Pot vs. Alcohol?
I just finished a 5 week truck driving course and one instructor drove home the fact that we will be driving with other drivers who were like us at one time. He meant think of your worst night after drinking or doing drugs trying to drive or just the time you got in an accident or were joy riding at high speeds. Most of us have done something like that at one time.
I don't smoke pot any more, but when I did I drove more cautiously than any of the other times I could think of. It is still general opinion that that is also not safe. I definately would rather see someone smoking a joint next to my truck than drinking some Jack Daniels. Alcohol is definately more dangerous. Pot makes you feel like what you are doing is out of control maybe the first few times but it's better than alcohol which blurs your vision and makes it so you turn the wheel to far and can't hold your head up straight.
On the flip side, I don't know if I would want to drive a 70 ton load while half baked. Truck drivers have to be quick and look out for other cars on the road that don't realize what they are doing when cutting us off and hiding in our blind spots. If you measure it for people who have to operate heavy machinery and vehicles you will never see it legalized. If it were legal, the patient or user would have to take time off work and return with a doctor slip. Maybe it isn't worth legalizing with all the hassles.