Modelling phased railway infrastructure upgrades deployment with a case study to ERTMS roll-out

Modernisation of railway infrastructure can lead to significant improvements in the efficiency of train services. However, the deployment of the modernisation requires huge financial investments and is carried out over decades. Consequently, infrastructure upgrade decisions must be strategically planned over time. In this paper, we introduce the Railway Infrastructure Upgrade Deployment Problem (RIUDP) in which we optimize phased deployment of infrastructure upgrades in a railway network so that societal benefits, measured by the reduction in the travel times of all passenger trains, are maximized. This requires to compute a timetable for each potential deployment plan of the upgrades. To compute this timetable, we assume that the structure of the timetable is given. We formulate the RIUDP as a Mixed Integer Linear Program and solve it to optimality. We compare optimised solutions with solutions that mimic rule of thumb decisions based solely on the theoretical cost effectiveness of infrastructure upgrades. A detailed case study on the roll-out of ERTMS on the main Dutch railway network reveals that severe gains can be achieved using optimized timetables instead of the rule of thumb decisions. Finally, we study the impact of specific practical considerations such as regional equity and connectivity constraints on the RIUDP.