Constructing underground pedestrian networks: A model based on the source-sink theory and a case study of Xinjiekou in Nanjing City, China

Underground pedestrian networks (UPNs), serving as a comprehensive approach for utilising urban underground spaces to address connectivity and spatial challenges, have undergone significant development in numerous major city centres. Well-designed UPNs are pivotal in developing compact cities, bolstering urban resilience, enhancing urban transportation systems, fostering urban renewal, and facilitating sustainable urban development. This study explores the construction methodology of UPNs by utilising the source-sink theory and relevant models. Using Xinjiekou District in Nanjing City as a case study, this study employs the minimum cumulative resistance model to simulate a UPN and conduct analysis of pedestrian flow clustering on the simulation results. The findings demonstrate that our proposed method effectively elucidates and predicts the connectivity of UPNs, enabling us to construct an optimal network with minimal cost. Moreover, the simulation network significantly enhances the optimisation of pedestrian flow distribution. Building upon these simulation results, the UPN in the study area is optimised by integrating real-world conditions and conducting degree centrality analysis. The findings are then utilised to propose policy recommendations for UPN layout planning in urban centres. This study serves as a valuable reference for underground space planning in the study area and provides insights for UPN construction in other urban centres.