Planning Proximity: A Critical Perspective on Measuring the 15-Minute City

Although the 15-minute city has become a prominent paradigm in contemporary urban planning, the conditions under which urban proximity can be meaningfully measured and operationalized remain insufficiently defined. While it has gained widespread recognition through its strong political and scientific appeal, it remains characterized by methodological and operational ambiguities, reflecting a persistent gap between its rhetorical appeal and its practical implementation in urban planning. Despite the growing number of proximity assessment approaches, no shared conceptual framework currently exists to organize the diversity of existing methodologies. Existing assessment approaches—predominantly grounded in GIS-based and quantitative methods—struggle to capture the multidimensional nature of urban proximity. This article presents a critical comparative review of 47 proximity assessment methodologies covering the period 2016–2025. Rather than conducting a systematic review, the study adopts a critical analytical approach to examine how urban proximity has been conceptualized, measured, and operationalized across different disciplinary traditions and urban contexts. Three principal findings emerge from the comparative analysis: the disciplinary compartmentalization of proximity assessment, largely dominated by engineering and GIS-based approaches; the absence of a shared conceptual framework despite the plurality of "X-minute city" models and assessment methodologies; and the underrepresentation of polycentric medium-sized cities, despite their strategic role within the European urban system. Building upon these findings, the article proposes the Integrated Proximity Matrix as a conceptual synthesis rather than as a new measurement indicator. The matrix integrates the complementary methodological dimensions identified across the reviewed literature into a coherent conceptual architecture intended to support the future development of context-sensitive proximity assessment methodologies. Developed within the broader context of an ongoing doctoral research project conducted in Prato (Italy), this framework constitutes the conceptual bridge between the comparative findings presented here and their future empirical implementation and validation in urban planning practice.