I think once you've been driving high for a little while your perceptions change, or adapt so your just as safe as sober. I mean, alot of people drive stoned - but you dont see it on TV, in the papers or on those stupid anti drug ad's because generally driving stoned means hightened concentration coupled with paranoia - and that means your being extra safe.

I still agree with what i said before though, i only do it after a couple of joints - if i'd just had a sesh i'd wait a bit for it to chill out/