ROADS AND PAVEMENTS 411 



desirable. Where the grade line has the same elevation at the 

 intersecting streets at both ends of a block, instead of making 

 the grade level between those streets, it should be elevated in the 

 center of the block sufficiently to cause the water to flow in each 

 direction toward the intersecting streets. If the street is sew- 

 ered, the grade may be depressed at the center of the block by 

 locating catch basins there; generally, however, it is better to 

 elevate the grade at the center of the block. 



VALUES OF q IN FORMULA FOR HEIGHT OF CROWN 



Character of Roadway V Q a f lu . e 



Common earth roadways 



Ordinary gravel roadways 



Broken-stone roadways 



Wooden-block pavement 



Cobblestone pavement 



Granite-block and concrete pavements 



Well -laid brick pavement 



First-class asphalt pavement 



Lateral Slopes of Sidewalks. For the purpose of drainage, 

 sidewalks should have a slight lateral slope toward the curb. 

 On business streets that are closely built up, in which the entire 

 width between the curb and the building line is occupied by the 

 sidewalk, this lateral slope of the sidewalk will fix the elevations 

 on the building line. The edge of the sidewalk adjacent to the 

 curb will be placed at the elevation of the curb, that is, at the 

 street grade, and the edge of the sidewalk adjacent to the build- 

 ing line will be higher or above grade an amount equal to the 

 width of the sidewalk in feet multiplied by the lateral slope per 

 foot. In some cities, a lateral slope of 2J%, or 1 in 40, is given 

 to the sidewalks; a slope of 2%, or 1 in 50, however, is generally 

 very satisfactory for this purpose. All that portion of the 

 street between the curb and the property line should have this 

 uniform lateral slope, whether wholly occupied by the sidewalk 

 or not. 



