Seeing Pedestrians at Night: Visual Clutter Does Not Mask Biological Motion

The phenomenon of biological motion – placing reflective markers on a pedestrians’ major joints – has been shown to make pedestrians more conspicuous to drivers at night. However most relevant studies have been conducted in scenarios relatively free of visual clutter. Because clutter could mask the perception of biological motion, we tested whether extraneous points of light degrade drivers’ ability to detect pedestrians. Twelve younger and 12 older volunteers drove along a closed road at night and indicated whenever they saw a pedestrian. A pedestrian walked in place wearing all black clothing alone or with retroreflective markings in one of four configurations. On half of the trials the pedestrian was surrounded by reflective cones and posts (clutter). Clothing configuration dramatically influenced conspicuity. The pedestrian was usually not seen when he wore no reflective markings or when he wore a reflective vest. But when he wore reflectors on his ankles and wrists the younger and older drivers responded at mean distances of 285 m and 141 m, respectively. Importantly, the presence of visual clutter did not significantly influence performance. These results confirm that biological motion can enhance the conspicuity of pedestrians; this effect is robust to the presence of visual clutter.