Our Washington traffic lawyers have been asked several times over the years if it is illegal to change lines while crossing an intersection. I think this was a rule instilled in many of us during driver’s education. I have never seen a single ticket issued for someone making a lane change in an intersection, and, to the best of our knowledge, there is no statute expressly barring that movement.
If the lane change is unsafe or you fail to signal, then such a change would still violate RCW 46.61.305. If you make a lane change in an intersection and then make a turn in the same intersection, that would violate RCW 46.61. 290, which requires someone to approach the turn in the applicable lane.
Here’s the bottom line: If you make the lane change safely and with a proper signal, it is legal to do so in an intersection. It should never result in a Washington traffic ticket being issued. If you are, however, issued a ticket, you should definitely challenge it.