Cant deficiency is the difference between the actual cant provided and equilibrium cant necessary for the maximum permissible speed on a curve.Cant deficiency should be as low as possible and is limited due to following reasons:
- Higher discomfort to passengers due to higher cant deficiency
- Higher cant deficiency results in higher unbalanced centrifugal force and hence extra pressure and lateral thrust on the outer rails, requiring strong track and more fastening for stability.
- Side wear and creep of outer rails of the track are more due to higher cant deficiency. Maximum values of cant deficiency as prescribed on Indian Railways On BG
- For speeds up to 100kmph = 76mm
- For speeds up to higher than 100kmph = 100mm
On curves, branch line meets the main line at certain places. The outer rail of the main line of curves meets the inner rail of the branch line. As the superelevation is provided on the main line, the outer rail of the main line is at the higher level than the inner rail. The inner rail of branch line will have to be kept at the higher level than inner rail. But here as the outer rail in branch line is at lower level than inner rail, the superelevation is known as ‘Negative superelevation’ or ‘Negative cant’.