Researchers at the University of Colorado School of Medicine have released a study which shows a substantial increase in drivers involved in fatal accidents who have tested positive for marijuana. While not claiming that all of these drivers were impaired, the study does draw a correlation between increased use and availability of marijuana since Colorado decriminalized it in 2009 compared to the years prior to to 2009.
Quoting directly from the press release by the University:
"The researchers found that fatal motor vehicle crashes in Colorado involving at least one driver who tested positive for marijuana accounted for 4.5 percent in the first six months of 1994; this percentage increased to 10 percent in the last six months of 2011. They reported that Colorado underwent a significant increase in the proportion of drivers in a fatal motor vehicle crash who were marijuana-positive after the commercialization of medical marijuana in the middle of 2009. The increase in Colorado was significantly greater compared to the 34 non-medical marijuana states from mid-2009 to 2011. The researchers also reported no significant changes over time in the proportion of drivers in a fatal motor vehicle crash who were alcohol-impaired within Colorado and comparing Colorado to the 34 non-medical marijuana states.
........"While the study does not determine cause and effect relationships, such as whether marijuana-positive drivers caused or contributed to the fatal crashes, it indicates a need for better education and prevention programs to curb impaired driving." See full text HERE.
Both Colorado and California have seen an upswing in drivers testing positively for THC in their bloodstream since the decriminalization in their states. California estimates 7% of nighttime drivers test positively, and now Colorado has seen a doubling in the rate of drivers in fatal accidents who test positively. No one can say exactly what this means for safety on the roads; I can predict that we will see an increase in pedal error accidents over time among drivers using marijuana, just as we would see an increase n such accidents if the consumption of beer were to suddenly double.
Clearly, more studies and more education will help identify and combat some of this problem. At the end of the day, all of us will need to be aware of the possibility that the car coming toward us might be driven by someone who is 'driving while high" -- so we need to protect ourselves just as we would if
The California research figure is cited here:
The statistics on causes of storefront crashes is our own analytical data which can be found here: