Why are roads banked on curved path?
When a vehicle moves round a horizontal curve on the road with sufficient speed, the necessary centripetal force is provided by the friction between the tyres and the road. So, to increase the centripetal force, friction should be increased which causes wear and tear of the tyres. If the road is banked on the curve, the necessary centripetal force is provided by the horizontal component of normal resistance.
i.e. Fc = Rsinθ
Here, centripetal force can be increased be increasing the angle of banking. So, roads are banked on curved path.