Are you okay to drive? That’s a question you have probably heard many times after an office party or a wine tasting. And the correct answer is nearly always no. Let’s face it: if you were staggering, falling down drunk, you would insist, with slurred voice, that you were all right. But even if you feel that you are clear headed and sober, your spouse or friend is more likely than you are to spot the signs.
Any amount of alcohol impairs driving ability, but our culture allows a certain amount of drinking and driving. One issue is the legal one: am I over the limit? In all 50 states and the District of Columbia, it’s now illegal to drive with a blood alcohol content (BAC) of .08 or over, which is relatively high by international standards. Australia, by comparison, has a .05 limit, which is strictly enforced through random roadside sobriety checks. Those caught driving over that level lose their driving privileges.
Your blood alcohol content varies with weight, gender, physical condition and individual differences as well as the amount of alcohol consumed. Generally a 180-pound male can expect a BAC of .08 after consuming four drinks within an hour. A 120-pound female may reach the same level after only two drinks. At a BAC of .08, a driver is 11 times more likely to have a single-vehicle crash than a driver who has not consumed alcohol. Without question, .08 BAC is illegal as well as unsafe for driving.
Better Safe than Sorry
The most important issue, however, is safety, and, even if you are under the legal limit, you should be aware of how alcohol may affect your driving and how you make decisions. Driving a car is far more difficult than most realize, involving motor coordination, good vision, awareness of what is happening outside the central lane of vision, tracking or steering, processing information and attention that sometimes must be divided between two or more tasks.
If you were ever stopped on suspicion of driving under the influence of alcohol, a police officer probably asked you to walk a straight line or perform tests to prove you have normal balance and coordination. These are not necessarily good signs of driving impairment because chronically heavy drinkers have learned to adjust and can perform these tasks even with very high alcohol levels.
But tracking or steering the car in the right direction and in the proper lane is more difficult than walking a straight line and that ability becomes increasingly impaired with each drink you take.
Perhaps even more important is information processing. Even after a small dose of alcohol, people are slower to respond on even simple tests involving the ability to recognize familiar objects shown in front of them. The more complex the task, the slower the reaction time (the time it takes to react to a situation) compared to that of a person who has consumed no alcohol. If you have had a few drinks, it’s going to take you longer to read a street sign or recognize a stop sign...and respond to it.
While your visual acuity (the way you see things) may not become noticeably impaired until you are way over the limit, the way your brain controls your eye movements changes much more quickly under the influence of alcohol. Your eye movements are not as quick, and they do not keep their focus as long on each image.
Narrowing the Field
One on-the-road study found that drivers tended to narrow their visual field with each degree of impairment– spending more of their time looking to the center of the driving scene and fewer to the side where important events may be developing, such as a deer, a pedestrian or another vehicle.
One of the most difficult things about driving is the need to divide your attention between steering the car and being alert for other vehicles, traffic signals, changes in the road surface and events taking place in the rear view mirror. Talking or listening to music, can make the task even more difficult.
When you are alcohol impaired, it is usually all you can manage to stay focused on one task–steering the car–and you may fail to notice soon enough that the road surface has turned from wet to slippery or that a vehicle is approaching you from the rear as you prepare to pass.
Concentration and alertness are also important, and both are likely to increase after a moderately high amount of alcohol. While a cup or two of coffee may improve alertness, it will not change the other effects of alcohol.
Judgment is yet another thing to consider. Alcohol is a depressant, and it lowers inhibitions–a potentially deadly combination. But regardless of their mood and attitude, drunks tend to make bad decisions–one of which is to deny they are unable to drive.
Learning too late that you are not “okay to drive” can have horrible consequences. Since 1982, alcohol-related fatalities in the United States have declined from 60 percent to 39 percent of all traffic fatalities, but that percentage is still way too high. Every 31 minutes someone dies because of an alcohol-related automobile accident. Every single one of those fatalities could have been avoided. Being more aware that you are unable to drive will not only be a good thing for you, but also for everyone else involved.
Written By: Kerri Musselman, Pharm.D.
