Green spaces have been proven to significantly enhance physical and mental health, and optimizing urban layouts is widely recognized as a key strategy to improve the accessibility of such beneficial environments. Based on the data of 450,000 individual questionnaires covering 59 cities nationwide, provided by the Ministry of Housing and Urban-Rural Development of China in 2021, this study uses an econometric model to explore the impact of urban compactness on individual green space accessibility and its underlying mechanisms. The findings show that compact urban form exerts a positive impact on green space accessibility, and this positive effect is mainly driven by relatively scattered and sprawling cities rather than already compact ones. The improvement effect of compact development on green space accessibility only has practical significance when the compactness index is >= 2. This moderate positive net effect stems from the balance of multiple mechanisms: the positive mediating role of transportation convenience is stronger than that of spatial proximity, while the crowding-out effect on green space scale serves as the primary negative constraint with a more significant impact than density discomfort. Optimizing urban form to improve green space accessibility is crucial for urban air purification, microclimate regulation, and residents' recreational well-being. The research results provide valuable references for policymakers to improve urban spatial structures and advance the construction of green cities.

By combining the city attribute data of sectoral employment in producer service and manufacturing and the intercity interaction data of population travel, internet, and patent cooperation from 2015 to 2019, the improved functional complementarity between core cities and their peripheral cities is measured. Using physical distance and expressway length as proxies for intercity distance, the analysis investigates the impact of intercity distance on functional complementarity by taking 11 Chinese megaregions as cases. The empirical results show that: (1) Intercity complementarity decreases with increasing intercity distance. (2) Considering intercity interaction in the measurements reveals the greater sensitivity of intercity functional complementarity to distance. (3) The negative effect of the distance becomes increasingly important over time if the interaction is highly sensitive to distance. (4) Among the sectors examined, leasing and business services show the weakest sensitivity to intercity distance while transportation services exhibit the most sensitivity. Our research emphasizes the significance of intercity distance on intercity functional relations in urban systems.

Obesity greatly threatens rural residents’ health and well-being, and addressing it requires urgent optimizations to the built environment (BE). However, few studies have explored the time lag impacts of the BE on obesity, as well as their influential pathways and gender heterogeneity, particularly in the rural context. Based on longitudinal data from China Health and Nutrition Survey (CHNS) between 2004 and 2015, fixed effects models combined with time lag variables were employed to examine the relationship between the BE and body mass index (BMI). Moreover, structural equation models were applied to test the mediation effects of physical activity for transport and exercise in the relationship. Results show that both current and time lag sport places and distance to bus stops are negatively correlated with BMI. Commuting by walking, auto ownership, and durations of exercise are mediators of the BE-BMI relationship. The BE has various associations with the mediators and BMI between women and men. These findings offer new knowledge to the literature and are important to design healthy villages for reducing residents’ risks of being obese.

Unlike prior studies that usually focus on the overall economic performance of megaregions, this study investigates whether and how the polycentricity of megaregions affects the economic performance of individual cities in China. Empirical results indicate that polycentricity promotes economic development of both large and smaller cities. This arises because spillover effects are more distance-sensitive than siphoning effects, so shorter intercity interaction distances in polycentric systems tilt the balance between borrowed size and agglomeration shadows toward net positive spillovers. Further analysis reveals that polycentric megaregions improve city economic performance through industrial optimization, factor mobility, and infrastructure connectivity. Moreover, the benefits of polycentricity are especially pronounced for lower administrative level cities, and particularly for those in eastern/coastal megaregions and nurturing and emerging megaregions. These findings provide policy implications for improving the performance of cities of different sizes.

The urban life cycle (ULC) theory, originally developed in European urban studies, divides urban spatial evolution into four sequential stages: urbanization, suburbanization, de-urbanization, and re-urbanization. Yet its long-term dynamics outside Europe remain insufficiently examined. Using population distributions between urban cores and rings, this study traces the evolution of the 50 largest U.S. metropolitan statistical areas from 1790 to 2020, providing one of the longest empirical assessments of the ULC model to date. The results indicate that large U.S. metropolitan areas broadly followed a transition from urbanization (1790–1920) to persistent suburbanization (1920–2020), but diverged from the classical framework in several respects. First, de-urbanization and re-urbanization were not universal evolution stages. Second, stage transitions followed gradual and symmetrical pathways instead of linear sequential shifts. Third, urbanization began with relative rather than absolute concentration, as both cores and rings grew simultaneously. Finally, certain evolution stages exhibited strong national synchronization shaped by technological, policy, and economic factors. These findings refine the classical theory and highlight the importance of path dependence, transition costs, and multi-scalar drivers in shaping the long-term evolution of large metropolitan areas, with implications for sustainable metropolitan planning and governance.

The classical Urban Spatial Change (USC) hypothesis efficiently summarizes urban development patterns through population changes across space but faces disputes regarding its generality and applicability due to its reliance on empirical research primarily from Western contexts. This paper provides the most up-to-date examination of the complete trajectory of Shanghai's remarkable urban transition from a small county to the world's third-largest megacity over 177 years (1843-2020), based on long-term population spatial changes within the USC hypothesis framework. The findings suggest that while Shanghai generally follows the conventional USC trajectory of centralization, decentralization, and recentralization, it also exhibits notable heterogeneities. Those include the bypassing of disurbanization and highly compressed processes following a sequence of urbanization, suburbanization and reurbanization, strong government interventions accompanied by a complex and dynamic interplay between market forces, and a central role of inter-regional migrants throughout Shanghai's urban life cycle. The results support the view that while the USC hypothesis provides a generalized summary of urban systems and offers a concise overview of urban changes, further refinement is necessary to accurately capture the diverse trajectories across different types of cities.

Employment centers serve as crucial drivers of intra-city development, especially in the ubiquitous polycentric transformation. Clarifying the role and impact mechanisms of centers in intra-city growth echoes both theoretical basis and actual needs. However, the empirical understanding is surprisingly limited. Thus, this paper proposes and examines a novel systematical framework with a particular and new focus on the centers' influence. Instead of focusing only on developed regions, both areas outside centers and two types of sub-centers are investigated in this research. The empirical results using Shanghai as a study case show that the effects of agglomeration of centers are mostly insignificant on average but conditioned by three types of proximities to centers. Geographic proximity strengthens the positive role of agglomeration of centers on areas outside centers within the city and developing sub-centers within a certain distance to main-center, but intensifies the siphonic effects for the case of stabilized sub-centers. The industrial proximity only positively moderates the effect of agglomeration of centers on developing sub-centers, while the moderating role of proximity of agglomeration scale to main-center is significantly negative in all areas. These discoveries provide valuable insights for urban spatial and development planning, especially in polycentric cities.

Obesity is a prominent risk contributor to health. However, few studies have explored the nonlinear relationships between commuting and built environments, particularly around workplaces, with obesity. Based on a sample of 1080 respondents in Shanghai, China, we used the gradient-boosting decision trees model to investigate the relative contributions and nonlinear relationships of commuting and built environments surrounding residences and workplaces with body mass index (BMI). Results showed that the built environment made greater contributions to BMI than sociodemographics and behavioral attributes. The built environment around workplaces was more important than that around residences, and commuting behavior rather than exercise or food intake contributed more. Gender and age were the most important predictors among all predictors. Moreover, most predictors were nonlinearly related to BMI. Car and bus commuters had higher BMI. Commuting distance (<20 km) was positively related to BMI and the duration of active modes (<20 min) was negatively associated with BMI. Around workplaces, green space (<0.28 km(2)) and population density (10,000-28,000 people/km(2)) had negative associations with BMI. Land use diversity around workplaces (>0.5) had a U-shaped relationship with BMI and the threshold was 0.78, but it around residences (0.82-0.85) had a positive effect. A longer distance to the subway station from residences (<1500 m) was associated with lower BMI. Men had higher BMI and age (24-47 years) was positively correlated with BMI. Beyond the thresholds, these predictors had limited contributions to BMI. We concluded that prioritizing interventions in the built environment around workplaces and commuting behavior to reach effective thresholds is important to reduce obesity.

The widely recognized rank-size law is being questioned as the single best rule for city size distribution by an increasing number of studies. However, these studies suffer from inconsistent findings and some deficiencies, including differing definitions of a city across countries, samples with few countries, less systematic examination of socioeconomic influencing factors and no attention being given to the dynamic changes in best-fit city size distribution types for a given country. With a larger sample of countries and a more comparable and consistent definition of cities, our empirical analysis supports two findings from the existing literature. First, there is no single, universal distribution but rather a plurality of national city sizes. Second, the main body of a country's city size distribution is generally characterized by a lognormal distribution, while the upper tail tends to follow a Pareto distribution. Furthermore, our exploratory analyses reveal that specific city size distributions are associated with nations' socioeconomic development and urbanization levels. Finally, this paper presents the changes in the best-fit city size distribution type of a country across different periods and proposes a hypothesis on the general evolutionary trend.

This is one of the first studies that explores built environments around both residences and workplaces, as well as their nonlinear and interaction effects on commuting satisfaction. Based on 1,044 respondents in Shanghai, China, we applied an extreme gradient boosting model to examine associations of the built environment with commuting satisfaction, adjusted by commuting characteristics and sociodemographics. Results show the built environment around workplaces is more important than that around residences. Workplace land use diversity promotes commuting satisfaction, while residential land use diversity reduces it. Around both residences and workplaces, areas of green spaces reduce commuting satisfaction and population density has inversed U-shaped associations with commuting satisfaction. Moreover, the effects of green spaces and land use diversity around workplaces are diminished by those around residences; while the effects of population density around workplaces are strengthened by those around residences. These findings highlight promoting commuting satisfaction by optimizing built environments.

Understanding the evolution of the urban spatial structure is of great significance for clarifying the stage and trajectory of urban development and formulating future urban development plans. Given that previous studies have marginally explored the long-term evolution of the urban employment spatial structure, this paper proposes a theoretical model hypothesizing five sequential stages of a complete evolution cycle from the perspective of mono- and polycentricity: mono-centralization, main-centralization, multi-centralization, de-centralization and re-centralization. Further empirical results based on 292 prefecture-level cities in China from 1997 to 2017 support the model and demonstrate that most cities present an evolution in line with the hypothesis, except a few cities experiencing short-term fluctuations, and approximately 60 % of cities are in the stage of multi-centralization, where subcenters have a growth advantage, and the main center has a scale advantage. Additionally, this paper reveals two characteristics of the evolution of the urban employment spatial structure in China: spatiotemporal compression and government intervention.

The urban knowledge network in China has undergone in-depth development in recent decades, intimately connecting the position characteristics of cities in the knowledge network to their knowledge production performance. While existing research focuses predominantly on the unidirectional relationship between network position and the knowledge production of cities, there is a notable dearth of studies exploring the bidirectional relationship between the two constructs. By proposing a conceptual framework, this paper empirically examines the interplay between network position and knowledge production of cities through simultaneous equation models. The results revealed a mutually reinforcing relationship between network position and knowledge production, and this relationship exhibits heterogeneous characteristics and spillover effects. Specifically, cities in the periphery block and the central-western region benefit more from the effect of network position on knowledge production, while cities in the core block and the eastern region benefit more from the effect of knowledge production on network position. Moreover, the interactive effect between network position and knowledge production of cities is significantly affected by the network position characteristics and knowledge production performance of their neighboring cities in geographically adjacent regions and relationally adjacent regions. These findings enhance the understanding of urban network externalities and the connotations of the knowledge production function.

Although owning a car allows people to access distant fitness centers and may promote exercise, car use may encourage sedentary behavior and reduce exercise. There is no empirical evidence on the relationship between car ownership, car use, and exercise, and whether improving the built environment is useful to encourage exercise by affecting car ownership and usage. Through a survey of 1049 respondents in Shanghai and subsequent path analysis, we investigate the relationship between the built environment around residences and workplaces, car ownership, car usage for work and non-work trips, and the duration of exercise weekly. While car ownership directly fosters exercise, it indirectly reduces exercise due to increased car usage for work and non-work trips, and the negative effects outweigh the positive. Moreover, the built environment around residences and workplaces affects exercise through car ownership and usage. People living in dense and downtown neighborhoods conduct more exercise because of the fewer likelihood of owning and/or using cars. More intersections and transit stops around residences and mixed land use around workplaces reduce exercise by increasing car ownership and/or car usage. We conclude that reducing car ownership and usage can promote exercise, and built environment interventions are effective in enhancing public health outcomes.

Emergency responders in coastal cities are anticipated to provide effective evacuation of at-risk populations during the preparedness and response phases of coastal floods due to land-falling storms or cyclones. However, existing contingency plans primarily focus on the evacuation of the general public rather than special arrangement for elderly populations who constitute a large proportion of flood fatalities. Here we present a system-level methodology to elaborate citywide coastal flood evacuation plans for optimal deployment of shelters and effective transfer of elderly people with special needs. We conduct a comparative analysis between Shanghai and New York City, which are both among the most exposed coastal cities to storm-induced flooding but represent two distinct institutional systems of emergency operation. The results show marked disparities in evacuation patterns for elderly residents in the two cities. Storm flood evacuation is more challenging in Shanghai due to insufficient provision of shelter capacity (~230,000). Implementing risk-informed and strategic planning could not only meet the potentially huge demand of vulnerable elderly (~520,000) but also improve the overall efficiency of evacuee transfer by a factor of 3. Our work provides new insights into operational emergency evacuation decisions and informs flood management policy development for major coastal cities globally.

Introduction: Improving neighborhood environments for healthy aging has attracted much attention. However, few studies have investigated the associations between multi-dimensional neighborhood environments and different aspects of older adults' health, and have paid attention to the mediation effects of various physical activities, particularly during the COVID-19 pandemic in Asia. Methods: Applying structural equation models to Chinese General Social Survey (CGSS) data in 2021, we investigated how neighborhood natural, built, and social environments are associated with older adults' physical, mental, and social health, focusing on the mediation effect of physical activity. Results: For older adults' physical and mental health, all neighborhood environmental dimensions had direct and positive effects, and the built environmental dimension was most important. For their social health, the social environment had a direct and positive effect. Regarding the indirect effect, the built environment was positively related to physical and mental health by increasing walking duration. Moreover, the built environment was related to decreased sedentary duration, leading to better mental health but worse social health. Conclusions: Our findings highlighted that neighborhood environments were important to older adults' physical activity and further contribute to health outcomes, even during the COVID-19 pandemic, which could shed some light on healthy aging in Asian countries.

This study revealed the non-linear impact of the internet on the spatial structure of intracity employment and how transportation infrastructure moderates this non-linear impact. Using data from 22.47 million enterprises from the China Economic Census of 2004, 2008 and 2013, we found that (1) on average, the internet promotes urban employment agglomeration, but this agglomeration effect diminishes marginally as internet penetration increases; (2) the internet promotes the secondary sector to agglomerate first and then disperse, while it only has an agglomeration effect on the tertiary sector; and (3) improvements in the transportation infrastructure diminish the internet's agglomeration effect.

It remains unclear whether a polycentric city can support more and higher-order consumer amenities. This paper presents new evidence from shopping malls in China and includes the effect of urban spatial structure on the order of consumer amenities and the moderating effect of transportation infrastructure, both of which have been neglected in previous empirical studies. We find that a monocentric city can provide a greater number and higher order of shopping malls than a polycentric city. Additionally, better transportation infrastructure can compensate for the disadvantage of polycentricity in the provision of low-order shopping malls, while it reinforces the merit of monocentricity in higher-order shopping malls. The findings advance the understanding of the relationship between polycentricity and the quantity and quality of consumer amenities and provide insights into polycentric structure policies.

Mixed land use (MLU) is recognized as a crucial means for urban planners to facilitate residents' subjective well-being (SWB). However, prior research has rarely explored the mediating effect of social capital on the MLU-SWB association and has overlooked the possibility that this association may be subject to spatial heterogeneity between residential and workplace neighborhoods. Based on a sample of 1028 survey participants in Shanghai from 2018 to 2019, a structural equation model is used to investigate the associations among MLU, social capital, and SWB in residential and workplace neighborhoods. We find that MLU has a negative and indirect association with SWB by decreasing social capital in residential neighborhoods, while it has a positive and indirect association with SWB by enhancing social capital in workplace neighborhoods with adjustments for other built environmental and sociodemographic attributes. That is, MLU has opposite associations with SWB mediated by social capital. Therefore, policymakers need to adopt different strategies to optimize MLU in residential and workplace neighborhoods to facilitate social capital and SWB.