Relation between time to falling asleep behind the wheel on a closed track and changes in subsidiary reaction time during prolonged driving on a motorway.

Twelve subjects drove on a closed 5-km track until they fell asleep behind the wheel or quitted for other reasons. The instances of falling asleep occurred after 7 to 12 hours of driving. Falling asleep could be characterized by nodding of the head, closing of the eyes and the car continuing in its previous course. On none of these occasions did the experimenter have to take over the control of the car and all subjects woke by themselves. The average duration between three instances of falling asleep was 24 min. After a break with a brisk walk the subjects fell asleep again after an average of 23 min. Two preceding sessions of 3 hours of driving on a motorway with subsidiary reaction time measurements predicted (r= — 0·72 and —0·17) the endurance on the closed track. [ABSTRACT FROM PUBLISHER]