Traffic-entry behavior and crash risk for older drivers with impairment of selective attention.

Current research suggests that older drivers with declines in selective attention would make more unsafe traffic-entry judgments than would older drivers with normal attention. This hypothesis was tested using an instrumented vehicle and a LIDAR speed and range detector. Participants were 20 older drivers: 10 (M=72.0 yr.) had impairments of selective attention, measured with the Visual Attention Analyzer, Model 3000, and 10 were nonimpaired (M=71.2 yr.). Drivers pressed a button to indicate the last possible moment they could safely cross a road in front of an oncoming vehicle. The speed and distance of the oncoming vehicles were measured and time-to-contact was calculated. Each driver's time-to-cross the roadway was independently measured. Attention-impaired drivers showed shorter time-to-contact values (5.60 sec. versus 6.86 sec.), took longer to cross the roadway (5.41 sec. versus 4.84 sec.), and had shorter safety cushions (the difference between time-to-contact and time-to-cross the roadway). Monte Carlo simulation showed that these performance differences increased the crash risk of the impaired group by up to 17.9 times that of the nonimpaired group.