An optimal age-usage maintenance strategy containing a failure penalty for application to railway tracks

Railway track maintenance plays a key role in enhancing the reliability and safety of railway transportation, as it reduces the potential risks of defects and derailments. A railway track degrades over time, due to its cumulative usage (in terms of million gross tons) that results from traffic movements. When the cumulative usage reaches a failure threshold, the railway track breaks and has to be replaced with a new section. Moreover, the infrastructure owner charges the maintenance agent a specific penalty due to traffic disrruption and passenger dissatisfaction. To avoid such costly defects, the railway tracks must be preventively replaced at regular time intervals. In this paper, we propose an optimal bivariate (age-usage) maintenance strategy for railway tracks such that the average long-run maintenance cost per unit time is minimized. The proposed model is applied to 60E1 track on a small part of the Swedish heavy haul line Malmbanan', and the results are compared with two conventional age-based and usage-based maintenance policies. The results show that the proposed maintenance policy has a substantial potential to reduce the servicing costs of railway track maintenance.