Drowsy drivers not taking enough breaks, AAA study reveals

March 30, 2023

Land Line Staff


Many passenger vehicle drivers are unaware of how drowsy they are while driving, according to a new AAA study.

In a AAA study looking into drowsy driving, participants were scheduled to begin the experiment at 11 p.m. or 2:30 a.m. after a day without napping or consuming caffeine. Participants drove 150 miles on a simulated interstate highway with a speed limit of 65 mph.

During the three-hour-long simulated driving experiment, participants were generally aware that they were drowsy. However, their perceived level of drowsiness was only “moderately correlated” with objective measures of drowsiness, according to the study.

Below are some key findings of the study:

  • Participants both underestimated and overestimated their levels of drowsiness relative to the objective eye-based measure. It was slightly more common for participants to underestimate how drowsy they were.
  • Agreement between self-reported perceptions of drowsiness versus objective measures of drowsiness was best at moderate levels of perceived drowsiness.
  • When drivers reported low perceived levels of drowsiness, the objective measure suggested that 75% of them were moderately or highly drowsy.
  • Participants rated their drowsiness as low on 25% of occasions when the objective measure indicated high drowsiness.

Drivers also had the opportunity to take breaks every 20 minutes through simulated rest areas. About half of the study’s participants did not take any breaks. Nearly 40% took one break, and 11% took two breaks. Among those who took breaks, approximately 40% indicated that their feeling drowsy was the reason for the break.

According to the study, taking breaks was rare among participants who rated their level of drowsiness as low or moderate. Even when participants rated themselves as extremely drowsy and had the opportunity to take a break, more than 75% chose to continue driving without taking a break. Objectively measured drowsiness, worsening vehicle control, and total time spent driving were only weakly correlated with decisions to stop and take breaks.

“Overall, the study provides insight into how drowsiness impacts decision making during long nighttime drives,” the study stated. “The results demonstrate a need to help drivers to improve their self-assessment of their own levels of drowsiness, as well as the need to educate drivers about the importance of heeding the early warning signs of drowsiness and stopping to rest before becoming extremely drowsy.” LL

Other AAA studies: