How Authorities Detect Cannabis Intoxication on the Road.

Various products are being tested out that might be used to measure impairment.

Posted September 3, 2021

Rewind to 1972, two years after Nixon started the War on Drugs. Around that time Nixon convened the Shafer Commission, which shocked the establishment by recommending legal possession and personal use of cannabis. However, fairly close to the end of its report, it entered into a discussion of “Marijuana and Driving.” “Within the context of public safety another issue which merits attention is the extent to which drivers under the influence of marihuana constitute a hazard on the nation's streets and highways,” their report read. “Although in recent years increasing attention has been given to this issue, at present little empirical evidence exists to inform discussion.”

Fast forward to Forty-nine years later, 36 states have made cannabis legal for medical use and 18 for adult use; however, the Shafer Commission’s statement still holds true for the most part. That’s because unlike alcohol, there is no standard per se measurement that effectively determines cannabis intoxication while behind the wheel (although six states do set it between one to five nanograms per milliliter of blood). Further complicating the issue is that, unlike alcohol, which is water-soluble and leaves the body quickly, cannabis metabolites can stay in the body long after the high wears off — a troublesome predicament for medical patients or frequent users. In short, there’s no good biomarkers for cannabis impairment while driving. This has led to several startups and academic researchers testing out various products. Considering how differently THC affects its users, a combination of any or all of these might be used to measure impairment.

Cannabis Breathlyzers

Everyone who’s ever been pulled over knows that if the breathalyzer measures a certain blood alcohol content, you can be found guilty of driving under the influence. Along those lines, several THC breathalyzers which purport to measure THC, ingested by either smoke or edibles, are currently being developed. Oakland, CA-based Hound Labs has garnered most of the press, and they’ve even developed a COVID-19 breathalyzer with the same technology. Similarly, researchers at the University of Pittsburgh have configured a device which is used to detect asthma and halitosis to scan for THC as well. And the Canadian-based Cannabix Technologies has a breath analyzer in the “advanced prototype” stage.

As Hound Labs CEO Mike Lynn acknowledges, devices like his only detect and measure the levels of THC in breath, which does not always correspond with impairment. As UCSD Psychology Professor Tom Marcotte explains, “When a person smokes marijuana, their blood levels go up very rapidly and then decline fairly rapidly. But a person could still be high, even when blood levels are declining." So Cannabix and Hound Labs may see greater use at workplaces such as warehouses or airports for sobriety spot checks.

Biometrics

Last month, Cannabis and Cannabinoid Research published a preliminary study which examined the ocular activity of 10 test subjects who operated a driving simulator, both before and five hours after consuming cannabis. The researchers filmed the eyes of the test subjects and correlated their activity with speed, how much they “weaved” on the simulated road and blood THC content. Specifically, features which corresponded to the eye’s saccades, such as velocity and scanpath picked up as impairment faded, and also corresponded most strongly with the driving variables measured. While the study did not possess a control group, such observational methods may be implemented in future biometrics devices that could eliminate the need for blood or urine tests.

Drug Recognition Experts

In addition to breathalyzers, police departments in all 50 states participate in the Drug Evaluation and Classification Program, which train Drug Recognition Experts to examine types of intoxication in the field, including botanical and synthetic cannabis. However, many officers have not received this training. In California, for instance, less than 3% of the police officers are trained in this program. Not only does training need to be more widespread, but field sobriety tests designed for alcohol won’t work for cannabis. “Studies have been done where people ingest marijuana, and that field sobriety test is given to them. About 50 percent of them pass it. And if they’re frequent users of marijuana, about 70 percent of them can pass it,” informs Barth Wilsey, an anesthesiologist who has worked with UCSD on cannabis field sobriety tests.

Cognitive Assessments

Researchers such as Wilsey and Marcotte have just wrapped up a three-year study at UCSD. During this test, 180 test subjects consumed cannabis, participated in driving simulations, and then completed tasks on an iPad as a form of application based test of intoxication. If the data supports it, this app-based sobriety test could be used in the field. The data they’ve gathered is currently being assessed by scientific journals and awaiting publication.

For public safety administrators, solving the DUI dilemma carries a sense of urgency. The National Highway Traffic Safety Administration has found that between the years 2007 to 2016, the presence of cannabinoids in the bloodstream of fatally injured drivers went up by 10%. The AAA continues to oppose cannabis legalization because of the challenges in standardizing cannabis impairment and the elevated risks it poses when combined with alcohol. A Discovery article written on the subject remarks on how it took from the mid-‘50s to the end of the ‘90s to settle on .08% BAC as the national standard — and how some argue it should be lowered to .05%. Almost a half-century has passed since the Shafer Commission published their findings, and those standards, which are important to develop in a society where cannabis is legal, are still being gradually developed.

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