Drowsy driving refers to motorists who are at high risk of falling asleep at the wheel. Fatigued driving refers to motorists who have driven long hours without rest and, though they may not be nodding off at the wheel, are severely compromised in their ability to react to sudden events on the road.
As with cell phone use, the influence of drowsy driving and fatigue on crashes often is not known unless the driver survives the crash and admits to having nodded off. Unlike both alcohol involvement and cell phone use, there is no scientific method even available for determining its presence. In addition, the U.S. currently has no standardized criteria for making the determination of drowsy driving in a crash, and most states offer little or no formal training to police for identifying drowsiness as a factor in crashes. Also, according to the National Sleep Foundation, six states (Alabama, Missouri, Arkansas, Delaware, Massachusetts, and Wisconsin) still do not have a code for drowsy driving on their crash reports.
That said, the government estimates conservatively that 1,500 peopled are killed annually as a result of motorists who fall asleep at the wheel, and another 71,000 are injured annually in such crashes. However, the National Sleep Foundation believes that drowsy driving and fatigue often play a role in crashes that are attributed to other causes. For example, the government lists driver inattention as the primary cause of approximately one million police-reported crashes each year. The sleep foundation points out that drowsy driving and fatigue make such lapses of attention more likely. These lapses can occur at any time of the day or night, but appear to be most prevalent at night, during the early morning, and in mid-afternoon.