The new numbers are part of a “historic number of fatalities that we’re seeing in the state,” according to CDOT communications manager Samuel Cole, who was part of a March 3 press conference warning Coloradans of poly-impaired driving, or driving under the influence of multiple substances, such as alcohol, marijauna or narcotics.
The mixing of alcohol and cannabis produces more dangerous driving outcomes than either would alone, according to Ashley Brooks-Russell, an associate professor at the Colorado School of Public Health. Among other intoxicating effects, she says, both substances can substantially slow reaction time, despite being processed differently within the human brain.
A 2021 report from AAA states that those who admit to using both cannabis and alcohol are also more likely to report speeding on residential streets, aggressive driving tactics and texting while driving.
Colorado Department of Public Safety DUI statistical analyst Allison Rosenthal has been monitoring impaired driving in Colorado using court and toxicology records dating back to 2018. Building off this data, the CDPS has released four annual reports. The most recent report, based on Colorado court data from 2019, discovered a “concerning prevalence of drivers who test positive for multiple drugs,” she said during the press conference.
Of drivers charged with a DUI and subsequently tested for drugs in 2019, 45 percent tested positive for multiple substances, with the most-noted combination being alcohol and Delta-9 THC. Other commonly detected and combined substances include cocaine, methamphetamine, sedatives and opioids.
The CDPS also reports that nearly 50 percent of 6,071 cases involving toxicology screens for marijuana showed positive tests of Delta-9 THC that were above the legal limit of 5 nanograms per milliliter of blood (5 ng/mL). Of those convicted of DUI charges in 2019, 92 percent displayed illegal Delta-9 THC results. However, the state's method of measuring marijuana impairment through THC nanograms has been criticized for potential inaccuracies and not being based in science, as regular users can test above the limit without having consumed for a day.
Poly-substance use also had a “significant impact on crash rates” among convicted users, Rosenthal said. According to her data, substance-combiners were involved in crashes one and a half times more than drivers testing positive for alcohol alone, and four times the rate of those testing positive for cannabis alone.
To address the problem, CDOT will conduct multiple traffic safety campaigns this spring and summer to raise more awareness about the dangers of impaired driving and combining substances. Next month, Colorado law enforcement officers can take part in drug recognition training in Castle Rock, according to the department.
“Because we have those [problematic] people out there that are just going to continue to re-offend, we have well-trained officers on our roadways to identify drugs, alcohol, cannabis and the whole gamut of things that are impairing people,” Cole concluded.