Aligning transit provision with urban morphology: A diagnostic assessment of Porto and Cagliari

Transit accessibility in cities is shaped not only by service provision but also by the extent to which transit networks align with the structural hierarchy of streets. This paper develops a reproducible, data-efficient framework that integrates angular segment analysis from Space Syntax, proximity-based transit catchments, and population-weighted exposure measures to assess how well transit stops correspond to high-integration corridors. Two indicators operationalise this assessment: the Gap Index, which identifies the share of population exposed to high-integration corridors lacking nearby transit service, and the Equity Ratio, which compares exposure levels across demographic groups. The framework is applied to Porto and Cagliari, two Mediterranean port cities that share comparable urban morphologies but exhibit contrasting mobility outcomes. Findings reveal a strong divergence. Porto demonstrates complete proximity coverage of its structurally high-integration corridors, indicating a close alignment between transit routing and the spatial configuration of the street network. However, Cagliari displays a pronounced proximity deficit, with a substantial share of high-integration corridors lying outside 300 m transit stop catchments. These results suggest that differences in accessibility between the two cities arise not from population distribution or morphological potential but from strategic choices in transit routing. The study shows how morphology-aware indicators can help planners detect accessibility gaps that conventional supply-side assessments overlook and highlights the value of integrating spatial configuration analysis into routine diagnostic practices. The proposed framework offers a transferable basis for monitoring alignment between street structure and transit provision, supporting more responsive and equitable mobility strategies in port-city contexts.