From SDOT, an alert for late-night drivers heading westbound toward West Seattle from I-5 or Beacon Hill tonight:

Tonight at midnight there will be an estimated 10-minute-long rolling slowdown of westbound traffic on the Spokane Street Viaduct (West Seattle Bridge), at the point just west of Sixth Avenue South. The contractor working for the Seattle Department of Transportation to widen the Spokane Street Viaduct must remove a light pole on the side of the bridge, working from below with a crawler crane to detach the pole and position it away from the Viaduct and onto the ground. As a safety precaution, Washington State Patrol will be on site to provide traffic control, leading a rolling slowdown until this brief construction task is completed.