Route-following and safety errors by drivers with stroke

Navigating a newly learned route is one of the multiple tasks during automobile driving that competes for a driver's cognitive resources. Stroke, a frequent cause of focal brain damage and cognitive dysfunction, has the potential to impair driving, especially when multitasking is required. The navigational abilities and driving safety errors of stroke patients (in the chronic phase of maximal recovery) were compared with those of healthy control subjects in a route-following task with an instrumented car. All subjects were legally licensed active drivers, and participation was voluntary. All drivers participated in an off-road battery of visual and cognitive tests of abilities that were critical to safe automobile driving. At the onset of the navigational task, each subject was required to recite and learn correctly a brief set of verbal directions to a destination. The main outcome measures were the number of (a) incorrect turns, (b) times lost, and (c) at-fault safety errors during the task. The drivers with stroke made significantly more incorrect turns, got lost more often, and made more at-fault safety errors than the neurologically healthy controls. These significant differences persisted for all outcomes except for getting lost after statistical adjustments for familiarity with the neighborhood. The navigational and at-fault safety errors were predicted by scores on standardized off-road tests sensitive to visual and cognitive declines in drivers with stroke. Drivers with stroke made more navigational and safety errors than neurologically healthy drivers on a route-following task that placed demands on driver memory, attention, and perception. The demands of following route directions probably increased the cognitive load during driving, which may explain the higher number of safety errors.