The effect of alcohol on an individual is determined primarily by two factors: the amount of alcohol consumed and the rate at which it is absorbed by the body. Other contributing factors include gender, body weight, alcohol tolerance, mood, environment and the amount of food consumed.
From the first drink, alcohol affects coordination and judgment. Even with a BAC well below .08 percent, a person's reaction time slows. The risk of being in a crash begins to increase between a BAC of .04 and .05 percent