Whenever a roadway (or railway) is laid on a curved path, then its outer edge is always made higher than the inner edge, to keep the vehicle in equilibrium while in motion.

The amount by which the outer edge is raised, is known as cant or superelevation. In case of roadways, the process of providing superelevation is known as banking of the road.

The general practice, to define the superelevation in roadways, is to mention the angle of inclination (also called angle of banking) of the road surface.
In case of railways, the general practice to define the superelevation, is to mention the difference of levels between the two rails.

The attainment of superelevation by rotation of pavement about the inner edge of the pavement avoids the drainage problem in flat terrain.