D4.3 DAC Running Safety Assessment Tool – report on development validation and operational results for improved train dynamics in DAC-based system

The running safety of freight wagons under longitudinal compressive forces must be assessed to mitigate the risk of derailment. A key value for the assessment is the endurable longitudinal compressive force (eLCF). This is a property of the wagon and its coupler system. The current European rules for the assessment of eLCF are not directly applicable to wagons with DAC.

There has been intensive research in Europe in the past decades. Centre buffer couplers with certain design features enable much higher eLCF than wagons with side buffers. A so-called stabilising joint plays a major role. Wagons with higher eLCF are favourable for railway undertakings to have as they allow for longer and heavier trains in more effective brake positions.

The recommended assessment methodology for the DAC is based on various proven procedures of the past combined with the possibilities of modern multi body simulations. Central component are virtual tests to determine the eLCF of a wagon and coupler combination. These simulations must be validated with real life tests. Automated simulations allow for a large number of virtual tests. All results will be stored in databases and serve as basis for generalised rules. These are assignments of (minimum) eLCF to clusters of wagon parameters. This procedure is very similar to European rules for the assessment of wagons with side buffers.

The simulations of tests to evaluate the eLCF show a good match with real-life tests. Both simulations and real-life tests show higher eLCF for wagons with DAC as for the same wagons with side buffers. There is currently no indication that wagons with DAC have lower eLCF if the DAC has a stabilising joint.

Methods for verification and validation of the virtual derailment tests have been introduced and applied. At the present time, a final validation of the approach is not possible as there have not been any real-life tests with DACs that fully comply with the TRANS4M-R specifications. Therefore, it is currently not possible to  derive the final “running safety assessment tool” as simple, practical guidelines, e.g. a set of rules, look- up-tables or diagrams. However, the recommended methodology can be applied to fully specified DAC and the respective test results as soon as they are available.

The proposed methodology is not proprietary. It can be implemented by any stakeholder who has the necessary capacities and expertise. We suggest a coordinated application of the methodology within the sector to ensure that all outcomes of simulations cumulate in simple, practical guidelines (“the tool”) that can then be used by the entire sector.