Mustafa Mutahari

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.

Urban accessibility is increasingly shaped by the interaction between physical mobility, digital service accessibility, and social relationships. However, most existing urban simulation models primarily focus on physical transportation networks and rarely incorporate digital accessibility or social interaction mechanisms. This limitation restricts the ability of conventional models to capture emerging behavioral patterns associated with digital service adoption and changing urban lifestyles. To address this gap, this study develops a multi-layer Social Dynamics Simulation (SDS) model that integrates three interdependent network layers: a real network representing physical accessibility, a virtual network representing digital accessibility, and a social network representing interpersonal relationships. The model introduces an integrated accessibility index that combines physical and digital accessibility based on a probabilistic service choice framework estimated using survey data (n = 6,210). 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. 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, transportation 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. The proposed framework contributes to computational urban systems modeling by incorporating digital service substitution and social interaction effects into a multi-layer simulation environment. The results highlight the importance of representing non-physical accessibility processes when evaluating urban dynamics in increasingly digitalized cities.

The Air-front Smart City (ASC) concept is proposed to address the stagnation of industries in developed countries and stimulate economic growth in developing countries while maintaining a higher quality of life for people and contributing to decarbonization and overall United Nations SDGs in an existing study. However, no studies have been conducted to assess ASC policies. Therefore, this study integrates the integrated accessibility index into the quality of life (QOL) and quality of business (QOB) evaluation models to assess the startup ecosystem in Aichi, Singapore, and Munich within the ASC concept. The study uses survey data conducted in Aichi to estimate monetary values of QOL and QOB component indicators, calculates the integrated accessibility indices, and estimates QOL and QOB. Furthermore, the study sets scenarios to assess the impacts of living and business urban policies in Aichi. Additionally, the study using Aichi parameters compares the startup ecosystem in Singapore and Munich. The result shows that the key drivers of startup attraction are corporate tax rate, economic growth, and safety; enhancing these indicators directly increases startups’ QOB, business partners, and residents’ QOL. It was found that QOB in Singapore is comparatively higher, whereas QOL is higher in Aichi.

A regenerative economy refers to an economic system that regenerates various forms of capital, including natural resources and social systems, for long-term use. Regenerating these forms of capital enables the sustained improvement of social well-being. This concept differs from a traditional consumption-based economy or a sustainable economy, which primarily aims to secure the satisfaction of future needs. Traditional capitalism has regenerated capital in production but has often consumed natural capital and sometimes degraded social capital. The concept of a regenerative economy provides principles for restoring these forms of capital. This paper discusses how digital transformation (DX) technologies can help realize a regenerative economy, using development projects for DX technologies as case studies. Airport-adjacent districts in three countries—Japan, the Philippines, and Thailand—representing different industrial sectors are examined, and the impacts of these technologies are analyzed based on Fullerton’s concept of a regenerative economy. Based on qualitative assessment, we found that these technologies are expected to contribute to improving some principles of a regenerative economy, but challenges remain in others. As a result, the concept of a regenerative economy can be useful for a conceptual yet holistic assessment of the regeneration of natural and social capital.

The Air-front Smart City (ASC) concept is proposed to address the stagnation of industries in developed countries and stimulate economic growth in developing countries while maintaining a higher quality of life for people and contributing to decarbonization and overall United Nations SDGs in an existing study. However, no studies have been conducted to assess ASC policies. Therefore, this study integrates the integrated accessibility index into the quality of life (QOL) and quality of business (QOB) evaluation models to assess the startup ecosystem in Aichi, Singapore, and Munich within the ASC concept. The study uses survey data conducted in Aichi to estimate monetary values of QOL and QOB component indicators, calculates the integrated accessibility indices, and estimates QOL and QOB. Furthermore, the study sets scenarios to assess the impacts of living and business urban policies in Aichi. Additionally, the study using Aichi parameters compares the startup ecosystem in Singapore and Munich. The result shows that the key drivers of startup attraction are corporate tax rate, economic growth, and safety; enhancing these indicators directly increases startups' QOB, business partners, and residents' QOL. It was found that QOB in Singapore is comparatively higher, whereas QOL is higher in Aichi.

Evaluation of an individual’s accessibility to urban services is crucial for urban planners and policymakers to assess various urban policies and scenarios. Most studies have emphasized accessibility in physical spaces, with limited attention to the role of Information and Communication Technology (ICT) in providing virtual access and its implications for quality of life (QOL) and sustainability. This study addresses this gap by examining the substitutability of physical activities with digital alternatives and their potential contribution to decarbonization. Using data from an online questionnaire survey in Japan, we analyze how individuals access services across both transportation and ICT networks. We propose an integrated evaluation framework that measures QOL by considering accessibility in both physical and virtual spaces. The analysis highlights differences in substitutability across activities such as shopping, working, schooling, and entertainment, while revealing that services like healthcare and physical tourism remain less substitutable. The results disclose that accessibility strongly influences individuals’ adoption of digital alternatives, which in turn offer significant benefits in terms of convenience and environmental impact. The proposed methodology provides valuable insights seeking to balance physical and virtual service accessibility, supporting sustainable urban development in line with UN Sustainable Development Goals 10 and 11.

Considering the rapid integration of digital services into daily life, it is crucial to analyze the impacts of the substitutability of physical services with digital alternatives. Limited studies have been conducted to investigate the relationship between service substitution and social networks and assess their impact on urban structure. Therefore, this study fills the gap by investigating how digital service substitution and social networks influence residential location choices and urban structure, aiming to support future sustainable urban modeling and planning tools. The study, through a comprehensive analysis incorporating cluster analysis, factor analysis, and binomial logistic regression on a web-based questionnaire survey (n = 6210), finds that socio-demographic factors significantly influence digital alternatives, and that digital service substitution and social networks impact sustainable urban structure. Younger individuals showed significantly higher adoption of digital alternatives, with age negatively associated with relocation likelihood. In urban areas, each additional year of age reduces the likelihood of relocation by approximately 4.4%, and individuals with high shopping substitution are 3.12 times more likely to consider relocation. These findings suggest that urban planners and policymakers to balancing physical and digital service provision to maintain a higher quality of life aligned with the SDGs and ensure sustainable urban development.

The analysis and evaluation of urban structure are important while considering sustainable urban policies. It is necessary to develop a method that can easily analyze the social dynamics that are the result of changes over time in urban transportation and land use. Therefore, by describing the relationships between various agents in urban areas as a network, it is possible to analyze them by focusing on their structures. However, since there are few existing studies on social dynamics using network-based methods, it is necessary to examine the validity and effectiveness of these methods. The purpose of this study is to examine the possibility of urban analysis and evaluation focusing on the network shape by describing the urban activities and modeling the dynamics with a multilayer network. In particular, we focus on household composition and individual facility access, examine what kind of interpretation is possible for network indicators, and mention the applicability of complex networks to urban analysis. The model was applied to a two-dimensional grid virtual city, and the household composition and individual facility accessibility were quantified using the centrality index.