Whenever on roads, curve has to be made, outer edge of the road on the curve is raised as compared to the inner edge. This is known as super elevation.
Whenever the vehicle is moving in a curved path, it is acted upon by the force outward the curve known as centrifugal force. This force is always acting in the horizontal direction through the center of gravity of the vehicle and always perpendicular to the weight of the vehicle. If Centrifugal force is greater than the force between the road and the tyres, then the vehicle will skid outward. If centrifugal force is less than the force between the road and the tyres, then the vehicle will overturn to the inside of the curve. Super elevation is to be provided in case of curves only. If the road surface is plain or flat i.e there is no curve, then the tendency of the centrifugal force is through the vehicle from the center line and the only force which will prevent the vehicle that is frictional force. This force depends upon centripetal force and the weight of the vehicle. The procedure in which outer edge is raised with respect to the inner edge is known as super elevation. Its units are meter/meter or feet/feet.
How we provide Super elevation in the field ?
- For the provision of super elevation in the field, we may provide rotation about the inner edge, when the cutting of the road is required.
- Similarly, rotation about outer edge is preferred, when the filling of the road is required.
- For the good appearance, rotation about outer edge is preferred.
Rotation about center is preferred when inner and outer edge are at same level.