158 AGRICULTURAL ENGINEERING 



Cost of Gravel Roads. The cost of gravel roads varies 

 widely, depending largely upon the availability of gravel. 

 The method of construction is another important factor. 

 The amount of gravel used varies widely with different con- 

 struction. In some cases as little as 1-10 of a yard of gravel 

 may be applied per foot of length. In other cases a cubic 

 yard may be applied per foot. 



Roads may be graveled lightly by the surface method at 

 a cost of from $200 to $500 per mile. Where the roads are 

 constructed by the trench method, the cost usually varies 

 from $1000 to $2000, but it may run as high as $3000 per 

 mile. 



Maintenance of Gravel Roads. Gravel roads should be 

 kept smooth and oval by the use of the road drag. The road 

 drag is not needed as often on gravel as on earth roads, yet 

 pockets and ruts should not be allowed to form. From time 

 to time additional gravel should be added to the surface. 



When repairing gravel roads in this manner, it is 

 customary to apply about two inches of gravel at a time, 

 except at the places where the road has been destroyed, in 

 which case it will be necessary to use more gravel. The 

 length of time in which the gravel road may go without an 

 application of additional material varies so much with the 

 traffic, grade of materials used, and other conditions, that 

 no attempt will be made to suggest an average period. 



QUESTIONS 



1. Under what conditions is the clay road at its best? 



2. How is a sand road improved? 



3. What principle is involved in the construction of the sand-clay 

 road? 



4. How much does a sand-clay road cost? 



5. To what conditions is the gravel road adapted? 



6. What are the requisites of good road gravel? 



