more for younger drivers than it does for drivers above the age of 21 (Zador, 1991). A more recent national analysis found that in all age and gender groups, there was at least an 11-fold increased risk of single-vehicle fatal crash involvement at a blood alcohol level of 0.08 percent (the legal limit for intoxication for adults in most states). However, for male drivers ages 16 to 20, there was a 52-fold increased single-vehicle fatal crash risk (Zador, Krawchek, and Voas, 2000).
The National Survey of Drinking and Driving conducted for NHTSA in 1999 (National Highway Traffic Safety Administration, 2000) reported that 2 percent of 16- to 20-year-old drivers drove within two hours of drinking in the past month. Though this percentage is substantially lower than the 12 percent reported by all drivers ages 16 and older, drivers ages 16 to 20 drove 12 million times in the preceding year within two hours of drinking (95 percent CI 4, 119). Those drinking driving trips averaged 11 miles in length compared to 14 for all drinking driving trips among drivers ages 16 and older. Particularly disturbing, however, was that when NHTSA calculated the average blood alcohol concentration (BAC) of drivers during their most recent drinking driving trip—based on weight, hours of drinking, gender, volume of consumption, length of drinking episode—and time since last drink, the average calculated BAC for 16- to 20-year-old drivers was 0.10 percent, more than 3 times the level for drivers of all ages and at or above the legal limit for adult drivers in every state. A 170-pound man would have to consume 5 drinks in an hour on an empty stomach to reach a blood alcohol level of 0.10 percent. Furthermore, 40 percent of those 16-to 20-year-olds were driving with another passenger in the vehicle during their most recent drinking driving trip, thereby risking not only their own life but the lives of others. Four percent were driving with children under the age of 15.
Of note, 44 percent of the 16- to 20-year-old drinking drivers believed they were driving at levels that exceeded the legal limit. In other words, nearly half reported engaging in behavior they knew was illegal. Of parallel concern, it is illegal for all persons under age 21 to drive after any drinking, and 56 percent, a majority, who did so did not recognize that they were engaging in illegal behavior. Studies of states that adopted laws making it illegal for persons under 21 to drive after drinking relative to other states have achieved 18 percent declines in driving after any drinking, 23 percent declines in driving after 5+ drinks (Wagenaar, 2001), and 21 percent decline in the type of fatal crash most likely to involve alcohol (single vehicle at night) among drivers under 21 (Hingson, Heeren, and Winter, 1994). In studies where teen awareness of the law has been heightened, significantly greater declines in alcohol-related crashes among drivers under 21 have been recorded (Blomberg, 1992).