Driving a car safely means getting a complicated piece of machinery from point A to point B, without crashing. The driving task taps almost all our basic skills - perception, attention, judgement, decision-making, physical reactions and our ability to coordinate these skills. Because alcohol influences each of these skills, it has many adverse affects on driving.

Perhaps the most important skill for drivers is to see or perceive. Even before hitting the road, the impaired driver may have trouble getting out from between parked cars. Our ability to judge distances between stationary objects is reduced at BACs over 80 mg. percent.

Once on the road, the ability to estimate distances between moving objects is also reduced. Some people are affected this way if their BAC is as low as 20 mg. percent. Virtually everyone's vision is affected at BACs of 100 mg. percent.

Driving at night involves additional problems, especially for older drivers who don't see as well in the dark as they used to. The ability to adjust from to sudden darkness, called darkness adaptation, is impaired at BACs at the legal limit and higher. The greater the concentration of alcohol in the blood, the longer the glare recovery time. This refers to the period of time during which a person is partially blinded when exposed briefly to bright lights and the to darkness. This happens each time the headlights of an oncoming vehicle pass you.