Alcohol and Drunk Driving

Medically reviewed by:

In the US, 32 people die every day due to drunk-driving related incidents. In 2020, the annual total rose to 11,654 – a 14 percent increase from the year before. These deaths occur because drivers’ BAC levels are above the legal limit, rendering them unfit to drive.

This page will discuss blood alcohol content levels, how alcohol impairs one’s ability to drive, and the risks of driving under the influence.

What is driving Under the Influence?

This involves driving or operating a vehicle when they are incapable of operating a motor vehicle safely due to being under the influence. Objectively, this means having a BAC level of at least 0.08 percent. Motor vehicles don’t just include cars, but motorcycles, jet-skis, and boats as well.

How Alcohol Affects the Brain

When the alcohol levels in your body rise, it leads to increasingly negative effects on the central nervous system. It’s absorbed through the small intestine and goes into the bloodstream. From there, it’s broken down by the liver. Your body’s alcohol concentration level is measured through blood alcohol content, which is in grams of alcohol per deciliter.

Poor Judgment

While driving a motor vehicle, you need to foresee potential issues to make clear decisions. Under the influence of alcohol, you lose awareness of your surroundings, which impairs your ability to make quick decisions.

Affects Vision

Excessive amounts of alcohol in the bloodstream can negatively affect vision. After having a couple of drinks, you may feel like your vision is blurry and that you’re not able to control your eye movement. It can affect your ability to judge the distance between your vehicle and others on the road. Similarly, you may see fewer objects when looking straight ahead.

Lowers Concentration

Regardless of the amount you consume, alcohol can affect your concentration. When you’re on the road, various things require your complete attention, such as traffic signals, other vehicles on the road, and staying in your lane. When you have a couple of drinks, your attention span reduces significantly, which increases the risk of getting into an accident.

Lack of Coordination

Heavy drinking can take a toll on your motor skills, which includes coordination between the hands, eyes, and feet. Without proper coordination, you won’t be able to swerve during a dangerous situation on the road. Some of the signs of poor coordination due to alcohol intake include the inability to stand straight, swaying, and having trouble walking in a straight line. Too much alcohol can even make it hard to get in your car and insert the keys into the ignition.

Slower Reaction Time

When there’s alcohol in your system, it impacts how quickly you can respond to urgent situations. Specifically, it increases your response time, which translates into a higher chance of facing an accident. Common examples of such situations include a pedestrian crossing the street or the car in front of you braking suddenly. If you’re under the influence of alcohol, it can take longer to process different stimuli and take the necessary action to prevent an accident.

Consequences of Driving When Drunk

If you drive under the influence and survive a crash that ends up injuring or killing other drivers, you’ll have to live with immense emotional burden and guilt. There are physical consequences of driving while under the influence as well. If you are involved in an accident due to impaired driving, it can cause brain damage, disfigurement, or paralysis. In some cases, it can lead to death.

It’s also a crime to drive while under the influence of alcohol in the US. Some of the common penalties you may face include license suspension, fines, jail time, and community service. You may even be required to install an ignition interlock device in your car. Fines can range anywhere between $500 and $2000, and it goes on your criminal record as well.

Blood Alcohol Content Levels and Effects on Driving

In the US, the legal alcohol limit is 0.08 percent, so it’s illegal to drive when your BAC is in excess of 80 mg/100 mL of blood. Even so, it’s important to remember that alcohol can affect various senses after just one drink. Here’s how different BAC levels affect your ability to drive.

  • BAC Level of 0.02 means causes a decline in visual functions, like keeping track of a moving target, and performing two tasks at one time through divided attention. You lose some of your judgment skills and feel relaxed.
  • BAC Level of 0.05 leads to poor coordination, impaired ability to track moving vehicles, difficulty in controlling the steering, and delayed response in emergency driving situations. You may show signs of exaggerated behavior, lose ability to focus the eyes, and have impaired judgment.
  • BAC Level of 0.08 can lead to low concentration and information processing ability, which affects your ability to detect signals. You may have impaired perception and short-term memory loss, making it difficult to navigate. This is due to poor muscle coordination, judgment, and reasoning.
  • BAC Level of 0.10 reduces your ability to brake when needed and stay in your lane. You show poor reaction time, impaired coordination, and slurred speech. You also experience slower thinking, which causes a delay in your response time.
  • BAC Level of 0.15 leads to considerable impairment in your control of the vehicle, attention to the road, and visual-auditory information processing. Your body shows much less muscle control and extreme loss of balance.

Risk Factors

Certain factors predispose you to a higher risk of driving under the influence. They are as follows:

Adolescents and Young Adults

Teenagers and young adults are part of the demographic that’s at most risk of being involved in alcohol-related car accidents. Compared to older people, young people are at a greater risk of being involved in a car crash at any BAC level.


Studies show that motorcyclists have a higher likelihood of being involved in a crash. In contrast to alcohol-impaired car drivers, they’re likely to be responsible for single-vehicle crashes.