The Impact of Streetlight Placement on Trends and Disparities in Pedestrian-Motor Vehicle Crashes

Pedestrian-motor vehicle crashes are a major cause of preventable injury in urban environments. They have increased markedly over the past several decades, especially overnight, and with a disproportionate impact on pedestrians of color. Streetlights represent a potential tool to combat these trends, but empirical studies of their relationship with pedestrian trauma are limited. We use geospatial data from Boston (2016-2023) to assess the relationship between streetlight density (lights/road kilometer) by census tract on (1) pedestrian crashes, (2) changes in crash rates over time, (3) racial disparities in crash incidence, and (4) proportion of crashes occurring overnight. Pedestrian crashes decreased from 2016 to 2023 from 616 (0.55/km) to 421 (0.37/km), with higher streetlight densities associated with greater overall reductions (an additional -0.002 crashes/km/year per streetlight/km (95% CI [-0.003, -0.001]). Persistent racial disparities were observed, with 0.04 additional crashes/km/year (95% CI [0.02, 0.06]) per 10% residents of color. However, this association decreased by 0.004 crashes/km/year (95% CI [-0.01, -0.001]), and higher streetlight densities were associated with greater reductions (additional annual decrease of 0.0004 crashes/km/year for every streetlight/km (95% CI [-0.001, -0.0001]). Finally, the proportion of crashes occurring overnight increased from 37.6% to 45.1%. Streetlight density was negatively associated with overnight timing (adjusted odds ratio of 0.991; 95% CI [0.986, 0.997] per streetlight/km) but had no relationship with the time trend. We conclude that there may be a beneficial relationship between streetlight density and pedestrian safety, where census tracts with higher streetlight densities demonstrated greater improvements in overall crash rates and racial disparities.