Earth, Sand-Clay, and Gravel Roads

1917

U.S. Department of Agriculture Bulletin Number 463

National Agricultural Library

According to recent statistics gathered by the Office of Public Roads and Rural Engineering, the aggregate length of all public roads in the United States is, roughly, two and one-half millions of miles. Of this total mileage, earth roads comprise about 89 ½ per cent, or considerably more than 2,200,000 miles; sand-clay nearly 2 per cent, or 44,000 miles ; and gravel about 4 ½ per cent, or 116,000 miles, which leaves only about 4 per cent, or about 110,000 miles, for all other types combined. The statistics also show that in the 10 years from 1904 to 1914 the increase in the mileage of improved roads, other than earth, sand-clay, and gravel, has been only from 2 to 3 per cent of the total, and that in States having the greatest mileage of improved roads, only about one-half of their aggregate mileage has yet been improved. From these figures it is evident that the construction and maintenance of earth roads will continue to be of considerable importance in connection with every comprehensive plan of public road improvement. Also, since sand-clay and gravel surfaces often constitute the first steps from earth roads toward the more highly improved surfaces, either one or both of these simple types may be expected to constitute in the future, as at present, no small part of the total improved mileage in practically every community. On account of this wide distribution of earth roads and their close relationship to sand-clay and gravel surfaces, public interest in these three types is both genuine and general and gives ample warrant for the issuance of this bulletin, the aim of which is to supply reliable information concerning the construction and maintenance of earth, sand-clay, and gravel roads.

LOCATION AND DESIGN

Since nearly all public roads are laid out originally as earth roads, and since the original location and design usually have such an important bearing on all subsequent improvements, it seems well to include in this bulletin a brief discussion of the fundamental principles underlying the proper location and design of a public road. But, before undertaking such a discussion in detail, it is desired to emphasize the all-important facts that for a particular road the best and most economical location depends largely upon individual judgment, and that well-balanced and experienced judgment regarding the relative importance of the various details involved is a much more valuable asset in undertaking to locate a road than mere technical skill in handling surveying instruments. No knowledge gained from books alone can give that complete grasp of the relations existing between a public road and the community it serves which is so necessary if the location and design of the road are to secure the greatest possible good from the money expended.

U.S. Department of Agriculture