A Multi-Layer Network Urban Simulation Model Integrating Real, Virtual, and Social Networks

Urban accessibility is increasingly shaped by the interaction between physical mobility, digital accessibility, and social relationships. However, most existing urban simulation models primarily focus on physical transportation and rarely incorporate digital accessibility or social interaction mechanisms. This limitation restricts the ability of conventional models to capture new behavioral patterns associated with digital service adoption and changing urban lifestyles. To address this gap, this study modifies a multi-layer Social Dynamics Simulation (SDS) model by incorporating three interdependent network layers: a real network representing physical accessibility, a virtual network representing digital accessibility, and a social network representing interpersonal relationships. The study introduces an integrated accessibility index that combines physical and digital accessibility based on a probabilistic service choice framework estimated using survey data (n = 6210). The proposed model is applied to a virtual city experiment to examine how digital service usage and social interaction preferences influence long-term urban dynamics. Additionally, the study compares scenarios with and without digital accessibility. The 30-year simulation results indicate that digital accessibility partially relaxes spatial constraints imposed by transportation networks, enabling households to maintain acceptable service access even in locations with lower physical accessibility. However, physical accessibility remains a dominant factor shaping residential concentration around transit nodes. The results further demonstrate that digital service substitution can reduce travel demand while reinforcing accessibility differences across population groups. Furthermore, scenario simulation results show that, with an increase in digital service adoption, high-accessibility zones lose population, while low-accessibility peripheral zones gain population, revealing a sharp dose–response relationship between digital service penetration and urban decentralization. By incorporating the service choice model and digital accessibility, this study provides a new analytical tool, grounded in shopping-related digital substitution, for evaluating sustainable urban development, equity in service access, and emerging smart city policies.