The influence of trapped foreign objects on railway switch control investigated by numerical simulations and field tests

Railway switches enhance operational flexibility but are a frequent source of traffic disruptions. A common cause is foreign objects becoming lodged between the switch and stock rails, leading to delays and increased maintenance costs. This study therefore aims to evaluate the consequences of trapped foreign objects on switch rail control as this may cause an inability to lock the switch, or impose gauge reductions that lead to an increased risk of derailment. To this end, a finite element (FE) model of a railway switch is developed and validated against field measurements. The validated model is a key contribution as it is able to accurately predict the deformation pattern of the switch rail when foreign objects interfere with its movement. The model is then used to perform parametric studies examining how the size and position of foreign objects influence switch control. The analysis aims to determine when foreign objects can be detected by the drive mechanisms alone and when additional sensors are necessary to identify critical gauge reductions. Results show that the coefficient of friction between the switch rail and slide chairs have a profound impact on object detection and overall control of the switch. A design modification is evaluated, and it is shown that the introduction of additional link connections between the switch rails improves object detection. The presented numerical approach offers significant benefits, including reduced dependence on physical testing and the ability to evaluate different switch configurations.