H3 Isochrones in the Context of the 15-Minute City

The 15-minute city concept has emerged as a framework for promoting more sustainable, inclusive, and accessible urban environments by enabling residents to reach essential daily services within a short distance from their homes. This study evaluates potential spatial accessibility to mapped points of interest in the Berceni neighbourhood, a socialist-era residential district in southern Bucharest, Romania. Walking isochrones were generated through network analysis and subsequently indexed and aggregated using the H3 hierarchical spatial system at resolution 10. Accessibility was assessed for seven social functions using three weighting specifications: 1:1:1, 3:2:1, and 5:3:1. The final analysis included 520 mapped POIs and 8465 H3 resolution 10 cells. The results reveal broadly consistent spatial patterns across the three weighting specifications, although the weighting assumptions influence local scores, the extent of high-accessibility areas, and the relative ranking of individual H3 cells. Caring has the largest mapped opportunity count and broad spatial coverage, whereas working and governing are the least represented functions and display comparatively low potential accessibility in several parts of the neighbourhood. A function-targeted scenario involving the addition of a childcare centre in the south-western part of Berceni produces a local improvement in working accessibility but does not eliminate the wider functional deficit. The findings demonstrate the applicability of combining network-derived isochrones with H3-based spatial aggregation for neighbourhood-scale accessibility assessment.