UNITED STATES DEPARTMENT OF AGRICULTURE 



mm BULLETIN No. 463 & 



<%lkS«S^il#» Contribution from the Office of Public Roads and Rural < 



4\&*^^U 



Contribution from the Office of Public Roads and Rural 

 Engineering, LOGAN WALLER PAGE, Director 



.sv£p"^s»r<L. 



Washington, D. C. 



February 21, 1917 



EARTH, SAND-CLAY, AND GRAVEL ROADS 



By Chaeles H. Moorefield, 

 Senior Highway Engineer. 



CONTENTS. 



Page. 



Location and design 2 



Earth roads 15 



Sand-clay roads 34 



Gravel roads 45 



Road maintenance 58 



Appendix: Typical specifications 63 



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^ per cent, 

 or considerably more than 2,200,000 miles; sand-clay nearly 2 per 

 cent, or 44,000 miles ; and gravel about 4J 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 1 



