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Abstract
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OBJECTIVE: When crossing an unsignalized street, pedestrians must judge whether or not the gap in vehicular traffic is of sufficient duration to allow them to reach the other side of the street or splitter island before the next approaching vehicle reaches them. Little is known however how well pedestrians can judge differences in gap duration based on using both visual and auditory information compared to judgments made with only visual in- formation. The aim of this study was to determine the accuracy of normally-sighted and visually impaired pedestrians at making correct street-crossing decisions using both visual and auditory information compared to using visual information alone.
METHODS: Using a 5 point rating scale, safety ratings for vehicular gaps of different durations were measured along an unsignalized, two-lane street of one-way traffic. Safety ratings were collected from 12 normally sighted and 10 visually impaired subjects for 8 different gap times under two sensory test conditions: (i) vision and hearing; and (ii) vision only. A subject‘s street crossing decision was classified as being "safe" when the subject‘s street crossing time was less than the gap time. The converse was true for "unsafe" street crossing decisions. The percentage of correct street crossing decisions (ie. correctly identifying "safe" and "unsafe" trials) was determined for each subject group, gap time and sensory condition.
RESULTS: We found that on average (ie. across all gap times), under the sensory condition of vision and hearing, normally-sighted and visually impaired subjects made correct street-crossing decisions 78% and 74% of the time respectively. Under the sensory condition of vision only, normally-sighted and visually impaired subjects made on average correct street-crossing decisions 73% and 77% of the time respectively. We found no significant difference in the percentage of correct street-crossing decisions between the normally-sighted and visually impaired subjects under the sensory conditions of vision and hearing (p>0.05) and vision only (p>0.05). We also found that performance for both subject groups under both sensory conditions changed as a function of gap time. In general, the level of accuracy for both subject groups was significantly worse for gap times that were either one second shorter or longer than the minimum time required for a safe crossing.
CONCLUSIONS: Our analysis of the data suggests that in our controlled street environment, visually impaired pedestrians can make safe street-crossing decisions like those of normally sighted pedestrians using either their impaired vision and (normal) hearing or simply using only their impaired vision. Our data also suggests that the reliability of using available sensory information in the environment for making street-crossing decisions depends on how far away the approaching vehicle is from the pedestrian. |