EARTH, SAND-CLAY, AND GRAVEL ROADS. 



9 



6. Avoid turning water from one intersecting road down the side 

 ditches of another. Also avoid draining adjacent fields into the 

 side ditches. 



CROWN. 



The proper crown to give the cross section of a road surface de- 

 pends on two opposed factors : 



(a) It is desirable to get water away from the surface as quickly 

 as practicable, so as to prevent the surface material from being 

 softened by saturation or washed away by water collecting in, and 

 flowing along, ruts. 



(b) It is desirable to keep the cross section of the road as flat as 

 is consistent with good drainage, because traffic distributes itself 

 over a flat road sur- 

 face much better 

 than over one that is 

 heavily crowned, and 

 an even distribution 

 of traffic makes to- 

 ward uniform wear 

 and comparatively 

 light maintenance. 

 There is also less 

 danger of skidding 

 on a road of flat 

 cross section than 

 where the surface is 

 crowned. 



In general, the 

 amount of crown 

 should be greater on grades than on level stretches of road, because 

 the tendency for water to wash away the surface by collecting in 

 and flowing along ruts depends largely upon the steepness of the 

 grade. Also the care with which a road is to be maintained may 

 have an important influence on the amount of crown that should be 

 given to the surface. It is evident that a road surface maintained 

 in a smooth uniform condition will shed water off to the side ditches 

 with much less crown than would be required where ruts are allowed 

 to form. 



Instead of crowning the road surface sufficiently to prevent water 

 from flowing along the traveled way and causing washes on steep 

 grades, resort is sometimes had to " water breaks," or " thank- 

 you-ma'ams," constructed across the road at short intervals. These 

 water breaks may consist of either broad, shallow ditches or flat 

 ridges constructed at a slight angle with the road so as to turn 



Fig. 1, 



OPBREI2252 



-Use of wooden breakers to prevent scour of side 

 ditch. 



