Cant (rail) on a road or railway is the difference in elevation of the two sides of the track to help go around curves.

In the case of railways, the cant helps steer around the curve, and also keep the wheels from touching either rail, so minimizing wear and tear.

The amount of cant has to be chosen for one speed, so if the trains travel at different speeds, the cant will either be too much or too little. Thus a compromise value of cant must be chosen.