It’s well known that drunk driving can have fatal consequences, but anew study suggests that alcohol is not the only drug that’s a danger onthe road.
It might make sense that drugs like marijuana or amphetamines wouldimpair drivers and lead to crashes. But few studies have actually lookedspecifically at the impact of other drugs on traffic deaths -- even asthere is an increasing push to pass “drugged driving” laws nationally.In the new study, reported in the July issue of the Journal of Studieson Alcohol and Drugs, researchers found that of U.S. drivers who died ina crash, about 25% tested positive for drugs. The most common drugs weremarijuana and stimulants, including cocaine and amphetamines, which eachaccounted for almost one quarter of the positive tests.
It’s not clear whether the drugs were to blame for the crashes, theresearchers say. Some people who use illegal drugs may simply bereckless drivers in general, for instance.
On the other hand, a recent government study found that of U.S. driverswho were randomly pulled over, 14% tested positive for drugs. The factthat drug use was almost twice as high among drivers in fatal crashessuggests that drugs do contribute to road deaths.
“The suspicion is there, because when you look at drivers who’ve been infatal crashes, the percentage using drugs is a good deal higher,” saidstudy co-author Robert B. Voas, Ph.D., of the Pacific Institute forResearch and Evaluation in Calverton, Maryland.
For the general public, the message is simple.
“Don’t drink or don’t consume drugs when you’re going to drive,” saidEduardo Romano, Ph.D., the lead author on the study.
The issue is more complicated, though, when it comes to lawmaking,according to the researchers.
With alcohol, drivers’ blood levels can be easily tested, and becausestudies have found that levels above a certain limit—.08%—impairdriving, that blood alcohol concentration is the legal limit in all U.S.states. With other drugs, however, there are no agreed-upon levels thatimpair driving, and testing drivers is not straightforward. For one,certain drugs can linger in the body for days or weeks after they are used.Right now, states differ in how they tackle drugged driving. More than adozen have drugged-driving “per se” laws. In most states, that means“zero tolerance” for any detectable amount of certain drugs in adriver’s blood or urine. The specific drugs that are prohibited vary bystate.
Last year, the White House announced that it would be encouraging morestates to adopt drugged-driving per se laws.
So it is important, Romano and Voas say, for researchers to keepstudying how various drugs might impair drivers.
The current findings are based on a government reporting system thatcollects data on all U.S. traffic deaths. All states report drivers’blood alcohol levels, whereas 20 test for drugs.
Between 1998 and 2009, there were more than 44,000 fatally injureddrivers with drug-test information—one quarter of whom tested positivefor drugs. Marijuana and stimulant drugs including cocaine andmethamphetamine were the most commonly implicated.
It turned it out that stimulants were linked to all types of crashfatalities—whether from speeding, failure to obey other traffic laws,inattention, or forgoing seatbelts. Marijuana, on the other hand, wastied only to speeding and seatbelt non-use. That lays out thepossibility that stimulants are particularly impairing, but that’s notyet clear, the researchers say.
Whatever the effects of different drugs, alcohol still appears to be thebiggest roadway hazard.
This study found that, in general, other drugs seemed to be key onlywhen drivers had not been drinking as well. That is, when someone drinksand does drugs, the alcohol is the main reason for impaired driving.
“Alcohol is still the largest contributor to fatal crashes,” Romano said.