The ageing of signalling equipment and the impact on maintenance strategies

Research projects of the SNCF (French railway) aim at reducing the costs of infrastructure possession and improving the operational equipment availability and safety. This permanent search for a better regularity led the SNCF to analyse the maintenance approach of signalling equipment in detail. Until now, it was commonly admitted that signalling equipment, which consists of many electronic devices, is not subject to ageing. In this study, a Weibull lifetime model, able to describe an ageing phenomenon, is used and it can be shown that the deterioration is statistically significant. The validity of the model is tested. We also analyse the influence of environmental covariates. We simulate different scenarios in order to investigate the impact of several maintenance strategies as well on future maintenance costs, on the amount of components to replace as on the mean age of the network. It can be shown that in most cases a systematic replacement strategy offers the best solution.