As cannabis use becomes increasingly common, law enforcement agencies across the United States are racing to adapt to the challenges of identifying drivers impaired by the drug. With more Americans using cannabis daily than alcohol, the potential for drug-impaired driving is on the rise, posing significant risks on the nation’s roads.
A 2023 study published in the International Journal of Drug Policy estimates that marijuana legalization has contributed to well over 1,400 additional traffic fatalities annually. Despite the risks, public awareness badly lags, with only 70% of drivers recognizing the dangers of driving an hour after consuming cannabis, compared to 94% who view driving after alcohol consumption as very dangerous, according to a 2022 AAA survey.
“There’s no simple test for cannabis impairment like there is for alcohol,” said Michael Whitekus, science director at Robson Forensic, a firm specializing in crash investigations. “Current tests can’t determine if someone’s actually impaired at the time of driving.”
Traditional drug tests, such as urine and blood tests, are inadequate for determining real-time impairment. Urine tests can detect cannabis use days after consumption, while blood tests measure THC levels that do not directly correlate with impairment. Moreover, the psychoactive effects of THC are difficult to gauge because THC is fat-soluble and metabolizes differently from alcohol, which is water-soluble and easier to measure.
New roadside oral-fluid tests offer a more immediate, though still imperfect, solution. These tests can confirm recent cannabis use within minutes, but they don’t measure the extent of impairment.
Training programs are also being developed to help officers detect signs of cannabis impairment. These programs involve live demonstrations where volunteers consume cannabis and then undergo sobriety tests. Officers are trained to look for telltale signs such as bloodshot eyes, sluggish movements, and difficulty following instructions. For example, when asked to estimate 30 seconds with their eyes closed, individuals under the influence of cannabis often misjudge the time, highlighting their impaired perception.
In one high-profile case, a truck driver involved in a fatal collision had used cannabis, but investigators could not conclusively determine how badly he was impaired at the time. This incident underscores the difficulty in drawing clear lines between cannabis use and driving impairment.
Studies suggest that combining cannabis with alcohol will dramatically increase impairment, further complicating efforts to ensure road safety. “It’s not just an additive effect; it’s a multiplication effect,” said Eric Jackson, executive director of the Connecticut Transportation Institute, which is studying a rise in wrong-way crashes.
As cannabis use continues to rise, law enforcement agencies must urgently work to piece together a clearer picture of pot and its impact on driving. The quest to develop reliable methods for detecting and proving cannabis impairment remains a critical challenge in ensuring public safety on Union City streets and our highways.
