From proximity to equity: Rethinking X-minute-city policies for accessibility equity through a spatial optimization perspective

Abstract

The 15-min city (15mC) framework has emerged as a transformative urban planning strategy to promote equitable access to essential urban services. However, existing studies predominantly focus on descriptive, static, and urban-core-based analyses of accessibility coverage, neglecting predictive insights into how this policy shift might impact systemic spatiotemporal disparities in suburban and peri-urban contexts. This study introduces a novel optimization-based evaluation framework that integrates temporal accessibility metrics to assess how different policy objectives—minimizing average travel time versus maximizing population coverage within 15-, 30-, and 45-min thresholds—shape spatial equity across urban-suburban gradients. Leveraging high-resolution data on COVID-19 testing sites in 10 Chinese megacities, we identify persistent suburban accessibility deserts, particularly under nighttime conditions, and quantify the implications of different planning strategies. Our findings reveal that proximity-driven goals, while effective in boosting 15-min coverage, often fail to mitigate temporal and spatial inequities, especially in underserved suburban areas. In contrast, efficiency-driven approaches not only enhance overall travel performance but also deliver disproportionate benefits to marginalized populations in peripheral zones. This study challenges proximity-centric assumptions embedded in current 15mC discourse and highlights the need for context-sensitive, temporally-aware equity metrics. Our methodological innovations offer transferable tools for equitable public service allocation and provide strategic guidance for suburban planning under both crisis and normal conditions.