Marijuana Facts

How many Coloradans are driving high? New report offers one answer

Four years after the legalization of recreational pot sales, state officials are another step closer to determining how the change is affecting the safety of Colorado’s roads — but many obstacles remain.

About 73 percent of some 4,000 drivers charged with driving under the influence in 2016 tested positive for marijuana, according to a new Division of Criminal Justice report. Of those who tested positive, about half of the drivers had more than the legal limit of Delta 9 THC — marijuana’s chief psychoactive compound — in their blood.

But the study also reveals a criminal justice system not prepared to deal with drugged driving. The authors of the report noted that inconsistent testing is one of the many challenges in collecting data on drug-impaired driving.

The 4,000 people screened for marijuana represent a small fraction of the 27,244 total court cases that involved at least one DUI charge filed statewide in 2016. The other defendants were never screened for drug use.

Law enforcement officers don’t always test for other substances if they’ve already determined a driver’s blood alcohol content is at or above the legal limit. It costs between $100 and $500 per blood sample to test for substances other than alcohol, according to the report. Further, suspects sometimes have to be transported to a different location before blood can be drawn for testing. During that time, the amount of THC in their blood decreases quickly.

“There is a wealth of information available on alcohol-impaired driving while there is a dearth of research on the problem of drug-impaired driving,” the report states. “As the national landscape of marijuana legalization continues to expand, it is critical to gain a better understanding of driving impairment associated with drugs, especially cannabis.”

Surveys completed by the Department of Transportation in 2016 and 2017 found that about half of marijuana users said they drove within two hours of using the substance. A Denver Post investigation found that the number of fatalities in crashes that involved drivers who tested positive for marijuana rose sharply between 2013 to 2016, when 51 people were killed. The total number of crash fatalities also rose during that time, from 482 deaths in 2013 to 608 in 2016.

Some agencies, like the Colorado State Patrol and the Colorado Bureau of Investigation, have made concerted efforts to test more drivers for drug use, said Patricia Billinger, spokeswoman for the Colorado Department of Public Safety.

“We do think that drug-impaired driving is probably underrepresented in the data because of the fact that it is easiest and cheapest for law enforcement to test for alcohol,” Billinger said. “We’d love to see more agencies testing.”

Other efforts to better understand how often people are driving after using drugs are underway.

The Colorado Bureau of Investigation is examining blood samples in previous DUI cases that weren’t previously tested for substances other than alcohol, but that data isn’t available yet. Earlier this year, the Colorado Department of Transportation launched an anonymous survey to ask drivers about their marijuana and alcohol use. The Department of Public Safety is also expected to release a broad study of the impact of marijuana legalization in September, Billinger said.