786 EXPERIMENT STATION RECORD. [Vol. 3G 



description of the systems of road administration, fiscal management, and 

 other factors affecting road improvement in the States of Alabama, Arkansas, 

 Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North 

 Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West 

 Virginia. 



The total revenues applied to roads and bridges in the Southern States in 

 1914 amounted to $52,516,559.73, including state appropriations, amounts de- 

 rived from local taxation, and expenditures from bond issues, both State and 

 local. The total county and district road and bridge bonds outstanding on 

 January 1, 1915, amounted to $64,639,060.83. The total road mileage as of 

 January 1, 1915, vs^as 814,565, of which 73,594.78 miles, or 9.03 per cent, were 

 surfaced. This does not include streets in incorporated cities and towns. Of 

 the surfaced I'oads 29,287.88 miles were sand clay, 21,377.37 miles were mac- 

 adam. 17,440.02 miles were gravel, 1,994.36 miles were bituminous macadam, 

 1,924.68 miles were shell, 379.81 miles were brick, 273.24 miles were concrete, 

 and 917.42 miles were surfaced with other materials. 



Earth, sand-clay, and gravel roads, C. H. Mookefield {U. S. Dept. Agr. Bui. 

 463 (1917), pp. 68, pis. 5, figs. 24). — This bulletin gives general information on 

 the location and design of roads and deals with the construction, maintenance, 

 and cost of earth, sand-clay, and gravel roads. ' 



With reference to grades, " tests made by the Office of Public Roads and 

 Rural Engineering indicate that, on a level road average farm horses un- 

 trained to the road can exert a steady pull for several consecutive hours 

 equivalent to from 0.08 to 0.1 of their own weight without undue fatigue, and 

 that by resting at intervals of from 500 to 600 ft. they can exert a pull equiva- 

 lent to about 0.25 of their weight, provided the foothold is good. The tests also 

 indicate that with a well-constructed wagon the pull required to move a gross 

 load of 1 ton over a level road varies about as foUow^s: Loose-sand road, 315 

 lbs.; average dry earth road (varies greatly), 150; firm earth or sand-clay 

 road, 105; average gravel road, 80; and first-class gravel or macadam road, 

 55. . . . 



" For economy the maximum grade for any particular road should be fixed 

 with due regard for the type of surface to be employed. Where the road is 

 through deep sand, a horse of [1,255 lbs. weight], by extraordinary exertion, 

 could pull his allowable continuous load of 760 lbs. for level grades up a short 

 grade of about 10 per cent, while in the case of a firm earth or sand-clay road 

 the allowable continuous load for level grades is 2,285 lbs., and the steepest 

 grade up which the horse could possibly pull this load is about 5 per cent. For 

 average gravel roads the corresponding comparison would show a maximum 

 grade of about 4 per cent. . . . According to the best current practice, where 

 the road is or is expected to become of sufficient importance to warrant a highly 

 improved surface, the maximum grade usually is fixed with reference to this 

 feature about as follows: Coastal plain and prairie regions, 2 to 3 per cent; 

 average rolling country, 4 to 6 ; and hilly or mountainous regions, 6 to 8." 



In dealing with gravel roads the results of a number of tests made on gravel 

 obtained from various parts of the country with reference to its suitability for 

 use in road surfaces are given. " In general, it has been found that satisfac- 

 tory gravel will conform to the following limits as to percentages of fine and 

 coarse material: (1) Material retained on a ^-in. sieve 55 to 75 per cent, (2) 

 material retained on a |-in. sieve not less than 15 per cent, (3) material (clay) 

 passing a 200-mesh sieve for the surface course 8 to 15 per cent, and (4) mate- 

 rial (clay) passing a 200-mesh sieve for the foundation course 10 to 15 per 

 «ent. The sand content should be at least twice as great as the clay content. 



