Three-dimensional walking accessibility to multi-type public open spaces: Spatial equality and planning implications

Accessibility to public open space (POS) is critical for promoting walking and outdoor physical activity. In dense, vertically developed cities, traditional two-dimensional accessibility measures fail to capture the complexities of vertical and slope movement. This study addressed this gap by incorporating three-dimensional (3D) distance into walking accessibility assessment and examining spatial equality across multi-type POSs. A research framework was established integrating Gini index-based equality measurement, regression analysis of influencing factors, and multivariate grouping of street blocks to inform planning strategies for equitable POS distribution. The framework was applied to the case of the Kowloon district in the vertical city of Hong Kong. Spatial (in)equality of 3D walking accessibility for different POSs, including local POSs, district and regional POSs, POSs with children’s playgrounds and POSs with fitness equipment for the elderly was measured and interpreted. The results suggested that small-scale local POSs were undersupplied compared to large ones, while accessibility inequality was more pronounced for child- and elderly-oriented facilities. Ethnicity was the most influential social-economic factor in the spatial heterogeneity of POS distribution. Spatial grouping analysis identified only 16.03% of the area as "optimizable zones" suitable for renewal interventions, with the remainder classified as "deadlock" (high-density constraints) or "stagnant" (low renewal urgency) zones. Future urban renewal projects should pay more attention to the improvement of POS quality and spatial equality. The proposed framework offers transferable methodologies for enhancing POS spatial justice in high-density cities through data-informed planning and governance.