Braking Questions - Extension of the ETCS conversion model for train lengths up to 1 500 m

To describe the braking performance of a train on ETCS lines, the UIC conversion model will be used to translate the λ-value into a speed-dependent deceleration function. This conversion model is currently only validated for train lengths up to 750 m (see B126.15 RP35). To operate longer trains on ETCS lines, an extension of the model is required.

The model consists of a deceleration function and a function for the brake development time. While the deceleration of the train will be almost independent of the train length, the brake development time will be influenced by the train length.

Brake tests with several train lengths and configurations were therefore performed on a pneumatic test rig. All the tests were conducted using the classic configuration with a loco at the front of the train plus wagons. The test methodology was in general the same as in 2004, when the UIC conversion model was developed. On the basis of these tests and by re-using the test results from 2004, it was possible to define a second set of parameters for the unchanged formula which is to be used to calculate the brake build-up time for train lengths of up to 1 500 m.

The UIC model is thus now able to allow trains of up to 1500 m in length to run under ETCS. The extended model is to become a part of ETCS baseline 3.

In addition, the WG was asked by SET 7 to clarify whether the requirements of UIC Leaflets 540, 541-03, 544-1 and 547 were sufficient to define the requirements for air brakes for trains longer than 750 m. Modifications are needed to UIC Leaflets 540 and 544-1.

Furthermore, as preparatory work for the 5th edition of UIC Leaflet 544-1, a function of the kappa factor was created for G-braked freight trains of length > 700 m.

However, it should be noted that all other issues with long lines (e.g. train dynamics) must be resolved before long freight trains can be operated.