It is difficult to attribute crashes to sleepiness because there is no test to determine its presence as there is for intoxication (i.e., a "breathalyzer"). In addition, there are no standardized criteria for making the determination of driver sleepiness and there is little or no police training in identifying drowsiness crash factor. Also, six states (Alabama, Missouri, Arkansas, Delaware, Massachusetts, and Wisconsin) do not have a code for sleepiness on their crash report forms.
The U.S. National Highway Traffic Safety Administration (NHTSA) estimates that approximately 100,000 police-reported crashes annually (about 1.5% of all crashes) involve drowsiness/fatigue as a principal causal factor. A conservative estimate of related fatalities is 1,500 annually or 4% of all traffic crash fatalities. At least 71,000 people are injured in fall-asleep crashes each year. NHTSA estimates these crashes represent $12.5 billion in monetary losses each year.
Drowsiness/fatigue may play a role in crashes attributed to other causes. About one million crashes annually — one-sixth of all crashes — are thought to be produced by driver inattention/lapses. Sleep deprivation and fatigue make such lapses of attention more likely to occur.
In a 1999 NSF poll, 62% of all adults surveyed reported driving a car or other vehicle while feeling drowsy in the prior year. Twenty-seven percent reported that they had, at some time, dozed off while driving. Twenty-three percent of adults stated that they know someone who experienced a fall-asleep crash within the past year.
In a 1996 postal survey of 9,000 male drivers in Britain, in which 51% responded (4,600), the drivers attributed 7% of their crashes in the previous three years to tiredness (sleepiness and/or fatigue).
At the 1995 National Truck Safety Summit driver fatigue was designated the number one priority for truck safety.
People tend to fall asleep more on high-speed, long, boring, rural highways. New York police estimate that 30% of all fatal crashes along the New York Thruway occurred because the driver fell asleep at the wheel.