Some things to take into account.
You can massage any statistic or set of numbers into supporting what you want to say. Most of the studies I found looking into this were presented by either closed minded get of my lawn types or the frito munching pro legalization set. By far, the pro legalization crowd had better presentation and citations.
http://norml.org/library/item/mariju...tific-evidence While the anti legalization is based mainly on law enforcement, who for the most part does not want the war on drugs to end, and the opinion pages.
http://www.azcentral.com/opinions/ar...dren-polk.html
As was stated in the other thread, there is no roadside test. So any statistics showing that a person in a wreck had MJ in their system only really be showing that they HAVE used it, but not that they WERE using it at that time.
The effects of MJ are pretty short in duration compared to alcohol. Twenty minutes or so, by both personal experience and observation. Compare that to being drunk for hours, again personal experience and observation.
Anyone who is toking while actually driving, was doing so WAY before it was legal. Personal observation.
No amount of discussion here will determine actual facts, much less present any solutions other than the opinion based one set in the mind pre-discussion.