According to the Florida Department of Highway Safety and Motor Vehicles, a person under the influence of alcohol experiences:
A decreased reaction time: The amount of time that a drunk person takes to respond is longer than someone who isnt drunk. This can translate to a driver not seeing or adequately avoiding an obstruction in the road, pedestrian, or another car.
Problems with short-term memory: A person who has been drinking may forget where they are, how they got in the car, or where they were beforehand.
Lessened hand-to-eye coordination: Alcohol even in small amounts affects a persons ability to coordinate movements between their hands or feet and other parts of the body. While driving, this impairment affects all of the actions needed to operate a motor vehicle, like steering the car, pressing the accelerator pedal, brake pedal, changing gears and using the clutch on a car with a manual transmission, and completing actions in the usual way. For example, a drunk driver may not be able to press the brake pedal to stop the car or remember to put the car in park.
Difficulty concentrating: Operating any type of vehicle requires great focus and alertness to surroundings like other vehicles and traffic lights. Someone who has consumed alcohol can become easily distracted or even oblivious to the task at hand, which is driving the car. Even if the person tries to concentrate, their intoxication prevents them from being able to. With shifted or no focus on driving, a car could crash into other vehicles or surroundings.
Problems with depth and distance perception: While driving, you must know when you should brake or your distance from a stop sign or traffic light. A drunk driver may have problems judging the proximity of other cars, stoplights, pedestrians, or obstacles. Because of this and their lessened response times, they cause crashes.