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According to the CDC (2018), about half (53%) of U.S. adults can be considered “regular” drinkers; that is, they have consumed at least 12 drinks during the previous year. An estimated 147 million trips are made annually by drivers with BACs of .08 g/dL or higher (Barry et al., 2022). The 2013-2014 National Roadside Survey found 8.3% of drivers on weekend nights have positive BACs, while 1.5% have BACs of .08 g/dL or higher (Berning et al., 2015). This represents a significant reduction from 2007, when 12.4% of drivers had positive BACs and 2.2% had BACs of .08 g/dL or higher. The percentage of drivers drinking on weekend nights has fallen dramatically since the first National Roadside Survey in 1973, which found that 35.9% of drivers had positive BACs and 7.5% of drivers had BACs of .08 g/dL or higher (Berning et al., 2015).

An AAAFTS survey of 2,725 U.S. residents conducted in 2020 found 94% believed it is extremely or very dangerous to drive after drinking enough alcohol to be over the legal limit. Nonetheless, 6% reported having done so within the past 30 days (AAAFTS, 2021). Seven percent of people reported having ridden with a drinking driver in the past 12 months (Fan et al., 2019).

Alcohol-impaired drivers include both drinkers who may occasionally drive after drinking too much, as well as persistent offenders who regularly drive while impaired. Impaired drivers may be considered “high risk” if they have high BACs, prior convictions, or alcohol use problems. For example, among drivers involved in fatal crashes during 2021 with positive BACs (.01 g/dL or higher), over half (55%) had BACs at or above .15 g/dL (NCSA, 2023a). Additionally, one-quarter of all drivers arrested for impaired driving and 30% of drivers convicted of impaired driving have had prior DWI convictions (Warren-Kigenyi & Coleman, 2014). In 2021 some 7% of drivers involved in fatal motor vehicle crashes with BACs of .08 g/dL or above had been convicted of DWI in the past 5 years, compared to 2% of sober drivers (NCSA, 2023a).

Other characteristics of drivers in alcohol-related fatal crashes include the following (NCSA, 2023a):

  • Sex: There are about four male alcohol-impaired drivers in fatal crashes for every female alcohol-impaired driver.
  • Age: Drivers 21 to 24 and 35 to 44 have the highest percentages (27% each) of alcohol impairment in fatal crashes of any age group.
  • Vehicle type: Motorcycle riders have a higher percentage (28%) of alcohol impairment in fatal crashes than drivers of passenger cars (24%), light trucks (20%) or large trucks (3%).
  • Restraint use: Among passenger vehicle drivers who were alcohol-impaired and killed in crashes, 65% were unrestrained.

Alcohol impairment among drivers involved in fatal crashes is nearly three times higher at night than during the day (NCSA, 2023a). Alcohol involvement is also much higher in fatal crashes on weekends (28%) than on weekdays (16%). Thirty-three percent of all drivers involved in single-vehicle fatal crashes are alcohol-impaired, compared to 14% in multivehicle fatal crashes. A substantial proportion of pedestrians killed in crashes also have high BACs—almost than one-third (30%) of fatally injured pedestrians have BACs of .08 g/dL or higher (NCSA, 2023b). These pedestrians tend to be older males, and the crashes typically occur on weekend nights at non-intersection locations (Hezaveh & Cherry, 2018). In addition, Blomberg et al. (2019) found that people with prior alcohol-related driving offenses may be at greater risk for being killed as high-BAC pedestrians than those without prior alcohol offenses.

Alcohol-impaired driving fatalities are affected by several external factors including geography, urbanization, road structure and conditions, and economic activity, as well as by a State’s laws and programs. For these reasons both the current level of alcohol-impaired driving and the progress in reducing alcohol-impaired driving vary greatly from State to State. For example, comparing all 50 States and the District of Columbia, the proportion of traffic fatalities involving drivers with BACs of .08 g/dL or higher in 2021 ranged from 20% in the lowest State, Mississippi, to 44% in the highest, Montana (NCSA, 2023a).

Four basic strategies are used to reduce impaired driving crashes and driving under the influence.

  • Deterrence: Enact, publicize, enforce, and adjudicate laws prohibiting impaired driving so people choose not to drive impaired.
  • Prevention: Reduce drinking and keep impaired drivers from driving.
  • Communications and outreach: Inform the public of the dangers of impaired driving and establish positive social norms that make driving while impaired unacceptable.
  • Alcohol treatment: Reduce alcohol dependency or addiction among drivers.

Deterrence Is Key

Deterrence works by changing behavior through the fear of apprehension and punishment. If drivers believe impaired driving is likely to be detected and impaired drivers are likely to be arrested, convicted, and punished, many will not drive while impaired by alcohol. This strategy, called general deterrence, influences the general driving public. An example of general deterrence would be well-publicized and highly visible enforcement activities, such as sobriety checkpoints. In contrast, specific deterrence refers to efforts to influence drivers who have been arrested for impaired driving so they will not continue to drive while impaired by alcohol. An example of this approach would include ignition interlocks or vehicle sanctions for DWI offenders.

Deterrence works when consequences are swift, sure, and severe (with swift and sure being more important in affecting behavior than severe). Deterrence, however, is far from straightforward, and complexities can limit the success of deterrence measures. For instance:

  • Detecting impaired drivers is difficult. Law enforcement agencies have limited resources and officers must observe a traffic violation or other aberrant behavior before they can stop a motorist for an investigation of impaired driving (except at checkpoints). There are times when a stop is for something completely unrelated, but the stop may turn into an impaired-driving investigation if indicators are present once the officer and driver are face to face.
  • Conviction also may be difficult. DWI laws are complicated, the evidence needed to define and demonstrate impairment is complex, and judges and juries may not choose to impose specified penalties if they believe the penalties are too severe.
  • The DWI control system is complex. There are many opportunities for breakdowns in the system that allow impaired drivers to avoid penalties and screening/assessment to address the underlying causes of substance use misuse.

A State’s DWI control system consists of its DWI laws and the enforcement, prosecution, adjudication, and offender monitoring policies and programs to support the laws. In this system, the operations of each component affect all the other components. Each new policy, law, or program affects operations throughout the system, sometimes in ways that are not anticipated. This guide documents 23 specific impaired-driving countermeasures in three groups: (1) legislation and licensing, (2) enforcement, and (3) other strategies for behavior change. But the overall DWI control system, including its management and leadership, is more important than any individual countermeasure.

Studies have highlighted the key characteristics of an efficient and effective DWI control system (Hedlund & McCartt, 2002; Robertson & Simpson, 2002):

  • Training and education for law enforcement, prosecutors, judges, and probation officers.
  • Record systems that are accurate, up-to-date, easily accessible, and able to track each DWI offender from arrest through the completion of all sentence requirements.
  • Adequate resources for staff, facilities, training, equipment, and new technology.
  • Coordination and cooperation within and across all components.

A few of the countermeasures discussed in this chapter, such as BAC test refusal penalties, alcohol-impaired-driving law review, and DWI courts are directed at improving DWI system operations. In some instances, the most important action that SHSOs can take to reduce alcohol-impaired driving is to review and improve DWI control system operations, perhaps using a State DWI task force or a State impaired-driving program assessment.

Ulmer et al. (1999) investigated why some States reduced alcohol-related traffic fatalities more than others. They concluded that there is no “silver bullet,” i.e., no single critical law, enforcement practice, or communications strategy. Once a State has effective laws, HVE, and substantial communications and outreach to support them, the critical factors are strong leadership, a commitment to reducing impaired driving, and adequate funding. Although 2 decades have passed, the basic findings are still applicable. SHSOs should keep this in mind as they consider the specific countermeasures in this chapter.

Many other traffic safety countermeasures help reduce impaired-driving-related crashes and casualties but are not discussed in this chapter. For example, improved vehicle structures and centerline rumble strips and barriers may reduce the likelihood of crashes or injuries sustained by impaired drivers. Additionally, higher alcohol taxes and reduced/limited alcohol sales/outlets can affect alcohol-impaired driving and crashes. These types of countermeasures are not included in this chapter as SHSOs have little or no authority or responsibility for them.