Drunk Driving Research: DUI, DWI

"Most impaired drivers are never stopped. Others are stopped, but police often miss signs of impairment. It has been estimated that close to 1,000 alcohol-impaired driving trips occur for every arrest. 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 of offenders is likely. Research has shown that likelihood of apprehension is more important in deterring offenders than is the severity of punishment. The key to creating this perception is enforcement. Merely putting strong laws on the books is not enough. Enforcement efforts must be sustained and well publicized and create a realistic threat of apprehension."

- The Insurance Institute of Highway Safety

Drunk Driving General Information

Fatality Facts (2002) - Progress has been made in the past 20 years to reduce the proportion of fatally injured drivers with BACs at or above 0.08 percent. Proportions are lower in all age groups. They're lower among drivers of passenger vehicles, tractor-trailers, and motorcycles. There has also been a substantial decline among those with very high BACs (>= 0.15 percent), who are often assumed to be "hard-core" drinking drivers. Progress has stalled in recent years and alcohol-impaired driving is still a major problem.

Drunk Driving Laws DUI / DWI (as of March 2004) - All 50 states and the District of Columbia have per se laws defining it as a crime to drive with a blood alcohol concentration (BAC) at or above a proscribed level, usually 0.08 percent.

National Drunk Driving Resource - Everything you need to know about first offender DUI/DWI, drinking, driving and drugs.

A Review of the Literature on the Effects of Low Doses of Alcohol on Driving-Related Skills - Historically, deterrence has been the principal approach for prevention of driving under the influence of alcohol. Legislatures have established blood alcohol concentration (BAC(1)) limits for driving and law enforcement agencies have enforced those laws. Scientists have contributed to the establishment of BAC limits with data from experimental and epidemiological studies to identify the alcohol levels which produce driving skills impairment and increased crash rates.

Relative Risk Of Fatal Crash Involvement By BAC, Age, And Gender (PDF) - This study estimated age and sex specific relative risk of fatal crash involvement as a function of BAC based on logistic regression analyses of FARS combined with exposure data from The 1996 National Roadside Survey. Results showed that drivers with non-zero BACs below .10, and 16-20 year old male drivers below .08 BAC pose substantially elevated risk both to themselves and other road users.

Impaired Driving in the United States (Cost Fact Sheet) - The Impaired Driving State Cost Fact Sheets were developed by Dexter Taylor, Ph.D., Ted R. Miller, Ph.D., and Kenya L. Cox, M.A., of the Pacific Institute for Research and Evaluation (PIRE), 2002. The estimates were produced under the National Highway Traffic Safety Administration (contract number DTNHZZ-98-D35079). The information and opinions presented are attributable to the authors alone and may not represent the official views of the sponsoring agency.

Alcohol: Deterrence and Enforcement (March 2004) - A question and answer session.

Drunk Driving: Questions and Answers

What is "drunk driving?"
The term "drunk driving" is an inaccurate characterization of the problems caused by motorists who are impaired by alcohol. The first criminal laws targeting this problem prohibited "drunk driving," encouraging the notion that the problem involved drivers who were visibly drunk. In fact, many alcohol-impaired drivers do not appear drunk in the traditional way. Research has shown that 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. For these reasons, the term "alcohol-impaired driving" is a more accurate and precise description of what is commonly referred to as "drunk driving."

What does blood alcohol concentration measure?
Blood alcohol concentration (BAC) describes the amount of alcohol in a person's blood expressed as weight of alcohol per unit of volume of blood. For example, at 0.10 percent BAC, there is 100 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 much more simply by analyzing exhaled breath.

What BAC is considered illegal?
Driving with a BAC of 0.10 percent is a crime in 5 states. It is a crime to drive with a BAC of 0.08 percent in 45 states and the District of Columbia. A BAC of 0.08 is evidence of an alcohol violation in Massachusetts. In response to a potential loss of federal highway funding, all states likely will have a BAC defining impaired driving at 0.08 percent within the next few years.

What is the effect of alcohol on driving skills and crash risk?
At BACs as low as 0.02 percent, alcohol affects driving ability and crash likelihood. The probability of a crash begins to increase significantly at 0.05 percent BAC and climbs rapidly after about 0.08 percent. For drivers age 35 and older with BACs at or above 0.15 percent on weekend nights, the likelihood of being killed in a single-vehicle crash is more than 380 times higher than it is for nondrinking drivers.1

How many drinks does it take to reach significantly impairing BACs?
The effects of alcoholic drinks vary greatly because the rate of absorption and BACs attained vary from person to person due to such factors as weight, amount of fat tissue, and stomach contents. Nevertheless, 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.

Are beer and wine less impairing than hard liquor?
Impairment is not determined by 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. Beer is the most common drink consumed by people stopped for alcohol-impaired driving or involved in alcohol-related crashes.

What proportion of all motor vehicle crashes is caused by alcohol?
It is impossible to say with certainty. Although alcohol is known to increase crash likelihood, its presence is neither necessary nor sufficient to cause a crash. Every crash in which a driver has a high BAC is not caused by alcohol. To learn the number of crashes caused by driving at various BACs, it would be necessary to find out how many trips that do not involve crashes are driven by people with positive BACs -- something that is only measured periodically in roadside surveys or special studies of motorists not involved in crashes.

What proportion of motor vehicle crashes involves alcohol?
The most reliable information about alcohol involvement comes from fatal crashes. In 2002, 32 percent of fatally injured drivers had BACs of at least 0.08 percent. Although alcohol may not have been a causal factor in all of the crashes, this statistic is frequently used to measure the change over time in alcohol involvement in fatal crashes.

In 2002, the National Highway Traffic Safety Administration (NHTSA) estimated that 35 percent of all traffic deaths occurred in crashes in which at least one driver or nonoccupant had a BAC of 0.08 percent or more and that any alcohol was present in 41 percent of all fatal crashes in 2002.2 Such statistics are sometimes cited as proof that a third to half of all fatal crashes are caused by "drunk driving" and that none of the crashes that involve alcohol would occur if the alcohol were not present. But this is incorrect and misleading because alcohol is only one of several factors that contribute to crashes involving drinking drivers. Furthermore, some fatally injured people in alcohol-related crashes are pedestrians with positive BACs, and these fatalities still would occur even if every driver were sober.

Alcohol involvement is much lower in crashes involving nonfatal injuries, and it is lower still in crashes that do not involve injuries at all. A study conducted during the 1960s estimated that 9 percent of drivers in injury crashes in Grand Rapids, Michigan3 -- 12 percent in Huntsville, Alabama and in San Diego, according to a study from the 1970s -- had BACs at or above 0.10 percent. Only 5 percent of drivers had BACs that high in noninjury crashes in the Grand Rapids study. During the same time, studies of fatally injured drivers found 40-55 percent had BACs of 0.10 percent or more.

How has the problem of alcohol-impaired driving changed over time?
The incidence of alcohol-impaired driving has been reduced in recent years but remains a major problem. The NHTSA and the Institute undertook a national roadside breath survey in 1996 -- it was patterned after 1986 and 1973 surveys -- and found that 83 percent of drivers had no measurable alcohol, a significant increase above the 74 percent rate of sober drivers in 1986 and the 64 percent rate in 1973.4 Impairment begins even at low BACs but increases rapidly after 0.05 percent. The proportion of drivers with high BACs has fallen but less so in recent years. Overall, 7.7 percent of 1996 drivers had 0.05 percent BACs or higher, compared with 8.4 percent in 1986 and 13.7 percent in 1973.

Do alcohol-related crashes differ by gender?
Crashes involving men are much more likely than those involving women to be alcohol-related. Among fatally injured male drivers of passenger vehicles in 2002, 39 percent had BACs of 0.08 percent or more.2 The corresponding proportion among women was 18 percent. Alcohol involvement in fatal crashes is highest for men ages 21-40.

There have been some reports that women are becoming an increasing part of the alcohol-impaired crash problem. According to national roadside breath surveys, more women now are driving at night. The percentage of women in a weekend nighttime sample of drivers increased from 16 percent in 1973 to 26 percent in 1986 to 31 percent in 1996.4 The increase from 1973 to 1986 was accompanied by a reduction in the percentage of women with high BACs. However, in the period between 1986 and 1996, the percentage of women drivers with high BACs has increased slightly, from 1.3 to 1.5 percent. During this period, the percentage of males with high BACs dropped from 3.9 to 3.5 percent.

When do alcohol-related 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 2002, 59 percent had BACs at or above 0.08 percent compared with 18 percent during other hours. Forty-five percent of all fatally injured drivers on weekends (6 p.m. Friday to 6 a.m. Monday) in 2002 had BACs of 0.08 percent or more. During the rest of the week, the proportion was 25 percent.

Are most alcohol-related crashes caused by repeat offenders?
No. It is true that drivers with prior convictions for driving while impaired by alcohol are overrepresented among drivers in fatal crashes. According to a federal study, drivers convicted of alcohol-impaired driving in the past three years are at least 1.8 times as likely to be in fatal crashes as drivers with no prior convictions during the same time period and are at least four times as likely to be in fatal crashes in which drivers have high BACs (0.10 percent or more).5 However, it is important to note that 87 percent of drivers with high BACs in fatal crashes have no alcohol convictions during the previous three years.

Drunk Driving Organizations

MADD - is a 501(c)(3) non-profit grass roots organization with more than 600 chapters nationwide. MADD is not a crusade against alcohol consumption - MADD's mission is to stop drunk driving, support the victims of this violent crime, and prevent underage drinking.

Century Council - The Century Council is a not-for-profit organization dedicated to fighting drunk driving and underage drinking. Headquartered in Washington, D.C. and Chaired by Susan Molinari, The Council develops and implements innovative programs and public awareness campaigns and promotes action through strategic partnerships. The Century Council promotes responsible decision-making regarding drinking or non-drinking of beverage alcohol and discourages all forms of irresponsible consumption through education, communications, research, law enforcement, and other programs.

Canadians for Safe and Sober Driver - We are constantly gathering information to highlight Impaired Driving activities in Canada's 10 Provinces as well as from those communities running the OPERATION LOOKOUT® program. Here you will find information on associated Canadians for Safe and Sober Driving programs, organizations and contacts.

Stop DUI - STOP DUI creates messages for public service announcements, billboards, bus shelters, bumper stickers, posters and electronic reader boards. Heightened awareness programs are presented on the four major holidays of the year.

Drinking Drivers Defense Network - National network of DUI/DWI attorneys, ways to avoid a DUI conviction, blood alcohol chart, myths about defending accused drunk drivers.

DWI Victims Panel - The DWI Victims Panel has become a model for use by courts from Alaska to Pennsylvania. Development information has been provided to inquiring judges throughout the country. The potential for utilizing this approach is not limited solely to the criminal justice system.

National Commission Against Drunk Driving - The mission of the National Commission Against Drunk Driving is to continue the efforts of the Presidential Commission On Drunk Driving to reduce impaired driving and its tragic consequences by uniting a broad based coalition of public and private sector organizations and other concerned individuals who share this common purpose.

What Do Police Officers Look For When Searching For Drunk Drivers On The Highways?

The following is a list of symptoms in descending order of probability that the person observed is driving while intoxicated. The list is based upon research conducted by the National Highway Traffic Administration:

• Turning with a wide radius;
• Straddling center of lane marker;
• "Appearing to be drunk";
• Almost striking object or vehicle;
• Weaving;
• Driving on other than designated highway;
• Swerving;
• Speed more than 10 mph below limit;
• Stopping without cause in traffic lane;
• Following too closely;
• Drifting;
• Tires on center or lane marker;
• Braking erratically;
• Driving into opposing or crossing traffic;
• Signaling inconsistent with driving actions;
• Slow response to traffic signals;
• Stopping inappropriately (other than in lane);
• Turning abruptly or illegally;
• Accelerating or decelerating rapidly;
• Headlights off.

Drugs - other than alcohol - Questions and Answers

Are drugs other than alcohol a factor in motor vehicle crashes?
The role of alcohol as a major factor in motor vehicle crashes is well established. Much less information is available concerning the contribution of other drugs. Many legal and illegal drugs other than alcohol can impair driving ability, even in moderate concentrations, and may increase crash risk. However, their use among drivers is apparently quite limited, and there is presently insufficient scientific evidence that any drug other than alcohol increases crash likelihood.

Which drugs are most likely to affect crash risk?
According to a 1988 report from the National Highway Traffic Safety Administration,1 the drugs with "the most potential to be serious highway safety hazards" are tranquilizers, sedatives and hypnotics (for example, barbiturates), and marijuana.

What is the potential contribution of drugs to motor vehicle crashes?
There is not much information on drug use among drivers or on driver impairment by drugs other than alcohol. Information on drivers' drug use comes primarily from tests on people killed in crashes or hospitalized with crash injuries. Most such studies have found drugs other than alcohol among fewer than 10 percent (usually fewer than 5 percent) of fatally injured or hospitalized car drivers. Also, drugs other than alcohol are infrequently found alone. They are more often found in combination with high blood alcohol concentrations. Car drivers' apparently low use of drugs other than alcohol, especially by themselves, limits the potential contribution of such drugs to the motor vehicle crash problem.

A 1992 federal study2 revealed that 18 percent of fatally injured drivers have other drugs in their systems but that these drugs are most often combined with alcohol. Alcohol was found in 52 percent of 1,882 fatally injured drivers. Forty-three percent had blood alcohol concentrations of 0.10 percent or more. Only 6 percent had drugs without alcohol, and researchers found no evidence that drivers with drugs but no alcohol are more likely to be responsible for their crashes, compared with drug-free drivers. The researchers did find drugs related to crash responsibility when combined with alcohol or when two or more drugs were found.

A 1993 study3 published in the New England Journal of Medicine focuses on drivers without alcohol in their systems who were stopped by police for reckless driving. Urine tests revealed 45 percent had marijuana and 25 percent had cocaine in their systems. Although the authors suggest these findings show drugs to be a bigger problem than alcohol, the data did not allow this conclusion. All studies that have appropriately addressed the issue have found alcohol to be by far the greater problem.

Are drugs other than alcohol a problem for any particular groups of drivers?
An Institute study of interstate tractor-trailer drivers found that 29 percent had evidence of alcohol, marijuana, cocaine, prescription or nonprescription stimulants, or some combination of these, in either blood or urine. Marijuana was found in 15 percent of the drivers' blood or urine. Nonprescription stimulants were found in 12 percent, prescription stimulants in 5 percent, cocaine in 2 percent, and alcohol was found in fewer than 1 percent.4 A National Transportation Safety Board investigation of fatal truck crashes found that stimulants were the most frequently identified drug class among fatally injured truck drivers (present in 15 percent).5

The extent of driver impairment attributable to drugs other than alcohol is uncertain because of the complex relationship between performance and drug concentrations. The effects of marijuana on driver behavior and crash risk at the concentrations detected are not known because the psychological and behavioral effects of marijuana often occur after the blood concentrations of its principal psychoactive constituent have peaked and returned to very low levels.

Estimating the effect of stimulants is also complicated. It is possible that occasional use of such substances may in the short term enhance the performance of some tasks by increasing alertness, but some tractor-trailer drivers may use these drugs to continue on the road for prolonged periods. Use of stimulants for this purpose is probably frequent and sustained, not occasional, and thus is potentially dangerous.

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