UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 463 
Contribution from the Office of Public Roads and Rural 
Engineering, LOGAN WALLER PAGE, Director 
Washington, D. C. ▼ February 21, 1917 
EARTH, SAND-CLAY, AND GRAVEL ROADS 
By Chaeles H. Mookefield, 
' Senior Highway Engineer. 
CONTENTS. 
Page. 
Location and design ". 2 
Earth roads 15 
Sand-clay roads 34 
Page. 
Gravel roads 45 
Road maintenance 58 
Appendix: Typical specifications 63 
According to recent statistics gathered by the Office of Public 
Roads and Sural 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 89J per cent, 
or considerably more than 2,200,000 miles; sand-clay nearly 2 per 
cent, or 44,000 miles ; and gravel about 4| 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 impor- 
tance in connection with every comprehensive plan of public road 
improvement. Also, since sand-clay and gravel surfaces often con- 
stitute the first steps from earth roads toward the more highly im- 
proved 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 rela- 
tionship to sand-clay and gravel surfaces, public interest in these 
three types is both genuine and general and gives ample warrant for 
61531° — Bull. 463—17- 
