Optimization for bilevel spatial configuration of underground space surrounding high-speed railway station in China from the perspective of urban morphology

The rapid growth of high-speed railways has led to the development of underground spaces surrounding high-speed railway stations (USSHRSs). The evolution of USSHRS has enhanced the space utilization efficiency. As USSHRSs expand, the layout of the underground connectivity network becomes increasingly intricate. Additionally, pedestrian behavior in USSHRSs transitions from mere passing to longer stays, and its spatial configuration becomes more difficult to evaluate. To date, studies have mostly focused on the structural analysis or inner underground space relationship of USSHRSs. A research gap exists in the field of USSHRS spatial configuration from the perspective of urban development. To fill this research gap, this study focused on the spatial configuration of the USSHRS from the perspective of urban morphology and established a quantitative analysis method for USSHRSs at both global and local levels. At the global level, we devised a method for measuring the USSHRS spatial configuration using pedestrian composite accessibility based on a complex network. At the local level, we used space syntax to study the inner spatial configuration problems of USSHRSs. Finally, we used the Shanghai Hongqiao Station (Shanghai, China) as a case study. The results revealed that the spatial configuration optimization of the USSHRS must improve the connectivity efficiency of the USSHRS, and the corresponding functional layout should also be optimized towards a centralized layout. This study aims to provide decision-making support for the planning and layout of complicated USSHRS and to highlight the role of USSHRS in urban sustainable development.