The Tacoma Spur begins as a continuation of State Route 7 underneath I-5 in Tacoma, and has a posted speed limit of for the entire length. Traveling northbound as a continuation of SR 7, the first exit is for South 26th Street, which provides access to the Tacoma Dome, and the Tacoma Dome transit hub and Amtrak station. A single-point urban interchange with SR 509 provides access to the University of Washington Tacoma campus, as well as the Port of Tacoma via the East 21st Street Bridge. The left two lanes of I-705 separate, providing access to A Street, as well as South 15th Street / Pacific Avenue, however travelers merging onto northbound I-705 can not access this exit. The Bridge of Glass, linking the Museum of Glass on the shorefront to downtown Tacoma, passes over I-705 as it continues north, paralleling the Thea Foss Waterway to the east, and Firemans Park to the west. A signalled at-grade intersection with Stadium Way marks the end of I-705 northbound. Traveling southbound towards I-5, I-705 begins with on ramps from Stadium Way South and from Schuster Parkway. Passing Firemans Park on the south, traffic from South 9th Street and A Street merge onto I-705. Traffic coming from Bates Technical College and South 13th Street join the freeway, as well as traffic from South A Street. A SPUI with SR 509 is the only exit in Tacoma, before either exiting onto I-5 southbound towards Portland, Oregon, I-5 northbound towards Seattle and Vancouver, British Columbia, or onto SR 7. Every year the Washington State Department of Transportation conducts a series of surveys on its highways in the state to measure traffic volume. This is expressed in terms of annual average daily traffic, which is a measure of traffic volume for any average day of the year. In 2011, WSDOT calculated that as few as 26,000 cars used the spur at the continuation point from SR 7, and as many as 72,000 cars between the onramp from I-5 and SR 509. The entire Tacoma Spur is listed on both the WSDOT List of Highways of Statewide Significance, which marks the highway as a critical to connecting major communities in the state, and the National Highway System, a system of roads that are important to the nation's economy, defense and mobility.
History
The opening of Interstate 5 and the Tacoma Mall in 1965 caused a reduction in the number of retailers in Downtown Tacoma, which was only accessible via local streets from the freeway. The lost business, combined with worsening congestion in Downtown Tacoma, prompted downtown retailers to ask the state government for an improved connection to Interstate 5. The state Department of Highways began studying a freeway connection between the Pacific Avenue Interchange and Downtown Tacoma in 1955, recommending a temporary one-way couplet that became part of SR 509 and an eventual freeway link. In 1968, the Department of Highways adopted the routing of a freeway into Downtown Tacoma along the western side of the City Waterway, to be constructed over railroad right of way. The project, then part of a new freeway corridor for State Route 509 through the Port of Tacoma, was approved by the Tacoma City Council in 1971, but further planning was suspended at the time due to funding issues. In 1978, the American Association of State Highway and Transportation Officials approved the designation of the Tacoma Spur as Interstate 705. The Washington State Legislature approved the addition of Interstate 705 into the state highway system in April 1979. While funding was identified in the 1970s, construction on the freeway was not completed until the next decade because of federal budget cuts. I-705 was dedicated on October 17, 1988, with a parade and ribbon-cutting; the freeway cost $102.3 million to construct and was the last new Interstate to be completed in the state of Washington. The Tacoma City Council in 1992 proposed to name the freeway Martin Luther King Way, however that name was finally applied to nearby K Street. Work on the single-point urban interchange, costing $29.4 million, was completed in 1993 to accommodate the changes that were made to SR 509 through Tacoma.
