CDL Practice Test

CDL Alcohol & Drugs Practice Questions

Alcohol & Drugs makes up 3 of every 50 questions on a Tigertest CDL practice test. Here are 10 of the 40 questions on it, each with the answer and the reason.

Updated 2026-11-10 by the Tigertest team. Covers the CDL general knowledge exam. 80% to pass on the real test.

1. 1. What is the maximum blood alcohol concentration (BAC) allowed for CDL drivers while operating a commercial vehicle?

   • A.0.02%
   • B.0.04%
   • C.0.10%
   • D.0.08%

   Answer: B. CDL drivers have a lower BAC limit of 0.04% while operating commercial vehicles, which is half the standard limit for regular drivers.

2. 2. When are CDL drivers subject to random drug and alcohol testing?

   • A.Only after accidents involving injury or property damage
   • B.Only during annual physical examinations and renewals
   • C.Only when showing obvious signs of impairment or intoxication
   • D.At any time during work hours without advance notice

   Answer: D. Random testing can occur at any time during work hours without advance notice, ensuring drivers remain drug and alcohol-free throughout their employment.

3. 3. You are taking a prescription medication that causes drowsiness. What should you do before driving?

   • A.Consult your doctor about driving safety
   • B.Take half the prescribed dose before your shift
   • C.Drink coffee to stay alert
   • D.Drive only in daylight and take extra breaks

   Answer: A. You must consult your doctor about the medication's effects on driving ability, as prescription drugs can impair your ability to operate a commercial vehicle safely.

4. 4. How does alcohol primarily affect your driving ability?

   • A.Enhances coordination and fine motor control skills
   • B.Improves night vision and reduces glare sensitivity
   • C.Reduces reaction time and impairs judgment
   • D.Increases alertness and concentration during long drives

   Answer: C. Alcohol slows reaction time, impairs judgment, reduces coordination, and affects vision, all of which are critical for safe driving.

5. 5. What happens if you refuse to take a required drug or alcohol test?

   • A.Nothing, it's your constitutional right to refuse testing
   • B.You get a warning and can take the test later
   • C.It's treated the same as a positive test result
   • D.You can take the test later when more convenient

   Answer: C. Refusing a required test is treated exactly the same as testing positive, resulting in immediate disqualification and removal from safety-sensitive duties.

6. 6. What is the minimum time you must wait between drinking alcohol and driving a commercial vehicle?

   • A.4 hours
   • B.8 hours
   • C.12 hours
   • D.24 hours

   Answer: A. Federal regulations require at least 4 hours between consuming alcohol and operating a commercial vehicle, though it may take longer for all alcohol to clear your system.

7. 7. Which over-the-counter medications can affect your driving ability?

   • A.Only prescription drugs affect driving
   • B.Vitamins, herbal supplements, and energy drinks only
   • C.Aspirin, ibuprofen, and other pain relievers only
   • D.Cold medicines, allergy medications, and sleep aids

   Answer: D. Many over-the-counter medications like antihistamines, decongestants, and sleep aids can cause drowsiness, dizziness, or impaired coordination.

8. 8. When must employers conduct post-accident drug and alcohol testing?

   • A.Only if police were called to investigate the scene
   • B.After a fatality, or a citation with an injury or tow-away
   • C.Only if the driver was injured and hospitalized
   • D.Only for accidents over $10,000 damage to vehicles

   Answer: B. Post-accident testing is required after any crash with a fatality. It is also required when someone is treated for injuries away from the scene, or a vehicle must be towed, and the CMV driver receives a citation for a moving violation.

9. 9. What is implied consent regarding drug and alcohol testing?

   • A.Only certain drivers must consent based on their record
   • B.By having a CDL, you automatically agree to testing
   • C.You must give written permission for each individual test
   • D.Testing is voluntary and you can decline anytime

   Answer: B. Implied consent means that by holding a CDL and operating commercial vehicles, you have automatically agreed to submit to drug and alcohol testing when required.

10. 10. How long does it typically take for one standard drink to leave your system?

    • A.30 minutes per drink
    • B.2 hours per drink
    • C.15 minutes per drink
    • D.About one hour per drink

    Answer: D. On average, the body processes one standard drink per hour, but this can vary based on body weight, food consumption, and other factors.