HIGHWAY CONSTRUCTION 



without a direct loss of tractive power. This inclination is that in 

 descending which, at a uniform speed, the traces slacken, or which 

 causes the vehicles to press on the horses; the limiting inclination 

 within which this effect does not take place is the angle of repose. 



TABLE 9. 



The angle of repose for any given road surface can be easily 

 ascertained from the tractive force required upon a level with the 

 same character of surface. Thus if the force necessary on a level 

 to overcome the resistance of the load is V of its weight, then the 

 same fraction expresses the angle of repose for that surface. 



On all inclines less steep than the angle of repose a certain 

 amount of tractive force is necessary in the descent as well as in 

 the ascent, and the mean of the two drawing forces, ascending and 

 descending, is equal to the force along the level of the road. Thus 

 on such inclines, as much mechanical force is gained in the descent 

 as is lost in the ascent. From this it might be inferred that when a 

 vehicle passes alternately each way along the road, no real loss is 



