Degradation functions for railway station equipment quality based on maintenance-influenced data

To find the optimal maintenance policies, the DB Station&Service AG - a railway infrastructure company which manages the majority of the railway stations in Germany - needs to describe the cause-effect-relationship between the funds for maintenance and the quality of the station equipment. To determine the influence of funding on the infrastructure quality, it is necessary to predict the cost and effect of maintenance measures as well as the behaviour of unmaintained items. However, the available degradation data do not contain any condition measurements of items which are not influenced by maintenance. Here, we provide a model which allows to describe the average maintenance intervals and the degradation during these intervals based on such maintenance-influenced data. This model can be used to predict the development of the equipment quality and is intended to be used to determine the necessary budget for a specific equipment quality or vice versa.