Washington State law RCW46.61.290
"(c) Upon a roadway where a center lane has been provided by distinctive pavement markings for the use of vehicles turning left from either direction, no vehicles may turn left from any other lane. A vehicle shall not be driven in this center lane for the purpose of overtaking or passing another vehicle proceeding in the same direction. No vehicle may travel further than three hundred feet within the lane. A signal, either electric or manual, for indicating a left turn movement, shall be made at least one hundred feet before the actual left turn movement is made."
I use the center lane as a get-on waiting spot to merge into traffic going left. A problem here locally is with the dimwits who turn left and wait in the oncoming traffic's left turn lane! Man---if the double yellow line is on your left, you are on the wrong side of the road!!
It's not what you look at that matters, it's what you see.
Henry David Thoreau