Railway Braking Systems. Kinematics and Performances

The first task of a railway braking engineer is to dimension the braking system of a vehicle or convoy. This dimensioning must take into account several constraints:

• constraints specific to the mechanical and thermal capacities of the vehicle's braking systems, the number and dimensions of which are partly determined by the space available in the vehicle's bogies;

• wheel-rail adhesion, one of the main constraints specific to the rail system;

• signalling systems, which ensure train spacing on the lines on which the vehicles will be operated, bearing in mind that interoperability between countries increasingly implies taking into account very different signalling systems, pending the widespread introduction of the ERTMS (European Railway Traffic and Management System). These directly define the braking performance to be achieved.

While railway braking calls on general mathematical and physical principles, its specific features have necessitated the development of special methods to characterize its performance.

After recalling the kinematic principles of braking and the various quantities involved in the braking process, we'll return to the various methods used to determine the braking performance of a train, and the parameters used to characterize this performance.

Finally, we give an overview of the braking performance observed for different categories of rail trains (streetcars, metros, passenger and freight trains).