Fortunately some research indicates that stoned driving is less cause for concern than drunk driving.

One study[1] has found that "THC's effects after doses up to 300 mcg / kg never exceed alcohol's at BAC's of 0.08 g %" and that "alcohol impaired performance relative to placebo but subjects did not perceive it", whereas "THC did not impair driving performance yet the subjects thought it had."

Another study[2] finds that "marijuana smokers tend to compensate effectively for their impairment by utilizing a variety of behavioral strategies such as driving more slowly, passing less, and leaving more space between themselves and cars in front of them", although it notes that the combination of marijuana and alcohol can impair even at doses that would be harmless for either drug alone.

[1] http://casr.adelaide.edu.au/t95/paper/s1p2.html

[2] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722956/

Do you not think it's common now? Maybe the reason why we don't have such a stigma towards it (in terms of worry being talked about surrounding legalization) is because the reports of stoned persons killing people is less common?

Do you feel like you could back up this fear with data, proving the fear reality, or do you feel like it might be a fear of the unknown?

In Washington state, where we recently decriminalized marijuana use, the DUI standards for pot are actually much stronger than for alcohol. This is despite the fact that pot use doesn't impair driving ability in the same way as alcohol.

Moreover, people are already smoking pot, a lot, millions of people. Stoned driving is probably already about as common as it ever will be.

You should probably stay off the roads then. The good news is the data suggests the roads will become safer as more states legalize (stoned drivers are vastly more cautious than drunk drivers).

Does it depend on pot being legalised or not though? I'd believe people who want to smoke pot do it already.

Regardless how dangerous stoned driving is, it's not clear whether pot legalisation will increase usage. Moreover, I believe that legalising will allow for more prevention and control.