The 3 Line (colored magenta) is a future light rail line in the Seattle metropolitan area in the U.S. state of Washington, to be part of Sound Transit's Link light rail system. It is planned to connect Everett and Snohomish County to Downtown Seattle and West Seattle. The 3 Line would share tracks with the 2 Line from southern Everett to International District/Chinatown station along the 1 Line corridor.
The line is planned to reuse existing tracks that are part of the 1 Line and its future expansions; the 1 Line will then be rerouted through a new Downtown Seattle tunnel to be built for the Ballard Link Extension. The Everett Link Extension to the north of Lynnwood will have six stations and is scheduled to open between 2037 and 2041. The West Seattle Link Extension will include two new stations southwest of SODO station and is scheduled to open in 2035. The 3 Line was created as part of the Sound Transit 3 program, approved by voters in 2016, which included both projects.
The West Seattle Link Extension would include a high bridge crossing the Duwamish River adjacent to the existing West Seattle Bridge. In 2024, Sound Transit and HNTB proposed a cable-stayed bridge design that would be long and have two towers that are tall. The western end of the line would be tunneled between Alaska Junction and Delridge, where trains would begin to use an elevated guideway. The Federal Transit Administration issued their preliminary approval for the project via a record of decision in April 2025. A station was previously proposed for the area near Avalon Way and 35th Avenue West, but it was removed in a May 2026 decision by the Sound Transit board of directors. The project is expected to cost $6.7 to $7.1 billion to construct and carry 26,000 daily passengers.
The Everett Link Extension includes a new operations and maintenance facility that is scheduled to open in 2034 at one of three sites near Paine Field and the Boeing Everett Factory. The project is estimated to cost between $5.05 billion and $6.9 billion and open either as a single phase in 2037 with its funding shortfall addressed or in two phases from 2037 to 2041.
Stations Names and locations for future stations are provisional.
Station City Location Plannedopening Type Connections and notes Everett Link Extension (Everett Station to Lynnwood City Center) Everett Station Everett 3201 Smith Avenue 2041 Elevated Transfer to Sounder commuter rail, Amtrak, Swift Bus Rapid Transit SR 526/Evergreen Everett State Route 526 at Evergreen Way 2041 Elevated SW Everett Industrial Center Everett State Route 526 at Airport Road 2037 Elevated SR 99/Airport Road Everett Airport Road at State Route 99 TBD Elevated Provisional station Mariner Everett 4th Avenue West at 128th Street Southeast 2037 Elevated 2 Line terminus Ash Way Lynnwood Interstate 5 at 164th Street Southwest 2037 Elevated West Alderwood Lynnwood Vicinity of Alderwood Mall 2037 Elevated West Seattle Link Extension (SODO to Alaska Junction) Delridge Seattle Delridge Way Southwest near Southwest Genesee Street 2035 Elevated Alaska Junction Seattle Southwest Alaska Street near California Avenue Southwest 2035 Underground
References
External links West Seattle Link Extension project page Everett Link Extension project page