The Conspicuity Benefits of Rear-Facing Bike Lights in Daylight

Abstract

Cycling with motor vehicle traffic on roadways is inherently risky for bicyclists, and it is important for bicyclists to make themselves conspicuous to drivers. This experiment used a closed-road method to test the daytime conspicuity of rear-facing bike lights. Participants provided subjective ratings of conspicuity from a test vehicle parked at two different distances from a bicyclist pedaling on a stationary bicycle with one of 16 configurations of bike lights. Some configurations featured lights on the bicyclist’s ankles to highlight the bicyclist’s biological motion. The results of this experiment provide a better understanding of the relative conspicuity benefits of bike lights in daylight as a function of light intensity, light placement, and viewing distance. The findings offer useful insights on the optimal intensity and placement of bike lights to enhance their own conspicuity during daylight.