Road illumination and nighttime pedestrian deaths: Evidence from moonlight

Abstract

Of the 7500 pedestrian road deaths recorded in the US in 2022, 79% took place during the night. Low lighting reduces visibility, potentially increasing the frequency and severity of vehicle-pedestrian collisions. I use complete US data on 193,000 nighttime pedestrian deaths, spanning 1975 to 2022. Nightly variation in moonlight provides a natural experiment that exogenously impacts road illumination. Across the US, nighttime pedestrian deaths are 5% lower when the moon is at its brightest, compared to a night with no moonlight. Under cloud-free conditions, peak moonlight causes a 17% drop in pedestrian deaths. In rural areas with low artificial lighting, the effect is 39%. I establish a clear causal relationship between road illumination and pedestrian safety. A small increase in ambient light causes a large improvement in pedestrian outcomes. The finding has policy implications for road safety and the artificial lighting of roadways.