Public Transit Simulation Model for Optimal Synchronized Transfers

The use of transfers in public transit has the advantage of reducing operational costs and introducing more flexible and efficient route planning. In contrast, the main drawback for passengers is the inconvenience of traveling multilegged trips. To diminish the waiting time caused by transfers, synchronized (timed) timetables were introduced. Their use, however, suffers from uncertainty about the simultaneous arrival of two (or more) vehicles at an existing stop. This can lead to deterioration in system reliability. To alleviate the uncertainty of simultaneous arrivals, operational tactics can be deployed, such as hold, skip-stop, and short-turn, to increase the chances of simultaneous arrival of both vehicles at the same station. Each tactic has positive and negative effects on the total travel time. A dynamic programming model was developed for minimizing the total travel time, resulting in a set of preferred tactics to be deployed. An optimization model based on dynamic programming and a public transit simulation that validates the benefits of such a model are described. The results of the simulation confirm the benefits of the model with a 10% reduction of total travel time and more than a 200% increase of direct transfers (transfers in which both vehicles arrive simultaneously at the transfer point).