Washington State Route 518

State Route 518
Route information
Auxiliary route of I-5
Defined by RCW 47.17.715
Maintained by WSDOT
Length:	3.42 mi (5.50 km)
Existed:	1964 – present
Major junctions
West end:	SR 509 in Burien
	SR 99 in Seatac
East end:	I-5/I-405 in Tukwila
Highway system
State Highways in Washington Interstate • US • State Former PSH • 1964 renumbering • Former ← SR 516 SR 519 →

State Route 518 is a state highway in the U.S. state of Washington. It extends just under 3.5 miles (5.6 km) from Burien in the west to Tukwila in the east.

Route description

Originating at State Route 509, SR 518 runs east past Seattle-Tacoma International Airport, just east of which is an interchange with State Route 99 (International Boulevard). It intersects with Interstate 5 just northwest of Westfield Southcenter and continues eastward as Interstate 405. It is a freeway its entire length.

A significant portion of Route 518's traffic is between the airport and the interstate.

The interchange between the SR 509 and SR 518 freeways currently is not a freeway to freeway junction. Traffic often backs up on the existing ramp from southbound SR 509 to get to SR 518. WSDOT has planned a project to improve the interchange by adding a flyover ramp to connect southbound SR 509 traffic to SR 518.^{[citation needed]}

Exit list

The entire route is in King County.

Location	Mile	Destinations	Notes
Burien	0.00	Southwest 148th Street, 1st Avenue South – Burien	At-grade intersection
	0.00	SR 509 – Des Moines, Seattle
	0.60	Des Moines Memorial Drive	Westbound exit and eastbound entrance
Seatac
	1.62	To SR 99 / South 154th Street	Eastbound exit and westbound entrance
	1.87	Sea-Tac Airport
	2.10	SR 99	Westbound exit and eastbound entrance
Tukwila
	3.12	51st Avenue South, Southcenter Parkway	Eastbound exit and westbound entrance
	3.42	I-5 – Tacoma, Seattle	Eastbound exit and westbound entrance
	3.42	I-405 north – Renton, Bellevue	Eastbound exit and westbound entrance

External links

• Highways of Washington State