Application of new UIC Leaflet 421 methodology to new freight train compositions with up to four traction units in distributed traction/braking

Current version of UIC Leaflet 421 provides a (not mandatory) methodology based on statistical analysis to accept train compositions whose limits exceeds 2500t and 700m in braking position “G”, for international traffic. This methodology does not consider explicitly trains with distributed traction/braking and their most relevant degraded modes. The paper shows a more general methodology to build statistically virtual trains, considering limits in terms of both train mass and length. These virtual trains can be computed efficiently and accurately by means of UIC software TrainDy. The paper also shows main enhancements of this software, and their corresponding experimental validation, to simulate wagons with Composite Brake Blocks (type LL and K). Results section reports the TrainDy computations of in-train forces for trains having up to four Traction Units (TU) communicating by means of GSM-R radio technology. In-train forces for 1500m train, heterogeneously loaded, carrying up to 4800t, with four TU, are like those of already running trains, at least in nominal mode, i.e. when there is a proper communication between the TU