Metropolitan Seattle Freeways

The metropolitan area of Seattle in the U.S. state of Washington contains one of the smallest freeway systems in the U.S.A. based on populations.

There are 20 different freeways and highways the make up the Seattle Metro system, they are Interstate 5, Interstate 405, Interstate 90, Interstate 705, SR 3, SR 16, SR 18, the Alaskan Way Viaduct/SR 99, SR 167, SR 303/Waaga Way, SR 410, SR 509, SR 512, SR 518, SR 520, SR 525, SR 526, SR 599, the Port of Seattle owned Airport Expressway, and the City of Seattle owned West Seattle Freeway. Interstate 5 is the major North-South route through the region. Interstate 5 is four or five lanes for most of its way through the metro area. The freeway connects the metro area to California, Oregon, and British Columbia.

The freeway system uses ramp meters to help keep traffic moving. WSDOT uses variable message signs to let travelers know if there is an accident, to tell drivers how long their drive will be to certain areas, and for Amber Alerts. Recently, WSDOT installed variable speed signs along SR 520 and I-90 between I-5 and I-405, and along I-5 between the West Seattle Freeway and SR 520. There are also HOV lanes to move buses and carpools faster on many freeways and arterials. The HOV lanes on I-405 allow general purpose traffic to use them after 7pm (till about 5am), and the lanes on SR 167 are actually HOT lanes (carpools may use the lanes free; solo drivers can use the lanes for a variable fee). There are 225 lane miles of HOV lanes built and another 100 unbuilt. Freeway improvements are paid for by two gas taxes, 2003 Gas Tax and 2005 Gas Tax.

Existing freeways

Interstate 5

This is Seattle's largest and widest freeway. Traffic back-ups going into Seattle from the North and South are very common during the morning and evening rush hours.

The freeway runs just east of Downtown Tacoma as it goes through the metro area. After going through Federal Way and the west side of Kent it passes by a major shopping mall, Southcenter in Tukwila, where it connects with the south terminus of Interstate 405. Then the freeway continues and passes by Seatac International Airport, in the inner southern suburbs of Seattle and passes very close to Boeing Field (also known as King County International Airport). As the freeway heads towards Downtown Seattle, reversible lanes, or express lanes, branch off the mainline and continue north through the city. The express lanes carry southbound traffic in the morning and northbound traffic in the afternoon. The Express Lanes merge with the main line in the Northgate area of North Seattle. After that, I-5 continues north through the cities of Shoreline, Mountlake Terrace, and Lynnwood. In Lynnwood it merges with Interstate 405 again. It continues north to the last large city in Seattle Metro area, Everett.

Interstate 405

Interstate 405 begins in Tukwila at I-5, SR 518, and Westfield Southcenter, and continues east through Renton and then turns north and runs through Bellevue, Kirkland, and Bothell, before turning northwest and crossing I-5 in Lynnwood (near Alderwood Mall), where it becomes SR 525, a freeway for its first few miles.