Structural Characteristics and Evolution Regularity of Urban Rail Transit Network: A Case Study of Xi’an, China

Urban rail transit plays a vital role in easing traffic congestion and promoting regional interconnection. In this paper, the evolution regularity of urban rail transit network (URTN) is uncovered from three aspects of network infrastructure attributes, node centrality, and network connectivity. The 2011–2025 rail transit network in Xi’an is taken as an example. The results show that the Xi’an rail transit network (XRTN) from 2013 to 2025 has the characteristics of a scale-free network, and it has the characteristics of scale-free and small-world network during 2022–2025. With the expansion of XRTN, the importance of each station in the network decreases to different levels, showing the characteristics of loop distribution. The potential number of loops gradually increases, but the potential number of edges progressively becomes smaller. The findings of the study not only help improving the theoretical system of URTN evolution, but can provide references for URTN planning of other cities.