The Effectiveness of Preventive Maintenance in Railways

Railway maintenance is crucial for ensuring system availability, punctuality, safety, and comfort. Though studies have shown that in reality, maintenance is ‘imperfect’-inspections do not reveal all defects and repairs do not return components to as good as new and may even leave them in a worse state, railway maintenance planning is still based on periodic block-type and age-based maintenance policies that take no account of this phenomenon. Moreover, due to funding constraints, adhering to the conceivably optimistic recommended levels of maintenance, which are derived from such planning, is also nearly impossible. Consequently, planners adopt other factors for prioritizing maintenance, albeit in a non-systematic manner. This suggests a need to develop maintenance policies that take into account the imperfect nature of maintenance and any other practical factors, if cost-effectiveness and reduced incidents are to be achieved. As a first step in this direction, this study uses a case of specific switches and crossings (S&C) components on the Swedish railway network: crossings, the tongue device, and the heating element, to assess the level of adherence to existing maintenance standards and the extent to which repairs deter failures i.e., evidence of imperfect maintenance. It was determined that on average, only 56% of S&C errors are fixed within the recommended time, with the heating element being prioritized over the other failures considered. A comparison of the survival rates (time to first failure) before and after repairs of the components provides evidence for imperfect repair of crossings and the tongue device but evidence of minimal repair of the heating element. Overall, timely repair is seen to improve survival. The survival rate of crossings decreases by approximately 0.07% for each day repair is delayed, while it decreases by 0.02% for the tongue device and 0.08% for the heating element. This study also serves to demonstrate a method for assessing the effectiveness of maintenance regimes.