Optimizing air-HSR intermodal service considering trade-offs in duration at airport: A game analysis in a vertically structured transport market

Empirical experience of air-HSR intermodal service (AHIS) indicates that transfer processes significantly influence passengers' travel experience and are key to the optimization of AHIS. Airports serve as key nodes for AHIS services, and passengers' waiting costs and service experience at airports are the primary measurements of transfer processes. This paper investigates the optimization of AHIS by considering the trade-offs related to the duration at airports within the airport-transport operator-passenger system. Using an economic game model, we explore the interactions of AHIS connection adjustments, service quality enhancements, and stakeholder incentives across different airline market structures. Key analytical findings suggest that with moderate baseline AHIS connection times, optimization increases passenger traffic and overall transport volume, especially under public airport ownership and duopoly airline markets. We conduct numerical studies based on the Beijing-Shijiazhuang-Shanghai market, finding that AHIS optimization always reduces overall transfer negative utility and improves consumer surplus and social welfare, mainly where passenger sensitivity to service quality is not low. However, the effects on concession revenue and airport profit are not stable. The effects are more pronounced in duopoly markets than in monopoly markets. The sensitivity analysis highlights that while increased concession revenue per passenger benefits the entire transport market system, excessive revenue per unit can paradoxically harm individual transfer experience. Model extensions incorporating variable AHIS coordination costs and endogenous maximum tolerable waiting time demonstrate stable traffic and welfare gains while boosting concession revenue compared to the base model. Finally, several policy and operation insights are discussed.