GRADE AND CLASSES OF ROADS. 209 



mules, ponies, &c., 100 in 173. For roads, Telford's rule was, 

 that for horses attached to ordinary vehicles to trot up a hill 

 rising 3 in one hundred, was equal to walking up one, of a 5 in 

 a hundred grade. 



Experiments have shown that, — 



1. On a road falling 2 in a hundred, vehicles would run down 

 of themselves. 



2. On the same kind of road, but having an inclination of 4 

 in a hundred, light vehicles had to be held back lightly, loaded 

 ones, with considerable force. 



3. On a road having a fall of 5| in a hundred, light vehicles 

 had to be held back with considerable force, or if a brake was 

 applied they had to be pulled, whereas heavy or loaded vehicles 

 had to be braked to keep the horses from being speedily 

 exhausted. 



On inclinations steeper than 5 in a hundred, the rain-water 

 running down the road is apt to do some damage to the road 

 surface. 



The regulations of different countries having a long experi- 

 ence in road building, such as France, Prussia, Baden, &c., vary 

 somewhat, but the following is the general result. 



In treating of roads, it often renders the subject much clearer, 

 to divide them into three classes : first, second and third class 

 roads, or, as we might also say, state, county and town roads. 

 Accepting this nomenclature, we have this : for first class or 

 state roads, the greatest inclination should not exceed 8-5 in a 

 hundred ; second class or county roads, 5-7 in a hundred ; 

 third class or town roads, 7-10 in a hundred. A road rising 10 

 in a hundred is not supposed ever to have any heavy teams upon 

 it. In ascending a hill it is well and proper to decrease the grade 

 as the top is reached, and in the same measure as the horses get 

 tired. Thus, if a first class road starts up hill with a grade of 

 4^ per hundred, it should gradually diminish to 4 and 3^ in a 

 hundred, and end near the top with a grade of 3 in a hundred. 

 If a grade of 4 or 5 in a hundred must needs be kept up for 

 some distance, then it is well to have resting places 40 or 50 feet 



in 120 feet, 100 inches in 120 inches, or 100 miles in 120 miles, all express 

 the same inclination to a level plane, and are more general in their appli- 

 cation than the ways of expressing grades in so many inches to the foot, 

 or feet in one mile, &c., &c. 



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