The Central Subway is a Muni Metro light rail tunnel in San Francisco, California, United States.

The project was initiated after the Embarcadero Freeway was demolished following the 1989 Loma Prieta earthquake, as activist Rose Pak "almost single-handedly persuaded the city to build" the Central Subway to compensate Chinatown for the loss of the fast cross-town connection.

[13] Due to the capital cost ($1.578 billion for the 1.7 mile light rail line), the Central Subway project has come under criticism from transit activists for what they consider to be poor cost-effectiveness.

[11][16] In October 2012, the Federal Transit Administration (FTA) announced it would provide $942.2 million for the project under its New Starts program[17] after indicating it would approve the grant in January.

[18] This award included the recognition that better, more comfortable service for an already intensively-used transit corridor, particularly for low-income residents as in Chinatown, justifies the investment even if it does not attract a high percentage of "new" riders the way a new rapid transit investment might somewhere that is not already served by extremely slow, uncomfortable high-ridership local service.

[19] A study released in 2000 called for the Central Subway as part of a larger plan to alleviate projected traffic gridlock which also included a light rail line along Geary.

The first phases of work included preparation of the tunnel boring machine launch site and headwalls for the Yerba Buena/Moscone Station.

[26] Preparations for tunnel boring began on June 12, 2012, with the start of excavation for the TBM launch box on Fourth Street between Bryant and Harrison.

[29] "Big Alma" began digging north in November 2013 at a slightly faster rate, 54 ft/d (16 m/d), compared to the 44 ft/d (13 m/d) average of "Mom Chung".

Muni General Manager Ed Reiskin announced a plan in December 2012 to extend the tunnel to Columbus and Powell, using the site of the long-closed Pagoda Palace theater to extract the TBMs, with a potential option to purchase the Pagoda as the site of a future North Beach station.

[13] In 2014, the San Francisco Controller's Office audited the project and predicted it would be completed on schedule in December 2018 and slightly under budget.

The other underground stations, Yerba Buena/Moscone and Union Square, were scheduled to be completed by the end of 2018 ahead of the then-scheduled December 2019 start of revenue service.

[62] SFMTA noted that of 37 schedule updates submitted by Tutor Perini between December 2014 and December 2017, 21 were rejected "due to multiple and repetitive issues that vary from incorrect working sequences to unrealistic forecasted completion dates to artificially steering the schedule longest path through certain portions of the project".

In January 2018, for example, TPC modified their construction sequence at Chinatown station and were able to shave 18 days off the schedule, changing the estimated revenue service date to November 22, 2019.

[70] Residents and workers near the 4th Street portal and North Beach extraction sites noted an increase in the visible number of rats after construction began.

[73] During the excavation, workers accidentally breached a water main in July 2014, causing basement-level flooding in shops along Geary between Stockton and Grant.

[75] Since Stockton Street has been closed between Geary and Ellis, starting in 2014, construction is suspended in December and the area is transformed into a pedestrian plaza known as "Winter Walk".

have called for Winter Walk to be made a permanent year-round fixture, but notable opposition included Rose Pak, who wanted to retain Stockton as a link from Market to Chinatown.

"One Hundred Years: History of the Chinese in America", a mural painted by James Leong originally for the Ping Yuen housing project in Chinatown, was enlarged, printed, and wrapped in 2012 around the Hogan & Vest building at Stockton & Washington, at the future Chinatown station site, prior to that building's demolition.

[94] A proposed third phase would build an extension beyond Chinatown, including new stations at Washington Square in North Beach and Fisherman's Wharf.

[95][96] Fourteen alternative routes were proposed in a 2014 study to extend the line, and daily ridership was projected to increase by 40,000 if the extension was completed.

[97] San Francisco Chronicle architecture critic John King wrote there was "a compelling power to the idea of an extension that, if nothing else, would make the Central Subway seem less like a boondoggle and more of a factor in the shaping of tomorrow’s city.

[99] A conceptual fourth phase has been advanced by SFMTA and transit advocates to further extend the line west of Fisherman's Wharf to the Presidio.