What is the purpose of Cant in railways?

The purpose of Cant (Superelevation) is to counteract centrifugal force on curves. This ensures that the weight of the train is distributed evenly across both rails and prevents passengers from being thrown sideways.

What is the difference between Cant and Superelevation?

There is no difference in meaning; they are regional terms for the same concept. 'Cant' is typically used in the UK and Europe, while 'Superelevation' is used in North America.

What happens if a train goes too fast for the Cant?

If a train exceeds the equilibrium speed for a given Cant, it experiences 'Cant Deficiency.' The train pushes against the outer rail, causing increased wear and potentially reducing passenger comfort.

The Art of Banking: Cant (Superelevation) Explained

Cant (Superelevation) is the raising of the outer rail on curves to counteract centrifugal force. Learn how this critical track geometry ensures passenger comfort and safety.

December 9, 2025 5:59 am

What is Cant (Superelevation)?

Cant, also known as Superelevation in North America, is the amount by which the outer rail is raised above the inner rail on a curved track. This design feature creates a “banking” effect, similar to a race car track or an airplane banking during a turn.

Without Cant, a train entering a curve at speed would experience strong lateral forces pushing it outward. By tilting the track, gravity helps pull the train inward, balancing the physics of the turn.

The Physics: Balancing the Forces

The primary goal of Cant is to neutralize Centrifugal Force. When a train moves around a curve, two opposing forces are at play:

Centrifugal Force: Pushes the train outwards (away from the center of the curve).
Gravity (Weight): Pulls the train downwards. By tilting the track, a component of gravity pulls the train inwards.

Ideally, the track is canted so that the resultant force acts perpendicular to the floor of the train. This means passengers feel neither pushed to the side nor tilted; they simply feel slightly heavier in their seats. This state is called Equilibrium Cant.

Cant Deficiency vs. Cant Excess

Since trains travel at different speeds (e.g., a fast passenger train vs. a slow freight train), engineers cannot design the track perfectly for every single train. This leads to two critical concepts:

Condition	Scenario	Effect on Passengers/Track
Equilibrium	Speed matches the angle exactly.	Perfect balance. No lateral force felt.
Cant Deficiency	Train is faster than the equilibrium speed.	Passengers feel pushed outwards. The outer rail wears faster.
Cant Excess	Train is slower than the equilibrium speed (or stopped).	Passengers feel pulled inwards. Risk of freight loads shifting inward.

Limits of Superelevation

You might wonder, “Why not tilt the track 45 degrees for super-fast trains?” There is a safety limit. If a train stops on a curve (due to a signal or breakdown), too much Cant would cause it to tip over inwards or make it difficult for passengers to walk inside the train. Therefore, standard Cant is usually capped at around 150mm to 180mm depending on the network.