Driving while impaired refers to operating a motor vehicle while under the influence of alcohol. In the United States, it is often defined as a blood alcohol content greater than or equal to 0.08%. Yet, every state has unique laws with BAC limits.
Becoming informed about how alcohol affects your ability to operate a vehicle is crucial to preventing the unnecessary injury and death caused by drunk driving.
The Reality of Drunk Driving

Approximately 30% of all traffic crash fatalities in the United States involve drunk driving. In every state, it is illegal to drive drunk.

Car crashes are a leading cause of death for teens, and one-quarter of those crashes involve underage age drinking.

Statistically, the highest percentage of drunk drivers are those aged 12 to 24.

Impaired driving costs the United States $44 billion annually.
How an Individual Can Prevent Drunk Driving
Everyone operating a vehicle in any capacity can be a responsible driver. If you are drinking, do not drive.
- Plan your ride home before the party starts.
- Do not let other people drink and drive, take their keys away.
- Call a taxi, Uber, ride service, use a designated driver, or take public transit.
- When hosting a party, ensure all guests leave with a sober driver.
How Communities Can Reduce or Prevent Impaired Driving
There are proven methods to prevent people from drinking and driving.
- Sobriety checkpoints operated by police. More widespread, frequent use of these checkpoints could save lives.
- Minimum legal drinking age laws. Keeping and enforcing 21 as the minimum legal drinking age.
- Ignition interlock devices prevent convicted alcohol-impaired drivers from operating vehicles if they have been drinking.
- Lower blood alcohol concentration limits.
- Zero tolerance laws make it illegal for people under the age of 21 to drive with any measurable amount of alcohol.
- Alcohol use disorder assessment and treatment programs.
- Alcohol screening and brief interventions. Identifying people who drink alcohol in excess and offer help.
- School-based instructional programs.
BAC Levels and What to Expect
Blood alcohol concentration is a standard measure of the amount of alcohol in your system. It is measured as a percentage where 0.01% would represent one part ethyl alcohol per 10 000 parts of blood. Driving with a BAC of 0.08% or higher in the United States is illegal. For people under the age of 21, the legal limit is between 0.0 and 0.2%, depending on the state. Although 0.08% is where driving becomes illegal, a much lower BAC could impair someone to the point where driving becomes dangerous. Different factors can impact blood alcohol concentration, including:
- Number of drinks
- How fast one drinks them
- How much a person weighs
- The digestive system of the individual
- The sex of the person as well as hormone levels
- Food intake before and while drinking
Below are the different levels of impairment corresponding to the BAC. However, each person is different, and the level of impairment could be worse even if the BAC is relatively low.
- 0.0% to 0.05%
At this level, one might experience mild speech, memory, attention, and coordination impairment. A person might feel more relaxed, and they can start feeling sleepy. Depending on how affected the individual is, it can be dangerous to get behind the wheel even at this stage.
- 0.06% to 0.15%
The relaxation begins to become intoxication, and speech, memory, attention, and coordination are further impaired. One experiences severe impairment in the skills required to drive. A person could start displaying some aggression. At this point, there is an increased risk of the person injuring themselves or others.
- 0.16% to 0.30%
A person becomes severely impaired (memory, speech, coordination, attention, reaction time), and other driving skills are also dangerously impaired. At this point, a person might have blackouts (they can do things and will not remember any of it when they sober up). They might start vomiting and exhibiting other symptoms of alcohol overdose. At this level, one can lose consciousness.
- 0.31% to 0.45%
This level of intoxication is life-threatening, and there is a risk of life-threatening alcohol overdose. A person can lose consciousness at this stage. Alcohol suppresses vital life functions in the drinker’s body and can be fatal if left untreated.