Traffic gap detection for pedestrians with low vision.

PURPOSE

Pedestrians with low vision have identified crossing the street as a difficult task. With the increasing complexity of the crossing environment (actuated signals and roundabouts), the challenges are increasing. The purpose of this study was to evaluate the effect of two types of vision loss (central or peripheral) on the ability to detect gaps in traffic.

METHODS

Forty-one subjects participated with 14 being fully sighted (FS), 10 having central vision loss from age-related macular degeneration (AMD), and 17 having peripheral vision loss from either retinitis pigmentosa or glaucoma. Standing at entry and exit lanes of a roundabout, subjects depressed a handheld trigger to indicate when there was a sufficient gap in traffic to cross the street. A total of twelve 2-min intervals were completed including four of those intervals with occluded hearing.

RESULTS

No difference was found in the ability of the three subject groups to identify crossable or short gaps. There were significant differences in latency and safety margin. The AMD subjects did not perform as well as the FS or the subjects with retinitis pigmentosa/glaucoma. When hearing was occluded, the two vision loss groups did not show a change in sensitivity but the FS group did, being more sensitive when hearing was occluded.

CONCLUSIONS

The purpose of this study was to evaluate the effect of low vision on the ability to detect crossable gaps in traffic. The findings suggest that subjects with AMD have an increased risk because they show significant latency in their identification of gaps and this in turn results in a reduction of safety margin.