HIGHWAY CONSTRUCTION 



Loss of Tractive Power on Inclines. In ascending in- 

 clines a horse's power diminishes rapidly; a large portion of his 

 strength is expended in overcoming the resistance of gravity due to 

 his own weight and that of the load. Table 5 shows that as the 

 steepness of the grade increases the efficiency of both the horse and 

 the road surface diminishes; that the more of the horse's energy is 

 expended in overcoming gravity the less .remains to overcome the 

 surface resistance. 



TABLE 5. 



Effects of Grades Upon the Load a Horse can Draw on Different 



Pavements. 



Table 6 shows the gross load which an average horse, weighing 

 1,200 pounds, can draw on different kinds of road surfaces, on a 

 level and on grades rising five and ten feet per one hundred feet. 



TABLE 6. 



The decrease in the load which a horse can draw upon an incline 

 is not due alone to gravity; it varies with the amount of foothold 



