Banking of roads:

The phenomenon of raising the outer edge of curved road above the inner edge is to provide required centripetal force to the vehicles to take the safer turn and the curved road is called as Banking of Roads. It is a phenomenon taking place everywhere. The curvature of the road should be inclined so as to control Centrifugal force of Vehicle. The angle at which the roads are inclined is called as banking angle. When the vehicle goes round a curved road, it needs some centripetal force. While the rounding curves, the wheels of vehicle have a tendency to leave the curved surface and regain straight line path. Force of friction in between wheels and the roads opposes this tendency of wheels. This force of friction therefore, acts towards the centre of circular track and provides the required centripetal force. When the vehicles go through turnings, they travel along a circular arc. There should be some force to produce required centripetal acceleration. Centripetal force is given to the vehicle by following 3 ways.

      1) By friction only

      2) By banking of roads only

      3) By friction and banking of roads both.

 The coefficient of friction in between tyres and road. The value of μ decreases when the road is extra smooth or wet or tyres of the vehicle are worn out. Therefore force of friction is not a reliable source for providing the needed centripetal force to the vehicle. Especially in hilly areas where the vehicle has to move constantly along curved track, the maximum speed at which the car can run will be very low. If any attempt is made to run it at a greater speed, the vehicle is likely to skid and go out of track. In order that the vehicle can go round the curved track at a reasonable speed without skidding, the sufficient centripetal force is managed for it by raising the outer edge of the track little above the inner edge. It is called as banking of circular track or Banking of Roads. Roads are banked for the average speed of vehicles passing over them. But, if the speed of a vehicle is rather less or more than this, the self adjusting state friction will operate in between the tyre and road and vehicle will not skid.