Federal scientists for the National Institute on Drug Abuse set out to observe the effects of marijuana consumption on driving abilities, potentially shedding more light on the hotly debated topic.
Study participants were required to consume various combinations of marijuana and alcohol, or a placebo for the control group, before getting behind the wheel of a vehicle in the National Advanced Driving Simulator at the University of Iowa, according to USA Today. The simulator experience included 40 miles of virtual roads and parking lots, complete with unpredictable motorists and jumpy deer.
After completing the course, the drivers submitted both blood and saliva samples to serve as dosage references. Data is now being analyzed to find relationships between the various combinations and their effects on driving abilities.
Prohibition supporters have focused on drugged driving in their campaign against legalization, arguing that marijuana is just as bad as alcohol and will result in more traffic deaths. Such extreme views have been widely dismissed, as alcohol and the psychoactive compounds in marijuana have different effects on the brain.
Crash data suggests that drivers with illegal drugs in their system are more likely to be involved in a fatal crash than ‘clean’ drivers, but at a far lower rate than drivers intoxicated by alcohol.
“While some studies find that cannabis consumption prior to driving increases the risk of collision, this is not true for all studies,” wrote Dalhousie University associate professor Mark Asbridge in a policy analysis published in the Canadian Journal of Public Health. “In fact, some studies suggest that those driving under the influence of cannabis may be less at risk for collision or injury compared to drug-free drivers.”
Further complicating enforcement proposals, separate studies have shown that levels of marijuana compounds in the blood of a regular user — measured days after the last use — can be much higher than the levels detected from an occasional user at peak impairment shortly after consumption. Impact on motor skills has also been observed to vary greatly between individuals.
With medical-marijuana provisions in nearly half of all US states, and full legalization in Colorado and Washington, legislators are under pressure to hastily implement drugged-driving restrictions and field tests modeled similarly to those for alcohol.
Most legalization proponents support restrictions on actual impairment, however many argue that roadside blood and saliva tests, combined with arbitrary thresholds, will likely result in charges against drivers who are not driving with reduced motor skills or attention difficulties.
“I can’t tell you if one joint is going to make you high to the point where you can’t drive,” Colorado State Trooper JJ Wolff told USA Today. “That’s a really hard question to answer at this point.”
Officers already have the ability to identify impaired drivers without relying on chemical tests, thanks to the NHTSA’s Standardized Field Sobriety Test system. By observing eye movement and asking drivers to stand on one leg and walk heel-to-toe in a straight line, officers can estimate intoxication. Many agencies are also training “drug recognition experts” that can be called in to help determine what category of drugs are causing impairment. Blood, saliva or urine samples can then be obtained to corroborate the officer evaluation.
The NIDA has been working on its study for three years, without hinting at any preliminary findings. Final results are expected to arrive on October.
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