Multibody simulation of derailment risk in railway switches due to gauge narrowing caused by foreign objects

Journal article, 2025

Railway switches are essential for ensuring efficient train operations, and efforts to improve their safety standards have driven the introduction of ‘switch rail control contact’ (TKK in Swedish) sensors in Sweden. These sensors monitor the gap between the switch and stock rail, complementing the switch rail position detection of the drives. Despite their benefits, TKK sensors are prone to faults, which in turn increase maintenance and operational costs. This study was therefore initiated to assess the utility of these devices in derailment prevention. To assess the risk of derailment caused by gauge narrowing induced by entrapped foreign objects, multibody simulation (MBS) of train switch interactions is performed. A state-of-the-art structural track model of a switch is modelled in Simpack. Simulations indicate that the train will not derail due to flange climbing when the foreign object is modelled with a failure criterion resembling crushing strength of ballast stones. An investigation featuring an unbreakable object showed that the critical gauge narrowing limit considering flange climbing is around 15 mm which is in accordance with the existing safety limit. The influence of track irregularities in combination with foreign objects is also investigated.