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Shirin Hassan; Do Pedestrians Make Safe Street-Crossing Decisions?. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5042.
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The aim of this study was to determine whether the street-crossing decisions of subjects with Age-related Macular Degeneration (AMD) are as safe as those made by young and older subjects with normal vision.
Street-crossing decisions and crossing times in 12 AMD subjects, 20 young and 20 older control subjects with normal vision were measured along an unsignalized street for nine different gap time categories. Using their habitual vision and hearing, subjects observed an approaching vehicle for two seconds. At the end of the two second period, subjects were required to make a crossing decision of whether or not they thought it was safe to cross the street. Subjects’ crossing decisions were then objectively classified as being “safe” when the measured gap time was longer than the subject’s street-crossing time. The converse was true for objectively classifying crossing decisions as being “unsafe”. The proportion of safe crossing decisions (ie. subjects reporting it was safe to cross for objectively safe gap times) and unsafe crossing decisions (ie. subjects reporting it was safe to cross for objectively unsafe gap times) was determined for each subject group and gap time category. A hierarchical logistic regression, with repeated measures for subject, was used to determine if the proportion of safe and unsafe decisions changed as a function of subject group and gap time category.
We observed that the older normally-sighted subjects made more unsafe crossing decisions compared to the AMD subjects for gap times that were between four and one second shorter than the time they needed to cross the street. However, the differences between these two groups were only marginally significant (p=0.06, p=0.05, p=0.04 and p=0.05 for gap times that were four, three, two and one second shorter than subjects’ crossing times, respectively). No significant difference in the proportion of unsafe decisions were found between the young and older normally-sighted subjects (p>0.05) and between the young normally-sighted and AMD subjects (p>0.05). No significant differences in the proportion of safe crossing decisions were also found between the different subject groups for gap times that were longer than subjects’ crossing times (p>0.05).
Our data suggests that older pedestrians with normal vision have a tendency to adopt a more risky crossing strategy than either the young normally-sighted or AMD pedestrians.
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