Exploring the potential of timetable fragility across multiple delay-related objectives

When looking at preventive actions for disturbance management, the focus is on designing robust timetables able to absorb secondary delays. Several approaches based on different robustness measures have been proposed in the last years. However, many of them consider predictions of knock-on delays without factoring in possible dispatching decisions, greatly reducing their validity in real-life settings. Given a timetable and suitable objective functions, the fragility concept is able to identify the train-resource pairs where a primary delay is more likely to generate large knock-on delays. In particular, the objective function should reflect real-time decision-making criteria adopted by dispatchers. Since no single, universally accepted measure exists, we explore some of the most common objective functions. Considering real-world data from a busy railway line in Norway, we propose additional analyzes, including exploring the impact of precedence constraints in optimal dispatching.