ROADS 475 



The wearing surface of a road must be in effect a roof; tliat is, 

 the section in the middle should be the highest part and the 

 traveled roadway should be made as impervious to water as 

 possible, so that it will flow freely and quickly into the gutters 

 or ditches alongside. Where the road is constructed on a grade 

 or hill the slope from the center to the sides should be slightly 

 steeper than that on the level road. Every wheel track on an 

 inclined roadway becomes a channel for carrying down the 

 water, and unless the curvature is sufficient these tracks are 

 quickly deepened into water courses which cut into and some- 

 times destroy the best improved road. 



Water breaks and side ditches. — In order to prevent the 

 washing out of earth roads on hills it sometimes becomes neces- 

 sary to construct water breaks; that is, broad shallow ditches 

 arranged so as to catch the surface water and carry it each way 

 into the side ditches. Such ditches retard traffic to a certain 

 extent, and often result in overturning vehicles; consequently 

 they should never be used until all other means have failed to 

 cause the water to flow into the side channels; neither should 

 they be allowed to cross the entire width of the road diagonally 

 but should be constructed in the shape of the letter V. This 

 arrangement permits teams following the middle of the road to 

 cross the ditch squarely and thus avoid the danger of overturn- 

 ing. These ditches should not be deeper than are absolutely 

 necessary to throw the water off the surface, and the part in the 

 center should be the shallowest. 



Where the road is built on a grade some provision should be 

 made to prevent the wash of the gutters into great, deep gullies. 

 This can be done by paving the bottom and sides of the gutters 

 with brick, river rocks, or field stones. In order to make the 

 flow in such side ditches as small as possible, it is advisable to 

 construct outlets into the adjacent fields or to lay underground 

 pipes or tile drains with openings into the ditches at frequent 

 intervals. 



Subdrainage. — In order to have a good road it is just as neces- 

 sary that water should not be allowed to attack the substructure 

 from below as that it should not be permitted to percolate 

 through it from above. Under drains are not expensive. On 

 the contrary, they are cheap and easily made, and if made in a 

 substantial way, and according to the rules of common sense, a 

 good under drain will last for ages. Slim fagots of wood bound 

 together and laid lengthwise at the bottom of a carefully graded 

 drain ditch will answer fairly well if stone or drain tile can not 



