T Third Street

The T Third Street is a Muni Metro line in San Francisco, California. It is the first new light rail line in San Francisco in more than half a century and the first fully accessible line in the system.
Route description.
Testing on the line took place in summer 2006, with limited service starting on January 13, 2007, and full service beginning on April 7, 2007. It runs along the newly constructed light-rail tracks on Third Street and Bayshore Boulevard in the Visitacion Valley, Bayview/Hunters Point, Dogpatch, and Mission Bay neighborhoods, connecting to the existing Muni Metro system along the Embarcadero and under Market Street.
In the future, the line may be going to Caltrain's Bayshore Station (to which it was originally planned to run) and, in the other direction, to San Francisco's Washington Square in North Beach through Chinatown Central Subway route.
Operation.
The T Third operates seven days a week, beginning at 5 a.m. on weekdays, and 6 a.m. Saturdays and 8 a.m. Sundays, operating until 1 a.m.
History.
Following service changes on June 30, 2007, the K Ingleside and the T Third Street lines were combined inside the Market Street subway tunnel. Though keeping their line designations, resulting in an upside-down, horseshoe-shaped route from Balboa Park to Bayshore and Sunnydale. At West Portal Station, inbound K trains heading towards downtown change their signs to the T line; at Embarcadero Station, T trains heading into downtown change signs to the K line.
The underground section of the line was closed west of Castro station from June 25 to August 24, 2018, due to the Twin Peaks Tunnel shutdown. On August 25, 2018, at the end of the shutdown, Muni began running two-car trains on the K/T line.
Central Subway.
Service on the Central Subway was initiated on November 19, 2022, with shuttle trains serving the four new stations. The T-Third will reroute north of the 4th and King Station starting on January 7, 2023. This change will disconnect the T from the K line, avoiding both King Street and the Market Street subway.