Camilla Pezzica, Diego Altafini, Federico Mara, Chiara Chioni
The X-minute city has gained prominence as a planning paradigm for promoting sustainable local living, yet its operationalisation remains methodologically heterogeneous. This paper conducts a systematic review (Scopus, last search 4 March 2026) of 45 quantitative, proximity-based studies to examine how modelling decisions shape X-minute city assessments. Using reflexive thematic analysis, this review shows that proximity “as-modelled” is not an inherent property of urban space but a construct produced through a sequence of interdependent decisions concerning: analysis scope; functional inclusion; analysis approach; spatial representation; modelling variables; and assessment logic. These decision cascades, often implicit or inconsistently reported, generate substantial variation in results and limit the comparability and transferability of existing X-minute city analyses. The paper identifies connections between decision domains, examines how upstream assumptions influence downstream analytical possibilities, and highlights dominant modelling pathways and methodological divergences. Beyond proposing future directions (e.g., use of multi-threshold scenarios, equity-sensitive parameters, hybrid data strategies, and uncertainty/sensitivity reporting), the study provides a grounded baseline framework and guidance for documenting modelling processes. This research ultimately supports more transparent, reproducible, and context-sensitive proximity assessments, thereby contributing both conceptually and practically to the robustness and policy relevance of X-minute city studies.