Transport disadvantage and accessibility gaps: Addressing equity in Porto’s metropolitan public transport system

The planning and design of public transport (PT) systems often neglect the transport needs of socially disadvantaged groups, resulting in uneven distribution of services based solely on higher demand. Despite extensive research on accessibility, there remains a gap in operational frameworks that explicitly integrate social vulnerability with travel activity to evaluate spatial equity in PT systems at fine spatial scales. Integrating social needs with travel demand in equity measures for PT planning can significantly enhance service delivery. In this study, transport needs are defined as the latent need for public transport arising from demographic and socioeconomic characteristics associated with transport disadvantage, while equity is conceptualized as the mismatches between these needs and access to PT services. This study proposes a composite transport needs index that integrates origin destination data with demographic and socioeconomic factors to better capture an area’s transport demand and social needs. Applied to Porto's Metropolitan Area (Portugal), the methodology measures PT accessibility at rail and bus stations using gravity models. It considers 14 variables encompassing demographics, socioeconomics, and trip data, weighted via principal component analysis to represent demographic structure, income, social class, and travel demand. By comparing PT service access with transport needs, the study identifies inequities across census tracts, quantifying disparities. The developed method offers a quantitative approach to identify the areas in a region where PT services are distributed inequitably. Furthermore, by integrating social and mobility dimensions within a unified, data-driven methodology, the proposed approach contributes to vertical equity and distributive justice principles, advances an equity-oriented planning-support tool for identifying underserved areas and informing the locations for future PT stations, as well as design new routes based on inequity patterns.