Pavements should be widened on a curve so that the inner row of vehicles may pass around on the same curvature as the outer row.
Superelevation.
—The superelevation of the outer side of a curved roadway can not at one and the same time be made suitable for all rates of speed. Works on mechanics give the formula for the elevations of the outer edge as
e = av2 gR
| where | e | = | the elevation in feet; |
| a | = | the width of road in feet; | |
| g | = | acceleration of gravity in ft. per sec. per sec.; | |
| v | = | velocity in ft. per sec.; | |
| R | = | radius in feet. |
Or if the velocity, V, is given in miles per hour and the elevation, E, in inches this reduces to
E = 121aV2 150R = 0.807aV2R
© Underwood and Underwood