Mapping the substitution potential of air–rail integration across Europe

Air–rail integration agreements are widely regarded as an important strategy to spark and stimulate a modal shift from air to rail. Intermodality has been consistently promoted by European transport policy over the last three decades. At the same time, the literature widely concurs on the potential benefits of air–rail integration for passengers, airports, airlines and rail operators. However, as of 2025, the availability of air–rail integration alternatives on the market is limited, and their potential benefits remain largely unexplored. Thus, this paper investigates the substitution potential of air–rail integration in Europe, compiling an inventory of rail connectivity at European airports and proposing a simple and interpretable indicator to quantify the Air–Rail Integration Substitution Potential (ARISP) at the route and airport levels. Our findings indicate that the substitution potential of air–rail integration in Europe is minimal: even when considering rail travel times within a 100% increase of existing air travel, the potential market represents less than 1% of the 1.2 billion intra-European air journeys. The modest competitiveness of rail travel times and the limited potential passenger flows on most substitutable routes suggest that air–rail integration should not be proposed as an environmental policy but rather as one to enhance connectivity. The ARISP indicator further reveals that the limited substitution potential is highly concentrated across a limited number of routes, airports, and geographical regions. Targeting them by directly connecting cities and airports’ railway stations with non-stop high-speed services (where possible) may enhance the effectiveness of air–rail integration on substitution. Our analysis shows that rail infrastructure and service provision at airports, as well as their position within the European railway network, are important determinants of the substitution potential of air–rail integration.