Unraveling the drivers of spatial (in)equity in bicycle crashes across four U.S. cities

The United States has recently seen a significant increase in bicycle ridership, driven by a growing interest in active lifestyles and the rise of bicycle-sharing services. Although the number of bicycle crashes has increased accordingly, and growing evidence indicates spatial inequities in these crashes, variations between cities and their underlying mechanisms remain poorly understood. This study examines the disparities in motor vehicle-bicycle crash outcomes in disadvantaged versus advantaged neighborhoods across four U.S. cities and identifies key factors contributing to these disparities.

Regression analyses are used to identify patterns of bicycle crash disparities between disadvantaged and advantaged neighborhoods. The Gelbach decomposition technique then assesses the statistical significance and relative importance of the factors contributing to these disparities.

Regression results indicate that, before adjusting for other factors, bicycle crashes occur more frequently in disadvantaged neighborhoods in Los Angeles and Austin. Conversely, patterns observed in Chicago and Washington, D.C. show fewer crashes in these areas. The decomposition analysis identifies the built environment-particularly proximity to the city center-as a critical factor explaining the unequal distribution of bicycle crashes between neighborhood types in all examined cities. Other important drivers, with varying significance across cities, include differences in commercial land share, bicycle exposure, and local street density between neighborhood types. Contrary to widely held assumptions, differences in bicycle infrastructure between neighborhood types are not a significant driver.

Transportation policymakers should not automatically assume spatial inequity in bicycle crashes exists in all cities based on past evidence. In cities with inequitable crash distributions, targeted interventions are needed to address the specific sources of these disparities. This study also demonstrates the potential of Gelbach decomposition analysis as a useful transportation planning tool for identifying key sources of disparities in traffic crashes and other equity issues.