The Central Puget Sound Regional Transit Authority, branded as Sound Transit (ST), is a public transit agency serving the Seattle metropolitan area in the U.S. state of Washington. It manages the Link light rail system in Seattle and Tacoma, regional Sounder commuter rail, and Sound Transit Express bus service. The agency also coordinates with the regional ORCA fare card system used by transit operators across the metropolitan area. In 2025, Sound Transit services carried approximately 51million total passengers and averaged over 153,000 riders on weekdays.
The agency was created in 1993 by King, Pierce and Snohomish counties to build a regional rapid transit system. After an unsuccessful proposal in 1995, the "Sound Move" plan for regional light rail, commuter rail, and express bus service was approved by voters in November 1996. Sound Transit began operating its express bus service in September 1999, taking over existing routes from local transit agencies. The region's first commuter rail line, between Tacoma and Seattle, started in December 2000; the agency's first light rail line, Tacoma Link (now the TLine), began service in August 2003. Light rail service in Seattle on Central Link (now the 1Line) began in 2009, and is the largest part of the Sound Transit system in terms of ridership. Union Station in Seattle has served as the agency's headquarters since its renovation in 1999.
Sound Transit is independent of local transit agencies and is governed by an eighteen-member board of directors, which consists of elected officials from member jurisdictions and the Secretary of Transportation. It is funded by local sales taxes, property taxes, and motor vehicle excise taxes levied within its taxing district in portions of King, Pierce and Snohomish counties. The agency has passed three major ballot measures to fund system expansion: Sound Move (1996), Sound Transit 2 (2008) and Sound Transit 3 (2016). Planning and construction of transit projects is scheduled to continue until 2041 under the Sound Transit 3 plan, which would expand the light rail network to and 83 stations.
Services
Sound Transit operates three main transit services across the Seattle metropolitan area: the Link light rail system, which serves as the rapid transit system for the region; the Sounder commuter rail system from Everett to Lakewood, via Seattle; and the Sound Transit Express bus system across the three counties. In 2025, these systems carried nearly 51million total passengers, averaging 153,430 riders per day on weekdays. A fourth service, Stride bus rapid transit, is planned to be introduced in the late 2020s. Sound Transit's services use a unified livery and paint scheme that consists of blue, teal, and green waves against a white background. Link, Sounder, and Stride all use the same naming scheme for lines and services, which switched from colors to numbers and letters in 2021.
, Sound Transit has a fleet of 574 vehicles for use on its services. The fleet is composed of 218 low-floor light rail vehicles for the 1 and 2 Lines; 8 streetcars for the TLine; 78 bilevel cars and 14 locomotives for Sounder; and 256 buses for Sound Transit Express. The entire Link and Sound Transit Express fleet is considered accessible, with level boarding or ramps and lifts. Sounder trains have a high platform with a designated level boarding area for ramps. All vehicles are also equipped to carry bicycles in racks; Sound Transit also provides bicycle cages at some stations. By 2027, the agency plans to deploy an additional 10 light rail vehicles for Link and 44 battery electric buses for the Stride bus rapid transit system, including double-decker buses.
Link light rail
The Link light rail system encompasses three lines with of track and 51 stations in three counties. The 1Line and 2Line are interconnected and share stations between Snohomish County and Seattle. After the two lines split in Seattle, the 1Line continues south to SeaTac and Federal Way; the 2Line travels east to Bellevue and Redmond. The TLine is disconnected from the rest of the system and operates entirely within Tacoma. Link trains carried 39.1million passengers in 2025 and averaged 113,394 passengers on weekdays across all three lines. It is the fourth-busiest light rail system in the United States by annual ridership, behind Los Angeles, San Diego, and Boston.
Link trains generally run seven days a week at frequencies of 4 to 24 minutes, with stops spaced closely together. All stations are accessible and most offer connections to nearby buses or a park and ride facility. The system is planned to expand to 83 stations and by 2050, with five lines serving all three counties. 1Line and 2Line trains are operated and maintained under contract with King County Metro and are able to use longer, four-car trainsets that have a typical capacity of 150 passengers in each car. The TLine uses low-floor streetcars, unable to be coupled into pairs, and are the only Sound Transit service to be directly operated and maintained by the agency rather than a contractor.
Sounder commuter rail
Sounder is the regional commuter rail service managed by Sound Transit and has two lines that intersect at King Street Station in Downtown Seattle. Trains generally run during rush hours with limited service at other times, including weekend trains for special events. The NLine connects Seattle to Everett, stopping at two intermediate stations in Snohomish County. The SLine connects Seattle to Tacoma and Lakewood, stopping at six other stations in Pierce County and southern King County. Trains are operated under contract by BNSF Railway crews on the company's leased tracks, while the vehicles are maintained by Amtrak. Sounder uses a fleet of Bombardier BiLevel Coach passenger cars that each have a seating capacity of 130 to 146 passengers depending on their configuration. They have restrooms, space for bicycles and wheelchairs, tables, cupholders, power outlets, and Wi-Fi. The SLine typically uses an eight-car configuration that carries 950 seated passengers, while the NLine uses two to three cars in normal service that can carry 300 to 450 passengers. In 2025, Sounder trains carried 2.1million total passengers and averaged 7,830weekday boardings.
Sound Transit Express
Sound Transit Express comprises 21 limited-stop express bus routes that provide regional service to cities in all three counties, primarily using a network of high-occupancy vehicle lanes (HOV lanes) on state-maintained freeways. Some routes operate seven days a week, while others are limited to rush hours only. These routes normally have wide distances between stops, which are primarily hubs and transfer points in cities and suburban areas where local routes operated by other agencies connect; many stops also have park and ride lots. Sound Transit funded the construction of new transit hubs, park and ride lots, and direct access ramps to the HOV lanes as part of the rollout and expansion of express buses. In 2025, the express buses carried 9.8million total passengers and had a weekday average of 32,206riders. The busiest route was Route 545, which connects Seattle to Redmond and carried 1.3million riders.
The fleet of 256 buses is owned by Sound Transit and includes double-decker buses with up to 81 seats, articulated buses, high-floor motorcoaches, and standard buses with a minimum of 42 seats. These buses include upholstered and cushioned seats that are able to recline, footrests, overhead luggage racks, air conditioning, reading lights, and bicycle racks. Sound Transit Express buses use diesel or compressed natural gas for fuel, along with several hybrid electric buses. They are operated and maintained under contracts with local transit authorities (Community Transit, King County Metro, and Pierce Transit) who also deploy shuttle buses during disruptions to rail services.
Stride
A bus rapid transit system, named Stride, was funded by the Sound Transit 3 ballot measure and is scheduled to open in the late 2020s. Stride is planned to have three lines: the S1 Line on Interstate 405 between Burien and Bellevue, scheduled to open in late 2028; the S2 Line on Interstate 405 between Bellevue and Lynnwood, scheduled to open in 2029; and the S3 Line on State Route 522 between Shoreline South/148th station and Bothell, scheduled to open in 2028.
Paratransit
Sound Transit contracts with Community Transit, King County Metro, and Pierce Transit to provide paratransit service along the Link light rail network in compliance with the Americans with Disabilities Act. Costs are split equally between Sound Transit and the contracted provider within the Link corridor. The agency is not required to operate paratransit service along Sounder and Sound Transit Express routes.
Fares All of Sound Transit's services accept payment via the regional ORCA card, a contactless proximity card with stored fares and passes. Passengers may also pay using contactless and mobile credit or debit cards, mobile ticketing through the Transit GO Ticket app, and with cash. , fares on Link and Sound Transit Express use a flat rate of $3.00, while Sounder passengers pay between $3.25 and $5.75, depending on the distance traveled. Discounts are offered for eligible low-income households, senior citizens, and people with disabilities. Youth passengers age 18 and under are not charged a fare as part of a statewide program. Sound Transit's light rail and commuter rail stations do not have faregates or turnstiles, instead relying on proof of payment that is enforced by fare ambassadors.
History
Background and early studies
The waters of Puget Sound and the surrounding region's navigable rivers were the primary transportation corridors for the indigenous Coast Salish peoples as well as later settlers who arrived in the 19th century. A series of scheduled steamboat trips in the 1880s grew into the "mosquito fleet", the main mode of passenger and freight transportation for the growing region through the turn of the 20th century. It waned in importance as railroads and streetcar systems were constructed around Puget Sound; these services, later supplemented by interurban trains, grew in the early 20th century to serve a growing number of passenger commuters. The Seattle Municipal Street Railway had a streetcar and cable railway system by 1935, while private companies ran interurban services north to Everett and south to Tacoma. These rail services were all abandoned or converted into bus routes by 1941 as automobile adoption in the Seattle area contributed to a need for more developed highways and later freeways.
The first major proposal for a rapid transit system to serve Seattle and the surrounding region was drafted by urban planner and civil engineer Virgil Bogue in 1911 as part of a comprehensive plan. Bogue's plan was rejected by a wide margin in the March 1912 municipal election; the city's three major newspapers had all opposed it. The Forward Thrust program, formed in the 1960s by civic activists, proposed the development of a subway system that covered Seattle, Renton, and Bellevue by 1985. Two-thirds of the $1.15billion (equivalent to $ in dollars) construction cost would be funded by the federal government, contingent on the approval of local funding. The first referendum in February 1968 failed to reach the 60percent supermajority needed to pass; a second attempt was made in May 1970, but failed amid a spree of layoffs by Boeing that severely affected the local economy. The federal earmark was instead used to build the Metropolitan Atlanta Rapid Transit Authority's subway system in Atlanta, Georgia.