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Alcohol, other drugs and illness

General Knowledge4 minManual section 2.22

Drinking and then driving is very dangerous. People who drink are involved in traffic crashes that cause over 20,000 deaths every year. Alcohol harms muscle coordination, reaction time, depth perception and night vision, and it acts on the brain areas that handle judgment and inhibition. Some people show impairment after just one drink.

How alcohol works

Alcohol goes straight into the bloodstream and is carried to the brain. After the brain, a small part leaves the body in urine, sweat and breath; the rest goes to the liver.

The liver can process only about one-third of an ounce of alcohol per hour — much less than the alcohol in one standard drink. This rate is fixed. Only time sobers you up — not black coffee or a cold shower.

If you drink faster than your body can remove alcohol, more builds up and your driving gets worse. The amount of alcohol in your body is measured as Blood Alcohol Concentration (BAC).

What is a drink? What sets your BAC?

These drinks have the same amount of alcohol:

  • A 12-ounce glass of 5% beer.
  • A 5-ounce glass of 12% wine.
  • A 1½-ounce shot of 80-proof liquor.

It is the alcohol that affects you, not the type of drink. Two beers, two glasses of wine or two shots have about the same effect.

Your BAC depends on: how much you drink (more = higher), how fast you drink (faster = higher), and your weight (a smaller person reaches the same BAC with less alcohol).

BAC is measured in milligrams of alcohol per 100 milliliters of blood. A BAC of .10 means 1/10 of 1% (1/1000) of your blood is alcohol. The liver handles about one drink per hour; the rest builds up. Rough chart rule: subtract .01% for each 40 minutes of drinking.

Alcohol and the brain; effects on driving

As BAC rises, alcohol affects more of the brain. The first part affected controls judgment and self-control. That is why drinkers often do not know they are getting drunk — and good judgment is exactly what safe driving needs.

All drivers are affected. Alcohol hurts judgment, vision, coordination and reaction time. It causes serious errors such as:

  • Reacting to hazards more slowly; speed that is too high or too low; being in the wrong lane.
  • Running over the curb; weaving; straddling lanes; quick, jerky starts.
  • Not signaling, not using lights; running stop signs and red lights; improper passing.

These raise your chance of a crash and of losing your license. Crash statistics show drinking drivers have a much higher crash risk.

BAC levels and their effects

  • .02: mellow feeling, slight body warmth; less inhibited.
  • .05: noticeable relaxation; less alert, coordination problems begin.
  • .08: definite impairment in coordination and judgment — the drunk driving limit for regular drivers in most states. CMV drivers face a stricter federal limit of .04.
  • .10: noisy, possible embarrassing behavior, mood swings; slower reaction time.
  • .15: impaired balance and movement; clearly drunk; unable to drive.
  • .30: many lose consciousness. .40: most lose consciousness, some die. .50: breathing stops, many die.

Other drugs

Laws forbid having or using many drugs while on duty. They forbid being under the influence of any controlled substance, amphetamines (“pep pills,” “uppers,” “bennies”), narcotics, or anything else that makes you unsafe. This can include some prescription and over-the-counter drugs such as cold medicines that make you drowsy.

Exception: you may have and use a drug a doctor gave you if the doctor tells you it will not affect safe driving.

  • Read warning labels and follow your doctor's orders about side effects. Stay away from illegal drugs.
  • Never take a drug to cover up tiredness. Rest is the only cure for fatigue.
  • Alcohol can make other drugs' effects much worse. The safest rule: do not mix drugs with driving at all.

Drug use can lead to crashes with death, injury and damage, and to arrest, fines, jail — and the end of your driving career.

Illness

Sometimes you may be so sick that you cannot drive safely. Then you must not drive. In an emergency, you may drive only to the nearest place where you can safely stop.

Check your state

The .08 limit in the chart is for ordinary driving in most states. When you drive a commercial vehicle, the federal limit is .04 (see the disqualification rules). Utah's general limit is .05. Check your state manual.

References and scope

The topic reference is listed below. Sources support verification; the lesson itself is here. The current content needs technical and language review before public launch.

Manual reference: 2.22

Official CDL handbook · Utah ↗StatesOur editorial approach

Put it into practice

Educational questions with explanations. The answer review also works without the interactive quiz.

Preparing your questions…

Review questions with answers

  1. About how much alcohol can the liver process per hour?
    1. One full drink of liquor
    2. Two beers
    3. About one-third of an ounce
    4. One ounce
    Show answer
    About one-third of an ounce

    The liver can process only about one-third of an ounce of alcohol per hour, less than a standard drink.

  2. A driver who has been drinking can sober up faster by drinking black coffee and getting some fresh air.
    1. True
    2. False
    Show answer
    False

    False. The liver works at a fixed rate. Only time will sober a person up.

  3. Which drink has the same amount of alcohol as a 12-ounce glass of 5% beer?
    1. A 5-ounce glass of 12% wine
    2. A 12-ounce glass of 12% wine
    3. Three ounces of 80-proof liquor
    4. A 24-ounce beer
    Show answer
    A 5-ounce glass of 12% wine

    A 12-oz 5% beer, a 5-oz glass of 12% wine and a 1½-oz shot of 80-proof liquor contain the same alcohol.

  4. A standard shot of 80-proof liquor is:
    1. 3 ounces
    2. 1 ounce
    3. 2½ ounces
    4. 1½ ounces
    Show answer
    1½ ounces

    One drink equals a 1½-ounce shot of 80-proof liquor.

  5. Which three things determine your Blood Alcohol Concentration (BAC)?
    1. Type of drink, time of day, food eaten
    2. Age, height, eye color
    3. How much you drink, how fast you drink, and your weight
    4. Mood, temperature, and coffee
    Show answer
    How much you drink, how fast you drink, and your weight

    BAC depends on the amount of alcohol, how fast you drink it, and your body weight.

  6. Which part of the brain does alcohol affect first?
    1. The part that controls judgment and self-control
    2. The part that controls breathing
    3. The part that controls hearing
    4. The part that controls balance
    Show answer
    The part that controls judgment and self-control

    Alcohol first affects judgment and self-control, which is why drinkers may not know they are getting drunk.

  7. Which is a common driving error caused by alcohol?
    1. Signaling too early
    2. Weaving and straddling lanes
    3. Driving with headlights on
    4. Leaving too much following distance
    Show answer
    Weaving and straddling lanes

    Alcohol causes errors like weaving, straddling lanes, wrong-lane driving, jerky starts, and running stop signs.

  8. Alcohol harms all of these EXCEPT:
    1. Reaction time
    2. Depth perception
    3. Night vision
    4. The engine's fuel economy
    Show answer
    The engine's fuel economy

    Alcohol impairs muscle coordination, reaction time, depth perception and night vision.

  9. A BAC of .10 means that:
    1. 10% of your blood is alcohol
    2. You had 10 drinks
    3. 1/10 of 1% of your blood is alcohol
    4. You are under the legal limit everywhere
    Show answer
    1/10 of 1% of your blood is alcohol

    A BAC of .10 means 1/10 of 1% (1/1000) of your total blood content is alcohol.

  10. According to the manual, people who drink alcohol are involved in traffic crashes that cause how many deaths each year?
    1. Over 20,000
    2. About 2,000
    3. About 500
    4. Over 200,000
    Show answer
    Over 20,000

    Drinking drivers are involved in crashes resulting in over 20,000 deaths every year.

  11. Some over-the-counter cold medicines can cause drowsiness that makes driving unsafe.
    1. True
    2. False
    Show answer
    True

    True. Some over-the-counter drugs such as cold medicines can make a driver drowsy.

  12. When may a driver use a prescription drug while on duty?
    1. Never
    2. Only on short trips
    3. Only if it is a low dose
    4. When the doctor says it will not affect safe driving
    Show answer
    When the doctor says it will not affect safe driving

    Using a drug from a doctor is allowed if the doctor tells the driver it will not affect safe driving ability.

  13. What is the only cure for fatigue?
    1. Rest
    2. Coffee
    3. Pep pills
    4. Loud music
    Show answer
    Rest

    Do not use drugs that hide fatigue. The only cure for fatigue is rest.

  14. "Uppers," "pep pills" and "bennies" are types of:
    1. Cold medicines
    2. Narcotics
    3. Amphetamines
    4. Antibiotics
    Show answer
    Amphetamines

    Amphetamines include pep pills, uppers and bennies. Being under their influence while on duty is prohibited.

  15. Mixing alcohol with other drugs:
    1. Cancels out the effects
    2. Can make the effects of the drugs much worse
    3. Is safe in small amounts
    4. Helps you stay awake
    Show answer
    Can make the effects of the drugs much worse

    Alcohol can greatly strengthen the effects of other drugs. The safest choice is to keep drugs and driving apart.

  16. You become so ill during a trip that you cannot drive safely. You should:
    1. Keep driving slowly to your destination
    2. Take a pep pill and continue
    3. Drive with flashers on
    4. Not drive, except in an emergency to the nearest place you can safely stop
    Show answer
    Not drive, except in an emergency to the nearest place you can safely stop

    If too sick to drive safely, you must not drive. In an emergency you may drive to the nearest safe stopping place.

  17. On the BAC effects chart, at what level is a person described as clearly drunk and unable to drive?
    1. .02
    2. .15
    3. .05
    4. .04
    Show answer
    .15

    At .15, balance and movement are impaired, the person is clearly drunk and unable to drive.

  18. The BAC chart shows .08 as the drunk-driving limit for regular drivers in most states. What is the federal BAC limit while you drive a commercial motor vehicle?
    1. .08
    2. .04
    3. .10
    4. .02
    Show answer
    .04

    The .08 figure applies to ordinary drivers in most states. When operating a CMV, federal rules set a stricter limit of .04.