Transit coordination with heterogeneous headways

We consider the transit coordination problem with heterogeneous headways. Timetables with heterogeneous headways improve coordination between transit lines and reduce transfer time for connecting passengers. Unfortunately, deviating from homogeneous headways impacts adversely on initial waiting times experienced prior to embarking on the initial vehicle of a trip. We focus on this trade-off between transfer waiting time and initial waiting time, which has not been explored previously, and develop a mathematical model to quantify the benefits of heterogeneous headways. We also propose a genetic algorithm (GA) to solve the transit coordination problem with heterogeneous headways and demonstrate the benefit of heterogeneous headways based on two examples from the literature and one real-life example based on the rail transit network of Istanbul. Computational results suggest that the GA solves the transit coordination problem within a reasonable time and significant benefits can be achieved by adopting timetables with heterogeneous headways.