Drowsy Driving

“Drowsy driving can be considered another form of distracted driving in that drivers experiencing drowsiness do not apply their full attention to the driving task”.

Danger Signals: How Sleepy Are You?

You can’t control your own sleep — ask anyone who’s had insomnia and when you are tired you can fall asleep at any time. If you are about to fall asleep, you will experience some or all of the following:

You have trouble keeping your eyes open and focused
You nod and can’t keep your head up
You daydream or have wandering, disconnected thoughts
You yawn a lot or need to rub your eyes
You find yourself drifting out of your lane or tailgating
You miss road signs or drive past your turning
You feel irritable, restless and impatient
On the motorway, you drift off the road and on to the hard shoulder

If you have even one of these symptoms you could be sleepier than you realize. So get off the road and get some sleep because it’s dangerous and possibly fatal to drive with your eyes closed.


Drowsy driving is a key factor in an estiminated 76,000 – 100,000 crashes occurring each year in the United States, resulting in 1,500 deaths and thousands of injuries. The actual toll may be considerably higher, since drowsiness also contributes to crashes by making drivers less attentive and by slowing their reactions and impairing their judgment.
As many as 1 million crashes are attributed to driver inattention and drowsiness may be a hidden factor in many of these crashes.


Persons that have been shown to be at higher risk for involvement in sleep – related crashes include young people, especially young males,1 persons with undiagnosed or untreated sleep disorders; drivers who have taken soporific medicines2 and night or rotating shift workers.
Commercial vehicle drivers are also at increased risk for nodding off whilst driving and sleep – related crashes due to such factors as extended driving times, irregular work and sleep patterns, higher frequency of nighttime driving and inadequate sleep.

For anyone who is already drowsy, consumption of alcohol can pose a special risk. Research has shown that alcohol and sleep loss interact synergistically to increase levels of sleepiness.3

Studies conducted using driving simulators show significant decrements in performance when low doses of alcohol are given to sleep-deprived subjects. Circadian factors have also been shown to play a role in drowsy driving crashes.
Our bodies are programmed for sleep during our nighttime sleep period and again 12 hours later and between 2 and 4 in the afternoon. This cyclic pattern of wakefulness has been demonstrated in time of day plots for drowsy driving crashes as well in other arenas where sustained vigilance is important for safety.4

Analysis of crash data can tell us who is most likely to be involved in a drowsy driving crash (young persons, males), when and where these crashes are most likely to occur (late night, rural roads, etc.), how they occur (run-off road, rear- end etc.), and the severity of injuries that result. For example, analysis of North Carolina crash data has revealed that 55% of drivers who fell asleep at the wheel and crashed were aged 25 or younger and 75% were males.

Surveys of the general driving population provide evidence of the prevalence of drowsy driving and drowsy driving crashes. In a 1994 survey of licensed drivers in New York State, 55% said that they had driven whilst drowsy in the past year, and 28% said they had fallen asleep at the wheel at once during their driving careers; 3% had fallen asleep at the wheel and crashed and an additional 2% had crashed when driving drowsy.5

In the UK, 29% of the respondents to a mail survey reported that they “had felt close to falling asleep while driving” in the past year6 and in Norway, 1 in 12 drivers reported that they had fallen asleep while driving during the past year, with 4% of these episodes resulting in a crash.7

In a research article entitled “Evaluation of ‘In -Car’ Countermeasures to Sleepiness: Cold Air and Radio”,8 opening the vehicle’s window or listening to the radio/tape player were among the most commonly used “helpful” methods employed by drivers for countering the effects of sleepiness. The article goes on to say there is little scientific evidence to support the efficacy of these putative “in-car” countermeasures to sleepiness.

Authoritative reviews of sleep loss give no guidance to the efficacy of cold air, music, conversation or acceptable noise levels for keeping people awake.
Prudent drivers should stop and take a break when sleepy. As to what to do during this break, many drivers believed that taking a walk is the best countermeasure to sleepiness.

However, laboratory findings of sleepy subjects have shown this to be ineffective, as the alerting effect on even heavy exercise is only transient. In contrast, drinking coffee or a nap- or better still- the two combined, are very effective countermeasures that can be utilized feasibly during a 30- minute break from driving.
During research, listening to the RADIO and COLD AIR to the face from the vehicle’s ventilation system had no significant effect on incidents,9 although there was a trend for the RADIO to reduce incidents, particularly during the first 30 minutes in the simulator, when AIR also had some effect. Compared with other countermeasures such as caffeine and a brief nap, which are more effective, AIR and RADIO are at best only temporary expedients to reduce driver sleepiness, perhaps enabling drivers to find a suitable place to stop, take a break and refresh themselves. While drowsy drivers may believe that these countermeasures (RADIO/AIR) are effective in improving their alertness, this is not reflected in their otherwise deteriorating driving.

From analyses of various accidents in the UK (“Road Audits”) it was found that about 20% of road traffic accidents on motorways and other major trunk roads are caused by sleepiness. Drivers in these sleep related vehicle accidents (SRVAs) are more likely to sustain fatal or serious injuries than in road traffic accidents as a whole.
It is almost impossible for a healthy driver to fall asleep at the wheel without warning.10 Hence most if not all SRVAs are preventable if drivers become fully conversant about recognizing these warning signs – dangers of driving whilst sleepy, driving at vulnerable times of the day, the need to plan one’s journey the use of appropriate countermeasures – all of which can be accomplished through proper education methods.

A driver who allows himself to be overcome by sleep so that a dangerous course of driving results is guilty of dangerous or careless driving, for he should have stopped when he felt sleep overtaking him.11

Finally, remember; if you feel the onset of drowsiness or tiredness do not continue driving because if you snooze you could “lose”.

Tom Harrington LLB M Inst. MTD, M CILT, RoSPA Dip. / Examiner I July 2005