Brake sizing
Railway rolling stock sizing

In traction, the effort is developed by the motorized machine, so the distance needed to get up to speed can be very long; the timetable takes this into account.

When braking, the stopping distance is a key factor in safety and traffic spacing, since for a given speed, it must be less than the distance at which warning and stop signs are installed.

This obligation imposes a retarding effort, and therefore an energy to be dissipated, which the motorized vehicle cannot produce on its own. Each towed vehicle must therefore contribute to braking as a direct result of its mass. Unlike traction, braking must be shared by all vehicles in the train.

Kinetic energy to be destroyed :$E=\frac{m{V}^2}{2}$