High-speed rail network and regional carbon emissions: Carbon lock-in or unlocking?

The rapid expansion of China’s high-speed rail (HSR) network has significantly contributed to regional economic growth and enhanced transportation efficiency. However, the impact of this development on carbon lock-in (CLI) and carbon unlocking remains under-explored, which is an area critical for understanding the potential of HSR in mitigating climate change. This study addresses this gap by analyzing data from 256 prefecture-level cities in China between 2009 and 2021. Urban CLI levels are quantified by a projection pursuit model based on genetic algorithms. Additionally, a High-Speed Rail Connectivity Index (HSRCI) is introduced to assess the current state of China’s HSR network. Our findings reveal that the HSR network effectively promotes carbon unlocking, especially in large and medium-sized cities, non-resource-based cities, and transportation hubs. It suggests that developing the HSR network can mitigate the increased carbon emissions associated with traditional transportation modes, thereby playing a crucial role in achieving China’s “dual carbon” goals. Furthermore, mechanism analysis indicates that increased urban economic density and population aggregation facilitate the expansion of the HSR network, effectively reducing CLI. Moreover, regional integration and innovation improvements significantly enhance the HSR network’s carbon-unlocking effect. Conversely, higher levels of fixed asset investment may, in some instances, exacerbate CLI. This study provides empirical evidence and policy recommendations to optimize the HSR network’s carbon-unlocking potential.