[author: Michele Bowman]
“I drive better when I’m high.” Have you ever heard anyone say that? An urban legend has grown up around the 
idea that while drinking and driving is obviously dangerous and illegal, smoking and driving somehow allows one to skirt DUI laws.
There is actually little evidence that smoking pot impairs driving. “Surprisingly, given the alarming results of cognitive studies, most marijuana-intoxicated drivers show only modest impairments on actual road tests,” noted a 2009 National Institutes of Health report on the effect of marijuana on driving, as compared to alcohol.
But a federal government study – the first of its kind – aims to specifically investigate the effects of driving while high.
State Laws Cover Driving while Smoking – Sort Of
Most states’ DUI/DWI laws cover controlled substances as well as alcohol. Some states – Nevado, Ohio, and Pennsylvania – make illegal certain levels of THC – the psychoactive ingredient in marijuana – or marijuana metabolites in a driver’s bloodstream or urine.
Others – Arizona, Georgia, Illinois, Indiana, Iowa, South Dakota, and Utah – have a zero-tolerance policy and can convict for DUI no matter the amount of the drug in one’s blood or urine. Then there’s California, which interprets “under the influence” to mean some degree of impairment, which is measured by a field sobriety test.
But the difficulty of detection combined with the vagaries of applying field sobriety tests can make it difficult for prosecutors to prove someone was driving while high. “The effects of cannabis vary more between individuals than they do with alcohol because of tolerance, differences in smoking technique, and different absorptions of THC,” according to the NIH.
The National Highway Traffic Safety Administration studied alcohol and drug use by drivers back in 2007. While the agency didn’t measure the prevalence of smoking marijuana (by itself) while driving, it did say that pot was the most common drug detected in drivers in the survey, which showed overall drug-positive rates of 11 percent of daytime drivers and 14.4 percent of nighttime drivers.
Study Targets High Driving
The study, which is being conducted by the National Highway Traffic Safety Administration and the National Institute on Drug Abuse, will use 20 volunteers to study the effects smoking pot may have on driving. The experiments are reported to be starting up at the end of September at the University of Iowa’s National Advanced Driving Simulator (NADS). The study will end on November 14, according to the NHTSA.
“The mixed results from previous cannabis-dosed driving studies have demonstrated that its effects on driving can be more difficult to detect than the effects of alcohol,” according to an NHTSA Research in Progress memo provided to Lawyers.com by the agency. “The NADS, a more sensitive data collection tool, is capable of detecting the more subtle changes in the driving behavior of cannabis-dosed participants.”
The research memo also says that the study will examine the effects of alcohol and cannabis together on driving, noting that “concurrent ingestion of cannabis and alcohol is common among impaired drivers.”
The study will assess driving performance, decision-making, psychomotor control, risk-taking, and divided attention tasks and will cost over half a million dollars to complete.
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