Most studies on public transport network design deal with single-level networks only. Urban public transport networks, however, not only offer transport services to and from the city center but also to stations of interurban public transport networks. A population's use of both types of public transport services implies a dependency between these networks. An analytical model was developed to analyze this dependency for two connected networks. For each network, the operator will adopt a certain objective in optimally designing the network. An analysis was made for the cases in which a single operator is responsible for both networks, or in which two different operators run each network. In all cases the objectives of profit maximization and welfare maximization were used. In the two-operator case, each operator may follow its own objective. The different scenarios led to sensibly different values for stop spacing, line spacing, and frequencies. For interurban public transport companies it appears to be profitable to cooperate with urban public transport companies or to pursue a strategy for local authorities to adopt the objective of welfare maximization for urban public transport network design. In the case of welfare maximization, that is, the authorities' perspective, the impact of two operators instead of a single operator is nearly negligible. The combination of welfare maximization for the urban public transport network and profit maximization for the interurban network indirectly subsidizes interurban public transport. These findings provide interesting insights for authorities responsible for commissioning public transport services.
Abstract