Improving Heavy Maintenance Management Efficiency under Limited Depot Resources: A Case Study of MRT Pink Line

Abstract

This research focuses on optimizing the heavy maintenance scheduling of the Pink Line MRT using two models: a non-flexible model (fixed at 120,000 km) and a flexible model, which allows a ±10% adjustment in the accumulated mileage (108,000 - 132,000 km). The study employs Mixed-Integer Linear Programming (MILP) and a two-year simulation to analyze the effects of key constraints, including depot capacity, repair duration, and flexibility levels. The results indicate that a 10% flexibility reduces unused accumulated mileage by 55.97% and increases utilized mileage by 10%, without requiring additional resources. However, increasing the flexibility to 15% yields diminishing returns, leading to higher operational costs and potential safety risks. Conversely, reducing flexibility to 5% helps control costs but increases maintenance frequency, affecting operational stability. Additionally, sensitivity analysis reveals that a depot capacity of C = 2 (2 maintenance tracks per day) with a 5-day repair duration is optimal, balancing efficiency and resource allocation.  C = 1 leads to maintenance congestion and reduced operational efficiency, whereas C = 2 effectively distributes maintenance workload without delays. Although C = 3 shortens repair time, it offers only marginal benefits compared to the increased costs. The findings highlight the importance of strategic flexibility management and optimized depot capacity to reduce maintenance frequency, enhance resource utilization, and improve overall train operation management. This research provides valuable insights for railway maintenance planning, contributing to cost reduction and long-term operational efficiency.