Congressional Hearing Highlights Concerns Over Cannabis-Impaired Driving
As cannabis legalization advances across the United States, concerns surrounding marijuana-impaired driving have taken center stage. During a recent congressional hearing, Michael Hanson, Director of Traffic Safety with Minnesota DPS, emphasized the importance of roadside drug testing to prevent fatal car accidents.
“One effective measure that could prevent tragedies from taking place would be conducting oral fluid roadside testing.” — Michael Hanson
Hanson responded to inquiries from Rep. Rob Bresnahan (R-PA) about instantaneous impairment detection methods. He advocated for saliva-based testing, which law enforcement could use to determine recent cannabis use.
Challenges in Testing for Cannabis Impairment
Catherine Chase, president of Advocates for Highway and Auto Safety, supported expanding zero-tolerance policies for drivers under 21 to include marijuana use. Yet, despite these efforts, no universally accepted roadside test currently exists for detecting marijuana impairment.
The National Institute of Standards and Technology (NIST) plans to host a cannabis breathalyzer discussion in April, addressing challenges in developing reliable technology for real-time impairment testing.
“Giving law enforcement the tools necessary to prevent impaired driving is absolutely essential.” — Michael Hanson
Trucking Industry and Safety Concerns
The trucking industry has expressed worries that marijuana legalization could undermine zero-tolerance drug policies vital for commercial driver safety.
Dennis Dellinger, CEO of Cargo Transporters Inc., testified that the industry currently relies on urine and hair tests, which detect past use but do not measure active impairment. He stressed the need for accurate testing methods to prevent legal challenges and public backlash in the event of accidents.
Saliva Testing: A Step Forward?
In 2023, the Department of Transportation (DOT) approved saliva-based testing, capable of detecting THC within one to 24 hours post-use. However, researchers, including Frances Scott of the DOJ’s National Institute of Justice, question whether THC levels in bodily fluids reliably indicate impairment.
“Chronic and infrequent cannabis users exhibit varying THC concentrations, making it difficult to establish universal impairment thresholds.” — Frances Scott
The Science Behind THC and Driving Ability
A 2023 preprint published on The Lancet analyzed 12 peer-reviewed studies on THC blood levels and driving performance. Surprisingly, 10 studies found no correlation between THC levels and driving impairment measures, such as:
- Speed control
- Lateral position (SDLP)
- Following distance
These findings highlight the complex relationship between cannabis use and driving performance, complicating rulemaking efforts.
Federal Efforts to Standardize Impairment Testing
Congress continues to explore solutions. Sen. John Hickenlooper of Colorado sought updates from the DOT on overcoming research barriers for developing roadside THC tests. The National Transportation Safety Board (NTSB) also raised concerns that marijuana rescheduling could hinder drug testing for federally regulated workers in safety-sensitive positions.
Despite these efforts, a 2019 National Highway Traffic Safety Administration (NHTSA) report concluded:
“It’s difficult to establish any correlation between THC blood levels and performance-impairing effects. Unlike blood alcohol content, THC concentration does not directly indicate driving impairment.”
Cannabis Reform and Industry Impact
The trucking industry faces an ongoing driver shortage, with record-high drug test refusal rates. According to an ATRI survey:
- 72.4% of truck drivers support relaxing cannabis laws.
- 66.5% advocate for federal legalization.
Rep. Earl Blumenauer (Oregon) pointed out that federal drug testing policies might be unnecessarily costing jobs and worsening supply chain issues.
Looking Ahead: Balancing Safety and Reform
The debate over cannabis-impaired driving reflects broader challenges at the intersection of public safety, legalization, and regulatory reform. As more states legalize marijuana, developing accurate impairment detection methods remains crucial for ensuring highway safety without unfairly penalizing drivers who are not impaired.