Tactical planning of a demand-responsive connector

We consider the tactical planning of a demand-responsive connector system, where passengers are transported by on-demand vehicles within a zone that is connected to a tram line via a scheduled transfer station. The system combines characteristics of fixed-route and demand-responsive transit systems. We propose the concept of service patterns that indicate the number of arriving and departing vehicles at the transfer station per tram arrival and give a hint on how the fleet should be utilized. Based on a network flow formulation on a time-expanded network, we use a two-stage stochastic programming model to determine service patterns. We conduct an extensive computational study to analyze the impact of several design factors on selected performance indicators from both an operator and customer perspective. The results show that service patterns are not only able to adapt to different demand distributions and describe the relations between system parameters in a concise way, but are also able to reduce the time spent on empty runs between 28%–80% compared to benchmark policies that use the same fixed number of vehicles at the transfer station for all tram arrivals. Lastly, we present a post-processing model to assess the quality of the tactical solutions on an operational level. The results indicate that solutions derived from our approximation are of high-quality and may thus help the operator to communicate their service to customers and obtain realistic estimates of the required fleet size.