The effects of retroreflectivity and biological motion on the visibility of pedestrians at night

Abstract

One factor that has been causally linked to nighttime pedestrian-vehicle collisions is pedestrians being insufficiently conspicuous to drivers. Placing retroreflectors on pedestrians' major joints in configurations that facilitate the perception of biological motion has been shown to enhance pedestrians' conspicuity. Retroreflector luminance, however, decreases with time as dirt accumulates and the retroreflector deteriorates. The impact of retroreflected luminance on pedestrian conspicuity in the presence and absence of biological motion was tested. For this on-road study 121 participants (18–23 years) were taken on a short drive and pressed a button when they were confident that a pedestrian was present. A test pedestrian either walked in place or stood still on the shoulder of a dark road while wearing all black clothing plus 200 cm² retroreflective material that was either placed on the torso or on the wrists and ankles. The retroreflective material was at a high, medium or low level of retroreflective intensity (581, 138 or 10 cd/lux/m²). Response distances were significantly greater when the pedestrian was walking and wearing retroreflectors on the wrists and ankles (119 m) compared to walking and wearing retroreflectors on the torso (24 m). Participants responded to the walking pedestrian wearing the high intensity retroreflectors at a marginally significant greater distance (92 m) compared to the walking pedestrian wearing the low intensity retroreflectors (47 m). Responses to the standing pedestrian wearing retroreflectors on the wrists and ankles were not significantly greater than responses to the standing pedestrian wearing retroreflectors on the torso. Participants responded to the standing pedestrian wearing the low intensity retroreflectors at a marginally significant greater distance (21 m) compared to the standing pedestrian wearing the high intensity retroreflectors (4 m). The results illustrate that the presence of biological motion has a greater impact on increasing pedestrian conspicuity than increasing retroreflective intensity.