Banking of roads at curve is necessary so as to avoid

Explanation

The road surface at a bend is tilted inward, i.e., the outer side of the road is raised above its inner side. This is called banking of road.
A car while taking a turn performs circular motion. If the road is level (i.e., horizontal), the necessary centripetal force is the force of static friction between the car tyres and the road surface. The presence of oil and water on the road. If the friction is inadequate, a speeding car may skid off the road. Since the friction changes with circumstances, it cannot be relied upon to provide the necessary centripetal force .
Moreover , friction results in fast wear and tear of the tyres. On a banked road, the resultant of the normal reaction and the gravitational force can act as the necessary centripetal force. Thus, every car can be safely driven on such a banked curve at a certain optimum speed, without depending on fiction. Hence, to avoid the risk of skedding as well as to reduce the wear and tear of the car tyres, a road should be properly banked at a bend .