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.