From informality to insight: Measuring inclusivity gaps in neighbourhood public space design through Informal Public Space Activity Diversity (IPSAD) in dense urban contexts

Inclusivity in public open space (POS) design remains underexamined, as equity research continues to emphasize supply-side metrics such as area and accessibility. As East Asian cities densify, the gap between formal provision and lived demand becomes increasingly pronounced. Existing public open space (POS) usage assessments emphasize planned, programmed, and infrastructure-bound activities, overlooking how residents adapt space through informal, spontaneous practices. However, the spatial distribution, intensity, and diversity of these behaviors offer critical insights for inclusive design under constraint. This study foregrounds leisure- and physical-oriented Informal Public Space Activities (IPSAs)—e.g., unplanned play, casual exercise, and spontaneous gathering—as a lens to examine spatial justice in dense urban contexts. Drawing on systematic on-site observation, GIS-based analysis, and linear mixed-effects modeling across 85 parcels in 31 planned POSs in Hong Kong, the study analyzes the distribution, co-occurrence, and contextual drivers of Informal Public Space Activity Diversity (IPSAD). Key findings show that lower-SES and POS-underserved communities exhibit higher IPSAD, suggesting a greater design emphasis on inclusion in underserved contexts. Seating, child-oriented features, and fitness amenities are positively associated with informal activity diversity. Informal sedentary and low intensity uses tend to cluster around greenery, while football fields and playgrounds exhibit exceptional multifunctionality—suggesting their strategic prioritization in disadvantaged areas. These findings support a behaviourally informed framework for inclusive, adaptable, and equity-responsive POS governance in compact urban environments. • Develops IPSAD to quantify informal recreation diversity in dense East Asia • Uncovers how gender, age, and activity adaptability shape informal space use • Highlights flexible design needs across varied SES, POS access, and densities • Shows spatial offerings drive diverse informal activities and adaptive use patterns • Offers a dashboard for context-aware, inclusive public space design decisions