The 15-minute city revisited: A GIS approach to measuring, visualizing, and analyzing accessibility by proximity and by public transport supply

The 15-minute city can offer a meaningful framework for measuring and analyzing accessibility to basic urban functions, if proper theoretical and methodological choices are made. This paper develops a comprehensive methodology and presents the steps for measuring, visualizing, and analyzing x-minute accessibility by proximity (walking accessibility) and accessibility by public transport supply (accessibility potential created by nearby public transport services) using geographic information systems (GIS). Five sequential steps are presented: project definition, data preparation, measuring accessibility, visualizing accessibility and insufficient accessibility, and analyzing accessibility using spatial statistical analysis and modeling. The proposed approach is applied to Copenhagen. Results indicate that, even in a city where sustainable mobility is prominent, there are spatial clusters of lack of accessibility and insufficient accessibility, lying mainly in suburban locations. Proximity-based accessibility and accessibility by public transport supply are found to highly overlap across space. Moreover, density was found to largely predict both 15-minute walking accessibility to local destinations and accessibility to other areas via public transport. This approach can be used as a guide by those aiming to understand the patterns and drivers of accessibility across space, reveal socio-spatial inequalities, and identify locations for potential interventions that improve walking accessibility and reduce car dependence.