Marijuana is legal in the state of Washington. But driving while under the influence of marijuana is not.
KIRO, the CBS affiliate in Seattle, produced the below report in which they got three people high and saw how it affected their ability to drive an automobile.
There was the prototypical stoner lady, a weekender smoker dude and an old guy who probably just smokes when he wants to put on a Steely Dan record and chill out. All of them got high. On camera. In front of cops.
Then, still on camera, they got high and drove with a trained driving professional while a police officer looked on. All the while, the reporter wags around bags of pot. If you're wondering what all has changed under I-502, this is a pretty good indication of the evolution of attitudes on this subject. Still though, don't drive stoned.