March 2014

  1. What is alcohol-impaired driving?

    What many people refer to as "drunk driving" is more precisely described as "alcohol-impaired driving." In fact, many alcohol-impaired drivers do not appear drunk in the stereotypical way. Even small amounts of alcohol can impair the skills involved in driving, but the persistent notion that the problem is predominantly one of drunk drivers has allowed many drinking drivers to decide they are not part of the problem. 

  2. What does blood alcohol concentration (BAC) measure?

    A BAC describes the amount of alcohol in a person's blood, expressed as weight of alcohol per unit of volume of blood. For example, 0.08 percent BAC indicates 80 mg of alcohol per 100 ml of blood. However, a blood sample is not necessary to determine a person's BAC. It can be measured more simply by analyzing exhaled breath.

  3. What BAC is considered illegal for drivers?

    All 50 states and the District of Columbia have per se laws making it a crime to drive with a BAC at or above 0.08 percent. In all 50 states, drivers younger than 21 are prohibited from operating a vehicle with any detectable blood alcohol. Most states define this as a BAC at or above 0.02 percent.

  4. What is the effect of alcohol on crash risk?

    In general, the probability of a fatal crash increases steadily with increasing driver BAC. Fatal crash risk increases substantially after 0.05 percent BAC and climbs more rapidly after 0.08 percent. Voas, R.B.; Torres, P.; Romano, E.; and Lacey, J.H. 2012. Alcohol-related risk of driver fatalities: an update using 2007 data. Journal of Studies on Alcohol and Drugs 73(3):341-50. At all BACs, the fatal crash risk is much higher among 16-20 year-old drivers than among drivers 21 and older. At a BAC of 0.08 percent compared to a zero BAC, the likelihood of involvement in a fatal crash is 10 times as high among 16-20 year-old drivers, 7 times as high among drivers ages 21-34, and 6 times as high among drivers 35 and older. At the same BAC, fatal crash risk is the same for male and female drivers in a given age group.

    The likelihood of involvement in a crash of any severity also increases steadily with increasing driver BAC. Peck, R.C.; Gebers, M.A.; Voas, R.B.; and Romano, E. 2008. The relationship between blood alcohol concentration (BAC), age, and crash risk. Journal of Safety Research 39(3):311-9.  The risks for drivers younger than 21 are much higher than the risks for drivers 21 and older across the range of BACs. At a BAC of 0.08 percent compared to a zero BAC, 16-20 year-old drivers are more than 7 times as likely to crash, and drivers 21 and older are about 1.6 times as likely to crash.

  5. How many drinks does it take to become significantly impaired?

    The effects of alcohol vary greatly because the rate of absorption and the BAC attained varies from person to person due to factors such as weight, amount of fat tissue and stomach contents. Some people can be substantially impaired after two drinks. In addition, women can attain higher BACs and become more impaired than men who weigh the same and consume the same amount of alcohol because alcohol is processed differently by women and men.

    Various organizations have developed charts intended to help people estimate their BACs based on the number of drinks consumed. These tables can be used to estimate BACs, but they are subject to error.

  6. Are beer and wine less impairing than hard liquor?

    Impairment is not determined by the type of drink but rather by the amount of alcohol ingested over a specific period of time. There is a similar amount of alcohol in such standard drinks as a 12-ounce glass of beer, a 4-ounce glass of wine, and 1.25 ounces of 80-proof liquor.

  7. What proportion of motor vehicle crashes involves alcohol?

    The most reliable information about alcohol involvement comes from fatal crashes. The proportion of fatally injured drivers with BACs at or above 0.08 percent has remained about a third since 1994 after declining from nearly half in 1982. Such statistics do not mean that a third or more of all fatal crashes are caused solely by alcohol because alcohol may be only one of several factors that contribute to a crash involving drinking drivers. An Institute study estimated that 10,600 deaths in 2010 were directly attributable to alcohol. Lund, A.K.; McCartt, A.T.; and Farmer, C.M. 2012. Contribution of alcohol-impaired driving to motor vehicle crash deaths in 2010. Arlington, VA: Insurance Institute for Highway Safety.   These lives could have been saved if all drivers had BACs of zero. An estimated 7,082 deaths would have been prevented if all drivers with BACs of 0.08 percent or higher were kept off the roads. Applying the same methods yields an estimate of 7,132 preventable deaths if all drivers with BACs of 0.08 or higher were kept off the roads in 2012.

    Alcohol involvement is much lower in nonfatal crashes, but it is still quite high. A study conducted during the 1960s estimated that 9 percent of drivers in injury crashes and 5 percent of drivers in noninjury crashes in Grand Rapids, Mich., had BACs at or above 0.10 percent. Borkenstein, R.F.; Crowther, R.F.; Shumate, R.P.; Ziel, W.B.; and Zylman, R. 1964. The role of the drinking driver in traffic accidents. Bloomington, IN: Department of Police Administration, Indiana University. A 1977 study found that 12 percent of drivers in injury crashes in Huntsville, Ala., and San Diego, Calif., had BACs at or above 0.10 percent, compared with 1 percent of a sample of drivers not involved in crashes. Farris, R.; Malone, T.B.; and Kirkpatrick, M. 1977. A comparison of alcohol involvement in exposed and injured drivers. Report no. DOT HS-400-954. Washington, DC: National Highway Traffic Safety Administration. More recently, a study conducted during 1996-98 gathered BAC measurements from drivers involved in evening and nighttime crashes of all severities in two cities and from a comparable group of non-crash-involved drivers. Blomberg, R.D.; Peck, R.C.; Moskowitz, H.; Burns, M.; Fiorentino, D. 2005. Crash risk of alcohol involved driving: a case-control study. Stamford, CT: Dunlap and Associates, Inc.  The proportion of crash-involved drivers with BACs of 0.09 percent or higher was 11 percent, compared to 2 percent for non-crash-involved drivers.

  8. How has the prevalence of alcohol-impaired driving changed over time?

    Alcohol-impaired driving has become less prevalent but remains a major problem. In 2007, the National Highway Traffic Safety Administration (NHTSA) undertook a national roadside breath survey in which data were collected during weekend nights. Patterned after 1996, 1986 and 1973 surveys, the 2007 survey found that 2.2 percent of drivers had BACs at or above 0.08 percent. Lacey, J.H.; Kelley-Baker, T.; Furr-Holden, D.; Voas, R.B.; Romano, E.; Torres, P. Tippetts, A.S.; Ramirez, A.; Brainard, K.; and Berning, A. 2009. 2007 National Roadside Survey of Alcohol and Drug Use by Drivers. Report No. DOT HS-811-248. Washington, DC: National Highway Traffic Safety Administration.  This compares with 4.3 percent in 1996, 5.4 percent in 1986 and 7.5 percent in 1973.  The percentage of drivers with any detectable alcohol in their systems declined almost as much from 1973 to 2007 as the percentage of drivers with BACs at or above 0.08 percent.

    Although the roadside surveys suggest that the prevalence of alcohol-impaired driving has gone down over time, the proportion of fatally injured drivers with BACs at or above 0.08 percent has remained about a third since 1994 after declining from nearly half in 1982.

  9. Does alcohol-impaired driving differ by gender?

    Male drivers are significantly more likely to have BACs at or above 0.08 percent than female drivers (2.6 percent versus 1.5 percent), according to the 2007 national roadside alcohol survey. Lacey, J.H.; Kelley-Baker, T.; Furr-Holden, D.; Voas, R.B.; Romano, E.; Torres, P. Tippetts, A.S.; Ramirez, A.; Brainard, K.; and Berning, A. 2009. 2007 National Roadside Survey of Alcohol and Drug Use by Drivers. Report No. DOT HS-811-248. Washington, DC: National Highway Traffic Safety Administration.  Both percentages were lower than in 1996, when 5 percent of males and 3 percent of females had BACs at or above 0.08 percent. Insurance Institute for Highway Safety. 2012. [Unpublished analysis of data from the U.S. Department of Transportation's and Insurance Institute for Highway Safety’s1996 National Roadside Survey of Alcohol Use by Drivers and  the U.S. Department of Transportation’s 2007 National Roadside Survey of Alcohol and Drug Use by Drivers]. Arlington, VA.

    Crashes among male drivers are much more likely to involve alcohol than those among female drivers. Among fatally injured male drivers of passenger vehicles in 2012, 38 percent had BACs at or above 0.08 percent. The corresponding proportion among female drivers was 20 percent. Alcohol impairment in fatal crashes was highest for males ages 21-40. In 1982, the proportion of fatally injured passenger vehicle drivers with BACs at or above 0.08 percent was 56 percent among males and 33 percent among females.

  10. When do alcohol-impaired driving crashes occur?

    They happen at all hours, but alcohol involvement in crashes peaks at night and is higher on weekends than on weekdays. Among passenger vehicle drivers who were fatally injured between 9 p.m. and 6 a.m. in 2012, 58 percent had BACs at or above 0.08 percent compared with 19 percent during other hours. Forty-six percent of all fatally injured passenger vehicle drivers on weekends (from 6 p.m. Friday to 6 a.m. Monday) in 2012 had BACs at or above 0.08 percent. At other times the proportion was 24 percent.

  11. Who qualifies as a "hard-core drinking driver"?

    The term was coined to refer to people who repeatedly drive while impaired and are resistant to changing their behavior despite previous sanctions, treatment or education. The underlying premise is that many, if not most, of these people are problem drinkers. Simpson, H.M. and Mayhew, D.R. 1991. The hard core drinking driver. Ottawa, Ontario: Traffic Injury Research Foundation. The term is not precisely defined, but hard-core drinking drivers are often identified as those with prior alcohol-impaired driving convictions or very high BACs (0.15 percent or higher) at the time of arrest for alcohol-impaired driving.

    The concept of hard-to-change, chronic heavy drinking drivers ignores many who account for a large portion of alcohol-impaired driving crashes. These include drivers who drink heavily on occasion and drivers who drink at more moderate levels that elevate crash risk. Among passenger vehicle drivers with illegal BACs (0.08 percent or higher) who died in crashes in 2012, 23 percent had BACs lower than 0.15 percent.

  12. Are most alcohol-impaired driving crashes caused by repeat offenders?

    No, although research shows that people with prior convictions for alcohol-impaired driving are overrepresented among drivers in fatal crashes. Fell, JC. 2013. Update: repeat DWI offenders: their involvement in fatal crashes in 2010. Traffic Injury Prevention, Advance online publication doi: 10.1080/15389588.2013.838230. In 2012, 7 percent of drivers in fatal crashes with BACs of 0.08 percent or higher had previous alcohol-impaired driving convictions on their records. The actual incidence of previous convictions is likely higher, because information on convictions is available for only the prior three years. In addition, some alcohol offenses are not included on driver records because of court programs that allow drivers to remove or avoid a conviction if they attend educational programs. Still, most alcohol-impaired driving fatal crashes do not involve drivers with a long history of multiple alcohol convictions.

  13. Do we need a separate set of policies to address the problem of hard-core drinking drivers?

    Some have argued that hard-core drinking drivers are resistant to countermeasures such as sobriety checkpoints and administrative license suspension that have reduced alcohol-impaired driving overall. In response, some states have passed laws mandating stiffer penalties for repeat offenders or drivers with very high BACs (e.g., 0.15 percent or higher).

    However, hard-core drinking drivers have not been immune to the general deterrence efforts of the past three decades. Between 1982 and 2012, there were large declines in all categories of illegal BACs among fatally injured passenger vehicle drivers: 0.08-0.14 percent, 0.15-0.19 percent, 0.20-0.24 percent and 0.25 percent and higher. During 1991-1995, about 12 percent of fatally injured passenger vehicle drivers with BACs at or above 0.08 percent had alcohol convictions during the previous three years. This percentage declined to 8 percent during 2008-2012. Previous alcohol convictions reflect both driving behavior and law enforcement patterns.

    These statistics do not support the claims that hard-core drinking drivers have become a larger part of the problem or that they have been unaffected by countermeasures directed at all drivers. Some countermeasures aimed at the hard-core group have been effective in reducing recidivism, Williams, A.F.; McCartt, A.T.; and Ferguson, S.A. 2007. Hardcore drinking drivers and other contributors to the alcohol-impaired driving problem: need for a comprehensive approach. Traffic Injury Prevention 8(1):1-10. and these countermeasures also may be effective in reducing recidivism among other offenders. Attention and resources also need to be given to general deterrent initiatives.

March 2014

  1. What is the goal of alcohol-impaired driving laws?

    State laws making it illegal to drive with high blood alcohol concentrations (BACs) serve as the cornerstone of all efforts to reduce alcohol-impaired driving. Many people think the principal goal of such laws is to arrest and punish the drivers who put everyone else at risk. But the more important goal is for the law to be a deterrent so that police find no alcohol-impaired drivers to arrest. This is commonly referred to as "general deterrence" because it targets and influences the general public. "Specific deterrence" refers to measures that seek to prevent individuals who have already committed an offense from re-offending.

  2. Why is general deterrence so important and how can it be achieved?

    Most impaired drivers are never stopped. Others are stopped, but police may miss signs of impairment. In studies based on telephone surveys and official arrest records, estimates of the chance of arrest when driving impaired range from small (about 1 in 50) to miniscule (1 in 480). Hedlund, J.H. and McCartt, A.T. 2002. Drunk driving: seeking additional solutions. Washington, DC: AAA Foundation for Traffic Safety. Zador, P.; Krawchuck, S.; and Moore, B. 2001. Drinking and driving trips, stops by police, and arrests: analyses of the 1995 national survey of drinking and driving attitudes and behavior. Report no. DOT HS-809-184. Washington, DC: National Highway Traffic Safety Administration. Dowling, A.M.; MacDonald, R.; and Carpenter, K.H. 2011. Frequency of alcohol-impaired driving in New York State. Accident Analysis and Prevention 12(2):120-7. Quinlan, K.P.; Brewer, R.D.; Siegel, P.; Sleet, D.A.; Mokdad, A.H.; Shults, R.A.; and Flowers, N. 2005. Alcohol-impaired driving among U.S. adults: 1993-2002. American Journal of Preventive Medicine 28:346-50. Bergn, G.; Shults, R.A.; and Rudd, R.A. 2011. Vital signs: alcohol impaired driving among adults - United States, 2010. Morbidity and Mortality Weekly Report 60(39):1351-6. Researchers in two cities combined arrest data with information on driver BACs gathered in roadside surveys, finding that the risk of arrest for a driver with a BAC of 0.10 percent or higher was between 1 and 6 in 1,000. Beitel, G.A.; Sharp, M.C.; and Glauz, W.D. 2000. Probability of arrest while driving under the influence of alcohol. Injury Prevention  6(2):158-61. Hause, J.M.; Voas, R.B.; and Chavez, E. 1982. Conducting voluntary roadside surveys: the Stockton experience. In M.R. Valverius (Ed.), Proceedings of the Satellite Conference to the 8th International Conference on Alcohol, Drugs and Traffic Safety, June 23-25, 1980, Umea, Sweden (pp. 104-113). Stockholm: The Swedish Council for Information on Alcohol and Other Drugs.

    Because the police cannot catch all offenders, the success of alcohol-impaired driving laws depends on deterring potential offenders by creating the public perception that apprehension and punishment is likely. Research has shown that the perceived likelihood of apprehension is more important in deterring offenders than the severity of punishment. The key to creating this perception is sustained and well publicized enforcement.

  3. How do laws define alcohol-impaired driving?

    Research establishing the relationship between BACs and impairment of driving skills made it possible to define alcohol-impaired driving offenses in terms of a BAC above a specific threshold. All states and the District of Columbia have per se laws making it illegal to drive with a BAC above a proscribed limit.

    If a police officer considers someone to be driving in a way that suggests impairment and that person exhibits signs of impairment after being stopped, the officer may charge the driver with impaired driving even if the person's BAC does not exceed the legal threshold or the person refuses an alcohol test.

  4. What does blood alcohol concentration measure?

    A BAC is the amount of alcohol in a person's blood, expressed as weight of alcohol per unit of volume of blood. For example, 0.08 percent BAC indicates 80 mg of alcohol per 100 ml of blood. For most legal purposes, however, a blood sample is not necessary to determine a person's BAC. It can be measured more simply by analyzing exhaled breath.

  5. What is the BAC threshold for per se laws in the United States?

    All 50 states and the District of Columbia have laws defining the illegal BAC threshold as 0.08 percent. In all 50 states, drivers younger than 21 are prohibited from operating a vehicle with any detectable blood alcohol. Most states define this as a BAC at or above 0.02 percent; others specify BACs lower than 0.02 percent.

    The threshold in the U.S. used to be higher than 0.08 percent, and in many countries it is lower. A review by the Centers for Disease Control and Prevention of research on the effects of lowering per se BAC thresholds from 0.10 to 0.08 percent in the U.S. found a median decrease of 7 percent in alcohol-related motor vehicle fatalities. Shults, R.A.; Elder, R.W.; Sleet, D.A.; Nichols, J.L.; and Alao, M.O. 2001. Reviews of evidence regarding interventions to reduce alcohol-impaired driving. American Journal of Preventive Medicine 21:66-88.

    The BAC threshold is lower in many other countries, ranging from 0.08 percent in the United Kingdom to 0.05 percent in Australia and 0.02 percent in Sweden. Almost all of the 27 European Union member states have BAC thresholds of 0.05 percent or lower. European Transport Safety Council. 2008. ETSC Fact Sheet: Drink driving fact sheet. ETSC Fact Sheet. Brussels, Belgium.

  6. Who can be stopped for alcohol-impaired driving?

    Anyone driving erratically can be stopped on suspicion of impaired driving. Typical signs of impairment are weaving, inability to maintain a consistent speed, making overly wide turns and stopping too close to or too far from traffic signs or signals. Impaired drivers are also found during stops for traffic offenses like speeding or signal violations. During the course of the stop the officer observes signs of impairment and an arrest for alcohol-impaired driving results.

  7. When can a driver be tested for alcohol?

    In the United States, police cannot stop an individual driver without first having a reasonable suspicion that the driver has committed an offense. If, after stopping a driver, an officer determines that the driver may be impaired, the officer initiates an investigation that includes asking the driver to perform standard field sobriety tests (e.g., one leg stand, walk and turn). Police can request a preliminary breath test using a hand-held device. These results are inadmissible in court, but are helpful in an officer’s evaluation. If the officer decides a driver is impaired, the driver is arrested. After arrest, the driver is asked to submit to a BAC test that is admissible in court. Refusal results in license suspension or revocation.

    Other countries have different laws for testing drivers for alcohol. For example, in Australia police officers are allowed to administer a breath test to any driver, regardless of whether or not an officer has reason to believe the person has been drinking.

  8. What happens if a driver refuses to be tested? How often does this happen, and what are the consequences?

    Drivers can refuse the alcohol test, but refusal will result in license revocation or suspension. This is provided under implied consent laws that establish that by driving in the state a person consents to alcohol testing. The law requires that test samples be taken shortly after arrest, typically within two hours. This is because BACs fall as alcohol is metabolized. Judicial warrants can be used to compel drivers to submit to tests. Some jurisdictions are using recent improvements in communications technology (e.g., emailing or texting) to expedite the warrant process, so that a warrant can be issued and a blood sample taken within the statutory time limit.

    Refusal rates vary greatly from state to state. An analysis of data on alcohol-impaired driving arrests in 2005 from 37 states, Puerto Rico and the District of Columbia found that breath test refusal rates ranged from 1 percent in Puerto Rico and 2 percent in Delaware to 81 percent in New Hampshire. Berning, A.; Beirness, D.; Hedlund, J.; and Jones, R. 2007. Traffic safety facts: breath test refusals. Report no. DOT HS-810-871. Washington, DC: National Highway Traffic Safety Administration. The weighted mean of the refusal rates, based on state population, was 21 percent, similar to the estimated mean rate in 1987 and in 2001.

    The penalties for refusal vary by state. National Highway Traffic Safety Administration. 2008. Blood alcohol concentration test refusal laws. Report no. DOT HS-810-884W. Washington, DC: U.S. Department of Transportation. More than 40 states and the District of Columbia impose some form of administrative, pre-conviction license suspension or revocation. Some states have criminal sanctions for refusals.

  9. What are sobriety checkpoints and which states conduct them?

    Checkpoints are a highly visible enforcement method intended to deter potential offenders, as well as to catch violators. Where permitted, police can use checkpoints to stop drivers at specified locations to identify impaired drivers. All drivers, or a predetermined proportion of them, are stopped. The checkpoint stop must be brief, and it must be done following strict guidelines to ensure there is no discriminatory stopping of some people and not others. The standard for administering a breath test is the same for checkpoints as for individual stops.

    Sobriety checkpoints are prohibited by state constitution or statute in 10 states (Idaho, Iowa, Michigan, Minnesota, Oregon, Rhode Island, Texas, Washington, Wisconsin, and Wyoming). In a 2002 Institute survey, 37 states and the District of Columbia reported conducting checkpoints. Thirteen reported not conducting them because of legal or policy reasons. Fell, J.C.; Ferguson, S.A.; Williams, A.F.; and Fields, M. 2003. Why are sobriety checkpoints not widely adopted as an enforcement strategy in the United States? Accident Analysis and Prevention 35(6):897-902. Only 11 states reported conducting checkpoints as often as once a week.

  10. Are sobriety checkpoints effective?

    Yes. If checkpoints are set up frequently over long enough periods and are well publicized, they can establish a belief in people's minds that impaired drivers will be apprehended. This belief is essential to general deterrence.

    Sobriety checkpoints have been criticized for producing fewer arrests per man-hour than dedicated patrols, but focusing on the number of arrests is a misleading way to assess the value of checkpoints. The primary purpose of frequent checkpoints is to increase public awareness and deter potential offenders. For example, in the Australian state of Victoria, which has had an extensive roadside breath testing program for many years, only 1 in 555 drivers stopped in 1993 tested positive for alcohol to the point of breaking the law. Cameron, M.; Diamantopoulou, K.; Mullan, N.; Dyte, D.; and Gantzer, S. 1997. Evaluation of the country random breath testing and publicity program in Victoria, 1993-1994. Report no. 126. Victoria, Australia: Monash University Accident Research Centre. In 1978, before the roadside breath testing program, the ratio was 1 positive to 45 negatives.

     A 1984 Institute study in two neighboring jurisdictions demonstrated how checkpoints can change public perceptions. Williams, A.F. and Lund, A.K. 1984. Deterrent effects of roadblocks on drinking and driving. Traffic Safety Evaluation Research Review 3:7-18. Washington, DC: National Highway Traffic Safety Administration. Fairfax County, Va., had a long history of vigorous enforcement of alcohol-impaired driving laws and used unpublicized drinking-driver patrols to achieve relatively high arrest rates. Nearby Montgomery County, Md., had historically lower arrest rates but used well-publicized sobriety checkpoints during the study period. Surveys of licensed drivers revealed that public awareness of enforcement programs was far greater in Montgomery County than in Fairfax County. Respondents in both counties incorrectly believed the probability of arrest was higher in Montgomery County, where checkpoints were conducted.

    These changed perceptions can lead to reduced alcohol-impaired driving and fewer crashes. In 1988, the Institute and the city of Binghamton, N.Y., implemented an integrated enforcement program that emphasized the publicized use of sobriety and safety belt checkpoints. During the program's first two years, the number of drivers stopped who had been drinking decreased about 40 percent. Late-night crashes decreased 21 percent while checkpoints were in place, and injury-producing nighttime crashes declined 16 percent. Wells, J.K.; Preusser, D.F.; and Williams, A.F. 1992. Enforcing alcohol-impaired driving and seat belt use laws, Binghamton, New York. Journal of Safety Research 23:63-71. In 1995, North Carolina implemented a statewide intensive three-week publicized enforcement campaign focusing on alcohol-impaired driving, including statewide checkpoints and roving saturation patrols. Drivers on the road with BACs at or above 0.08 percent declined from 198 per 10,000 before the program to 90 per 10,000 after. Williams, A.F.; Wells, J.K.; and Foss, R.D. 1995. The North Carolina Governor's Highway Safety Initiative: initial results from "Booze It and Lose It." Proceedings of the 13th International Conference on Alcohol, Drugs, and Traffic Safety, 1:347-51. Adelaide, Australia: NHMRC Road Accident Research Unit, University of Adelaide.

    In 2002, the Centers for Disease Control and Prevention reviewed studies evaluating sobriety checkpoint programs. The median decline in crashes thought to involve alcohol was about 20 percent. Elder, R.W.; Schults, R.A.; Sleet, D.A.; Nichols, J.L.; Zaza, S.; and Thompson, R.A. 2002. Effectiveness of sobriety checkpoints for reducing alcohol-involved crashes. Traffic Injury Prevention 3(4):266-74. A 2012 review of 10 more recent studies found a median relative percentage decrease in alcohol-involved fatal crashes of about 9 percent. Guide to Community Preventive Services. Reducing alcohol-impaired driving: publicized sobriety checkpoint programs: task force finding and rational statement. Atlanta, GA: Centers for Disease Control and Prevention. Accessed at: http://www.thecommunityguide.org/mvoi/AID/RRsobrietyckpts.html. A 2009 meta-analysis (a statistical analysis that aggregates the results of multiple studies) found sobriety checkpoints reduced crashes involving alcohol by 17 percent or more and all crashes by about 10-15 percent. Erke, A; Goldenbeld, C.; and Vaa, T. 2009. The effects of drink-driving checkpoints on crashes — a meta-analysis. Accident Analysis and Prevention 41(5):914-23.

  11. Are sobriety checkpoints constitutional?

    The U.S. Supreme Court held in 1990 that properly conducted sobriety checkpoints are legal under the Constitution. Most state courts that have addressed the issue have upheld checkpoints, too, but some have interpreted state law to prohibit checkpoints. Michigan Department of State Police v. Sitz, 496 US 444 (1990).

  12. If sobriety checkpoints are so effective, why aren't they more widely used?

    Sobriety checkpoints are prohibited in 10 states. When surveyed by the Institute about their use of checkpoints, states who used them infrequently pointed to a lack of funding and police resources, a preference for saturation patrols over checkpoints, and the use of large numbers of police officers at checkpoints. Fell, J.C.; Ferguson, S.A.; Williams, A.F.; and Fields, M. 2003. Why are sobriety checkpoints not widely adopted as an enforcement strategy in the United States? Accident Analysis and Prevention 35(6):897-902. Some police departments believe a large number of officers are required, placing checkpoints beyond the resources of small police agencies and draining the personnel and financial resources of larger agencies. However, small-scale checkpoints with as few as 3-5 officers can be conducted successfully and safely Lacey, J.H.; Ferguson, S.A.; Kelley-Baker, T.; and Rider, R.P. 2006. Low-manpower checkpoints: can they provide effective DUI enforcement for small communities? Traffic Injury Prevention 7(3):213-8. Stuster, J.W. and Blowers, M.A. 1995. Experimental evaluation of sobriety checkpoint points. Report no. DOT HS-806-989. Washington, DC: National Highway Traffic Safety Administration. and can be effective in reducing alcohol-impaired driving Lacey, J.H.; Ferguson, S.A.; Kelley-Baker, T.; and Rider, R.P. 2006. Low-manpower checkpoints: can they provide effective DUI enforcement for small communities? Traffic Injury Prevention 7(3):213-8. and alcohol-related crashes. Stuster, J.W. and Blowers, M.A. 1995. Experimental evaluation of sobriety checkpoint points. Report no. DOT HS-806-989. Washington, DC: National Highway Traffic Safety Administration. The federal government encourages states to do frequent, low-manpower checkpoints with 3-5 officers. National Highway Traffic Safety Administration. 2006. Low-staffing sobriety checkpoints. Report no. DOT HS-810-590. Washington, DC: U.S. Department of Transportation. 

  13. What types of enforcement other than sobriety checkpoints are effective?

    Measured in arrests per man-hour, dedicated police patrols are an effective method of apprehending offenders. Officers experienced in alcohol-impaired driving enforcement are assigned to patrols dedicated exclusively to finding alcohol-impaired drivers. Absent an emergency, they are relieved of other patrol duties. Especially where sobriety checkpoints cannot be conducted, roving dedicated patrols may serve as general deterrence if their activities are publicized and become widely known. Michigan Department of State Police v. Sitz, 496 US 444 (1990).

    The federal government cites saturation patrols as an effective enforcement strategy. National Highway Traffic Safety Administration. 2009. Saturation patrols & sobriety checkpoints guide. Report no. DOT HS-809-063. Washington, DC: U.S. Department of Transportation. Saturation patrols target a specific area to identify and arrest impaired drivers, often combining the efforts of multiple agencies to concentrate their resources.

  14. How can passive alcohol sensors aid in enforcement?

    Many people can effectively mask the overt behavioral symptoms of alcohol impairment for short periods, but it is much more difficult to hide the evidence of impairment from a passive alcohol sensor, which identifies alcohol in the exhaled breath near a driver's mouth. Passive alcohol sensors are screening devices that help an officer detect possible impaired drivers for further testing. The sensors are not intrusive and therefore do not violate constitutional prohibitions against unreasonable search and seizure. In a 1993 Institute study of sobriety checkpoints in Fairfax County, Va., police officers using sensors were able to detect more offenders compared with officers who did not use sensors. Ferguson, S.A.; Wells, J.K.; and Lund, A.K. 1995. The role of passive alcohol sensors in detecting alcohol-impaired drivers at sobriety checkpoints. Alcohol, Drugs, and Driving 11(1):23-30. Police without sensors detected 55 percent of drivers whose BACs were at or above 0.10 percent. With sensors, police successfully detected 71 percent of the drivers with BACs at or above 0.10 percent. Results of the Fairfax study parallel previous Institute evaluations. In a checkpoint program in Charlottesville, VA., use of a passive alcohol sensor by officers increased arrests almost by a factor of 3. Voas, R.B. 2008. A new look at NHTSA's evaluation of the 1984 Charlottesville sobriety checkpoint program: implications for current checkpoint issues. Traffic Injury Prevention 9(1):22-30.

    Passive alcohol sensor

    Passive alcohol sensor


  15. Is license suspension an effective sanction?

    Laws providing for the suspension or revocation of licenses have been shown to reduce the subsequent crash involvement of drivers convicted of alcohol offenses. Zador, P.L.; Lund, A.K.; Fields, M.; and Weinberg, K. 1989. Fatal crash involvement and laws against alcohol-impaired driving. Journal of Public Health Policy 10:467-85. Peck, R.C.; Sadler, D.D.; and Perrine, M.W. 1985. The comparative effectiveness of alcohol rehabilitation and licensing control actions for drunk driving offenders: a review of the literature. Alcohol, Drugs and Driving; Abstracts and Reviews 1(4):15-39. Even after the suspension, the effects last. Although many suspended drivers continue to drive, McCartt, A.T.; Geary, L.L.; and Berning, A. 2003. Observational study of the extent of driving while suspended for alcohol impaired driving. Injury Prevention 9(2):133-7. they tend to drive less. License suspension also has led to a general reduction in fatal crashes in states where the threat of this sanction has been made more certain through laws that provide for administrative license suspension.

  16. What are alcohol ignition interlocks? Do they have a role in deterrence?

    An alcohol ignition interlock has a breath-testing unit that is connected to a vehicle's ignition. In order to start the vehicle, the driver must blow into the device and register a blood alcohol reading that is below a predetermined level. If the blood alcohol reading exceeds this level, the interlock prevents the vehicle from starting. An estimated 313,400 interlocks were in use in 2013 in the United States. Roth, R. 2013. 2013 survey of currently-installed interlocks in the U.S. Available:http://www.rothinterlock.org/2013_survey_of_currently_installed_interlocks_in_the_us_revised-12_17_13.pdf. Accessed March 25, 2014.

    Studies have shown that alcohol ignition interlocks are effective in reducing recidivism. In a 1999 Institute study, multiple offenders eligible for license reinstatement were randomly assigned interlock-restricted licenses or unrestricted licenses coupled with the conventional post licensing treatment program. The interlock restriction reduced the risk of committing an alcohol-related traffic violation within the first year following conviction by 64 percent. Beck, K.H.; Rauch, W.J.; Baker, E.A.; and Williams, A.F. 1999. Effects of ignition interlock license restrictions on drivers with multiple alcohol offenses: a randomized trial in Maryland. American Journal of Public Health 89:1696-1700. A systematic review and meta-analysis of studies of ignition interlock programs found the programs seemed to reduce recidivism while the devices were installed in offenders' vehicles, but found no evidence of effectiveness once the devices were removed. Willis, C.; Lybrand, S.; and Bellamy, N. 2004. Alcohol ignition interlock programmes for reducing drink driving recidivism. Cochrane Database of Systematic Reviews 2004, Issue 4. Art. no.: CD004168. Oxfordshire, England: The Chochrane Collaboration.

    In 23 states and four California counties, all alcohol-impaired driving offenders, including first-time offenders, must install interlocks to resume driving. An additional 12 states (Delaware, Florida, Maryland, Michigan, New Hampshire, New Jersey, North Carolina, Oklahoma, South Carolina, Texas, Wisconsin, and Wyoming) require interlocks for first-time offenders with high BACs (usually 0.15 percent or higher) and for repeat offenders, 8 states (California, Georgia, Idaho, Kentucky, Massachusetts, Montana, Pennsylvania, and Tennessee) require them only for repeat offenders, and 1 state (Nevada) only for high-BAC offenders. Six states (Indiana, Iowa, North Dakota, Ohio, Rhode Island, and South Dakota) and the District of Columbia have no mandatory interlock requirements.

    An Institute study showed that mandatory interlock laws for all offenders are effective. McCartt, A.T.; Leaf, W.A.; Farmer, C.M.; and Eichelberger, A.H. 2013. Washington state’s alcohol ignition interlock law: effects on recidivism among first-time DUI offenders. Traffic Injury Prevention 14(3):215-29.  Researchers looked at what happened in Washington when the state expanded its interlock requirement in 2004 to cover everyone convicted of DUI, not just those with multiple offenses or high BACs. They found the recidivism rate fell 12 percent for first-time offenders with BACs under 0.15 percent. The law change was associated with an 8.3 percent reduction in single-vehicle late-night crash risk, suggesting a general deterrent effect of the expanded interlock requirement.

    However, even when laws require offenders to have interlocks if they drive, many people don’t go through with the installation. In the Washington study, only about a third of the first-time offenders with BACs under 0.15 percent obtained interlocks. (If all of them had, it is estimated that their recidivism rate would have fallen by nearly half.) McCartt, A.T.; Leaf, W.A.; Farmer, C.M.; and Eichelberger, A.H. 2013. Washington state’s alcohol ignition interlock law: effects on recidivism among first-time DUI offenders. Traffic Injury Prevention 14(3):215-29.  In some states offenders may skip the interlock stage by serving the suspension. In a pilot program in Santa Fe County, N. M., when judges imposed house arrest via electronic monitoring as the alternative to an interlock, 70 percent of offenders installed interlocks, compared with only 17 percent in other counties. Roth, R.; Marques, P.R.; Voas, R.B. 2009. A note on the effectiveness of the house-arrest alternative for motivating DWI offenders to install ignition interlocks. Journal of Safety Research 40: 437-41. When the program ended, the Santa Fe installation rate declined.

  17. Are treatment and rehabilitation programs effective?

    Although studies have had mixed results, research has shown that treatment and rehabilitation programs may have a small, positive effect on the subsequent behavior of alcohol-impaired driving offenders. Several evaluations of 35 alcohol treatment programs implemented in the 1970s found lower reoffense rates for first offenders but not for repeat offenders, and no effect on crash rates. Nichols, J.L. 1990. Treatment versus deterrence. Alcohol Health and Research World 14:44-51. A 1995 examination of more than 200 studies of the effects of various treatment and rehabilitation programs found a reduction of 7-9 percent, on average, in subsequent alcohol-impaired driving events, including repeat offenses and crashes. Wells-Parker, E.; Bangert-Drowns, R.; McMillen, R.; and Williams, M. 1995. Final results from a meta-analysis of remedial interventions with drink/drive offenders. Addiction 90(7):907-26. A 1997 study of California programs found that treatment combined with driver license penalties was more effective than license penalties alone in reducing repeat offenses among first and repeat offenders. DeYoung, D.J. 1997. An evaluation of the effectiveness of alcohol treatment, driver license actions, and jail terms in reducing drunken driving recidivism in California. Addiction 92(8):989-97. Treatment and rehabilitation in lieu of license sanctions or other penalties have not been shown to be effective in reducing recidivism or alcohol-involved crashes. Nichols, J.; Weinstein, E.; Ellingstad, V. and Struckman-Johnson, D. 1978. The specific deterrence effect of ASAP education and rehabilitation programs. Presented at the National Safety Congress. Chicago, Illinois. Nichols, J.; Ellingstad, V. and Struckman-Johnston, D. 1978. An experimental evaluation of the effectiveness of short term education and rehabilitation programs for convicted drinking drivers. Presented at the National Council on Alcoholism Annual Forum, St. Louis, Missouri.

  18. Are new technologies being developed to prevent drivers from operating vehicles with illegal BACs?

    Yes. A cooperative venture of motor vehicle manufacturers and the federal government is overseeing the development of advanced in-vehicle alcohol detection technologies that would be suitable for all drivers, not just convicted offenders. The goal of the Driver Alcohol Detection System for Safety program is to develop a device that can quickly, accurately and unobtrusively measure BACs and keep drivers from operating vehicles when their BACs exceed 0.08 percent.

    Institute research indicates that about 7,000 deaths would have been prevented in 2010 if all drivers with BACs of 0.08 percent or higher had been kept off the roads. Lund, A.K.; McCartt, A.T.; and Farmer, C.M. 2012. Contribution of alcohol-impaired driving to motor vehicle crash deaths in 2010. Arlington, VA. Applying the same methods yields an estimate of about 7,100 preventable deaths if all drivers with BACs of 0.08 percent or higher were kept off the roads in 2012.

    A 2009 survey showed that 2 out of 3 members of the general public support universal alcohol detection technology to prevent any driver from operating a vehicle after having too much to drink. McCartt, A.T; Wells, J.K.; and Teoh, E.R. 2010. Attitudes toward in-vehicle advanced alcohol detection technology. Traffic Injury Prevention 11(2):156-64.

February 2014

  1. What is an administrative license suspension law?

    Administrative license suspension (ALS) laws authorize police to confiscate the licenses of drivers who either fail or refuse to take a chemical test for alcohol. Drivers are given a notice of suspension, which also serves as a temporary permit to drive. Depending on the state, this permit may be valid for anywhere from seven to 90 days, during which time the suspension may be challenged. If there is no challenge or if the suspension is upheld, the license is suspended for a prescribed period of time. Suspensions for first offenses vary among jurisdictions but most commonly are 90 days. Longer suspensions are specified for repeat offenders and those who refuse testing. It is important to note that ALS laws do not replace criminal prosecution, which is handled separately through the courts.

  2. How do ALS laws differ from traditional license suspension?

    The administrative licensing action is triggered by failing or refusing to take a chemical test, not by conviction, so anyone arrested is immediately subject to suspension. People whose licenses are suspended have the right to a prompt administrative hearing to determine the validity of the arrest and any alcohol testing.

  3. Is license suspension an effective sanction?

    Yes. Well-designed studies have found reductions in crashes and recidivism among offenders who receive ALS or judicial suspension compared with offenders whose licenses are not suspended. The reductions in violations and crashes associated with license suspension continue well beyond the suspension period. Peck, R.C.; Sadler, D.D.; and Perrine, M.W. 1985. The comparative effectiveness of alcohol rehabilitation and licensing control actions for drunk driving offenders: a review of the literature. Alcohol, Drugs and Driving; Abstracts and Reviews 1(4):15-39. Stewart, K.; Gruenewald, P.; and Roth, T. 1989. An evaluation of administrative per se laws. Washington, DC: National Institute of Justice, U.S. Department of Justice. Voas, R.B.; Tippetts, A.S.; and Taylor, E. 2000. Effectiveness of the Ohio vehicle action and administrative license suspension laws. Washington, DC: National Highway Traffic Safety Administration.

    Longer periods of license suspension may be expected to have stronger effects, while those of short duration may have very limited effects. 

  4. How effective are ALS laws?

    An Institute study found ALS laws reduce the number of drivers involved in fatal crashes by about 9 percent during nighttime hours when alcohol is very likely to be involved. Zador, P.L.; Lund, A.K.; Fields, M.; and Weinberg, K. 1989. Fatal crash involvement and laws against alcohol-impaired driving. Journal of Public Health Policy 10(4):467-85. Another study reported that among 17 states implementing ALS either alone or in combination with other laws, the median effect was a 6 percent decrease in fatal crashes likely to be alcohol-related. Klein, T.M. Changes in alcohol-involved fatal crashes associated with tougher state alcohol legislation. Report no. DOT HS-809-511. Washington, DC: National Highway Traffic Safety Administration. A long-term study (1976-2002) of the effects of pre-conviction license suspension laws in 38 states found a 5 percent reduction among drivers with positive blood alcohol concentrations (BACs) involved in fatal crashes. Wagenaar, A.C. and Maldonado-Molina, M.M. 2007. Effects of drivers' license suspension policies on alcohol-related crash involvement: long-term follow-up in forty-six states. Alcoholism: Clinical and Experimental Research 31(8):1399-1406.

  5. What's the advantage of ALS?

    ALS laws, which apply to both first and repeat offenders, remove impaired drivers from the road quickly and ensure that penalties will be applied. ALS laws result in far more suspensions than do laws that require a criminal conviction. They reduce the incentive for offenders to delay their criminal cases to avoid suspension. They also reduce the likelihood of future alcohol-related violations and crashes. A well-publicized and enforced ALS law increases public perception that punishment for alcohol-impaired driving is likely to occur and will be swiftly applied and appropriately severe — a perception that is necessary to deter potential offenders.

  6. Are all ALS laws the same?

    No. Forty-one states and the District of Columbia have ALS laws, but the laws vary with regard to the length of time a temporary license is valid, the period within which a hearing must be held and the length of suspension. In some states, the licensing action is stayed pending the hearing. Difficulties in conducting administrative hearings in some states have inhibited the use of ALS laws. These difficulties include case backlogs, scheduling conflicts that make it difficult for law enforcement officers to appear at hearings and the use of technicalities to rescind the license suspension. Jones, R.K.; Lacey, J.H.; and Wiliszowski, C.H. 1998. Problems and solutions in DWI enforcement systems. Report no. DOT HS-808-660. Washington, DC: National Highway Traffic Safety Administration.

    Some states allow hardship licenses so that offenders may drive to work. But studies have shown that suspended drivers rarely lose their jobs. Baker, S.P. and Robertson, L.S. 1975. How drivers prevented from driving would reach work: implications for penalties. Accident Analysis and Prevention 7(1):45-8. Wells-Parker, E. and Cosby, P.J. 1988. Behavioral and employment consequences of driver's license suspension for drinking and driving offenders. Journal of Safety Research 19(1):5-20. Knoebel, K.Y. and Ross, H.L. 1997. Effects of administrative license revocation in employment. Accident Analysis and Prevention 29(5):595-612. A four-state study of the impact of ALS on the employment and income of first and repeat offenders found no major impact on jobs or income. Knoebel, K.Y. and Ross, H.L. 1997. Effects of administrative license revocation in employment. Accident Analysis and Prevention 29(5):595-612.

  7. Are ALS laws constitutional?

    Yes. Courts have held that although licenses are taken prior to a hearing, due process is provided because ALS laws allow for prompt post-suspension hearings. Defendants have claimed that the double jeopardy clause of the U.S. Constitution prohibits the state from prosecuting an offender whose license has been suspended under ALS. But high courts in several states have found that a criminal prosecution following ALS does not violate the double jeopardy clause.

  8. Are ALS laws costly to implement?

    No. They can pay for themselves. In most states, drivers who have their licenses suspended must pay a reinstatement fee to receive a new license at the end of the suspension period. These fees can cover or exceed the cost of the program. A study of three state programs found not only that direct revenues exceeded expenses but also that state costs associated with nighttime crashes declined dramatically. Lacey, J.; Jones, R.; and Stewart, J. 1991. Cost-benefit analysis of administrative license suspensions. Report no. DOT HS-807-689. Washington, DC: National Highway Traffic Safety Administration.