Frequent Questions on Alcohol Safety
What is "drunk driving?"
It has been known for decades that alcohol impairment contributes to crashes, but the term "drunk driving" is an inaccurate characterization of the problem of alcohol-related motor vehicle crashes. 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. 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 concentration of alcohol in a person's blood expressed as weight per unit of volume. For example, at .10 percent BAC, there is a concentration of 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?
A BAC of .08 percent or greater is a crime in Kansas for drivers 21 years of age and older.
A BAC of .02 percent or greater is a crime in Kansas for drivers under 21 years of age.
How many drinks does it take to reach significantly impairing BACs?
The effects of alcoholic drinks vary greatly because the rate that alcohol is absorbed into the blood differs from person to person. Other factors, such as the amount of food in the stomach, also affect alcohol absorption. 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. Even after controlling for differences such as age, sex, and weight that are known to affect BACs, an individual's peak BAC may differ markedly from the average indicated on the charts.
What is the effect of alcohol on driving skills and crash risk?
The probability of a crash increases at any BAC higher than zero. At a BAC as low as .02 percent, alcohol affects driving ability and crash likelihood. The probability of a crash begins to increase significantly at .05 percent BAC and climbs rapidly after about .08 percent. For drivers age 35 and older with BACs at or above .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.
Are beer and wine less impairing than hard liquor?
Impairment is not determined by type of drink. It is measured by the amount of alcohol ingested over a specific period of time. There is an equivalent 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 limited roadside surveys.
What proportion of motor vehicle crashes involves alcohol?
The most reliable information about alcohol involvement comes from fatal crashes. In 1999, 28 percent of fatally injured drivers had BACs of at least .10 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 1999, the National Highway Traffic Safety Administration estimated that 30 percent of all traffic deaths occurred in crashes in which at least one driver or nonoccupant had a BAC of .10 percent or more and that any alcohol was present in 38 percent of all fatal crashes in 1999. 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, Michigan -- 12 percent in Huntsville, Alabama and in San Diego, according to a study from the 1970s -- had BACs at or above .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 .10 percent or more. No recent studies of BACs in nonfatal crashes are available, but similar relationships would be expected.
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 1999, 34 percent had BACs of .10 percent or more. The corresponding proportion among women was 16 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. 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 with high BACs has increased -- but not significantly.
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 1999, 53 percent had BACs at or above .10 percent compared with 15 percent during other hours. Thirty-nine percent of all fatally injured drivers on weekends (6 p.m. Friday to 6 a.m. Monday) had BACs of .10 percent or more. During the rest of the week, the proportion was 21 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 over represented 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 ( .10 percent or more). 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.