Fifteen-Minute City Implementation, Active Mobility Mode Share, and Neighborhood-Level Social Equity: A Multi-City Comparative Study of 24 European Urban Cores

This study investigates 15-minute city implementation fidelity, active mobility mode share change, and neighborhood-level socioeconomic equity in access improvements across 24 European urban cores with formally adopted 15-minute city frameworks within the context of urban planning and sustainable mobility research, an area of growing scientific importance given its implications for 15-minute city policy design, equity-centered active mobility investment prioritization, and urban proximity index methodology for comparative evaluation. Using 15-minute proximity index (15MPI) computed from OSM network + POI data for each city, regressed against observed active mobility mode share change (cycling + walking trips) and equity access gap between lowest and highest income quintiles, we examine proximity-led urban design increasing walkable access to daily needs reducing need for motorized trips, with cycling/walking infrastructure investment amplifying active mode shift, moderated by socioeconomic barriers to active mobility in lower-income neighborhoods in 24 cities across 12 European countries with pre-post mobility survey data (mean n=12,400 respondents per city), 15MPI computed at 250 m resolution for all residential parcels drawn from 24 cities including Paris, Barcelona, Amsterdam, Vienna, Copenhagen, Helsinki, and 18 others with formally adopted 15-minute city policies and at least 2-year post-implementation data. Results indicate that 15MPI increase of 10 points is associated with 4.2 percentage point increase in active mode share (p<0.001, R2=0.62) but access gains are 38% larger in highest income quintile neighborhoods; lower-income neighborhoods require additional investment to close equity gap (p < 0.001), with +4.2 pp active mode share per 10 15MPI points; 38% equity gap by income quintile as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to urban planning and sustainable mobility research and carry actionable implications for the design of programs and policies targeting 15-minute city policy design, equity-centered active mobility investment prioritization, and urban proximity index methodology for comparative evaluation.