Scientific investigations have produced 50 years of accumulated evidence showing a direct relationship between increasing blood alcohol concentration (BAC) in drivers and increasing risk of a motor vehicle crash. There is scientific consensus that alcohol causes deterioration of driving skills beginning at 0.05% BAC or even lower, and progressively serious impairment at higher BACs. Drivers aged 16 to 24 years have the highest representation of all age groups in alcohol-related road crashes; young drivers involved in alcohol-related fatal crashes have lower average BACs than older drivers. Alcohol impairs driving skills by its effects on the central nervous system, acting like a general anesthetic. It renders slower and less efficient both information acquisition and information processing, making divided-attention tasks such as steering and braking more difficult to carry out without error. The influence of alcohol on emotions and attitudes may be a crash risk factor related to driving style in addition to driving skill. Biologic variability among humans produces substantial differences in alcohol influence and alcohol tolerance, making virtually useless any attempts to fix a "safe" drinking level for drivers. The American Medical Association supports a policy recommending (1) public education urging drivers not to drink, (2) adoption by all states of 0.05% BAC as per se evidence of alcohol-impaired driving, (3) 21 years as the legal drinking age in all states, (4) adoption by all states of administrative driver's license suspension in driving-under-the-influence cases, and (5) encouragement for the automobile industry to develop a safety module that thwarts operation of a motor vehicle by an intoxicated person.
Alcohol and the Driver. JAMA. 1986;255(4):522-527. doi:10.1001/jama.1986.03370040096031