Marijuana, Opioids Found in High Percentage of Drivers Killed in Car Crashes

June 11, 2018

More than half of drivers killed in car accidents who were tested for drugs had marijuana, opioids or a combination of the two in their system, according to a new report.

The Governors Highway Safety Association (GHSA) report found that in 2016, overall, 44 percent of fatally-injured drivers with known results tested positive for drugs, up from 28 percent just 10 years prior.

The report found that among the fatally-injured drivers who tested positive for drugs in 2016, 38 percent tested positive for some form of marijuana, 16 percent tested positive for opioids, and 4 percent tested positive for both marijuana and opioids.

The report, Drug-Impaired Driving: Marijuana and Opioids Raise Critical Issues for States, was funded by the Foundation for Advancing Alcohol Responsibility (

While alcohol-impaired driving remains a significant threat to traffic safety, presence of alcohol in fatally-injured drivers is slightly lower than it was a decade ago, decreasing from 41 percent in 2006 to 38 percent in 2016.

The authors of the report say that some of the strategies that have been used to address alcohol-impaired driving can also be employed to deter drug-impaired driving, but drug impairment presents several unique challenges. Among the challenges: the lack of a nationally-accepted method for testing driver drug impairment; the number of drugs to test for is substantial; and different drugs have different impairing effects in different drivers.

“Drugs can impair, and drug-impaired drivers can crash. But it’s impossible to understand the full scope of the drugged driving problem because many drivers who are arrested or involved in crashes, even those who are killed, are not tested for drugs. Drivers who are drug-positive may not necessarily be impaired,” report author Dr. Jim Hedlund, former senior National Highway Traffic Safety Administration (NHTSA) official.

The use of multiple substances simultaneously is another concern. In 2016, 51 percent of drug-positive fatally-injured drivers were found positive for two or more drugs. Alcohol is often in the mix as well: 49 percent of drivers killed in crashes who tested positive for alcohol in 2016 also tested positive for drugs.

Alcohol-impaired driving and drug-impaired driving should no longer be treated as separate issues, according to Ralph Blackman, president and CEO of “[W]e have to think about the combination of substances drivers are often putting into their systems at the same time,” he said.

GHSA and provide training for police officers through two grant programs: Advanced Roadside Impaired Driving Enforcement (ARIDE) and Drug Evaluation and Classification (DEC). They teach law enforcement the signs and symptoms of impairment by different categories of drugs.

“Too many people operate under the false belief that marijuana or opioids don’t impair their ability to drive, or even that these drugs make them safer drivers,” said GHSA Executive Director Jonathan Adkins. “Busting this myth requires states to expand their impaired driving campaigns to include marijuana and opioids along with alcohol to show drivers that impairment is impairment, regardless of substance.”

The researchers compare 2016 results with those of a decade ago in 2006. In 2006, 27.8 percent of drivers with known drug test results were drug-positive compared to 43.6 percent in 2016. In 2006, 41.0 percent of all drivers with known test results were alcohol positive compared to 37.9 percent in 2016.

The report’s data is from two sources: NHTSA’s Fatality Analysis Reporting System (FARS) and NHTSA roadside surveys in the United States and Canada. The authors acknowledge that no data sources accurately document drug testing of drivers and that testing rates vary considerably by state. However, they contend FARS is the best data source that includes data from all states.

The authors further caution that drug presence does not imply impairment, that some drugs tested are known to not impair driving and that the effect of marijuana or drugs on crash risk is unclear.

While there are many recent studies on marijuana, they tend to have methodological flaws and are complicated by the difficulty in estimating a driver’s THC at the time of a crash, the authors say. Thus, the GHSA study concludes, the “most supportable conclusions are that marijuana has caused or contributed to some crashes; that it can, but need not necessarily, increase crash risk in a driver; and that the best overall estimate of marijuana’s effect on crash risk in general is an increase of 25-35 percent, or a factor of 1.25 to 1.35.”

According to FARS data, in 2016, 54.3 percent of the fatally-injured drivers were tested for marijuana. This means that 22.3 percent— almost one-quarter—of all fatally-injured drivers were known to have been marijuana positive. While the authors cite the limitations of FARS data, they assert that certain general conclusions are clear: “Marijuana is the most common drug found in fatally-injured drivers and marijuana presence has increased substantially in the past decade.”

Estimating the effect on crash risk is even more difficult for opioids than for marijuana, according to the authors, who write that the “most supportable conclusion” is that opioids can increase crash risk by a factor of no more than about 2. They assert the general conclusions that opioids are present about half as frequently as marijuana in fatally-injured drivers and opioid presence has increased in the past decade.

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