HIGHWAY CONSTRUCTION 



77 



described in Part I. The curve should l>e used Ixith in the crown of 

 the street and in the curl) and footpath. 



\Yhere the grade is level between intersections, sufficient fall for 

 surface drainage may lie secured without the aid of accommodation 

 summits, by arranging the grades as shown in Fig. 40. The curb is 

 set level between the corners; a summit is formed in the gutter; and 

 receiving basins are placed at each corner. 



Transverse Grade. In transverse grade the street should be 

 level; that is, the curbs on opposite sides should be at the same level, 

 and the street crown rise equally from each side to the center. But in 

 hillside streets this condition cannot always l)e fulfilled, and opposite 



Fig. 50. 



Fig. 51. 



^ Side walk 



: $^:V^*pg^ 



sides of the street may differ as much as five feet; in such cases the 

 engineer will have to use his discretion as to whether he shall adopt a 

 straight slope inclining to the lower side, thus draining the whole street 

 by the lower gutter, or adopt the three-curb method and sod the slope 

 of the higher side. 



In the improvement of old streets with the sides at different levels, 

 much difficulty will be met, especially where shade trees have to be 

 spared. In such cases, recognized methods have to be abandoned, and 

 the engineer will have to adopt methods of overcoming the difficulties 

 in accord a net* with the conditions and necessities of each particular 

 Figs. 50, 51, arid 52 illustrate several typical arrangements in 



