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Question: One of our night shift workers fell asleep at the wheel and was involved in a (fortunately not fatal) accident.

What can we do to reduce drive-home accidents among our evening and night shift staff?


Answer: The best way to reduce drowsy driving accidents is to educate your employees on both the risk factors for falling asleep behind the wheel and on the most effective fatigue countermeasures.

3 Risk Factors for Falling Asleep at the Wheel

Make sure workers know the three biggest risk factors for falling asleep at the wheel:

1) Sleep debt. Shiftworkers typically get an hour or two less sleep per day than day workers. During a string of consecutive shifts, the lack of sufficient sleep builds up and can lead to a state of chronic fatigue and impaired performance leaving the person more vulnerable for having a drowsy driving accident.

2) Time since sleeping. Prolonged wakefulness can also impair human performance. For example, a worker who wakes up at 9 a.m., stays up all day and then works that night and gets off at 7 a.m. the next morning, is driving home after being awake 22 hours. How bad is this fairly common practice? Well, research has shown that being awake for 22 consecutive hours produces the same impairment in humans as having a blood-alcohol content of 0.08 (which is legal limit in the United States and many other countries) (1).

3) Time of day. Human body rhythms make it particularly difficult to stay alert during the overnight hours; particularly between 3 to 5 a.m. But even when driving home at 7 or 8 a.m., after a night shift alertness levels are still relatively low.

Evaluating Fatigue Countermeasures

Next, make sure workers know which fatigue countermeasures are effective and which are not:

Minimally effective: Exercise, radio, air conditioning, etc. Exercise and stretching provide only a temporary boost of alertness. Within a few minutes of getting back on the road, a driver is back to his previous low alertness level. Singing along with the radio and opening the windows provide little or no benefit and may actually be counterproductive because they can give a sleepy driver a false sense of security.

Moderately effective: Caffeine, carpooling. Caffeine does boost alertness and performance, but it can make it difficult for the worker to sleep once he or she arrives home. Carpooling offers some advantages, both because having someone to talk with keeps the driver’s mind engaged and also because the passenger can monitor the driver’s behavior. However, it’s not a surefire solution because passengers also can fall asleep, thus leaving drivers on their own.

Highly effective: Sleep, napping. Getting enough sleep is by far the most important thing anyone can do to avoid attention lapses on the road. And, short of calling a cab, taking a nap before driving home is the number one thing a drowsy driver can do to reduce his or her accident risk.

1) Dawson D. and Reid K. “Fatigue, alcohol and performance impairment” Nature 388, 235 (17 July 1997).

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