Equity of access to rail services by complementary motorized and active modes

The public transport system only serves its true purpose when people living in the region have adequate and direct access to its services. Rail systems, including light rail, metro, urban, suburban, and long-distance trains, are the key fixed structural elements of any transport system that provide faster access for both shorter and longer trips and are regarded as a more efficient and environmentally friendly option to move a larger number of passengers than road transport. However, it is not feasible in terms of investment and financial sustainability to provide rail services everywhere, especially in rural zones. Thus, connectivity with all the other available (active and motorized) modes is crucial to improve accessibility and reduce inequities. In this paper, we developed a methodology to quantify and contrast the access to the existing rail services between zones of a metropolitan area and corresponding inequities. We considered not only the usually analyzed active modes, pertaining to a certain level of proximity to the rail stations, but also motorized modes (e.g., car and bus) that can enable the connection to rail services where these are not easily accessible by walking or cycling. First, the accessibility to the existing rail stations is quantified using place-based gravity measures, considering the travel times for the complementary modes with and without incorporating the stations' attractiveness, measured by service frequency. Second, the global inequity levels of the spatial distribution of the rail network in the metropolitan area are evaluated using the Gini index. Third, local inequities, at a scale of small census blocks, are measured considering the access (supply) and the population (potential demand). While the local-scale analysis allows to identify the most unfavored zones, the global inequities by complementary modes aim to inform targeted strategies to improve the integration of those modes with rail services. The methodology was applied to the Metropolitan Area of Porto, Portugal, where we observed a non-uniform distribution of rail services and a decrease in access towards the periphery. However, considering the population living in each zone, both underserved and well-served zones are mostly present in the most populated/central areas.