Minimizing waiting times in integrated fixed interval timetables by upgrading railway tracks

The integrated fixed interval timetable of a railway network guarantees zero waiting times for passengers changing trains. For a periodically served network such a timetable exists if and only if the running times of the trains are feasible with a group equation system. If the running times are infeasible with this equation system, there will remain a certain amount of waiting time. A modification of the running times can be achieved by reforming the actual state of certain track segments. In this paper we discuss the cost-benefit between the investigation for reforming track states and the quality of the resulting timetable measured by the remaining waiting times. This leads to a complicated bi-criteria optimization problem. We generate sub-optimal solutions by a hybrid genetic algorithm including fuzzy logic.