SR 599 is 1.75 miles (2.82 km) long and travels on a four-lane freeway located entirely within the city of Tukwila in suburban King County.

[1] It begins at a Y interchange with I-5 near Foster Memorial Park, approximately 1.4 miles (2.3 km) north of the Southcenter Mall and the terminus of Interstate 405.

The interchange lacks connections to the north side of I-5, which are provided by the parallel Interurban Avenue, and has a direct offramp to the high-occupancy vehicle lanes on southbound I-5.

[5] SR 599 then turns west to travel around a King County Metro bus base, which has a direct onramp to the southbound freeway,[4] and crosses under the light rail tracks at East Marginal Way South.

[3] SR 599 is maintained by the Washington State Department of Transportation (WSDOT) and is designated as a minor route of the National Highway System.