Evolutionary Process, Characteristics Comparison, and Practical Reflections on Express Rail Systems in Metropolitan Areas

Given that urban rail lines with an average operating speed below 45 km/h are insufficient to support long-distance travel demand within metropolitan areas in China, the development of express rail systems has become increasingly urgent. However, the theoretical foundation for the construction of express rail systems remains relatively underdeveloped, which has led to fragmented implementation practices nationwide. This study adopts a comparative case study methodology by selecting three developed metropolitan areas—Paris, Tokyo, and Seoul—whose spatial structures are comparable to those of Chinese metropolitan areas. The paper systematically reviews the evolutionary processes and key characteristics of their express rail systems and conducts an in-depth comparison between these three cases and representative Chinese metropolitan areas. The findings are as follows: ① Express rail systems generally emerged during the mid-to-late stages of urbanization; new construction in China and other countries is now proceeding in parallel. ② In the three case metropolitan areas, express rail services were largely developed in the early stages through the upgrading of existing suburban railways via technical transformation. In contrast, Chinese metropolitan areas lack such pre-existing conditions, leading to a distinctive development model. ③ Significant institutional barriers hinder the integrated operation of multi-type rail networks in Chinese metropolitan areas. Among the cases examined, the development conditions and trajectory of Seoul’s express rail system are more comparable to those in China and therefore merit closer attention. ④ Diameter lines should serve as the primary mode of provision, and there is an urgent need to strengthen route control in related detailed planning.