Strategic Planning for Integrated Mobility-on-Demand and Urban Public Bus Networks

Traditional planning for urban transportation usually assumes a given or calculated split between motorized individual transport and public transportation. However, app-based services and ridesharing in the field of mobility on demand (MoD) create an intermediate mode of transport, whose long-term role in the urban mobility landscape and within public transport systems is not fully understood as of today. If the public transport industry wants to capture the opportunities these new services offer and mitigate the risks that come with them, planning tools for integrated intermodal networks are indispensable. In this work, we develop a strategic network planning optimization model for bus lines that allows for intermodal trips with MoD as a first or last leg. For an existing public transport network, we decide simultaneously on the use of existing lines and segments in the future fixed-route network, on areas of the city where an integrated MoD service should be offered, on how MoD interacts with the fixed route network via transfer points, and on passenger routes. The objective is the optimization of the financial performance of the resulting network, including the additional demand and revenues induced by enhanced network coverage. The model provides several options for modeling MoD costs, which allows for linking with operational models such as dial-a-ride. Moreover, our model considers a range of additional important strategic decisions like subsidies for a potential private sector operator of MoD services and the interplay between the demand for public transport and the role of MoD. We develop a path-based formulation of the problem and a branch-and-price algorithm as well as an enhanced enumeration-based approach to solve real-world instances to proven optimality. The model is tested on instances generated with the help of real-world data from a medium-sized German city that currently operates around 20 bus lines.