you're logic reeks of absolutism. By your methodology, I could state that anyone who doesn't go to church is a criminal. Church gives a set of ethics that governs people's lives for the better, but when they fall out of church attendance, they become debauched and lawless.
Of course, we all know there are many upstanding citizens who never step foot in a church, but that doesn't mean there aren't some people who actually would lose grip on their lives if they didn't have something like a church to guide them.
In the same sense, you could state that total avoidance of any intoxicant is necessary for safe driving. Jim is as sober as a priest as he drives along, so much in fact that he has no reason to doubt his driving ability. He is so confident in his safe-driving, he doesn't see why he can't also eat a sandwich while driving, since he is so in control of his faculties. When a gob of mayonnaise falls on his pants, he is startled into driving off into the median.
Chemical influences are not the only influences involved in driving.
Here is a *STUDY*, but it's up to you whether it *PROVES* anything.
MARIJUANA A LESSER DRIVING HAZARD THAN ALCOHOL
This is one on the other side of the argument. Oh No! 17% of nonfatal traffic accidents involved marijuana! I'd wager that 17% of any group at any time would test positive for MJ.
Friends Drive Sober - Impaired Driving Prevention
This one only had a brief comment on driving, which I pasted below it.
Drug Policy Alliance: Myths and Facts About Marijuana
Myth: Marijuana Use is a Major Cause Of Highway Accidents. Like alcohol, marijuana impairs psychomotor function and decreases driving ability. If marijuana use increases, an increase in of traffic fatalities is inevitable.
Fact: There is no compelling evidence that marijuana contributes substantially to traffic accidents and fatalities. At some doses, marijuana affects perception and psychomotor performances- changes which could impair driving ability. However, in driving studies, marijuana produces little or no car-handling impairment- consistently less than produced by low moderate doses of alcohol and many legal medications. In contrast to alcohol, which tends to increase risky driving practices, marijuana tends to make subjects more cautious. Surveys of fatally injured drivers show that when THC is detected in the blood, alcohol is almost always detected as well. For some individuals, marijuana may play a role in bad driving. The overall rate of highway accidents appears not to be significantly affected by marijuana's widespread use in society.
Take it for what it's worth. You'll probably reject any citation of a clinical study that's pro-mj driving because you think the author is probably pro-mj. I doubt there will be an anti-mj studies that are unbiased.
I think you've shown yourself to be the type that should avoid driving after smoking, and you've also shown yourself as one who is not helping the cause of showing cannabis to be benign by making general classifications about its effects. ;)
