Economic Impact of China’s High-Speed Railway on the Income Inequality in the Regions Along the Line

China’s high-speed railways, as a vital channel for capital flow, have undergone substantial development over the past two decades, exerting a pivotal influence in stimulating economic growth, expediting information dissemination, and optimizing resource allocation. While high-speed rail demonstrates evident advantages across various domains, a pressing issue is how to achieve fairness in fostering widespread prosperity. Based on tournament theory and fairness theory, this study constructs two unfairness indicators at the enterprise level, namely, absolute income gap and relative income gap. The study delves into the relationship between high-speed rail and income inequality, leveraging a data set comprising Chinese A-share listed companies from 2010 to 2020. The results show that high-speed rail does not have an immediate effect but gradually narrows income gaps as service frequency increases. Moreover, transportation infrastructure and the economic environment are inseparable. We found that the impact of high-speed rail is weakened by economic uncertainty. Furthermore, this study unveils that the opening of high-speed rail and its service frequency exhibit both synergistic and complementary effects. This study not only enriches the research on the external governance of high-speed rail but also provides evidence-based measures for achieving relative fairness.