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DENVER (KDVR) — Several state agencies are highlighting a troubling trend Thursday: more Coloradans are getting behind the wheel under the influence of multiple substances, putting them more at risk of crashing and dying on the road.

2021 was the deadliest year on Colorado roads since 2002, with 691 deaths. Fatal crashes have gone up 50% since 2011 and one in three traffic fatalities involved an impaired driver this past year, according to the Colorado Department of Transportation.

“Since 2019 there’s been a 44% increase in the number of fatalities involving impaired drivers, many of whom are impaired by multiple substances or combinations,” said CDOT Highway Safety Manager Glenn Davis.

The increasing trend is something that worries Allison Rosenthal, an analyst with the Colorado Division of Criminal Justice, who recently crunched the numbers on 2019 DUI court case data in a recently published report.

“Of drivers that were charged with a DUI that were drug tested, 45% tested positive for multiple substances,” Rosenthal said.

When analyzing poly-impaired driving, researchers found a combination of alcohol and marijuana was the most common, followed by alcohol and other drugs including cocaine, methamphetamines or opioids.

“Drivers who tested positive for alcohol, other drugs and or cannabis were involved in crashes at one-and-a-half times the rate who tested positive for alcohol alone and at four times the rate of convicted drivers who tested positive for cannabis alone,” Rosenthal said.

You can watch the discussion on FOX31 NOW.