Environmental and Accessibility Impacts of High-Speed Rail
Authors: Arning Leonard 
Published: August 2024

High-speed rail (HSR) is commonly assumed to cause fewer specific greenhouse gas emissions than alternative transportation systems such as aviation or road transport. Therefore, HSR projects leading to a mode shift from these modes to HSR are supposed to be beneficial to the environment by mitigating climate change. HSR can also provide new and speedy connections between peripheral regions and economic centers. It is thought that by providing peripheral regions with easier access to goods and service only available in large urban centers, HSR improves the economic competitiveness of these regions as well as spatial equity. To investigate the current state of research regarding these issues, I first systematize accessibility and environmental impacts from transportation in general and HSR specifically. I then carry out a systematic literature review across three scientific databases, using two search strings, resulting in a literature corpus of 79 unique sources. Results from these sources are analyzed and summarized in five research fields: spatial equity, carbon intensity, mode shift to HSR, induced HSR demand and complementary effects. I find that HSR improves accessibility of all regions, even those that have no direct access to HSR service. However, the impact on economic growth and spatial equity can be negative or positive depending on case characteristics. Carbon intensity of HSR is highly variable, in some cases even exceeding that of air transport. I find extreme cases of 10 and 283 gCO2/pkm. High ridership, a low share of tunnel and bridge sections, as well as a green electricity mix are crucial to ensure that HSR exhibits lower specific carbon emissions than alternative modes and has the potential to reduce overall GHG emissions. Mode shift and induced demand are also highly dependent on the individual project’s case, with induced demand typically being between 10 and 20 % of the total HSR demand. Concrete values of complementary effects, which is the additional demand in modes competing with HSR, are the least extensively studied. Especially air transport appears not only to compete with HSR, but also to exhibit several complementary relationships such as price competition and an increased attractiveness of long-haul flights. I conclude that, assuming no additional policy measures being taken, expanding HSR does not lead to a reduction of overall greenhouse gas emissions from air transport. The environmental impact of a HSR project can be estimated through a vigorous project appraisal process only. Important policy implications include the enhancement of appraisal processes as well as the overall need for deploying HSR projects in push-and-pull packages with other, supply-restricting policies. Future research should direct more attention towards HSR and airfares. I propose study designs for a national flight emission study and including passengers’ destination choice in existing research approaches. I also suggest using the results of this student research paper to carry out a Monte Carlo simulation on HSR projects’ recuperation periods.