Even drivers who would never think of getting behind the wheel of a vehicle after drinking alcohol may not think twice about driving while drowsy or fatigued. Many people are either unaware of the dangers of drowsy driving or severely underestimate them. However, according to the National Safety Council, drowsiness can affect driving ability similarly to the way that alcohol does. Judgment, attention and reaction time may all become impaired by drowsiness as by alcohol or drugs. 

Drowsy driving is a significant problem, with estimates suggesting that it causes approximately 72,000 crashes per year, resulting in 800 deaths. However, the Centers for Disease Control states that those estimates are too low and that drowsy driving may actually be responsible for up to 6,000 deaths annually in the United States. In either case, the risk of a car crash increases by a factor of three for fatigued drivers. 

Warning signs 

When asked to describe their experience of the previous 30 days, approximately 4% of drivers admitted to having fallen asleep while behind the wheel. There are warning signs that a driver is too fatigued to drive. These include drifting to the side of the road, where the vehicle may hit a rumble strip, or over the center line into the other lane. Drivers who are fatigued may find that they do not remember the last few miles they drove, or they may find themselves blinking and yawning more frequently than usual. Drivers who recognize these warning signs should pull over immediately 

Risk factors 

Potentially, all drivers are at risk for drowsy driving if they do not get enough sleep on a given night. People who have persistent sleep disturbances or disorders are at greater risk, particularly if these go untreated. Sleepiness is a common side effect of many medications, and people who take these medications are at greater risk if they attempt to drive while taking them. Commercial drivers and shift workers are also at increased risk because of the working hours they keep.