An iterative fragility-based approach to timetable design

To proactively manage disturbances in railway systems, it is crucial to design robust timetables that can effectively absorb secondary delays. In practice, when route planners are tasked to produce a robust timetable, they usually start from an existing timetable and follow a complicated, iterative, and time-consuming trial-and-error process to build a new one. Given the increase in traffic demand, decision support systems are becoming essential to guide practitioners through this complex task. While several robustness measures have been proposed in the last few years, many overlook the impact of dispatching decisions on knock-on delays, limiting their real-world applicability. In this work, we introduce a fragility-based approach to timetable design, inspired by the concept of fragility recently proposed. Our approach focuses on identifying and addressing the most critical sections of the timetable to enhance the overall robustness. Specifically, we show how timetable fragility can be actually exploited by route planners to design new and more robust timetables. We propose a MILP model that aims to enhance timetable robustness by focusing on its most critical part. Considering real-life scenarios from a Norwegian railway line, our iterative approach demonstrates the ability to enhance timetable robustness, even when employing conservative strategies for potential improvements.