State Route 518 (SR 518) is a

state highway A state highway, state road, or state route (and the equivalent provincial highway, provincial road, or provincial route) is usually a road that is either ''numbered'' or ''maintained'' by a sub-national state or province. A road numbered by a ...

located entirely within King County in the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

. The freeway begins in Burien at an interchange with SR 509 and travels east to serve

Seattle–Tacoma International Airport Seattle–Tacoma International Airport , branded as SEA Airport and also referred to as Sea–Tac (), is the primary commercial airport serving the Seattle metropolitan area in the U.S. state of Washington. It is in the city of SeaTac, which ...

and intersect SR 99 in SeaTac. SR 518 continues east into Tukwila and ends at an interchange with Interstate 5 (I-5), as the freeway becomes I-405. The highway was codified in 1937 as the western segment of Secondary State Highway 1L (SSH 1L) and designated as SR 518 during the 1964 highway renumbering. During the 1970s, the roadway was widened into a freeway to serve the airport and serves over 100,000 vehicles per day.

Route description

SR 518 begins at a

partial cloverleaf interchange A partial cloverleaf interchange or parclo is a modification of a cloverleaf interchange. The design has been well received, and has since become one of the most popular freeway-to-arterial interchange designs in North America. It has also bee ...

with SR 509 east of Burien and travels east as a divided freeway, passing north of

Highline High School Highline High School is a public high school in Burien, Washington, United States, located about 3.5 miles from Seattle–Tacoma International Airport. Highline High School, the flagship high school of the Highline Public Schools district, opene ...

. The freeway intersects Des Moines Memorial Drive and 154th Street north of

and continues east into SeaTac. SR 518 intersects the Airport Expressway and International Boulevard, signed as SR 99, south of the

Tukwila International Boulevard station Tukwila International Boulevard station is a light rail Metro station, station in Tukwila, Washington, United States. It is located between SeaTac/Airport station, SeaTac/Airport and Rainier Beach station, Rainier Beach stations on the 1 Line ...

. The freeway follows the

Central Link The 1Line, formerly Central Link, is a light rail line in Seattle, Washington, United States, and part of Sound Transit's Link light rail system. It serves 19 stations in the cities of Seattle, SeaTac, and Tukwila, traveling nearly between ...

light rail line into Tukwila and intersects 51st Avenue before an interchange with

I-5 Interstate 5 (I-5) is the main north–south Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels through the states of Californi ...

. At the interchange, located northwest of the Westfield Southcenter Mall, the Central Link turns north along I-5 and SR 518 ends as the roadway continues east as I-405 towards Renton. Every year, the

Washington State Department of Transportation The Washington State Department of Transportation (WSDOT or WashDOT, both ) is a governmental agency that constructs, maintains, and regulates the use of transportation infrastructure in the U.S. state of Washington (state), Washington. Establi ...

(WSDOT) conducts a series of surveys on its highways in the state to measure traffic volume. This is expressed in terms of

average annual daily traffic Annual average daily traffic, abbreviated AADT, is a measure used primarily in transportation planning, transportation engineering and retail location selection. Traditionally, it is the total volume of vehicle traffic of a highway or road for a y ...

(AADT), which is a measure of traffic volume for any average day of the year. In 2011, WSDOT calculated that between 38,000 and 102,000 vehicles per day used the highway, mostly between Seattle–Tacoma International Airport and I-5. SR 518 are designated as part of the National Highway System and as a Highway of Statewide Significance for serving Seattle–Tacoma International Airport.

History

A highway between Burien and Tukwila has existed since the 1890s and was first codified in 1937 as a segment of SSH 1L, which extended from PSH 5 in Renton west to intersect PSH 1 and US 99 in Tukwila and end at SSH 1K south of

Sunnydale Sunnydale is the fictional setting for the U.S. television drama ''Buffy the Vampire Slayer'' (1997–2003). Series creator Joss Whedon conceived the town as a representation of a generic California city, as well as a narrative parody of the all ...

, later renamed Burien. The section between PSH 5 in Renton and PSH 1 in Tukwila was removed in 1957 after the construction of the

, located on PSH 1 and US 99. The remaining highway was later re-designated as SR 518 during the 1964 highway renumbering, being codified as such in 1970. The western terminus of SR 518, an interchange with SR 509, was opened to traffic in November 1968, while the Airport Expressway was opened in 1970 and widened in the 1990s by the

Port of Seattle The Port of Seattle is a government agency overseeing the seaport and airport of Seattle, Washington, United States. With a portfolio of properties ranging from parks and waterfront real estate, to one of the largest airports and container t ...

. The freeway segment between SR 99 and

was built in the 1970s. No major revisions to the route of SR 518 have occurred since the 1990s, however SR 99 from SR 518 to SR 599 was removed to the highway system in 2003. Beginning in 2005, an elevated light rail guideway was constructed on the north side of SR 518, for

Sound Transit Sound Transit (ST), officially the Central Puget Sound Regional Transit Authority, is a public transit agency serving the Seattle metropolitan area in the U.S. state of Washington. It operates the Link light rail system in Seattle and Tacoma, r ...

line serving Downtown Seattle, the Rainier Valley and Sea-Tac Airport. The construction led to nighttime closures of the highway and other interruptions until construction finished in 2007.

was built to the north of SR 518 at its interchange with SR 99 (International Boulevard) near Sea-Tac Airport.

Exit list

References

External links

Highways of Washington State
{{Authority control 518 Transportation in King County, Washington