few miles of London. ' In this same year he 
 succeeded in getting an inquiry before a committee of the House 
 of Commons as to his system, and he had constructed a full 
 set of road-making implements, so that he could better explain 
 the principles of his method. As a result, the merits of 
 macadamized roads were publicly admitted and acknowledged, 
 and Parliament voted, first, $10,000, and later raised this to 
 $40,000, to compensate him for the money he had personally 
 expended in bringing his system into practical and general 
 use. He declined a baronetcy, but in 1827 he was appointed 
 Surveyor-General to the Commissioners of Metropolitan 
 Turnpike Roads, and his system was adopted throughout the 
 kingdom. He died Nov. 26, 1836. 
 
 Thomas Telford was born in the district of Eskdale, in 
 Scotland, on August 9, 1757, and obtained the rudiments of 
 his education in the parish school at Westerkirk. 
 T \f^^ He learned the trade of a. mason, then took up 
 architecture in Edinburgh and later in London, and 
 being a man of exceptional ability, he soon established himself 
 as a leading engineer. 
 
 He became a bridge builder of note, making this his special 
 study; but he also carried out many other engineering works, 
 particularly that of locating and constructing new roads in 
 all parts of Great Britain. His first undertaking as a road- 
 maker on an extensive scale was in the Highlands of Scotland, 
 where he was sent by the government in 1802 to report as to 
 the best means of developing the resources of the country. 
 He advised the opening out of the country by a complete 
 
BROKEN-STONE ROADS 159 
 
 system of roads, so as to bring the interior parts into communica- 
 tion with the towns and the coast. 
 
 Under his direction, and by the aid of parliamentary grants 
 amounting to nearly one million dollars, about 920 miles of 
 road were scientifically laid out and constructed, and owing to 
 the hilly and rugged nature of the countr}^, works of considerable 
 magnitude had to be undertaken, including 1117 bridges. 
 This work was carried out in the course of eighteen years, 
 under 120 contracts, and without recourse to a court of law 
 in any one instance. _ 
 
 No work on roads is written to-day without an explanation 
 of Macadam's and Telford's, principles, so it will not be out of 
 place to mention them and to discuss them in connection with 
 the more extended knowledge and better appliances of the 
 present day. 
 
 The following specifications show the difference in the methods 
 of the inventors. 
 
 Tresaguet's Method, 1764 (Fig. 113).— "The bottom of 
 the foundation is to be parallel to the surface of the road. 
 The first bed or foundation is to be placed on edge , 
 
 and not on the flat, in the form of a rough pave- t?^^^*^ 
 ment, and consolidated by beating with a large 
 hammer; but is unnecessary^ that the stones should be even 
 one with the other. The second bed is to be equally placed 
 
 Fig. 113. — Cross-section of French Road Built by Tresaguet. 
 
 by hand, layer by layer, and beaten and broken coarsely with 
 a large hammer, so that the stones may wedge together and 
 no empty spaces remain. The last bed, three inches in thick- 
 ness, is to be broken to about the size of a nut with a small 
 hammer, or a sort of anvil, and thrown upon the road without 
 a shovel to form the curved surface. Great attention must 
 be given to choose the hardest stone for the last bed even if 
 one is obliged to go to more distant quarries than which furnish 
 the stone for the body of the road. The solidity of the road 
 
160 THE ART OF ROADMAKING 
 
 depending on this latter bed, one cannot be too scrupulous as 
 to the quality of the materials which are to be used for it." 
 Telford's Method, 1S24 (Fig. lU). — '' Upon the level bed 
 prepared for the road materials a bottom course or layer of 
 T If d' stones is to be set by hand in the form of a close, 
 method ^^^ pavement. The stones set in the middle of the 
 road are to be seven inches in depth; at nine feet 
 from the center, five inches; at twelve feet from the center, 
 four inches; and at fifteen feet from the center, three inches. 
 They are to be set on their broadest edges lengthwise across 
 the road, and the breadth of the upper edge is not to exceed 
 four inches in any case. All the irregularities of the upper 
 part of the said pavement are to be broken off by the hammer, 
 and all the interstices to be filled with stone chips firmty wedged 
 or packed by hand with a fight hammer, so that when the whole 
 pavement is finished there shall be a convexity of four inches 
 in the breadth of fifteen feet from the center. 
 
 ^—6ft. >4< /sr/ >t< — ert — -H ^^ 
 
 vGrmefor \ ^i <^^^^^ f^"J. \\,3in 
 
 Fig. 114. — Telford's Shrewsbury and Holyhead Road. 
 
 ''The middle eighteen feet of pavement is to be coated with 
 hard stones to the depth of six inches. Four of these six 
 inches to be first put on and worked in by carriages and horses; 
 care being taken to rake in the ruts until the surface becomes 
 firm and consolidated, after the remaining two inches are to 
 foe put on. 
 
 '*The paved spaces on each side of the middle eighteen ieet 
 are to be coated with broken stones or well-cleaned gravel 
 up to the footpath or other boundary of the road, so as to 
 make the whole convexity of the road six inches from the center 
 to the sides of it, and the whole of the materials are to be 
 covered with a binding of an inch and a half of good gravel 
 free from clay or earth." 
 
 Macadam's Method. — Macadam omitted the foundation of 
 large stones, claiming that it was not only useless but injurious. 
 He placed on the natural soil, a layer of stone broken into 
 cubes of about one and a half inches in their greatest 
 dimensions, and spread equally over the surface of the road, 
 to a depth of ten or twelve inches. 
 
BKOKEN-STONE ROADS 
 
 161 
 
 No binding material was used, the stone being left to work 
 in and unite by its own angles under the traffic. Macadam 
 preferred the test of weight to that of measure- 
 ment, and insisted that no stone should weigh ^^^ .^ ^ 
 more than six ounces, which is the weight of a cube 
 of one and a half inches of hard compact limestone, and his 
 
 K-— 7/'/ >t^ W/?-- 
 
 I I 
 
 ■rnmsmm 
 
 -7/-/- 
 
 i^ 
 
 Fig. 115. — Modern Telford Road as Built in New Jersey. 
 
 overseers were provided with small scales and a six-ounce 
 weight to test the larger stones. Macadam was the pioneer 
 of scientific road construction in England, but he had been 
 anticipated in the promulgation of the system of a regularly 
 broken-stone covering by a Mr. Edgeworth, an Irish proprietor, 
 who wrote a treatise on roads, early in the nineteenth century. 
 This contains the results of his experiments on the construction 
 
 -2lft- 
 
 FiG. 116. — Modern Telford Road in Excavation for Massachusetts State- 
 Aid Roads. 
 
 of roads, with some useful rules, in which he advocated the 
 breaking of the stone to a small size, and their equal distribu- 
 tion over the surface, also that the interstices should be filled 
 with small gravel or sharp sand — a practice which, though 
 condemned by Macadam, is now advocated by the best road- 
 makers. 
 
 Modern '* telford " consists of a layer of stones eight inches 
 thick, set by hand, on a natural-soil bed, properly graded. 
 These are arranged and wedged as described by « , 
 Telford. On this stone foundation, a layer of telford and 
 broken stone of a size not exceeding three inches Diacadam. 
 is evenly spread and rolled and this surface is covered with 
 
BROKEN-STONE ROADS 163 
 
 a layer of sand one-half inch thick, and the rolling continued. 
 A layer of stone not larger than two inches diameter is then 
 spread to the depth of four inches and rolled, followed as 
 before with a layer of sand, which is also rolled. Finally, a 
 coating of clean, sharp sand is applied, well watered, and the 
 rolling continued until the surface becomes smooth. 
 
 Modern "macadam " pavements are constructed in the same 
 manner but omitting the stone foundation, and the depth of 
 the stone varies from four to twelve inches. 
 
 The principal defects of the telford system are: 
 
 1. The large percentage of voids always left between the 
 foundation stones, giving free access to water and thus defeat- 
 ing one of the main objects of the road covering. Defects of 
 
 2. The crushing of the smaller surface stones on telford 
 the harder rock of the foundation by the traffic. system. 
 
 3. The high cost of construction due to the stone foundation. 
 
 The principal defects of the macadam system, when con- 
 structed as directed by Macadam is the looseness of the layer 
 of broken stones. This cannot be impervious. Defects of 
 because the interstices which compose a considerable macadam 
 portion of the bulk of loosely spread stones, cannot system, 
 be reduced by any amount of rolling more than one-fourth, 
 leaving a space that will be filled by the rising of the sub- 
 soil when moistened. The lower stones are then forced down 
 by the weight of the traffic until the whole becomes a mass of 
 mud and stones. 
 
 The advantages of broken-stone pavements are: 
 
 1. Good foot-hold for horses. 
 
 2. Easy traction when in good condition. and^defe^ts 
 
 3. Moderate first cost. of broken- 
 
 4. Comparative noiselessness. stone 
 Defects common to all broken-stone roads are: P^'^®°^®^ s- 
 
 1. Muddy when wet and dusty when dry, 
 
 2. High cost of maintenance. 
 
 3. Difficulty in cleaning. 
 
 These defects prevent the use of broken stone for city streets, 
 but when properly constructed and maintained, broken stone 
 forms the most pleasant, the safest, and the most economic 
 
164 THE ART OF ROADMAKING 
 
 surface for suburban streets and main country highways 
 
 connecting centers of population, on which there is a moderate 
 
 volume of travel. It is usually too expensive, however, for 
 
 country roads other than the main ways. 
 
 The main difficulties in the construction of ideally perfect 
 
 broken-stone roads lie in: 
 
 Difficulties i^ The quality of materials suitable for road- 
 in construe- ■, • j. i ■ i-™- j. i tj.* 
 
 tion makmg found m different localities. 
 
 2. The conflicting properties possessed by these 
 
 materials. 
 
 3. The following of methods of construction used and 
 
 precedents established under entirely different conditions 
 
 of climate and traffic. With methods of construction suitable 
 
 to local conditions and with a thorough knowledge of the 
 
 "^•^y^mi^w^m^^mm^m^^^^^^^^" 
 
 Fig. 118. — Cross-section of Roadway laid on Compact Earth and Made 
 Solid and Permanent by Rolling. 
 
 nature of the available materials under any given conditions 
 satisfactory construction of broken-stone roads can be assured. 
 
 The essentials requisite to the successful construction of 
 broken-stone pavements are: 
 
 1. The removal from the roadbed of all vegetable or per- 
 ishable matter. 
 
 _ ,. , 2. The removal of the natural soil to such a 
 
 Essentials ^• -, ^ 
 
 for success- depth as may be necessary according to the char- 
 
 ful construe- acter of the soil and the thickness of the intended 
 
 °* covering. 
 
 3. Thorough sub-surface drainage wherever required. 
 
 4. The thorough compacting of the natural-soil bed. 
 
BROKEN-STONE ROADS 165 
 
 5. The use of sand or gravel for the foundation. 
 
 6. The use of the best materials available either locally or 
 imported from other places, according to the nature of the 
 traffic. 
 
 7. The reduction of the voids in the mass of broken stone 
 to the least possible amount, by properly proportioning and 
 distribution of the different sizes of stone used. 
 
 8. The complete exclusion of clay or loam from the broken 
 stone. 
 
 9. The use of sand or stone dust and screenings in quantity 
 sufficient to fill the voids. 
 
 10. The thorough compacting of the broken stone with a 
 roller of sufficient weight and suitable form. 
 
 Fig. 119. — Cross-section showing Wasteful use of Material. 
 
 Among the errors in broken-stone road construction which 
 make the road very unsatisfactory and defective, are: 
 
 1. A permeable foundation in humid climates, gj-j-ors in 
 
 2. The use of excessively hard stones which can- construe- 
 not be consolidated by rolling. t^o^- 
 
 3. The use of improper binding material, such as loam and 
 clay. 
 
 4. An undue proportion of soft among hard stones. 
 
 5. Use of .stones of too large size. 
 
 6. Use of stone from which the smaller fragments have 
 been excluded by screening. Unscreened stones may be used 
 for the lower course, but its use for the surface is unsatisfactory, 
 as it wears unevenly, and owing to the differences in the size 
 of the fragments, the variation in the proportions, and their 
 unequal distribution in the mass, it is impossible to decrease 
 the amount of voids. 
 
166 THE ART OF ROADMAKING 
 
 7. Laying the stone in layers, according to the size of the 
 stone. The practice of building up a road with strata of 
 screened stone assorted in different sizes and growing smaller 
 towards the top is erroneous, as the smaller stone will sink 
 to the bottom, and the larger stone will work to the surface, 
 making the road porous and permitting the quick formation 
 of ruts. The stone should be assorted by screening into the 
 several sizes, then remixed in proper proportions to produce 
 a mass containing the least possible amount of voids or a density 
 as nearly equal to that of solid rock as is possible. 
 
 8.. Covering the surface of the compacted stone with a 
 layer of stone dust. 
 
 9. Use of an excessive quantity of binding material, or of 
 water when rolling. 
 
 As stated in Chapter VI, the materials used for broken- 
 stone roads must necessarily vary according to 
 the locality, and on account of the many differences 
 in climate and traffic it is evident that no single material is 
 adaptable to all cases. As in practically every department 
 of engineering, each problem requires individual solution 
 according to local conditions, and to secure the best results 
 in roadwork, the material selected and the method of con- 
 struction employed must be adapted to the conditions under 
 which the road is to be used and maintained. The specifica- 
 tions of Telford and Macadam were drawn up for use in a 
 country with a moist climate. The water was useful in the 
 construction of the road by aiding in the binding together 
 of the material, but its removal was a necessity and made 
 drainage of both the roadbed and the surface an important 
 item in the maintenance of the road. In localities having 
 little or no rain, drainage becomes relatively unimportant, 
 and the methods for preservation of a well-bonded surface 
 are of great consequence. 
 
 For ordinary country roads, experience has shown that the 
 broken-stone way need not be more than from 12 to 15 feet 
 wide, if suitable shoulders are built on each side. Twelve feet 
 allows two vehicles to pass each other safely. Fifteen feet 
 allows a little more space for comfort, particularly when 
 
BROKEN-STONE ROADS 
 
 167 
 
 Eaxly Eigbteeath Centur7 Boadi 
 
 Late Eighteenth Century Road. 
 
 Modern Macadam Road. 
 
 (From Judson's " Cilij Roads and Pavements.") 
 Fig. 120. — Relative Thickness of Ancient and Modern Roads. 
 
168 THE ART OF ROADMAKING 
 
 motor vehicles are passing each other, and including the 
 Dimensions ^^'^^^'^^^s, this width will permit a team to stand 
 of the beside the road while two vehicles are passing. If 
 
 macadam the stone is less than 12 feet wide there is a likeli- 
 hood that the edges of the macadam will be sheared 
 off by the wheels unless the shoulders are made of especially- 
 good material. Whatever maybe the width of the stone, the 
 shoulders should be firm enough to permit the occasional 
 passage of wheels over them. 
 
 Until within comparatively recent years it has been almost 
 universally the practice to build thick macadam roads. Roads 
 less than 8 inches thick were rarely heard of, and often a thick- 
 ness of at least 12 inches of macadam was thought to be nec- 
 essary for good work. 
 
 The modern practice is to make the macadam surface as 
 thin as possible, yet with sufficient body to stay in place, the 
 theory being that the macadam is only a wearing surface. 
 By lessening the thickness of the macadam much expense 
 may be saved, since the foundation materials are usually less 
 costly than broken stone. The macadam should be hard^ 
 smooth, and impervious to water. Much attention must be 
 given to the foundation. It should be composed of porous 
 material free from clay or loam, firm, and sufficiently strong 
 to sustain any load likely to come upon the road at any time 
 of the year. 
 
 In new work, where no macadam has been laid before, 3 
 inches of macadam after rolling is the least thickness which 
 is practicable, and, except in unusual cases, a depth greater 
 than 6 inches after rolling is rarely necessary if the foundation 
 is suitable. 
 
 The ordinary macadam road is usually from 12 to 16 feet 
 wide, with shoulders in addition 3 to 5 feet in width on each 
 side of the broken stone. The thickness of the macadam is 
 usually 6 inches at the center and 4 inches at the sides, or a 
 uniform depth of 6 inches throughout. While the width and 
 depth of the stone are often less than these dimensions, only 
 in exceptional cases are they increased. 
 
 The actual construction of the road consists essentially of 
 
BROKEN-STONE ROADS 
 
 169 
 
 three operations: (1) The preparation of the subgrade, or 
 the natural-soil foundation on which the stone is placed; 
 (2) Spreading of stone; (3) Rolling and finishing. 
 
 The preparation of the subgrade to enable it to sustain the 
 superstructure and the weights brought upon it requires the 
 observance of certain precautions, the neglect of 
 which will sooner or later result in the deterioration 
 or possible destruction of the road covering. 
 
 Subgrade. 
 
 It is not enough 
 
 
 Fig. 121. — Cross-section of Sub-grade as Shaped by Grader. 
 
 that the roadway shall be graded with reasonable care. The 
 surface upon which the broken stones are to be placed must 
 be! hard, smooth, and carefully crowned. If the foundation 
 is not hard and firm the stones will be pressed into it by the 
 roller and wasted. If not crowned, an unnecessarj^ quantity 
 of stone will be used. 
 
 Fig. 122.— Shaping the Subgrade with Road Roller. 
 
 Primarily a well-drained, good foundation is a recognized 
 necessity. This should be shaped as shown in Fig. 121. Most of 
 the dirt to be moved in making the trench for the broken stone 
 is ploughed and thrown out with an ordinary road grader, and 
 the trimming up to the lines shown in Fig. 121 is then done 
 by hand. The trench should be made as deep at the sides as 
 
170 
 
 THE ART OF ROADMAKING 
 
 the stone is to be after rolling, the shoulders being made two 
 or three inches higher than their final shape, to allow for their 
 being compacted by the roller. 
 
 When the roadbed has been brought to shape, the trench 
 is thoroughly rolled until it is hard and firm and shaped as 
 shown in Fig. 122. Hollows and bumps are removed by 
 cutting or filling, and the whole subgrade made hard, smooth 
 and even, and of the same cross slope as that of the finished 
 road. After the trench is made drains should be cut through 
 the shoulders to the side ditches in all low places at intervals 
 
 Fig. 123. — Spreading the First Course. 
 
 of 50 feet on both sides. This will save many days' work in 
 laying stone, as it will keep the subgrade dry when otherwise 
 it would be flooded at every rain. These drains should be 
 filled with the three-inch stone when the stone for the first 
 course is spread; they then serve as permanent drains for the 
 stone roadbed if water by any chance gets into it. 
 
 When the subgrade has been thoroughly rolled the first 
 course of stone is spread. This ordinarily consists 
 of stone broken to sizes varying from 2 to 3-^ 
 inches and need not be of especial hardness or 
 toughness — ordinary good hard stone of any kind may be used. 
 
 First 
 course, 
 
BROKEN-STONE ROADS 
 
 171 
 
 The thickness of this stone, like every feature of the road, 
 varies with local conditions. On good soil 4 inches loose is 
 sufficient, but in some cases 5 inches and even 6 inches should 
 be used. A course of over 6 inches cannot be thoroughly 
 rolled and should never be used. Twelve inches of stone 
 loose in the two courses is all that is ever necessary on a well- 
 drained road, that is, two courses of 6 inches each without 
 the dust. 
 
 It is often specified that stone for any course should not 
 be dumped on the place where it is to be used; that is, that after 
 each load of stone is dumped it should be raked or shoveled into 
 place, moving each stone from the place it was dumped, and 
 thus preventing unevenness in the road. While this is ad- 
 vantageous, it is sometimes impracticable and costly to have 
 
 Fig. 124. — Rolling the First Course, 
 
 this shoveling and raking done, especially on the second course 
 of stone, and good results are obtained by taking care in 
 raking down the stone from the pile. Rolhng then levels all 
 the stone to a uniform thickness, making a road smooth enough 
 for all practical purposes. The screenings, however, must not 
 be dumped directly on the road surface, but must be spread 
 from piles or directly from wagons. 
 
 When 100 feet or more of stone is spread and shaped, rolling 
 is commenced and is carried on until the stone is thoroughly 
 compacted. 
 
 The first course having been thoroughly rolled, the second 
 course should be spread the same width as the first. 
 This course should consist of the best material 
 economically available; which means the material 
 that for a fixed sum will produce the greatest road value, not 
 for a year, but for twenty years or more. 
 
 Second 
 course. 
 
172 
 
 THE ART OF ROADMAKING 
 
 The stone should be broken in size from | to 2 inches, 
 and be screened as closely as possible to these sizes. It should 
 be spread to a depth of not less than 3 inches nor more than 
 5 inches in any case, varying with the hardness of the stone, 
 etc., and the total depth of road desired. This course must be 
 spread with the same care as the first course and rolled in 
 the same manner until the stone is firmly in place and the 
 whole is firm and even. 
 
 FiG„ 125. — Rolling the Second Course. 
 
 Third 
 course, 
 
 The road is then ready for the third or binder course, which 
 should consist of stone screenings varying from dust to |-inch 
 in size. It is usual to have this of the same material 
 as the second course, though small gravel or sand 
 can be used for binder for some rocks with good 
 results. The dust should be spread with shovels from the 
 wagons or from piles alongside the road, but never dumped 
 directly on the stone surface. It should be applied with a 
 quick, jerky motion^ so that a shovelful goes over a large area, 
 until the second course of stone is entirely hidden and there 
 is a uniform- coat of about I of an inch over the whole surface 
 of the stone. Then the road should be rolled as before until 
 the dust is well pressed into the space between the stone and 
 a coating left on the surface. Bare places as they appear 
 should be covered with more screenings until the whole is 
 firm and hard and none of the second course stone show. 
 
 The road should then be thoroughly sprinkled with water 
 from an ordinary street sprinkler to wash the screenings into 
 the voids in the stone, and when it flushes or rises to the sur- 
 face it shows that the voids in the stone have been filled. 
 A road is properly flushed when the steam roller following 
 
BROKEN-STONE ROAD,^ 
 
 173 
 
 close behind the sprinkler has a wave of water continually 
 going before the wheels. This flushing causes the dust to 
 settle, and bare places that show again should be covered 
 with more screenings and sprinkled and rolled until the whole 
 is firm and hard, and uniformly covered with a thin coat of 
 dust. Just enough dust should be applied to cover the stone 
 
 Fig. 126.— Rolling the Binder. 
 
 at all stages of the finishing. Too much dust soon ruts, travel 
 becomes concentrated in these ruts, and water standing in 
 them causes a soft place in the stone below and the ultimate 
 destruction of what would otherwise have been an excellent 
 road. 
 
 After a section of road has been flushed and finished it 
 should be closed a day or two before permitting travel upon it; 
 this gives the road an opportunity to, dry out and harden and 
 prevents the raveling and picking up of the road surface which 
 sometimes occurs when a newly finished road is opened too 
 soon and in too wet a condition. 
 
a. Method of Construction, Showing Curb to Prevent Washing. 
 
 h. Road Under Water, 
 
 ' . '-+^-' 
 
 
 """. '1 
 
 mim^^ 
 
 M^^^ 
 
 M,a^»&» 
 
 jvWMhMHRsJhS^^^a, M^ ^ 
 
 ^^^1 
 
 ^^^^^^^l^^^b.^^^^ ''^ffib 
 
 ^HH^Bm^^^ 
 
 ■ -o 
 
 v^P^^^I^^^HlBi 
 
 ^^^^p^^*" , , 
 
 
 ' ^''^^^^iSSHHIH 
 
 ?#<^~ ■ 
 
 
 ^^ 
 
 L-.-. ■ 
 
 
 ..-J 
 
 c. Completed Road. 
 
 Fig. 127. — Macadam Road Built through River Bottom (Auburn, Neb.)- 
 
 174 
 
BROKEN-STONE ROADS 175 
 
 When the operations outhned above are about finished a 
 road machine with the blade set to the proper slope should 
 be run carefully over the shoulders and all surplus 
 dirt removed^ and the slope from the center of the 
 road to the ditches made smooth and uniform so that water 
 falling on any part of the road surface is quickly carried into 
 the ditches. 
 
 The broken-stone road of to-day is quite a different structure 
 from the type of road built by Macadam, who used hand- 
 broken stone that was practically uniform in size, laid in the 
 road without the addition of a binder of stone dust or sand and 
 left to be compacted by passing wheels. Improvements in 
 methods of construction have reduced the thickness from 
 the 36 inches of the Romans to the 18 inches of Telford, to 
 the 12 and even the 6 inches of Macadam, to the 6 and in some 
 cases the -1 inches of to-day; the chief factors being: (1) proper 
 drainage and rolling of the earth foundation, (2) the use of 
 machine-broken and screened stone with the screenings for 
 a binder, (3) thorough consolidation with a steam roller; 
 and it is safe to say that an economic road cannot be built 
 unless all of these factors enter into its construction. 
 
 Efficient rolling is a matter of great importance; many 
 roads coated with material of good quality suffer and become 
 loose when the water in the binding has dried out. 
 The condition to be aimed at is to solidify the coat- 
 ing with a suitable binding alpplied in small quantities by rolling 
 so as to approximate the original bulk occupied by the material 
 in the solid. All excess binding should be squeezed out b}^ 
 repeated passages of the roller and swept off. This produces 
 a solid crust capable of resisting most effectually the action 
 of ordinary wheel traffic and containing the least quantity 
 of soluble matter to form mud in wet, and dust in dry, weather. 
 
 The non-professional reader may have wondered why a 
 mass of broken stone, when sprinkled and rolled, finally be- 
 comes a solid pavement, impervious to water, acting in all 
 respects like concrete, although no cement mortar has been 
 used. That such a result could be obtained seems not to have 
 occurred to anyone before the time of Tresaguet, and even he 
 
176 ' THE ART OF ROADMAKING 
 
 did not trust to the broken stone alone to sustain loaded 
 wagons, for he used an underpinning or ^' bottoming ' ' of 
 large paving stone. It was Macadam who, by omitting the 
 bottoming, showed conclusively that broken stone possesses 
 the . property of knitting together, or becoming cemented 
 under the rolling action of passing wheels, but it is doubtful 
 if Macadam himself understood the philosophy of this cement- 
 ing action. 
 
 It is not the roller, that, by shaking and pounding a mass 
 of loose, broken stones placed on a road, finally compresses 
 the stones together until they are almost, if not 
 What holds quite, as compact as solid rock. In the first place, 
 maca am ^j^^ roller does not compress the stone to its original 
 together. volume, that is, it does not reduce the voids to 
 zero; and second^, a road is never bound when 
 the rolling is finished, unless a binder has been added. The 
 screenings or binding materials are essential, but there are 
 various views as to their action. Mr. H. P. Gillette in a dis- 
 cussion of this cementing action,* says: 
 
 "A true explanation of the phenomenon seems to be found 
 in a study of the sand on a seabeach. 
 
 '^ Where the waves break, the sand is firm and makes a very 
 fair road itself, while a little farther back, beyond the reach 
 of the waveS; the sand is loose and yielding. , The waves have 
 evidently been the means of binding the sand. 
 
 ''Each wave as it rushes up on to the beach carries in sus- 
 pension an amount of fine sand that is precipitated upon the 
 surface of the beach where the wave breaks and is washed 
 down into the voids of the larger particles of sand, thus puddling 
 or filling up all large interstices; but there is one more nec- 
 essary condition to secure firmness and sustaining power — 
 the sand must be moist. The fine capillary pores hold the 
 water, or rather the water in the pores holds the sand together 
 by virtue of its surface-tension, a well-known physical phenom- 
 enon; and it is this surface-tension or viscosity of water that 
 binds^the sand together and makes of the sand beach an ex- 
 cellent surface to walk or drive over. Strange as it may seem, 
 dust and water, commonly considered the two greatest enemies 
 of good roads, are, when in their proper places, the two 
 
 * "Economics of Road Construction," p. 21. 
 
BROKEN-STONE ROADS 177 
 
 elements that prevent the disintegration of macadam. The 
 writer conceives that macadam is first bound, not by cementing 
 action, but by the surface-tension of water on the capillary 
 voids of the screenings, and he offers the following facts as 
 evidence of the truth of this theory. 
 
 1. A road built without screenings will not bind unless it is 
 
 left long enough under the action of hoofs and wheels 
 to produce screenings. 
 
 2. A road built with screenings will not bind if all the dust 
 
 has been taken out of the screenings, leaving only the 
 coarser particles, but will bind immediately upon the 
 addition of the dust and water. The writer has tried 
 this experiment under the direction of a "good roads 
 expert" who had ordered all the dust to be screened 
 out, under the mistaken idea that it would be injurious 
 to leave it in; but, as stated, it was found impossible 
 to bind the road until the dust was spread over its sur- 
 face and washed into the voids. 
 
 3. A road will not bind until sprinkled, even after the screen- 
 
 ings or binder have been added. 
 
 4. Time for iron-rust or other cementing action to take place 
 
 is not necessary. A newly bound road, one that can 
 be picked to pieces without evidence of any cementa- 
 tion, will uphold a heavy wagon, behaving exactly 
 like an old road. 
 
 5. The screenings of a very hard rock like trap bind slowty, 
 
 sometimes not at all, due to insufficiency of dust nec- 
 essary to produce capillary voids; but upon addition 
 of a little sand or road-sweepings, bind immediately. 
 Conversely, the screenings of a soft rock, like lime- 
 stone, rich in dust, bind quickly. 
 
 6. Hygroscopic rocks (those that condense moisture upon 
 
 their surfaces), hke limestone, furnish better screenings 
 for binding and do not ravel as quickly in dry weather 
 as siliceous or quartz-like rocks. 
 
 7. Long-continued drought causes macadam to ravel and 
 
 finally go all to pieces, while it immediately knits 
 together again after a rain, 
 
 8. Macadam in tunnels, where not sprinkled, soon ravels, 
 
 as do likewise windswept roads that are kept free from 
 
 sufficient dust and moisture. 
 "The writer is not to be understood as advocating the use 
 of dust and water alone to produce binding, rolhng being 
 quite as important a factor, if a road is desired that will re- 
 tain a smooth surface. Rolling in the first place so con- 
 
178 
 
 THE ART OF ROADMAKING 
 
 solidates the stone that there is little chance for play or move- 
 ment, while the screenings and water added render appreciable 
 movement impossible. 
 
 "Sand and water, or screenings and water, though not a 
 true mortar, serve the same purpose, as we have seen, and the 
 less mortar in any masonry structure the more perfect and 
 durable it is/' 
 
 Steam rollers are made in different weights and used accord- 
 
 FiG. 12S.— Steam Roller. 
 
 Steam 
 rollers, 
 
 ing to the condition of the road to be treated, and the class of 
 material employed for repairs. Consideration also 
 must be given in regard to gas and water mains 
 and other pipes under the roadway, which, in many 
 instances, are quite near the surface, or have but a limited 
 cover. The weight of rollers principally used are 12 to 15 
 tons; the latter is mostly employed in localities where the 
 roadstones are hard and of good wearing quality. For good 
 country roads a so-called "10-ton roller" is sufficiently heavy, 
 as most of the culverts and many of the bridges are too weak 
 to sustain, with safety, the heavier rollers. The prices of such 
 rollers range from $2500 to $3500. 
 
 Breaking stone for road purposes was formerly done by hand, 
 
BROKEN-STONE ROADS 179 
 
 but since the invention of the mechanical stone crusher the 
 cost has been reduced from 50 to 200 per cent and 
 the daily output has been increased by 50 per /"^^ *^ 
 cent. In some European countries, however, hand- 
 broken stone is still preferred on the ground that it is better 
 broken and has sharper angles than that broken by the crusher, 
 and in many districts the occupation affords employment for 
 persons who would otherwise be thrown upon the public for 
 support. 
 
 The main objections to machine-broken stone are: 
 
 1. Want of uniformity in size of stones. 
 
 2. The stone is frequently flaky with round edges, which 
 is a very disadvantageous form for compacting. 
 
 3. Very tough stones have frequently to be passed several 
 times through the machine before they are properly broken. 
 
 4. Very soft stone are crushed to powder. 
 
 There are two types of crushers now in common use: the 
 
 "Oscillatory" (Fig. 129) and the "Gyratory'^ (Fig. 130). 
 
 The former consists of a strong iron frame, near 
 
 one end of which is a movable iaw, operated back- *°°^ 
 
 . "^ ' ^ crushers. 
 
 ward and forward a slight distance by means of a 
 toggle-joint and an eccentric. As the jaw recedes, the size 
 of the opening increases and the stone descends; as the jaw 
 again approaches the frame, the stone is crushed, the size 
 of the product being determined by the distance the jaw plates 
 are from each other at the lower edge. 
 
 The second form consists of a solid conical iron shaft sup- 
 ported within a heavy iron mass shaped somewhat like an 
 inverted bell. In the pattern shown in Fig. 130, an eccentric 
 sleeve, driven by a removable steel gear, rotates around a sta- 
 tionary central shaft, crowding a lined crusher-head outwardly 
 along horizontal lines, and producing the stroke which causes 
 the stone to be crushed as it descends. It is claimed that this 
 form has an advantage over the "oscillatory" in that no time 
 is lost in crushing, and the power is uniform and continuous. 
 
 The arrangement of the plant for handling and crushing the 
 stone is very important. It should be arranged so that the 
 stone may be delivered from the quarry or from the field on a 
 
180 
 
 THE AUT OF ROADMAKING 
 
 66 67 66 69 
 
 Fig. 129. — Oscillatory Crusher. 
 
 The main frame (50), a solid piece, with front and rear inside ends planed for the 
 seats of the stationary jaw plate (58) and the removable shims (75). (56) is the steel 
 swing jaw. having a jaw seat planed for the jaw plate (55). The steel pitman (52) is 
 lined with babbitt, and means of taking up the wear of bearing is effected by the tapered 
 keys (74) and the bottom half box (54). The toggle bearings (62) are of steel, and are 
 held in position by means of wedge blocks (63). 
 
 {Courtesy of The T. L. Smith Co.) 
 
 Fig. 130. — Gyratory Crusher. 
 
BROKEN-STONE ROADS 181 
 
 level with the mouth of the crusher, and thus save lifting the 
 entire product and throwing it into the machine. stone- 
 The crushed stone should be elevated to bins or crushing 
 pockets, one for each size, so arranged as to dis- plant. 
 charge directly into the carts or wagons that haul it to the 
 road. The bins should have a considerable capacity so as to 
 prevent stoppage of the machine if the roads are too bad for 
 hauHng or if for any other reason the removal of the crushed 
 stone is delayed. There should be ample room around the 
 plant to prevent the interference of teams coming and going. 
 
 Revolving screens made of steel plates perforated with holes 
 are used in the crushing plant to separate the stone into the 
 different sizes and to remove the tailings. Dust jackets are 
 used in connection with the screens, to separate the dust from 
 the crushed stones. 
 
 There are several kinds of portable plants which may be 
 bought at prices ranging from $1600 to $2500, which are 
 admirably adapted for country use. These plants include the 
 stone crusher, engine, and boiler, portable bins, revolving 
 screen, and an elevator to lift the stone after it is broken and 
 to discharge it into the screen. 
 
 The outfits are mounted on wheels and may be moved from 
 place to place at a comparatively small cost. Under ordinary 
 conditions from $50 to $100 will pay the expense of shifting 
 such a plant from its old location to a new location several 
 miles distant. 
 
 Stone distributing carts (Fig. 133a) are specially designed 
 to distribute broken stone on roads. The bottom of the cart 
 slopes downward to the back and the tail-board 
 is hinged at its upper edge and is furnished with Stone- 
 two adjusting chains by which the opening or ^^^^ " ^°^ 
 swing of the lower edge is regulated. Steel wings 
 are attached to the sides of the cart at the tail-board for the 
 purpose of spreading the stone the full width between the 
 wheels. The cart is tilted by a rack and pinion operated by 
 the driver and may be fixed at any desired angle. As the 
 stone flows from the rear of the cart it is leveled by a scraper 
 attached to the bottom of the tail-board; this scraper is piv- 
 
1S2 
 
 THE ART OF ROADMAKING 
 
BROKEN-STONE ROADS 
 
 183 
 
 oted at the center and can be adjusted so as to spread the 
 stone to any required thickness and over any desired width 
 equal to or less than the guage of the cart^ and thicker on one 
 side than the other. 
 
 Scarifiers (Fig. 134) are machines or mechanical devices 
 used for picking or breaking up of broken- 
 stone roads preparatory to the applying of new 
 road material. There are two types; one fashioned in the form 
 
 Scarifiers. 
 
 Fig. 132.— Portable Crushing Plant. 
 
 of ploughs and harrows, and the other based on the principle 
 of the rock drill or ore-stamping mill. They are drawn by 
 horses or tractors. The shoe is usually reversible and adjust- 
 able, and provided with a sharp and blunt point, according 
 to the class of work. When using scarifiers, it is essential 
 to have the road thoroughly soaked with water. 
 
 The Straight-edge, or Road Level (Fig. 135) is used for 
 obtaining the proper transverse form of roads. It consists 
 of a horizontal bar having in the center of its length 
 a plummet for ascertaining when the straight- ^t^aig 
 edge is level. Adjustable gauges formed of up- 
 right pieces of wood marked off in inches are placed at every 
 four feet. 
 
 Since water is alwavs needed in rollins; the macadam, a 
 
1S4 
 
 THE 
 
 a ART OF ROADMAKING 
 
 Fig. 
 
 133a.-Stoiie Distributing Cart. 
 
 (Courtesy of Climax 
 
 Road 
 
 Machine Co.) 
 
 Fig. 133b 
 
 .^Automatic Distributing Wagon. 
 
BROKEN-STONE ROADS 
 
 185 
 
 The road 
 
 watering cart or sprinkler should be provided, 
 official cannot often afford to wait for rain. A 
 cart with a capacity cf from 450 to 600 gallons 
 will be sufficient. Most of these carts are pro- 
 vided with extremelv broad tires, so that the cart assists in 
 
 Water 
 carts. 
 
 Fig. 134. — Scarifier. 
 
 consolidating the stone, instead of rutting it. Many communi- 
 ties are provided with one or more watering carts, so that it 
 is often unnecessary to purchase a new one for road building. 
 Comparisons of average costs of roads in one locality with 
 
 Fig. 135. — Straight-edge. 
 
 those in another are of little instructive value, for the reason 
 
 that the condition in the two localities compared 
 
 are never precisely similar, and but rarely even ^^^^ of 
 
 approximately alike. Particularly is this true surfaces. 
 
 of such details as earthwork and drainage. Even 
 
 the costs of broken-stone surfacines, which at first thought 
 
BROKEN-STONE ROADS 
 
 1S7 
 
 might be considered to be comparable^ one locality with 
 another, often lead to wrong conclusions. There are too 
 many factors which are dependent on local conditions. With 
 this caution, certain cost data of macadam work alone are 
 given below. The data are from the records of State work 
 in Massachusetts and New Jersey. In each case the measure- 
 ments and costs are of the stone in place and rolled, and the 
 lengths and costs are estimated upon the basis of a roadway 
 15 feet in width. Tables X and XI relate to the macadam 
 work alone and do not include the expenses of grading, drainage 
 or any other incidental items, and Table XII gives the average 
 of these items exclusive of macadam. 
 
 Table X 
 AVERAGE COSTS OF MACADAM WORK IN MASSACHUSETTS 
 
 Source 
 
 Depth of 
 Stone at 
 Center. 
 Inches. 
 
 Depth o( 
 Stone at 
 
 Sides. 
 
 Inches. 
 
 Total 
 
 Distance 
 
 Built. 
 
 Miles. 
 
 Cost 
 
 per 
 
 Mile. 
 
 Dollars. 
 
 Cost per 
 Square 
 Yard. 
 
 Dollars. 
 
 / 6 
 
 4 
 
 8.25 
 
 5496 
 
 0.6245 
 
 \ 4 
 
 4 
 
 6.97 
 
 4746 
 
 0.5393 
 
 [1 
 
 4 
 
 21.74 
 
 3696 
 
 0.4201 
 
 4 
 
 6.56 
 
 3459 
 
 0.3931 
 
 Cost per 
 Ton(2000 
 Pounds). 
 Dollars 
 
 Imported stone (trap 
 rock) 
 
 Local stone 
 
 1.956 
 2.025 
 1.396 
 1.583 
 
 Table XI 
 AVERAGE COSTS OF MACADAM WORK IN NEW JERSEY* 
 
 Depth 
 of Stone. 
 
 Inches. 
 
 Total 
 
 Distance 
 
 Built. 
 
 Miles. 
 
 Cost per 
 Mile. 
 
 Dollars. 
 
 Cost per 
 Square Yard. 
 
 Dollars. 
 
 4 
 5 
 
 6 
 8 
 
 6.441 
 
 1.772 
 
 7.129 
 
 21.748 
 
 2148 
 3652 
 5637 
 6187 
 
 0.2422 
 0.4150 
 0.6299 
 0.6958 
 
 * Report of the Commissioner of Public Roads of New Jersey for 1905 
 
1S8 THE ART OF ROADMAKING 
 
 Table XII 
 
 AVERAGES OF CONTRACT PRICES FOR THE SEVERAL 
 CONSTRUCTION ITEMS, EXCLUSIVE OF MACADAM.— 
 MASSACHUSETTS HIGHWAY COMMISSION 
 
 Excavation per cubic yard $0.4352 
 
 Borrow * ' . 5622 
 
 Ledge excavation " 1 . 78 
 
 Cement concrete masonry " / . . 8 . 85 * 
 
 Shaping road for broken stone per square yard 0. 281 
 
 Vitrified 12-inch clay pipe, in place per linear foot 0.7662 
 
 Vitrified 10-inch clay pipe, in place " . ti436 
 
 Vitrified 8-inch clay pipe, in place " 0.5700 
 
 Vitrified 18-inch clay pipe, in place.' " 1 . 57 
 
 12-inch iron water pipe, in place " 2 . 20 
 
 18-inch iron water pipe, in place " 3 . 75 
 
 Stone filling for V-drains, in place per cubic yard 0.8271 
 
 Guard rail, in place per linear foot 0.2770 
 
 Catch-basins, in place (including catch-basin frames and grates) 
 
 Each 35.74 
 
 Setting stone bounds *' 1 . 85 
 
 * This price does not include the cement or the steel reinforcement, 
 which may be estimated at about $3 additional. 
 
CHAPTER IX 
 ROADS IN MOUNTAINOUS DISTRICTS 
 
 Probably the greater part of the roads in mountainous 
 districts have been built for strictly utilitarian purposes; in 
 the United States most of them have been built to meet a 
 need arising in some way from the existence of 
 mineral deposits. The prospector, with his tools, Evolution of 
 blankets, and simple food packed upon his burro, j-oads 
 goes ahead; for him neither roads nor trails are 
 necessary or specially desirable. He finds the mineral; the 
 news gets abroad, and at once others flock in to the new^y 
 explored region. Then comes the trader with supplies, men 
 to buy the mineral output, and miners to work the new finds. 
 The freighter with his mule teams furnishes transportation, 
 and for his use are built the first mountain roads. The first 
 desideratum seems to be a route over which vehicles on four 
 wheels can travel without tipping over. It is often so steep 
 in places that wagons can only be pulled up with blocks and 
 tackle, and descend with wheels rough locked and dragging 
 a heavy log behind. 
 
 Next come roads to particular mines, toll roads, county and 
 State roads, usually of such bad construction that it ma}^ be 
 truthfully said that the money squandered in traveling over 
 them would, in five years or less, build new ones intelligently 
 located and properly constructed. Such roads would make 
 available vast deposits of minerals now lying idle, furnishing 
 new markets for labor, mining machinery, and farm products, 
 and benefiting directly or indirectly ever}^ industrial and 
 financial enterprise in the country. 
 
 But mountain roads must not be considered alone from an 
 industrial standpoint — the inspiring, health-giving effects of 
 mountain air and mountain scenery are universally conceded 
 
 189 
 
190 
 
 THE ART OF ROADMAKTNG 
 
 Fig. 137. — ^The Mesa and Roosevelt Stage Road, Salt River Project, 
 
 Arizona. 
 
ROADS IN MOUNTAINOUS DISTRICTS 191 
 
 and for both those Uving in them, and those who come to them 
 for business, pleasure, or health, the need for roads which can 
 be traveled in safety and comfort is just as imperative as it 
 is elsewhere. The sentiment which demands good roads is 
 increasing steadily and will not halt at the foot of the moun- 
 tains. 
 
 The location and construction of roads in mountainous 
 countries present greater difficulties than in an ordinary 
 undulating country. The most important consideration is 
 grade. As stated in Chapter I for freight traffic the maximum 
 grade admissible is 12 per cent. Four animals, 
 together with the wagons used on a "fountain 
 road, are all that one driver can safely and properly handle 
 on steep grades. When he uses two wagons, lead and trail, 
 at every stop ascending he must hold both wagons by the 
 brakes on the lead; in descending with heavy loads, he must 
 control his wagons with brakes on both and when the road is 
 icy he must control the descent by rough-locking one or more of 
 his rear wheels. To do this, he attaches some rough device, 
 like a piece of chain, or a short steel runner, grooved on the 
 upper side to fit tRe tire and with projecting prongs on the 
 lower, to the rear wheel, and a chain attached firmly to the 
 center of the forward axle is then tightly fastened to this 
 rough-lock. Thus secured, as the wagon descends the hill, 
 the wheel remains rigid and the rough-lock plows into the 
 surface of the road. 
 
 Experience in heavy freighting has shown that wagons can 
 be actually and satisfactorily controlled in all weathers on 
 12 per cent grades, but that they can not be thus controlled 
 on steeper grades, and that where much heavy freighting has 
 been attempted on steeper grades it has almost invariably 
 been attended with terrible accidents. On a properly con- 
 structed dry road four animals, averaging 1300 pounds each in 
 weight, will, haul 6500 pounds, total weight, distributed 
 between wagons and contents, up a 12 per cent grade, at the 
 rate of about IJ miles per hour. Descending, the four animals 
 will haul all that a wagon can hold up, but in practice this 
 amount rarely exceeds 16,000 pounds on a single wagon or 
 
192 
 
 THE ART OF ROADMAKING 
 
 Fig. 138.— Ute Pass, Colorado. Fig. 
 
 139. — Ouray and Silverton 
 Toll Road, Colorado. 
 
ROADS IN MOUNTAINOUS DISTRICTS 193 
 
 20;000 pounds on a lead and trail, and the average is probably 
 about 10,000 pounds or 14,000 pounds. 
 
 Mountain roads are routes of travel between points of 
 different altitudes and the most common, as well as the most 
 serious, mistake made in their location is the attempt to 
 cover this distance by too short a line. On a 12 per cent grade 
 every pound of freight going up is elevated 12 feet for each 
 100 feet of horizontal distance traveled. On an 8 per cent 
 grade it is elevated 12 feet in 150 feet of horizontal distance 
 traveled, while on a 6 per cent grade it is elevated the same 
 amount in 200 feet of horizontal distance; or, in other words, 
 the distance required to get a 12 per cent grade must be 
 increased one-half for an 8 per cent grade and doubled for a 
 6 per cent grade. The limit of load which a team can pull 
 on any road is determined by the steepest place in that road, 
 and it is putting it very moderately to say that a team will 
 haul up 50 per cent more load in the same time between two 
 given points on a road with an 8 per cent maximum than it 
 could haul on one of similar surface with a 12 per cent maximum. 
 A 12 per cent grade is admissible as a maximum and it is 
 rare that a mountain road is built with a less maximum gradient, 
 but it is also true that there are very few places where it was 
 not feasible to secure a maximum under this, and the extra 
 length that would be required is generally much less than 
 might at first be supposed. 
 
 Besides the advantage in upfreighting, the 8 per cent road 
 is vastly safer for both light driving and freighting; on 
 passenger vehicles brakes, while desirable, are not essential to 
 safety; with heavy loads, if the brake fails, there is a fair 
 chance of escape for driver, team, and wagon. Such a road 
 is not seriously damaged by rain and melting snows, which 
 work much injury on steeper grades; damage from rough 
 locking is enormously reduced, and as such practice can be 
 to a great extent avoided, the time thus consumed is saved. 
 Repair bills on wagons and harness are lessened, and the life 
 of wagons is greatly prolonged. It is a pleasure to drive 
 down an 8 per cent grade, but as gradients become steeper 
 the sense of danger grows more and more keen. As a rule, a 
 
194 
 
 THE ART OF ROADMAKING 
 
 lower gradient than 8 per cent means too long a route without 
 commensurate advantage, while a higher means an unnecessary 
 loss in the very purpose for which a road is required. The 
 maximum adopted in the old Government pike crossing the 
 Alleghenies was 7 per cent. 
 
 Next in importance to grade is location. The worst obstacle 
 encountered on mountain roads is snow. The snow slide, or 
 avalanche, comes sweeping down the mountain side, carrying 
 along everything it meets and depositing its accumulations 
 
 Courtesy of The Literary Digest. 
 Fig. 140.— The Devil's Elbow, Isle of Wight. 
 
 when the momentum is exhausted. The customary routes of 
 
 these slides are generally quite apparent to the 
 
 Importance JJ]LQ^ntaineer, and in layino; out a mountain road, 
 of location. ' .iii- ^ i- •, -i 
 
 they can be avoided by crossmg to the farther side 
 
 of the gulch and placing the line so high that the snow slide 
 
 will always stop beneath it. If a snow slide covers a road it 
 
 is rarely practicable to clear it for heavy traffic for months. 
 
 The accumulation of ice, snow, rocks, trees, and debris of all 
 
 kinds is so enormous, and the cost of removing it during the 
 
 cold, short days of winter so excessive that a snow slide generally 
 
 remains where it falls until warm w ather aids in its removal. 
 
ROADS IN MOUNTAINOUS DISTRICTS 195 
 
 In roads designed for heavy traffic, it is the wisest economy to 
 avoid snow slides at almost any cost. 
 
 Next to snow slides in obstructive effect are snowdrifts. 
 These are due to air currents and act with remarkable uni- 
 formity from year to year. The places where these drifts 
 accumulate in excessive amount can generally be located 
 and avoided by careful attention. Deep ravines almost 
 always catch snow. In a snow region it always pays to go 
 around a point by a sidehill grade in preference to cutting 
 through it. 
 
 Roads should always be located on slopes facing south and 
 east in preference to slopes facing north and west, as they 
 afford the sun greater power to settle and melt the snow. 
 
 Very steep sidehill slopes and hard rock increase the cost of 
 road building, but it is often possible to avoid them to a greater 
 or less extent. In fact, many of the problems in road location 
 that at first seem impossible of practicable solution can be 
 solved by observation and study. Thousands of miles of 
 mountain railroad have been replaced at enormous cost, 
 because of mistakes in original location, which more intelligent 
 study would have avoided, and the same principle applies in 
 road building. 
 
 In level regions roads are drained to protect their foundations ; 
 
 in the mountains they are drained principally to protect the 
 
 surface. Water naturally runs off from a slope, 
 
 and in doing so it must always leave more or less ? •'.^*^* ° 
 ^ , '' drainage, 
 
 effect. Every mountam road must run through a 
 
 valley or along a hillside. If in a valley, the surface should 
 
 have a crown of at least 6 inches, with gutters and ditches 
 
 and drains just as in properly constructed roads in a level 
 
 region. In mountain roads on hillsides, the outside of the 
 
 road must be the highest, with the view of conducting the 
 
 water as quickly as possible towards the inside bank, where 
 
 it should find a gutter to carry it to the nearest drain. This 
 
 prevents the water from spilling over and washing away the 
 
 outside bank, and also has a tendency to keep it from running 
 
 down in the ruts and enlarging them. Another reason for 
 
 keeping the outside of the road on hillside grades higher than 
 
196 THE ART OF ROADMAKTNG 
 
 the inside is that there is always a tendency for the wheels of 
 a heavily loaded wagon to slew toward the lower side, which 
 becomes very serious when the road surface is slippery, and 
 terrible accidents have resulted. Rain or melting snow 
 always wears down some of the material from the inside bank. 
 If the road surface slopes outward, this debris follows the 
 drainage across the road, continually increasing the slope, 
 sometimes very rapidly in cold weather; hence, the roadbed, 
 for the protection both of the bed and the trafhc, should be 
 constructed and maintained with an inward slope of at least 
 one-half inch to the foot. The inside gutter should empty 
 into drains crossing the roadbed diagonally at suitable intervals, 
 determined by the amount of drainage. 
 
 The importance of batter * in mountain road building is 
 almost universally ignored. It is very common to see hill- 
 side grades constructed with an insecure vertical 
 Necessity for c];.ii-,]~,ing constituting the outside of the roadbed; 
 slope ^ ^^^ inside bank cut as nearly vertical as possible, 
 and three-quarters of the entire width of the road 
 perhaps built of material filled in, the filling generally including 
 all the trash available (boughs, sticks, boulders, etc.), with a 
 covering of such material as the bank affords; and of insufficient 
 width, to hold a wagon when the road is first built. The 
 destructive forces of nature act vigorously on such a roadbed 
 from the start. Ice and water rapidly wear down the inside 
 bank, and the debris falls upon the roadbed; the trash founda- 
 tion settles and the road sinks, sloping outward; water finds 
 its way through this loose material and undermines the roadbed. 
 The cribbing settles, rots, and soon disappears altogether and 
 unless the road is practically rebuilt in a few years it grows 
 more and more dangerous, and finally becomes absolutely 
 impassable. 
 
 Cribbing is temporary in character, its use costly, and 
 always to be avoided wherever practicable; when indispensable, 
 it should have a batter not steeper than one horizontal to 
 four vertical. Roads excavated in solid rock should have 
 
 * The side slope of a cut, embankment, or wall. 
 
ROADS IN MOUNTAINOUS DISTRICTS 197 
 
 an inside batter of one horizontal to four vertical, which affords 
 some latitude for projecting loads. 
 
 Cost; amount of traffic, safety, and comfort are the factors 
 which must determine the width of a wagon road. Comfort 
 and convenience are of course promoted by a 
 double track; extensive traffic demands it; safety 
 requires so much of it that teams can pass and never be caught 
 unawares on a single track. 
 
 The proper width for double track and heavy teams is 16 
 feet, while it is possible for them to pass with extra caution on 
 a 14-foot track on a straight road. For single track and 
 greatest safety a desirable width is 12 feet, while 10 feet is 
 generally safe, and an 8-foot roadbed can be driven over if 
 the inside bank has sufficient batter, so that vehicles will not 
 be crowded off. 
 
 Double tracks for turnouts should never be less than 75 feet 
 long. These should be visible from each other and from every 
 foot of the intervening distance. Before laying out a road, 
 the maximum distance between turnouts should be determined 
 from all the conditions, especial consideration being given 
 to the amount of travel likely to occur at night, and this 
 maximum should never be exceeded. Where this maximum 
 is over 100 feet for turnouts adapted to heavy traffic, the road 
 should be widened for short distances at intervening intervals, 
 for light vehicles. A width of 12 feet will allow light vehicles 
 to pass each other in an emergency and where the utmost 
 economy must be observed, this extra width for a short 
 turnout can often be secured by cutting into the bank. If 
 this has been constructed with proper batter, the cutting 
 makes the inside bank too steep at the turnout, but it is a 
 choice of evils in the interest of greater convenience and 
 safety to light traffic. 
 
 It is obvious that in sidehill grades excavated in easy ground, 
 that portion of the road that is formed from the original 
 material in place must for a time be more solid than the 
 portion built out. It is consequently desirable on roads 
 designed for very heavy traffic that all the wheels of heavily 
 loaded wagons should rest upon the original solid formation. 
 
198 
 
 THE ART OF ROADMAKING 
 
 Standard vehicles are either 4 feet 6 inches^ or 5 feet between 
 centers of tires. A very heavily loaded wagon can not be 
 restricted to the same width of roadbed as light vehicles, but 
 
 Fig. 141. 
 
 should be allowed a latitude of 8 feet for varying conditions 
 of draft, road surface, etc. 
 
 Table XIII 
 
 WIDTHS OF ROADBED FOR VARIOUS SIDEHILL SLOPES, 
 WITH AMOUNT OF MATERIAL EXCAVATED PER 100 
 
 FEET 
 
 Sidehill 
 Slope 
 
 Width Made by Fill (m), 
 Feet. 
 
 Total Width (e6). 
 Feet. 
 
 Excavation per 100 
 Feet. Cubic Yards. 
 
 {cad) , 
 Deg. 
 
 8-ft. 
 Cut. 
 
 6-ft. 
 Cut. 
 
 5-ft. 
 Cut. 
 
 8-ft. 
 Cut. 
 
 6-ft. 
 Cut. 
 
 5-ft. 
 Cut. 
 
 8-ft. 
 Cut. 
 
 6-ft. 
 Cut. 
 
 5-ft. 
 Cut. 
 
 5 
 10 
 15 
 20 
 25 
 30 
 35 
 
 7.89 
 7.83 
 7.72 
 7.52 
 7.29 
 6.87 
 5.94 
 
 5.92 
 
 5.87 
 5.79 
 5.64 
 5.47 
 5.15 
 4.45 
 
 4.93 
 
 4.89 
 4.83 
 4.70 
 4.56 
 4.30 
 3.71 
 
 15.89 
 15.83 
 15.72 
 15.52 
 15.29 
 14.87 
 13.94 
 
 11.92 
 11.87 
 11.79 
 11.64 
 11.47 
 11.15 
 10.45 
 
 9.93 
 
 9.89 
 9.83 
 9.70 
 9.56 
 9.30 
 8.71 
 
 11.26 
 
 25.33 
 
 43.41 
 
 67.41 
 
 103.41 
 
 161.78 
 
 276.59 
 
 6.33 
 
 14.25 
 24.41 
 37.89 
 58.15 
 91.0 
 155.59 
 
 4.40 
 9.97 
 16.96 
 26.33 
 40.41 
 63.19 
 108.06 
 
 A hillside composed of picking or plowing ground is rarely 
 ever steeper than 35° and a grade formed by cutting 8 feet 
 into such material makes an excellent road. The inside 
 
ROADS IN MOUNTAINOUS DISTRICTS 199 
 
 8 feet of it is solid and adapted to the heavest traffic, and the 
 bs-lance, made by the fill, is sufficiently wide to allow lighter 
 wagons to pass. The following table shows the total width 
 of roadbeds for various sidehill slopes and the amount of 
 material which must be excavated for each 100 feet of roadbed 
 for 8-, 6- and 5-foot cuts into plowing or picking ground. 
 
 From these tables it will be seen that while there should be 
 a cut of 8 feet into the bank for a double-track road, a cut of 
 5 feet will give a practical single-track road with only ff- as 
 much excavation, or that the double-track road requires more 
 than two and one-half times as much excavation as a single 
 track. 
 
 In sidehill grades in rock the conditions are very different. 
 
 Fig. 142. 
 
 Rock excavations are made by blasting, which throws a large 
 proportion of the rock down the hill, and consequently the 
 material thus broken out can not be depended on with any 
 certainty for fill. That which does remain available increases 
 in bulk about 50 per cent. 
 
 When the natural surface of the rock is too steep to hold 
 a fill it is often the better practice to cut the entire roadbed 
 out of the solid rock as in Fig. 142, Such a roadbed is absolutely 
 secure and in no danger of giving way without warning, 
 through the failure of cribbing or retaining walls. For a 
 single track this roadbed should be 10 feet wide, carefully 
 protected on the outside by a guard log firmly bolted to the 
 rock. The amount of excavation in solid rock on different 
 hillside slopes to obtain such a roadbed is shown in the follow- 
 ing table, which can be used for deeper cuts by using the 
 rule that the amount of material varies as the square of the 
 
200 
 
 THE ART OF ROADMAKING 
 
 depth of the cut. For instance, an 11-foot cut will require 
 \ 11- the excavation shown in the table; a 12-foot cut, -\-^-l-, etc. 
 
 
 Table 
 
 XIV 
 
 
 AMOUNT OF 
 
 EXCAVATION IN 10-FOOT CUT INTO SOLID 
 
 
 ROCK 
 
 Sidehill Slope 
 {bad). Degrees. 
 
 Excavation per 100 
 Feet. Cubic Yards, j 
 
 Sidehill Slope 
 (bad). Degrees. 
 
 Excavation per 100 
 Feet. Cubic Yards. 
 
 5 
 
 16.30 
 
 25 
 
 97.78 
 
 10 
 
 34.07 
 
 30 
 
 125.19 
 
 15 
 
 53.33 
 
 35 
 
 157.04 
 
 20 
 
 74.07 
 
 40 
 
 196.30 
 
 Curves. 
 
 The minimum curve allowable on mountain roads has the 
 arc of a circle with a 30-foot radius for its outer edge. All 
 sharp curves and their approaches from each direc- 
 tion should be level, a principle of great importance 
 to the efficiency and safety of mountain roads. 
 
 Where a road zig-zags backward and forward up a hill in 
 approximately parallel lines the turns are called switchbacks. 
 They are expensive and very undesirable, and where possible, 
 they should be avoided. 
 
 Wherever a bridge is approached by a curve its end should 
 be flaring and the roadbed made wide and level, as curved 
 approaches to bridge are very undesirable and should be 
 avoided if practicable. 
 
 In the mountains the hillside slopes are often covered with 
 broken stone of various sizes, called "slide rock." This slide 
 rock may be very coarse and the surface extremely 
 ragged, when it is called "heavy slide"; it may be 
 fine and bound together by soil, in which case it can be plowed 
 or it may be fine and dry and run just like dry sand when 
 disturbed, when it is called "fine slide rock." To construct a 
 road in coarse slide a retaining wall is built on the outside of 
 the grade, of large rocks weighing not less than 75 pounds 
 each. The roadbed is then made as smooth as possible with 
 the material at hand, and covered with fine slide. Coarse and 
 
 Slide rock. 
 
ROADS IN MOUNTAINOUS DISTRICTS 201 
 
 rough heavy sHde may give the very best results when care- 
 fully handled, furnishing an absolutely solid, perfectly drained 
 road foundation, unaffected by the elements, and requiring 
 less outlay for repairs than any other variety of mountain 
 road. 
 
 Probably the most difficult material which the mountain road 
 builder encounters is fine shde rock; it appears to be so utterly 
 unstable in every way that it seems impossible to obtain 
 either definite or satisfactory results. It cannot be plowed 
 or scraped and neither man nor animal can keep a footing in 
 it, but fortunately, such patches arc never very long, and 
 while the process of making a road across it is tedious and 
 expensive, it can always be successfully accomplished. 
 
 In la3'^ing out mountain roads a spongy soil filled with 
 water is often encountered which almost invariably proves 
 to be shallow, with a substratum of good road 
 material. This surface soil must be removed and 
 a system of drainage adopted to keep surface water from 
 running onto the roadbed. Occasionally corduroy is used 
 to meet such conditions, but it is a very undesirable expedient, 
 and is adopted only in extreme cases. 
 
 A thorough system of both cross and longitudinal drainage 
 must be adopted to protect the corduroy from quickly rotting 
 and to keep its foundation from settling unevenly. 
 
 As all mountains vse made of rock, the soil with which they 
 are in places covered being merely a product of rock decom- 
 position and water concentration, a rock dressing 
 prepared by nature can generally be found within 
 convenient distance of a mountain road. A hard rock in 
 angular fragments of two inches or iess diameter makes an 
 excellent road covering if some suitable fine material is put 
 on top of it. Sometimes it is best to mix two kinds of rock, 
 one hard and durable and the other disintegrating more 
 rapidly through wear and chemical decomposition. 
 
 Most mountain roads at first require dressing only in stretches, 
 and later for repairing holes and ruts and for maintaining a 
 suitable inward slope. With a covering of 3 inches, 600 tons 
 of rock dressing will completely cover a full mile of single- 
 
202 THE ART OF ROADMAKING 
 
 track road, and on the average mountain road that amount 
 would be sufficient for 2 miles. 
 
 As in all broken stone roads if the surface is to wear evenly, 
 it should be homogeneous, and not built or repaired in spots 
 with different kinds of materials; a clay road should not be 
 patched with gravel nor a gravel road with clay. Holes or 
 ruts should be filled with material of the same kind as con- 
 stitutes the road surface. Detritus, resulting from traffic, 
 which is washed by rains into the gutters, should not be placed 
 back upon the surface, for it has lost its power of cementation; 
 it should be thrown away and replaced by fresh material. 
 
CHAPTER X 
 IMPKOVEMENT AND MAINTENANCE OF COUNTRY ROADS 
 
 Reconstruction and Improvement 
 
 The reconstruction or improvement of existing roads is 
 chiefly a question relating to the waste of effort and the sav- 
 ing of expense. Good roads reduce the tractive resistance of 
 loads, and consequently the cost of moving the load. 
 
 The financial value of the benefits of a proposed improve- 
 ment must be carefully estimated before any work is under- 
 taken and this value must be ascertained for each portion of 
 the road. To obtain this the following data are required: 
 
 1. The quantity and quality of the traffic using the road. 
 
 2. The cost of haulage. 
 
 3. Plan and profile of the road. 
 
 4. Character and cost of the proposed improvement. 
 
 The defects of existing roads are generally: (1) unnecessary 
 ascents and descents; (2) unnecessary length; (3) imperfect 
 surface ; and the improvement may be divided 
 into three branches : Defects of 
 
 1. Rectification of alignment and grades, con- ^^*^^°6 
 sisting of the application of the principles laid 
 
 down for the location, etc. , of new roads. This includes 
 straightening the road by eliminating unnecessary curves and 
 bends, improving the grade by either avoiding or cutting 
 down hills and embanking valleys, increasing the width 
 where requisite, and rendering it uniform throughout (Fig. 
 13). 
 
 2. Drainage, consisting of the application of the principles 
 laid down for the drainage of new roads, and in the construc- 
 tion of the necessary works. 
 
 3. Improvement of the surface, in the best possible manner. 
 
 203 
 
204 THE ART OF ROADMAKING 
 
 Among the benefits of decreasing length and reducing 
 grades are: 
 
 1. Saving in time. 
 
 2. Reduction in wear and tear of horses and equipment, 
 
 3. Saving the cost of maintenance of such un- 
 Benefits of necessary portion, 
 ments ^* I^^duction in the cost of haulage. 
 
 5. Saving by the return of the land previously 
 occupied by the road to other and perhaps more renumerative 
 uses. 
 
 6, Decrease in the working time of the horses and a slight 
 increase in the load. 
 
 The benefits of improving the surface are a reduction in the 
 cost of haulage and in wear and tear of horses and vehicles. 
 
 Clay soils can be improved only by means of thorough 
 drainage. 
 
 If sand, gravel, ashes, coal-dust, furnace-slag, or shells can 
 
 be obtained, a coating of any one of them, 4 inches thick, well 
 
 compacted by rolling, will form an improvement; 
 
 ^^ if none of these materials can be obtained, the clay 
 
 itself may be utilized by being burned, as described 
 
 in Chapter VII. 
 
 In the maintenance of clay roads sods and turf should not 
 be used to fill holes or ruts, as they soon decay and form soft 
 mud; neither should the ruts be filled with field-stones, as they 
 will not wear uniformly with the rest of the road, but will 
 produce hard ridges. As all the sun and wind possible are re- 
 quired to keep the surface in a dry and hard condition, trees 
 and close hedges should not be allowed within 200 feet of a 
 clay road. 
 
 In the improvement of sand roads the aim is to make the 
 wheelway as narrow and well-defined as possible, so as to 
 have all the vehicles run in the same track. An 
 ^° abundant growth of vegetation should be en- 
 
 couraged on each side of the wheelway, to prevent 
 as far as possible the shearing of the sand. Ditching beyond 
 a slight depth to carry away the rain-water is not desirable, 
 for it tends to hasten the drying of the sands, which is to be 
 
MAINTENANCE OF COUNTRY ROADS 205 
 
 avoided. Where possible the roads should be overhung with 
 trees, the leaves and twigs of which catching on the wheelway 
 will serve still further to diminish the effect of the wheels in 
 moving the sands about. If clay can be obtained, a coating 
 6 inches thick will be found a most effective and economical 
 improvement. A coating of 4 inches of loose straw will in a 
 few days' travel grind into the sand and become as hard and 
 firm as a dry clay road. 
 
 Maintenance and Repairs 
 
 Proper maintenance is as important as good construction. 
 This consists in keeping the roadway, as nearly as practicable, 
 in the same condition as it was when originally made; the 
 repair of a roadway is the work rendered necessary to bring 
 it up to its original condition after it has become deteriorated 
 by neglect to maintain it. There is a wide distinction between 
 the two operations; the former keeps the road always in good 
 condition while the latter makes it so only occasionally. 
 
 No matter how well a road may be made, or how carefully 
 the materials used have been inspected, it will soon show de- 
 fects which it is almost impossible to guard against, 
 
 such as variableness in the quality of the material, ^^^^^^'T' or 
 
 ^ *' ' maintenance, 
 
 and slighting on the part of the workmen. More- 
 over, every material, whether natural or artificial, is con- 
 tinually undergoing a process of deterioration by the action of 
 the elements. The materials employed for pavements are 
 not only subjected to the destroying action of the elements, 
 but also to abrasion and concussion, which by themselves are 
 powerful destroying agents. 
 
 The essential requisite to the preservation of a good sur- 
 face is eternal vigilance. If a depression appears in conse- 
 quence of settlement, defective material, or other causes, it 
 must be at once eliminated; if not, it will be quickly deepened 
 and enlarged by each succeeding vehicle, and will thus become 
 an obstacle to safe traveling. 
 
 Good maintenance comprises: 
 
 1. Constant attention to repair the damages made by traffic 
 and the elements. The character and quantity of these re- 
 
206 
 
 THE ART OF ROADMAKING 
 
 {From Good Roath Magazine.') 
 Fig. 143. — Section of Country Road before Improvement. 
 
 (From Good Roads Magazine.) 
 Fig. 144. — Section of same Road after Improvement. 
 
MAINTENANCE OF COUNTRY ROADS 
 
 207 
 
 pairs will vary with the character of the pavement and the 
 manner of its construction. With granite blocks laid on a 
 concrete foundation they will be the least; with broken stone 
 they will be the greatest; the other materials, as wood, asphalt, 
 and brick, lying between. 
 
 2. Cleaning, i.e., removing the detritus caused by 
 horse-droppings, and other refuse. (See Chapter XIX). 
 
 wear. 
 
 (From Good Roads Magazine.) 
 Fig. 145. — Section of same Road showing effects of Travel, resulting 
 from improper Maintenance. 
 
 3. Laying the dust. (See Chapter XI.) 
 
 The most obvious feature in road maintenance is the ap- 
 phcation of new materials, but the prevention of avoidable 
 wear, by keeping the surface and the body of the road in good 
 condition, is hardly less important; and the removal of the 
 materials from the road after they are worn to detritus, the 
 care of the surface, and attention to drainage, are essential 
 parts of a good sj^stem of maintenance. Experience proves 
 that a road with sufficient strength, good surface, and thor- 
 ough drainage can be kept in first-rate order with a itluch 
 smaller quantity of materials than an inferior, ill-kept road 
 
208 THE ART OF ROADMAKING 
 
 requires, and though a greater amount of manual labor may 
 be necessary, a good road, on the whole, is generally more 
 cheaply maintained than a bad one, especially when there is 
 an}' considerable amount of traffic. 
 
 There are three principal systems of maintaining pavements : 
 
 1. By contract, at a fixed price per square yard per annum 
 
 for a fixed period. This method is used for asphalt 
 
 ys ems o pavements in both the United States and Europe 
 maintenance. ^ . ^ 
 
 and for wood pavements in Europe, but rarely in 
 
 America. It has the advantage of having someone admittedly 
 responsible for the condition of the pavement, but it is the 
 most costly system and there is always difficulty in determin- 
 ing the exact condition of the pavement at the expiration of 
 the contract. 
 
 2. By independent contracts for the labor and materials, 
 the tools and supervision being furnished by the city. 
 
 3. By men in the employ of the city. This is the most 
 extensively used and most satisfactory system. 
 
 As soon as a country highway is finished and opened to 
 traffic a system of maintenance must be instituted. No style 
 .of construction is sufficiently permanent to admit 
 T'""* X"''^ of the road being left to take care of itself. Whether 
 roads. built of earth or stone, it will eventually wear 
 
 into ruts and holes, the time depending upon the 
 quality of the material, the form of construction and the 
 amount of traffic. The chief object in the maintenance of 
 an earth road is to get rid of the watex as quickly and as fully 
 as possible. In maintenance, as in construction, water is 
 the great enemy of good roads. The secret of success in main- 
 tenance is to keep the surface smooth and the side ditches 
 open. There are three systems in vogue: (1) By contract with 
 private parties; (2) By personal service; (3) By men per- 
 manently employed for the purpose by the community. 
 
 1. The contract system is unsatisfactory, owing to the 
 difficulty of getting a proper observance of the terms of the 
 contract from the contractor or his employers. 
 
 2. The personal-service or labor-tax system is not applicable 
 to the maintenance of improved roads, nor, in fact, to any 
 
MAINTENANCE OF COUNTRY ROADS 209 
 
 class of roads; it is unsound in principle, unjust on its opera- 
 tion, wasteful in its practice, and unsatisfactory in its results. 
 
 3. The system of permanently employing men for the pur- 
 pose by the community has been adopted by France, Germany,, 
 and nearly all European countries and by the New York State 
 Highway Commission, and has many advantages. The men 
 so employed become familiar with the peculiarities of their 
 sections and with the best way to deal with them, and good 
 men soon learn to take an interest in the road which it is 
 their business to keep in order. 
 
 The maintenance, or keeping of the road in proper order, 
 consists of: 
 
 1. Removal or prevention of the detritus either in the form 
 of dust or mud, and removal of the horse-droppings and other 
 rubbish. 
 
 2. Filling of ruts or depressions. 
 
 3. Cleaning out of the ditches, catch-basins, and water- 
 courses. 
 
 4. Keeping down the dust in dry weather. The dust pro- 
 duced by the disintegrating action of the weather and the 
 friction of the traffic renders the road heavy for traffic and 
 annoys passengers and horses. 
 
 The errors commonly committed in the maintenance of 
 broken-stone roads are: 
 
 1. The unskilled application of materials. 
 
 2. Use of improper and unsuitable materials. Errors in 
 
 n T.T 1 4. i ' maintenance. 
 
 3. Neglect of repairs. 
 
 4. Insufficient and unskillful manual labor. 
 Well-made roads are frequently allowed to go to ruin through 
 
 these wrongful methods of maintenance, requiring at some 
 period that the neglect be made good at one time, instead of 
 the work being spread out in proper maintenance over a period 
 of years. 
 
 The cost of maintenance varies widely, depending princi- 
 pally upon the degree of perfection with which the road was 
 originally constructed, and is largely influenced by 
 the class of labor employed in maintenance. ^^^} ^^ 
 
 The factors of cost of maintenance are: 
 
 1. The quantity of material that will be required to replace 
 
210 THE ART OF ROAD MAKING 
 
 the annual wear caused by traffic and the weather, and re- 
 moved in the form of mud and dust, depending upon: 
 
 a. Width of road. 
 
 b. Nature of foundation, drainage, and thickness of 
 crust. 
 
 c. Situation of the road. 
 
 d. Quahty of the stone to be appHed. 
 
 2. Cost of the material procured either by contract or by 
 day labor under the supervision of the authorities, this de- 
 pending upon: 
 
 a. Cost of quarrying. 
 
 b. Cost of breaking. 
 
 c. Cost of hauling from quarry to roadside. 
 
 d. Cost of stacking at the roadside. 
 
 e. Cost of loosening the stones in the heaps. A con- 
 
 siderable item in frosty weather or when the 
 stones have lain for some time. 
 
 f. Cost of hauling stones from depots to the portion 
 
 of the I'oad where they are to be used. 
 
 g. Cost of preparing the road-surface to receive the 
 
 stone, 
 h. Cost of spreading the stone. 
 
 3. Cost of compacting the stone. 
 
 4. Cost of cleaning and scraping. 
 
 5. Cost of cleaning up the side of the road, ditches, etc., 
 and keeping open watercourses, depending upon the frequency 
 with which it will have to be done, usually three times a year 
 is sufficient. 
 
 6. Cost of dust prevention. 
 
 To these items must be added a certain sum per mile for 
 repair and replacing of tools, etc., and about 5 per cent on the 
 total cost to cover the administrative charges. 
 
 Combining these factors in the following manner will give 
 the probable cost of maintenance per mile of a given road.* 
 
 * Byrne, "Highway Construction," p. 66S. 
 
MAINTENANCE OF COUNTRY HO ADS 211 
 
 Let A^ = average number of cubic yards of stone spread per 
 mile; 
 A = cost per cubic yard of stone in depots; 
 L=cost of preparing road-surface and spreading stone; 
 R=cost per cubic yard of rolling; 
 
 C= average number of times sides will require cleaning; 
 c=cost of cleaning sides, etc., per mile; 
 ^=average number of times road will require cleaning; 
 s =cost of cleaning per mile; 
 T7= average number of times road will require sprink- 
 ling; 
 ii;=cost of sprinkling per mile; 
 
 D= annual depreciation and renewal of hand tools; 
 7= cost of administration, say 5 per cent of total cost; 
 X = cost of maintenance per mile per annum. 
 Then 
 
 X=N{A+L+R)+Cc+Ss + Ww+D+L 
 
 If stone is quarried b}' d&y's labor, its cost will be 
 
 A=q+b+h+j), 
 
 in which g=cost of quarrying; 
 6=cost of breaking; 
 /i=cost of hauling; 
 p— cost of stacking. 
 
 Where funds have been provided for road improvements, 
 efforts are usually directed toward building as much road as 
 possible, while the matter of maintenance is entirely over- 
 looked, and no funds are provided for needed repairs. The 
 fact that no great inconvenience or damage arises from a 
 slight depression in the road surface, or from a few loose stones, 
 occasions neglect, and the condition of the road is allowed 
 to become gradually worse. When the surface becomes, in 
 time, so rough as to be a public nuisance, it is found that the 
 cost of restoring the road is considerable; moreover the rough- 
 ness of the road in the meantime has caused a ''wear and tear'' 
 
212 THE ART OF ROADMAKING 
 
 to wagons, carriages, horses, etc., which is, in the aggregate, 
 of considerable importance. 
 
 This neglect of repairs to public roads is very poor economy. 
 It would be a remarkably well-constructed road that would 
 not show some defects soon after it began to be extensively 
 used. With the greatest possible care an earth roadbed can- 
 not be made strictly uniform as to solidity, and heavy loads 
 passing over the crust formed by the stones will press some of 
 the stones into soft places in the earth bed, and this in time 
 will cause a defect on the surface of the road. A very shght 
 depression will at first appear, which may be detected only 
 after a rain (by the water which will remain for some time in 
 the depression). If this depression is permitted to remain 
 it will soon become deeper and broader. As the wagon wheels 
 go in and out of it they grind out the stone softened by water, 
 and cut down the sides, so that what was at first a slight de- 
 pression soon becomes a hole. Such neglect causes subsequent 
 repair to be expensive. 
 
 Some of the causes which make repairing necessary, and 
 
 which should be avoided or removed as far as possible are: 
 
 - 1. Defective construction of earth bed. 
 
 Causes 
 
 which make 2. Failure to cut off under-ground water by 
 
 repairs drainage. 
 
 necessary. ^ Rain or storm water permitted to lie in 
 
 pools along the roadsides or in side ditches which do not 
 
 carry the water from the road. 
 
 4. The side slope being insufficient to carry the storm water 
 from the road to the side ditches. 
 
 5. The longitudinal grade of the road being greater than the 
 slope from center to sides. 
 
 6. The formation of ruts. 
 
 7. Raveling, or picking up loose stone. 
 
 8. Surface stone not of proper quality and not uniform. 
 
 9. Roadbed not sufficiently compacted. 
 
 10. Accumulation of trash or rubbish on the road. 
 
 When the road reaches the condition where restoration is 
 necessary the work should be done in sections as large as 
 convenient. The periods at which the restoring or recoat- 
 
MAINTENANCE OF COUNTRY ROADS 213: 
 
 ing of a broken-stone road will be required depend upon the 
 quantity of the traffic, and vary from one to five or 
 more years. 
 
 The methods practiced for recoating are: (1) the surface is 
 cleaned from mud and dirt and the new stone spread over it; 
 sprinkled and rolled in the same manner as a new construc- 
 tion; (2) the surface is "scarified/' or loosened or broken up 
 by picking or ploughing, before spreading the new stones. 
 The object of this is to enable the new stones to become more 
 completely incorporated with the old material. 
 
 For the proper care of the roadway, an adequate number 
 of skilled laborers are necessary. This labor should be per- 
 manently employed by the community, and should be under 
 the direct orders and supervision of the engineer in charge of 
 the road. The force should consist of the engineer in charge^ 
 assistant engineers or inspectors, chief foreman, foremen and 
 laborers. 
 
 The following instructions to Roadmen* will be found 
 useful: 
 
 " 1. Never allow a hollow, a rut, or a puddle to 
 remain on a road, but fill it up at once with chips /^^tructions 
 f , 1 , 1 ^ ^ to roadmen. 
 
 from the stone-heap. 
 
 2. Always use chips for patching, and for all repairs during 
 the summer months. 
 
 3. Never put fresh stones on the road if by cross-picking and 
 a thorough use of the rake the surface can be made smooth and 
 kept at the proper strength and section. 
 
 4. Remember that the rake is the most useful tool in your 
 collection, and that it should be kept close at hand the whole 
 year round. 
 
 5. Do not spread large patches of stone over the whole width 
 of the road, but coat the middle or horse track first, and when 
 this has worn in, coat each of the sides in turn. 
 
 6. Always arrange that the bulk of the stones may be laid 
 down before Christmas. 
 
 7. In moderately dry weather and on hard roads, always pick 
 up the old surface into ridges six inches apart, and remove 
 all large and projecting stones before applying a new coating. 
 
 * Road Improvement Association, London, England. 
 
2U THE ART OF ROADMAKING 
 
 S. Xever spread stones more than one stone deep, but add a 
 second layer when the first has worn in, if one coat be not 
 enough. 
 
 9. Use a steel-pronged fork to load the barrels at the stone- 
 heap, so that the siftings may be available for ''binding" 
 and for summer repairs. 
 
 10. Never shoot stones on the road, and crack them where 
 they lie, or a smooth surface will be out of question. 
 
 11. Go over the whole of the new coating every day or two 
 with the rake, and never leave the stones in ridges. 
 
 12. Remove all large stones, blocks of wood, and other 
 obstructions (used for diverting the traffic) at nightfall, or 
 the consequences may be serious. 
 
 13. Never put a stone upon the road for repairing purposes 
 that will not pass freely in every direction through a 2-inch 
 ring, and remember that still smaller stones should be used 
 for patching and for all slight repairs. 
 
 14. Recollect that hard stone should be broken to a finer 
 gauge than soft, but that the 2-inch gauge is the largest that 
 should be employed under any circumstances where no steam 
 roller is employed. 
 
 15. Never be without your ring-gauge. It should be to 
 the roadman what the compass is to the mariner. 
 
 16. If you have no ring-gauge, remember Macadam's advice 
 that any stone you cannot put easily into your mouth should 
 be broken smaller. 
 
 17. Use chips, if possible, for binding newly laid stones to- 
 gether, and remember that road-sweepings, horse-droppings, 
 sods of grass, and other rubbish, when used for this purpose, 
 will ruin the best road ever constructed. 
 
 18. Remember that water-worn or rounded stones should 
 never be used upon steep gradients, or they will fail to bind 
 together. 
 
 19. Never allow dust or mud to lie on the surface of the road, 
 for either of these will double the cost of maintenance. 
 
 20. Recollect that dust becomes mud at the first shower, 
 and that mud forms a wet blanket which will keep a road in a 
 filthy condition for weeks at a time, instead of allowing it to 
 dry in a few hours. 
 
 21. See that all sweepings and scrapings are put into heaps 
 and carted away immediately. 
 
 22. Remember that the middle of the road should always be a 
 
MAINTENANCE OF COUNTRY ROADS 215 
 
 little higher than the sides, so that the rain may run into the 
 side gutters at once. 
 
 23. Never allow the water-tables, gutters, and ditches, to 
 clog up, but keep them clear the whole year through. 
 
 24. Always be upon your road in wet weather, and at once 
 fill up with " chips" any hollows or ruts where the rain may lie. 
 
 25. When the main coatings of stone have worn in, go over 
 the whole road, and, gathering together all the loose stones, 
 return them to the stone-heap for use in the winter to follow; 
 for loose stones are a source of danger and annoyance and should 
 never be allowed to lie on any road.'' 
 
 The proper season for laying the bulk of the fresh materials 
 is in the autumn and early winter. The precise time at which 
 it can be begun will depend on the climate, weather, 
 
 subsoil and the nature of the material. As soon as ^^.son tor 
 
 repairs. 
 the surface of the road softens from the wet, patch- 
 ing of hollows, or wheel tracks, and channels worn by water, 
 should be commenced, the mud having been previously re- 
 moved where necessary. The greater part of the new materials 
 should be put on before the end of the year, so that the}^ may 
 be at least partially worked in before winter, when they are 
 most required in the road, and before severe frost comes. 
 Unconsolidated materials are more annoying to the traffic in 
 frosty weather, and there is waste by the stones being crushed 
 and scattered instead of being incorporated in the road. Stones 
 laid late in the winter seldom consolidate thoroughly, and those 
 laid in the spring hardly set at all, but work loose in the dry 
 weather, if they are not of a binding nature. If a road from 
 any cause shows weakness in the spring, and requires stoning, 
 everything must be done to aid consohdation, and great atten- 
 tion to the newly laid materials will be required. All stones 
 which do not bind must be raked off as the season advances 
 and there is no longer any prospect of their working in. 
 
 The autumn work on roads is generally commenced after 
 harvest, as the additional men which are required are then 
 more easily to be had. Cleaning up the sides cannot be well 
 done in dry weather, but the constant laborers should take 
 advantage of suitable moist weather to get forward with it, 
 so that the water-tables may be cleared, the outlets to the side- 
 
216 
 
 THE ART OF ROADMAKING 
 
 ditches opened, and the sod bordering trimmed before the wet 
 weather sets in. If the manual labor be allowed to get behind- 
 hand in the autumn, there is often little chance of roads re- 
 covering it until the winter is over. Scraping is very necessary 
 as soon as rainy weather commences, to get rid of the mud 
 which then forms on the surface from the effects of the wear 
 in the summer. As soon as the cleaning up of the sides is 
 finished, and the scraping is well forward, the laying of materials 
 
 Fig. 146.~A Well-kept Country Road. 
 
 in small patches should begin. The first patches should be 
 laid in places naturally damp, and when the road generally 
 begins to soften from the wet weather, spreading materials 
 and scraping will take up all the constant laborers' time, and 
 usually requires casual labor besides until the middle of De- 
 cember, or even later. In the beginning of the year, after the 
 great bulk of materials has been spread, less labor is necessary; 
 only small patches to make good weak places which have 
 shown themselves during the winter remain to be laid, and 
 scraping is hin^jered by frost, and by the consolidated materials 
 
MAINTENANCE OF COUNTRY ROAD.S 217 
 
 about the road. As the spring advances more scraping will 
 be required in damp weather, and in dry weather the stones 
 which have not worked in will require the roadman's attention, 
 and must be raked off if they will not set. The spring and 
 early summer is the best season for cleaning out side-ditches 
 which are not too wet. The stuff is moved easier when still 
 moist, and it is well to get forward with work of this sort in 
 the spring, and not to leave it till the autumn, when there is 
 so much other work to be done. 
 
CHAPTER XI 
 THE CONTROL AND PREVENTION OF ROAD DUST * 
 
 On wood, asphalt, stone, and brick pavements, the wear is 
 so slow as to be practically negligible, and dust arising from any 
 of these surfaces is produced by extraneous matter brought 
 to the road in various ways from outside sources. But in the 
 case of macadamized roads one of the most important problems 
 that has yet been forced to the attention of road engineers and 
 municipal officials is the suppression or prevention of dust 
 arising from the road itself. There is hardly a section of the 
 country in which this problem has not had the consideration of 
 local officials, and the lack of information as to how 
 Importance iq overcome it has resulted in many cases of trans- 
 Drevention foi"i^ing the ''dust nuisance" into a mud or slime 
 nuisance. This is especially so in rural districts 
 where many officials have purchased oil without proper 
 knowledge of its ingredients and its adaptability for use 
 on the roadways of their districts, and have spread the 
 oil broadcast over the highways, transforming them into 
 slippery mires and making them unsafe for traffic of any kind. 
 
 The ''dust nuisance" is not, however, so much the result 
 of the natural formation of dust by ordinary and reasonable 
 traffic, as it is of the use of automobiles, the wheels of which 
 draw out and throw into the air the particles that would other- 
 wise fill the crevices and act as a bond between the broken 
 stones of the macadam construction, f 
 
 -Dust has always been a feature of broken-stone roads, being 
 at the same time the result of use and a check upon excessive 
 
 * The best general treatise on this subject is "Road Preservation and 
 Dust Prevention," by William Pierson Judaon, from which much of the 
 data of this chapter has been drawn. 
 
 t See Appendix III, "Concerning the Wear of Roads by Automobiles." 
 
 218 
 
THE CONTROL AND PREVENTION OF ROAD DUST 219 
 
 wear. Whenever the surface becomes free from dust, by wind 
 
 effect or otherwise, it has been necessary to spread a thin layer 
 
 of sand or screenings, or other fine material, as a 
 
 protection to the stone fragments forming the road, Value and 
 
 . . effects of 
 
 and to prevent them from "raveHng" or losmg road dust. 
 
 their bond. When these stones or the screenings 
 
 forming the protective layer, or both, consist of limestone, 
 
 the resulting impalpable dust is most objectionable to people 
 
 driving upon the road and even more so to those living along 
 
 it. When this hmestone dust is wet, the resulting mud is 
 
 the most slippery and dangerous for rubber-tired wheels, 
 
 causing more side-slip than any other material used for 
 
 roads. 
 
 In 1905, when automobiles became common, the raising and 
 scattering of road-dust increased greatly, and in the summer 
 of 1906, when their use greatly increased both in Europe 
 and in the United States, the subject at once became acute, 
 and road-builders everywhere found that a new condition had 
 suddenly developed, particularly on those mac- 
 adam roads radiating from the cities where auto- Effects of 
 mobiles were most used. They found that the traffic 
 preservation of the roads demanded a better and 
 more enduring surface, and one that will neither require nor 
 produce the loose surface layer which had heretofore been a 
 necessary feature. 
 
 In the Minutes of Proceedings of the Institution of Civil 
 Engineers (London) for September, 1906, it is said: 
 
 "Experience has proved that the broad pneumatic tires of 
 heavy motor-cars at high speed draw out the small particles 
 which bind the material of a macadamized road. On the main 
 roads ^ more than half the traffic is of motor-cars, which may 
 reasonably be expected to become a more and more popular 
 means of travel, to which the roads must now be adapted by 
 introducing into them some material which would make them 
 dustless; for which purpose, tar, or some tar derivative, is 
 the only remedy now in sight. Motors have come to stay, 
 
 * Of England. 
 
Before Treatment. 
 
 (Courtesy of Standard Oil Company.) 
 After Treatment. 
 
 Fig. 147. — The Dust Nuisance and Its Abolition. 220 
 
THE CONTROL AND PREVENTION OF ROAD DUST 221 
 
 and the road-builders mean to make the roads fit to carry 
 them." 
 
 That this condition equally concerns the road-builders of 
 the United States is shown in the 1907 report of Logan W. Page, 
 Director of the U. S. Office of PubUc Roads, in which he 
 says : 
 
 *'In recent years perhaps the most important and certainly 
 the most difficult problem which has engaged the attention of 
 highway, engineers is the prevention of dust. Until the general 
 introduction of motor vehicles, dust was considered as neither 
 more nor less than a nuisance. The problem has now, how- 
 ever, assumed a more serious aspect. The existence of our 
 macadam roads depends upon the retention of the road-dust 
 formed by the wearing of the surface. But the action of 
 rubber-tired motor-cars moving at high speed soon strips the 
 macadam road of all fine material, the result being that the 
 road soon disintegrates. . . , This is a subject which should 
 engage the earnest attention of the National Government at 
 once. No matter how important we may deem the building 
 cf good roads, we cannot but consider it even more important 
 to preserve those which have already been constructed." 
 
 James Owen, M. Am. Soc. C.E., one of the most experienced 
 cf American road engineers^ in a paper on '* Highway Con- 
 struction," before the 1906 meeting of the American Society 
 cf Municipal Improvements, said: 
 
 "Every system of road construction should be immediately 
 supplemented by a maintenance organization, as in time the 
 construction department disappears, but the maintenance de- 
 partment is permanent, and is the vital point in the future 
 road-development of the country. . . . The automobile 
 is demanding attention from engineers as to whether there 
 should not be new means and methods for road mainten- 
 ance." 
 
 Similar statements of motor-car effects, made by govern- 
 ment commissioners, civil authorities, engineers, and in period- 
 icals, all tend to show the dangers of road dust and the im- 
 portance of its prevention. 
 
 The demand for relief comes not only from recognized 
 
222 
 
 THE ART OF ROADMAKING 
 
THE CONTROL AND PREVENTION OF ROAD DUST 223 
 
 authorities and from the road users, but also from the property 
 owners who live along the roads , and pay for 
 them, and who find that the former dust to which Necessity 
 they had objected has become an hundred-fold prevention 
 worse and not to be endured ; some country 
 residences which have long been desirable and valuable, have 
 suddenly become neither tenantable nor salable, and others 
 have been sold for half their cost because of the dust from 
 adjacent roads. In Massachusetts passing motor-cars have 
 even thrown up fragments of road-stones into the windows of 
 houses. 
 
 The situation is well stated in the following quotation from 
 the 1907 report of the Massachusetts Highway Commission, 
 which has built and maintains the main parts of one of the 
 finest road systems in the United States: 
 
 "Perhaps the most important discovery of the year is the 
 extraordinarily destructive effects upon stone roads of the large 
 number of swiftly moving automobiles. Practically all the 
 main roads are thus affected. It has been noted that the binder 
 is swept from the road, and that the number-two stone (^-in. 
 to H-in. size) is disturbed; in some instances standing on the 
 surface, and in others being left in windrows along the road- 
 side. The Commission is satisfied that a material change in 
 the methods of maintaining stone roads must be made. While 
 old methods have proved satisfactory in the past, they fail 
 under the present usage. The automobile has come to stay 
 and will increase in numbers, and it must be reckoned with." 
 
 The 1908 report of the Commission says: 
 
 "The destructive work of automobiles during the past year 
 was even more marked than it was in 1906." 
 
 These conditions and the opinions of various authorities, 
 have led to a great amount of experimental work, and to the 
 invention of many processes and devices having for their object 
 either temporary treatments which should hold the dust in 
 place, or better, the adoption of more permanent methods 
 which will prevent the formation of dust, and which will be 
 apphcable to the many thousands of miles of existing fine roads 
 of broken-stone which Europe has had for nearly a century and 
 
224 
 
 THE AR'l OF ROADMAKING 
 
 ^^9HH 
 
 
 HE?'" ■"■ ^^ B^ 
 
 
 JjW^ 
 
 EHMIH 
 
 
 
 
 m ^ 
 
 ^WI|^^BB 
 
 
 ^fcfijX \ 1 
 
 
 Mm. 
 
 ■hH 
 
 
 »i^/"\ 
 
 
 .W'S '■/'' '■ 
 
 jMH^HH 
 
 
 Ki>^M 
 
 
 I^^K 
 
 ■I^H 
 
 
 
 
 HH 
 
 I^H 
 
 
 
 
 n 
 
 
 
 
 
 ^H 
 
 uS^K^KE.'' -' ^^w'-^^^^h^^I 
 
 
 SF^!*^^^^^?tr7^^^^lMWKi 
 
 
 MH 
 
 ^^^^^^^B^^^.^^ 
 
 ^^-' 
 
 
 ^S| 
 
 ^n 
 
 ^^^Hi^' 
 
 
 
 
 ^^Wil 
 
 ^^^^^^^^S!^'^' '- 
 
 IL 
 
 
 
 ^■■"■i 
 
 {Courtesy of the Barrett Mfg. Co.) 
 
 Fig. 149. — Weston, Mass. On Boston-New York Automobile Route. 
 A turn protected for two years with tarvia. 
 
THE CONTROL AND PREVENTION OF ROAD DUST 225 
 
 parts of America for one-tenth as long, and which must now 
 be saved from threatened destruction. 
 
 The Enghsh engineers have had the advantage of an abun- 
 dant and cheap supply of coal-tar, and have taken the lead in 
 efforts to find ways to get the best results from applying it 
 — as well as various oil-emulsions — to parts of their great 
 extent of fine and old roads. The French engi- 
 neers, whose national road system in its general General 
 scheme and organization and in the details of exDeriments 
 its execution and maintenance, is the finest in 
 the world, have devised and widely used methods for apply- 
 ing bituminous binders and coatings to road surfaces, while 
 American engineers have produced the best form of bituminous 
 macadam, or bitulithic, as well as the appliances for making 
 it of uniform rehability and upon a large scale. 
 
 Americans have also invented a method for the consolidation 
 and asphaltic treatment of sandy and other soils, using a 
 peculiar "roUing tamper" and heavy asphaltic oil, and have 
 made in CaUfornia many hundreds of miles of dustless roads 
 which are comparatively cheap and which there, in the absence 
 of heavy rains and deep frosts, are durable. 
 
 The dust problem is open to two methods of attack: (1) by 
 
 applying materials to the road which will hold down the dust 
 
 formed, or (2) by methods of construction designed 
 
 to reduce the formation of dust, and therefore the Methods 
 
 wear of the road, to a minimum. ^ ^^,. 
 
 ' prevention. 
 
 The foUowmg are the general methods in use for 
 preventing or reducing dust. Each method more or less 
 retains or agglomerates the dust already formed or prevents its 
 formation; the first form being classed as temporary binders 
 and the last two as permanent binders. 
 
 1. Sprinkling roads with fresh water. 
 
 2. Sprinkling roads with natural salt water. 
 
 3. Sprinkling roads with mixture of water and calcium 
 chloride. 
 
 4. Sprinkling roads with an oil emulsion. 
 
 5. Impregnating roads with special crude oils. 
 
 6. Impregnating road surfaces with special coal-tar products. 
 

 -^i 
 
 >, * < ^ " vt ^W* ' 
 
 41 _^ 
 
 m ' '■ 
 
 ^^^i 
 
 
 '"'■ ' ^ ^^ 
 
 iL;--- 
 
 
 ^n|pfe|^c^L tj^hmrsI^^^m 1 7 
 
 1^ 
 
 
 
 Fig. 150. — Studebaker Road Oiler. 
 
 Fig. 151. — The "Topping" Oiler in Operation. 226 
 
THE CONTROL AND PREVENTION OF ROAD DUST 227 
 
 The most common and the most costly way to prevent dust 
 and to preserve roads is to sprinkle them with water. To 
 keep roads always wet entails expense which is ' . 
 prohibitive even foi city streets and park roadways, 
 on some of which $700 to $900 per mile per year is expended 
 for sprinkling thirty to forty feet width, in order to make them 
 dustless during an average of six hours per day. During dry 
 and hot weather the sprinkUng to be effective must be repeated 
 several times per day and the surface alternates between mud 
 and dust. When tried on rural roads it has usually been in- 
 effective, costly, and soon abandoned. 
 
 Sea-water is used with results even more unsatisfactory, for 
 although the hygroscopic effect of the deposited salt prolongs 
 the duration of moisture on the road, its presence 
 in the dust and mud adds to their injurious effects; 
 the salty, sticky mud damaging vehicles, corroding metals, 
 and loosening the fragments of stone. Moreover, the accumu- 
 lated salt, when dry, hurts throats and eyes, damages cloth- 
 ing, furniture and to some extent the feet of horses. 
 
 Calcium chloride in solution has been used as a substitue for 
 
 water, giving a shghtly better effect at about the same cost. 
 
 The principle of this method is that this salt is 
 
 hydroscopic and when mixed into the road surface Calcium 
 ,, r 1 • - • T • . chloride. 
 
 (by means of having it m solution m the water 
 
 of the sprinkling cart) it absorbs additional moisture from the 
 air, thus rendering continuous moisture without the frequent 
 sprinkling necessary with water. It also has a feeble chem- 
 ical action which unites some of the silicates of the macadam. 
 While the limited experiments in this country have met with 
 some success, its principal use is in England, where the moist 
 climate offers favorable conditions and where over two hundred 
 of the local road authorities are using it increasingly. Its weak 
 solution is non-corrosive and harmless. 
 
 The process is best suited to special, hmited cases of fine 
 residence streets adjoining large cities, where a municipal 
 supply of hydrant-water is available for sprinkling, and it is 
 specially appUcable as preparation for parades or road' races. 
 At the best, the effects of calcium chloride are temporary and 
 
228 
 
 THE ART OF ROADMAKING 
 
 make no radical betterment in the road surface. It is not 
 applicable to the great extent of existing broken-stone roads 
 which have no water supply, and which demand permanent 
 treatment to check wear in order to reduce dust, which is more 
 or less true also of all patented solutions. 
 
 Oil emulsions are practically mixtures of water, oil and alkali 
 (as ammonia or potash) ; they are more easily and cheaply 
 applied than oils and they avoid some of the obvious 
 
 i 
 
 
 
 
 
 i 
 
 fl-iiliilMMM 
 
 
 iiiB 
 
 'i 
 
 rt ^B m \_ 
 
 H 
 
 
 ..-.. 
 
 
 
 
 
 ."■■rsr^i,^^^^:,,/ ..... 
 
 rS!^r:r:.-y- 
 
 -■-- -^^^^^^^'_ 
 
 2 
 
 r 
 
 ■i-ii 
 
 
 (Courtesy of Standard Oil Company) 
 Fig. 152. — Sprinkling Road Oil Emulsion from Ordinary Watering Can- 
 
 objections to the use of oils. Their effects on road-dust are 
 Oil Emul- usually only temporary, but the results are im- 
 sions. mediate and travel is not interrupted. 
 
 There are in use many processes, patented and otherwise, 
 for making and applying emulsions of oil, including vegetable 
 oils, crude petroleum, residual oil, creosote-oil, oil-tar, coal-tar, 
 and similar materials, in all of which cases some way is found 
 to emulsify the oily or bituminous material in water, so that 
 the mixture can be spread by a sprinkling or a spraying device, 
 or usually by an ordinary watering-cart. The results are more 
 lasting than those from the chemical salts mentioned above. 
 
THE CONTROL AND PREVENTION OF ROAD DUST 229 
 
 Many unsuccessful attempts have been made to use Pennsyl- 
 vania and Ohio oils having a paraffin base, or some of the Rus- 
 sian oils having a naphtha base, both in their crude form and 
 in emulsions; but these have all failed, because such petro- 
 leums are not suited to roadwork, refusing to bind the road 
 materials, having an ill order and forming a greasy slime. 
 
 Oils having an asphaltum base, like some of the petroleums 
 of California, Texas, Oklahoma, Kansas, and Kentucky in the 
 United States, and some from Galicia and from Baku in Europe, 
 are the only ones suitable; but if any kind of oil is sprayed or 
 sprinkled in its crude form on a hard macadam road, the re- 
 sult is liable to be most objectionable in regions of normal rain- 
 fall, which may mix the oil into injurious mud. 
 
 All oil mixtures in which acids or alkalies are used to form 
 soapy emulsions which will mix with water, may be expected 
 to cause the subsequent road-dust, even though it be slight in 
 quantity, to be irritating and injurious to the throat, eyes and 
 skin, in proportion to the acridity of the solvent, and some of 
 the mixtures have been disused for that reason. 
 
 Attempts have been made since 1894 to use crude petroleum 
 or some of its derivatives, or some oily by-product of gas manu- 
 facture, to control and prevent dust. These at- 
 tempts, many of them unsuccessful, have led to 
 knowledge as to the kinds of oil which are unsuitable and as to 
 the conditions which cause failure. Experience has also shown 
 that oils of certain characteristics, properly applied under the 
 right conditions, give good results at reasonable costs. There 
 will undoubtedly be a great increase in the near future in the 
 use of heated asphaltic oils, not only to prevent dust, but also 
 to improve sandy roads and to preserve gravel and broken- 
 stone roads. 
 
 Crude petroleums, which contain the largest proportion of 
 pure asphaltum, give the best results. Petroleum, without 
 asphaltum, having a paraffin base, and those having a naphtha 
 base, are useless, as mentioned above. Some of the Cali- 
 fornia oils as they come from the wells, especially those in 
 the Bakersfield district, producing petroleums having 60 to 
 84 per cent of pure asphaltum, are valuable mainly for their 
 
230 THE ART OF ROADMAKING 
 
 use on roads and are used in a crude state with most satis- 
 factory results. Petroleums with asphaltic bases from Texas, 
 Kentucky, Kansas and Oklahoma, some of the Russian oils 
 from Baku, and those from Galicia (Austria) and Borneo 
 are valuable mainly for their volatile parts, leaving residuum 
 which is effective for roadwork after distillation has removed 
 the naphtha, gasoline, illuminating-oil, and other elements 
 which would be detrimental to roads. The by-products 
 thus left are variously known as " residual oil," " roadbed 
 oil," ''steamer-oil," and other trade names. 
 
 California crude petroleum, heavy in asphaltum, which is 
 98 per cent pure, was first used for roadwork at Santa Barbara 
 in 1894 and its use in its native state has since been general and 
 in most cases successful; but its general use throughout the 
 country is prevented by difficulties of transportation. 
 
 It has been a common thing during the past few years for 
 some county official, to whom all oils look alike, to buy a 
 car-load of oil of unknown quality and to have it sprinkled 
 from watering-carts in unrestricted quantity, without experi- 
 enced direction or regard to details of road con- 
 Inexperience (^ition or of weather, and without attempt to 
 in handling 
 road oils. remove or to cover the greasy mud caused by 
 
 sudden rainfall, or to warn the traffic to avoid 
 the fresh oil. It gets on everything — on plants, bushes, 
 trees, vehicles, and clothes, and the results have often been 
 most objectionable to residents and have caused opposition 
 and waste which good management would have avoided. 
 
 It has been demonstrated, however, that the objectionable 
 features are avoidable by the successful use of crude and 
 residual oils in various parts of this and other countries. 
 It has also been shown that the oil sprinkled over the surface 
 of a macadam road does not save the road from wear but 
 merely stops the dust; and that a light coating of sand 
 shaken over the freshly-oiled surface will stop spattering of 
 the oil, which was the cause of many of the complaints. 
 
 The types of oiled roads peculiar to Cahfornia have been 
 evolved from the local conditions of material and climate, and 
 the results have been such as to induce efforts to adapt the best 
 
THE CONTROL AND PREVENTION OF ROAD DUST 231 
 
 of these constructions to other conditions elsewhere. This 
 consists in mixing heated asphaltic oil with loosened, mois- 
 tened soil, and consolidating with a " rolling tamper " into 
 a firm, smooth, six-inch layer, which is durable and dustless. 
 In the best practice the crown of a road of soft materials 
 to be oiled must be high and its sides well drained, 
 because water with or without freezing floats General 
 much of the oil or gets under the oiled crust and ^in^g roads. 
 softens it. The hotter the oil when applied, the 
 warmer the weather and dryer the road, the better. 
 
 In California, according to soil, from 175 to 400 and some- 
 times 600 barrels (of 42 gallons each) of asphaltic oil are 
 needed per mile of 10- to 16-foot road per year. Two or 
 three treatments are needed on a new road during the first 
 year if the road is of a loamy or sandy nature. After a road 
 has been well oiled and a crust is formed, care must be taken 
 not to break through the crust. Prompt repairs are impera- 
 tive. It is better to use several successive applications than 
 to flood the road with oil. 
 
 Road materials, which if wet would pack firmly under 
 roller or traffic and still remain slightly porous, are the 
 materials which are the best for use by saturating with 
 suitable thick adhesive oils. Such oils suppress dust and 
 harden the road. Road materials of certain clays, earths, 
 gravels, which when wet pack tight or bake in the sun and 
 which pulverize into dust, must be either loosened by harrow- 
 ing, or otherwise made porous before being oiled, and then 
 must be covered with sand, screenings or the material of 
 the road. Oiling roads is a case where a little knowledge 
 is dangerous, and where much knowledge- and experience must 
 be employed to select suitable oils and to use them correctly. 
 
 Refined coal-tar, produced in gas manufacture and treated 
 to remove its injurious parts and yet to preserve its ductility 
 and to secure uniformity, has been generally ac- 
 cepted by the road authorities of France and Eng- Coal-tar 
 land, and also by those road-engineers in the United tfons ^^~ 
 States who have given the subject most attention, 
 as being the best material with which to improve broken- 
 
232 
 
 THE ART OF ROADMAKING 
 
 -^ ^ ^ flij ^ ^ 
 
 3 a o QJ a ■ G:S 
 
 m § ?} m 0== --^ 
 
 S (D -3 3 ^1 . Jd 
 
 ■u C c3 -J "^.o fS ^ f 
 
 72 E g -g ^ ^ 2 ^ ^ 
 
 == " F= -1: a -S q . 
 
 I 
 
 P^ 
 
 y O 
 
 •S J3 tn ^^ G r- O 
 
 a S 2 ^ a'^-SS 
 ij E w (rt Ki L --H ■ 
 
 = ^ 
 
 
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 tn O 
 
 .a .s ^ -^ S .j 
 
 ) >> o C ■ 
 
 ; t£H- 
 
 tfl o ri .t; N (!3 
 
 a to w) ™ n 3 tc-TJ 
 
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 ri >^_-^ « d ^ ^ 
 
 QJ « rf ^ 5 .t; ^ .;2 
 
 1 -i « t:; 
 
 -fl o 
 
 •3 «^ 
 ^ ■*- H 
 
THE CONTROL AND PREVENTION OF ROAD DUST 233 
 
 ■stone roads; binding the surface of existing roads and bettering 
 the construction of new roads, thereby preventing the forma- 
 tion of road dust. Experience in 1910 favors use of asphaltic 
 residual oils or hquid asphalt. 
 
 For success in the use of tar, its quahty is most important. 
 If it is heated too much and "refined" too far, it becomes 
 brittle and makes black dust. If not refined enough, the light 
 oils and ammonical liquors will disintegrate it. A reliably 
 uniform product is essential. Good tar, properly applied, is 
 the cheapest and best form of dust-preventer and 
 
 road-saver, beina; more effective and durable than Success of 
 
 ... " tar via t- 
 anj other now known, except asphaltic oil. This ■ » 
 
 decision was reached by the Massachusetts Highway 
 
 Commission after a year of use and careful observation. It 
 
 also accords with the opinion of the best-recognized English 
 
 and French authorities on road construction. 
 
 The success of *'tarviating'^ depends, however, upon the 
 quahty of the tar, which must be the best possible; the state 
 of the weather, which must be clear and warm; the condition 
 of the road-surf acC; which must be clean and dry; the manner 
 of application, which must be rapid and complete. 
 
 Too much tar on the surface will be worse than the former 
 mud and dust, being sticky when warm and slimy when wet; 
 and to avoid these serious objections the tar, either hot or cold, 
 is forced in a fine spray into the minute voids and spaces be- 
 tween the stone fragments, by means of pneumatic pressure 
 from a "tar-sprayer," by which the quantit}- and the distribu- 
 tion are made uniform, and small pools of tar are not left on 
 the surface. Such a tar-sprayer must work so rapidly that full 
 advantage can be taken of warm, dry weather, during which 
 to treat one-half of the width of several miles of load per dav. 
 
 From this it will be reahzed what an important part the 
 tar-sprayer plaj^s in the process of " tarviating/' and why 
 inventors have been busy devising various machines for 
 increasing the speed and decreasing the cost of application. 
 Eight machines made for this purpose in England j^_ 
 and France were subjected to a competitive trial, spraying 
 in 1907, by the Enghsh Roads Improvement machines. 
 Association, before road-engineers and representatives of 
 
234 
 
 THE ART OF ROADMAKING 
 
 {From Judson's '"Dust Pretention") 
 Fig. 154. — Spreading Tarvia by Hose from Tank. (Michigan Boulevard, 
 
 Chicago.) 
 
 {From Judson's " Dust Prevention^") 
 
 Fig. 155.— Spreading Tarvia from a Slotted Sprinkler. 
 
THE CONTROL AND PREVENTION OF ROAD DUST 235 
 
 associations from all parts of Great Britain as well as from 
 France, Germany, Italy, and Egypt. 
 
 Some of these machines spread both hot and cold tar under 
 pressure through spraying nozzles, giving rapid and uniform 
 flow and distribution without the need of sweepers; others 
 distributed hot tar by gravity and spread it by automatic trail- 
 ing brushes. The pneumatic spreading machines are each very 
 effectiye, having done much good work in England and France, 
 and it is said that their best features may yet be combined in 
 one machine. Few, if any, are yet used in the United States, 
 where distribution is still made by slow gravity flow, usually 
 requiring that the tar be heated and be spread by hand- 
 brooms, at high cost for labor, and at a rate of progress about 
 one-twentieth of that at which better work is done in Europe. 
 
 The term "coal-tar" is very indefinite, the products of 
 different gas-works varying widely with the kinds of coal used 
 and the methods of treatment, each of which is frequently 
 changed, even at the same gas works. This 
 knowledge has led to careful tests and analyses ^^i^ta 
 of different types of coal-tar to determine, if 
 possible, why some succeeded and others failed in road work. 
 Treatments have been made by experts to remove objection- 
 able components and those which would be soluble in rain- 
 water, and to add desirable ones which might increase fluidity 
 or add to the permanence of ductility and adhesiveness, which 
 should be such that after boiling, the coal-tar may be drawn 
 out in long threads. Many failures which had formerly 
 occurred were explained by the former omission of such tests 
 and absence of such qualities, but most road engineers lack 
 the time and equipment to analyze each lot of tar, or to inter- 
 pret the results of such tests, which are at best costly and 
 uncertain and are of little general utility with the present 
 knowledge of the subject. 
 
 There can be no successful system of tarring roads unless 
 there is available a uniform standard and a reliable supply of 
 refined tar. The lack of these in England accounts for many 
 failures, and has so far prevented the universal use which 
 would be expected from knowing of the many successes. 
 
236 
 
 THE ART OF ROADMAKING 
 
 (^ 
 
 Ol 
 
 o 
 
 f"^ 
 
 O 
 
 Ol 
 
 
 1—1 
 
 t 
 
 pq 
 
 
 d 
 
 
 
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 > 
 
 ^ 
 
 t~t 
 
 a 
 
 a 
 
 cq H 
 
 g 
 
 
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 is 
 
 Q 
 
 Ti 
 
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 <3h 
 
 H 
 
 •g 
 
 3 
 
 c3 
 
 S 
 O 
 03 
 
 OJ 
 
 CO 
 CO 
 
 I 
 
 CD 
 iQ 
 I— I 
 
 d 
 
THE CONTROL AND PREVENTION OF ROAD DUST 237 
 
 Every city has its gas-works — often several of them — each 
 using various grades of coal, and frequently changing their 
 methods of treatment to make gas. Even when these features 
 are constant, the quality of crude tar from a given supply- 
 tank will vary as the quantity in the tank varies, the tar drawn 
 from the bottom of a full tank sometimes differing materially 
 from that drawn when the same tank is nearly empty. The 
 resulting crude coal-tars are therefore produced in great variety, 
 so that road-construction which succeeds at one time may fail 
 at another, as most failures have resulted from the use of poor 
 tar. 
 
 In "tarviating'' experiments in the United States some very 
 crude apphances have been used, but no doubt, as the im- 
 portance and demand for better roads increases, there will be 
 a relative improvement in the mechanical devices used. The 
 number and the variety of foreign machines for rapidly ap- 
 plying tar are indications of the general recognition of the need 
 for means to quickly treat great lengths of roads during the 
 short periods when weather conditions are favorable, all authori- 
 ties agreeing that tar should only be applied w^hen both air 
 and road are warm and dry. 
 
 Coal-tar and its products are used in the general group 
 
 of pavements called tar-macadams, composed of hot crushed 
 
 stone and specially prepared tar or bituminous 
 
 cement, mixed while hot and compressed in place. ^^" , 
 
 . ' . . ^ ... macadam. 
 
 Of this group, that which is known as bitulithic 
 pavement seems the most successful for streets, and in lighter 
 form for suburban roads and the interior of villages and small 
 towns. 
 
 There is a considerable difference between a tar-macadam, 
 and tarring a macadam road. The latter is a surface treat- 
 ment while the name " tar-macadam ' ' is applied to any 
 crushed-stone, or crushed-slag construction, in which coal-tar, 
 or a bituminous cement, or a material containing coal-tar 
 or bitumen, or both, is used (instead of water) in binding 
 the filler between the fragments of stone, or slag. The tar 
 or bitumen remains as a fixative to hold in place the stone 
 chips, scre.enings, or sand forming the filler, binder, or matrix 
 
238 
 
 THE ART OF ROADMAKING 
 
 
THE CONTROL AND PREVENTION OF ROAD DUST 239 
 
 for the fragments, thus aiming to better the road (as compared 
 with ordinary, water-built macadam) by excluding water, 
 reducing wear and preventing dust. 
 
 Tar-macadam may consist of a tarred layer only, or of tar- 
 ring all the fragments in the entire road, either before spread- 
 ing or after spreading in place on the road. 
 
 Any good form of the cheaper tar-macadams costs about 
 one-third more than the ordinary water-built macadam of 
 the same kind and depth of stone, because of the added cost 
 of the tar or bituminous cement, the necessary restrictions 
 as to working only in warm and dry weather, and also the 
 need of repairing the injuries done by rain coming on incom- 
 plete work. But these initial increased costs are offset, 
 when the construction succeeeds, by longer life of the road 
 and by less expense for cleaning, maintenance, and repairs. 
 
 When good, a tar-macadam road is practically dustless 
 and noiseless, offers little tractive resistance, and endures the 
 passage of the rubber tires of high-speed motor-cars; and as 
 it sheds water, it is not heaved nor disintegrated by frost. 
 It has the disadvantage, in common with other pavements, 
 of being shppery when frosty. 
 
 Tar-macadam roadways were first built on the London Road 
 at Nottingham, England, at a date variously stated from 1840 
 to 1845, and at Sheffield soon after. Other similar roads 
 have since been built at many times and places in England 
 and in France, and some in the United States since 1900. 
 The earlier ones used crude coal-tar, mixed by hand with 
 various kinds of stone, and often produced failures because of 
 the poor quahty of the crude tar, or because of rain or cold 
 during construction. Many of the old ones, however, are still 
 in satisfactory use, as well as many new ones. 
 
 In recent years the necessity of having properly refined tar 
 
 has become generally known, and improved apphances for 
 
 heating and hand-mixing the tar and stones have 
 
 been used with much better results than formerly ^*^°S ^^' 
 
 macadam. 
 as to cost and character; the mixing has been 
 
 effectively done in some cases with an ordinary concrete 
 
 mixer. 
 
240 
 
 THE ART OF ROADMAKING 
 
 Fig. 158. — Petrolithic Outfit at Work, Ventura, California. 
 
 
 
 
 
 
 "1 
 
 ''^ 
 
 
 
 
 
 
 m^C'--^ 
 
 
 
 
 
 
 H^^w'^'' 
 
 
 
 
 
 
 ^KgSVi^ikJii'^.:? J^wB 
 
 gjife^ 
 
 
 
 
 
 
 ■t^. 
 
 
 ■'^. -■■>•'■ '■■'"■ 
 
 
 
 1^^.. : mm^m 
 
 HHHHH^ 
 
 
 
 
 
 
 I^HHii ^^r^^^Pr^^ '' ^^ 
 
 
 
 
 
 
 ir 
 
 
 
 
 
 MKgj^^MWMJHfe MBSHMHKS'^ " 
 
 
 
 
 
 
 fiME^E^^K^~' ' 
 
 -'>^!ii^^ 
 
 
 
 1^ 
 
 
 
 IH^'^^4- ^xELl^oMK^I^Bi^^B 
 
 
 
 ^^ 
 
 
 
 "_~" ^'-^':'^. ''"^f^^ 
 
 
 
 
 1 
 
 Fig. 159. — Petrolithic Pavement through the Orange Groves, California. 
 
 Grade 10^ 
 
THE CONTROL AND PREVENTION OF ROAD DUST 241 
 
 Steam-operated machines have been produced which me- 
 chanically heat and mix stones and tar, preparatory to spread- 
 ing it, cold, upon the roads. The tar-spraying machines and 
 tar-spreading machines adapted to tarring the stone in place,, 
 after it has been spread on the road, have not as yet been 
 much used for making tar-macadam, but for which they are 
 well suited, although the methods of construction have been 
 very radically improved since 1905. 
 
 The "Gladwell" system is a method of surfacing macadam 
 roads, either old or new ones, with a tar-macadam top which 
 gives some of the effects of tar-macadam, and at a less cost. 
 It consists in imbedding a two-stone course of 
 untarred, clean, crushed stone in and between two '^^^ 
 layers of tarviated, dustless stone chips, forming system 
 a matrix which is worked, by judicious rolling, 
 into the spaces between the stone fragments from below 
 upv/ard and from above downward, finally sealing the surface 
 so as to be waterproof by hot tarvia and granite chippings. 
 
 The system was devised by Arthur Gladwell, who has 
 charge of road construction and maintenance at Eton, near 
 Windsor, England, and was first used by him in July, 1906. 
 It has since been successfully used on the roads along the 
 Thames, and elsewhere in England. Its low cost and ease 
 of construction, and especially the fact that most of the work 
 may be done in ordinary weather, will no doubt lead to its 
 extensive use in the United States. 
 
 There is as yet no general use of tar-macadam on rural 
 roads of the United States and Canada, such work having 
 been done only on a small scale in an experimental 
 way by the road departments of some of the States, ^se of tar- 
 and by a few towns and villages. The use of the Ame^f^^ '"^ 
 high-class bitulithic and similar pavements has 
 been confined to urban and suburban streets. The United 
 States Office of Public Roads has done some useful work at 
 Jackson, Tennessee, and the results as published have been 
 generally read and used as the basis for other experiments. 
 The report says: 
 
 "A tarred street is dustless in the same sense that an asphalt 
 
242 
 
 THE ART OF ROADMAKING 
 
 J'- ■ 
 
 ' M K ' ''' 
 
 '•* n Jit «' V ' 
 
 Fig. 160. — Spike Disc Harrow, used for pulverizing clods and mixing 
 oil in Petrolithic pavement construction. 
 
 Fig. 161.— Roller Tamper. 
 
THE CONTROL AND PREVENTION OF ROAD DUST 243 
 
 street is dustless, though a fine sandy powder wears off as 
 in the case of asphalt. In driving over a tarred macadam 
 road, the lessening of vibration and noise is at once noticeable. 
 The ordinary macadam produces a constant succession of 
 slight jars upon a steel-tired wheel and there is a relief felt 
 at once in driving upon a road treated with tar." 
 
 The Office of Public Roads continued to give special 
 attention to the subject during 1908 and 1909, and expressed 
 the opinion that surface tieatments were palliatives rather 
 than dust-preventiveS; and that a more lasting method 
 would be "the use of well-tarred sand as part of the binding 
 material and to fill voids/' applying a layer of such taried 
 sand to the rolled base-course, over which the top course 
 should be spread and rolled until the tarred sand should work 
 down into the base-course and up into the top-course. The 
 surface being then finished by an application of tar covered 
 with fine chips or sand and rolled until smooth and uniform. 
 This suggested method is practically the same as the "Glad- 
 well" system. 
 
 Rock asphalt macadam construction gives good results, 
 but the cost of transportation has limited its use 
 to the vicinities of the natural formations of the ^^^^ ^^ 
 peculiar sandstones and limestones which are adam 
 impregnated with bitumen and are known as 
 ""rock-asphalts." 
 
 The natural formations which occur in Arkansas, Oklahoma, 
 and Kentucky, are sand-rock impregnated with a proportion 
 of bitumen varying from a trace to a maximum of thirteen 
 per cent, six per cent being about the least useful proportion. 
 
 The European supphes are those of France, Sicily, and 
 Switzerland, and are bituminous limestones formed by natural 
 combinations of about twelve per cent of bitumen with about 
 eighty-eight per cent of amorphous carbonate of hme, and 
 were first used for roads in Paris in 1854, and since then have 
 made the comparatively small extents of asphalt pavements 
 in European cities, being too costly for general use and much 
 more shppery than the similar city pavements made from the 
 American sand-rock asphalts. 
 
244 
 
 THE ART OF ROADMAKING 
 
 For less costly roadways in the cities of the southwestern 
 portion of the United States, sand-rock asphalts from the 
 formations in Arkansas and Kentucky have been combined 
 with ordinary macadam, making a pavement that is not 
 slippery because the fragments of stone imbedded in the 
 ground sand-rock asphalt give a good foothold, but which 
 needs considerable care and which must be kept clean. 
 
 The bitulithic pavement is the best known combination 
 
 (From Judson's "City Roads and Pavements.") 
 Fig. 162. — Laying Bitulithic Pavement, Toronto, Ont. 
 
 Bitulithic 
 pavement 
 
 of crushed stone and bituminous binder, and is composed of 
 fragments of stone which are held firmly and free 
 form attrition, and hence form no dust. It differs 
 from other bituminous macadams in that the 
 proportions of the several sizes of fragments of crushed stone, 
 from two inches in size down to dust (which form about 
 nine-tenths of the final mass), are accurately determined and 
 are so combined in such proportions of the six or more sizes 
 that the final voids between the fragments after rolHng do 
 not exceed 10 per cent, or less than half the ordinary voids 
 
THE CONTROL AND PREVENTION OF ROAD DUST 245' 
 
 in rolled stone. This puts the fragments into actual and 
 firm contact, so that the addition of 10 to 12 per cent by 
 weight (12 to 16 per cent by bulk) of bituminous compound 
 fills the remaining voids and makes a solid and impervious 
 mass. This result requires experienced care and skill in 
 selecting and combining the best materials, including testing 
 and analyzing the components of the bituminous cement. 
 The pavement thus produced is one which water cannot 
 penetrate, and it supports the passage of heavy and high- 
 speed vehicles without any loosening of the l^ituminous filler 
 and without abrasion of the fragments of stone, so that no 
 dust comes from the pavement or its materials. 
 
 With the present general knowledge of this form of pave- 
 ment which has been acquired since 1901, opinions are now 
 of less moment than in its first years o^ use, but the general 
 opinion of the leading authorities is substantially that ex- 
 pressed by the Massachusetts Highway Commission: 
 
 ''The bitulithic pavement is undoubtedly the best form 
 of pavement to give the desired results (durability and free- 
 dom from dust under fast motor-car travel), but it is too ex- 
 pensive for many locations. '^ 
 
 It was first used in 1901 in Pawtucket, R. I., where it was 
 laid on a 12 per cent grade, and during the same year sample 
 areas were built in seven- cities, aggregating about one mile of 
 30-foot width. The success was immediate, and the use in- 
 creased each succeeding year, so that at the close of 1907, 
 6,500,000 square yards, equal to 422 miles of 30-foot road- 
 ways, had been laid in one hundred and sixty-six cities of 
 the United States and Canada, including cities in the region 
 of extreme cold, as at Edmonton, Province of Alberta, Canada, 
 and Glace Bay, Nova Scotia, and in the South at El Paso, 
 Texas, and at Atlanta, Georgia. This widespread success 
 has induced imitations and consequent litigations, which are 
 further evidences, if such were needed, of the merits of the 
 construction. 
 
 The elaborate outfit of laboratory and machinery and 
 skilled direction required to successfully produce this pave- 
 ment would at first seem to limit construction to the vicinitv 
 
(From Judson's " D^lst Prevention.") 
 
 Fig. 163. — One-car Portable Bitulithic Railroad Plant. (Set up ready 
 
 for operation.) 
 
 (From JudsorCs *' Dust Prevention") 
 Fig. 164. — Semi-Portable Bitulithic Paving Plant. — End view. 246 
 
THE CONTROL AND PREVENTION OF ROAD DUST 2i7 
 
 of permanent plants, and this idea is strengthened by visit- 
 ing such a plant and examining the work in progress. There 
 have, however, been built and patented a number of "semi- 
 portable bitulithic paving-plants," each permanently set 
 upon a platform-car. These outfits make it possible to build 
 this pavement in many widely distant places and to give to 
 all of them equally reliable results. The accompanying 
 illustrations, showing this semi-portable bitulithic paving-plant, 
 are lettered to accord with the following key : 
 
 A. Boiler and engine. 
 
 B. Rotary driers for heating and drying stone. 
 
 C. Elevators for delivering the stone to the driers. 
 
 D. Elevators for conveying the heated stone to the sep- 
 
 arating-screens. 
 
 E. Sectional screen for separating the stone into several sizes. 
 
 F. Sectional bins for storing the several sizes of stone after 
 
 separation, and deUvering same to the weighing-box. 
 
 G. Weighing-box resting on a multiple seven-beam scale for 
 
 accurately weighing each size of stone in predeter- 
 mined proportions and delivering same into the mixer. 
 
 H. Twin pug mechanical mixer, having two shafts revolving 
 in opposite directions with arms or blades inter- 
 locking each other. 
 
 I. Mixing platforms under which wagons back for taking 
 the bitulithic mixture as delivered from the mixer. 
 
 J. Ogee-bottomed bitumen-melting tanks. 
 
 K. Bitumen weigh-bucket conveyor and dial-scale, so. ar- 
 ranged as to indicate both gross weight and tare. 
 
 L. Rotary exhaust fan for providing induced draft to the 
 rotary driers. 
 
 M. Dust-separator for reclaiming dust drawn by the exhaust 
 fan from the stone while it is drying. 
 
 N, Steel frame for supporting the mixing-platform, mixer, 
 scale, sectional hot-stone bin^ and sectional screens. 
 
 O. Steel car on which the semi-portable or railroad plant 
 is permanently set. 
 
CHAPTER XII 
 STATE AID LAWS* 
 
 Most of the state-aid laws are accumulations of laws and 
 amendments passed session after session without definite 
 logical arrangement, and without any carefully thought out 
 general plan in mind. New York, however, appointed a 
 special commission which studied the question very carefully 
 for a year, both in their own state and in neighboring states. 
 This commission proposed a bill which was passed, and went 
 into effect in January, 1909. This bill replaces all previous 
 highwa3^s law, and rearranges the whole highway work of 
 the state, counties and towns so as to bring the separate units 
 into logical relations to each other. 
 
 As a result of the study of the different state laws, a model 
 bill providing for state aid was drawn up by the United States 
 Office of Public Roads at Washington, D. C, to embody the 
 best results of the experience of all of the states based on the 
 workings of each of the state aid laws under their local con- 
 ditions. 
 
 Briefly stated, the three things that are most fundamental 
 for the successful working of state aid are: (1) an equitable 
 plan for distributing funds; (2) putting the spending of the 
 money in the hands of expert men; (3) providing for such a 
 form of commission that the work will be carried on without 
 regard to political considerations. 
 
 On looking over the summaries of the state aid laws, it will 
 be found that the various states pursue a variety of methods 
 in distributing the aid to the localities where it is used. Some 
 states leave this matter entirely in the hands of the com- 
 
 * Abstracted from First Biennial Report of the Highway Division, 
 Wisconsin Geological and Natural History Survey, 1909. 
 
 248 
 
STATE AID LAWS 249 
 
 mission, or limit the commission only by stating that not 
 over a certain maximum or not less than a certain 
 minimum amount shall be spent in any county. One Distribution 
 state divides the amount equally between the funds 
 counties; another divides the money between the 
 counties on the basis of the total number of miles of road in 
 each county; other states divide the money in proportion to 
 the county ; other states divide the money in proportion to the 
 amounts asked for, so that if the aggregate of the amounts 
 of state aid petitioned for is twice that which the legislature 
 has appropriated for the purpose each town or county peti- 
 tioning receives one-half of what it asked for. 
 
 On account of the almost necessarily inequitable manner in 
 which taxes are generally assessed upon property, it will be 
 very evident that the distribution of the fund must become 
 more or less inequitable in certain particular cases. 
 
 In the first place, the method of leaving the distribution of 
 the money entirely in the hands of a commission is distinctly 
 inadvisable, as it puts altogether too much responsibility on 
 a very small group of men, whose l«nowledge of conditions, 
 even though they may be ever so well intentioned, would 
 hardly be broad enough to qualify them to do justice to all 
 the counties and to the several hundred towns in any large 
 state. 
 
 To divide the money equally among the counties would be 
 very markedly wrong, as counties with a comparatively scat- 
 tered settlement would receive as much as large, well-settled 
 counties. 
 
 To divide tne money on the basis of the total number of 
 miiles of road in each county would also be inequitable, as some 
 of the less wealthy and less populous counties might have as 
 many or even more miles of road per square mile of area than 
 some of the wealthier and more settled counties. 
 
 To divide the money pro rata with the amounts asked for 
 would do injustice in that counties w^hich are able to ask for 
 large sums might prevent poorer counties able to ask for only 
 very small sums from getting their proper share. For instance, 
 ■one county, which is neither large nor wealthy, might petition 
 
250 THE ART OF ROADMAKING 
 
 $1000 of state aid. Another county, comparatively populous 
 and wealthy, might ask for $40,000 or $50,000 a year. If the 
 total amount of state aid asked for were twice the state 
 aid appropriation, the former county would only get $500 
 where it should have had $1000, while the latter would get 
 $20,000 where in justice it might only have been given 
 $15,000. 
 
 The idea of the most just apportionment of the state aid 
 fund that first occurs to anyone studying the question is a 
 distribution on the basis of valuation. Such a distribution, 
 however, presents difficulties in that the amount of state aid 
 given to some of the poorer counties would not be sufficient 
 to amount to anything unless an exceedingly great state aid 
 fund were appropriated. 
 
 The second important point to which attention should be 
 directed is the final authority in the supervision of the actual 
 construction. It will be noticed by the summary 
 Supervision of the state laws that follows, that every state 
 struction giving state aid gives authority to its state highway 
 officers to say what methods of work shall be 
 pursued and how the roads shall be constructed. This matter 
 is important because it has to do with the primary purpose 
 of state aid; that is, to secure efficient, well-planned work 
 on our highways, and the careful expenditure of the state 
 aid money, instead of the haphazard work, entirely lacking 
 in plan, which is secured under the present system. 
 
 In order to get efficient spending of our road money we must 
 profit by the experience of other countries. In France the 
 best engineers that their colleges produce are taken into the 
 Department of Roads and Bridges, and the state's money is 
 spent under their direction. If we are to build the best roads 
 with least cost we must have efficient engineering departments 
 in charge of the work with authority to say that the best 
 methods only shall be used. In order that such an engineer- 
 ing force might not be so large as to be unwieldy, and to pro- 
 mote economy, it should be provided that it should work, 
 in so far as possible, through competent county highway com- 
 missioners. But in order to secure efficiency and uniformity 
 
STATE AID LAWS 251 
 
 in the work the final authority should rest in the state engineer- 
 ing department. 
 
 One of the most important questions to be considered in 
 framing a state aid law that will work successfully is the form 
 of the state commission or body that has general 
 
 control of the work. The importance of this point °^°^ ? . 
 
 ^ , ^ commi ssion. 
 
 lies entirely in whether or not the state highway 
 work is to be controlled by political considerations with the 
 resulting inefficiency of the actual road building, or whether 
 it is to be controlled entirely in the interest of efficient road 
 work without regard to political considerations. Of course 
 no one would say anything else than that this work must 
 be kept out of politics. But there is great danger that po- 
 litical influences may creep in as they nearly always do, under 
 the guise of cheapness or efficiency of administration. For 
 this reason the following statements deserve particular atten- 
 tion from everyone interested in the success of the state aid 
 movement, 
 
 A study of the laws of the various states reveals the fact 
 that there are four distinct plans for the control of the state 
 highway department. 
 
 1. One state highway commissioner or engineer appointed 
 by the governor for a definite term of years. Five states have 
 this plan. 
 
 2. A commission of three men paid for their full time and 
 appointed by the governor for a definite term of office. Two 
 or three states have this type of board. 
 
 3. A commission appointed by the governor for a definite 
 term of office, but serving without pay and giving only general 
 direction to the work, which is under the active direction of a 
 state engineer selected and hired by them for a period coin- 
 cident with satisfactory service. This and the fourth method 
 are analogous to a business corporation with its board of 
 unsalaried directors and the general manager carrying out the 
 details of the general policies laid down by them. Six states 
 have boards of this kind. These states get able men of wide 
 experience and good business ability to serve on their com- 
 missions. 
 
252 THE ART OF ROADMAKING 
 
 4. An ex-ofRcio board such as is recommended in a model 
 state aid bill by the United States Office of Public Roads 
 for the particular purpose of avoiding politics in the state 
 aid work. That bill makes the professors of civil engineering 
 in three different colleges members of the state highway board 
 by virtue of their position. Such a commission maintains 
 its existence without regard to what particular man holds 
 one of these professorships. It need not be made in this 
 way^ however, but could be composed of the holders of any 
 non-political positions either in state employ or otherwise, 
 and the same freedom from politics enjoyed. Seven states 
 have this form of commission. In no one of them, so far as 
 information is available, has politics become a factor in the 
 state road work, but the same cannot be said of states having 
 other forms of commissions. 
 
 DIGEST OF STATE AID LAWS 
 
 In the following digest of the laws of various states, the 
 states considered are not all of those providing for state aid 
 for road building, but are sufficient in number to give a fair 
 idea of the various methods used in all states. The states 
 whose laws are summarized are: 
 
 New York New Jersey 
 
 Maryland Washington 
 
 Virginia Ohio 
 
 Massachusetts Michigan 
 
 Connecticut Maine 
 
 Pennsylvania Rhode Island 
 
 In order to make it as easy as possible to compare the pro- 
 visions of the laws they are grouped under various headings. 
 These headings are: 
 
 State Highway Department. 
 State Aid Highways. 
 State Aid Fund. 
 Powers and Duties of Counties. 
 County or District Highway Engineers. 
 How Localities get State Aid. 
 Construction of State Aid Highways. 
 Payment for State Aid Highways. 
 Maintenance of State Aid Highways. 
 
STATE AID LAWS 253 
 
 State Highway Department 
 
 In the model bill of the United States Office of Public Roads 
 the state highway commission is made up of the professors 
 of civil engineering in three different colleges. A 
 commission of this kind was selected for the ex- Model bill. 
 press purpose of avoiding political influences in 
 the work. These commissioners receive no salary^ but are 
 paid their actual expenses in attending meetings, etc. They 
 exercise general supervision over the state highway work, 
 appoint the state engineer to hold office during satisfactory 
 service, and fix his salary. This engineer has charge of ail 
 the state road work and appoints his engineering assistants 
 and clerical force, subject to the approval of the commission. 
 The state engineer may be consulted by county, cit}- or town 
 officers concerning roads and bridges. 
 
 New York has a state highway department in charge of 
 three commissioners appointed b}^ the governor for a term 
 of six years, one of them going out of office every 
 two 3'ears. One of these commissioners must be New York. 
 a practical civil engineer with experience in the 
 construction of highways and bridges. The chairman of the 
 commission, who is designated by the governor, is paid 16000 
 a year and the other two commissioners S5000 a 3'ear each. 
 This commission has general supervision over all state aid 
 work. They appoint a chief road engineer, a chief bridge 
 engineer, and such clerks and assistants as are needed. This 
 commission apportions the state highway money among the 
 various counties of the state in a manner they think equitable. 
 They have authority to regulate the digging up for any pur- 
 pose of any road built with state aid, and are instructed to aid 
 in promoting highway improvements and to carr}^ on exper- 
 iments in road construction. 
 
 This state has put the general supervision of its highwaj^ 
 work in the hands of an ex-officio commission, the Geological 
 Survey Board. The commission is composed of 
 the holders of the following positions: Governor Maryland, 
 of the state ; Comptroller of the state ; President of 
 Johns Hopkins University; President of the State Agricultural 
 College. This board receives no salary, but is reimbursed its 
 actual expenses for attending meetings, etc. They appoint 
 the chief engineer and fix his salary. They allot the state aid 
 money to the various counties of the state as petitioned for, 
 the allotment to each county being made on the basis of total 
 
254 THE ART OF ROADMAKING 
 
 road mileage. The chief engineer makes the surveys, plans, 
 and specifications for roads built under state aid. 
 
 The state highway commission is an ex-ofhcio board com- 
 posed of the professors of civil engineering at the University 
 . . of Virginia, Virginia Agricultural and Mechanical 
 
 irgmia. College, and the Virginia Military Institute. Under 
 their direction is the state highway commissioner, who is ap- 
 pointed by the governor for a six-year term. This commis- 
 sioner must be a civil engineer well versed in road building, 
 and a citizen of the state. His salary is $3000 per year. The 
 commission serves without pay, but is reimbursed actual 
 expenses for attending meetings. The state commissioner 
 has authority to hire engineers and assistants. The commis- 
 sion apportions the state aid money in proportion to the amount 
 of state taxes paid by each county. This state also aids the 
 counties in road construction by loaning them its convicts to 
 work upon the roads. 
 
 This state has a highway commission of three men appointed 
 by the governor for a term of three years, one term ending 
 each year. The president of the commission receives 
 Mas^sachu- CJ3500 and the other two members $2500 each per 
 annum. This commission appoints a secretary who 
 is practically state engineer, and fixes his salary. They exer- 
 cise general supervision over the state aid work, and employ 
 such engineers, clerks, etc., as are necessary. The apportion- 
 ment of the state highway fund is left entirely in the hands 
 of this commission, with the single restriction that they can- 
 not build more than ten miles of road in any county in a 
 year. The commission has absolute authority over the dig- 
 ging up of state aid roads for any purpose. They can pur- 
 chase such machinery as is needed in the building of state aid 
 roads. 
 
 This state has a single highway commissioner appointed 
 by the governor for a four-year term at a salary of $3000. 
 In addition to his salary he is provided by the 
 state with a touring car and a man to run it to 
 assist him in getting about the state in connection with his 
 duties. The commissioner appoints such deputies and en- 
 gineers as are needed and fixes their salary with the provi- 
 sion that the total limit of salaries is $25,000 a year. 
 The commissioner allots the state highway fund among the 
 various towns. He has authority to purchase stone crushers 
 and loan them to the towns in the state desiring them. 
 
 This state has a highway department under the direction 
 of a single commissioner paid a salary of $6500 per annum and 
 
STATE AID LAWS 255 
 
 appointed by the governor for a term of four years. The law 
 specifies that this commissioner "shall be a competent ^^^ ^_ 
 
 civil engineer and experienced in the construction vank7 
 and maintenance of improved roads." This com- 
 .missioner appoints a deputy at a salary of $3600, and an as- 
 sistant deputy at $3000^ twelve engineers and a chief drafts- 
 man at $2400 each and such other assistants and clerks as are 
 needed. Among his duties are the promotion of highway im- 
 provement, the regulation of the digging up of the state aid 
 roads for any purpose, and the collection of information re- 
 garding road building. 
 
 This state has one highway commissioner appointed by 
 the governor for a term of three years, at a salary of $5,000 
 per annum. No qualifications are specified in the 
 law. The regulation of the digging up of state aid ^^ ■* 
 highways is left to the counties. The state commissioner 
 has supervision over the surveys and plans for state aid roads, 
 and the location of roads to be improved must meet his 
 approval. He has authority to reject all unsatisfactory 
 road contracts which the county boards may desire to enter 
 into. He appoints the supervisors on all work done on state 
 aid roads, both in construction and maintenance. 
 
 This state has a highway board composed of the state 
 auditor, the state treasurer ex-officio, and the highway com- 
 missioner, who is appointed by the governor for a^ , . 
 four-year term at a salary of $2500 per aimum. ^^ ^^^ °°' 
 This commissioner must be an experienced civil engineer. He 
 has authority to appoint needed engineers and assistants. 
 The state highway board apportions the state money among 
 the counties and lets all contracts for the building of state aid 
 roads. 
 
 There is a single state highway commissioner appointed 
 by the governor for a term of four years at a salary of $2500. 
 The law requires him to be a competent civil en- 
 gineer with experience in highway construction. 
 It is his duty to instruct and assist town and county officers 
 in the making of improved roads, and to collect information 
 and make tests and experiments in road building. The loca- 
 tion of all roads to be improved must meet his approval and 
 all contracts for their improvement are let by him in the name 
 of the state. He appoints his assistants and inspectors for 
 the state aid work. 
 
 There is one highway commissioner appointed by the gov- 
 ernor for a term of four years at a salary of $2500. The only 
 
256 THE ART OF ROADMAKING 
 
 qualification specified in the law is that he shall be a citizen 
 of the state. He has authority to appoint needed 
 igan. cieri^g a^n^ ^ deputy commissioner, and is instructed 
 to hold public road institutes in each county, at which the 
 attendance of town and county highway officers is required. 
 These local officers draw their regular pay and expenses for 
 attending these meetings. The state commissioner furnishes 
 plans and specifications for roads and bridges, and allots the 
 state aid fund to the towns or counties petitioning. He has 
 authority to refuse to allot any money to a town or county 
 which does not maintain its state aid roads properly. When 
 state aid roads are completed it rests with him to decide 
 whether or not they have been well enough constructed to 
 merit the payment of the state money. 
 
 There is one highway commissioner appointed by the gov- 
 ernor for a term of four years at a salary of 12500; he must 
 be a civil engineer. He appoints an assistant, who 
 must be a civil engineer also, and must have the 
 further qualification of being experienced in road building. 
 He also appoints his clerks and stenographer. It is his duty 
 to advise the towns on road and bridge construction, to ap- 
 portion the state aid money in accordance with the law, make 
 all surveys for the improvement of state aid roads and determine 
 the location of the roads to be improved. He appoints in- 
 spectors for the work under progress. Meetings are held in 
 each county once a year by the highway commissioner. 
 
 This state has a board of five members appointed by the 
 governor for a five-year term of office, one member being 
 -pt, J appointed each year. This board receives no salary, 
 
 J , ° f but the members are reimbursed their expenses for 
 
 traveling done in connection with their duties. 
 They have complete authority over the state roads, and 
 employ such engineers and let such contracts as they see fit. 
 
 STATE AID HIGHWAYS 
 
 This provides the state aid highways are to be selected by 
 the country boards, subject to the approval of 
 * ' the state highway department. 
 This state has three systems of roads: (1) roads built en- 
 tirely at state expense, which are selected by the legislature; 
 (2) county roads, which are selected by the county 
 ew or . lyQ^^^Q^ subject to the approval of the commission, 
 50 per cent of the cost of which is paid by the state, 35 per 
 cent by the county and 15 per cent by the town; (3) local 
 
STATE AID LAWS 257 
 
 roads, which are aided by the state, but receive no county aid. 
 The state pays from one-third to one-half of the cost of the 
 local roads. The local roads to be improved are selected by 
 the town board and the town highway superintendent, sub- 
 ject to the approval of the commission. 
 
 No road in the state of New York is improved with the as- 
 sistance of the state until both the location and the manner 
 of improvement have been passed upon favorably by the 
 commission. 
 
 The highways to receive state aid are selected by the county 
 commissioners subject to the approval of the state highway 
 department. If the county commissioners refuse 
 to act in regard to any road the owners of two- ^^^^ • 
 thirds of the adjoining lands can compel them to petition the 
 state highway department by agreeing to pay 10 per cent of 
 the cost. 
 
 The state aid roads are selected by the county board, but 
 both the location and the method of work must . . 
 
 approved by the state commissioner before any irgima. 
 state money is granted. 
 
 The Massachusetts law provides that counties, cities and 
 towns may petition the state highway commission 
 for aid. The location and manner of construction ^^^^T 
 of roads must be approved by the state highway 
 commission before aid is granted. 
 
 The highways to receive state aid are selected by the state 
 commissioner. The local people of a township may petition 
 for state aid, but this petition is general and the 
 particular road to be improved is selected by the *^°^®'^ ^*^^*- 
 commissioner, who is directed by law to improve only the 
 main highways leading from one town to another. 
 
 In this state the township supervisors or couiity commis- 
 sioners desiring state aid petition the state highway com- 
 missioner, who may grant the petition if he ap- 
 proves of the location. The kind of road to be Pennsyl- 
 built rests entirely with the state commissioner. 
 
 Roads to be improved with state aid are selected by the 
 county boards, who may also adopt as a state highway any 
 road which has been previously improved without ._ 
 state aid. The location and kind of road to be ^^ Jersey, 
 built must have the approval of the state highway commis- 
 sioner before state aid is granted. 
 
 This state has four kinds of roads: (1) state roads constructed 
 entirely by the state, which are selected by the legislature; 
 
258 THE ART OF ROADMAKING 
 
 (2) state aid roads; (3) improved roads which are paid for 
 
 entirely by the county; (4) town roads which are 
 
 Washington. ^^.^^ ^^ ^^^ ^^^^j people. The location and method 
 
 of improvement of state aid roads must have the approval 
 of the state highway board before state aid is granted. 
 
 The roads to be constructed by state aid are selected by the 
 county board. If the county board does not act the owners 
 of 51 per cent of the linear frontage may petition. 
 ^°* The location and kind of road to be constructed 
 
 are subject to the approval of the state commissioner. If 
 more petitions are made in one year than there are funds 
 available the state commissioner and the county board to- 
 gether decide which shall be constructed first. 
 
 In this state the county board of highway commissioners 
 
 selects the roads to be built with state aid. After the road is 
 
 completed the state highway commissioner must 
 
 igan. appi-Qye the method of construction before state 
 
 aid is granted. 
 
 The roads to be built with state aid are selected by the 
 . towns subject to the approval of the state com- 
 
 missioner. 
 This state has no roads which are built with state aid. The 
 only classes of roads which it has are those paid for entirely 
 by the state, which are selected and constructed 
 T 1 ° d ^^ ^^^ state board, and the local highways, con- 
 
 structed and maintained by the localities without 
 any state assistance. 
 
 STATE AID FUND 
 
 This bill provides that the money shall be raised by a gen- 
 M d 1 h*ii ^^^^ ^^"^ ^^^ apportioned according to the as- 
 sessed valuation of the counties. 
 
 The state aid fund in this state consists of a bond issue of 
 $50,000,000, It is apportioned by the state commission among 
 „ . the counties "equitably and without discrimina- 
 tion," taking road mileage and improved roads 
 into consideration. 
 
 The state aid fund is made up of a general appropriation 
 of $200,000 annually and a five-million-dollar bond issue. 
 The annual appropriation is apportioned by the 
 ^^^ ' state board according to the total road mileage. 
 The five-million-dollar bond issue is used to pay the whole 
 cost of certain state roads which are selected by the state 
 board. 
 
STATE AID LAWS 259 
 
 The state aid granted by Virginia is in two forms. They 
 loan state convicts to the counties and have an appropria- 
 tion of $25,000 for the transportation and caring . . 
 for these men. They also have an annual money irgmia. 
 aid appropriation of $250,000, with a separate appropriation 
 of $16,000 for the support of the state highway commission. 
 In addition 10 per cent of the state aid fund may be used for 
 the necessary engineering on the roads under construction. 
 
 The state aid is apportioned by the commission on the basis 
 of the amount of state taxes paid by each county. If any 
 county does not apply for its share it is divided among other 
 counties asking for more than is first apportioned. 
 
 The state fund of this state is made up of an annual ap- 
 propriation of $450,000, with aseparate appropriation 
 of about $40,000 for the support of the commission, tf^^ « 
 approximately $60,000 received from automobile 
 license fees which is used in maintaining roads. The state aid 
 is apportioned by the commission as they think equitable and 
 under the restriction that not over 10 miles of road can be 
 built in a single township in one year. 
 
 The state aid fund is made up of an annual appropriation 
 of $750,000. This is apportioned by the state commissioner 
 under the limitation that not more than $10,000 ^ 
 
 1 , • , • Connecticut. 
 
 can be spent m any town m one year. 
 
 The state aid fund is made up of an appropriation of 
 $2,000,000 for 1908. This is apportioned by the state 
 commissioner among the counties in proportion to 
 to total road mileage. Apportionments not called Pennsyi- 
 for by any county are reapportioned among the 
 counties desiring more than their first apportionment. 
 
 The state aid fund is an annual appropriation of $400,000. 
 
 This is apportioned among the counties by the ^, 
 
 , J. r- i,^'^ • - ° ^ New Jersey. 
 
 state highway commissioner. •' ^ 
 
 The state aid fund is made up of an annual tax of one-half 
 mill on all the property in the state. This is used for the 
 building of " state aid " roads. ^' State roads," 
 which are paid for by the state alone, are covered »ngton. 
 
 by separate appropriation of $225,000 for the year 1908. The 
 state aid fund is apportioned to the counties in the order in 
 which petitions for the improvement are received. 
 
 The state aid fund is an appropriation of $158,000 annually. 
 It is divided equally among the counties. Counties 
 which have previously built roads at their own ex- ***' 
 
 pense are entitled to reimbursement from the state aid fund. 
 
260 THE ART OF ROADMAKING 
 
 For the year ending June 30, 1909, the Michigan appro- 
 priation was $150,000. The salaries and expenses of the office 
 of the state highway commissioner were paid from 
 ic igan. ^^^ state general fund in addition to this. State 
 aid money is apportioned among the towns and counties on the 
 basis of work done in the order in which the applications are 
 received. 
 
 The state aid fund is an annual tax of one-third of a mill 
 on ail the property in the state. It is apportioned to the 
 . counties by the state highway commissioner on the 
 
 basis of total road mileage. The county appor- 
 tionment is then divided among the various towns in the county 
 on the pasis of valuation. 
 
 The state aid fund is a bond issue of $600,000 for the two 
 
 years 1907 and 1908. It is apportioned as the 
 
 ?'. ° ~f state board sees fit within the limits that not over 
 
 one-third nor less than one-seventh of the total 
 
 amount can be spent in one county during the year, 
 
 POWERS AND DUTIES OF COUNTIES 
 
 The authority of the county board ends with selecting the 
 road and paying their share of the cost of construc- 
 1 . |.'qj^ ^^^ maintenance ; both construction and 
 maintenance being looked after by the state. 
 
 In this state the county board may levy a tax for permanent 
 improvements. They may borrow money in anticipation 
 y oi taxes. They must provide lands for the right 
 
 ew or . ^£ ^^y 1^^ ^^^ state or county roads. They may 
 elect a county highway superintendent for a four-year term, 
 but if they do not choose to elect such a man the state com- 
 mission appoints a district superintendent over a number of 
 counties and the count^^ is then obliged to pay its share of his 
 salary. The removal of the county superintendent of highways 
 is in the hands of the state commission. The town is liable 
 for all damages due to defects in any road. 
 
 In this state the county commissioners petition for the 
 road improvement. They let the contract for the construc- 
 tion of roads subject to the approval of the state 
 ary an . ^^Q^j-t^i^ must provide lands for the right of way and 
 relocation, may elect a county highway engineer, and must 
 keep the state aid roads in a condition of repair satisfactory 
 to the state board. 
 
 The county board petitions for the road improvement, and 
 after this has no further authority or responsibility excepting 
 
Massa- 
 chusetts. 
 
 STATE AID LAWS 261 
 
 to pay their share for the construction and maintenance, both 
 of these being in the hands of the state commissioner. . . 
 
 The county engineer, if there is one in the county, *^^^°^ 
 is selected by the state highway commissioner, but paid by 
 the county board. 
 
 After petitioning for state aid the county has no 
 further authority or responsibility excepting to pay 
 for its share of the cost. 
 
 In this state the county is not an important unit of gov- 
 ernment, and the state deals only with the towns. 
 After the town has petitioned for state aid matters 
 are entirely in the hands of the state commissioner. 
 
 The county may petition for the improvement of a road, 
 and may enter into a contract with the state to 
 do the actual work of construction. The county vania^ ' 
 elects a county highway engineer, and is responsible 
 for all damages due to defects on state aid roads. 
 
 The counties may raise a tax for the construction and repair 
 of state aid roads amounting to five mills. They may bond 
 for as much as 3 per cent of the assessed valuation 
 for road purposes. Counties have the authority -^ ^^^' 
 
 to acquire property and machinery for road purposes. They 
 must elect a county supervisor of roads as soon as the first 
 state aid road is completed in that county. This supervisor 
 may be removed by the county or by the state commissioner. 
 The county has control of the state aid roads within its bound- 
 aries and must keep the same in a state of repair satisfactory 
 to the state commissioner. The county must accept as a 
 state highway any road built by the local people in a manner 
 approved by the state highway commissioner. The county 
 has authority to regulate the digging up of state aid roads for 
 any purpose. 
 
 The counties may levy a four-mill tax for road improve- 
 ment and can bond to the amount of 5 per cent of the valua- 
 tion. They may acquire property and machinery 
 for road purposes. The county surveyor must be ^^ mgton. 
 a civil engineer, and his title is changed by the highway law 
 to county engineer. The counties must maintain the state 
 aid roads under the orders of the state commissioner. 
 
 The county board may levy a tax of not to exceed one mill 
 for road improvements and may issue bonds to pay 
 for state aid roads. They may elect a county ***' 
 
 highway engineer. They may secure lands for right of way 
 
262 THE ART OF ROADMAKING 
 
 and must maintain the state aid roads in a manner satisfactory 
 to the state commissioner. 
 
 The county elects by popular vote a county board of high- 
 way commissioners of not over five men. This board of high- 
 way commissioners may levy a tax of not to ex- 
 Michigan. ^^^^ ^^^ mills for permanent improvements. The 
 counties may bond up to 5 per cent of their valuation, and 
 must maintain the state aid roads to the satisfaction of the 
 state commissioner or be cut off from further state aid. The 
 county is responsible for damages due to defects in state 
 aid roads. This board selects the system of county roads to 
 be improved with state aid. 
 
 The county boards designate the roads to be permanently 
 improved on the petition of the towns^ subject to the approval 
 of the state commissioner. They may levy a tax 
 Maine. ^£ one-third mill for improvements on state aid 
 
 roads. This amount must be spent under the direction of 
 the state commissioner. Towns may raise an additional 
 amount if they want state aid. 
 
 Rhode This state does not deal with the counties at all 
 
 Island. in its permanent improvements. 
 
 COUNTY OR DISTRICT HIGHWAY ENGINEERS 
 
 County engineers are appointed by the state engi- 
 bill, ^^gj, ^^ ^YiQ approval of the commission. 
 
 The county board elects a county highway engineer for a 
 term of four years and fixes his salary. If the county board 
 does not choose to elect, the state commission 
 ^^ ^^ ' appoints a district engineer to have charge of the 
 work in several counties. Ea.ch of these counties is then 
 obliged to pay its share of his salary. The qualifications of 
 the county highway engineer are set by the state civil service 
 commission, and only those who have passed a satisfactory 
 examination are eligible. His duties are to advise with towns 
 and village officers, have charge of the construction of new 
 roads in his county, and the maintenance of all state aid roads, 
 and such other duties as the commissioner or the county board 
 assign to him. 
 
 The county engineer, when there is one, is appointed by the 
 county commissioners. His term is indefinite, and continues 
 with satisfactory service. The law specifies that 
 Mary an . j^^ must be a civil engineer. He has charge of all 
 the county road work, and the local road superintendents are 
 under his direction. 
 
STATE AID LAWS 263 
 
 The county engineer is appointed by the state highway 
 commissioner and the law provides that he shall . . 
 
 be paid at not to exceed the rate of $1200 a year irgmia. 
 for the time actually employed. He must be a civil engineer. 
 
 This state has no county engineers, but the state commission 
 appoints division engineers to have charge of the 
 work in each of the five divisions of the state. These ^^^^^ ^" 
 engineers are paid by the state and must be ex- 
 perienced civil engineers. 
 
 This state has no county or division engineers. The state 
 highway commissioner and his assistants do all 
 the engineering work, usually hiring engineers for ^^^^^ ^^" * 
 each particular job. 
 
 The counties in this state have county engineers 
 who make plans and surveys subject to the ap- ennsy- 
 proval of the state commissioner. 
 
 The county board must elect a county supervisor of roads 
 on the completion of the first state aid highwaj^ in that county. 
 His term is three years, and his compensation is 
 fixed by the county board. In some counties the ^^J^'^sey. 
 engineer is paid as much as $6000 a year. He may be re- 
 moved by the county board or by the state commissioner. 
 He has charge of the improvements made in his county and the 
 maintenance of the roads. The only qualification named is 
 that he shall be a '^suitable person." 
 
 The county engineer is elected by popular vote for a two year 
 term. His salary is $5 per day for time actually spent on the 
 work in the smaller counties, and the same as the 
 county auditor in large counties. The law pro- ^^ i^gton. 
 vides that he must be a civil engineer. Among his duties are 
 the keeping up of a county road map and the preparation of 
 profiles of roads, reporting on proposed improvements and 
 supervising the road work done in his county. 
 
 It is optional with the county boards to elect county engi- 
 neers. The state highway commissioner's office, 
 however, does practically all the engineering on 
 state aid roads. 
 
 They have no county highway engineers in this state, but 
 instead have a county board of highway commissioners elected 
 by the people. This board may be from one to 
 five men as the county board chooses, and the term J^ichigan. 
 depends on the number. One man goes out of office every 
 two years. If there are five men the term is ten years, if there 
 are three men the term is six years and so on. The only 
 
Maine, 
 
 Model biU. 
 New York. 
 
 264 THE ART OF ROADMAKING 
 
 qualification named is citizenship in the county. This board 
 has all authority over county roads. Their salaries are fixed 
 by the county board. 
 
 They have no county or district engineers in this 
 state. 
 Rhode There are no county or district engineers in this 
 
 Island. state. 
 
 HOW LOCALITIES GET STATE AID 
 
 The county board petitions the state highway 
 department. 
 
 The county board petitions the state highway 
 commission. 
 
 The county board petitions the state highway department, 
 but if the board refuses to act the owners of two- 
 Mary and. thirds of the adjoining lands may force the county 
 to petition by agreeing to pay 10 per cent of the cost. 
 
 . . The county board petitions the state highway 
 
 irgmia. commissioner. 
 
 Counties, cities or towns may petition the state 
 assa- highway commissioner, for aid, but the commission 
 
 has practically nothing to do with cities. 
 The towns vote money for road improvement and petition 
 the state highway commissioner, who selects the road to be im- 
 proved. If a town fails to vote money to improve 
 onnec icu . ^^ important road which needs it badly the state 
 commissioner is empowered to go ahead on his own initiative 
 to improve the road, and the town's share of the expense is 
 taken out of any subsequent allotments that may be made by 
 the state. 
 
 The town petitions the county, and the county then peti- 
 tions the state commissioner. Towns may petition the state 
 commissioner directly if they are willing to pay the 
 ennsy - county's share of the cost as well as their own. 
 The owners of a majority of the assessed valuation 
 of the real estate in the town can by petition compel the town 
 board to request the county board to apply for state aid. 
 The petitioners as such are not obliged to assume any part of 
 the cost of building the road. 
 
 The governing board of any town, county, borough or 
 
 village may petition the state highway commissioner. If 
 
 the property owners on a particular highway de- 
 
 ew Jersey. ^-^^ ^^ have it improved and the officials refuse to 
 
 act they can improve the road at their own expense and the 
 
STATE AID LAWS 265 
 
 county board is obliged to accept it as a state highway and 
 thereafter maintain it. 
 
 The county petitions the state highway board. The owners 
 of two-thirds of the property on any road may com- 
 pel the county to petition for improvements on ^^ mgton. 
 that road. 
 
 The county board petitions the state highway commissioner 
 for aidj and if they do not act voluntarily the own- 
 ers of 51 per cent of the frontage may compel 
 them to act. 
 
 The town or the county may petition the state highway 
 commissioner. If they issue bonds and build several miles 
 of road in one year they receive their share of state 
 aid on two miles of this road each year until they ^^ ^^^^' 
 receive the total amount of state aid which they are entitled to. 
 
 In order to get state aid the towns must raise an extra high- 
 way tax of from 1-12 to 1-4 miU, according to . 
 the valuation of the town, and petition the state ^^^^° 
 highway commissioner. If he approves the petition the road 
 is built. 
 
 Rhode Island does not deal with the localities at 
 all but builds the roads directly under the state , , ® 
 
 commission. 
 
 CONSTRUCTIO.V OF STATE ROADS 
 
 The construction is in the hands of the state engineer, who 
 makes plans, surveys, estimates, etc. The machinery nec- 
 essary is provided by the state and its operation paid 
 for by the county. All work costing over S2000 ^°^^^ ^^^' 
 is let by contract. The state engineer lets all contracts in the 
 name of the state. Partial payments on work in progress must 
 not exceed So per cent of the cost according to the engineer's 
 estimate. The inspection of the work during construction is 
 entirely in the hands of the state engineer. 
 
 Grades and width of improved surface are fixed by the state 
 engineer. 
 
 The construction of state aid roads is entirely subject to the 
 state commission. Plans, estimates and surveys are made 
 under their direction and they let all contracts for 
 work. The county must furnish the right of way York, 
 
 for relocations. Towns or counties may bid on the construction 
 the same as any contractor, and if they are low bidders the 
 commission lets the contract to them. The inspection of the 
 
266 THE ART OF ROADMAKING 
 
 work during construction is done by the state, and if the work 
 is not being properly carried on the state has authority to 
 stop it and relet the contract. 
 
 Grades and width of improved surface are fixed by the state 
 commission. 
 
 The construction of state aid roads is all under the super- 
 vision of the chief engineer of the highway division. Plans, 
 estimates and surveys are made by him. Contracts 
 
 aryan . ^^^ work are let by the county board subject to 
 the approval of the engineer. The inspection during the 
 progress of the work is done by the state. 
 
 Grades and width of improved surface are fixed by the state. 
 Plans, surveys and estimates of state aid work are made 
 by the state highway commissioner. All work is done under 
 . . contract let by the state commissioner. The coun- 
 
 irgmia. ^-^^^ may bid on work in competition with other con- 
 tractors. The inspection of the work in progress is done by 
 the state commissioner or some of his assistants. 
 
 Grades and width of improved surface are fixed by the state. 
 The work of building state aid roads is in the hands of the 
 state highway commission, under whose direction plans, surveys 
 and estimates are made. The state pays for a new 
 assa- right of way in case a relocation of the road is 
 
 necessary. The highway commission has machinery 
 which it loans to the local people. All contracts are let by 
 the commission, and cities or towns may take contracts at 
 the estimate of the commission without calling for competitive 
 bids on the work. The inspection of the work during prog- 
 ress is done by the state commission. 
 
 The maximum grade allowed is 6 per cent. Width of im- 
 proved surface is fixed by the state. 
 
 Plans, estimates and surveys are made by the state high- 
 way commission. Towns may submit competitive bids for 
 doing the work. Contracts are let by the state 
 tonnec icu . ]^jg]^-^g^y commissioner, and inspection of the work 
 during progress is made under his direction. 
 
 Grades and width of improved surface are fixed by the state. 
 The law of this state provides that all state aid highways 
 shall be built according to the standards adopted by the state 
 highway department. This department gives the 
 Pennsyi- ^oads thorough inspection during the period of 
 vania. construction. The law provides that no state aid 
 
 roads shall be built less than 12 feet wide. Grades are fixed 
 
STATE AID LAWS 267 
 
 by the state commissions. The state aid work is done under 
 contracts let by the state highway commissioner. Counties 
 and towns may bid on work if they so desire. 
 
 In this state the surveys and plans are made by the county 
 engineer, but are subject to the approval of the state highway 
 commissioner. The county provides the right 
 of way for relocations. All work is done by con- ^^ Jersey. 
 tracts let by the county board subject to the approval of the 
 state highway commissioner. The state inspects the roads dur- 
 ing their construction. 
 
 Grades and width of improved surface are subject to the 
 approval of the state commissioner. 
 
 Plans and surveys are made by the state highway commis- 
 sioner. The maximum grade must not be over 5 per cent and 
 the width of improved surface must not be less than 
 8 feet nor over 16 feet, unless the locality wishes '^^^^^^Ston. 
 to pay the whole cost of the excess width. All state aid work 
 is done under contracts let by the state highway commis- 
 sioner. Counties may bid on these contracts if they so de- 
 sire. In case relocation is necessary the county provides the 
 right of way. The county engineer inspects the roads during 
 construction under the direction of the state highway com- 
 missioner. 
 
 The construction of state aid roads is in charge of the state 
 highway commissioner, who makes all plans, estimates and 
 surveys. The width improved must not be less 
 than 8 feet nor greater than 16 feet unless the 
 locality wishes to pay the cost of the excess width. The grades 
 must be such as will meet the approval of the state highway 
 commissioner. The work is done under contracts let by the 
 state highway commissioner, and the inspection during con- 
 struction is done by him. 
 
 Surveys for improvements to be made with state aid are made 
 by the county, but the plans must be submitted to the state 
 commissioner for his approval. The county or 
 town has direct charge of the work, but the state M^^^^gan. 
 inspects it carefully when completed. The Michigan law con- 
 tains specifications according to which the roads must be 
 constructed in order to receive state aid. All work is let by 
 contracts by the town or county if it exceeds $500 in amount. 
 No grades may exceed 6 per cent and the width of improved sur- 
 face must not be less than 9 feet in order to receive state aid. 
 
 The work of improving state aid highways is under the super- 
 vision of the state highway commissioner. His force inspects 
 
26S THE ART OF ROADMAKING 
 
 them while they are under construction, and makes the plans 
 
 . and surveys before construction is begun. Work is 
 
 ^*°®' done under contracts which are let by the towns sub- 
 
 ject the approval of the state commissioner. 
 
 Construction is in charge of the state board, who make all 
 plans and surveys and let contracts and do the 
 J ° ^ inspection while the road is under construction. 
 
 The law provides that the roads shall not be im- 
 proved for a less width than 14 feet. 
 
 PAYMENT FOR STATE AID HIGHWAYS 
 
 The state pays two-thirds of the cost in the poorer counties 
 and one-half in the richer counties. The whole cost is paid 
 . at first by the state and the counties repay their 
 Model bill. qY^^yq ^q ^^xe state. No part of the cost of the im- 
 provements is assessed on abutting property. 
 
 On county highways the state pays 50 per cent of the cost, 
 the county 35 per cent and the town 15 per cent. On town 
 roads the state pays from 33^ to 50 per cent and the 
 ®^ °^ * town 66f to 50 per cent, depending on whether the 
 town is rich or poor. The county's share is paid to the con- 
 tractor by the county treasurer and the state's share is paid 
 direct to the contractor by the state treasurer. New York 
 formerly assessed 15 per cent on abutting property owners 
 if they originated the petition for the improvement, but this 
 assessment has been done away with. The state does not 
 pay any share of the cost of bridges exceeding five feet in length. 
 The county first pays the whole cost of the road and the 
 state repays half the cost to the county. If the property 
 owners force the county board to act they have to 
 ary an . ^^^ -^q ^^^ ^^^^ ^^ ^^^ ^^^^^ ^^^ county 40 per cent 
 
 and the state 50 per cent. All bridges on the highway to be 
 improved are considered as part of the highway and the state 
 pays its share of the cost. No part of the cost is assessed on 
 abutting property except as mentioned. 
 
 The county treasurer pays the contractor on the certificate 
 of the state highway commissioner. The state treasurer turns 
 . . the state's allotment over to the county treasurer 
 
 irginia. upon the certificate of the state highway comniis- 
 sioner. The state pays half of the expense of the permanent 
 improvement and leaves it to the county to decide how much 
 shall be borne by the county as a whole and how much assessed 
 to the local road district. There is no provision, however, 
 for an assessment of the cost upon the abutting property. If 
 
STATE AID LAWS 269 
 
 the allotment of the state aid fund to any county is $2500 or 
 less^ that county may use it to aid in paying for the building 
 of permanent bridges under plans made or approved by the 
 state highway commissioner. The county must put in an 
 equal or greater sum, however, so that the state does not pay 
 more than half the cost of the bridges. 
 
 The state treasurer pays the whole cost of the work on the 
 order of the highway commission. The counties 
 have six years in which to pay back to the state one- -h^^^^t 
 fourth of the cost. No part of the cost of the roads 
 is assessed on the abutting property owners. 
 
 The state pays the full amount to the contractors and the 
 towns afterward pay back to the state one-quarter or one-eighth 
 of the cost, depending upon the wealth of the town. 
 None of the cost is assessed on abutting property, ^^^^^^i*^"*- 
 Nothing is said in the law regarding aid for bridges on state 
 aid roads. 
 
 The state pays three-quarters of the cost and the county and 
 town each one-quarter. The total cost is first paid 
 by the state, and the counties and towns afterward ennsy - 
 
 pay their share to the state treasurer. The state 
 pays the same share of the cost in building bridges that it pays 
 for building roads. No part of the cost of roads is assessed 
 on abutting property. 
 
 The state treasurer pays one-third the cost of the roads and 
 the county teasurer pays the contractor on the estimates of 
 the engineer. Formerly 15 per cent was assessed 
 on abutting property, but now no part of the cost ^^ Jersey, 
 is assessed in this way. New Jersey does not give state aid 
 for bridges. 
 
 The state and the county each pay half of the cost of the 
 state aid roads. Each treasurer pays direct to the contractor 
 on vouchers of the state highway commissioner. 
 Thirty-five per cent of the cost is paid from the ^^'^'""Ston. 
 county funds, and 15 per cent from the road district funds. 
 If the property owners petition, 15 per cent is paid by the owners 
 of all property lying within a half mile either side of the road. 
 Nothing is said in the law about state aid for bridges. 
 
 The state pays 25 per cent, county 50 per cent, the town 
 10 per cent, and abutting property owners 15 
 per cent. The law says nothing about state aid Ohio. 
 
 for bridges. 
 
 The total cost of the road is paid in the first instance by the 
 town or county and the state afterward "rewards" themj 
 
270 THE ART OF ROADMAKING 
 
 pa3ang its share if the road is finished according to specifica- 
 
 tions. The rewards vary from $250 to $1000 per 
 
 ic igan. -j^-^iIq^ depending on the kind of road built. No 
 
 part of the cost is assessed upon the abutting property and no 
 
 aid is given for the building of bridges. 
 
 The town pays for the cost of the roads in the first instance 
 on the order of the state highway commissioner, and the state 
 . then pays to the town its share. This share varies 
 
 aine. . from two-thirds of the cost, in poor towns, to three- 
 sevenths of the cost in towns having a valuation of over $1,000,- 
 000. No part of the cost is assessed on abutting property, 
 and nothing is said in the law about state aid for bridges. 
 
 Rhode The cost of the roads is entirely paid by the 
 
 Island. state. 
 
 MAINTENANCE OF STATE AID HIGHWAYS 
 
 The state engineer has charge of the maintenance of state 
 aid highways. The county reimburses the state 
 ^ ' one-third or one-half the cost of maintenance accord- 
 ing to whether the county is poor or rich. 
 
 The maintenance of all roads built with state aid is under 
 the direct regulation of the commission. The commission 
 is directed to provide a system of patrol of state high- 
 New York. y^oy-Q gQ lY^Q^i each section may be under constant 
 supervision. The state pays the cost of the maintenance in the 
 first instance, and each town in which a state aid road hes 
 repays $50 a year to the state for each mile. The town super- 
 intendents of highways carry out the work of maintenance 
 under the direction of the commission. 
 
 The county boards must maintain the state aid highways 
 at county expense. If they are not maintained in 
 Maryland. ^ manner satisfactory to the state engineer no 
 further state aid is granted to the county. 
 
 The state commissioner has charge of the main- 
 Virginia. tenance of state aid highways. 
 
 The maintenance of state aid roads is in the hands of the 
 highway commission. They must contract with towns to 
 maintain the roads properly. Each town pays 
 Massa- ^^q p^j, ^-^^ ^^^ annum for maintaining the state 
 
 c use s. ^^^ roads and the remainder is paid by the state. 
 The expense of snow removal is borne by the town alone. 
 
 The maintenance of state aid highways is in the hands of 
 
STATE AID LAWS 271 
 
 the state highway commissioner and the state pays the whole 
 cost at first. The towns reimburse the state one- 
 fourth the cost of maintaining their roads. onnec icu . 
 
 The towns are charged with the maintenance of the state 
 aid roads and pay only one-fourth of the cost. The state 
 pays three-fourths of the cost and if the roads are 
 not properly maintained the state commissioner ennsy - 
 may take the work out of the hands of the town, in 
 which case the town must pay 25 per cent of the cost to the state. 
 
 The county highway engineer is charged with keeping the 
 state aid roads in good condition, and the expense is all borne 
 by the county. If the roads are not maintained 
 in a manner satisfactory to the state highway com- ^^ jersey. 
 missioner he is instructed by law to refuse any further peti- 
 tions for state aid from that county until the roads are re- 
 paired in an acceptable manner. 
 
 The state aid roads are maintained at county expense by the 
 supervisors of the districts through which they 
 pass. These supervisors act under the direction ^^ mgton. 
 of the state highway commissioner. 
 
 State aid roads must be maintained by the coun- 
 ties at their own expense. *°' 
 
 State aid roads must be maintained by the county or town 
 petitioning for their construction. If they are not 
 properly maintained the state commissioner does ^^ ^^^^' 
 not grant any further state aid to them. 
 
 Towns must maintain state aid roads at their own . 
 
 expense to the satisfaction of the state highway ^"^^' 
 
 commissioner. 
 
 The state maintains all roads built by the state 
 and charges none of the cost to the locality except- t i ° d 
 
 ing that the town must keep the roads free 
 from snow. 
 
 CONVICT LABOR ON ROADS. 
 
 Connected with an active interest on the part of the state 
 in road building one feature that always attracts a great deal 
 of attention is the possibility of employing the state convicts 
 in either preparing the material or in actually constructing 
 the roads. A number of the southern states have had very 
 good success in using gangs of convicts to construct the state 
 roads. Almost every highway commissioner from the north- 
 
272 THE ART OF ROADMAKING 
 
 ern states who has examined into the practical operation of 
 this system in the south has returned with the opinion that it 
 would not be readily adaptable to northern conditions. A 
 large percentage of the convicts in the south are negroes in 
 prison for petty offenses, and very good results have been 
 obtained in using gangs of them in road work. No northern 
 state, in which the convicts are almost all white men, has ever 
 attempted, on any large scale, to use their convicts in this 
 manner. 
 
 The only northern state that has used its convicts to any 
 extent in road construction is Illinois, In that state they 
 have adopted the plan of estabhshing stone-crushing plants 
 at the two penitentiaries. The stone produced at these plants 
 is given by the state without charge to the towns or counties 
 desiring to use it, under the restriction that it must be used 
 according to the directions of the state highway commission. 
 
 EXCERPTS FROM SPECIFICATIONS USED IN CON- 
 STRUCTING STATE AID ROADS IN MASSACHU- 
 SETTS, NEW JERSEY, NEW YORK, CONNECTICUT, 
 PENNSYLVANIA, AND MARYLAND.* 
 
 MASSACHUSETTS 
 
 Earthwork 
 
 The roadbed shall be graded for the width of true to the lines 
 
 and grades given by the engineer and in conformity with the plans, 
 profiles, and cross-sections furnished by the commissioners, and so shaped 
 that after the broken stone is rolled in place the surface of the roadway 
 shall have a crown of three-quarters of an inch to the foot. 
 
 All clay and spongy material shall be removed to a depth to be deter- 
 mined by the engineer, and the space thus made shall be filled with 
 such material as the engineer may direct. 
 
 In general, embankments will be made from material from within the 
 location of the road, as will also all filling and grading, but there if is not 
 sufficient suitable material in the excavation, in the opinion of the 
 engineer, the contractor shall find such material outside of the highway 
 location. Such material will be classed as borrow. 
 
 Embankments shall be formed of successive layers of not more than 
 
 * Abstracted from Office of Public Roada Bulletin No. 29. June, 1907. 
 
STATE AID LAWS 273 
 
 twelve (12) inches in thickness, each layer to be thoroughly rolled by a 
 roller weighing not less than two tons. 
 
 All trees, stumps, and roots within the roadbed and on slopes shall be 
 grubbed up and removed as the engineer may direct, without additional 
 compensation. 
 
 Ditches of such width and depth as the engineer may direct shall be 
 excavated by the contractor wherever the engineer may order them, at 
 the contract price for excavation. 
 
 All surfaces in slopes or on embankments, whether old or new, shall 
 be left with neat and even surfaces according to the lines, grades, and 
 directions given by the engineer, without additional compensation. 
 
 All measurements of earthwork shall be made in excavation. 
 
 Material obtained from excavation within the limits of the location and 
 used in embankments, or for any other purpose, will be paid for as 
 excavation only. 
 
 Allowance for culvert excavation will include only one (1) foot outside 
 of the masonry sections, as shown on plans. 
 
 Borrow 
 
 When, in the opinion of the engineer, there is not sufficient suitable 
 material within the limits of the highway location of the section under 
 contract, to form the necessary embankments, or for subgrading, or for 
 shoulders, the contractor shall obtain such material from outside the 
 highway location. This material shall be known as borrow, and may 
 be of any quality satisfactory to the engineer for the purpose for which 
 it is required. 
 
 If found within a radius of one thousand (1000) feet from any point on 
 said section under contract it will be paid for at the borrow price. 
 
 If, however, in the opinion of the engineer, no suitable material can be 
 obtained within the limit just described, the contractor shall find satis- 
 factory material at a greater distance. In this event, in addition to the 
 regular borrow price, the sum of one-half (j) cent per cubic yard for each 
 one hundred (100) feet of overhaul shall be allowed him for all material 
 so supplied, the length of haul to be measured from the pit along the 
 shortest available route to the one thousand (1000) foot limit above 
 described. 
 
 Borrow pits will be cross-sectioned and all quantities will be measured 
 in the pits. 
 
 Ledge Excavation 
 
 Only such ledge as requires blasting for its removal, and boulders of 
 one-half (^) a cubic yard or more in volume, will be estimated as ledge 
 excavation. 
 
 No allowance for ledge excavation in the roadbed shall be made outside 
 of or for more than twelve (12) inches below the lines indicated on the 
 
274 THE ART OF ROADMAKING 
 
 cross-sections showing the finished surface, the side slopes to be one- 
 fourth (i) to one (1). 
 
 Allowance for ledge in drains will be made on the basis of a width of 
 trench of two (2) feet and a depth of four (4) inches below the invert of 
 the pipe; allowance for ledge in gutters will be made on the basis 
 of the width of the gutter and (12) inches in depth below the proposed 
 surface. 
 
 Culverts 
 
 Reinforced Portland cement-concrete culverts shall be constructed 
 where ordered by the engineer to the lines and grades given by him. 
 
 Culvert ends shall be laid parallel to the center line of the roadway. 
 All culvert masonry shall be measured in accordance with the dimen- 
 sions shown on the plans. 
 
 No allowance shall be made for cofferdams, pumps, labor, etc., which 
 may be necessary on account of water. 
 
 Portland Cement Concrete Masonky 
 
 The concrete shall be composed of broken stone or screened gravel, 
 and sand — all of which shall be clean, hard, durable, sharp, and free 
 from clay, dirt, and other objectionable material — Portland cement and 
 fresh, clean water. 
 
 To each part of Portland cement there shall be by volume two (2) 
 parts of sand and five (5) parts of broken stone or srceened gravel, and 
 such a proportion of water as the engineer may from time to time deter- 
 mine. 
 
 The broken stones or gravel stones shall be of the following sizes: 
 
 For all work less than six (6) inches in thickness the stones may vary 
 in their longest dimension from one-quarter (^) of an inch to three- 
 quarters (I) of an inch; between six (6) inches and twelve (12) inches, 
 from one-quarter (|) of an inch to one and one-quarter (1|) inches; more 
 than twelve (12) inches in thickness, from one-quarter (|) inch to two 
 and one-half (2^) inches. 
 
 The cement and sand shall first be thoroughly mixed dry, in the 
 proportions specified, in proper boxes. Clean water shall then be added 
 and the materials thoroughly mixed. The broken stone, previously 
 drenched with water, shall then be deposited in this mixture and the 
 ingredients thoroughly mingled and turned over until each stone is 
 covered with mortar. The batch shall then be carefully deposited without 
 delay and thoroughly rammed in layers not more than six (6) inches 
 in depth until the water flushes to the surface and all the voids are filled. 
 
 The concrete shall not be allowed to fall from any considerable height. 
 
 Before the concrete is placed in the moulds, a sheet-iron plate, six or 
 eight inches in width and about six feet long, or of such other dimensions 
 as the contractor may find convenient, shall be held in position one and 
 
STATE AID LAWS 275 
 
 one-half (H) inches from the surface of the mould or form. The space 
 between the form and this separator shall be filled with mortar, composed 
 of one part of Portland cement and one part of sand, mixed to such a 
 consistency as the engineer may direct, and, if he shall so direct, the 
 mortar shall be thoroughly spaded after it is placed. Only a small 
 batch shall be mixed at a time, and then only as needed. Immediately 
 after the space between the separator and the form is filled with mortar 
 the ordinary concrete shall be placed behind the separator, the separator 
 removed, and the backing and facing thoroughly rammed together to 
 a close bond. No delay shall be permitted in placing the concrete 
 backing, and both the facing and the backing shall be done as nearly 
 simultaneously as is possible. 
 
 Should voids be discovered when the forms are taken down, the 
 defective work is to be removed and the space refilled with one to one 
 cement mortar. The exposed surfaces shall be smoothed over with a 
 neat Portland cement grout, laid on with a brush, until a smooth surface 
 is secured. 
 
 Centers and forms, satisfactory to the engineer, shall be provided by 
 the contractor. They shall be made of planed lumber and shall fit the 
 curves and shapes of the work. The sheathing shall be laid tight and 
 shall be made clean before using. 
 
 The centers shall be true to the lines, satisfactorily supported and 
 firmly secured, and shall remain in place as long as the engineer may 
 direct, and shall be replaced by new ones when they lose their proper 
 ■dimensions or shape. 
 
 In connecting concrete already set with new concrete, the surface shall 
 be cleaned and roughened and mopped with a mortar composed of one 
 part Portland cement and one part sand. 
 
 When work is done under such conditions that the mortar is liable to 
 freeze, the contractor shall provide the necessary means for and shall 
 thoroughly heat all materials, and also the water, and shall thoroughly 
 protect the masonry from damage by rain and frost during and after 
 laying. 
 
 During warm and dry weather, and whenever the engineer may direct 
 all newly built concrete shall be kept well shaded from the sun and well 
 sprinkled with water until set. 
 
 In laying concrete under water the concrete shall not fall from any 
 considerable height, but be deposited in the allotted place in a compact 
 mass. The concrete must not be rammed, but leveled with a rake or 
 other suitable tool immediately after being deposited. No concrete shall 
 be laid in running water. 
 
 Expanded metal or twisted rods, to be furnished to the contractor by 
 the commission, shall be imbedded in the concrete by the contractor Si-3 
 directed by the engineer, without extra compensation. 
 
 No back-filling or loading whatever shall be placed on or against the 
 concrete masonry until ordered by the engineer. 
 
276 THE ART OF KOADMAKING 
 
 The Massachusetts highway commission will furnish all cement to be 
 used in this work and will deliver it to the contractor at the nearest 
 railroad freight station. The contractor shall, at his own expense, team 
 the cement to the work and store it, and protect it from the weather to 
 the satisfaction of the engineer. 
 
 The price to be paid per cubic yard for concrete masonry shall include 
 the back-filling and all necessary centers and forms, and all work on the 
 same, and no allowance shall be made for cofferdams, pumping or bailing, 
 or for any materials or labor necessary on account of water. 
 
 All concrete shall be measured in accordance with the dimensions 
 shown on plans. 
 
 Shaping Surface for Broken Stone 
 
 Before the broken stone is spread the roadbed shall be shaped to a 
 true surface, conforming to the proposed cross-section of the highway 
 and rolled by a steam roller, unless otherwise ordered by the engineer. 
 All depressions occurring must be filled with suitable material and again 
 rolled, until the surface is smooth and hard, the width to be paid for 
 to include only the width of broken stone. 
 
 Broken Stone • 
 
 Broken stone, consisting of , shall be spread and rolled on the 
 
 roadbed prepared as hereinbefore described, as follows: 
 
 The width of the broken stone shall be { — ) feet. 
 
 All broken stone used shall be laid in layers or courses. The bottom 
 course shall consist of stones from one and one-quarter (1^) inches to 
 two and one-half (2^) inches in their longest dimension; the upper course 
 of stone from one-half (^) inch to one and one-quarter (1|) inches in 
 their longest dimension. 
 
 The bottom course shall be — — ( — ) inches deep at the center and 
 
 {—) inches deep at the sides after rolling. The top course shall 
 
 be ( — ) inches deep at the center and ( — ) inches deep at 
 
 the sides after rolling. 
 
 After the two courses above described are thoroughly compacted, 
 broken-stone screening shall be laid on, watered, and rolled until the 
 mud flushes to the surface. The screenings so used shall not be larger 
 than will pass through a half-inch mesh and shall contain all the dust. 
 Care must be taken to lay on only enough of the screenings to cover the 
 larger stones. 
 
 Each course, bottom, top, and binder shall be rolled separately by a 
 steam roller and evened up with material of the same size and quality as 
 has been used in that particular course, and to the satisfaction of the 
 enffineer. 
 
STATE AID LAWS 277 
 
 All broken stone shall be spread from the carts by hand, or from a 
 dumping board, of from self-spreading carts. 
 
 No soft or disintegrated stone shall be used. 
 
 If so ordered by the engineer the thickness of the broken stone shall 
 be increased or diminished at such points as he may direct. 
 
 The grade of the finished surface of the road shall present a crown of 
 three-quarters (|) of an inch to the foot. 
 
 If local stone or stone not shipped by rail is used, it shall be weighed 
 on scales furnished by and at the expense of the contractor. Said scales 
 shall be satisfactory to the engineer and they shall be sealed at the 
 expense of the contractor as often as the engineer may deem necessary 
 to insure their accuracy. 
 
 A sworn weigher, to be appointed and compensated by the Massa- 
 chusetts highway commission, shall weigh all broken stone required to 
 be weighed as above provided. 
 
 If the stone is shipped by rail the car weights will be accepted. 
 
 Vitrified Clay Pipe and Iron Water Pipe (for Culverts) 
 
 Vitrified clay pipe and iron water pipe shall be furnished and laid 
 where directed by the engineer. 
 
 All clay pipe shall be of first quality, salt glazed, free from blisters 
 and cracks, straight and round. If eighteen (18) inches or more in 
 diameter the pipe shall be "double strength," or if ordered by the 
 engineer, ordinary pipe may be used and laid in concrete, which shall 
 be tamped about the pipe to the satisfaction of the engineer. If, how- 
 ever, concrete is used it shall be paid for at the regular price for con- 
 crete. 
 
 All iron pipe shall be of the best quality of water pipe and free from 
 imperfections of any kind. 
 
 All pipe shall be laid true to the lines and grades furnished by the 
 engineer. Nothing but selected fine material, free from large stones, 
 shall be placed around and under the pipe, and all material placed under 
 and about the pipe shall be thoroughly tamped in place by a thin iron 
 tamping bar. All joints shall be made of first quality natural cement 
 mortar, mixed in proportion of one (1) part cement to one (1) part of 
 clean, sharp sand, carefully filled in all around the pipe. The ends of 
 pipe drains used as culverts must be protected by concrete masonry or 
 concrete walls. The price per foot paid for pipe laid as above includes 
 the cost of trenching and back-filling, and all incidental work except 
 the masonry ends; providedy however, that when the depth of the trench 
 exceeds five (5) feet all excavation necessary on account of additional 
 depth shall be paid for by the cubic yard at the regular contract price 
 for excavation. 
 
278 THE ART OF ROADMAKING 
 
 Guard Rail 
 
 Fencing shall be placed on edges of embankments and at such other 
 places along the road as the engineer may deem necessary. It shall be 
 of the section shown on plan; the posts shall be of well-seasoned, straight, 
 sound chestnut or cedar, not less than six (6) inches in diameter, spaced 
 eight (8) feet apart on centers, the bottom of each post to be sawed oft' 
 square and set plumb in straight lines, three (3) feet into the ground 
 and three and one-half (3^) feet above the ground, and the back-filling 
 thoroughly tamped. All bark shall be removed before setting, all knots 
 hewn down to face and the exposed surfaces shaved. The top rails shall 
 be four (4) inches square and the side rails of two by six (2X6) inch 
 well-seasoned, straight-grained spruce, or other wood satisfactory to the 
 engineer, planed, free from loose or unsound knots, and both top and 
 side rail shall be notched into and securely fastened to the posts, as 
 shown in the plan, and be long enough to extend over three (3) posts 
 and break joints. 
 
 All parts of the exposed surface of the fence shall be painted with one 
 coat of white lead and linseed oil. 
 
 At culverts square iron posts, one and one-quarter (1^) inches square, 
 shall be used, set into the coping stone at least four (4) inches, and leaded. 
 The side rail shall be bolted to the iron posts with two bolts set in holes 
 drilled through each post. 
 
 Side Drains 
 
 Drains will be built where directed by the engineer. 
 
 All drains must be carried to an outlet approved by the engineer. 
 
 The drain trench shall be excavated to a width of twelve (12) inches 
 at the bottom and fifteen (15) inches at the top, and shall be excavated 
 only as fast as the drain can be finished. 
 
 When the grade of the finished road is three (3) inches or more to the 
 hundred (100) feet, the bottom of the drain trench must be three and 
 one-half (3^) feet below the finished surface of the road at that part of 
 the cross-section. 
 
 On the bottom of this trench shall be placed two (2) inches of gravel 
 or broken stone which will pass through a one and one-quarter (1^) 
 inch mesh, and not through a half (I) inch mesh. 
 
 On this material shall be laid a five (5) inch salt-glazed vitrified clay 
 pipe, with bell and spigot joints, unless otherwise ordered, with open 
 joints, and the bell ends toward the rising grade. 
 
 All pipe must be laid true to a line and grade, and no pipe is to be laid 
 on a grade of less than three (3) inches in one hundred (100) feet. 
 
 Gravel or broken stone of the sizes already described shall be filled 
 about the pipe and over it for a depth of one (1) foot. This must be 
 carefully tamped about and rammed over the pipe. The remainder of 
 
STATE AID LAWS 279 
 
 the trench is to be filled with stone which will pass through a three (3) 
 inch and not through u, one (1) inch mesh, and this material shall be 
 thoroughly tamped. Any sand, silt, or earth getting into the pipe or 
 the interstices of the stone in the trench must be removed by the con- 
 tractor at his own cost, even if it be necessary to rebuild the drain. 
 
 Where, in the opinion of the engineer, it is necessary to extend a drain 
 to an outlet beyond the section needing to be drained, the pipe will be 
 laid with cement joints, true to line and grade, and the gravel or stone 
 in the trench omitted, the trench being back-filled with the material 
 excavated from the same. 
 
 Where a pipe is carried through a bank the outlet must be protected 
 by masonry, as provided in pipe culverts. 
 
 The price per lineal foot includes the cost of trenching and refilling 
 with gravel or broken stone, the cost of the pipe and laying, as well as 
 all incidental work. 
 
 No allowance will be made for pipe larger than above specified laid in 
 any drain unless the larger pipe has been ordered in writing by the 
 engineer. 
 
 Stone Filling 
 
 At such places as the engineer may direct, stone filling shall be placed. 
 Excavations shall be made to the lines shown on the cross-sections. The 
 stones may be either wall stones or cobbles ranging in size from the 
 smallest obtainable to those not exceeding eight (8) inches in their 
 longest dimension, and the larger stones shall be placed at the bottom. 
 
 The excavation will be paid for at the regular price for excavation. 
 
 The stone filling will be measured according to the original cross- 
 sections, without allowance for shrinkage or settlement, and paid for 
 by the cubic yard. 
 
 Catch Basins 
 
 Catch basins will be built of brick masonry or Portland cement concrete, 
 as shown on plan and in accordance with the directions of the engineer. 
 
 All bricks used shall be well formed and hard burnt and shall be well 
 soaked in water before laying. 
 
 The joints shall be thoroughly flushed full of mortar, consisting of one 
 part of natural cement of the best quality and two parts of coarse, clean, 
 sharp sand, free from loam and pebbles. 
 
 No joint on the face shall be greater than one-quarter inch. 
 
 After the bricks are laid the joints shall be neatly pointed on the inside. 
 
 As the walls are laid up they shall be well plastered with mortar on 
 the outside. 
 
 The contractor is to furnish all labor, tools, and materials necessary 
 for the basins, excepting the frames and grates, which will be furnished 
 
280 THE ART OF ROADMAKING 
 
 by the commission, and delivered at the railroad freight station nearest 
 to the site of the work. The price paid for each basin will include all ex- 
 cavation, back-filling, and incidental work. 
 
 Cobble-Stone Gutters 
 
 Paved gutters will be built where directed by the engineer, the same to 
 be laid by journeymen pavers. 
 
 No gutter is to be laid until after the broken stone has been rolled, unless 
 otherwise ordered by the engineer. 
 
 In no case is the roller to pass over any part of any paved gutter. 
 
 Gutters not exceeding four hundred (400) feet in length shall be three (3) 
 feet wide with a shoulder one (1) foot wide and a dish of three (3) inches. 
 
 Gutters exceeding four hundred (400) feet in length shall increase the 
 dish above this length at the rate of one (1) inch to each three hundred 
 (300) feet. 
 
 All stone used in gutters shall be rounded field, bank, or river stone; 
 no flat, shaky, or rotten stone shall be used. 
 
 The stone may, on the average, lay from four (4) to six (6) square 
 yards to the ton. A cubic yard may be estimated to weigh one and one- 
 third (1^) tons. 
 
 The larger selected stone will be laid in the gutter row and on the edges 
 to a true line and grade, with the largest diameters lengthwise of the road. 
 All other stone will be laid with the longest diameters across the gutter. 
 
 The trench shall be excavated to a depth of twelve (12) inches below the 
 finished grade of the gutter; gravel shall then be spread and rammed 
 to a depth of four (4) inches. A layer of bedding sand, or gravel free 
 from stone larger than one-half (4) inch in diameter, shall then be spread 
 of a sufficient thickness to bring the gutter stone which are bedded in it 
 to the proper grade and cross-section after they are thoroughly rammed. 
 
 Each stone is to be rammed to an unyielding foundation. The con- 
 tractor shall employ one rammer to every two pavers. The surface 
 shall then be covered with coarse sand or fine screened gravel free from 
 clay or dirt, which must be well broomed into all joints. The stone shall 
 then be rerammed and the surface left smooth and even. If from any 
 cause the stone in a gutter shall have been disturbed and left uneven, 
 they must be relaid by the contractor and at his cost. Sand or screened 
 gravel shall then be spread over the entire surface of sufficient depth 
 to fill all interstices. 
 
 The edge of the gutter toward the road shall be left one-quarter (^) 
 inch below the surface of the adjoining broken stone; in no case must it 
 project above it. 
 
 All broken stone which may be disturbed during the paving of the 
 gutter must be carefully replaced and thoroughly rammed. 
 
 The bank on the outside of the gutter must be sloped to the gutter, so 
 as to have no bunches or depressions on its surface. 
 
STATE AID LAWS 281 
 
 NEW JERSEY 
 
 SUBFOUNDATIONS 
 
 When the excavations and embankments have been brought to a proper 
 depth below the intended surface of the roadway, the cross-section thereof 
 conforming in every respect to the cross-section of the road when finished, 
 
 the same shall be rolled with u ton roller until it is inches 
 
 below the intended surface of the road and is approved by the engineer 
 and supervisor. If any depressions form under such rolling, owing to 
 improper material or vegetable matter, the same shall be removed and 
 good earth substituted, and the whole reroUed until thoroughly solid 
 and to above-mentioned grade. Water must be applied in advance of 
 the roller when, in the opinion of the engineer and supervisor, it is 
 necessary. 
 
 Stone Construction 
 
 telford foundations 
 
 After the roadbed has been formed and rolled, as above specified, 
 and has passed the inspection of the engineer and supervisor, a bottom 
 
 course of stone, of an average depth of inches, is to be set by hand 
 
 as a close, firm pavement, the stones to be placed on their broadest edges 
 lengthwise across the road in such fanner as to break joints as much as 
 possible, the breadth of the upper edge not to exceed four (4) inches. 
 The interstices are then to be filled with stone chips, firmly wedged by 
 hand with a hammer, and projecting points broken off. No stone of 
 greater length than ten (10) inches or width of four (4) inches shall be 
 used, except each alternate stone on outer edge, which shall be double 
 the length of the others and well tied into the bed of the road. All 
 stones with a flat, smooth surface must be broken. The whole surface 
 of this pavement must be subjected to a thorough settling or ramming 
 
 with heavy sledgehammers, and thoroughly rolled with a ton 
 
 roller. No stone larger than two and one-half (2^) inches shall be left 
 loose on top of telford. 
 
 Macadam 
 
 first course of broken stone 
 
 After the roadbed has been formed and rolled, as above specified, 
 and has passed the inspection of the engineer and supervisor, the first 
 layer of broken stone, consisting of two and one-half (2^) inch stone, 
 or stone that will pass through a ring three (3) inches in diameter, shall 
 
 be deposited in a uniform layer, having a depth of inches, and rolled 
 
 repeatedly with u. ton roller until compacted to the satisfac- 
 tion of the engineer and supervisor. No stone in this course shall be less 
 than two (2) inches in length. 
 
282 THE ART OF ROADMAKING 
 
 The depth of loose stone in this and all other courses must be measuroJ 
 by blocks the required thickness of the said loose stone. These blocks 
 must be placed at frequent intervals amid the loose stone when being 
 spread . 
 
 Binder between First and Second Course for Telford or Macadam. 
 
 On the first course of stone a quantity of binder shall be spread 
 
 in a uniform layer, and the whole rolled until the stones cease to sink 
 or creep in front of the roller. The quantity and quality of this and all 
 other binding shall be subject to the approval of the engineer and super- 
 visor. Water must be applied in advance of the roller, if ordered by the 
 engineer or supervisor. 
 
 Second Course of Broken Stone for Macadam or Telford 
 
 The second course of broken stone shall consist of one and one-half 
 (1^) inch stone; that is, every piece of stone shall be broken so that it 
 can be passed through a ring two (2) inches in diameter, and no stone 
 shall be more than two (2) inches or less than one (1) inch long. This 
 
 course shall be spread in a uniform layer inches in depth and rolled 
 
 until thoroughly settled into place to the satisfaction of the engineer and 
 supervisor. Water must be applied as ordered by the engineer or super- 
 visor. • 
 
 Binder on Second Course of Stone 
 
 Binder on this course of stone must be applied in the same manner as 
 binder on first course of stone, as directed by engineer and supervisor. 
 
 Surface 
 
 When the two courses are rolled to the satisfaction of the engineer and 
 supervisor, a coat of fifty (50) per cent of three-quarters (|) inch stone 
 and fifty (50) per cent of screenings, properly mixed, is to be spread of 
 sufficient thickness to make a smooth and uniform surface to the road, 
 then again rolled until the road becomes thoroughly consolidated, hard 
 and smooth. 
 
 Rolling must be done by the contractor with a ton roller, 
 
 approved by the engineer. 
 
 Any depressions formed during the rolling, or from any other cause, 
 are to be filled with one and one-half (1^) inch stone, or three-quarter 
 (I) inch stone, or both, and screenings, approved by the engineer, and the 
 roadway brought to the proper grade and curvature as determined by 
 him. 
 
 Water must be applied in such quantities and in such manner as di- 
 rected by the engineer or supervisor. 
 
STATE AID LAWS 283 
 
 Manner of Rolling 
 
 In the rolling the roller must start from the side lines of the stone bed 
 and work toward the center, unless otherwise directed. The rolling 
 shall at all times be subject to the directions of the engineer and super- 
 visor, who may, from time to time, direct such methods of procedure as 
 in their opinion the necessities of the case may require. 
 
 Quality of Material 
 
 All stone must be as nearly cubical as possible, broken with the most 
 approved modern stone-crushing machinery, free from all screenings, 
 earth, and other objectionable substances, of uniform size, and the same 
 kind and quality, or as good in every particular, as that shown in the 
 engineer's office. The one and one-half (H) inch stone, three-quarter 
 (I) inch and screenings for binder and final finish must be of the best 
 trap rock, free from loam or clay. 
 
 The contractor must furnish samples to the engineer of the kind of stone 
 to be used in the work before the opening of the bids, and to the state 
 commissioner of public roads before the approval of the contract by him. 
 
 Entrances to Dwellings 
 
 All driveways leading to dwellings along the road shaU be macadamized 
 with the second course and finished in the same manner as prescribed for 
 the main road. The macadamizing shall be carried to u, distance of not 
 more than six feet beyond the gutter line of the road, as indicated by the 
 engineer's stakes, but in no case shall the macadamizing be carried beyond 
 the side line of the road as indicated by the fences. 
 
 Shouldering 
 
 A shoulder of firm earth or gravel is to be left or made on each side, 
 extending at the same grade and curvature of road to side ditches or 
 gutters. This shoulder is to be rolled according to the directions of the 
 engineer. 
 
 NEW YORK 
 
 Rolling Subgrade 
 
 After the surface of the subgrade has been properly shaped, and before 
 any broken stone or other material is put on, it shall be thoroughly rolled 
 and compacted. This rolling shall be done Avith a steam road roller 
 weighing approximately ten tons, and so built that its wheels shall cover 
 when rolling the entire width of its track. The roller must be of a kind 
 approved by the state engineer. All hollows and depressions which 
 
284 THE ART OF KOADMAKING 
 
 develop during the rolling shall be filled with material acceptable to the 
 engineer and the subgrade shall again be rolled. This process of filling 
 and rolling shall be repeated until no depressions develop. The shoulders 
 also shall be rolled in the same manner, but in places where the character 
 of the material makes the use of a ten-ton roller impracticable a lighter 
 roller shall be used . 
 
 In places where the material of the subgrade or of the shoulders is 
 unstable, and will not consolidate under the action of the roller, and is so 
 great in extent that its removal is impracticable, it shall be formed to the 
 desired shape and treated in such manner as may be necessary to con- 
 solidate and compact it, and to give the best results in providing a stable 
 foundation for the entire roadway. 
 
 The expense of all such special work shall be borne by the contractor 
 and must be considered by him in making his proposal. 
 
 The bottom course shall not be placed on any subgrade until the sub- 
 grade has been accepted by the engineer. 
 
 Surface of Roadway 
 
 The surface of the roadway shall be formed of broken stone macadam 
 or any other material shown on the plans or ordered by the state engi- 
 neer. When formed of broken stone macadam it shall have the thick- 
 ness shown on the plans. In general it will be formed of three courses — 
 a bottom course three inches thick after being rolled, a middle course 
 two or three inches thick after being rolled, and a top course one 
 inch thick after being rolled. 
 
 Broken Stone Macadam 
 
 Where shown on plans, called for in the specifications, or ordered by 
 the state engineer, at prices named in the supplementary bidding sheet, 
 broken stone macadam shall be placed in accordance with the specifi- 
 cations. 
 
 Broken Stone 
 
 The contractor shall submit with his bid a written statement of the 
 quarries, ledges, or other sources of supply from which he proposes to 
 obtain the stone for the road. If the proposed quarries are thoroughly 
 developed and n uniform product, satisfactory to the state engineer, 
 can be obtained from them, this will be accepted and the contractor 
 will be so informed. If after trial it is found that partially developed 
 quarries, ledges, or other sources of supply do not furnish a uniform 
 product, of if for any reason the product from any source at any time 
 proves to be unsatisfactory to the state engineer, he may decline to 
 continue its use and can require the development of other quarries, or 
 he may require the contractor to furnish other sources of supply, and the 
 
STATE AID LAWS 285 
 
 contractor shall have no claim for increased payment on account of such 
 requirement. Immediately after the crusher is in operation the con- 
 tractor shall furnish to the engineer in charge a sample consisting of 
 about ^ of a cubic foot of each size of the crushed stone to be used, showing 
 character and size. If the character and size of the stone submitted are 
 satisfactory to the state engineer and are accepted by him, the samples 
 will be retained by the engineer, and all stone which are inferior in char- 
 acter or size to these samples will be rejected. 
 
 Quality of Broken Stone 
 
 Broken stone and screenings must be of a hard and compact texture 
 and of a uniform grain. The fragments shall have rough surfaces such as 
 are obtained by fracture. Water-worn pebbles will not be accepted. 
 Disintegrated and rotten stone from the surface of a quarry or elsewhere 
 will not be accepted. All stone shall be thoroughly clean before crushing 
 and must be well screened and free from injurious matter of every nature. 
 
 The broken stone shall be spread in three courses when the top course 
 is built of trap rock, granite, gneiss, or any of the harder grades of stone; 
 in two courses when the top course is built of limestone or any of the softer 
 grades of stone. The number of courses shall be as shown on the plans 
 or ordered by the engineer. 
 
 Bottom Course 
 
 The bottom course, in either case, after it is rolled shall have the thick- 
 ness shown on the plans or indicated on the quantity sheet, and may 
 consist of approved trap rock, granite, gneiss, or any of the harder grades 
 
 of limestone or tough sandstone broken in fragments that will 
 
 pass through a three-inch circular ring but will not pass through a two- 
 inch circular ring. 
 
 When local stone is crushed to form the bottom course only, all frag- 
 ments that will pass through a three-inch circular ring but will not pass 
 through a one-half inch circular ring may be used. Care must be taken 
 to distribute evenly the smaller stone among the larger stone. 
 
 Filler for Bottom Course 
 
 The filler for the bottom course shall be either screenings or sand. 
 Screenings shall consist of fragments of the kind and quality of stone speci- 
 fied, that will pass through a one-half-inch circular ring. They shall be 
 free from any injurious material and shall contain all the dust of fracture. 
 If sand is used, it shall not be excessively fine and must be satisfactory 
 to the engineer. 
 
286 THE ART OF ROADMAKING 
 
 Middle Course 
 
 When the road is built in three courses, the middle course after it is 
 
 rolled shall have the required thickness shown on the plans or indicated 
 
 on the quantity sheet, and shall consist of broken into fragments 
 
 that will pass through a two-inch circular ring but will not pass through 
 a one-inch circular ring. 
 
 Top Course 
 
 When the road is built in three courses the top course after it is rolled 
 shall have the required thickness shown on the plans or indicated on the 
 
 quantity sheet, and shall consist of broken in fragments that will 
 
 pass through a one-inch circular ring but will not pass through a one- 
 half inch circular ring. 
 
 When the road is built in two courses the top course after it is rolled 
 shall have the required thickness shown on the plans or indicated on 
 the quantity sheet, and shall consist of Umestone broken in frag- 
 ments that will pass through a two-inch circular ring but will not pass 
 through a one-half inch circular ring. Care must be taken to distribute 
 the smaller stone evenly among the larger stone. 
 
 Binder for Middle and Top Courses 
 
 Screenings for binder for middle and top courses shall consist of frag- 
 ments of the kind and quality of stone specified, that will pass through 
 a one-half inch circular ring. They shall be free from any injurious 
 material and shall contain all the dust of fracture. 
 
 Sprinkler 
 
 The sprinkler shall be built without a reach to allow short turns. 
 The tires on the wheels shall be at least six inches wide and the axles 
 shall be of unequal length, so that the front and rear wheels will not 
 roll in the same track. 
 
 Spreading and Rolling 
 
 After the subgrade has been prepared and has been accepted by the 
 engineer, ix layer of broken stone of the approved size and quality for 
 bottom course shall be spread evenly over it to such depth that it shall 
 have, when rolled, the required thickness. The depth of the loose stone 
 shall be fixed by laying upon the subgrade cubical blocks of wood of 
 the required size (Ij times thickness of course to be formed) and spread- 
 ing the stone evenly to the same thickness. 
 
 The roller shall be run along the edge of the stone backward and for- 
 ward several times on each side before rolling the center. Before put- 
 
STATE AID LAWS 287 
 
 ting on the filler the bottom course shall be rolled until the stones do not 
 creep or weave ahead of the roller. In no case shall the screenings or 
 sand for filler be dumped in mass upon the crushed stone, but they shall 
 be spread uniformly over the surface from wagons or from piles that 
 have been placed on the shoulders. It shall then be swept with rattan 
 or steel brooms and rolled dry. This process shall be continued until 
 no more will go in dry, when the surface shall, if required by the engi- 
 neer, be sprinkled, to more effectually fill the voids. No filler shall be 
 left on the surface. 
 
 The middle course of stone shall be spread on the bottom course to 
 such a depth that it shall have, when rolled, the required thickness. 
 Blocks of wood (H times thickness of course to be formed) shall be used 
 to fix the depth of the loose stone; care shall be taken to preserve the 
 grade and crown. Before putting on the screenings it shall be rolled 
 dry until the stones do not creep or weave ahead of the roller. It shall 
 then be filled with screenings, leaving none on the top, and rolled dry. 
 
 The top course of stone shall be spread on the middle course to such 
 a depth that it shall have, when rolled, the required thickness. Blocks 
 of wood (1^ times thickness of course to be formed) shall be used to fix 
 the depth of the loose stone; care must be taken to preserve the grade 
 and crown, also to prevent a wavy surface. It shall then be covered 
 with dry screenings, swept and rolled dry, after which the road shall 
 be sprinkled until saturated, the sprinkler being followed by the roller. 
 More screenings shall be added, if necessary, and the sweeping, sprink- 
 ling, and rolling shall continue until a grout has been formed of the 
 screenings, stone dust, and water that shall fill all the voids and shall 
 form a wave before the wheels of the roller. The road shall be puddled 
 as many times as may be necessary to secure satisfactory results. 
 
 After the wave of grout has been produced over the whole section of 
 the road, this portion of the road shall be left to dry, after which it shall 
 be opened to travel. Where necessary, enough screenings or approved 
 sand shall be spread on top of the macadam to leave a wearing surface 
 at least three-eighths of an inch thick. This wearing surface shall be 
 maintained and renewed, if necessary, until the whole road has been 
 accepted. 
 
 Method of Carrying on the Work 
 
 All work shall be carried along together where practicable. The 
 stone shall be rolled and promptly filled after being spread, and travel 
 upon loose stone shall not be permitted. 
 
 No extra allowance will be made for material driven into the sub- 
 grade by the roller, wagons, or by other means, or for any mistake made 
 by the contractor in preparing subgrade. Lighter rollers, rammers, or 
 other suitable implements shall be substituted for the ten-ton steam 
 roller, if the engineer so directs. 
 
2S8 THE ART OF ROADMAKING 
 
 Before a road will be finally accepted the macadam surface must be 
 firm, hard, smooth, regular, well bound, and must be covered with a proper 
 wearing surface. The shoulders must be well formed and the ditches 
 clear. The spoil-banks, borrow-pits, and all slopes along the roadsides 
 must be left in regular form. All waste materials must be removed 
 and the whole put in a neat and workmanlike condition. 
 
 CONNECTICUT 
 Kind of Stone 
 Unless otherwise specified, trap rock will be required. 
 
 Courses of Stone 
 
 There shall be two courses of broken stones under finishing course; 
 first course to be 4 inches, and second course to be 2 inches over all 
 when rolled; no allowance to be made for settling. 
 
 Dimensions of Broken Stone 
 
 The stone for the first course shall be from | of an inch to 2 inches 
 longest diameter, mixed in the screens (not in the bins), the smaller sizes 
 to predominate. vStone for the second course shall be from 1 inch to 
 1^ inches longest diameter. No tailings shall be used in either course. 
 
 First and Second Courses 
 
 The stone shall be dumped on the side of the road where it is possible; 
 if not, it can be dumped on the side of the roadbed and scattered with 
 shovels; the reason for this is that the stone will have a uniform pressure 
 in rolling. If a patent spreading wagon is used by the contractor, it 
 will not be necessary to dump the stone, but it can be spread by the 
 wagon. After stone has been spread for the first course, sufficient to 
 roll down to 4 inches, a roller shall be run over the stones a sufficient 
 number of times to make this course soUd and firm, after which the second 
 course of 2 inches shall be applied in the same manner as specified for 
 the first course, and also receive the same roller treatment. If in the 
 putting on of either course any settling is found, all such places must be 
 brought up to grade level before any other course is commenced. In 
 the rolling of these courses the roller work must be continued until the 
 broken stone settles down into a firm and compact condition. 
 
 Finishing Course 
 
 This course shall be 1 inch thick when finished. Trap rock screen- 
 ings, including dust (no screenings larger than ^-inch stone will be al- 
 lowed), shall be used as a finishing course. The screenings (after the 
 
STATE AID LAWS 289 
 
 rolling has been done on the last course of broken stone) shall be carted 
 on the sides of the road proper and dumped at suitable intervals, after 
 which all wheel tracks and foot-marks of horses shall be carefully filled 
 and then rolled down firmly. Then the screenings shall be scattered 
 dry over the surface so. as to fill all interstices, and the roller shall be 
 run over the surface to shake in the dust. Immediately after, a sprink- 
 ling cart shall be used and the screenings washed in, after which more 
 screenings must be added and sprinkled and rolled again, and the screen- 
 ings, sprinkhng, and rolling must be continued until all the coarse stones 
 have been covered and interstices completely filled and the road is firm 
 and Smooth and will shed water and measure in depth 1 inch of screen- 
 ings for wearing surface. The contractor will not be allowed to put 
 on the screenings all at one time, but must spread them on as described 
 above, and will not be allowed to deviate from the above treatment 
 in any way. The contractor must not wet the screenings before they 
 have been scattered on the broken stone, and, furthermore, they must 
 be perfectly dry before they are put on the road. 
 
 PENNSYLVANIA 
 
 KOADBED 
 
 The graded roadbed must be rolled until firm with a steam roller 
 weighing not less than 16,000 pounds nor more than 20,000 pounds. 
 Any depressions formed under such rolling must be filled and rolled 
 again until the subgrade presents a uniform appearance and is identical 
 in form with the cross-section of the road when finished. Under no 
 circumstances must stone be laid until the subgrade has been thoroughly 
 rolled to the satisfaction of the engineer or inspector in charge. 
 
 Macadam 
 
 Only good solid stone shall be used in macadamizing. Bidders will 
 name the kind of stone they propose using in said work, and also its lo- 
 cation, unless the kind of stone required to be furnished is mentioned in 
 the specifications. On the prepared roadbed shall be placed the bottom 
 course, extending feet on each side of the center line, and com- 
 posed of crushed stone not larger than will pass through a 3-inch ring 
 in all directions nor smaller than 1^-inch size. After being evenly spread 
 the course shall be thoroughly rolled with the roller hereinbefore specified 
 until none of the stone moves under the roller. All material must be 
 added dry, but water must be applied ahead of the roller. The bottom 
 course must be inches deep. 
 
290 THE ART OF ROADMAKING 
 
 Telford Macadam 
 
 Only good solid stone shall be used in teiford construction. Bidders 
 will name the kind of stone they propose using in said work, and also 
 its location, unless the kind of stone required to be furnished is men- 
 tioned in the specifications. On the proposed roadbed shall be placed 
 
 the bottom course, extending feet on each side of the center line, 
 
 the stones composing the course to be 9 to 12 inches long by 3 to 5 inches 
 
 wide and inches deep, placed vertically by hand on their broadest 
 
 edges. Stones are to be laid in lengthwise courses across the road, and 
 all interstices filled with broken stone wedged y/ith a hammer. All 
 projecting points must be broken off to bring the surface of the stone 
 true to grade, the course to be thoroughly rolled with the roller here- 
 inbefore specified until the stone does not rock under the roller. Good 
 hard native stone can be used for the teiford course. 
 
 After completion of the bottom course, the second course, to be 
 
 inches deep, shall be applied, of crushed stone not larger than will pass 
 through a 1^-inch ring in all directions, nor smaller than f-inch size, 
 and rolled as previously directed until firm and solid, water being applied 
 ahead of the roller. 
 
 The finishing course shall be 1 inch thick, of the same material as the 
 second course and composed of rock screenings, at least 50 per cent of 
 which must be of sizes from ^ inch to I inch. It shall be applied dry 
 and rolled once before wetting, then alternate applications of water and 
 rolling until finally completed, when the surface must present a uniform 
 appearance and conform to the shape and grade fixed by these specifi- 
 cations and the accompanying plans. 
 
 The several courses of materials used in the construction of the road 
 must each be of the required depth after rolling (allowance for com- 
 pression should be at least one-half). 
 
 Trap rock or good hard blue limestone must be used for the second 
 and top courses. 
 
 The rolling must be done with the utmost thoroughness in each of 
 the courses. In all rolling the roller must start from the side lines of the 
 roadbed and work toward the center. The contractor shall sprinkle 
 and roll the finished road every day for at least one week after the com- 
 pletion of the work. 
 
 Road Intersections 
 
 All intersections of roads are to be graded and macadamized in ac- 
 cordance with the plan, and in addition thereto broken stone of the 3- 
 inch size must be spread beyond the macadam to a depth of 6 inches 
 for a distance of 100 feet on the intersecting roads, and also at the ends 
 of the macadam on the road being improved for at least 100 feet; berms 
 shall be built to hold this stone in place. 
 
STATE AID LAWS 
 
 291 
 
 The contractor will be required to grade and put in a condition satis- 
 factory to the state highway commissioner all existing approaches of 
 roads of lanes leading off the road. 
 
 MARYLAND 
 
 Macadam construction is to be used wherever directed by the engineer 
 or provided for in the plans. The width and thickness required at 
 different points is to be that designed by the engineer. 
 
 Classes A, B, and C 
 
 There to be class of macadam construction to be 
 
 known as Class A, B, and C, respectively. class shall consist 
 
 of three courses of broken stone. The thickness after rolling of the 
 various courses in class is to be as follows: 
 
 
 First Course. 
 
 Second Course. 
 
 Third Course. 
 
 Class A 
 
 Class B 
 
 Class C 
 
 4 inches 
 
 5 inches 
 
 6 inches 
 
 2 inches 
 
 3 inches 
 
 4 inches 
 
 (To be as herein- 
 after described.) 
 
 Each course of broken stone is to be applied as herein specified. 
 
 Roadbed 
 
 MATERIAL 
 
 The roadbed for macadam construction is to consist of the natural 
 earth roadbed, prapared and rolled until firm and hard in the following 
 manner : 
 
 If sandy or other soil be encountered which will not compact readily 
 under the roller, a small amount of clay, or other means satisfactory 
 to the engineer, shall be used until a firm, hard surface is obtained after 
 rolling. 
 
 CUTS AND FILLS 
 
 In cuts and fills, unless otherwise specially directed, the roadbed is 
 
 to be graded to a width of feet, and is to be free fronl all spongy 
 
 and vegetable matter, roots, and stumps. The portion of the roadbed 
 
 prepared for the broken-stone surface is to be feet wide and 
 
 brought to the grades and cross-sections as shown on the plans and 
 rolled with a steana roller until firm and hard. All depressions that may 
 appear during the rolling are to be filled with earth and rerolled until an 
 even surface with a proper grade and cross-section is obtained. 
 
292 THE ART OF ROADMAKING 
 
 OLD EARTH ROADBED 
 
 Where no change from the present grade of those portions of the road 
 not already surfaced with stone is shown on the profile, the roadbed is 
 to be shaped to the proper cross-section and slight elevations with con- 
 tiguous depressions removed so as to form an even and smooth surface. 
 The roadbed is to be rolled to a, firm, smooth surface before the appli- 
 cation of the broken stone. 
 
 TRENCH FOR THE BROKEN STONE 
 
 The portioD of the roadbed prepared for the broken stone is to be 
 below the sides by an amount equal to the thickness of the first course 
 of stone so as to prevent the broken stone spreading at the sides. 
 
 SHAPE 
 
 The shape for the roadbed is to be as shown on the accompanying 
 plans, and is to have a cross slope of inch to 1 foot. 
 
 First Course 
 material 
 
 The first course of the macadam construction is to consist of sound 
 stone broken to sizes varying from 3 inches to 2 inches, no piece to have 
 a dimension greater than 3 inches. This is to be known as "No. 1" 
 size. 
 
 No material is to be used which, in the opinion of the engineer, is 
 unfit for the work. If any such material is put upon the road it shall 
 be removed immediately upon notice from the engineer and replaced 
 by proper material at the contractor's expense. 
 
 SPREADING 
 
 No broken stone is to be spread before the roadbed has been made as 
 specified. 
 
 The broken stone is to be spread upon the roadbed, prepared as herein 
 described, with shovels from piles alongside the road or from a dumping 
 board, or it may be spread directly from wagons especially constructed 
 for this purpose and approved by the engineer; but in no case shall the 
 broken stone be dumped directly upon the roadbed. 
 
 ROLLING 
 
 After the broken stone for the first course has been spread to an uni- 
 form thickness, and has a proper cross-section, it is to be rolled with a, 
 steam roller, weighing not less than 10 tons, until it is compacted to form 
 
STATE AID LAWS 293 
 
 a firm, smooth surface. Should any difficulty be experienced while 
 rolling in having the stone readily compact, water shall be sprinkled 
 or sand or other material be spread, as the engineer may direct. The 
 rolling must begin at the sides and work toward the center, thoroughly 
 covering this space with the rear wheel of the roller. 
 
 UNEVENNESS OR DEPRESSIONS 
 
 Should any unevenness or depressions appear, during or after the 
 rolling of the first course, they are to be remedied immediately with 
 broken stone and rerolled until a firm, even surface is obtained. 
 
 THICKNESS 
 
 The thickness of the first course of broken stone, after thorough rolling, 
 is to be that of the class of macadam construction specified for any 
 particular place as described under class A, B, and C. 
 
 If, for any reason, a. greater thickness than specified is made by the 
 contractor no extra allowance for such additional thickness will be made. 
 
 Shoulders 
 
 After the first course has been made as herein described earth shoulders 
 are to be constructed along each side of the road for a width of at least 
 feet as shown on the accompanying plans. 
 
 Against these shoulders is to be spread the broken stone for the second 
 course as herein described. The shoulders are to contain d sufficient 
 quantity of earth so that a smooth and continuous slope will be obtained 
 after the shoulders and second course are rolled. The shoulders with 
 
 the feet of stone will make a total width of feet to be 
 
 shaped with a cross slope of inch to 1 foot. 
 
 Material for the shoulders must be free from roots, stumps, or other 
 vegetable matter and thoroughly compacted by the roller. Material 
 with a proportion of sand such as prevents it when dry compacting 
 readily under the roller, is not to be used. 
 
 No material which is considered unfit for the work by the engineer 
 is to be used and where any such is put on the work it shall be imme- 
 diately removed, upon notice by the engineer, at the contractor's expense. 
 
 Second Course 
 
 The second course of the macadam construction is to be the same 
 width as the first course. 
 
 material 
 
 The second course is to consist of stone broken to sizes varying from 
 1 inch to 2 inches; no piece to have a greater dimension than 2 inches. 
 This will be known as "No. 2" size. 
 
294 THE ART OF ROADMAKING 
 
 Unless otherwise specified the stone for this course shall be trap rock 
 with a, "coefficient of wear," as determined by tests made at the lab- 
 oratory of the highway division of the Maryland geological survey, of 
 not less than 15, or limestone with a "coefficient of wear" of not less 
 than 10. 
 
 SPREADING 
 
 The broken stone for the second course is not to be spread before the 
 first course has been completed and shoulders made as herein specified. 
 
 The broken stone is to be spread upon the first course, prepared as 
 herein described, with shovels from piles alongside the road or from a 
 dumping board, or it may be spread directly from wagons especially con- 
 structed for this purpose and approved by the engineer; but in no case 
 shall the broken stone be dumped directly upon the first coui;se. 
 
 ROLLING 
 
 After the broken stone for the second course has been spread to a 
 uniform thickness, and has a proper cross-section, it is to be rolled with 
 a steam roller, weighing not less than ten tons, until it is compacted 
 to form a firm, smooth surface. Should any difficulty be experienced 
 while rolling in having the stone readily compact, water shall be sprinkled, 
 or sand or other material be spread, as the engineer may direct. 
 
 The rolling is to begin at the sides, the shoulders first being rolled 
 firm so as to prevent spreading of the broken stone in the second course. 
 When completed the surface of the shoulders and of the second course 
 of broken stone should be smooth and continuous with a cross slope of 
 inch to 1 foot. 
 
 UNEVENNESS AND DEPRESSIONS 
 
 If any unevenness or depressions appear during or after the rolling 
 of the second course, either on the surface of the shoulder or the broken 
 stone, suitable material shall be added to remove all such unevenness 
 or depressions, earth being used on the shoulders and No. 2 stone for 
 the broken-stone surface. 
 
 THICKNESS 
 
 The thickness of the second course of broken stone, after thorough 
 rolling, is to be that of the class of macadam construction, specified for 
 any particular place, as described under classes A, B, and C. 
 
 If, for any reason, a greater thickness than specified is made by the 
 contractor, no extra allowance for such additional thickness will be 
 made. 
 
STATE AID LAWS 295 
 
 Third Course 
 
 material 
 
 The third course of the macadam construction is to consist of trap 
 rock screenings varying in size from dust to 1-inch pieces. Other material 
 than trap rock screenings may be used if approved by the engineer. 
 Limestone screenings shall be used with a limestone second course. 
 
 SPREADING 
 
 After the second course of No. 2 stone has been rolled and completed 
 as above described the screenings are to be spread, but in no case are 
 screenings to be used until the second course has been thoroughly rolled 
 and compacted. The screenings are to be spread dry with shovels from 
 piles alongside the road, or from dumping boards, but in no case are the 
 screenings to be dumped directly on the second course. The quantity 
 of screenings used is to be such as will just cover the second course. 
 
 WATERING AND ROLLING 
 
 After the screenings are spread they are to be sprinkled with water 
 from a properly constructed sprinkling cart, and then rolled with a steam 
 roller weighing not less than ten tons. The amount of water necessary 
 is to be determined by the engineer. The rolling is to begin at the sides 
 and to continue until the surface is hard and smooth and shows no per- 
 ceptible tracks from vehicles passing over it. 
 
 If, after rolling the screenings, the No. 2 stone appears at the surface, 
 additional screenings shall be used in such places. 
 
 The rolling and watering shall continue until the water flushes to the 
 surface. The rolling is to extend over the whole width of the road, 
 including the shoulders. 
 
 ITNEVBNNESS AND DEPRESSIONS 
 
 If any unevenness or depressions appear in the road surface after 
 rolling the screenings, No. 2 broken stone and screenings shall be used 
 until they are removed and the finished surface conforms to the proper 
 cross-section, as shown on the accompanying plans, and presents a 
 smooth, even appearance. 
 
PART HI 
 CITY STREETS AND PAVEMENTS 
 
 CHAPTER XIII 
 
 THE DESIGN OF CITY STREETS * 
 
 Most cities grow up gradually, without any comprehensive 
 or prearranged street plan, and without adequate regulations 
 governing suburban development. Streets are laid out in 
 the interests of individuals, and cities are developed under 
 the stimulus of real estate speculation, regardless of the 
 interests of the public. It is usually after the city has grown 
 to a considerable size, that the remedy is applied for this 
 ungoverned development, and in some instances cities have 
 
 spent vast sums in correcting what might have 
 Objects in been prevented by an adequate plan of street design. 
 city streets. -^^ planning the streets of a city, the objects to 
 
 be kept in mind are: 
 
 1. The subdivision of the area to give the maximum effi- 
 
 ciency for business and residence purposes. 
 
 2. Sufficient accommodation for the pedestrian and vehic- 
 
 ular traffic on the streets. 
 
 3 . Good drainage and easy communication between the 
 
 different parts of the city. 
 In the subdivision of the area, it is desirable to make the 
 size of lots such that few of them will be further subdivided, 
 as clearness of identity is always maintained by referring 
 
 * Prof. I. O. Baker, in his "Roads and Pavements," deals more 
 thoroughly than any other writer with this feature of municipal work. 
 
 296 
 
THE DESIGN OF CITY STREETS 297 
 
 to the original number in transferring or assessing the property. 
 Experience has shown that a frontage of 25 feet and a depth 
 of from 100 to 150 feet is the best. This size is suitable for 
 business purposes, and for residence streets two or more lots 
 give proper grounds. 
 
 "With a rectangular system of streets, the blocks are pref- 
 erably long and narrow, since the distance required between 
 streets in one direction is only that necessary to 
 give the proper depth of lots, while in the other m^\° 
 
 direction the streets need be only close enough to 
 provide convenient channels for the traffic. For conven- 
 ience, especially in business districts, it is best to have an 
 alley, from 16 to 20 feet wide, run lengthwise through the 
 block. 
 
 Sizes of blocks vary in any particular city and still more 
 between different cities. The following are the sizes of some 
 typical blocks: 
 
 Boston 200X400 ft. and 100x550 ft. 
 
 New York 200X900 '' and 200X400 '' 
 
 Philadelphia 400x500 '' and 500X800 '' 
 
 Washington 400x600 '' and 300X800 '' 
 
 Montreal 250x750 '' 
 
 Chicago 300X350 '' and 300X500 '' 
 
 Fig. 165 is given by Baker * to illustrate the advantages 
 to be derived from a careful study of the best size of blocks 
 and of the most advantageous arrangement of streets. The 
 left-hand side of the diagram shows the t^^pical arrangement 
 of streets and blocks in the residence district of New York 
 City, the shaded portions representing the usual buildings. 
 Here the three center blocks comprise an area of 720X800 
 feet, and contain 480,000 sq.ft. of building area and 96,000 
 sq.ft. of streets. The right-hand side shows a much superior 
 arrangement in which in a corresponding area there are 
 481,000 sq.ft. of building area and 94,200 sq.ft. of streets. 
 
 * " Roads and Pavements/' p. 309. 
 
298 
 
 THE ART OF ROADMAKING 
 
 The two plans, therefore, give substantially the same area 
 for buildings and for streets. In the first case the length of 
 streets is 1,600 feet, in the second 1,520 feet; therefore the 
 two plans have practically equal light and air, but the second 
 arrangement is the better in the following particulars: 
 
 1. Number of corner sites. 
 
 2. Accessibility of rear entrances for delivery of provisions, 
 
 3 
 
 STR^ELT 
 
 ■tg 
 
 ^^^^M^;^M$^$M^^» 
 
 1 
 
 '"-"? COURT t^ 
 
 ,:■,:;::, wmim. 
 
 5TR£E:-r 
 
 'S 
 
 Fig. 165. — Improved Arrangement of Streets and Block?. 
 
 coal, etc., and the removal of garbage, ashes, etc., 
 and in case of fire. 
 
 3. Removal from the street of dangerous and cramped cellar 
 
 entrances. 
 
 4. Removal from the main and primary streets of the 
 
 loading and unloading of trucks. 
 
 5. Increased transportation facilities in a direction per- 
 
 pendicular to the length of the original blocks. 
 In planning a system of streets, drainage and easy com- 
 munication between the different sections of the city should 
 
TliE DESIGN OF CITY STREETS 299 
 
 be carefully considered. Surface drainage, sewerage and 
 traffic must follow the general slope of the land, 
 and therefore if there is much irregularity of ^ ^ 
 contour in the site, a location of the streets with 
 reference to the contours will afford at once the best drainage 
 and the easiest communication between different parts of 
 the city. If the site is nearly level, the relationship between 
 the slope of the land and the direction of the streets is com- 
 paratively unimportant; but the arrangement of the street 
 plan to afford the greatest facilities for communication between 
 the different parts of the city is still an important matter. 
 The conclusion is, therefore, that on a site of irregular con- 
 tour, the streets should be located with reference chiefly to 
 the topography, and on a level site primarily to secure the 
 most direct and easiest intercommunication. 
 
 Surface drainage, sewerage and traffic should follow the 
 slope of the country, and any attempt to deviate from this 
 becomes a serious question in the building of a city upon any 
 but nearly level ground. The streets are of necessity the 
 drainage lines of the city and should be placed in the natural 
 valleys, and the failure so to locate the streets in many cities 
 where the land is very irregular in contour has led to great 
 expense in the construction of the streets and of a system 
 of storm-water sewers. The upper half of Fig. 166 shows 
 an actual case of a S3'stem of rectangular streets located with- 
 out any reference to the topography of the site; and the 
 lower half of the same diagram shows a proposed arrangement* 
 that would save much expense in grading the streets and at 
 the same time give a quick entrance into the center of the 
 city, and also long easy grades from the heart of the city 
 to the higher outlying districts. 
 
 There are three distinct general plans for location of city 
 streets with reference to directness and ease of communica- 
 tion. One consists of a system of parallel streets crossing a 
 similar system at right angles, often called the '' checker- 
 board," but more properly the "rectangular" system, since 
 
 * By W. D. Elder, in Proc. Mich. Eng. Soc, 189S, p. 52. 
 
300 
 
 THE ART OF ROADMAKING 
 
 JL 
 
 nnni 
 
 11 11 ^1 ^1 ^1 ^1 ^1 II \\7e.rerof 
 
 I I I Citt 
 
 \Ce/?ferof 
 
 Fig. 166. — Location of Streets with Reference to Contours, 
 
THE DESIGN OF CITY STREETS 301 
 
 the blocks are not necessarily square. This arrangement, 
 which is the most common, gives a maximum Qg-gj.„i 
 area for blocks, and also furnishes blocks of the plans for 
 
 best form for subdivision into lots. The second location of 
 arrangement of streets consists of a rectangular ® ^^^ ^' 
 system with occasional diagonal streets along the lines of maxi- 
 mum travel. This system, sometimes called the "diagonal'' 
 system, was employed by L'Enfant in planning the city of 
 Washington, and to a limited degree, was adopted in laying 
 out the city of Indianapolis, which has four broad diagonal 
 avenues converging to a circular park in the center. 
 
 The chief advantage of the diagonal streets is the economy 
 due to the saving of distance by traversing the hypothenuse 
 instead of the two sides of a right triangle. The two American 
 cities mentioned are the only places of importance in which 
 the system was adopted in advance of the building, but in 
 Rome, London, Paris, and in numerous smaller places in 
 Europe, whole districts have been razed to make way for new 
 streets to serve as arteries for increased traffic. A second, 
 and by no means an unimportant advantage of the diagonal 
 system, is the open squares and spaces so grateful to the eye 
 and in compactly built cities of no little sanitary value. 
 
 Although the diagonal avenue occupies ground that might 
 otherwise be used for building purposes, there is a compensat- 
 ing advantage in the greater length of street front obtained.* 
 In many cases the total cost of cutting diagonal streets through 
 built-up districts has been paid by the increased value of 
 the property on and near the street thus opened up. 
 
 The third arrangement of city streets is the "ring" or 
 "concentric" plan, which is very popular in Europe. The 
 most noted example is Vienna with its Ring-strasse (Ring 
 street) within and its Gurtel-strasse (Girdle street) without. 
 The former is 187 feet wide and encircles the public buildings 
 and the leading houses of business and amusement. The 
 enclosed network of streets intersect the Ring-strasse at 
 
 * For a discussion of this phase of the subject, see an article by L. 
 M. Haupt, in Journ. Franklin Inst., Vol. 103, p. 252. 
 
302 
 
 THE ART OF ROADMAKING 
 
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 Fig. 167.— Street Plan of Washington, D. C. 
 
THE DESIGN OF CITY STREETS 303 
 
 forty points, and outward from it extend fifteen main radial 
 avenues. 
 
 The width of city streets is important on account of its 
 influence upon the ease with which traffic may be conducted 
 and also because of its effect upon the health and 
 comfort of the people by determining the amount gti-ggts 
 of light and air which may penetrate into thickly 
 built-up districts. The streets of nearly all large cities are 
 too narrow, being crowded and dark. A more liberal policy 
 in planning streets would probably be of pecuniary advantage, 
 as wide streets usually give a high financial value to adjoining 
 property. A lot 100 feet deep on a street 80 feet wide is 
 usually more valuable than a lot 110 feet deep on a street 
 60 feet wide; that is to say, within reasonable limits land is 
 usually more valuable in the street than on the rear of the 
 lot. Wide streets are especially needed where they are 
 bordered by high buildings or are to carry street railway 
 lines. 
 
 In order properly to accommodate the traffic in business 
 districts of cities of considerable size, a street should have 
 a width of 100 to 140 feet, the whole of it being used for 
 roadway and side-walks; while residence streets in a city 
 of considerable size, where the houses are set out to the 
 property line and stand close together, should have a width 
 of 60 to 80 feet. Although it is advantageous to have a 
 wide street, it is not necessary, nor even desirable, that the 
 whole width be paved; the central portion may be paved, 
 a strip on either side being reserved for grass plats. The 
 width of the pavement should be adjusted to the amount of 
 traffic, which varies greatly accordingly as the street is a 
 business street, a thoroughfare, or an unfrequented residence 
 street. 
 
 The width of the streets in different cities varies greatly. 
 In the older places in New England and the Central States, 
 many of the streets are only 30 to 40 feet wide; but in the 
 West a street is seldom less than 60 to 66 feet wide. In both 
 regions the principal streets are often 80 to 100 feet wide, 
 and in many of the larger cities the boulevards and great 
 
304 
 
 THE ART OF ROADMAKING 
 
 avenues are 150 to 180 feet. The main avenues in Washing- 
 ton are 160 feet wide, in New York 135, and in Boston 180 
 feet. 
 
 At present the regulations governing the width and the 
 arrangements of additions and subdivisions of Washington, 
 a city which has the best street plan of any in America, are: 
 
 "No new street can be located less than 90 feet in width, 
 and the leading avenues must be at least 120 feet wide. Inter- 
 mediate streets 60 feet wide, called places, are allowed within 
 blocks; but full- width streets must be located not more 
 than 600 feet apart." 
 
 The proportion of the area of the city devoted to streets 
 varies greatly, particularly between the older 
 and the newer cities. The following is the per 
 cent of street area in a few extreme cases of 
 American cities:* 
 
 Area of 
 
 streets. 
 
 Minimum Street Per 
 
 Area. Cent. 
 
 1. Taunton, Mass 3.20 
 
 2. Worcester, Mass 5.43 
 
 3. Binghamton, N. Y 7.55 
 
 4. Philadelphia, Pa 8.42 
 
 5. Boston, Mass 8.76 
 
 6. Lowell, Mass 8.92 
 
 7. Fall River, Mass 9.17 
 
 Maximum Street Per 
 
 Area. Cent. 
 
 Duluth, Minn 86.7 
 
 Dallas, Tex 78.3 
 
 Denver, Colo 73.9 
 
 Indianapolis, Ind. . . . 56.4 
 
 Washington, D. C. . .. 43.5 
 
 Davenport, la 42.1 
 
 Evansville, Ind 40.8 
 
 The area devoted to streets and alleys in a few of the 
 principal cities of the world is as follows: 
 
 Area of Streets and Alleys. 
 
 1. Washington 
 
 2. Vienna 
 
 3. New York City 
 
 4. Philadelphia 
 
 5. Boston 
 
 6. Berlin 
 
 7. Paris 
 
 Per Cent. 
 54 
 35 
 35 
 29 
 26 
 26 
 25 
 
 * Census Bulletin, No. 100, July 22, 1891, p. 16. 
 
THE DESIGN OF CITY STREETS 305 
 
 Table XV 
 Acres required per Mile for Different Widths of Roadway. 
 
 Width. 
 
 Acres 
 
 Widtli. 
 
 Acres 
 
 Width. 
 
 Acres 
 
 Width. 
 
 Acres 
 
 Width. 
 
 Acres 
 
 Feet. 
 
 per mile. 
 
 Feet. 
 
 per mile. 
 
 Feet. 
 
 per mile. 
 
 Feet. 
 
 per mile. 
 
 Feet. 
 
 per mile. 
 
 i 
 
 .030 
 
 19 
 
 2.30 
 
 40 
 
 4.85 
 
 59 
 
 7.15 
 
 80 
 
 9.70 
 
 i 
 
 .061 
 
 30 
 
 2.42 
 
 41 
 
 4.97 
 
 60 
 
 7.37 
 
 81 
 
 9.82 
 
 1 
 
 .131 
 
 31 
 
 2.55 
 
 4U 
 
 5.00 
 
 61 
 
 7.39 
 
 83 
 
 9.94 
 
 2 
 
 .343 
 
 23 
 
 2.67 
 
 43 
 
 5.09 
 
 63 
 
 7 53 
 
 83^ 
 
 10.00 
 
 3 
 
 .364 
 
 23 
 
 2.79 
 
 43 
 
 5.21 
 
 63 
 
 7.64 
 
 83 
 
 10.06 
 
 4 
 
 .485 
 
 34 
 
 2.91 
 
 44 
 
 5.33 
 
 64 
 
 7.76 
 
 84 
 
 10.18 
 
 5 
 
 .606 
 
 24J 
 
 3.00 
 
 45 
 
 5.45 
 
 65 
 
 7.88 
 
 85 
 
 10.30 
 
 6 
 
 .737 
 
 25 
 
 3.03 
 
 46 
 
 5.58 
 
 66 
 
 8.00 
 
 86 
 
 10.43 
 
 7 
 
 .848 
 
 26 
 
 3.15 
 
 47 
 
 5.70 
 
 67 
 
 8.12 
 
 87 
 
 10.54 
 
 8 
 
 .970 
 
 27 
 
 3.27 
 
 48 
 
 5.83 
 
 68 
 
 8.24 
 
 88 
 
 10.66 
 
 8i 
 
 1.00 
 
 38 
 
 3.39 
 
 49 
 
 5.94 
 
 69 
 
 8.36 
 
 89 
 
 10.78 
 
 9 
 
 1.09 
 
 29 
 
 3.53 
 
 49i 
 
 6.00 
 
 70 
 
 8.48 
 
 90 
 
 10.90 
 
 10 
 
 1.21 
 
 30 
 
 3.64 
 
 ' 50 
 
 6.06 
 
 71 
 
 8.61 
 
 90| 
 
 11.00 
 
 11 
 
 1.33 
 
 31 
 
 3.76 
 
 51 
 
 6.18 
 
 73' 
 
 8.73 
 
 91 
 
 11.03 
 
 13 
 
 1.46 
 
 32 
 
 3.88 
 
 53 
 
 6.30 
 
 73 
 
 8.85 
 
 93 
 
 11.15 
 
 13 
 
 1.58 
 
 33 
 
 4.00 
 
 53 
 
 6.43 
 
 74 
 
 8.97 
 
 93 
 
 11.37 
 
 14 
 
 1.70 
 
 34 
 
 4.13 
 
 54 
 
 6.55 
 
 74i 
 
 9.00 
 
 94 
 
 11.39 
 
 15 
 
 1.83 
 
 35 
 
 4.34 
 
 55 
 
 6.67 
 
 75 
 
 9.09 
 
 95 
 
 11.51 
 
 16 
 
 1.94 
 
 36 
 
 4.36 
 
 56 
 
 6.79 
 
 76 
 
 9.21 
 
 96 
 
 11.63 
 
 m 
 
 2.00 
 
 37 
 
 4.48 
 
 57 
 
 6.91 
 
 77 
 
 9.33 
 
 97 
 
 11.75 
 
 17 
 
 3.06 
 
 38 
 
 4.61 
 
 571 
 
 7.00 
 
 78 
 
 9.45 
 
 68 
 
 11.87 
 
 18 
 
 2.18 
 
 39 
 
 4.73 
 
 58 
 
 7.03 
 
 79 
 
 9.-58 
 
 99 
 
 100 
 
 13.00 
 12.13 
 
 Width of 
 pavement. 
 
 It is wise to make the streets of residence districts of liberal 
 width for sanitary and aesthetic reasons, and also because 
 the future of the street cannot be certainly fore- 
 seen — the residence street may become a business 
 street, or an unfrequented street a thoroughfare. 
 However, it is not necessary that the whole width should be 
 devoted to wheelways and sidewalks, particularly in small 
 cities. A grass plat between the sidewalk and the pavement, 
 in which shade trees are set, adds to the beauty of the street 
 and to the comfort of the residents, by removing the houses 
 farther from the noise and dust of the pavement. The grass 
 plat, or parking, also affords an excellent place in which to 
 place water or gas pipes, telephone and electric-light conduits, 
 etc. In large cities where the street front is built up solid 
 with houses of several stories, it may be necessary to dispense 
 with the grass plat, and devote the entire street to sidewalks 
 and roadway. 
 
306 THE ART OF ROADMAKING 
 
 For some reason, it has long been the custom to pave streets 
 from curb to curb. Possibly this practice grew out of the 
 necessity of paving business streets from curb to curb, and 
 as business streets are the first to be paved in every city, 
 it was not unnatural that when later the residence streets 
 were also paved, similar designs prevailed. The idea that 
 all of the street must be paved is often shown in the sudden 
 increase in the width of metalled roadway, where a macadam 
 road enters a city. Thus, on several of the streets in Rochester, 
 N. Y., the width of macadam is more than double the width 
 of macadam on the road just beyond the city limits, and that 
 this practice is widespread is shown by the reports of many 
 city engineers. 
 
 There is little justification for the expenditure of money 
 
 involved in paving residence streets their full width; rarely is 
 
 -, . . . there a residence street where traffic is great 
 Driving in ^ ° 
 
 middle of enough to justify a paved trackway greater than 16 
 road ^ or 18 feet in width, and if the passing vehicles on 
 e uc ive. ^^y residence street are watched it is seen that they 
 cling closely to the center. No argument will convince the 
 public that it is poor pavement economy to always travel in 
 the one narrow path, and in spite of signs, and warning 
 notices, both horse and driver will continue to use the cen- 
 ter of the road. The horse finds it easier travelling in the 
 center where all four feet are on a level, and the driver finds 
 it pleasanter riding where the seat is also level; so animal 
 and human comfort take precedence over pavement economics. 
 Some time ago the Massachusetts board of highway commis- 
 sioners caused to be erected along the highways of that state 
 signs requesting drivers of all kinds of vehicles not to drive 
 in the middle of the road. This action was taken because 
 driving in the center of the road was believed to be respon- 
 sible for the heavy repair expenditure necessary. After 
 the sign idea had been given a fair trial the commis- 
 sioners reported that the cost of repairs was much less where 
 the order was obeyed than where it was disregarded. Fig-. 
 168 shows such a sign on a state highway near Sterling, Mass. 
 Since, then, the center of a street receives practically all the 
 
THE DESIGN OF CITY STREETS 
 
 307 
 
 WORCESTER -^ 
 WESTBOYLSTON 
 
 CAMPGROUND 
 
 1^ PRINCETON 
 
 WEST STERLING 
 
 travel, there seems little reason for paving areas seldom used 
 except by occasional carriages and delivery wagons stopping 
 in front of houses. This area 
 might economically be left un- 
 paved, as an earth road is usually 
 only very bad during the wet season 
 of the year, and then its badness 
 varies directly with the amount of 
 traffic that it must bear. It is not 
 the occasional passing of a wheel 
 over an earth road that cuts it 
 into ruts, but the repeated passage 
 of many wheels which churn the 
 water and the earth together, until 
 deep ruts are formed ready to re- 
 ceive the very next fall of rain and 
 store it there. 
 
 In Venice, California, a sea-side 
 town fifteen miles from Los Angeles, 
 center-walks have superseded side- 
 walks. 
 
 The innovation practically con- 
 verts the many short streets lead- 
 ing from the ocean front into recreation grounds, where 
 children may play in safety without fear of being ^ , 
 dispersed or injured by passing vehicles. By walks 
 mutual agreement between the property owners and instead of 
 the city officials, all vehicular traffic is excluded ^* ®^^ ^' 
 from certain streets, the tradesmen and others being rele- 
 gated to the use of 20-foot alleys which abut upon the rear 
 of ail lots fronting upon the cross streets. 
 
 Park avenue, shown in the accompanying view, is one of over 
 thirty streets which have been improved at the expense of 
 the abutting property owners with the centerwalk system. 
 
 From houseline to houseline, the " street " is 40 feet in width, 
 extending 350 feet at right angles with the ocean. The walk 
 down the center varies, according to the choice of property 
 owners, from 10 to 15 feet in width. It is laid strictly according 
 
 Fig. 168. 
 
308 
 
 THE ART OF ROADMAKING 
 
THE DESIGN OF CITY STREETS 309 
 
 to specifications, recommended by the city engineer, approved 
 by the board of trustees and filed at the city hall. 
 
 The specifications call for 3^-inch concrete foundation, laid 
 upon the sand composing the street. No joints are permitted, 
 except where work is stopped from day to day, and at such 
 points a reinforcement of chicken-wire must be laid, the full 
 width of the walk, where the concrete work is renewed. 
 
 The specifications also call for a continuous strip of chicken- 
 wire netting reinforcement, 3 feet wide, of not more than 3-inch 
 mesh, on each side of the center line of the walk, midway 
 between the middle and the outer edge. 
 
 On top of the concrete base is spread a ^-inch finishing coat, 
 composed of equal parts of cement and sand. The surface is 
 neatly marked off in squares, while moist, and coloring matter, 
 usually red or slate gray, is added to give the finished walk 
 any hue desired. 
 
 One detail of the specifications, which tends to guarantee 
 good workmanship, is the direction that the contractor must 
 stamp his name in letters not less than |-inch in height and 
 |-inch deep in the pavement at least once in every 60 linear 
 feet of the work. 
 
 In the pavement shown herewith, the contract figures for 
 the walk were 12 cents per square foot for the pavement 
 and 16 cents per linear foot for the curbing. The latter, in 
 most instances, is made a part of the walk, extending down 
 into the sand on either side for 6 or 8 inches, thus acting as an 
 anchor for the whole. 
 
 With the exception of a few thoroughfares which connect 
 with county roads in the interior, all of the streets bordering 
 upon the waterfront in Venice have been paved with a center- 
 • walk, built either of concrete or wood. 
 
 Freedom from the noise of passing vehicles, with the 
 consequent clouds of dust; the safety and comfort of residents 
 and the exceptional opportunity for ornamental effects offered 
 by the exclusion of traffic and the conversion of the roadways 
 into footways are distinctions peculiar to this system of street 
 design. 
 
 It is universaUy admitted that pavements are desirable; 
 
310 THE ART OF ROADMAKING 
 
 but often, owing to the unwillingness of at least some of the 
 people to pay for them, or to the idea of some that they must 
 have a pavement from curb to curb or none at all, it is diffi- 
 cult to secure them. Within reasonable limits of cost wide 
 pavements are desirable, but length is more valuable than 
 width. Excessive width delays or prevents the getting of any 
 pavement at all; hence one help toward securing a pavement 
 is to make the pavement only wide enough to accommodate 
 the traffic. A narrow pavement not only costs less to con- 
 struct, but also costs less to clean, while the cost of mainte- 
 nance depends chiefly (or, with a pavement not subject to 
 natural decay, wholly) upon the amount of traffic and hence 
 is practically independent of the width. 
 
CHAPTER XIV 
 STONE BLOCK PAVEMENTS 
 
 Stone in a variety of forms has been used for paving 
 purposes from the earhest times. In the form of blocks its 
 earliest systematic use was by the Romans, whose roads 
 were practically works of solid masonry construction, built 
 of irregularly shaped stones, but finished to a smooth and 
 true surface. These roads were wasteful of material but were 
 remarkable for their strength, durability and excessive cost, 
 which,, however, was principally in the lives of captives, who 
 were forced to build these highways for the armies of their 
 conquerors. 
 
 Under Julius Caesar, Rome was in complete communication 
 with all the principal cities of its great empire by 
 such paved roads, which were distinguished by o^an 
 
 the names Victj Actus, Iter, Semita, Trames, 
 Diverticulum, Divertium, Callais, etc. 
 
 The Via corresponded with our common roads, and had a 
 width of 8 Roman feet. 
 
 The Via Miliiari and other important roads in the neighbor- 
 hood of Rome had a double width, 16 Roman feet (15 ft. 6 ins. 
 English), and margines, or sidewalks, 8 feet wide. The middle, 
 convex portion was paved with blocks and divided from the 
 sidewalks by a curb of low wall, 2 feet wide and 18 inches 
 high. The middle was for the infantry; the margines for car- 
 riages and equestrians. 
 
 The Actus was 4 feet wide, for single carriages. 
 
 The Iter, for horsemen, pack animals, and pedestrians, the 
 width of which was 3 feet. Semita was only half the breadth 
 of the Iter, and was called Diverticulvm, or Divertium when it 
 branched across fields. The Semita on steep grades was 
 frequently in the form of steps. 
 
 311 
 
312 THE ART OF ROADMAKING 
 
 The Callais was a mountain path, used principally by 
 shepherds. 
 
 The Via Appia, Appian Way, was not only the earliest 
 military road, but the best constructed. It extended from 
 Rome to Brindusium (now Brindisi), a distance of 360 miles, 
 and was constructed principally by Julius Caesar. The mode 
 of construction, which was, in general, the same as used in all 
 ■important military roads, was as follows: 
 
 The course being decided upon, in as nearly straight lines 
 as possible, it was marked by two parallel trenches excavated 
 at varying distances apart according to the importance of the 
 highway. This also showed the nature of the subsoil, from 
 which the level of the foundations was determined; all unsta- 
 ble materials were removed to a depth of about 3 feet, the 
 
 I .-^-^.l. l^-JiZ -.JiL<L'.— .\.?.'PIX~ ?L3\ j 
 
 Fig. 170. — Cross-section of Roman Road (Appian Way). 
 
 bottom was consolidated by ramming until a solid foundation 
 was obtained. In this undrained trench the road materials 
 were placed in more or less regular la3^ers. 
 
 The statunieit, or base, consisted of two courses of large flat 
 stones laid in lime mortar, and was usually about 15 inches 
 thick. Upon this was laid the ruduSj or rubble, consisting of 
 a 9-inch course of small fragments of stone embedded in suffi- 
 cient lime mortar to fill their voids. 
 
 Upon this, the nucleus was formed of fragments of gravel, 
 stone, pottery and brick mixed with lime mortar to form a 
 concrete, which was laid while hot and consolidated by ram- 
 ming, and was made about 6 inches thick. The summa 
 crusta (top crust) or pavimenium (hard surface) was formed 
 of closely jointed, irregular stones, which formed a mosaic 
 about 6 inches thick, the top of which was practically on a 
 level with the adjoining natural surface of the ground. 
 
STONE BLOCK PAVEMENTS 
 
 313 
 
 In and near the cities the pavimentum was formed of larger 
 irregular blocks of basalt, or porphyry or lava, 2 to 2-^ feet in 
 length and width and 12 inches to 15 inches in thickness, 
 which were dressed and fitted together with extreme accuracy 
 and were bedded in cement. On these roads were carried 
 huge columns, obelisks, and other blocks weighing hundreds 
 of tons, without any injury to the surface. 
 
 The earliest pavements were constructed in almost every 
 case of rough stone, which were the most available and at the 
 same time, most durable. As the need for better pavements 
 increased with the growth of cities, the rough cobble-stone 
 was gradually superseded by stones formed into the shape of 
 blocks which gave a comparatively smooth surface. This was 
 the beginning of the modern stone-block pavement, and in 
 
 Fig. 171. — Cross-section of Cobblestone Pavement. 
 
 European countries the pavements have improved until they 
 
 had developed into something of a standard made of blocks 
 
 about 6 by 8 inches square, and of depths varying according 
 
 to the traffic. 
 
 In this countr}^, however, the original pavements were all 
 
 of cobble. Most of the cities were poor and the 
 
 cobblestones being available and cheap, naturally Co^'^^l^stone 
 
 . ° . ^' *' pavement, 
 
 came mto quite common use. They gave good 
 
 service, but were rough, uneven and very noisy. 
 
 Little, if any, cobblestone pavement is now being laid. 
 
 In a few localities where the property owners pay the first 
 
 cost and are then relieved of further cost of maintenance or 
 
 relaying, its cheapness has been a sufficient inducement to, 
 
 cause it to be used, but is never gives satisfaction and is really 
 
 only a makeshift for a pavement. In the days when pave^ 
 
314 THE ART OF ROADMAKING 
 
 merits of this class were extensivel}^ laid and the demand for 
 the stones became so great that suitable ones were obtained 
 only at considerable expense and with some difficult}^, almost 
 anything in shape and size was permitted to be used^ and the 
 specifications were most shamefully abused. The result was 
 that cobblestone pavements were even worse than they would 
 have been had they been properly laid. The specifications 
 generally provided that the stones should be the best selected 
 water or bank cobblestones, of a durable and uniform quality, 
 with round heads and well-shaped large ends. They should 
 be not less than 4 inches nor more than 8 inches in diameter 
 across the head, nor less than 5 inches nor more than 10 inches 
 in depth; no triangular, split or otherwise ill-shaped stones 
 should be used, nor any which are soft or rotten. 
 
 Since the introduction of asphalt and brick pavements and 
 since the decrease in the cost of stone-block pavement by the 
 introduction of improved methods of quarrying, and in the 
 cost of broken-stone roads by the invention of the rock-crusher 
 and the road-roller, there is little excuse for the construction 
 of the cobblestone pavement. In some cities it has been 
 prohibited by law, but the old pavements still exist in such 
 quantities that it will require some years of active work in 
 repaving before it is entirely .extinct. Practically the only 
 paving for which cobblestones are now used is in yards and 
 alleys, and for gutters and crossings of unpaved streets. 
 
 Following the cobblestone and in response to the demand 
 for an improvement on them, came what has always been known 
 in this country as the " Belgian block." In shape it was a trun- 
 cated pyramid, with base about 5 or 6 inches square, and a 
 depth of from 7 to 8 inches, the bottom of the block being 
 of dimensions of not more than 1 inch different from the top. 
 This was an improvement on the cobblestone and when well 
 shaped and of proper material made a very good pavement. 
 It was introduced into New York and vicinity about 1850^ 
 and it soon became quite popular. 
 
 This form of pavement was the result of a development in 
 Europe from the early pavements, made of large rectangular 
 blocks. These had several square iee^ of top surface and 
 
STONE BLOCK PAVEMENTS 
 
 315 
 
 were laid lengthwise of the street, but as traffic increased, it 
 
 was found that the long joints, being parallel to 
 
 the direction of travel, rapidly wore into ruts and the ^^^^^^ 
 
 pavement became rough and uneven. To obviate pavement. 
 
 this, the blocks were made square and were laid 
 
 with their sides at an angle of 45 degrees with the line of the 
 
 street. These large blocks soon proved unsuitable for heavy 
 
 traffic, as it was difficult to bed them so that they would keep 
 
 their place, and as their large surface did not afford a good 
 
 Fig. 172.— Cobblestone 
 Hammer. 
 
 Fig. 173.— Stone Paver's 
 Hammer. 
 
 Fig. 174.— Cobble- Fig. 175.— Stone block 
 stone Rammer. Rammer. 
 
 foothold for horses. This led to the use of smaller square 
 blocks with their edges parallel and perpendicular to the line 
 of the street. For many years this form of pavement has been 
 common in the cities of Europe, the blocks usually having a 
 top surface of 5 to 7 inches square and a depth of 6 inches. 
 The first use of this form of pavement was in Brussels, Belgium. 
 In New York and vicinitj^ it has been laid almost entirely 
 of trap-rock from the Palisades of New Jersey. This rock is 
 hard and durable, but after some wear becomes smooth and 
 slippery. On account of its being, at first, made of this trap- 
 rock, all trap-rock pavements have been called "Belgian 
 
316 
 
 THE ART OF ROADMAKING 
 
 pavements/' but when made of the oblong blocks similar to 
 those of the ordinary granite they have been called in dis- 
 tinction, ''specification Belgian/' This is a complete mis- 
 nomer, as the name refers distinctly to the shape and not to the 
 character of the material, as some Belgian pavements have 
 been made of granite. 
 
 The objections to the Belgian block are: 
 
 1. On account of the size and form of the blocks it is difficult 
 to keep them in place. 
 
 2. The blocks are of such size and form as to give horses a 
 poor foothold. 
 
 3. The blocks being square there is always a considerable 
 
 Fig. 176. — Cross-section of Stone-block Pavement. 
 
 length of joints parallel to the line of travel, which causes 
 ruts to form in the pavement. 
 
 As the blocks became more common, deviations were al- 
 lowed from the specifications, with the result that the blocks 
 were too small on the base to allow a solid bearing. Also 
 under traffic they soon got out of position, and in consequence 
 the pavement became rough. An improvement in the Bel- 
 gian block was to make the block an exact cube. Many 
 European cities at the present time lay blocks of that shape. 
 Just as the Belgian block supplanted the cobblestone, it 
 has itself been gradually displaced by the introduction of 
 rectangular blocks of granite. Blocks of com- 
 Granite paratively large dimensions were at first employed, 
 
 pavement, being merely placed in rows on the subsoil, per- 
 functorily rammed, the joints filled with sand, and 
 the street thrown open to traffic. The unequal settlement 
 of the blocks, the insufficiency of the foothold, and the diffi- 
 
STONE BLOCK PAVEMENTS 317 
 
 culty of cleansing them led to the gradual development of the 
 later type of stone-block pavements, consisting of narrow 
 rectangular blocks of granite, properly proportioned, laid on 
 an unyielding and impervious foundation, with the joints 
 between the blocks filled with an impermeable cement. This 
 type is practically a return to the system of the Romans, but 
 with blocks of lesser dimensions than they used. 
 
 Experience has proved that this type of pavement is the 
 most enduring and economical for roadways subjected to 
 heavy and constant traffic. Its advantages are: 
 
 1. Adaptability to all grades. 
 
 2. Suitable for all classes of traffic. 
 
 3. Exceedingly durable. 
 
 4- Fair foothold. tn^deS 
 
 5. Easily kept in repair. 
 
 6. Yields little dust or mud. 
 
 7. Moderately easy to clean. 
 Its defects are: 
 
 1. Greasy and slipper}^ surface when damp. 
 
 2. Noisy. The constant noise of the traffic over it is an 
 
 intolerable nuisance and is claimed by physicians to 
 be injurious to the nerves and health of persons who 
 live or do business near it. 
 
 3. Wear on horses resulting from the continual j arring 
 
 produced in their legs and hoofs. 
 
 4. Discomfort to persons riding over it. 
 
 5. If smooth-wearing rocks are used, the surface quickly 
 
 becomes slippery and unsafe. 
 
 The harder and more durable rocks like basalt and true 
 granite are unsuitable, as they have the fault of wearing smooth 
 when subjected to heavy traffic, and under certain 
 conditions of the weather they become greasy and v^^ ^.^ ° 
 slippery. The less durable rocks, such as syenite, 
 and the harder sandstones, are the most suitable; they do not 
 polish and afford a good foothold for the horses. 
 
 The size of the blocks has varied considerably, and a great 
 variety of forms and dimensions are to be found in all cities. 
 For stability a certain proportion must exist between the 
 
318 THE ART OF ROADMAKING 
 
 depth, the length, and the breadth. The depth must be 
 such that when the wheel of a loaded vehicle passes 
 Size and Qyg^^ qj^q Q^gQ of its upper surface it will not tip 
 blocks ^P' otherwise the maintenance of a uniform surface 
 
 is impossible. To fulfill this requirement it is not 
 necessary to make the block more than seven inches deep. 
 
 The maximum width of the blocks is controlled by the size 
 of horses' hoofs. To afford good foothold to horses drawing* 
 heavy loads, it is necessary that the width of each block 
 measured along the street shall be the least possible consistent 
 with stability. It is desirable, therefore, that the width of a 
 block should not exceed three inches, or that four taken at 
 random and placed side by side will not measure more than 
 fourteen inches. 
 
 The length measured across the street must be sufficient 
 to break joints properly, for two or more joints in a line lead 
 to the formation of grooves. For this purpose the length of 
 the block should be not less than nine inches nor more than 
 twelve inches. 
 
 The blocks should be well squared and must not taper in any 
 direction, and both sides and ends should be free from irregular 
 projections. 
 
 The blocks should be laid in parallel courses, with their 
 
 longest side at right angles to the axis of the 
 
 Manner of street, and the longitudinal joints broken by a lap 
 
 blocks ^^ ^^ least two inches, to prevent the formation 
 
 of longitudinal ruts, which would happen if the 
 
 blocks were laid lengthwise. 
 
 At junctions or intersections of streets the blocks should 
 be laid diagonally from the centre to prevent the traffic crossing 
 the intersection from following the longitudinal joints and thus 
 forming depressions and ruts, and affording better foothold for 
 horses turning the corners. 
 
 The foundation of the blocks must be solid and unyielding, 
 and for this, hydraulic cement concrete is exten- 
 oun a- sively used. The thickness must be regulated ac- 
 cording to the traffic, but should not be less than 
 four inches and need not be more than nine inches. A thick- 
 
STONE BLOCK PAVEMENTS 319 
 
 ness of six inches will sustain a traffic of 600 tons per foot of 
 width. 
 
 Between the surface of the concrete and the base of the 
 blocks there is placed a cushion-coat formed of fine^ clean and 
 dry sand, which readil}'' adjusts itself to the irregularities of 
 the base of the blocks and transfer the pressure of the traffic 
 uniformly to the concrete below. 
 
 The blocks are laid stone to stone, so that the joint may be 
 
 of the least possible width; wide joints cause increased wear 
 
 and noise and do not increase the foothold. The 
 
 courses are commenced on each side and worked .f^V^^ ^ 
 
 blocks. 
 
 toward the middle, and the last stone should 
 fit tightly. 
 
 After the blocks have been set they are well rammed down^ 
 and the stones which sink below the general level are taken 
 up and replaced with a deeper stone or brought to level by 
 increasing the sand-bedding. 
 
 All stone-block pavements depend for their water-proof 
 qualities upon the character of the joint-filling. Joints filled 
 with sand and gravel are of course, pervious, while 
 a grout of lime or cement mortar does not make a i,??"*" 
 
 . . filling. 
 
 permanently water-tight joint, as it becomes dis- 
 integrated under the vibration of the traffic. An impervious 
 joint can only be made by employing a filling made from 
 bituminous or asphaltic material; this renders the pavement 
 more impervious to moisture, makes it less noisy, and adds 
 considerably to its strength. 
 
 The bituminous materials employed are: 1. The tar pro- 
 duced in the manufacture of gas, which, when redistilled, is 
 called distillate, and is numbered according to its density; this 
 material, under the name of paving-pitchj is extensively used 
 both alone and in combination with other bituminous sub- 
 stances; 2. Combinations of gas- or coal-tar with refined 
 asphaltum; 3. Mixtures of refined asphaltum, creosote, and 
 coal-tar. 
 
 Stone blocks may be employed on all practicable grades, 
 but on grades exceeding ten per cent, cobblestones afford a 
 better foothold than blocks. If stone blocks are used, they 
 
320 
 
 THE ART OF ROADMAKING 
 
 Fig. 177. — Filling in Stone-block Pavement with Asphalt Bitose Filler. 
 
STONE BLOCK PAVEMENTS 
 
 321 
 
 must be laid, when the grade exceeds five per cent., with a 
 
 serrated surface, made by slightly tilting the blocks 
 
 on their bed so as to form a series of ledges or Pavements 
 
 steps against which the horses' feet being planted, grades. 
 
 a secure foothold is obtained. Another method 
 
 consists in placing between the rows of stones a course of 
 
 slate, or strips of creosoted wood, rather less than one inch 
 
 in thickness and about an inch less in depth than the 
 
 blocks; or the blocks may be spaced about one inch apart, 
 
 and the joints filled with a grout composed of gravel and 
 
 cement. 
 
 The average life or durability of granite blocks under heavy 
 
 Fig. 178. — Arrangement of Stone Blocks on Steep Incline. 
 
 traffic may be taken at fifteen years; but since the nature of 
 the traffic, the state of cleanliness and other con- 
 ditions must be taken into account when inquiring Durability 
 into the durability, it follows that in no two streets blocS"^ ^ 
 is the endurance and the cost the same, and the 
 difference between the highest and the lowest period of en- 
 durance and amount of cost is very considerable. The practice 
 followed in European cities is to remove the worn blocks, 
 re-dress them and re-lay them in other and secondary thorough- 
 fares. Thus the duration of life of the blocks may be doubled, 
 or more than doubled. In fact, with the exception of the 
 portion worn off by the friction of the traffic, not a fragment 
 of granite paving may be said to be lost. After passing its 
 first years in a leading thoroughfare it goes into a secondary 
 thoroughfare until completely worn down and rounded, and 
 
322 THE ART OF ROADMAKING 
 
 not even a fragment that is knocked off the component stones 
 when undergoing the operation of being dressed into shape 
 is lost^ as it is made available either for macadamizing or for 
 concrete to form the foundation of other pavements. Granite 
 can only be said to be worn out when it has been broken up 
 for macadamizing and then crushed into powder by the 
 vehicles. 
 
 Stones from different quarries and even from the same quarry 
 will show considerable variation in the amount worn away 
 in a given time under exactly similar conditions. Therefore 
 no statement of wear can be given which will be applicable 
 to all varieties of stone. 
 
CHAPTER XV 
 BRICK PAVEMENTS 
 
 Brick pavements consist of bricks laid on edge on a 
 suitable foundation of concrete, gravel; sand, or wood. Al- 
 though brick is one of the oldest materials used for paving, 
 its first use for this purpose in the United States was in 
 Charleston, W. Va., about 1870. Since then the use of brick 
 as a paving material has steadily increased, and in localities 
 with moderate traffic it has given satisfaction. 
 
 The advantages of brick pavements are: 
 
 1. Ease of traction. 
 
 2. Good foothold for horses. 
 
 3. Not disagreeably noisy. Advantages 
 
 and detects. 
 
 4. Yields but little dust and mud. 
 
 5. Adapted to all grades. 
 
 6. Easily repaired. 
 
 7. Easily cleaned. 
 
 8. But slightly absorbent. 
 
 9. Pleasing to the eye. 
 
 10. Expeditiously laid. 
 
 11. Durable under moderate traffic. 
 
 In many localities brick is superior to wood or broken stone, 
 and in cities and towns will often be found superior to stone 
 blocks. 
 
 The principal defects of brick pavements arise from (1) lack 
 of uniformity in the quality of the bricks, and (2) the lia- 
 bility of incorporating in the pavement bricks of too soft or 
 porous structure, which crumble under the action of traffic or 
 frost. 
 
 The employment of unsuitable brick may be Quality 
 fostered by a desire to help a local industry °^ ^'^^^^ 
 without due regard to the quality of the local clays for 
 
 323 
 
324 
 
 THE ART OF ROADMAKING 
 
 the manufacture of good paving brick. A paving brick is 
 simply a brick which, through careful selection of material 
 and through skillful manufacture, is so hard and tough that 
 it will resist the crushing and abrading action of the 
 traffic. 
 
 The quahties essential to a good paving brick are the same 
 as for any other paving material, viz.: hardness, toughness, 
 and ability to resist the disintegrating effects of water and 
 frost. These qualities are not obtained by ''vitrifying" the 
 bricks, as is commonly supposed. Vitrification is the process 
 
 Fi.;. 170. 
 
 Brick Puver's 
 
 HummiT. 
 
 Fig. 180. — Brick Pavement laid on Sand. 
 
 of converting into glass by fusion or the action of heat, and adds 
 nothing to the strength, but really defeats the object for which 
 the bricks are made. The required qualities are imparted to 
 the brick by a process of annealing, by which the bricks are 
 burned to the point of fusion, then the heat gradually reduced 
 until the kiln is cold. This process produces a brick of uniform 
 texture, thoroughly compact, hard and tough, but if the cooling 
 off is done quickly, it will produce a brittle brick that will 
 speedily go to pieces under traffic. 
 
 There are three distinct classes of clays employed in the 
 manufacture of paving brick — surface clays, impure fire clays, 
 
BRICK PAVEMENTS 325 
 
 and shales. Surface clays are almost exclusively used for 
 the manufacture of building bricks, but are not 
 ordinarily suitable for making paving bricks, since it ^^^ 
 
 is practically impossible to burn them hard enough 
 without their losing their shape. Pure fire clay is also unsuit- 
 able for paving brick on account of its infusibility, but impure 
 fire clay makes a fair quality of paving brick, although the proc- 
 ess is expensive. Most paving bricks are made from shale, 
 an impure, hard, laminated clay which has been subjected to 
 great earth pressure, and which is widely distributed. 
 
 In determining the value of a brick clay the following 
 physical properties are important factors: 
 
 1. Plasticity. 
 
 2. Amount of water required to make a plastic mass. 
 
 3. Amount of shrinkage, both in burning and in drying. 
 
 4. Rapidity of drying and of burning. 
 
 5. Temperature of incipient and complete fusion. 
 
 6. Density before and after burning. 
 
 7. Strength of the burned brick. 
 
 The production of paving brick in 1894 was restricted within 
 narroTv limits in Pennsylvania, Ohio, Indiana, and Illinois on 
 the west, which produced the special quality of 
 material required for this purpose, differing entirely egion of 
 from that used in ordinary building bricks. 
 
 There are now a number of places outside these limits where 
 paving bricks are produced in large quantities, one of the large 
 plants being on the Hudson river at Catskill, from which have 
 been furnished bricks for pavements in many cities and towns 
 in the eastern and the southern states. 
 
 In the manufacture of the brick, the soft, Manufacture 
 homogeneous clay is run through rollers, to crush ^^^..^j^g^'^^ 
 the lumps; it is then mixed with water and worked 
 into a plastic mass, which then goes to the brick machine. 
 Hard clay and shales are usually reduced to a powder, w^hich 
 is screened and then mixed with water. The more thoroughly 
 the clay is worked, or tempered, the more uniform and better 
 will be the brick. 
 
 Paving bricks are usually made by the " stiff mud " process, 
 
326 THE ART OF ROADMAKING 
 
 the molding being done by an auger machine which forces the 
 tempered clay or stiff mud through a die. This gives a con- 
 tinuous bar of compressed clay which passes under an auto- 
 matic machine that cuts the bar into bricks of the desired 
 size. These bricks are re-pressed to make them more 
 symmetrical in form and of better appearance, and are then 
 placed on trucks and conveyed to the dry-house. Thorough 
 drying facilitates the burning of the brick. 
 
 The process of burning is the most critical in the manufac- 
 ture of paving bricks. They are usually burned in down- 
 draft brick-ovens having fire pockets, or furnaces, built in 
 their outer walls. The bottoms of the kilns are perforated 
 to allow the gases to pass through the flues, which are be- 
 neath the floor, and which lead to the chimney. The fire 
 passes up from the furnaces into the kilns, then down through 
 the bricks to be burned to the fines, and thence to the chimney. 
 At first the heat is applied slowly to drive off the water without 
 cracking the bricks; this low heat is continued until the 
 smoke passing off shows no further signs of steam, after which 
 the fires are gradually increased until the temperature through- 
 out the kiln is sufficient to fuse the bricks. This tempera- 
 ture is for shales, from 1500° to 2000° F., and for impure 
 fire-clays from 1800° to 2300° F. From seven to ten days 
 are required to raise the entire kiln to this temperature. 
 
 After the burning process is completed, the kiln is tightly 
 closed and allowed to cool slowly, rendering them very tough. 
 This process requires several days; it is often completed in 
 three to five days, when seven to ten days would materially 
 improve the product and usually would be worth the extra 
 cost. Slow cooling is the secret of toughness, and the slower 
 the cooling the tougher the brick. 
 
 Bricks have passed through much the same process that 
 stone and wood blocks have passed through in being stand- 
 ardized as to size and shape. Experience has shown that 
 with the proper foundation neither odd shapes, grooves, lugs, 
 nor other devices are necessary, and that the most economical 
 and desirable size for paving bricks is that of the standard 
 building brick. Bricks of this size can be made more cheaply. 
 
BRICK PAVEMENTS 327 
 
 burned more uniformly, and those which are unsuitable for 
 paving can be utilized for building purposes, which 
 would be impracticable with odd shapes. The im- ^*^® ^^^ 
 perfect ones of odd or peculiar shape are so much bricks 
 waste material, and the cost of their manufac- 
 ture must be added to the price of the good ones in order 
 to protect the manufacturer from loss. Moreover, with 
 irregular sizes and odd shapes it would be necessary for the 
 towns employing brick pavements to keep a large stock of 
 the different bricks on hand to make repairs, which would be 
 expensive and troublesome. 
 The sizes in common use are: 
 
 1. The "paving brick," measuring 8^^ x 2^ x 4 inches, weigh- 
 
 ing about 7 pounds and requiring 58 to the square 
 yard. 
 
 2. The '^paving block,'' measuring 3x4x9 inches, weigh- 
 
 ing about 9J pounds and requiring 45 to the square 
 yard. 
 
 Both bricks and blocks are made with either flat sides and 
 square edges or flat sides and rounded edges, some users 
 claiming that the rounded edge wears better than the square 
 edge. A variation from the flat sides is made by grooves and 
 projections formed during the re-pressing, the object of which 
 is to facilitate the introduction of the joint filling and to in- 
 crease its holding power. The grooves are formed either by 
 having the name of the maker in sunken letters or one or more 
 horizontal grooves on sides and ends. Some makers form 
 both horizontal and vertical grooves; horizontal grooves are 
 by some considered objectionable, for the reason that the 
 brick is liable to spall or fracture down to the groove. The 
 projections are formed by having the name of the maker in 
 raised letters or by either round or square buttons. The 
 depth of the grooves and height of the projections vary with 
 the maker from one-eighth to three-sixteenths inch. 
 
 The brick should be reasonably perfect in shape, free from 
 marked warping or distortion, and uniform in size, so as to 
 fit closely together and make a smooth pavem_ent. 
 
 In the matter of testing, it is always important to have 
 
328 
 
 THE ART OF ROADMAKING 
 
 a definite method of testing the qualities of any artificial 
 material, since then all parties may know exactly 
 bricksf *^^ grade called for, and since the results obtained 
 by different observers with different materials may 
 be compared. This is particularly true of brick, as the clays 
 differ greatly in quality and also as a slight variation in each 
 step of the manufacture materially affects the result. The 
 
 Fig. 181. — Grooved Paving Blocks. 
 
 object of testing paving brick is (1) to determine whether 
 the material is suitable for use in a pavement, and (2) to 
 enable comparisons to be made between different classes of 
 brick. The various methods of inspecting and testing paving 
 brick, together with the objects to be attained by these methods, 
 are treated fully and in detail in Baker's " Roads and Pave- 
 ments." 
 
 In the construction of brick, as of other pavements, the 
 foundation must first be considered. Each brick should have 
 an adequate support from below, as otherwise the loaded 
 wheels will force it downward and make the surface uneven. 
 Various materials may be used, but experience has shown 
 that the best foundation is a bed of concrete. On this a 
 layer of sand is spread to secure a uniform bearing for the 
 
BRICK PAVEMENTS 329 
 
 bricks. The sand used for this cushion layer should be 
 clean^ moderately coarse and free from loam and construc- 
 vegetable matter, and from pebbles of any size tion of 
 that will cause the bricks to set unevenly. pavement 
 
 The bricks should be laid on edge, as closely and compactly 
 as possible, in straight courses across the street, with the 
 length of the bricks at right angles to the axis of 
 the street. At street intersections and junctions Manner 
 the bricks should be laid diagonally — a compro- bricks. 
 mise position between the directions of the travel 
 on the two streets. Street intersections need special care in 
 construction, since they are exposed to the traffic of two streets. 
 To provide for the expansion of the pavement, both longi- 
 tudinal and transverse expansion-joints are used; the first 
 are formed by placing a board templet seven-eighths of an 
 inch thick against the curb and abutting the brick thereto. 
 The transverse joints are formed at intervals varying between 
 25 and 50 feet, by placing a templet or building-lath three- 
 eighths of an inch thick between two or three rows of brick. 
 After the bricks are rammed and ready for grouting, these 
 templets are removed, and the spaces so left are filled with 
 coal-tar pitch or asphaltic paving-cement. After 25 or 30 
 feet of the pavement is laid, every part of it should be rammed 
 with a heavy rammer, a plank being laid on the surface parallel 
 to the curb to receive the blows of the rammer, or a steam- 
 roller weighing not to exceed 5 tons may be used. After the 
 ramming Portland-cement grout should be poured into the 
 joints until it appears on the surface, then the whole surface 
 should be covered with a layer of dry sand one-half inch deep. 
 
 The character of the material used in filling the joints be- 
 tween the brick has considerable influence on the success and 
 durability of the pavement. Various materials have been 
 used, as sand, coal-tar pitch, asphalt, mixtures of coal-tar 
 and asphalt, Portland cement, and various patented fillers, 
 and there is much difference of opinion as to which gives the 
 best results. The office of a "filler'' is to prevent water from 
 reaching the foundation, and to protect the edges of the brick 
 from spalling under traffic. In order to meet both of these 
 
330 
 
 THE ART OF ROADMAKING 
 
 Fig. 182. — Herring-bone Pattern. 
 
 Fig. 183. — Double Diagonal Pattern. 
 
 Brick Paving at Street Intersection. 
 
BRICK PAVEMENTS 331 
 
 requirements every joint must be filled to the top and remain 
 so, M'earing down with the brick. Sand does not meet these 
 requirements, as it soon washes out and leaves the edges of 
 the brick unprotected and consequently much more liable to 
 be chipped. Coal-tar and the mixtures of coal-tar and asphalt 
 have an advantage in rendering the pavement less noisy and 
 in cementing together any breaks that may occur by upheavals 
 from frost or other causes; but unless made very hard they 
 have the disadvantage of becoming soft in hot weather and 
 flowing to the gutters and low places in the pavement, there 
 forming a black and unsightly scale and leaving the high 
 parts unprotected. The joints thus deprived of their filling 
 become the receptacles of water, mud, and ice in turn, and the 
 edges of the brick are quickly broken down. 
 
 The best results seem to be obtained by using a high grade 
 of Portland cement containing the smallest amount of lime 
 in its composition. 
 
 Brick has been used for upwards of a hundred years in the 
 Netherlands, and pavements laid half a century ago are still 
 in good condition. There are several brick pave- 
 ments in the United States from ten to eighteen Durability, 
 years old which are still in good condition. The 
 general experience with pavements formed of suitable brick, 
 laid on an unyielding foundation, with the joints properly 
 filled, is that they furnish a smooth and durable surface, well 
 adapted to moderate traffic. Failures of the earlier pave- 
 ments were caused by defective foundations, and the use of 
 ordinary building bricks of the locality. 
 
 The durability of the bricks seems to depend on: 1. The 
 clay from which they are made being practically free from 
 lime; 2. The thorough grinding and mixing of the clay, so 
 as to have no lumps in the bricks; 3. The bricks being thor- 
 oughly annealed. 
 
 The amount of maintenance required by a brick pavement 
 depends upon the quality of the brick and the character of 
 the foundation. With good bricks and concrete foundation 
 the amount will be small, with a weak foundation and inferior 
 bricks it will be large. 
 
332 
 
 THE ART OF ROADMAKING 
 
 Me 'S^was t%ZjZr £i 
 
 
 Fig. 184. — Brick at Entrance to Union Station, laid in 1893. (Stone-block 
 pavement in foreground.) 
 
 Fig. 185. — Alley Paved with Brick in 1894. Brick Pavements, St. Louis, 
 
 1901. 
 
 (From Judson's '''City Roads and Pavements.") 
 
BRICK PAVEMENTS 
 
 333 
 
 The successful use of vitrified brick for the paving of streets 
 brought about much discussion of its adaptability 3j.jj,j^ j^j. 
 to country roads in sections where good stone for country 
 macadam is not really obtainable, and it has been roads. 
 
 Fig. 186. — Cross-section of Country Road with Earth Side Road. 
 
 used for this purpose in various parts of the country with 
 success. 
 
 In making a brick country road in Ohio * the foundation 
 material consisted of broken vitrified sewer pipe, broken to 
 
 Fig. 187.— Brick Country Road. 
 
 pass through a 2i-inch ring, with sufficient finer material to fill 
 voids after rolling and to prevent the sand cushion from passing 
 downward. Upon the foundation, and between the curbing, 
 a layer of clean sand was placed, and on this the brick paving 
 
 * Engineering \ews, Sept. 25, 1902. 
 
334 
 
 THE AKT OF ROADMAKING 
 
 was laid. This was laid on edge at right angles to the center 
 line of paving, and kept in even straight lines. 
 
 The brick was covered with fine dry sand, well broomed 
 
 i \ \\4 Brick 
 
 30- 
 
 Sand 
 
 ■>\*ZZ^-'- 5-->\ 
 
 6rave! ^^ li ! 1 
 
 Vf^^l^7sn^-(?7r^Yp^?7rg'«r'W(S^^^^^^ HoiiowVit Block . 
 
 30 'Street Section Curb and Drain 
 
 4\ 
 
 — ■>l^-|<---4 -->\ 
 
 4 Brick., i |-<i- 
 
 ^ Hollow //f. ~ ^■^'■'''''''■''■"'■"-^■■'"^"^F^IT?^^^ 
 
 Block Curb '-\=' " '"^ '"'■'■ "' ' 
 
 vnd Drain Allegheny County Road Section 
 
 Fig. 188. — Brick-paved Street and Highway with Vitrified Clay Curbing. 
 
 in, sufficient only to fill the interstices or joints. The surface 
 was then rolled and evenly covered with \ inch of clean dry 
 sand. 
 
CHAPTER XVI 
 WOOD BLOCK PAVEMENTS 
 
 For more than seventy years, wood has been used for 
 street paving, with little success, however, at the beginning, 
 owing to incomplete knowledge of the materials and wrong 
 methods in their use. It is only within the last decade that 
 wooden pavements have been laid with any great degree of 
 success. Wood has many qualities which especially adapt 
 it for paving, and, with a better knowledge of the fitness of 
 woods other than those now used, and of the effect of pre- 
 servatives upon durability, it is almost certain that its use 
 for this purpose will steadily increase. 
 
 For many years, longleaf pine was practically the only 
 wood used for creosoted block pavements in the United 
 States, the only important exception being in Minneapolis, 
 where Norway pine and tamarack were laid in 1902 and 
 have proved successful. Longleaf pine has advanced in 
 price so rapidly as to make its use for paving very costly, 
 and as the United States has a large variety of commercial 
 woods, the Forest Service undertook a study of the subject, 
 with the object of finding some woods cheaper and more 
 abundant than longleaf pine, which would prove suitable for 
 pavements. 
 
 The first use of wood for paving is said to have been in 
 
 Russia, where rude blocks were laid several centuries ago. 
 
 Wood was introduced into New York City in 1835-36 
 
 and in London in 1839. Continental Europe Progress of 
 
 was slower to take it up. Many forms of wood 
 
 ^ ^ -' paving. 
 
 pavements have been built, but the only form 
 now in actual construction is that of chemically treated 
 blocks. The corduroy roads of a century ago are now past 
 history although there can yet be found, crossing swamps 
 
 335 
 
336 THE ART OF ROADMAKING 
 
 on the line of the old military road built in 1812 across the 
 Adirondack wilderness, from the Mohawk valley at Schenec- 
 tady to Ogdensburg on the St. Lawrence, and to Sackett's 
 Harbor on Lake Ontario, sections of corduroy road, which 
 are still as sound as when laid, having been preserved from 
 decay by the water which has usually covered them, although 
 huge forest trees have meantime grown up in the old and 
 abandoned roadway near at hand.* 
 
 The plank roads of a century ago are nearly gone, with 
 the toll-gates which were the objects of their beginning and 
 the cause of their ending; though it is of interest that there 
 are still two plank roads leading from the, westward into the 
 city of Albany, N. Y., having five toll-gates on ten miles of 
 road; but these relics of old days are of only historic interest, 
 as are the majority of the many patented and forgotten forms 
 of wood pavements which had their rise and fall thirty to 
 forty years ago. 
 
 At that time, the chief consideration seems to have bee;i 
 the form of block. The large and unequal interstices between 
 the round blocks then commonly used permitted the edges 
 to wear off rapidly into a corduroy condition which was 
 uncomfortable to the traveler, and which hindered both 
 drainage and cleaning, thus making the pavement unsanitary 
 and hastening its decay. It was to remedy this that many 
 different forms of blocks were devised during the period 
 between 1840 and 1870, of which perhaps the most con- 
 spicuous was the ''Nicholson," patented in 1S4S and laid 
 extensively in the ten years following the civil war. This 
 block was rectangular, which gave equal interstices; but 
 this by no means solved the problem, and results were no 
 better than before. Little thought was given to the kind of 
 wood used, and as soft a wood as white pine was frequently 
 laid. The blocks were neither seasoned nor treated with 
 chemical preservatives, and quickly decayed. Wide joints 
 permitted water to get under the pavement, where it was 
 absorbed by the blocks, with the result that they swelled, 
 
 * "City Roads and Pavements," by William Pierson Judson. 
 
WOOD BLOCK PA YEMENIS 337 
 
 SO that the pavement often heaved from its foundation. 
 Finally, the foundation was usually of untreated planks, 
 laid directly upon earth, so that they soon decayed, while 
 the pavement sank into ruts and holes. 
 
 Round blocks, mostly of white cedar, were extensively laid 
 in the Middle West, and with most success in Chicago. They 
 made neither a durable pavement nor in any way 
 a satisfactory one. But they were cheap and Woods 
 served a good purpose in tiding fast-growing paving 
 cities over a critical period. There have also 
 been laid in various cities pavements of oak, cypress, white 
 pine, hemlock, Washington red cedar, cottonwood, mesquite, 
 Osage orange, redwood, Douglas fir, and tamarack. In 
 nearly all these cases the blocks were untreated, or at most 
 dipped or boiled for a short time in tar, asphalt, or other 
 mixture of supposed preservative value, and they failed to 
 give satisfactory results. Untreated American red gum was 
 tried in England, and for a time raised great hopes, but it 
 finally proved unsatisfactory. 
 
 Some species of eucalyptus, especially jarrah and karri, 
 have been laid extensively in England.* In London these 
 woods have shown a life of from fifteen to twenty years, but 
 continued use has not entirely justified the hopes first enter- 
 tained for them. Their structure is too dense to permit 
 impregnation with chemical antiseptics, without which they 
 absorb water and swell. They wear much more slippery 
 than most native woods, and they are not immune from 
 decay, though because of certain antiseptic gum-resins which 
 they contain they are more so than any untreated native 
 
 * Jarrah {E. marginata) and Karri {E. diversicolor) are very dense 
 and hard woods, growing plentifiilly in Western Australia. Jarrah is 
 bright to dull red in color; short grained; free sphtting, breaking with 
 a clean fracture, and burns with a black ash. When seasoned, it has 
 a specific gravity of LOl and it absorbs about 10 per cent of moisture 
 when immersed forty-eight hours, as against the absorption by most 
 soft woods of 20 to 25 per cent. Karri is very similar in appearance to 
 jarrah but somewhat lighter in color, is interlocked in the grain and is 
 difficult to split; it splinters in breaking and burns with a white ash. 
 When seasoned, it has a specific gravity of L12, and absorbs about 
 7 per cent of water when immersed forty-eight hours. 
 
338 
 
 THE ART OF ROADMAKING 
 
 This machine cuts 240,000 blocks per day. The upper half of the machine has 
 been raised in order to show the circular saws and the planks of wood entering the 
 machine. 
 
 Fig. 189. — Machine for Cutting Wood Paving Blocks. 
 
WOOD BLOCK PAVEMENTS 
 
 339 
 
 woods. In England, however, they are still used. Jarrah 
 blocks were laid on Twentieth street, New York City, in 1895, 
 but were removed in 1904. The cost of this pavement was 
 about $5.00 per square yard, which would exclude these 
 woods from extensive use in America even should they make 
 a better pavement than our best creosoted native woods, 
 which is not likely. 
 
 After the failure of untreated native woods, attention w^as 
 turned to wood preservatives. For the treatment of wood 
 paving, the tendency has been to narrow down to the use of 
 
 Fig. 190. — Method of Cutting Planks from Logs. 
 
 one material, the dead oil of coal-tar, commonly called creosote, 
 either pure or in mixture with resin, pitch, or other materials. 
 Creosoted southern pine paving blocks are said to have been 
 laid in the United States at Galveston, Tex., as early as 1873. 
 This pavement, in spite of being laid on a foundation of sand, 
 gave satisfactory service for nearly thirty years, and was 
 destroyed only by the great flood of 1900. But this good 
 beginning was not at once followed up, and onl}^ within the 
 last ten years has the matter received systematic attention 
 in this country. 
 
 The success of the modern wood block pavement is due to 
 several things. The wood is carefully selected, both as to 
 
340 THE ART OF ROADMAKING 
 
 kind and quality; it is cut accurately into rectangular blocks, 
 is put through seasoning processes and is preserved 
 Qualities of from decay by chemical means. Its liability to 
 ^avement*'^ absorption of water and the consequent expansion 
 and contraction of the pavement are reduced 
 to a minimum. The blocks are then laid with the grain 
 vertical, over an accurately surfaced cushion on a solid 
 foundation of cement-concrete. They are close-jointed, and, 
 in the best practice, the joints are made water-proof. The 
 result is a pavement having the advantages of: 
 
 1. Comparatively good foothold for horses. 
 
 2. Smoothness and resiliency, offering less resistance to 
 
 traction than stone and slightly more than asphalt. 
 
 3. Suitability for all classes of traffic. 
 
 4. Adaptability to grades up to five per cent. 
 
 5. Even wear and moderate durability. 
 
 6. Cleanliness, yielding no mud and but little dust. 
 
 7. Moderate first cost. 
 
 8. Comparative noiselessness. 
 Its principal disadvantages are: 
 
 1. Slipperiness under certain weather conditions. 
 
 2. Difficulty in opening to gain access to underground 
 
 pipes, and the necessity of removing a rather large 
 surface for this purpose and of leaving it for some time 
 after being repaired before traffic can be resumed upon 
 it. 
 
 3. In spite of its many advantages it is claimed by many 
 
 to be unhealthy. 
 
 The opinions of engineers -of a number of American cities 
 as to the qualities of treated wood block in comparison with 
 other paving materials, obtained by the Forest Service of the 
 U. S. Department of Agriculture, have already been presented 
 in tabulated form on page 32.* 
 
 The cost of creosoted wood pavement in the United States 
 
 * In the course of this inquiry much information was obtained in 
 relation to creosoted wood block pavements, which has been published 
 under the title "Wood Paving in the United States," by C. L. Hill, Forest 
 Assistant, Circular 141, Forest Service, U. S. Department of Agriculture. 
 
WOOD BLOCK PAVEMENTS 341 
 
 has varied from $2.40 to $3.50 per superficial square yard laid. 
 As shown in Table IV (page 32), the average cost 
 per yard for all cities which reported was $3.10. 
 The basis of judgment upon a pavement should be the returns 
 upon its total cost for the life period, considered as an invest- 
 ment. In Europe this is done, but in the United States the 
 first cost is in most cases given undue weight. For a pave- 
 ment such as creosoted wood, the first cost of which is high, 
 this method is very unfair and reduces the pavement's total 
 standing much below its service value. Table IV takes into 
 account the factors of pavement value more systematically 
 than do other methods used in this country, but it does not 
 provide a basis of investment returns. A better way would be 
 to express the cost item in terms of total annual charge; this 
 would take into account the factor of durability, and would 
 remove it from separate listing in the table. The result 
 would be much more consistent and accurate. 
 
 Disregarding cost, and basing the comparison upon service 
 qualities only, the difference in favor of creosoted wood is 
 materially increased. Wood ranks very high in 
 every quality listed, except in freedom from 
 slipperiness and, to a less extent, in durability. It is highest 
 in those qualities which contribute to the acceptability of 
 the pavement. 
 
 There is in the United States almost no wood pavement 
 of the modern kind which has yet been down long enough to 
 show its durability. The values assigned by the 
 engineers to durability are, therefore, based prin- 
 cipally on general impressions and inference from European 
 experience. There are, however, a few cases in the United 
 States which offer pertinent evidence. 
 
 In Baltimore, Md., in the summer of 1901, there were laid 
 several adjacent strips of experimental pavements, including 
 sheet asphalt, creosoted wood, and several kinds of brick. 
 After five years' service, and after passing through the great 
 fire, the wood was in better condition than any of the others. 
 
 On Michigan avenue, Chicago, is a creosoted longleaf pine 
 pavement, laid in the year 1900. Adjoining it an area of 
 
342 THE ART OF KOADMAKING 
 
 asphalt block was laid at the same time. In 1905 the asphalt 
 blocks were removed and replaced with wood. In the five 
 years the asphalt had worn down on an average one inch, 
 but very unevenly, so that ruts had formed and the blocks 
 were badly rounded. The wooden blocks during this time 
 had worn off only one-eighth of an inch, and the surface, 
 except for a badly constructed gutter at one point, was still 
 perfectl}^ smooth and of even grade. 
 
 In 1902 the Metropolitan Street Railway Company, of 
 New York City, decided to experiment with creosoted wooden 
 blocks for paving between its tracks.- A small area of long- 
 leaf pine was laid on Hudson street, the wood being flanked 
 at either end by granite, the material hitherto used. At the 
 point selected there is a very heavy trucking traffic from 
 the North River wharves, and the stresses on the pavement, 
 where the trucks run with one wheel just outside the car 
 rail, are so great that the granite begins to show a rut in six 
 months, and is renewed almost annually. At the end of 
 four years the wood, though showing a heavy rut, was still 
 sound and in position and good for at least one more year. 
 The granite on either side had been renewed three times during 
 the four years. 
 
 These few examples can not of course be regarded as final 
 as there have been instances in which creosoted blocks have 
 given poor results, caused principally by improper preservative 
 treatment of the wood or faulty construction of the pavement. 
 The many cases of successful pavement indicate that such 
 errors are responsible for the failures which have occurred, 
 and that wood block pavement, properly prepared and laid, 
 should be credited with a durability greater than 14 in a 
 scale which rates asphalt blocks at 14 and whose standard 
 is granite at 20, as in Table IV. 
 
 Nor is this conclusion invalidated by the fact that European 
 wood pavements, as compared with granite, show a dura- 
 bility relatively less than this. American longleaf pine is 
 a harder, denser wood, and has greater resistance than the 
 European pine used for paving. While wood preservation 
 has in general, attained a greater perfection in Europe than 
 
WOOD BLOCK PAVEMENTS 343 
 
 in America, yet American creosote treatment of wood paving 
 blocks is more thorough than the European. 
 
 Resistance to traction and freedom from sHpperiness are 
 opposing qualities, so that gain in one is likely to be made 
 at the expense of the other. Table IV shows 
 creosoted wood and the asphalts equal in the ^^^^^ 
 matter of tractive resistance, while on the score of 
 freedom from slipperiness, wood is placed below both of 
 the others. This is hardly consistent, as recent experiments 
 indicate that in these respects American sheet asphalt varies 
 considerably with the temperature. In cold weather it js 
 exceedingly hard, smooth, and slippery, but in hot weather 
 its softening causes it to cling to the tires and increases its 
 tractive resistance to a point greatly beyond that of wood. 
 
 Of two neighboring cities in which the conditions affecting 
 the pavements are practically the same, the engineer of one 
 believes wood to be more slippery than asphalt, while the 
 engineer of the other believes asphalt to be more slippery 
 than wood. This is but an example of the difference of 
 opinion which exist on this point, due in large measure to 
 the variation in the asphalt under different conditions. In 
 both tractive resistance and slipperiness wood appears to be 
 more constant than sheet asphalt. In hot weather, therefore, 
 wood is likely to be more shppery than asphalt, while in cold 
 weather it is likely to be less slippery. Wood and asphalt 
 are both most slippery when slightly wet. Between different 
 kinds of wood there may also develop considerable difference 
 in slipperiness. Experience has shown that Norway pine 
 wears much less slippery than longleaf. 
 
 The maximum gradient recommended by the majority of 
 engineers for either pavement is from two to five per cent, 
 according to the conditions of climate and traffic. 
 
 The problems to be met in wood paving are (1) problems 
 
 peculiar to wood and wooden pavements, and (2) 
 
 problems of construction common to all pave- Quality of 
 
 ments. One of the drawbacks in the use of wood Tl°° „^^^„ 
 
 tor paving, 
 
 for paving has been a lack of knowledge of the 
 
 wood itself. For example, sapwood has always been thought 
 
344 THE ART OF ROADMAKING 
 
 to be both weaker and more subject to decay than heartwood. 
 It is rigidly excluded from most wood paving specifications, 
 and all-heart blocks demanded. The inclusion of sapwood 
 undoubtedly caused the untreated blocks of former years 
 to wear unevenl}' and to decay quickly. But the preservative 
 treatment now applied provides against this decay. Recent 
 tests show that under equal conditions of moisture content, 
 the sapwood of many species is as strong as the heartwood. 
 It is usually less strong because wood is rarely used under 
 conditions where the moisture content of the sapwood is as 
 low as that of the heartwood. Preservative treatment, with 
 proper previous seasoning, reduces the moisture content of 
 each to an approximately even minimum, and the heavy 
 charge of oil now customary in American wood paving treat- 
 ment prevents subsequent absorption of moisture, beyond 
 a small per cent. After five years' service, there is no dis- 
 cernable difference in wear between the heart and the sap 
 portions of unseparated Norway pine blocks laid in Minneapolis. 
 
 A wood pavement fails through wear and decay, and many 
 methods have been invented to prevent the decay and increase 
 the durability of the timber. Timber thus treated 
 Wood ^ is used for piles, railroad ties, and other purposes, 
 methods ^® ^^^^ ^^ ^^^ paving blocks. Experiments in the 
 preservative treatment of wood date back, as far as is 
 known, to 1657, when Glauber recommended treating wood 
 with tar. Since that time an almost endless list of substances 
 has been experimented with, but the methods that have 
 stood the test of time and are at present in use, consist of 
 injecting different kinds of antiseptics into the pores of the 
 wood. 
 
 The results to be obtained by preservative treatment for 
 wood paving, are: 
 
 1. Preservation from decay. 
 
 2. Mechanical filling of the pores, to prevent the absorption 
 
 of fluids, which further accomplishes: 
 
 a. Elimination of expansion, 
 
 b. Increase of resistance to wear, 
 
 c. Maintenance of sanitary value. 
 
WOOD BLOCK PAVEMENTS 345 
 
 The methods of treatment best known are those called: 
 
 "Kyanizing/' using a corrosive sublimate, 
 
 ''Burnettizing/' using a solution of chloride of zinc, 
 
 "Boucherizing/' using sulphate of copper, 
 
 "Creosoting/' using creosote oil, which is the method most 
 used in the United States. 
 
 Creosote oil seems to meet the requirements better than 
 any other preservative commonly used. The other pre- 
 servatives are mostly water solutions, which are easily leached 
 out of the wood and thus lose their preservative effect. More- 
 over, being themselves largely composed of water, they do 
 not prevent expansion in the blocks, do not increase their 
 resistance to wear, and do not maintain them in a sanitary 
 condition. 
 
 Creosoting has generally been supposed to weaken timber. 
 The results of experiments conducted b}^ the Forest Service 
 indicate, however, that the creosote itself does 
 not lessen the strength of timber, but that this 
 result in practice has been due chiefly to certain methods 
 used in the impregnation. 
 
 The Rush Street bridge in Chicago, 111., is said to carry 
 a traffic as heavy as any in the city. It has tAvo 20-foot road- 
 way's, which were paved in 1899, one with creosoted longleaf 
 pine blocks, the other with uncreosoted blocks. The creosoted 
 pavement, after a service of seven years, was still in good 
 condition and was expected b}^ the chief engineer to last 
 several years more, while the uncreosoted pavement had to 
 be renewed in 1902. 
 
 The explanation of these facts lies in the antiseptic qualities 
 of the creosote and its physical action in filling the pores of 
 the wood and decreasing its absorption of water. Every 
 pavement is wet a large part of the time, and wood, when 
 saturated with water, has generally less than 40 per cent of 
 its kiln-dr}^ strength. The creosoting treatment, by lessening 
 the absorption of water, maintains the strength at much 
 nearer the dry-wood value, and thereby increases the actual 
 service strength. 
 
 This action is most effective only when the wood is well 
 
346 THE ART OF ROADMAKING 
 
 seasoned before being creosoted. In the United States most 
 creosoters attempt to dry the wood by applying steam and 
 vacuum. Recent experiments have shown that wood will, 
 except when very green, weigh more after such treatment 
 than before. That is, by this process, it will take up moisture 
 rather than lose it, which would destroy any possible gain in 
 strength through the creosote treatment. Not only is the 
 steaming in most cases valueless, but if carried too far, as it 
 often is, it seriously injures the wood. Natural, seasoning, 
 which in Europe is used almost entirely, would certainly 
 contribute to increased excellence of results in the United 
 States. 
 
 The common opinion among engineers in regard to the 
 creosoting of wooden pavements is expressed by a prominent 
 paving engineer, who says: 
 
 "For wood paving creosoting is only of contingent value. 
 If the traffic is heavy enough to wear out the pavement before 
 it decays, which it will do on most city streets, it is a waste 
 of time and money to creosote the blocks. Creosoting is only 
 economically desirable, therefore, when the traffic is so light 
 that decay will reduce the block before it fails from wear." 
 
 This would be true if creosoting treatment had no effect 
 on wood pavements other than the preservation of the wood 
 from decay. But creosoting effects, through the increased 
 service strength of the blocks, an additional and quite different 
 gain. It is believed that there is already enough evidence, 
 such as that offered by the Rush Street Bridge, to overthrow 
 the traditional doctrine of the limited value of creosote pre- 
 servative treatment for wood paving. 
 
 Creosote is an oil of tar from which the ammonia has been 
 expelled. Its effect on the wood is to coagulate the albumen 
 and thereby to prevent its decomposition, and also to fill 
 the pores of the wood with a bituminous substance which 
 excludes both air and moisture, and which is obnoxious to 
 the lower forms of animal and vegetable life. 
 
 In the United States, the timber for paving purposes is im- 
 pregnated by the vacuum-pressure method. Closed cylinders, 
 usually about six feet in diameter by about 100 feet in 
 
WOOD BLOCK PAVEMENTS 347 
 
 length, are used. The amount of oil usually injected into the 
 wood is sixteen pounds per cubic foot, though in 
 some eases it reaches twenty-two pounds. To many Impregna- 
 engineers this has seemed an unusually large amount, timber. 
 constituting an item of expense in the already 
 high cost of wood paving which might profitably be reduced. 
 But the necessity for the prevention of moisture absorption 
 under conditions more exacting than those in which almost 
 any other creosoted wood product is subjected, makes imper- 
 ative the impregnation of wood paving blocks with an amount 
 of oil per cubic foot greater than that ordinarily given to 
 railroad ties or construction timbers. The tendency is toward 
 heavier charges than the reverse, to secure for wood pave- 
 ment a service so greatly enhanced as to yield better returns 
 upon the investment, even at the higher cost. 
 
 In Paris the blocks are usually impregnated by merely 
 soaking for a short period in an open tank, and the amount 
 of oil injected per cubic foot is small. The life of Paris pave- 
 ment so treated is from six to fourteen years only, according 
 to the traffic; and, because of the small impregnation, expan- 
 sion in the pavements is large and calls for the laying of 
 longitudinal courses of blocks at the curbs, which are removed 
 as it becomes necessary. The vacuum-pressure method for 
 the treatment of wood paving blocks, is of comparative recent 
 introduction. This is the reason for the statement that 
 American creosote treatment of wood paving is superior to 
 that of Europe. The excellence of European wood pavements, 
 despite this defect, is largely due to better construction, 
 maintenance and repair. 
 
 The creosote as ordinarily used is an effective preservative 
 in itself, but it tends to form an emulsion with water, and is 
 in time washed out by rains, and it also tends to evaporate 
 half to three-fourths on exposure to the sun and the weather. 
 To avoid these defects has been the object of two recent 
 modifications of the treatment; one called the "kreodone- 
 creosote,'' and the other the "creo-resinate'^ process. 
 
 This consists in impregnating the seasoned selected blocks 
 Under pressure with ten pounds per cubic foot of an oil derived 
 
348 
 
 THE AKT OF ROADMAKING 
 
 from creosote oil, possessing the original preservative proper 
 ties with a longer endurance, and also having the 
 
 Krcodone- effect of forming a varnish-like film or coating 
 
 «rr.<^oec on the outer surface of the wood, protectmg it 
 
 from the elements. The seasoned blocks are 
 
 sterilized by subjecting them to dry heat of 240° Fahr., for 
 
 Tea- ton roller. 
 
 Coaipletod paTemtoC. 
 
 Fig. 191. — Kreodone-Creosote Wood-block Pavement, Meridian Street, 
 Indianapolis, in Progress of Construction. 
 
 {From Judson's " City Roads and Pavements ") 
 
 eight hours. The kreodone-oil is then forced into the fibers 
 of the wood, under a pressure of seventy pounds per square 
 inch maintained for two or three hours, or until twelve pounds 
 have been absorbed by each cubit foot of the wood. 
 
 The special features of this process are the preliminary 
 treatment in dry heat to kill the germs of decay, and the 
 
WOOD BLOCK PAVEMENTS 349 
 
 mixing with the creosote of 50 per cent of melted rosin which 
 is forced into the fibers with the creosote, where it 
 soHdifies and seals the pores of the wood and pre- Creo- 
 vents the evaporation of the creosote or its displace- process 
 ment by water, which can find no entrance, so that 
 the pavement does not swell and heave when wet. 
 
 It is claimed that this process increases the density of the 
 wood and also its resistance to impact and abrasion over 
 either untreated or creosoted wood. It is further claimed 
 that the more porous blocks take up more of the creo-resinate 
 mixture than the denser ones, and consequently increase 
 in density and strength to a greater degree, the process thus 
 making the blocks more uniform in quality. 
 
 For the most satisfactory service, wood-block pavement 
 requires a concrete foundation. This is usually made from 
 5 to 6 inches thick, although some engineers reduce 
 it to 4 inches on lightlv traveled residence streets. ^^^ ^**P^ 
 
 ° " . and cushion. 
 
 As a top cushion for the foundation either Portland 
 cement mortar or sand is used, the former being considered 
 the better. The bearing for the blocks is permanent, and, if 
 carefully surface-trued, can be made as even as desired; and 
 if the grout is mixed slightly damp and the blocks laid in 
 it immediately, it provides equally as good a compensation 
 for minor inequalities in the height of the blocks as sand does. 
 If tar can be used, a better method of accomplishing the same 
 object is to mix the grout in the usual way and let it thor- 
 oughly set, after which a coating of tar should be applied 
 and the blocks bedded in it. This is the method oftenest used 
 in Europe. Sand makes a satisfactory cushion where the 
 slope is negligible and the foundation is solid. It is some- 
 times preferred on the ground of greater elasticity and power 
 of accommodation, and it has the merit of being cheaper 
 than cement. On a gradient, however, if water, by any 
 possibility, gets under the blocks, it is likely to carry the sand 
 to the bottom of the slope and seriously derange the pave- 
 ment. On bridges, also, if there is much crown on the road- 
 way, the vibration of the structure is likely to shift the sand 
 from the center of the crown tov/ard the gutter. For bridges 
 
350 
 
 THE ART OF ROADMAKING 
 
 PL, 
 
 CQ 
 
 CD C3 
 
 > 
 
 O 
 O 
 
 o 
 
 
WOOD BLOCK PAVEMENTS 351 
 
 the usual practice is to lay the blocks directly on carefully 
 creosotcd planking. 
 
 The blocks should be r43ctangular, 3 inches wide, 4 to 6 
 inches deep and 9 inches long. They should be cut from 
 sound timber, free from sap wood, and should be 
 rigidly inspected, especially as to imperfections 
 of sawing, as to knot-holes, decay, or defective corners or 
 edges, as to squareness of the angles, and as to thoroughness 
 of impregnation. Voids due to imperfections in any of these 
 respects often can not be properly filled by the joint filler, 
 and are very detrimental to the pavement. In European 
 practice no variation greater than one-sixteenth inch in any 
 dimension of the blocks, and no measurable variation in the 
 depth, are allowed. There the blocks are also required to 
 be kept carefully protected from sun and weather after 
 treatment and until they are laid. Deterioration from 
 checking, which in America, is often considerable, is thus 
 prevented. 
 
 Exclusion of second growth material from wood-paving 
 specifications is immaterial, except in so far as young trees 
 contain a greater proportion of sapwood than older trees; 
 and, since sapwood is separately provided for in most cases, 
 the specification prohibiting second-growth timber could 
 well be abandoned, Sapwood is entirely excluded by most 
 woocl-paving specifications. Under existing market condi- 
 tions, however, it is quite impossible to obtain strictly all- 
 heart southern pine such as the specifications demand. The 
 true longleaf pine * has usually so narrow a sapwood that it 
 could be neglected without danger to the life of the pavement. 
 In loblolly pine the sapwood is often very wide; Ijut this 
 is one of the species for which it has been proved that the 
 
 * The terms "longleaf" and "shortleaf" pine are descriptive of 
 qualities of Southern yellow pine, rather than of botanical species. Thus, 
 "shortleaf pine" would cover such species as are now known as North 
 Carolina pine, loblolly pine and shortleaf pine "Longleaf pine" is 
 descriptive of quality, and if Cuban, shortleaf, or loblolly pine is grown 
 under such conditions that it produces a large percentage of hard summer 
 wood, so as to be equivalent to the wood produced by the true longleaf, 
 it would be covered by the term "Longleaf Pine." 
 
352 
 
 THE ART OF ROADMAKING 
 
 sapwood under equal conditions of moisture content is as 
 strong as the heartwood. Therefore, when effective season- 
 ing of paving material can be assured before the creosote 
 treatment, the prohibition of sapwood in southern pine 
 material is needless, and might well be omitted from specifica- 
 tions. 
 
 A more pertinent specification would be one excluding 
 fast-grown timber in pine paving-block stock — say all showing 
 less than eight rings to the inch — since it is the porous wood 
 resulting from fast growth, rather than the presence of sap- 
 wood, which unfits timber for this use. 
 
 The angle at which the courses are laid in wood pavement 
 is a matter of some importance. The most obvious angle 
 
 Curb 
 
 -JOINT 
 
 f-LONfilTUDINAL 
 C0U«*5C 
 
 '■ JOINT 
 
 LONQITUCIInAI. 
 COUBSC 
 
 eooy couR3£^ 
 
 Fig. 193. — Different Angles used in Laying Pavement. 
 
 is that of 90° with the curb, which takes the courses straight 
 across the street. Probably the greater part of the "wood- 
 block pavement in the United States is so laid. 
 
 ^^^ ^ But this angle permits the calks of horses' shoes to 
 courses. .... 
 
 strike m a direct Ime with the joints, and subjects 
 the pavement to a wear and tear which may largely be 
 avoided by laying the courses at an oblique angle. Moreover, 
 if expansion occurs, transverse as well as lateral expansion 
 j oints are necessary to provide against it, and transverse 
 joints of this character in wood pavement are always un- 
 desirable. With the courses laid at an oblique angle, the 
 thrust of the pavement in case of expansion will impinge in 
 both directions upon the curb, and the transverse expansion 
 joint may be entirely dispensed with. 
 
 The oblique angle which most naturally suggested itself 
 
WOOD BLOCK PAVEMENTS 353 
 
 was 45°, and a large amount of pavement has been so laid. 
 There has, however, developed an objection to this angle. 
 Transverse expansion in wood takes place in two directions, 
 tangentially to the rings of annual growth, and radially to 
 them. Of these the transverse expansion is greater than the 
 radial. As will be seen from the accompanying diagram of 
 the common method of sawing lumber^ a majority of blocks 
 have their long axes in a plane tangent to the annual rings 
 of the wood, or at least nearer to that plane than to the radial. 
 Therefore the force due to tangential expansion will be 
 exerted chiefly in the direction of the courses in the pavement, 
 and the lesser or radial force will be exerted at right angles 
 to that direction. The angle of 45° does not compensate 
 the differential expansions in the wood, and in uncreosoted 
 or poorly creosoted pavements twisting strains have devel- 
 oped. 
 
 The angle between 45 and 90° from the curb has therefore 
 been bisected by some engineers, making the angle with the 
 curb consequently 67-2-° This solution of the problem was 
 an entirely empirical one, but it seems to avoid the difficulties 
 experienced with the previous angle. 
 
 All untreated wood blocks absorb water and expand to 
 a considerable extent, and treated blocks expand appreciably. 
 Unless this expansion is provided for it is likely to 
 
 disturb the curbs or lift the blocks from their ?^Pf^sion 
 r. ^ ■ ■ ■ joints. 
 
 foundation. Transverse expansion joints are alto- 
 gether bad. The objection is the same as that against wide 
 body joints, that the filler wears away faster than the blocks, 
 leaving a depression which permits the edges of the blocks 
 to wear off and destroys the smoothness of the pavement. 
 Expansion joints should be longitudinal at the curb, with 
 a longitudinal course of blocks between the expansion joint 
 and the body of the pavement, and between each expansion 
 joint, if more than one is used. The most satisfactoi*}^ results 
 have been obtained by leaving the expansion joint open for 
 a few days, when it may be filled with sand, or if pitch is 
 used to fill the body joints, with sand up to within one-half 
 inch of the surface, and the remainder with pitch. 
 
35i 
 
 THE ART OF ROADMAKING 
 
 The customary width of this joint is from 1| to 2 inches on 
 each side of a 60-ft. roadway, though in some places 3 inches 
 is allowed, and this is filled up with either a hot mixture of 
 pitch and creosote oil, sand, or clay. 
 
 Considerable creosoted block pavement in the United 
 States has been laid without any expansion joints, and where 
 the creosoting of the blocks, as well as the laying of the 
 pavement, has been well done, little serious trouble has 
 been experienced; but it is safer to provide expansion 
 joints. 
 
 There is some uncertainty among engineers as to the best 
 joint filler for wood pavement. One prominent engineer 
 gives it as his opinion that if the traffic is heavy, so that 
 
 ''////^/r 
 
 y/^//. 
 
 //////MM/M. 
 
 ^^^ 
 
 Fig. 194. — Cross-section showing Joint Filling. 
 
 Filler. 
 
 the joints between the blocks will be speedily obliterated, 
 a sand joint may be used as well as any other, and 
 it is considerably cheaper than the others. But 
 if the traffic is not heavy enough to obliterate the joints, sand 
 permits the ingress of water, and gradually w^orks down and 
 leaves a space to be filled with debris, which lowers the sanitary 
 value of the pavement. Cement mortar as a filler is water- 
 proof at first, but it soon crumbles and becomes then no 
 better than sand. Besides, it is too inelastic and increases 
 the noise from the pavement. 
 
 Except under heavy traffic, therefore, some substance like 
 coal-tar pitch is preferable. But pitch has this disadvantage 
 — that a grade which will not crack under the cold of winter 
 is likely to become soft and sticky in the heat of summer: 
 
WOOD BLOCK PAVEMENTS 355 
 
 Care is necessary to select a quality which shall avoid these 
 difficulties. There are some proprietary preparations on 
 the market which offer specific advantages as fillers, since 
 their range of stability is greater than that of pitch, so that 
 they become neither brittle nor sticky, at least under natural 
 conditions in a temperate climate. To fill the joints effectively, 
 pitch should be heated to about 300° F. when applied, so as 
 to insure perfect fluidity. 
 
 The top dressing for wood pavement is usually of screened, 
 sharp sand or of finely crushed stone, about one-half inch in 
 thickness. This is allowed to remain on the pave- 
 ment about two weeks, or longer when convenient.- ,°P . 
 The top dressing benefits wood pavement in several 
 ways. A certain amount is ground into the surface of the blocks 
 and both increases their resistance to abrasion and reduces 
 slipperiness. If sand has been used for a joint filler the sur- 
 face sand keeps the joints filled as they settle, and if the joint 
 filler is pitch the sand takes up any surplus pitch from the 
 surface of the blocks and leaves the pavement cleaner than 
 it would without it. A subsequent occasional light sanding 
 is a distinct advantage to the pavement. 
 
 In the care of the pavement after it is laid American cities 
 fail more seriously, perhaps, than in any other particular. Once 
 laid, the pavement is often expected to take care of 
 itself without any further attention. This is often Repairs 
 due to causes beyond the control of the engineer; tenance 
 but the fact remains that such treatment may go 
 far to defeat the best manufacture and construction. In 
 Europe wood pavements are cleaned with regularity and care. 
 They are frequently flushed with water and are never allowed 
 to dry out, as they often do to an excessive degree in the 
 summer droughts in America. They are sanded at regular 
 periods, as well as on any occasions of special slipperiness. 
 Most American cities appear to consider that such maintenance 
 as is given in Europe is impossible here. A few, however, 
 do give adequate care to their pavements, and it is believed 
 that for many others greater attention in this direction would 
 be a paying investment rather than an expense. 
 
356 THE ART OF ROADMAKING 
 
 Practically the only repairs required aside from replacing 
 blocks taken up to get at water and gas pipes, etc., is to 
 remove soft or decayed blocks and to insert new ones. 
 The hole caused by a single decayed block is speedily 
 enlarged by the impact of wheels dropping into the depres- 
 sion. 
 
CHAPTER XVII 
 ASPHALT PAVEMENTS 
 
 Asphalt exists in various forms over widely distributed 
 parts of the earth, and has been in somewhat common use for 
 different purposes since the dawn of history; con- 
 sequently the terms employed to designate it t**^^^*^ 
 have been varied. The following definitions are gen- 
 erally accepted and are sufficiently exact for ordinary purposes: 
 
 "Bitumen is a natural hydrocarbon mixture of mineral 
 occurrence, widely diffused in a variety of forms which grade 
 by imperceptible degrees from a light gas to a solid, some- 
 times found in a pure state, but usually intermixed 
 with organic and inorganic matter. The bitumen 
 series includes the following, in order of their density: Natural 
 gas, natural naphtha, petroleum, naphtha (at ordinary tem- 
 peratures soft and sticky), asphalt (at ordinary temperatures 
 stiff and non-sticky), glance pitch (dry and brittle). 
 
 " Asphalt is a general name for the solid forms of the natural 
 mineral bitumen. Asphalt is distinguished from coal in 
 being soluble in bisulphide of carbon and in ben- 
 zole. Coal, peat, etc., are called pyro-bitumens 
 because they yield an artificial bitumen by distillation. 
 Asphalt is usually found associated with various mineral and 
 organic substances. Asphalt is sometimes popularly called 
 mineral pitch and mineral tar ; and different varieties of 
 asphalt are called grahamite, albertite, gilsonite, wurtzelite, 
 imitatite, turrellite, etc. 
 
 "The term ^ asphalt' is the English equivalent of ' asphaltum,^ 
 the Latin form. Asphalt and bitumen are frequently used 
 synonymously, but usually in paving literature bitumen is 
 employed to designate the valuable hydrocarbon compounds 
 in the native asphalt. 
 
 357 
 
358 THE ART OF ROADMAKING 
 
 " Crude asphalt is the native mixture of bitumen, sand, clay, 
 water, organic matter, etc. 
 
 ^'Refined asphalt is the native mixture after it has been 
 freed wholly or in part from water and organic and inorganic 
 matter by being heated. Commercial refined asphalt contains 
 considerable earthy matter ; in fact , commercial refining 
 consists virtually in driving off the water and volatile oils, 
 and incidentally in removing a little earthy matter, 
 
 "Rock asphalt is a limestone or sandstone naturally im- 
 pregnated with asphalt. Rock asphalt is the principal form 
 of asphalt used in Europe for paving purposes and is usually 
 there designated as * asphalt.' 
 
 " Asphaltic or bituminous limestone is a limestone naturally 
 impregnated with asphalt. 
 
 " Asphaltic or bituminous sandstone is a sandstone naturally 
 impregnated with asphalt. 
 
 "Compressed asphalt. In Europe, particularly in France, 
 a rock-asphalt pavement is frequently referred to as being 
 made of 'compressed asphalt.' 
 
 "Asphalt mastic is a term frequently applied to refined 
 asphalt, particularly to that obtained from bituminous rocks, 
 and is usually in the form of cakes, which are melted and mixed 
 with sand and used for making pavements and sidewalks. 
 
 " Asphaltic cement is refined asphalt which has been mixed 
 with some solvent to increase its plasticity, adhesiveness 
 and tenacity. 
 
 "Asphalt pavement is a pavement composed of sand or 
 pulverized stone held together by asphalt. In America an 
 asphalt pavement is ordinarily understood to be a compara- 
 tively thin layer of sand held together by asphalt laid upon 
 a bed of hydraulic cement concrete; but in Europe the term 
 asphalt pavement is understood to be a comparatively thick 
 layer of asphaltic limestone or asphaltic sandstone with or 
 without a hydraulic concrete base. 
 
 "Asphaltic concrete is broken stone bound together with 
 asphaltic cement." * 
 
 * "Roads and Pavements," by I. O. Baker, p. 385. 
 
ASPHALT PAVEMENTS 359 
 
 In going back to the earliest times in which asphalt is 
 known to have been used it is necessary to refer to the mineral 
 pitch, or bitumen, as being the material quoted. The first 
 use of asphalt spoken of was the cementing in the erection of 
 the Tower of Babel; next we read that Noah 
 pitched the Ark within and without {" biiuminahis 
 cum bitumine'^), and also in Genesis we read, ^' Et asphaltus 
 fuit eis vice cimentiJ^ 
 
 Felltham wrote in the beginning of the seventeenth century 
 of the '' Bituminated walls of Babylon '\- the source of its 
 supply, the fountains of Is, on a tributary of the Euphrates, 
 still yelds asphalt. 
 
 Xenophon speaks of the Median Wall as being built of " Burnt 
 brick laid in asphalt," and Diodorus Siculus describes the 
 process of laying the walls of Nineveh with material from the 
 same source. He says: ''In order to bind the bricks they 
 "were covered with a layer of asphalt, instead of simple tempered 
 clay, and were arranged in courses, and between each thir- 
 teenth course a bed of reed canes was introduced." The 
 burning of Sodom and Gomorrah has been attributed to the 
 accidental ignition of petroleum or bitumen, but the word 
 petroleum not having been known to ancient writers, the 
 legend probably refers to maltha or bitumen. Other ancient 
 authors mentioning asphalt were Herodotus, Aristotle, Strabo, 
 Pliny, and Homer. 
 
 The Egyptians spread bitumen upon the bandages wound 
 around their mummies, and its wonderful preservative proper- 
 ties in this connection can be seen in the museums of to-day. 
 Asphalt was also used by the Egyptians in the foundations of 
 the Pyramids, and for the coating of the external and internal 
 walls of the ground floors of houses, and in the construction 
 of cisterns, silos, and other work where waterproofing was 
 necessary. 
 
 It will be seen, therefore, that from before the time of the 
 Deluge, asphalt has been used and referred to, but there is no 
 record of its use for street paving until 1838, and not until 
 1854 was it employed to any great extent. The laying of 
 macadam roads in Val de Travers, Canton of Neuchatel 
 
360 THE ART OF ROADMAKING 
 
 Switzerland, led to the discovery that the brown bituminous 
 limestone rock, found in the district, under traffic and the 
 summer heat became welded into a continuous sheet. 
 
 In 1854 some streets in Paris were paved with this ma- 
 terial, and it was introduced into London in 1869. The 
 success which attended these early pavements led to its 
 extensive use throughout Europe, and to its introduction into^ 
 America. 
 
 In 1870 the first sheet asphalt pavement in this country was 
 laid in Newark, N. J., in front of the City Hall. In 1873 
 a small piece was laid in Fifth Avenue, New York, and a few 
 other experimental sections were laid; but its first test on a 
 large scale was in 1876 on Pennsylvania Avenue in Washington,. 
 D. C. Preceding 1882, outside of Washington, D. C, there 
 were not more than half a dozen streets in this country paved 
 with any form of asphalt; but since that date, asphalt pave- 
 ments have increased so rapidly that they now rank first 
 in extent of use and in satisfactory qualities. 
 
 These pavements were at first made of materials imported 
 from Europe, but the great cost involved made the pavement 
 so expensive as to induce American inventors to seek to 
 manufacture a material having similar qualities. The result 
 was the introduction of many substitutes and imitations, the 
 majority of which proved defective. The cost of the imported 
 material and the failure of the substitutes directed attention 
 to the deposits of natural bitumen on the island of Trinidad, 
 and experiments were made which demonstrated the possi- 
 bility of making a mastic with this bitumen as its cementing 
 material, as strong, elastic, and durable as that imported from 
 Europe; but it was only after some years that this process 
 was introduced and made a commercial success. 
 
 The difference between the asphalt pavements of Europe 
 
 and those of America is due to the character of the materials. 
 
 -, The former are composed of limestone rock natu- 
 
 European . f . 
 
 and rally impregnated with bitumen, while the latter 
 
 American are composed of an artificial mixture of bitumen, 
 pavements. ii];nestone, and sand. The limestone in the Euro- 
 pean pavements becomes hard, smooth, and slippery under 
 
ASPHALT PAVEMENTS 361 
 
 traffic, and is thus objectionable for general use in frosty 
 latitudes. The granular nature of the sand used in preparing 
 the Trinidad asphaltum diminishes the tendency to wear 
 smooth and materially lessens the slipping of horses. 
 
 Many deposits of bituminous rock are found in the United 
 States, but they have been used only to a limited extent, 
 the principal sources of supply at present being the Island of 
 Trinidad, Bermudez, Venezuela, and California. 
 
 The cost of preparing the different varieties of asphaltum 
 for street pavement is nearly the same; and as all appear to 
 be about equall}^ durable, the exclusive use of any one of 
 them is due merely to local conditions. 
 
 An artificial asphalt pavement consists primarily of: 
 
 1. A foundation of hydraulic cement concrete, or an old 
 
 pavement of cobblestones, granite blocks, bricks, etc. 
 
 2. A binder course composed of broken stone and a ^.^ ■ i 
 
 asphalt cement. sheet 
 
 3. A wearing coat 1^ to 2 inches thick composed asphalt 
 
 of asphaltic paving cement mixed with sand. P^"''^™®^*^- 
 The advantages of this pavement are: 
 
 1. Ease of traction. 
 
 2. Comparative noiselessness under traffic. 
 
 3. Impervious to water.. 
 
 4. Easily cleaned. 
 
 5. Produces neither mud nor dust. 
 
 6. Pleasing to the eye. 
 
 7. Suitable to all classes of traffic. 
 
 8. No vibration or concussion in traveUing over it. 
 
 9. Expeditiously laid, causing little inconvenience to traffic. 
 
 10. Openings to gain access to underground pipes easily 
 
 made. 
 
 11. Durable. 
 
 12. Easily repaired. 
 The defects are: 
 
 1. Slippery under certain conditions of the atmosphere. 
 
 2. Disintegrates if excessively sprinkled or otherwise sub- 
 
 jected to constant moisture, although asphaltum is im- 
 pervious and insoluble in either fresh or salt water. 
 
362 
 
 THE ART OF ROADMAKING 
 
 Fig. 195. — Carroll Street, Brooklyn, N. Y., before Covering Cobble Pavement with 
 
 Sheet-asphalt in 1900. 
 
 (^FTom Judson's "City Roads and Pavements.") 
 
ASPHALT PAVEMENTS 
 
 363 
 
 Fig. 196. — Carroll Street, Brooklyn, N. Y., after Paving with Trinidad Sheet- 
 asphalt in 1900. 
 
 {From Judson's ''City Roads and Pavrmtnt^.") 
 
364 THE ART OF ROADMAKING 
 
 3. Becomes soft under traffic in extreme heat and presents 
 
 a wavy surface, and under extreme cold may crack and 
 become friable. 
 
 4. Not adapted to steep grades. 
 
 5. Necessity of quick repairs. The material has little 
 
 coherence, and if from irregular settlement of the founda- 
 tion or local violence, a break occurs, the passing wheels 
 rapidly shear off the sides of the hole. This is prevented 
 in some cities by the constant attention of workmen 
 who traverse the streets with a light repairing outfit, 
 and wherever a defect is observed it is patched at 
 once and so effectually that the spot cannot be distin- 
 guished. 
 Asphaltum itself is one of the most imperishable substances 
 in nature. Among the oldest monuments of human industry 
 that survive are constructions of asphalt. With 
 asphalt pavements the systems adopted for main- 
 tenance render it difficult to ascertain the actual life of the 
 pavement under traffic. They are repaired immediately they 
 need it, and as each repair is so much new material laid, the 
 whole surface is really relaid in the course of years. Experience 
 has shown that asphalt will last without extensive repairs 
 from four to six years, and that in the course of ten years, 
 the entire surface will have been renewed. 
 
 Asphalt is to a certain extent elastic and does not begin 
 to wear until this elasticity is overcome by thorough com- 
 pression. This is the case with no other paving material; 
 stone and wood begin wearing from the day traffic commences. 
 Under ordinary traffic it may be estimated that it will take 
 two years to complete the compression of asphalt, and the 
 weight of a square foot of this pavement will at the expiration 
 of that time be nearly the same as on the day it was laid, 
 though the thickness is reduced during the first two years as 
 much as it will be in the following eight. 
 
 The extent to which the thickness has been reduced is said 
 to be as much as one-fourth the original thickness. A pave- 
 ment in Paris which had lost more than one-fourth of its 
 thickness was found to have lost only 5 per cent of its weight 
 
ASPHALT PAVEMENTS 
 
 365 
 
 after sixteen years' use^ and the pavement in Cheapside, London, 
 after fourteen years' use, shows a reduction, where not repaired, 
 from its original thickness of 2 J to If inches. 
 
 Construction of the Pavement 
 
 The sheet asphalt wearing surface has no power in itself 
 to support the traffic, so that a solid unyielding foundation 
 
 Fig. 197. — Laying Bituminous Foundation, Rome, N. Y. 
 
 (From Judson's "City Roads and Pavements.") 
 
 Foundation. 
 
 is indispensable, otherwise the w^eight of the traffic would crush 
 
 it. If the street has never been paved, the base of 
 
 the proposed asphalt pavement is made of hydraulic 
 
 cement concrete 4 inches thick for light traffic, or 6 inches 
 
 for heavy city traffic. 
 
 Sometimes the asphalt is laid upon a bituminous concrete, 
 the advantage claimed being that the asphalt adheres more 
 firmly to it than to the hydraulic concrete and prevents 
 weather cracks and waves. It is also less expensive, but repairs 
 
366 THE ART OF KOADMAKING 
 
 are more difficult. This form of foundation has never been 
 common and is now very little used. 
 
 With cement concrete, the bond between the foundation 
 and the wearing surface is not very great, hence it is very 
 easy to strip off the surface in case repairs are necessary; 
 but it sometimes slips on the foundation, and rolls into waves 
 and irregular surfaces, and sometimes cracks with sudden and 
 great changes of temperature, A cement concrete foundation 
 must be set and thoroughly dry before the asphalt is laid, 
 as the best asphalt laid in the most skilful manner on first-class 
 but damp concrete will rapidly go to pieces. When the hot 
 asphalt is applied to a damp surface the water is immediately 
 sucked up and turned into steam, which tries to escape through 
 the heated material ; the result is that coherence is prevented, 
 and, although the surface of the asphalt is smooth, the mass is 
 really disintegrated from underneath by the water. As soon 
 as the pavement is subjected to the action of traffic, the fissures 
 formed by the steam appear on the surface, and the whole 
 pavement quickly falls to pieces. For the same reason asphalt 
 should be laid only in dry weather. 
 
 The binder course consists of a layer about 1^ inches thick 
 
 of broken stone cemented together with asphaltic paving 
 
 cement and rolled in place while hot. This binds 
 
 inder ^-^q wearing coat and the foundation toe:ether, and 
 
 course. ° . . 
 
 prevents the former from liftmg from the latter 
 or being pushed along in a wave. On account of the expense 
 of maintaining the necessary appliances for mixing the stone 
 and asphalt of the binder course, this course is sometimes 
 omitted, and a thin course of material of the same composition 
 as the wearing coat is laid instead, and is called a " cushion 
 coat." This is usually from J to 1 inch thick, and being 
 richer in cement adheres more firmly to the foundation than 
 
 would the top coat. 
 Composition Asphaltum in a refined or pure state is valueless as 
 surTa«"°^ a cementing medium, owing to its hardness, brittle- 
 
 ness, and lack of cementitious properties; therefore 
 it is necessary to add some substance which will impart to 
 it the required plastic, adhesive, and tenacious qualities. 
 
ASPHALT PAVEMENTS 367 
 
 This substance must be one that will partially dissolve the 
 asphaltene and form a chemical union by solution instead of 
 a mechanical mixture. The duty which it has to perform is 
 an important and peculiar one: if it is a perfect solvent of the 
 constituents of the bitumen, the adhesive qualities will be 
 destroyed; if it is an imperfect one, the asphaltum will 
 retain its brittleness. 
 
 This prepared cement is termed the "matrix," and forms 
 one of the two essential parts of asphalt cement pavements, 
 the other part being the "aggregate." The success or failure 
 of the pavement will depend upon the care exercised in the 
 selection of these materials and the skill displayed in com- 
 bining them and laying the pavement. Each has a distinct 
 function to perform: the cementing material, or the matrix, 
 preserves the coherency of the mass; the resisting material, 
 or the aggregate, resists the wear of the traffic. 
 
 The aggregate consists of sand and stone dust or Portland 
 cement. The sand must be clean and free from loam and 
 vegetable impurities, and it should be composed of angular 
 grains ranging from coarse to fine and having as small a pro- 
 portion of voids as possible. 
 
 In the making of the wearing surface, the asphaltic cement 
 
 and the sand are separately heated. The proper amount of 
 
 cement and sand are weighed out and simultaneously ,_. . 
 
 , , . . •^ Mixing and 
 
 poured into a mechanical mixer consisting of two spreading 
 
 sets of interlocking revolving blades which thor- wearing 
 oughly mix the materials, the process usually ^"^^^^^■ 
 requiring 1 to 1^ minutes. When completed, sliding doors in 
 the bottom of the mixer are opened, and the material drops 
 out into carts or wagons which carry it to the street. 
 
 The mixed cement and sand is brought upon the street 
 at a temperature of about 280° F. It is dumped upon the 
 binder course and evenly spread over the surface with shovels 
 and rakes, precautions being taken that no leaves, straw, 
 pieces of paper, or other rubbish become mixed with the 
 paving mixture. Care must be taken to secure an even dis- 
 tribution of the loose material to prevent the formation of 
 depressions or elevations in the finished surface. The depth 
 
368 
 
 THE ART OF ROADMAKING 
 
 a. Asphalt on Stone Blocks, 
 
 b. Asphalt on Macadam. 
 
 CONCftCT£S" 
 
 ■■<riS^.} 
 
 c. Heavy Traffic Pavement. 
 
 ASPHALTS 
 CONCRCTE-*- 
 
 d. Light Traffic Pavement. 
 Fig. 198. — Type Sections of Asphalt Pavements. 
 
ASPHALT PAVEMENTS 
 
 369 
 
 of the mixture is regulated by chalk lines on the curb, by the 
 length of the teeth of the rake, and sometimes by rods sup- 
 ported on feet of a length sufficient to bring the top of the 
 rod to the level of the uncompacted asphalt mixture. The 
 thickness after being rolled is usually about 2 inches. 
 
 The first compression is given by hand rollers and tamping 
 
 Fig. 199. — Tools and Appliances for Laying Asphalt Surface. 
 
 irons. The hand roller has a fire-pot inside for heating it, and 
 the tamping irons, which are used around manhole covers and 
 curbs, etc., where the roller cannot conveniently be used, are 
 heated in a fire in an iron basket, which is moved from place 
 to place on wheels. 
 
 After this first compression, men with tamping and smooth- 
 ing irons, finish the gutters, joints, and all angles which cannot 
 be reached with the heavier rollers. 
 
370 
 
 THE ART OF ROADMAKING 
 
 The first compression having been given, some natural 
 hydraulic cement or any impalpable mineral matter is dusted 
 over the surface to give it a more pleasing color and to prevent 
 adhesion to the roller; and then the surface is rolled with a 
 special pattern of steam-roller, until the roller leaves no mark. 
 This rolling should closely follow the spreading of the material, 
 so that it shall not have time to cool before the final com- 
 pression is obtained. The state of the weather is also an 
 element to be considered, for if a strong wind be blowing, the 
 
 Fig. 200. — Hand Asphalt Roller with Fire-pot. 
 
 material, spread over a broad surface only 2 to 3 inches thick, 
 will cool much more rapidly than on a calm day, even if the 
 temperature is considerably lower. 
 
 When the rolling is completed, the pavement may be thrown 
 open, as traffic, if not too heavy, is of advantage to a newly- 
 laid asphalt pavement, since the pressure of the wheels aid 
 in consolidating the wearing coat and in closing the surface. 
 
 The top of the binding course should be perfectly dry when 
 the wearing surface is laid, to prevent its being separated 
 from the course below by the formation of steam. Asphalt 
 
ASPHALT PAVEMENTS 
 
 371 
 
 Fig, 201. — Street Kettle for Asphalt. 
 
 Fig. 202. — Asphalt Gutter Painters. 
 
372 
 
 THE ART OF ROADMAKING 
 
 should not be laid in cold weather, as the paving mixture may 
 become chilled between the mixing plant and the street, and 
 particularly when it comes in contact with the cold foundation. 
 The chief points requiring skill in the spreading of the 
 asphalt surface are: 
 
 1. To avoid inequalities of the surface, especially depressions 
 which prevent the rapid removal of storm water. 
 
 ?Si;*V' ^ 
 
 EmC) News: 
 
 Lt. Gutter in which Water Flows. 
 Fig. 203. — Action of Water on Gutters of Street Paved with Asphalt. 
 
 2. To secure thorough consolidation of the gutters, which 
 
 otherwise rot rapidly. 
 
 3. To give it a thorough rolling; the asphalt mixture cannot 
 
 be fully compacted by simple pressure, but requires the 
 kneading action of repeated passages of the roller. 
 
 asphalt There have been frequent failures of asphalt 
 
 pavements, pavements, which may have been due to any one, 
 or more, of the following causes: 
 
ASPHALT PAVEMENTS 
 
 373 
 
 1, Unsuitable Materials: 
 
 Asphaltum which has been so changed by natural causes 
 as to possess little or no cementing power. 
 
 Fluxing agents, such as those which are not solvents of 
 asphaltene, and thus form a mechanical instead of a 
 chemical union, or such as those which, for other 
 causes, render the pavement brittle, in which condition 
 it is easily broken up under the action of the traffic. 
 
 b. Gutter Carrying no Water. 
 Fig. 203. — Action of Water on Gutters of Street Paved with Asphalt. 
 
 Sand, either too coarse or too fine, or containing loam, 
 vegetable matter, or clay. 
 
 Free oil in binder. 
 Improper Manipulation: 
 
 Too high heat in refining the crude asphaltum, which 
 reduces or entirely destroys its cementing qualities. 
 
 Improper consistence: if the cement is too hard, the pave- 
 ment will have a tendency to crack during cold weather; 
 
374 THE ART OF ROADMAKING 
 
 and if too soft, if will push out of place and form waves 
 under the traffic. 
 
 Insufficient quantity of cement. This varies with the 
 character of the sand — a fine sand requires more 
 cement than a coarse one, and the proportion of cement 
 must be varied to suit the character of the sand to 
 be used. 
 
 Inadequate mixing of ingredients, whereby the cement 
 and the particles of sand are not brought into intimate 
 contact. 
 
 Rich binder. If an excess of asphalt or coal-tar is used 
 in the binder course, it is likely to work to the surface 
 and then becoming absorbed by the wearing surface, 
 cause it to disintegrate. 
 
 Chilling of the cement while being transported from the 
 mixing plant to the street. 
 
 Separation of the cement and sand. If the distance from 
 the plant to the street is long and there is any unusual 
 dela}'", some of the asphaltic cement may work to the 
 bottom of the load, and when the material is dumped 
 there will be both rich and lean spots, both of which 
 are equally objectionable. 
 
 Laying the paving composition on a damp or dirty 
 foundation, prevention it from uniting firmly with the 
 foundation. 
 
 Inadequate compression, thus allowing the admission of 
 rain and other water falling upon the surface of the 
 pavement, with its destroying effects. 
 3. Natural Causes: 
 
 All materials in nature are undergoing changes due to the 
 action of the elements, and asphaltum is no exception. 
 
 Ordinary wear decreases the thickness, due to the loss of 
 material by the abrasion of hoofs and wheels, but in the 
 case of asphalt pavements this loss of material is very 
 slight. 
 
 Natural decay. Under the action of heat and water all 
 bitumens undergo a change, and when the maximum 
 of hardness is attained, natural decay sets in, and 
 under the combined action of the elements, the mate- 
 rial gradually rots and disintegrates. 
 
 Weak or insufficient foundation will, by unequal settle- 
 ment, cause cracks and depressions in the asphalt sur- 
 face which, under traffic, will speedily enlarge. 
 
 Leaky joints with curbs, crossings, etc., which permit the 
 entrance of water under the asphaltic covering. 
 
ASPHALT PAVEMENTS 
 
 375 
 
 Porous foundation, which permits the ground-water _ to 
 rise, by capillary action, to the underside of the wearing 
 surface, where by freezing it may break the bond 
 between the top layer and the base, and thus permit 
 the wearing surface to be pushed out of place and 
 broken. 
 
 Illuminating gas, escaping from leaky pipes under the 
 
 Fig. 204. — Destructive effects of Gas Leaks on Asphalt Pavement. 
 
 {From Judson's "City Roads and Favcments.^') 
 
 pavement, is absorbed by the pavement, and causes the 
 
 disintegration of the asphalt. 
 Cracks, due to the contraction of the wearing surface, after 
 
 the pavement has lost part of its cementing power by 
 
 several years use. 
 Shifting under traffic, due to too soft a wearing surface. 
 
 Bonfires which are sometimes built upon the asphalt 
 
 pavement are likely to cause considerable 
 
 damage. ^«P^^^- 
 
 The repairs necessary in the maintenance of asphalt pave- 
 ments may be classified as those due to : 
 
376 
 
 THE ART OF ROADMAKING 
 
 1. 
 2. 
 3. 
 4. 
 5. 
 
 6. 
 
 Settlement of the subgrade. 
 
 Disintegration of the pavement in spots. 
 
 Formation of waves. 
 
 Formation of cracks. 
 
 Disintegrating effect of water in the asphalt gutters, 
 necessitating frequent "painting" with rich asphalt or 
 bitumen. 
 
 Defects next to the street-car rails, crossing stones, man- 
 hole covers, etc. 
 
 ^:< 
 
 Fig. 205. — Surface Heater for Repairing Asphalt Pavements. 
 
 Asphalt Block Pavement 
 
 The manufacture of paving blocks from crushed stone and 
 
 asphaltic cement was begun in San Francisco in 1869, but in 
 
 consequence of imperfectly prepared materials and 
 
 Manufac- crude appliances, the blocks were weak and friable 
 
 ture. rj- ? 
 
 and the results were unsatisfactory. Improve- 
 ments have been made since that time in both the proc- 
 esses and the machinery, resulting in the production of 
 tougher and more durable blocks, which are now used ex- 
 tensively in various parts of the United States. 
 
 The blocks are composed of crushed stone and asphaltic 
 cement in the proportions of 87 to 90 per cent of stone and 
 13 to 10 per cent of cement. The materials are heated to 
 300° F. and are mixed in a rotary mixer until all the faces of 
 every particle of the crushed stone are perfectly coated with 
 the mixture of asphaltic cement and limestone dust. The 
 
ASPHALT PAVEMENTS 377 
 
 product is then put in molds 12 inches long, 4 or 5 inches wide, 
 and 3 or 4 inches deep, and subjected to a pressure of 2 to 2^ 
 tons per square inch and then slowly cooled in water. The 
 blocks weigh from 22^ , to 24 pounds each, according to the 
 specific gravity of the stone employed, and about twenty-six 
 blocks are required per square yard. 
 
 The blocks are laid on the street in close contact, in the 
 same manner as stone paving blocks, either with or without 
 an artificial foundation, the foundation usually employed being 
 gravel, or gravel and sand, or sand alone. 
 
 The advantages and defects of the sheet asphalt pavement 
 are equally applicable to asphalt block pavements, but they 
 have the special advantage over *' sheet asphalt" in that they 
 can be made at a factory located near the materials, whence 
 they can be transported to the place where they are to be 
 used, and laid by ordinary pavers without the aid of skilled 
 labor; whereas sheet pavements require special machinery 
 and skilled labor in each city where they are laid. 
 
 Compared with stone blocks they are much smoother and 
 less noisy, and they form a practically impervious pavement, 
 because under the action of the sun and traffic the asphalt 
 cements the blocks together. 
 
 For narrow well-travelled streets they do not make a suitable 
 pavement, but where the traffic is of such a character, as on 
 residence streets, to warrant their use they make, when laid 
 upon a concrete foundation, an excellent pavement, smooth, 
 durable, and easily cleaned, healthy, and pleasant to the eye. 
 
 Coal-tar Pavements 
 
 In their earlier construction, the wearing surface of coal-tar 
 pavements consisted essentially of small gravel, sand, and 
 stone dust, cemented by a product of coal-tar. In the later 
 pavements, a certain proportion of bitumen is mixed with the 
 tar with beneficial results. 
 
 Wherever laid in the United States, coal-tar pavements, as 
 a rule, have given little satisfaction, their failure being due to 
 the presence of volatile oils in the tar, which on exposure to 
 
378 THE ART OF ROADMAKING 
 
 atmospheric influence -slowly oxidize and become inert, thus 
 
 destroying the cementing qualities of the tar. If these oils 
 
 are removed before the tar is used the resulting material is 
 
 brittle, and soon crumples to pieces after being laid. Coal-tar 
 
 is also very sensitive to heat: in summer it is soft, in winter 
 
 brittle. On account of these defects, the use of coal-tar alone, 
 
 as a cementing material for pavements, has been almost 
 
 entirely abandoned. 
 
 To overcome the defects of coal-tar when used alone, the 
 
 practice has arisen of mixing the gas tars with 
 
 Coa-tar bitumen, and this has been successful in propor- 
 and asphalt. . ' . r r 
 
 tion to the amount of the bitumen used. 
 
 Advantages of coal-tar and asphalt pavement are: 
 
 1. Cheapness. 
 
 2. A surface more granular and less slippery than asphalt. 
 
 3. The binder binds the base and wearing surface firmly 
 together and eliminates to a great extent the faults of weather 
 cracks and wave surfaces. 
 
 4. Can be laid from curb to curb, as it will not ''rot'' in the 
 gutters as does the asphalt. 
 
 5. Low cost; pavements constructed of carefully selected 
 and combined materials and properly laid will cost but little, 
 if any, more than the asphalt for maintenance. 
 
 Defects of coal-tar and asphalt pavement are: 
 
 1. The wearing surface consists of 75 per cent of coal-tar, 
 which material can rarely be obtained of uniform quality. 
 
 2. The wearing surface, being only IJ inches thick, requires 
 renewal at frequent intervals. 
 
 3. The pavement is not so pleasing to the eye as asphalt 
 in color. 
 
 4. The use of the bituminous base gives rise to many 
 problems in the grade of the streets on which it is used, due 
 to the fact that the base, the binder, and the wearing surface 
 coalesce so as to form a solid mass. The wear on the surface 
 is never quite uniform; and when the binder or base becomes 
 exposed on the most travelled part of the street, the pavement 
 near the gutter may be worn but slightly. To resurface 
 properly, the remnants of the old surface must be removed, 
 
ASPHALT PAVEMENTS 379 
 
 and the new surface laid directly upon the binder. It is, 
 however, impracticable to strip a coal-tar surface. It may 
 be broken by the pick and bar, but it breaks as readily in the 
 base or binder as at the original line of demarcation. In 
 fact, there is no such line. The practice is to cut out what 
 may be necessary near the curb and put a new surface on the 
 roadway as it stands. The result is to raise the level of the 
 roadway at every resurfacing, or, if the original level at the 
 curb be maintained by the method of cutting out as stated, 
 to increase the crown of the street; but as such pavements 
 will not, as a rule, require resurfacing at more frequent intervals 
 than every fifteen years, and as the surfacing should not 
 raise the level more than one-half inch, the upward growth 
 will not exceed 3^ inches per century. 
 
 If the surface is tarred over every year with a brush and 
 sprinkled with sand, the life is lengthened. 
 
CHAPTER XVIII 
 CONCRETE PAVEMENTS 
 
 Portland cement forms in combination an artificial stone 
 which increases in hardness and strength with age; it is 
 displacing natural stone in many kinds of construction and 
 has recently had much consideration as a paving material. 
 Concrete has long been used for the foundation of pavements 
 (see page 399) and in a few cities, principally in Philadelphia, 
 alleys have been paved with concrete laid in the same manner as 
 for sidewalks, but owing to its high cost, concrete has not met 
 with the approval of leading paving authorities for the wearing 
 surface of roadways. This principal objection may be said 
 to have been met now that the enormous growth in its pro- 
 duction has greatly decreased its cost^ and its use for highway 
 purposes will undoubtedly increase. 
 
 In recognition of the growing importance of concrete in 
 road construction, the Committee on Concrete Review of 
 the Association of American Portland Cement Manufacturers 
 offered two prizes, one of $75 and one of |25, for articles on 
 this subject, the medium selected for publication being Good 
 Roads Magazine/^' 
 
 * The first prize was awarded to Ernest MoCulIough, C.E., Chicago, 
 and the second prize to Charles W. Ross, C.E., Street Commissioner of 
 Newton, Mass., On the subject of the awards the Committee, whose 
 members were George W. Tillson, E. L. Powers, and Percy H.Wilson, 
 sent the following communication to Albert Moyer, of New York, Chair- 
 man of the Committee on Concrete Review: 
 
 "The Jury of Award appointed to judge the papers submitted through 
 the Good Roads Magazine, met on March 19, 1909, and after carefully 
 considering the merits of the papers presented, decided to award the 
 first prize of $75 to paper No. 2099. 
 
 "Our reasons for doing this were; First, on account of the able dis- 
 cussion of the merits of a concrete roadway as compared with roadways 
 built of other materials; and, second, owing to the comprehensive details 
 
 380 
 
CONCRETE PAVEMENTS 381 
 
 The advantages of concrete as a paving material, and the 
 methods of its appHcation as brought out in the first prize 
 paper and summarized in this chapter, constitute 
 all the available information on the subject, based Advantages 
 on the experience of a practical road engineer, concrete. 
 Mr. McCuUough has endeavored to show that con- 
 crete offers a paving material containing an extreme!}^ large 
 per cent of all the desirable quahties given in Baker's table 
 of relative values (page 29) of the items forming an ideal 
 pavement, and in almost the exact ratios. 
 
 In respect to first cost concrete is without a competitor, 
 for the materials lie within easy reach of all who want paving 
 material. Few districts are without stone good 
 enough for the main body of the pavement and 
 when sand is not to be had readily, crushed stone is good. 
 The binding element, the cement, is within the reach of every 
 village, town and city in the country at approximately two 
 dollars per barrel, and a very small amount of this is required 
 when proper methods are adopted to proportion the concrete. 
 There are no patents to conflict, so that every man who can 
 mix concrete may become his own paving contractor. The 
 principal question in the selection of "^'paving materials is this 
 one of first cost, and the desire so many have to see all their 
 money spent near home, which has always been a source of 
 trouble, will not be so hard when concrete is more generally 
 adopted. It is the one material that is low in first cost and 
 yet economical in the end. 
 
 The presence to-day of the magnificent roadwa3^s of old 
 
 Rome gives evidence of the low cost from the maintenance 
 
 standpoint of a properly constructed concrete 
 
 pavement. All that is necessary is to do the work ^^} ° 
 
 \ . '^ . maintenance. 
 
 right. The setting of concrete is ,\ a process of 
 
 crystallization, that proceeds best, when just enough moisture 
 
 of construction; third, that, in our .opinion, when constructed it would 
 make the best roadway of those discussed in the papers. 
 
 "The second prize of $26 we awarded to paper No, 2101. First, because 
 of the comprehensive description of a concrete roadway which can be 
 used for country work, and, second, because of the logical manner in 
 which the whole subject has been treated." 
 
382 
 
 THE ART OF ROADMAKING 
 
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CONCRETE PAVEMENTS 383 
 
 can reach the concrete. This process continues for years. 
 Concrete roadbeds being embedded in the earth, where they 
 will be continually kept moist by the water absorbed from the 
 soil, and wet almost daily by rain or snow from above, must 
 grow stronger with age and it then becomes merely a question 
 of doing the work properly at first. This means careful 
 selection of the cement, the sand and the principal aggregate, 
 the mixing and the depositing, and the prevention of jarring 
 until the material shows evidence of having set enough to 
 withstand ordinary traffic. 
 
 The manufacture of Portland cement has reached so perfect 
 a plane that little or no trouble can be experienced in the 
 cement. More trouble arises from improper selection of sand 
 and stone and poor mixing than from the cement used, for 
 to-day American Portland cement is a standard article pro- 
 duced by thousands of mills all working to turn out a product 
 that will pass tests that are standard over the whole world. 
 Therefore it can be truthfully said that a properly constructed 
 concrete roadway is the lowest in cost of all roadways from 
 the standpoint of maintenance and is practically everlasting. 
 The elements do not affect it. It is impervious to acids, 
 gases, oils and all the other things that attack other paving 
 materials and it requires no coating with costly materials 
 to protect it. 
 
 Tractive resistance can be shown best by com- Ease of 
 
 •^ traction. 
 
 parison with other materials. An estimate made 
 
 in Indiana years ago gave the following costs for horse-power 
 
 per ton mile to haul goods over various pavements: 
 
 Asphalt. ... 2.7 cts. 
 
 Block stone pavement (average) . . . 
 
 5.3 '' 
 
 Macadam in good order . . 
 
 80 '' 
 
 Gravel road 
 
 8.8 '' 
 
 Earth road, hard and dry 
 
 18.0 '' 
 
 Macadam with ruts 
 
 26.0 '' 
 
 Wet sand 
 
 32.0 '' 
 
 Earth road with ruts and mud 
 
 . 39.0 '' 
 
 Dry sand 
 
 . .. 64.0 '' 
 
384 
 
 THE ART OF ROADMAKING 
 
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CONCRETE PAVEMENTS 385 
 
 No mention is made of wood or of brick but experiments 
 made in many places indicate that these materials are prac- 
 tically on a par with asphalt. On this point the following 
 table gives the force required to draw one ton on * 
 
 Material . 
 
 Iron .... 10 lbs. 
 
 Asphalt 15 
 
 Wood 21 
 
 Best stone blocks 33 
 
 Inferior stone blocks 50 
 
 Average cobble stone ... 90 
 
 Macadam 100 
 
 Earth 200 
 
 Considering that a concrete roadway may be made per- 
 fectly smooth if desired, or can be roughened as much as 
 the contractor thinks is right, it is hard to fix a value that 
 will represent ease of traction. It may be made fully as 
 smooth as iron if desired, and thus present exactly the same 
 resistance value, or it may be cut into block form to resemble 
 a first-class Belgian block pavement and thus have a value 
 equal to that set for the best stone blocks. Expressing it 
 in cost per ton-mile it may range from one cent to six cents. 
 There is never any occasion for it to be higher as the material 
 is more easily repaired than any other and a good surface 
 may always be maintained. 
 
 Good foothold depends entirely upon surface, and the 
 top surface is capable of so many degrees of roughness that 
 the pavement, properly constructed and finished 
 will never offer a poor foothold for horses and will 
 always have a good surface for automobiles. Should it 
 become too hard and smooth, it is a very easy and inexpensive 
 matter to roughen the surface. Any desired finish can be 
 given it and thus all objections on the ground of lack of good 
 foothold can be removed. 
 
 * Captain (now General) Francis V. Greene, in Harper's Weekly, of 
 August 10, 1889. 
 
386 
 
 THE ART OF ROADMAKING 
 
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CONCRETE PAVEMENTS " 387 
 
 Concrete is not so noisy as other pavements, in spite of 
 its being a hard pavement, — a fact borne out by residents 
 on streets paved with concrete. The reason is 
 easy to find. Like asphalt, it is smooth so that 
 wagons going over the surface make a minimum 
 of noise. It has, however, the advantage that the pavement 
 and foundation are monohthic. When bricks or paving 
 block3 are used there must be a concrete base. It often 
 happens that an arching action, caused by the effect of the 
 temperature in the pavement, makes it rise above the founda- 
 tion base in places and producing a rumbling noise that is 
 ver}' distressing at times. Therefore, expansion joints are 
 placed at frequent intervals in the pavements laid on a con- 
 crete base. The concrete pavement consisting only of the 
 concrete base used for other pavements and a finish, there 
 can be no separation to cause a rumbling, and outside of 
 this, noise is caused only by the condition of the surface which 
 is entirely within the control of the men putting down the 
 roadway. 
 
 Ease of cleaning and healthfulness should be considered 
 together. A concrete pavement can be washed with a hose 
 at any time, and as it contains no joints, no dirt 
 can collect on the surface. Its healthfulness, Cleanliness 
 therefore, cannot be questioned. It yields no fj^jjegs 
 detritus of itself and therefore the mud and dust 
 that may appear on the surface must be brought on b}^ wagon 
 wheels from other streets, or is thrown on in other ways. In 
 itself a concrete pavement is absolutely free from mud and 
 dust. 
 
 Concrete is one of the poorest conductors of heat known 
 and being light colored is a reflector of heat rather than an 
 absorber. It has been noticed that cement side- 
 w^alks after nightfall are much cooler to the touch hrf^ ^~ 
 than asphalt paved roadways and early in the 
 mornings the cement sidewalks are cool to the hand, while 
 the roadway paved with asphalt is still warm from the heat 
 absorbed the day before. A pavement that is highest in ease 
 of traction; offers perfect foothold for animals and a perfect 
 
388 THE AE.T OF ROADMAKING 
 
 hold for fast traveling automobiles; that is always clean; 
 practically noiseless; free from dust and dirt; non-absorbent 
 of heat; must be comfortable to use in a degree denied other 
 pavements. 
 
 The preparation of the surface of the earth for the laying 
 
 of the pavement is no different from the preparation required 
 
 for pavements of other materials. The cross- 
 
 ons rue- gection must be crowned, the crown depending 
 
 upon the grade of the road or street as well as upon 
 
 the material. For concrete roadways the crown recommended 
 
 is that used for stone. 
 
 The ground should be formed carefully to the contour of 
 the finished surface and at a distance below this surface 
 equal to the amount required by the specifications. It should 
 be carefully excavated and all soft spots should be dug out 
 and refilled with good, clean, hard material, after which it 
 should be alternately sprinkled and rolled until a wagon with 
 two-inch tires loaded with two tons of material can be drawn 
 over it without making an appreciable indentation. 
 
 The foregoing requirements are for a clay or heavy soil, 
 but when the material is sandy or gravelly, of course such 
 hardness in the rolled surface cannot be obtained. The dis- 
 tance of the earth surface below the finished surface of the 
 roadway likewise depends upon the character of the soil over 
 which the road will go. If it is sandy or gravelly, then the 
 concrete can rest directly upon it. If it is clay or heavy 
 soil, there should be at least three inches of sand, gravel, 
 broken stone, or hard cinders between the earth and the 
 concrete. This cushion coat is placed to minimize the danger 
 from frost. 
 
 All fills in the sub-base should be made in thin layers well 
 moistened and rolled. For a monolithic pavement, such as 
 concrete, this perfect preparation of the sub-base is of great 
 importance and extra care should be used. 
 
 A half-inch board should be set on edge on a line on each 
 side of the street about three or four feet away from the 
 edge of the roadway; about where the edge of the gutter 
 would be if the gutter were constructed. This board should 
 
CONCRETE PAVEMENTS 389 
 
 be slightly beveled and be coated heavily with oil on either 
 side. When the concrete is deposited this board is lifted 
 and the space should be poured with a preparation of 
 asphalt made for the purpose. This joint on each side is a 
 longitudinal expansion joint and there are many prepared 
 fillers for expansion joints on the market. A good one 
 can be made of asphalt mixed with coal tar from which 
 has been removed, by boiling, all moisture, leaving the 
 pitch. Coal tar alone may be used and is frequently used 
 for this purpose. 
 
 An expansion joint, to be such, must not be allowed to 
 fill with dirt or sand, so the plastic filling is a necessity. 
 Sheets of cork, tar and sawdust, tar and cork dust, as well as 
 strips of tarred paper heavily coated with cork, have ail 
 been used with success. At intervals of about fifty feet 
 there should be similar expansion joints laid across the pave- 
 ment. Although there has been some discussion over the 
 necessity for such joints in concrete pavements, there are 
 many such pavements in use and so far none have been con- 
 structed without expansion joints. 
 
 No work should be done when the temperature, either 
 night or day, falls below 35° Fahr. 
 
 One form of concrete pavement is patented under the name 
 of the Hassam pavement, after the inventor. After the road- 
 way has been thoroughly compacted, it is covered 
 
 with broken stone to a depth of practically the ^ssam 
 
 ^ ^ -^ pavement. 
 
 pavement thickness m the same manner as that 
 
 generally specified for a macadam pavement, and the stones 
 
 are so graded that the voids are reduced to a minimum. 
 
 After the stone has been rolled until it practically ceases to 
 
 move under the weight of the roller, a thin grout composed 
 
 of Portland cement, one part and sand two parts, is poured 
 
 on the stone until the voids are filled and the grout rises to 
 
 the surface. The rolling or tamping continues during the 
 
 process of grouting. Then a very thin layer of pea gravel 
 
 is placed all over the surface and rolled until the grout fiushes 
 
 up through it. 
 
 Another form of concrete pavement, not patented, is to mix 
 
390 THE ART OF ROADMAKING 
 
 stone, sand and cement together precisely as in mixing con- 
 crete, but no water is added. This dry material, reall}^ a 
 macadam, is then spread over the surface and treated as 
 macadam is treated. When sprinkled and rolled, of course 
 it is converted into regular concrete, but as it has consider- 
 able solidity before wetting, the roadway is very solid. It 
 has been used greatly as ballast for surfacing tracks of elec- 
 tric roads and permits of good work being done in this way. 
 The track can be perfectly aligned and adjusted and then 
 the concrete wetted and permitted to set afterwards. 
 
 The best way to make a concrete roadway, however, is 
 to make it in the regular way by depositing layers of concrete 
 until the desired thickness is obtained, and then finish the 
 surface according to what is considered best for that par- 
 ticular locality. 
 
 Concrete is composed of sand and cement mixed together 
 to form a paste and with some aggregate that 
 will combine with this paste to make a good stone. 
 The best aggregate is, of course, stone. 
 
 The following specifications for materials for Portland 
 cement sidewalks, adopted by the National Association of 
 Cement Users, January 24, 1908, serve to show what is con- 
 sidered good practice in selecting the materials: 
 
 "Sand shall pass a No. 4 screen and be free from foreign 
 matter, excepting loam or clay, which will be permitted if 
 the quantity does not exceed five per cent, and when these 
 ingredients do not occur as a coating on the sand grains. 
 
 ''Not more than 40 per cent shall be retained on a No. 
 10 sieve, or 
 
 35 per cent pass a No. 10 and be retained on a No. 20 sieve, 
 20 per cent pass a No. 20 and be retained on a No. 30 sieve, 
 30 per cent pass a No. 10 and be retained on a No. 40 sieve, 
 40 per cent pass a No. 40 and be retained on a No. 50 sieve. 
 
 "Not more than 20 per cent shall pass a No. 50 sieve, or 
 
 70 per cent pass a No. 10 and be retained on a No. 40 sieve, 
 70 per cent pass a No. 20 and be retained on a No. 50 sieve. 
 
 "Stone shall be crushed from clean, sound, hard, durable 
 
CONCRETE PAVEMENTS 391 
 
 rock, be screened dry through a f-inch mesh, and be retained 
 on a ^-inch mesh. 
 
 "Screenings from the crushed stone specified above, which 
 shall meet the requirements for sand, may be substituted 
 for sand if so approved. 
 
 "Gravel shall be clean, hard, and var}^ in sizes from that 
 retained on a -J-inch mesh to that passed by a ^-inch mesh. 
 
 "Unscreened gra^-el shall be clean, hard and contain no 
 particles larger than J-inch. The proportions of fine and 
 coarse particles must be determined and corrected to agree 
 with the requirements for concrete. 
 
 "Water shall be reasonably clean, free from oil, sulphuric 
 acid and strong alkalies." 
 
 In the foregoing requirements those for sand are first- 
 class, and nothing can be added. In regard to the use of 
 stone screenings in place of sand, it is well to note that all 
 dust must be screened out and the screenings used should 
 comply with the specifications for sand as to size of grains. 
 The dust is apt to ball up badly and prevent a good, thorough 
 mixing. It also requires more water. 
 
 The unscreened gravel referred to means ordinary gravel 
 as this term in understood by the average man. As an 
 excess of sand is weakening to concrete care should be taken 
 to see that the proportions are about right when using such 
 ready mixed gravel. It is always best to screen gravel and 
 remix in proper proportions. 
 
 The caution about using clean water is a good one. It is 
 a common practice for sidewalk men to use water from gutters 
 and drains on their work and then blame the cement for 
 failures. 
 
 When working in sections of the country where there is 
 considerable alkali the water should be tested and should 
 never be used if it contains alkali. The gravel should also 
 be tested as well as the sand. If it is impossible to obtain 
 other material within a reasonable cost, samples of the water, 
 sand and gravel should be taken to a competent chemist for 
 analysis in order to see whether the alkali contained is likely 
 to be harmful to the concrete, as some of the salts known 
 commonly as "alkah" are not harmful. 
 
392 THE ART OF ROADMAKING 
 
 The stone used for concrete roadways can be slightly 
 larger than specified, but should not exceed one and one-quarter 
 inches in the largest dimension and should be as nearly cubical 
 in shape as possible. Rounded gravel packs better than 
 broken stone and occasionally broken stone comes from a 
 formation that is rather brittle and the crusher causes small 
 cracks that extend throughout the stone and are apt to be a 
 source of weakness. 
 
 In building concrete roadways, however, one is not compelled 
 to use stone only. Concrete can be made with stone, broken 
 brick, burnt clay ballast, slag, clinkers, chats, and, in fact, 
 any good firm material that is able to stand exposure to the 
 weather without breaking down, that will not melt or be too 
 readily attacked by moisture or acids. The bed of the pave- 
 ment can be made of good concrete materials and the topping 
 or surfacing of good sand. 
 
 The standard sidewalk specifications of the National Asso- 
 ciation of Cement Users further say: 
 
 "The concrete for the base shall be so proportioned that 
 the cement shall overfill the voids in the sand by at least 
 five per cent and the mortar shall overfill the voids in the 
 stone or gravel by at least ten per cent. The proportions 
 shall not exceed one part of cement to eight parts of the 
 other materials. When the voids are not determined the 
 concrete shall have the proportions of one part of cement, 
 three parts sand or screenings and five parts stone or gravel. 
 A sack of cement (94 pounds) shall be considered to have 
 a volume of one cubic foot. 
 
 *'To determine voids, fill a vessel with sand and let net 
 weight of sand equal B. Fill same vessel with water and 
 let net weight of water equal A. 
 
 Per cent of voids = 100(2.65A-5)/2.65yl 
 
 *'This formula may also be used in determining voids in 
 crushed stone and screenings by substituting for 2.65 the 
 specific gravity of the stone." 
 
 The following is a more simple method for determining 
 voids in coarse aggregates: "Fill a vessel with the aggre- 
 gate and let net weight equal B. Add water slowly until it 
 
CONCRETE PAVEMENTS 393 
 
 just appears on the surface and weigh. Let net weight equal 
 A. Fill the same vessel with water and let net weight equal C. 
 
 Per cent of voids = 100(A-5)/C 
 
 "Use a vessel of not less than one-half cu.ft. capacity. 
 The larger the vessel the more accurate the result." 
 
 These specifications are very good, but the men who do 
 the work are generally opposed to all the weighing, and the 
 formulas, simple as the calculations are. The following 
 method is recommended: Make a box two feet 
 wide, five feet long and one foot deep of two-inch ^^t O" °' 
 tongue and grooved plank, white leaded in the 
 seams so it will not leak. Fill this box level with the larger 
 aggregate. Then pour into it slowly and carefully water 
 from cans of definite size. When the box is full the amount 
 of water in cubic feet represents the per cent of voids in 
 the stone, because the box contains exactly ten cubic feet. 
 Empty the box and spread the stone on a platform. Measure 
 out sand that will represent the voids found in the stone 
 and mix the sand and stone together, then fill the box 
 with the mixture. After this is leveled off, pour in water, 
 carefully measuring it as it goes in, and the amount of 
 water will represent the voids in both stone and sand. 
 If this does not exceed ten per cent, it will represent 
 the amount of cement required, but if it exceeds ten per 
 cent, then some fine sand should be used to fill part of the 
 voids. Density is wanted and the most dense concrete is 
 obtained when the materials are graded in size. 
 
 It does not do to go to too much expense in grading the 
 
 concrete materials, but some expense should be 
 
 gone to in this regard for the quality of the Proportion- 
 
 ... " mc 
 
 material obtained will pay for the extra work, materials. 
 
 The most commonsense method of ascertaining 
 
 the right proportions is that given by Wm. B. Fuller:* 
 
 Use a piece of iron pipe about ten inches in diameter 
 
 * Taylor and Thompson, " Concrete." 
 
394 THE ART OF ROADMAKING 
 
 and weigh it carefully. Mix some concrete in the propor- 
 tions intended for use on the work and tamp it into this pipe 
 and note the height to which the pipe is filled. Weigh the 
 pipe with its contents and throw the concrete away before 
 it sets. Now make another batch with the same amounts of 
 materials, but in different proportions. Weigh this like the 
 first one. Make a number of batches in which the cement 
 shall be one-eighth of the mass, but in which the sand and 
 stone proportions will be altered. That batch in which the 
 clyinder is filled the least, and which weighs the most per 
 unit of volume is the most dense concrete. This method is 
 sensible, because the materials at hand must be used and 
 no expense be incurred in screening and separating in order 
 to make exact proportions. By proportioning by Mr. Fuller's 
 method, a 1 : 2.5 : 5.5 mixture may, for example, be used 
 instead of a 1:3:5 mixture. The sand may be coarse or be 
 in fact a very fine gravel containing considerable sand, in which 
 case a 1:3.25:4.75 mixture might be used. 
 
 The concrete should be mixed in a machine, as this gives 
 
 superior concrete at a much less cost than hand mixing. With 
 
 batch mixers, each batch is certain to contain the 
 
 ixmg. exact proportions called for and to receive the right 
 amount of turning. There are, however, a number of con- 
 stant delivery, or continuous, mixers that can be safely used, 
 provided a constant watch is kept on the cement feed. This 
 is the most important and the one that gives the most trouble. 
 Hand mixture for concrete roadways can be done more 
 cheaply than the hand-mixing usually called for in building 
 work. Two steel platforms, twelve feet long and six feet 
 wide, are used, which are turned up at each end and have a 
 heavy plank on each side, so they resemble in appearance 
 river scows, having a depth of one foot. Over one end is 
 spread the stone in the number of inches that corresponds 
 to the proportion required in the mixture. Over the stone 
 is spread the sand in its proportion. Over the sand is spread 
 the cement. Some men spread the sand first and put the stone 
 on top, then cover with cement. The reason is that they 
 say some of the sand will sink into the voids in the stone and 
 
CONCRETE PAVEMENTS 395 
 
 thus more sand is used than should be. If the sand is put 
 down first the stone will not be lost in it and as the cement 
 is measured in bags anyhow that if some cement goes down 
 into the voids it does not matter. The difference is not 
 worth wrangling over. 
 
 Say^ for example, the mixture is 1:3:5. A layer five 
 inches deep of stone will be spread over the platform and 
 upon that will be spread three inches of sand. One inch of 
 cement will cover it evenly. The measuring is not done by 
 guess, but by boxes. A frame of wood five inches high and^ 
 say, five feet square, is placed on the platform and this is 
 filled even to the top. Then another box, the same size 
 (without a bottom), is placed on it, but this frame has a 
 height of only three inches instead of five. This is filled 
 with sand, after which the frames are lifted by handles at 
 the corners and the stone and sand spread. The cement is 
 determined by a certain number of bags to the batch and 
 this number of bags is placed over the sand. 
 
 When this is done the frames are taken to the next plat- 
 form alongside the first and the same process followed. On 
 the first platform are standing men with rubber boots and 
 having long-handled hoes, such as plasterers use. For a 
 platform six feet wide five men will be necessary. As soon 
 as the material has been smoothed, these men commence 
 with their hoes to pull it over about a foot at a time. They 
 take a slice about a foot wide off the front edge and pull it 
 ahead about two feet, then take another foot in the same 
 manner until the whole mass has been gone over. Then they 
 start at the front and pull it again in the same way. Three 
 pullings and it is at the far end of the platform when they 
 immediately begin to pull it back. This time, however, 
 two men start in to sprinkle it with rose nozzles and the 
 three times the mass is turned it is turned wet. This makes 
 a total of three turnings dry and three turnings wet. By 
 this time the other platform is ready for their attention and 
 the men go there while the wheelbarrow loaders shovel the 
 mixed concrete into wheelbarrows from one end of the plat- 
 form while another batch is being prepared for the men with 
 
396 THE ART OF ROADMAKING 
 
 the hoes, at the far end. Sometimes it is possible to arrange 
 these mixing platforms so the concrete can be thrown directly 
 into place without using wheelbarrows. However, it does 
 not always pay to substitute shoveling and long throwing 
 for wheelbarrow work. 
 
 The usual methods of hand mixing can just as well be 
 followed, of course, but the method described is the lowest 
 in cost and produces excellent results. The concrete should 
 be very quaky and in fact should flow readily, but should not 
 run like thin milk. It should be like a sticky heavy cream. 
 
 The concrete must be solid, not porous. Tamping or 
 rolling should be insisted upon. 
 
 The topping should be not less than one inch thick. Some- 
 times it is two inches thick, but that is extravagant. It 
 should be put in place within thirty minutes after 
 oppmg an ^^^ hsise has been placed if possible, but under no 
 
 finishing. . r- I- 7 
 
 circumstances should it go on after an hour. First 
 
 spread a thin mortar coat of nearly pure cement mortar 
 
 over the base to the depth of about an eighth of an inch 
 
 and then put on the topping. 
 
 The topping should consist of pebbles about one-quarter 
 of an inch in size. The voids should be determined and one- 
 half the voids filled with material about an eighth of an inch 
 in size. The remainder of the voids should be filled with 
 clean, coarse sand. This mixture composes one-half the 
 topping, the other half being cement. Some men use one 
 and one-half parts of this mixture to one part of cement. 
 Trial had best be made by the party doing the work, for 
 so much depends upon the coarseness of the materials. Fine 
 sand is usually round and requires more cement. 
 
 This topping is floated with wood floats, as steel floats 
 produce too smooth a surface. It is cut through at the ex- 
 pansion joints and lined off into blocks the size and shape 
 of stone paving blocks. The cuts over the expansion joints 
 in the base are filled with the regular expansion joint com- 
 position. 
 
 Sometimes the surface is not floated but the topping is 
 put on and tamped somewhat, after which it is swept with 
 
CONCRETE PAVEMENTS 397 
 
 a very coarse broom. Occasionally we see the surfaces 
 treated with acid to eat away the cement before it is fully 
 set, so the stones will appeal and make the surface rough 
 for foothold. Sometimes after the topping is on and before 
 it is set, a covering of pea gravel is put on and rolled in with 
 a lawn roller. 
 
 When the surface is finished, there should be a covering 
 of sand or straw put over it and this covering should be kept 
 wet for a week, after which it is taken off and the street sur- 
 face exposed for three days longer, when.it is ready to be 
 thrown open to traffic. Sometimes no covering is put on 
 and sometimes a covering or burlap is used. Each method 
 has its advocates and each has been used with success. 
 
 The street surface should be wet ever}^ day, and if possible, 
 kept pretty wet for two or three weeks after completion. 
 When a very fine surface is placed on the road and it is 
 blocked off to imitate paving blocks the roadway is generally 
 thrown open for travel within eight or ten days. Sometimes 
 one week is considered long enough. When a rough surface 
 is made it is usual to make traffic wait longer. 
 
 The cost of such roadways is less than the cost of any 
 other pavement used, for it consists of just about the thick- 
 ness of concrete used for such roads. It costs just a little 
 more than the bare concrete used for the foundations of 
 pavements of wood, asphalt, stone or brick, and the cost of 
 the topping is much less than the cost of these wearing 
 surfaces. 
 
 Figures on cost vary greatly in different sections of the 
 country, and the work done so far on concrete roadways in 
 the United States has been generally done in good-sized 
 cities by experienced contractors with trained men. Not 
 much work of this kind has been done in small towns by 
 contractors and until more of it has been done it is hardly 
 right to publish cost data on the work. 
 
 In spite of the many advantages of cement roads brought 
 out by the writers of these papers the limited experience of 
 engineers in this form of road has shown that its rigid surface 
 does not for long withstand the constant blow of horses' 
 
398 
 
 THE ART OF ROADMAKING 
 
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 BSp, .-' ' 
 
 
 
 "^^^fe*!S 
 
 BH^jgi^- -v 
 
 ^^^^^^'t- 
 
 . 
 
 
 Fig. 209. — Preparing the Surface. 
 
 Fig. 210.— The Finished Road Surface. 
 Experimental Concrete Cube Roadway. 
 
CONCRETE PAVEMENTS 399 
 
 hoofs and the action of the iron tire, while its rigidity also 
 makes it injurious to horses. 
 
 Figs. 209 and 210 illustrate an experimental Road surface 
 road surfacing of two-inch concrete cubes, built by ° , o'^cre e 
 the Highway Commission of New York State.* 
 
 A trackway constructed of concrete blocks is J^^^^l ^ v 
 described and illustrated in Chapter XXI. way. 
 
 Concrete Foundations 
 
 The best specification is the one adopted by the National 
 Cement Users Association at its meeting in Cleveland in 
 January, 1909, as follows: 
 
 Specifications for Proportioning Ingredients for Port- 
 land Cement Concrete Foundation for Street 
 
 Pavements. 
 
 Fine Aggregate shall consist of sand, crushed stone, gravel, 
 or slag varying in size, passing when dry through a screen 
 with openings -^-in. in diameter; shall be of siliceous material, 
 clean, coarse, free from vegetable loam or deleterious matter 
 and not more than 6% shall pass a screen having 100 meshes 
 per lin. in. 
 
 Coarse Aggregate shall consist of crushed stone, gravel, 
 brick or "slag which is retained on a screen having openings 
 {-in. in diameter and pass through a screen having openings 
 3 in. in diameter; shall be clean, hard, durable and free from 
 all deleterious materials. 
 
 Mortar shall be made with fine aggregate as above specified, 
 mixed with such proportions of cement as will over-fill the 
 voids in the fine aggregate by at least 5% of such voids. 
 
 Concrete shall be made of coarse aggregate mixed with such 
 proportion of mortar made as above specified in sufficient 
 quantity to over-fill the voids in the coarse aggregate by at 
 least 10%- 
 
 Surface. — In the case of brick or other form of block pave- 
 ments, the surface of the concrete shall be as smooth as 
 practicable. In the case of asphalt or bitulithic or other 
 sheet pavement, the foundation shall be finished as rough as 
 practicable in order that the plastic surface will as thoroughly 
 
 * Engineering Xews, March 3, 1910. 
 
400 THE ART OF ROADMAKING 
 
 as practicable unite with the concrete foundation and prevent 
 sHpping or separation between the concrete and the wearing 
 surface. 
 
 In all cases the general contour of the surface of the con- 
 crete shall be as closely as practicable parallel to and the 
 requisite depth below the surface of the completed pavement 
 in accordance with the grades established, and the directions 
 of the city engineer. 
 
 If any portion of the concrete when tested by a template 
 or a straight-edge 6 ft. in length shall show a surface more 
 than ^2 ill- above or -J in. below the grade established by the 
 city engineer, then the high places in such concrete shall be 
 picked or otherwise brought down to the proper grade and the 
 low places shall be filled to the proper grade with fine concrete. 
 
 Test for Voids.— To determine the voids in the ''coarse 
 aggregate" or "fine aggregate/' prepare a vessel, the cubical 
 contents of which is exactly 1 cu. ft. (1728 cu. ins.); being 
 smaller at the top than at the bottom. Fill the vessel with 
 the aggregate thoroughly dried " coarse " or " fine " as the case 
 may be, which is to be used. Thoroughly shake or jar the 
 vessel containing the aggregate until it is compacted as 
 thoroughly as possible and the vessel is level full. Then 
 ascertain the net weight of the fine aggregate in the vessel, 
 deduct this weight from 166 (the weight of a 1 foot cube of 
 mineral of which the fine aggregate is composed) divide the 
 difference thus obtained by 166. The result is the percentage 
 of voids. 
 
 The advantage of this specification is that if either the fine 
 or the coarse aggregate furnished is of uniform size, the 
 contractor will be required to use enough cement to fill the 
 then large proportion of voids in the fine aggregate and enough 
 mortar to fill the then large percentage of voids in the coarse 
 aggregate. On the other hand, if materials are available 
 which will produce a smaller percentage of voids in either 
 the fine aggregate or the coarse aggregate, the contractor 
 can figure his proposal accordingly and the city get the benefit 
 of the lower cost of construction. 
 
CHAPTER XIX 
 THE CLEANING AND SANITATION OF CITY STREETS* 
 
 Street cleaning, considered as a problem in sanitation call- 
 ing for engineering skill, is of comparatively recent develop- 
 ment, both in Europe and America, and was only- 
 rendered possible by first providing some manner of Early his- 
 hard surface to work upon. Rome had its " tribuni deanine 
 verum inteniium^' at an early date — officials who 
 were charged with the care and cleaning of the streets, 
 markets, temples, baths, and other public places. Ordinances 
 were framed, and more or less severely enforced, forbidding 
 the throwing of any manner of filth into the river or into the 
 streets of Rome. 
 
 For some centuries after Paris was paved every citizen 
 was compelled to repair the street before his house and to 
 clean it at his own expense, in accordance with an edict of 
 Philip the Bold, issued in 1285. This law was practically 
 unobserved, however, and in the fourteenth century the streets 
 of Paris are described as being in a horrible condition. Later 
 laws made street cleaning compulsory, for nobles as well as 
 for the common citizen, and in 1501 a company was formed 
 for cleaning streets by contract with individuals. Street 
 cleaning at pubhc expense, in Paris, was inaugurated in 1609, 
 and the sum of 70,000 livres was appropriated for this purpose 
 from the pubUc fund. In 1704 the city collected 300,000 
 livres for cleaning streets and maintaining lamps. 
 
 A pig figures prominently in the first Parisian ordinances 
 forbidding the dehberate dirtying of the streets. The young 
 King Phihp, son of Louis "the Fat," was killed in 1131, as the 
 
 * Condensed partly- from Beckman's ''History of Inventions and 
 Discoveries" (1846) and partly from "Modern Methods of Street 
 Cleaning" (1909), by George A. Soper, Ph.D., M. Am. Soc. C.E. 
 
 401 
 
402 
 
 THE ART OF ROADMAKING 
 
THE CLEANING AND SANITATION OF CITY STREETS 403 
 
 result of a fall from his horse brought about by a pig in the 
 streets. As a consequence of this accident an order was 
 issued forbidding swine running loose en the streets of the city; 
 but this order was bitterly opposed by the monks of the Abbey 
 of St. Anthony, who resented this affront to the charges of 
 their patron saint, and demanded liberty for the swine to go 
 where they pleased. After some time spent in controversy, 
 the pigs belonging to this abbey were granted a special dis- 
 pensation and permitted to wallow at will, provided that 
 they had bells attached to their necks. 
 
 Up to the fourteenth century, in Paris, and as late as 
 1750 in Edinburgh, citizens were permitted to throA\ from 
 their windows into the streets before the house, any manner 
 of slops, provided that they called out three times before doing 
 so. This privilege, so inconvenient to the passer-by, was 
 strictly forbidden in Paris in 1395, and from this time may 
 be dated the first introduction into that city of sanitary con- 
 veniences. It is interesting to note that when Columbus 
 sailed for the Indies, the palace of King Ferdinand of Spain 
 was destitute of any conveniences of this nature. 
 
 In Germany the cleaning of streets was at first considered 
 as a most dishonorable employment, which is some places 
 was assigned to the Jews and to the servants of the public 
 executioner. Up to the beginning of the seventeenth century 
 the streets of Berlin were never swept, and pigs ran at large 
 throughout the city. In 1624 the Elector desired the council 
 to have the streets cleaned, but the council replied that it 
 was impossible, as the citizens were busy on their farms. The 
 •dirt in the public market place accumulated to such an ex- 
 tent that in 1671 a law was passed compelling every country- 
 man to take out of the city one load of dirt every time he came 
 to market. Pig-sties in the streets were common until 1681, 
 when an order was issued forbidding the feeding of swine 
 within the city limits. Large puddles of filth were, however, 
 allowed to collect, even before the doors of the best houses, 
 and in the summer these puddles emitted a horrible stench. 
 Mr. Beckman remarks of this city that, "If bronze and marble 
 could smell, Blucher and Bulow, Schwerin and Liethen, and 
 
404 
 
 THE ART OF ROADMAKTNO 
 
 mm^sjmi,^ 
 
 
 (From Soper's ''Modern Methods of Street Cleaning.") 
 Fig. 212. — The Center of London on a Holiday 
 
 {From Soper's "Modern Methods of Street Cleaning.'^) 
 Fig. 213. — London. — Orderly Bin and Hand-carts used in Street Work at 
 Entrance to London Bridge. 
 
THE CLEANING AND SANITATION OF CITY STREETS 405 
 
 duck-winged angels and two-headed eagles unnumerable^ 
 would be found on their pedestals, holding their noses instead 
 of grasping their swords." 
 
 These filthy labyrinths which for centuries passed for 
 highways and byways in foreign cities have given way to 
 broad, handsome streets, and congested districts which thirty 
 years ago were a reproach to civiUzation, have been entirely 
 ehminated. In place of over-concentration of population 
 within the limits cf military fortifications, the great con- 
 tinental cities now cover large, i-oomy areas in which the 
 needs of pubhc health and welfare are provided for as nowhere 
 else in the world. 
 
 The sanitary regeneration which European cities have 
 experienced within the last half century has had no counter- 
 part in America, where there has been no necessity for such 
 revolutionary changes. American cities were all small when 
 the world began to learn that efficient sanitation was an in- 
 dispensable feature of every municipality. There was never 
 such overcrowding, or such slums to clean, no such foci of filth 
 to eliminate in the United States as existed abroad fifty years 
 ago. In 1860 there were only sixteen cities in the United 
 States with a population of 50,000 or more, as against one 
 hundred and forty-eight in Europe. 
 
 The significant feature of municipal growth in America 
 as compared with municipal growth in Europe has been less 
 the expansion of cities already large than the 
 great number of small cities which have sprung Municipal 
 into existence. Hundreds of these cities have America. 
 passed, and are still passing, rapidly through periods 
 of infancy, youth, and middle age, toward a maturity which 
 foreign cities had reached half a century ago; and their sanita- 
 tion takes place as they grow. 
 
 That branch of scavenging which has to do with the ques- 
 tion of street cleaning is not at first troublesome to the young 
 American city. The streets are merely highways which run 
 from one town to another and the houses which are built 
 upon these highways are few and far between. 
 
 In course of time, as the population increases, the main 
 
406 THE ART OF ROADMAKING 
 
 highway is paralleled and intersected by cross roads; these 
 again are crossed and recrossed to satisfy the growing require- 
 ments of the place. Capacious gutters make their appear- 
 ance on one or both sides of the streets, but, except for an 
 occasional drain to some brook or creek, a final disposition 
 of surface water is not provided for. 
 
 The first important public sanitary improvement to be made 
 in the village is a public water-supply. The subject of street 
 paving is then considered and some macadam is laid down. 
 Means are sometimes provided in summer to keep down the 
 dust, but the dirt which falls upon the pavement is removed 
 only by wind, rain^ and other natural agencies. 
 
 A sewage system is installed later in the town's growth, 
 and the houses are gradually built closer and closer to one 
 another until they stand in immediate contact. More atten- 
 tion is given to the pavement of the streets. Macadam is 
 laid and sometimes brick ; stone and asphalt come later. 
 The ditches or gutters at the sides of the streets are elimi- 
 nated and the storm water is collected from the well-graded 
 streets through catch-basins into the sewers, along with house 
 sewage. 
 
 The streets are not yet systematically cleaned. Dirt is 
 often allowed to collect until the pavement is hidden from 
 sight. Garbage and ashes are generally removed at public 
 expense by contract. Sometimes the wastes are separated 
 into two parts by the householders so that the refuse of the 
 kitchens may be collected separately from the ashes and 
 other wastes, and sometimes all the wastes are collected in 
 one receptacle. 
 
 The city has now reached its period of adolescence — often 
 one of high mortality due to the absence of proper sanitary con- 
 trol, and fraught with many dangers to the future of the place. 
 
 The period of maturity, that is, the period in which civic 
 responsibility begins to express itself in such forms as the 
 regulation of building construction, the control of traffic, 
 the adoption of well-considered plans to insure public health 
 and safety, is long delayed. The paving and cleaning of 
 streets and the collection and disposition of city refuse are apt 
 
THE CLEANING AND SANITATION OF CITY STREETS 407 
 
 to be the last matters to which the municipality gives itself 
 proper concern. 
 
 In appearance and use the city street is in strong contrast 
 with the rural highway^ yet the street always remains simply 
 a highway in the public regard. The houses are now close 
 (together, offering a solid masonry front as of one compact 
 structure. The streets are paved across from house line to 
 house line. The earth has disappeared beneath a casing of 
 brick, mortar, and stone which is, or should be, impenetrable 
 to water. The pavements should also be treated as though 
 they were impenetrable to man, but in American cities they 
 )are being constantly broken through. They are torn up 
 with little or no regard to the integrity and smoothness of 
 the surface and with the sole idea of reaching the pipes and 
 conduits beneath. The integrity of the surface has much to 
 do with the cost of street cleaning. 
 
 As the city grows the height of buildings becomes greater 
 and greater, making the streets relatively narrower, and in- 
 terfering with free access of air and sunlight; it leads to over- 
 crowding of the sidewalks and carriageways. 
 
 The city uses its streets in a very different way than does 
 the village. They connect every household and are not only 
 arteries of travel, but are also places of amuse- 
 ment, health resorts, and business places for the ^^^^ ^^^ 
 people. The city man not only moves through 
 the streets, he carries the dirt of the street into his home on 
 his boots and clothing; he gets his food and air through the 
 streets. Unfortunately; both food and air are often con- 
 taminated with the product of the ceaseless wear and tear of 
 everything perishable in the city. Ground into impalpable 
 powder and raised from the pavements by the wind this city 
 dust hangs in the atmosphere and can plainly be seen in the 
 air hke a haze on a calm day. The quantity held constantly 
 in suspension is so great that it affects the city's climate; 
 it discolors both persons and their clothing; it turns marble 
 and even granite, yellow and black, and can be found in masses 
 which weigh pounds even at the tops of the highest buildings 
 •of New York. 
 
408 
 
 THE ART OF ROADMAKING 
 
 {From Soper's Modern Methods of Street Cleaning.") 
 Fig. 214. — Westminster. — Orderly with Hand-cart. 
 
 {From Soper's ''Modern Methods of Street Cleaning.") 
 Fig. 215.— Westminster.— Sand Bin Filled for Use. Street Refuse is 
 Shovelled into a Compartment at the Top. 
 
THE CLEANING AND SANITATION OF CITY STREETS 409 
 
 Of all the many sources of street dirt, the greatest amount 
 which becomes scattered over the street pavement originates 
 from vehicular traffic. The ceaseless movement of vehicles^ 
 with their horses, contributes materially to the soiling of city 
 'streets. The transportation of sand, coal, hay, manure, and 
 
 Fig. 216. — Westminster. 
 
 (From Soper's ''Modern Methods of Street Cleaning."^') 
 —Street-crossing Sweeper near Houses of Parlia- 
 ment. 
 
 other loose material m poorly constructed and overfull wagons 
 
 adds to the quantity of refuse in the streets, and in the average 
 
 city the cleaning department itself adds materially 
 
 to the work which it has to do. The carts are 
 
 generally unsuitable for the conveyance of the 
 
 kind and quantity of refuse they have to carry. In conse- 
 
 Sources of 
 street dirt. 
 
410 
 
 THE ART OF ROADMAKING 
 
 quence, dry refuse is blown from the carts and wet refuse 
 drips from them. 
 
 Failure to collect house refuse with fiequency and regularity 
 causes it to be cast into the carriageways by the people and 
 to fall upon the streets from overfull receptacles. It com- 
 monly happens that street-sweepers brush refuse into piles 
 and leave it there for many hours without removing it. Traffic 
 
 Fig. 217.- 
 
 {From Soper's "Modern Methods of Street Cleaning.") 
 -Paris. — Street Sprinkling by Hose. 
 
 and the elements pulverize and scatter the refuse under these 
 circumstances and double the labor necessary to collect it. 
 
 In many places earth from country roads is dropped upon 
 the pavements by the movements of vehicles. The opening 
 of pavements to reach piping and other underground struc- 
 tures is an important source of street dirt. In some towns 
 peddlers and push-cart merchants add materially to the dirty- 
 ing of city streets. Finally, as sources of street dirt may be 
 mentioned the improper storing of sand and other building 
 
THE CLEANING AND SANITATION OF CITY STREETS 411 
 
 materials and the sanding of paveme-nts by street-car com- 
 panies and street-cleaning authorities. 
 
 As cities grow and become more and more congested, the 
 need and difficulty of keeping the sidewalks and carriage- 
 ways free from dust and litter increase; but in spite of praise- 
 worthy efforts here and there, the streets of but few cities 
 are kept in a satisfactorily clean condition. There are almost 
 always large parts of even the cleanest cities which are very 
 dirty. 
 
 One of the reasons for this unsatisfactory condition of city 
 streets lies in the fact that the business of keeping a city clean 
 is rarely understood by the pubhc or by the officials in charge 
 of the streets. In American cities of small size it is still cus- 
 tomary to clean most of the streets not regularly and sys- 
 tematically, but spasmodically and ineffectively — 
 often only when the conditions become so bad Reasons for 
 that public endurance will no longer tolerate them. ^^^^^^ 
 The persons assigned to the labor are often recruited 
 from the ranks of the unemployed and are likely to be either 
 incompetent or unwilling to do a fair day's work. Some- 
 times men of advanced age, inmates of poorhouses and even 
 convicts, are put upon the streets to clean them. Any kind 
 of labor seems to some good enough, and it is small wonder 
 that the results are so often unsatisfactory. 
 
 The aim of sanitation is to get control of wastes as soon 
 as possible after they are produced and maintain this con- 
 trol until they are permanently disposed of. It 
 is both easier and cheaper to collect large par- sanitation 
 tides of refuse and small particles when present in 
 relatively large and compact masses, than to allow the refuse 
 to be broken up and scattered before attempting to gain pos- 
 session of it. 
 
 In order to facilitate the work of the street-cleaning depart- 
 ment, and insure its success, cooperation is desirable between 
 those city departments which are responsible 
 for the paving of streets, the opening of pavements, i.eauij'*d *°^ 
 the regulation of traffic, the storing of building 
 materials, and the management of markets, as well as with 
 
412 
 
 THE ART OF ROADMAKING 
 
 householders. Effective cooperation, of this kind is rare in 
 America, but in Europe all these matters, and more, are not 
 uncommonly attended to b}^ one central authority. 
 
 The city waste materials may be divided into three divisions : 
 
 (From Soper's "Modern Methods of Street C leaning. ^^) 
 Fig. 218. — Berlin. — Electrically-driven Machine for Cleaning Streets. — 
 The Highest Development which Street-cleaning Machines have thus 
 far Attained. 
 
 (1) sewage, (2) city refuse, (3) trade refuse. The city refuse, 
 of which the city should provide for the collection 
 and disposal, is separable into six classes: 
 
 1. Garbage — animal, vegetable and food waste 
 
 from kitchens, markets, slaughterhouses, etc., principally 
 
 water and putrescible organic matter. 
 
 Varieties of 
 city waste. 
 
THE CLEANING AND SANITATION OF CITY STREETS 413 
 
 2. Ashes — steam and household. 
 
 3. Rubbish — paper, wood, rags, metals, bottles, broken 
 glasSj sweepings from buildings and miscellaneous inorganic 
 matter from houses and manufactories. 
 
 4. Street sweepings — animal manure, pavement dirt, drop- 
 pings from carts, materials from building construction, leaves, 
 
 {From Soper's ^'Modern Methods of Street Cleaning.") 
 
 Fig. 219. — Charlottenburg, near Berlin. — Watering-cart and Rubber 
 Squeegee for Cleansing and Drying the Streets. June, 1909. 
 
 and other waste materials collected from the sidewalks and 
 roadways. 
 
 5. Dead animals. 
 
 6. Snow — including the resulting ice and slush. 
 
 To dispose of the dirt which soils the streets, two general 
 methods exist: It must be picked up and hauled away in 
 carts or it must flow with water into the sewers. 
 
 In some cities, notably Paris, the sewers have been built 
 with the idea of carrying off all the street dirt that can reason- 
 
414 
 
 THE ART OF ROADMAKING 
 
 
 {Courtesy of " The Engineering Magazine"^ 
 Fig. 220. — Two-ton Sprinkling Wagon used in Berlin. — Mann's (English) 
 Steam-driven Street Sprinkling Wagon. 
 
THE CLEANING AND SANITATION OF CITY STREETS 415 
 
 ably be emptied into them, but the be>st engineering opinion 
 is that a city's sewers can, and should, be made to carry off 
 only the fine dirt from the streets; the large, bulky, heavy 
 particles must be removed otherwise. 
 
 Good pavements in good repair are indispensible to good 
 work in street cleaning. 
 
 The easiest to clean, but the pavement which requires the 
 greatest amount of attention, is asphalt. Macadam is the 
 most expensive pavement of all to keep clean, comparative 
 Wood-block pavements are more expensive than cleanliness 
 asphalt and less expensive than granite block to o* P^^^- 
 keep in good sanitary condition. Fine, dusty °^ ^ 
 dirt is most conspicuous on asphalt. A good granite pave- 
 ment has a capacity for holding a considerable quantity of 
 fine dirt in its small irregularities without causing the re- 
 mainder to be offensively apparent either as dust or mud. 
 
 To remove large particles of refuse from the street pave- 
 ments, the custom both in Europe and America is to employ 
 handworkers. Their object is to pick up papers, ^ h r 
 horse droppings, and other refuse which they can 
 easily and quickly remove, and to leave the pavement without 
 conspicuous litter. In many European cities these workers 
 are boys; in America they are often old men. 
 
 The refuse thus collected is put into barrels, bags or hand- 
 carts or thrown temporarily into bins or pits situated inside 
 the curbline. In Am.erican cities small metal barrels are car- 
 ried through the streets on light carriages which the workman 
 pushes along before him. 
 
 Although the hand-workers are usually provided with 
 shovels, iron scrapers, and brooms, and in some cases hand- 
 propelled sweeping-machines, they do not and „ , . 
 cannot remove all the dust and mud which it is employed 
 desirable to remove from a city pavement. This i^ street 
 can only be done by the use of water. Nor can ^ eanmg 
 hand workers compete with horse or motor-propelled rotary 
 brooms in removing large amounts of dirt from the pavements. 
 Handwork is best on pavements which are in poor repair. 
 In machine work the secret of success lies in having unob- 
 
416 
 
 THE ART OF ROADMAKING 
 
 structed streets and good pavements, but the attempts made 
 to use sweeping-machines are often decidedly crude. The 
 brooms are not always preceded, but are sometimes actually 
 followed, by sprinkling-carts. Too often no sprinkling ac- 
 companies the sweeping, the result being that dirt is raised 
 through the air in clouds of dust to settle again upon the 
 pavements and in the houses. Hand-sweeping is open to 
 the same objection, for when sprinkling is done by persons 
 
 (From Soper's ''Modern Methods of Street Cleaning.") 
 
 Fig. 221. — Hamburg. — Street Cleaner with Apparatus about to Empty a 
 Hand-cart Full of Sweepings into a Temporary Storage Pit Beneath 
 the Sidewalk. 
 
 in connection with this work, it is often perfunctory and in- 
 effective. 
 
 The facility with which street dirt may be removed from 
 pavements and carried through the sewers in the presence of 
 an abundance of water should be remembered when showers 
 and rainstorms occur. At such times a street-cleaning force 
 can, with hose or with simple rubber hand scrapers, clean an 
 immense amount of fine refuse from asphalt streets by way 
 of the sewers with comparatively little expenditure of energy 
 
THE CLEANING AND SANITATION OF CITY STREETS 417 
 
 and of water; but instead of taking advantage of the oppor- 
 tunity, most street-cleaners seek shelter on the approach of 
 rain. 
 
 One of the most efficient ways used in Europe for cleaning 
 smooth pavements, such as asphalt, is by means of abundant 
 water, speedily followed by scraping with rubber squeegees. 
 In this case the dirt is first lubricated, then scraped away 
 and the pavements partially dried by the scraping. Machine- 
 scrapers hauled by horses are widely employed in Europe to 
 clean asphalt streets. Where the amount of dirt on the pave- 
 ment is large, most of it should first be removed by brooms 
 before the more thorough cleansing with water begins. One 
 of the advantages of scraping with rubber squeegees is that 
 it leaves the pavements comparatively dry. 
 
 There is usually a lack of system and method about the 
 whole undertaking of street cleaning in American cities, l^ut 
 in European cities the streets are well cleaned and the pave- 
 ments are kept in good repair. It is recognized by the author- 
 ities that not only is the cost of cleaning dependent upon the 
 condition of the pavements, but also that it is quite impossible 
 to keep bad pavements clean. 
 
 It is usual in the greatest cities for the heads of street clean- 
 ing departments to be engineers who have had considerable 
 experience in this class of work, as the cleaning 
 and removing of refuse from the streets is recog- Street 
 nized to be one of first importance among mu- authority 
 nicipal sanitary undertakings and a proper per- 
 formance of the work of managing a street-cleaning depart- 
 ment is considered to require thorough competence and a 
 long training. 
 
 The street-cleaning department is often a branch of a larger 
 department which has charge of the construction and repair 
 of all structures between the house lines. 
 
 In the city of London the control of street conditions by 
 the central authority is so complete that it includes not only 
 street cleaning and refuse removal, but the construction 
 and maintenance of sewers, sidewalks, pavements, fire hy- 
 drants, public comfort stations, subways for purposes other 
 
41S 
 
 THE ART OF ROADMAKING 
 
 than passenger transportation, lighting, the removal of dan- 
 gerous structures, the erection of scaffolds for building pur- 
 poses, and even the care of public clocks. This authority- 
 is called the Public Health Department and the work is done 
 under the direction of an engineer of high standing. In other 
 large cities the control of various matters which have to do 
 with the condition of the streets, is also much centrahzed. 
 
 {From Soper's "Modern Methods of Street Cleaning.") 
 
 Fig. 222. — Amsterdam. — Modern Type of Metal Dumping Wagon Fitted 
 with Crane for Raising Heavy Receptacles. 
 
 That the great cities of Europe are cleaner than the great 
 cities of America is due largely to the quality of the labor em- 
 ployed; much depends upon the capacity of the ultimate 
 personal unit. In Germany the streets are cleaned by Ger- 
 mans; in France by Frenchmen; in England by English- 
 men; in America by Italians, Irishmen, negroes and often 
 by persons who have lost caste in every community. 
 
 Considerable difference exists in different cities concern- 
 
THE CLEANING AND SANITATION OF CITY STREETS 419 
 
 ing the organization of the forces engaged in cleaning the 
 streets, particularly as to the number of men em- 
 ployed and the extent to which military discipline Organiza- 
 prevails among them. In German cities it is the rule forces, 
 to employ workmen who have done military duty, 
 and in most places none but men of good phj'-sique and energy 
 are used. In some other countries it is evident that much 
 less care is exercised with regard to the physical qualifica- 
 tions of the workmen; occasionally men can be seen who 
 are superannuated and in other ways incapable, and in a 
 few small places on the continent women take part in the 
 work of street cleaning. In all cases responsibility is assigned 
 in the street forces very much as in military organizations. 
 At the head is a superintendent who has officers under him 
 upon whom he can rely for a prompt and competent execu- 
 tion of his orders. These officers are in turn above foreman 
 and working foremen who come in close touch with the actual 
 work. 
 
 In the cities which have the cleanest streets there are 
 usually two divisions of the work of cleaning — day and night 
 work. The efforts in the daytime are usually directed chiefly 
 toward removing refuse which, when scattered about, make 
 streets appear disordered and dirty. The work of more 
 careful cleansing is done at night. This consists in watering 
 the streets and then either sweeping them with horse brooms 
 or horse-propelled squeegees, or flushing them with a stream 
 from a hose accompanied by work with hand brooms or 
 squeegees. 
 
 In every case the cleaning begins by a thorough sprinkhng 
 of the streets — ^in some cities this covers the sidewalks. In 
 Paris the preUminary wetting is followed by sweeping with 
 a lotary broom and in many cases by squeegees propelled 
 by horses. Rotary brooms, and rotary or fixed rubber squee- 
 gees hauled by horses, are used in nearly all cities. 
 
 In Paris, much street dirt is flushed into the sewers, which 
 are unprovided with catch basins, and when built were in- 
 tended to be sufficiently capacious to carry off all the refuse 
 which might get into them. In other cities much of the 
 
420 
 
 THE ART OF ROADMAKING 
 
 finely comminuted street refuse goes to the sewers also, but 
 some of it is caught by catch basins. 
 
 The custom of flushing gutters exists generally throughout 
 Europe in cities of every size, but Paris makes the most use 
 of it. In London the streets are flushed every night, except 
 when the weather is so cold that ice might form. 
 
 (From Soper's '^Modern Methods of Street Cleaning") 
 Fig. 223. — Antwerp. — Sprinkler, Sweeper, and Collector for Street Dirt. 
 
 As the methods of street cleaning differ in different cities, 
 so there is great diversity among the types of apparatus em- 
 ployed. Motor-propelled water wagons of large 
 ^°^* capacities are in use in London and Berhn. In 
 Antwerp there is a machine which sprinkles the street, sweeps 
 it, picks up the refuse and carries it away. Mechanical sweepers, 
 
THE CLEANING AND SANITATION OF CITY STREETS 421 
 
 however, cannot dispense with hand labor. Moreover, they 
 require a fairly smooth pavement to work well. 
 
 The material swept from the streets of foreign cities is some- 
 times turned to advantage, but the principal object is under- 
 stood to be to get it out of the way. Theoretically of much 
 value as a fertilizer, and possibly of some use as a fuel, the 
 practical difficulties of utilizing its useful ingredients are too 
 great to make it of substantial benefit. 
 
 In Paris, the refuse from the streets is, as far as practicable, 
 swept into the sewers and carried with house drain- 
 age to farms or emptied into the River Seine be- gtre^t^dirt 
 low the city. Seme of this refuse and other solid 
 matters which are carried by the sewage have to be removed 
 before the sewage is utilized. 
 
 The most usual way to dispose of street dirt is to use it to 
 raise the level of low-lying land. Some difficulty is expe- 
 rienced in this direction, for there is not always suitable land 
 to be filled. Furthermore, unless the refuse contains a large 
 amount of indestructible matter, such as sand, it is not gen- 
 erally considered wholly suitable for this purpose. In many 
 instances, where transporation is cheap because of special 
 canal or river facilities, street sweepings are barged away to 
 the country with other city wastes. 
 
 An important part of the work of the street-cleaning de- 
 partment is the removal and disposal of house refuse. It 
 is an almost universal custom to collect this 
 refuse in a mixed condition, but the component Removal of 
 parts of the mixture vary in different cities and j-gfuse 
 at different seasons of the year. 
 
 More or less sorting of refuse is done nearly everywhere 
 and in some places to an extreme limit. In Paris, the house- 
 hold refuse is sorted by ragpickers upon the sidewalks, by 
 men and women in the carts which collect the refuse from 
 the houses and at depots in the outskirts of the city where the 
 material is hauled. 
 
 In most British cities house refuse is thrown by the house- 
 holders into piivate pits where it remains for periods of time 
 ranging from a few days to several months. On the Con- 
 
422 THE ART OF ROADMAKING 
 
 tinent portable cans and boxes are more often used. In some 
 instances the cleaning department furnishes receptacles, carry- 
 ing them away from the houses when full and returning them 
 empty after they haA^e been cleaned and disinfected. 
 
 In Great Britain the destruction of household refuse by 
 burning in special furnaces was begun about thirty years ago 
 and is now generally considered a desirable procedure wherever 
 it can be followed. 
 
 To partly offset the cost of burning refuse, efforts are usually 
 
 {From Soper's "Modern Methods of Street Cleaning.") 
 
 Fig. 224. — Where Street-cleaning is unknown. — Highway between Vollen- 
 dam and Edam, Holland. 
 
 made to utilize the heat produced to raise steam for produc- 
 ing electric light, to pump sewage or water, to operate ma- 
 chines, and for many other purposes. The residue is used 
 for such purposes as the making of concrete, mortar, bricks, 
 and asphalt pavements. 
 
 On reviewing the different subjects thus briefly covered, 
 
 a number of points which go far to account for 
 
 good results should be particularly mentioned. 
 
 Most of these points have a general application to American 
 
 conditions. 
 
THE CLEANING AND SANITATION OF CITY STREETS 423 
 
 1. Centralization of responsibility for the repair and clean- 
 ing of street pavements is desirable. 
 
 2. A competent person should be at the head of the street- 
 cleaning department — preferably an engineer experienced in 
 sanitary work. 
 
 3. An organization somewhat military in character is best. 
 But it is unnecessary that the military spirit should be car- 
 ried beyond the point required to fix responsibility and in- 
 sure a proper execution of orders. 
 
 4. Good pavements in good repair are indispensable to 
 efficiency and economy in street cleaning. 
 
 5. Asphalt is the easiest pavement to clean, but the hardest 
 to keep looking well because it will not hide dirt. 
 
 6. It is possible to clean streets without the use of water, 
 but the results are only measurably satisfactory in most in- 
 stances. For the best work there should be sufficient water 
 used to carry off the finer dust by the use of water from a 
 hose preceded by thorough lubrication with water from a 
 sprinkling cart. 
 
 7. Sewers should be used to carry away all street refuse 
 and sand which can be put into them without obstructing 
 them or adding seriously to the problems connected with the 
 disposal of the sewage. 
 
 8. Economy demands that refuse be removed as soon as 
 possible after it is produced and unnecessary littering pre- 
 vented. 
 
CHAPTER XX 
 SIDEWALKS, CURBS AND GUTTERS 
 
 The term sidewalk, as ordinarily applied, refers to the 
 pavement usually placed on the side of the carriageway 
 pavement. Its object is to provide a serviceable roadway 
 for pedestrians, and the conditions that render a road well 
 adapted to its purpose are very much the same as those 
 required for a walk. It is not subject to the effects of heavy 
 loads such as use the roadway, but the destructive action of 
 water and frost is the same in either case, and the various, 
 questions of economics, location, width, grade, and materials 
 that affect the roadway must also have careful consideration 
 in connection with the sidewalk. 
 
 In business districts the sidewalk usually extends from the 
 building line to the curb. On residence streets, however, it 
 is not so important to use this full width and there is a choice 
 of location, as to whether it be brought up to the property 
 line and the curb, or a distance from either or both to allow 
 a margin of grass and a row of trees. 
 
 The width, exclusive of any space occupied by grass and 
 
 shade trees, should be sufficient to comfortably accommodate 
 
 the traffic. On business streets this should be at 
 Width 
 
 least one-third the width of the carriageway, and 
 
 on residential streets, from 4 to 6 fegt is the usual width, 
 except where the streets are solidly built up with houses 
 several stories high, when the walk should be 8 or 10 feet 
 wide, or in case the walk is used as a promenade or an im- 
 portant thoroughfare, when the width is even greater. 
 
 There should be a surface-slope from the property to the 
 curb, to shed water toward the gutter, varying 
 from 1 inch in 3 feet to 1 inch in 5 feet, accord- 
 ing to the roughness of the surface, and the longitudinal 
 
 424 
 
SIDEWALKS, CURBS AND GUTTERS 425 
 
 slope should conform, as nearly as practicable, to the grade 
 of the street. 
 
 The foundation is of as great importance as in roadways. 
 Whatever material may be used for the surface, if the 
 foundation is weak and yielding the surface will 
 settle irregularly and become extremely objectionable, if not 
 dangerous, to pedestrians. 
 
 The principal requirements of a good sidewalk are: 
 
 1. Smoothness, but not so as to be slippery. 
 
 2. Non-absorbent of water, so that it may dry Req^*^^- 
 
 . „ „ . J J ments of a 
 
 rapidly after ram. good ^alk. 
 
 3. Not easily abraded. 
 
 4. Uniform quality throughout, so that it may wear evenly. 
 
 5. Must neither scale nor flake. 
 
 6. Durability. 
 
 7. Low in first cost. 
 
 Of these 1, 2, 6 and 7 are the most important. 
 
 The materials most generally used for sidewalks are: 
 asphalt, brick, cement, concrete, cinders, gravel, 
 macadam, stone slabs (natural and artificial), tar aenas 
 
 concrete, and wood planks. 
 
 The relative order of these materials as compared with the 
 essential requirements is as follows: 
 
 Smoothness: 
 
 Readiness of drying: 
 
 Durability: 
 
 Asphalt and cement 
 
 Asphalt and cement 
 
 Brick 
 
 Stone slabs 
 
 Stone slabs 
 
 Cement 
 
 Brick 
 
 Brick 
 
 Stone slabs 
 
 Plank 
 
 Plank 
 
 Gravel and macadam 
 
 Gravel 
 
 Macadam 
 
 Asphalt 
 
 Macadam 
 
 Gravel 
 
 Plank 
 
 Cost varies with the locality and the form of construction 
 so that it is impossible to give their rank except in particular 
 cases. While stone slabs have been most common in the 
 past, cement and brick are now the most used materials, the 
 former where a first-class walk is desired and the second where 
 cheapness is a prime requisite. Roots of trees damage brick 
 walks much less than those made of cement. 
 
 Of the natural stone, sandstone is most extensively used. 
 
426 
 
 THE ART OF ROADMAKING 
 
 Sandstone, 
 
 This forms an excellent paving material, standing high in all 
 the necessary qualifications of a good sidewalk. It is found in 
 the quarries in layers of from one inch to three feet 
 in thickness, and is used in all sizes, many of the 
 slabs used for flagging in New York being 20 feet long, 15 feet 
 wide and 8 to 10 inches thick, while blocks from 25 to 60 feet 
 long are often lifted from the bed. A walk made of split 
 flagstones is ordinarily a little smoother than one made of 
 brick, but is not so smooth as a cement walk. 
 
 
 Fig. 225. — Section of Suburban Street, showing Broken-stone Roadway, 
 Paved Gutter, Tile Drain and Gravel Walk. 
 
 Granite 
 
 Wood. 
 
 Granite is also extensively employed; it is durable, but is 
 expensive and wears slippery, so that its surface 
 must be frequently roughened to keep it in a safe 
 condition. 
 
 Wood planks have long been used for sidewalks, especially 
 in small communities. They are cheap, but not durable, 
 and they require constant repair to keep them from 
 becoming dangerous. They were more common in 
 earlier days when the cost of wood was low, but in later years, 
 owing to its increasing cost and to the comparatively low cost 
 of brick and concrete, board walks are much less common than 
 formerly. 
 
 Brick sidewalks are very common and when well made are 
 cheap and durable and make an excellent footway 
 for residential streets or for the business streets 
 of smaller towns. They consist ordinarily of hard-biirned 
 building brick laid upon a porous bed of sand or cinders, but 
 
 Brick, 
 
SIDEWALKS, CURBS AND rjUTTERS 
 
 427 
 
 in districts where the travel is heavy, the bricks are set on 
 edge and the joints are filled with cement mortar. The 
 ordinary building brick is, however, not suitable, as it soon 
 wears out and breaks; hard-burned paving brick, with plane 
 parallel surfaces and sharp right-angled edges should be used, 
 
 pTt^JttHTi 
 
 m.n 
 
 1- I '-' 1 — * T ' ■' r 
 
 (a) Longitudinal Herring-bone Method. 
 
 (6) Diagonal Herring-bone Method. 
 
 rtzj 
 
 (c) Square-course Method. 
 Fig. 226. — Methods of Laying Brick Sidewalks. 
 
 and great care must be exercised in the method of laying 
 the bricks to prevent unevenness. 
 
 Bricks are very advantageously and extensively used for 
 street crossings on unpaved streets and on streets paved with 
 stone block, in the former case to provide a clean crossing for 
 pedestrians and in the latter to provide a smooth surface. 
 
 "Brick sidewalks are cheap, fairly smooth and not slippery; 
 and if made of hard brick are dry in damp weather and durable 
 
42S 
 
 THE ART OF ROADMAKING 
 
 under very heavy travel. Their defects are: (1) they are 
 rough in comparison with asphalt; cement and the best stone 
 slabs; (2) they are untidy, since grass and weeds are likely 
 to grow in the joints/' * 
 
 Artificial stone is extensively used. There are many 
 varieties manufactured under different names and subject to 
 several patents, the most common being those 
 stone known as: granolithic^ monolithic; and kosmocrete. 
 
 When well made and placed with proper drainage 
 provision, any one of these forms a durable, inexpensive and 
 altogether satisfactory pavement. 
 
 Gravel is largely employed for walks in suburban streets, 
 
 '^J^ff^^^ 
 
 Fig. 227. — Section of Park Walk, showing Manner of Removing Surface 
 
 Water. 
 
 Gravel. 
 
 country roads, parks and pleasure grounds, principally because 
 of the natural harmony of its color with such surroundings 
 and because of the informality and ease of its appearance 
 as compared with asphalt and cement. This method 
 of construction is substantially the same as in the 
 case of gravel roadway pavements. A good example of the 
 adaptability of gravel for pathways is found in the case of 
 Central Park, New York, where they are laid on every variety of 
 ground from level and smooth to rocky and precipitous, winding 
 along rugged hillsides; gently undulating over meadows and 
 lawns, and sometimes expanding into broad and capacious 
 promenades. They are carried over and under roads, and 
 over brooks, by archways and bridges of various kinds, 
 
 * Baker, "Roads and Pavements," page 602. 
 
SIDEWALKS, CURBS AND GUTTERS 
 
 429 
 
 ornamental and rustic ; through rough gorges and ravines, and 
 along the water edge of lakes and ponds. They are made in 
 various widths from 3^ to 35 feet, and adapted to nearly 
 every circumstance of position, locality, use, and convenience 
 that ordinarily occurs in walks for rural or park purposes. 
 
 {Copyright, 1909, by The Chas. H. Elliott Co.) 
 Fig. 228. — Cinder Path, Lehigh University Campus, So. Bethlehem, Pa. 
 
 The principal causes of the deterioration of this kind of 
 walk, and the greatest source of trouble and expense in repairs, 
 is the wash from water brought from the adjoining slopes. 
 Sometimes a single shower will cause damage that will involve 
 a heavy expense for repairs, so the necessity of liberal and 
 ample provision to guard against this trouble will be seen to 
 be warranted by sound economy. 
 
430 
 
 THE ART OF ROADMAKING 
 
 The most permanent form of sidewalk and the form that is 
 
 daily growing in favor is of Portland cement construction. 
 
 The Portland cement concrete sidewalk, when 
 
 Cement and pp^pg^.^y constructed, meets all the requirements ^ 
 concrete. x- x- j 7 ^ 
 
 of evenness, solidity and permanency, and m prac- 
 tically all localities, can be built at a comparatively low cost. 
 The possibilities of concrete are well appreciated, but often, 
 through lack of knowledge of the material and inexperience 
 in handling it, man}^ walks are built w^hich, sooner or later, 
 become more or less defective. 
 
 There are certain rules which should be observed in all cases, 
 and in some cases additional precautions are necessary. The 
 
 (a) Improper Construction. (6) Proper Construction. 
 
 Fig. 229. — Method of Constructing Driveway Across W.alk. 
 
 location of a walk is determined regardless of the natural 
 fitness of the foundation, the soil and drainage conditions, and 
 it is important, therefore, that these matters be carefully 
 studied; materials available should also receive careful atten- 
 tion, their selection being made wath reference to quality 
 rather than with reference to cost. Weather conditions 
 seriously affect the behavior of concrete and must be taken 
 into account to assure permanence of the walk. Poor work- 
 manship, which includes improper proportioning of materials, 
 the placing of a walk on an improperly prepared foundation 
 and failure to take into account weather conditions, is respon- 
 sible for practically all failures that occur. Very few cement 
 walks, if any, have been worn out. 
 
 Cement sidewalks are usually made of cement stone slabs 
 
SIDEWALKS, CURBS AND GUTTERS 431 
 
 framed in place on the job.* To accomplish permanency, 
 it is necessary that these slabs remain hard, tough and in the 
 original position, and to achieve this, methods of manu- 
 facture must be employed which will avoid settlement cracks, 
 upheaval by frost, crumbling due to work done in freezing 
 weather, contraction and expansion cracks, separation of 
 top from base, and disintegration. 
 
 A great many walks have slabs warped into saucer-like 
 shapes, without any signs of cracking, which slabs, unless 
 the walk is on a grade, act as basins holding water after each 
 rain. These warped slabs occur both in walks of large area 
 made up of a number of rows and in single slab suburban 
 walks flanked by lawns. In the latter case there is, in addition, 
 usually a longitudinal crack along the center of the walk, as 
 shown in Fig. 230. Suburban walks flanked on one side by a 
 terrace are generally the worst. A great many walks are 
 cracked at curved corner curbs, and at the ends of walks 
 next to the curb at cross streets; often slabs in the middle of 
 long walks buckle up, as shown in Fig. 231. In many cases 
 the expansion in the cement walk has either pushed the curb 
 out of line or broken it off entirely. 
 
 In concrete walks, as usually built, the earth is excavated 
 to 10 or 12 inches below the finished surface and 6 or 8 inches 
 of cinders are laid for foundations on which the 3-inch concrete 
 walk is laid, with a 1-inch cement covering surface, ^^'hen 
 no additional drainage is provided, water enters the foundation 
 of the walk through the lawns on either side, and at all the 
 joints between the slabs. Naturally, this moisture is greatest 
 at the sides and near the joints, where its enters, very little 
 reaching the center of the slab. Subsequent freezing causes 
 greater upheaval of the foundation near the edges of the slab 
 than at the suspended center, and the slab finding bearing only 
 on the edges, acts as a beam. The load, while not great, is 
 applied continuously and simultaneously, with changes in 
 
 * Correct methods of construction are available in the form of trade 
 pamphlets issued for gratuitous distribution by several of the leading 
 cement companies, and there are also several cheap books devoted ex- 
 clusively to this subject. (See BibUography, Appendix V.) 
 
432 
 
 THE ART OF ROADMAKING 
 
 c3 
 
 a 
 a 
 
 o 
 O 
 
 
 
 ■p^ 
 
SIDEWALKS, CURBS AND GUTTERS 
 
 433 
 
 temperature, and finally causes a flow of the material, resulting 
 in depression and permanent set. 
 
 The dissimilarity in density of the concrete base and the 
 top coat or wearing surface, which causes a different ratio of 
 
 .-Cement 
 
 ■ nmiim'" ' f^ -' ..."." '• ^ ■■■' ■ ' ^■ ' J.'I^ ' !1 ' Wl"'* ' 
 
 ISjpjs t^:;' 
 
 Longitudinal 
 
 Secl-ion 
 
 A-B. 
 
 Cinders 
 '■'"■Broken Stone 
 
 Transverse Section . 
 Fig. 231. — Details of Drains for Concrete Sidewalks. 
 
 expansion and contraction in the base from that in the top, 
 also results in warping. 
 
 To avoid this sagging and upheaval, perfect drainage in 
 the sub-foundation is of utmost importance. Fig. 231 repre- 
 sents a walk in which drainage is taken care of by 
 trenches about 10 inches deep and of a convenient Sub-founda- 
 width across the sidewalk, extended to the curb, ^^ ^° 
 and filled with broken stone. The ditches are dug 
 across obliquely, so as to take advantage of the slope of the 
 
43J 
 
 THE ART OF ROADMAKING 
 
 
 3 
 Q 
 -a 
 
 ;3 
 
 u 
 I 
 
 
SIDEWALKS, CURBS AND GUTTERS 
 
 435 
 
 sidewalk. Fig. 233 shows a section of concrete walk as specified 
 by the city of Pittsburg, which provides an outlet for drainage 
 to the curb somewhat like that on Fig. 231. 
 
 Upheaval by tree roots can very easily be avoided by 
 cutting out any roots which will run under the 
 pavement less than a depth of six inches under ^^ ^^J ^ 
 bottom of drainage foundation. 
 
 Broken stone and gravel are sometimes used for foundation, 
 but cinders are most frequently used and are preferable. 
 The thickness of the cinder foundation required 
 varies in the different city specifications from 4 
 to 12 inches. A thickness of 6 inches is ample. A greater 
 thickness, unless deep enough to go below the freezing line, 
 
 Foundatioi^. 
 
 / Wearing 
 Surface—-. 
 
 Rise, '4 -12 
 
 ..-3 Portland Cemenf, 
 Concrete 
 
 
 ,,, ^^, ....... . - . . ^_- . . ........ ...... 
 
 - -^ 
 
 '"Broken Stone ''6 'Coarse Cinder 
 
 Drain every 25 or Broken Stone 
 
 Fig. 233. — Suggested Design for Concrete Sidewalk. 
 
 Ens. 
 News. 
 
 would really be detrimental, as the upheaval of frozen cinders 
 would be proportional to its thickness. Cinders that have 
 been placed in a walk for some time before placing the cement 
 should be picked loose and retamped so that the entire mass 
 has even compaction. If some places are packed harder 
 than others, the flag will not have an even bearing and may 
 break. One of the causes of inferior concrete in the base is 
 the absorption of water from the mixture by the porous founda- 
 tion before it has set; therefore, a thorough wetting of the 
 foundation just before placing the concrete is desirable. 
 
 The concrete in the base of concrete walks is generally 
 the most inferior concrete made. The capital and equipment 
 necessary for doing this kind of work is comparatively small, 
 and the construction work apparently easy, the result being 
 
436 
 
 THE ART OF ROADMAKING 
 
 Firiisliing Trowel, 
 
 1 
 
 m 
 
 Roller. 
 
 Blade for Cutting Concrete Ba=e. 
 
 Edger, Rammer. 
 
 Fig. 234. — Tools used in Construction of Concrete Sidewalks. 
 
SIDEWALKS, CURBS AND GUTTERS 437 
 
 that many walks are put down by inexperienced contrac- 
 tors and competition has reduced the price so that 
 good work cannot be done profitably. But even ^^^^ 
 with as good material and workmanship, it is hardly 
 possible to get as good concrete in cement sidewalk base as in 
 structures of larger volume, such as retaining walls, abutments, 
 etc., as in tamping a thin layer of concrete laid on a cinder 
 bed, the concrete may compact a little under each blow, but 
 a great part of the force is expended in forcing the concrete 
 up at another place and possibly dislodging the cinder bed. 
 This is one of the reasons why it is necessary to have the cinder 
 bed thoroughly compacted before placing concrete, and why 
 it is advisable to so mix the concrete and have it of such 
 constituency as to reduce the amount of tamping necessary. 
 
 Insufficient water is often used in mixtures for concrete 
 base. More water should be used, and thorough mixing 
 adhered to, as well-mixed concrete is more dense than poorly- 
 mixed and requires less tamping. 
 
 A great many failures are due to a lack of bond between 
 the top coat or wearing surface and the concrete base. In 
 the laying of the walk, and in order to accomplish 
 much work, the concrete base is sometimes allowed °^ ^^^ ' 
 to get its initial set before applying the top coat, consequently 
 there is little bond, the upper wearing surface becomes loose 
 and easily breaks. If the upper surface of the base is troweled 
 or smoothed off, the strength of the bond is reduced; it is 
 important, therefore, to leave the base free of troweling. 
 
 When concrete walks were first laid, forms defining the 
 blocks were used and the concrete placed in alternate blocks. 
 When these had set the remaining spaces were 
 filled in. This scheme made positive joints and -^"^^ ^' 
 prevented breaking of flags on account of settlement. While 
 this is still required in some specifications the greater proportion 
 of work is done in continuous sheets, the walk being cut at 
 the joints by a knife and sledge. Some specifications require 
 the joint to be filled with sand and the surrounding concrete 
 tamped, and others require tar paper put into joint. After 
 the top coat or wearing surface is put on, it is cut through 
 
438 
 
 THE ART OF ROADMAKING 
 
 Fig. 235. — Curb Broken Away by Expansion, showing Necessity of 
 Expansion Joints. 
 
 Fig. 236. — A Miserable Piece of Sidewalk Construction. 
 
 /ipparently every rule and precaution necessary for the production of first-class 
 work was disregarded in the placing of this walk. The fill was insufficiently and 
 improperly prepared and was not protected. The base was weak, failing to support 
 the top, which was not bonded to the base. This is an extreme exam,ple of shoddy 
 construction. 
 
SIDEWALKS, CURBS AND GUTTERS 439 
 
 over the joint in the base. The cutting is often indifferently 
 done and sometimes the cut through the wearing surface is 
 not directly over the cut through the base. Then if there 
 is any settlement the top will crack in an irregular line. Water 
 will also get in at the joint under the top coat and freeze, 
 causing it to break. The objections to laying the alternate 
 blocks in a walk are that it is hard to get the different blocks 
 In a true plane, the appearance, therefore, is not so good. 
 Another objection is the increased cost and time required. 
 It would seem that the method now most generally followed of 
 building a continuous course and cutting up into blocks with 
 ^ tool designed for that purpose is the best. The tool should 
 i)e so shaped as to make the top edges of the groove firm, 
 Smooth and slightly round, and should be long enough to 
 cut entirely through the top coat and the concrete base. 
 
 The greatest failures are from expansion, and to take care 
 of this it is well, in addition to the block joints, to provide 
 extra joints from 1 to 1^ inches wide about every 100 feet of 
 walk when more than this distance is laid at one time; also at 
 the ends of walks next to the curb at cross streets and along 
 the curb where the sidewalks are ver}' wide and have curved 
 curb corners. These joints are usually filled with sand. 
 It is not necessary or desirable to have sharp sand ; sand with 
 rounded grains will answer better. Pitch and asphalt have 
 also been used for the large joints and will prevent to some 
 extent moisture reaching the cinder bed. 
 
 The size of the blocks should be limited to about 6x6 feet. 
 When the sidewalk extends from a building to the curb or 
 in subways from the abutment to the curb or curb wall, as 
 the case may be, the cement walk should not be built tight 
 around the building, abutment, curb or curb wall, but an 
 open joint about 1 inch wide should be left. There is likely 
 to be some settlement in either the building, abutment, curb, 
 curb wall or sidewalk and irregular cracks will result. 
 
 Some cracking is caused by the upper surface of the walk 
 drying out faster than the bottom, acting very much as dried 
 mud in a river bottom, where the sun dries the top first, which 
 shrinks and breaks up into small blocks. Subsequent shrink- 
 
440 
 
 THE ART OF ROADMAKING 
 
 Fig. 237. — Section of Walk showing Careless Construction. 
 
 Fig. 238. — Showing Change of Grade. 
 
 The comfort of pedestrians demands that the grade in a walk shall not change 
 suddenly exrepting where steps are advisable. 
 
SIDEWALKS, CaiRBS AND GUTTERS 441 
 
 ing in the lower stratum only increases the width of the cracks. 
 For this reason^ it will be well to keep the top of the walk 
 moist for several days during dry weather. It is known 
 that wetting the surface will also produce a whiter walk than 
 one that is allowed to dry out quickly. 
 
 Portland cement concrete sidewalks, when properly con- 
 structed, are no doubt superior to all others. The cost of 
 construction is not much greater than other sidewalks, so 
 that their more extended use depends upon their permanency. 
 It is advisable, therefore, that the best material and work- 
 manship be used so as to get best possible results. 
 
 STANDARD SPECIFICATIONS FOR PORTLAND CEMENT CON- 
 CRETE SIDEWALKS OF THE NATIONAL ASSOCIATION 
 OF CEMENT USERS 
 
 Materials. — The cement shall meet the requirements of the specifica- 
 tions for Portland cement of the American Society for Testing Materials, 
 and adopted by this Association (Specification No. 1), January, 1906. 
 
 Aggregates. — Fine Aggregate shall consist of sand, crushed stone, or 
 gravel screenings, graded from fine to coarse, passing when dry a screen 
 having |-inch diameter holes, shall be preferably of silicious materials, 
 clean, coarse, free from vegetable loam or other deleterious matter, and 
 not more than 6 per cent shall pass a sieve having 100 meshes per linear 
 inch. 
 
 Mortars composed of one part Portland cement and three parts fine 
 aggregate by weight when made into briquets shall show a tensile 
 strength of at least 70 per cent of the strength of 1 : 3 mortar of the 
 same consistency made with the same cement and standard Ottawa 
 sand. 
 
 Coarse aggregate shall consist of inert material, graded in a size, such 
 as crushed stone or gravel, which is retained on a screen having ^-inch 
 diameter holes, shall be c'ean, hard, durable, and free from all deleterious 
 materials. Aggregates containing soft, flat or elongated particles shall 
 be excluded. 
 
 The maximum size of the coarse aggregate shall be such that it will not 
 separate from the mortar in laying and will not prevent the concrete 
 fully filling all parts of the forms. The size of the coarse aggregate shall 
 be such as to pass a 1^-inch ring. 
 
 Water shall be clean, free from oil, acid, strong alkalies, or vegetable 
 matter. 
 
 Forms. — Forms shall be free from warp, and of sufficient strength 
 to resist springing out of shape. All mortar and dirt shall be removed 
 from forms that have been previously used. 
 
 The forms shall be well staked to the established lines and grades, and 
 their upper edges shall conform with finished grade of the walk, which 
 shall have sufficient rise from the curb to provide proper drainage; but 
 this rise shall not exceed | inch per foot, except where such rise shall 
 parallel the length of the walk. 
 
442 THE ART OF ROADMAKING 
 
 A\\ forms shall be thoroughly wetted before any material is deposited 
 against them. 
 
 Size and Thickness of Slabs. — Slabs shall not contain more than 36 
 square feet or have any dimension greater than 6 feet. For greater area^ 
 slabs shall be reinforced with ^-inch rods, not more than 9 inches apart, 
 or other reniforcement equally as strong. 
 
 The minimum thickness of the pavement shall not be less than 4 inches. 
 
 Sub-Base. — The sub-base shall be thoroughly rammed, and all soft 
 spots removed and replaced by some suitable hard material. 
 
 When a fill exceeding one foot in thickness is required, it shall be 
 thoroughly compacted by flooding and tamping in layers of not exceeding 
 6 inches in thickness, and shall have a slope of not less than 1 to 1|. 
 
 The top of all fills shall extend at least 12 inches beyond the side- 
 walk. 
 
 While compacting, the sub-base shall be thoroughly wetted and shall 
 be maintained in that condition until the concrete is deposited. 
 
 Base. — The concrete for the base shall be so proportioned that the 
 cement shall overfill the voids in the fine aggregate by at least 5 per cent, 
 and the mortar shall overfill the voids in the coarse aggregate by at least 
 10 per cent. The proportions shall not exceed one part of cement to 
 eight parts of the fine and coarse aggregates. When the voids are not 
 determined the concrete shall have the proportions of one part cement, 
 three parts fine aggregates and five parts coarse aggregates. A sack of 
 cement (90 lbs.) shall be considered to have a volume of one cubic 
 foot. 
 
 Mixing. — The ingredients of concrete shall be thoroughly mixed to 
 the desired consistency, and the mixing shall continue until the cement 
 is uniformly distributed, and the mass is uniform in color and homo- 
 geneous. 
 
 a. Measuring Proportions. Methods of measurement of the proportions 
 of the various ingredients including the water, shall be used which will 
 secure separate uniform measurements at all times. 
 
 h. Machine Mixing. A\'hen the conditions will permit, a machine 
 mixer of a type which insures the proper mixing of the materials through- 
 out the mass shall be used. 
 
 c. Hand Mixing. AVhen it is necessary to mix by hand, the mixing 
 shall be on a water-tight platform and especial precautions shall be taken 
 to turn the materials until they are homogeneous in appearance and 
 color. 
 
 d. Consistency. The materials shall be mixed wet enough to produce 
 a, concrete of such a consistency as will flush readily under light tamping, 
 and which, on the other hand, can be conveyed from the mixer to the 
 forms without separation of the coarse aggregate from the mortar. 
 
 e. Retempering. Retempering mortar or concrete, i. e., remixing with 
 water after it has partially set, shall not be permitted. 
 
 Placing of Concrete. — a. Methods. Concrete after the addition of 
 water to the mix shall be handled rapidly to the place of final deposit, 
 and under no circumstances shall concrete be used that has partially 
 set. 
 
 b. Freezing weather. The concrete shall not be mixed or deposited 
 at a freezing temperature unless special precautions are taken to avoid 
 the use of materials containing frost or covered with ice crystals, and in 
 providing means to prevent the concrete from freezing after being placed 
 in position and until it has thoroughly hardened. 
 
 Sidewalks shall be laid in such a manner as to insure the protection of 
 the pavement from injury due to changes in foundations or from con- 
 traction and expansion. 
 
SIDEWALKS, CURBS AND GUTTERS 443 
 
 Workmen shall not be permitted to walk on freshly laid concrete, 
 and where sand or dust collects on the base it shall be carefully removed 
 before the wearing surface is applied. 
 
 Wearing Surface. — The wearing course shall have a thickness of at 
 least 1 inch. 
 
 The wearing surface shall be mixed in the same manner as the mortar 
 for the base, but the proportion one cement to two of fine aggregate, and 
 it shall be of such consistency as will not require tamping, but will be 
 readily floated with a straight-edge. 
 
 The wearing surface shall be spread on the base immediately after mixing, 
 and in no case shall more than 50 minutes elapse between the time that the 
 concrete for the base is mixed and the time that the wearing course is 
 floated. 
 
 After being worked to an approximately true surface, the slab markings 
 shall be made directly over the joints in the base with a tool which shall 
 cut clear through to the base and completely separate the wearing courses 
 of adjacent slabs. 
 
 The slabs shall be rounded on all surface edges to a radius of not less 
 than |-inch. 
 
 When required the surface shall be troweled smooth. 
 
 The application of neat cement to the surface in order to hasten the 
 hardening is prohibited. 
 
 On grades exceeding 5 per cent, the surface shall be roughened. This 
 may be done by the use of a grooving tool, toothed roller, brush, wooden 
 float or other suitable tool; or by working coarse sand or screenings into 
 the surface. 
 
 Where color is used it shall be incorporated uniformly and the quantity 
 and quality shall be such as to not impair the strength of the wearing 
 surface. 
 
 Single-Coat Work. — Single-coat work shall be composed of one part 
 of cement, two parts of fine aggregate and three parts of coarse aggregate, 
 and the slabs separated as provided for in the specifications for two-coat 
 work. 
 
 The concrete shall be firmly compacted by tamping and evenly 
 struck off and smoothed to the top of the form. Then with a suitable 
 tool the coarser particles of the concrete shall be tamped to a depth which 
 will permit of finishing the walk as under ''Wearing Surface." 
 
 Protection and Grading. — When completed, the walk shall be kept 
 moist and protected from traffic and the elements for at least three 
 days. 
 
 Grading after the walks are ready for use should be on the curb side of 
 the sidewalk, 1^ inches lower than the sidewalk, and not less than -^-inch 
 to the foot fall towards the curb or gutter. On the property side of the walk 
 the ground should be graded back at least 2 feet and not lower than 
 the walk; this will insure the frost throwing the walk alike on both 
 sides. 
 
 Curbs. — The trench shall be excavated to a depth not greater than 
 the bottom of the curb and a width not greater than the thickness of the 
 curb plus 6 inches. 
 
 The thickness of the curb shall not be less than 6 inches. 
 
 After the forms are set about 1 inch of wearing surface shall be placed 
 on the inside of the curb form, then the concrete shall be deposited at 
 one operation and firmly tamped to within 1 inch of the top of forms. 
 The top wearing surface shall then be placed and be of the same composi- 
 tion as that specified for sidewalks. 
 
 Joints shall be made three-fourths the depth of the curb, continuous 
 with joints of the sidewalk and in no case more than 6 inches apart. 
 
444 THE ART OF ROADMAKING 
 
 The forms shall be removed as soon as practicable and the faces finished 
 at one operation, floating down 6 inches with a one to one mixture of 
 cement and fine aggregate of sufficient thickness to produce a smooth 
 surface. 
 
 Where a combination curb and gutter is required, they shall be cast 
 at the same time and finished at one operation. 
 
 Curbs and Gutters 
 
 Curbstones are employed for the outer side of the foot- 
 ways to sustain the coverings and form the gutter. 
 Their upper edges are set flush with the sidewalk, 
 so that the water can flow over them into the gutters. 
 
 The disturbing forces which the curb has to resist are: (1) 
 the pressure of the earth behind it, which is frequently aug- 
 mented by piles of merchandise, building materials, etc., 
 tending to overturn it, break it transversely, or move it bodily 
 on its base; (2) the pressure due to the expansion of freezing 
 earth behind and beneath it, especially where the sidewalk 
 is partly sodded and the ground is accordingly moist, tending 
 to thrust the curb forward; (3) the concussions and abrasions 
 caused by the traffic, the defacement and injury to the curb 
 from fires built in the gutters, and the breaking, displacing 
 and destruction resulting from posts and trees set too near 
 the curb. 
 
 The use of drain-tiles under the curb is a subject of much 
 difference of opinion among engineers. Where the subsoil 
 contains water naturally, or is likely to receive it from outside 
 the curblincs, the use of drains is of decided benefit, but 
 great care must be exercised in jointing the drain-tiles lest the 
 soil shall be loosened and removed and cause the curb to 
 drop out of alignment. 
 
 The materials employed for curbing are the natural stones, 
 as granite, sandstone, etc., artificial stone, fire-clay, and cast 
 iron. 
 
 The dimensions of curbstones vary considerably in different 
 localities, and according to the width of the footpaths: the 
 wider the path the wider should be the curb. It should, 
 however, never be less than 8 inches deep, nor narrower than 
 4 inches. Depth is necessary to prevent the curb turning over 
 
SIDEWALKS, CURBS AND GUTTERS 
 
 445 
 
 towards the gutter. It should never be in less lengths than 
 3 feet. The top surface should be beveled off to conform to 
 the slope of the footpath and the front face should be hammer- 
 dressed for a depth of about 6 inches, in order that there may 
 be a smooth surface visible against the gutter. The back for 
 3 inches from the top should be also dressed, so that the 
 flagging or other paving may butt fair against it. The end- 
 
 FiG. 239. — View Showing Expansion of Concrete Sidewalk, Chicago. 
 
 joints should be cut truly square, the full thickness of the 
 stone at the top, and so much below the top as will be 
 exposed; the remaining portion of the depth and bottom 
 should be roughly squared, and the bottom should be fairly 
 parallel to the top. 
 
 Setting curb requires care and an experienced workman, 
 
446 
 
 THE ART OF ROADMAKING 
 
 for as it is set dry, great care must be exercised to set it true 
 
 to level and line. It must be well rammed and 
 
 betting bedded or it will sink, turn slightly over or move, 
 
 even months after it has been set. Curbstones 
 
 carelessly set will never present a pleasing appearance. 
 
 Curbstones to be set in concrete should be first set and 
 blocked in position on grade and line. The blocking should 
 
 ^-4>^ 
 
 Fig. 240. — Vitrified Clay Block for Street and Road Curbing. 
 (See also Fig. 188, Chap. XV.) 
 
 Fig. 241. — Concrete Curb and Gutter. 
 
 be done with brick, paving-stones, or other imperishable 
 material. 
 
 For tamping the concrete under and around curbstones, a 
 wooden tamper made of a piece of seasoned oak 2 inches 
 by 4 inches, about 5 feet long, shod with ^-inch iron, forms 
 an excellent tool. 
 
 The concreting of the curbs (which should be done in advance 
 of the roadway concreting) is best performed by first filling 
 
SIDEWALKS, CURBS AND GUTTERS 
 
 447 
 
 underneath from the roadway side^ then upon the face and 
 'back up to the grade of the roadway; then fiUing up behind 
 ■the stones to the required height, removing all blocking as 
 the concrete is tamped in, taking care not to disturb the 
 alignment of the curb and to see that every space is filled solid 
 with the concrete. 
 
 In setting curbstones the ends should be kept from actual 
 contact, by strips of J-inch iron temporarily inserted as they 
 are set and, after the roadway concrete is laid, the joints 
 should be filled with a thin grout composed of equal parts of 
 Portland cement and sand. This should be done by first 
 
 Slapej/e -f 
 
 K - — ^4" >i 
 
 Fig. 242. — Concrete Curb and Gutter. 
 
 pressing a small amount of stiff mortar into the joints at the 
 face and back and then pouring the grout in from the top 
 until the joint is full. If these joints are not filled solid, but 
 simply smeared over the surface with a little mortar which 
 penetrates but a half-inch or less, it will only be a question 
 of a short time when it will drop off and leave a cavity between 
 the stones. 
 
 In localities where stone is not obtainable, artificial stone, 
 fire-clay curb, and cast iron afford excellent substitutes. 
 Fire-clay curbing is extensively used v^^ith brick pavements. 
 
 Cast iron cast in L-shaped sections is employed in some 
 cities in France. 
 
 In streets covered with broken stone, a stone gutter is 
 
448 
 
 THE ART OF ROADMAKING 
 
 Gutters. 
 
 necessary. It may be formed of either stone slabs or paving- 
 blocks, the latter being the better, and it should 
 be not less than 18 inches wide. If formed of paving- 
 blocks, the blocks should be laid with their length parallel 
 to the curb, bedded on gravel, and well grouted in with bitu- 
 minous cement. 
 
 When stone slabs are used, they should be not less than 
 3 feet long, 6 inches thick, and from 10 to 15 inches in width. 
 They should be laid so that they will not be of uniform width, 
 
 JFiG. 243. — Type of Concrete Curb with Slanting Outer Face. 
 
 Country Work. 
 
 Used in 
 
 otherwise the continuous longitudinal joint between the gutter 
 and the rest of the pavement will quickly wear into long deep 
 ruts or grooves, causing severe strains upon the running-gear 
 of vehicles when attempting to leave it. 
 
 The gutter should have the same slope as the roadway, and 
 the curb should show 7 inches or more above it. 
 
 In streets paved with asphalt, granite blocks, or bricks the 
 same material is used for the gutters; the blocks being laid 
 with their length parallel to the curb, instead of transversely 
 as in the street itself. 
 
 Street-crossings are formed of two or more rows of stone 
 
SIDEWALKS, CURBS AND GUTTERS 449 
 
 slabs, usually with one or more rows of paving-blocks between 
 
 them. The stone used should not be less than 
 
 3 feet long, 10 inches wide, and 6 inches thick, with rossmg 
 
 °' ' ' stones. 
 
 the top surface hammer-dressed, the ends cut to 
 
 a bevel of about 15 degrees, and dressed so as to form a close 
 
 joint for the full depth of the stone. The reason for beveling 
 
 the joints is to cause the traffic to travel across the joint 
 
 instead of along it, and thus prevent the formation of the 
 
 ruts which happens with right-angled joints. The beveled 
 
 joints must point towards the center of the intersection, 
 
 otherwise the desired result will not be obtained, and ruts 
 
 will be formed. 
 
CHAPTER XXI 
 
 MISCELLANEOUS ROADS AND PAVEMENTS 
 
 Stone trackways were used in ancient Egypt for lowering 
 the tractive resistance in moving great weights, and in 
 modern times they have been used in nearly every European 
 
 country and in America. (See p. 8.) Their use 
 trackways ^^ ^^ extensive scale has, how^ever, been abandoned 
 
 except in Northern Italy. Those in use in Italy 
 consist of two parallel lines of granite blocks, 14 inches wide 
 by 8 inches deep by 5 feet long, bedded in a layer of sand. 
 The lines are 28 inches apart, with a footway for horses be- 
 
 FiG. 244. 
 
 tween, paved with cobbles. This footway has a slight inclina- 
 tion downwards towards the center, thus serving as a channel 
 to receive the surface water, which finally escapes into the 
 sewers through stone gratings. 
 
 The steel trackways that have been constructed consist of 
 two parallel lines of steel plates, 8 inches wide, laid at a suffi- 
 cient distance apart to receive the wheels of vehicles 
 
 ^ ^^, of the standard saueie. The plates are provided on 
 
 trackways. ■ n • • i 
 
 one edge with a flange J mch wide, and on the 
 
 under side with a flange about 6 inches deep, which, when 
 
 bedded in the earth of the roadway, supports the rail without 
 
 the use of cross-ties. Tie-rods are used at intervals of about 
 
 10 feet. 
 
 450 
 
MISCELLANEOUS ROADS AND PAVEMENTS 
 
 451 
 
 The advantages claimed for the steel-track wagon road are: 
 (1) that it can be built without greater cost in most cases, 
 and probably with less cost in many cases, than any other 
 hard and durable road; (2) that it will last many times as 
 long as any other known material for road purposes and with 
 much less repair; (3) that the power required to move a 
 
 Fig. 245.— The Steel Track as a Bicycle Path. 
 
 vehicle over the steel-track road is only a small fraction of 
 the power required to move the same vehicle over any other 
 kind of road. 
 
 During 1892 a steel trackway was constructed between 
 Valencia and Grao, Spain, to replace a stone road which cost 
 So470 a year to maintain. It is traversed daily by an average 
 of 3200 vehicles, each of which pays a toll of about eight- 
 tenths of a cent, and the annual cost of maintenance is about 
 
452 THE ART OF ROADMAKING 
 
 $380, but for various local reasons this cannot be taken as a 
 guide for American practice. 
 
 In regard to durability, the claim is true only as far as the 
 steel rails are concerned, as the surface adjoining the rails, 
 whatever it may be, will in a comparatively short time, be 
 worn into ruts by vehicles turning on and off the steel 
 rails. 
 
 The most serious disadvantages of the steel trackway is 
 that if it does not have a permanent footway for the horses, 
 it is least effective in a muddy time, when it is most needed; 
 and if it does have a permanently hard surface between 
 the rails, the cost is unreasonable. If a steel trackway is laid 
 in a broken-stone road, the additional cost will be (1) the cost 
 of the metal, (2) the cost of placing the metal, including the 
 increased cost of compacting the broken stone, and (3) the 
 increased cost of maintenance. 
 
 Another objection is that owing to the narrow space between 
 the rails, the horses are compelled frequently to step upon 
 the rails, the smooth surfaces of which interfere with their 
 footing, which in a measure neutralizes the advantages of a 
 smooth track for the wheels. Still another objection is that 
 the gauge of vehicles varies considerably, and consequently 
 either the face of the rail must be very wide, which increases 
 the expense, or some vehicles cannot be accommodated. The 
 conclusion is, therefore, that trackways are out of date, that 
 they are more expensive and less effective than good macadam 
 roads, and that for a country where an ordinary macadam 
 road does not suffice, a first-class pavement or a railroad 
 should be built. 
 
 Concrete blocks have frequently been experimented with in 
 connection with trackways, but their uses for horse-propelled 
 vehicles are subject to the same, or even more serious. 
 Concrete- disadvantages, as the stone and steel trackways, 
 trackways ^^^^^^ ^^^ ^^^7 however, been successful in con- 
 nection with automobile traffic, by decreasing not 
 only the resistance, but also the wear on the road and the 
 cost of maintenance. 
 
 Fig. 246 shows a section of a concrete-block trackway built 
 
MISCELLANEOUS ROADS AND PAVEMENTS 
 
 453 
 
 Fig. 246. — Concrete-block Trackway, Orlando, Fla. 
 
 
 Fig. 247. — Reversible Concrete Block. 
 
454 
 
 THE ART OF ROADMAKING 
 
 Fig. 248. — Road Making as a Fine Art. 
 
 Laborers engaged in building a special motor-car road in Paris, each individual 
 bit of stone being carefully placed by hand. 
 
MISCELLANEOUS ROADS AND PAVEMENTS 455 
 
 near Orlando, Florida, which, in two years of continual use, 
 required no repairs. 
 
 The block is 12 inches wide, 8 inches thick, and 24 inches 
 long, with a groove 1^- inches deep and 6 inches wide at the 
 bottom, curving in a convex form to the flange on the outside, 
 the flange showing a surface of 2 inches. When laid, the 
 surface of the flange should be flush with the surrounding 
 soil. The blocks are held together with a tongue and groove 
 arrangement that keeps the ends from working up or down, 
 and the flange on the bottom of the block keeps it from having 
 any side motion, ever}^ block being thus held rigidly in position. 
 The blocks are reversible, so that when one side shows any 
 effect of wear, it can be turned over and the road given a 
 new surface. 
 
 It is claimed that heavily loaded wagons can be turned out of 
 this track road with little difficulty, without the road suffering 
 from such wear. The block are made of carefully mixed and 
 tamped concrete and can be made along the road on which 
 they are to be used, and if sand and gravel of good character 
 are near the highway, the road can be resurfaced at very 
 low cost. 
 
 Artificial granite blocks are formed from the chippings of 
 granite quarries, mixed with Portland cement in sufhcient 
 quantity to make a thorough bond between the 
 pieces. It is put down in blocks or squares, and Artificial 
 the surface is kept comparatively rough by the blocks^ 
 cement wearing below the points of the granite. 
 Its only advantage is cheapness. 
 
 In localities where timber is abundant and other materials 
 are unobtainable, planks may be employed to form pave- 
 ments. The first plank road on the continent was 
 
 built in Canada in 1S36; they then became some- ^, 
 
 . . roads. 
 
 what common m the heavily timbered portion of 
 
 the northern United States and of Canada, and were very 
 
 advantageous in the building up of new districts, but very 
 
 few of them are now in existence. 
 
 When new and when kept in repair, plank roads make a 
 
 comparatively smooth roadway possessing some advantages 
 
456 THE ART OF ROADMAKING 
 
 for both light and heavy traffic. The planks are, however, 
 very likely to be displaced, even when spiked down, and are 
 likely to be floated away, when not spiked down, and when 
 in this condition they make a very disagreeable road. Main- 
 tenance is expensive, as being alternately wet and dry, the 
 plank rots rapidly and at best does not last more than five 
 years, and often only two. 
 
 In construction, plank roads are usually about 8 feet wide, 
 and occupy one side of an ordinary earth road, the other 
 side being used to turn out upon and for travel during the dry 
 season. The method of construction most commonly followed 
 is to lay the boards perpendicular to the axis of the road, as 
 this position is more favorable to their wear and tear than 
 any other, besides being the most economical. 
 
 Their ends are not in an unbroken line, but so arranged 
 that the ends of every three or four project alternately, on 
 each side of the axis of the road, 3 or 4 inches beyond those 
 next to them. This presents a short shoulder to the wheels 
 of vehicles to facilitate their coming upon the plank surface 
 when they may have turned aside and prevents the formation 
 of long ruts at the edges of the road. Often the boards have 
 been spiked to the sills, but this is \innecessary, the stability 
 of the boards being best secured by well packing the earth 
 between and around the sills, so as to present a uniform 
 bearing surface to the boards, and b}^ adopting the usual 
 precautions for keeping the subsoil well drained and preventing 
 any accumulation of rain-water on the surface. The boards 
 were often covered with gravel, sand, or loam to protect them 
 from wear. 
 
 Corduroy, or log, roads are make-shifts employed in tim- 
 bered districts to carry a road over soft, swampy ground 
 always kept moist by springs and which cannot be drained 
 without too much expense. They are built by felling a 
 sufficient number of young trees, as straight and as uniform 
 as possible, and laying them side by side across 
 Corduroy ^^yQ road at right angles to its length. Though its 
 successive hills and hollows offer great resistance 
 to draught and are very unpleasant to persons riding over 
 
MISCELLANEOUS ROADS AND PAVEMENTS 457 
 
 it, it is nevertheless a very valuable substitute for a swamp, 
 which in its natural state would at times be utterly impassable, 
 and with sufficient care such roads may be made fairly smooth 
 when new, but they grow exceedingly rough with age. 
 
 In some of the Western States, where wood is abundant 
 and cheap, and gravel scarce, roads for light traffic have 
 been made by felling and burning the timber, and 
 covering the road with the charcoal. Poles from 
 6 to 16 inches in diameter are cut and piled lengthwise along 
 the road about 6 feet high, being 9 feet on the bottom and 
 2 on top, and then covered with straw and earth, or simply 
 with sods, and burned in the manner of coal-pits. The 
 covering is taken from the sides of the road, and the ditches 
 thus formed afford good drainage. After the timber is con- 
 verted into charcoal, the earth is removed to the side of the 
 ditches, the coal raked down to a width of 15 feet, leaving 
 it 2 feet thick at the center and 1 foot at the sides, and the 
 road is completed. The charcoal, being soft and friable, should 
 be covered with a thin layer of earth or gravel for greater 
 durability, and to prevent it from blowing or washing 
 away. 
 
 Slag and cinders from iron and copper works may be em- 
 ployed with advantage when they are procurable, and when 
 no stone sufficiently tough to withstand the action 
 of heavy traffic can be obtained. The slag from 
 modern steel furnaces is comparatively light, has a sponge- 
 like structure, and contains a large amount of lime. When 
 used for roads this variety compacts very readily and forms 
 an even and hard surface. Steel-furnace slag dust has a 
 high cementing power. 
 
 Coal-slack is sometimes used for road building where neither 
 stone nor gravel is obtainable at reasonable cost. The slack 
 is friable and easily grinds to powder, but makes 
 a fair road for light traffic. In many localities, Coal-slack 
 where there are quantities of slack, it could be 
 profitably spread upon the roads, and being light, the haulage 
 is easy. 
 
 The clinkers produced by burning street sweepings and 
 
458 
 
 THE ART OF ROADMAKING 
 
 1^ 
 
 
MISCELLANEOUS ROADS AND PAVEMENTS 459 
 
 garbage and the debris produced in the manufacture of gas, 
 consisting of the clinkers, old retorts, fire-bricks, 
 ash-pan and coke refuse, have all been tried for 
 paving both footpaths and carriageways, with some satisfac- 
 tion in the former, but in the latter with failure. The ma- 
 terials are prepared by crushing to a size of about one inch; 
 the crushed material is then screened, and the portion that 
 will not pass through a ^-inch screen is used for the top 
 finish, and the coarser portion for the foundation. The 
 materials so separated are mixed with either Portland cement 
 or coal-tar, and laid in place in the usual manner, or they 
 may be formed into blocks at a factory and shipped to the 
 place of use. 
 
 In several cities where crematories are employed for the 
 destruction of the garbage, etc., the clinker therefrom is 
 used for making concrete slabs. The clinker is 
 
 ground very fine, and mixed with Portland cement. ^^ "^"f °^ 
 ^ "^ '. , concrete. 
 
 The mass of chnker and cement is then passed 
 
 through a hydraulic press and formed into slabs 2 inches in 
 
 thickness, and are used for footpath paving under the name 
 
 of '^Destructor'' concrete. 
 
 Around the Chesapeake Bay and the Gulf of Mexico, oyster 
 shells have been used to a considerable extent to make roads 
 for light traffic. They are spread loosely over the 
 road and speedily become consolidated by the traffic. |: 
 
 The shells have a high cementing power but a very 
 low resistance to crushing, and while they make a smooth 
 road surface, it is soon ground to powder, producing a dis- 
 agreeable dust, and requiring the constant application of new 
 shells to keep it from rutting. 
 
 Pavements made from granulated cork mixed with asphalt 
 and other cohesive substances have been employed in London 
 and other European cities to deaden the noise in 
 the neighborhood of hospitals and churches. The 
 ingredients are compressed into blocks measuring 9X-i-J-X2 
 inches, which are imbedded in tar and rest upon a concrete 
 foundation 6 inches thick. 
 
 It is claimed that as a paving material it is non-absorbent. 
 
460 THE ART OF ROADMAKING 
 
 non-slippery, practically noiseless, more durable than wood, 
 perfectly sanitary, and not subject to expansion and con- 
 traction. Blocks which have been under traffic for a number 
 of years have given very satisfactory results. 
 
 Paving-bricks are made in Germany from copper slag. The 
 
 slag is run into heated cast-iron moulds having a capacity 
 
 of thirty-six bricks; immediately after filling, the 
 
 opper moulds and their contents are thickly covered with 
 
 slag. . -^ 
 
 sand and allowed to stand undisturbed for seventy- 
 two hours. When thoroughly cooled each brick is struck 
 a strong blow with a hammer, and those containing blow- 
 holes crack. 
 
 Vulcanized india rubber in large sheets of about one inch in 
 
 thickness has been used in some European cities, with excellent 
 
 satisfation. It is laid on a concrete foundation, 
 
 India finished to a smooth bed, on which the sheets of 
 
 rubber, . / . . 
 
 rubber are laid and held m place by strips of iron. 
 
 It has met nearly all the requirements of a perfect paving 
 material, being exceedingly durable, not slippery, absolutely 
 noiseless and impervious, but its cost prohibits its more 
 general use. 
 
 Rubber has been used in London on two roadways passing 
 under the hotel of the Euston terminal station of the London 
 &, Northwestern Ry. This was laid in 1881 at a cost of $5.60 
 per square 3^ard for concrete foundation and $27.10 per square 
 yard for the rubber paving, 2 inches thick. In 1902 the thick- 
 ness had been reduced by wear to -J-inch in some places and 
 1 to 1^ inches at others. Bids for new rubber paving in that 
 year were from $27.00 to 186.22 per square yard. 
 
 Artificial paving stones are manufactured in Germany from 
 a mixture of coal-tar, sulphur, chlorate of lime, glass, or 
 
 furnace slag, by mixing the tar and sulphur at 
 Artificial ^ moderate temperature and adding the chlorate of 
 stones lime. This mixture is allowed to cool, then is broken 
 
 into small fragments and mixed with fragments of 
 glass or blast-furnace slag. It is then heated to a moderate 
 temperature, placed in moulds of the desired form, and sub- 
 jected to a pressure of about 3000 pounds per square inch. 
 
MISCELLANEOUS ROADS AND PAVEMENTS 
 
 461 
 
 The advantages claimed for this material are: durability 
 equal to that of many stone roads; resistance to changes of 
 temperature; a roughness of surface which gives horses a 
 good foothold; non-transmission of sound; facility of clean- 
 ing on account of the closeness of the joints. 
 
 A roadway for heavy automobile traffic, used extensively 
 
 ^Z.l^£^^^^\ 
 
 Fig. 250. — Pavement known as "Durax." 
 
 in England and Germany is called ''Durax." It is made 
 of 3-inch irregular cubes of hard stone, laid in small 
 segments of circles. The stones are cut by ma- ^^^ 
 
 chinery, and are comparatively inexpensive, and 
 are laid without grout. It is cheap, almost as smooth as 
 macadam, comparatively noiseless, affords an excellent foot- 
 hold for horses, and is very durable. 
 
462 
 
 THE ART OF ROADMAKING 
 
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CHAPTER XXII 
 THE ROADSIDE 
 
 No matter how smooth and well constructed the travelled 
 way may be, if the roadsides are not cared for, the road, as 
 a whole, will not give a good impression. All rubbish should 
 be removed and the excavations and embankments smoothed 
 and planted with grass wherever it will grow. (See Fig. 22.) 
 Unsightly brush should be cut and grubbed out. Sometimes, 
 however, the brush and the small trees, if suitably trimmed, 
 add to the attractiveness of the roadside. 
 
 Air and sunshine are necessary for the preservation of roads 
 in good order; water and want of light are among the most 
 destructive agents in nature, and no road can be 
 kept in order which is always in a damp state and p® ges an 
 on which the sun never shines. Everything, there- 
 fore that prevents a perfect circulation and distribution of the 
 air and obstructs the revivifying effects of sunshine is to be 
 avoided. 
 
 Considered from a purely engineering point of view, there 
 is no doubt that a road would be all the better without hedges 
 and fences of any kind, but inasmuch as a barrier of some 
 kind or other between roads and the adjoining fields is 
 absolutely necessary on other grounds, e.g., to keep cattle 
 from straying from one to the other, to mark the limits of 
 property, etc., a hedge may be considered a necessary evil, 
 and the point for the consideration of the engineer is how to 
 minimize the evil. The higher and thicker the hedge the 
 more obstruction must it offer to the sun and wind. The 
 object to be borne in mind should be to erect such a barrier 
 that (1) shall allow the greatest amount of light and air to 
 pass through it, and (2) shall best answer the non-engineering 
 purposes for which it is required. 
 
 463 
 
464 
 
 THE ART OF ROADMAKING 
 
 According to 
 
 Fig. 252.— Sketch 
 of a young sap- 
 ling, often taken 
 from the woods 
 to save expense. 
 The roots ex- 
 tend long dis- 
 tances in search 
 of food, and 
 these and the 
 branches are 
 lopped off as in- 
 dicated. 
 
 these principles the best barrier would be 
 one of iron, or of iron and 
 wood combined, provided 
 that it was sufficiently strong 
 to resist being broken down 
 by cattle, horses, etc. Iron 
 wire should not be used, as 
 it is easily bent out of shape, 
 and cattle and horses are 
 very apt to injure themselves 
 in attempting to jump over 
 the fence or to force them- 
 selves through it, while 
 barbed wire is still more ob- 
 jectionable. 
 
 A strong iron fence forms, 
 perhaps, the best barrier, 
 but it is costly, and few 
 authorities would be prepared to go to 
 the expense of putting it up, especially as 
 it deteriorates with time and entails a 
 constant charge for maintenance in conse- 
 quence of the corrosion of the iron and the 
 necessity for periodically painting it. 
 
 Wood is not a suitable material for a 
 fence, as it is easily destroyed and rots 
 under the effects of the atmosphere; but, if 
 used, it should be oak or some other kind 
 which resists rot as long as possible. Most 
 kinds of wood are perfectly useless for the 
 purpose. 
 
 The commonest 
 fence in England is 
 the hedge, and its 
 almost universal use 
 is perhaps due to the 
 fact that it is cheap 
 and requires no skilled 
 
THE ROADSIDE 465 
 
 labor to maintain, but a good hedge cannot be established 
 without care in planting and constant subsequent watch- 
 fulness. 
 
 One of the first engineers who drew attention to the im- 
 portance of hedges in connection with roads was John Walker, 
 who said: 
 
 " The fences on each side form a very material and important 
 subject with regard to the perfection of roads; they should in 
 no instance be more than 5 feet in height above the center of 
 the road, and all trees which stand within 20 yards of it 
 ought to be removed, I am sure that 20 per cent of the 
 expense of improving and repairing roads is incurred by the 
 improper state of the fences and trees along the side of it, 
 on the sunny side more particularly. This must be evident 
 to any person who will notice the state of a road which is 
 much shaded by high fences and trees, compared to the other 
 parts of the road which are exposed to the sun and air. My 
 observations with regard to fences and trees apply when the 
 road is on the same level as the adjacent field; but in many 
 cases on the most frequented roads in England more stuff 
 has been removed from time to time than was put on; the 
 surface of the road is consequently sunk into a trough or 
 channel from 3 to 6 feet below the surface of the fields on 
 each side. Here all attempts at drainage or even common 
 repairs seem to be quite out of the question; and by much 
 the most judicious and economical mode will be to remove 
 the whole road into the field which is on the sunny side 
 of it." 
 
 'Mr. Law ^ in his work on "Roads,'' make some very useful 
 observations : 
 
 " Few persons are aware of the extent to which a road 
 may be injured by high hedges or lines of trees. Trees are 
 worse than hedges, because they not only deprive the road 
 of the action of the air and sun, but they further injure it 
 by the dripping of rain from their leaves, as a consequence 
 of which the road is kept in a wet state long after it would 
 otherwise have become dry. 
 
 "When fences are indispensable they should be placed as 
 far as may be from the sides of the road, and should be kept 
 as low as possible. When there is a deep ditch on either side 
 of the road it becomes necessary, to prevent accident, that 
 the fence should be placed between the road and the ditch. 
 
466 
 
 THE ART OF ROADMAKING 
 
 Fig. 253.— Type of the 
 " Undesirable Citi- 
 zen." 
 
 This represents two 
 kinds of trees — often 
 imposed upon innocent 
 customers; one kind, 
 an overgrown nursery 
 tree, passed over for 
 bome defect and gen- 
 erally sold cheaply — 
 after being ''pre- 
 pared" as shown. It 
 is first cut back so that 
 the tall, rambling top 
 may not overdraw on 
 the impaired vitality 
 of the mangled roots 
 — which have been cut 
 off near the tixink to 
 save the excavation 
 and cost of caring for 
 full roots. The other 
 kind is a young sap- 
 ling taken from the 
 woods — overgrown 
 and cut back, and the 
 roots greatly extended 
 in search of susten- 
 ance, are cut off, with 
 the effect noted. 
 
 i 
 
 Tms Tree can Never Grow a 
 Natural Characteristic Top, 
 AND WILL Disclose Many De- 
 fects IN Development. 
 
 but in other situations the fence 
 should be placed on the field 
 side of the ditch. In so doing 
 the surface draining of the road 
 into the side ditches is less 
 interfered with and the action 
 of air and sunshine is less ob- 
 structed by the fence. 
 
 ''The different descriptions of 
 fence which may be employed 
 are various. In districts where 
 stone is plentiful, and especially 
 in the immediate neighborhood 
 of quarries, where stone rubble 
 can be obtained at a trifling 
 cost, dry rubble walls, without 
 any mortar, are very good and 
 cheap and require little or no 
 repair. 
 
 ''For the road itself, an open 
 post-and-rail fence is the best 
 which can be employed, because 
 it scarcely impedes the action of 
 the wind and the sun upon the 
 surface of the road, but the great 
 practical objection to timber 
 fences is their liability to decay, 
 which occasions frequent and 
 constant expense for renewal. 
 
 " The most common, and, all 
 things considered, the most use- 
 ful fence is the quickset hedge. 
 If properly planted and care- 
 fully attended to for 
 the first few years, a 
 natural fence may be 
 obtained sufficiently 
 strong to resist the 
 efforts of cattle to 
 break through, and 
 very economical in cost 
 for maintenance. A 
 bank or mound of 
 earth at least 2 feet 
 in depth should be 
 
THE ROADSIDE 467 
 
 prepared for the reception of the quicks, which should be three 
 years' plants which have been transplanted two years. The 
 best kind of soil is one of a light sandy nature admitting 
 sufficient moisture to nourish the plants and retaining moisture 
 in dry seasons. Heavy clay soils are not sufficiently pervious 
 to water, and plants placed in such soils are never found to 
 thrive. A mixture of rotten leaves is of great use and causes 
 the plants to grow with much vigor. The quicks are most 
 commonly planted in a single row, at distances of about 
 4 inches apart. But a much better hedge is formed by plant- 
 ing them 6 inches apart in a double row, as shown below, with 
 a space of 6 inches between the rows, 
 
 
 
 
 
 and so arranged that the plants in one row are opposite the 
 spaces in the other. By this arrangement, although the 
 plants are realty not so crowded, and have more space around 
 their roots from which to derive nourishment than in a single 
 row, they form a thicker hedge. The proper time for planting 
 quicks is during the autumn or the spring, and, in fine seasons, 
 the operation may be continued during the whole winter. 
 A temporary fence should be put up to protect the 3'oung 
 plants from injury, and the fence should be retained until the 
 hedge has attained sufficient strength to require its prptection 
 no longer — a period, under favorable circumstances, of three 
 or four years -after the quicks are planted. That the plants 
 may thrive they must be carefully attended to at first, and it 
 is essential that they should be properly cleaned and weeded 
 at least twice every year. Once every year toward the end 
 of the summer the hedge should be judiciously trimmed, not 
 to such an extent as to produce stunted plants, but by merely 
 cutting off the upper and more straggling shoots, so as to 
 bring it to a level and even surface. By proceeding in this 
 manner, a neat, strong, and compact hedge of healthy plants 
 will be obtained in about three years after planting." 
 
 Trees, however much they may add to the picturesqueness 
 of a road, add still more to the difficulty of keeping it in repair; 
 
 and thick avenues, i.e., trees planted close to each 
 
 ■ • • Trees 
 
 other on both sides of a road, are quite incom- 
 patible with the due preservation of the surface. The evil is 
 worse the narrower the road is, for then very little sunshine 
 can get to the road at all, so that the macadam is constantly 
 damp and wears away much more rapidly under traffic. 
 
468 
 
 THE ART OF ROADMAKING 
 
 " As to the desirability of 
 trees on roads and streets, 
 some claim that they do 
 more harm than good; that 
 they impede the circulation 
 of the air, and that, as 
 for the shade they afford, 
 people who do not hke 
 sunshine have only to keep 
 on the shady side of the 
 way; that they deprive the 
 road surface of the drying 
 action of the sun and air, 
 and that in wet weather 
 the constant dropping of 
 water from their branches 
 keeps the road in a muddy 
 state. Others claim that 
 trees, especially in streets, 
 temper the heat and serve 
 as a protection against 
 dust, that the evaporation 
 from their leaves tends to keep the sur- 
 rounding air cool and moist; that the 
 perpetual vibration of their foliage and 
 swaying of their branches, whilst admit- 
 ting a sufficient amount of light, serve 
 to protect the eyes from the noonday 
 glare; that they act as disinfectants by 
 drawing up and absorbing the organic 
 matters contained in the filth from which 
 the streets of a town are never free and 
 which, infiltrating the ground, are a fre- 
 quent cause of fevers and infection; and 
 it is asserted that on soil 
 roads some varieties of 
 trees both drain the road 
 and help to hold its 
 earthen surface together 
 by their root fibers." * 
 
 All trees that are orna- 
 mental , o r that have 
 
 Fig. 254. — Sketch of Type of Desirable Genehal ^ ■d,„„ j„ "'T'^„«+;^« «« ni^u 
 Characteristics of a Young Tree. * Byrne S Treatise on Hlgh- 
 
 2i to 3 in. in diam. way Construction," p. 727. 
 
 Specification for Street 
 Tree. 
 The tree sh'all be a 
 nursery-grown tree — 
 sound, straight stem- 
 clear 7-8 ft. with well- 
 balanced natural 
 grown head on top; 
 roots full — compact 
 and fibrous. Such roots 
 afford the greatest 
 amount of feeding 
 function . Pruning and 
 in cutting — defer till 
 planting, and after- 
 wards — when under 
 proper hands, its nat- 
 ural form, etc., may be 
 assured. 
 
 ^U.M,r. Alff.JL 
 
 .../A#^//.i//zii/:' 
 
THE ROADSIDE 469 
 
 value as shade trees, should be preserved and protected, 
 unless they grow so closely that they make too dense a 
 shade. In hot, dry climates, particularly, and, indeed, in 
 most places, trees are a considerable factor in reducing the 
 cost of maintenance, since they lessen the evaporation of the 
 moisture from the macadam. In exposed places where the 
 sweep of the wind would be otherwise unbroken, they serve to 
 prevent in a measure the blowing away of the binder from the 
 road surface. Unfortunately, in such places it is often difficult 
 to make trees grow. 
 
 Care in the selection of the kinds of trees best suited to the 
 locality is important. In Massachusetts, sugar, Norway and 
 white maples and American elms have been set out to a con- 
 siderable extent along the state roads with satisfactory 
 results. These trees grow fast and at the same time are 
 fairly long lived. 
 
 Trees should be selected with reference to the climate, 
 locality, quality of soil, extent of space, and circumstances 
 of surroundings in general. 
 
 Large-growing varieties should be selected for ^ ^ ^'^^ 
 places of great extent, smaller varieties for places of 
 less extent. A low compact tree is not suitable for street 
 planting. 
 
 The qualities necessary in a good street tree are that it 
 must be hardy, must not be affected by a long-continued 
 drought, heat must not wither it nor make it look rusty; it 
 must be able to withstand dust, smoke, soot, foul air, and the 
 insidious attacks of insects, and be able to recover from any 
 malicious or accidental injury it may receive. 
 
 The tree must be of rapid growth and develop a straight, 
 clean, stem with shady foliage. It must be graceful either 
 in full leaf or when bare, as in winter; its roots must not 
 require too much room, and they must be able to withstand 
 the effects of pollution or rough treatment. 
 
 Whatever variety of tree is selected, the following precautions 
 should be taken to insure its flourishing: 
 
 1. The young tree should have been well nourished in the 
 nursery; it should .nat be planted on the street until its stem 
 
470 THE ART OF ROADMAKING 
 
 is over S feet in height and about 3 inches in diameter. The 
 stem should be clean and straight^ and the whole tree sym- 
 metrical. 
 
 2. The ground where a tree is to be set should be suitable 
 for tree growth. If it is not, all poor material should be 
 removed and good soil substituted. The amount to be re- 
 moved depends upon circumstances and can be determined 
 by examination. A tree to flourish must have plenty of good 
 ground in which to grow; it should be good to the depth of at 
 least 3 feet, and an equal distance in all directions from the 
 trunk when practicable. The amount of good soil is of greater 
 importance than the shape it is in. The further the tree is 
 planted from the curb the better, so as not only to give it a 
 larger body of soil, but to lessen the risk of killing the tree 
 by the pollution of the ground with gas from defective pipes 
 and also excess of moisture from the gutters. 
 
 Trees should be placed so far from one another that at 
 maturity they will not meet. Such distances will enable them 
 to develop in their natural beauty. To determine 
 the proper distance apart measure the spread of 
 full-grown trees of the same variety as those to be planted; 
 it will vary from 30 to 50 feet. The trees should alternate 
 on opposite sides of the street. AYhere streets cross at right 
 angles or nearly so, two trees of large-growing varieties may be 
 placed on each corner, far enough from the corner of the curb 
 not to interfere with the catch-basin when there is one. Each 
 tree should be placed on the tree line of one street and the 
 fence line of the other; this will require eight trees to every 
 intersection. The trees so planted should form a handsome 
 mass of foliage and afford an agreeable shade where most 
 needed. At some intersections it may not be possible to plant 
 all the eight trees, but as many as can should be placed. 
 Each tree should be protected with a light iron railing to 
 prevent damage to the trunk from cutting or otherwise. 
 
 A good arrangement along roadsides for trees with large 
 tops is to set them about 50 feet apart on each side, but 
 alternated so that there be a tree for every 25 feet along the 
 road. 
 
THE ROADSIDE 471 
 
 The Tree-planting Association of New York * has endeavored 
 to interest property owners to plant street trees in the city 
 streets, etc., and, despite lack of cooperation on the part 
 of the city authorities, it has had some success. ■ 
 Several years ago the Tree-planting Law passed the ^^^^' 
 legislature, by which the control of street planting Association, 
 and the care of existing trees outside of the parks, 
 was placed under the park commissioner. The conditions 
 prescribed by the park department under which tree planting 
 must be carried on in the city embody mtiny restrictions 
 which tend to discourage the enterprising property owner 
 in the work of adorning and improving his own property and 
 benefiting his neighbor and the public at the same time. 
 
 City trees in New York are limited in varieties by the park 
 department to the maples, the elms, the planes, the lindens — 
 pin oak mainly. The poplars (the Cardicia poplar in some 
 respects quite desirable) are interdicted. Of the maples, the 
 Norway, sugar, white, scarlet, etc.; of the elm, the English, 
 American (most graceful of tree form), the Dutch, the Hunting- 
 don; of the lindens, the American or European, etc. The 
 Cardicia poplar is a lusty, quick grower with clear bright 
 foliage seldom afflicted with insects, but ages early and the 
 wood is brittle. Trees like the sugar maple, the American 
 elms, the plane,- require the wider roadways, as too much 
 incutting spoils characteristic growth of the larger trees. 
 In the city, one of the requirements as to pit is almost pro- 
 hibitory, namely, soil equal to 3 cubic yards. It is difflcult 
 to provide such an exacvation in many places and with the 
 necessary soil, and the usual opening in the flagging or con- 
 crete walk of a round or square space, brings up the cost of the 
 tree, the planting, and the ground to between from $22 to $30. 
 
 * Secretary, Joseph L. Delafield, 35 Nassau Street, New York City. 
 
APPENDIX I 
 
 SPECIFICATIONS AND CONTRACTS* 
 
 Between the individual or corporation desiring the work done and 
 the contractor who performs it, stands the engineer who has designed 
 it and who usually superintends its execution. He is in the employ 
 of the persons promoting the enterprise, and it devolves upon him to 
 make sure that those who retain him receive an honest and fair return 
 for their money. 
 
 In order that the contractor may understand the scope of the work 
 to be performed and the details of its construction, written descriptions 
 and plans more or less complete, defining the methods of construction, 
 material, etc., to be used, are prepared by the engineer for the approval 
 of the company having the work done and for the guidance of the con- 
 tractor. These written documents are the Specifications, and together 
 with the Contract, of which they form a part, they fix definitely the 
 relations that shall subsist between the company or corporation and 
 the contractor. 
 
 No matter how simple a structure may be, there must be a plan, if 
 it is to be constructed intelligently and efficiently. As the size and 
 importance of the structure increase, the plan becomes more and more 
 complex, and hence the greater necessity for putting it in some fixed 
 and definite form which conveys the exact idea existing in the mind of 
 the engineer. To secure the proper execution of the work of any magni- 
 tude, specifications are absolutely necessary, and they should be prepared 
 with great care and exactness. t 
 
 Theoretically, three general classes of engineering specifications may 
 be noted. In the first the aim of the engineer is to specify the end or 
 result that it is desired to secure, leaving the contractor free to originate 
 and follow the methods by which these results are to be attained. In 
 the second the engineer aims to secure the desired end, by specifying in 
 
 * Condensed from Waddell and Wait's "Specifications and Contracts," and Whinery's 
 *' Specifications for Roads, Streets, and Pavements." 
 
 *}■ In addition to their value as memoranda and aids in preparing specifications 
 for a particular project, carefully prepared general specifications, embodying the 
 latest approved practice, sometimes supply the must useful and acceptable brief 
 treatises upon any particular branch of engineering work. 
 
 473 
 
474 THE ART OF ROADMAKING 
 
 detail the materials and the methods which in his opinion will accomplish 
 the purpose, he himself assuming responsibihty for the results. Either 
 of these two classes of specifications is permissible, and the engineer may- 
 choose the one which in his opinion seems best adapted to the character 
 of the work to be done, and the conditions under which it must be 
 prosecuted. 
 
 In the third class of specifications, met with more frequently than 
 they should be, the engineer undertakes to prescribe not only the char- 
 acter of the materials to be used and the methods to be pursued, but also 
 the results to be attained. The position thus assumed is illogical, and 
 often unreasonable, and may lead to complications between the engineer 
 and the contractor. If a contractor be required to turn out a product 
 which shall conform to certain standards, he may properly be given 
 much, if not full, latitude, as to how the stipulated results shall be secured, 
 and may be held fully responsible for the outcome; if on the other hand 
 the engineer chooses to specify with more or less minuteness the character 
 of the materials to be used and the methods of construction to be followed, 
 and enforces compliance therewith, it seems fair and just that he should 
 assume responsibility for the results produced, and therefore unfair to 
 hold the contractor to responsibility for consequences arising from the 
 use of materials and methods which he was allowed no choice or latitude 
 in selecting. 
 
 In street paving work, of well known and standard character, the 
 second class of specifications seems preferable for a number of reasons, 
 the leading one being that the time required to develop the good or bad 
 quality of the work must usually exend over a. considerable number 
 of years, and the conditions to which the pavement may be subjected 
 in the meantime are likely to vary so widely that it may be very difficult, 
 if not impossible, to prescribe a satisfactory standard of service and 
 endurance. Disputes are therefore liable to arise between the munici- 
 pality and the contractor as to the latter's liability, or conditions may 
 make it difficult or impossible to hold the contractor to strict account 
 for that liability. 
 
 For convenience of reference and for clearness, specifications are usually 
 divided into clauses, which may be classed as "general" and "specific.'* 
 General clauses refer to the business relations that shall exist between 
 the parties to the contract. In them is found the general description 
 of the work as a whole without any particular reference to details. Times 
 and methods of making payments, adherence to specifications, inspection, 
 and other analogous headings make up their subject matter. They 
 should be comprehensive in their scope, and should not contradict one 
 another. It is well to avoid a double description of any particular 
 thing, as contradictory clauses are sure to be a stumbling block that 
 will create friction and cause delay. At first glance one would say that 
 such clauses are easily eliminated, but care is necessary to accomplish 
 this. 
 
SPECIFICATIONS AND CONTRACTS 475 
 
 Specific clauses have to do with the details of construction and the 
 description of the particular features of design. They embody the special 
 ideas that the engineer wishes to incorporate in the work, and they should 
 be just as minute in detail as is requisite to set forth the exact plan 
 desired. Detailed drawings may be necessary to indicate clearly just 
 what is to be done, and these drawings either should be prepared before 
 the specifications are written, or at least should be sufficiently matured 
 in the mind of the engineer to enable him to write his specifications in 
 accordance with them. 
 
 The ideal specification is one that furnishes a wholly sufficient guide 
 to the accomplishment of the desired purpose; that provides for every 
 possible contingency which may arise, and is couched in language which 
 not only means exactly what it was intended to mean, but is incapable 
 of any other interpretation. It is needless to say, however, that no 
 example of such a specification can be instanced as a model, as the 
 engineer is, in common with all men, fallible, and he can hardly hope, 
 in the preparation of specifications, to make them perfect; to cover 
 every item and particular; or to escape some ambiguities of expression, 
 and some degree of indefiniteness. 
 
 Specifications should look to the accomplishment of an end rather 
 than to the means of its attainment, and it must be remembered that 
 under these circumstances the contractor cannot be held responsible 
 for the mistake of the engineer. 
 
 The specifications form a part of the contract, and when the latter is 
 signed, the contractor agrees to all the conditions they set forth. It is 
 proper to assume that he has read the specifications and is familiar with 
 their requirements, and he signs the contract and makes his bond with 
 the full knowledge of what is before him. 
 
 The dividing line between the specifications and contracts is most 
 difficult to draw, for in any particular case two engineers will rarely 
 agree as to what clauses pertain properly to the specifications and what 
 to the contract. The preference is to throw as much of the matter as 
 possible into the specifications and reduce the size of the contract proper 
 to a minimum, avoiding repetition of statement in the two parts of the 
 work, but of necessity treating certain subjects in both parts, though 
 from different point of view. All clauses that relate to methods of 
 construction, qualities of materials, character of the work, rules limiting 
 the functions and powers of the contractor and defining the authority 
 of the engineer, directions to bidders, and transportation of men and 
 materials, unquestionably belong to the specifications; alterations of 
 plans, damages, extras, payments, responsibiUty for accidents, the 
 spirit of the specifications, strictness of inspection, liquidated damages, 
 scope of the contract, and time of completion might perhaps be properly 
 inserted in either division, but it is customary to include all of 
 these clauses and others of like character and scope, in the specifica- 
 tions. 
 
476 THE ART OF ROADMAKING 
 
 The following general clauses and enumeration of specific clauses, 
 will give an idea of the ground covered by a thorough set of specifications:* 
 
 For Grading and Paving, or Repaying 
 
 with Pavement . 
 
 on a Foundation, the Roadway 
 
 of 
 
 Street, from 
 
 to 
 
 together with all work incidental thereto. 
 
 General Description of Work. The work embraced in and to be 
 done under this contract consists of grading the entire street from curb 
 to curb between the limits named, including the removal or readjust- 
 ment of the pavement now on the roadway, setting and resetting curbing, 
 laying or relaying sidewalks where required, furnishing all neW material 
 and performing all the labor required for paving the roadway, together 
 with all incidental work necessary to complete the whole in a proper 
 manner, in accordance with the contract, the plans on file in the office 
 of the city engineer, these specifications and the instructions of the city 
 engineer, herein referred to as the engineer, or his authorized agents. 
 
 References. The numbered divisions of these specifications are 
 herein designated as "sections," each being referred to by the number 
 standing at its beginning. 
 
 The plans and drawings relating to this work, on file in the office of 
 the city engineer are designated as 
 
 Authority, 1. Wherever, in these specifications, the words, the City 
 are used, they shall be understood to refer to the duly constituted munici- 
 pal government of the city of 
 
 or its authorized agents, acting within the authority specifically conferred 
 upon them by the said municipal government-t 
 
 Wherever, in these specifications, the words, the engineer, shall be 
 used, they shall be understood to refer to the city engineer of said city, 
 or his deputies or assistants acting within the authority conferred upon 
 them by the city engineer. 
 
 But no agent of the city shall have power to revoke, alter, enlarge 
 or relax the stipulations or requirements of these specifications, except 
 in so far as such authority may be specifically conferred in or by the 
 specifications themselves, without the formal authorization so to do, 
 conferred by ordinance, resolution or other usual official action of the 
 city.t 
 
 Interpretation. 2. In case of any actual or alleged disagreement 
 or discrepancy between the contract, these specifications, and the plans 
 for the work on file in the office of the engineer, the language and pro- 
 visions of the contract shall take precedence and prevail; and the engineer 
 
 * From "General Specifications for Roads, Streets, and Pavements," by S. Whinery, 
 1907. 
 
 t In specifications to be used in any particular city the official name of the city 
 government, as the City Council, the Commissioners of Public Works, etc., should 
 be used instead of this general designation. 
 
 I Such a proviso as this seems proper in justice to both the city engineer and the 
 contractor; the former should not be held repsonsible for the acts of his assistants 
 when they should transcend the authority conferred upon them, and the latter should 
 be put upon his guard with reference to requirements which he is not satisfied are 
 eanctioned or approved by the city engineer. 
 
SPECIFICATIONS AND CONTRACTS 477 
 
 shall determine in each case whether the specifications or the plans shall 
 be followed. 
 
 Quality of Material and Work. 3. The judgment and decision 
 of the engineer as to whether the materials supplied and the work done 
 under this contract comply with the requirements of these specifications, 
 shall be conclusive and final. No material shall be used in the work 
 until it has been examined and approved by the engineer, or his author- 
 ized agents. All rejected material must be promptly removed from 
 the work and replaced with that which is acceptable to the engineer, 
 and all improper or defective work must be corrected, and, if necessary, 
 removed and reconstructed so as to comply with these specifications 
 and the instructions of the engineer. 
 
 Inspection. 4. The engineer may provide for the inspection, by 
 assistants and inspectors under his direction, of all materials used and 
 all work done under this contract. Such inspection may extend to all 
 or any part of the work, and to the preparation or manufacture of 
 materials to be used, whether within the limits of the work on the street, 
 or at any other place. The engineer and his inspectors shall have free 
 access to all parts of the work, including mines, quarries, manufactories, 
 or other places where any part of the materials to be used is procured, 
 manufactured or prepared. The contractor shall furnish the engineer 
 all information relating to the work' and the material therefor which 
 the engineer may deem necessary or pertinent, and with such samples 
 of materials as may be required. The contractor shall, at his expense, 
 supply inspectors with such labor and assistance as may be necessary 
 in the handling of materials for proper inspection. Inspectors shall 
 have authority to reject defective material and to suspend any work 
 that is being improperly done, subject to the final decision of the engineer. 
 Inspectors shall have no authority to permit deviations from, or to 
 relax any of the provisions of these specifications without the Avritten 
 permission or instruction of the engineer; nor to delay the contractor 
 by failure to inspect materials and work with reasonable promptness. 
 
 The payment of any compensation, whatever may be its character 
 or form, or the giving of any gratuity, or the granting of any valuable 
 favor, by the contractor to any inspector, directly or indirectly, is strictly 
 prohibited, and any such act on the part of the contractor will constitute 
 a violation of these specifications.* 
 
 Injuries to Persons and Property. 5. The contractor shall be 
 held alone responsible for all injuries to persons, and for all damages 
 to the property of the city or others, caused by or resulting from the 
 negligence of himself, his employees or agents, during the progress of, 
 or connected with the prosecution of the work, whether within the limits 
 of the work, or elsewhere. He must restore all injured property, including 
 sidewalks, curbing, sodding, pipes, conduits, sewers and other public 
 or private property to a condition as good as it was when he entered 
 upon the work. 
 
 Sanitary Conveniences; Nuisances. 6. The contractor shall pro- 
 
 * It may be objected that this requirement is unusual and unnecessary, since sucli 
 practices are recognized as wrong, and as presumptive of fraud and malpractice on 
 the part of both of the contractor and the inspector. It cannot, however, be denied 
 that in many cities such means are employed by contractors to unduly inflence the 
 action of inspectors and that not Infrequently the latter not only accept, but per- 
 sistently demand, valuable considerations from the contractor. Silence of the 
 specifications on this point cannot, of course, be construed into consent, but there 
 is no good reason for the silence. There should be left no excuse for misconception 
 of the position of the city or of the engineer upon this point. 
 
478 THE ART OF ROADMAKTNG 
 
 vide all necessary privy accommodations for the use of his employees 
 on the street, and shall maintain the same in a clean and sanitary con- 
 dition. He shall not create nor permit any nuisance to the public or 
 to residents in the vicinity of the work. 
 
 Public Conveniencs. 7. No material, or other obstruction shall 
 be placed within five feet of fire hydrants, which must be at all times 
 readily accessible to the fire department. 
 
 During the progress of the work the convenience of the public and of 
 the residents along the street must be provided for as far as practicable. 
 Convenient access to driveways, houses and buildings along the street 
 must be maintained wherever possible. Temporary 'approaches to 
 and crossings of intersecting streets and sidewalks must be provided 
 and kept in good condition, wherever practicable. 
 
 Barriers, Lights, Watchmen. 8. The contractor shall provide 
 and maintain such fences, barriers, "street closed" signs, red lights, 
 and watchmen as may be necessary to prevent avoidable accidents to 
 residents and to the public. 
 
 Disorderly Employees. 9. Disorderly, intemperate, or incompetent 
 persons must not be employed, retained, or allowed upon the work. 
 Foremen or workmen who neglect or refuse to comply with the instruc- 
 tions of the engineer, shall, at his request, be promptly discharged, and 
 shall not thereafter be re-employed without his consent. 
 
 Order and Progress op Doing Work. 10. The work under this 
 contract shall be prosecuted at as many different points, at such times, 
 and in such sections along the line of the work, and with such forces as 
 the engineer may from time to time deem necessary, and direct, to 
 secure its completion within the contract time. Not more than one 
 thousand (1,000) linear feet of the street shall be torn up, obstructed or 
 closed to travel at any one time without the written permission of the 
 engineer. Completed portions of the pavement shall be opened to 
 travel as directed by the engineer, but such opening shall not be construed 
 as an acceptance by the City of the work done. Where thus opened to 
 public travel by the direction of the engineer, the contractor will not 
 be held responsible for injuries to the work caused by such travel or 
 public use, pending the final completion and acceptance of the whole 
 work. 
 
 Measurement and Estimates. 11. Final estimates will be based 
 upon the actual quantities of completed and accepted work, customary 
 or conventional methods of measurement and computation to the con- 
 trary notwithstanding. 
 
 Grade and Contour op Pavement. 12. Roadway pavements shall 
 be laid to such grades, crown and contour of surface as the plans may 
 show or the engineer may direct, and the surface of the completed pave- 
 ment shall conform accurately to such grades, crown and contour. The 
 designed surface of the completed pavement shall be considered as the 
 datum or plane of reference in fixing the location or level of the sub- 
 grade, of the pavement foundation, and of structures connected there- 
 with. It will be hereafter referred to in these specifications as "the 
 pavement datum." 
 
 City Monuments or Stakes. 13. The contractor must carefully 
 protect from disturbance or injury all city monuments, stakes and bench- 
 marks, and shall not excavate nearer than five feet to any of them 
 without the permission of the engineer; or until they have been removed, 
 witnessed, or otherwise disposed of by the engineer. 
 
 Old Material. 14. All material or structures removed from the 
 street and not required for the new construction, but which the city 
 may desire to reserve, shall be delivered and neatly piled up in a corpora- 
 
SPECIFICATIONS AND CONTRACTS 479 
 
 tion yard or elsewhere, by the contractor, as the engineer may direct. 
 Such reserved material shall be considered in the custody of the contractor 
 until delivered at the place designated, and he will be held responsible 
 for its care and protection, and must make good any losses occasioned 
 by damage, theft, or misappropriation while it is on the street or en 
 route to the place of storage. If the contractor shall be required to haul 
 such reserved material more than one-half mile, he shall be paid a reason- 
 able price, to be agreed upon in advance, for the haul exceeding that 
 distance. 
 
 Material taken from the work which is to be used in the new construc- 
 tion shall be compactly piled where it will least obstruct the sidewalks 
 or adjoining sections of the street, and properly protected by the contractor 
 until it is required for use. 
 
 All old material removed from the work, including the material excavated 
 in preparing the sub-grade, not reserved by the city nor to be used again 
 in the work, shall belong to the contractor and must be removed by him 
 from the street as promptly as possible. It must not be placed on the 
 sidewalks or adjacent streets, nor on any other street or property belong- 
 ing to the city, nor on the property of private owners, without the written 
 consent of the engineer, or the owner of the property. 
 
 Storage of New Material. 15. The material for construction when 
 brought upon the street shall be neatly piled so as to cause as little 
 obstruction to travel as possible, and so that it may be conveniently 
 inspected. 
 
 Rebuilding and Adjusting Street Structures. 16. Catch basins, 
 manhole, sewer and water frames and covers, sewer inlets, water pipes 
 and other conduits, belonging to the city and within the limits of the work, 
 shall, if necessary, be reset to the new lines and grades of the street and 
 for this purpose good brick masonry of the original thickness, laid in 
 Portland cement mortar shall be used. Great care must be taken to 
 set all such structures as project through the pavement exactly to the 
 grade and contour of the new street surface, and any defects in the 
 conformity of such structures to the pavement datum, discovered at the 
 time, or during the progress of the work, or during the guaranty period, 
 stipulated in Sec. 108,* shall be promptly remedied by the contractor. 
 
 Noiseless Manhole Covers. 17. Asphalt-filled noiseless covers, 
 complete, for water and sewer manholes, of approved design, shall be 
 furnished and set by the contractor wherever directed by the engineer. 
 They shall be made according to general plans and details furnished 
 by the engineer, and of such dimensions as to properly fit their frames. 
 
 Clean Sidewalks. 18. During the progress of the work, the side- 
 walks and portions of the street adjoining the work, or in its vicinity, 
 must not be obstructed or littered more than may be absolutely necessary, 
 and the adjacent sidewalks must be kept clean. 
 
 Final Cleaning Up. 19. Immediately after the completion of the 
 work or any consecutive portion of it, the contractor shall remoA-e from 
 it all unused material, refuse and dirt placed by him on or in the A'icinity 
 of the work, or resulting from its prosecution, and restore the street to 
 a condition as clean as before the work was begun; and the new pave- 
 ment shall be properly cleaned. 
 
 Incidental Work at Contractor's Expense. 20. All the work 
 to be done by the contractor, specified and enumerated in sections 3 4 
 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18 and 19, as well as any minor 
 details of work not specifically mentioned in the specifications, but 
 obviously necessary for the proper completion of the work, shall be 
 
 * See page 481. 
 
480 THE ART OF ROADMAKING 
 
 considered as incidental, and as being a part of and included with the 
 work for which prices are named in the contract. The contractor will 
 not be entitled to any extra or additional compensation therefor. 
 
 Extra Work. 21. The city may require the contractor to furnish 
 such additional materials and to do such additional work, not provided 
 for in the contract and these specifications, but which may be found 
 necessary or pertinent to the proper prosecution and completion of the 
 work embraced in the contract, at prices to be agreed upon in writing, 
 in advance. But no work other than that included in the contract and 
 these specifications and which is covered by and to be paid for at the prices 
 named in the contract, shall be done by the contractor except upon a 
 written order from the engineer. In the absence of such written order 
 from the engineer the contractor will not be entitled to payment for any 
 such additional or extra work. 
 
 Curbing to be Completed in Advance. 22. The setting of all new 
 curbing and guttering and the redressing, resetting or readjustment of 
 all old curbing must be completed at least 100 feet in advance of the 
 construction of the street foundation. 
 
 Preparing the Sub-Grade. 23. The whole area to be occupied by 
 the pavement and its foundation shall be excavated to a sub-grade at 
 such a depth that after being compacted by the roller, the surface will 
 
 be inches below the pavement datum, and truly parallel 
 
 thereto. In excavating, the earth must not be disturbed below the 
 sub-grade. Plowing will not be permitted where the depth of earth to 
 be removed is less than six (6) inches, and in no case must the plow be 
 allowed to penetrate to within less than one inch of the sub-grade. 
 Places that are found to be loose, or soft, or composed of unsuitable 
 material, below sub-grade, must be dug out and refilled with sand, or 
 other material as good as the average of that found on the street. After 
 the excavation is completed and the surface neatly trimmed, the whole 
 area shall be well compacted by rolling with a roller weighing not less than 
 five tons. Areas inaccessible to the roller shall be rammed until they 
 are as well compacted as the rolled surface. When the rolling is completed 
 the surface must be nowhere more than three-fourths inch below, nor 
 more than three-eighths inch above the true sub-grade. If, after the 
 rolling is completed and before the pavement foundation is laid, the 
 surface shall become disturbed in any way, it must be replaced and properly 
 compacted. 
 
 Where the natural surface of the ground shall be below the sub-grade, 
 or shall become so by the removal of old pavement or other structures, 
 it must be filled to the sub-grade in layers not exceeding five inches in 
 depth, and each layer shall be thoroughly rolled or rammed before the 
 next layer is placed upon it, and when the filling is completed the filled 
 area must be properly trimmed and compacted by rolling or ramming 
 to the true sub-grade, as in excavation. The material excavated from 
 the street may be used for such fiUing, provided it be of suitable quality. 
 Where it cannot be thus procured from the street it must be obtained 
 by the contractor elsewhere, in which case the actual quantity so obtained, 
 measured after it is compacted in the street, will be paid for at the 
 contract price for "earth filling." The price bid for "earth excavation" 
 will be paid for all material excavated above the sub-grade, measured 
 in place on the street, which price includes the cost of disposing of the 
 excavated material, whether as waste or filling, and of trimming and 
 rolling or ramming the sub-grade, and of making it ready for the pave- 
 ment foundation. 
 
 Where the soil composing the sub-foundation is found to be wet or 
 "springy," a system of soft tile drains, discharging into the street drainage 
 
SPECIFICATIONS AND CONTRACTS 481 
 
 system, shall be constructed by the contractor, as directed by the 
 engineer. The tile shall be laid in trenches about one foot wide and 
 from one to two feet deep. After the tile is in place the trenches shall 
 be filled with compacted crushed stone or gravel. The tile will be paid 
 for at the contract prices for the same, which shall include the cost of 
 excavating and filling the trenches. 
 
 Then follow specific clauses covering all details in regard to foundations, 
 laying the pavement, etc.^ according to the special form of structures used. 
 
 Guaranty.* 24. The contractor shall guarantee that all the materials 
 used and all the work done under this contract shall fully comply with 
 the requirements of these specifications, the plans hereinbefore referred 
 to and the instructions of the engineer. Any defects in the completed 
 work, or any part of it, or any failure of the work to fully perform or endure 
 the service for which it was intended, which, in the opinion of the engineer, 
 are attributable to the use of materials, skill, or workmanship not in 
 compliance with the said specifications, plans and instructions, that may 
 
 appear in the work, or any part of it, within a period of 
 
 years after the date of the certificate of completion and acceptance, shall 
 be regarded as prima facie and conclusive evidence that the contractor 
 has failed to comply with the said specifications, plans and instructions. 
 And the contractor shall, at his own expense, at such time and in such 
 manner as the engineer may direct, repair or take up and reconstruct 
 any such defective work, in full compliance with the original specifications, 
 plans and instructions. And as surety for the performance of this 
 guaranty the contractor's bond, required by the contract, shall remain 
 
 in full force until the expiration of the period of 
 
 years above stipulated in this section. 
 
 The importance of drafting contracts properly cannot well be over- 
 estimated. An incorrectly drawn agreement is almost certain to involve 
 serious trouble and often pecuniary loss to an innocent party; hence it 
 behooves the engineer to study thoroughly and fundamentally the science 
 or art of contract writing. But before he can draft ix contract, he must 
 have clearly in mind a full and well-defined idea of all the conditions 
 and desiderata, and he should epitomize these systematically before 
 beginning to write. It is advisable to keep constantly in view the 
 possibility that each party to the contract may be unscrupulous and 
 willing to take every possible advantage of every weakness which the 
 contract may contain and which will tend to his own profit. 
 
 The essential elements of any contract, according to Mr. John Cassan 
 Wait,t the noted authority, are as follows: 
 
 "1. Two parties with capacity to contract. 
 
 "2. A lawful consideration — a something in exchange for its legal 
 equivalent, a quid pro quo. 
 
 * These specifications are designed to secure the construction of the pavement 
 in a proper manner, the city assuming responsibiUty for the character and utiUty 
 of the work. The guaranty here proposed is therefore intended to cover only a proper 
 compliance with the specifications, for which the contractor may properly be held 
 responsible, and not the sufficiency or utility of the work, if constructed according 
 to the specifications. The period of guaranty should therefore be short, not exceed- 
 ing two years, 
 
 t "Engineering and Architectural Jurisprudence." 
 
482 THE AET OF ROADMAKING 
 
 "3. A lawful subject-matter, whether it be a promise, an act, or a 
 
 material object. 
 "4. Mutuality — a mutual assent, a mutual understanding, a meeting 
 
 of the minds of the parties.*' 
 Without these four elements no contract is binding in law. The 
 essentials of a well-drawn contract that " comes within the province of 
 the engineer, however, are as follows: 
 
 1. A proper and customary form. 
 
 2. A full and correct description of all parties to the agreement. 
 
 3. A thorough and complete preamble. 
 
 4. A statement of when and under what conditions the contract is 
 
 to become operative. 
 
 5. The limit, if any, for duration of contract. 
 
 6. An exhaustive statement of what each party to the contract binds 
 
 himself, his executors, his administrators, successors, or assigns, 
 to do or to refrain from doing. 
 
 7. A clearly defined enunciation of the consideration which each 
 
 party is to receive; this is, the essential raison d'etre of the instru- 
 ment. 
 
 8. Forcasting of all possible eventualities that would materially 
 
 affect the agreement, and a, full statement of everything that 
 is to be done, in case of each eventuality. 
 
 9. Penalties for failure to comply with the various terms of the agree- 
 
 ment. 
 
 10. Provision for possible cancellation of contract. 
 
 11. Provision for settlement of all business relations covered by the 
 
 contract, or resulting therefrom in case of cancellation, taking 
 into account all possible important eventualities. 
 
 12. Mention of the place where the agreement is drawn or the place 
 
 where it is to be put in force, so as to show the state under the 
 laws of which the validity of the contract is to be determined, 
 should suit be necessary to enforce it. 
 
 13. Methods of payments, if any are to be made. 
 
 14. Provisions for extra compensation, and the limitations connected 
 
 therewith. 
 
 15. Provision for possible changes in contract. 
 
 16. Provision for transfer of the contract, or for subletting. 
 
 17. Provision for settlement of disputes. 
 
 18. Provision for satisfactory and sufficient bonds, if any be needed. 
 
 19. Provision for defense of law suits, if such provision be necessary. 
 
 20. Definition of names used in contract, such as "engineer," "com- 
 
 pany," "contractor," or "trustee." 
 
 21. Dating of contract. 
 
 22. Proper signature and the necessary seals, if the latter be required. 
 
 23. Witnesses to the signatures, or execution before a notary public. 
 As illustrating these points, the following example of a good typical 
 
SPECIFICATIONS AND CONTRACTS 483 
 
 contract may be reproduced. This is the standard "Form for Contracts*' 
 of Waddell and Harrington, engineers, of Kansas City, Mo., for appending 
 to construction specifications drawn up in their office. 
 
 Memorandum of Agreement, made and signed this day 
 
 of 19 . . , by and between the 
 
 the party of the first part, and sometimes termed in this agreement and 
 
 in the specifications, the "company," and 
 
 the party of the second part, and sometimes termed in this agreement 
 and in the specifications the "contractor." 
 
 Whereas, 
 
 ••• 
 
 Now This Agreement Witnesseth: 
 
 First. The party of the second part, for and in consideration of cer- 
 tain payments to be made to it, as hereinafter specified, will 
 
 all in accordance with the plans and specifications hereunto annexed 
 and made a part hereof, and will fully finish and complete the same 
 
 by 
 
 unless, in the opinion of the engineer, the party of the second part be 
 delayed or prevented by circumstances that are absolutely beyond his 
 control. 
 
 Second. The party of the second part shall begin the work of con- 
 struction as soon as practicable after the signing of the contract, and 
 shall push the same to completion as rapidly as possible, and within 
 the time limit or limits set in the accompanying specifications. 
 
 Third. All important dimensions and characteristics of the struc- 
 tures are fully described in the accompanying drawings and specifica- 
 tions, which form a part of this contract. 
 
 Fourth. In consideration of the performance by the party of the 
 second part of its convenants and agreements, as hereinbefore set forth, 
 the party of the first part hereby covenants and agrees to pay to the 
 party of the second part as follows; 
 
 In case that there be any other materials furnished by the contrac- 
 tor that are not included in this list, they shall be paid for on the basis 
 of actual cost to the contractor plus ten (10) per cent for his profits. 
 
 It is understood that no payments, either partial or final, are to be 
 made for any material which is to be used for false work or plant, but 
 only for such material as is left permanently in the finished construction. 
 
 Fifth. The schedule prices to be adopted in making partial pay- 
 ments for all work as it progresses are to be as follows: 
 
 Sixth. All material paid for by the party of the first part shall be 
 deemed to be delivered to, and to have become the property of the said 
 first part, but the party of the second part hereby agrees to store it and 
 to become responsible for it during the continuance of this agreement. 
 If any of it be damaged, destroyed, or lost from any cause, including, 
 
484 THE ART OF KOADMAKING 
 
 among others, floods, washouts, and fires, the contractor shall repair 
 or replace the same at his own expense to the satisfaction of the engineer. 
 
 Seventh. In case the party of the first part, notwithstanding the 
 failure of the party of the second part to complete its work within the 
 time specified, shall permit the said second party to proceed, and con- 
 tinue and complete the same, as if such time had not elapsed, such per- 
 mission shall not be deemed a waiver in any respect, by the first party, 
 of any forfeiture or liability for damages arising from such non-com- 
 pletion of said work within the time specified, and covered by the " Liqui- 
 dated Damages" clause of the specifications; but such liabilities should 
 be continued in full force against the said second party, as if such per- 
 mission had not been granted. 
 
 Eighth. No change or alteration shall be made in the terms or condi- 
 
 'iions of this agreement without the consent of both parties hereto in 
 
 writing, and no claim shall be made or considered for any extra work 
 
 unless the same shall be authorized and directed in writing by the engineer. 
 
 Ninth. In the event of any delay in completing the work embraced 
 in this contract, the party of the second part shall be entitled to no extra 
 compensation on account of such delay, as it is hereby assumed that in 
 submitting its tender it took its chances for the occurrence of such delay. 
 If, however, in the opinion of the engineer, the contractor be delayed 
 by any act of the company to such an extent as to cause him serious 
 hardship, such as temporary cessation of the work, the company shall 
 allow the contractor whatever compensation for such delay as may ap- 
 pear to the engineer to be just and equitable. 
 
 Tenth. The party of the second part hereby agrees that it will not 
 assign or sublet the work covered in this contract, or any portion of it, 
 without the written consent of the party of the first part, but will keep 
 the same within its control. 
 
 Eleventh. The decision of the engineer shall control as to the inter- 
 pretation of drawings and specifications during the execution of the 
 work under them; but if either party shall consider itself aggrieved by 
 any decision, it may require the dispute to be finally and conclusively 
 settled by the decision of the three arbitrators, the first to be appointed 
 by the party of the first part, the second by the party of the second part, 
 and the third by the two arbitrators thus chosen. In case that the 
 two first chosen fail to agree upon a third, the latter shall be appointed 
 
 by 
 
 By the decision of these three arbitrators, or by that of a majority of 
 them, both parties to this agreement shall be finally bound. 
 
 Twelfth. As, according to the terms of the accompanying specifica- 
 tion, which form a part of this contract, the party of the second part is 
 to indemnify the party of the first part against all liability or damages 
 on account of accidents occasioned by the omission or negligence of 
 itself, its agents or its workmen during the continuance of this agree- 
 ment, and against all claims for royalties or patents; it is hereby agreed 
 that the party of the second part shall be promptly and duly notified in 
 writing by the party of the first part of the bringing of any such suit 
 or suits, and shall be given the privelege of assuming the sole defence 
 thereof. The party of the second part is to pay all judgments recovered 
 by reason of accidents or patents in any suit or suits against the party 
 of the first part, including all legal costs, court expenses, and other like 
 expenses. 
 
 Thirteenth. The contractor further agrees to give the company a 
 surety-company bond, satisfactory to the party of the first part in the 
 
SPECIFICATIONS AND CONTRACTS 485 
 
 sum of 
 
 for the faithful performance of this contract and the specifications, and 
 of all the terms and conditions therein contained, and for the prompt 
 payment of all materials and labor used in the manufacture and con- 
 struction of the structures, and to protect and save harmless the com- 
 pany for claims on patents and from all damages to persons or property, 
 caused by the negligence or claim of negligence of the contractor, his 
 agents, servants, or employees in doing the work, or in connection there- 
 with, and from injury to or loss of materials paid for by the company 
 either partially or in full before the completion and acceptance of the 
 construction or constructions. 
 
 Fourteenth. The word "Engineer" as used in this contract refers to 
 
 the Consulting Engineers of the 
 
 or their duly authorized representative. 
 
 In Witness Whereof, the parties to this agreement have hereunto 
 set their hands and seals. 
 
 Dated the day, month, and year first herein written. 
 
 Witnessed by 
 
APPENDIX II 
 
 PAVEMENT GUARAXTEES: REASONS FOR SHORTENING 
 OR ABOLISHING THEM ^ 
 
 Many miles of pavements, although under bonded guaranty for good 
 condition, are in bad order on many streets of many cities. Municipal 
 officials and taxpayers are rapidly realizing that pavements, when first 
 laid, should be properly constructed under the responsible and direct 
 supervision of the city engineering department, and that bonded time 
 guaranties should not be relied upon, but be abolished or at least reduced 
 to the short time needed to enable poor construction to be discovered 
 and replaced. Who would think of having a city hall, water works or 
 other kinds of public works built and rely upon guaranties that these 
 things would be good and durable? Private works are not conducted 
 on a basis of guaranties, but upon quality. 
 
 From the point of view of municipalities and property owners, the 
 principal objections to long-time guaranties are as follows: 
 
 First. Municipal officials are naturally often careless in awarding 
 contracts when accompanied by bonded time guaranties. They depend 
 on the bond rather than on the reliability and experience of the contractor 
 in the special class of work to be done. They often investigate the 
 quality of the bond instead of the quality of the paving material offered. 
 They fail to have complete specifications and fail to depend principally 
 upon efficient supervision by the city engineer of the materials and work 
 during construction. It is often stated by officials of boards of public 
 works, paving committees, etc., in awarding contracts to persons or 
 companies whose lack of experience is known and the quality of their 
 materials unknown or whose price is suspected of being too low for good 
 work, that " a good surety bond for so and so many years is offered and 
 we can safely rely on that." There are hundreds of poor pavements 
 in our cities built under "good bonds"; but a "good bond" in a city 
 file is not a good pavement on a city street. The time guaranty bond 
 is a very unsatisfactory, slow and uncertain way to convert a poor pave- 
 ment into a good one. It takes a pavement from the control of the 
 engineering department and puts it for a long period as a burden on the 
 legal department of a city. 
 
 ' Abstracted from paper on "Pavement Guarantees; the Use and Abuse," by J. 
 W. Howard, C.E., read before the Board of Trade, Newark, N. J., December, 1907, 
 
 487 
 
488 THE ART OF KOADMAKING 
 
 Second, Long-time guaranties have very seldom proved efficient for 
 getting poor pavements made good. Nearly every city has many pave- 
 ments where guaranties have not been complied with. There are but 
 a few instances of recovery by a city of damages under a guaranty 
 bond. Because law is a slow process, the pavements meanwhile become 
 more dilapidated. I speak from an experience of some years during 
 which, aside from other engineering work connected with pavements, 
 I have examined poor pavements and my reports and testimony have 
 helped cities collect damages from defaulting contractors or from bonds- 
 men. The chief engineer of pavements of Chicago in a recent paper 
 showed how slow and unsatisfactory the legal proceedings are, in the 
 cases pending in Chicago for more than three years, to compel contractors 
 or bondsmen to put their pavements in order. Many contractors and all 
 bonding companies have attorneys paid by the year. It is easier and 
 much cheaper for them to prolong litigation than to repair pavements. 
 
 Third. The price for a well-constructed pavement, when time guaranty 
 bonds are required, is much increased by reason of the cost of surety 
 company bond premiums, the cost of reserves to cover unforseen liabilities 
 and contingencies, probable lawsuits, political obstruction, which are 
 factors which cannot be ignored by the contractor, and which are included 
 in the price he charges for the pavement. A city and property-holder 
 receives practically no return for these added charges for time guaranties. 
 
 Fourth. Incompetent, inexperienced, scheming or politically affiliated 
 contractors sometimes bid low prices to construct pavements without 
 including sufficient to cover the cost of proper repairs and other liabilities 
 of the guaranty. They sometimes deliberately figure on the basis that 
 if the pavement should fail they will be able, in some way, by friendship, 
 political influence or legal process, to avoid the liability of the guaranty, 
 and they often succeed. Cities are too likely to accept such bids. Under 
 the unfortunate laws of some states, cities are required to accept such 
 low, "cheap" bids, although offered in competition with the bids of 
 experienced and conservative contractors, who must bid higher to 
 furnish durable and, in the end, cheaper pavements for the city. In 
 states requiring its cities to award contracts to lowest bidder, it is easy to 
 abolish time guaranties and to provide complete specifications, thorough 
 inspection of construction, and thus quickly eliminate the cheap-poor- 
 work-bidder. It is not good policy nor do cities wish to pay for anything 
 less than cost to the contractors. They are willing to pay a fair profit 
 to contractors for good work. 
 
 Fifth. Time guaranties remove from the municipal engineer or officials 
 in direct charge of the work the right to fully direct important details 
 of construction in accordance with their best judgment, either during its 
 first construction or during the period of guaranty. If the engineer 
 exercises his prerogative in directing how any of the details are to be 
 done, the contractor and the bondsmen are thereby often found to be 
 relieved from the guaranty. In a recent decision of the New Orleans 
 
PAVEMENT GUARANTIES 4S9 
 
 District Court, Shea v. New Orleans^ to recover money for work alleged 
 by the city to be defective, the court relieved the contractor from his 
 guaranty, because the work was done in accordance with directions of the 
 engineer. 
 
 Sixth. A city should not lose complete control of its streets at all 
 times by having the pavements on the surfaces under partial control of 
 private contractors, as they practically are during guaranty periods. 
 No one can foretell the needed uses of the streets, as changes, construction 
 above, below or adjacent to the streets. No such changes, etc., can be 
 made for the benefit of the city or otherwise without, in a measure, the 
 city or property holder losing the asset of repairs of pavements not yet 
 performed during the balance of a guaranty subsequent to the changes, 
 etc., in connection with the street which are needed and accomplished. 
 A city cannot properly control the car-track pavements when they or 
 even the adjacent pavements on a street are under guaranties. 
 
 Seventh. It is often illegal to require long-time guaranties in contracts 
 for construction to be paid for by assessment, because the laws require the 
 general repair to pavements due to general use of pavements shall be paid 
 from general funds of the city and forbid such repairs to be assessed as 
 a part of the original charge or otherwise against abutting property. 
 If maintenance guaranty is included in the original contract price, it 
 generally thereby illegally assesses the cost of maintenance on the 
 abutting property. 
 
 Eighth. A city whose pavements are well constructed and free from 
 time guaranties can make subsequent repairs due to wear or other causes, 
 either by using its own employees or by taking advantage of new com- 
 petition which constantly arises. It can avoid being tied up with 
 possible monopolies or being kept from repairing its streets for long 
 periods by having annual repair contracts and paying for the repairs 
 each time they are made. A city thus avoids the heavy bonding and 
 extra indefinite expenses of time guaranties. 
 
 Ninth. Many municipal engineers and honest experienced city officers 
 are of the opinion that it is not for the interests of cities to require 
 guaranties beyond such period as will bring out defects due to neglect 
 or accident and that such defects appear within one or two years. It 
 seems now the universal opinion that a contractor shall not be permitted 
 to guarantee a pavement beyond a term of five years, because not 
 economical nor best for a city. It is a well known fact that the largest, 
 most conservative and responsible paving companies charge into the 
 cost of work an extra cost for "reserve for maintenance guaranty,"where 
 time guaranties are required in their contracts. 
 
 In conclusion, we can feel sure that engineering and legal experience 
 shows that a pavement guaranteed for longer than five years is neither 
 economically nor legally safe or best for city or taxpayer. Two years 
 are sufficient to demonstrate the quality of a pavement laid under 
 inspection of competent men. The best plan for city, taxpayer and all 
 
490 THE ART OF ROADMAKING 
 
 concerned is a guaranty or an abeyance of final acceptance for two 
 years from the first of June first following the completion of the pavement, 
 June being selected because experience and observation demonstrate 
 that a guaranty should terminate, not in wet or cold winter weather, 
 but in early summer, so that any defects will be fully visible, the pavement 
 easily inspected, the repairs properly made by the contractor and the 
 city receive a good pavement. 
 
APPENDIX III 
 
 CONCERNING THE WEAR OF ROADS BY AUTOMOBILES 
 
 Several statements have already been given in Chapter X to demon- 
 strate the fact that high-speed automobiles are injurious to the ordinary 
 road surface, but in these, the cause of the damage is not explained. 
 As an example of this damage "Engineering News" recently published 
 an abstract from a German contemporary showing the result of a con- 
 centrated traffic of passenger automobiles upon a short section of high- 
 way in Germany. 
 
 Unusual circumstances subjected this short stretch of road to very 
 heavy traffic of automobile busses for a period of five months, and in 
 that period some interesting studies of road wear were made. The traffic 
 was much heavier, both in amount and in loading, than normally occurs 
 even on heavily traveled main highways, and the results represent what 
 might be called an accelerated test of road destruction by motor-car 
 traffic. The showing made is rather alarming, but in reality it only 
 puts into specific figures what has been more or less generally recognized 
 as true. 
 
 The two groups of cross-sections shown herewith as Figs. 1 and 2 give 
 typical illustrations of how rapidly the traffic cut through the hard sur- 
 face of the highway. The circumstances of the case were as follows: 
 
 A railway tunnel between the towns of Mettlach and Ponten caved 
 in on Nov. 27, 1907; this interrupted the line from Trier to Saarbriicken 
 and necessitated the employment of auxiliary means of transportation 
 to bridge the gap for passengers and baggage. An average of 10 passen- 
 ger-trains each way per day had to be taken care of. 
 
 For a fortnight local vehicles, such as cabs, farm wagons, etc., were 
 employed. On Dec. 6, two closed motor-cars holding 12 to 15 passengers 
 each were obtained. A week later ten large motor-busses belonging 
 to the Grosse Berliner Motor-Omnibus Co., were put into service on 
 the portage and the two smaller busses were dismissed. These ten busses 
 were in service till early in February, when four of them burned, after 
 which the remaining six handled the service. 
 
 The tunnel was restored ready for traffic by May 1, 1908, making the 
 period of road portage practically five months. During this time the 
 motor-busses averaged 80 trips between Ponten and Mettlach, though 
 in the Christmas weeks the number of trips was increased to as high as 
 140 per day. 
 
 491 
 
492 
 
 THE ART OF ROADMAKING 
 
 0;3 C.3 O,6J0,B 
 
 Fetor Zb. 1908 
 
 ,iS i,9S 
 
 ""l-r-^ 
 
 
 
 A_^ 
 
 
 
 ^'SA 
 
 ^'--■'■^■'^•v^ 
 
 ^-^^-Ji;: 4:^ 
 
 ^fefe 
 
 ^ 
 
 ■ > •T, ',',,■.- 
 
 ^ ^! 
 
 
 s 
 
 ! Si J 
 
 , 
 
 
 March II, 1908 
 
 Fig. 1. — A Typical Cros;s-.section of the North Slope. 
 
 °i °ig °1 a_JL±U_ 
 
 March 21,1908. 
 
 Fig. 2. — A Cross-section on the Upland. 
 
THE WEAR OF ROADS BY AUTOMOBILES 
 
 493 
 
 The stretch of road in question, excluding the terminal portions which 
 lay in paved streets, is slightly under two miles long. A short stretch 
 near the middle is level, lying on the ridge through which the railroad 
 tunnels, while the rest is steeply sloped down toward the two ends. 
 The northerly slope averages 6.9 per cent grade, the southerly slope 8 
 per cent. The road had a broken-stone pavement, generally a kind of 
 Telford, i.e., there was a base course of shingle or cobbles. The upper 
 course consisted of quartzite, stated to be very suitable for road purposes. 
 
 Fig. 3. — View of the Rutted Road Surface in Winter. 
 
 The age of the road surfacing varied, but the important feature is that 
 the older parts had been kept in careful repair, and the entire two-mile 
 length was in first-class condition. 
 
 Perceptible wear began when the large motor-busses came into ser- 
 vice. A picking-up action was noticed in the tire tracks, and in a few 
 days the road was covered with fragments of stone torn out of the sur- 
 facing. Further, although the gage of the rear wheels was larger than 
 
494 THE ART OF ROADMAKING 
 
 that of the front wheels, the concentration of wear from tracking soon 
 produced the results shown in the sketches. 
 
 These large busses are described as follows: Weight, empty, 13,000 
 lbs., of which nearly 9,500 lbs. was on the rear axle; capacity, 25 pass- 
 engers; weight loaded, about 17,000 lbs.; tires, solid rubber, width 
 4 ins. front, S^ ins. rear; gauge, 5.9 ft. front, 6.6 ft. rear; speed, 6 to 15 
 miles per hr. 
 
 The rutting of the road once started, it developed in a short time 
 so far as to form grooves up to 6 ins. deep by 12 ins. wide, and ridges 
 formed alongside the ruts from the displaced material. The ruts were 
 not clean but contained much loose material, which the following wheels 
 either pushed aside or crushed. 
 
 Repair work was started as soon as the destructive actions were no- 
 ticed, and was continued to the end of the period. Coarse broken stone 
 was placed in the ruts and pressed down with a steam roller, whereupon 
 a binding course of small stuff such as cinders and coarse sand was sim- 
 ilarly applied. This could be done only when the road was not frozen. 
 
 Two weeks often sufficed to destroy the repair work completely. 
 During the last three months it was a constant struggle to keep the road 
 in passable condition. If heavy continued rains had occurred in March 
 or April it would have been impossible to maintain the traffic. 
 
 The wear and grooving was worse in December. Freezing weather 
 in January and the first part of February held matters stationary and 
 preserved the road, though in badly rutted condition. Thereafter the 
 southerly slope thawed first, and repair work was concentrated on it, 
 the northerly slope being taken up later. 
 
 The five-month's maintenance cost about $4,000, or over $2,000 per 
 mile. About 1,250 cu. yds. broken stone and an undetermined amount 
 of sand and cinders were used. Mr. M. Gorz, who reports the details, 
 says that but for good weather, a convenient supply of materials and 
 the availability of labor from the railway department it would not have 
 been possible to keep up the road. These favorable factors, we conclude, 
 also operated to reduce the cost. 
 
 The influence of the heavy weight concentrations upon the destruc- 
 tion of the road was evident in one of the paved streets at one end of the 
 route. A street newly paved with stone block, but apparently without 
 concrete base, was used temporarily to detour around the main street. 
 But in a few days the surface was deeply grooved, the wheels crushing 
 the stone blocks down into the soil, and the busses had to use another 
 street. 
 
 This is a most graphic example of the serious damage done by auto- 
 mobile tires to road surface. Yet, around the suburbs of any of the 
 larger cities we can find almost equally serious examples of wear at 
 any place where automobile traffic is concentrated, particularly where 
 high speeds are possible and around curves. 
 
 Commmenting on this, "Engineering News" says: 
 
THE WEAR OF ROADS BY AUTOMOBILES 
 
 495 
 
 "A dozen years or so ago, prophecies were common that a golden age 
 for roads and streets would come when horses should be displaced by 
 self-propelled vehicles. The horse, it was claimed, was the chief instru- 
 ment in the wear of our roads and highways, by digging up the surface 
 with the calks on his shoes. The iron tire of horse-drawn vehicles, too, 
 was referred to as a crushing mill which was continually reducing to 
 powder the material of the roadway surface. 'Only give us vehicles 
 without horses, with the wheel treads fitted with rubber tires,' it was 
 said, 'and the wear on the roads will be reduced practically to nothing.* 
 
 "It is interesting to reflect on these ideas so commonly held a dozen 
 years ago, and to compare them with the actual experience with the 
 automobiles of the present day. 
 
 "The question may well be asked; why should the theory of a dozen 
 years ago be so far apart from the experience of to-day? Why does the 
 automobile tire, which was expected to produce no wear at all upon 
 roads, actually wear them so terrifically? 
 
 "It is worth while studying this question, because when the answer 
 is found it is an excellent illustration of the fact that really theory and 
 practice are not in conflict, as might at first sight appear. The only 
 trouble with the theory of a dozen years ago was that it did not take 
 all the facts into consideration. Hindsight is proverbially better than 
 foresight; and now that we know how badly the automobile wears our 
 road surfaces, it is not difficult to see why this wear occurs. 
 
 " In the first place, one important factor is the driving or propelling 
 action of the automobile wheels. With horse-drawn vehicles, of course, 
 there is no driving action by the wheels, and they exert only a downward 
 pressure or lateral pressure on the road. The rear tires of an automo- 
 bile, however, exert not only a downward pressure upon the road sur- 
 face, but a powerful tangential push to the rear. The average power 
 
 Direction 
 of Motion 
 
 V^^-— - 
 
 
 
 ^ 
 
 x^^$^^ 
 
 n; 
 
 
 'j^ 
 
 ■^ 
 
 
 A, "^ 
 
 
 Fig. 4. 
 
 D C 
 
 Fig. 5. 
 
 of the automobiles in common use to-day is probably from 15 to 40 H.P., 
 and the speeds, outside of city streets, will average not less than 15 to 
 30 miles per hour. If we consider the elements of a rubber wheel-rim in 
 contact with the surface of the ground. Fig. 4, it may be easily seen 
 that the point A, which has just come into contact with the road surface, 
 exerts no tangential action upon the road. As the wheel moves for- 
 
496 THE ART OF ROADMAKING 
 
 ward from A to B, however, this tangential push of the surface of the 
 rubber tire against the road rapidly increases from zero at .4 to a max- 
 imum at B, and as the tire lifts from the road at B and the pressure 
 is released, the tendency is to push backward the material of the road 
 just beneath it. 
 
 "There is another reason why the automobile tire rapidly digs a rut 
 for itself on any road where automobiles follow each other and keep 
 nearly in the same track. The vehicle fitted with iron tires has a flat 
 tread; the rubber tire, either pneumatic or solid, has a tread which is 
 more or less rounded. Suppose, in a given automobile wheel. Fig. 5, 
 the diameter at the center of the tread at C is 30 ins.; then the diameter 
 toward the sides of the tread at D may be ^-in. or ^-in. less, depending 
 upon the pressure to which the tire is pumped, the contour of the tire 
 cross-section, the weight carried by the automobile, etc. If we take 
 only \-in. difference in diameter at the points C and D, we have a dif- 
 ference in circumference between the central part of the tread and the 
 sides of the tread of about f-in. That means that at every revolution 
 of the wheel, either the center of the tread must slip f-in. forward, or 
 the sides of the tread must slip ^-in. backward; that is to say, there must 
 be, theoretically and actually, this difference in the relative movement 
 of the center and the sides of the tread upon the roadway. Actually, 
 of course, this slip is going on all the time in the movement of a rounded 
 tire. There is some point between the center and the side where no 
 slip occurs, and toward the center or toward the side there is all the 
 time a slight slip forward or backward. As a result of this action, the 
 round-tired vehicle has more rolling friction than a vehicle with flat 
 tires. Of course, on an ordinary roadway such as a brick pavement or 
 a smooth macadam, the pneumatic tire, notwithstanding its rounded 
 surface, may move with little friction because the small stones and sim- 
 ilar obstructions which would be crushed by the iron tire will simply 
 indent the pneumatic tire. On an ordinary dirt road, however, the 
 rounded rubber tire has more resistance to traction than a flat iron tire. 
 
 "It is probable that the wear of the rubber tire on the roadway is 
 more rapid as a rut begins to form and the width of contact of the tire 
 with the road is thus increased. In the rut the sides of the tread — 
 points where the tire diameter is an inch or even two inches less than 
 at the center — may be in contact with the road. If the center of the 
 tire moves in the rut without slip, the sides of the tire where the diameter 
 is 2 ins. less must slip 6 ins. forward against the sides of the rut at every 
 revolution. Thus the retarding action of the sides of the rut tends to 
 increase the tangential force of the center of the tire upon the roadway 
 and to dig the rut deeper. 
 
 " We are aware that the tearing out of the macadam surface by the 
 pneumatic tires of an automobile has been frequently ascribed to the 
 'suction' of the tire upon the roadway. We do not see, however, in view 
 of the foregoing explanation, that any 'suction* hypothesis is needed 
 
THE WEAR OF ROADS BY AUTOMOBILES 497 
 
 to explain the disintegration of a macadam road surface by automobiles. 
 Of course there is a wind current — an upward and forward suction — 
 produced at the rear of the tires of a fast running automobile, and this 
 wind current raises the fine dust loosened by the tire from the surface 
 and sends it high in the air. Observation of this easily seen phenom- 
 enon has given rise to the common idea that the suction of the wheel 
 on the road surface is what loosens the stone. Some such suction there 
 doubtless is and it may possibly be a slight contributing cause of destruc- 
 tion; but any force exerted in this way must be very small compared 
 with the terrific backward push of the rubber tire treads. 
 
 "In the light of the above discussion it is evident that little can be 
 hoped for in the way of help for the roads through changes in automobile 
 construction. Flat steel tires in place of pneumatic tires might possibly 
 reduce the wear upon the roads; but the success of the automobile is 
 dependent on noiseless and easy-riding rubber tires. Further, we are 
 only at the threshold of our troubles with highways due to automobile 
 wear. For two years automobile factories have been working over- 
 time, and it is said that 200,000 automobiles are to be built next year. 
 The burden on taxpayers to build and maintain roads to carry automo- 
 bile traffic promises to become so great that a road repair tax may have 
 to be laid on the vehicles themselves." 
 
APPENDIX IV 
 
 STATISTICS OF PUBLIC ROADS OF THE UNITED STATES* 
 
 In the year 1904 there were 2,151,570 miles of public roads in the 
 United States. This does not include roads in Indian Territory, 
 Alaska, and the island possessions, as Indian Territory and Alaska were 
 not organized, by counties in 1904, and it was impossible to secure com- 
 plete information from Porto Rico, Hawaii, the Philippines and Guam. 
 Neither does this total mileage of roads include streets or boulevards in 
 incorporated cities and villages. Of this mileage 108,232.9 miles were 
 surfaced with gravel, 38,621.7 miles with stone, and 6,809.7 miles with 
 special materials, such as shells, sand-clay, oil, and brick, making in all 
 153,664.3 miles of improved road, or 7.14 per cent of all the roads in this 
 country. 
 
 A comparison of the total road mileage with the area of all the states 
 and territories, shows that there was 0.73 of a mile of road per square mile 
 of territory, and a similar comparison with population shows that there 
 was one mile of road to every 35 inhabitants, and one mile of improved 
 road to every 492 inhabitants. 
 
 The majority of all the roads in this country were originally laid out 
 along the boundary lines of farms, with little regard for drainage, topog- 
 raphy and alignment. In the eastern states the boundary lines of farms 
 were very irregular, and consequently many of the roads are crooked 
 and badly located with reference to grades. In the middle west, where 
 the land was laid out by the Government, the roads follow the section 
 lines, and in thickly settled communities the quarter-section lines. In 
 compiling these figures the aim was to include only the mileage of roads 
 actually open and in use ; but in reports from some of the counties in the 
 middle west may have included a greater or less mileage of section lines, 
 which have been set apart by law as public roads, but which have not 
 been opened up or used for this purpose. 
 
 Only four states have more than 100,000 miles of roads. Texas stands 
 first, with 121,409 miles; Missouri second, with 108,133; Iowa third, 
 with 102,448; and Kansas fourth, with 101,196. The District of Colum- 
 bia has only 191 miles of roads, Rhode Island has 2,361 miles, which is 
 
 * Abstracted and condensed from, " Public Road Mileage, Revenues and Expenditures 
 in the United States, in 1904"— Public Document, Bulletin No. 32, U. S. Dept. of 
 Agriculture, in which the road statistics for all the States and Territories are given. 
 
 499 
 
500 THE ART OF ROADMAIvING 
 
 the smallest mileage of any state. Delaware has only 3,000, and Arizona 
 only 5,987 miles. 
 
 By comparing the road mileage with the areas in square miles, the 
 District of Columbia is found to stand first, with 3.18 miles of road per 
 square mile of area, while Connecticut is highest among the states with 
 2.90 miles. Rhode Island has 2.24 miles, and Pennsylvania 2.21 miles 
 per square mile of area. Arizona has only 0.05 of a mile, the smallest 
 mileage per square mile; Utah has 0.08 and Wyoming 0.10 of a mile per 
 square mile. 
 
 A comparison of the mileage of roads with population shows that the 
 District of Columbia, which embraces a land area of 60 square miles and 
 which includes the city of Washington, has the largest population per 
 mile of public road, i.e., 1.459. Rhode Island has the largest population 
 per mile of any state, i.e., 181 inhabitants; Massachusetts has 164, New 
 Jersey 127, and Connecticut, 64. On the other hand, Nevada has only 
 3 persons per mile of public road; North Dakota has 5 persons; South 
 Dakota has 7 ; Wyoming 8 ; Idaho and Oklahoma, 9 each ; and Montana, 
 10. 
 
 Assuming the average width of the rights of way of country i-oads in the 
 United States to be 40 feet, the area of such rights of way in 1904 amounted 
 to 10,431,727 acres. Estimating the value of this land on a basis of the 
 valuation of farm lands in each state, the approximate value of the rights 
 of way of all the public roads would be 1341,899,306. A much higher 
 valuation would be amply justified by the fact that in sections where the 
 mileage of roads is greatest the land is considerably above the average In 
 value. A much higher estimated value would also result from assuming 
 that the rights of way of roads are as valuable as the contiguous farm 
 lands, which are always worth considerably more than the general 
 average. The value of the rights of way, however, constitutes a very 
 small part of the value of the roads when we take into consideration the 
 amount that is expended in material and labor in improving and main- 
 taining them. The approximate value of rights of way is therefore given 
 merely as an item of some importance in any calculations which may be 
 made as to value. 
 
 It was generally believed at the time when railroad building was 
 first undertaken in this country that the railroad would supplant the 
 wagon road, and this line of reasoning account in a large measure for the 
 neglect of the common roads from about 1835 until about 1890. It is now 
 clearly demonstrated that in spite of the fact that the United States leads 
 the world in railroad building, having a total of 213,904 miles in 1904, 
 the necessity for the improvement of our common roads is impressing 
 itself upon the people more now than at any time in the history of the 
 country. Our mileage of public roads is greater now than it has ever 
 been, and the extension of railroad and trolley lines has induced such an 
 amazing development of the country's resources as to bring about a 
 remarkable increase in traffic over the common roads. The heads of 
 
PUBLIC ROADS OF THE UNITED STATES 501 
 
 the great railroad systems are now seriously directing their efforts toward 
 securing the improvement of the common roads, which they recognize 
 as feeders to their railroad lines. In this connection it is interesting to 
 observe that for every mile of railroad we have about ten miles of wagon 
 roads. 
 
 Mileage of Improved Roads. Of the 153,662 miles of improved 
 roads in the United States, Indiana has the largest mileage—that is, 
 23,877 miles. Ohio occupies the second place, with 23,460 miles; Wis- 
 consin is third, with 10,633 miles; Kentucky fourth, with 9,486 miles; 
 California fifth, with 8,803 miles. Illinois, Massachusetts, and Michigan 
 have over 7,000 miles each; Minnesota over 6,000 miles; New York over 
 5,000 miles; Tennessee over 4,000 miles; Connecticut, Maine, Missouri, 
 New Jersey, Oregon, Pennsylvania, and Texas over 2,000 miles each; 
 and Alabama, Georgia, Iowa, Maryland, New Hampshire, North Carolina, 
 Rhode Island, South Carolina, Vermont, Virginia and Washington over 
 1,000 miles each. 
 
 In about two-thirds of the states gravel has been the principal 
 surfacing material used in improving the roads. The largest mileage of 
 gravel roads was found in Indiana, Ohio, Wisconsin, Massachusetts, 
 Michigan, Minnesota, Illinois and California. In eight states the mileage 
 of macadam roads exceeds that of gravel, and in a few others it is nearly 
 equal. Kentucky has the largest mileage of road surfaced with stone — 
 over 8,000 miles — and Ohio is second, with a little over 7,000. Other 
 states with large mileage of this class are Indiana, New York, Pennsyl- 
 vania, Texas, and New Jersey. About one-third of the improved roads 
 of California were treated with oil; and almost all of the improved roads 
 in South Carolina were surfaced with mixtures of sand and clay. 
 
 Percentage of Roads Improved. The district of Columbia occupies 
 the first place in its percentage of roads improved, having 65.58 per cent 
 improved. Massachusetts has 45.89 per cent, the highest percentage 
 of any state. Rhode Island comes next, with 43.26 per cent; then follow 
 Indiana, with 34.94; Ohio, with 33.78; California, with 18.87 ; Connecticut 
 with 16.75; Wisconsin, with 16.72; Kentucky, with 16.60; New Jersey, 
 with 16.32; Michigan, with 10.13; Maine and Maryland, each with a, 
 little over 9; Illinois, New Hampshire, Tennessee and Utah, each with 
 over 8; and Minnesota, New York and Oregon, each with over 7 per cent. 
 All of the states and territories except Oklahoma report some improved 
 roads. Eleven of the states, however, report less than 1 1 per cent 
 improved. 
 
 A comparison of the percentage of roads improved with the population 
 per mile of road shows that in most cases the states which have the 
 highest percentage of improved roads have the largest population per 
 mile of road, and vice versa. While it cannot be claimed for improved 
 roads that they invariably lead to an increase in population, good roads 
 are certainly a powerful factor in encouraging immigration, especially 
 in sparsely settled regions. 
 
502 THE ART OF ROADMAKING 
 
 The percentage of improved roads in any community or state depends 
 upon a variety of causes, the most important of which may be summed 
 up as follows : 
 
 (1) Availability of suitable road-building material. 
 
 (2) Wealth of the state in agriculture, manufactories, transportation, 
 etc. 
 
 (3) Requirements of traffic. 
 
 Prosperity promotes a desire for the advantages and benefits to be 
 derived from the improvement of the roads; but whether a community 
 is rich in agriculture or otherwise, if it has to depend on materials 
 imported from distant places, progress in the improvement of the roads 
 will be much slower than if local materials are abundant. To illustrate 
 this point: Mississippi expended in money and labor about the same 
 amount on roads in 1904 as Tennessee ; yet Mississippi, which is very 
 poor in road surfacing materials, has only .38 per cent of the roads 
 improved, while in Tennessee, which is well supplied with such materials, 
 8.74 per cent of the roads are improved. 
 
 There are several other reasons why the percentage of improved roads 
 is higher in some of the states than in others. The high percentage 
 of improved roads in Massachusetts, Rhode Island, Connecticut, and 
 New Jersey is due principally to the facts that suitable road-building 
 materials abound, that these states are densely populated, and that 
 many of the roads have been built through the aid of the states and under 
 the direction of competent state authorities. Indiana and Ohio have an 
 unusually high percentage of improved roads, because these states are 
 abundantly supplied with good road-building stone and gravel and 
 because the social and economic conditions were favorable to the making 
 of public improvements. 
 
 A comparison of the percentage of roads improved with the acreage 
 values of farm lands in the United States shows that the average percent- 
 a,ge of the improved roads in all states where the land is worth less than 
 $20 per acre is 1.9 per cent, whereas in the states showing an acreage 
 value of more than $20, improved roads constitute an average of 9 per 
 cent of the total mileage. 
 
 Expressed inversely, the states showing a high percentage of improved 
 roads have on the average relatively high acreage values, while those 
 showing a low percentage have Ioav acreage values. 
 
 In Mississippi, for instance, the farm lands are worth on the average 
 only $15.94 per acre, and in 1904 the percentage of improved roads was 
 0.38 of 1 per cent, while in Indiana we find that the farm lands are valued 
 at $54.96 per acre, and the improved roads in 1904 constituted 35 per 
 cent of the total mileage. In Arkansas the farms are worth $16.67 per 
 acre, while the percentage of improved roads in 1904 was only 0.7 per 
 cent. The corresponding figures for Ohio are: acreage value of farms, 
 $57.43, and percentage of improved roads, 33.7 per cent. 
 
 While there are many factors, such as quality of the soil, the proximity 
 
PUBLIC ROADS OF THE UNITED STATES 503 
 
 of farms to markets, and the relative population and wealth, which afTect 
 the value of the land, the figures given above indicate that the improve- 
 ment of the roads constitute a most important factor in the enhancement 
 of farm values. Records are on file to show that farm lands have been 
 known to advance in value from 50 to 500 per cent on account of the 
 improvement of the roads connecting them with market towns. 
 
 Of the 108,232.9 miles of gravel road in the United States, Indiana 
 has 20,582 miles, and leads all other states in this class of roads; Ohio 
 comes second, with 16,159 miles, Wisconsin has 9,899.8 miles, and Illinois 
 6,800 miles. The large mileage of gravel roads in these states is due in 
 part to the fact that they are abundantly supplied with gravel suitable 
 for road building, most of this being of glacial origin. 
 
 Of the 38,622 miles of road surfaced with stone, Kentucky leads with 
 8,078 miles; Ohio stands next with 7,160.5 miles; Indiana has 3,295 
 miles ; New York and Pennsylvania have over 2,000 miles each, and Illinois, 
 Massachusetts, New Jersey, Tennessee, and Texas have each over 1,000 
 miles. 
 
 One of the largest limestone belts in the United States extends through 
 Kentucky, Ohio, and Indiana, and most of the stone roads in these states 
 are built of this material. Furthermore, Kentucky has been building stone 
 roads since 1829, most of them being constructed under the turnpike or 
 toll system. This state also aided in this work for several years, and 
 at the close of 1837 had invested $2,509,473 in turnpike roads. At that 
 time 609 miles of first-class stone roads had either been constructed or 
 were under construction. 
 
 In 1829 the old National or Cumberland road was completed in parts 
 of Ohio, this being apparently the first stone road built in the state. 
 From 1840 to the present time the building of stone roads has continued 
 steadily. Some were built under the toll system, some under the one 
 and two mile assessment plans, and others from bond issues. 
 
 The first macadamized road in Indiana was built in 1839. It was the 
 first and only road built by the state, and extended from New Albany 
 to Paoli. From 1850 to 1890 many stone roads were built in that state 
 under the turnpike or toll system, and in 1885 the construction of free 
 gravel and stone roads began — that is, roads on which travelers were not 
 required to pay toll. From 1893 to the present time many miles of 
 stone roads have been built by the various townships from funds received 
 from bond issues. 
 
 Of the 6,807 miles of road in the United States surfaced with special 
 materials, California has 2,541 miles surfaced with oil; South Carolina 
 has 1,630 miles, nearly all surfaced with sand-clay mixtures; Florida 
 and Georgia has each over 500 miles mostly surfaced with sand-clay 
 mixtures; North Carolina has 438 miles surfaced with sand-clay; Mary- 
 land has 250 miles of roads surfaced with shells, and Ohio has 140.7 miles, 
 most of which is surfaced with brick. 
 
 Oyster shells from Chesapeake Bay have been extensively used for a 
 
504 THE ART OF ROADMAKING 
 
 » 
 number of years in building shell roads in Maryland and Virginia. A 
 considerable mileage of shell roads is also reported for most of the Atlantic 
 and Gulf Coast States. Ohio and Illinois appear to be the only states 
 which have made progress in building roads of brick. Cuyahoga County, 
 Ohio, stands first in mileage of brick roads. 
 
 Expenditures. The total expenditures for public roads during 1904, 
 by states, counties, townships, and districts, from property and poll 
 taxes, bond issues, and state-aid funds, together with the valuation of 
 the labor expended under the statute-labor law, amounted to $79,771,- 
 417.87, not including Indian Territory, Alaska, or our island possessions. 
 
 Of this amount $53,815,387.98 was expended from property and poll 
 taxes payable in cash, $19,818,236.30 was the value of the labor taxe^, 
 $3,530,470.93 came from bond issues, and $2,607,322.66 was expended 
 from state-aid funds. By comparing the total expenditures in all the 
 states and territories with the total mileage of all public roads and with 
 the total population of the United States, it is found that the expenditures 
 for road purposes amounted to $37.07 per mile of public road, or $1.05 
 per inhabitant. 
 
 As a bridge is usually considered a part of a road, and as taxes are, in 
 most cases, levied and assessed for both at the same time, it was im- 
 practicable to separate road and bridge expenditures, except in the state 
 of New York, and the total expenditures for roads has therefore been 
 made to include those for bridges. 
 
 The amount which was expended on public roads in the United States 
 in 1904 would represent the interest on $1,994,285,446.25, if computed 
 on a basis of 4 per cent. AVhen it is considered that the expenditure 
 which this vast sum represents was for the construction and maintenance 
 of 2,151,570 miles of public highways, enough roads to reach around the 
 earth at the equator 86 times, it is somewhat surprising that the expend- 
 iture was not greater. 
 
 A comparison which is more to the point is that the National Govern- 
 ment spent in the fiscal year 1903-4, $82,372,360.10 for deepening the 
 waterways, which is about 1.3 times as much as was expended by all the 
 states, counties, townships, and districts in the United States for the 
 construction and maintenance of all the public highways. 
 
APPENDIX V 
 BIBLIOGRAPHY OF ROADS, STREETS, AND PAVEMENTS 
 
 The following list of books, government pamphlets, etc., has been 
 compiled from various sources, the selection being made for the his- 
 torical and practical value of the works. Many British parliamentary- 
 reports, American and foreign government bulletins, and books in 
 foreign languages have been omitted, partly on account of their 
 inaccessiblity and their comparatively limited usefulness and partly 
 in order to bring the list within reasonable limits. 
 
 For convenient reference, the list is divided into three sections, (1) 
 Previous to 1800; (2) 1800 to 1899; (3) 1900 to date, the latter period 
 including practically all the works of current value, and in many cases, 
 brief descriptive notes are added to indicate something of the scope 
 of the book. Also short lists of the principal works on such allied 
 subjects as Highway Bridges, Earthwork, Tunnels, and Forestry are 
 given. 
 
 The publishers, or the author, will be pleased to give further informa- 
 tion, to anyone desiring it, of any of these works regarding which such 
 information is available. 
 
 SECTION I.— PREVIOUS TO 1800 
 
 1583. Lambard, William. — The Duties of Constables Surveyours of 
 
 the Highwaies, &c. Further editions: 1584, 1587, 1594, 1599, 
 1602, 1606, 1610. 
 
 1610. Proctor, Thomas. — A Profitable Worke to this Whole Kingdome 
 concerning the Mending of all Highways, as also for Waters 
 and Iron Workes. 
 
 1625. Norden, John.— An Intended Guyde, for English Travailers, Shew- 
 ing in Generall how Far one Citie, and Many Shire-Tounes in 
 England, are Distant from Other. 
 
 This book bears witness to the existence of a "Dark Age" period in the 
 history of English roads, when milestones were unknown und unthought 
 of, since at the foot of every page is printed the legend " Bear with Defects " 
 The distances were calculated, with some curious reaults, from the rude 
 maps then in use. 
 
 1635. . — A Direction for the Enghsh Traviller by which he 
 
 shall be Inabled to Coast about all England and A\'ales. 
 
 Contains a reference to the existence of sign posts and is an improve- 
 ment over Norden's former book, having a small circular map of England, 
 and miniature outline drawings representing the various counties. 
 
 505 
 
506 THE ART OF ROADMAKING 
 
 1641. Layer, John. — The Office and Duty of Constables . . with the 
 Office of Surveyors of the Highways. 
 
 1671. Broadsheet against New Buildings. A Proclamation Respecting 
 Highways. 
 
 1675. Mace, Thomas. — Profit, Conveniency, and Pleasure to the whole 
 Nation; Being a short Rational Discourse . . concerning the 
 Highways of England. 
 
 1675. Ogilby, John. — Britannia, or an Illustration of the Kingdom of 
 England and Dominion of Wales, by a Geographical and His- 
 torical Description of the Principal Roads thereof. 
 
 The first road book from an accurate survey, the measurements being 
 taken by means of a wheel, with a dial attached, for recording the number 
 of revolutions made. This book was so excellent that it formed the basis 
 of many editions for a century afterwards. 
 
 1682. The Infallible Guide to Travellers, giving a most exact account of 
 
 the four Principal Roads of England. 
 
 1683. J. M. — The Traveller's Guide and the Country's Safety, Being a 
 
 Declaration of the Laws of England against Highwaymen and 
 Robbers upon the Road; what is requisite and necessary to be 
 done by such persons as are robbed in order to the recovering 
 their damages; against whom they are to bring their action; 
 and the manner how it ought to be brought. 
 
 1692. Littleton, E. — Proposal for Maintaining and Repairing the High- 
 ways. 
 
 1694. Mereton, George. — A Guide to Surveyors of the Highways in their 
 Duty. 
 
 1696. Mather, "William. — Of Repairing and Mending the Highways. 
 
 1697. D[aniel De] F[oe]. — An Essay upon Projects; "Of the High- 
 
 ways." 
 1712. Bergier, Nicholas (Translation from). — The General History of the 
 
 Highways in all Parts of the World, more particularly in Great 
 
 Britain. Ch. XXX: "The Fabulous and the True History of 
 
 the Highways in England." 
 1715. [Signed J. P.] — Mending the Roads of England. 
 
 1718. The Laws concerning Travelling. 
 
 1719. Gardner, L. — A Pocket Guide to the English Traveller, being a 
 
 Complete Survey and Admeasurement of the principal Roads, &c. 
 
 1720. The Office and Duty of . Surveyors of Highways, Bridges, and 
 
 Causeways in Ireland. 
 
 1724. [Watts, John.] — A List of the Subscribers for Mending the 
 Road from Reading to Caversham, with an account of how the 
 money has been laid out. 
 
 1726. The Complete Parish Officer; containing the Authority and Pro- 
 ceedings of . . . Surveyors of Highways. 
 
 1734. A Short Specimen of a New Political Arithmetic containing some 
 Considerations concerning Public Roads. By an F.R.S. 
 
BIBLIOGRAPHY OF ROADS 507 
 
 1737. Phillips, Robt. — A Dissertation concerning the Present State of the 
 
 Highroads of England, especially of those near London. 
 1745. Nelson, W. — Office and Authority of a Justice of the Peace, shewing 
 
 also the Duty of . . . Surveyors of the Highways. 
 1745-6. Newball, John. — A Concern for Trade, and the Various Conse- 
 quences relating to the Encrease and Decrease and the Equal 
 
 and Unequal Circulation of Trade. 
 1748. Defoe, Daniel. — A Tour through the whole Island of Great Britain. 
 174Q. Shapleigh, John. — Highways: A Treatise showing the Hardships 
 
 and Inconveniences of Presenting or Indicating Parishes, Towns, 
 
 &c., for not Repairing the Highways. 
 1750. Collier, James. — Remarks on Road Bills in General, and on the 
 
 Wisbech Road Bill in Particular. 
 1753- Proposals at large for the Easy and Effectual Amendment of the 
 
 Roads by some further Necessary Laws and Regulations. By a 
 
 Gentleman, 
 1756. A New and Accurate Description of the Present Great Roads and 
 
 the Principal Cross Roads of England and Wales. 
 1756. An Appendix; or Further Reasons in Support of of the Plan or 
 
 Proposals for the Amendment of the Roads by Way of Answer 
 
 to Several Objections. By a Gentleman. 
 1763. Bourn, Daniel. — A Treatise upon Wheel Carriages. 
 
 1763. Hawkins, John (afterwards Sir). — Observations on the State of the 
 
 Highways, and on the Laws for Amending and Keeping them in 
 Repair. 
 
 1764. Burn, Rev. Richard. — History of the Poor Laws. 
 
 1765. Homer, Henry. — Inquiry into the Means of Preserving and Improv- 
 
 ing the Public Roads. 
 1765. Whitworth, R. — Some Remarks upon a Plan of a Bill Proposed to 
 
 Parliament for Amending the Highways by Assessment instead 
 
 of Six Days* Labour. 
 1768. [Young, Arthur.] — A Six Weeks' Tour through the Southern Counties 
 
 of England. 
 1770. . — A Six Months' Tour through the North of England. 
 
 Second Edition. Four vols. 
 1771. . — The Farmers' Tour through the East of England. 
 
 Four vols. 
 1771. Paterson, Daniel, Lt.-Col. — A New and Accurate Description of all 
 
 the Direct and Principal Cross Roads in Great Britain. Second 
 
 Edition, 1773. Sixteenth Edition, 1822. 
 
 1771. Whitworth, Sir Charles. — Observations on the new Westminster 
 
 Paving Act. 
 17^2. [Collection of Acts of Parliament relating to Roads in Surrey and 
 Sussex, 1717-1770]. 
 
 1772. Acts relative to the Roads leading from Westminster and Black- 
 
 friars Bridges (1750-1768), with Index. 
 
508 THE ART OF ROADMAKING 
 
 1773. Bayley, Thos. Butterworth. — Observations on the General Highway 
 
 and Turnpike Acts. 
 1773- Jacob, J. — Observations on the Structure and Draught of Wheel 
 
 Carriages. 
 
 1773, Bourn, Daniel. — Some Brief Remarks upon Mr. Jacob's Treatise on 
 
 Wheel Carriages. 
 
 1774. Jacob, Joseph. — Animadversions on the Use of Broad Wheels, and 
 
 the Preservation of the Public Roads. 
 
 1774. Postlethwaite's Dictionary. — Roads. 
 
 1776. Mostyn, John Armstrong. — An Actual Survey of the Great Post 
 Roads between London and Edinburgh. 
 
 1778. Scott, John. — Digests of the General Highways and Turnpike Laws. 
 
 1782. Bowles's Post-Chaise Companion; or Travellers' Directory through 
 England and Wales. Being an Actual Survey of all the Direct 
 and Principal Cross Roads, with the Milestones Expressed as 
 they Stand at Present. Two Volumes. Second Edition. 
 
 1787. Godschall, John. — A General Plan of Parochial Police. 
 
 1787. Paterson, Daniel, Lieut.-Col. — A TraveUing Dictionary; or Alpha- 
 betical Tables of the Distance of all the Principal Cities, Borough, 
 Market, and Seaport Towns, in Great Britain from each Other, 
 Comprehending about Fifty Thousand Distances. Fifth Edition. 
 
 1790. Anstice, Robert. — Remarks on the Comparative Advantages of 
 Wheel Carriages of Different Structure and Draught. 
 
 1792. Newton, Everard. — The Whole Duty of Parish Officers, containing 
 all the Laws now in force relative to . . . Surveyors of High- 
 ways. 
 
 1792. The Road from the Port of Milford to the Severn. 
 
 1794-1810. Board of Agriculture. — Many Volumes of Surveys of Counties, 
 containing incidental accounts of Roads and Road Maintenance. 
 
 1795. Metcalf, John. — The Life of John Metcalf. 
 
 1797. Gumming, Alexander. — Observations on the Effects which Carriage 
 
 Wheels, with Rims of Different Shapes, have on the Roads. 
 
 1798. Gary, John. — Cary's New Itinerary; or an Accurate Delineation of 
 
 the Great Roads throughout England and Wales, with many of 
 the Principal Roads in Scotland, from Actual Admeasurement. 
 The Eleventh Edition, with improvements, appeared in 1828. 
 
 First made by command of his Majesty's Postmaster-General for official 
 purposes in connection with the mail coaches. Some of the southern cross 
 roads were measured by a peculiar method, since the compiler engaged 
 the services of George Wilson, a celebrated pedestrian, who claimed to 
 estimate distances most exactly by the time occupied in walking from one 
 place to another. 
 
 1798. The Duty of Surveyors of Highways, in a Charge to be Delivered 
 
 to them at their Appointment, being first Signed and Sealed by 
 the Justices in their Petty Sessions. By a County Magistrate. 
 Another edition, 1807. 
 
 1799. The Surveyor's Appointment and Guide. Sixth Edition. 
 
BIBLIOGRAPHY OF ROADS 509 
 
 SECTION II.— 1800-1899 
 
 1800. Report of a Committee of Trustees of the Hammersmith and 
 
 Brentford Turnpikes. 
 
 1801. [Barry, J. B.] — The Laws respecting Highways and Turnpike Roads. 
 1805. Owen, William. — A new Book of Roads, or a Description of the 
 
 Roads of Great Britain. Other Editions, 1808, 1827. 
 
 1808. Report of the Secretary of the Treasury on the Subject of Public 
 
 Roads and Canals. 
 
 1809. Gumming, Alexander. — A Supplement to the Observations on the 
 
 Contrary Effects of Cylindrical and Conical Carriage Wheels. 
 
 181 1. Bird, J. G. — The Laws respecting Travellers and Travelling, com- 
 prising all the Cases and Statutes, &c. Second Edition. Another 
 Edition, 1819. 
 
 1811. Duane, William J. (1780-1865). — Letters, addressed to the People 
 of Pennsylvania Respecting the Internal Improvement of the 
 Commonwealth by Means of Roads and Canals. 
 
 1813. Edgeworth, Richard L. (1744-1817). — An Essay on the Construction 
 
 of Roads and Carriages. 
 
 1814. Melish, John (1771-1822).— A Description of the Roads of the 
 
 United States. 
 
 1816. Bird, J. G. — The Laws respecting Highways and Turnpike Roads, of 
 
 Changing, Stopping, and Repairing Highways, &c. Third Edition. 
 
 1817. Edgeworth, R. L. — An Essay on the Construction of Roads and 
 
 Carriages. 
 
 1818. Clarke, James. — Practical Directions for Laying Out and Making 
 
 Roads. 
 1818. Dupin, Baron Charles. — Memoires sur la Marine et les Fonts et 
 Chauss^es de France et de I'Angleterre. 
 
 1818. Greig, William. — Strictures on Road Police, containing Views of 
 
 the Present System on which Roads are Repaired. 
 
 1819. Communication to the General Assembly of Maryland on the 
 
 Subject of Turnpike Roads. 
 1819. Macadam, John Loudon. — A Practical Essay on the Scientific 
 Repair and Preservation of Public Roads. 
 
 1819. Report of the Secretary of War Relative to Roads and Canals. 
 
 1820. Egremont, John. — The Law relating to Highways, Turnpike Roads, 
 
 Public Bridges, and Navigable Rivers. Two vols. 
 
 1820. Fry, Joseph Storrs (d. 1815). — An Essay on the Construction of 
 Wheel Carriages as they Effect both the Roads and the Horses. 
 
 j:820. General Rules for Repairing Roads. Published by Order of the 
 Parliamentary Commissioners for the Improvement of the Mail 
 Coach Roads from London to Holyhead, and from London to 
 Liverpool, for the Use of the Surveyors to these Roads. Third 
 Edition. 
 
510 THE ART OF ROADMAKING 
 
 1821. The Improvement of the Public Roads urged during the Existing 
 Dearth of Employment for the Poor. 
 
 1821. Macadam, John Loudon (1756-1836). — Remarks on the Present 
 
 System of Road-Making, with Observations deduced from 
 Practice and Experience. Further Editions, 1823, 1827. 
 
 1822. Bateman, Joseph. — The General Turnpike Road Act. Another 
 
 edition, 1852. 
 1822. [A Clerk to Trustees.] — A Digest of the Laws relating to Turnpike 
 Roads. 
 
 1822. Dupin, Baron Charles (1784-1873). — Application de G^om^trie et de 
 
 M^chanique, k la Marine, aux Ponts et Chauss^es. 
 
 1823. Cordier, Joseph L. Etienne (1775-1849). — Ponts et Chauss^es. 
 
 Essais sur la Construction des Routes, etc. 
 1823. Bateman, Joseph. — A Supplement to the General Turnpike Road 
 
 Act of 3 Geo. IV. 
 1823. Dehany, William K, — The General Turnpike Acts. 
 1823. Locker, E. H. — Report on the State and Condition of the Roads 
 
 and Mines on the Estate of Greenwich Hospital in the Counties 
 
 of Cumberland, Durham, and Northumberland. 
 1823. Markland, J. H. — On the Early Use of Carriages in England, and 
 
 on the Modes of Travelling. 
 1823. Wake, Bernard John. — Turnpike Roads: Lenders of Money on 
 
 Mortgage of Tolls, &c. 
 
 1823. Statement concerning the Thirsk and Yarm Road by the Com- 
 
 mittee of Trustees. 
 
 1824. A Collection of Acts of Parliament now in Force for Regulating the 
 
 Turnpike Roads in England. 
 1824. Cobbett, William, Jun. — The Law of Turnpikes. Commentaries on 
 the General Acts relative to the Turnpike Roads of England. 
 
 1824. Dupin, Baron Charles (17S4-1S73). — Voyages dans la Grande 
 
 Bretagne. Vols. V. and VI.: Troisieme Partie, Force Commer- 
 ciale, Tome Premier, Voies Pubhques. 
 
 1825. Dupin, Baron C. — Commercial Power of Britain. Streets, 
 
 Roads, Canals, Aqueducts, Bridges, Coasts, and Maritime Ports. 
 
 Translated from the French. Two vols. 
 1825. Highways Improved. 
 1825. Macadam, J. L. — Observations on the Management of Trusts for 
 
 the Care of Turnpike Roads. 
 
 1825. Statement of the General Laws respecting Highways and Turnpike 
 
 Roads. 
 
 1826. Ipswich Turnpike. General Statement of the Income and Expendi- 
 
 ture between the 30th August, 1S25, and the 30th August, 1826. 
 
 1826. Bateman, Joseph. — Metropolitan Turnpike Act. 
 
 1827. [Bateman, Joseph]. — A Second Supplement to the General Turn- 
 
 pike Road Acts. 
 
 1828. Delane, W. F. A. — Arrangement of the Turnpike Acts. 
 
BIBLIOGRAPHY OF ROADS 511 
 
 1828, A Collection of Acts of Parliament now in force for regulating 
 
 Turnpike Roads in England. 
 
 1829. Wellbeloved, R. — Treatise on the Law relating to Highways. 
 
 1829. Woolrych, H. W. — A Treatise on the Law of Ways. 
 
 1830. A Plan of the Intended Turnpike Road from Saint Marylebone 
 
 into the Great North Road. (Prospectus and Map.) 
 1830. Broadsheet, printed by J. Catnach. The New Invented Steam 
 
 Carriage, with Woodcut of Two Steam Carriages Travelling on 
 
 the Road, also Explanation, Full Account, and a "New Song'* 
 
 on the Subject. 
 1830. Saco, Jos€ Antonio (1800-1879). — Memoria sobre Caminos, en la 
 
 Isla de Cuba. 
 1832. Index to the General Turnpike Act for Scotland. 
 
 1832. Phillips, Sir Richard. — A MilHon of Facts in the Entire Circle of the 
 
 Sciences, &c. 
 
 Frontispiece of the Steam Carriage Running from Paddington to the 
 Bank of England, 1832, and particulars of other steam coaches running on 
 the roads fromi London. 
 
 1833. MacNeill, Sir John, LL.D. — Tables for Calculating the Cubic Quan- 
 
 tity of Earthwork in the Cuttings and Embankments of Canals, 
 
 Railways, and Turnpike Roads. Second Edition, Enlarged. 1846. 
 1833. Parnell, Henry Brooke (Baron Congleton). — A Treatise on Roads. 
 1833. Aldborough Turnpike. General Statement of the Income and 
 
 Expenditure between the 15th September, 1832, and the 16th 
 
 September, 1833. 
 
 1833. Ipswich Turnpike. General Statement of the Income and Expendi- 
 
 ture between 30th August, 1832, and 30th August, 1833. 
 
 1834. Mills, Robert. — Substitute for Railroads and Canals; Embracing 
 
 a New Plan of Roadway. ' 
 1834. Grahame, Thomas. — Treatise on Internal Intercourse in Civilised 
 
 States, particularly in Great Britain. 
 1834. Gamier, Francois Xavier P. (1793-1879). — Traits des Chemins de 
 
 toute Espece. 
 
 1834. Penfold, Charles (1799-1864).— A Practical Treatise on the Best 
 
 Modes of Making Roads. 
 
 1835. Bateman, Joseph. — The General Highway Act, 1835. 
 1835. Bramwell, George. — New Code of General Turnpike Acts. 
 
 1835. Delane, W F. A. — The Present General Laws for Regulating 
 Highways in England. 
 
 1835. Shelford, Leonard. — The General Highway Act ot 5 and 6 William 
 IV. Another edition, 1845. 
 
 1835. Ipswich Turnpike. General Statement of the Income ahd Expendi- 
 ture between the 1st day of January and 31st December, 1S34. 
 
 1835. Navier, Claude L. M. H. (1785-1836). — Considerations sur les Prin- 
 cipes de la Police de Roulage et sur les Travaux d'entretien des 
 Routes. 
 
512 THE ART OF ROADMAKING 
 
 1836. The Office of Surveyor of the Highways. By a Magistrate. 
 1836. Barclay, H.— The Law of the Road. 
 
 1836. Fry, A. A. — A Familiar Abridgement of the General Highways Act. 
 
 1837. Leigh's , Road Book. 
 
 1837. Pratt, John Tidd.— The General Turnpike Road Acts. 
 1837. Woob-ych, H. W. — New Highway Act, 5 and 6 William IV., with 
 Notes. Second Edition. : 
 
 1837. Report of the Chief Engineer of the State of Tennessee on the 
 
 Surveys for the Central Turnpike. 
 
 1838. Bloodgood, Simeon DeWitt. — A Treatise on Roads; their History, 
 
 Character and Utility. 
 1838. Report of the Street Committee (New York City) Upon the Resolu- 
 tion on Continuing the Wooden Pavement in Broadway, and the 
 Relative Merits of Macadamizing and Wood for Paving Streets. 
 
 1838. Hughes, Thos. — The Practice of Making and Repairing Roads. 
 1833. Rickman, John, Edited by. — Life of Thomas Telford, Esq. By 
 
 Himself. 
 
 1839. The Roads and Railroads, Vehicles and Modes of Traveling of 
 
 Ancient and Modern Countries; With Accounts of Bridges, 
 Tunnels and Canals in Various Parts of the World. 
 
 1841. Husson, Armand (Jean Christophe Armand) (1809-1874). — Traits 
 de la Legislation des Travaux Publics et de la Voirie en France. 
 
 1841. An Abstract of Accounts for 14 Years ending Whitsuntide, 1840 
 of the Pious Uses Trustees . . . Published by Order of the 
 Board of Surveyors of Highways for the Township of Leeds. 
 
 1843. Bayldon, Richard. — Suggestions for Consolidating the Funds and 
 Management of Turnpike Roads, and Management within the 
 Borough of Leeds. 
 
 1843. Bayldon, Richard. — Remarks, with a Tabular Statement, showing 
 the Operation of the 19th Clause of the proposed General Turn- 
 pike Bill on the Roads within the Borough of Leeds; with an 
 Appendix on Road Management. 
 
 1843. B., J. F. [Burgoyne, J. F.] — Remarks on the Maintenance of Macad- 
 amised Roads. 
 
 1843. Lee, Wm. — On Modern Carriage Ways. 
 
 1843. Report on the Patent Road Cleansing Machine (of Sir Joseph 
 Whitworth). 
 
 1843. Road Work on Railways. A Statement made by the Trustees of 
 the Cheltenham District of Turnpike Roads. 
 
 1843. Simons, Frederic W. (1803-1865). — Treatise on the Principles and 
 
 Practice of Levelling . . principally in the Construction of 
 Roads; with Mr. Telford's Rules for the Same. (New Edition, 
 1870). 
 
 1844. Leahy, E. — On Making and Repairing Roads. 
 
 1844. Pratt, J. Tidd. — The Law relating to Highways, &c. Fourth 
 Edition. 
 
BIBLIOGRAPHY OF ROADS 513 
 
 1845. Pagan, Wm. — Road Reform (in Scotland). 
 
 1845, Isle of Wight System of Roads and System of Guardians of the 
 
 Poor not a Model but a Warning to the Legislature. 
 1847. Balydon, Richard. — Turnpike Traffic and Tolls. 
 1847. Ricardo, David. — Rebecca at Stroud: or a Few Words about the 
 
 Turnpike Trusts. 
 1847. Gillespie, W. M. — Principles and Practice of Road Making. (New 
 
 York.) 
 1850. Law, H. — Rudiments of the Art of Constructing and Repairing 
 
 Common Roads. 
 1850. Report of the Secretary of State (N. Y. State) of Plank Road 
 
 Statistics of New Y^ork. 
 
 1850. Owen, Robert Dale (1801-1877). — Treatise on the Construction and 
 
 Management of Plank Roads. 
 
 1851. Kingsford, William (1819-1898). — History, Structure and Statistics 
 
 of Plank Roads. 
 
 1851. Gregg, William. — Essay on Plank Roads. 
 
 1852. The Highway Surveyor's Guide. 
 
 1853. Whitworth, Sir Joseph. — On the Advantages and Economy of 
 
 Maintaining a High Degree of Cleanliness in Roads and Streets. 
 
 1853. Gillespie, William M. (1816-1868).— Manual of the Principles and 
 
 Practice of Road Making; comprising th^ Location, Construc- 
 tion, and Improvement of Roads and Rail-roads. 
 
 1854. Bateman, Joseph, and Welsby, W. N. — The General Turnpike Road 
 
 Acts. 
 
 1854. Oke, George C. — The Laws of Turnpike Roads; practically arranged, 
 
 with Cases, Notes, Forms, &c. Second Edition, 1860. 
 
 1855. Nicholson, Samuel. — The Nicholson Pavement. (Second Edition, 
 
 1859). 
 1857. Bayldon, Richard. — Treatise on Road Legislation and Management. 
 i860. Bella, Giuseppe. — Cenni sui Lavori Esequiti per le Nuove Strade 
 
 Nazionali Nell' Isola di Sardegna. — Torino, Italy. (The Roads 
 
 of Sardinia.) 
 i860. Glen, William Cunningham. — A Treatise on the Laws of Highways. 
 1861. Laws of the State of Michigan Relative to Highways and Bridges. 
 1861. Rogers, Fairman (1833-1900). — Lectures on the Construction of 
 
 Roads and Bridges. 
 1861. Burgoyne, Sir J. F., and Mallet, R. — The Art of Constructing Roads. 
 
 1861. Smiles, Samuel (1812-1904).— Lives of the Engineers. Vol. L, 
 
 Part^ III.: Early Roads and Modes of Travelling. Vol. IL, 
 Part VIII.: Life of Thomas Telford. (Second Edition, 1S67\ 
 
 1862. Glen, William Cunningham. — The Act for the Better Management 
 
 of Highways. Other editions 1863, 1864, 1879. 
 
 1863. Medley, Julius George. — Roads— Roorkee, Ind*ia. 
 
 1863. Barclay, H. — Law of Highways in Scotland. Fourth Edition. 
 1863. Bateman, Joseph. — The General Highway Acts. 
 
514 THE ART OF ROADMAKING 
 
 1863. Exemplification of Glen's Highway Board Accounts. 
 
 1863. Owston, H. A. — Highway Laws. 
 
 1864. Glass, Henry Alexander. — Lectures on Roads and Roadmakers. 
 
 1864. Owston, H. A.— Highway Acts of 1862 and 1864. Second Edition. 
 
 1865. Glen, W. Cunningham. — The Law of Highways. Other editions 
 
 1885. 
 
 1866. Planta, Peter C. (1815- ).— Die Bunder Alpenstrassen. — St. 
 
 Gallen, Switzeland. 
 
 1867. Johnson, Frank G. (1835- ). — The Nicholson Pavement, and 
 
 Pavements Generally. 
 
 1868. Beckwith, Arthur. — Report on Asphalt and Bitumen, as Applied 
 
 to the Construction of Streets and Sidewalks in Paris. 
 1868. [Various Authors]. — Rudimentary Papers on the Art of Constructing 
 
 and Repairing Common Roads. 
 1870. Herschel, C, Milla, S. F., Onion, H. — Prize Essays on Roads and 
 
 Road Making. 
 
 1870. Paget, Fred A. — Report on the Economy of Road Maintenance and 
 
 Horse Draught through Steam Rolling, with Special Reference to 
 the Metropolis. 
 
 1871. First Annual Report of the Citizens' Association, for the Improve- 
 
 ment of the Streets and Roads of Philadelphia, Pa. 
 
 1874. Browne, Sir James F. M. (1823- ). — On the Tracing and Con- 
 struction of Roads in Mountainous Tropical Countries. 
 
 1874. An Act Revising and Embodying all the Laws Authorizing Post- 
 roads, in force December 1, 1873. 
 
 1874. Haywood, Wm. — Report on Accidents to Horses on Carriageway 
 
 Pavements. 
 
 1875. Campbell, John I. — A Road System in Statutory Form, for Creating, 
 
 Constructing, Repairing and Maintaining PubUc Highways. 
 1875. Rennie, Sir John. — Autobiography. 
 
 1875. Society of Arts. — Report of, on the Application of Science and Art 
 
 to Street Paving and Street Cleansing of the Metropolis. 
 
 1876. Gilmore, Quincy Adams (1825-1888). — A Practical Treatise on 
 
 Roads, Streets, and Pavements (New York). 
 
 1878. Chambers, G. F. — The Law relating to Highways. 
 
 1879. Ludwig Salvator, Archduke of Austria (1847- ). — Die Kara- 
 
 wanen-strasse von ^gypten nach Syrien. — Prag, Austria. 
 
 1879. Foot, C. H. — Consolidated Abstracts of the Highway Acts, &c. 
 Second Edition. 
 
 1879. Glen, Alexander.— The Highway Acts, 1862-1878, &c., with Intro- 
 duction, &c. 
 
 1879. Wilkins, H. St. Clair, Lieut.-General. — Treatise on Mountain Roads. 
 
 1879. Willcocks, George Waller. — Roads and Roadways. 
 
 1880. AUnutt, Henry. — Wood Pavements, as Carried Out on Kensington 
 
 High Road, Chelsea, &c. 
 1880. Baker, T. — Law of Highways. 
 
BIBLIOGRAPHY OF ROADS 515 
 
 1880. Cresy. — Encyclopaedia of Civil Engineering. 
 
 1880. Glen, Alexander. — The Powers and Duties of Surveyors of High- 
 ways. Other editions 1881, 1888. 
 
 1880. Goudy, Henry, and Smith, William C. — Local Government in 
 Scotland. Deals with the Law of Roads. 
 
 1880. Thropp, James. — Highways and Locomotives Act, 1878. Report 
 
 on Main Roads (Lincolnshire). 
 
 1881. Situacion de las Carreteras del Estado — Madrid, Spain. 
 
 1881. Spearman, R. H. — The Law relative to Highways in England and 
 North Wales. 
 
 1 88 1. Chambers, C. H. — Public Health and Highways. 
 
 1882. Harcourt, E. W. — Maintenance of High Roads. 
 
 1882. Higgins, E. — Letters on Highway Legislation. 
 
 1883. Boulnois, H. Percy. — The Municipal and Sanitary Engineers' Hand- 
 
 book. 
 
 1883. Glen, William Cunningham and Alexander. — The Law relating to 
 
 Highways, &c. Another edition, 1897. 
 
 1884. Burrows, A. J.^ — ^The Maintenance and Construction of Roads. 
 
 1884. The Highway Laws of Indiana. 
 
 1885. Harris, S. — The Coaching Age. Chapters on Highways. 
 
 1885. Laws of Indiana Respecting Highways, Free Roads, and Free 
 Bridges. 
 
 1885. New Highway Law of Indiana. 
 
 1886. Proceedings of -a. Conference on Highway Management (at 
 
 Gloucester) . 
 1886. Codrington, T.— Roads and Streets. Encyl. Britt., Vol. XX. 
 1886. Malo, Leon. — On Asphalte Roadways. 
 1886. Postu, Burton Willis. — The Road and the Roadside. (New Edition, 
 
 1893.) 
 
 1886. Garard, Louis F. — Compilation of the Road Laws of the State of 
 
 Georgia. 
 
 1887. Law, H., and Clark, D. Kinnear. — Construction of Roads and 
 
 Streets. 
 
 1887. Thropp, J. — Repairs of Roads. 
 
 1888. Glen, W. C. — Highway Surveyor's Guide. Second Edition. 
 1888. Maudslay, A. — Highways. 
 
 1888. Proposed Street Improvements in the City of Brooklyn. 
 
 1889. Codrington, T. — Local Government Board Report on Road Main- 
 
 tenance. 
 1889. Jusserand, J. J. (Translated by Lucy Toulmin Smith). — English 
 
 Wayfaring Life in the Middle Ages. Part I.: English Roads, 
 
 pp. 35-174. 
 1889. Phillips, J. E. — The Local Government Act, 1888, as it affects 
 
 Highways. 
 1889. Smith, Urban. — Maintenance of Main Roads in the County of 
 
 Hertford. 
 
516 THE ART OF ROADMAKIMG 
 
 1889. Jenks, Jeremiah W. (1S56- ). — Road Legislation for the Ameri- 
 can State. 
 
 1889. Pope, Col. Albert A. (1843-1909). — Highway Improvement. 
 
 1890. Herskell, Ferdinand. — Treatise on Roads and Prohibition. 
 
 1890. Haupt, Lewis M. (1844- ). — Country Roads; Their Relations 
 to Other Lines of Communication and to the State. 
 
 1890. Love, Edward G. — Pavements and Roads; their Construction and 
 Maintenance. 
 
 1890. Pope, Col. Albert A. — The Movement for Better Roads. The 
 Relation of Good Streets to the Prosperity of a City. 
 
 1890. Dykes, J. E., and Stuart, D. — Roads and Bridges Manual (Scotland). 
 
 1890. Smith, Urban. — The Country Roads of England. 
 
 1891. Streets and Highways in Foreign Countries — Reports from U. S. 
 
 Consuls on Streets and Highways in their Several Districts. 
 
 1891. Potter, Isaac B. — The Gospel of Good Roads. 
 
 1891. Bacon, A. P. — California Asphalt: God's Natural Paving Material. 
 
 1891. Fletcher, W. — History of Steam Locomotion on Common Roads. 
 
 189 1. Sydney, William Connor. — England and the Enghsh in the Eigh- 
 teenth Century. Vol. II., Ch. XI.: Roads and Travelling. 
 
 1891. Winstone, Benjamin. — Minutes of the Epping and Ongar Highway 
 Trust, 1769-1870. 
 
 189 1. Streets and Highways in Foreign Countries. Reprinted Reports of 
 the United States Consuls. 
 
 1891. Philadelphia. Committte on Better Roads. Essays on Road 
 
 Making and Maintenance. 
 
 1892. Report of the Dept. of Public Works of New York City on Street 
 
 Pavements, with Special Reference to Asphalt Pavements. 
 1892. Whinery, Samuel (1845- ). — The Effect of Street Paving on the 
 
 Value of Abutting Property. 
 1892. Burke, Mile D. (1841- ). — -Brick for Street Pavements. 
 1892. Byrne, Austin T. (1859-- ). — Treatise on Highway Construction. 
 
 (New Editions, 1896, 1900.) 
 1892. Codrington, T.— Maintenance of Macadamized Roads. 
 1892. Harper, C. G. — The Brighton Road. 
 
 1892. Spinks, W. — Law and Practice as to Paving Private Streets. 
 
 1893. Holmes, Joseph Austin (1859- ). — Road Materials and Road 
 
 Construction in North Carolina. 
 
 1893. Potter, Isaac B. — County Roads: An Illustrated Primer of Road- 
 
 Making. 
 
 1894. Burke, 1(1. D., C.E. — Brick for Street Pavements. An Account of 
 
 Tests idado with Bricks and Paving Blocks. 
 
 1894. Wright, R. S., and Hobhouse, Henry. — An Outline of Local Govern- 
 ment, England, and Wales. Second Edition. Deals with the 
 Law of Roads. 
 
 1894. Judson, William Pierson (1849- ). — City Roads and Pavements 
 for Oswego, N. Y. 
 
BIBLIOGRAPHY OF ROADS 517 
 
 1894. Spalding, Frederick P. (1857- ). — Text-book on Roads and 
 
 Pavements. 
 1894. Herschel, C, and North, E. P. — The Science of Road-making 
 
 Construction and Maintenance of Roads. 
 1894. Stone, Roy. New Roads and Road Laws in the United States. 
 1894. . — Earth Roads: Hints on their Construction and Repair. 
 
 (Government Bulletin.) 
 1894. . — State Laws Relating to the Management of Roads, 
 
 enacted in 1888-93. (Government Bulletin.) 
 1894. Information Regarding Roads and Road-making Materials in 
 
 Certain Eastern and Southern States. (Government Bulletin.) 
 1894. Information Regarding Roads and Road Materials in Certain 
 
 States North of the Ohio River. (Government Bulletin.) 
 1894. Information Regarding Road Materials in Certain States West of 
 
 the Mississippi River. (Government Bulletin.) 
 1894. Sheffield, 0, H. — Improvement of the Road System of Georgia. 
 
 (Government Bulletin.) 
 1894. Brauner, John Caspar. — Report on Road-making Materials of 
 
 Arkansas. (Government Bulletin.) 
 
 1894. Ordinances Concerning the Improvement of Streets, Alleys, Side- 
 
 walks, etc., of Louisville, Ky. 
 
 1895. Shaler, Nathaniel S. (1841-1906).— The Geology of the Road- 
 building Stones of Massachusetts. 
 
 1895. Report of the Joint Committee to Examine into the Condition of 
 the Roads and 'Public Highways of Rhode Island. 
 
 1895. Stone, Roy. — Best Roads for Farms and Farming Districts; Cooper- 
 ative Road Construction. 
 
 1895. . — State Laws Relating to the Management of Roads; 
 
 Enacted in 1S94-05. (Government Bulletin.) 
 
 1895. "- . — Historical and Technical Papers on Road Building 
 
 in the United States. (Government Builletin.) 
 
 1895. . — Good Roads; Extracts from Messages of Governors. 
 
 (Government Bulletin.) 
 
 1895. . — Wide Tires. Laws of Certain States Relating to 
 
 their Use. (Government Bulletin.) 
 
 1895. Crump, M. H. — Kentucky Highways. History of the Old and New 
 Systems. (Government Bulletin.) 
 
 1895. Perkins, George Arthur. — State Highways of Massachusetts. 
 
 1895. Holmes, Joseph A. — Improvement of Public Highways of North 
 Carolina. 
 
 1895. Shaler, Nathaniel S. (1841-1906). — Preliminary Report on the 
 Geology of the Common Roads of the United States. 
 
 189s. Wheeler, Herbert A. (1859- ). — Vitrified Brick Paving. 
 
 1895. Wallace, W. W,, Jr. — Brick Pavements. 
 
 1895. Willmann, Leo von (1848- ). — Strassenbau. — Leipzig. 
 
 1895. Boulnois, H. P. — The Construction of Carriageways and Footways. 
 
518 THE ART OF ROADMAKING 
 
 1895- Harper, C. G.— The Dover Road. 
 
 1895. . — The Portsmouth Road. 
 
 1896. Hunter, (Sir) Robert. — Preservation of Open Spaces and Footpaths 
 
 and other Rights of Way. 
 T896. Petsche, Albert. — Le Bois et ses Applications au Parage. — Paris. 
 1896. Lefebvre, Georges (1860- ). — Voie Publique. — Paris. 
 1896. Shaler, Nathaniel S. — American Highways; a Popular Account of 
 
 their Condition. 
 1896. Rockwell, Alfred P. (1834- ). — Roads and Pavements in France. 
 
 1896. Neely, Samuel T. — Traction Tests. (Government Bulletin.) 
 
 1897. Merrill, Frederick J. H. (1861- ). — Road Materials and Road 
 
 Building in New York. 
 1897. Pratt, J. T., and MacKenzie, Wm. — Pratt's Law of Highways. 
 
 Fourteenth Edition. 
 1897. Whittle, C. L. — The Forces which Operate to Destroy Roads, 
 
 with Notes on Road Stones and Problems therewith connected. 
 
 (Government Bulletin.) 
 
 1897. Highway Maintenance and Repairs. Taxation; Comparative 
 
 Results of Labor and Money Systems; Contract System of 
 Maintaining Roads. (Government Bulletin.) 
 1S98. Laws of the State of Illinois in Relation to Roads and Bridges. 
 
 1898. The Highway Law of New York State. 
 
 1899. Sioussat, St. George L. — Highway Legislation in Maryland. 
 1899. Cartland, John Henry. — Ancient Pavings of Pemaquid, Me. 
 1899. Eldridge, Maurice Owen. — Good Roads for Farmers. 
 
 1899. ___ _ .^Construction of Good Country Roads. 
 
 1899. Dodge, Martin. — Steel Track Wagon Roads. 
 
 1899. Report on the Highways of Maryland (Geographical Survey). 
 
 1899. Laws of Maryland Relating to Highways. 
 
 1899. Conder, J. B. R. — Handbook of Highway Cases. 
 
 1899. Harper, C. G. — The Bath Road. 
 
 1899. .—The Exeter Road. 
 
 1899. Maxwell, W. H. — The Construction of Roads and Streets. 
 
 1899. Holmes, J. A. (1859- ). — Some Recent Road Legislation in 
 North Carolina. (Government Bulletin.) 
 
 1899. Maxwell, William H. — The Construction of Roads and Streets. 
 With Historical Sketch of the Development of the Art of Road- 
 making. London. Cloth, 4^X61 ins.; 256 pages; illustrated. 
 Price, $1.30. 
 
 A ri5sum(? of the English practice in road-building and street construction* 
 with notes on the character of materials, calculation of quantities and 
 the various methods of systems now in use. 
 
 While the work is avowedly a com,pilation from many sources, it is 
 ^seful as a compilation of British methods of road construction and main- 
 tenance of that time. 
 
 n. d. Cook, John. — Cursory Remarks on Wheeled Carriages, 
 n. d Dawson, G. F. Crosby. — Street Pavements. 
 
BIBLIOGRAPHY OF ROADS 519 
 
 n. d. Edgworth, J. — New Mode of Constructing Streets. 
 
 n. d. Gilbert, Davies, M.P., F.R.S. — A Treatise on Wheels and Springs for 
 
 Carriages, 
 n. d. Parry, A. W. — The Use of ^team Rollers. 
 
 SECTION III.— 1900 TO DATE 
 
 The publications in this section comprise all the works of current 
 interest and many government documents. Each edition is listed 
 separately and brief descriptions, with prices, are given of several stand- 
 ard works which can be recommended for further study. 
 iQoo. Allen, A. T. — Footpaths: Their Maintenance, Construction, and 
 
 Cost. 
 1900. Harper, C. G. — The Great North Road. Two vols. 
 1900. Laws Relating to Roads, Ferries and Bridges of Mississippi. 
 1900. Eldridge, Maurice Owen. — Progress of Road Building in the United 
 
 States. 
 1900. Elliott, Byron K., and Elliott, William F. — Treatise on the Law of 
 
 Roads and Streets. 
 1900. Road Laws of the State of Iowa. 
 
 1900. Aitken, Thomas. — Road Making and Maintenance. (Third Edition) . 
 1900. Tillson, George William (1852- ). — Street Pavements and 
 
 Paving Materials. 
 1900. Johnson, Sarah Alice. — Facts, Suppositions, and Theories, or Road 
 
 Mending, &c. 
 
 1900. Wheeler, W. H. — The Repair and Maintenance of Roads. 
 
 1901. Clemens, Gasper C. — Manual of the Laws of Roads and Highways 
 
 in the State of Kansas. 
 
 190 1. Road Laws of Oregon. 
 
 190 1. Laws of the State of Missouri Relating to Roads, Highways, and 
 Bridges. 
 
 1901. Recent Road Legislation in North Carolina. 
 
 1901. Abbott, James Whitin. — Mountain Roads. (Government Bulletin.) 
 
 1901. Pope, Logan Waller. — The Selection of Materials for Macadam 
 Roads (Government Document). 
 
 1901. McCallie, Samuel W. (1856- ). — Report on the Roads and Road- 
 building Materials of Georgia. 
 
 1901. Le Strade di Milano — Milan, Italy. 
 
 1901. County Councils Association. — A Digest of Answers to a Series of 
 Questions with Regard to the Management of Main Roads and 
 Highways. 
 
 1901. Greenwell, Allen, and Elsden, James Vincent. — Roads: Their Con- 
 struction and Maintenance, with Special Reference to Road 
 Materials. 
 
 1901. Harper, C. G. — The Norwich Road. 
 
520 THE ART OF ROADMAKING 
 
 1902. Laws of Iowa Relating to Roads, Bridges and Ferries. 
 
 1902, Holmes, Joseph A. — Roadbuilding with Convict Labor in the 
 
 Southern States. (Government Bulletin.) 
 1902. Dodge, Martin. — Government Cooperation in Object-lesson Road 
 
 Work. (Government Bulletin.) 
 1902. Progress of Road Legislation and Road Improvement in the 
 
 Different States. 
 1902. Abbott, James Whitin. — Mountain Roads as a Source of Revenue. 
 
 (Government Bulletin.) 
 1902. Weicht, A. H. — Bau von Strassen und Strassenbahnen. — Berlin, 
 1902. Judson, William Pierson (1849- ). — City Roads and Pavements 
 
 suited to Cities of Moderate Size. (Second Edition.) 
 
 1902. Spalding, Frederick P. (1857- ). — Text-book on Roads and 
 
 Pavements. (Second Edition.) 
 
 1902. . — The Cambridge, Ely, and King's Lynn Road. 
 
 1902. . — The Holyhead Road. 
 
 1903. Connecticut Law for the Improvement of Public Roads. 
 
 1903. Laws of the State of Missouri Relating to Roads, Highways and 
 Bridges. 
 
 1903. Fox, William F. (1840- ). — Tree Planting on Streets and 
 Highways. 
 
 1903. Laissle, Friedrich. — Der Strassenbau Einschliesslich der Strassen- 
 bahnen. — Leipzig. 
 
 1903. Abbott, James Whitin. — Use of Mineral Oil in Road Improvement. 
 
 1903. Page, Logan Waller. — The Testing of Road Materials. (Government 
 Bulletin.) 
 
 1903. Buckley, Ernest Robertson (1872- ). — Highway Construction in 
 Wisconsin. 
 
 1903. Baker, Ira Osborn (1853- ). — Treatise on Roads and Pavements. 
 (First Edition.) 
 
 1903. Codrington, T. — Roman Roads in Britain. 
 
 1903. Gilbey, Sir Walter, Bart. — Early Carriages and Roads. 
 
 1903. Jeffreys, W. Rees. — Highway Administration in England and Wales 
 at the Beginning of the Twentieth Century. 
 
 1903. Latham, F. — Construction of Roads, Paths, and Sea Defences. 
 With Portions relating to Private Street Repairs, Specification 
 Clauses, Prices for Estimating, and Engineer's Replies to Queries. 
 
 1903. Stephens, J. E. R. — Digest of Highway Cases, with all the chief 
 Statutes on Highways, Bridges, and Locomotives. 
 
 1903. Tillson, George W. — Street Pavements and Paving Materials. A 
 
 Manual of City Pavements; the Methods and Materials of Their 
 
 Construction. For the Use of Students, Engineers and City 
 
 Officials. New York. Cloth, 6X9 ins.; xii + 532 pages; 60 
 
 illustrations. Price, $4.00. 
 
 Contents: History and Development of Pavements; Stone; Asphalt; 
 Brick-Claya and the Manufacture of Paving Brick; Cement, Cement Mortar 
 and Concrete; Theory of Pavements; Cobble and Stone-Block Pavements; 
 
BIBLIOGRAPHY OF ROADS 521 
 
 Asphalt Pavements; Brick Pavements; Wood Pavements; Broken-Stone 
 Pavements; Plans and Specifications; Construction of Street-Car Tracks 
 in Paved Streets; Width of Streets and Roadways, Curbs, Sidewalks, etc.; 
 Asphalt Plants. 
 
 1903. Latham, Frank. — The Construction of Roads, Paths, and Sea 
 
 Defences. With Portions relating to Private Street Repairs, 
 
 Specification Clauses, Prices for Estimating, and Engineers' 
 
 RepUes to Queries. London. Cloth, 6X9 ins. Price, $3.00, net. 
 
 This book discusses the necessity of good roads for traction, line of 
 roadway, setting out, drainage and coverings of roads, road-rolling, stone- 
 breaking, paving with wood, stone, brick, artificial slabs, etc. Short chap- 
 ters also deal with scavenging, watering, and snow removal from roads. 
 A portion of the book is devoted to sea-walls, with illustrations of walls at 
 Penzance and Margate (England), and also short chapters on rCad bridges 
 and artificial stone plants. Useful specification clauses on roads and streets, 
 sewers, and sea-walls, and also a table of approxim.ate prices of road 
 materials, are added at the end of the book, and in a pocket in the cover 
 is a tabulated statement of details of road construction, compiled from 
 replies of various engineers and of interest for reference. 
 
 1904. The New State Aid Road Law (Maryland). 
 
 1904. Maxwell, William H. — British Progress in Municipal Engineering. 
 
 1904. Beery, P. B. — Portland Cement Sidewalk Construction. 
 
 1904. Page, Logan Waller. — ^The Cementing Power of Road Materials. 
 
 (Government Bulletin.) 
 1904. Craig, A. — The Railroads and the Wagon Roads. (Government 
 
 Bulletin.) 
 1904. Drummond, R., C.E., F.S. A. (Scot.) . — The Evolution of Road 
 Making in Scotland. Paper Read before the Scottish Auto- 
 mobile Club. 
 1904. Fairless, Michael. — Roadmender. Re-issue. 
 1904. Ferguson, James. — The Law relating to Roads, Streets, and Rights 
 
 of Way in Scotland. 
 1904. Forbes, N. A., and Burmester, A. C. — Our Roman Highways. 
 1904. Hasluck, Paul N, — Road and Footpath Construction. 
 
 The British and Irish Road Book.^Issued by the CycUsts' Touring 
 Club. 
 Vol. I. — Southern and South- Western Counties. Sixth Edition. 
 Vol. 11. — Eastern and Midland Counties, including Wales. 
 
 Second Edition. 1898. 
 Vol. III.— Northern Counties. Third Edition. 1899. 
 Vol. IV.— Scotland. Second Edition. 1901. 
 Vol. v.— Southern Ireland. 1899. 
 Vol. VI.— Northern Ireland. 1900. 
 
 The most complete description of British roads available at the present 
 time, through which, and similar volumes contained in this list, the gradual 
 growth of the roads can be traced over a period of nearly three centuries. 
 
 1904. Spoon, William Luther. — Building Sand-clay Roads in Southern 
 
 States. (Government Bulletin.) 
 1904. Richardson, Robert W. — ^Progress of Roadbuilding in the Middle 
 
 West. (Government Bulletin.) 
 1904. Asphalt Paving. — Report of Commissioners of New York City. 
 
522 THE ART OF ROADMAKING 
 
 1905. Harper, C. G. — The Oxford, Gloucester, and Milford Haven 
 
 Road. 
 1905. Richardson, CUfford (1856- ). — The Modern Asphalt Pavement. 
 1905. Wallace, Henry (1836- ). — How to Make Good Dirt Roads. 
 1905. Lancaster, Sam C. — Practical Road-building in Madison Co., 
 
 Tennessee. (Government Bulletin.) 
 1905. Cushman, AUerton S. — A Study of Rock Decomposition under the 
 
 Action of Water. (Government Bulletin.) 
 1905. Manual for Iowa Highway Officers. 
 1905. Hurlbert, Archer Butler (1873- ). — The Future of Road-making 
 
 in America. 
 1905. Connecticut Law for the Improvement of Public Roads. 
 1905. Statutes of the State of Oregon Relating to Roads, etc. 
 1905. Road Laws of the State of Idaho. 
 
 1905. Improvement, Repair, and Maintenance of Public Highways of the 
 
 State of New York. 
 
 The publication of this book of instructions and suggestions was made 
 advisable by the numerous changes in the highway laws of the State of 
 New York. It sets forth a uniform system, of town accounting of highway 
 funds and also contains a compilation of statistics of the cost and main- 
 tenance of liighways and bridges throughout the state. 
 
 .1905. Allen, A. Taylor. — New Streets: Laying Out and Making Up. 
 
 London. Cloth, 6X9 ins.; 175 pages. Price, SI. 20, net. 
 
 The purpose of this book is chiefly to serve as a condensed form of 
 reference and examples of carrying out the essential parts and work entailed 
 by the British "Surveyor under the Public Health Act" of 1875, and the 
 "Private Street Works Act" of 1892. It deals strictly with British practice. 
 
 1906. Proceedings of the Good Roads Conference held at Denver, Colo., 
 
 1906. 
 
 1906. Pennsylvania Road Laws. 
 
 1906. Report of Royal Commission on Motor Cars. — London. 
 
 1906. Guinn, James Miller (1834- ). — El Camino Real. An Investiga- 
 tion into the History of early Roads in California. 
 
 1906. Lovegrove, E. J. — Attrition Tests of Road-making Stones. With 
 
 Petrological Description by John S. Flett, M.A., D.Sc, and 
 
 J. Allen Howe, B.Sc. London. Cloth, 8^ + 11^ ins.; xix + 80 
 
 pages; 79 illustrations. Price, S2.00. 
 
 These studies relate chiefly to sspecific rocks in Great Britain, but they 
 contain considerable information of general interest. After a few para- 
 graphs outlining the character of his investigations, the author subnaits 
 tables giving attrition tests from a large number of quarries and a con- 
 siderable variety of stones. The petrological descriptions are classified by 
 granite, porphyry, basalt, and other groups, and are accompanied by 
 photomicrographs. The descriptions are also supplemented by general 
 conclusions. 
 
 1906. Baker, Ira 0. (1853- ). — Drainage of Earth Roads. 
 
 1906. Tar and Oil for Road Improvement. (Government Bulletin.) 
 
 1906. Spoon, William Luther. — Construction of Sand-clay and Burnt-clay 
 
 Roads. (Government Bulletin.) 
 1906. Hotchkiss, William Otis, — Rural Highways of Wisconsin. 
 
BIBLIOGRAPHY OF ROADS 523 
 
 1906. Gillette, Halbert Powers (1869- ). — Economics of Road Con- 
 struction. Second Edition, Enlarged. Cloth, 6X9 ins.; 49 
 pages; 9 illustrations. Price, $1.00, net. 
 
 This small book gives a great deal of useful information in clear, brief, 
 and concise language. The contents are: Historical Review; Earth Roads 
 and Earthwork (Profile of Cross-section of Road, Longitudinal Profile, 
 Gutters and Drains, Embankments, Cost of Earthwork, Surfacing, Traction 
 and Tractive Power, Location); Gravel Roads; Macadam Roads (What 
 Holds Macadam Together, Quahty of Stone, Relative Wearing Powers of 
 Stone, Quarrying, Dynamite, Crushing, Hauling, Spreading, Rolling, 
 Sprinkling, Quantity, and Cost)- Telford Roads; Repairs and Maintenance 
 (Continuous vs. Intermittent System, Sandstone Macadam); Suggested 
 Improvements in Existing Road Specifications (Kind and Sizes of Broken 
 Stone, Depth of Pavement, Final Surfacing, Material for Embankments, 
 Thickness and Width of Pavements) ; Summary and Conclusions. 
 
 1906. Laws Relating to Highways and Bridges of Michigan. (Supple- 
 ment, 1907). 
 
 1906. AUen, A. Taylor. — Footpaths: Their Maintenance, Construction 
 and Cost. 
 
 1906. Baker, Ira 0. — The Construction and Care of Brick Pavements. 
 
 Reprint of part of a report on "The Paving Brick Industry of Illinois," 
 prepared for the Illinois State Geological Survey. 
 
 1907. Lord, Edwin C. E. — Examination and Classification of Rocks for 
 
 Road Building, Including the Physical Properties of Rocks with 
 Reference to Their Mineral Composition and Structure. (Govern- 
 ment Bulletin.) 
 
 This pamphlet is decidedly technical in character, but for engineers and 
 othei-s who wish to go thoroughly into the science of macadam-road building 
 materials it contains information of much value. 
 
 1907. Page, Logan W. — Object-lesson Roads. (Government Bulletin.) 
 1907. Whinery, Samuel (1845- ). — Specifications for Street Roadway 
 
 Pavements. New York. Paper, 6X9 ins.; 56 pages. Price, 50 
 
 cents, net. 
 
 "The large and successful experience of the author in the construction of 
 pavements, and his studious habits and carefulness of language, make 
 any article he may write upon the subject of especial interest. 
 
 "The author's conclusions respecting guarantees, taken in connection 
 with the form of the guarantee of work and material, should meet ^ath 
 general approval both by municipalities and contractors, . . . The pam- 
 phlet is a valuable contribution to the literature upon the proper con- 
 struction of pavements." — Engineering News, Aug. 15, 1907. 
 
 The specifications cover General Work, Foundations, Bituminous Pave- 
 ments, Granite, Brick and Wood Block Pavements. 
 
 1907. Road Laws of New Castle County, Delaware. 
 
 1907. Connecticut Law for the Improvement of PubUc Roads. 
 
 1907. Byrne, Austin Thomas (1859- ). — A Treatise on Highway Con- 
 struction. Designed as a Text-book and Work of Reference for 
 all who may be engaged in the Location, Construction and 
 Maintenance of Roads, Streets and Pavements. Fifth Edition, 
 Revised and Enlarged. New York. Cloth, 5|X9i ins.; 
 xliii + 1,024 pages; 309 illustrations; 92 tables. Price, $5.00. 
 
 In the preface to the first edition of this work, published in 1892, the 
 author states: 
 
 "Although volumes have been written on the subject of highway 
 construction, still, the matter is widely scattered through the pages of 
 
524 THE ART OF ROADMAKING 
 
 the standard works on engineering, technical journals, and periodicals, 
 
 in pamphlets and reports of city engineers, and is, therefore, not 
 
 always easily accessible when wanted. The author, having found the 
 
 need of a comprehensive and practical work of reference upon the 
 
 many subjects connected with highways, hag in the following pages 
 
 endeavored to collate the varied mass of information." 
 
 In order to keep abreast of the times, further editions of the book were 
 
 issued in 1896 and 1900, and in the present one, an extensive revision was 
 
 made, bringing the work thoroughly up to date. 
 
 The book treats of every branch of the subject and may be said to be 
 cyclopedic in character. The titles of the chapters are: Pavements, 
 Materials employed in the Construction of Pavements, Stone Pavements, 
 Wood Pavements. Asphaltum and Coal-Tar Pavements, Brick Pavements, 
 Broken-Stone Pavements, Miscellaneous Pavements, Foundations, Resist- 
 ance to Traction, Location of Country Roads, Width and Transverse Con- 
 tour, Earthwork, Drainage and Culverts, Bridges, Retaining Walls, Pro- 
 tection Works, Tunnels, Fencing, City Streets, Foothpaths, Curbs, Gutters, 
 Reconstruction and Improvement of Country Roads, Maintenance-Repairing, 
 Cleansing, Watering, Trees, Staking Out the Work, Specifications and 
 Contracts, Implements and Prices, Miscellaneous Notes Four Appendices: 
 Naming and Numbering Country Roads and Houses; Methods of Assessing 
 the Cost of Street Paving; Ordinance Regulating the Width of Wagon- 
 tires; Cycle Paths. 
 
 The treatment of the various chapters is quite full and satisfactory. 
 There are over three hundred illustrations and there is a remarkably com- 
 prehensive index, covering 93 pages. 
 
 1907. Hirst, Arthur R. — Road Pamphlets. Wisconsin, Geological and 
 
 Natural History Survey. No. 1: Earth Roads. No. 2; The 
 
 Earth Road Drag. No. 3: Stone and Gravel Roads. No. 4: 
 
 Culverts and Bridges. 
 
 These are popular expositions on the subjects indicated, and should be 
 useful for their intended purpose of aiding in the good road movement. 
 
 1907. Buckley, Ernest Robertson (1872- ). — Public Roads; Their 
 
 Improvement and Maintenance. 
 1907. Eldridge, Maurice Owen. — Public-road Mileage Revenues and 
 
 Expenditures in the United States in 1904. (Government 
 
 Bulletin.) 
 
 Gives statistics by states and counties showing the character and extent 
 of public roads, the expenditures therefor and the way in which the money 
 is raised, also contains a synopsis of the road laws of various states and a 
 tabular comparison by states of the percentage of improved roads, the value 
 of farm lands, and the value of rights of way. 
 
 1907. Fletcher, Austin B. — The Construction of Macadam Roads. (Gov- 
 ernment Bulletin.) 
 
 Gives a good idea of methods employed in constructing macadam roads, 
 especially as carried out under the direction of the Massachusetts Highway 
 Commission. The materials and appliances used are described; drainage, 
 preparation of the subgrade and the placing of the macadam are discussed. 
 Extracts from specifications used in various states are given, also cost data, 
 and drawings of culverts. 
 
 1907. Annual Report of the Commissioner of Highways for the Year 1908. 
 
 (Maine.) 
 
 Reviews the work of the year and gives some interesting cost data. A 
 reprint of the proceedings of the First New England Road Conference, 
 held in Boston, Nov. 23-24, 1908, is given. 
 
 1907. Patton, W. M. — A Treatise on Civil Engineering. New York. 
 
 Second Edition. Cloth, 6X9 ins.; 1,672 pages; 464 illustrations 
 
 and diagrams. Price, $7.50. 
 
 In this voluminous treatise, nearly all branches of engineering science 
 that could be grouped under the general title of "Civil Engineering," have 
 
BIBLIOGRAPHY OF ROADS 525 
 
 been treated. Location of Highways and Country Roada has been covered 
 in one chapter, followed by a chapter on Location of Lines of Communi- 
 cation by Topographical Maps and one on Resistance to Traction on High- 
 ways. 
 
 1907. Goodhue, W. F. — Municipal Improvements. A Manual of the 
 
 Methods, Utility and Cost of Public Improvements for the 
 
 Municipal Officer, Third Edition. Cloth, 4 X 6 in. ; viii -h 207 
 
 pages; illustrated. Price, $1.50. 
 
 This book is intended not for the technical reader, but for the members 
 of the town council and for the non-professional reader. There are 30 
 chapters, of which two treat of street surface and street grades and one of 
 highway bridges. 
 
 1908. Leighton, Henry. — Road Materials of Southern and Eastern Maine. 
 
 1908. Hubbard, Prevost. — Dust Preventives. (Government Bulletin.) 
 
 This circular is rather a summary and compilation of principles than a 
 record of experimental work. 
 
 1908. Page, Logan W. — Dust Preventives. (Government Bulletin.) 
 1908. Progress Reports of Experiments with Dust Preventives. (Govern- 
 ment Bulletin.) 
 1908. Hill, Gary LeRoy. — Wood Paving in the United States. (Govern- 
 ment Bulletin.) 
 
 This pamphlet takes up the progress of wood paving, the qualities of -jreo- 
 soted wood pavem,ent, problems in wood paving, laying the pavement, laain- 
 tenance and a descriptive discussion of an experimental pavement. 
 
 1908. Palliser, Charles. — Modern Cement Sidewalk Construction . A 
 
 Practical Treatise for the Workman. New York. Cloth, 5X7 
 
 ins.; pp. 64; illustrated. Price, $0.50. 
 
 The construction of cement sidewalks, curbs and gutters is concisaly ex- 
 plained in this book, directions being given regarding the selection and test- 
 ing of the cement, sand, stone, gravel, etc., the special tools used ; the laying, 
 finishing, seasoning, coloring, etc.; together with cost data for a number of 
 cases, with complete specifications for each. Simple language has been used 
 throughout the book, and all technical terms introduced are clearly defined. 
 
 1908. Ryves, Reginald Arthur .^The King's Highway. The Nature, 
 
 Purpose and Development of Roads and Road Systems. London 
 
 and New York. Cloth, 8^X111 ins.; 96 pages; 34 illustrations. 
 
 Price, $2.00, net. 
 
 This book is largely devoted to English roads and in many ways it is 
 quite different from other road books. There are 21 comparatively short 
 chapters dealing with Foreign (outside of Great Britain) Road Systems, 
 Some Points of Foreign Practice, Road Administration in the United 
 Kingdom, The Departmental Committee of 1903, Highway Law, Mechan- 
 ical Power Traction, Width and Safety, The Road Crust — Wearing and 
 Weathering Roads, Road Lamps and Carriage Lamps, Special Roads, 
 Maintenance and Repair, Road Stones, Tests of Road Stones, Wheels, 
 Dust and Prevention — Tar-Maoadam, Bridges, Climate, and Geology, The 
 Roadside, Frost, Wind and Snow. 
 
 1908. Richardson, Clifford (1856- ). — The Modern Asphalt Pavement. 
 Second Edition, Revised and Enlarged. New York. Cloth, 
 5^X91 ins.; 629 pages; 42 illustrations. Price, $3.00. 
 
 "The object of this book is to demonstrate the nature of asphalt 
 pavements and the causes of defects in them, to bring about improve- 
 ment in the methods of their construction, and to show how this can 
 be done. 
 
 "The conclusions which are advanced are the results of twenty 
 years' experience in the industry by the writer with pavements in 
 
526 THE ART OF ROADMAKING 
 
 over one hundred cities in the United States and several in England, 
 Scotland, and France, involving the construction of between twenty 
 and thirty million yards of surface." — Extract from Introduction. 
 The contents are divided into nine parts: The Foundation and Inter- 
 mediate Course; The Materials Constituting the Asphalt Surface Mixture; 
 Native Bitumens in Use in the Paving Industry; Technology of the Paving 
 Industry; Handling of Binder and Surface Mixture on the Street" The 
 Physical Properties of Asphalt Surfaces; Specifications for, and Merits 
 of Asphalt Pavements; Causes of the Defects in, and the Deterioration of 
 Asphalt Surfaces; Control of Work; Appendix. 
 
 This is one of the recognized standard books on the subject of road 
 work — in a lengthy review of the first edilion (1905) Engineering News 
 speaks in most favorable terms of it and says; *'It is not too much to say 
 that Mr. Richardson's book should be classed with those which appear 
 too infrequently, but whose appearance mark epochs in the industry to 
 which they relate." 
 
 1908. Spalding, Frederick Putnam (1857- ). — A Text-book on Roads 
 
 and Pavements. Third Edition, Revised and Enlarged. New 
 
 York. Cloth, 4| X 7^ ins. 340 pages; 51 illustrations. Price, 
 
 $2.00. 
 
 "The aim of this work ia to give a brief discussion, from, an 
 engineering standpoint, of the principles involved in highway work, 
 and to outline the more important systems of construction with a 
 view to forming a text which may serve as a basis for a systematic 
 study of the subject." — Extract from Preface. 
 
 "While it is primarily intended as a text-book for classes in engi- 
 neering schools, it will be found a convenient and satisfactory hand- 
 book for non-professional and general readers who wish to inform 
 themselves in the elementary principles of designing and constructing 
 roads and pavements. . . The arrangement of subjects and 
 chapters does not differ materially from the other leading books 
 on roads and pavements, . . . but within the appropriate scope of 
 a college text-book, the author has accomplished all that could 
 reasonably be demanded." — Engineering News, Dec. 17, 1908. 
 Contents: Road Economics and Management; Drainage of Streets 
 
 and Roads; Location of County Roads; Improvement and Maintenance 
 
 of Country Roads; Broken Stone Roads; Foundation for Pavements; 
 
 Brick Pavements ; Bituminous Pavements ; Wood-Block Pavements ; 
 
 Stone-Block Pavements; City Streets. 
 
 1908. Morrison, Charles Edward. — Highway Engineering. New York. 
 
 Cloth, .51 X9 ins.; 315 pages; 60 illustrations. Price, $2.50. 
 
 The preface states that this book was prepared as a text-book for second- 
 year students in the Civil Engineering department of Columbia University, 
 with a view to furnishing a text in which the fundamentals of the subject 
 should not be buried in a mass of detail; and further states that the book 
 is not a reference work, but rather one in which it has been the endeavor 
 to outline and emphasize those basic principles which are essential to 
 good highways. The contents cover: Road Resistances, Earth Roads, 
 (i ravel Roads, Broken-stone Roads, Miscellaneous Roads, Street Design, 
 Stone Pavements, Brick Pavements, Asphalt Pavements, Modern AVooden 
 Pavements. 
 
 1908. Brandt, Charles Edward (1847- ). — Road Locating and Building 
 
 Simplified. For Use in the Common Schools. Boards, 5X7| 
 
 ins.; 106 pages; illustrated. Price, $1.00. 
 
 This book was written for use in the common schools and is of little 
 practical value to the engineer. It contains the rudiments of road making 
 and endeavors to simplify the art of road location and construction to 
 the level of elementary studies with the hope of educating the school pupils 
 up to the good-roads idea. 
 
 1908. Byrne, Austin T., and Phillips, Alfred E. — Highway Construction. 
 
 A Practical Guide to Modern Methods of Roadbuilding and the 
 
 Development of Better Ways of Communication. Cloth, 6^X9f 
 
 ins.; 136 pages; 79 illustrations and 2 plates. Price, $1.00. 
 
 This is an elementary book consisting mainly of a brief epitome of 
 Byrne's cyclopedic volume, "A Treatise on Highway Construction." 
 
BIBLIOGRAPHY OF ROADS 527 
 
 1908. Boorman, Thomas Hugh (1851- ). — Asphalts: Their Sources 
 
 and UtiUzations. New York. Cloth, 6^X9^ ins.; 216 pages; 
 
 48 full-page plates. Price, $3.00. 
 
 A comprehensive manual in the asphalt industry. The first eleven 
 chapters are devoted to descriptions of the occurrence, properties, and uses 
 of the various forms of asphaltic substances. Two chapters then follow 
 on the developm,ents of the asphalt industry. Asphaltic oils and their 
 application to roads for the purpose of miakiDg them dustless are discr.ssed 
 in the succeeding six chapters. There are then included chapters dealing with 
 municipal asphalt plants, asphalt waterproofing, asphalt for manufacture, 
 and a short chapter on asphalt machinery. 
 
 1908. Supplement to Pennsylvania Road Laws. 
 
 1908. Coane, John M., Henry, E., and John M., Jr. — Australasian Roads. 
 A Treatise, Practical and Scientific, in the Location, Design, 
 Construction and Maintenance of Roads and Pavements. 
 Melbourne, Australia. Cloth, 5|X8| ins.; 334 pages; 13 illus- 
 trations. 
 
 The title of this book is somewhat misleading. Instead of being a treatise 
 on the method of road building in Australia, as one might expect from 
 the title, it is a compilation of data on the best practice in road engineer- 
 ing in other countries for the guidance of Australasians. 
 
 1908. Judson, William Pierson (1849- ). — Road Preservation and 
 Dust Prevention. New York. Cloth, 5^XSJ ins.; 146 pages; 
 illustrated. Price, $1.50, net. 
 
 Mr. Judson hag rendered the road engineers and the road makers of the 
 country a valuable service in collecting and sifting the great mass of data 
 on the subject of dust prevention scattered through periodicals and society 
 transactions and in reducing this material to a condition that permits of 
 comparisons being made, giving officials who are not experts reliable 
 information to guide them in the selection of a suitable remedy for the 
 cure of their own local troubles. 
 
 The opening chapter treats of the origin of road dust and its economic 
 value in the preservation of the road surface. The other eight chapters 
 deal with the various means of treatment^ and construction with a view 
 toward dust prevention, taking up, lespectively. Moisture, Oil Emulsions, 
 Oils, Coal-tar Preparations, Tar-spraying ilachines, Tar-macadam, Rock- 
 A,sphalt, Macadam and Bitulithic Pavement. Each chapter describes tlie 
 general process, its variations and details of experiments, giving methods 
 of use, results, costs, a.id a summary of conclusions arrived at based on a 
 consideration of the details of many experiments. The comparative values 
 of the various methods and their suitability for local conditions as brought 
 out, will enable road builders to profit by the experience of others and 
 thus save m.uch of the cost of experimenting for themselves. 
 
 1908. The Control of Street Openings. A Discussion Concerning an Ulti- 
 mate Remedy for the Destruction of City Pavements by Openings. 
 
 1908. Baker, Ira 0, — A Treatise on Roads and Pavements. New York. 
 New Printing of 1903 Edition. Cloth, 6X9 ins.; 655 pages; 
 65 tables; 171 illustrations. Price, $5.00. 
 
 Consists of two parts: I. — Country Roads, including matters relating 
 to earth, gravel and broken-stone roads in rural districts; II. — Street 
 Pavements. The reason for this division is given in the introduction: 
 
 "The problems involved in the construction and maintenance of rural 
 highways differ materially from, those which are encountered in the improve- 
 ment and care of city streets . . In each division of the subject certain 
 general principles will first be considered, and the further discussion will 
 be divided according to the several materials in use for the road surface. 
 
 In a review in Engineering News (February 19, 1903) the merits and 
 limitations of this book were compared in detail with those of the various 
 other works on the subject, and the conclusions reached were summarized 
 in one paragraph: 
 
528 THE ART OF ROADMAKING 
 
 "Having considered the whole treatise somewhat in detail, we may 
 say that as a text-book for students this new work is superior to Byrne, 
 but partly because it is more recent. It is also superior to Tillson, but 
 chiefly because it is more comprehensive. Tillson wrote with a much 
 wider experience than has any other author of a manual on pavements, 
 but he held himself closely to that subject, even to the exclusion of 
 sidewalks. This limitation 13 commendatory, but must be borne in mind 
 when assigning Tillson a place among other treatises on road and street 
 work. But when we look at Baker's work from the viewpoint of the 
 engineer already possessed of most of the American works above men- 
 tioned, we find very little that is not to be found in them and in recent 
 current literature. The author has compiled with excellent judgment, 
 but excepting some original data on traction, voids in sand and stone, 
 and analyses of certain gravels, we find no real contribution to the stock 
 of engineering knowledge of roads and pavements." 
 
 1908. King, David W. — The Use of the SpUt-log Drag on Earth Roads. 
 (Government Bulletin.) 
 
 igoS. McCuUough, Ernest. — Engineering Work in Towns and Small 
 Cities. Second Edition. Chicago. Cloth, 4| X7| ins.; 510 
 pages; illustrations and tables. Price, $3.00, net. 
 
 In the introductory chapter the author writes: 
 
 "This book is written for two classes of officials in towns and cities 
 having a population of less than 20,000 inhabitants, and it may be 
 found useful in some larger places. 
 
 ' ' Elected officials and those who have no technical education 
 belong to the fii-st clasi. They come into intimate relations with 
 men who have charge of engineering work, are interested in it, often- 
 times direct it, and therefore may be benefited by reading this 
 book. 
 
 "The second class is composed of engineers and surveyors holding 
 the position of town or city engineer, especially those with little 
 or no previous experience in muninipal engineering." 
 
 Three chapiers (100 pages) are devoted to Hoads and Streets; 
 Walks, Curbs, and Gutters; Street Pavements. 
 
 1908, Aitkin, Thomas. — Roadmaking and Maintenance. A Practical 
 Treatise for Engineers, Surveyors and Others. With an His- 
 torical Sketch of Ancient and Modern Practice. Second Edition. 
 London. Cloth, 6X91- ins.; 525 pages; 167 illustrations. Price, 
 21s.; American, $6.00, net. 
 
 This is a British book, but its recognized usefulness h"3 made it a 
 standard work in Amerira as well as in England. The results of a wide 
 experience are set down in a clear and orderly fashion, supplemented by 
 well-chosen illustrations. 
 
 The contents are divided into two parts: (1) Macadamized Roads and 
 (2) Carriageways and Footpaths. The titles of the chapters are: Part I. 
 — Road-Making and Maintenance — Historical Sketch; Resistance to Trac- 
 tion — Wheels and Weights on Them; Laying Out New Roads and the 
 Improvement of Existing Lines of Communication; Earthwork, Drainage, 
 Retaining Walls, Culverts, Bridges and Protection of Roads; Road-Making 
 Materials; Quarrying; Stone-Breaking and Haulage; Road-Rolling and 
 Scarifying; The Construction of New and the Maintenance of Existing 
 Roads; The Prevention of Dust. Part 11. — Carriageways and Footways — 
 Preliminary Remarks — Foundations and Pitch ed Pavements ; Wood 
 Pavements; Asphalt Pavements; Brick Pavements for Carriageways; 
 Tar Macadam ■ Conclusions ; Footways-Paving ilaterials for Footpaths, 
 Curbs, Channels, Gutters; Testing the Surfaces of Carriageways; Subways. 
 
 The first edition of Mr. Aitkin's book was brought out in 1900 and was 
 very favorably received. It appeared at a time when the art of road- 
 making had not advanced to as high a state of perfection in this country 
 as in Great Britain, and it was particularly useful as recognizing the value 
 and describing the methods of substituting machine for hand labor in both 
 construction and maintenance. It also gave detailed figures of cost and, 
 while these are, of course, of far less use in this country than in England, 
 owing to the variation in local conditions and in currency systems, the 
 fact that many of these were inserted to show the relative advantages of 
 different methods, make them of some interest to American engineers. 
 The present edition has been thoroughly revised. The greater part of the 
 
BIBLIOGRAPHY OF ROADS 529 
 
 volume relates to the construtcion of macadam and like roads, but the 
 various kinds of city pavements are also considered. 
 
 In an Appendix of 50 pages is given the full text of a report on "The 
 Resistance of Road Vehicles to Traction," made to the British Association 
 for the Advanr',em,ent of Science, by a committee of which the author was 
 a member. 
 
 1909. Judson, William Pierson (1849- ). — City Roads and Pavements. 
 
 Suited to Cities of Moderate Size. Fourth Edition, Revised. 
 
 New York. Cloth, 5|X8| ins.; 197 pages; 69 illustrations. 
 
 Price, $2.00, net. 
 
 This book deals especially with the many varieties of hard-surfaced 
 roads, and has for a number of years been considered a standard guide 
 to the building of rural highway and town streets, as well as of city pave- 
 ments. 
 
 Some interesting historical matter in early stone wheel tracks in America 
 are given; also tables for determining standard crowns, giving the cost 
 of asphalt pavement?, grades and costs of different kinds of pavements 
 and other valuable information of like character. 
 
 The titles of the chapters are: Preparation of Streets for Pavements; 
 Ancient Pavements; Modern Pavements; Concrete Base for Pavement; 
 Stofie-Block Pavements; Concrete Pavements; Wood Pavements; Iron- 
 Slag Block Pavements ; Vitrified -Brick Pavements ; American Sheet- 
 Asphalt, Artificial and Natural; Bitulithic Pavement; Broken Stone Roads. 
 
 1909. Smith, J. Walker. — Dustless Roads. Tar Macadam. A Practical 
 
 Treatise for Engineers, Surveyors and others. London. Cloth, 
 6X9 ins.; 225 pages; 24 illustrations. Price, $3.50, net. 
 
 This book is baaed largely upon a long continued intimate personal 
 experience in dealing with the subject of tar macadam. 
 
 Over thirty pages are devoted to the production and refinement of tar. 
 The standardization of the matrix and associated tests, the aggregate, the 
 different methods of preparing and laying tar macadam (four chapters), 
 and naechanical mixing are then taken up and later in the book the effects 
 of wear, porosity, density, and distribution of weight, scavenging or road 
 cleansing, watering, and maintenance generally; camber or crown, grade, 
 noiselessness, and hygienic advantages and wearing and tractive effort are 
 considered. 
 
 The final chapter, entitled "Tar Spraying or Spreading Ordinary Macadam 
 Surfaces," contains considerable information on tar spraying, as well as 
 interesting but brief history of the practice. An appendix gives in tabulated 
 form replies received to inquiries regarding "tar macadam and the tarring 
 of macadam surfaces," made by various British municipal engineers. These 
 returns are also drawn upon by the author from time to time throughout 
 a large part of his text, thus supplementing his own experience and ideas 
 with those of others. 
 
 1909. Vinsonneau, Jules. — Le Route Moderne. — Paris. 
 
 1909. Harris, G. Montagu. — The First International Road Congress, Paris, 
 
 1908. London. Cloth, 6X9 ins.; 140 pages; Price, $1.50. 
 
 1909. Thomson, Sanford E. — Concrete in Highway Construction. §1.00. 
 
 1910. Frost, Harwood. — The Art of Roadmaking. New York. Cloth, 
 
 6X9 ins.; 544 pages; 260 illustrations. Price, $3.00, net. 
 
 An explanation of the problems involved in the building of roads, the 
 various roadmaking materials, qualities of roads suited for various purposes, 
 md other information written in a style suitable for the general reader. 
 
 EARTHWORK AND ROCK EXCAVATION 
 
 Allen, C. F. — Tables for Earthwork Computation. $1.50. 
 Baker, B. — Lateral Pressure Earthwork. $0.50. 
 Crandall, C. L. — Railway and Other Earthwork Tables. Third 
 Edition. $1.50. 
 
530 THE ART OF ROADMAKING 
 
 Crockett, C. W. — Methods for Earthwork Computations. $1.50. 
 Cunningham, D. W.— Earthwork Tables. $4.25. 
 Gillette, H. P.— Rock Excavation, Methods and Cost. 1904. $3.00. 
 1903. Gillette, H. P.— Earthwork and Its Cost. New York. Cloth, 
 
 5X8 ins.; 244 pages; tables, folding plates and illustrations. 
 
 Price, $2.00, net. 
 
 There are 17 chapters treating of: The Art of Cost Estimating; Earth 
 Shrinkage; Earth Classification and Cost Data for all kinds of work in 
 connection with excavating, grading, dredging, digging, filling, etc. 
 
 1905. Gillette, H. P. — Handbook of Cost Data for Contractors and Engi- 
 neers. A Reference Book giving Methods of Construction and 
 Actual Costs of Materials and Labor on Numerous Engineering 
 Works. Chicago. Morocco, 4^X6| ins.; 610 pages; 30 illus- 
 trations and many tables. Price, $4.00, net. (See page 533.) 
 
 As explained by the title, this book is a record of costs of actual work. 
 It deals with many classes of engineering practice, one section (Sec. II.) 
 being devoted to "Cost of Earth Excavation"; one (Sec. III.) to "Cost 
 of Rock Excavation, Quarrying, and Crushing," and one (Sec. IV.) to 
 "Cost of Roads, Pavements, Walks," etc. Macadam and telford roads, 
 the various kinds of pavements, curbs, gutters, and walks are discussed 
 and their detail costs set forth. The first two sections are principally a 
 synopsis and condensation of the author's books ; ' ' Earthwork and Its 
 Cost ' ' and ' ' Rock Excavation — Methods and Cost, ' ' both of which are 
 elsewhere noticed. 
 
 1907. Henderson, R. S. — Earthwork Tables. New York. Heavy paper; 
 
 oblong; 32 pages. Price, $1.00, net. 
 
 Divided into two parts: 
 
 Part I. — Preliminary Earthwork Tables, giving cubic yards per 100 feet 
 for level sections, to which is added a graphical method of estimating 
 quantities from a profile. 
 
 Part II. — Earthwork Tables, giving the volume in cubic yards of pris- 
 moids 100 feet long by the average and area method. 
 
 This is a very useful book of tables; exceptionally complete, wide in range 
 and compact in arrangement. 
 
 Grace's Earthwork Tables for Calculating the Cubical Contents 
 of Cuttings. 1908. 15.00. 
 
 Housden, C. E.— Practical Earthwork Tables. 1907. $0.90. 
 
 Howard, C. R. — Earthwork Mensuration. $1.50. 
 
 Hudson, J. R. — Tables for Calculating Cubic Contents of Excava- 
 tions, etc. $1.00. 
 
 Morris, E. — Easy Rules for Measurement of Earthwork. $1.50. 
 
 Prelini, C— Earth and Rock Excavation. 1904. $3.00. 
 
 Taylor, T. U. — Prismoidal Formulae and Earthwork. $1.50. 
 
 Trautwine, J. C. — Method of Calculating Cubic Contents of Excava- 
 tions and Embankments by Diagrams. Ninth Edition. $2.00. 
 
 "Warner, J. — New Theorems, Tables, and Diagrams for Computation 
 of Earthwork. $4.00. 
 
 BLASTING AND EXPLOSIVES 
 
 Andre, G. G.— Rock Blasting. $3.00. 
 Berthelot, M. — Explosives and Their Power. $9.60. 
 Daw, A. W., and Z. W. — Principles of Rock Blasting. Part I. 
 $6.00. 
 
BIBLIOGRAPHY OF ROADS 531 
 
 Eissler, M. — Hand-book on Modern Explosives. $5.00. 
 
 .—Modern High Explosives. Third Edition. $4.00. 
 
 Foster, J. G. — Submarine Blasting in Boston Harbor. $3.50. 
 Guttman, O.— Blasting. $3.00. 
 
 Maurice, W. — Electric Blasting Apparatus and Explosives. $3.50. 
 Sanford, P. G.— Nitro-Explosives. $3.00. 
 
 CULVERTS AND DRAINS 
 
 Chamberlain, W. I.— Tile Drainage. $0.35. 
 
 Dempsey, G. D. — Drainage of Lands, Towns, etc. $1.80. 
 
 Jones, E. R. — Notes on Drainage. $1.00. 
 
 Klippart, J. H. — Principles and Practice of Land Drainage. $1.00. 
 
 Marston, A. — Sewers and Drains. $1.00. 
 
 Miles, M. — Land Draining. $1.00. 
 
 Scott, J. — Draining and Embankment. $0.60. 
 
 Waring, G. E.— Drainage for Profit and Health. $1.00. 
 
 HIGHWAY BRIDGES 
 
 Boiler, A. P. — Construction of Iron Highway Bridges. $2.00. 
 
 1721. Gautier, Hubert (1660-1737). — Traite de la Construction des 
 Chemins. 
 
 1850. Geddse, George. — Observations on Plank Roads. 
 
 1899. Report on the Highways of Maryland. 
 
 1901. Cooper, T. — General Specifications for Foundations and Substruc- 
 tures of Highway and Electric Railway Bridges. $1.00. 
 
 1901. Law, Henry. — The Construction of Roads and Streets. Sixth 
 Edition. 
 
 1904. Fowler, C. E. — Ordinary Foundations. $3.50. 
 
 n. d. Osborn Engineering Co. General Specifications for Highway Bridge 
 Superstructures. $0.25. 
 
 n.^. Thacher, E. — ^General Specifications for Highway Bridges. SO. 25. 
 
 1906. Buel, Albert W. — General Specifications for Steel Railroad Bridges 
 and Structures, with a section making them applicable to High- 
 way Bridges and Buildings. $0.50. 
 
 1908. Watson, W. J. — General Specifications for Concrete Bridges. $1.00. 
 
 1908. Ketchum, Milo S. — The Design of Highway Bridges and the Calcu- 
 lation of Stresses in Bridge Trusses. New York and London. 
 Cloth, 6X9 ins; xxi + 554 pages; 309 illustrations; 77 tables. 
 $4.00, net. 
 
 "The aim in writing this book has been to give a brief course in the 
 calculation of the stresses in bridge trusses, followed by a systematic dis- 
 cussion of the details and design of highway bridges. 
 
 "While there are many excellent books in which the different types 
 of railway bridges are discussed in detail, little attention has heretofore 
 been given to the design of highway bridges. As a consequence of this 
 neglect, many of our highway bridges have been very badly designed; 
 the design of these structures being ordinarily left to an engineer without 
 experience, or to the agent of some bridge company, who is more interested 
 
532 THE ART OF E.OADMAKING 
 
 in the resulting profits than in obtaining a good design. The calculation 
 of the stresses in highway and railway bridges are similar, but the problems 
 in the design of the two types are very different, due to the different require- 
 ments and conditions, 
 
 "In the course of the calculation of stresses, both the algebraic and the 
 graphic methods of calculating stresses in bridge trusses are described 
 in detail." — Extract from Preface. 
 
 The above extract from the Preface will give a general idea of the nature 
 of the book. It was primarily written for the purposes of a text-book 
 for engineering schools, but, on the other hand, it is also intended to meet 
 the needs of municipal and county engineers, surveyors, and all men 
 engaged in highway bridge construction, whose duties require a knowledge 
 of design and construction, and as the first book on the specific subject 
 of highway bridges that has been pubhshed for some time, it is deserving 
 of the most cai-eful consideration. 
 
 The contents are divided into three parts: Stresses in Steel Bridges; 
 The Design of Highway Bridges; and a Problem in Highway Bridge 
 Details. Part I. deals with Types of Steel Bridges; Loads and Weights 
 of Highway Bridges; Methods for the Calculation of Stresses in Framed 
 Structures; Stresses in Beams; Stresses in Highway Bridge Trusses; 
 Stresses in Railway Bridge Trusses; Stresses in Lateral Systems; Stresses 
 in Pins; Eccentric and Combined Stresses; Deflection of Trusses; Stresses 
 in Rollers and Camber; the Solution of Problems in the Calculation of 
 Stresses in Bridge Trusses. Part 11. takes up Short Span Steel Highway 
 Bridges; High Truss Steel Highway Bridges; Plate Girder Bridges; Design 
 of Truss Members- The Details of Highway Bridge Members; The Design 
 of Abutments and Piers- Stresses in Solid Masonry Arches; Design of 
 JIasonry Bridges and Culverts; The Design of Timber and Combination 
 Bridges; Erection, Estimates of Weight and Cost of Highway Bridges; 
 General Principles of Design of Highway Bridges. Part III. discusses in 
 detail the design of a 160-ft. Pratt truss span. 
 
 1909. Tyrell, H. S. — The Longest Simple-Truss Span Highway Bridge. 
 Paper, 6X9 ins.; 22 pages, 15 diagrams, and 1 half-tone view. 
 Price, 50 cents. 
 
 This pamphlet describes the highway bridge over the Miami River at 
 Elizabeth town, Ohio, which is remarkable as being the longest simple- 
 truss span in existence. 
 
 FORESTRY 
 
 Brown, J. P.— Practical Arboriculture, 1906. $2.50. 
 
 Bruncken, E.— North American Forests and Forestry. $2.00. 
 
 Fernow, B. E. — Economics of Forestry. $1.50. 
 
 Fuller, A. S. — Practical Forestry. $1.50. 
 
 Gifford, J. — Practical Forestry for Beginners. $1.20. 
 
 Hough, F. B.— Elements of Forestry. $.1.50 
 
 Hough, R. B. — American AVoods. Each part, $5.00. 
 
 Houston, E. J.— Outlines of Forestry. $1.00. 
 
 Nisbet, J.— Studies in Forestry. $2.00. 
 
 Roth, F.— First Book of Forestry. $1.20. 
 
 Schwartz, G. F. — Forest Trees and Forest Scenery. $1.50. 
 
 Schlich, W.— Manual of Forestry. 5 vols. $17.20. 
 
 Springer, J. S. — Forest Life and Forest Trees. $1.50. 
 
 Typical Forest Trees. 3 ser. $1.00. Each, $0.40. 
 
 Unwin, A. H.— Future Forest Trees, 1906. $2.25. 
 
 TUXXELING 
 
 While this branch of engineering is not necessarily connected with 
 the work of the municipal engineer and road builder, a knowledge of 
 tunnel practice is useful. 
 
BIBLIOGRAPHY OF ROADS 533 
 
 1905. Prelini, Charles. — Tunneling: A Practical Treatise. New York and 
 
 London. Cloth, 6X9 ins.; 326 pages; 150 illus. Price, $3.00. 
 
 The general purpose of this book is to explain all the operations that 
 are required in tunneling and to illustrate by suitable examples the actual 
 application of these methods in practice. 
 
 1906. Stauffer, David McN. — Modern Tunnel Practice. Illustrated by 
 
 Examples taken from Actual Recent Work in the United States 
 
 and in Foreign Countries. New York. Buckram, 6X9 ins.; 
 
 322 pages; 138 illustrations. Price, .$3.50, net. 
 
 The material used in this book is taken largely from the detailed 
 descriptions of modern tunnel work found in the pages of technical journals, 
 personal notes and in the proceedings of engineering societies, supplemented by 
 the experience of m.any engineers and contractors. In every ease the descrip- 
 tion of any especial method is prefaced by a brief statement of the physical 
 conditions which called for some particular treatment. The composition, 
 nature, and use of modern explosives have been treated at considerable 
 length. An important feature is a glossary of all the technical and some 
 of the more unusual terms uued in tunnel work, 
 
 1910. Gillette, H. P. — Handbook of Cost Data for Engineers and Con- 
 tractors. Second Edition. Chicago. Morocco, 4-?rX6| ins.; 
 1854 pages;, illustrated. Price, $5.00, net. 
 
INDEX 
 
 PAGE 
 
 A 
 
 Abutments for bridges 83 
 
 Adaptability of pavements. ... 34 
 Administration of highways. . . 23 
 Advantages, asphalt pavements 361 
 
 coal-tar pavements 37S 
 
 concrete pavement 381 
 
 good roads IV 
 
 paved city streets 20 
 
 straight and curved roads . . 39 
 
 wood block pavement 340 
 
 American systems of road man- 
 agement 24 
 
 Aneroid barometer 43 
 
 Angle of internal friction 55 
 
 Angles for laying wood block 
 
 pavement 352 
 
 Anglesea, improvement in old 
 
 road 39 
 
 Application of new materials to 
 
 roads 207 
 
 Area of streets 304 
 
 Artificial granite blocks 45.3 
 
 paving stones 460 
 
 sheet asphalt pavement 361 
 
 stone sidewalks 428 
 
 Ascent, curves on 49 
 
 Asphalt, definition 357 
 
 pavements 357 
 
 appliances 369 
 
 rock 243 
 
 Asphalt-block pavement 376 
 
 Automobile traffic, effects of, 
 
 219, 491 
 Autumn works on roads 215 
 
 B 
 
 Balancing earth work 54 
 
 Basalt 113 
 
 JBatter, mountain roads 196 • 
 
 PAGE 
 
 Belgian block pavement 315 
 
 Bench-marks 43 
 
 Benefits of improvements 204 
 
 Bibhography 505 
 
 Bniding macadam roads 173 
 
 Bitulithic pavement 244 
 
 Bitumen 357 
 
 Blocks, size of 297 
 
 Borrow, specifications 273 
 
 Breaking stone 179 
 
 Brick clays 325 
 
 pavements 323 
 
 sidewalks 426 
 
 Bricks for country roads 333 
 
 paving, size and shape 327 
 
 Bridge sites 49 
 
 trusses 71 
 
 Bridges 69 
 
 Broken stone roads. .' 154 
 
 advantages and defects. . . 163 
 
 difference in construction. 164 
 
 errors in construction. . . . 165 
 
 essentials to succfess 164 
 
 specifications 276, 2S4 
 
 Buck scrapers 141 
 
 Burnt clay roads 133 
 
 Calcium chloride for dust pre- 
 vention 227 
 
 Calculation of load on gradi- 
 ent 16 
 
 tractive force 12 
 
 California crude petroleum. . . . 230 
 
 Carts for distributing stone . .. 181 
 
 Catch basins, specifications 279 
 
 Causes destruction of roads ... 93 
 
 making repairs necessary ... 212 
 
 tractive resistance 10 
 
 Cement sidewalks 430 
 
 535 
 
536 
 
 INDEX 
 
 PAGE 
 
 Cementing action of broken 
 
 stone, theory of 176 
 
 value of stones 100 
 
 Center walks 307 
 
 Characteristics of country. ... 41 
 
 Charcoal roads 457 
 
 "Checkerboard" plan of loca- 
 tion of streets 299 
 
 Chemical agencies of road de- 
 struction 95 
 
 City pavements, maintenance. 26 
 
 materials employed 34 
 
 methods of payment 22 
 
 opening for pipes 27 
 
 questions affecting design . 22 
 
 City streets, cleaning 401 
 
 design of 296 
 
 paved, advantages of 20 
 
 use of 407 
 
 City wastes, varieties 412 
 
 Classification, earth work 53 
 
 highway bridges 71 
 
 rocks 101 
 
 Clay 115 
 
 for brick making 325 
 
 region of production 325 
 
 roads 126 
 
 improvements of 204 
 
 Cleaning city streets 401 
 
 ('learing roadsides 215 
 
 country roads, tools 137 
 
 Clinker roads 459 
 
 Coal-slack roads 457 
 
 Coal-tar pavements 377 
 
 tests of 235 
 
 use for dust prevention 231 
 
 Cobblestone gutters, specifica- 
 tions 2SU 
 
 pavement 313 
 
 Commission, state-aid 251 
 
 Comparative values of various 
 
 pavements 31 
 
 Compass 43 
 
 "Concentric" plan of location 
 
 of streets 301 
 
 Concrete bridges 7!) 
 
 cubes 399 
 
 foundations 39!> 
 
 pavements 3S(J 
 
 sidewalks 430 
 
 PAGE 
 
 Concrete-block trackways 452 
 
 Concreting curbs 446 
 
 Conglomerate, metamorphic 
 
 rock 105 
 
 Connecticut, construction of 
 
 state roads 266 
 
 county highway commis- 
 
 • sioners 263 
 
 how to get state aid 264 
 
 maintenance of state aid 
 
 highways 271 
 
 payment for state aid high- 
 ways 269 
 
 powers of counties 261 
 
 specifications for state aid 
 
 roads 288 
 
 state aid fund 259 
 
 state aid highways 257 
 
 state highway department. . 254 
 Construction, asphalt pave- 
 ments 365 
 
 brick pavements 329 
 
 broken stone roads 164 
 
 concrete pavements 38S 
 
 earth roads 118 
 
 gravel roads 125 
 
 state aid roads 250 
 
 specifications 272 
 
 state roads 265 
 
 works 53 
 
 Contour lines 43 
 
 Contractor's guarantee .... 26, 487 
 
 Contracts 473 
 
 Control of road dust 218 
 
 Convict labor 271 
 
 Co-operation in street cleaning. 411 
 
 Copper slag roads 460 
 
 Corduroy roads 456 
 
 on mountains 201 
 
 Cork pavements 459 
 
 Cost, burnt clay roads 137 
 
 concrete pavements 381 
 
 earth work 61 
 
 macadam surface 185 
 
 maintenance 209 
 
 pavements 36 
 
 sand clay roads 132 
 
 transportation 21 
 
 wood block pavements 341 
 
 County highway commissioners 262 
 
INDEX 
 
 537 
 
 PACE 
 
 Country roads, advantages of . 19 
 
 brick 333 
 
 improvement and mainte- 
 nance 203 
 
 location 37 
 
 maintenance 25 
 
 materials employed 34 
 
 Creo-resinate process 349 
 
 Creosote oil 346 
 
 Creosoting 345 
 
 Crossing stones 449 
 
 Crown of road surface 67 
 
 Crushing plants 181 
 
 Culverts SI 
 
 earth roads 121 
 
 specifications 274 
 
 Curbs 424, 444 
 
 Curved roads, advantages 39 
 
 length 37 
 
 Curves 48 
 
 mountain roads 200 
 
 Cushion, wood block pavement 34!) 
 
 D 
 
 Defects of existing roads 203 
 
 of broken-stone roads 149 
 
 Design of city streets 296 
 
 Desirability of pavements 31 
 
 Destructor concrete roads 459 
 
 "Diagonal" plan of location of 
 
 streets 301 
 
 Digest of state aid laws 252 
 
 Dimensions of curbstones 444 
 
 Diorite 112 
 
 Disadvantages, asphalt pave- 
 ments 361 
 
 coal-tar pavements 378 
 
 wood block pavement 340 
 
 Disposal of street dirt 421 
 
 Distance, value of saving 45 
 
 Distribution of state aid funds . 24!> 
 
 District highway commissioners 262 
 Disturbing forces affecting 
 
 curbs 444 
 
 Drag scrapers 140 
 
 Dragging earth roads 145 
 
 Drainage 62 
 
 city streets 299 
 
 concrete sidewalks, founda- 
 tion 433 
 
 PAGE 
 
 Drainage, curbs 444 
 
 earth roads. 119 
 
 mountain roads 195 
 
 retaining walls 8!) 
 
 Draining tools 137 
 
 Driving in middle of road, 
 
 effects of 306 
 
 Dump cars 144 
 
 wagons 144 
 
 DurabiUty, asphalt pavements. 364 
 
 brick pavements 331 
 
 granite blocks 321 
 
 pavements 36 
 
 stones 99 
 
 wood block pavement 341 
 
 "Durax" roads 461 
 
 Dust prevention 218 
 
 E 
 
 Earth road drag 145 
 
 Earth roads 117 
 
 Earthwork 53 
 
 specifications 272 
 
 Economy, bridges 87 
 
 location 39 
 
 road improvements 21 
 
 Elevating graders 142 
 
 Embankments 55, 58 
 
 Errors in maintenance 209 
 
 Equalizing earthwork 54 
 
 European asphalt pavements . . 360 
 
 systems of road manage- 
 ment 24 
 
 Excavation 55 
 
 Expansion joints, wood block 
 
 pavement 353 
 
 Experiments, dust prevention. 225 
 
 tractive resistance 12, 14 
 
 F 
 
 Failures, asphalt pavements... 372 
 
 concrete sidewalks 433 
 
 sand clay roads 12S 
 
 Fences 463 
 
 Filler, brick pavements 331 
 
 joints of wood pavement . . . 354 
 
 Final grade, establishing 48 
 
 selection of route 51 
 
 Finishing, concrete pavements . 396 
 
 Firing burnt clay roads 136 
 
538 
 
 INDEX 
 
 PAGE 
 
 First course, macadam roads. . 170 
 
 Floor beams for bridges 83 
 
 Flushing streets 420 
 
 Foundations 62 
 
 concrete 399 
 
 concrete sidewalks 435 
 
 stone block pavement 318 
 
 wood block pavement 349 
 
 Fuel for burnt clay roads 135 
 
 Funds for state aid purposes. . . 248 
 
 G 
 
 "Gladwell" system 241 
 
 Government tests of rocks .... 116 
 
 Grades 15, 45 
 
 final 48 
 
 maximum 46 
 
 method of expressing 18 
 
 method of overcoming 46 
 
 minimum 48 
 
 most advantageous 47 
 
 mountain road 191 
 
 Grading tools 137, 145 
 
 Granite Ill 
 
 block 455 
 
 pavement 316 
 
 sidewalks 426 
 
 Gravel 115, 123 
 
 paths 428 
 
 roads 123 
 
 Gravity, effect on roads 94 
 
 Guarantees, pavement 487 
 
 Guard rail, specifications 278 
 
 Gumbo clay 133 
 
 Gutters 424, 444, 448 
 
 cobblestone, specifications . 2X0 
 
 Gyratory crushers 179 
 
 H 
 
 Hand level 43 
 
 Hardness of stones 96 
 
 Hassam pavement 389 
 
 HauUng power of horses 16 
 
 Heat, effects on roads 94 
 
 Hedges 463 
 
 High truss bridges 77 
 
 Highway administration 23 
 
 bridges 69 
 
 PAGE 
 
 Highway commissioners, coun- 
 ty 262 
 
 Historical sketch of road de- 
 velopment 1 
 
 Horses, hauling power 16 
 
 How localities get state aid . . . 264 
 
 I 
 
 Ideal pavement 29 
 
 Igneous rocks 102 
 
 Improvement of country roads 203 
 Inclines, arrangement of stcne 
 
 blocks 321 
 
 India rubber pavements 460 
 
 Instructions, dragging roads . . 151 
 
 roadmen 213 
 
 Instruments used in location . . 43 
 Intersections, specifications . . . 290 
 
 J 
 
 Jarrah, use in paving 337 
 
 Joint filling, stone block pave- 
 ment 319 
 
 Joints, concrete sidewalks 437 
 
 K 
 
 Karri, use in paving 337 
 
 Kreodone-creosote processs . . . 348 
 
 L 
 
 Labor tax system 25 
 
 Laws of states regarding control 
 
 of roads 251 
 
 Ledge excavation, specifica- 
 tions 273 
 
 Leg bridge 75 
 
 Length of straight and curved 
 
 roads 37 
 
 Levels 4S 
 
 Limestone 114 
 
 Loads drawn by horses on gra- 
 dients 17 
 
 Location, bridges 49, 69 
 
 country roads 37 
 
 economy in 39 
 
 mountain roads 194 
 
 streets 299 
 
 Low truss bridges 77 
 
INDEX 
 
 539 
 
 M 
 
 Macadam, John Loudon 156 
 
 method of 161 
 
 compared with Telford's 154 
 
 defects 163 
 
 Macadam, essential qualities . . 96 
 
 roads, construction of 169 
 
 cost of 185 
 
 dimensions of surface 168 
 
 specifications 281, 2S4, 289 
 
 theory of cementing action . . 176 
 Machinery employed in street 
 
 cleaning 415 
 
 Maine, construction of state 
 
 roads 268 
 
 county highway commis- 
 sioners 264 
 
 how to get state aid 265 
 
 maintenance of state aid 
 
 highways 271 
 
 payment for state aid high- 
 ways 270 
 
 powers of counties 262 
 
 state aid fund 260 
 
 state aid highways 258 
 
 state highway department. . 256 
 Maintenance, city pavements . . 26 
 
 country roads 25, 203 
 
 earth roads 121 
 
 necessity for 205 
 
 state aid highways 270 
 
 systems of 208 
 
 wood pavement 355 
 
 Marble 115 
 
 Maryland, construction of state 
 
 roads 266 
 
 county highway commis- 
 sioners 262 
 
 how to get state aid 264 
 
 maintenance of state aid 
 
 highways 270 
 
 payment for state aid high- 
 ways 268 
 
 powers of counties 260 
 
 specifications for state aid 
 
 roads 291 
 
 state aid fund 258 
 
 state aid highways 257 
 
 state highway department . . 253 
 Masonry bridges 79 
 
 Masonry bridges, Portland ce- 
 ment concrete, specifi- 
 cations 274 
 
 Massachusetts, county high- 
 way commissioners 263 
 
 construction of state roads . . 266 
 
 highway commission 24 
 
 how to get state aid 264 
 
 maintenance of state aid 
 
 highways 270 
 
 payment for state aid high- 
 highways 269 
 
 powers of counties 261 
 
 specifications for state aid 
 
 roads 272 
 
 state aid fund 259 
 
 state aid highways 257 
 
 state highway department . . 254 
 Materials, broken stone roads. . 166 
 
 concrete pavements 390 
 
 employed for curbing 444 
 
 for different purposes 34 
 
 in road construction 91 
 
 in sidewalks 425 
 
 new, application to country 
 
 roads 207 
 
 telford and macadam 161 
 
 Maximum grade, determina- 
 tion 46 
 
 most suitable 47 
 
 Mechanical agencies of road 
 
 destruction 95 
 
 Memoir 43 
 
 Method of cutting planks from 
 
 logs 339 
 
 drainage 65 
 
 dust prevention 218. 225 
 
 expressing grade 18 
 
 employed in location 41 
 
 Michigan, county highway 
 
 commissioners 263 
 
 construction of state roads . . 267 
 
 how to get state aid 265 
 
 maintenance of state aid 
 
 highways 271 
 
 payment for state aid high- 
 ways 270 
 
 powers of counties 262 
 
 state aid fund 260 
 
 state aid highways 258 
 
540 
 
 INDEX 
 
 Michigan state highway depart- 
 ment 256 
 
 Minimum grade, estabUshment 4S 
 
 Miscellaneous roads 450 
 
 Model bill, construction of state 
 
 roads 265 
 
 county highway commis- 
 sioners 262 
 
 how to get state aid 264 
 
 maintenance of state aid 
 
 highways 270 
 
 payment for state aid high- 
 ways 26S 
 
 state aid funds 25S 
 
 state aid highways 256 
 
 state highway department . . 253 
 
 Moisture for dust prevention. . 227 
 Morin's experiments, general 
 
 results 14 
 
 Mountain roads 189 
 
 Municipal growth in America. . 405 
 
 N 
 
 Natural slope of embankments 55 
 New Jersey, construction of 
 
 state roads 267 
 
 county highway commis- 
 sioners 263 
 
 how to get state aid 264 
 
 maintenance of state aid 
 
 highways 271 
 
 payment for state aid high- 
 ways 269 
 
 powers of counties 261 
 
 specifications for state aid 
 
 roads 2S1 
 
 state aid fund 259 
 
 state aid highways 257 
 
 state highway department. . 255 
 New York, construction of state 
 
 roads 265 
 
 county highway commis- 
 sioners 262 
 
 how to get state aid 264 
 
 maintenance of state aid 
 
 highways 270 
 
 payment for state aid high- 
 ways 268 
 
 powers of counties 260 
 
 PA3E 
 
 New York, specifications for 
 
 state aid roads 283 
 
 state aid funds 25S 
 
 state aid highways 256 
 
 state highway department. . 253 
 
 O 
 
 Object of pavements 28 
 
 roads 10 
 
 Objection to steep grades 18 
 
 Odometer 43 
 
 Ohio, construction of state 
 
 roads 267 
 
 county highway commis- 
 sioners 263 
 
 how to get state aid 265 
 
 maintenance of state aid 
 
 highways 271 
 
 payment for state aid high- 
 ways 269 
 
 powers of counties 261 
 
 state aid fund 25!» 
 
 state aid highways 258 
 
 state highway department. . 255 
 
 Oil emulsions 228 
 
 Oiling roads, rules for 231 
 
 Oils for dust prevention 229 
 
 Opening of pavements 27 
 
 Organic agencies of road de- 
 struction 96 
 
 Organization in street cleaning 419 
 
 Oscillating crushers 179 
 
 Overcoming grades, methods. . 46 
 
 P 
 
 Park drives, materials em- 
 ployed 34 
 
 Patching country roads 216 
 
 Paths for parks 428 
 
 Pavements, asphalt block 376 
 
 Belgian block 315 
 
 brick 323 
 
 coal-tar 377 
 
 cobblestone 313 
 
 comparative cleanliness 415 
 
 comparative values 31 
 
 concrete 380 
 
 concrete cubes 399 
 
 definition 28 
 
INDEX 
 
 541 
 
 PAGE 
 
 Pavements, economics 19 
 
 granite block 316 
 
 guarantees 487 
 
 Hassam 389 
 
 history 5 
 
 miscellaneous 450 
 
 selection of 28 
 
 steep grades 321 
 
 width of 305 
 
 wood block 335 
 
 Paving blocks, essential quali- 
 ties 96 
 
 bricks, manufacture 325 
 
 stones Ill 
 
 Payment for city pavements . . 22 
 
 state aid highways 268 
 
 Pedometer 43 
 
 Pennsylvania, construction of 
 
 state roads 266 
 
 county highway commis- 
 sioners 263 
 
 how to get state aid 264 
 
 maintenance of state aid 
 
 highways 271 
 
 payment for state aid high- 
 ways 269 
 
 powers of counties 261 
 
 specifications for state aid 
 
 roads 289 
 
 state aid fund 259 
 
 state highway department . . 255 
 
 state aid highways 257 
 
 Petroleum for dust prevention . 229 
 Physical agencies causing road 
 
 destruction 93 
 
 properties of rocks 107 
 
 Pipe, specifications 277 
 
 Plank roads 455 
 
 Planning city streets, object of 296 
 Plans for location of city streets 299 
 Planting trees on roadside. ... 471 
 
 Plate girder bridges 79 
 
 Pleasure drives, materials em- 
 ployed 34 
 
 Ploughs for road work 139 
 
 Portable bitulithic paving 
 
 plants 247 
 
 crushing plant 181 
 
 'Power, loss on inclinations. ... 16 
 required to move vehicles. . . 11 
 
 PAGE 
 
 Power of teams 16 
 
 Powers and duties of counties, 
 model bill and various state 
 
 laws 260 
 
 Preservation of wood 344 
 
 Prevention of road dust 218 
 
 Primary mineral constituents 
 
 of rocks 105 
 
 Profile of road section 67 
 
 Progress in wood paving 335 
 
 Properties of an ideal pave- 
 ment 29 
 
 Protective works 53 
 
 Q 
 
 Quality, brick for pavements . . 323 
 
 treated wood pavement. . . . 340 
 
 wood used for paving 343 
 
 Qualities, concrete pavements. 385 
 
 road-making stone 96 
 
 R 
 
 Re-coating country roads 213 
 
 Reconnoissance 41 
 
 Reconstruction of country 
 
 roads 203 
 
 " Rectangular" plan of location 
 
 of streets 299 
 
 Refuse removal 421 
 
 Removal of household refuse. . 421 
 
 Repairs, best season 215 
 
 country roads 205 
 
 methods of 213 
 
 earth roads 121 
 
 effects of neglect 212 
 
 wood pavement 355 
 
 Report of U. S. Office of Public 
 
 Roads on tar macadam. 241 
 Requirements of a good pave- 
 ment 28 
 
 Requisites to preservation of 
 
 surface 205 
 
 Resistance due to gradient. ... 15 
 
 to traction 10 
 
 Retaining walls 87 
 
 Rhode Island, construction of 
 
 state roads 268 
 
 county highway commis- 
 sioners 264 
 
542 
 
 INDEX 
 
 PAGE 
 
 Rhode Island, how to get state 
 
 aid 265 
 
 maintenance of state aid 
 
 highways 271 
 
 payment for state aid high- 
 ways 270 
 
 powers of counties 262 
 
 state aid fund 260 
 
 state aid highways 258 
 
 state highway department. . 256 
 
 Right-of-way, width 50 
 
 Roadbed, earth roads 119 
 
 specifications 289. 291 
 
 Road construction, materials 
 
 used 91 
 
 on slopes 59 
 
 Road, definition 28 
 
 development, history 1 
 
 dragging 145 
 
 dust, control and prevention 218 
 
 value and effects 219 
 
 economics 19 
 
 graders 141 
 
 improvements, value of 20 
 
 leveling 144 
 
 making, early methods 155 
 
 management 23 
 
 object of 10 
 
 oils, handling of 230 
 
 statistics 499 
 
 Roadmen, instructions 213 
 
 Roads, miscellaneous 450 
 
 American and European .... 4 
 
 mountainous districts 189 
 
 Peru 3 
 
 Roman 3, 311 
 
 Roadside, protection of 463 
 
 Roadway, width 49 
 
 Rock asphalt macadam 243 
 
 Rock slopes, construction on. . 60 
 
 Rocks, classification of 101 
 
 road making Ill 
 
 Rolling friction 13 
 
 macadam roads 175 
 
 Roman roads 3, 311 
 
 S 
 
 Safety of pavements 35 
 
 Salt water for dust prevention. 227 
 
 Sand 115 
 
 PA.GE 
 
 Sand-clay roads 127 
 
 improvements of 204 
 
 Sandstone 113 
 
 sidewalks 426 
 
 Sandy roads 126 
 
 Sanitation, aim of 411 
 
 city streets 401 
 
 Saturation of sand and clay ... 127 
 
 Scarifiers 183. 
 
 Scrapers 140' 
 
 Scraping roads 216 
 
 Screening rock 181 
 
 Sea walls 89 
 
 Season for repairs 215 
 
 Second course, macadam roads. 171 
 
 Sedimentary rocks 103 
 
 Selection of materials 92, 
 
 pavements for different pur- 
 poses 28 
 
 trees for roadside 470 
 
 Service, wood block pavement . 341 
 Serviceability of pavements ... 34 
 
 Setting curbs 446 
 
 Shape of blocks for wood block 
 
 pavement 351 
 
 paving bricks 327 
 
 Shaping surface, specifications . 296 
 
 Shell roads 459 
 
 Short span bridges 75 
 
 Shrinkage of earthwork 56 
 
 Side ditches 66 
 
 drains, specifications -278 
 
 slope of mountain roads. . . . 196 
 
 Sidewalks 424 
 
 Size, blocks 297 
 
 wood, stone 351 
 
 paving bricks 327 
 
 wheels, effect of 14 
 
 Slag roads 457 
 
 Slide rock 200 
 
 Slope, sidewalks 424 
 
 Slopes, construction on 59 
 
 Specifications 
 
 construction of state aid 
 
 roads 272 
 
 Portland cement concrete 
 
 sidewalks 441 
 
 Portland cement pavements 390 
 
 proportioning concrete 399 
 
 street trees 469 
 
INDEX 
 
 543 
 
 PAGE 
 
 Springs, effect of 14 
 
 Sprinkler, specifications 286 
 
 Sprinkling of roads 227 
 
 Stability of road service 63 
 
 State aid, how to get 264 
 
 funds, model bill and various 
 
 state laws. . , 258 
 
 highways, maintenance of . . 270 
 model bill and various states 256 
 
 payment for 268 
 
 specifications for construe- ■ 
 
 tion 272 
 
 laws 248 
 
 State highway department, 
 model bill and various 
 
 states 253 
 
 State roads, construction of . . . 265 
 Statistics of American roads . . . 499 
 
 Steam rollers 178 
 
 Steel trackways 450 
 
 Stone block pavements. . . 311, 317 
 
 crushers 79 
 
 crushing plants 181 
 
 distributing carts 181 
 
 specifications 288 
 
 Stone filling, specifications .... 279 
 
 Stone trackways 7, 450 
 
 Straight edge 183 
 
 roads, advantages 39 
 
 length 37 
 
 Straightness in country roads. 39 
 
 Street cleaning . . . 401 
 
 dirt, disposal 421 
 
 sources 409 
 
 trees, specifications 469 
 
 Streets, area of 304 
 
 city, design of 296 
 
 location of 299 
 
 width 303 
 
 Subfoundations, specifications, 
 
 281, 283 
 
 Subgrade macadam roads 169 
 
 Suburban streets, materials 
 
 employed 34 
 
 Superstructure for bridges .... 83 
 Supervision of construction . . . 250 
 
 Surface drainage 67 
 
 earth roads 119 
 
 graders 144 
 
 Syenite 112 
 
 Systems, drainage 65 
 
 maintenance 208 
 
 T 
 
 Tables, I. Standard tractive 
 
 resistances 11 
 
 II. Resistances due to gra- 
 dient 15 
 
 III. IV, and V. Comparative 
 values of various pave- 
 ments 31 
 
 VI. Amount of transverse 
 
 rise required for differ- 
 ent i^avements 68 
 
 VII. General classification of 
 rocks 102 
 
 VIII. Primary mineral con- 
 stituents of rocks used 
 for roadmaking 107 
 
 IX. Physical properties of 
 
 rocks for roadmaking. . 107 
 X. Average costs of mac- 
 adam work in Massa- 
 chusetts 187 
 
 XI. Average costs of mac- 
 adam work in New Jersey 187 
 XII. Averages of contract 
 prices for the several 
 construction items, ex- 
 clusive of macadam. — 
 Massachusetts Highway 
 Commission 188 
 
 XIII. Widths of roadbed for 
 various sidehill slopes, 
 with amount of mate- 
 rial excavated per 100 
 feet 198 
 
 XIV. Amount of excavation 
 in 10-foot cut into solid 
 rock 200 
 
 XV. Acres required per mile 
 for different widths of 
 
 roadway 305 
 
 Tables, use of, in selection of 
 
 pavements 33 
 
 Tar macadam 237, 241 
 
 Tarring roads 235 
 
 Tar spraying machines. . . 233, 241 
 Tarviating 233, 237 
 
544 
 
 INDEX 
 
 PAGE 
 
 Tearing up pavement 27 
 
 Telford foundation, specifica- 
 tions 281, 290 
 
 Telford, Thomas 158 
 
 method of 160 
 
 defects 163 
 
 Testing paving bricks 328 
 
 Tests, road-making stones .... 96 
 
 rocks by government 116 
 
 Theory of road dragging 149 
 
 Thickness of road surfaces. . . . 175 
 
 Third course, macadam roads. - 172 
 
 Timber, use on bridges 79 
 
 Tires, rubber and pneumatic. . 13 
 
 Toll roads 6 
 
 Tongue scrapers 141 
 
 Tools, asphalt pavements 369 
 
 concrete sidewalk 436 
 
 country road 137 
 
 Top dressing for wood pave- 
 ment 355 
 
 Topographical map 43 
 
 Toughness of stones 97 
 
 Trackways, concrete block. . . . 452 
 
 steel 450 
 
 .stone 450 
 
 Tractive resistance, causes of . . 10 
 
 concrete pavements 383 
 
 woo'd block pavement 343 
 
 Transverse balancing 54 
 
 contour 67 
 
 Trap rock 113 
 
 Tree-planting association 472 
 
 Trees for roadside 468 
 
 Tresaguet's method 159 
 
 Trimming macadam roads. ... 173 
 Trusses, types of for highway 
 
 bridges 73 
 
 Types of bridge trusses 73 
 
 U 
 
 Unclean streets, reason for . 
 
 411 
 
 V 
 
 Value of improvements 203 
 
 Varieties of road-making rocks 111 
 
 Venice, Cal., center walks 307 
 
 Virginia, construction of state 
 
 roads 266 
 
 PAGE 
 
 Virginia, county highway com- 
 missioners 236 
 
 how to get state aid 264 
 
 maintenance of state aid 
 
 highways 270 
 
 payment for state aid high- 
 ways . 268 
 
 powers of counties 261 
 
 state aid fund 259 
 
 state aid highways 257 
 
 state highway department . . 254 
 
 Vitrification of bricks 324 
 
 AV 
 
 Washington, D.C., regulations 
 governing width of 
 
 streets 304 
 
 Washington (state), construc- 
 tion of state roads 267 
 
 county highway commis- 
 sioners 263 
 
 how to get state aid 265 
 
 maintenance of state aid 
 
 highways 271 
 
 payment for state aid high- 
 ways 269 
 
 powers of counties 261 
 
 state aid fund. 259 
 
 state aid highways 258 
 
 state highway department . . 255 
 Water, effect on road founda- 
 tions 93 
 
 carts 185 
 
 Wear of roads by automobiles . 491 
 Wearing surface, asphalt pave- 
 ment 366 
 
 Wheel scrapers 141 
 
 tires, effect on earth roads. . . 122 
 
 Wheels, effect of size 14 
 
 Width, city streets 303 
 
 mountain roads 197 
 
 pavement 305 
 
 roadway 49 
 
 sidewalks 424 
 
 Wind, effect on roads 04 
 
 Wood, used in paving 337 
 
 preserving methods 344 
 
 sidewalks 426 
 
 Wood block pavement 335 
 
 Wooden bridges 79 
 
Illiiiii 
 
 • 11* 
 
 iilil