Drunk driving is operating a motor vehicle while impaired by alcohol, and it remains one of the leading causes of traffic deaths in the United States. In 2023, 12,429 people were killed in alcohol-impaired driving crashes, accounting for 30 percent of all traffic fatalities. That works out to one death every 42 minutes.
How the Law Defines It
Most states set the legal blood alcohol concentration (BAC) limit at 0.08 grams per deciliter. Utah is the exception, with a lower threshold of 0.05. Reaching 0.08 does not require heavy drinking for most people. Body weight, food intake, hydration, and how quickly you consume drinks all affect how fast your BAC rises.
You may see different acronyms depending on your state. DUI (Driving Under the Influence) and DWI (Driving While Intoxicated) are the most common, but some states use OWI (Operating While Intoxicated). The differences are more than cosmetic. “Operating” is broader than “driving.” In states that use OWI, you can be charged for sitting in a parked car with the engine running while intoxicated, even in your own driveway. OWI also typically covers impairment from any substance, including prescription drugs and marijuana, not just alcohol.
For drivers under 21, the rules are far stricter. Federal law pushed all states to adopt zero tolerance policies, making it illegal for minors to drive with a BAC of 0.02 percent or higher. Some states go further, treating any detectable alcohol as a violation, even a BAC of 0.00 if there’s evidence of recent drinking.
What Alcohol Does to Your Driving
Impairment begins well below the legal limit. At BAC levels above 0.05, laboratory research shows significant declines in tracking ability, reaction time, fine motor coordination, and balance. More complex tasks suffer too: the ability to quickly choose between competing responses and the ability to stop yourself from reacting when you shouldn’t both deteriorate at these levels.
One of the most dangerous effects is that alcohol erodes your ability to judge how impaired you are. At BACs as low as 0.07, people consistently overestimate their fitness to drive. This creates a gap between how capable you feel and how capable you actually are, which is a large part of why so many impaired drivers get behind the wheel in the first place.
How Your Body Processes Alcohol
The body eliminates roughly one standard drink per hour from the bloodstream. A standard drink is 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of distilled spirits. If you have four drinks over two hours, you still have about two drinks’ worth of alcohol in your system when you stop, and it will take approximately two more hours before your BAC returns to zero.
Time is the only thing that lowers your BAC. Coffee, cold showers, fresh air, and food do not speed up alcohol metabolism. They might make you feel more alert, but your reaction time, coordination, and judgment remain impaired until your liver finishes processing the alcohol.
What Happens During a Traffic Stop
When an officer suspects impairment, the stop typically moves through phases. After initial observation (swerving, erratic speed, running lights), the officer will look for physical signs during conversation: slurred speech, bloodshot eyes, the smell of alcohol.
If suspicion continues, you’ll be asked to perform standardized field sobriety tests. The National Highway Traffic Safety Administration recognizes three. The first is Horizontal Gaze Nystagmus, where the officer moves an object in front of your eyes and watches for involuntary jerking of the eyeball, a neurological response that becomes more pronounced with alcohol. The second is the Walk and Turn test: nine heel-to-toe steps along a line, a turn, and nine steps back. Officers watch for eight specific clues, including losing balance during instructions, missing heel-to-toe contact, stepping off the line, and using arms for balance. The third is the One Leg Stand, where you hold one foot six inches off the ground for 30 seconds. Swaying, hopping, using arms, or putting your foot down are all recorded as signs of impairment.
A breathalyzer or blood test typically follows. Every state has an implied consent law, meaning that by driving on public roads, you’ve already agreed to submit to chemical testing if an officer has probable cause. Refusing the test doesn’t protect you from charges. It triggers an automatic license revocation, often before your case even goes to court.
Penalties for a First Offense
Consequences vary by state, but a first-offense DUI is not treated lightly anywhere. Using Michigan as a representative example, a first offense with a BAC below 0.17 can carry fines up to $500, up to 93 days in jail, up to 360 hours of community service, and a license suspension of up to 180 days. Six points go on your driving record.
Higher BAC levels bring escalated penalties. In Michigan, a first offense at 0.17 or above raises potential jail time to 180 days, fines to $700, and license suspension to a full year. It also triggers mandatory alcohol treatment and requires installation of an ignition interlock device, a breathalyzer wired to your car’s starter that won’t let the engine turn on if it detects alcohol on your breath.
Beyond the court-imposed penalties, the financial ripple effects are substantial. Insurance premiums typically spike for years after a DUI conviction. Many employers run background checks, and a DUI can affect job prospects, professional licenses, and, for underage offenders, college admissions.
Consequences for Underage Drivers
Because of zero tolerance laws, a driver under 21 can face charges after consuming as little as one drink. Punishments for underage DUI almost always include a license suspension of at least one year and fines ranging from several hundred to several thousand dollars. Some states impound the vehicle. Mandatory educational classes on the dangers of impaired driving are common, and courts may also require enrollment in an alcohol rehabilitation program. Jail time is rare for underage offenses but remains a legal possibility depending on the circumstances.
Why the 0.08 Limit Is Misleading
Many people treat 0.08 as a line between “safe” and “unsafe,” but impairment is a spectrum that starts with the first drink. Measurable declines in coordination and decision-making appear at 0.05, and your self-assessment of impairment becomes unreliable at 0.07. Utah’s decision to lower its limit to 0.05 reflects the research showing meaningful driving deficits below 0.08. You can also be arrested below the legal limit if an officer observes clear signs of impairment during a stop. The per se limit is the point at which no additional evidence of impairment is needed for a charge, not the point at which impairment begins.