> theres really no other substance that even comes close..

Actually, research has shown that cell phones are about as bad as alcohol. Donno if you count a cell phone as a substance or not.

The big difference with cannabis impaired drivers is that they know they are impaired and they tend to slow down and pay more attention to driving. I'm not advocating driving while under the influence of anything, be it a cell phone call or THC. However, if I had to choose any group of "impaired drivers" in the world to share the road with, it would be those with THC in their system over any other substance.

One thing I was wondering about... I have read the procedures used for two different driving while inoxicated on cannabis studies. In both cases, they used volunteers. My gripe here is that people get better at driving impaired over time. If I toss a person behind the wheel the first time they smoke a joint, they are going to do much worse than somebody that has been smoking (and driving) for twenty years. Because cannabis is illegal where the studies were conducted, and because the studies didn't bother to check (or didn't want to publish the results of their check), one must assume that the volunteers were all "virgin smokers". This would lead me to believe that these studies represent an absolute worst case scenario as opposed to the average of how the population as a whole would perform.