Air-rail integrated flight network design

This study investigates a rail-integrated flight network design problem in a multimodal environment shaped by the expansion of high-speed rail (HSR). While HSR intensifies competition, it also creates potential opportunities to enhance multimodal connectivity through intermodal coordination. However, decision support tools for systematically evaluating such integration at the network level remain limited. To bridge this gap, we develop an integrated modeling framework that formulates a mixed-integer non-convex program to support high-level strategic assessment of air-rail integration within airline network development. The model jointly captures network design, tactical decisions, and passenger choice across air, rail, and intermodal itineraries. A tailored discretization approach is proposed to linearize the non-convex demand function. Computational experiments and a real-world application to the Chinese domestic market demonstrate the effectiveness and tractability of the framework, providing novel perspectives and strategic insights into how airlines can evaluate and potentially capitalize on air-rail integration to strengthen multimodal connectivity and expand effective network coverage at scale.