ATRI: Imprecise Tests for Pot Impairment Endanger Truckers

March 13, 2019 by Alan Adler, @AlanAdler

Relatively few truck drivers test positive for driving high on marijuana, but they are at greater risk of being in a crash as states legalize recreational use of the drug.

Those are the findings of a study released Wednesday by the American Transportation Research Institute. Without precise ways of testing for impairment, truckers, who spend hours at a time on the road, are more in jeopardy.

Ten states have passed recreational marijuana laws, and 31 states allow it for medical reasons. Marijuana use is federally prohibited, meaning it cannot be used when crossing state lines.

“The increased frequency of marijuana-positive drivers operating on the same roadways as trucks makes marijuana-impaired driving a critical safety issue for the trucking industry,” said ATRI, the research arm of the American Trucking Associations.


In 2016, random testing identified drugs in 0.7 percent of commercial drivers, according to the Federal Motor Carrier Safety Administration.

Under federal law, commercial driver’s license holders must be tested for marijuana use before hire, after a crash involving a fatality or when a truck is towed from a crash scene. Urinalysis is the most common form of testing, but it can only detect drug use within a few days of testing. Hair follicle testing can discover months-old drug use.

mariuana plant

Two types of testing can determine marijuana use: a urinalysis and a hair-follicle test. The latter is believed to be more accurate.

Motor carriers J.B. Hunt Transport Services Inc. and Schneider National Inc. conduct both forms of testing and report hair testing is more accurate.

“While these companies are attempting to keep unsafe drivers from operating trucks, it is likely that applicants failing the hair tests simply seek jobs at other companies that do not require hair testing,” ATRI said.

A national clearinghouse that tracks trucker testing will go into effect in 2020, requiring any company that releases a trucker for a failed drug test to file a report.


Drunken driving was involved in 25 percent of the 37,133 traffic fatalities reported by the National Highway Traffic Safety Administration for 2017. But NHTSA said it lacked state-level data about marijuana use by drivers to determine its involvement in crashes, injuries and deaths.

Many states and courts make no distinction between drug-impaired driving and alcohol-impaired driving in DUI cases.

“Whether or not the federal government recognizes the legality of marijuana, it should take the lead on related federal data-collection programs,” ATRI said.


Compared with testing for alcohol by measuring its content in the blood, testing for driving under the influence of marijuana is complex. Tetrahydrocannabinol, or THC, deteriorates rapidly in a user’s blood, and low levels do not always indicate impairment.

Because marijuana was illegal for many years, little research on its effects on driving has been conducted. Marijuana smokers stopped for suspicion of driving under the influence are unlikely to confess to using marijuana because DUI penalties are severe, ATRI said.


Younger drivers tend to think that driving high does not increase crash risk, according to the AAA Foundation.

In 2018, NHTSA launched the “If You Feel Different, You Drive Different” advertising campaign to combat the perception that drugged driving is not dangerous.

Some states are doing outreach on the dangers of marijuana-impaired driving and the legal consequences of driving under the influence of marijuana. In Colorado, a “Drive High, Get a DUI” advertising campaign targets marijuana retail stores.

Alan Adler October 4, 2018
Trucking fatalities from crashes rose 9 percent in 2017, the most in 29 years and counter to a overall drop in roadway fatalities

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