Crossing a street is a complicated, high-risk activity of daily living. In making an appropriate decision of when it is safe to cross, pedestrians must judge gaps in vehicular traffic that is of sufficient duration to allow them to reach the other side of the street or a splitter island. Pedestrians identify crossable gaps by processing complex sensory information acquired from the environment. Undoubtedly, visual sensory information plays an integral role in the accuracy and efficiency of detecting crossable gaps. Little is known however, about the relative importance of other sources of sensory information when visual information is reduced. Auditory sensory information may play an important role in street crossing when visual information is degraded since blind people can successfully cross a street safely and independently. To determine if auditory sensory information augments visual sensory information in street crossing for visually impaired pedestrians, a reliable, empirical method of assessment must first be established. The proposed research has the goal of validating the use of receiver operating characteristic (ROC) curves to assess visual and auditory information processing for street crossing in people with low vision. Using a 5 point rating scale, safety ratings for crossable gaps of different durations will be measured in normally sighted, visually impaired and blind subjects. For the normally sighted and visually impaired subjects, safety ratings will be collected under 3 sensory test conditions: (i) visual and auditory information; (ii) visual information only; and (iii) auditory information only. The safety ratings of blind subjects will be from auditory information only. Constructing ROC curves on normal-deviate (z-score) coordinates will test whether or not ROC curves as applied in the proposed study is a valid metric for assessing sensory information processing for street crossing in low vision. Comparing the discriminability (d') of different gap durations between test conditions and subject groups will establish the range over which the metric can measure an auditory effect as well as changes in performance in the visual sensory channel. Given that pedestrian safety has been recognized as a major public health concern, the proposed research will provide data to form an objective base for the development of training programs, mobility devices and environmental changes designed to assist visually impaired pedestrians cross a street. ? ? ?
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