Falling asleep at the wheel can be just as dangerous as drinking and driving. Drowsiness can produce the same types of effects as alcohol — slowed reaction time, decreased awareness and impaired judgment, all of which increase the chances of having an accident. While it is common knowledge that it is dangerous to drink and drive, few realize the very real danger of driving drowsy.

In a National Highway Traffic Safety Administration (NHTSA)/AAA Foundation for Traffic Safety survey among police officers, nearly 90 percent of the respondents said they had stopped a driver who they believed was drunk, but who turned out to be drowsy.

Fatigue-related accidents tend to be single-vehicle crashes in which a vehicle leaves the roadway and then turns over or hits a fixed object. And as might be expected, research shows that people have a greater tendency to fall asleep while driving on the long, uninteresting stretches of road, characteristic of many highways and interstates.

The NHTSA says drowsiness or fatigue is a principal causal factor in up to 100,000 police-reported crashes annually. These result in some 71,000 injuries and 1,500 fatalities.

The numbers could be higher, but it is difficult to attribute crashes to sleepiness because there is no standard test for drowsiness, as there is for intoxication.

The body has an internal clock, typically referred to as a biological clock. The scientific term is circadian rhythm, which influences the hormones that play a role in sleep and wakefulness, metabolic rate and body temperature. Research shows that while most people’s internal clocks run on a daily rhythm of approximately 24 hours, individual “body time” varies from person to person. For example, there are “morning people” — those who feel most alert early in the day, and there are “night owls” — those who seem to come alive at night.

Night time is particularly risky for drivers as sleep can become an irresistible urge, safety experts warn. Most people’s biological clocks are programmed to sleep when it is dark. The sleep urge is strongest between 12:00 a.m. and 6:00 a.m., which is when drivers are especially likely to have sleep-related crashes.

Another sleepy danger time zone, point out safety experts, is in the middle of the day. Many sleep-related crashes happen between 1:00 p.m. and 5:00 p.m., a period known as the afternoon lull or slump. It is this time of day when people feel tired and lethargic, and may have difficulty staying alert and focused.

To be a safer driver, safety officials suggest that drivers become aware of their own biological clock. What times of day do your drivers feel most alert? What times do they feel most drowsy?

Once they are aware of their own personal cycle, the officials say, drivers can take extra care when they are likely to be feeling sleepy.

Continuing to drive when drowsy puts a driver — and others — at serious risk of being involved in a fatigue-related crash, safety officials stress. The obvious thing to do is to find a safe spot to stop and get some sleep. Even a power nap — no more than 20 to 30 minutes long — serves to rejuvenate one’s self by maximizing the benefits of sleep vs. time.

Since stopping for some sleep is not always practical, here are some suggested countermeasures that safety officials say may be effective for the short-term:

• Take regular breaks and get out of the truck. Stretch, do some exercises or walk around a bit to “get the blood flowing.” This can help a driver feel more refreshed and invigorated.

• Drink a caffeinated beverage. Caffeine acts as a stimulant to boost energy temporarily. It takes about 30 minutes for caffeine to enter the bloodstream. For those who regularly drink caffeinated beverages, caffeine won’t have much effect. Drinking too much caffeine at one time can make a person feel nervous or jumpy.

• Avoid medications — over-the-counter and prescription — that may cause drowsiness and impair one’s driving abilities. Always read the label and check with a doctor or pharmacist to be sure.

• Open a window for fresh air, which can be invigorating.

• Listen to radio talk shows or loud, annoy-ing music.

Understanding the risks, symptoms and countermeasures associated with drowsy driving are the keys to avoiding it, emphasize safety officials. But the bottom line is: the only certain cure for drowsiness is sleep.

David Kolman is a veteran truck communicator, keynote speaker and long-haul trucker. Commissioned as an Honorary Colonel on the Kentucky governor’s staff for his work promoting traffic safety, he actively participates in trade associations and reports news and information about the trucking industry for broadcasting and print media.

Being aware of the symptoms associated with drowsy driving can help drivers stay safe. Among the signs of fatigue and sleepiness:

• Difficulty remembering the last few miles driven

• Drifting out of a lane or onto the shoulder

• Being jarred alert running over rumble strips

• Finding one’s self jerking the vehicle back into position

• Abnormal speed, tailgating or missing traffic signs and signals

• Struggling to keep one’s eyes open or focused

• Seeing things that aren’t really there

• Wandering or disconnected thoughts

• Frequent yawning and eye rubbing

• Having trouble keeping one’s head up

• Nodding off

According to the National Sleep Foundation, sleepiness or fatigue causes the following:

• Impaired reaction time, judgment and vision

• Problems with information processing and short-term memory

• Decreased performance, vigilance and motivation

• Increased moodiness and aggressive behaviors

A study by researchers in Australia has shown that being awake for 18 hours produced impairment equal to a blood alcohol concentration (BAC) of 0.05 percent, and 0.10 percent after 24 hours. A BAC of 0.08 percent is considered legally drunk.