The answer is surprisingly complicated. Both are dangerous. While law enforcement attributes far more traffic fatalities to drunk driving than drowsy driving, it’s also harder to recognize drowsy driving, causing officers to attribute such crashes to another factor. In other words, we may not really know how many fatal crashes are caused by sleep-deprived drivers.
Experts have reason to suspect that drowsy driving is far more common than the statistics indicate. For example, according to the Sleep Foundation, at least half of all American adults admit that they have driven while they felt sleepy. Twenty percent of American drivers admit they have fallen asleep behind the wheel in the past year. One in 25 drivers say they’ve fallen asleep while driving during the past month.
Moreover, federal transportation regulations allow commercial drivers to drive as long as 11 hours or more in a row, as long as they spend 10 consecutive hours off duty. Many experts believe this allows truckers to drive when they are too tired, which could cause accidents.
According to National Highway Traffic Safety Administration (NHTSA), alcohol impairment is involved in almost 30% of all traffic fatalities. The Sleep Foundation’s analysis estimates that the real percentage of fatalities caused by sleep-deprived drivers is 21%. Drowsy driving, therefore, might be nearly as dangerous as drunk driving.
Sleep deprivation can impair drivers about as much as alcohol
It’s more than the risk that you could fall asleep behind the wheel. Sleep deprivation seriously affects a driver’s judgment, attention, coordination, decision-making, vigilance and reaction time.
There is a risk that drowsy drivers won’t be able to maintain their lane position or distance from other drivers. They may be unable to react quickly enough to an obstacle or emergency situation. And, a significant number of accidents occur when a drowsy driver veers out of their lane or off the roadway at high speed.
Because alcohol impairment and drowsy driving both impact reaction time, alertness and decision-making, some researchers have found that drunk and drowsy driving result in similar numbers of crashes.
The Sleep Foundation says that, when a driver has been awake for 18 hours, their reaction time, hand-eye coordination and vigilance are similar to someone with a blood alcohol content of 0.05%. At 20 hours of no sleep, they compare to someone with a blood alcohol content of 1.0% — higher than the legal level for alcohol.
However, even milder, shorter-term sleep deprivation can cause impairment. The AAA Foundation for Traffic Safety found that people who slept between 6 and 7 hours per night had double the crash risk of people who slept 8 hours. The risk doubled again for people who got less than 5 hours of sleep.
Drowsy driving is common in people who sleep less than 6 hours per night, along with people who suffer from sleep disorders. Young people, shift workers and professional drivers are most at risk.
Caffeine and other hacks are not enough
When you’re on the road, pay attention to these symptoms of sleep deprivation:
- Frequent blinking, heavy eyelids
- Drooping head
- Restlessness, aggressiveness or irritability
- Daydreaming or trouble focusing
- Drifting between lanes
- Hitting rumble strips on the side of the road
- Poor recall of the past few miles
- Missing signs or exits
If you find your eyes heavy while you’re on the road, you might try opening up a window, turning up the radio or drinking a caffeinated beverage. These tricks can help, but they are a short-term solution. Unfortunately, you could still be vulnerable to “microsleeps,” where you fall asleep for a few seconds at a time.
Instead, find a safe place to take a nap. A 20-minute nap could be enough to substantially increase your safety as a driver. In general, take frequent breaks to keep your drowsiness from affecting your driving.
Drowsiness could be a cause of crashes
It’s important to keep in mind that drowsiness could be a crucial factor in many crashes, especially those involving commercial trucks. Far too often, truckers exceed their hours of legal service. Sometimes, this is due to pressure from their company or customer. If so, it could be an important factor in determining who should be held responsible.