ATRI study: Marijuana impairment emerges as issue for trucking

A recent study by the American Transportation Research Institute (ATRI) addressed the growing issue of marijuana-impaired driving as an increasing number of truckers are sharing the roadways with automobile drivers operating under the influence of marijuana.

ATRI’s research sought to document the most promising methods to identify and deter marijuana-impaired driving.

The study recommends: increased data collection on the frequency and impacts of marijuana-impaired driving; public education and information on the risks of impaired driving; better equipping law enforcement and the court system to intercept and ultimately prosecute impaired drivers; and targeting tax revenue generated from marijuana sales to fund these activities.

“While increased access to marijuana has not directly impacted the trucking industry in terms of truck drivers testing positive for marijuana, 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,” concluded the ATRI report.

After decades in which marijuana was an illegal substance in the United States, 33 states have legalized marijuana for medical use, and 10 states and the District of Columbia have legalized recreational use of the drug.

“The motivator for this report being picked as a top priority by our research board was the recognition that regardless of how you feel about the legalization of marijuana, it is going to have a resulting safety impact,” ATRI President Rebecca Brewster told Transport Topics. “We’re going to be sharing the road with more drivers impaired from marijuana. Our board decided to get ahead of this issue to identify the challenges and potential recommendations to improve roadway safety.”

One of the study’s most significant conclusions was that while accurate tools to test for and prosecute drunken driving exist, similarly accepted tools and methods are not available for marijuana-impairment testing. “As a result, truck drivers in many states now face the significant risk of having legal marijuana users drive impaired (and illegally) alongside their trucks.”

“Recent national statistics for marijuana-positive drug tests, for instance, indicate that 2.6 percent of drug tests were marijuana-positive in 2017 — a 4 percent year-over-year increase from 2016,” the ATRI study said. “Marijuana-positive drug tests for federally mandated, safety-sensitive occupations have also increased by nearly 8 percent from 2016 to 2017.”

While it may be legal in some states to consume marijuana, the intoxicating effects of tetrahydrocannabinol or THC, include poor judgment, decreased motor coordination and decreased reaction time. The key findings of research on marijuana’s impact on behavior and driving-related cognitive functions also include divided attention, inability to maintain lane position and attempts to compensate by increasing following distance and being less likely to pass other vehicles, the ATRI study said.

While standard roadside field sobriety tests are used for alcohol, such testing is not evidence of active impairment or intoxication for marijuana due to the body’s mechanisms for processing THC, ATRI said.

“Unlike alcohol, THC in blood tests are not reliable indicators of driver impairment,” the ATRI report said. “However, the National Highway Transportation Safety Administration, for instance, offers evidence that some state laws allow an individual to be charged with a DUI if they test positive for THC derivatives in urine following arrest, which indicates marijuana use in the past 30 days but not necessarily recent marijuana use.”

ATRI said that while federal funds are being used to educate prosecutors and judges on drug-impaired driving cases, efforts to prosecute drug-impaired driving have been met with numerous setbacks.

“For example, Arizona requires ‘proof’ of impaired driving but does not have per se limits on THC blood concentrations,” the report said. “Conversely, Massachusetts has challenged the ability of field sobriety tests to accurately identify marijuana impairment.”
The ATRI study said that documenting the prevalence of drug-impaired driving is critical to understanding the magnitude of the issue.

“Whether or not the federal government recognizes the legality of marijuana, it should take the lead on related federal data collection programs,” ATRI said. “Key to this role is identifying and conveying standards for state- and local-level data collection by law enforcement and the criminal justice system.”

Specifically, transportation and law-enforcement officials should collect data on the marijuana-impaired number of crashes, injuries, and fatalities; number of drug tests administered and rate of negative drug tests; number of marijuana-related DUI charges and conviction rates; and the prevalence of marijuana use while driving.

“Law enforcement officers also need additional resources to support DUI investigations with biological testing,” ATRI said. “The rapid degradation of THC in blood necessitates testing a DUI suspect for drugs quickly.”