Marijuana testing bottlenecks commercial driver availability

Positive marijuana tests push many drivers out of the industry, aggravating an existing recruiting and retention challenge.

Education and messaging can help keep drivers up-to-date on DOT rules—but how significant is the rate of positive marijuana tests among drivers?

Since 2020, the Federal Motor Carrier Safety Administration's Drug & Alcohol Clearinghouse has logged 233,910 positive drug tests. Of those positive tests, 159,550—nearly 70%—found evidence of marijuana use.

That is a large number of drivers forced to immediately cease operation of any commercial vehicle on public roads. Some of this is due to a national trend toward cultural and legal acceptance of the substance, causing confusion for drivers. Another major contributor is the massive detection window for marijuana in drug tests.

“A lot of folks are testing positive for marijuana because marijuana stays in your system for 30 days,” Michael Precia, president and CSO of Fleetworthy, said. “That doesn’t necessarily mean those drivers were driving stoned at all; they weren’t necessarily using while driving. But it stays with you for such a length of time that you’re going to get positive for a test even if you’re casually using in your off-duty time.”

See also: 4 steps to incentivize safe driving

Not only is marijuana one of the most popular illicit substances subject to Department of Transportation testing, but it also has the largest detection window by a significant margin.

Impairment testing is tricky

The legal acceptance of off-time alcohol use is a common analogy for arguments that defend marijuana use. If an employee can have a couple of beers on the weekend and return to work sober, it seems unjust that any marijuana use—at any time—should cost the employee their livelihood.

Similar to alcohol use, marijuana use makes unsafe drivers. Marijuana impairment limits executive function and motor control, and marijuana use increases the risk of causing a fatal accident.

However, marijuana impairment works a bit differently from alcohol.

Marijuana impacts the brain in different ways than alcohol, bringing different impairments to mood, memory, and cognitive performance that last for different lengths of time. And, while alcohol has breathalyzers to measure intoxication, marijuana has no functional equivalent.

“The whole idea is to keep the industry safe, and if you’re not using while driving, in theory that would be safe,” Jeffrey Short, VP of the American Transportation Research Institute, said. “Here’s the problem, of course: Marijuana impairment tests are very elusive. There is not an accepted marijuana impairment test. It just doesn’t exist. Whoever invents it is going to be a billionaire. It’s very much needed for our industry, for other industries, and for the general public.”

With no impairment test, the only available tests for marijuana look for metabolites in urine. Marijuana has some of the longest detection windows of any illicit substance subject to urine testing. Its metabolite, Δ9-THCA, can be found in urine for as long as seven to 30 days after use. This is a large timeframe and hardly indicative of impaired driving.

However, there is no better federally-accepted alternative to tell whether a driver might operate under the influence of marijuana. And, in today’s challenging legal landscape for the trucking industry, any evidence of a driver’s marijuana use can be very harmful to carriers.

“Clearly, plaintiffs’ attorneys will hone in on just about anything they can find if a driver screens positive for marijuana in a post-crash, regardless of whether it was a factor,” Short said.

Metabolite testing for a history of marijuana use is the best available option in determining whether a driver is at risk of driving impaired. Precia compares this testing to hours-of-service regulations.

“The whole goal of hours of service is just to make sure that a driver is not fatigued and not impaired," Precia explained. "Fatigue in itself is not illegal, right? It’s really trying to figure out ways to ensure that the driver is not impaired.”

“There is no impairment standard,” Brenna Lyles, director of safety policy for the American Trucking Associations, said. “Until that exists, the test for marijuana is critical because use is the only thing that we can use right now to indicate safety.”

Marijuana test results in recent years

Marijuana use nearly doubled since 2012. Motor carriers have found an increase in drivers’ positive pre-employment tests and walk-outs. However, the Federal Motor Safety Administration’s count of positive marijuana tests decreased over the last two years.

According to the National Institute on Drug Abuse, overall marijuana use in the U.S. continues to rise. Among surveyed adults aged 19 to 30, an all-time high of 44% of respondents in 2022 reported using marijuana within the last year. That is nearly double 2012’s reported use rate of 28%.