Multi-criteria optimization for regional timetable synchronization in public transport

The need for synchronizing timetables occurs when several public transportation companies interact in the same area, e.g. a city with busses, trains and trams. Existing approaches that optimize a global, waiting time oriented objective function reach their limit quite fast concerning real-life applications. While optimizing public transportation timetables, \winners" and \losers" will inevitably come about and the traffic planner has to keep control of this process. Thus, we propose an optimization approach that enhances the overall situation without losing sight of the defienciencies arising at particular stations. In our concept for optimizing public transportation timetables, the goal is to synchronize a set of lines (e.g. busses, trains, ...) by changing their starting times such that passengers can transfer more conveniently. For this, we do not take the often used approach of simply minimizing waiting times, but we use a concept of trying to achieve transfers that can be called convenient. For these, the time should not be too long, but also not too short, in order to reduce the risk of missing a transfer if the arriving vehicle is delayed. For optimization purposes, we assign to all possible waiting times at a transfer a corresponding penalty-value. One of our goals is to minimize the sum of these penalties over all transfers.