Effects on Operating a Vehicle

When alcohol is consumed, many of the skills that safe driving requires–such as judgment, concentration, comprehension, coordination, visual acuity, and reaction time–become impaired.


The mental faculties are the first to be affected by drinking. Alcohol levels as low as .02% (well under the legal limit in many states) can lessen the capacity to reason, making it difficult to plan ahead or respond appropriately to one’s immediate surroundings.


Individuals who have consumed small amounts of alcohol experience a notable decline in their ability to focus on the task at hand. Many alcohol-related traffic accidents are caused because an intoxicated driver has a very short attention span. Drunk drivers are a lot more likely to become distracted, and as soon as they stop focusing on the road, crashes are likely to occur.


Drivers must be able to receive and interpret sensory information. On the road, the ability to make reasonable assessments at a moment’s notice is an indispensable skill. Research has shown that when a driver is intoxicated, the amount of sensory input they are able to correctly interpret and respond to is decreased.


Alcohol assails our ability to see clearly and control the movement of our eyes. Studies have shown that when a person is intoxicated, they tend to focus on a single, often central, point for a long period of time. Drunk drivers are therefore less cognizant of important peripheral zones.

Visual acuity and motor control of the eyes also decline as alcohol is absorbed into the bloodstream. These skills are affected at a very slow rate, however, and many researchers do not believe their impact is significant enough to account for alcohol-related traffic accidents.

Reaction Time

Studies have shown that when under the influence of alcohol, drivers are not able to respond to stimuli as quickly as when sober. In an ordinary state, a driver would be able to respond to a car breaking suddenly or a child running across the street with enough time to prevent serious damage.

When a driver is drunk, it takes longer for his or her brain to process all of the data being received. Attention spans are shortened, vision may be blurred, ability to interpret information is diminished, and judgment may be skewed. All of these skills are prerequisites for driving a motor vehicle, and when they are impaired by alcohol, drivers should refrain from starting the engine.