 WSDOT has been installing high-occupancy vehicle lanes (HOV lanes) on SR 16 as part of a Pierce County HOV system, scheduled for completion by 2022. Beginning in the early 2000s, frontage roads and the Scott Pierson Trail were built along the freeway and sound walls were erected near residential areas in Tacoma. From Tacoma to Gig Harbor, WSDOT began installing exit numbers to interchanges with SR 16 that correspond to its milepost. The Nalley Valley Viaduct was replaced by a new westbound structure in 2011, carrying all four lanes of SR 16 towards I-5 in Tacoma, while the original viaduct was closed and demolished. The eastbound Nalley Valley Viaduct began construction in November 2011 and is scheduled to be completed by WSDOT in 2014, with the westbound viaduct being widened to its full planned width.
