Brakes - Braking performance

This IRS defines braking performance and describes the method for determining the braking performance of railway vehicles and trains. Braking performance can be expressed via a braked weight or via decelerations.

The IRS also details the conversion of the braked weight to the braked weight percentage of a vehicle or train for operating purposes. Reference is also made to limiting features arising during operational application of the braked weight percentage of a train calculated from the vehicles' specified braked weight, for different train formations.

By default the brake assessment is made using the brake position "P". However, the IRS also indicates reference values for stopping distances which can be obtained in the brake position "G".

The assessment curves are presented as graphs and in mathematical terms.

The assessment in the shape of a braked weight is valid for trains and individual vehicles at speeds up to 200 km/h. Assessment via decelerations is valid only for trains, though irrespective of speed.

Braking performance is defined based on a number of standardised conditions (e.g. gradient) and a mean in-service vehicle condition. Brake assessment thus does not assume the worst possible vehicle condition, which may be the result of e.g. braking force tolerances, friction coefficient scatter, downgraded efficiency etc.

Furthermore the IRS provides pointers for calculating the performance of the screw brake with hand wheel and the spring-loaded brake.