Abstract

Urban congestion and social disparity are persistent problems in large cities worldwide. However, congestion is typically assessed from a mobility perspective using traffic performance measures, with limited attention to its impact on urban accessibility inequality. Here, we propose reframing congestion, not merely as problem of slower speeds and longer travel times, but as lost access to opportunities due to excess time in traffic, that mostly affects lower income communities. To illustrate this, we estimate the impact of congestion on employment accessibility in Brazil's 20 largest cities, analyzing how these effects vary spatially and by income level. Using historical GPS-based traffic speed data, we compare the number of jobs reachable by car within a 15–45-minute window during morning peak versus free-flow conditions. Across all cities, low-income communities face the most severe impacts, with an average 24.8% reduction in accessibility, compared to just 5.6% among high-income groups. These findings are used to discuss broader research and policy implications of reframing congestion as lost access that reinforces spatial social disparities. From an equity standpoint, this paradigm shift enables a more comprehensive understanding of how the adverse effects of congestion are distributed across social groups – an insight not captured by traditional traffic metrics. This approach also reveals the spatially and socially uneven impacts of congestion, opening avenues for future research on how it may exacerbate accessibility poverty and inequality.