Driving Under the Influence
Alcohol, drugs, and even some medications can disqualify you from driving.
The rules
- A blood alcohol concentration (BAC) of 0.08% is the legal limit for drivers 21 and older in most states (0.05% in Utah).
- Drivers under 21 are subject to "zero tolerance" laws — any measurable alcohol can lead to license suspension.
- Implied consent laws mean refusing a chemical test will result in automatic license suspension.
- Marijuana, prescription drugs, and over-the-counter medications can impair driving and lead to a DUI charge.
- A first DUI conviction typically includes fines, license suspension, alcohol education classes, and possible jail time.
Why this topic appears on the permit test
State DMVs build their permit exams around the situations that most often cause crashes for new drivers. The rules collected on this page — about driving under the influence — show up because they prevent predictable, common, and high-cost mistakes. The federal National Highway Traffic Safety Administration (NHTSA) publishes annual reports on crash causes, and DMVs use those reports to weight the topics on their knowledge exams. Spend extra time on this section if you're newer to driving in the United States.
How questions are usually phrased
You'll typically see this topic in one of three formats. The first is a direct rule recall — "What is the maximum speed in a school zone when children are present?" The second is a scenario — "You are approaching a four-way stop and another car arrives at the same time on your right. What do you do?" The third is a comparison — "Which of the following actions is allowed in this situation?" In every format, the underlying skill is the same: know the rule and know why it exists.
What to remember on test day
Don't try to memorize each bullet word-for-word. Instead, picture each rule as a real driving situation. The brain remembers stories better than abstractions, and most permit-exam questions are short stories asking you to make the right call. If you can imagine yourself in the situation and visualize what the safe, legal action looks like, the right answer almost always becomes obvious.
Ready to test yourself? Take any state's practice test and watch how often this topic appears.