Caltrans is continuing to work on replacing the Salsipuedes Creek Bridge on Highway 1 near Lompoc.
A temporary traffic signal will go into place March 18. The signal is expected to stay there until May 2020.
Drivers should expect delays of up to 20 minutes.
Crews are building a retaining wall and fish passage.
Traffic control is monitoring the area Wednesday through Friday from 8 a.m. to 3 p.m.