The problem is the studies that show that MJ use is far less of an impact on driving than talking on a phone... The paranoia over stoned drivers is a little high (no pun intended)

Not saying it should be ignored as an issue all together, but it seems to be the last issue the opposition can attach itself to and sound sane, and its getting a little carried away.

With self driving cars on the horizon it will at some point become a moot point.

Even if that's true the drugs effect is different on each person and the amount you take will vary the effect it has on your driving ability. A couple of puffs probably won't make a difference. But you can also take enough that it's hard to even get out of a chair. The easiest solution and one that should appease everyone would be a total ban on driving within 12/24 hours of last taking marijuana imo.

I get that... its a legitimate concern, as I said. However, its no more legitimate than the other 100s of prescription drugs that can cause drowsiness or slowed reaction time. Or driving with the flu, or driving tired.

Thats the point - there are literally 100s of other ways to be just as (if not more) impaired while driving and be completely legal. We don't parade those issues around (namely because the big pharma companies would like people to not realize just how impairing their products are)

The difference is that there is a large enough group opposed to legalization that they make this issue a primary one in their fight against legalization and blow it vastly out of proportion to the actual scale of the problem.

That's true with alcohol, too, though, it effects people differently. .08 was basically just resolving legal ambiguity by picking a reasonable BAC; it's not like at .079 you can operate a car safely but at .08 you're a danger to everyone on the road.

You can actually be arrested for an 'OUI' in some states, an Operating Under the Influence, for when you are clearly impaired, but fall below the legal cutoff for a DUI. This would likely necessitate being the same sort of thing, a legal recognition that you were driving recklessly, and you exhibit the signs of recent marijuana usage (or if we have some way of actually measuring it, then that too).

12/24 hours?? Have you ever smoked? I'd say the effects mostly wear off within 2 hours...

A total ban on driving for 24 hours is scientifically unsound, and would only play into fearmongers' hands who want more legally dubious checkpoints and reasons to do intrusive tests on drivers.

That only applies to a point. I've been high enough that I had trouble walking (fun with poorly calibrated edibles...); driving would have been impossible. Luckily 'couch-lock' tends to limit how much mischief people get up to while heroically high.

There is no reliable way to chemically measure intoxication from marijuana. All the tests show is the presence of THC in the system. Hair tests can detect use as far back as 6 months, urine tests for 3 weeks, blood tests for 72 hours (typically used in accident investigations). Saliva tests, having a shorter duration of ~12 hours would be more ideal, but have an effectiveness cutoff of 50ng. The current legal limit in CO and WA is 5ng.

All that said, there's little correlation between the amount of THC in one's system and the level of intoxication. A chronic user (no pun intended) will have a much higher concentration of THC in their system and be affected less by it as compared to say, a tourist coming in and trying it for the first time in 20 years.