Despite declines in teen drinking, alcohol continues to be a big factor in teen crashes. In 2021, 26 percent of fatally injured passenger vehicle drivers ages 16-19 had positive blood alcohol concentrations (BACs).
Young drivers are less likely than adults to drive after drinking alcohol, but their crash risk is substantially higher when they do. This is especially true at low and moderate BACs and is thought to result from the relative inexperience of young drivers with drinking, with driving, and with combining the two (Mayhew et al., 1986).
At the same BAC, drivers ages 16-20 are far more likely than older drivers to get into a fatal or nonfatal crash (Peck et al., 2008; Voas at al., 2012).
Drivers ages 16-20 with BACs of 0.05-0.079 percent are 12 times more likely to be killed in single-vehicle crashes than sober teenage drivers (Voas at al., 2012). At BACs of 0.08-0.099, fatality risk is even higher, 32 times that of sober drivers. At the same BAC, the risk of involvement in a fatal crash and the risk of dying in a single-vehicle crash are the same for 16-20 year-old male and female drivers.
The drinking age of 21 limits access to alcohol among teenagers. In the 1960s and early 1970s, many states lowered their minimum purchasing ages from 21 to 18 or 19 (McCartt et al., 2010). However, states gradually restored higher minimum purchasing ages so that, by the end of 1984, 22 states had minimum purchasing ages of 21 in effect. Federal legislation was enacted to withhold highway funds from the remaining 28 states if they did not follow suit. Since July 1988, the minimum alcohol purchase age has been 21 in all 50 states and the District of Columbia.
When many states lowered the minimum alcohol purchasing age in the 1960s and early 1970s, Institute research indicated an increase in the number of drivers younger than 21 involved in nighttime fatal crashes (Williams et al., 1975). As states restored the minimum legal drinking age to 21, numerous studies found that doing so reduced teenage crashes (Williams et al., 1983; DuMouchel et al., 1987; General Accounting Office, 1987; O'Malley & Wagenaar, 1991; Shults et al., 2001; Wagenaar & Toomey, 2002). The National Highway Traffic Safety Administration estimates that laws establishing 21 as the minimum purchase age in every state saved 2,624 lives during 2012-16 (NHTSA, 2016).
In all 50 states and D.C. people younger than 21 are prohibited from driving after drinking. Typically, these laws prohibit driving with a BAC of 0.02 percent or greater. Federal legislation enacted in 1995 that allowed for the withholding of highway funds played a role in motivating states to pass such zero-tolerance laws.
Studies of zero-tolerance laws indicate they reduce crashes among drivers younger than 21. A study of 12 states that passed zero-tolerance laws reported a 20 percent reduction in the proportion of fatal crashes that were single-vehicle nighttime events (a category of crashes likely to involve alcohol impairment) among drivers ages 15-20 (Hingson et al., 1994). A more recent study considered relative contributions of a wide range of alcohol possession, consumption, and intoxicated driving laws on teen drivers and concluded that future reductions in alcohol-related crashes among teen drivers would be achieved through policies and efforts that targeted teen drinking behavior, rather than by further limiting teen driving (Romano, et. al., 2015).
The percentage of high school seniors who report driving after drinking declined from 16 percent in 2001 to 9 percent in 2011, according to a nationally representative survey (O'Malley & Johnston, 2013). A different nationally representative annual survey found that, in 2015, within the 30 days prior to taking the survey, 8 percent of high school students drove after drinking alcohol, and 20 percent reported riding with a driver who had been drinking (Kann et al., 2016).
States and communities could further reduce teen drinking and driving by making it more difficult for teenagers to obtain alcohol. A study of 45 communities in Oregon conducted in 2005 found that alcohol was sold to youthful-looking decoys on 34 percent of purchase attempts (Paschall et al., 2007).
According to an annual survey of young people in the United States, the perceived availability of alcohol has declined significantly among eighth and 10th graders since 1996 but has been fairly steady among high school seniors (Johnston et al., 2019). In 2018, 86 percent of high school seniors believed it was fairly easy or very easy to get alcohol.
IIHS researchers found zero-tolerance laws difficult to enforce in some states because police must suspect that a young driver has a high BAC before administering an alcohol test for any measurable BAC (Ferguson et al., 2000). Offenders with low BACs may not display the erratic driving that leads to a traffic stop. Surveys of young people in three states found limited knowledge about zero-tolerance laws, and many of those who knew about the laws did not believe they were enforced often (Ferguson & Williams, 2002).
When zero-tolerance laws are enforced they can be effective. An IIHS study of Washington state’s zero-tolerance law found that it increased the likelihood that an underage person would be sanctioned for drinking and driving, especially among drivers with BACs less than 0.08 percent (McCartt et al., 2007). An IIHS study in West Virginia found that a college community’s program of publicized, strong enforcement of minimum alcohol purchasing age laws and drinking and driving laws, including the zero-tolerance law, was associated with significant reductions in young drivers’ BACs, relative to young drivers in a comparison community without an enforcement program (McCartt et al., 2009).