‘Safety in Numbers’ for Walkers: Effects of Pedestrian Volume on Per-Pedestrian Crash Rate and Severe Injury Probability

Abstract

The ‘safety in numbers’ phenomenon is very intriguing to many walking advocates. Some studies have examined the phenomenon for walkers, but they mostly focused on the relationship between pedestrian volume and the likelihood of vehicle–pedestrian crash occurrences. This study evaluated the effects of the ‘safety in numbers’ phenomenon not only on the risk of crash occurrences, but also on the probability of severe or fatal injuries. Pedestrian volume and crash data obtained from the six districts in Seoul Metropolitan City and Jeju Island were jointly analyzed to examine the expected pedestrian crash rate and the probability of severe or fatal injury as a function of pedestrian volume. The analysis confirmed that the expected pedestrian crash rate and the probability of severe or fatal injuries decline as pedestrian volume increases, although the absolute number of crashes and injuries increases. The increase in the number of pedestrian crashes is less than the increase in pedestrian volume. In addition, the probability of severe or fatal injuries tends to diminish with a larger pedestrian volume. These findings can be used as logical evidence to support future policies promoting walking trips, and they suggest that policy measures encouraging walking trips can deliver additional benefits beyond the well-known economic, health, and environmental benefits.