Drivers who test positive for marijuana in
their urine do not experience elevated risks for having a motor vehicle
accident, according to case-control data to be published in the July issue
of the journal Accident Analysis & Prevention.
From the abstract
The driving performance is easily impaired as a consequence of the use of alcohol and/or licit and illicit drugs. However, the role of drugs other than alcohol in motor vehicle accidents has not been well established. The objective of this study was to estimate the association between psychoactive drug use and motor vehicle accidents requiring hospitalisation.
A prospective observational case-control study was conducted in the Tilburg region of The Netherlands from May 2000 to August 2001. Cases were car or van drivers involved in road crashes needing hospitalisation. Demographic and trauma related data was collected from hospital and ambulance records. Urine and/or blood samples were collected on admission. …
All blood and urine samples were tested for alcohol and a number of licit and illicit drugs. The main outcome measures were odds ratios (OR) for injury crash associated with single or multiple use of several drugs by drivers.
The risk for road trauma was increased for single use of benzodiazepines (adjusted OR 5.1 (95% Cl: 1.8–14.0)) and alcohol (blood alcohol concentrations of 0.50–0.79 g/l, adjusted OR 5.5 (95% Cl: 1.3–23.2) and≥0.8 g/l, adjusted OR 15.5 (95% Cl: 7.1–33.9)). High relative risks were estimated for drivers using combinations of drugs (adjusted OR 6.1 (95% Cl: 2.6–14.1)) and those using a combination of drugs and alcohol (OR 112.2 (95% Cl: 14.1–892)). Increased risks, although not statistically significantly, were assessed for drivers using amphetamines, cocaine, or opiates. No increased risk for road trauma was found for drivers exposed to cannabis. [emphasis added]
Let me repeat that:
No increased risk for road trauma was found for drivers exposed to cannabis.
This adds more to the already significant body of information on this site regarding marijuana and driving.
Update: I suppose I should have given the normal disclaimer. I am not advocating driving while stoned. It’s a bad idea. (I don’t advocate driving while fatigued or talking on a cellphone either.) What the studies continually show, however, is that the hype from the Drug Czar’s office regarding the dangers of “drugged driving” is completely overblown and intended to attack marijuana users through zero tolerance laws, not increase safety.
What this study says is that there is no additional odds of being involved in an accident requiring hospitalization if you’ve smoked marijuana. And that fits with other studies that have shown that marijuana smokers realize that they’re impaired, and slow down and increase caution to compensate.