Beyond proximity: How racial and income differences are reflected in mobility patterns across neighborhoods in American cities

Although urban segregation has been widely studied, how race- and class-based neighborhood differences affect everyday mobility is less understood and in need of consistent metrics. Such social dimensions of travel are not reflected in conventional spatial accessibility measures or theoretical models of intra-urban mobility, potentially omitting an important aspect of travel behavior. Using Census Block Group–level cellphone mobility data from the 498 largest U.S. cities, we examine how differences in social characteristics between neighborhoods are manifested in where people travel within their city. Specifically, we propose a novel time-equivalent measure that expresses how racial and income differences between neighborhoods are associated with reduced travel between them, allowing a quantitative comparison in and across cities. We find that racial differences demonstrate a stronger negative association with cross-neighborhood mobility than income differences—associated with reductions in travel equivalent to adding 17% versus 8% of average travel time. Our findings suggest that human mobility in American cities reflects not only by geographic proximity but also social affinity, with important implications for inequality and access to opportunity.