Rethinking urban inequality through a behavioural lens: Informal public space activities (IPSAs) as diagnostic tools for behavioural equity and public space resilience in urban planning

Creating sustainable and healthy cities requires more than just equitable access to public open spaces (POS); it also depends on how residents interact with these environments through health-promoting daily activities. Land scarcity, standardized design, and social vulnerability are frequently barriers to such engagement in high-density urban areas, particularly among socioeconomically disadvantaged populations. Because of these limitations, informal, self-directed behaviors are an important but understudied dimension for evaluating inclusive urban sustainability. This study takes a behavioral approach, using Informal Public Space Activities (IPSAs) as diagnostic indicators for identifying spatial inclusion gaps, POS resilience deficits, and underutilized opportunities to improve public health. We operationalize a set of "Layered Healthy Use" indicators using SOPARC-based systematic observations from 85 Hong Kong POS parcels and multilevel Generalized Estimating Equation (GEE) models. These include IPSAs diversity, participation outcomes by age and gender, moderate-to-vigorous physical activity (MVPA), and social interaction level. The findings show that women have higher MVPA needs, whereas adolescents and older adults have higher IPSA diversity and stronger social engagement in low-income neighborhoods. Key spatial features such as shaded seating, tree cover, circulation paths, and a variety of surface texture and greenery are consistently associated with more inclusive participation. Solitary use, communicative interaction, and senior engagement all appear to be highly responsive to environmental affordances. Furthermore, group-specific spatial preferences—such as sittable edge zones commonly used by older men or childcare-associated micro-spaces used by women—emphasize the importance of resilient and gender-responsive planning. This study provides a context-sensitive and demographically appropriate approach to designing equitable, inclusive, and health-supportive public spaces in densely populated urban areas by incorporating IPSAs into planning and evaluation frameworks.