how to calculate the super elevation of road on horizontal curve?

Answer 1

The intent of superelevation (banking) is to cancel the centripetal force on a curve, so that the road is at right angles to the total vehicle force at some specified constant velocity. The ideal bank angle, just as in a level turn in aviation, is ARCTAN(lateral acceleration / gravitational acceleration). Lateral acceleration is V^2 * R, V being the velocity and R the turn radius. Note V, R and gravitational acceleration must be in compatible units. Superelevation often is limited below the ideal value to prevent inward slippage on icy road at low speed (ref.).