Iowa CDL — General Knowledge practice
Iowa 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
12 questions · pass with 10 correct. You get instant feedback and an explanation after every answer.
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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.
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1. After you drink, where does the bloodstream carry the alcohol?
Correct answer: Directly to the brain
Alcohol goes straight into the bloodstream and is carried to the brain, where it first affects judgment and self-control.
Source: Iowa Commercial Driver's License Manual — Section 2.22.1, Alcohol and Driving
2. According to the National Sleep Foundation poll cited in the manual, about what share of Americans admit to having fallen asleep at the wheel?
Correct answer: About 36 percent
The poll found 60 percent had driven while sleepy and 36 percent, more than one-third, admitted actually falling asleep behind the wheel.
Source: Iowa Commercial Driver's License Manual — Section 2.11.2, Driver Factors
3. On the manual's table of BAC effects, at about what level does it say many people lose consciousness?
Correct answer: .30
The table puts loss of consciousness for many people at .30. By .40 most lose consciousness and some die, and at .50 breathing stops for many.
Source: Iowa Commercial Driver's License Manual — Section 2.22.1, Alcohol and Driving (Effects of Increasing Blood Alcohol Content)
4. Before taking a legitimate medicine while on duty, what does the manual tell you to pay attention to?
Correct answer: Its warning labels and your doctor's orders about possible effects
Read the warning labels on legitimate drugs and medicines and follow your doctor's orders about their possible effects on driving.
Source: Iowa Commercial Driver's License Manual — Section 2.22.2, Other Drugs
5. Which of these does the manual list as a way to stay alert while you're driving?
Correct answer: Avoid heavy foods and keep the cab cool
Tips for staying alert include avoiding heavy foods, keeping cool with an open window or air conditioning, wearing sunglasses against glare, and taking regular breaks.
Source: Iowa Commercial Driver's License Manual — Section 2.11.2, Driver Factors
6. To help prevent drowsiness, when does the manual suggest scheduling your trips?
Correct answer: During the hours you're normally awake
Schedule trips for the hours you are usually awake rather than the middle of the night, and get adequate sleep beforehand.
Source: Iowa Commercial Driver's License Manual — Section 2.11.2, Driver Factors
7. On the BAC effects table, at about what level does the manual note reduced reaction time along with mood swings and noisy behavior?
Correct answer: .10
The table describes .10 as noisy, possibly embarrassing behavior with mood swings and a reduction in reaction time.
Source: Iowa Commercial Driver's License Manual — Section 2.22.1, Alcohol and Driving (Effects of Increasing Blood Alcohol Content)
8. You often feel sleepy during the day, have trouble sleeping at night, or take frequent naps. What does the manual suggest?
Correct answer: Consult your physician
Among its steps for preventing drowsiness, the manual advises seeing your doctor if you have daytime sleepiness, trouble sleeping at night, or take frequent naps.
Source: Iowa Commercial Driver's License Manual — Section 2.11.2, Driver Factors
9. Most alcohol is processed by the liver. How does the small share that isn't leave the body?
Correct answer: Through urine, sweat, and breathing
After alcohol passes through the brain, a small percentage leaves in urine, perspiration, and breath, and the rest goes to the liver.
Source: Iowa Commercial Driver's License Manual — Section 2.22.1, Alcohol and Driving
10. Why does a heavier person usually reach a lower BAC than a lighter person from the same drinks?
Correct answer: A larger body has more blood to dilute the alcohol
BAC depends on how much blood you have, which goes up with body weight, and on how much alcohol you take in over time.
Source: Iowa Commercial Driver's License Manual — Section 2.22.1, Alcohol and Driving (Effects of Increasing Blood Alcohol Content)
11. You just flew in from another time zone and are about to start a driving shift. How does the manual treat that situation?
Correct answer: As a risk factor for drowsy driving
The manual's list of drowsy-driving risks includes flying and changing time zones, along with sleep loss, night driving, sedating medicines, and long hours.
Source: Iowa Commercial Driver's License Manual — Section 2.11.2, Driver Factors
12. Besides being under their influence, what do laws prohibit regarding many drugs while a driver is on duty?
Correct answer: Possessing them
Laws prohibit both possession and use of many drugs while on duty, including controlled substances, amphetamines, and narcotics.
Source: Iowa Commercial Driver's License Manual — Section 2.22.2, Other Drugs
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