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The 1 Line, 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 23 stations in King and Snohomish counties, traveling 33 miles (53 km) between Lynnwood City Center and Angle Lake stations. The line connects Lynnwood, Mountlake Terrace, Shoreline, the University District, Downtown Seattle, the Rainier Valley, and Seattle–Tacoma International Airport. The 1 Line carried over 26 million total passengers in 2023, with an average of nearly 80,000 daily passengers on weekdays. It runs for 20 hours per day on weekdays and Saturdays, with headways as low as six minutes during peak hours, and reduced 18-hour service on Sundays and holidays.
Trains are composed of three or more cars that each can carry 194 passengers, including 74 in seats, along with wheelchairs and bicycles. Fares are paid through the regional ORCA card, paper tickets, or a mobile app. Sound Transit uses proof-of-payment to verify passenger fares, employing fare ambassadors and transit police to conduct random inspections. Until August 2024, fares were calculated based on distance traveled. All stations have ticket vending machines, public art, bicycle parking, and bus connections, while several also have park-and-ride lots.
Voters approved Central Link in a 1996 ballot measure and construction began in 2003, after the project was reorganized under a new budget and truncated route in response to higher than expected costs. The light rail line, which followed decades of failed transit plans for the Seattle region, opened on July 18, 2009, terminating at Westlake in the Downtown Seattle Transit Tunnel and Tukwila International Boulevard near Sea–Tac Airport. It was extended south to SeaTac/Airport in December 2009, north to the University of Washington in March 2016, and south to Angle Lake in September 2016. The line was temporarily renamed the Red Line until its designation was changed to the 1 Line in 2021, coinciding with an extension to Northgate.
The first cross-county extension, north to Lynnwood, opened in August 2024. A further southern extension to Federal Way is planned to open in 2026. The 2 Line, planned to connect Seattle to the Eastside suburbs, will form a multi-line network via its connection with the 1 Line in 2025. Further expansion under Sound Transit 3 will divide the current corridor between two lines, the 1 Line from Ballard to Tacoma and the 3 Line from Everett to West Seattle.