Travel-Time in a Grid: Modelling Movement Dynamics in the “Minute City”

The concept of the 15-minute city has gained growing attention as a sustainable urban development model aimed at improving people’s quality of life while reducing environmental footprint from urban transport demand. Effectively implementing this concept requires urban analysists and planners to assess the distribution of urban functions and propose actions that promote equitable access to services within a reasonable commuting time, primarily using soft mobility modes. However, there is currently no consensus on modelling principles and methods for producing reliable minute-city representations. Additionally, there is uncertainty about the spatial, positional, configurational, and socioeconomic parameters to consider in such models. This paper starts to address this significant knowledge gap by tackling the often-overlooked issue of examining the implications of technical modelling decisions on minute-city evaluations based on an isochrone analysis. One such choice is selecting an ideal point from which to calculate the 15-min travel radius, as it determines the area where functional centres should be located. The paper conducts a sensitivity test on selected key steps of a typical 15-minute city modelling process, using Rome as an illustrative case. The results shed light on the impact of technical decisions on the outcomes of the 15-minute city analysis. This study provides initial insights and recommendations for developing more robust 15-minute city models. It emphasises the importance of technical modelling steps in determining the mapping outputs which support the assessments of 15-minute cities.