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PREFACE vii

THE PURPOSE AND UTILITY OF HIGHWAYS

Transportation Problem--National in Scope--Development in Traffic--Location or Farm to Market Traffic--Farm to Farm Traffic--Inter-City Traffic--Inter-County and Inter-State Traffic--Rural Education--Rural Social Life--Good Roads and Commerce 1-12

HIGHWAY ADMINISTRATION

Township Administration--County Administration--State Administration--Federal Administration--Special Assessments--Zone Method of Assessing--General Taxation--Vehicle Taxes--Sinking Fund Bonds--Annuity Bonds--Serial Bonds--Comparison of Methods of Issuing Bonds--Desirability of Road Bonds 13-28

DRAINAGE OF ROADS

The Necessity for Drainage--Importance of Design--Surface Drainage--Run-off--Ordinary Design of Ditches--Underground Water--Tile Drains--Lying Tile--Culverts--Length of Culvert-- Farm Entrance Culverts--Metal Pipe--Clay and Cement Concrete Pipe--Concrete Pipe--Endwalls for Culverts--Reinforced Concrete Box Culverts--Drop Inlet Culverts 29-41

ROAD DESIGN

Necessity for Planning--Road Plans--Problems of Design-- Preliminary Investigations--Road Surveys--Alignment-- Intersections--Superelevation--Tractive Resistance--Rolling Resistance--Internal Resistance--Air Resistance--Effect of Trades--Energy Loss on Account of Grades--Undulating Roads-- Guard Railing--Width of Roadway--Cross Section--Control of Erosion--Private Entrances--AEsthetics 42-62

EARTH ROADS

Variations in Soils--Variation in Rainfall--Cross Sections Elevating Grader--Maney Grader--Slip Scraper--Fresno Scraper--Elevating Grader Work--Use of Blade Grader-- Costs--Maintenance--Value of Earth Roads 63-73

SAND-CLAY AND GRAVEL ROADS

The Binder--Top-soil or Natural Mixtures--Sand-clay on Sandy Roads--Sand-clay on Clay or Loam--Characteristics--Natural Gravel--The Ideal Road Gravel--Permissible Size of Pebbles-- Wearing Properties--Utilizing Natural Gravels--Thickness of Layer--Preparation of the Road--Trench Method--Surface Method--Maintenance 74-88

BROKEN STONE ROAD SURFACES

Design--Properties of the Stone--Kinds of Rocks used for Macadam--Sizes of Stone--Earth Work--Foundation for the Macadam--Telford Foundation--Placing the Broken Stone-- Rolling--Spreading Screenings--Bituminous Surfaces--Maintenance Characteristics 89-97

CEMENT CONCRETE ROADS

Destructive Agencies--Design--Concrete Materials--Fine Aggregate--Proportions--Measuring Materials--Preparation of the Earth Foundation--Placing Concrete for Two-course Road--Curing the Concrete--Expansion Joints--Reinforcing--Bituminous Coatings on Concrete Surfaces--Characteristics--Maintenance 98-105

VITRIFIED BRICK ROADS

Vitrified Brick--Paving Brick--Repressed Brick--Vitrified Fiber Brick--Wire-cut-lug Brick--Tests for Quality--Other Tests-- Foundation--Sand Bedding Course--Sand Mortar Bedding Course-- Green Concrete Bedding Course--Bituminous Fillers--Mastic Fillers--Marginal Curb 106-115

BITUMINOUS ROAD MATERIALS AND THEIR USE

Classes of Bituminous Materials--Coal Tar--Water Gas Tar--Natural Asphalt--Petroleum Asphalt--Mixtures--Classification According to Consistency--Road Oils--Liquid Asphalts--Asphalt Cements-- Fillers--Bitumen--Specifications--Surface Treatments--Applying the Bituminous Binder--Finishing the Surface--Patching-- Penetration Macadam--Foundation--Upper or Wearing Course-- Patching Characteristics--Hot Mixed Macadam--Foundation--Sizes of Stone--Mixing the Wearing Stone--Placing and Wearing Surface--Seal Coat--Characteristics--Asphaltic Concrete-- Bitulithic or Warrenite--Topeka Asphaltic Concrete--Foundation --Placing the Surface--Characteristics 116-129

MAINTENANCE OF HIGHWAYS

Petrol Maintenance--Gang Maintenance--Maintenance of Earth, Sand-clay, Gravel and Macadam Roads 130-134

Index 135

AMERICAN RURAL HIGHWAYS

THE PURPOSE AND UTILITY OF HIGHWAYS

THE DEVELOPMENT OF HIGHWAY SYSTEMS

Until recent years, highway improvement in the United States has been subordinated to other more pressing public improvements, but during the World War the inadequacy of the transportation system of the United States became apparent. While such an unprecedented load upon transportation facilities may not recur for many years, it has become apparent that more rapid progress in highway improvement is necessary and in the United States the subject is now likely to receive attention commensurate with its importance.

The advent of the motor driven vehicle in the United States has resulted in a greatly increased use of the public highways of agricultural areas, even of those that are sparsely populated, because of the convenience of the motor vehicle both for passenger and for freight service. Probably in excess of 90 per cent of the tonnage passing over the rural highways in the United States is carried by motor vehicles. This class of traffic has really just developed and no one can predict what it will be in ten years, yet it has already introduced into the highway problem an element that has revolutionized methods of construction and maintenance.

A different set of traffic conditions exists in those parts of the United States where large areas are devoted primarily to industrial pursuits, the agricultural development being of secondary importance. Public highways connecting the industrial centers are indispensable adjuncts to the business facilities in such communities and are ordinarily subjected to a very large volume and tonnage of traffic consisting principally of motor vehicles. The roads first selected for improvement will not be those serving the agricultural interests of the district, but rather those serving the industrial centers. Inter-city roads of great durability and relatively high cost are necessary for such traffic conditions.

Not infrequently the transportation needs will require a system of both inter-city and rural highways in the same community. There are few areas in the United States where there is no agricultural development. It is apparent therefore that the nature of the highway systems and the administrative organization under which they are built and maintained will differ in various states or areas according to the nature of development of that area agriculturally and industrially. In planning improvements of highway systems, it is recognized that one or more of several groups of traffic may be encountered and that the extent and nature of the improvement must be such as will meet the requirements of all classes of traffic, the most important being first provided for, and that of lesser importance as rapidly as finances permit.

KINDS OF TRAFFIC ON PUBLIC HIGHWAYS

In industrial districts there is a large volume of this class of traffic consisting of motor passenger vehicles used for business and for pleasure and of motor freight vehicles used for general business purposes. In addition, there is certain to be a large amount of motor truck freight traffic incident to the particular industrial pursuits of the cities. Where adequate public highways connect industrial centers, there is invariably a very large amount of inter-city traffic, due in part to the needs of industry and in part to concentration of population in industrial centers.

PUBLIC HIGHWAYS AND COMMUNITY LIFE

It is well to recognize the intimate relation public highways bear to the economic progress of a nation. Normal development of all of the diverse activities of a people depends very largely upon the highway policy that is adopted and whether the actual construction of serviceable roads keeps pace with transportation needs.

If there is opportunity for those who live in the cities to get some adequate idea of rural life and the conditions under which farming operations are carried on it will correct many misunderstandings of the broad problems of food production and distribution. Reference has frequently been made to the seeming desire on the part of city people to get into the country, and, by facilitating the realization of this desire, a great social service is rendered.

The whole commercial structure of a nation rests upon transportation, and the highways are a part of the transportation system. The highway problem can never receive adequate consideration until public highways are recognized as an indispensable element in the business equipment of a nation.

During the World War all transportation facilities were taxed to the limit, and motor trucks were utilized for long distance freight haulage to an extent not previously considered practicable. As a result, the interest in the motor truck as an addition to the transportation equipment of the nation, has been greatly stimulated. Many haulage companies have entered the freight transportation field, delivering commodities by truck to distances of a hundred miles or more.

The part the motor truck will play in the future can only be estimated, but it seems clear that the most promising field is for shipments destined to or originating in a city of some size and a warehouse or store not on a railroad spur, and especially when the shipments are less than car load lots. The delays and expense incident to handling small shipments of freight through the terminals of a large city and carting from the unloading station to the warehouse or other destination constitute a considerable item in the cost of transportation.

Engineering News Record, July 10, 1919.

"It costs today as much to haul a ton of farm produce ten miles to a railway station as it does to haul it a thousand miles over a heavy-traffic trunk-line railway. It often costs more today to transport a ton of merchandise from its arrival in a long train in the freight yard on the outskirts of a great city to its deposit in the warehouse of a merchant four or five miles away than it has cost to haul it over a thousand miles of railway line."

Nevertheless it seems probable that new methods of operating the motor truck transport, and possibly new types of trucks or trucks and trailers will be developed so that freight traffic over many roads will be of considerable tonnage and an established part of the transportation system of the nation. In the article above referred to are given the following data relative to the cost of hauling on improved roads by motor truck and these cost estimates are based on the best information available at this time. They should be considered as approximate only, but serve to indicate the limitations of the truck as a competitor of the steam railway.

TABLE 1

INDIRECT CHARGES PER DAY

TABLE 2

OVERHEAD CHARGES PER YEAR FOR A 5-TON CAPACITY GASOLINE MOTOR TRUCK RUNNING AN AVERAGE OF 50 MILES PER DAY FOR 240 DAYS PER YEAR

Overhead charges per day for 240 days in the year, actual operation .15 Overhead charges per mile for 50 miles per day .463

In the above table the driver's wages have been placed under overhead charges because the driver is paid by the month and his wages continue even though the truck is idle because of repairs, bad weather or lack of business, unless, of course, the idleness should be of long duration, when the driver might be laid off.

DIRECT CHARGES PER DAY AND PER MILE FOR 5-TON TRUCK OPERATED AS ABOVE

Total of overhead and direct charges for 240 days per year operation, per day .15 Per mile .603 Cost per ton-mile for full loads one way and empty returning .2412 Cost per ton-mile for full loads one way and half load returning .16

In view of these facts it seems reasonable to suppose that motor vehicles for use on the public highways are more likely to be employed to supplement the rail transport than to compete with it. To the actual cost of operation of motor trucks given in Table 2, there should be added the proportionate cost of maintaining the highway for the use of the truck, which is partly covered by the item "License Fee" in the table. The license fee would necessarily be considerably larger if it were to compensate adequately for the wear on the highways over which the trucks operate. This will still further increase the cost of hauling by motor truck.

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