Citation: Sugimori, S.; Hayashi, Y.; Takeshita, H.; Isobe, T. Evaluating the Regional Economic Impacts of High-Speed Rail and Interregional Disparity: A Combined Model of I/O and Spatial Interaction. Sustainability 2022, 14, 11545. https://doi.org/ 10.3390/su141811545 Academic Editors: Piotr Rosik, Andrzej Szarata and Bartlomiej Rokicki Received: 22 July 2022 Accepted: 9 September 2022 Published: 14 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Evaluating the Regional Economic Impacts of High-Speed Rail and Interregional Disparity: A Combined Model of I/O and Spatial Interaction Shuji Sugimori 1, *, Yoshitsugu Hayashi 2 , Hiroyuki Takeshita 2 and Tomohiko Isobe 1 1 Department of Constructional Engineering, Graduate School of Engineering, Chubu University, Kasugai 487-8501, Aichi, Japan 2 Center for Sustainable Development and Global Smart City, Chubu University, Kasugai 487-8501, Aichi, Japan * Correspondence: tc20801-0718@sti.chubu.ac.jp Abstract: Among the benefits of high-speed rails (HSRs) discussed from various aspects, indirect benefits may contribute to medium- and long-term economic impacts such as an increase in service supply and gross regional product (GRP). In order to estimate the economic impacts, we modeled I/O–spatial interaction by combining the inter–industrial transactions shown on the I/O table with the geospatial distance decay of economic mass through passenger transportation. In addition, the regional economic impacts, as a part of the indirect benefits, were evaluated by the model applied to the Mumbai–Ahmedabad High-Speed Rail (MAHSR) corridor in India, which is an emerging country with remarkable economic growth. The results showed the economic impacts on each zone and each industry along the MAHSR corridor as a relative distribution. The unique feature of this approach is that it is possible to evaluate the geographic distributions and interregional disparity of economic impacts by combining the industrial I/O relationships with the changes in passenger accessibility associated with a large-scale transportation project such as an HSR. Moreover, this method can be applied to various countries and regions where detailed I/O statistical data, such as interregional I/O tables, are difficult to obtain, as well as various transportation project evaluations taking into account interregional equity. Keywords: high-speed rail; regional economic impacts; input–output table; spatial interaction 1. Introduction High-speed rail (HSR) has been developed in many countries and regions, beginning in Japan with the opening of the Tokaido Shinkansen in 1964. The Shinkansen brought a paradigm shift in the flow of business and tourist passengers to the 500 km-long metropolis, resulting in remarkable economic development and changes in the social environment. The benefits of HSRs are discussed from various aspects and perspectives. In the planning and construction phase of the HSR, economic multiplier effects will be generated in the short term through the construction of the HSR and its surrounding facilities and through investment and demand inducement in related industries in anticipation of the opening of the HSR. Subsequently, during the operational phase, direct benefits will accrue to travelers through time savings and improved comfort when traveling between cities along the HSR in the short term. On the other hand, indirect benefits may contribute to medium- and long-term impacts associated with the stimulation of business-to-business communication and industry interaction as well as an increase in service supply and gross regional product (GRP). As an example of an HSR project, the Mumbai–Ahmedabad High-Speed Rail (MAHSR) connecting Mumbai and Ahmedabad (Figure 1) is currently under construction. The MAHSR is the first HSR in India, which is an emerging country with remarkable economic growth. This project is being heralded as a milestone in the establishment of a nationwide Sustainability 2022, 14, 11545. https://doi.org/10.3390/su141811545 https://www.mdpi.com/journal/sustainability