The Third Street Light Rail Project was the construction project that expanded the Muni Metro system in San Francisco, California, linking downtown San Francisco to the historically underserved southeastern neighborhoods of Bayview-Hunters Point and Visitacion Valley along the eastern side of the city. Construction was finished in late 2006, non-revenue weekend service began on January 13, 2007, and full service began on April 7, 2007. The new service, as the T Third Street Metro line, replaced the 15 Third bus line, which ran south from the Caltrain Depot at 4th and King streets, along Third Street and Bayshore Boulevard to the southeastern neighborhoods.