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 2024, Sound Transit services carried a total of 42 million passengers and averaged over 134,000 riders on weekdays.