As per Indian Road Congress (IRC) for roads: At curves, a vehicle is subject to centrifugal force the intensity of which depends on the travelling speed and the degree of curvature. Design requirement warrants that a portion of this force (equal to the force developed at 75 per cent of the design speed) should be counteracted by super elevation (super elevation rate should be subject to maximum of 7 percent for plain, rolling and snow-bound hilly terrains, and 10 percent for nonsnow-bound hilly terrain) and the balance by side friction subject to a maximum ratio of 0.15.