Railway transportation offers the potential of transporting a large number of goods and people in a fast and environment-friendly way. A tendency seen over the last decades is a growing demand for capacity, and the increased number of operating trains has led to a high capacity consumption and a delay-sensitive system. Frequent delays result in high costs for the train operating companies, the infrastructure provider as well as high costs for the travellers and society overall. Robust timetables are essential to reduce delays and keep them from propagating. In this thesis, we analyse how timetable robustness can be assessed and increased. The primary aim is to establish quantitative indicators of timetable robustness that can be used to evaluate the robustness and identify weaknesses. The second aim of the thesis is to develop an approach for how the indicators can be used to increase the robustness.

The thesis addresses both theoretical and practical gaps regarding timetable robustness. It introduces the concept of critical points and contributes with two new robustness indicators, Robustness in Critical Points (RCP) and Robustness in Passing Points (RPP). Both RCP and RPP capture the connection between heterogeneity, runtime supplement and headway time in a unique way. The thesis also contributes with a method to measure and increase timetable robustness. The method is implemented in an optimisation tool, to illustrate how robustness can be automatically improved in the future. It is also implemented as real-world planning rules that can be used to support timetable planners in their daily work. The results show that it is possible to increase robustness with the use of RCP and RPP. Higher indicator values lead to less train delays and an increased punctuality.

This thesis consists of two parts. First, the scope of the research is described, with background knowledge on the problem, followed by the motivation, research framework, contributions and conclusions. The second part consists of five appended papers where the research is presented in detail.