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Tennessee CDL — General Knowledge practice

Alcohol & Drugs

Blood alcohol limits, zero-tolerance and implied-consent laws, and how alcohol and drugs — legal or not — affect your driving.

Questions reviewed against the official Tennessee driver handbook · July 7, 2026

14 questions · pass with 11 correct. You get instant feedback and an explanation after every answer.

Study questions with answers

12 sample Alcohol & Drugs questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.

  1. 1. What is the only thing that will actually sober up a person who has been drinking?

    Correct answer: Time

    Only the passage of time sobers you up; black coffee, a cold shower, or fresh air will not.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Alcohol, Other Drugs, and Driving)

  2. 2. At what blood alcohol concentration is it illegal to operate a commercial motor vehicle?

    Correct answer: .04 percent or higher

    It is illegal to operate a CMV with a blood alcohol concentration of .04 percent or higher.

    Source: Tennessee CDL Manual — Section 1: Introduction (Alcohol and Disqualifications)

  3. 3. What is the penalty for a second major alcohol or drug offense in a CMV?

    Correct answer: Loss of the CDL for life

    A second offense results in loss of the CDL for life.

    Source: Tennessee CDL Manual — Section 1: Introduction (Alcohol and Disqualifications)

  4. 4. How long will a driver lose the CDL if the alcohol offense occurs while hauling placarded hazardous materials?

    Correct answer: At least three years

    If the offense happens while the vehicle is placarded for hazardous materials, you lose the CDL for at least three years.

    Source: Tennessee CDL Manual — Section 1: Introduction (Alcohol and Disqualifications)

  5. 5. Which part of the brain does alcohol affect first as the BAC rises?

    Correct answer: The part controlling judgment and self-control

    Alcohol first affects the part of the brain that controls judgment and self-control, which are essential for safe driving.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Alcohol, Other Drugs, and Driving)

  6. 6. A prescription drug given by a doctor may be used while driving only if what is true?

    Correct answer: The doctor says it will not affect safe driving ability

    You may use a doctor-prescribed drug on duty only if the doctor tells you it will not affect your safe driving ability.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Alcohol, Other Drugs, and Driving)

  7. 7. What happens to a driver found with a detectable amount of alcohol below .04 percent while operating a CMV?

    Correct answer: Placed out of service for 24 hours

    A driver with any detectable alcohol under .04 percent is placed out of service for 24 hours.

    Source: Tennessee CDL Manual — Section 1: Introduction (Alcohol and Disqualifications)

  8. 8. By operating a CMV, what have you agreed to regarding alcohol testing?

    Correct answer: Consent to alcohol testing

    By operating a CMV you are deemed to have given consent to alcohol testing.

    Source: Tennessee CDL Manual — Section 1: Introduction (Alcohol and Disqualifications)

  9. 9. How can common over-the-counter cold medicines affect a driver?

    Correct answer: They can make the driver drowsy and unsafe

    Cold medicines and other legal drugs can make a driver drowsy or otherwise impair safe driving ability.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Alcohol, Other Drugs, and Driving)

  10. 10. Which driving abilities does alcohol impair?

    Correct answer: Reaction time, depth perception, night vision, and muscle control

    Alcohol dulls your reaction time, depth perception, night vision, and muscle coordination while also clouding judgment.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Alcohol, Other Drugs, and Driving)

  11. 11. Which of these servings contains about the same amount of alcohol?

    Correct answer: A 12-ounce beer, a 5-ounce glass of wine, and a 1.5-ounce shot of liquor are about equal

    A 12-ounce beer, a 5-ounce glass of table wine, and a 1.5-ounce shot of 80-proof liquor all contain about the same amount of alcohol.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Alcohol, Other Drugs, and Driving)

  12. 12. About how much alcohol can the liver process in an hour?

    Correct answer: About one-third of an ounce per hour

    The liver removes only about one-third of an ounce of alcohol per hour, and this rate is fixed.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Alcohol, Other Drugs, and Driving)

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Every Tennessee question is written from the official Tennessee driver handbook and checked against its current edition. DMV Test Free is a free, independent study resource — not affiliated with any DMV or government agency. About DMV Test Free