A new study suggests that drivers consistently underestimate how tired they are and how much fatigue affects their driving. The findings are scary because crashes caused by tired drivers tend to be severe – nod off behind the wheel, and you won’t be alert to brake or swerve to avoid anything.
Researchers asked the drivers to rate their fatigue on a 9-point scale. They then compared their subjective opinions to an objective measure – the percentage of time their eyelids spent closed.
The result? Participants significantly underestimated their drowsiness. “When drivers reported low perceived levels of drowsiness, the objective measure suggested that 75% of them were moderately or highly drowsy,” AAA says. A quarter of those whose eyes spent more than a quarter of each minute closed thought they weren’t very tired.