Each year, drowsy driving causes 100,000 accidents and 1,550 fatalities in the US alone (Source).
According to research conducted by the United States National Highway Traffic Safety Administration (NHTSA), drowsiness or fatigue has been indicated as a primary factor in 3.6 percent of fatal crashes (Source).
Research indicates that fatigue is second only to alcohol as the most common cause of serious injury vehicle crashes.
Visual Signs
frequent yawning
increased blinking
relaxed posture
Non-Visual Signs
heavy eyes
blurred vision
decreased heart rate and brain activity
decreased judgement while driving
slower reaction times
decreased alertness
Not all sleep-related crashes are reported to the police since many are drive-off-the-road crashes (Source).
Additionally, standardized reporting for drowsy driving does not exist (Source).
No blood, breathalyzer, or other objective test can be performed at the scene of a crash to determine if the cause of a crash was fatigue or drowsy driving (Source).