Construction of the new terminal was necessitated by the 1989 Loma Prieta earthquake , which damaged the 1939-opened Transbay Terminal , and voters approved funds for the new Transbay Transit Center in 1999 . Construction on the first phase , the aboveground bus terminal , began in 2010 . Limited Muni bus service began in December 2017 , and full service from AC Transit and other regional and intercity bus operators began in August 2018 . Full funding has not yet been secured for the second phase of construction , the Downtown Rail Extension , which hopes to add an underground terminal station for Caltrain and California High-Speed Rail
1989 Loma Prieta earthquake
1989 Loma Prieta earthquake
Transbay Transit Center