Maintenance on the Hood Canal Bridge will result in closures during the early morning hours on Thursday.
Delays of up to 90 minutes are expected between midnight and 4 a.m. while workers test the mechanical and electrical systems for the draw span.
The work, which is not weather-dependent, will require a series of draw span openings.
The state Department of Transportation is advising motorists to delay their trips or use an alternate route along Highway 101.