To the best of my knowledge, there is no reliable way to test whether a driver is actively intoxicated from pot. Existing blood tests will tell you if a person has used it in the past week or two, but not whether they've used it in the past hour.

So average measured blood-levels could well be up because more Coloradans are smoking, but that's no proof at all that more Coloradans are driving under the influence.

I wouldn't necessarily say that weed is harmless or safer than alcohol, but articles like the Denver Post one are written with an unfair bias.