Evaluating last-mile access in the 15-minute city

Abstract The 15-Minute City (FMC) framework seeks to promote sustainable urban mobility, reduce last-mile car dependency, and enhance proximity-based access to essential services, primarily through walking and cycling. However, the feasibility of active mobility as the main mode for last-mile access in cities with complex topographies remains underexplored. This study evaluates the applicability of the FMC model in Trieste, Italy, a coastal city with significant elevation variations, using gradient-sensitive accessibility modelling, spatial equity analysis, and local travel behaviour assessment. The research employs network-based isochrone mapping, adjusting for elevation constraints using Tobler’s Hiking Function (walking) and Parkin-Rotheram’s Cycling Model to measure accessibility across multiple transport modes. Findings reveal walking-based spatial disparities in access to education, healthcare, recreation, and public amenities, with central districts largely meeting FMC criteria while peripheral, high-elevation areas experiencing significant accessibility gaps. Despite a dense public transport network, last-mile connectivity barriers persist, particularly in hillside neighbourhoods where walking and cycling adoption is lower. Travel behaviour analysis highlights persistent car dependency for school and shopping trips, with mode choices influenced by terrain, service distribution, and perceived infrastructure limitations. While cycling and e-bikes improve accessibility, limited infrastructure, lack of e-bike sharing services and safety concerns hinder widespread adoption. The study underscores that fostering active last-mile access via the FMC implementation in hilly cities requires relevant adaptable policies beyond conventional active mobility strategies. Recommendations include expanding cycling infrastructure adapted to steep gradients, e-bike sharing schemes for hillside connectivity, implementing vertical mobility solutions such as inclined elevators, improving intermodal public transport links, and decentralizing essential services to improve accessibility in high-slope neighbourhoods. This research advances analytical methodologies by integrating gradient-sensitive accessibility modelling with travel behaviour analysis, offering a replicable framework for assessing FMC feasibility in topographically complex cities. The application to Trieste illustrates how such a method can identify spatial inequalities and inform context-specific policy adaptations.