2.22  Alcohol, Other Drugs, and Driving

What is a drink?

It is the alcohol in drinks that affects human performance. It doesn't make any difference whether that alcohol comes from "a couple of beers," or from two glasses of wine, or two shots of hard liquor.

Figure 2.22: Approximate Blood Alcohol Content caused by Number of Drinks and Body Weight in Pounds and its Effects
Drinks 100 pounds 120 pounds 140 pounds 160 pounds 180 pounds 200 pounds 220 pounds 240 pounds Effects
0 .00 .00 .00 .00 .00 .00 .00 .00 Only Safe Driving Limit
1 .04 .03 .03 .02 .02 .02 .02 .02 Driving Skills Significantly Affected - Criminal Penalties
2 .08 .06 .05 .05 .04 .04 .03 .03 Driving Skills Significantly Affected - Criminal Penalties
3 .11 .09 .08 .07 .06 .06 .05 .05 Driving Skills Significantly Affected - Criminal Penalties
4 .15 .12 .11 .09 .08 .08 .07 .06 Driving Skills Significantly Affected - Criminal Penalties
5 .19 .16 .13 .12 .11 .09 .09 .08 Driving Skills Significantly Affected - Criminal Penalties
6 .23 .19 .16 .14 .13 .11 .10 .09 Driving Skills Significantly Affected - Criminal Penalties
7 .26 .22 .19 .16 .15 .13 .12 .11 Legally Intoxicated - Criminal Penalties
8 .30 .25 .21 .19 .17 .15 .14 .13 Legally Intoxicated - Criminal Penalties
9 .34 .28 .24 .21 .19 .17 .15 .14 Legally Intoxicated - Criminal Penalties
10 .38 .31 .27 .23 .21 .19 .17 .16 Legally Intoxicated - Criminal Penalties

Subtract .01 % for each 40 minutes of drinking. One drink is 1.5 oz. of 80 proof liquor, 12 oz. of beer, or 5 oz. of table wine.

Effects of increasing Blood Alcohol Content (BAC)

Blood Alcohol Content is the amount of alcohol in your blood recorded in milligrams of alcohol per 100 milliliters of blood. Your BAG depends on the amount of blood (which increases with weight) and the amount of alcohol you consume over time (how fast you drink). The faster you drink, the higher your BAG, as the liver can only handle about one drink per hour - the rest builds up in your blood.

Figure 2.23: Effects on Body and Driving Condition of Increasing Blood Alcohol Concentration
BAC Effects on Body Effects on Driving Condition
.02 Mellow feeling, slight body warmth. Less inhibited .
.05 Noticeable relaxation. Less alert, less self-focused, coordination impairment begins.
.08 Definite impairment in coordination & judgment. Drunk driving limit, impaired coordination & judgment.
.10 Noisy, possible embarrassing behavior, mood swings. Reduction in reaction time.
.15 Impaired balance & movement, clearly drunk. Unable to drive.
.30 Many lose consciousness.  
.40 Most lose consciousness, some die.  
.50 Breathing stops, many die.  

A BAC of .10 means that one-tenth of 1% (or one thousandth) of your total blood content is alcohol

2.22.1 Alcohol and Driving

Drinking alcohol and then driving is very dangerous and a serious problem. People who drink alcohol are involved in traffic accidents resulting in over 20,000 deaths every year. Alco­hol impairs muscle coordination, reaction time, depth perception, and night vision. It also af­fects the parts of the brain that control judgment and inhibition. For some people, one drink is all it takes to show signs of impairment.

How Alcohol Works.

Alcohol goes directly into the blood stream and is carried to the brain. After passing through the brain, a small per­centage is removed in urine, perspiration, and by breathing, while the rest is carried to the liver. The liver can only process one-third an ounce of alcohol per hour, which is consider­ably less than the alcohol in a standard drink. This is a fixed rate, so only time, not black cof­fee or a cold shower, will sober you up. If you have drinks faster than your body can get rid of them, you will have more alcohol in your body, and your driving will be more affected. The Blood Alcohol Concentration (BAC) commonly measures the amount of alcohol in your body. See Figure 2.22.

All of the following drinks contain the same amount of alcohol:

  • A 12-ounce glass of 5% beer.
  • A 5-ounce glass of 12% wine.
  • A 1 ½-ounce shot of 80 proof liquor.
What Determines Blood Alcohol Concen­tration?

BAC is determined by the amount of alcohol you drink (more alcohol means higher BAC), how fast you drink (faster drinking means higher BAC), and your weight (a small person doesn't have to drink as much to reach the same BAC).

Alcohol and the Brain.

Alcohol affects more and more of the brain as BAC builds up. The first part of the brain affected controls judgment and self-control. One of the bad things about this is it can keep drinkers from knowing they are getting drunk. And, of course, good judgment and self-control are absolutely necessary for safe driving.

As BAC continues to build up, muscle control, vision, and coordination are affected more and more. Effects on driving may include:

  • Straddling lanes.
  • Quick, jerky starts.
  • Not signaling, failure to use lights.
  • Running stop signs and red lights.
  • Improper passing.

See Figure 2.23.

These effects mean increased chances of a crash and chances of losing your driver's li­cense. Accident statistics show that the chance of a crash is much greater for drivers who have been drinking than for drivers who have not.

How Alcohol Affects Driving.

All drivers are affected by drinking alcohol. Alcohol affects judgment, vision, coordination, and reaction time. It causes serious driving errors, such as:

  • Increased reaction time to hazards.
  • Driving too fast or too slow.
  • Driving in the wrong lane.
  • Running over the curb.
  • Weaving.

2.22.2 Other Drugs

Besides alcohol, other legal and illegal drugs are being used more often. Laws prohibit possession or use of many drugs while on duty. They prohibit being under the influence of any "controlled substance," amphetamines (including "pep pills," "uppers," and "bennies"), narcot­ics, or any other substance, which can make the driver unsafe. This could include a variety of prescription and over-the-counter drugs (cold medicines), which may make the driver drowsy or otherwise affect safe driving ability. However, possession and use of a drug given to a driver by a doctor is permitted if the doctor informs the driver that it will not affect safe driving ability.

Pay attention to warning labels for legitimate drugs and medicines, and to doctor's orders regarding possible effects. Stay away from il­legal drugs.

Don't use any drug that hides fatigue--the only cure for fatigue is rest. Alcohol can make the effects of other drugs much worse. The safest rule is don't mix drugs with driving at all.

Use of drugs can lead to traffic accidents re­sulting in death, injury, and property damage. Furthermore, it can lead to arrest, fines, and jail sentences. It can also mean the end of a person's driving career.