Assessing the Potential of Policies Targeting Air-to-Rail Modal Substitution

Qc 20250915

Abstract

The growing environmental concerns and the present constraints of technological development drive the search for alternative solutions to decarbonise aviation. In particular, rail is widely recognised as a potential substitute for short-haul flights (SHF), enabling considerable savings in CO₂-equivalent (CO₂e) emissions while offering comparable travel times and level of service. As the pace of modal substitution from air to rail in Europe remains below expectations, policies to further stimulate this process are increasingly being explored. Thus, this thesis investigates the potential of two such strategies SHF bans and air-rail integration through two papers based on air supply and demand data, travel times of available rail alternatives, and current capacity utilisation on the Swedish rail network.

Paper I serves as a stress test for SHF bans, often regarded as a low-hanging fruit for reducing transport emissions due to their relative ease of implementation. The analysis of trade-offs between rail travel time thresholds and CO₂e savings reveals that their attractiveness diminishes rapidly as the policy scope expands to include a larger number of flight cancellations, precisely where the environmental benefits would be most significant. Implementing SHF ban policies with broader thresholds and wider geographical scopes requires complementary measures to mitigate the associated risks and address railway infrastructure capacity constraints. By demonstrating that the plausible environmental benefits of SHF bans are limited and highly conditional, even under an idealised scenario of a complete modal shift to rail, this paper provides critical insights into the constraints of such policies and supports more informed decision-making by policymakers.

Paper II explores the substitution potential driven by air-rail integration across Europe, proposing a simple and interpretable indicator. The indicator reveals that this potential is highly concentrated along a limited number of key routes and major hubs, indicating that targeted interventions, such as expanding the supply of non-stop high-speed rail services between cities and airport stations on high-demand corridors, could effectively encourage modal shift from air to rail. However, the findings also highlight the limited scope of air-rail integration, constrained by the availability of rail infrastructure and services at many airports, as well as the relatively small share of routes and passengers affected. While air-rail integration alone is unlikely to deliver substantial contributions toward the European Commission’s environmental targets, its wide-ranging strategic benefits for airports, airlines, and passengers, combined with relatively low implementation costs, make similar initiatives worth pursuing.

The contribution of both SHF bans and air-rail integration to the overall decarbonisation of aviation is found to be limited. Consistent with previous research, our findings indicate that these measures alone are insufficient to meet the ambitious European environmental targets and should be integrated into a broader, more comprehensive strategy for reducing aviation emissions. In particular, complementary measures are required to curb emissions from flights for which rail is not a viable substitute, including long-haul services and routes serving remote regions. Demand management strategies can contribute to reducing reliance on technological readiness by providing effective, albeit limited, short-term measures to limit aviation emissions. Within this wider framework, both competition and integration play a critical and complementary role and should be embedded within a broader and more comprehensive set of coordinated policies. However, the potential of these policies ultimately relies on the quality, availability, and competitiveness of rail services.

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