upgraded to a freeway during the 1980s; however, at-grade intersections remained at Mullenix Road until 1993 and Burley-Olalla Road until 2009. Two at-grade intersection remain to access businesses and a cemetery from the westbound lanes north of the Wollochet Drive interchange. WSDOT began installation of high-occupancy vehicle lanes (HOV lanes) on SR 16 as part of a Pierce County HOV system, which was constructed from 2000 to 2022 across several freeways. 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 was completed by WSDOT in January 2014. The third viaduct, carrying HOV lanes, began construction in 2017 and was completed in November 2019. On February 23, 2016, a section of SR 16 from the Kitsap–Pierce county line to Gorst was dedicated as the Tony Radulescu Memorial Highway, in honor of a Washington State Patrol trooper who was killed on that stretch of highway four years earlier. The northern terminus of SR 16 in Gorst is a major traffic bottleneck and forms a gap between the two main freeways on the Kitsap Peninsula. A proposal to rebuild the intersection into a grade-separated interchange was considered in 2019 but did not move forward in a legislative session. A rebuilt interchange, estimated to cost around $500 million, has been sought to improve access to Bremerton National Airport and local military installations. Tacoma Narrows Bridge The Tacoma Narrows Bridge, which carries SR 16 across the Tacoma Narrows between Tacoma and the Kitsap Peninsula, was first proposed by locals during the late 19th century—the earliest being local rancher John G. Shindler while traveling through the Narrows by steamboat in 1888. The Northern Pacific Railway planned to build a trestle bridge over the Narrows to connect its western terminus in Tacoma to the proposed Puget Sound Naval Shipyard in Port Orchard. The Washington State Legislature, after extensive lobbying by local auto groups and businesses, authorized the construction of a road bridge over the Narrows in