Young drivers' evaluation of driving impairment due to alcohol

Ninety-six college students, 18-20 years of age, were selected from three drinking categories (abstain-light, moderate, and heavy) based on their self-reported drinking habits. Subjects rated the relative importance of three driving components (attention, control/maneuvering, and emergency responses) for safe driving and the impairment each component and overall driving ability would sustain after driver drinking. Impairment ratings were made of the effects of drinking the number of drinks that would have resulted in the rater having blood alcohol concentrations (BACs) of .05%, .10%, and .15%. Subjects also estimated the number of drinks that they could consume in one hour and then safely drive after after different time periods, the time they should wait before driving after drinking various amounts of alcohol, and the number of beer, wine, wine cooler, and whiskey drinks that would cause them to reach a .10% BAC. While the driving components were rated to be of approximately equal importance for safe driving, the emergency responses component was judged to be more impaired following alcohol consumption than any of the other components, or overall driving ability. Heavy drinkers judged that there was significantly less driving impairment due to alcohol than did light or moderate drinkers in the case of overall driving ability and all of the driving components except emergency responses. Heavy drinkers also judged it safe to consume a number of drinks before driving that would result in higher mean BACs than those of light and moderate drinkers. Both drinking category and gender differences were found in the estimated BAC values that would have occurred at the time of driving after waiting periods judged by subjects to be sufficient for safe driving.