The WSP reported its figures for the first six months of 2013 last month. They say that they found evidence of THC, the substance found in marijuana, in 745 drivers during that period, as compared to around 1,000 in a given year. On the surface, this might indicate that more people are smoking pot and driving. But when you look more closely at the numbers, you'll start to see a different story.
Of those 745 people, only 420 (I know "420") of them had more than 5 nanograms per milliliter of blood equivalent in their systems, which is the legal limit in Washington.
When you look at it that way, the WSP's numbers are roughly similar to those seen in past years. The WSP admits as much. A spokesman says that since the new law was approved, patrolmen have been watching out for drivers who are under the influence of pot, and are likely ordering more blood tests than they did in the past. So while law enforcement appears to be getting more vigilant about catching impaired drivers, the actual number of those impaired by marijuana use hasn't actually risen sharply since the new law was passed.
Another test will be once Washington begins selling pot at the retail level. That is scheduled to begin sometime early next year.