Transit Network Re-timetabling and Vehicle Scheduling

In the transit planning literature, network timetabling and vehicle scheduling are usually treated in a sequential manner. In this paper, we focus on combining important features of these two steps, and underline how their simultaneous optimization is meaningful and can bring important improvements to both quality of service and level of resources required. We deal with the objectives of networkwide quality of service through number and quality of the transfers and evenness of the line headways, and with the resources side through number of vehicles needed. Our approach is adapted to the problem faced by regulating authorities, treating among others intermodality, multi-periods for headways and travel times, and complex timetable schemes. We introduce an optimization procedure based on Iterated Local Search and present computational experiments carried out on a real large transit network, showing substantial improvements in both quality of service and level of resources compared to the current practice.