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Stacy A. Balk, Thomas L. Carpenter, Johnell O. Brooks, James S. Rubinstein, Richard A. Tyrrell; The conspicuity of pedestrians at night: How much biological motion is enough?. Journal of Vision 2005;5(8):19. doi: 10.1167/5.8.19.
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© ARVO (1962-2015); The Authors (2016-present)
Most collisions between vehicles and pedestrians occur at night and inadequate visibility has been implicated as a key causal factor. Earlier research has shown positioning reflective markers to depict biological motion greatly enhances pedestrian conspicuity at night. To determine the extent to which enhanced conspicuity can be achieved with fewer biological motion elements, we measured the distance at which passengers pressed a button to indicate their confidence that a pedestrian was present. 120 university students (18–24 years) were driven along a 5.1 mile residential route using low beams. At two dark locations along the route a pedestrian (an experimenter) had been positioned to the right of the roadway. The pedestrians, who either stood still or walked in place, wore either black clothing or black clothing plus 304 cm2 of retroreflective material in four different configurations (a rectangular vest; ankles; ankles & wrists; full biological motion). The mean response distance for the vest condition (23.8 m) was not significantly different from the mean response to the black condition (30.6 m). When pedestrians were walking in place, all conditions with markings on the extremities were significantly more conspicuous, with response distances ranging from 88.9 m (ankles) to 113.5 m (biomotion). Although the advantages of marking the extremities was reduced when the pedestrians were standing still, the biological motion configuration (63.2 m) and the ankles & wrists configuration (45.4 m) remained significantly more conspicuous than the other conditions. Marking the ankles only (where low beam illumination is maximal) was effective when the pedestrian was walking but was ineffective when the pedestrian stood still. These results confirm that incorporating biological motion substantially enhances pedestrian conspicuity at night. Interestingly, our results also suggest that motion patterns alone can not explain the conspicuity advantages of biological motion.
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