Idaho Car / Permit practice
Idaho Car / Permit: 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
14 questions · pass with 11 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. Which alcohol concentration applies to someone operating a commercial vehicle in Idaho?
Correct answer: .04 or above
Commercial operation carries its own limit of four hundredths, sitting between the under-21 figure and the general adult figure.
Source: Idaho Driver's Handbook — Driving Under The Influence
2. How does marijuana affect a driver, according to the Idaho handbook?
Correct answer: It slows reaction time and distorts judgment of time and distance
It stretches out reaction time and distorts a driver's sense of how much time and distance are available, which is different from the aggression tied to stimulants or the drowsiness tied to opioids and sedatives.
Source: Idaho Driver's Handbook — Impaired Driving
3. What does the Idaho handbook say begins to happen after roughly two to four drinks?
Correct answer: Reaction time, coordination, and balance start to suffer
By that point alcohol is dulling reaction time, coordination, and balance, and it is also degrading vision and the ability to judge distance, all of which make hazards harder to handle.
Source: Idaho Driver's Handbook — How Drinking Affects You
4. How does an ignition interlock device work in Idaho?
Correct answer: It requires a breath sample and blocks starting if alcohol is at or above a preset level
The driver blows into the unit before the engine will crank, and if the reading meets or passes the preset level the vehicle stays off; installation, upkeep, and monthly charges come out of the driver's pocket.
Source: Idaho Driver's Handbook — Ignition Interlock Device
5. An Idaho court upholds an officer's findings after a driver's first refusal to be tested. What is the result?
Correct answer: A one-year suspension with absolutely no driving privileges
A first sustained refusal costs the driver a full year of driving with no restricted privileges of any kind, and it stacks on top of anything a DUI conviction brings.
Source: Idaho Driver's Handbook — Test Refusal for Alcohol, Drugs, or Other Intoxicating Substances
6. At what alcohol concentration is a driver 21 or older considered to be driving under the influence in Idaho?
Correct answer: .08 or above
For an adult driver the threshold sits at eight hundredths, while younger drivers and commercial operators are held to lower numbers.
Source: Idaho Driver's Handbook — Driving Under The Influence
7. According to the Idaho handbook, how much does crash risk increase once a driver reaches an alcohol concentration of .10?
Correct answer: It is about six times as great
The handbook charts risk climbing steeply: it doubles just past five hundredths, reaches six times at one tenth, and is twenty-five times greater at fifteen hundredths.
Source: Idaho Driver's Handbook — How Much is Too Much
8. How does Idaho's open container law apply to passengers?
Correct answer: Passengers are covered too, and an opened container must ride in the trunk, or behind the rearmost upright seat when there is no trunk
The ban on drinking, or even holding an opened alcoholic beverage, reaches passengers exactly as it reaches the driver, and anything already unsealed must travel in the trunk, or behind the rearmost upright seat in a vehicle without one.
Source: Idaho Driver's Handbook — Open Container Law
9. What will actually lower the alcohol already in a person's bloodstream?
Correct answer: The passage of time and nothing else
Coffee, food, exercise, cold air, and every other folk remedy leave the alcohol where it is; the body needs time to clear it.
Source: Idaho Driver's Handbook — How Drinking Affects You
10. Under Idaho's implied consent provision, what happens if you refuse an officer's request for an evidentiary test?
Correct answer: Your license is suspended and you owe a civil penalty of $250
Anyone driving or in physical control of a vehicle has already agreed to testing, so a refusal brings a license suspension along with a civil penalty of two hundred fifty dollars.
Source: Idaho Driver's Handbook — Test Refusal for Alcohol, Drugs, or Other Intoxicating Substances
11. What blood-alcohol level makes an Idaho driver under 21 guilty of driving under the influence?
Correct answer: .02 or above
Drivers below the legal drinking age face a much lower ceiling, set at two hundredths, well beneath the adult figure.
Source: Idaho Driver's Handbook — Driving Under The Influence
12. What should an Idaho driver do before taking an over-the-counter medicine and driving?
Correct answer: Read the label, and skip driving if it advises against it
Non-prescription remedies are required to carry usage directions, so the label is where you learn whether the product warns against getting behind the wheel.
Source: Idaho Driver's Handbook — Drugs & Driving
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Every Idaho question is written from the official Idaho 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