King County Metro provides frequent stop bus service within the city and surrounding county, as well as a South Lake Union Streetcar line between the South Lake Union neighborhood and Westlake Center in downtown. Seattle is one of the few cities in North America whose bus fleet includes electric trolleybuses. Sound Transit currently provides an express bus service within the metropolitan area; two Sounder commuter rail lines between the suburbs and downtown; its Central Link light rail line, which opened in 2009, between downtown and Sea-Tac Airport gives the city its first rapid transit line that has intermediate stops within the city limits. Washington State Ferries, which manages the largest network of ferries in the United States and third largest in the world, connects Seattle to Bainbridge and Vashon Islands in Puget Sound and to Bremerton and Southworth on the Kitsap Peninsula.