It is legal to pull into the intersection on green or yellow, and wait until it is clear (often when the light turns red) to turn left in Seattle. It is the correct/legal way to make a left turn. Otherwise you are just going to sit there blocking traffic for multiple cycles during busy times.
The oncoming traffic doesn't stop until the light turns red. When the light is yellow, they're actually more likely to _speed up_ in order to "make the light" rather than stop. So when the light inevitably turns red and you're in the middle of the intersection, do you either:
a) Just sit there, in the middle of the intersection, blocking traffic.
b) Attempt to back up, hoping there are no other cars behind you in the left turn lane blocking your path.
c) Continue through the intersection.
Unless the law says "never stop in the intersection in the first place", I can't imagine it enforcing any option other than c.
I've found that Seattle drivers are unusually respectful of amber lights - probably because getting pulled over for abusing it is more common than never.
Interestingly, yellow light laws are different in different states — so in some places people are very respectful of yellow lights.
Most states say it's OK if you enter the intersection on yellow, but a handful (not including WA, but including neighboring OR) require that you clear the intersection before the red appears.
I've sometimes wondered if "entering the intersection" includes entering the crosswalk adjacent to the intersection.
A family friend crashed into an oncoming car because of this ambiguity. They were waiting to make the turn, thought the other car should stop (because it was yellow going on red). Apparently it even looked like they were slowing down but then sped up at the last minute. Police said both at fault.
> The oncoming traffic doesn't stop until the light turns red.
Wait, why? No new car should enter the intersection when the lights turn to yellow. The yellow light should last long enough for everyone to be able to safely drive off the intersection, in orderly manner.
In the states, there's often a 1-second all red cycle to let the intersection clear, because drivers treat a yellow light as a green that's about to expire. Even with this, I often see 2 or 3 cars enter the intersection after I already have a green signal.
> No new car should enter the intersection when the lights turn to yellow.
Cars will obviously enter the intersection under a yellow. It's why we have a yellow.
Even if everyone wanted to stop for every yellow, at 35 mph with average reaction time, cars will travel a minimum of 100 feet after the yellow phase starts. Some of those cars will enter the intersection.
With a typical 4 second yellow, some drivers don't even choose to stop for the first half of the yellow, of course.
