Drowsy Drivers

To investigate the risk factors for sleep-related crashes, HSRC researchers analyzed crash data and conducted in-depth interviews among drivers who had recently been involved in a crash caused by being drowsy.

HSRC found that drivers who work night shifts, long hours or more than one job are at increased risk for being involved in a crash caused by falling asleep at the wheel or fatigue. Other factors strongly associated with having a drowsy driving crash include sleeping less than six hours per night, being awake for 20 hours or longer and frequent driving between midnight and 6 a.m.

Highlights of the study’s findings include:

  • Drivers in sleep and fatigue-related crashes were 4 to 5 times more likely than drivers in the control crash group to work night-shift jobs. Working 60 or more hours a week also increased drivers' risk.
  • Twenty-seven percent of the drivers involved in sleep-related crashes worked 60 or more hours a week compared to 17 percent of the drivers in the control crash group.
  • Drivers in sleep-related crashes were nearly twice as likely as drivers in the control crash group to work more than one job.
  • Between 8 and 10 percent of the drivers in sleep and fatigue crashes reported taking medications that may cause drowsiness, while less than 2 percent of the control crash group fell into this category.
  • Three percent of the drivers in sleep crashes reported having a diagnosed sleep disorder.
  • The vast majority of people in the study who crashed as a result of driving while drowsy either got too little sleep on a routine basis and built up what sleep researchers describe as ‘sleep debt,' or they got far too little sleep before trying to drive.

With funding from the AAA Foundation for Traffic Safety, researchers from the Center interviewed 1,403 North Carolina drivers identified by police crash reports and driver records. These included phone interviews with 467 drivers involved in recent crashes caused by falling asleep at the wheel or being fatigued, 529 phone interviews with drivers recently involved in crashes not catalogued as fatigue- or sleep-related and 407 phone interviews with drivers who hadn't been in a crash within the past three years.

Full Report

Why Do People Have Drowsy Driving Crashes? Input from Drivers Who Just Did. J.C. Stutts, J.W. Wilkins, and B.V. Vaughn. Washington, D.C.: AAA Foundation for Traffic Safety, 1999.