Market Street Subway

The Market Street Subway is a tunnel that carries both rapid transit and light rail traffic in San Francisco, California. It runs under the length of Market Street between Embarcadero Station and Castro Street Station and is used by both Muni Metro and BART. The upper level is used by Muni Metro lines and the lower level is used by BART lines. BART does not run through the whole subway; it turns south and runs under Mission Street southwest of Civic Center Station. The eastern end of the BART level is connected to the Transbay Tube. On the Muni Metro level, the southwestern end of the Market Street Subway connects to the much older Twin Peaks Tunnel, and the northeastern end connects to the surface along the Embarcadero. The Embarcadero portal was not originally part of the Market Street Subway and was opened in 1998. It is used by the N Judah and the T Third Street lines.

The K Ingleside, L Taraval, M Ocean View, and T Third Street Muni Metro lines run through the entire tunnel and into the Twin Peaks Tunnel. The J Church and N Judah lines leave the tunnel through an exit that connects to Church Street.