¥;y: li 'Will' li m^ Cornell University Library TE 145.H27L8 The location, grading an*, HmHMi^w^W^^riiSjWKi f-?^ wsmmv^i Fig. 2. — A wagon trail (Montana) . The first stage of pioneer road improvement. principle of design may therefore be stated as: the construction of the greatest possible mileage of connected roads of a type suitable to the stage of development of the community and its existing traffic. Mileage is the first and foremost factor of service. Needlessly short mileage is the most serious criticism that can be made of any general policy dealing with an incomplete road system. The practical application of this principle eliminates all non- 6 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Fig. 3. — Well built natural soil roads. The second stage of progressive im- provement (Pioneer Districts). ECONOMIC HIGHWAY DESIGN 7 essential expenditure but encourages necessary expenditures on essential features. To illustrate we may say that a reasonable policy of service reqxiires radically different methods of approach in different locaUties. Road design ranges from the low-type e arth roads of sparsely settled districts to the hard-surfaced pave - ments of densely populated sections . For these extreme condi- tions the issues are clear-cut; the first requires the greatest possible mileage with Hmited funds, and the last the most suitable design /or present conditions regardless of first cost. Intermediate cases are handled by merging the requirements of the extremes. A reasonable design for any case depends on the needs and re- FiG. 4. — Typical single track gravel road (New York state) . Very satisfactory for local traffic in agricultural districts. (The third stage of progressive im- provement.) sources of the local community, considered in connection with the importance of the improvement to the general transportation scheme of the country and the outside aid that will be granted on account of its general importance. In pioneer districts mile- age is the only important consideration, and a sufficiently cheap type of construction must be adopted to obtain a line of communi- cation to the point desired; an ordinary earth road is all that can be reasonably expected for the greater part of these districts. Scattered agricultural commum'ties require primarily roads that are usable the year around and that will handle ordinary farm traffic; gravel or similar, fairly cheap constructions are the only reasonable solutions for the greater part of these districts. 8 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Densely populated districts with closely located cities require the highest, strongest type of rigid pavements for the main connecting routes and macadam and gravel constructions for the secondary and local roads. To design a needlessly expensive road even in a rich community is as poor poUcy as to build a road that will not handle the present traffic. It is not necessary to worry about future trafiSc, The future has a habit of talcing care of itself. The permanent fea- tures of construction such as route, alignment, gra;des, etc. should be designed for the future but the pavement surface is at its best only temporary and extremely expensive pavements are Fig. 5. — Typical penetration bituminous macadam (State Route No. 16 New York). Carries approximately 1500 vehicles per day. Note the easy shoulder slope which adds to the safety of traffic. not justified unless present traffic demands them. Appropria- tions for the original construction of improved highways over routes on which the existing roads are poor may well be spent on the principle of mileage service. After a system of reasonably good roads is attained a Reconstruction Program of Boulevards is justified if the money is available from the proper sources. The community at large can generally afford to shoulder the burden of the original construction of reasonably good roads but it can rarely afford to pay for boulevards. The direct road user can well afford to shoulder the burden of the maintenance of reasonably good roads and he should be given the opportunity of paying for reconstruction if he wants the additional comfort and ease of a boulevard system. ECONOMIC HIGHWAY DESIGN 9 Some conclusion of this nature governs the decision as to the method of financing various stages of improvement programs. Demands of Traffic and Their Effect on Design.— To fulfill the principle of service, roads shoul d be located and designed to serve the great majority of d irect users with the least inconvenience. and the fewest restrictions that are feasible, but a few indiv iduals who, for s o me reason, find it convenient to use extremely heavy unit vehicles, must be r uled off from the majorit y of the highways . It will be financially impossible for any community to construct and maintain all of its rural highways and bridges without regu- lation of heavy traffic. Roads Uke any other engineering struc- FiG. 6. — Typical rigid pavement highway (Industrial District Ohio) . Note the shallow ditch which adds to the safety of traffic. ture should be built for normal and not for abnormal use. The highway engineer would prefer not to restrict traflSc but it is a practical necessity. It is not feasible or desirable to restrict average traffic but we cannot permit a small percentage of the users to operate exceptionally heavy units which if considered in the design of local service roads would raise the total cost of a general road system beyond reason. The second principle of design appears to be: Traffic regulation is necessary not only to save past investment but also to enable the community to finance any enduring general system of roads and to make economic engineering design possible. The application of this principle hinges on the usual range and popular methods of hauling. 10 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS ' Range of Traffic. — All the available data indicates that prob- ably 90 to 95 per cent, of road traffic can be classed as local service. That is, it has its origin and finish within a compara- tively short radius and consists of the hauUng of garden truck to cities, produce to shipping points, social visits and short rec- reational trips. The other 10 per cent, may be classed as long distance traffic consisting of pleasure touring, light passenger cars of commercial travelers and long distance motor hauUng of freight between cities. These ratios of general traffic do not, of course, apply to any one road and may be actually reversed on certain special touring routes but they probably apply to the road systems as a whole in most states, counties and towns and they indicate the basis for locating improvements and for appor- tioning county, state or federal aid. Any highway program to render the greatest service to the community may well be laid out on the principle of serving first the local and second the through traffic. It is certain that a county that adopts the policy of getting some kind of a road that is usable the year round in front of every farm is nearer right than if it spent the funds for a skeleton system of needlessly high-class roads routed primarily for through traffic. There is no reason why the program should not con- sider both factors in their proper proportion but the danger has of late years been more often on the side of favoring through traffic to the detriment of local service. The third principle of design may be formulated as: Local traffic is entitled to first con- sideration in the location of roads and their design except for a com- paratively small mileage of special service highways. To apply the second and third principles, it is necessary to arrive at a reasonable conclusion in regard to traffic routes and also as to what types of vehicle will probably best serve the great major- ity of direct road users. Weight of Traffic. — Twenty years ago road traffic was entirely horse drawn. Today it is largely motor, particularly where an improved road system has been completed. It is safe to say that highway transport on improved roads will be largely by motor vehicles although it is not hkely that horse traffic will entirely disappear. Motor traffic for commercial success re- quires a higher speed and greater unit vehicle load than horse traffic and consequently controls the foundation design and sur- facing of the roads of today although in some features of the design ECONOMIC HIGHWAY DESIGN 11 it is probably better to modify this conclusion in order to satisfy the requirements of horse traffic also. For the usual farming community where the hauls do not ex- ceed 10 to 20 miles to market or shipping points and where each farmer owns his truck all available information indicates that the light ^^- to 23^-ton truck with pneumatic tire equipment will probably be the most popular type for hauling.^ The popu- larity of this type seems to be based on a reasonable first cost, moderate upkeep, high speed, comfort and general utiUty. This kind of truck does not seriously injure any of the improved roads Fig. 7. — ^Moderate size general utiUty truck. that are in general use provided they are well designed and main- tained. Such truck traffic and the usual pleasure car need not be subjected to regulation to the extent of modifying any of their desirable features. That is, probably 90 to 95 per cent, of road users can be served with moderate priced roads. For long distance motor freight hauling in competition with railroad freight the 5-ton or heavier truck appears to be the logical unit. At the present time, there does not seem to be a large proportion of road mileage that wiU be subjected to this class of traffic. It is, however, an increasingly important phase of serv- ice, but as the conditions which make it economical do not apply 1 See U. S. Dept. of Agriculture Bulletin No. 919 for data on the use of trucks by farmers. 12 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS to large areas a comparatively small number of special service roads ought to satisfy any reasonable demands of such users. TraflB.c of this kind reqmres a heavy rigid type of pavement, the shortest possible distance between terminals, the elimi- nation of needless rise and fall, and easy grades. Special service roads should be built but it is reasonable to restrict the operation of heavy trucks or trailer trains to these routes and rule them off of the secondary and feeder roads. Special per- mits to 5-ton trucks could be granted for a special fee for emer- gency trips over local service roads during the dry season of the year. Regulations of this nature would not be an unreasonable hardship on the commercial interests manufacturing or using such units as the great field for their popularity is apparently confined largely to city territory or to well-defined hauling routes. The tractor trailer system is apphcable to special conditions but reasonable gross weights and wheel pressures are not a hard- ship to the manufacturer or user and regulation of these outfits make them feasible for use on special service roads. They do not necessarily require a rigid pavement surface but generally do require a greater road foundation strength than most secondary or feeder roads and should be ruled off of such roads. It therefore seems feasible to regulate traffic to the point where the community can afi'ord to build improved road systems, with- out unfairness to the manufacturers of trucks or annoying inter- ference with the choice of the individua,Jij in his car. Present sentiment favors the design of secondary and feeder roads on the basis of a 10-ton gross vehicle load, a 7-ton gross back axle load and a wheel pressure per hnear inch of tire not exceeding 600 lb. Special service roads may well be designated to carry a gross vehicle load of 15 tons, a 10-ton back axle load and a wheel pres- sure of 800 lb. per linear inch of width of tire. Practically all authorities are agreed that heavy traffic must be regulated for both load and speed. The present sentiment on solid tire truck speed regulation appears to lie between 12 and 15 miles per hour; the effect of speed on impact and the amount of such impact on pavements is under investigation by the U. S. Bureau of Roads. The fourth principle of design may be assumed to be: the strength of pavement foundations and bridges should be designed for the maximum regulated load for the class of service for which the road is intended. No attempt should be made to reduce construction cost by using a weak foundation. ECONOMIC HIGHWAY DESIGN 13 The practical action of this principle results as a rule in rigid pavement construction on special service roads and in some form of macadam, gravel, sand-clay, or earth roads for the secondary and feeder systems. Under certain conditions of material sup- ply a rigid pavement is desirable even on secondary roads but the case is the exception rather than the rule considering the first principle of design, Mileage Service. INFORMATION TO TRUCK OPERATORS The essential points in Section 1, par. 282-a of the Highway Law, as enacted by the New York State Legislature of 1920, are as follows : 1. No truck, with load, shall weigh more than twenty- five thousand pounds. 2. No truck body, including load, shall be more than eight feet wide. 3. No truck body, including load, shall be more than twelve feet six inches high. 4. No wheel shall carry more than eight hundred pounds per inch width of tire. NEW YORK STATE DEPARTMENT OF HIGHWAYS, Fred'k Stuart Greene, Commissioner. Truck Dimensions and Loading Under the state law of Pennsylvania (1920) commercial vehicles are divided into seven classes. The maximum weights allowed for these classes, including chassis, body and load, are as follows: Class AA, 7,000 lb.; class A, 11,000 lb.; class B, 15,000 lb.; class C, 20,000 lb.; class D, 24,000 lb.; class C and F, 26,000 lb. No commercial vehicles may travel at a rate of speed in excess of that shown in the following table: Class AA, 20 miles per hour; class A, 20 miles; class B, 18 miles; class C, 15 miles; class D, 15 miles; class E, 12 miles; class F, 10 miles. Truck Speeds 14 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Pavement Tsrpe, — The use of different pavements for different service can be well shown by a quotation from a recent article on a general scheme of Highway Improvement in Monroe County, New York."- Monroe County has an unusually good general highway system. J. Y. McCUntock,. the County Super- intendent of Highways, is one of the most level headed highway engineers in the country today. The following material is briefed from his report (see Fig. 14, opposite page 42, for map of this territory) : Monroe County has an area of 650 squaremiles A total population of approximately 350,000 A population. City of Rochester, approx 280,000 A population outside of the city, approx 70,000 An assessed valuation (real) of $327,000,000 A total mileage of roads, outside of the city and villages of 1,360 approx. A total mileage of improved state roads of 330 approx. A total mileage of improved town roads of 700 approx. A total mileage of unimproved roads of 330 approx. The total number of motor licenses 22,000 approx. The total number of truck licenses 3,000 approx. (Approximately 85 per cent, of these trucks are less than 2-ton rated capacity). The demands of traffic in this county are more extreme than for most localities except in metropohtan areas. The county has had all kinds of pavements in use under a great range of traffic for a number of years and we feel that we have sufficient data in regard to maintenance costs and the hf e of surf acings to come to a reasonable conclusion as to the future policy of completing the road system. The conclusions are summarized as follows: "We advocate the original construction of cross roads of thick modern waterbound macadam utilizing local materials as much as possible and maintained by surface oiling. "We advocate the original construction of our secondary radial roads, of penetration, bituminous macadam, utilizing local materials to their fullest reasonable extent and maintained by surface oiling. "We advocate the construction of our Main Trunk Line heavy hauling roads of rigid pavements, using the best materials that can be obtained, but varying the type to secure, in each case, the cheapest first cost pavement, always considering the possible use of local materials proper for the type of road in question. For these roads we have no choice ' This particular district is a rich highly developed country. For pioneer territory or scattered agricultural districts the same general principle applies but relatively cheaper road surfaces must be used. ECONOMIC HIGHWAY DESIGN 15 between cement concrete, brick, sheet asphalt, asphalt block, or stone block on concrete bases. "We advocate the gradual resurfacing of the heavier traffic macadam roads with Topeka mix, small brick cubes, etc. We have successfully utilized this method in reducing high surface maintenance costs where the macadam foundation was sohd enough for the traffic, and have adopted this method for a number of our roads. We have examples which have stood a 10 years' test successfully. "We believe that the community has been better served by construct- ing 10 miles of macadam in place of a possible 6 miles of rigid pavement. "We believe that the county has been better served in the past and will be best served in the future by variable road designs using for the majority of the mileage modern macadam for the original construction, later modified, if necessary, for a very limited mileage by recapping with a lower maintenance cost surface. We advocate rigid pavements eventually for, approximately, 10 per cent, of the total mileage of our roads and for approximately 35 per cent, of our State System." The fifth principle of design becomes: Vary the type of pavement to suit the demands of existing traffic. Avoid the use of rigid pave- ments on local service roads except for unusual conditions of ma- terial supply. Pavement Width. — The number and width of vehicles using the road controls the design of pavement width and. in many cases the type of pavement surface. It is, however, well to bear in mind that, in order not to violate the first principle of design, namely, Mileage Service, the basis for the selection of width should be the expected volume of traffic in the immediate future and not the far distant future. It is always possible to widen or improve the pavement under a Maintenance or Re- construction program. The sixth rule of design may be stated as : the number of vehicles and the percentage of horse traffic govern the width of the pavement and its surfacing. The practical application of this rule may be indicated in a rough general way as follows: Single track pavements 8 to 12 ft. wide built of good natural soil materials, gravel or macadam serve very satisfactorily if properly maintained under a local service traffic up to about 300 vehicles per day in the busy season. In well settled commu- nities a road of this kind is generally a cross road. Double track pavements 15 to 16 ft. wide built of thick modern waterbound or bituminous macadam with special shoul- ders if necessary will serve satisfactorily up to approximately 1800 local service vehicles per ten-hour day in the busy season if 16 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS properly maintained. In well settled communities a road of this class is generally a secondary radial road or it may constitute the least used portion of a main road connecting large cities located more than 100 miles apart. If traffic exceeds this amount macadam maintenance generally results in too much interference with traf&c even if the vehicles are light units although there have been cases of the successful use of penetration bituminous macadam up to 3500 vehicles per day, 300 of which were trucks. As a rule a volume of traffic of over 1800 rigs per ten-hour day in the busy season means that ^B^^K^^^K^ WB^- 1 |M|i 1 JL ■^ Mfl ■ ^o-'." Kj Ul^I I^H H ^^^ J^m PPHI K 1 . - ■ ,* : VKK-t ^- - 1 Fig. 8. — Typical unprotected mountain road. Illustrates the necessity for careful driving. Continuous guard rail would be prohibitive in cost except on a few of the main transcontinental routes. the road should be classed as a special service road entitled to a high cost rigid pavement. Roads of this class are generally main roads between large cities located less than 100 miles apart or main Radial Roads for a distance of 5 to 40 miles from cities or special Industrial Roads. Rigid pavements less than 18 ft. wide are rarely satisfactory to traffic on account of the formation of ruts in the shoulders along the edge of the pavement. Present sentiment favors 20-ft. width of rigid pavements on main roads near cities. In very unusual cases a pavement width of 29 or 38 ft. is desirable. ECONOMIC HIGHWAY DESIGN 17 The relative mileage of single and double track pavements will, of course, vary for each locality but it is not likely that even in the more populous states that more than lOlto 20 per cent, of the roads need to be designed as double track roads and it is not probable that at the present time over 1 to 5 per cent, can be classed as special service roads. Safety and Convenience of Traffic. — The amount of money that it is desirable to spend on safeguards to traffic is largely con- trolled by the volume of traffic. kA^ ofltiafaRKWfSSOfilVfPS ' Extreme danger should be avoided on any improved road but on the lighter travelled roads considerable must be left to the care of the driver. On such roads about all that is justified are danger signs and cheap guard rail that warn instead of actually pro- tecting and on many mountain roads even cheap guard rail is out of the question (see Fig. 8). On heavy travel special service roads all possible safe- guards should be employed, such as the eHmination of rail- road grade crossings, sub- stantial strong concrete guard rail or retaining walls, widen- ing and banking the pavement on curves, a safe "sight dis- tance" ahead at all times, shallow ditches, and warning and guide signs for the direction of travel. The seventh rule of design covers safety of traffic. On light traffic roads confine safety provisions to warnings. On heavy traffic routes spend all the money that is necessary to make the road as nearly fool proof as possible. Materials and Their Effect on the Selection of Pavement Tj^e. — The proper use of available local road building material is a fundamental economic principle in road design and properly controls the selection of pavement type. This principle is rarely disregarded in small local programs where the funds are 2 Pig. 9. — An unusual and effective warn- ing sign on an unprotected road. 18 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS limited and the officials are in close contact with the taxpayer, or in State aid Work in the sparsely settled States where the funds are small. Unfortunately its violation is quite frequent in State Aid Work in the rich States committed to very high class pavement design and is probably due to the tendency of large state organizations to generalize too broadly both on the minimum acceptable requirements of materials and on the selection cf pave- ment type. That is, they often fail to analyze each job carefully, to make comparative estimates of cost and to modify a general specification to make it adaptable to special conditions. They are working with large appropriations and have not much per- sonal incentive for clean cut efficiency. The proverbial drunken sailor is sometimes a piker in comparison. I do not mean by this that the roads are not well constructed for as a rule the con- struction is A number one and is in fact much better than that obtained under local control but the amount of money spent in the process is often needlessly high. It is well worth while to make a systematic effort to stop all the small leaks which amount to large figures in the aggregate. This does not mean that local control of Highway Design is better than State or National Control. We have had enough experience with both methods to demonstrate the very marked advantage of State and Federal Control in improving the general character of programs but this particular weakness can and ought to be corrected. The desirability of the proper use of local material does not seem open to argument and the eighth rule of design becomes: inferior material should never be used, but the type of pavement should be varied to permit the proper use of existing local materials or the cheapest imported materials. In practice this requires very thorough investigation of all local supplies. It necessitates a common sense attitude of the testing laboratory; it requires a reasonably flexible specification but it results in saving more money than any other single detaU of design. The requirements of materials are discussed in the second book of this series, but to illustrate the practical application of this principle in a general way a couple of possible cases will be outlined. Suppose a local service road carrying approximately. 400 vehi- cles per day is to be built. That a hmited supply of coarse gravel is available fit for bottom course macadam construction but not fit for concrete pavement or concrete paving base. That there is enough of this gravel to build a satisfactory bottom course for ECONOMIC HIGHWAY DESIGN 19 1 iflile of road with a short haul. Suppose at the other end of the road there is a local quarry of stone fit for bottom course but not hard enough for macadam top or concrete pavement. Under such conditions comparative estimates of original construction cost, maintenance and renewal for the different possible types will generally show a distinct saving in both first cost and ultimate cost for a macadam road utilizing the local gravel for 1 mile of bottom, the local stone for 3 miles of bottom and a hard imported stone top. Under these conditions the author has seen time and again either the entire elimination of the gravel if macadam is used or entire elimination of local materials by the adoption of concrete pavement for the full distance. It is against this ten- dency that we wish to throw the weight of existing evidence. Suppose a local service road handling approximately 1500 ve- hicles per day is to be built and that a first class local stone is available fit for any grade of macadam or concrete but that con- crete pavement sand has to be imported. Suppose that compara- tive estimates of construction cost show that an 18 ft. concrete pavement will cost only $8,000 per mile more tha» a satisfactory 16 ft. Bituminous Macadam with special macadam shoulders, and that there are enough funds available to construct the entire length of the proposed improvernent with concrete. Under these con- ditions considering the factors of Hf e, maintenance and renewal it is probably desirable to select the concrete pavement. If the difference in cost had been say $9,000 per mile for price conditions prevailing in the year 1920 it is probable that the selection of Bituminous Macadam would be the proper solution The de- ciding point in comparative costs of different constructions will vary for different localities, different traffic and different years as discussed later but some such basis of selection must be borne continually in mind if you expect to give a rational explanation of the selection of type. Each road must be analyzed on this basis as it often happens that within a couple of miles of each other, two different roads will require entirely different conclu- sions. Thereis too much generahzation in type selection. Time after time the author has been forced to build inadequate maca- dam roads because there happened to be a reaction against high grade pavements that particular year. This is as short- sighted as the opposite tendency noted above. The actual working out of highway programs is rarely logical as there are too many con- flicting interests to be considered but wherever it is possible to do 20 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS SO a reasonable analysis should be given the selection of type. Type selection is also often befogged by various arguments con- nected with the method of financing the improvement. ,«i «°o ft cog =N5 •a a -h. ^-J=r A / -7'- H ^ S\\^ \\\V xV^'* ^^ ^^^^ \\^ \\\^ M^^^\^\\N\\\4^\bs\4^^»j^^»^ ^ 2 t) -HI?- 111! \.^ ^> 5S61 0S6I stei- S>^J^^ \\^fe:^ 0961 a a «3 ^ S Otei % ■s^ei o?ei 9261 0261 sjio||0o'suoi4.io|jdojddv 'i|-"2%)k Financing Improvements (Effect on Design) .^ — Reasonable finance programs are based on the relative cost and length of life of the temporary and permanent features of road construction. Improvements are as a rule financed in one of three ways: 1. "Pay as you go" policy. ECONOMIC HIGHWAY DESIGN 21 •a fl ■a o a a o a 2. Serial bonds whose terms are based on the life of the im provement. 3. Long term bonds (sinldng fund method). The comparative total cost to the taxpayers of these methods is illustrated by Charts A and B. The "Pay as you go" poUcy is, of course, the least expensive in total cost but has a number of drawbacks The serial bond method is in more favor at pre- sent than either the first or third method. The total cost to the taxpayer increases with the length of the bond term Long term bonds have been used in the past as they provided a more or less painless method of extracting the necessary money but the additional total cost of a fifty year term bond, which has often been used, and its evident fault of throwing too much of the burden on the future has re- sulted in practically eliminating such a long term method. Bond issues of some sort for the original construction of a highway system have the advantages of making it possible to carry out a co-ordi- nated scheme more easily than J the "Pay as you go" poHcy They make it easier to get a con- tinuous program of construction ^^4k44^^iLi^ and to organize and operate a § § | § | g g | reasonably effective engineering I § § g § 1 1. i §. g ° organization for the design and sjD|ioa''3uo!4cudaidciv R|j>»a construction. The serial bond method based on a twenty-five or thirty year term and financed by general tax levy seems reasonable for the original construction tC 9 o ^ §2 ft a u O n 22 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS of a general system of highways composed of all the different types of pavement that would ordinarily be used to serve the average road user. The "Pay as you go" policy or serial bonds of about a fifteen year term financed by auto licenses or some other form of direct vehicle tax seem reasonable for a Reconstruc- tion Program of boulevards or special Commercial Roads. It is self evident that maintenance funds should be "Pay as you go" and probably financed by direct vehicle taxes. The methods of raising road funds vary for the different States and are changed from year to year. The Highway Green Book issued yeaily by the American Auto Assoc, affords a con- venient reference for up to date data on road laws and methods of raising funds. Appendix A reprints their discussion of Highway Bonds. Reasonable bond terms are based on the following general data. On well built roads the pavement surfacing or resurfacing and other minor elements such as gutters, guide signs, etc. are the temporary features. The other items of work such as grading, well built culverts, and foundations are relatively permanent. The top course of double track macadam type roads use up as a rule from 40 to 50 per cent, of the total cost of original construc- tion and last from 8 to 12 years on local service roads before a new top course is necessary. That is, the deterioration of macadam roads can be assumed to be 40 per cent, in ten years and after that time there is very little further deterioration of the original construction. The resurfacing of rigid type of pavement can be assumed to cost about 60 per cent, of the total original cost of the road and resurfacing is generally required in from 15 to 20 years. The deterioration for such roads can be assumed roughly as 60 per cent, in 15 years after which there is very little further depreciation on the original investment. Any scheme of financing which pays off 40 per cent, of the original loan in 10 years and 60 per cent, in 15 years appears reasonable for any general improvement program covering roads of different types. The twenty five year serial bond accom- phshes this making it possible to reconstruct these pavement sur- facings at the proper time without pyramiding loans. For reconstruction programs, however, the term should not exceed 15 years as the total expenditure is on temporary features. Programs based on 50 year bond issues can not by any ex- pedient of the engineer be made reasonable from the standpoint ECONOMIC HIGHWAY DESIGN 23 of the relation of the life of the surfacing to the term of the bond but this fact should not influence the engineer in his choice cf pavement type if he has to work under such a bond issue. The following attitude has had considerable publicity. "If our bonds are 50 year bonds, build o\rr roads to last for 50 years. Build Permanent Pavements. Build Concrete or Brick or Sheet Asphalt (depending on the business connections of the speaker)." As a matter of fact no large mileage of concrete will last for 50 years without resurfacing, neither wiU brick, neither will sheet asphalt, neither will macadam. As a matter of fact, the only road that does not need resurfacing in 50 years is a natural earth road. Why therefore cut down needed mileage and reduce mileage service, the first principle of design, by the use of rigid pavements on side roads where there is no engineering justification for them. A well designed macadam road under traffic for which it is suited will not cost any more for 50 years including mainte- nance, renewals, and interest on first cost than a rigid pavement on the same road. A long bond term never justified the use of rigid pavements on local service roads and the ninth rule of design becomes: Every effort should be made to obtain a reasonable term of bond but if a long term is used, do not permit the term of bond issue under which the improvement is made to influence the selection of pavement type. Contract Relations. — Assuming that the road is well designed it is necessary to get it well built. Sound business relations be- tween contractors and the directing engineering organizations is manifestly the only possible means of getting good work at a reasonable cost. Any element of unnecessary risk or uncer- tainty which the contractor must assume raises the bid price of the work. Any doubt as to whether the work will be let provided a reasonable bid is secured tends to keep away responsible con- tractors. Prompt decision and uniform treatment are essential. Reasonable profits are necessary to insure good work, for the community usually gets just what it pays for. The author has heard public officials say that they figured to catch a sucker at every, letting. They often did, but the result was that they either got a rotten job or had the difficulty of finishing the work themselves with all the usual complications. Fortunately this attitude has few supporters today and it may be stated as a general principle that uncertainty must be eliminated 24 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS as far as possible, reasonable prices must be paid and the size of contracts should be varied in order to interest organizations that can best handle the road in question. "The uniform use of long mileage contracts is no more desirable than the use of short contracts. Large organizations have a high overhead and equipment charge and there are generally not enough of them to insure lively competition. They can afford to provide labor saving machinery which is a distinct advantage during times of labor shortage. The award of long contracts to large organizations is probably desirable for high priced rigid pavements, particularly in sparsely settled communities. Short co ntracts tejid-^ to encourage competition . They can generally be finished in one working season which eliminates considerable uncertainty in the labor situation and the cost of materials. They can generally be handled with local labor, par- ticularly in well settled districts; they cause less inconvenience to the travelling public during construction. They are probably desirable for the construction of roads in well settled districts, particularly where the macadam form of pavement is used. Uncertainty in bids can be reduced by complete and definite plans and specifications that have the reputation of being en- forced. By definite statements of the requirements of materials and the location of acceptable supplies of these materials. By the publication of the engineer's estimate of cost with a state- ment as to the maximum bid that will be considered in award- ing the contract and by the provision that in case a responsible contractor makes the low bid under the limit stated and no award is made that he will receive a reasonable fee for making the bid. To determine reasonable prices every large state organiza- tion can afford to develop a construction department which can do certain jobs each year to gauge reasonable construction costs and to take over for completion any contracts that may be can- celled for non performance. Maintenance. — ^The final cost and length of life of pavement surfaces depend on the efficiency of maintenance. Mainte- nance is the most disagreeable feature of road programs. If is well to remember that the only permanent feature of road work is Repair and that no pavement will last long no matter what its original cost. Maintenance is something that we have always with us, that is the fly in the ointment, that makes the Highway Commissioner grayheaded if he is inclined to worry ECONOMIC HIGHWAY DESIGN 25 and that in many cases has not been handled with much fore- sight by the legislative bodies responsible for maintenance appropriations. Efficient maintenance can only be accomplished by preventing damage instead of repairing damage and it is very difficult to per- suade a non technical legislative body that large sums of money are necessary for this work before they have some physical evi- dence of the necessity. Such evidence is only supphed by a road that has been allowed to go to pieces and that the pubHc is com- plaining about. This involves reconstruction which is not prop- erly classed as maintenance and is much more expensive than preventive measures. Maintenance policy is an excellent example of the fact that the future has a habit of taking care of itself. In the author's home state, New York, no adequate maintenance poUcy was adopted at the start of State aid road construction. In a short time the necessities of the situation gave the necessary impetus for some improvement in maintenance work and this improve- ment has been steady. In the last eight years (1913-1920) the organization has reached a stage where it has demonstrated its abihty to handle all kinds of pavement repair with moderately good results provided the necessary yearly appropriations are made. Such appropriations are not yet up to the requirements of really farsighted efficient maintenance but we hope it is only a question of time until this is also accomplished. This gradual development of efficiency is very typical of the average com- munity. Reasonably effective maintenance has been accomplished and can be accomplished in spite of the practical difficulties of the job. The comparative cost of flexible and rigid pavement main- tenance will be discussed in detail in the second book of this series but at this point it is sufficient to note that under poor maintenance flexible gravel or macadam construction is worthless; that under moderately effective maintenance they compare favorably with rigid pavements in ultimate cost on local service roads where all classes of road material are locally available and that under really good maintenance macadam has a distinct advantage over rigid pavements up to about 1800 vehicles per ten hour day in the busy season. It is well not to permit the fear of inadequate main- tenance in the immediate future to influence the selection of pavement type. 26 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS The fact that maintenance has been poorly handled in some cases, resulting in a short Ufe of the macadam pavements has led a number of Engineers to dodge the difficulty by building rigid pavements. As a matter of fact the slogan of the concrete men, the brick men, etc., "Build the maintenance into the road" has considerable merit provided we admit that the American Public .Official can not handle maintenance. The man in charge of maintenance has a hard job. His work is not spectacular. If he keeps the roads in excellent condi- tion it is taken as a matter of course. If the roads are not kept in good shape very little charity is extended in his direction even though he has been handicapped by a shortage of funds. Legis- lators as a rule do not appreciate the large amount of money re- quired and apparently take delight in cutting the estimates where they would not think of tampering with construction ap- propriations. Maintenance is a convenient way of dispensing minor patronage, etc., but good work has been done and can be done and if the community ever expects to complete a general system of roads it must be done. There is one thing certain, the pohcy of "building the main- tenance into the road" by the use of a short mileage of extremely high priced pavements on account of the fear that it will be im- possible to maintain a less expensive type violates the first prin- ciple of Mileage Service. It also often puts the hidden burden of maintenance on the community at large as part of the original 'construction cost instead of on the road user as a yearly charge. This last contingency has been avoided in some cases by finan- cing original construction with auto license fees but the wisdom of this method is open to argument where this robs needed main- tenance funds and the short mileage result can not be overcome. Needlessly short mileage is the most serious criticism that can be made of any general pohcy dealing with an incomplete Road System. The last principle of design becomes: efficient maintenance is essential. The lack of a well defined maintenance policy should be remedied by making the maintenance effective and not by side- stepping the issue with a needlessly short mileage of high first cost, low maintenance cost pavements. Summary of General Principles. — The foregoing principles may be summarized as foUows: ECONOMIC HIGHWAY DESIGN 27 First. — The construction of the greatest possible mileage of connected roads of a type suitable to the stage of development of the community and its existing traffic . Mileage is the first and foremost factor of service. Second. — Traffic must be re^julated not only to save past investment but also to enable the community to finance any enduring general system of roads and to make economic engineering design possible. Third. — Local traffic is entitled to fir st consideration in the location of roads and their design except for a comparatively small mileage of special service roads. Fourth. — The maximum regulated load for the class of service for which the road is intended should govern the strength of the pavement founda- tion and bridges and no attempt should be made to reduce construction cost by using weak foundations. Heavy traffic must be ruled off from local service roads. Fifth. — The varying demands of traffic require variations in pavement type. As a general rule avoid the use of rigid pavements on local service roads except for unusual conditions of material supply. Sixth. — The number of vehicles and the percentage of horse traffic using the road govern the width of pavement and its surfacing. Seventh.^Volame of traffic controls the designs of safeguards. On light traffic roads confine safeguards to warnings. On heavy traffic roads make the road as near fool proof as possible. Eighth. — Inferior material should never be used but the type of pave- ment should be varied to permit the proper use of existin g local materials or the cheapest imported materials. Ninth. — ^tlvery effort should be made to obtain a reasonable term of bond but if a long term bond has been adopted do not permit the term of bond issue under which the improvement is made to influence the selection of pavement type. Tenth. — Uncertainty must be eliminated as far as possible in contract relations, reasonable prices must be paid to insure good work and the size of the contract should be varied in order to interest organizations that are best fitted to handle the roads in question. Eleventh. — Efficient maintenance is essential. The lack of a well de- fined maintenance policy should be remedied by making the maintenance effective and not by sidestepping the issue with a needlessly short mileage of high first cost, low maintenance cost pavements. Conclusion. — These principles will serve as a basis for the development of detail design practice. While they may not apply to all cases, some such general scheme that will fit the requirements of the locality in question is a necessary step in any reasonable scheme of design and construction. They serve as a fixed goal to aim at and are very useful as a guide when the Engineer is floundering in detail or badly hemmed in by circumstances. CHAPTER II PROPORTION AND ECONOMY IN DESIGN The Relative Importance of the Detail Elements of Design. — Most roadwork can be classed as a step in progressive improve- ment; the highway is gradually bettered from a trail to a high- class, modern, heavy-trafl&c thoroughfare as its use or prospective use warrants the expenditure. In the majority of cases the money at hand is not sufficient for the complete construction of Fig. 10. -Expensive rigid pavement highway with dangerous alignment, dan- gerous section, flimsy guard rail and weak bridging. all the features that are desirable even at the time when the im- provement is made, and it is never sufficient to build a road that will completely fill the requirements of the future. Some fea- tures have to be omitted or slighted. It therefore seems well worth while to encourage first the construction of reasonably good fundamental elements which act as a basis for the final improvement, and then in logical order as many of the other desirable parts as can be built. Where the funds are inadequate for a completely satisfactory design the results often show a lack of proportion. Figure 10 28 PROPORTION AND ECONOMY IN DESIGN 29 will perhaps show in a general way the point I have in mind. It shows a high-class pavement with dangerous alignment, dan- gerous section, flimsy guard rail and weak bridging. It certainly pays to construct what is done so that it can be readily strengthened and widened as the future requires, without losing the benefit of previous work. The following tentative list illustrates an order of importance of design ele- ments which probably applies to most cases, with some minor variations : Fig. 11. — ^Substantial modern bridge with well designed approach protected with concrete guard rail. DESIGN FEATURES First, selection of the best general route. (a) Best location for the development of the territory. (b) Longest open season. (c) Least rise and fall. (d) Length and cost. Second, selection of the most natural engineering location following the desired general route (a) Reasonable grades. (6) Exposure. Avoid north exposure and areas of deep snow. (c) Character of excavation. Avoid rock, slides, etc. (d) Drainage problems. Avoid flood areas, stream crossings, etc. (e) Avoid artificial restrictions such as section line locations, etc. Third, detail requirements of design. (a) Eeasonable maximum grade, considering future requirements. (6) Economical intermediate grades. 30 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS (c) Safe and economical alignment, considering future requirements. (d) Width of roadway safe for traffic, eliminating dangerous ditches. (e) Width of roadway convenient for traffic. (/) Sufficient culverts and bridges to protect the roadway, considering the future. (g) Permanent construction of these culverts and bridges. (h) Sufficient width of clearing for sun to reach road, (i) Safety provisions. Protection for traffic at dangerous places. {j) Provision of liberal width of right-of-way, considering future widen- ings and development. Fourth, improvement of the road surface, (o) By selective soil treatment. (b) By gravel, chert, macadam, etc. (c) By rigid pavements. Fifth, improvements for the future, (a) A higher-grade surface, (i) A wider hard surface, (c) Provision of sidewalks for pedestrians. id) Planting trees, etc. An examination of the roads in almost any locality leaves the impression that a little more emphasis on and attention to the better construction of the fundamental features will add to the reasonable proportion of design and be a move in the right direction. The following typical cases illustrate the usual problems that occur and indicate their general solution. General Solutions Pioneer Districts. — Where no road exists and the funds are entirely too small for good construction, a sufHciently cheap design is used to complete the entire length. Under these conditions the only requirement that must be met is the proper selection of general route, although it is probable that for the greater part of the distance the final engineering location can be followed. Considerable work of this kind has been done in the southwestern states, and the solutions are in- genious. Satisfactory wagon and automobile trails have been constructed under favorable conditions for as low as $20.00 per mile, while in difficult locations advantage has been taken of all possible expedients to keep the cost down. Where a poor but usable road exists between the terminal points, or for a portion of the distance, either the uncompleted or worst sections of the route are first considered. Under such circumstances the funds are generally sufficient to permit a moderately good engineering design, which must prvoide for a reasonably good grade and drainage scheme on the improved PROPORTION AND ECONOMY IN DESIGN 31 sections, although the drainage structures may be cheap and temporary and the roadway narrow. Where a fair road has been previously built over the entire route, no improvement should be attempted unless it provides for a first class engineering design of grades, alignment, section and permanent drainage structures. Where a first-class natural soil road is in use the next step in progressive improvement requires either selected soil, gravel or hard surfaced construction of the traveled way. General Solutions Well Settled Districts. — The application of the order of importance of design elements for hard surfaced pavement work can be shown by three cases: Under the most favorable conditions in rich communities, the improvement is considered final and its design is based on an effort to obtain the most useful, and in the end the most economi- cal form of construction regardless of first cost. In this case all the engineering requirements may be fulfilled. In many communities, however, the funds are only sufficient to build a moderately good pavement, which will have to be bettered by reconstruction in a few years, to meet the increasing demands of the traffic. An improvement of this kind should be permanently and completely designed for proper grades, ahgn- ment, section, drainage and safety provisions, up to a certain rea- sonable hmit and the balance of the money spent on the best type of hard surface that can be afforded. The third case is reconstruction, which usually confines the problem to consideration of the most suitable type of resurfacing, utiUzing previous work to the best advantage. It also sometimes involves improved relocation. Reasonable Economy in Design. — The mileage to be con- structed is so great (see Table I) and the amount of money involved so impressive that it seems desirable to use all reasonable care to produce as many miles of road as possible with the avail- able funds. During the years 1913-1920 the author has made a careful review of some 2000 miles of road plans from different sections of the country with the idea of forming a reasonable con- clusion as to the trend of highway design and to see how closely current practice follows the well recognized principles of high- way engineering. The results of the analysis of these plans were, roughly, as follows : About 25 per cent, could be classed as first- class designs from an economical standpoint. Practically all 32 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Table. 1. — Road Mileage in the United States in 1914. (Bulletin U. S. Public Roads) Total road mileage Miles sur- faced Per- centage surfaced Total mileage Surfaced mileage State Per sq. mile of area Per 1000 rural popula- tion Per sq. mile of area Per 1000 rural popula- tion 55,446 12,075 50,743 61,039 39,780 14,061 3,674 17,995 80,669 24,396 95,647 73,347 104,074 111,052 57,916 24,563 23,537 16,459 18,681 74,190 93,517 45,779 96,041 39,204 80,272 12,182 14,020 14,817 11,873 79,398 50,758 68,796 86,354 107,916 36,819 91,555 2,170 42,226 96,306 46,050 128,960 8,810 14,249 53,388 42,428 32,024 75,707 14,797 4,988 253 1,097 10,279 1,193 2,975 243 2,830 12,342 679 11,606 30,962 614 1,148 12,403 2,067 2,762 2,489 8,505 7,828 3,967 2,133 6,712 609 1,204 262 1,659 5,897 261 15,635 6,003 955 30,669 121 4,726 9,982 693 •3,270 363 8,102 10,526 1,153 1,442 3,909 4,922 1,064 13,399 468 8.99 2.09 2.16 16.84 3.00 21.16 6.62 15.72 15.30 2.78 12.02 42.20 0.59 1.03 21.40 8.42 11.74 15.10 45.53 10.55 4.24 4.66 6.98 1.55 1.50 2.14 11.83 39.80 2.20 19.60 11.82 1.38 35.16 0.11 12.83 10.90 31.95 7.74 0.37 17.69 8.16 13.09 10.12 7.32 11.61 3.30 17.60 3.10 1.08 O.U 0.96 0.39 0.38 2.92 1.86 0.33 1..37 0.29 1.71 2.03 1.87 1.35 1.44 0.54 0.79 1.65 2.32 1.29 1.15 0.98 1.39 0.27 1.04 0.11 1.55 1.97 0.09 1.66 1.04 0.98 2.12 1.55 0.38 2.22 2.03 1.38 1.25 1.10 0.49 0.11 1.56 1.32 0.63 1.33 1.37 0.15 31.3 85.5 36.9 67.2 100.9 122.3 34.9 '33.6 38.9 95.4 44.2 47.1 67.3 92.7 33.4 21.1 65.3 25.8 77.5 50.0 76.3 28.8 50.6 161.5 91.0 177.8 79.9 23.5 42.3 41.2 26.8 138.8 41.0 80.7 100,6 30.2 120.8 32.7 189.8 26.4 43.6 43.9 76.2 33.7 79.0 32.3 56.9 147.9 0.097 0.002 0.020 0.066 0.011 0.617 1.240 0.052 0.210 0.008 0.207 0.858 0.001 0.014 0.308 0.050 0.092 0.250 1,058 0.136 0.036 0.046 0.097 0.004 0.001 0.002 0.184 0.784 0.002 0.328 0.123 0.013 0.750 0.002 0.049 0.220 0.649 0,107 0.004 0.194 0.401 0.014 0.158 0.097 0.073 0.044 0.242 0.005 2.82 1.79 0.80 California 11.32 3.02 Connecticut 25.89 2.32 Florida 5.29 5.96 Idaho 2.65 5.37 19.88 0.39 Kansas 0.96 7.15 Louisiana 1.78 7.65 Maryland 1 3.90 Massachusetts Michigan 35.29 5.28 2.42 Mississippi 1..34 Missouri 3.54 2.51 Nebraska 1.36 3.82 New Hampshire 9.47 9.40 New Mexico New York.. 0.93 8.10 North Carolina North Dakota Ohio 3.18 1.86 14.54 Oklahoma 0.09 12.89 Pennsylvania Rhode Island South Carolina South Dakota 3.29 38.59 2.53 0.72 4.64 Texas 3.56 Utah 5.76 7.71 2.46 9.17 West Virginia 1.07 10.08 Wyoming 4 56 United States 2,445,760 257,291 10.52 0.82 49.5 0.086 5.21 the designs showed minor wastes, but for the plans classed as good, revisions would not result in any practical advantage. About 75 per cent, of the plans showed a material expenditure of money for which no adequate return was obtained, amounting to from 5 to 20 per cent, of the cost. On some of the roads which, as built, served the traffic well, this excess might better have been spent on other jobs. On some of the roads which, as built, were PROPORTION AND ECONOMY IN DESIGN 33 not up to the requirements of the traffic, the waste might better have been applied to their own improvement in fundamental features. The general faults most noticeable were: Too much spent on the reduction of intermediate grades. Too much spent to obtain long straight grades. Too much spent on sections with deep ditches. Not enough spent on realignment at dangerous locations. Not enough spent on relocations necessary to get reasonable maximum grades. Not enough spent on long-span bridges. Too much spent on width of macadam. Not enough spent on depth of macadam. Too much spent on imported materials where local materials were avail- able in limited quantities. One of the objects of these books is to discuss in detail various proved means of effecting economies without reducing the use- fulness of the roads. At this point, however, it is not necessary to more than indicate the different parts of design that are par- ticularly susceptible to such saving. Systematic grading design will often reduce the work from 500 to 2500 yd. per mile, amounting in money, on an average, to from $500 to $1000 per mile. The proper use of local material particularly in foundations is a large factor in economy and will often reduce the cost from $1000 to $3000 per mile. Reasonable variations in pavement width and in the thickness of surfacing courses is effective and in many cases saves from $1000 to $2000 per mile. A very conservative estimate of savings due to these systematic minor alterations is from $1000 to $2000 per mile. These savings are not spectacular for any one job but if consis- tently used their advantage on any large program is very evi- dent. They will more than pay for all the necessary engineering work in connection with the entire program. The small addi- tional work required for a careful analysis is the best pos- ible engineering investment for the community that can be made. Tests of Designs. — It is certainly well worth while to test out each finished design to see if it complies with the general princi- ples which have been discussed and also with the detail economies that will be taken up later. The following list of questions in- dicate in a general way the points to be considered : 34 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Questionnaire Is the alignment suitable for all reasonable requirements of the future? Is the ruling grade suitable for all reasonable requirements of the future? Is the section, ditch to ditch, safe and suitable for present traffic? Is the right-of-way wide enough for future requirements? Are there ample culverts for all requirements of the future? Are the culverts proportioned properly as to size considering run-off? Are the culverts long enough to be sate and large enough to maintain? Are the bridge superstructures strong enough for present traffic? Have all permanent culverts and bridges been designed strong enough and wide enough for, say, 50 years? Are the bridge abutments for new temporary superstructures solid enough for future permanent superstructures? Are the ditches road ditches and not farm drainage ditches? Are the safety provisions real safeguards or are they only warnings? Is the road surface thick enough to handle present traffic without founda- tion failure, considering the subsoil conditions? Is the road surface wide enough for present traffic ? Is the surface of the general type required by present traffic? So much for Proportion — now for Economy: Does the grade line conform with the principles of economical design? Do the sections fluctuate to conform to economical design? Has the selection of pavement type been based on the most economical use of local materials? Has the design been varied to use limited supplies of local material with short hauls? Is the width reasonable, and has it been varied on a road that has heavy traffic part of the distance and light traffic part of the way? Has the depth of macadam been varied to meet the different require- ments of the soils and kept to a reasonable minimum? Have the culverts and bridges been designed for the most economical type for the span in question? Have the types of culverts been varied to get the cheapest result, con- sidering local materials, in comparison with market quotations and cost of long hauls on imported materials? Are the specifications flexible enough to permit the reasonable use of local material? Does the testing laboratory make an effort to approve the reasonable use of local material, or is it inclined to hold arbitrarily to the highest stand- ards, regardless of the relative importance of the job in hand? The designer should, however, bear in mind that imperfections in construction and indeterminate factors make too close a theoretical design impracticable and that a certain factor of safety must be provided in all his plans for such possibilities. The application of this to the different elements of design will be discussed throughout the books. PROPORTION AND ECONOMY IN DESIGN 35 Order of Work. — -The detail methods employed in the field and office work are described in the third book of this series. In pioneer districts the general order of work is as follows: A preliminary investigation is made to determine the general route, the best engineering location and the approximate cost of construction. It forms the basis for the general scheme of financing and design. It is the most important feature of new road location, and if well done insures the completion of a rea- sonable program of construction with the funds at hand. It also prevents wasteful expenditure on ill considered or unsuitable location surveys and plans. The detail location survey based on the preUminary conclusions is next made to secure the data for the final office design, which carries out in detail the recom- mendations of the first report and completes the work prelimi- nary to construction. In well settled communities the order of work is the same. The character of the information for the preliminary inves- tigation is different, but the object is identical; namely, to pro- vide a basis for appropriations and reasonable design. The preliminary data deals largely with probable traffic, available local materials and the most suitable and economical pavement type. The location survey provides the essential data for design, using somewhat better methods than for mountains conditions, and the office work is more detailed and complete. Conclusion of Chapter. — During the last ten years, road de- sign has been improved -by standardization. This is a necessary step in the development of efficient organizations but it is only a prehminary step which has already been carried up to or be- yond its desirable limit in many states. The more or less preva- lent stereotyped use of Standards not only results in a needless expenditure of public funds for construction but tends to dis- courage independent thinking by the rank and file of the force. Standards serve their purpose by providing a minimum standard of excellence and by saving time and duplication of effort in designing ordinary structures; that is about their limit of use- fulness. Further improvement in general highway practice Ues very largely in an educational policy along the lines of system- atic economical design and the use of engineering judgment in the apphcation of standards. The natural tendency of the man new to roadwork is to copy ex- isting local practice with very little thought as to its reasonable 36 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS application. If designers will think for themselves a long step forward is accomplished. They are not so apt to be stampeded by trade propaganda or to develop a habit of mental laziness that is willing to accept any method that will, to use a slang phrase, "Get by." Any technical analysis is of value only when its application is based on common sense. It is very evident that any system of design which does not take advantage of and encourage the initiative of the intelligent and experienced men on the force is radically wrong. It is probably true that a few of the usual Civil Service Engineers and Inspectors are not active mentally. For this class of men an effective way to encourage reasonable design and force the designer to make an analysis which he can defend is by "Check Lists." This method is illustrated in ,detail in the third book of this series. However, it is just as well to emphasize the fact that there is a genuine personal enjoyment in a complete, reasonable, economic analysis of road design. A great many young men have said that it took them a long time to realize this and that they were as a rule indebted to some older Engineer for the point of view. I have seen the radically different results obtained by these men after they had developed the habit of analysis and it is hoped that the economic advantages of careful engineering can be effectively shown throughout the books and particularly in Volume III by examples of actual design worked out in the usual standard manner and then modified by systematic criticism. The success of any program depends very largely on the per- sonnel of the directing organization. The national tendency of making public work the football of partisan politics may add interest to life but it certainly does not add efficiency to a road program. It is often extremely difficult to c.arry out any well balanced plan. We generally get the roads somehow and some way but main strength and awkwardness play a large part in the game. It is well to bear in mind that while present procedure can undoubtedly be improved that the net result of Highway programs to date has been excellent and the communities have received entirely satisfactory returns on their investment in im- proved roads. State and Federal control has radically improved engineering design and methods of financing. It has eliminated most of the petty local interference with sound design but the danger to guard against from centralizing the authority lies in too much generalization, lack of flexibility and the beaurocratic PROPORTION AND ECONOMY IN DESIGN 37 attitude which tends to smother the development of the promising younger men. Any method which tends to stabilize general policy or improves the character of the engineering organization is a move in the right direction. Careful layouts and complete classifications which are well made and well advertised have some effect in preventing radical changes by successive administrations. These expedients are discussed in the next chapter. CHAPTER III CLASSIFICATION, ROUTE AND GENERAL ENGINEERING LOCATION Road Systems. — The first step of road improvement programs is to plan the system and classify the roads. A general layout is necessary to insure a well connected and serviceable system for both local and long distance traffic. A great deal of thought has been given to the layout of state and county highways and the general plans are fairly well fixed in most localities. Comparatively few engineers will have the opportunity to assist in planning large systems but it will do no harm to give a short discussion of the general principles governing layout, classifica- tion and the selection of route. Layout of Systems. — ^Layouts are based on the part that the highways play in the general transportation scheme for the locahty in question. From the standpoint of heavy hauling, highway systems generally act as short feeders for railroad freighting. This has been somewhat modified by motor truck development, as discussed later, but as far as long-distance hauling is concerned highways as a rule are not a large factor. However, long-distance freight hauling becomes a deciding factor for special districts removed from railroad facilities or for metropoUtan districts with closely located cities. Light vehicles have a greater range of action and are not as closely confined to definite routes. Local topography modifies the various schemes but the traffic requirements usually result in a system of main roads radiating from shipping points, cities, county seats, etc., connected at proper intervals by cross roads. Each local system is tied to the adjacent system by a reason- ably direct route. (See Fig. 13, Western New York State & County System.) (See Fig. 14, for Local System Monroe County.) The advantages of a complete plan of this nature is very evident. Single bond issues or appropriations are rarely comprehensive enough to complete even a skeleton system of roads for large areas but if a more or less complete system of 38 GENERAL ENGINEERING LOCATION 39 Hammooi Fig. 12. — Indiana state road system. (Skeleton through routes.) 40 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS roads is laid out at the time the improvement program is started it is possible to see at a glance the part each road plays in the general scheme. This makes it easier to design individual roads to fit into the finished system, and it is also easier to decide on a reasonable order of construction. Systems are laid out by careful study of maps, field inspections of alternate routes, conferences with local people and sometimes are affected by traffic estimates on rival roads. The value, of any proposed highway system can be roughly indicated by traffic counts; to illustrate, the State of IlUnois concluded from such counts that 15,000 miles of her roads out of a total of 95,000 miles carried 90 per cent, of the total traffic. It should, however, be remembered that road improvements often change the move- ment of traffic and that existing trafiic routes should not outweigh evident advantages of other locations. Such a count may not determine exactly which roads to improve, but it indicates that a well laid-out system containing 15,000 miles will probably give excellent service as a system of Main Roads. Complete State or National Road maps may well be compiled showing the existing movement and volume of traffic (see page 45); the condition of existing roads and bridges; the location of road materials; the location of industries affected by high- way haulage; the location and character of natural resotu-ces dependent on highways for their development. Such data aids reasonable layout and design. Preliminary data of this kind is rarely well worked out on account of the time and money required for careful study. The insistent demand for immediate construction regardless of where the dirt flies is responsible for many disappointing programs. Classification of Roads. — Highways are classified in two ways; to apportion funds and to determine pavement type. The classification as National, State, County or Town High- ways depends on their location and relative importance to the present or future transportation needs of the country. Such a classification not only furnishes a reasonable basis for the appor- tionment of funds but it also provides a sliding scale of excellence for the design of the fundamental featiores of different classes of road improvements. This does not mean that because a road is designated as a State or National road that it is necessarily entitled to ex- pensive construction. Extensive State and National programs Missing Page GENERAL ENGINEERING LOCATION 41 cover a wide range of construction from thickly settled districts to pioneer territory. The location and demands of existing traffic or the expected traflBc in the near future control the desirable present expenditure on any road whether it is a town or national highway, but if the road is designated as a national route it- is probable that in the future it will carry a large volume of traffic, and it indicates that the progressive stages of improvement may well provide liberally for right of way, alignment, grades, etc. Classification for Financing. — A complete layout and classi- fication scheme aids the proper apportionment of funds. The distribution of Federal, State and County aid to through routes and to local service roads is an extremely difiicult problem from a practical standpoint but considering that about 90 per cent, of traffic is local, too much help or too much stress on the immedi- ate completion of a skeleton system of through routes is open to question unless such routes can be located and built to act as the main arteries of local traffic. Unless the local service pro- gram is fairly well completed, large amounts cannot be reasonably spent on high priced connecting links through sparsely settled outlying districts which have very little value except for tourist travel. If no line of communication exists a moderate priced road is a good investment but excessive expenditures are to be avoided. We have no system of National Highways as yet but in all probability it is only a matter of a short time before a start will be made. Federal Highway aid is an accompUshed fact. The present law (1920) requires State or State-County co-operation and is laid out apparently with the idea of improving general administrative conditions in road programs. The actual con- struction done under this act includes local service roads as well as through routes, which is a sound proposition. Work of this kind can, however, be well supplemented by a National Trunk Line System, provided the local service program is not pushed into the background by the more spectacular through fines. National Highways are naturally confined to the most im- portant interstate routes or special highways necessary for mili- tary purposes. Some very ambitious programs of mileage have been proposed but it is not Ukely that such a system will aggre- gate over 1 to 2 per cent, of the road mileage of the country. Such roads may well be constructed and maintained by Federal 42 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS funds or by co-operation with the states under Federal supervision. The general principles of route selection later discussed govern the layout of these roads. State Routes cover the main inter-city routes or the main natural transportation or tourist routes. They do not as a rule include more than 4 to 6 per cent, of the total road mileage. They are usually financed by State funds or may receive Federal Aid. County roads include the main local service roads. They do not as a rule aggregate over 15 per cent, of the total road mileage. They are financed by county funds or may receive state or federal aid. While National, State and County roads do not probably include more than 15 to 25 per cent, of the total mileage in the country, they probably carry from 80 to 90 per cent, of the total traffic during some portion of its journey. Town roads constitute from 75 to 90 per cent, of mileage and while they are generally fight traffic roads they act as feeders for the main system and are of very great economic importance to the general transportation scheme. It is certainly extremely poor poficy to over-emphasize the value of the main roads and neglect the feeders. Expensive construction is not usually re- quired on such roads but they should be passable the year round and any comprehensive road scheme must deal liberally with these Ught traffic local roads. Town roads are financed bytown funds and may receive county or state aid but rarely federal aid. Classification for Details of Construction Design.^ — ^The decision as to general type and width of pavement and section depends on the kind and volume of traffic expected in the near future. On any road the amount and class of traffic will fluctuate. The first improved roads in any locaUty may for a time carry more than their share of the travel, which is naturally reduced by the subsequent construction of adjacent improvements, or it may be increased by the finking up of isolated improvements into a continuous route of improved roads between large centers of population. It can be readily seen that it is difficult to judge the amount of traffic a new road will have and that a short time traffic census is valueless as a basis for a definite conclusion. The general design is usually based on a comparison of the be- havior of different kinds of previously built roads that serve - Town Macadam W//M Town Gravel i^Hi Sfate and County RoadA ^vo/j L I n /I a W.BLOOMFI^LD ^y CHARACTERISTIK OF MOHROE COUNTY ROADi November ht ISIS " Tokil mileage of highways outside of city and vHlayes Ij363. 03 mleage of State anditate-Cmnty Highways completed or under contract- ' 310. 2S GOOD ROADS COMMITTFF wiLiiiiM e. mtreir, aairman eeoRoe A. JOHNSON ^,City.fRoch^ter^.„d,rie.afterJan.Ut.tSie t,,Lpoy^^'5%ads,aidforl,^co.n^andto.ns S.Vs ^ZtTZ^ ^^f^^ "'"'^tt.m.er. ont.. ma.are not lo.n.m^rs. '^^f^'^^' ^fr.% ^^^^^^f^rintenden..r.r,.cu.roc. butfortheread^identlficationofa_riyiet.t,anofread 'oral mileage of improved roads 963.16 Fig. 14. {Insert facing page 42) GENERAL ENGINEERING LOCATION 43 districts similar to that under consideration and this can better be determined by a study of the locality than by a locahzed traffic census. Roads on which high type macadams or rigid pavements are suitable may be divided into four general trafl&c classes. Class I. — Main trunk roads between large cities not over 100 miles apart along natural transportation routes which accom- modate through truck freight traffic. Main radial roads for 5 to 40 miles out of cities of say 50,000 and upward and in the business section of villages which carry the concentrated farm and truck traffic of a large area and are subjected to continuous heavy load travel. A Class I road usually carries more than 2000 rigs per day in the busy season. Class II. — Main through automobile routes at greater dis- tances from the cities, which have a large touring car traffic and medium heavy farm traffic and some heavy trucking. A Class II road generally carries from 500 to 2000 rigs per day. Class III. — Secondary or feeder roads and cross roads having a medium heavy farm traffic and light pleasure travel. Class III also appHes to main roads in sparsely settled districts. Class IV. — -Pleasure or scenic roads that carry a large number of pleasure autos but hght steel tire traffic. Class I roads as a rule require rigid pavement construction while Classes 2, 3 and 4 are generally more economically served by thick modern bituminous or waterbound macadam (oiled) or gravel construction. Value and Limitations of TraflBlc Census. — Complete traffic counts taken at regular intervals provide definite data concerning volume and character of traffic and the direction of its movement. Such a census has an indisputable value in indicating the general character of our highway traffic. Even the usual short time census has some value in determining the general character of the traffic. The usual short time census however has a very hmited value in connection with definite decisions of design. As far as design is concerned a well taken census can be given some weight when apphed to a road system before an improve- ment program is started. It has a very decided value for use in reconstruction programs where the improved system has been completed and traffic routes established. It has practically no value for a partially completed system where traffic may go out of the way to use the first improved roads. Any traffic census should be fairly complete and represent the seasonal variations 44 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS of traffic. Detail methods are described in the second book of this series. Take a concrete example to illustrate the discussion. (See Traffic Map, page 45) . This map applies to the partially completed state aid road system shown in Fig. 13, page 41. It was devised by Mr. Percy Waller of Rochester, N. Y. for use on Division No. 7 and is a much better method of summarizing the census than the usual tabular form. This particular map represents total volume of traffic. Similar maps can be prepared to indicate tonnage, or truck traffic, etc. It is a very effective way of showing the relative use of the roads and the distribution of travel at junction points. It is a valuable guide provided the data on which it is based is complete. This particular map however was based on the usual New York State short time census taken for two days (Aug. 14th and 15th, 1920) from 7 A. M. to 7 P. M. On account of the lim- ited scope of the data the census or any other similar census must be used with caution. Suppose we analyze the data. The estimate does not show seasonal variation in classes of traffic (horse and motor). It does not give a reasonable basis for total traffic considering seasonal variation and night travel. It has some value in representing the relative traffic on the roads during the summer season but falls down in numerous instances on account of summer resort travel, special fairs, Dollar day at Batavia, special picnics and the fact that some of the shorter main line roads are not yet completed. That is, this census is not in itself complete enough to have much value and the road system is not near enough completed to give the probable traffic move- ment in some cases. If we had a 24-hour count for Monday in January, Tuesday in February, etc., we could eliminate much of the uncertainty provided the system was completed and the count was to be used in deciding on pavement types for reconstruction. Suppose we cite a few cases where the traffic figures would be misleading unless modified by a common sense study of the territory. In the first place the census was taken in the height of the auto touring season. It over-emphasizes the traffic on the through routes as compared with the secondary lines. GENERAL ENGINEERING LOCATION 45 46 LOCATION, GRADING AND DRAINAGE -OF HIGHWAYS A census taken in the winter, fall or spring months would probably show a larger percentage of horse traffic particularly on the local service roads. The roads marked S are summer resort roads and a seasonal census would change the volume radically. The roads marked P where affected by large picnics or county fairs. Batavia had a dollar day sale, Caledonia had a fair and all the farmers flocked to town The roads were unusually crowded. The road marked A will in the future be reUeved by the com- pletion of the road marked B which will radically change the volume on these roads. On one unimportant road the local people asked a friend of mine to drive up and down as many times as he could to swell the count and said they were all doing it in order to help get a concrete resurfacing job on that road. One or two of the roads are in such bad shape from a lack of maintenance funds that the traffic count was less than normal. These points are mentioned to illustrate the statement that the most rehable basis for design of a road in a new or incomplete road program is a common sense study of the territory. A com- mon sense study, however, includes a well-taken traffic census; not the usual incomplete count. Example of Classification by Location and Census Combined. — A concrete example of a design classification by location and census is shown in Fig. 13 and explained as follows: Its value as a basis for a continuous policy is self evident. This particular territory is selected to illustrate the discussion as its problem is typical of the usual road conditions. It illustrates a wide range of conditions and with slight modifications will apply to most of the States. By means of a definite illustration we hope to strengthen the discussion of general principles. The roads shown in red are class one, entitled to strong rigid pavement construction or reconstruction. The roads shown in green are in the doubtful class designated 2A. The use of rigid pavements or high-class macadam depends largely on the relative cost for each road. Any reconstruction should provide for a low maintenance cost surface although the existing macadam base may be utiHzed if firm and solid. The roads shown in black are class two, served most economi- cally, in most instances, by a thick modern bituminoTis macadam, with reconstruction of the same type. GENERAL ENGINEERING LOCATION 47 The roads shown in yellow are class three, on which the usual well-b\iilt modern waterbound macadam, maintained by surface oihng, will serve satisfactorily. The roads shown in green, black or yellow with red dots mean that a rigid pavement is desirable on account of water flooding and not on account of traffic action. Such a classification should be carefully made utilizing the best judgment of the entire engineering force and local authorities. It should be reviewed and co-ordinated by the chief engineer. If well made and given enough publicity it tends to stabiUze the general construction and reconstruction programs as any new administration would hesitate to change it radically unless they could make an excellent argument for so doing. One of the most troublesome difficulties that the highway engineer has to contend with is the constant change of general policy inaug- urated by successive admim'strations and any method which tends to minimize such changes is a move in the right direction. The tentative classification shown in Fig. 13 was made by the author with the help of five other engineers, some of the mainte- nence men and local officials. It was prepared to illustrate this manuscript. It is not an official classification. General plans of this nature are not yet in ordinary use but it is only a question of a short time before they probably will be. In order to give an idea of the percentage of the different classes of road in the district shown, the following tabulation is inserted. Road classification Approx. percentage of state and county system, approx. total 1350 miles Approx. percentage of total road mileage, approx. total 6700 miles Class 1 Class 2A. . , Class 2. . . . Class 3 Town roads 3 2 9 6 80 In order to show the range in classification for different terri- tories the following tabulation shows Wyoming county (a poor district) and Monroe county (a rich thickly settled county). 48 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Wyoming County Road classification Approx. per cent, of state and county sys- tem, approx. total mileage 175 Approx. per cent. total road mileage, approx. total mileage 1076 Class 1 4 42 54 1 Class 2A. . Class 2 Class 3. Town roads 7 9 83 Monroe County Road classification Approx. per cent, of state and county sys- tem, approx. total miles 400 Approx. per cent, of total road mileage, approx-total miles 1368 Class 1 12 20 42 26 4 Class 2A 6 Class 2 Class 3 Town roads 12 8 70 The outstanding feature of this classification is the comparatively small mileage of roads requiring rigid pavements at this time (1920). The value of a classification of this kind for design, apportion- ment of funds and appropriation estimates is illustrated as follows: National Routes. — It is self evident that the natural location of a national route should follow along the New York Central Railroad via Corfu, Batavia, Bergen, Churchville, Rochester, Fairfort and east to Syracuse. Such a road is class 1 for the entire distance in this territory. (Fig 13, page 41). State Routes (Fig. 13). — ^The state roads as actually built or proposed aggregate approximately 370 miles. To illustrate the statement previously made that the designation of a road as a state route does not necessarily entitle it to expensive construc- tion, the tabulation below shows the approximate number of miles of such state routes under a reasonable classification. GENERAL ENGINEERING LOCATION 49 Approx. mileage Per cent, of total Class I 90 80 160 40 24 Class 2A 22 Class 2 44 Class 3 10 Comparison of Actual Construction with this Illustrative Classification (Fig. 13). — As a whole the actual construction de- signs are fairly reasonable for the various roads. We have some under-designed Class 1 roads and some over-designed Class 2A, 2 and 3 roads. The main roads built between the years 1900 and 1912 would be classed today as under-designed. This is due to 'the re- markable increase in volume and weight of motor traffic. The secondary roads of this period are satisfactory even today. The increase in traffic, the change in its character and a lack of ade- quate yearly maintenance funds, resulted disastrously in some cases which caused a swing in sentiment to very expensive pave- ments even on Class 2 and 3 roads. For the last few years there is too much tendency to spend excessive sums on Class 2 and 3 roads. Class 1 roads are not over-designed and are in fact still under-designed. The more or less prevalent tendency to build $40,000 a mile roads on Class 2 and 3 highways tends to curtail needed mileage and is a very dangerous policy as it is Uable to discredit State and National aid. We have been very much disturbed over too many cases of this kind and beheve it well to emphasize the danger of such design. Appropriation Estimates for Construction (Fig. 13). — By as- suming a reasonable maximum expenditure for each class of road and not exceeding it when the road is put under construction, appropriations will more nearly accompHsh what they are ex- pected to do. The recent change in general price level has about doubled the cost of construction as compared to prewar conditions. This has caused a necessary curtailment of mileage for funds raised before the war but in a great many previous cases the lack of reasonable appropriation estimates resulted in failures to obtain anything hke the mileage expected and has caused a great deal of dissatisfaction and in some cases dis- credited an improvement program. 50 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS For the district shown in Fig. 13 (1920 cost conditions) a tentative scale of costs per mile may be assumed as follows: Class 1 not to exceed $50,000 on an average. Class 2A not to exceed $40,000 on an average. Class 2 not to exceed $30,000 on an average. Class 3 not to ejcceed $20,000 on an average. Main town macadam roads, $7000 to $10,000 on an average. On this basis the complete state and county system, 1350 miles (Fig. 13), would cost approximately $41,000,000 exclusive of in- terest. This would be a fairly heavy burden but is not unreason- able with proper State and Federal aid if the construction period was stretched out over a reasonable term of years (15 to 20) and the twenty-five year serial method of financing used. Funds for the original construction of such a system may weU be raised largely by a general tax levy supplemented in some cases by vehicle taxes to help take care of the interest on the bonds. The tentative scale of prices is for a rich district. For the first stages of improvement programs in poorer districts a lower order of improvement must be adopted. This is discussed in more detail in the second book of the series. The following tabulations taken from the Highway Green Book of the American Auto Assoc, 1920, show the total cost and average yearly costs of serial bonds. Total Cost of Serial Bond.— Total cost of a $100,000 serial bond bearing 3, 4, 5 or 6 per cent, interest and maturing at different periods from 5 to 50 years. Term in years 3 per cent. 4 per cent. 5 per cent. 6 per cent. 5 $109,000 $112,000 $115,000 $118,000 10 116,500 122,000 127,500 133,000 15 124,000 132,000 140,000 148,000 20 131,500 142,000 152,600 163,000 25 139,000 152,000 165,000 178,000 30 146,500 162,000 177,500 193,000 35 154,000 172,000 190,000 208,000 40 161,500 182,000 202,500 223,000 46 169,000 192,000 215,000 238,000 50 176,500 202,000 227,500 253,000 GENERAL ENGINEERING LOCATION 51 Average Annual Cost Serial Bond. — Average annual cost of a $100,000 serial bond bearing 3, 4, 5 or 6 per cent, interest and maturing at different periods from 5 to 50 years. Term in years 3 per cent. 4 per cent. 5 per cent. 6 per cent. 5 821,800 822,400 823,000 823,600 10 11,650 12,200 12,750 13,300 15 8,267 8,800 9,333 9,866 20 6,575 7,100 7,625 8,150 25 5,560 6,080 6,600 7,120 30 4,883 5,400 5,917 6,434 35 4,400 4,914 5,429 5,943 40 4,037 4,550 5,063 6,576 45 3,756 4,267 4,778 5,289 50 3,530 4,040 4,550 5,060 For a more complete discussion of Highway Bonds. (See Ap- pendix A). Prevailing Rates, General Road Tax. — In 1920 a state wide road tax was levied in 22 states varying from ^{o to 4 mills. The general county road tax by towns for Monroe County, 1920 (this territory being used for illustrative discussion) varies from 2 to 5 mills and averages about 2^^^ mills. Preliminary General Yearly Maintenance and Renewal Esti- mates (Fig. 13). — It is generally believed that the road user should pay a large proportion of money necessary for the upkeep of the highways. This includes maintenance and renewals as the pavements are worn out. A relatively small percentage of such funds may properly be raised from general tax funds but only a small percentage as the community at large have usually done their share by constructing the roads under a general tax levy.' To approximate the probable yearly bmrden that will fall on such users and that will be collected by auto licenses or some form of direct vehicle tax we may assume the following values for a road system that has been completed long enough to require the normal maintenance and reconstruction necessary to prevent deterioration in its value. The cost of maintenance, renewals and length of life of pavements is discussed in detail in the second volume of this series. ' This is discussed in more detail in the second book of the series. 52 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Class 1 roads Approximately $2500 per mile per year Class 2A roads Approximately 12200 per mile per year Class 2 roads Approximately $2000 per mile per year Class 3 roads Approximately $1500 per mile per year On this basis for the district shown in Fig. 13 we may expect eventually a yearly expenditure of approximately $2,600,000 for maintenance and renewals of the main roads. To raise any such amount the auto license fees will have to be materially increased or some other form of tax adopted. The increase necessary is not however beyond the bounds of reasonable taxation. The maintenance funds have never been adequate for this territory which results in excessive expenditures for reconstruc- tion at intervals. Maintenance must be put on a business basis. The usual maintenance programs are often far from reasonable. General Distribution of Tax Burden. — At a number of places in the text we have indicated the quite generally accepted prin- ciple of paying for the original construction of modern highways largely by general tax levy and for the maintenance and recon- struction of such highways largely by vehicle taxes. While this is believed to be essentially sound there is opposition and disagreement from different sources and it is perhaps just as well to summarize very briefly the basis for such a distribution of the improvement burden. A successful tax program is based roughly on three main points. First. — The final burden shall fall on each individual as nearly as possible in proportion to the direct and indirect benefi,t received. Second. — The direct tax shall be paid by the individuals receiving the immediate direct benefi,t if they are financially able. Third. — The tax must be levied on a definite source comparatively easy to assess and be collected from individuals having the ready money for payment. No tax scheme works out without minor injustice. Libraries have been written on the subject but for this particular problem of road improvement one point of view may be expressed roughly as follows. Real property, motor vehicles, tractor or horse vehicles are definite sources of taxation owned by individuals presumably with ready cash to pay any reasonable tax burden. Most of the immediate and direct benefit of improved highways GENERAL ENGINEERING LOCATION 53 is received by the owners of vehicles operating on the roads. The adjacent property owners and a small part of the community at large get some immediate benefit even if they are not direct road users. Some of the final direct and indirect benefits of a modern highway system are as follows: The improvement of the social and economic conditions of rural life which tends to prevent an unhealthy loss of rural population and stabahzes the fundamental relation of local food supply to healthy city development. The development of the natural resources of sections de- pendent on highway transport. The increase in the scope and power of the transportation system of the country which is at present taxed to the hmit. The cheapening of short haul transportation of food stuffs. The raise in rural land values. Added recreational possibilities for the community at large. Military value in time of war. A well constructed modern highway system promotes the general welfare of the entire nation and each individual whether a road user or not gets some direct or indirect benefit. The cities cannot get along without the country. An increase in prosperity of the rural districts increases the prosperity of the cities; an increase in the prosperity of one state has some effect on the prosperity of all the others. The nation can only develop on the principle that the prosperity of the country depends on the prosperity of even the new poor districts. This is the foundation for State and Federal Highway Aid. The inauguration of a highway system is a benefit to every individual in the community. While the road user gets most of the direct benefit, it is rarely feasible at this stage of the improvement to tax him directly for a large proportion of the cost of construction. That is, before improved highways are an accomplished fact, the vehicles are fewer in number and operated by financially poorer individuals. The completion of a modern highway system increases the number and effectiveness of vehicles and adds to the ability and willingness of the owners to assume a larger tax burden. It is therefore generally beheved that the original construction of such a modern system under a proper classification based on reasonable regulation of traffic should properly be paid for largely by a general real property tax levy 54 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS which is eventually qtiite evenly distributed over the community by rents, etc. The cost of mamtenance and the renewal of pavements depends on the volume and kind of traffic. The largest share of the benefit of keeping a road continually in excellent shape goes to the vehicle owner. There are two general classes of traffic, pleasure traffic and business trafiic. If a pleasure vehicle is taxed a fair amount to cover the damage it does to the road, this is a luxury tax borne by the owner. If a business vehicle is taxed a fair amount to make the highway self supporting, the charge is added to the other operating costs which go into the price charged to the consumer and the pubhc at large foots the bill. The principle of a vehicle tax for maintenance and renewal apparently has a sound basis in fairness. The minor practical difficulties in connection with justly applying this principle are no more serious than those encountered in the apphcation of any other tax principle not essentially as sound so that any emphasis that may be placed on minor injustice of assessment has no real weight as an argument against the value of this basis for taxation. A large part of any possible injustice in its appli- cation can be reduced by a well thought out graduated license fee. It is certain that if maintenance and renewal were paid by general tax levy that the pleasure traffic would escape its fair luxury tax and the business traffic particularly heavy hauUng would have an unfair advantage in competition with other transportation methods which pay their own cost of track or waterway construction and maintenance. In 1919 the average motor vehicle license fee in the U. S. was approximately $9.00 and ranged from $5.00 per average motor vehicle to $20 per average motor vehicle. Horse drawn traffic paid no fees. It is very evident, particularly in the States which have constructed a large mileage of modern roads, that the present (1920) Uscense fees are an entirely inadequate share of the highway tax burden and that so far vehicle owners of all kinds have escaped nearly scot free from their share of the burden. A moderate raise in license fees, not beyond the bounds of reason, gradually increasing as a road system grows will handle the situation satisfactorily. Public road tolls are not feasible except for a few special cases as they restrict the free movement of traffic so that some form of graduated vehicle Ucense seems the most reasonable form of tax GENERAL ENGINEERING LOCATION 55 for a large part of the cost (say 80 per cent.) of the upkeep of highways. Order of Construction. — The order of construction of individual roads dovetails in with the problem of apportionment and is also a fruitful source of trouble. Considering the third principle of design, Local Service, probably the safest policy where all the roads are in poor shape is to start the improvements from well-defined shipping points, county seats, cities, etc., and gradually extend the mileage until adjacent districts come together producing the finished through routes. If some of the existing roads are fairly satisfactory for traffic it is often desirable to modify this method by selecting the poor sections of the main roads for first considera- tion which ehminates the worst features of the system at once and results in quicker general use of the roads. Selection of Route. — The selection of route depends on the purpose of the road, the topography between controlling points and the stage of development of the community. Each case is a special problem but there are certain fundamental facts worth considering. The basis of decision on general route rests on good common sense and is not entirely an engineering problem. The road must go where it will do the most good and it is up to the engineer to locate it in detail along the general route. The route location rests on reasonable answers to questions of the following nature: Where will the road do the most good to develop the natural resources of pioneer districts or how can we locate this route to serve the greatest number of people in well- settled communities or how can we buUd this scenic road to give the most pleasure? If an attempt is made to solve all these problems strictly on the basis of the shortest distance and the easiest grades between terminals we would be in hot water. Any satisfactory solution considers the broad engineering principles of short distances, reasonable grades and the smallest amount of rise and fall but the final decision does not always rest on close analytical ton mile cost hauling figures. To illustrate; recreational roads through national and state parks or forests are usually laid out to afford the most pleasure; grades and dis- tance are sacrificed to obtain vistas, bold outlooks, and to reach points of historical interest or summer resorts. The cost of operating a car on such roads has no bearing on its usefulness and a location based on a close analytical ton mile hauling cost would be merely ridiculous. Suppose we consider a national 56 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS highway from New York to San Francisco. Some through tour- ing will occur but its volume is very Ught and the cost of addi- tional distance is not of any consequence to this class of traffic. More touring will go one-half or one-quarter of the way but even this is of no great factor in comparison with the short distance traffic on the route. To lay out any long route on the basis of the shortest distance and easiest grades between terminals for through traffic and to disregard passing through or close to the most cities and villages on the route is evidently poor pohcy. This illustration is exaggerated to bring out the principle of route selection in well-settled communities which is namely: To pass through the most populous areas, and either close to or through the most cities and villages that can be consistently done without too mvuih additional distance. This same principle applies to state and to purely local roads and may be summed up as direct contract with the greatest number of people. As the distance between controlling points becomes less the factor of commercial hauling has a larger bearing on the selection of route until we reach a point where the engineering require- ments of location govern the selection. That is, a reasonably low ton mile hauHng cost governs the short integral parts of any long route location. At the present time (1920) motor freight hauUng in competition with railroads is rarely economical for a distance of over 80 to 100 miles between terminals. This limit will probably fluctuate but it is not Hkely to increase much and for the time being it does not seem desirable to permit the factor of long distance motor freight hauling to influence the selection of route between large cities directly connected by rail over 100 miles apart. Where large cities are located closer than this and there is a large volume of heavy motor hauling it is possibly better to save distance by omitting some of the local service. Where large cities are isolated heavy trucks rarely operate to outlying towns farther than 30 to 40 miles. Take a concrete instance to illustrate this principle (see Fig. 13, opposite page 41). Rochester, New York, a city of about 280,000 population is located 80 miles from Buffalo, a city of approximately 400,000 people. The first State Route completed between these cities is shown on Fig. 13 as far as Batavia, a city of 14,000 people, and is designated on this map as Route A. This route was laid out in conjunction with State Route 6, the main east and west route, on the principle of local service and it has served very satisfac- GENERAL ENGINEERING LOCATION 57 torily for through traffic also. From the standpoint of through traffic between Rochester and Buffalo the route marked B on the map (Fig. 13) is the logical route and this will undoubtedly be built in the near future. That is, our experience indicates that it is better to first care for the local service and then in the future as the traffic requires it build new routes or partially re- locate old routes for the further advantage of long distance travel. A comparison of these two routes between Rochester and Batavia follows and shows the distinct advantage of Route B from the standpoint of through travel and Route A for local service. Length, miles Total rise and fall, feet Number of railway shipping points served . Total railroad crossings Railway grade crossings Overhead or subway railway crossings Route A Route E 37 31 1850 1400 15 9 13 4 9 1 4 3 To give an idea of the traffic on this route in 1919 the following census (average 10 hour count in summer season) is shown at different points: Route A Horse traffic Motors 1 horse 2 horse Cars Trucks Total Between Rochester and Scotts- ville 30 70 85 15 30 40 65 10 850 700 1600 1200 100 no 180 85 1010 Between Scottsville and Cale- donia 920 Between Caledonia and Le Roy.. Between Le Roy and Batavia 1930 1310 As an additional point of interest the new proposed through Route B from Bergen to Batavia fails to pass through two small settlements Byron and South Byron because it would be neces- sary to use 2 miles extra distance for this local service. That is, Route B primarily considers through service. These villages can be served by a stub line. It is often desirable to by-pass villages and even certain cities on through routes on account of traffic congestion and the annoyance and danger of a large volume 58 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS of high speed traffic in the communities in question. These places can be served by stub lines or supplementary loops. As a rule, villages desire to have the main road pass directly through them on account of state aid in connection with their street paving and the additional business derived from traffic but the last feature does not amount to much unless they happen to be so MoT^cspa Fig. 16. — Bardine Redstone proiect (State of Colorado). Note how this road shortens the communioation from Paonia to Carbondale. located on the line that the traffic would naturally stop for some reason. Pioneer Location. — To give an idea of the factors entering into the selection of route in mountain districts, an example will be cited in Colorado (see Fig. 16). The project referred to is the Bardine-Redstone road through the Sopris national forest. GENERAL ENGINEERING LOCATION 59 This road was selected for improvement and advanced in order of construction by the U. S. Forest Service for the following reasons. An examination of the map will show that by a short road about 30 miles long over McClure's pass the Carbondale and Paonia valleys can be directly connected. Without this road, it took a day's travel by rail to get from Carbondale to Somerset. The second reason for the road was to open up a promising farm- ing section along the upper Blackwater which had heretofore been confined to a cattle and sheep range on account of the impossibility of getting produce to the railroads. By the con- FiQ. 17. — Example of engineering grade reduction. Newly located wagon road to the right and above. Pack trail in foreground. U. S. forest road project. struction of moderately low cost natural soil road on a 5 or 6 per cent, grade over the low pass 3000 ft. above the valleys, inter- communication and new territory could be developed and a day's time in travel saved between two flourishing sections. The foregoing discussion indicates in a general way some of the factors governing route selection. Engineering Location, — A good detail location along the re- quired general route results in the most effective road for the traffic that can be obtained for the available funds. We control our desires for perfection by the limitations of the community pocketbook. It is obviously desirable to obtain short distance, easy alignment, reasonable grades and to avoid locations which 60 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS call for extremely expensive construction such as rock work, flood areas, etc. It is obviously desirable to avoid locations where snow drifts badly or fails to melt promptly in the spring as the number of days in a year that a road is open has a large effect on its usefulness. A summary of the engineering principles of location are given on page 148. Extreme Refinements Impracticable. — An economic engineering location for commercial roads might be theoretically developed on the lowest ton mile hauhng cost to traffic. Practically it is not yet reasonable to do this in many cases for the ordinary highway and the reasons for disregarding this factor as the decid- ing element seem sound. Railroads have spent large sums to reduce the ton mile cost and in their location the engineers make extremely careful comparative estimates of construction cost against operating cost. They consider the elements of shorter dis- tance, curvature, light and heavy grades, etc. Many railroad engineers wonder why these considerations are not given more weight on highway work considering the increase in mechanical transport. One of the evident reasons is that railroads get a di- rect tangible money return in dividends for their expenditure and the return to the community on a public road investment is too intangible. However, as a matter of interest we include a discussion of the approximate relation of distance, rise and time as it affects operating costs on pages 79 to 114. This data has been used by the author for some time as a basis for judgment in the comparison of lines. It is undoubtedly true that to get the full value of an improved road system the engineering location must be made for the most efficient use of motor transport but at the present time there is no possibihty of obtaining or any justification for spending extremely large sums to reduce the hauling cost below that obtained by the usual modern highway design. If we had un- Umited funds provided by truck owners a careful analysis would be justified on special commercial roads but we must consider the following facts: the location of roads in well settled districts are practically confined to existing rights of way except for minor relocations to avoid extreme grades or for safety reasons; this is necessary as the community has grown up along these well set routes and the principle of direct contact holds. These rights of way were not necessarily laid out with any regard to economic road location and in fact are often arbitrarily fixed by land GENERAL ENGINEERING LOCATION 61 section lines or locations where a poor road could be constructed in the past without much labor or cost. The cost of new rights of way for entire new locations and the difficulties of acquiring are prohibitive at this stage of development in road building except for unusual cases. The improved roads of today are only a progressive stage in the development of highway transport. The demand for them and the satisfaction in their use lies mainly in the fact that they provide a, firm surface which can be used the year round, that they materially cheapen the cost of hauling that they make the use of light automobiles feasible for long and fast trips. The community is willing to pay a certain amount for the improvement in road conditions which the usual practice in modern road construction gives but it is not willing to pay large additional sums for further reduction in ton mile hauling costs. In the first place only a comparatively few men would get a direct benefit from such expenditure. The indirect return to the community is too intangible. Much of the road traffic is pleasure traffic and a few more gallons of gas means nothing. If the owner did not spend his surplus for gas, he would spend it for ice cream soda or the movies. There seems to be no way of making the few road users who would benefit by a further reduction in hauling cost pay the price of the neces- sary construction. It may be that for certain toll roads some time in the future or for exceptional present cases in metro- poHtan districts we can use a ton mile cost location analysis but we are not yet up to this standard for the usual road. This does not mean that the engineer should not make an effort to get the best possible location that he can but he should bear in mind that the first principle of general policy considering a comprehensive road system is Mileage Service and aim to get the greatest mileage of road that will serve the purposes of the great majority of road users. For all roads except special service commercial roads probably 90 per cent, of the traffic does not demand nor would it be particularly benefited by excessive refinements. Poor grades or alignment should never be used on high class roads as they are the fundamental features of the improvement and the only permanent features of construction. Liberal expenditures are justified but there is a limit to expend- itures for refinements that reduce mechanical operating costs to a minimum. The detail analysis of grade alignment section, etc. given in Chapters 4 & 5 are intended to bring out the re- 62 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS quirements of road design that are necessary for the satisfaction, safety, comfort and comparative cheap hauling requirements of the average road users. These are the fundamentals which must be provided. We will attempt to show the road value of different limiting engineering requirements with their effect on construction cost. Additional refinements beyond the fundamental requirements are desirable if the funds are available from the proper sources. By the proper sources are meant the actual road users benefited by the additional cost of construction. Fig. 18. — A Utah road location. Saving in distance is valuable, saving in total rise is valuable, easy grades and the elimination of sharp curves are desirable. Every effort is made to accomplish these results utiHzing the existing roads where we have to, making minor relocations to avoid extreme grade or danger because the sentiment of the community approves these measures but always bearing in mind that today and for a long time to come mileage is the prime requisite of programs. It is possible and desirable in the sparsely settled communities to make better engineering locations and for such districts we can more nearly accompHsh a reasonable analysis as far as right of way handicap is concerned but in these districts shortage of funds often plays havoc with our intentions. GENERAL ENGINEERING LOCATION 63 Value of Saving Distance and Rise. — It is well to bear in mind what distance saving is worth and what a saving in total rise is worth. The data given is, of course, of only general value as the fluctuating cost of motor operation, the types of hauling, special conditions of all sorts affect the figures. They, however, show in a general -way that it is well worth while to reduce traffic losses arising from these elements of needlessly poor location or design. Mr. A. R. Hirst gives the following conservative figures on the value of saving distance: " If the very conservative sum of 10c. per mile is allowed for each mile of travel saved, the saving of a mile in distance on highways carrying the following average number of vehicles per day will save the traveling public the given amount per year, which is the interest at 5 per cent, on the amount given in the third column. Value of a Mile in Highway Distance Saved Average number of Saving to owners Saving capitalized vehicles per day per year at 5 per cent, equals 100 $ 3,650 $ 73,000 250 9,125 182,500 500 18,250 365,000 750 27,375 547,500 1,000 36,500 730,000 2,000 73,000 1,460,000 5,000 182,500 3,650,000 10,000 365,000 7,300,000 The value of eliminating rise cannot be figured with any degree of accuracy as there are too many indeterminate and vari- able factors but in the author's opinion it is not likely that the capitaHzed value of saving in yearly operation due to ehmination one foot of rise and fall per 100 vehicles per day on long routes will exceed $30 on light grades or $400 on heavy grades. For small grading reductions on short hills the time factor is of no consequence and the practical value of saving a foot rise and fall is not probably more than one-third of these figures (see pages 79 to 114). It is very evident that considerable expenditure is justified to reduce distance and rise but it is also evident that it would be impracticable to carry this method of location to its logical conclusion by expenditures in any way approximating the figures given. That is, the location of a free pubUc road financed by a 64 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS general tax with no direct revenue return can hardly be analyzed from the same point of view as a trunk line railroad. Relocations of Existing Highways. — We all would prefer to have scientifically located highways. A great many engineers beheve that the time has come to make extensive relocations. It is self evident that relocations which reduce the construction cost of the proposed road as well as reduce motor operation costs should be made at once. It is surprising how often even Fig. 19. — Relocation Galena-summit highway. U. S. forest road project (State of Idaho). Old road, 15 to 20 per cent, grades. New location (dotted line), 6 per cent, compensated on sharp curves. Note. — Relocations of "this kind are most certainly justified at the present stage of our highway programs. such relocations are not made and it is desirable to impress on the men in charge of surveys that they should continually bear in mind the necessity of such relocations and not feel that they must follow the present road lines where these conditions prevail. There seems to be no question that expenditures for relocations necessary to obtain reasonably good grades and alignment are justified at the present stage of our road programs but the author believes that extensive relocations involving excessive GENERAL ENGINEERING LOCATION 65 refinements must be gradually worked out except for a few ex- treme cases and that practically it will be easier to accomplish and fairer to the general public to do most of this work under Reconstruction Programs financed by direct vehicle taxes rather than to attempt it at this time.' In case a relocation is necessary no halfway measures should be allowed. In too many cases even on fairly important state roads in rich communities relocations have been made on the basis of 9 per cent, grades when it was perfectly possible to get 7 per cent, or less. Halfway treatments of this kind are worse than nothing. Fig. 19A. — Airplane view of bridge approach relocation (New York state). Minimum radius curvature old road 60'. Minimum radius curvature new road 670'. This relocation adds materially to the safety and convenience of travel. To illustrate present practice on relocations the following quotations from the Iowa Highway Dept. Field Manual is given. The limiting grade of 6 per cent, mentioned does not agree with the author's recommendation given on page 1 16, but the general scope of the data strengthens the discussion at this point. I See pages 104r-107 for an approximate basis of comparing the value of alternate location. 66 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Relocation.^ — "Where the topography is flat or gently rolUng the profiles readily lend themselves to satisfactory grades at a moderate cost, and relocations to any extent are seldom necessary. But in the rougher country relocations wiU frequently be necessary and the field man must constantly watch for opportunities to better the alignment, avoid steep hills, or improve stream crossings by relocations. The necessity for or advisabiUty of relocating must always be balanced against the cost, and in general it is true that a proposed change of any magnitude is advisable only when it can be shown that such change will be economical or wiU produce a decidedly better road. It is therefore important that the cost of relocation be thoroughly investi- gated. In this connection the field man must remember to take into consideration the various improvements along the exsiting road, such as farm buildings, orchards, permanent bridges and culverts, heavy cuts and fills , etc. The following instructions should be followed: (a) In all cases where it appears that an excessive amount of earth- work will be required to reduce the present road to 6 per cent, grades, the possibihty of relocations to reduce grades to 6 per cent, or less shall be fully investigated. (6) In cases where there is a succession of grades which may be re- duced to 5 or 6 per cent., but which cannot be reduced below that figure without considerable work, the question of relocation should be fully investigated. (c) In case of doubt as to the feasibihty of any relocation, a survey should always be made. (d) In all cases where relocations are surveyed a survey shall be made on the old road also. (e) In the case of minor relocations the margins of the old roadway should always be shown by a sketch indicating the old roadway by dotted lines, and by data in the cross section notes. In such cases the survey of the old road may consist only of extending the cross sections over the same. (/) The notes shall show which location is to be used or shall state that the determination of which route to follow cannot be made until the notes are worked up in the ofiice. The chief of party shall enter this notation in the field notes after consultation with the district engineer." Conclusion. — ^Large bond issues have the habit of disappearing without accomplishing as much as they were expected to accom- plish and any unusual feature of design, either location or pave- ment, which raises the average cost per mile must be used with caution. The great need of most localities is a fairly complete 1 Iowa Highway Dept. Manual. GENERAL ENGINEERING LOCATION 67 road system usable the year round. Until this is accomplished extreme refinements have a doubtful value. Before large expenditures are made for unusual refinements in location it is just as well to get a reasonably complete mileage of good usable firm surfaced roads, as 100 miles of the usual modem improved road with reasonably good grades and alignment are more valuable to the community as a whole than 50 miles of more scientifically located highways. Needlessly short mileage is the most serious criticism that can be made of any general policy dealing with an incomplete road system. It is not probable that the foregoing general discussion is of much interest to most of the younger engineers. It has been included more in the nature of a general survey of the problem. Nine-tenths of the road men are more interested in how to make a detail design of a definite road. The detail theory of design will be taken up in the following order: Grades, alignment, sections, drainage (pavements, Vol. 2.) CHAPTER IV GRADES AND ALIGNMENT GRADES Grade line design considers the proper use of maximum, mini- mum, intermediate and adverse grades and their vertical curve connections. Grade line design in connection with ab"gn- ment considers the relative values of distance against rise and fall. The effect of grade may be roughly summarized as follows : An increase in the rate of grade decreases the load that can be hauled up the grade for a fixed power. An increase in the rate of grade increases the expenditure of energy to maintain a fixed speed chmbing the grade. An increase in the rate of grade decreases the speed for a fixed power. An increase in the rate of grade increases the wear and tear on mechanical outfits. The mechanical energy expended in climbing is partially balanced by the reduction of energy expended on down grades. The mechanical energy expended in climbing affords a very definite basis of comparison of the value of travel in one direction. The expenditure of energy on down grades is indefinite and while it effects the total operating cost on a grade it cannot be given as much weight in the conclusion as the first method. The effect of grade on the depreciation and repair of mechanical equipment is indefinite but it is certain that it bears some relation to the rate of grade. Grade selection depends on considerations of safety, con- venience, traffic operating cost, and the cost of construction and maintenance. Cost of trafl&c operation is not always the most important factor. It must often give way to considerations of safety or initial construction cost. Reasonably low rates are desirable. The whole question of grades lies in the decision of what is reasonable for a specific case. 68 GRADES AND ALIGNMENT 69 A summary of practical rules for location and cut and fill grade line design is given at the end of the chapter. Maximum Grades. — Suppose we consider the subject of maxi- mum grades from the following standpoints : 1. Relative importance of horse and automobile traffic in the selection of grade. 2. Effect of grade on horse traffic. 3. Effect of grade on motor traffic. 4. Current practice in maximum grades. 5. Practical considerations governing the selection of grade. 6. Effect of ruling grade on cost. 7. Recommended general practice. Relative Importance of Horse and Auto Traffic in the Selection of Maximum Grade. — Tables 2 and 2A show the rapid growth of motor traffic on the main roads of Massachusetts and the general character of the traffic on secondary roads in Western New York. Table 2 1912 1915 1918 Per cent. of increase 6 years Automobiles and trucks. . . Motor cycles 50,132 5,034 65,600 $616,236 102,633 9,5'20 133,700 $1,235,723 191,019 12,708 225,272 $2,159,257 280 150 Operators and chauffeurs. Motor vehicle fees 240 250 Average Daily Traffic on M AiN Roads in Massacht JSETTS 1909 1912 1915 1918 Per cent. of increase, 9 years 91 88 68 88 40 72 24 43 - 73K — 51 Heavy horse 179 131 156 280 17 112 555 45 67 923 75 - 62H +604 +3411 Automobiles and light trucks . 131 297 eoo 998 +661 Total vehicles 310 453 712 1,065 +243 ' In 6 years, 70 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Per Cent, of Total Trafpic - 1909 1912 1915 1918 Light horse 29 28 15 19 10 2 Heavy horse 4 57 43 34 4 62 15K 6H 78 6 Trucks 7 Motors 87 Table 2A. — Daily Traffic Counts on Selected "Local Service" State County Roads in Western New York Number Number of miles Horse traffic Motor traffic of roads 1 horse 2 horse Total horse Light cars Trucks Total motors 14 60 45 39 84 250 ' 36 286 Horse traffic per cent, of total 23 Motor traffic per cent, of total 77 Note. — On the main State Route Roads the percentage of horse traffic corresponds very closely with the Massachusetts results given in Table No. 2. We are all famiHar with this change in the character of highway traffic. Maximum grades have a radically different effect on horse and single unit motor traffic and it is necessary to come to some reasonable conclusion as to which kind of travel should govern the design. There is a strong tendency to consider grade Une design from the standpoint of single unit motor hauling on account of the predominance of this traffic on improved roads. As far as distance and total rise and fall are concerned this is probably sound. As far as rate of grade is concerned the author has no hesitation in saying that he considers it better to give horse traffic the preference on all town and county roads and that the conclusions as to grade that wUl be satisfactory for horse traffic will probably satisfy motor traffic on most state and national routes also. This conclusion is based on a number of factors. As long as horses are used for general farm utility they will be used for some hauhng even under conditions favorable for GRADES AND ALIGNMENT 71 trucks (see Table 2A). In the northern states snow and ice handicap motor transport for a portion of the year particularly on side feeder roads. It is not likely that horse traffic will be entirely eliminated from our improved roads. Maximum grades Umit the load a team can haul but they do not handicap single unit truck operation on firm surfaced roads as all the hght and heavy motors have sufficient excess power to haul their rated load up any grade within reason. Steep grades do Hmit the appUcation of the long trailer train mode of hauhng. Where this method is popular or where special conditions make its adoption hkely maximum grades may well be reduced below even the rates considered satisfactory for horse traffic. The long trailer train, however, is not a general utiHty system and need not as a rule determine the ruHng grades except for a few special service roads. Long steep grades do affect the ease of motor traffic by forcing the driver to drop into second or low gear but they do not reduce single unit truck capacity nor do they have much effect on fuel consumption provided the total rise and fall and distance between terminals is the same. It therefore seems safer to design maximum grades for a reasonable load for the weaker mode of hauhng and in this way satisfy all classes of traffic. The final selection of grade is also affected by considerations of safety, convenience and the cost of construction and maintenance. MAXIMUM GRADES FROM THE STANDPOINT OF HORSE TRAFFIC Difficulty of Ascent and Safety of Descent. — The factors controlhng ease and safety of ascent and descent have different values for different surfaces, but as most of the roads will in time be hard surfaced and as all parts of the design should fit into the final improvement, this part of the grade argument is made primarily for hard surfaced conditions. European observers claim that on a stone road 5 per cent, is the maximum grade that can be descended safely by a trotting team without brakes and that 12 per cent, is the maximum that can be safely descended with brakes. By the use of the shding shoe or locked wheels freighters in the Rockies descend 20 per cent, grades without much difficulty on ordinary natural soil roads. Safe descent with brakes need not be considered except in rare cases as it would result in a grade far beyond ordinary 72 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS practice. Safe and easy descent without brakes is more impor- tant for light rigs than for heavy hauUng but as this class of traffic has been practically eliminated by cheap automobiles it need not be given much weight. Descent, therefore, plays only a minor part in grade selection except where the alignment is bad. Hauling Power. — The writer knows of no careful records of actual maximum loads that can be hauled up different hard surfaced grades by an ordinary team; it is probably better to discuss this point theoretically as any experiments would be affected by too many variable local conditions to be worth much as a basis of comparison. As a check on the theoretical discus- sion records of loads on extreme mountain grades are given on , page 78 which show that for all practical purposes. Table 8 of theoretical loads is fairly close and is on the safe side. A summary of Prof. I. 0. Baker's discussion of maximum team loads is given below, and through his courtesy we are enabled to include a collection of tables taken from his work, "Roads and Pavements." Various trials have determined that the normal tractive power of a horse travehng three miles per hour for ten hours a day is approximately one-tenth of its weight; that when hauhng up a steep grade it can exert one-fourth of its weight for a short time; that for a continuous exertion of one-fourth, the grade should not be over 1200 ft. long and if over that, resting places should be provided every 600 to 800 ft. ; that in starting and for a distance of 50 to 100 ft., one-half of its weight can be used; and that the net tractive power ordinarily exerted by a horse on a grade equals 04, its weight) — (the effort required to Uft itself) or approxi- mately (0.25 W) — (W X per cent, of grade expressed in hundredths), i.e., (0.25 TF — 0.04 W) for a 4 per cent, grade. This undoubtedly gives a reasonable basis for ordinary hauling conditions but from data obtained by the author in connection with freight hauhng in mountain regions it is evident that a good draft horse will exert more than 0.25 W on moderately short sharp pitches of a long climb if allowed to rest at intervals of 200 to 300 ft. The evidence indicates that a value of 0.35 Tl^ is about right for such conditions. Table 3 shows the effective power developed by an ordinary team of 1200-lb. horses with moderate exertion and Table 3A the power of a first class team of 1600-lb. horses exerting their full strength. GRADES AND ALIGNMENT 73 Table 3. — Okdinaby Stock Moderate Exertion Grade, Theoretical net Tractive per cent. tractive effort effort in lbs. Level 0.10 w 240 2H 0.25 W -PW 540 w = weight of team 2400 lbs. 4 0.25 W -PW 504 6 0.25 W -PW 480 p = per cent, of grade in hun- 6 0.25 W -PW 456 dre dths. 7 0.25 W -PW 432 8 0.25 W -PW 408 9 0.25 W -PW 384 10 0.25 W -PW 360 Table 3A. — ^Draft Stock Full Power Grade, Theoretical net Tractive per cent. tractive effort effort in lbs. 5 0.35 TT -PW 960 6 0.35 W -PW 928 7 0.35 W -PW 896 W = weight of team 3200 lbs. 8 0.35 W -PW 864 10 0.35 W -PW 800 P = per cent, of grade in hun- 12 0.35 W -PW 736 dredths. 14 0.35 W - PW 672 16 0.35 W -PW 608 18 0.35 W -PW 544 20 0.35 W -PW 480 22 0.35 W -PW 416 Grade and Rolling Resistance. — This power is used in over- coming axle friction, gravity resistance and rolling resistance. The axle friction is small amounting to three or four pounds per ton for American farm wagons. Grade resistance (gravity) equals (load X per cent, of grade expressed in hundredths) and expressed in pounds per ton of load equals (2000 X P). The rolling resistance varies for different surfaces and for each surface depends on the diameter of wheel, width of tire, speed of travel and the presence or absence of springs on the wagon. The best diameter of wheels, best width of tires and the use of springs as they affect the ease of hauling for both farm and road use are problems for the wagon manufacturers. 74 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Morin, a French engineer, concluded from a series of careful experiments that the harder the surface of the road the less effect width of tire had on rolling resistance. We are arguing from the standpoint of comparatively hard surfacing and are deahng with small differences in wheel diameter and can dis- regard these factors. As a matter of interest Tables 4 to 6 are Table 4. — Effect of Width of Tire upon Tractive Power' Resistances in Pounds per Ton Description of the road surface Diameters of the front and rear wheels respectively Hef. No 3'-6" & 3'-I0" 3'-6" & 3'-10" 3'-8" & 4'-6" 3'-6" & 3'-10" 3'-8" & 4'-6" Width of tires IW 4" IH 4" IH" i" IH" 3" IH" 3" 1 Sod 268 171 98 61 304 164 117 70 236 141 83 35 254 168 80 46 283 152 239 162 54 189 114 265 66 28 228 114 228 2 3 4 Earth road (hard) Earth road (muddy) Sand road (hard) 199 371 51 108 243 162 351 49 6 6 7 Gravel road (good) Wood block (round) 76 38 ' Pamphlet by Studebaker Brothers Manufacturing Company, 1892. Table 5. — -Effect op Size op Wheels on Tractive Resistance* Pounds per Ton Ref. No. Description of road surface Mean diameter of front and rear wheels SO" 38" 26' 1 2 3 4 5 6 7 8 9 10 Macadam, slightly worn, fair condition Gravel road, sand 1 in. deep, loose stones Gravel road, upgrade 2.2 per cent., ^ in. wet sand, frozen below Earth road. Dry and hard Earth road. J^ in. sticky mud, frozen below Timothy and blue grass sod, dry grass cut Timothy and blue grass sod, wet and spongy Cornfield; flat culture across rows, dry Plowed ground; not harrowed, dry and cloddy Average value of tractive power 57 84 123 69 101 132 173 178 252 61 90 132 75 119 145 203 201 303 130 148 70 110 173 79 139 179 281 265 374 186 1 Experiments of Mr. T. I. Mairs at the Missouri Agricultural Experi- ment Station, GRADES AND ALIGNMENT •75 included to show the results of expferiments on different soils and roads. The question of wide tires affects road design chiefly in con- nection with the distribution of load over a safe area and will be taken up under "Foundations" (second book of this series). Table 6. — Tractive Resistance of Broad and Narrow Tires' Resistance in Pounds per Ton Ret. No. Description of road surface Width of tire IM" No. of trials 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Broicen stone road; liard, smooth, no dust, no loose stone Gravel road; hard and smooth; a fewJoose stones Gravel road ; hard, no ruts, large quantity of sand Gravel road; new gravel, not compact, dry Gravel road; wet, loose sand 1 to 2H in. deep Earth roads. Loam, dry, loose dust 2 to 3 in. deep Earth roads. Loam, dry and hard, no dust, no ruts, nearly level Earth roads. Loam, stifiF mud, drying on top, spongy below Earth roads. Loam, mud 2}^ in. deep, firm below Earth roads. Clay, sloppy mud, 3 to 4 in. deep, hard below Earth roads. Clay, dry on top but spongy below -. . Earth roads. Clay, dry on top but spongy below Earth roads. Clay, Stiff deep mud Mowing land. Timothy sod, dry, firm, and smooth Mowing land. Timothy sod, moist Mowing land. Timothy sod, soft and spongy Pasture land. Blue grass sod, dry, firm, and smooth Pasture land. Blue grass sod, soft Pasture land. Blue grass sod, soft stubble land. Corn stubble, no weeds, dry enough to plow stubble land. Corn stubble, some weeds, dry enough to plow Stubble land. Corn stubble, in Autumn, dry and firm. . . Plowed land. Freshly plowed, pot harrowed, surface rough Plowed land. Freshly plowed, harrowed, smooth, com- pact ^ 121 182 239 330 246 90 149 497 251 286 472 618 825 317 421 569 218 420 578 631 423 404 510 466 98 134 157 260 254 106 109 307 325 406 422 464 551 229 305 327 156 273 436 418 362 256 283 323 1 Missouri Agricultural Experiment Station Bulletin No. 39, Table 7 gives the average rolUng resistance in pounds per ton of load on different pavements for the ordinary farm wagon driven at ordinary speeds. Efifect of Grade on Loads. — For a comparative estimate we will take a value of 40 lbs. per ton of load, including axle friction, on macadams and rigid pavements and 100 lbs. per ton for earth roads in fair shape. The resistance to the effective tractive 76, LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Table T- Kind of pavement Rolling resistance in lbs. per ton of load Asphalt 30 to 70 Brick or concrete. . 15 to 40 Cobble stones 50 to 100 Earth roads 50 to 200 Gravel roads 50 to 100 Macadam roads 20 to 100 Plank 30 to 50 Stone block 30 to 80 Wood block 30 to 60 'Baker's "Roads and Pavements." power of the team per ton of load is therefore 40 + (2000 X P) on hard surfaced roads, and 100 + (2000 X P) for earth roads, and the maximum load expressed in tons for any grade equals / Effective tractive power of team for that grade \ \ Resistance per ton of load for that grade / Using the tractive powers of the ordinary team shown in Table 3, the following table is constructed. It is chiefly useful for a comparison of the effect of grade on load but all evidence indicates that the loads given correspond closely to practice. Table 8A shows loads for extreme team exertion as compiled in Table 3A. The loads given include weight of wagon. Table 8 Effective tractive effort, lbs. Improved roads Earth roads Grade, per cent. Kesistance in lb. per ton of load Maximum load in tons Kesistance, lb. Max. load, tons Level 2)4 4 6 6 7 8 9 10 240 540 504 480 456 432 408 384 360 40 90 120 140 160 180 200 220 240 6.0 6.0 4.2 3.4 2.9 2.4 2.0 1.7 1.5 100 150 180 200 220 240 260 280 300 2.4 3.6 2.8 2.4 2.1 1.8 1.6 1.4 1.2 GRADES AND ALIGNMENT Table 8A. — Dbaft Stock Extreme Exertion 77 Hard surfaced roads Earth roads Grade, per cent. tractive effort lbs. Resistance in lb. per ton Maximum load in tons Resistance in lb. per ton Max. load in tons 5 960 140 6.8 200 4.8 6 928 160 5.8 220 4.2 7 896 180 5.0 240 3.7 8 864 200 4.3 260 3.3 10 800 240 3.3 300 2.7 12 736 280 3.0 340 2.2 14 672 380 1.6 16 608 420 1.4 18 544 460 1.2 20 480 500 1.0 22 416 540 0.8 Effect of Length of Grade on Maximum Load. — ^In mountain road design where a long ruhng grade is used it is often economical to introduce short stretches of steeper grade to avoid extremely expensive construction and to improve ahgnment. In order to determine the maximum short grade (not exceeding 300 ft. in length) that can be used in connection with a long ruhng grade without reducing the team load we have compiled Table 8B for a 2400-lb. team. Table 8B. — Equivalent Long and Short Grades for Hard Surfaced Conditions Long Euling Grades Tractive effort 0.25 W 2400 lb. team Short Maximum Grades Tractive effort 0.35 W 2400 lb. team Grade, per cent. Maximum load, tons Grade, per cent. Maximum load, tons 6 6 7 8 3.4 2.9 2.4 2.0 7 9 10' 12 3.7 2.8 2.5 2.0 > 12 per cent, is the practical limit (on account of safe descent) on any road of sufficient importance to be considered from an engineering standpoint. This principle can also be appUed to a long cut and fill grade reduction with a very material saving in cost but if used the steeper rate should not be over 250 to 300 ft. long and should be at the bottom of the hill. 78 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS RECORDS OF TEAM LOADS We are indebted to Mr. H. G. McPheters and F. F. Roberts for the following data on team freighting in the Rocky Mountain region. It is practical data obtained from personal experience and strengthens the force of the theoretical discussion. The loads given are net and do not include wagon weights. They represent usual freighting loads which are practical maxima. Hebeh Fbuitland Road, State op Utah Daniels Canyon Section Earth road in fair shape. Long 8 per cent, grades. Short 15 per cent, grades. Net load for four horse team 3500 lb. (during summer). Galena Summit Road, State op Idaho (See Illustration, page 64) Natural soil road in fair shape Maximum grade (Salmon River side) 20 per cent. Maximum grade (Wood River side) 17 per cent. Load for one team 1800 lb. (during summer). Load for two teams 4000 lb. (during summer). Load for three teams (six horses and two wagons loaded 5000 lb. on lead wagoh and 4000 lb. on trail taking one wagon at a trip up the mountain.) Trail Ckebk Summit Road, State op Idaho Natural soil road (fair condition during summer). Maximum grade 22 per cent. Load for one team 1200 lb. Load for two teams 2600 lb. When freighting by teams was the principal mode of transportation, there were used on this road several outfits of twenty-four mules hooked to four wagons loaded about as follows: Lead 14,000 lb.; lead swing 10,000 lb.; swing 8,000 lb. and trail 4000 lb. Two men handled the whole outfit which was certainly a man's job. Rocky Bar Atlanta Road Over Bald Mountain Natural soil. Maximum grade 16 per cent. Load for one team '2000 lb. Load for two teams 4000 lb. A large amount of freight is carried over this road by auto trucks at the present time. GRADES AND ALIGNMENT 79 The Theoretical Advantage of Certain Grades. — From Tables 8, 8A and SB and the previous discussion we can pick out the grades that theoretically fulfiU certain traffic requirements. I. On hard surfaced roads the same load that can be drawn up a 21^ per cent, grade by reasonable extra exertion of a team, can be hauled on a level with ease. This makes a perfectly balanced design from the standpoint of team hauling. The theoretical load is six tons. For earth roads 5 per cent, fulfills this same condition with a theoretical team load of 2.4 tons. II. Five per cent, is the maximum grade that fulfills the re- quirement of safe descent at a trot without brakes. This is of little importance under modern traffic conditions. III. The same load that can be hauled up a 7 per cent, hard surfaced grade can be drawn on a level dirt road in fair condition; a 7 per cent, grade therefore does not reduce the load of a team which must travel over even a level earth road for part of the distance. The theoretical load is 2.4 tons. IV. The use of short maximum grades of greater rate than the long ruling grades does not reduce the maximum load pro- vided they are proportioned as follows for hard pavements and do not exceed 250 ft. to 300 ft. in length. Long 6 per cent. Short 7 per cent. Long 6 per cent. Short 9 per cent. Long 7 per cent. Short 10 per cent. Long 8 per cent. Short 12 per cent. V. Twelve per cent, is the practical limit of grade for even unimportant roads on account of safe team descent with heavy loads. As a matter of fact the selection of grade depends more on the requirements of the traffic and the topography of the country than on these theoretical advantages. Effect of Grade Selection on Motor Traffic. — It is not possible with the data at hand to analyze the cost of motor operation closely for different rates of grade but certain fundamental principles of road location can be estabUshed by the principles of mechanics modified by judgment. Reduction in distance, time of travel and needless rise and fall are desirable but it is very difficult to put a money value on such savings particularly the elements of time and rise. Practically, a little extra gas means nothing to a large pro- 80 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS portion of road traffic and a little extra time means even less, for we all waste a good share of our time despite the teachings of efficiency. Therefore to attempt to place a construction value on the saving of a little fuel and time hardly looks reasonable for most conditions. Under certain conditions, however, such as long distance main roads particularly where regular systematic truck freighting occurs the time element is a real factor and should be considered. The author has been in the habit of eUminating the time factor in considering motor traffic on Local Service roads but gives it some weight for Special Service Com- mercial roads. This, as a general rule, means that about twice as much expenditure is theoretically justified for saving dis- tance and about three times as much for saving rise on Special Service roads as on Local Service Roads. The discussion will first develop certain general principles of principles of location and then a rough approximation of operat- ing costs on different grades. The theoretical discussion is followed by data modified for practical use. (See table 12B.) The author hesitated to include tables 11 to 125 in this book but finally decided to do so largely as a matter of academic interest as it is necessary for some one to make a start along these Unes. The tables will undoubtedly be subjected to severe criticism. They can most certainly be improved by investiga- tion and experiment but they have been used for some time as a basis for judgment and their appUcation has resulted in what appears to be rational conclusions. They certainly demonstrate general principles of design and their use for detail conclusions is better than guesswork. They are submitted as a pioneer attempt which I hope will arouse discussion and further experimental investigation. EFFECT OF MAXIMUM GRADE ON MOTOR TRAFFIC Ascent and Descent. — ^Light and heavy single unit trucks (trucks without trailers) are commonly operated on firm surfaced roads up and down 15 per cent, grades. Light passenger cars have no difficulty in climbing 15 per cent, grades even on fairly poor natural soil roads. The safety of descent depends largely on the alignment, the condition of the road surface and the brakes but for a well equipped car on safe alignment it is not a noticeable factor in design up to 12 per cent, which is beyond GRADES AND ALIGNMENT 81 the reasonable bounds of modern practice in grade selection. That is, the factors of climbing power and safe descent do not affect the selection of grade from the standpoint of single unit motor transport. Trailer train motor transport, however, demands low ruling grades. It should, however, be remembered that this type of hauling is comparatively slow. That it increases the danger to ordinary traffic and clutters up the road. That it can not be considered as a probably popular general utility method and that only in rare special cases would we be justified in large expenditures at this time for the purpose of reducing maximum grades below that required for a truck with one trailer in order to increase the train capacity. Record of Truck Performance. — We are indebted to the Pierce Arrow Motor Car Company for the following chart which shows the ability of their trucks to pull on different kinds of road surfaces and different grades. This data confirms the previous statement that modern trucks have sufficient power to easily handle their full loads on any grade that would be selected for horse traffic on improved roads. (Chart, page 82.) Convenience of Operation. — Drivers dislike to be forced into second or low gear. If it is possible to approximately determine the rate of grade at which most cars or trucks shift gear this has some bearing on grade selection. It. is, of course, difficult to figure this closely as motor design improves, gear ratios vary; cars run on varying degrees of efficiency, gasoHne varies in quahty, etc., but as a matter of interest the author's experience indicates that the average fight pleasure car of the year 1919 shifts into second gear at about 7 per cent, and that very fittle gear shifting is necessary on long 6 per cent, grades. W. C. Slayton, a truck fleet manager, says that his 5-ton standard, gear ratio trucks generally drop into second at about 5 per cent, and that very httle shifting would be required on long 4 per cent, grades. Passenger autos drop into low at about 10 per cent, and the 5-ton trucks into low at about 8 per cent. From the standpoint of convenience in driving pleasure cars these premises, if they apply, indicate that if for any reason a 6 per cent, grade can not be obtained you might just as well use a 10 per cent, and that heavy expenditure to get a 7 per cent. or an 8 per cent, has no bearing on the convenience of the road. This appfies only to scenic routes. In the same way for truck hauling if you cannot get a 4 per cent, there is no object from 6 82 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Optional Gearing on Five-ton Model The first option is our standard gearing and will be supplied on all orders unless otherwise specified. This gearing should be used where the truck is to traverse good hard roads at all times, and where the grades do not exceed 10 per cent. The second option gives great pulling power on the low speeds, and the standard speed of 14 miles per hour on high gear. This gearing should be used only where the truck has to pull through a very short portion of poor road and the great majority of the running is done on direct drive. This option is popular with contractors, etc. The third option is especially suited for districts where by nature of roads {Continued at bottom page 83). GRADES AND ALIGNMENT 83 the standpoint of convenience in using less than an 8 per cent. Other factors, however, apply to reduce this extreme jump as discussed later. It should, however, be borne in mind that if trucks are operating regularly over a stated route that special gear ratios can be and are used to meet the existing grades (see Chart C, Note, page 82). Convenience therefore plays a minor part in grade selection. Mechanical Energy Expended on Plus Grades. — For an equal distance between terminals and an equal rise the mechanical energy expended on a trailer is not greatly affected by the rates of grade. If, however, the selection of rate of grade affects the distance, but not the rise, the lower rate of grade will increase the expenditure of mechanical energy. To illustrate: Suppose a tractor is hauling a train of farm wagon trailers on a hard surfaced road. The roll- ing and grade resistance of the trailers per ton of load can be approximated from Table 8, page 76. Suppose there are two villages A and B (see Fig. 20) 10,000 ft. apart and 100 ft. different in elevation. The theoretical energy in foot-pounds per ton of load to haul the trailers from A to B is for all practical purposes the same for any ordinary maximum grade as shown in Table 9 (page 84) . For traffic going from B to A there is some advantage in the lower rate of grade. Operation costs on minus grades are discussed later. If we assume that the fuel consumption is proportional to the energy expended, Table 9 indicates that under these conditions for a car climbing A to 5 no appreciable saving in fuel consump- tion results from the xise of a low grade. This is not strictly true when applied to a car carrying the motive power generator but it is near enough to help towards a general conclusion. It is probable, however, that the time factor makes the lower grade somewhat cheaper on which to operate (see discussion of time factor, pages 92 to 114). This adds considerable strength to the contention that very little practical advantage results from reducing grades on local service roads below a reasonable maximum or traflBic conditions a high speed is undesirable, or in hilly country, where the road surfaces are good. This gearing is standard equipment on the long wheel base model. The fourth option should only be used where the road surfaces are ex- ceedingly poor, and the country very hilly. We do not advise using this gearing except in extreme cases. 84 LOCATION, GRADINO AND DRAINAGE OF HIGHWAYS where the distance and rise remain fixed and indicates that the use of long straight rates of grade in place of a combination of various rates does not materially affect the fuel consumption provided the total rise aud fall and distance remains constant. Fig. 20. Table 9 Hate of grade, per cent. Resistance per ton of load, in lbs. Length of grade to rise 100 ft., feet Foot-lb. of energy to rise 100 ft. on grade shown, ft.- lb. Remaining distance on level, feet Ft.-lb. to haul on level for the re- maining dis- tance Total ft.- lb. energy from AtoB 2K 90 4,000 360,000 6,000 240,000 600,000 4 120 2,500 300,000 7,500 300,000 600,000 5 140 2,000 280,000 8,000 320,000 600,000 6 160 1,666 266,640 8,334 333,360 600,000 8 200 1,250 250,000 8,750 350,000 600,000 10 240 1,000 240,000 9,000 360,000 600,000 Vertical. . . 2,000 100 200,000 10,000 400,000 600,000 Resistance per ton of load on level 40 lb. Now suppose A and B were only 1000 ft. apart in distance and 100 different in elevation. A road between them on a 10 per cent, grade would be only 1000 ft. and would take only 240,000 ft.-lb. of energy per ton of load on the trailer (see Table 9). A road on a 2}^^ per cent, grade would have to develop additional distance to rise 100 ft. It would be 4000 ft. long and would require 360,000 ft.-lb. of energy to haul 1 ton of load. From this it is possible to see that where the rise remains fixed and the distance depends on the rate of grade the selection of the lower rate increases the fuel consumption. Under these conditions it is desirable to use the highest rate of grade that will satisfy the GRADES AND ALIGNMENT 85 other requirements of traffic and construction cost such as reasonable Hmiting loads for teams or trailer trains, convenience in the matter of gear shifts and the cheapest construction location and maintenance cost (see page 116). Effect of Distance Rise and Time on the Cost of Motor Opera- tion. — A close analysis of this problem is desirable but hardly possible yet. With the great variety of cars, trucks, etc. oper- ating under different degrees of efficiency it is hopeless to arrive at very definite conclusions. General principles based on the laws of mechanics can be derived but actual definite costs are another matter which the author frankly leaves to someone in the future. Long alternate routes can be advantageously com- pared in value for the elements of distance, rise and time but the value of a close operating cost analysis of grade Une design has a very hmited application as previously discussed. The time element has not much practical value on short trips as we all waste considerable time during the day anyway but on com- mercial hauling routes it plays a noticeable part in the cost and for this reason we have analyzed some of the problems in two ways. As a matter of general interest the following approx. data is included. This data has been used by the author per- sonally for some time but merely as a basis for judgment. Cost of General Operation. — We all have heard the cost of tires, repairs, gas, etc. talked by the hour for the ordinary pleasure car. Each reader probably has his own data but we will assume that the total operating cost on hard surfaced roads in 1919 for the ordinary passenger car including interest on investment, depreciations, insurance, repairs, gas, oil, storage, etc. runs from $0.05 to $0.12 per mile. Say $0.08 average, and that of this gas and oil cost say $0.0234, assuming 14 miles per gallon. We will assume that 5 ton trucks cost about $28.00 per day to operate. That the total cost of operation will run from $0.30 to $0.50 per mile, on improved roads and will probably average about $0.40 per mile. These trucks get about 3 to 5 miles on a gallon of gas and the cost of fuel wiU be assumed at $0.08 per mile. Two ton trucks under similar service probably cost about $20.00 per day to operate or about $0.30 per mile with a fuel cost of say $0.05 per mile. It can be seen that the cost of fuel is only a small percentage of the operation of a truck. 86 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Value of Distance Saved on Average Grades Provided Rise is not Increased. — Traffic counts, or the general character of territory served, by the road in question, can be used as a rough guide as to the probable proportion of horse trafl&c, passenger cars and trucks. Taking the ratios of traffic shown in Table, 2 page 69, for the main roads of Massachusetts we get the following average value per vehicle for a saving of 1 mile of distance. Horse traffic 6 per cent, of total. ... 6 X $0.30 per mUe = $ 1.80 Light cars 87 per cent, of total 87 X 0.08 per mile = 6.96 Trucks 7 per cent, of total 7 X 0.35 per mile = 2.45 $11.21 100 100 $11.21 10.11 per mUe, say $0.10 per mile for the main roads. This data agrees with the assumptions of Mr. A. R. Hirst given on page 63. For convenience his tabulation is repeated at this point. This tabulation assumes average going and does not consider various rates of grade. It includes the time factor and is intended for the comparison of long routes or Special Service Commercial Roads. If used as a basis for estimating the value of saving distance on a local service road it is just as well to divide the figures by 2. Table 10. — Value op a Mile in Highway Distance Saved (Based on a car mile operating cost of $0.10) Average Number of Vehicles per Day Saving to Owners per Year Saving Capitalized at 5% equals 100 $ 3,650 $ 73,000 250 9,125 182,500 500 18,250 365,000 750 27,375 547,500 1,000 36,500 730,000 2,000 73,000 1,460,000 5,000 182,500 3,650,000 10,000 365,000 7,300,000 Note. — ^The capitalized value of 1 foot of distance saved for 100 vehicles per day equals $14. Value of Rise Saved Provided Distance is not Increased and the Time Factor is Ignored. — (Cut and Fill Grading Methods). GRADES AND ALIGNMENT 87 The elimination of needless rise and fall between terminals provided the distance is not increased is evidently valuable. There are so many indeterminate factors that we will take refuge in simple theoretical mechanics using the simplest data available and then modify the results arbitrarily. The tabular results given have been used by the author in the absence of reliable data as a rough guide in comparing cut and fill grade reductions for small changes in rise. They do not consider the time factor as it does not have much real practical value for short grade changes. Time is, however, very noticeable on long steep cUmbs. For comparing total rise and fall on long routes it is better to use Table 11 A, page 91, as this considers the time factor. Table 12B, page 104, is perhaps more convenient for general use and has been modified to meet certain practical objections to the more theoretical figures. Suppose a farm wagon trailer or an automobile is travelling over a hill, Fig. 21. Fig. 21. If a car started at A from rest and there was no rolling resist- ance, no air resistance, no friction of any kind, no loss of energy from the engine running while coasting down the grade from C to B or from the application of brakes while descending from C to B, the potential energy of the vehicle at the top of the hill C would be equal to the energy in foot-pounds required to haul it up the hill from AtoC and the kinetic energy at B would be the same due to its speed developed by coasting. Under these theoretically perfect conditions no energy is required to move the load from A to 5 on the level. The energy in foot-pounds per ton of load would be 2000 lb. X 100 ft. rise = 200,000 ft.-lb. If the car was stopped at B by braking this energy would be lost and the total energy expended would have been 200,000 ft.-lb. In a similar way the energy expended over the same hill 88 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS cut down 10 ft. to C would have been 2000 lb. X 90 ft. rise = 180,000 ft.-lb. The saving in energy resulting from cutting down the hill 10 ft. is 20,000 ft.-lb. or 2000 ft.-lb. per ton of load per foot of rise saved provided the car is stopped at B. In case the car is not stopped at B and the coasting cars partially cHmb another hill beyond B on their own momentum there is no saving at all accompUshed by cutting down the hill shown from C to C as the car having a kinetic energy of 200,000 ft.-lb. will go farther on its own momentum than the one having a kinetic energy of 180,000 ft.-lb. The introduction of friction and rolling resistance merely adds a constant loss of energy in the normal grade direction which is practically the same in amount no matter how much the hill is cut down as the difference in the distances ACB, AC'B and AB is not appreciable for ordinary road grades. As a matter of fact the cars are rarely stopped at the bottom of each hill and it is evident that the saving in expended energy due to grading down a knoll depends on how much of the potential energy at C or C is lost in descending the grades CB or C'B. That is, if half the potential is lost through braking an actual saving of per ton of load of 1000 ft.-lb. of energy results from cutting down the hill 1 ft. If three-fourths of the potential energy is wasted a saving of 1500 ft.-lb. results, etc. Suppose we carry through a simple case of a farm wagon trailer train starting from rest at A. Full power is applied chmbing AC and the energy used per ton of load is (2000 lb. X total rise in feet) -|- (rolHng resistance in pounds per ton of load X distance travelled in feet). The potential energy of the train at C per ton of load equals 200,000 ft.-lb. in Fig. 1ft and the energy used in overcoming roUing resistance is a dead loss and equals 40 lb. (rolhng resistance per ton of load from Table 8) X distance AC in feet. In a similar way the potential energy at C equals 180,000 ft.-lb. per ton of load and the energy lost in overcoming the rolling resistance is the same as the first case. In descending the hill from C to 5 or C to B practical wastes of the potential energy occur through keeping the engine running while coasting; through the apphcation of brakes to control the speed on steep grades or through throwing the engine into second or low gear and keeping it engaged to act as a brake. Rolling resistance also eats up its regular supply of energy. On low GRADES AND ALIGNMENT 89 grades no shifting of gears occur as a rule nor is the engine thrown out; the driver merely cuts down his gasoline and takes advantage of the gravity help. That is, there is less potential energy wasted on a light grade than on a heavy grade. This is the principle we wish to develop as it indicates that from a practical standpoint the actual saving in operation cost for eliminating a foot in rise and fall over a hill is less important on light grades than on heavy grades. This adds a certain theoretical strength to the contention that for light intermediate grades there is very Uttle advantage to traffic through cutting the top of every knoll and filling every hollow. Prof. I. 0. Baker developed this same general principle in the 3rd edition of his book published in 1918. For purposes of a rough approximation we will assume that 80 per cent, of the potential energy is lost on a 10 per cent, grade; 50 per cent, on a 6 per cent, grade and 10 per cent, on grades of 2 per cent, and less. This is based on Table 8 which shows that on a level the rolUng resistance per ton on the level is 40 lb. and that on a 10 per cent, grade the rolUng resistance plus gravity = 240 lb. per ton. The down hill gravity pull amounts to 200 lb. per ton. Forty pounds of this is effective in overcoming rolling resistance. We probably lose by brake action 200 — 40 = 160 lb. or i^^oo = 80 per crent. plus engine running waste say 2 per cent. = 82 per cent. This is arbitrarily reduced to 80 per cent. In a similar way the other two values are derived modified by the probability that less brake action and engine loss occur on the 6 per cent, grade. Theoretically no loss occurs on grades of 2 per cent, or less on the basis of a 40 lb. rolling re- sistance but we have assumed a loss of 10 per cent, as a common sense value. The saving of gas on down grade operation is extremely variable and depends on the regulation of the minimum gas feed and the drivers personal system. These are factors which add uncertainty to any figures. The theoretical potential energy per foot rise per ton is 2000 ft. -lb. The loss on these grades may therefore be assumed as 10 per cent, grade 80 per cent, loss of 2000 ft.-lb. = 1600 ft.-lb. 6 per cent, grade 50 per cent, loss of 2000 ft.-lb. = 1000 ft.-lb. 2 per cent, grade or less 10 per cent, loss of 2000 ft.-lb. = 200 ft.-lb. If we assume that the roUing resistance of the farm wagon trailer on a level road is 40 lb. per ton we can convert the saving of energy per foot rise into equivalent distance. 90 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 1600 ft.-lb 1 ft. rise on 10 per cent, grade = -,>, r. ,, 1000 ft.-lb. 1 ft. rise on 6 per cent, grade = 40 200 = 40.0 ft. of level distance. = 25.0 ft. of level distance. = 5.0 ft. of level distance. 1 ft. rise on 2 per cent, grade = .„ Assuming an average fuel cost for all classes of traffic on the road at $ 0.027 per mile on the level the fuel cost per 100 feet of rise per car becomes: On a 10 per cent, grade ^^ X $0,027 = $0.02 On a 6 per cent, grade -^^ X 0.027 = 6.014 On a 2 per cent, grade ^^ X 0.027 = 0.003 Using these figures we can compile a table of capitahzed value at 5 per cent, for saving 1 ft. of rise without increasing distance. This table has some value as indicating about the extreme expenditure that is justified for the elimination of needless rise and fall by grading down small hills by cut and fill on Local Table 11. — Capitalized Value of Saving 1 Ft. of Rise and Fall WITHOUT Increasing Distance (Based on fuel cost, per mile per car on a level grade, of $0,027) (Time factor not considered) Yearly saving 5 per cent, capitalized value vehicles per day 10 per cent, grade 6 per cent, grade 2 per cent, or less 10 per cent, grade 6 per cent, grade 2 per cent. 100 260 500 750 1,000 2,000 3,000 4,000 5,000 10,000 $ 7.66 18.90 37.75 66.66 75.50 151.00 226.50 302.00 377.60 755.00 $ 5.10 12.75 25.60 38.25 16.00 102.00 163.00 204.00 255.00 610.00 $ 1.10 2.75 5.50 8.25 11.00 22.00 33.00 44.00 55.00 110.00 $ 151 378 755 1,133 1,510 3,020 4,530 6,040 7,560 15,100 $ 102 266 610 766 1,020 2,040 3,060 4,080 5,100 10,200 $ 22 55 110 165 220 440 660 880 1,100 2,200 Note. — This table can be used as the extreme basis of cut and fill reduc- tions on local service roads in order to save fuel alone. If we assume that fuel means nothing to 75 per cent, of the traffic divide by 4. GRADES AND ALIGNMENT 91 Service roads; it does not consider the time factor of operation as this does not have much practical bearing on minor changes in rise as there is a certain amount of time wasted during the day anyway but this factor becomes very noticeable on long steep cUmbs and should be considered in comparing long routes, Special Service roads or in making radically different relocations, see Table llA or 12B. Table llA. — Capitalized Value op Saving 1 Ft. of Rise and Fall WITHOUT Increasing Distance (Based on $0.11 per mile per car' total operating cost on a +1 per cent. grade) (Time factor included see pages 92 to 114 for discussion of time factor) Yearly saving 5 per cent, capitalized yearly saving vehiclee per day 10 per cent. 6 per cent. 2 per cent, or less 10 per cent; 6 per cent. 2 per cent. grades 100 $ 21 $ 14 $ 3 $ 427 $ 275 $ 30 250 52 36 7 1,067 687 75 500 105 70 16 2,135 1,376 150 760 168 105 23 3,202 2,062 226 1,000 210 140 30 4,270 2,750 300 2,000 420 280 60 8 540 6,600 600 3,000 630 420 90 12,810 8,250 900 4,000 840 560 120 17,080 11,000 1,200 5,000 1,050 700 160 21,350 13,750 1,500 10,000 2,100 1,400 300 42,700 27,600 3,000 Note. — This table can be used for the comparison of long routes or indicates about the maximum allowable expenditure for cut and fill re- duction on special service commercial roads. Considering the fact that extra fuel and gas means very httle to most road traffic one-fourth of these values would be a liberal expenditure at the present time for such refinements. Inefficient Operation. — In order not to lose the sense of value of any such figures it is just as well to bear in mind that the American public are not particularly careful of small savings. The average motor car is not kept in a high state of efficiency. If the owner himself does not think it worth while to save gasohne by keeping his car in shape how can we expect the community at large to make heavy appropriations for construction 92 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS features of design whose value is based on purely theoretical small additional savings. There is undoubtedly more gasoline wasted from careless upkeep and driving than we could ever save by the refinements of the most scientific location and for this reason the author is not inclined to give analyses of this nature much weight except as they indicate general principles, namely: that the elimination of rise and fall is more valuable on Special Service Commercial roads than on Local Service Roads and of more value on steep than on light grades. Distance Balanced Against Rise. — It is even more difficult to analyze such a combination than the simpler cases preceding. At present a definite estimate is not possible. With more data on motor operation a closer approximation will be possible in the future but the great variety of cars, etc. will probably even then tend to "weaken the value of the figures. In order to show the effect of the time factor a simple case will be outlined (Fig. 22). Fig. 22. Assume two villages A and B 2000 ft. apart separated by a hill 100 ft. high with 10 per cent, grades on both sides. Assume an operating cost of a truck as $24 per ten hour day or $0.04 per minute exclusive of fyel and oil. Assume the fuel cost as $0.08 per mile operating on the level. Assume a rolling resistance of 40 lb. per ton on the level. Under these assumptions if the truck starts from A and stops at B coasting down grade from C to 5 and stopping at B, the energy expended per ton of load would be approximately (1000 ft. distance X 240 lb. pull) + (an allowance for the engine run- ning free from C to B, say 10 per cent, of energy required for running 1000 ft. on the level or 10 per cent, of 40,000 ft.-lb.) = 244,000 ft.-lb. The amount of energy required per ton of load from A to 5 on the level would be 2000 ft. distance X 40 lb. pull = 80,000 ft.-lb. Assuming that the fuel expenditure is directly pro- GRADES AND ALIGNMENT 93 portional to the expenditure of energy the fuel consumption over 244 000 the hill would be on'nnn ~ ^ times as great as on the level or in money at $0.08 per mile on the level it would be Kosn ^ $0.08 X 3 = $0.09. The fuel consumption on level = $0.03. Suppose we consider the time factor. Assume that the maximum speed on the level is regulated by law to 12 miles per hour. The time consumed to go 2000 on the level is approxi- mately 2 minutes which amounts in money at $24 per day to approximately $0.08. Suppose the truck makes 3 miles per hour in low gear travelling from A to C and 8 miles per hour coasting down hill from C to B. The time over the hill would be approximately 5 minutes or in money $0.20. The total operating cost over the hill would be approximately $0.29 and on the level $0.11 or a difference of $0.18. If these assumptions were correct we could afford to increase the length of the road to 5300 ft.- on the level or 2K times as ~if% far to avoid the hill as far as the operating cost of the truck is concerned. These assumptions are not necessarily correct but in the absence of more reliable data the author would have no hesitation in increasing the distance by from 2 to 2}4 times for truck traffic based on such an analysis. The cost of construction of the two routes would of course be balanced against the operating cost. Take the same case for the two villages A and B 4000 ft. apart on 5 per cent, grades. The energy over the hill per ton of load is assumed as (2000 X 140) + (10 per cent, of 2000 X 40) = 288,000 ft.-lb. The energy on the level = 160,000 ft.-lb. Fuel consumption over the hill = $0.11 Fuel consumption on level = $0.06 The speed cUmbing the 5 per cent, grade would probably be about 6 miles per hour and about 12 miles per hour coasting down 94 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS the hill provided the alignment is good as the extreme control necessary on a 10 per cent, grade is not required. The time over the hill becomes approximately 5 minutes The time on the level becomes approximately 4 minutes The time cost over the hill approximately $0.20 The time cost on the level approximately 0. 16 Total cost over hill 0.31 Total cost on level . 22 In this case we could afford to increase the distance 40 per cent, to get a level road from the standpoint of truck operating cost. Light motors would not justify any such increase as later discussed. Sfa 187 A 3— — /v Ham Y Roctci S+an* Stoi 196 -5ta EOOA Plan. s^ci>!~j^i note: Time factor modified 'Curves ta Z. Fuel cost not cons ialerec^ for SO % of light motors Curves la S CmvENQZ Mefin Intercity - {state l?oads. Prabable Future Local Service ^oad. and Secondary State Roads, Traffic 1800 or Mare 130 RO 110 loo; 90 80 TO 60 50 40 50 0123456789 10 Rate of Grade^PerCent Fig. 26.- — Graph of table 12B. A practical basis of comparison. This graph assumes that the alignment is fairly good, (see also page 141). This graph assumes that J^ the travel is up hill and J^ down hill. 106 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Column 2 applies to Main inter-city Routes. Column 3 indicates possible expenditures, sometime in the future, for Special Truck hauling roads constructed and maintained by a direct tax or toll on the trucks using the road. Examples of the Value and Limitations of Table 12B. — These examples are included as much to show various practical con- siderations in grade hue designing as they are to illustrate the general value of Table 12B. No rules or standards can be used without judgment. Case I. Comparison op Short Alternate Locations (Distance Balanced Against Rise) Use the Pugsley Hill relocation described on page 94. A practical comparison of value of the two lines is not entirely based on the relative operating and construction costs. Suppose we compare this relocation assuming that this road might be either a Local Service Road carrying 500 motors per day; a State Inter-city Route carrying 2000 motors per day or a Future Commercial Truck Road carrying 2000 trucks per day. Use Table 12B, columns 1, 2 and 3. Local Service Classification Existing road location, 2200 ft. on 7 per cent, grade @ $11.20 = $24,640 New location, 2600 ft. on 4 per cent, grade @ 9.40 = 24,440 Approx. advantage of Relocation per 100 vehicles = 200 Total advantage for this case, 5 X $200 =$ 1,000 From the standpoint of operating cost this relocation can be assumed to warrant an additional CKpenditure of — — = $500. For a local service road the saving in operation cost is neghgible (not over 1 per cent.). As a matter of fact the approximate nature of the figures makes it doubtful if there is any saving. As previously stated page 103 the relocation was warranted by im- provements in snow conditions, reduction of maximum grade for a long road and a reduction in construction cost. Inter-city Road Classification Existing location, 2200 ft. on 7 per cent, grade @ $15.80 = $34,760 Relocation, 2600 ft. on 4 per cent, grade @ 12.80 = 33,280 Approximate value Relocation per 100 motors = 1,480 Total advantage for this case, 20 X $1480 = 29,600 ■ , $30000 Allowable expenditure — - — = $15,000 Under these conditions the relocation is desirable. GRADES AND ALIGNMENT Future Truck Road Classification (Construction financed by road users) Existing location, 2200 ft. on 7 per cent. @ 195.00 Relocation, 2600 ft. on 4 per cent. ® 63.90 Approximate value of relocation 100 trucks Total advantage for this case, 20 X $43,000 Approximate allowable expenditure = $500,000. 107 $209,000 166,140 43,000 860,000 For a road of this character the relocation would not only be justified but a further reduction to a 2 per cent, grade by cut and fill could probably be made at a cost of only a fraction of 1500,000. Comparison of Cut and Fill Grade Line Profiles. — In comparing all alternate cut and fill grade lines it is assumed that the road is well located or that it is fixed for some practical reason by existing rights of way. Case I. Comparison of the Use of a Reasonable Maximum Grade AND A Reduction in Total Rise with a Lower Rate of Grade AND No Reduction in Rise. (Distance Fixed) THC^e ARIAS CBUAL 7^ fti ,— ^"^ C/Xwp>>^ ■^ «■ -"^^ip/ OraUe-' ■"V^ ■Orade"A' it S Gro de"B^ V^^' f\j 1^ b^^ ^ r^.s' ..^-1 Nafural'^^' ^ — "^<" f-^ i^ js*^"^" 'fl Suffoic^ ►» ^ ^ 1 ' " " '"" ^ 1 _ I i 4 5 6_ 7 ( 9 10 I' 12 Stations Fig. 27. Grade line "A" uses a 5 per cent, maximum and decreases the height of the hill 9 feet. Grade line "B " uses a 4 per cent, rate and does not reduce the height of the hill. The Amount of Excavation is the Same for Both Lines. — For a given expenditure of money in rolh'ng topography is it better to use a reasonable maximum and reduce rise or use a lower rate of grade and fail to reduce rise? Suppose we compare this fine first" from the standpoint of the mechanical energy required for climbing from Sta. 9 + 24 to 2 + 00. 108 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Energy Expended Grade Line A 400 ft. on 5 per cent. Grade @ 140 lb. per ton = 56,000 ft.-lb. 324 ft. on Level @ 40 lb. per ton = 12,96 ft.-lb. • Total = 68,960 ft.-lb. Grade Line B 724 ft. on 4 per cent. Grade @ 120 lb. = 86,880 ft.-lb. The expenditure of energy on the down grade is indefinite and is due very largely to the driver. He may coast and let bis engine run free or use the minimum gasolene and use the engine as a break. The chances are that he will use slightly less on Grade B than on Grade A but not enough less to balance the advantage of Grade A on the cUmb. The probabilities are all in favor of the supposition that Grade A is the best grade on the score of fuel consumption. Now suppose we use Table 12B to compare these two lines. This table considers the indefinite items of down grade operation and wear and tear on the car. Compare the operating cost on these two profiles. Use column I Table 12B. Local Service Roads. Grade "B" 724 ft. on 4 per cent, grade @ $9.40 =$6805 o J -w^-,.,s;^a» pHB ■^1- ^.MJ^SSW Kli tL:'t:.^yMf "v^^-':''''v7--- ■■■''".-. Fig. 41. — Alignment following grade contour closely (New Mexico). Fig. 42. — Example of crooked alignment on steep mountain slope, above and to the left. Old road below and to the right. New road 144 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS as sharp as 80 ft. at the head of gullies where the driver can see across the curve or a radius of 100 ft. on the outside curves around points where the sight distance depends on the radius. Even these Umits are impracticable in very rough country where radii of 40 ft. are considered reasonable. All outside curves having a sight distance of less than 250 ft. should be posted with danger signs. The arbitrary Umitation of minimum radius has a large effect on cost. The following example will illustrate this point. These revisions were made by C. H. Chilvers on the Rabbitt Ears Pass Road in Colorado to show the effect of alignment on excavation. The office method of plotting a good cheap alignment are described in detail in the third volume of this series. Rabbit Eaks Road, State of Colorado, Side Hill Section Original design First revision Second revision Length, 8.79 miles. Length, 8.81 miles. Length, 8.94 miles. Width of roadway, 16 ft. Width, 16 ft. Width, 16 ft. Maximum grade, 8 per Maximum grade, 8 per Maximum grade, 8.5 per cent. cent. cent. Grades flattened on No grade compensation No compensation on switchback turns. on curves. curves. Minimum radius 100 ft. Minimum radius, 100 ft. Minimum radius, 40 ft. Firs t-class alignment First-class alignment Poor, crooked alignment throughout. but more curving elimi- nating many expensive tangents. carried to extremes. Total amount of exca- Amount of excavation. Amount of excavation. vation, 91,000 cu. yd. 65,000 cu. yd. 38,000 cu. yd. First-class design but First-class design shows Illustrates extreme effect needlessly expensive. effect of careful, intelli- of alignment on cost. gent alignment engi- From an engineering neering. point of view there was no justification for this design for the topography in question. Note. — On one switchback turn on this road a 100-ft. radius required 5000 cu. yd excavation and a 40-ft. radius 500 cu. yd. or one-tenth as much. Short radii are justified in isolated cases but their continuous use to save small amounts is poor practice. GRADES AND ALIGNMENT 145 Fig. 43. — First class switchback design. Note flattening of grades on sharp turns. Fig. 44.^Poor switchback design, alignment too sharp. Grades not reduced on turns. 10 146 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS I^H ^PP ^i5?^^P ^^fl^^:%.. pM|p^^ PiQ. 45. — Excellent switchback layout on spur location. Note grade flattened on curve. Fig. 46. — Retaining wall switchback construction. GRADES AND ALIGNMENT 147 Effect of Railroad Grade Crossings on Alignment and Grade. — Railroad grade crossings are sources of continual danger; they should be eliminated on all main routes. The discussion of sub- way and overhead eliminations is given in Volume III . If a grade crossing is necessary the best practice calls for a tangent crossing at least 400 ft. long 200 ft. on each side of the track. It is not advisable for the tangent to make an angle of less than 60° with the center line of the track. The approach grades should not exceed 5 per cent, and a level grade at least 60 ft. long should be provided on both sides of the track to permit the better control of the vehicle as it approaches the crossing. Anyone owning an automobile is familiar with the dangerous element of driving where precautions of this nature are neglected. ■:.,«^ WM IH wpm ^ggg-^^^^Hf ^m ^m ^n "^ ;^ '^^'^^^MWm ^ 9 SH ' m ISBBa U-Zif^ li^WUkfiai^ . m f ^ s Fia. 47. — Example of flattening grade on switchback turn. Also note guard rail built of stone posts and wire cable. Reconunended Alignment Practice. — -The following summary agrees with general current practice and can often be used with- out raising the cost beyond the bounds of reason. A summary of this nature is of course of only general value. Each case must be worked out on its own merits. Broad generalizations of detail requirements are dangerous if used indiscriminately. Main Commercial Roads. {Well Settled Districts.) Minimum sight distance 300 to 400 ft. Minimum radius of curvature at right angle turns on level outside of villages where sight distance does not control. . 250 to 400 ft. Minimum radius of curvature on steep grades or at the foot of such grades depending on the central angle where the sight distance is not the controlling factor 400 to 600 ft. 148 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Ordinary Agricultural Roads. {Local Service.) Minimum sight distance 200 to 250 ft. Minimum radius of curvature at right angle turns on level outside of villages 100 to 200 ft. Minimum radius of curvature on steep grades where sight distance does not govern 300 to 400 ft. Mountain Roads. No limitation on sight distance. Warning signs used where necessary. Minimum radius on steep grades 100 ft_ Minimum radius in extremely rough country 40 ft. Grades not to exceed 3. per cent, for a 40-ft. radius and not to exceed 4 per cent, for an 80-ft. radius. Any grade up to 8 per cent, on a 100-ft. radius, although it is desirable not to exceed 5 per cent, on a 100-ft. radius curve with a large central angle. Summary of Principles of Location. — Climatic, drainage and soil conditions govern a location in respect to avoiding bad snow conditions, flood areas, needless stream crossings, slide or swamp formations and excessive rock work. The general requirements of line and grade discussed in this chapter are summarized as follows: the various principles are repeated conversely under the headings of Grade, Alignment, Distance, Rise and Fall and Cut and Fill grade reductions. First. — Reasonable maximum grades are essential. Recom- mended reasonable rates for various kinds of roads are given on page 116. The following treatment is allowable to get a reasonable maximum. (o) Any expenditure necessary. (6) Distance may be increased in order to get a reasonable maximum grade but should not be increased for a fixed rise to reduce grades below a reasonable maximum. (c) Poor alignment may be used if necessary to get a reasonable maximum grade if funds are low but poor alignment should never be introduced to reduce grades below a reasonable maximum. Where poor alignment is necessary maximum rates must be reduced at the danger points (see page 140). (d) For a fixed rise and distance, it is generally better to use a short length of reasonable maximum and the balance of the distance a low rate than to use a uniform moderate rate grade for the entire distance; this is not strictly in accord with the principles of cheap motor operation (table 12B, page 104) but the net practical results are generally better. This means that if a road is running up a valley on an easy grade and must leave the bottom land and climb on a side hill location to reach a pass that it is generally better to make the climb as short in distance as possible as a side GRADES AND ALIGNMENT 149 hill location usually introduces poor alignment and generally increases the excavation per mile over a valley location. Second. — Alignment should be made as safe as possible con- sidering the funds available. Safety of traffic governs alignment practice. Cost of traffic operation has no practical effect. (a) Good alignment should never be sacrificed to reduce grades below a reasonable maximum. For safe alignment practice (see page 147). (6) Good alignment may be sacrificed to get a reasonable maximum but this condition necessitates the reduction of grade at the danger points. fSee page 140.) (c) Improved alignment warrants increased distance only when danger is eliminated. Increased distance is not warranted merely to make an easy curve easier. (d) It is better to use a steeper grade (up to a reasonable maximum) with good alignment than to use poor alignment and a lower rate. (e) Exceptionally, good alignment (practically straight) may in some cases warrant an increase in the reasonable maximum grade above the rates recommended on page 116. This modification would not however apply unless it was impossible to locate and grade the lower rate location so that the sight distance on it was at least 250 ft. (/) An alignment and grading design which results in a sight distance of 250 to 350 ft. is safe and desirable but large expenditures to still further in- crease the sight distance must be used with caution unless the funds are practically unlimited. Increase in maximum grade above the recommended maximum in order to increase sight distance above 250 to 300 ft. is rarely warranted. Third. — Short distance is desirable provided considerations of safety, rise and fall, or reasonable maximum grades do not modify the conclusions. (o) Distance may be increased to reduce danger by better alignment at bridge approaches, railroad crossings, or to avoid difficult topography. Recommended minimum radius of curvature are given on page 147. (6) Distance should be increased to get a reasonable maximum for a fixed rise but rarely to reduce the grade below a reasonable maximum for a fixed rise. (c) Distance should never be increased to reduce rise and fall on grades of 2 per cent, or less. (d) Distance may be increased to reduce rise and fall on grades over 2 per cent, (use table 12B for comparisons of this kind) but for grades not exceeding the maximum it is rarely desirable to increase distance unless a noticeable rise and fall can be eliminated by a small additional distance. For ordinary easy rolling topography the principle of the straight line location is generally sound. 150 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Fourth. — The elimination of needless rise and fall is desirable modified by certain conditions. (a) The elimination of rise on steep grades is desirable. Distance may be increased to accomplish this provided the disadvantage of increased distance is balanced against the value of less rise (see table 12B, page 104). (b) The elimination of rise on grades of 2 per cent, or less is of no value from a practical standpoint. (c) Adverse grades may be used to eliminate dangerous alignment or shorten distance provided the shorter distance is of more value than the disadvantage of the extra rise (see table 12B). Summary of Cut and Fill Grade Reductions. — Grade reduc- tions by cut or fill assume that the road location is fixed for some reason and that further improvement must be by cut or fill. The distance is always fixed. Reasonable maximum grades are essential. (a) For a fixed rise there is no practical advantage in reducing the rate of grade below a reasonable maximum. (6) Reduction of total rise and fall on steep grades is desirable. (c) Reduction of rise and fall on light grades has no practical advantage. (d) The use of short adverse grades of 2 per cent, or less on a long climb has no practical disadvantage. The sources of justifiable economy in cut and fill design lie in the use of the short maximum in connection with the long ruling grade and the use of a rolling grade profile for all inter- mediate rates. The application of these principles in conjunction with the "spotting method" of profile design generally results in a satis- factory road at a moderate grading cost. The violation of these principles of location and cut and fill profile design occur quite frequently. Conclusion of Chapter. — The considerations discussed in this chapter govern the engineering field location and in conjunction with the variation in road cross section determine the effective- ness and economy of the grading design. The methods of their practical application are taken up in the third book of this series by means of actual designs worked out in detail and modified by systematic criticism. Grades and alignment are fundamental permanent features of highway improvement. There should be no hesitation in spend- ing all the money that may be required to get satisfactory results for average traffic but extreme refinements of location may will well be avoided if they materially increase the cost. ^ .c CHAPTER V CROSS SECTIONS OF RURAL ROADS, WIDTHS OF PAVE- MENT, RIGHT OF WAY AND CLEARING The shape and width of road cross sections have considerable effect on the safety and convenience of the highway for traffic and they also affect the economy of grading design. It is desirable to obtain features that are fundamentally required for the satisfac- tion of traffic but it is also desirable to avoid arbitrary standard- ization which adds materially to the cost without any adequate benefit. The problem of sections can be summed up as the determination of the minimum widths of grading, pavement, etc., the mim'mum depth of surface ditches in cut and variations in shape and width that will serve the present traffic requirements. At the time a road is improved, right of way should be ac- quired of such a width that it will permit the future widening of section, pavement, etc. Liberal right of way can be obtained more easily during the first stages of road improvements than at a later time when the land is worth more and buildings have been erected close to the road. That is right of way considers the future requirements of the road but grading widths can only reasonably consider the requirements of existing traffic. Sections. — Sections can be considered from the standpoints of Safety, Convenience and Economy. Safety requires a grading shape that permits the rig to use any part of the road from ditch to ditch without overturning or if this is not possible various expedients such as the one way crown, banking on curves, guard rail or wall protection will very mate- rially help the traffic. Safety requires a liberal sight distance which on sharp curves can be obtained by " Daylighting " the section (see Figs. 35 and 36, page 136). Convenience requires sufficient width for vehicles to pass at any point in ordinary topography and provides special turnouts at short intervals on Mountain Roads. It also calls for crown and shoulder slopes that permit driving without an uncomfort- able side tilt to the rig. 151 152 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Economy of grading calls for various combinations of widths, ditch depths, back slopes, etc. which most nearly fit the natural conditions at all points. That is the section must be flexible. It is, perhaps, best to develop the discussion of sections and pavement widths first for the high class road in ordinary topo- graphy and second for pioneer roads in mountainous conditions. High Type Roads (Premises of Design). — The points to be considered in the development of a normal section are: Fig. 48. — Banked curve on high class road protected by substantial concrete guard rail. 1. What is a safe driving slope? 2. What is a comfortable driving slope? 3. What pitch is required to drain different surfaces? These factors determine the shape of the section. 4. What is the commonly used width and the maximum width of the travelled way? These factors determine the width of pavement and shoulder. 5. What is the minimum allowable depth of surface ditch? 6. What are stable slopes for cut and fill outside of the limits of the travelled section? CROSS SECTIONS OF RURAL ROADS 153 These factors affect the economy. The first three questions have been pretty well settled by current practice; the last three are not so well defined. We will, however, assume the following premises which can be modified for special conditions: 1. Three inches to 1 ft. or 4:1 is the maximum safe driving slope. 2. One inch to 1 ft. or 12:1 is the maximum agreeable driving slope. 3. One inch to 1 ft. or 12:1 is the minimum slope at which an earth shoulder will shed water without too much maintenance. Three-fourth inch to 1 ft. or ^i in. to 1 ft. is a satisfactory crown for a single track Waterbound Macadam Road and J^ in. to 1 ft. is a satisfactory crown for a double track Waterbound Macadam pavement. Three-eighth inch or }4 iii- to 1 ft. is a satisfactory crown for double track Bituminous Macadam pavements or waterbound macadam treated with tar or asphalt flush coats. One-fourth inch or J^ in. to 1 ft. serves very well on rigid pavement types such as brick, concrete, sheet asphalt, etc. Circular arc or parabolic crowns are more satisfactory than the straight line section for the pavement proper. 4. The width of roadbed subjected to hard wear by traffic on the lighter traveled roads (single track roads) ranges from 8 to 10 ft. and on double track roads from 14 to 17 ft. The maximum width of roadway subjected to some wear by traffic turning out to pass ranges from 18 to 22 ft. 5. The minimum ditch depth below crown grade depends on keeping the longitudinal surface water outside of the travelled way and is rarely less than 10 in. ; it depends largely on the amount of surface water that must be cared for. 6. The stable cut and fill slopes depend on the climate and the material and range from K:l to 4:1. Before proceeding further, it will be just as well to discuss a little more fully, items 4, 5 and 6. Widths of Travelled Way (Item 4), — The width of roadway carrying the greater portion of the travel and the maximum widths when rigs turn out to pass are not well established. They are affected by the volume and speed of traffic, the pavement crown, and .the width of vehicles. Effect of Crown. — Crown has a marked effect on width of heavy travel. A crown such as % in. to 1 ft. or 1 in. to 1 ft. tends to concentrate the traffic in the center and is a detriment on a heavy traffic road. With crowns of H in- to 1 ft. or less there is no tendency to concentrate. For single track macadam or gravel roads where the traffic tends to stay in the center of its own accord on account of infrequent passing of rigs a fairly heavy crown is desirable as it is easier to maintain. On double track roads a crown of }i in. to 1 ft. or less should be used both on account of 154 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS J ^^HBlHfll ^^Bl ;n KP.™-' ^SHHh ■■ iS '^"' hH^^^H H| jf^^H HI SvgV'.^ffiMHIHi^BSI ^n|| Ffll'iv^j "Sb^BH^^^^^H^SBH^ ^^H^B ^^jjfP B""''-.-i ^^^BH^^H HI W^K/^^K^^^^* / -f i j-i^ 'S^B^m^' ' HD"""* a '^^SmB^' < jmi, ^; ^KBs^^m^ ' ' ** i'i^^^^^H ^p^/ ^^ ' ' 1 s ^^'^In ^^^f ^l^j li ■^" ,^ "J 1 " '"fl H ''j ^j \ ^^j^M ". .k ») ^ i^ >• . , . ' ^' "^^^^^^ssXSSM ' t i ' ^ ' '^^^^^^^M^j^^^S i ■* ll « ^ J^r '^^^■rjQ^^^^^l^J^SSS^^^R i ' ' A * 1 ' ^ ^^^^^^^^ M#-. ; ". * -^■i^^T^mffi 9r^> j^'^ rsjA'. "^ 4 1 -4 m 1^ s •»■ IHillil H ^M$ ^^^^^^^H Hm P^- BH^H Hi ■a a CROSS SECTIONS OF RURAL ROADS 155 convenience to traffic and to more evenly distribute the wheel wear (see premises of design, page 153). Widths Actually Used. — Probably the most systematic record of widths actually used by traffic can be found in the reports of the Massachusetts Highway Commission reports during the years 1896 to 1900. These results were obtained under the old horse drawn traffic conditions and do not apply closely for the conditions of today. They are included in connection with this discussion to illustrate the change which modern automobile traffic has made in width requirements on the heavier traffic roads. They, however, show a general relation between areas of light and heavy traffic on the lighter travelled agricultural roads. Table 19 gives the results on a few roads showing the fornii used and the variations from year to year. The footnote gives a summary of 160 roads and shows the results much better than by printing the table in full. Stated briefly the widths subjected to continuous wear on unimportant roads ranged from 8 to 10 ft.; on well travelled roads 10 to 14 ft. and in unusual cases 14 to 16 ft. The maximum widths for turn out traffic varied from 12 to 14 ft. on side roads and 17 to 18 ft. on the main roads. Modern traffic has changed conditions on the main roads but does not greatly affect these figures on the lighter travel roads up to about 300 vehicles per day. The author has measured similar widths on New York State main roads and found that they checked the widths of heavy travel of 14 to 16 ft. but that the maximum turn out widths were more, running from 20 to 22 ft. This can be explained by the increase in automobile traffic which on account of its higher speed requires more room in passing. Even a single track pavement should have ample shoulder width to permit traffic to turn out and pass easily. That is the total width of pavement and driving shoulder no part of which should have a slope of more than 1 in. to 1 ft. is practically the same for single or double track roads. Efifect of Vehicle Widths. — The width of modern vehicles has a decided bearing on double track pavement and shoulder turnout widths. The ordinary pleasure automobile is about 5 ft. 6 in. wide. The ordinary truck about 7.0 ft. wide with a wheel gauge of about 6.0 ft. Traffic regulations generally limit the width of vehicles to 96 in. except traction engines which may 156 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS be 110 in. The outside wheel of any rig oUght to be about a foot inside of the edge of the driving shoulder and there ought to be at least a foot and a half clearance between passing vehicles, on straight alignment and at least three feet on sharp curves. Table 19. — Showing Widths or Traveled Way County Maximum width of travelled way Widtll of commonly travelled way Town or City 1896, ft. 00 . 1899, ft. 1896, ft. oo* 00 ,-1 1899, ft. Athol Worcester Worcester Middlesex Hampden Berkshire Worcester Hampshire Middlesex Plymouth Berkshire Franklin Bristol 17 15 15 20 15 15 15 15 15 15 17 15 16 20 15 9 15 14 10-12 16 20 16 13 12 20 20 14 11 15 12 13 16 20 20 14 15 20 21 18 11 15 11 14 20 15 18 14 15 20 16-21 18 12 15 12 15-20 20 18 10-12 20 10 7 10 8 8-10 10-12 10-15 ,12 9 8 12 16 10 8 9 9 9 12 10 14 7 10 12 18 15 9 10 7 10 15 8 Barre Bedford 8 g Dalton 12—18 Fitchburg (W.) .... Huntington 14 8 10 Marshfield North Adams 7 12 15 7 12 Width of traveled way on 160 roads in Massachusetts, measured during the years 1896, 1897, 1898, and 1899, and printed in the report of the Massachusetts Highway Commission for 1900. The width of stone on these roads is given as 15 ft. wide on 130, 12 ft. wide on 3, and 10 ft. wide on 2. It should be remembered that the stone is put on very much thicker in the middle than at the edges. The maximum width of traveled way as 9 ft. wide on 2 roads 10 ft. wide on 6 roads 11 ft. wide on 2 roads 12 ft. wide on 28 roads 13 ft. wide on 8 roads 14 ft. wide on 23 roads 15 ft. wide on 30 roads 16 ft. wide on 8 roads 17 ft. wide on 1 road The width of commonly traveled way i 7 ft. wide on 12 roads 8 ft. wide on 17 roads 9 ft. wide on 25 roads 10 ft. wide on 32 roads 11 ft. wide on 10 roads 12 ft. wide on 30 roads 13 ft. wide on 3 roads I measured was as follows: 18 ft. wide on 23 roads 19 ft. wide on 1 road 20 ft. wide on 10 roads 21 ft. wide on 10 roads 22 ft. wide on 1 road 24 ft. wide on 2 roads 25 ft. wide on 4 roads 26 ft. wide on 1 road 33 ft. wide on 1 road is Hieasured was as follows: 14 ft. wide on 8 roads 15 ft. wide on 13 roads 16 ft. wide on 2 roads 18 ft. wide on 4 roads 20 ft. wide on 2 roads 22 ft. wide on 1 road 25 ft. wide on 1 road On this basis roads having much truck traffic would require a minimum turn out width of about 18 ft. which is probably about right for the minimum width of rigid pavement on such roads but hardly hberal enough for total shoulder width to take care of exceptional cases which occur more or less frequently. CROSS SECTIONS OF RURAL ROADS 157 Recommended Practice. — The available data obtained from observations on actual trafl&c movement indicates that a mini- mum turn out width of 20 ft. is desirable on single track side roads, 22 ft. on secondary double track roads and 24 ft. to 26 ft. on main double track special service roads. For a triple line of traffic 34 ft. and a four track road 42 ft. From this data it appears that modern practice on single and double track roads requires a width of solid pavement of from 10 to 20 ft. and a total driving width including shoulders of from 20 to 26 ft. -J u, , J-"i.„\l"f„ ,„ Shoulder Hope Crov/nA rol? '"ft l"fo ft- We have now practically developed a standard for the portion of the section used for driving (Fig. 50). The pavement that is to carry the heavy traffic has a specified crown for each variety and ranges from 34 to % in. to 1 ft. The shoulder slope from the edge of the pavement to the limits of the driving width (20 to 26 ft.) has a slope of 1 in. to 1 ft. or possibly ^ in. to 1 ft. That is, the shape of the driving portion of the normal section is fixed. The flexibility of the section depends on the portion out- side of this driving width. The function of the extra width is to keep the longitudinal drainage of surface water beyond the portion used for driving. To do this we are Hmited to a minimum slope of 1 in. to 1 ft. to insure transverse drainage and a maximum of 3 in. to 1 ft. on the score of safety. It is by the good j udgment of the designer in using various slopes between these limits and various widths and depths of ditches, combined with the possibilities of different grades that the economies in earthwork are affected and at the same time the design is made appropriate to the local conditions. Depth of Ditches (Item 6). — The author's experience indicates that an open ditch does not have much effect on ground water; that its part in the design is to drain the surface water and that if ground water is encountered underdrains must be used. These conclusions have been borne out in practice and are advocated by many engineers notably Irving W. Patterson of Rhode Island 158 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS who has had unusual success with his drainage and foundation designs. The principle we wish to emphasize is that deep surface ditches below the elevation of the bottom of the pavement foundations are useless. Deep ditches are not only useless but dangerous and the best practice calls for the least depth of ditch that will handle the surface water. A great many road men seem to feel that a deep open ditch really helps drain the subgrade but as stated the author has ^ Wcrf-er m Shoule/er Soil ^1 Foc refwai, Fig. 51. never been able to prove by cases where foundation failure occurred that the depth of surface ditch had any well defined bearing on the matter provided the ditch carried away the sur- face water promptly. Some soils have a strong capillary action and the water works up through them. In impervious soils such as clay a surface ditch 1-5 ft. from the center line can not have much drawing action as in numerous cases small holes dug in the roadbed (Fig. 51) fill with water at a much higher elevation 'than the side ditch. Fro2en 3houlclt?r5 - Fig. 52. In many instances in the northern states the ground under the pavement proper thaws out before the shoulder material which is protected by a sod coating and the following result is obtained (Fig. 62). Under these conditions the moisture in the center is held even in porous soils. As a matter of fact all pavement foundation design must be predicated on the assumption that even with the best drainage schemes the subgrade will at times soften somewhat and for this reason the use of deep ditches which are inconvenient CROSS SECTIONS OF RURAL ROADS 159 to traffic and which increase the grading cost are not in as much favor as in the past. Frequent culverts are desirable to rid the ditches of excess water. It should be remembered that road ditches are to protect the road and not furnish farm drainage and that deep farm ditches should be kept away from the road section. The following Rhode Island standard grading sections show the use of the shallow 12 in. ditch which is advocated wherever a small amount of surface water is expected. "'^3 H<- 9- ■>!<- <''. J. J. :, Cenfer Ora do : .-9- V^j'^ /'.'•■■? s+omdoircil ^ectlon-.Shoillow Ditch'? '-^i "JiZT^IZ '' . —>krS-x-4----^lk— X Fig. 53. — Rhode Island standard grading sections. The following section (Fig. 54) represents a good typical mini- mum width and minimum ditch depth grading section for single or double track roads which has been proved by practice to be satisfactory where small amounts of surface water are encountered. This section results in about the least feasible amount of cut and fill in grading design for light cuts and fills. The approximate .1 ,,.. "^1 .Crewn^foifolft ! iEkvafianThsorefical Gr ade \ ^^ \or}i"^\ \c- ------- lo'MB'---------^ I 1^ zo'foze , ->| Z^'toiB P"iG. 54. — Typical minimum width grading section. carrying capacity of ordinary road ditches and the limitations of use of the shallow and medium road ditches are discussed under "Longitudinal Drainage," p. 262. Efifect of Grading Width on Cost. — The width of grading from ditch to ditch has a distinct effect on cost but no general relation can be established for the ordinary road improvement where an old road forms the basis for the new grading. Two examples are given to show the value of reasonable reduction in sectional widths. 160 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 1. Indian Falls-Cokfu Road in New York State Length 1.85 Miles No change in profile No change in ratio of cut to fill Original Design Revised Design Width of macadam, 14 ft. Width of Macadam, 14 ft. Width of section, 30 ft. Width of section, 24 ft. Depth of ditch, 18 in. Depth of ditch, 14 in. Original estimated excavation, 7500 Revised estimated excavation, 5200 cu. yd. cu. yd. This change in section alone resulted in a saving of 2300 cu. yd. excava- tion or at the rate of 1240 cu. yd. per mile, or in money about $600.00 per mile with excavation at $0.50 per cu. yd. 2. PiTTSFORD-NoBTH HENRIETTA RoAD IN NeW YoRK StATB Length, 2.67 miles Original Design Revised Design Width of section, 30 ft. Width of section, 24 ft. Depth of ditch, 18 in. Depth of ditch, 12-14 in. Ratio of cut to fill, 1.35 per cent. Ratio of cut to fill, 1.25 per cent. Maximum grade, 6.0 per cent. Maximum grade, 5.0 per cent. Profile — Designed with straight in- Profile — Rolling grades and reverse stead of rolling grades and tangents vertical curves used. of 100 ft. between vertical curves. Original estimated excavation. Revised estimated excavation, 6620 11,450 cu. yd. cu. yd. A saving of 4820 cu. yd.; 1800 cu. yd. per mile, or in money, approximately $900.00 per mile. The revised design on this road is a good example of what can be saved by the use of a section that fits the conditions, a rolling grade, and a ratio of cut to fill that we have found from experience to be sufficient. Stable Cut and Fill Slopes.^ — ^Economy of design and mainte- nance is affected by the selection of reasonably stable slopes. For the class of grading usually encountered on roads built in ordinary topography their effect on construction cost is not great and they do not generally receive much attention but for mountain roads cut and fill slopes are an important consideration in the design and their effect on cost are worth considering. Table 23, page 200, shows the effect in detail of various cut and fill slopes on yardage of the ordinary sidehill mountain road sections. To illustrate the point we will quote one typical case for say an ordinary double track section (S-14), Table 23. CROSS SECTIONS OF RURAL ROADS 161 Natural ground Approximate yardage per mile elope degrees Cut slope VA : 1 Fill 11/2 : 1, cu. yd. Cut IH : 1 Fill VA : 1, cu. yd. Cut 1 : 1 Fill VA : 1. cu. yd. 5 1,100 950 900 10 2,200 2,000 1,900 15 4,000 3,600 3,300 20 7,900 7,000 6,100 25 11,700 10,200 30 19,600 FiQ. 65. — Example of excessively steep cut slopes. Steep grading slopes of this nature are a common fault in mountain road construction. Occasional slides can not be avoided, but continual slipping shows poor design and makes both the maintenance costly and travel dangerous. 11 162 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Stable slopes vary for different materials and for the same material under different climatic conditions. A combination of moisture and frost requires the flattest slopes for ordinary soils. On account of the great variety of circumstances affecting the design no hard and fast rules can be laid down but the following table, based on railroad and highway practice, indicates the slopes that are generally used. In this table and throughout the text slopes are referred to as l}i:l, etc., meaning l}i hori- zontal to 1 vertical. In some of the State Standard illustrations, however, slopes are shown as 1 on 13^^ meaning 1 vertical on IJ-^ horizontal. It is unfortunate that an engineering requirement is expressed by two different methods in such a conflicting order and care must be taken to understand which expression is used. TABtE 20. — Stable Cut and Fill Slopes Material Climatic conditions Combined rain and heavy frost Cut llain but not much frost Cut Fill Arid regions not much frost Cut Fill Sand I Gravel Loam Clay Boulders and earth Large rock slabs extend- ing back into hill and earth Disintegrated rock Solid rock 1,4:1 2 :1 IK 2 1 :1 H:l 2 :1 1^:1 1^:1 1>^:1 4 :1 1>^:1 1J^:1 1K:1 1 :1 1K:1 2 :1 1J^:1 1 :1 1M:1 1 :1 1 :1 K:l >i:l 2 :1 1^:1 1.4:1 1^:1 3 :1 1,4:1 14:1 14:1 1 :1 2 :1 4 :1 1^:1 1 :1 1K:1 1 :1 1 :1 ^4:1 K:l 2 :1 4 :1 1K:1 1^:1 1M:1 1J^:1 1,4:1 1 :1 Pavement Widths and Their Effect on Cost. — The hard pavement is the most expensive single item in a road improve- ment. While it is necessary to provide a width sufficient to handle traffic, additional widths which merely add to convenience must be used with care unless the funds are practically unlimited. Pavement width is modified on sharp curves as discussed later. To give an idea of the cost of pavement width the following table is compiled for 1920 price conditions. The difference CROSS SECTIONS OF RURAL ROADS 163 of even one foot in width makes a large difference in cost when appHed to a State System and the most suitable widths are open to argument. Type of pavement Assumed cost per sq. yd. Cost per ft. width 1 mile long Brick $4.50 3.50 3.20 2.20 1.80 $2700 Asphalt concrete Cement concrete 2100 1920 Penetration bituminous macadam . . . Waterbound macadam 1320 1080 Widths in Use. — -Blanchard's Handbook states that in Austria government roads have a pavement width of about 21 ft. and provincial roads 14 to 16 ft. In northern France many of the main roads have a 15 ft. width of pavement proper with 23^^ ft. of stone shoulders on each side making a total of about 20 ft. The French national roads have a metalhng width of about 23 ft. and the English main roads run from 16 to 22 ft. In this country there are two sets in general use 10, 12; 15 and 18 and 12, 14, 16 and 20. In the author's opinion the first will serve satisfactorily and is naturally more economical using the 10 or 12 ft. width with special stone shoulders if desired for secondary local service roads; the 15 ft. width with first class special stone shoulders on the main double track local service roads and the 18 ft. width for rigid pavements on double track special service roads. A 20 ft. width near large cities adds materially to the comfort and ease of traffic on commercial roads and is probably justified if the funds are available. For each additional line of traffic add about 9.0 ft. provided the traffic regulations permit a 96 in. width of truck body. There are two ways of solving the problem. The first is to build the strong metaling just wide enough to comfortably take the heavy traffic and if the nattiral shoulder material is not suit- able treat the shoulders to a width of from 16 to 22 ft. with gravel, crusher run or 2^ in. stone filled and rolled or if desired puddled or tarred making them suitable and wide enough for the turnout traffic. Referring to the widths actually used by hard traffic previously discussed this method results in the 10 or 12 and 15 ft. widths. The second way is to make the full depth of metaling just wide enough to allow traflac to pass by careful 164 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS driving' not giving the shoulders any special treatment! This method results in the 14 ft. width on unimportant roads. The 16 ft. width is harder to justify as on the main roads it is wider than necessary for moderately heavy local service travel and too narrow for automobile "turnout traffic." Where rigid pave- ments are needed 18 ft. is the minimum width recommended as ■■■■^^^^^■^ III Ill Jl 'J ^^ Fig. 56. — Illustrates normal traffic clearance, on different pavement widths. dangerous ruts develop along the edges where the 15 or 16 ft. width is used and even with careful maintenance this condition can not be avoided under heavy truck traffic on special service roads. While shoulder treatment is desirable on the main travelled roads its importance on side roads should not be overestimated. A record of a trip from Albany to Binghamton, New York, showed that rigs were passed on an average once every 4 miles outside of villages. From this it would seem that for secondary roads of this character shoulder treatment is not worth while even CROSS SECTIONS OF RURAL ROADS 165 for the 12 ft. width unless particularly bad soil conditions are encountered. Where the 10 ft. width is used solid turnouts should be provided at frequent intervals to allow heavily loaded vehicles to pass. In the writer's opinion 10 or 12 ft. should be used in preference to 14 ft. on side roads where the shoulder material is good and that 12 or 14 ft. with special shoulders if desired should be used where the shoulder material is poor. On the main local service roads a 15 ft. macadam is as satisfactory as the 16 ft. width and is cheaper under all conditions as the 16 ft. width does not overcome the necessity for a good shoulder. Where rigid pavements are required 18 ft. is the minimum width that will give satisfaction on double track roads. Effect of Curvature on Pavement Width and Shape. — Sharp curves modify the width and crown of road pavements. Width is increased to provide greater clearance between fast moving vehicles (approximately 3 ft.) and also to take care of the back wheel encroachment of long wheel base rigs (see Table 18, page 140). The crown is usually changed to a "banked" or "one way crown" similar to superelevation of a railroad curve to make it easier to take the curve at reasonable speed and to reduce the side thrust of the wheels on the pavement and the danger of skidding. Amount of Widening. — Current practice based on experience, which is the safest guide, favors the following widths on curves. note: Lengf-h ciffang(?rrh rvnaffis approj(ima-h/y 20 X Adtdiiional Width in feet (See Tabia Hail) Fig. 57. On local service roads use (Table 21). On special service commercial roads use Table 21A. The pavement is widened on the inside of the curve. The full widening is carried around practically the entire curve from close to the P. C. to a point 166 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS near the P. T. (see Fig. 57). The tangent runoff to the normal width is made from 50 to 100 ft. long to look well according to the judgment of the constructor. This is an easy layout to make in the field and serves the traffic satisfactorily. The widths given in Table 21 permit two outfits, each consisting of a 7 ft. width truck with one trailer, to pass easily. Trucks 8 ft. wide without trailers can also pass easily. The widths given in Table 21 A permit comfortable passing of 8 ft. trucks with one trailer. Table 21. — Pavement Widths on Curves of Local Service Roads AND Secondary State Routes. (See Fig. 57) Radius of road center line, ft. Total pavement width on curves for a double track road (local service), ft. Ijength tangent runoff in ft. 50 29 100 75 25 100 100 23 100 150 22 90 200 21 90 300 20 80 400 20 80 500 19 70 600 18 50 Note. — Normal pavement width (15 to 18 ft.) used on all curves having a radius greater than 600 ft. Table 21 A. — Pavement Widths on Curves of Special Service Commercial Roads Hadius of road center line in ft. Total pavement width in ft. Length tangent runoff in ft. •100 25 100 150 24 90 200 23 90 300 22 80 400 22 80 500 21 70 600 21 70 Note. — Normal pavement widths of 18 to 20 ft. used on all curves having a radius greater than 600 ft, CROSS SECTIONS OF RURAL ROADS 167 Amount of Superelevation. — Superelevation of the pavement can not be figured as there are too many variable factors. Cars take easy curves at higher rates of speed than the sharper curves which fact tends to equalize the bank crown. The pavement must not be tipped enough to make it dangerous for slow moving vehicles. The full superelevation is carried around the entire curve from P. C. to P. T. and reduced to the normal crown at P Exirot Wiolemng C.L of normal Wie^i-h >^C L.of Pervermrrt NOTEl CarrLj Thcoreitcal Profile Crown Grade arounal the PavGrrjent Cerjfer Lint? w I . Etevofhon ouHinle |<- Curve - > Profile of Transition from Normoil toBomkeol Section Fig. 58. points from 100 to 200 ft. along the tangents from the P. C. or P. T. The normal grade is carried around the center line of the pavement and the outer edge raised and inner edge low- ered to produce the required side tilt (see. Fig. 58) . Current practice favors the following one way crown slopes on curves. Table 22. — Table op Crown Slopes on Banked Curves Radius of Road Center Line in Feet 60- 200 200- 500 500- 800 800-1000 Recommended Uniform Crown Slope IK in. to 1 ft. 1 in. to 1 ft. M in. to 1 ft. K in. to 1 ft. Note. — Curves having a radius of over 1000 ft. are not generally banked. 108 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Current Practice in Standard Sections. — The following Standard Sections give an idea of current practice. Fig. 59. — Pennsylvania. Fig. 63. — Alabama. Fig. 60. — New Jersey. Fig. 64. — Maine. Fig. 61. — -Indiana. Fig. 65 — Wyoming. Fig. 62.— California. Fig. 66.— West Virginia. Figs. 67-69. — Recommended Practice. Header l:e:3 Concrete l^'t.'^f"'^'""'''- ''ffr/'""*"^ !R,3ehCn,«ni:§perl^/ /*'"='^'-C<«"-« ,l-S'3Concn ■.tl,"-J....iHBB« Headv Curbing Di+uminous Specification OasA A J'T-JConcrefe: —■^■—y\i \—l6' |< 4--?6^ ^ Hadiusl Header Curbing /•l'2'3 Concrefe ^ 5- ■\ Radius i^ Bi't'iiminous Specifica'l-ion Class B,^D, ^ .yn y Radius f , ^Reinfordng Niial i Rise to CrmniV / o„_„-, 5" One Couree Cemen+ Concrete. iReinfordngMifaf 7'^'J'"^^'/ Course Mimxfure. , 'j- Rise to Crown f- 1 o , , , , Two Course Potj+land Cemen+ Concre+o. ,5' Broken Stone ^"Macadam „ , / Rse to Crom | -'i 'perl ' / ,8"Telford Bituminous MocadanT ftnetra+ion Method . Fig. 59. State of Pennsylvania. CROSS SECTIONS OF RURAL ROADS 169 i'CemenfSand/'^ '^TcZ^. /tei^r XS* ,,../...r5w^... H — 6-.;|-|<. .75- ..u< ;;...7.g-. Vitrifiei 6!o(JH A ""*''/'"■*"? k'Cemenf Sand Bed MHiihire ■ SlggfJL'^i kJ ' ' ■ ■ ■'"■ ■III " I'i ICemmtScmdSed .M Mixture or /J'Sand Bed ->IK6" /Wood BiQcK Stone DlocK ^i'fo'^]5fone I Block Table Showing Drstance belowCen+er , Table Showinq Additional Widths of Surfacing on foreqchi^'Vfiath Rjirrtforgni) Crown g^S' Curves of Dtfferent R qdii,gnd Superelevation per R -.ffftfth Curb ?-j- 4' 5-|6- 7- a" HHiM /»•/* ^^ ?t1j* JA- <>/^' ,*" '/,■ » /" /A" i>; /* £■ ii.. »■ * a- i4' *■ j» ;* a/Fite 0-0- °- o- "■ 0" (?■ (ah Proportions for Concreit as \ shown on Cross-Sedions are J $ubjeci-hsuch Vanationsas \an 5hhd in the Specificaf-ions. Radius of C+rLinfiiH flddftiorwl Hid+h JO B.0 4-0 70 GO &0 BO so too 4.5 leo 40 140 40 /BO 35 /BO 35 SQO 30 £20 30 140 25 eeo 25 280 2S 300 20 Kind erf Surface fgjg Vitrified BlocFT^ WoodBIOckT Bi fumin p iJSSurfa a Concrefz Burfvce. f^hrbound Haaxiam Nofef (In Widening and Superelevahon Curves, carry fhe neqvlarOrade through onthe Center Ltne of the Roadrfau, and make all Widwing on Inside of Curves Fig. 59. — (Continued) State of Pennsylvania. 170 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Standard Sections of Highways of New Jersey State Highway Department ^* 3'->{<-J'->K— -,— 9' ->*<■ 9' »-< J'-^K- ^'-H Sl' t ! ->^ r^:.- 1 J'^'^f'lleii •'■*>' J<>'"l/'l'er^Sand Cushion- 1' -JwCh*- I S§f,^' Concrete' 10'' Brick -Trolljcy m CcNTtn IF. ml » , &r^nife or Behian Block ,,, IS- .>f^ — isjjt'fcl' nc--''"-*r< — *" * S' 3^^(_J*?^A«l™!^^-.w/j!:<- ^ -: ' I 1 . .J.'. ... - -■■ - t« .J ^-^.^'g^' \ 2'Bituminoas Concrete Z'Laifer of Clean Sfone 5'Mkimum Macadam, BiTUMfNous Concrete-Trollev atSide Fig. 60. — Typical Sections (New Jersey). CROSS SECTIONS OF RURAL ROADS 171 cil^y^a'a^^'' ' 0nFilli0/er4Ft- Standard Section V -ig'-o-"-. Standard Section B l<-j^o^>l^-^- 18-0-- '>^3-o''>¥-3'-0->iJk ifs3-0->tt-3-a->\/Vtil- ffacM ' Typical Rock Section 5-....- » ^rade as shown on Profile 'm^^m^^s^m^m^^m^:^ ■^"\ ir m -5'-0- -d*. ■18-0- ■tWTE: S Shoulder^ used Plain Concrete on fiUs above 1- -i.. -S-0-- tonaeteCurb: Qntdeai shown on Profile Mmm^iffhiax.'^ I fmarmg Course, ^/ I'simlei; iCrpwrt ^''^Jj^l^^ff. ^A, ^^^W%--S'-0^'---^--'^-^^-'-^-l8'^0^'^^^^^^ A0?l»'*''^i*,^'y'*'5/*®^ Bituminous Concrete WP^' onfillsabove4' ^ OradeasshownonProfile "^Z ;4"8nc/r iftrom... impelperjt "' ■' ^ Crowned Monolithic BricK Fig. 61. — Typical sections (Indiana). 172 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS I Jf 3" I ^"Concreiv Base ™'''"' K - ■ 2i*-' - ->r Type A I2 A&phalHc Concrete, X f^,^ r J.,5''Mocadam8as e. pm 4,-i Cui-l-l5tope. I" /j Sheet Asphal-t or AsphalHc Concrei^ ■' ^'Concrete Base ''ill'*-' Cu+li'l Slope-'^'hJ^—^^ Fill*' I Slope Cot l^- 1 Slope -^ TypsC. ^'Concrete Base ,^v"8it\jminited Cushion FIII4:l r "'■? ^ ?^ \ « ^ " \ Surfaced with Local Mate n'al. I* -e- A Type E. Slope ZufHIHope-' %. iff_ Ji f^l. ax HacaclamSurface^ ^l Fillli'l * 7-'e— ■■>!>■'■■— 7-e--—>W-'f-e-: U ,lf.-.f .,. "°'^^' I ''4"6ravelkase The Thickness oF Pavemerrh shov/n isfhe Minimum^if so ordered byi-he ^ p Highwaij Engineer itis increased, 'yp® "" Fig. 62. — Typical Sections (California). CROSS SECTIONS OF RURAL ROADS 173 -V^K---e-o-'' -->t<- Uof Lea than U-1 \ ^, ^ .l,,„,llJl!'!!!".'"l"""l'^^'/l»"""""IHI>}i,/,„ ■- ->(<--•- 6'-0'-->\l-6V~- ■ This Slope may tio varied ^'^'^ Section to be Used '."here Material in Excavation depenaingon Class of is Suitable for Finished Surface " ^ afin EKovurfion Hot Less than 1 " ■ " " " -M* Mate rial in EKovarfion Hot Less than l'-e'^-3-0y3-0-''>K-4'-0-">\^ ------ l6'-0- ->^-4'-0"-^-3'0"->r-J^">\l'-6\'- 5 Road fobe Graded wi'ff? aSlighfCrown^"tol' y ■■■.■^..-j,jjj This Section to be Used where a Natural if smaller Pitch than One %\ Mixture of Sand-Clay is Placed ona Clay Base shown /s Sufficient- use the ^ ti One Indicated ty Pelted Line '^'2 ..^li0L....sio-"--»<-4!-O--^- - 'd-z:;^. Not Less than - — l6'-0"- 6% />j>. ' //J^'77j/^^^^^'j!^^0fi^:i/!^W^/! -if-4'-0"-->Y----6'-O^'--->\l'-6^-iA ^, . ^ .. 7", ,, . Road to be Graded Flat- and m Depth of Pitch mau be This Section to be Usedwhere be Pished as shown with R?ad Kmsed in well Draimd Sand ? SP^""?' Mixture of Sand-Clay Mach by Raising Sides and IS Placed on a Sand Base Lowering Cent before nl/rrt'nrr '^/yn/J f~[/ji/ MSH'- — -6'-0'----f--4-P-->\fi-- I 1 67.^,'! /lot Less than 16-0 i"/' placing SandClaj/. ...■^--4lo''->^—-6'-(^"—->(ls'i I a'l.^"\ I ^le It , ti ' >t<-j-r ■ This Section to be Used where clan tabe placed Looseli/fo a Pure Clay is Placed on a Sand Base Depth ofAppraitimatslii6"on Flat Subgradeandtobe thoroughly mixed with Sand Base by Plowing Hot Less than and Harrowing ,■1 ;a, jK-. 4.i-oi:.ii<^'.o--MJ'-o-wm ,10' i^'^ ThisSectiontobeUsedwhere '^X^rf&foSrJ&d Sand IS Placed on a Clay Base sCbgradeandfobe thoroughly mixed with Clay Base by Plowing and Harrowing Fig. 63. — Typical sections (Alabama). Sand Clay Roads. 174 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS CROSS SECTIONS OF RURAL ROADS 175 <--- (?ise .^%. ■O'l ->|< IZ'-O- ->i 7/g?_-->J<- 7-6- ---,-->! J &echon"A" Asphaltic Grcivgl toS+a+ion -I ^11 , Rue to Crow n if o I.' 1-0 sU^v, ->j<: glol-'-—-y, b^S^ SecVion"c" Gravel Track \H^ Station to Station r C. L. IZ'-O- -if- static Concrete to Station |< -io-o"foiz'-o'^----%---io'-o'%iz'-o^'—-i\ I i f^'^s fo Crown i "a, / ' L- jk- ->l ^t^ Section "E" tarth ^^^ Section Station to Station y,...,..io'-o'J- ^.- -lo'-o'^ ^ Eqrth(Mactiine Work) Section F Station toStation Fig. 65. — Typical sections (Wyoming). 176 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 1st- 111 CROSS SECTIONS OF RURAL ROADS 177 ' >AIIPoads shontn here are PO CfoC. ofPrtches- h — -j|-/4'- I /' k- Concrete C'afSides,mfCenfer. ■■ -^J Type ( Plain. I Etev-otTheorefigalSrode . ■X /' K- ConcreteS of Sides, 7c tCeir/er 2: ■. -K- >■ »» ^^@ g^^gy OnSvepSrades Beinforcinq Meia!. Types Reinforced. ^-'6.'i«-, 9 Concrete 6'of Side,6iaf'CenlKr S Slope I" per Foot] Type 3 Plain. ->I/'K- ' S' ->)<— -3'— X— -i!-> :T Concrete 6 e{tsides,6zattenten "" i^ ' Slope \" g^S Slope I' per Foot ' Subgrade % Flat etcepitaf Shoulders. --H / ' K- Typ6 4 Plain. Fig. fiG.— (Continued). Recommended Practice in Typical Sections High Type Roads. — The following figures illustrate the author's ideas in regard to desirable sections for high class roads under different grading conditions. Macadam Roads (Figs. 67 and 68) Single and double track. Rigid Pavements (Fig. 69) Double track. Car Track Sections (Figs. 70 and 71) 12 178 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS OrcuhrArc PnvemenfCrmm, Cut Slope 1^:1, jlFillSlope4:, of hills or where there is a small amounl-of surface wafer in the elifches -ZS-SO' Typical Sec1-ion (Shallow Ditch) s>k- iS'-So'-- -^ -SO 'folOO 'ffighfoflVac/ I -d^^ Circular Arc Pavement Crowrr,, ■Crown Srai^e Cut Slope 1^: I.. 10 folZ -20-0- H <- -24'fo28'- — - — > Typical Section(Meolium Ditch) Circularfirc PavemerrtCmwn ,11 i ^CrvwnOmc /e fi ~^-^^\<-- Typical Half Section DeepCut^ on Grades le5sttian57oaiil IgLg'L. Typical Section (Shallow Ditch) hacadam or Gravel Shaulders-. Circular Arc PavementCro^n S*./ i 5\o£' Typical Section (Medium Ditch) eo'fo IBokghtofWay— •^ Difch ^ ■ Typical Shallaiv Pitch Secfim - Typical Section (Special pitches) Hafural '^ZZ^rJ^i?eji^3. Ditch note: Wiiere a large amount of water must be carried alorrg theRoadj separate the fecial ditch from the Road Section and keep If- as near the fence line as passible Bench Cut out of Slope on Curves to increase Sight Distance Typical Half Section Deep Cuts on Grades less than 5% Concrete Guard Rall—'r\ ^-Crown Typical Half Section Deep Cuts on Oracles of 5% or more v\ Typical Side Hill Section J/: Ditch in Half Section Fills less than4'Deep Half Section Fills over4'Deep Ditch in Cut \ Fig. 68. — Double trank macadam roads. (Suitable for local service or second- ary state routes carrying from 300 to 1800 vehicles per day in the summer season.) 180 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Y" - -Pavement Prop) ^ . ^-Backfill Bofhm Course Macadam Top of Rock Excavation Typical Rock Section notes: Rock excavation will be paid for to an eievafion IZinches, below ttre surface of the finished road and no rock excavation will be paid for below Ihis elevaf/'or? orouhide of the neat side slopes shown on the plans- No part of the solid rock shall be closer than 6 inches to the top of the finished ^K f ion. All depressions under the pavement p''Oper lower than the bottom of the bottom coarse of thepavement shall be backfilled witt? stone chi'ps,filled with band or gravel j^xnd rolled or lamped until firm and haird. This back fill 15 included in the price bid ivr rock excavation . ^^ S^ "SI "fel I -fej^ /^ / A ■ & I 2 Total Superelevaffon Superelevation ^! b' _ , . , ,' ' «: £=! Theoretical Grade ■ C.L.of Pavement;' Table of Pcivernent Widening | Radius of Rood Center Line in Feet Total Width Pavement on Curves "t" Feet 5C Feet IS « 100 •' 200 « 400 •' 29 Feet- 25 n 2i •> 21 1 20 20 •' 19 » 18 " 100 100 so 90 10 SO note: Uie normal Favemenf Wiel+h on Ci/rve& havin0 oi radius of more than 600 feet Tabic of Recommenoieol Total Depth of Macadam Pavements on Different Soils Rxftjment in Cut or Fi'M In Cut OnFillslessfhanlft deep » " IftfoSft y » over 3 ft. " Soils Sand or Gravel Loam 9 'toll 9 "to 12" 9" 8" ori^idfsflnj IS"fo24„ IB'to?4" l2'fo!S" 9' FiQ. 68. — iPoniinueS). CROSS SECTIONS OF RURAL ROADS 181 182 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS iT'^'ExjxmsmJam^ Mvay Rail Channel Filler nZHix fun. Expansion Joints p^f^Cnmnf:!'/! K JikifieJ arWood Bloch. i'Cement Sand Bed! ^^ **' 5" ConMe hl-B w KS' YiMffed Block Gu#er l4Mi,fimorr^ndBed,""^T^\^'°f .. , , ^':J''T°»* ^ Construction for &ngle Car Track Roads ^ ^5 Expansion Joinh^ Jbilmy Rail Chaniiel filler ' li^tlixfuri Expansion MM- ^^^ ^ Cwwnj'l /) I \ ^.-ViMfied orWood Blocks i 5>|K- 5'Cotxreh 5'*^\> iXemenf Sand Bed /-SS Mllixfureori'Sand Bed Vitrified Bloch Concreh Suffer Bituminous Construction for Double Car Track Roads Fig. 70. —-I7.5' Fig. 71. — Car track sections. ^• MOUNTAIN ROAD SECTIONS Discussion. — The desirable requirements for mountain road sections are the same as for the roads previously discussed but on steep sidehill work the width of grading used for ordinary topography would be prohibitive in cost. As most of these roads are natural soil roads the crown is the only element of the section not covered in the previous discussion. For the gravel or stony Symme+riccil Crown wi+h 6uarcl Rail One Way Crown No 'euard Roil. Fig. 72. material usually encountered % in. to 1 ft. is generally satisfac- tory. For sand or heavy soils 1 in. to 1 ft. is better practice. The old idea that crown should be increased on steep grades has been abandoned for while that expedient undoubtedly helped the drainage it caused more inconvenience to traflSc CROSS SECTIONS OF RURAL ROADS 183 than it was worth. In many cases present practice decreases the crown on steep grades to give better vehicle control. Crowns on mountain roads are also affected by the absence of guard rail or other safety provisions. The ordinary symmetrical crown* is used where wall or guard rail protects the dangerous outside slope but on many roads so much rail would be needed that it is prohibitive in cost and where it can not be used the road is tipped one way in a continuous slant toward the hill so that if Fig. 73. — Good example o£ the "one way crown' careful clearing. section. Note also the a machine skids it will slide in against the cut slope. This kind of a section is not as comfortable to ride as the ordinary crown but if the surface is at all greasy the element of increased safety outweighs any minor inconvenience of side tilt. Effect of Width on Cost. — The width of section has more effect on cost than any other part of the design. On a new side hill location the relation of width to cost can be roughly established. It will of course vary for different side slopes of the hill and different cut slopes of the excavation but the relation will be 184 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS approximately as follows, for balanced sections (Table 23, page 200). AsStTMBD 25° SiDEHILL SlOPE 1 : 1 slope in cut. 1 J^ : 1 slope in fill (S- 8) 10 ft. width (ditch to outside of shoulder).. (S-10) 12 ft. width (ditch to outside of shoulder).. (S-14) 16 ft. width (ditch to outside of shoulder).. (S-16) 18 ft. width (ditch to outside of shoulder).. (S-18) 20 ft. width (ditch to outside of shoulder).. . 4,300 cu. yd. per mile . 6,100 cu. yd. per mile . 10,200 cu. yd. per mile . 12,800 cu. yd. per mile . 15,400 cu. yd. per mile We may say that in general a 20 ft. width requires about 33''2 times as much excavation as a 10 ft. width. The relative cost of Fig. 74. — "One way crown" section. Note the ridge of earth on the outside of the fill. This is often done to increase safety and reduce side slip. It is in the nature of a wheel guard. different widths is also affected by the amount of rock excavation which is generally much greater for the wider widths. This depends on the depth of soil overlying the rock. This element affects the cost so much that in certain cases it has been found cheaper to build two separate single track roads for short dis- tances rather than one double track highway. Mountain roads are classed roughly as double track or single track, meaning the same as for railroad work, a double line of traffic or a single line with turnouts to allow passing. As each foot of extra width is costly it is important to determine the CROSS SECTIONS OF RURAL ROADS 185 minimum width of grading that will serve the purpose for these two classifications. Minimum Width Sidehill Section. — If the roadbed is benched out of solid rock a narrower width will serve as the entire width is firm and stable. If the section is a balanced section part in cut and part in fill it must be wider as embankments on steep Fig. 75. slopes are hable to settle, slide or washout and it is not safe to drive as closely to the edge as in the first case. The amount of the road "in solid" is therefore the prime requisite and . . "ft. in solid" is often used as the specification for contract road jobs where engineering design is not used. Present practice favors a minimum single track, total grading width of 10 ft. in rock or where the outer embankment is sustained by a retaining CASE NO. J All"ln Solid Fig. 76. wall and a total width of 12 ft. for the ordinary balanced section, in earth. Balanced sections are generally used up to 30° side slopes and beyond that toe walls or retaining walls are necessary for earth sections. For a 30° side slope a total grading width of 12 ft. results in approximately 7 to 8 ft. in solid cut. A double track section requires a minimum total grading width of 14 ft. in rock or wall sections and 16 ft. in balanced earth section which 186 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Fig. 77. — Narrow single track through cut section. Fio. 78.- -High turnpiking (gravelled) with deep ditches to raise road on flat above spring floods (Utah). CROSS SECTIONS OF RURAL ROADS 187 FiQ, 79. — Ordinary mountain road turnpiking (Colorado). Fig. 80. — Simple turnpiking in easy location Targhee national forest (Idaho). Note the comparatively narrow width of clearing for small Jack Pine growth. 188 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Fio. 81. — Temporary timber cribbing to hold fill. ^^5f* Fig. 82. — Example of ordinary rough rubble retaining wall section. Note. — This is not first class work as the face of the wall is too nearly vertical. A larger face batter is desirable. CROSS SECTIONS OF RURAL ROADS 189 gives approximately 10 ft. in solid. These same limiting widths apply to turnout sections on single track roads. Where guard rail is used 1 ft. should be added to these widths. These widths are, however, very skimpy and if the money is available at least 2 ft. additional should be used. K^BS^^^^afe.'' ^^^Hfi^l ^^^s%»^^ ESktv ^m^ ■ i-fe;a*^'t ■'#"%. ^ 1 w'^^i kv' ^-^l^rjl mWBKK m ,1^ p ^^*^^"'<^ ^m ^ mw''~w^:'-^^ H^^M r|"^.^X,.,,"C '^«^lfe feStrfvIC'' .- '."^Ci m t..X^t^fM 'lg^Z:m ^^K Pig. 83. — An example of poor unsafe wall eonstruetion. Turnouts. — On single track roads turnouts are constructed at sufficiently frequent intervals so that drivers can see between them and there will be no danger of meeting at impassable spots. This generally requires from 5 to 10 to the mile. The minimum satisfactory length of turnout is about 60 ft. and the grade should be as easy as possible at these points. 190 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS a O H^l .9 ^ in ia ■a '> ■3 O T 00 d CROSS SECTIONS OF RURAL ROADS 191 Fill Sections. — Through fill sections must be constructed wider than sidehill sections as the sides are bound to slough off under weather action and all the elements of wear tend to decrease the width; 14 ft. is considered the minimum width for a single track road and 20 ft. the minimum for a double track. A symmetrical crown is advisable on fills even on curves. Where guard rail is used increase these widths 2 ft. These sections occur on only a small per cent, of the length of mountain roads. •" j^^^H| ^S^^^M "^fw^ j^^^M 1 ^^I^K^Kt^^^^^^^^IP'j- ', ^i 1 ■ ^ ^^^ M Fig. 85. — "Bench section." Through Cut Sections. — These sections are rare in occurrence; the minimum width, ditch to ditch, for single track roads can be considered as 12 ft. and for double track 18 ft. The use of minimum widths for either through cut or fill sections on moun- tain roads has small effect on cost and for that reason more liberaUty in their widths is allowable. Turnpike Sections. — Where the natural ground cross slope is less than 5° turnpiking is the usual construction and the difference in cost of a single or double track is so small that it is not worth considering. For this class of section a minimum of 22 ft. be- 192 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS tween ditches will apply to any road and a width of 24 ft. is generally used. Selection of Section. — Plate D, pages 194 to 199, illustrates typical mountain road sections, pioneer districts. The turnpike section is used up to natural ground side slopes of 5° for continuous balanced work. Fig. 86. — Tunnel section. The sidehill sections are used above 5° for continuous balanced work. The one way crown is used on all single track sidehill sections where guard rail is lacking. The one way crown is used on unprotected double track roads where the side slope is greater than 15°. The sjTiimetrical crown is used on protected double track roads and on unprotected sections where the side slope is less than 15°. Through cut and fill sections are used where required by the profile. CROSS SECTIONS OF RURAL ROADS 193 Superelevation is used on curves in cut but rarely on high through fills. The ditch on the upper side of a superelevated through cut section can be omitted if the cut is short. Cut and fiU slopes depend on the natural material and climate and were discussed on page 160. There is too much tendency to use steep slopes to save on construction cost although exces- sively flat slopes are not necessary or advised, it being cheaper to take care of minor slides by maintenance. (For effect of cut slopes see Table 23, page 200.) Fig. 87. — Half tunnel section. Wall Sections. — -These sections are used where the natural hill slope is practically as steep or steeper than the stable em- bankment slope. Toe or retaining walls are necessary for earth embankments where the natural slope exceeds approximately 30° and for rock fills where the natural slope exceeds approximately 40°. Wall details are described in Volume II and III. Sur- charged breast walls are to be avoided if possible. Intercepting Ditches. — ^Where considerable water runs down the uphill slope intercepting ditches are used to protect the cut 13 194 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS slope and relieve the road ditch of excess water. These ditches discharge to the nearest cross culvert and are an important part of the design. Bench Sections. — Bench sections are used in rock ledge work. (See Sections S-10, Plate D, and Table 23, page 208.) Plate D. — Mountain Pioneek Roads. Typical Super-Elevafed Sections on Curves. Never use aSuper Eleva+ed Secfion where the Inside of fhe Curve is on a Dangerous Down ward Slope. Use Super-Elevaftona only on Curves havinqa Radius Less+hanSOO-fh Use fine same Super-Elevation on 300-ff- Radius Curves as on 1 00' Radius Curves. The CenferLine Elevafion and PorHon of the Section on fhe Inside of fhe Curve remains Normal^ fhe Porfion of fhe Section on fhe Outside of the Curve is changed as indicated below. C.L. C.L.Croivn Any Width Uniform Slofie^ ' / immiliimm CM. Profile _Qrgde_-ji Typical Super-EI«va+jon In Fill. 'PCSfi!e,6rad^ 'Standard Depth Typical Super-Eleva+ron I Super In Cut. CROSS SECTIONS OF RURAL ROADS 195 Plate D. — (Continued) Typical Turnpike Sections De»lgnai-ecl T-Sec+ion. Crown Elevation i 16' J,/*? I I CLPro-fi. e Qrade Sec+ion T-12 Crown2-'+ol' 4 5-->* —16' — -f-^'-H ? &rade Sec+ion T-I6 Crown^+ol' ♦-5 '—• >l« r?0'- Crown Elevafion I 75 GiOote 20 ,.>k— f— > _c%!2h'li Section T-20 Crown^"+o l' Note' I Where Side Slopes lie between SDeg.andlSDeg use a Combinertion of 5 and I' Sections, usina is Sectionsin the Cut Side and i F Sections onfheFillSider- Note.- Use Turnpilte Sections on Slopes up to SDeq. 196 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Plate D. — {Continued) Typical Through FillSeo+ions Designated FSec+ion&. No-tv' Fill Slopes I'l Rocif Fills. li'l Ordinary Earth. I^'l Special Cases. Utilise Wasfe Excavation by Flaltemng 5lopss in Fills. C.L. of Crown Elzva+ion . -i X C L. 16- ^ Crown Flevciion C.L of Crown flevafion^., L f., rrafile&radei -20 J vmimmkimm C.L Prvfils 5racle Ooo-i-ion V-ZO Crov/n 3-! l' -^4 C.L.Profile CROSS SECTIONS OF RURAL ROADS 197 Plate D. — {Continued) Typical Side HillSec+ions nofe: Oesigncrt-ed S Sec+ion&.. (Use these Sections onlu where Side slope is greater than ISDeg. On Side Slopes between SDeg. and ISDeg use Two-Wag Crown, except in Section S-lo. Frecjuent Turn out Widenings must be used with this Section. SectionS-8 Is the Mintmumm Rock. Section 5-10 is the Minimum in Earth, C.LPntfi/e I Srade: !• zr_ IS'. One-way Crown j+al' CLof Crown I Elevation-. CL.of Crown Elevation. J/' / 'f/le 0rade 14" Hion &-I4- One-Way Crown^to l' —16' ¥s'l CL of Crown \ Elevation- '■ T" '•; Ssc+ioh S-16. One-Way Crown ^tol la.' >!|<" " t-l U 3- S (J a '^ n N >. 10 3 00 H H H rovO 1 •2 -d- - M CO li >> 3 fi ft 32 = ■a M CJ 10 10 pi to s CO »o w +» ^ .3 1 T)- . fi] >." - Eh S p. 3= S (J Ss U ^o •d 000 a s u rS 10 10 •ST, o o p< Q H 0^ « w 00 tl " < 1 »v a o> § t T3^ - Is tfl IH 0) X- - s^ tf a bl 3 ^ :; ,■3 " h •d u « 3 1 .2S 5 U Ih ClO OJ ■2s Efl 5 U 1 -d- - >> oj a M h ■^ m ft 3- ; P a H N '^- 000 < H >. xo VI a 5 r^ 10 C 4) ■$■3 oi Cb u 3. « Ph ■d, - ft) > < en \ ^ !>. •d i1 !>, cno 3 M royD ?l \n g H g 5i u Pi i ChOO g eg to 3 H gS CO **H U ?l pi i tl ^ pi 01 *a3o 1. " D bo l-^s ja ^ p -1 KH 2 3^ I. 3 gt CROSS SECTIONS OF RURAL ROADS 201 ^001 jad 'pX *n3 9d0]g ^nQ 3ITUI J9d -pX -TIQ ooo ooo oo a^Ttti jaa *pA "nQ ^oHrfNHw mw OOO ooo Oi lo in »^- o o w H H « (*)10 00 ^xx :s^s: s?: ooo ooo ■"to O OOO H N (0*000 ooo OOO lOO O OOO ooo rf t^ HOD H N roo O OOO O »r O M ro^t t- w o H w OOO O o o too o o 0\0 N N )Rx:sx^ ooo O 00 O O O OkOOco 00 i-K>-f>>>-K iJs H H H H 0»00 t- O t-00 O "t M N fo ^ ifl r-00 ooo ooo oo loo w o wo »oo ° 1 «H H S 8-S u :3 3 d u « o 5J P « S ^ _. M S Q) +J w y w d rt O ^ .2 5 ^ 1 -"^l O 0) ■** •S .'S "S .2 o ° V. fc So " mIS O ft (0 4J . •M 'J Ih CO t; « 2 5 ^e <"- ojK>' 202 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS / 06? c3'3 "m do .S Q S ** :3'3.S «j g,« els oo t^-oo ooo 000 00 •a a a P.6S U 0} o d ^:| C B-J oli>,n n (^ g} S ^-o .2 0-" m oj-S '^1 s ■ V4J M a taji B1 •S-3 S"3 Tg.S 8-S rt 4)43 o S a I 'IS *^ M O El pJi^Sg'l &£ E Bl3'"'3 CROSS SECTIONS OF RURAL ROADS 203 U 04» ***+* bo It: I si ""So u g *■ c.a "5«^ 5 00 o" **** 2-« >^ V ^ bO ot32 o ^p. g «13.9 t^tJ ■ < 32 r « o fl '•" H *< d t- S* 3ni ro *-< «>0 M CO «0 O Ov r-io ro woo H roo w Oi r~ M M fp _ ooo 1/1 o o O OvO W fO o o o o o t* 00 00 CO (NO H N OOO OOO H N O H N «t :ss;;sx O\o0 »~. O t-oO O -t o o ooo 00 .o S ■2^ ^ b o 9 u o rt o a d Q> « h fr 204 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 2 .S H O o a < o Pi 1h Q) *; C3 tf) ■2-2 -2 g3 ■frets s S o o m « •goa.S-g o S t^ « •*-<+? o c 3 . -. O J5 C 10 ifl ^ c tots 6?a « o mS •"•3 °t3'Cti ° o S a" 0.33 c " " " " ffl g ^.-s Sg<:j3-o« « "• . 3 1^ 3.S 3 °^t O 3 « « rt. .2«iBoi3 3I!M-'3 ^ooi Jad -p^ -HQ 3*ois rod adois jnO 'IJPJ -tsa •p_x^ -no ,ooi jad *pj^ 'TiQ s^oiS IM adoig jno anM jad -p,^ -nQ ^ooi jad ■p_;^ -TlQ 3-fsF4\ rHSii4\ OOO romo TfOO O M « lO >^f-Kr-N f-K Qicc r- %o r-oo o ■* ooo ooo oo loom owo mo H w N CI m fO ^ o da °o ss 0} 0) +2 rt ■o a s? ■3S £-2 og-S E2-S|5 Ills! < bHjjU CROSS SECTIONS OF RURAL ROADS 205 O & o 9 o « •*-<'3 ^ U fl P« o.S » 3 S c " _^5o §13 o « •0'"*a HO J1 ■a J; o b O !>.*3- I S3.a "9 u a 3I!W ■i3no •^ » in H K S "n £ HgSS •saa ooo ooo oo oooo ooo oo ro O 00 t^oo n »o in wwro »0t-0 ■*« >^S.rf\iH\ t4\T-A.r4\ F^i-\ ooo ooo o M M ^ O Ol'^ 't 00 »OC0 H M P< OOO OOO O loO OOO t^OO OOO Oi l-l H W M h VFVfVjil VfV*V* OOO OOO H «10 OOO OOO 00 -^OO OtWOv 00 OiO . w M to W l-l W M H M »;s;xx^^ OOO O o to o o o o r-rl-oO M It O »0 Vf^JiVJi V»V* OOO O lOO O O H ro-O N 3::3;3;x Nflqv^'v^ Vfl <\f?^fK Osoo t* vo r-oo o ■^ ooo ooo oo uiom 0»00 »oO ■OS? H a u 3 2 o «-,3 3 f'S g rS^ (1) ■^ >» Si tfl . •S3 c rt ^ M 1 u ■»» s T^i •d "rt ^ 2; ■» .y .1^ as •ri Hu ■s Si: ■5 H'SU. g-a.s-og 19 B iS S 2 ^111 ^^•^S^ a^op. M3 J, "g <1 aH a, a S -S-S 206 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 8S3J3Sa "I SPISlliH JO aaoiS 6B0J3 CROSS SECTIONS OF RURAL ROADS 207 Tablb 23. — Appboximatb Quantities Wall, Section Minimum Single Track Road Section W-8 Double " " " W-12 l.E or 3.0 TYPICAL SECTIONS 30° & 35° Slopes Ditch Excavation Makes Fill Back of Wall TYPICAL SECTIONS 40 & 45 Cross Slopes Borrow Pill Required Note. — Rough rubble masonry walls to have outside face batter of 3" to i' and a bottom width of M the height. The foundation to be carried to a firm strata. Natural Ground Cross Slope Approximate Quantities per 100' of Road for W-8 SEcnoN Wall Masonry Ditch Excavation Used in Pill Borrow Excavation for Balance of Fill Wall Excavation Waste Total Excavation 45° 46 cu. yd. 55 " " 100 " 135 " ■' 55 ou. yd. 80 " •' 30 " " 45 " " None None 90 cu. yd. 100 " " 15 cu. yd. 20 " " 35 " " 45 ■' " 70 cu . yd. 100 " ** 155 " " 200 '• " Table for Minimum Double Track Section W-12 Natural Ground Cross Slope Approximate Quantities per 100' Wall Masonry Ditch Excavation Used in Pill Borrow Excavation for Balance of Fill Wall Excavation Waste Total Excavation •30° K 45° 65 cu. yd. ?° '.'. '.'. 180 " " 250 " " 100 cu. yd. 140 " " 30 " " 45 " " None None 200 cu. yd. 250 " " 15 cu. yd. 20 *' " 115 cu. yd. 160 " " 275 " " 375 '■ " Note. — Above 45° ground slope use Rock Bench Sections, except in un- usual cases. * Retaining wall section on 30'' cross slope is not usually economical. 208 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Table 23. — Table of Approximate Quantities Road Benched out of Rock Using S-8, S-io, S-12, S-14, S-16 Natural Slope of Face of Rock Ledge Cut Slope Approximate Excavation in Cu. Yd. per lOo' for Different Sections •S-8 S-io "S-12 S-14 S-16 50° 60° 70° So- Vertical Half Tunnel 350 cu yd 600 " " 560 " " 460 " " 500 cu yd 850 " " 800 " •' 550 " ■' 660 cu yd 1,200 " •' 1,050 ■' " 680 '• " 870 cu yd 1,550 " " 1,400 •* " 1,100 cu yd 2,000 " " 1,800 " " ' Minimum width single track in rock. '* Minimum width double track in rock. Summary of Sections. — The Standard Sections in current use are generally well designed but their use in actual design is too uniform and mechanical. That is, considerable needless grading often results from the failure to vary the section shape to conform to short special local conditions. This point is taken up in detail in the third book of this series and results in noticeable con- struction savings. Ditches are also often needlessly deep and dangerous and fail to regulate ground water which is the only excuse given for their use. The use of road ditches for farm drainage is poor policy. Any system of special farm drainage should be separated from the road design except in the matter of culvert elevation. Right of Way and Clearing Widths.— The width of Right of Way is determined by required grading widths, by required clearing widths, by possible future widening of the grading and by a minimum sight distance where buildings may be erected directly on the road boundary or where a heavy stand of brush or trees grow on the land back of the road boundary. While it CROSS SECTIONS OF RURAL ROADS 209 is desirable to provide sufficient width for all the requirements of the future the use of a needless width results in waste land which might better be utilized for farming or b\iilding purposes. There have been cases of rights of way 500 ft. wide in flat country which were merely ridiculous. U -24'fo32'- -- eo'fe lo'Minimum- FiG. 88. The ordinary double track improved road section varies from 24 ft. to 36 ft. ditch to ditch. The cut and fill slopes back of the ditch line rarely take up more than 10 ft. in ordinary topography and experience indicates that a 50 ft. width of right of way will as a rule be satisfactory as far as the grading of the ordinary rural road is concerned. Practically all engineers are agreed FiQ. 89. — Parallel rows of trees, uniformly spaced, make for attractive roadsides. A state highway near Lenox, Mass. Note also shallow ditch and the safety of this entire roadway. that tree planting and sidepaths for pedestrians are only a matter of time and that an allowance for improvements of this kind are reasonable. Such an allowance would naturally increase the normal right of way width for the usual local service road to approximately 60 ft. 14 210 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS On State and National routes where four lines of traffic are anticipated a normal width of 80 ft. ought to serve satisfactorily except as modified for deep cuts and fills, sight distance on sharp curves and clearing widths. Modifications for deep cuts and high fills show up on the cross sections. Modifications for sight distance can be worked up diagrammatically for each case but in order to give some idea of the approximate increase in right of way widths for sharp curves the following tables are inserted. Table 24. — TABiiE of Distance Between C^ of Road and Right op Way Line on the Inside of the Curve to Permit Certain Specified Sight Distances Assuming that the Line of Sight is not Ob- structed Within the Limits of the Right of Way and the Curve IS Longer than the Sight Distance Required 200 ft. Sight distance 300 ft. Sight distance 400 ft. Sight distance 500 ft. Sight distance line radius in ft. Values given below are the distance from the road center line to the right of way on the inside of the curve to give the sight distance shown at the head of each column. 100 150 200 250 300 400 500 100.0 38.0 26.8 20.8 17.1 12.7 10,1 150.0 64.3 50.0 40.2 29.2 23.0 200.0 100.0 76.3 53.6 41.8 250.0 134.0 87.6 67.0 Table 25. — Table of Radii of (^ Required for Different Sight Distances and Different Right of Way, Widths Assuming that THE Line of Sight is Tangent to the Right of Way Line. — This permits building being erected on the line. This table indicates minimum curvature for certain limiting right of way widths metropolitan districts. Total width of right of way in ft. 200 ft. sight distance 300 ft. sight distance 400 ft. sight distance 500 ft. sight distance (tl of road located in center of right of way Values given below are the approximate radii in ft. of the road (£_ to give the required sight distance 50 60 80 100 212 182 145 125 463 390 301 250 812 682 520 425 1262 1056 801 650 CROSS SECTIONS OF RURAL ROADS 211 Modifications for clearing depend on the height and thickness of the growth. The object of clearing is first to remove growth within the slope lines, second to provide a clear view and third to clear sufficient width to allow the sun to reach the road, dry it out and melt snow. This last depends a good deal on the direc- tion in which the road is running, the altitude and geographical location. It is entirely a matter of judgment (see Figs. 39, page 139, and 80, page 187) but should be liberal in the forest districts and ranges from 30 ft. in low growth to 150 ft. in adverse locations and high growth. In high altitudes roads are at their best closed in winter and if careful location and Uberal clearing will increase the length of the open season it is well worth while as in effect it increases the usefulness of the road by 15 to 25 per cent. Recommended Practice. — All the evidence seems to indicate that the following normal Right of Way widths will be satis- factory provided they are modified for unusual conditions of grading, sight distance and clearing. Main routes, ft. Secondary roads, ft. Local roads, ft. Mountainous regions (cheap land) Farming country (moder- ately cheap land) Metropolitan districts (ex- pensive land) 150 100 80 100 70 60 100 50 50 CHAPTER VI DRAINAGE The success of any road depends largely on an effective drain- age design. The fundamental idea underlying the various schemes is to prevent ground water from reaching the'subgrade and to^get jthe-surface- water away f rom 4;he_travelled_ way and out of the longitudinal ditches as soon as possible. Fig. 90. — TJndrained road conditions (Wyoming). The problem of drainage may be divided into three parts : 1. Cross Drainage. 2. Longitudinal Surface Drainage. 3. Underdrainage. 1. Cross Drainage includes Culverts and Bridges located at natural stream crossings, natural swales, artificial drainage or irrigation ditches, low points on the road profile, equaMzing culverts where the road passes through a naturally depressed sump area, overflow culverts in flooded areas and ditch relief culverts on long grades. Long span bridge design is a specialized subject ajid no attempt is made to discuss it in a book of this kind which will only con- sider culverts and small span bridges. 212 DRAINAGE 213 The points to be considered in culvert and bridge design are: (a) Location of structure. (6) Area of waterway. (c) Slope and elevation of inverts. (d) Design strength for dead and live loads. (e) Length of structure. (/) Economical type of structure. If the funds are limited the cheaper types may be used but all necessary structures must be built not only to protect the road but to establish a reasonable drainage scheme which is recognized Fig. 91. — Temporary timber box culvert (Utah). and becomes fixed by usage as the country develops; it is very difficult to change surface drainage in well settled districts without annoying and expensive lawsuits. Justifiable economy in culvert and bridge design' lies very largely in the selection of the most economical type of structure. This is important and well worth while from a money standpoint. The omission of structures, reduction of reasonable waterway, dangerous shortening of length, weakness for reasonable modern loads or high waterways causing ponding are poor economies. For high class macadam or rigid pavement roads, the cost of ordinary culvert work exclusive of long span bridges does not generally exceed on the average over 3 to 8 per cent, of the total 214 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS cost of the road indicating that liberaUtyin the essentials of design do not add noticeably to the total cost of a general road system, (a) Location of Structure. — Poor location of structures is the most prevalent fault of the usual road drainage scheme. A good location fulfils the fundamental requirement of getting the water across and away from the road as soon as possible. It also con- FiG. 92. — Good example of log stringer bridge (State of Utah). siders the desirability of a fairly uniform velocity of flow of the water in the channel and through the structure in order to minimize scour or silting up of the waterway. Sharp changes of direction in the flow of water are undesirable. SIMPLE ILLUSTRATIONS OF CULVERT LOCATIONS Case I. — Simple right angle stream crossing (Fig. 93). There is never any doubt in this case. The structure is placed directly in the stream line and at right angles to the road center line. :Si-rQam Channel C.L.of Roaa!,, F^nce ■■ i-Sj-recxm Channst Fig. 93. Case II. — Stream crossing on skew angle (Fig. 94). In a case of this kind it is desirable to place the culvert in line with the natural stream channel. DRAINAGE 215 The right angle location marked "Poor" saves length of culvert but generally requires four sharp changes in direction of flow which tends to check the velocity of flow and to produce scour and silting up at the angles. Considering maintenance costs it is generally poor economy unless the creek channel can be changed for some distance. Unusual relocah'on ofChonmbY /..■Usual sharp angle Fig. 94. Case III. — Where stream must be carried along road for some distance (Fig. 95). The location marked "Good" gets the water on to the low side of the road as soon as possible, minimizes sharp changes in the direction of flow and is desirable unless houses or barns are located on the low side of road between where the stream strikes and leaves the road. „• Fence / Poor -A 4> jT C.L.oflfoad' locofHon \^ ''LociPl^ion Ho. 2 jf\ 1^0. 3 T if^^ream Channel -^ <^ood loca-Hon Culvert- No. I Fio. 9.5. Location No. 2 is desirable where houses are located on the low side of the road but not on the high side. Location No. 3 is not desirable under any conditions as it checks flow and causes trouble by reducing the culvert capacity and encouraging scour and silting. The author has a number of cases in mind where locations of this nature have proved very unsatisfactory. 216 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Case IV. — Ditch relief culverts on side hill location (Fig. 96) . Ditch rehef culverts on side hill locations are very desirable as they minimize ditch scour. They are placed at any natural gully Profile y Fence [< Spacing c?fCulveris n Fig. 96. formation and on uniform slope formations are spaced from 300 to 500 ft. The spacing between these ditch relief culverts on sidehill locations depends on the grade, soil, ditch hning and width of Fig. 97. — Open slat top relief culvert. Note angle with (^ of road. Pioneer road Colorado. section. A narrow 10 ft. mountain road requires more rehef than a 20 ft. road in the same location as even a small washout will put the narrow road out of commission while a moderately DRAINAGE 217 bad ditch scour will not stop traflBc in the second case. No set rules on spacing can be given but current practice favors ditch relief culverts on 8 per cent, grades at intervals not exceeding 300 ft. and on 5 per cent, grades not exceeding 500 ft. If cobble gutter Fig. 98. — Typical inlet (mountain road) for pipe ditch relief culvert. or concrete ditch Hning is used the distance can be materially increased but is not advised. On long cut and fill hills drop inlets into storm sewers are sometimes necessary to prevent overloading of the ditch. Main Road Macadam Side Culvert Set Backon Side Road Case V. — Side Culverts (Fig. 99). In designing culverts under side roads, the length must be great enough to provide an easy turn for traffic; many times a saving in length can be made by placing the culvert a short distance down the side road as shown 218 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS in Fig. 99 but this should of course not be done on steep grades. Don'ts, — The main fault to avoid in the location design of culverts and bridges is the use of the right angle location where this is not the natural and reasonable layout. The right angle layout is desirable on account of economy where it fits the con- ditions. Do not omit culverts on side hill locations and run the water for long distances in the road ditches. (b) Area of Waterway.- — -The size of opening is usually deter- mined by noting the size of the old structure or, if none exists, the size of other structures over the same stream and by inquiries of neighboring residents or the road commissioner as to how the existing structure has handled the water in the past. As a general rule the size of opening or span should not be reduced below that of the present structure but in the case of steel bridges that have been sold to town boards by enterprising bridge companies it is often found that the span is needlessly long. The evidence of existing structures is the most reliable basis of design but the conclusions should be checked theoretic- ally and for small drainage areas in villages and all drainage areas affecting new locations in sparsely settled districts either the physical evidence of high water or some maximum run off formula must be used. Run off formulae are based on the rate of rainfall, area of the watershed, topography and soU. The rate of rainfall varies for different geographical locations and the length of the storm. Reliable information for any locality can be obtained from the weather bureau. Short storms develop the greatest intensity and produce the largest runoff for small watersheds. The rates reached by these storms should be con- sidered in designing ditch relief culverts or cross culverts with small drainage areas. A liberal basis for these cases is the 5 or 10 minute duration rate of Table 26, page 220, Table 27, page 221, illustrates the method. Most culvert design is based on a 24 hour precipitation as illustrated in Table 28, page 222, and applies to watersheds of say 0.5 sq. mi. and up. Streams requiring structures of over 10 ft. span generally produce phys- ical evidence of high water which can be safely used. Table 30, page 224, gives the size of opening used by the Santa F^ Railroad; Table 31, page 226, gives the size of opening for small culverts used by the New York Central. Table 32, DRAINAGE 219 page 226, gives the size of culvert used by the Iowa Highway Commission. These tables serve to illustrate the application of this principle of design. Weather bureau records show maximum 24 hour precipitations of 7.66 in. at Portland, Oregon, 5.12 in. at Los Angeles, Cali- fornia, 2.06 in. at El Paso, Texas, 7.03 in. at Kansas City, Missouri, 9.40 in. at New York City and 8.57 in. at Savannah, Georgia. These rates are rarely used for runoff computations as they represent extreme cases of rare occurrence. Good practice uses a 24 hour r ate of from 4 to 6 i nches. Openings based on these rates where the culvert" wiIT handle the water without quite running fuU will take care of unusual cases by the forced discharge due to the formation of a shallow pond on the up stream side of the road. Examples of Use of Tables. — Table 29, page 223, gives the normal discharge of small culverts laid at different rates of grade. To illustrate the use of Tables 27 to 32 three examples will be given. Suppose water from 2 sq. mi. of flat farming country in the North Atlantic States is to pass through a culvert having a natural slope of 0.5 ft. to the hundred. Table 28 is figured for a 4 in. rainfall in 24 hours which is reasonable for this section. This table shows a runoff of 334 second ft. for flat farm land. For a slope of 0.5 ft. per 100 table 29 shows that a 5 ft. X 5 ft. culvert will carry the water. Suppose we have steep rocky ground of say 200 acres or 3^ sq. mi. in Oklahoma and a culvert slope of 2 ft. per 100. The best data is the Sante F6 Table 30 which gives an opening of 51 sq. ft. at 10 ft. per second or a run off of 510 second ft. Table 29 shows that a 5 X 4 ft. culvert on a 2 per cent, grade will carry this but that the velocity is high and the culvert must have a soUd bottom and riprap protection at both ends. Where pipes or solid bottom culverts are used high velocity is not objectionable but where the bridge type is used a suflSciently large opening to keep the velocity down to 10 ft. per second or less is advisable. Suppose a ditch relief culvert drains 2 acres in the cloudburst region and can be laid on a slope of 3 ft. in a hundred. Use last column Table 27 which gives 12 second ft. which from Table 29 gives a 16 in. pipe. Practical Considerations Governing the Size of Waterway. — For moderate sized drainage areas the culvert opening is pro- 220 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Table 26. — Rates of Rainfall. Short Stokms Short storms of the greatest intensity occur as cloud-bursts in the mount- ain and arid regions between the Sierras and the foothills of the Rockies. The intensities of these storms are not well recorded but partial records indicate as high a fall as 11 in. in 1 hour. For these regions culverts for small drainage areas should be made at least twice as large as for eastern or southern conditions. (See last column, Table 27.) Maximum intensity of Rainfall for different periods taken from the U. S. Weather Bureau Records. Intensity at rate of inches per hour. Location 5 minute duration, inches per hour 10 minute duration, inches per hour One hour duration, inches per hour 5.6 6.7 6.6 5.6 3.6 7.2 3.6 6.5 7.4 7.8 6.6 8.2 5.8 6.0 5.4 6.6 4.8 7.5 5.5 5,0 5.9 3.7 3.3 6.0 2.4 5.6 7.1 4.2 4.8 . 4.9 5.5 4.8 4,0 6.0 3.8 5.1 1.5 Boston, Mass 1.7 1.6 Cleveland, Ohio. 1 1 Denver, Colo 1.2 2.2 Duluth, Minn 1 4 Galveston, Tex 2 6 2.2 Milwaukee, Wis. ... 1 3 Memphis, Tenn 1.9 New Orleans. La. 2 2 Norfolk, Va 1 6 1.6 Philadelphia, Penna Savanah, Ga 1.5 2 2 St. Louis, Mo 2 3 Washington, D. C 1.8 DRAINAGE 221 Table 27. — Maximitm Runoff. Small Watersheds Burkle-Ziegler, Sewer Formula Av. cu. ft. rainfall per second per acre during heaviest fall. V Av. slope of ground in feet per 1000 No. of acres drained Cubic feet per second per acre = C X reaching culvert. C = 0.75 for paved streets and built up business blocks. C = 0.625 for ordinary city streets, C = 0.30 for villages with lawns and macadam streets. Assumed C = 0.25 for farming country. NoTB.^This value is high from the standpoint of sewer design but culverts are short and might better be liberal in size. One inch of rainfall per hour equals 1 cu. ft. per second per acre. DiacHARQB IN Cubic Feet per Second Rate of rainfall 4 in. per hour lAsBumed Runoff steep Area in acres FaU 5 ft . in 1000 Fall 20 ft . in 1000 Fall 50 ft . in 1000 stony moun- tain slopes C = 0.30 C = 0.25 C = 0.30 C = 0.25 C = 0.30 C = 0.25 Rainfall 8 in. per hour 1 1.8 1.5 2.5 2.1 3.1 2.7 6 2 3.0 2.5 4.2 3.5 5.4 4.5 12 3 4.1 3.4 5.7 4.8 7.2 6.0 18 4 5.0 4.2 7.2 6.0 9.0 7.5 23 6 6.0 5.0 8.5 7.1 10.7 8.9 28 6 6.8 5.7 9.7 8.1 12.2 10.2 33 7 7.7 6.4 10.9 9.1 13.7 11.4 38 8 8.5 7.1 12.0 10.0 15.1 12.6 42 9 9.3 7.8 13.2 11.0 16.5 13.8 46 10 10.1 8.4 14.3 11.9 18.0 15.0 50 20 16.9 14.1 24.0 20.0 30.2 25.2 90 30 23.0 19.2 32.5 27.1 40.7 33.9 120 40 28.5 23.8 40.3 33.6 50.9 42.4 150 50 33.6 28.0 47.7 39.8 60.0 50.0 180 60 38.6 32.2 54.6 45.5 68.7 57.3 200 70 43.3 36.1 61.4 51.2 77.3 64.4 225 80 48.0 40.0 67.9 56.6 85.2 71.0 250 90 52.4 43.7 73.9 61.6 93.1 77.6 275 100 56.7 47.3 80.2 66.8 100.8 84.0 300 200 95.4 79.5 134.6 112.2 169.7 141.4 550 300 129.0 107.7 182.9 152.4 229.7 191.4 750 400 160.0 133.0 227.0 189.2 285.6 238.0 880 500 190.0 158.0 268.0 223.5 336.6 280.5 980 600 216.0 180.0 307.0 256.0 387.0 322.8 1,050 640 230.0 n92.0 323.0 269.0 406.3 338.6 1,100 1 Baaed on Santa Fe Table 30 ' 200 second feet by Table 28. 222 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Table 28. — Maximum Runoff, Dickens Formula D = C-y^M' Runoff expressed in second feet The following tabulation is for a 24 hour precipitation of 4 in. rain and for topography similar to the farming sections of the Eastern Atlantic States. For 6 in. in 24 hours correct the quantities in proportion to C as follows : 4-in. rainfall 6-in. rainfall Flat country C = 200 Flat country C = 300 Rolling country C = 250 Rolling country C = 325 Hilly country C = 300 Hilly country C = 350 For steep stony watersheds and a ft-in. rainfall use the Oklahoma Column of Table 30. Area in square miles Flat country C200 Rolling country C250 Hilly country C300 0.1 =64 acres 36 45 54 0.2 60 75 90 0.3 81 101 121 0.4 100 125 150 0.5 119 149 180 0.6 136 170 204 0.7 153 191 229 0.8 169 211 253 0.9 185 231 277 1.0 200 250 300 2.0 334 417 501 3.0 1 456 670 684 4.0 664 705 846 5.0 668 835 1002 6.0 764 955 1146 7.0 860 1075 1290 8.0 950 1188 1426 9.0 1038 1297 1556 10.0 1122 1402 1682 20,0 1890 2362 2834 30.0 2560 3200 3840 40.0 3180 3975 4770 50.0 3760 4700 5640 60.0 4310 6400 6480 70.0 4840 6050 7260 80.0 5360 6700 8040 90.0 5840 7300 8760 100.0 6320 7900 9480 For areas under 0.1 square mile, see Table 27. DRAINAGE 223 u H « (H M H i> B Fi S o o ^ m m g u p* n E3 ^ o O P n H CD OS (N Tl< 1^ Oi -^ iHi-l^i-(N di 1" irjiNOb-coww ^* fi ^ IN PO M - lO 00 T-i Tf* O 00 o rH^rtrtlM Oi" .a W h- Tt< CTi "* 00 — ( i_i P i-l --1 N N CO M Tf d .a ^t^oiTiieoMO «o S > lO t- O CO »0 1> C3S w^-_- pi .2 Oi N 00 tH 1ft OO*^ i-i i-Ci-HMMtMCO CDb- o b-CO a 000(NMM>f3 tHO ■«5 > "5 !> O (N Tt< to t>- tH 1-1 r-l .-< i-H ^ Ph' .a CO 03 CO 50 00 O CO Q OS CO u iHO ^ ■O 00 (N (N i-H O N (D > ^ CO OS tH CO "* CD C^' "i ■ • OS -< N •*»( lO H-i • • rHi-lrHiH o ON d • 'COCOOOCOeO tHO ■* pi • •wo'-teo-* i-H • • T-li-HiHrH Oh* - -COlNOOOlO Q do* ■-• ■ "*(NeD00O (M ^ ■ -t^OSOi-tCO iH 1 42 P3 d "ftOOOOOO s"= 1 O "-I N CO Tjf lO CD 19 9 I "■5 0W50 OOCO COt^W weoio OS ^ t* CO r-t«COTt< COb-OO-^ 00COb»«D OOTjfQOO cOOOeOi-HcO i-rr-tMCCeO OOOOifliO OOONOOcDOO t- fH IC 00 1-1 Tt* i-HtHiHM W t>l>0>000 b- CO -I (N 00 OS tH,h\ 1 224 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS <1 siouim V uumioo JO % 08 aen jo^-Baa^g jo ^sa^ii V uuinjoo JO %09 ^^n jo^eaj^g jo ■jSBa C-^OOOOOOiflOiftiOiCiCOOOOOiflOkOiOifSO 0'-t'-'(N(McocO':H'^»n»f3coi>ooaiO'-i.-4MeoTt<'>#ir:(o O»0OOOOO»0OOO"5OOOOOOOO»0"2Oo i>^cooTtioocq»oirn(N>ocorHoo»n(NoO'#ooo.-i2'^« CJOO^^.-iMNNC0CC-*»0»C«3l>t>C00S0SOOi-HN s3|Tui aj-enbs Ul panrejpBajy OCqTfe000OW-*OC0O»CO»0O'0O"5OiCOi0OO Cq (N M (N (N CO «) CO CO CO "# ■* O >0 O O t^ t- 00 00 Oi O) o ^ CO >> Li CD ^ . o " Li < siourni V aranpo jo %08 ae^ Jo^Baji^e jo ^saj^^ V ntun[oo jo %09 as" jo^Baa^g jo ^sb^ i is OJcotooTticocnntfl«)|>l>t-OOOOOOOlOlOJO w Pi o o if COI>OCOU5COa>COOO>WNrtO.-HOOiOL'5iOiOOO»0 O'-'COTtiiOOOOCOiOt-OMTH^Ot-'-H'^WOODCCiOHN^ ■^■^*I^t^t-.0000C0M0S01 02 nt psurejp ■eaiy (N'#eDCiOO>raCiiOO>flCnOOiOOOOOOOOOOO ni Tt<"*'t^OO«0)CTiOi-H(NCOTt(iOOI>«0 g 1 ^ . i Li eioniiii V umn^oo jo % 08 ^sn jo^'Boi^g jo ^sa^ y uraTi];oo jo %0Q asn jo^^'saj'jg jo ^s-ea ■< 5° oooooooooooooooooooooooo T wtl>0-^'-i.-^.-<'-H(N(N(N(N(NCO-*^-*-.#OiO(NOS-»** a!OiOio^(Nco'#»ocoi>ciooscicq-rttcoooocMTti>o3 rt .-1 ,-( ,-1 ^ « ^ rH ^ 1-H (N (M cq IN (N CO CO CO CO ffO CO o CO oooooooooooooooooooooooo s 3 H »-i-:t STOUTjn V uinnioo jo % Qg asn jo^Baj^g p ^sa^ y uoinioo jo %09 aen jo^Baj^g jo ^SBg :^6 000»00i00»00000000000000000 (N-*jHOI>.OJO(NCO»OOiONOOTfHr-f©(Mi:DO'^OOi-tiCOO rHrH^,-IWCqCOCOTtflOlC«50t>t^|>000000 'hi. OOOiOOiOOiOOOOOOOOOOOOOOOOO (MTt010(NfO»0'r>iClMOO-t<'-iCD(MCDOTHCO'-liOOO rHWrtr-C-XMCOCOTt^lClOOCDb-t^t^OOOOOO Area drained in square miles ri?2SSISG'^'^'*<^c>w50icoiooioou50»oouao OOOOOOOOO^rH(N(NCOCO^^«CioScOt-SM ooooooooodoodo'odooooodoo DRAINAGE 225 V uuin(oo JO ^ y uuin[oo jo ^ , 08 3Bn jo^Baj^g jo ^ea^^ ,09 asn jo^^aj^g jo ^sug; ooomooooioioiowaio •H ^ ci c^M T)<"»ra lo" «D r-T 00 CO cj' OOusOOOiiSOiOOOOO 00 N «D m CO «D Tt* i-t CC »0 O «3 --I 00 o?03 oa"o"o i-h' NN eo' -"Ih" rP wa (NMCq(N«C0m'^rJ t* od w' 00 OS oToi ffl o"o o" r-H OOOOiOOOOiOOUSOiO T}tMC0C0O(0«00N«D0sai OS^N "^^t^OS "-JCO CO ooooooooooooo loomoooooooooo OOOSOSOr-iMCO-^iCeOt-COOl y uuinpo JO %08 asn joq.'Eaj^g jo ^sa^ y uuin[oo jo %09 asn jo^'saiijg jo ^SBg oooooooirao'O'Ooo oso-^NOcONt^Tjicncoh-o CD 00 O M ■^ CO OS «-< ■'f CD W_.-^ Th ■^ TjJ" ifl ifl lO lO lO CD CO CD' CD"t>r b^ lOOOiOiOiOOiOOOOOO i-it-OC0CDQ0'-i(NC0C0(N'^O CO t* OJ_0_i-<^eO CD 00 0_N Tn CO 00 CO CO CO ■**^ ^"■^■*" u5 irj" ui" U3 lO OiftO "5 000000000 01M'Ot--OtOOiOOiOOiCO COCOCOCOT(i'*iOiOCDcDt-t>00 y utan|oo JO % qs asn jo^BSJ^jg jo %s&j^ y uiunioo jo %09 as" JO^^Bai^g jo ^evji 0>OOOOiOOiO»OONOO MiO00' 00 OS OS >-^^(M_CO "* N N « N N oTci (N m" CO CO Co" CO OOOOOOOOOOOOO (NCOTjfiOcOt^OOOSON'^t'CDOO S "0 I I I oj S^H t. S 3 "■" c! O OJ O o ■a.2.3 s55.2 ■« a-o * «a.§ t« S O >H tn W _ gggo o.s s o a g.S£ j-g g a a s|-§s«s-| -I a S OS'S >,3 a „ Wapiti I I ° o^-g-o-- a S ^g^lSSog g 3 _- « S o; o> 0) a a; h». BT3 ■^ » a 22 o •^ a h a ffl-** t.,^ a PI 15 226 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Table 31. — New York Central and Hudson River R. R. Culverts FOR Small Drainage Areas Steep, rocky ground . Acres Flat cultivation, long valley. Acres Size. Diameter in inches Equivalent capacity. Pipes 5 10 10 10 . 20 12 20 40 16 25 50 18 two 16-in. pipes 30 60 20 two 16-in. pipes 45 90 24 two 18-in. pipes 70 140 30 two 24-in. pipes 110 220 36 two 30-in. pipes 150 300 42 two 30-in. pipes 180 360 48 two 36-in. pipes 280 560 60 Note. — To be used only in the absence of more reliable information particularly existing culverts over the same stream. Table 32. — Culvert Design. Iowa State Highway Commission Size of culvert opening, ft. Maximum acres Minimum acres 2X2 70 28 4X4 376 140 6X6 1300 520 8X8 2700 1120 10 X 10 5000 2000 portioned to the runoff but for small areas the size is determined by the convenience of cleaning rather than by the discharge capacity. Where sufficient fall can be obtained to make the culvert self-cleaning, a 12 in. pipe is feasible under shallow fills but where the flow is sluggish, nothing less than a 16 or 18 in. pipe will serve satisfactorily. Long culverts under deep fills should never be smaller than 2 ft. wide and 3 ft. high to permit cleaning by hand if necessary. The self-cleansing velocity of flow for sand and earth particles is about 1 ft. per second; for coarse gravel about 3 ft. per second (Ogden's Sewer Design, page 134). A pipe laid on a slope that gives a velocity of 5 ft. per second when flowing one quarter full should keep clean. This requires a fall of approximately DRAINAGE 227 2 ft. per hunderd for a 12 in. pipe and is the minimum grade at which the 12 in. size should be used. It is probable that a culvert should have the same slope as the stream bed. If given a greater slope the outlet end tends to clog and if a lesser the inlet end will plug. It is unusual for culverts to fill badly except when placed at the foot of a steep hill- side where the stream velocity is naturally reduced. At such points an extra large structure should be designed with the idea of providing sufficient waterway even after the contraction caused by this settlement has occurred. Such a culvert should be cleaned after each freshet. The use of short paved dips in the roadway at such points in place of culverts is not advised as they are dangerous and cause accidents unless very gradual. /fbad Profth Portion of Road ■' '-Low.Wafer Culvert efesicfnectas spiltina Profile ..■FIoobI Lsvsl Concrete Pavement and Shoutders Section A-A Fig. 100. Natural Ground A man not familiar with the road often loses control of his car. If, however, too much trouble is experienced in carrying large infrequent floods under the road a small culvert can be used for the low water flow which does not as a rule carry much silt and the flood flow can be carried over the roadbeci by paving the entire surface with concrete from toe of slope to toe of slope and giving the longitudinal road profile a slight dip safe for traffic to locaUze the flooded portion of the road. (Fig. 100). More trouble is experienced from culverts becoming filled with ice due to alternate freezing and thawing weather. This is particularly true of small culverts draining springs. Culverts as large as 2 X 2 have frozen soHd in this manner and if this difiiculty is anticipated the size should be regulated accordingly or trouble will be experienced during the spring break up. The following ingenious expedient has been successfully used on roads where the culverts fill with ice and snow during the 228 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS DRAINAGE 229 winter. A small pipe is suspended inside of the normal culvert. In the fall this small pipe is plugged and in the spring just as the snow begins to melt the plugs are, removed and the first water flowing through the. small pipe melts the ice and snow rapidly for the entire length of the culvert so that it is generally completely free to handle the main spring runoff. Pjg 102. Grade and Elevation of Inverts. — As previously Smaii pipe in stated it is desirable to prevent silting up of the culvert due to abrupt changes in the velocity of flow. For this reason culverts are normally given the same slope as the stream bed. The elevation of the invert is always made low enough to drain all surface water from the upstream adjacent lands and if the elevation of the outlet permits it is desirable to make the culvert low enough to act as an outlet for farm underdrains. In hilly country underdrainage need not be given much weight but in flat country it often controls the elevation of the culvert invert. In order to prevent serious ponding and damage to crops in flat country, all culverts or bridges on channels of any importance should be placed at such an elevation that the top of the waterway opening is as low or lower than the surrounding farm land. That is, the culvert elevation and shape of opening is designed for the hydraulic grade of maximum flood flow. - STTW"^"^ 1 W//£/ Cot/ni-n/. No changer I of serious pondmcf Fig. 103. Figure 104 illustrates this point. The waterway areas of two culverts A and B are the same in size. However in order to get the full capacity of A the water would have to back up and overflow the surrounding lands. Culvert B carries the flood flow without serious ponding. The use of bridge openings similar to 4 is very common practice in both railroad and highway design as it generally cheapens the culvert but is undesirable as causing needless damage to the abutting properties. 230 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Depth of Cushion under Pavement. — A cushion of earth be- tween the top of a concrete culvert or pipe and the bottoni of the pavement is desirable. .This is more important where the pavement is a rigid type such as brick or concrete than where it is a macadam construction. The depth of this cushion sometimes controls the culvert invert elevation where the topography and road grade makes a low invert needlessly expensive or impracticable. Hydraulic Grade A -, Flood Elev. A-. '. Flood £lev. B y ■ ■^■■;-n i' :Hydre(ulic Grade B Vri.^»JfMI^'*^K!j/K^/M> ^-Inveri--' 'eqneral BIsvafion Surrounding Farmland Fig 104. For rigid pavements the minimum desirable depth of cushion is approximately 6 in.; if less than this is used the chances are that the pavement will crack over the side walls of the culvert unless the pavement base is specially thickened and reinforced with steel. For macadam pavements a 6 in. cushion is desira- ble but no great damage occurs if the bottom course is laid di- rectly on the culvert top. Even with a cushion settlement often develops each side of culverts having less than 2 to 3 ft. of cover but it can be easily fixed by the maintenance gang. Top o f Culvert- Pavemenh Ectrfh Cushi'on between Pavemenl- oinol Culvert- '////////// ////^//^//////////////^/7777}. Fig. 105. {d) Dead and Live Loads. — Dead loads are readily determined but reasonable live loads are a matter of judgment. Many of the states limit a vehicle load to 15 tons on improved roads without special permission but loads in excess of this occur now and then. The old culverts and bridges on our roads aire practically without exception too light for modern traffic. Permanent culverts should be designed to carry the dead load plus a 20 ton vehicle load with 25 per cent, impact. Standard DRAINAGE 231 culverts often seem needlessly strong but small concrete culverts are generally backfilled and used during construction before they develop their full strength and practical considerations require the excess material. A design load of a 20 ton vehicle with 30 per cent, impact is desirable for small permanent solid floor bridges of 10 ft. to 50 ft. span and this loading is often used for even timber bridges in states similar to Wyoming where oil development, etc., requires the movement of heavy machinery, although usually where timber is used a 10 ton live load with 50 per cent, impact is considered good practice and for mountain roads 6 tons will usually be acceptable. For long span solid floor steel or masonry structures a live load of 150 lb. per sq. ft. plus a 20 ton vehicle with 30 per cent, impact is first class modern practice. This value is higher than generally used. These loadings are safe for military purposes as the following statement of Major General W. M. Black, Chief of Engineers 1917 will show. "Our existing ordinance liable to accompany a field army will have its heaviest representative in a 12-inch howitzer weighing about 27,000 lb., 18,600 lb. of which are on the front wheels. The base or distance between the front and rear axles is 18 ft., width of track 7 ft. 4 in., width of tire 8 inches; width of tire shoes 12 inches. This howitzer is drawn by a 75 hp. caterpillar tractor weighing 25,000 lb. Comparison with the largest present day commercial trucks shows that a road or bridge substantial enough for such will suffice for the ordinance load." The safe load for steel I beams, timber, reinforced concrete beams and slabs are given in the third book of this series. (e) Length of Structure. — Culverts are made long enough to accommodate the normal road section. There is nothing more unsightly or dangerous than the narrowing of the normal section at a culvert. First class design widens the section at culvert locations and even with minimum head room uses a clear roadway width between parapets of not less than 20 ft. on single track roads and not less than 26 ft. on double track roads. Short span permanent bridges up to about 25 ft. span on high type road improvements may well have a clear width of not less than 22 ft. between parapets. Above 25 ft. spans the roadway width depends largely on the location of the structure and probable traffic but for most main roads a 20 ft. clear roadway is satisfactory for permanent structures and a 16 ft. roadway for 232 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS DRAINAGE 233 temporary timber structures. Figures 114 to 128 illustrate cur- rent practice. (/) Economical Type of Structure. — The selection of type for any particular structure depends on the foundation soil, the requirements of topography and the relative economy of the different designs suitable for the location. On dry firm foundations any type is satisfactory. On wet or moderately soft soils tile or concrete pipe culverts should be cradled in concrete; the concrete box type of culvert is probably more desirable for these conditions as the load is transmitted Vertically in well defined directions. On quicksand or muck foundations the flat slab vertical side wall box type with timber sub foundation or pile and grillage is in general favor. Con- sidering the usual foundation conditions the author prefers the flat slab or girder type of small span bridge in most cases unless there is a noticeable economy in some other form. For small drainage areas some form of pipe culvert is generally used which will be discussed later in more detail. From 2 ft. to 5 ft. spans the box culvert type is popular. From 5 ft. to 20 ft. spans the slab, stringer or parapet girder form of construction is reasonable except under deep fills where the semicircular arch is better practice; from 20 ft. to 50 ft. spans pony truss or parapet girder types are available for most conditions or arches where the foundation is suitable. Pony trusses are desirable up to about 80 ft. span and beyond that the through Truss type. The following list illustrates the practice of the Iowa Highway Commission. 1. Box culverts and slab bridges 2 to 20 ft. span. Not economical over 20 ft. span. 2. Reinforced concrete arches 8 to 100 ft. span. Foundation must be excellent. 3. Pony truss steel .bridges with solid concrete floor 30 to 80 ft. spans. 4. Reinforced concrete girders 20 to 50 ft. span. Very economical but require careful design and construction. Not economical over 50 ft. span. In the matter of type the author desires to emphasize the desirability of simple design particularly for small structures. Mass concrete for sides and bottoms is preferable to thin rein- forced sections (see New York Standards, page 246). It may not be as scientific or theoretically as cheap but better results 234 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Fig. 107. — Simple concrete box culvert with straight high parapets (Town toad construction) . g^p^ ' -'""^"^^SS^ffl^S^m^, ' "-— Fig. 108. — Double box culvert (town road construction). DRAINAGE 235 Fig. 109. — A crude log stringer bridge. Pioneer road work. Fig. 110. — Usual type of timber stringer bridge (unimportant roads). 236 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Fig. 111. — Parapet girder bridge (concrete). High class road. Span 25 ft. Width of reading 22 ft. Approximate cost (1920) $5000. Actual cost (1914) $2300. Fig. 112. — Arch type on rook foundation. This is a view of the bridge the plans of which are shown in detail in Fig. 128. Total span 50 ft. Approx. cost (1920) $5000. Actual cost (1915) $2500. DRAINAGE 237 238 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS are obtained with the usual inspectors. Road commissioners often do not understand the object of the reinforcement and either leave it out altogether or get it in the wrong place. For large structures where a competent inspector can be employed this objection does not hold but even for such structure mass concrete for abutments, retaining wall, etc., is to be preferred. Mass concrete 1:3:6, mixed with embedded boulders is satisfactory. Reinforced culvert concrete is usually made 1:2:4 mix. Pipe Culverts.--— The pipe culverts in common use are as follows (see Figs. 115 to 118, pages 241 to 244, for typical pipe): CtFLVEBT Designs Corrugated metal Semi-permanent construction Vitrified tile Semi-permanent construction Reinforced concrete pipe Semi-permanent construction Vitrified tile incased in concrete Permanent construction Reinforced concrete pipe cradled in concrete. Permanent construction Cast iron pipe : . Permanent construction These types of culvert are suitable on firm foundations and generally economical for small drainage areas. The relative cost will fluctuate for each contract which makes it impossible to generalize as to the economy of selection. Box Culverts. — The two general types favored are the plain mass concrete bottom and side wall with reinforced cover slab and the lighter box reinforced on all sides (see Figs. 120 and 121). Relative Economy of Culverts. — Comparative estimates of cost must be made for each contract but to give a general idea of the method of economical selection the following table is inserted for 1920 cost conditions prevailing in western New York. The semi-permanent types should not be used on high class improvements except for driveway culverts. Comparative estimates similar to Table 33 furnish a rational basis for judgment provided only the permanent types are compared and provided the comparison is made for each contract considering the special conditions prevailing due to location, market quotations on materials and local materials available. For conditions similar to Table 33, Western New York, 1920 permanent pipe culverts are not economical over 18 in. in diameter. For drainage areas requiring a culvert waterway area of over 2 sq. ft. the box type is preferable. Of the box types the simple mass concrete structures are in the author's opinion more satis- DRAINAGE 239 factory, considering construction difficulties than the thin wall reinforced type although they cost somewhat more than the thin sidewall type. This, however, is a matter of personal judgment. Table 33. — Approximate Relative Cost of Pipe and Box Culverts 30 Ft. Long Including He ad walls (Exclusive op Excavation) Area waterway, sq. ft. Style of construction Size culvert pipe, in. Corru- gated metal Vitrified tile Vitrified tile incased in concrete Reinforced concrete pipe Reinforced concrete pipe cradled in concrete Cast iron pipe 12 14 18 24 30 36 42 48 0.78 1.07 1.76 3.14 4.88 7.05 9.60 12.52 $60 70 90 120 140 170 200 230 $50 60 80 120 180 260 $65 75 110 160 230 310 $75 80 100 135 180 240 300 $90 95 130 175 230 290 360 $100 130 170 260 Area waterway, sq. ft. Style of construction, concrete boxes ■ Size culvert opening span-height, Mass concrete bottom and sides (Fig. 120) Thin Reinforced Sides and bottom (Fig. 121) Total cost Cost per sq. ft. waterway Total cost Cost per sq. ft. waterway 2 X 1.5 2X2 3X2 3X3 3X4 4X2 4X3 4X4 5X3 5X4 5X5 3 4 6 9 12 8 12 16 15 20 25 $160 190 210 260 300 250 300 340 350 400 450 $67 50 37 30 26 31 25 21 23 20 18 $150 200 230 300 350 $35 22 30 20 17 Examples of Current Practice in Pipe & Box Culverts. — The following cuts illustrate typical practice in small culvert design. 240 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS ■^■S I ■§■£ §^ o c cs u ^- t O B 5 ■S ^ "s ^ =§ -8"*- "S-S a -t ~j -K w * 4e iS -o •£ 6'^ o 6, '^ DRAINAGE 241 i 1 1 1 5 t 1» ' 1 or t ^ s * s s K f i •1 t s » ? ? 1 s s s * o i St ty ^ «) s s § .E e E E l.i'M.|.i.|. ^ .O S ^ tS 16 242 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS <--4'Max ■■■>\ n'lBcrW," 'Cl.dfCuK^rfi Half Plan . ,^ SmffleTrackl?aad MinimurpJI '^' ""Haubh •! >> » 75 Half Section OP Cu Iverf Center Line Well Tamped Backfill fHafurotI Mahrial) /ifLeasti'l ftiin.. I -.3:5 Concrete Jackst ■A Plank if - necessary CLAYOR LOAM or in firm soils, wh<3re cushion,. 16 less man 12" UNSTABLE SOILS FIRM SOILS-ASr/rfto GrawlarCixirseSana, provided ihere is a minimum cushion of at least 12" SECTION A-A-Showing Treatment in Different Soils- FiG. 116. — Typical vitrified pipe culverts. Approximate Weights, Dimensions, Etc. of Standard Sewer Pipe Calibre, in. Price "Weight, per Depth of Annular Thickness, per foot foot, lbs. socket, in. space, in. m. 12 81.35 45 2M M 15 1.80 60 2J^ y^ IH 18 2.50 85 2M H Vi 20 3.00 100 3 Vi m 22 4.00 130. 3 V2 w% 24 4.50 140 3M H \% Double Strength Pipe [Calibre, in. Price Weight per Depth of socket, in. Annular Thickness. per toot foot, lbs. Bpace, in. in. 15 $1.80 75 2H K IK 18 2.50 118 2% ^ 13^ 20 3.00 138 3 H 1% 22 4.00 157 3 Yi \% 24 4.50 190 3M M 2 DRAINAGE 243 <--4Max-->^ iiis'oris!' '' 'CL.oTCuIierTC ' Half Plan Jt Sindo Track Road Minimurp II '^i* 'Doubh » ') " IS ^ ^ Ml n'imum\\ Invert Grade- '^% Hocif Section on Cu Ivert Center Line Well Tamped Backfill rNatunHnahrial) fifLeastbl z"Mln.. "jacklV^^ UNSTABLE SOIL& ?\KV\%0\\S-Hantl'm Gravel or Coarse Sana, provided ihere is a minimum cusiiion afaf least 12" SECTION A-A-Showmg Treatment in Different Soils- CLAYOR LOAM or in firmsoik where cushion,, islsssthani?" W/>Wf^^W^ -i?^ ,ji V , l^w^^^/^^^tf^g^ TABlt OF DIMENSIONS AHD REINFOKEt^NT FOR PIPE Table of Dimensions D Inches L-Max. Feet T Inches B-Min. Inches E Inches \Z I 2 2'/f 2/? 5 i 2, 2 '/a 1(5 8- I 2fe 3 24 I. J 3 3fe Effective Area of Circumferal Reinforcement Per Foot Length of Pipe 2 0.058 Sq.lnches 5 0.05S n r. 18 0.080 " j> S4 0,126 » » Approx mateweioht i^er Linear Foot of Fine n. 90 lbs 15 10 » i8 10 r, 24 260 .; Fig. 117. — Typical reinforced concrete pipe culverts. 244 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS I , Z'ifof less than. #te ^ ^^:if^^&)'^l/ ll ,.l',^J,,L.yyw ^^d' ^6] Hot Less than.- ^'iMUssfhan. Lon^ifudinal Sec'^fon, Fig. 118. — Cast iron pipe culvert. New York State standard. ■8 .f*-- -1 5 S E ~ '^ - E"6 ; * ci ?^il!tfll ■« o i5 8 § 8 r u Tl "* *) o a, v. C -K-O C 5 £ .g O .C c DRAINAGE 245 < .J \ lf^" « + + C V = s- e C t& it .'> O^ f.-^--'ti l^i — ^. - t> o S oo-oo D £T 10 c o o * -o > « fi»5o P c = " f S o ^ I II I o'fe Is a a o o ±± 33 a tot; sfe ■c *•<> Eh. ^ .8 0..S ft, "^ ^^ I 5 -a a: 5. 5 eg ^ -:a <£ o +."♦•«»-&, tO -P ^ H- g^ -:f.-f-f->[-;?r^pt1>S ill! --T", 5 ^ O +- c -a ^8 , -tifM 5 a E q: 1 i 1 j 1 } 1 1 1 ■ft § ft TO K s 1 5 1 m N !3 ^ ^ s i5 £ K £ s £ r :; ^ Si > ^ 5* ■fr eo tu * c •f iii i p 1 ■^ 1 1 1 •< «Q OQ o Ci UJ u. vo II 00 r-i a o (3 ««5 246 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS . J. , ? . (ytH /ixS'andZ'xZ' End Wall. Longitudinal Section. CulnerhlobeBijih-with E L I H i z'o- 6" 12" o.e 3'0" 6' 12' i.t 4V 6- IS- 1.2 U:d a- Lii: I.Z Tableof Dimensions. Il tomrefi Auumption lor Live Loadi m "longitudiml Hods lO'iaVtitC igilij^ii!!^ I,,, long.Rodsmt- I 5 H2K morethanlB'Oif'i ^"■f-Spanshssthanefk ,„ Comers notkss than 6. H iMfJMiSiimS^taS/au arm aem/rfit ■:s:^ -Tf.-thO>nmt •n crCcmirlMs Cross Section of Culvert. 1 I ^ .1 si t^t^M M MOO »r(cj o\q *« HHtOf<7Q(20Ht^o^i^tO(Ot>. ^oq O 0 •'too 6 ^Q'*H\O.M« 0*0 l-tt*.« « »p «9 w^ ^ * wo «ot*e*r-.&OiO O Oto>0 qw «ooobo?>^999 ci w M C4 « w w « T*"??"?'? ^' ».' v' •J -^ -J .*^ *^ *i *t V »T »T *■ *» *. *■' *' *• ^' •"' *. ^' •i' *. ». v "k "k •i^-v^ «^ W m iiok. K.' «. >. *. ^i^ «k M M Ul-I U M Ut TTS m tfi t<1 m tTi fiVi *f. •^■^ ^Viinvv VO'QVOOOOO v'qiQiM M HI-I HMMW5rO«0«*5WJ»0«*i«i*': £>£> « -^^t^e*** n< l_S_5_i.5.^Si* * * *fc^*fc*»fci t fc ft ft » fc^i hOiChChOiOtQ O Oci « « W rOfOrO^**"*^*^!^^ ^^ *0 « *0 Vf Aft*ftt*fc**»*lr fe*& fe»fe* ^ ****** * * *.* ii B '^1 >^Af o^^^ ^^

fr^9 9Mp^fooc}oj}opop9^99^^^^ 9 H H H,Nf H M I IM« «««««««« M«tO»Ot*>tO«OtO«*J*0(f ******* ::*******************'*.* •^\0<0 I*-"*-*" « «*0'0'0*Orof'>«OrO»OtO«0« M « « «« w w M *k*ib**«%kfe*««% % * * » ft * * * * * * * * \.5 W M («3«)«0^^^»'9HMHWMMM ******* ********^***ft'%feVfe^ ■*'r«W.^H W HW.0 <0 VO "O « ^0 O <& x6 \0 « « « ******fc**ft»t:ft« • » * 5_* S_5. * ■***********•*%* tu'l * * * * * ft ft-ft^ ft*, ft ft ft ftft ft ft ft ft ftft*ftft^i.*A.%>t^^^ ^Vu) b^ v)V)mu7W) w) w)\oo>oOO i-.r«»*>r«r«oooooooOMoOoooo, 0>0 0i0>0 »K* *t*****************t****te* * » •4NHNHN* ft ft **t V) %rV^ "r-00 w "VoViovD Voo "b>"S ■.•.».ftftftftft*ftftft*ftftftft.ftftftft.ftftftftft.^ftftft^kftft M MW w «i w « ra 00 00 M 00 cO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 db 00 00 Fig. 121. 248 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS SMALL SPAN BRIDGES Economic small span bridge design is susceptible to con- siderable variation of type. Size of waterway, width of roadway; live and dead loading have been outlined. The superstructure up to a span of 25 ft. is generally the slab or reinforced concrete parapet girder design on high class roads and the timber stringer on king post truss design on pioneer roads. Figures 122 to 128 illustrate current practice. George C. Wright, bridge designer for Monroe County, New York, states that for conditions prevailing in this country the parapet girder type is more economical than the slab design for spans greater than 10 to 15 ft. The parapet girder type should nothow- ever be used unless the construction inspection is intelligent and rigid. Foundation Soils. — The foundation design and to a certain extent the type of superstructure is affected by the soil. Most ordinary soils afford satisfactory foundations for small span bridges but piles must be used for muck or quicksand and are advisable if much scour is anticipated which can not be pre- vented by rip rap protection. Pile foundations are required for all large structures where rock foundations are not available and are desirable for any concrete structm-e over 30 ft. span. Where much ice occurs piers ia small streams should be avoided. They can be used to advantage to reduce cost, how- ever, if there is no danger of ice or debris jams particularly if the flow is sluggish and in the latter case for wide shallow streams the trestle design is appropriate. The safe foundation load on various soils recommended by "Baker's Foundations" are as follows: Rock (poor) 5 tons per sq. ft. Rock (solid and first quality) 25 tons per sq. ft. Dry clay 4 tons per sq. ft. Medium dry clay 2 tons per sq. ft. Soft clay 1 ton per sq. ft. Cemented gravel 8 tons per sq. ft. Compact sand 4 tons per sq. ft. Clean dry sand 2 tons per sq. ft. Quicksand and alluvial soil J^ ton per sq. ft. Pile Loading. — Where piles are used for types of construction where slight settlement is not objectionable (slab, girder or truss DRAINAGE 249 uoi+oag ■Sf/ogezr/ Vg 250 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS C/l Z o «2 z ■< :^ go WO SS ft ft 00 t- «o MO wo wd ?? wo wo WO o o mo St fc 1« a I 1 I I fc % % te N» "SSSI I 11° O Oi t-f^ o OOt*t-l>xXXX:, ft fc % ft +; J J J J J '^'^■^'' ^ ft (fl fc ft ft vji*; 'C'CJft ft ft w woo n pp^i>i>i>XXXXfe ft St ^ ft w -* 00 NOO ^„ ft ca ft ft ft >flll4i »c)iaft ft ft t-< woojQ oCL^t-t-^XXX^ ft ft ft ft NflO ..- :t(jSias>(JS«\ ^•"SSSI I I II O woo ** M ■* >• >»«0 00 O !>t >i >t >i >» C O m" S O B C g B a'3 S'S'S'jSs's'S'S! *c c '~' n n n 03 pq(x;,l,p:,p:iOK»KCl< a o DRAINAGE 251 ^ -k. V ^ *. fe » o CO 00 00 "b GOOOOOOOOO HO « M X X X X X X xxxxxx s° « 4 « «: ft ft ft ft ft ft ft ft « N « N « N o ■^■q-ocoo wd X X M H X X X X xxxxxx *n'n t: « ft b ft ft ft ft ft ft ft ft Ob 1- fO ■* fO ■* n ■* ■^ ■* IN N N « i i i L 4 I iiiiii w w H *^ o -o55< "b ooo^ 3 "b "©"bo oo o o o>o wd H H 11 1- H H H H H H M N M ?s 55 X XX>( ; X xx> ( X XXX XXXXXX tt ft ft fc ft ft ft ft ft ft ft !l ft ft ft ft ft ft ft^ ■* M N T !■ ■^ N « -« t ■* M N -:J- o-^^oooo 9 Si wo H V; M H M M M H H h W H 35 ^ « X°XX> ; x°xx> <. x°xxx XXXXXX O UJ g ?r % VV. %, VV^. f*) VVn ft ft ft ft ft ft 77"? r ^ T -o-o> H i A\ t 6) (N M.^ „^ ^i^ CJ ON N W N 1 , M H M' H MM l-t is 1 ,ir\ N M^si ^ N00< > *w 'w'bo "n^s'n'n'nsO M ^ P^O M tH M H H M H V M W W H 1-. 55 X XXX C X xx> C X XXX XXXXXX b fc «: ^ % ft b ft ft ft ft ft ft ft ft ft ft ft e u « £ O ^W ■«; Y O ■*« ■* to -^N Tj- •o -*' c x°xxx XXXXXX p, ?? 5* fe fe St >,ft ft ft ft >,% fe: ft ft ft ft ft ft ft * >,Ti--0 B s M H |i lU g M H H o o vb^ 1 gllMII 01 -p5 jS J U) 2 s HO 1 M WH ? H NW;>.MHMMM M B5 ss o X XX •^ * fc fe i X XX H ft ft ft -i X xxSxxxxxx N ft ft ft Tft ft ft ft ft ft ^o « ^ t »o « ^ (■ O « «* *0 ■'f^'OaOO >« S HO H M H H H H fc « X XX X x> ' X XX xxxxxx T? V V. ft ft ft ft ft ft ft ft ft -*-o O OOvC o o>o ■^o o o oo s ^ WO « M H « W H « « H H M « « « Q jl o o X XX X XX X XX xxxxxx U +»-p ts fc ft «! ft fe ft ft ft ft ft ft ft ft ft 00 « -s I- CO « 'S \- 00 « Tj- vO ■+ -^-O CO >0 HO H H H H H H "£ k « X XX X XX X XX XXXXXX 1^ T? V V.S ft ft *: ft ft ft ft ft ft ***+« M « Ci -ii 1 u 1 11 1 1 1 IIIIII ■ir w N fO 'tw N n N M et M « M H W JH N , cr z b c ' 1 i t •S " -3 ^ 'S ° O (i! « 252 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS o .3 J >i J -' -g t N M M ,_ O O SB 3; I aacca .a 0.0 o^-3 xxxxxxx rrmir xxx>^xxx rrrrrrr N C4 C4 C4 N C4 n xxxxxxx rrrtrrr N N N « N « N OO « M OtCO>0 DRAINAGE 253 •a a o o i3 0< El poximii'i'ij.e 254 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Dimensions and Quantities for Superstructuke Capacity is-Ton Truck Panel Intermediate Panel Length Size Floor Total Washers, of Joists Joists Railing Details Lumber Spikes, Nails Feet Inches Ft. B. M. Ft. B. M. Ft. B. M. Pounds 10 6X12 590 800 1390 80 4X14 6X12 460 840 1300 II 650 870 1520 90 4X14 SOO 920 1420 1640 12 6X12 700 940 90 4X16 620 990 1610 8X12 lOIO 1020 2030 13 6X14 880 1020 1900 90 4X16 670 1070 1740 8X12 1080 1090 2170 14 6X14 950 1090 2040 90 4X16 720 II40 i860 IS 8X12 1150 1170 2320 100 6X14 1010 II70 2180 i6 10X12 1530 1240 2770 6X14 1070 1240 2310 100 «Xl6 1230 1240 2470 17 10X12 1620 1340 2960 8X14 iSio 1340 2850 120 6X16 1300 1340 2640 l8 10X12 1710 1410 3120 8X14 1600 1410 ■ 3010 130 6X16 1370 1410 2780 19 10X12 1800 1490 3290 8X14 1680 1490 3170 130 ■6X16 1440 1490 2930 20 «Xi4 1760 1360 3320 130 8X16 2020 1560 35 80 21 10X14 2310 1640 3950 140 8X16 2110 1640 3750 22 10X14 2410 1710 4120 150 8X16 2210 1710 3920 Dimensions and Ouantitiks — Substructuri Grade to Ground Sway Bracing — Intermediate Bent Sets Length Lumber Bolts Feet No. Reqd. Feet Ft. B. M. Pounds 10-12 12-ls IS-18 18-23 23-26 One cap 10" X 12 I I I 2 2 "Xl7'-o" 18 20 22 18 & 20 20 90 100 no 190 200 170 35 35 35 60 60 10 Grade to Ground Bulkhead— End Bent 1 Lumber Spikes Feet Ft. B. M, Pounds 4 5 6 7 8 270 360 460 S50 640 5 5 10 10 10 Fig. 124. — (Continued). DRAINAGE 255 Elevation . Sa>/vmlV«0ioft/ie kj^.j-.^ Abufmenfs natlesjt/an''^^''^ 4 of Total Height front Bottom ofAlatmenTtoTopofSlmb. v Section onCenterUne Note All rods to have a defoimed cross-section. All rib metal to be of medium steel. 2d class concrete in all slabs and parapets. 3d dass concrete in wings invert and abutments. Wing walls on the outlet end of aU square culverts with concrete floors to be built parallel to the center line of the culvert. -Round all exposed edges to i| inch radius. rRoch inSloh to be Eften- \ dedS4Diams.beytiii \ Neat Lines of \ Abutminti Foe Typical Section "F" Where culvert coveis become a part of con- crete base for brick pavement, transverse reinforcement should be extended i2« beyond bacic of abutment into concrete base. yffor'MirlS'A KodsinSlabtobe Extended 24 Diams. beyond Neat Lines of ttre Abutments. Dimensions of slabs on page 256. Fig. 125, — New York State slab bridges. 256 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS Span Tbickness of Slab* Net Area of Rods Rod Spacing C-C Length Dowels S 8" o.2Ssq." 4i" 12' 6 9' (( 4" (( 7 lo" o.39sq-" sr it 8 IO» (( sr tl 9 II' It s' tt 10 12" 11 4j" tt 11 12" o.s6sq." 6i" tt 12 13" (( 6" 18' 13 13" U sr (( 14 14" (( sr u IS 14" (1 s" cc i6 IS" " 4|" (1 17 IS" u 41-" (( i8 16" (( 4l" (( 19 17" (( 4r tt 20 18" o.77sq." sr tt 21. 18" (( si' tt 22 19" K s" 24" 23 19" U s" it 24 20" It 4r " 2S 21" i.oosq." si" tt For Spans s' to 19' W = 18" For Clear Height 10' or less " " s' to 19' W = 24" " " " 11' to is' " " 20' to 2S' W = 24" " " " is' or less For Clear Height 7' or less E = 3'- o* " 8' to 10' E = 4'- o' " above 10' E = s'- o» * Note. — The thickness of slab given is for shallow fills. For the effect of deep fills see Volume III. Fig. 125. — {Conliniied), DRAINAGE 257 J.§UOi45S5 siunsg J-S: ■5 ^-13 S 3 ^\^i fi » e » = ¥1 = S4SJ0UOJ Sigg^^>*^^SSfef ior:) m E-i o M 17 258 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS ui p .2 1 5 1 t> « - 1 e 1 1 s i 1 K e t j . ? J. 1 g 4> t E = = =■ :? 1 t t» 1 « 1 ^ = , i i ^ > ~ : . - g 3 ^ ^ £ S5 is is s ? 3> ft ^0 s 1 g «t. !> * 1 S3 !? •^ s ^ rk) Si ^ ' ' ~ ;_ ^ « « ■■ » s *» t. « » ^* ^S:]p <> » s « & G c ^ 1 !SS « <0 *d)V % CO £ """""£SS«SS s J3^J3«^"jJ (S iJJhJkSJiJ u 3 o o WMMWM H MN O Id tn t4 t4 1-4 l-j h 1 1 OOOOOUUUOOU g r-t-ooroOflCtiflCC 3 O MO M^OOOOOO C/3 (2 H M M « «oooc3c3o s 'd'd'd'd'd'd •| J2 't^'^'^p*?*^ V "H jj j5 jj ^ jj ji s >3 a i H H M w nHo t-inw irt t-H " C C > OO OQO lO O O O N ro 1 s e s s s a ■p -tJ ■*->+> +* bD u u u o o ^g (J k % 1" 1 ft. i; piK-Kfe 4J Is • c & .3 rfSc^r-Nf\r^ D) N-U'^ :3g «^^^« C ^-l| 'a -2 -2 99 1 f Sand-Cushion noHleqiilredln SanfySoit SizecfStDneS-9.') Cobble Gutter. Third Class Concrefe Ditch Lining. f'( Usual Wij fr^i ririiiriiiiiT.j<