Missouri CDL — General Knowledge practice
Missouri CDL — General Knowledge: Alcohol & Drugs practice test
Blood alcohol limits, zero-tolerance and implied-consent laws, and how alcohol and drugs — legal or not — affect your driving.
Content reviewed against official driver handbooks · August 12, 2026
13 questions · pass with 10 correct. You get instant feedback and an explanation after every answer.
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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.
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1. Why can common over-the-counter cold medicines be a concern for drivers?
Correct answer: They can make you drowsy or affect safe driving
Certain prescription and over-the-counter drugs, such as cold medicines, can make a driver drowsy or otherwise reduce safe-driving ability.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
2. Should you ever use a drug to hide the feeling of fatigue while driving?
Correct answer: No, because the only cure for fatigue is rest
You should not use any drug that masks fatigue; the only real cure for being tired is rest.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
3. Which driving abilities does alcohol impair?
Correct answer: Coordination, reaction time, depth perception, and judgment
Alcohol dulls your coordination, slows reaction time, and weakens both depth perception and night vision, and it affects the brain's judgment and inhibition.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
4. Which of these contains about the same amount of alcohol as the others?
Correct answer: A 12-ounce beer, a 5-ounce glass of wine, and a 1.5-ounce shot are about equal
A 1.5-ounce shot of 80-proof liquor holds about as much alcohol as a 5-ounce pour of 12% wine or a 12-ounce serving of 5% beer.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
5. As blood alcohol concentration rises, which mental function is affected first?
Correct answer: Judgment and self-control
The earliest part of the brain impaired controls judgment and self-control—which can even prevent a drinker from realizing they are getting drunk.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
6. What is the only thing that will actually reduce your blood alcohol level?
Correct answer: The passage of time
Because the liver clears alcohol at a fixed rate, only the passage of time will sober you up—not black coffee or a cold shower.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
7. According to the manual, how much alcohol does it take to begin showing signs of impairment?
Correct answer: For some people, just one drink
For some people, a single drink is enough to start showing signs of impairment.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
8. Which factors determine a person's blood alcohol concentration?
Correct answer: The amount and speed of drinking, and body weight
BAC depends on how much alcohol you drink, how fast you drink it, and your body weight, since a smaller person reaches a given level with less alcohol.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
9. How does alcohol interact with other drugs a driver might take?
Correct answer: It can make their effects much worse
Alcohol can intensify how other drugs affect you, so the safest rule is to never combine drugs with driving.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
10. What do the regulations say about being under the influence of a controlled substance while on duty?
Correct answer: It is prohibited
The rules bar a driver on duty from being impaired by any controlled substance, amphetamine, narcotic, or other product that could make driving unsafe.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
11. Under what condition may a driver use a drug prescribed by a doctor?
Correct answer: If the doctor says it will not affect safe driving
A driver may use a doctor-prescribed drug if the doctor confirms it will not interfere with the ability to drive safely.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
12. About how much alcohol can the liver process in an hour?
Correct answer: Roughly one-third of an ounce
The liver removes only about a third of an ounce of alcohol each hour, which is less than what a single standard drink holds.
Source: Missouri CDL Manual — Section 2.22: Alcohol, Other Drugs, and Driving
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