Whoa... I never realized how strongly some smokers feel about smoking while driving and being high while driving. I go on blunt rides all the time, as do a lot of people I'm familiar with. To me, road trips are synonymous with smoking weed in a car for extended periods of time. I've never been incapacitated from smoking weed the way other substances have had me...
It might sound cliche` and ignorant but I'm just willing to take that chance-- in my experience I've always felt I drive a bit more cautiously, a bit more slowly, and with a bit more awareness of the people I'm sharing the road with when I'm high, whereas I know and recognize when I'm drunk or on other drugs that I cannot safely drive myself anywhere. In other words, I really do feel like being high makes me a better, calmer driver, and with that in mind I view smoking a blunt/joint while driving as nothing more serious than smoking a cigarette while driving (from a safety viewpoint, the legal concerns are a whole other matter). That could just be rationalization but, for me and in my mind and experience, this holds absolutely true.