A Petri net approach to assess the effects of railway maintenance on track availability

The railway infrastructure includes a portfolio of assets that are subjected to degradation and failure processes due to both usage and ageing. As a consequence of degradation and failures, speed restrictions and line closures may be imposed to control the risk of derailment. Such actions have a direct impact on service, as they lead to delays and journey cancellations. Maintenance is implemented to control the state of the assets. Different maintenance strategies determine different asset conditions and performance profiles and, consequently, a different impact on service. This paper presents a simulation tool based on Petri nets, which combines degradation and maintenance processes to predict future track geometry conditions, including the probability of those failure modes leading to speed restrictions and line closures. Such a model is a valuable feature of an effective infrastructure-asset-management system that intends to support cost-effective informed decisions on railway maintenance.