Drivers under the influence of marijuana pose far fewer risks on roadways than do drivers intoxicated by alcohol, a new University of Toronto study suggests. The study corroborates earlier research demonstrating that marijuana is not a significant causal factor in traffic accidents.
“The failure of the Toronto University researchers to observe a significant effect of marijuana on driving culpability is consistent with findings from earlier studies,” NORML Foundation Executive Director Allen St. Pierre said. He noted that a May 1998 study by the University of Adelaide (South Australia) Department of Clinical and Experimental Pharmacology determined, “There was no evidence of any increase in the likelihood of being culpable for [automobile] crash[es] amongst those injured drivers in whom cannabinoids were detected. … [Their] culpability rates were no higher than those for the drug free group.”
Toronto researchers analyzed new data as well as several controlled international studies and concluded that marijuana-impaired drivers compensate by driving more slowly and cautiously.
“The more cautious behavior of subjects who received marijuana [in studies] decreased the drug’s impact on performance,” said Alison Smiley of the University’s Mechanical and Industrial Engineering Department. “Their behavior is more appropriate to their impairment, whereas subjects who received alcohol tend to drive in a more risky manner.”
The new study appears in the March issue of Health Effects of Cannabis, a publication of Toronto’s Center for Addiction and Mental Health.
Previous marijuana and driving studies performed in the U.S. by the National Highway Traffic Safety Administration also found “no indication that marijuana by itself was a cause of fatal accidents.”
For more information, please contact either Allen St. Pierre or Paul Armentano of The NORML Foundation @ (202) 483-8751. California NORML Coordinator Dale Gieringer is also available for comment @ (415) 563-5858.