Source: Adapted from Commission for Integrated Transport, London (2004) High-speed rails: international comparisons, Steer Davies Gleave.
Over many regional transport systems, high-speed rail is competing with air transportation, often considering time and distance factors. Airports are usually located far from city centers, while conventional and high-speed train stations are much closer. For short distances of less than 150 km, conventional rail services are usually more competitive (air transport is almost never flown over these distances) than high speed. This is mainly due to higher frequencies of services for conventional rail, but more frequent stops due to intermediary stations.
The main service window for high-speed rail is between 150 and 775 km, a segment over which it generally has a time advantage over air transportation. For distances over 800 km, air transportation is usually more advantageous. However, if there were no high-speed rail services, air transportation would be more advantageous over distances of 350 km.
This relationship bears similarities with the basic transport costs comparison between road, rail, and maritime modes.