Synchronized optimization of EMU train assignment and second-level preventive maintenance scheduling

This paper addresses the synchronized electric multiple unit (EMU) train assignment and maintenance scheduling problem for a weekly planning period. To guarantee the safe operation of railways, the focus of this study is to coordinate the maintenance plans of all the EMU trains with a given fleet size, so as to make trains available to meet operational requirements. A 0 and 1 programming model is proposed to mathematically describe the problem. The objective is to minimize the mileage losses of all EMU trains by considering the train operational requirements and depot capacity restrictions. An important feature distinguishing this model from existing literature is that it is able to handle multi-day maintenance packet scenarios. To make the model computationally manageable, we apply various linearization techniques to refine the model into a linear one. A real-world case is considered to demonstrate the proposed solution approach, which indicates that the model can be solved to the optimum within a very short computational time using a state-of-the-art optimization solver.