24 BULLETIX 1077, IT, S. DEPART^.IEXT OF AGPJCULTUEE, 



SHOULDERS AND DITCHES. 



The ^vidth and kind of shoulders necessarj' for concrete pavements 

 will depend upon the width of pavement and the volume of traffic. 

 On single-track pavements the shoulders must be sufficiently wide 

 to provide for safety of passing vehicles and must be composed of 

 material which will support them satisfactorily. On double-track 

 pavements the .shoulders should he of sufficient width to allow for 

 irregular and unexpected actions by inexperienced drivers or fright- 

 ened animals, and, where the volume of traffic is large, to permit auto- 

 mobiles to turn out onto the shoulders for minor adjustments or 

 tire repairs without blocking the traveled way. The width of each 

 shoulder, then, should be not less than 5 feet ; a width of 6 or 7 f e"et 

 is preferable. 



It has generally Ijeen customary to construct gravel or macadam 

 shoulders to single-track roads on clay soils. This may be accom- 

 plished by constructing gravel or macadam strips 3 feet wide on 

 each side of the pavement, or in the ca.se of a single-track pavement 

 Ijuilt on one side of the center line by placing the gravel or macadam 

 strip all on one side and making the width 6 feet. These gravel or 

 macadam strips are usually 4 to 6 inches thick. On soils of a 

 gravelly nature which have rather good supporting power when wet, 

 metaled shoulders are not used. A double-track road should be wide 

 enough to permit the passing of vehicles without turning out on the 

 shoulders, so no shoulder should be necessary for this pavement other 

 than the natural soil. 



The slope of the .shoulder should be such as will readily dispose of 

 the water, and at the same time not be so steep that it will appear dan- 

 gerous to drive on. Shoulders along a low-crowned pavement should 

 have a slope as flat as possible so as not to accentuate the change in 

 sloj^e. A slope of ^ inch to 1 foot should prove satisfactory. Inas- 

 much as the shoulders of a concrete road are seldom rolled, some slight 

 settlement takes place, and it is usuallj'- found that if a very flat shoul- 

 der is constructed it will have all the slope necessary after the road 

 has been opened to traffic for a short time. 



Surface ditches are usuallj- constructed of two general shapes — the 

 V shape, and the trapezoidal shape. In rolling country, where the 

 surface water can be turned away from the road at frequent intervals, 

 the V-shaped ditch has proved verj' satisfactory. Where it is neces- 

 sary to carry water in the ditches for considerable distances the trape- 

 zoidal ditch should be used. The bottom of the ditch should be at 

 least 18 inches lower than the center of the road ; and when a large 

 volume of water is to be carried the minimum depth should be 24 

 inches. The slopes to the ditches from the shoulder should not be 

 steeper than 2 to 1. 



