Abstract

Recent studies have examined socio-spatial inequalities in public transport accessibility in Global South cities, consistently showing that lower-income groups face reduced access. However, most rely on scheduled GTFS data to estimate travel times, ignoring day-to-day travel time variability caused by congestion or service disruptions. This oversight limits our understanding of how such variability impacts accessibility levels and inequalities – especially when using more robust indicators that account for competition over opportunities. Emerging research points to a complex interplay between travel time variability and competition for activities, with potential to bias inequalities assessments. Yet, these effects remain underexplored. This study addresses such gap by integrating GPS and GTFS data to assess how daily fluctuations in transit performance affect job accessibility and inequality estimates using both cumulative and competition-based metrics. Using data from Fortaleza, Brazil, our findings show that day-to-day variability significantly influences both accessibility levels and inequalities – regardless of the indicator used. When jobs competition is considered, socio-spatial inequalities widen, as variability is generally lower in central areas and higher in the periphery. Moreover, competition-based measures – adding the interaction between the population distribution, the location of job opportunities, and the level-of-service of the public transport system – amplify the effects of variability, leading to greater observed disparities than cumulative metrics. These findings highlight a critical link between transit reliability and accessibility inequalities, underscoring the need for future studies and policy evaluations to consider travel time variability and competition effects when assessing equitable access to opportunities in Global South metropolises.