Yes, it is illegal.  See Seattle Municipal Code 11.53.190 regarding driving in a bicycle lane.

The operator of a motor vehicle shall not drive in a bicycle laneexcept to execute a turning maneuver, yielding to all persons ridingbicycles thereon.

Is it illegal to drive a vehicle in bicycle lanes?

 

A: Yes, it is illegal.  See Seattle Municipal Code 11.53.190 regarding driving in a bicycle lane.

The operator of a motor vehicle shall not drive in a bicycle lane
except to execute a turning maneuver, yielding to all persons riding
bicycles thereon.