The prohibitionists are out of ammunition. But being the masters of half truths in their arguments, they keep trying to come up with bogus studies showing that Marijuana is an increasing cause of traffic fatalities. This study http://seattle.cbslocal.com/2014/02/04/study-fatal-car-crashes-involving-marijuana-have-tripled/ plays fast and loose with the numbers, and does not take into account that the presence of metabolites in the body does not indicate current impairment.
Let’s start with the idea that Marijuana is not alcohol. They are two completely different substances, having two completely different sets of effects on the human body. Alcohol definitely affects motor skill and eye-to-hand coordination. Marijuana’s negative effects are primarily limited to the passage of time, in that one may think an hour has passed when it has only been 10 minutes. Experience with Marijuana and one’s quality of driving are important factors.
Most peer reviewed, replicated double blind studies on “Stoned” driving show, to quote a frequently found phrase in the research that Marijuana users are “Insignificantly worse” than a driver who is not high on anything.
This 2011 article from Slate.com accurately describes the “Stoned” driving situation: http://www.slate.com/articles/health_and_science/explainer/2011/11/does_marijuana_make_you_a_more_dangerous_driver_than_alcohol_.html
There is no way of accurately determining current impairment, though the “Swab” test is about 60% accurate in determining recent contact and blood tests are showing some small accuracies. Other tests show metabolites, the non-psychoactive components of Cannabis. Marijuana is oil (fat) or alcohol soluble. In other words, the by-products remain in your body for up to 90 days, depending on your amount of body fat, physical activity and diet. The psychoactivity lasts, usually, no more than 12 hours on the outer edge, with the advent of concentrates and edibles. For your average, traditional joint of about a gram of high quality Marijuana, the time of psychoactivity is about four hours. The presence of metabolites does not indicate current impairment.
Life experience plays a role, too. If you are an experienced user of Cannabis, you are likely to be more aware, and better in control of yourself and your driving than an inexperienced user. Same goes for driving ability. If you’re an experienced driver, you’re going to make fewer driving mistakes than inexperienced drivers. Health, fatigue and other factors play into this as well.
The National Organization for the Reform of Marijuana Laws (NORML) has always preached personal responsibility in the use of Marijuana. If you’re not a good driver while stoned, don’t drive. As responsible citizens, we should never do anything that is going to harm others or ourselves. But this doesn’t mean we are at the mercy of those with vested interests lying in efforts to impede our freedom.