Central Subway

Central Subway tunnel at the 4th Street Portal

transparent spacer image Above: The completed tunnel at the portal at 4th St., under I-80. Below: The roof slab for the Chinatown station is now complete. Bottom: construction at Stockton and Market.
Chinatown station roof slab complete
Market Union Square station construction


The Central Subway is the second phase of the Third Street Light Rail line, which opened in 2007. The Central Subway will extend this line northward from its current terminus at 4th and King Streets to a surface station south of Bryant Street and go underground at a portal under I-80. From there it will continue north to stations at Moscone Center, Union Square—where it will provide passenger connections to the existing Powell Street BART and Muni Station— and at Chinatown, where the line will terminate. The Central Subway is expected to carry nearly 73,000 passengers a day, making it the second most utilized rail project in the Federal New Starts Program. On March 30, 2010 the Transportation Authority Board adopted a Baseline Budget, Schedule and Funding Plan for the project. Revenue service is scheduled for late 2018. 

The total project budget is $1.58 billion, and the San Francisco Municipal Transportation Agency (SFMTA) has full funding commitments from a combination of local, state, and federal sources. The primary funding source for the Central Subway is the federal New Starts program. To date, the project has received $140.5 million in funds programmed by the Transportation Authority (including $124 million in Prop K funds) and $620 million in federal New Starts funds. It also received $61.3 million in Prop 1A High Speed Rail connectivity funds. 

On October 11, 2012, the SFMTA received the Central Subway project’s Full Funding Grant Agreement (FFGA), from the Federal Transit Administration (FTA), the most significant funding-related milestone in the New Starts process The FFGA represents the FTA’s official commitment of the $942 million in federal New Starts funds to the project, a major milestone that allowed the project to move forward into the main construction phase.

Final Design was completed in October 2012. It was delivered under three contracts: DP1-Tunnels, DP2-Stations, and DP3-Systems. The project is being delivered in four construction packages, all of which have been awarded: Utility Relocation 1, Utility Relocation 2, Tunnels, and Stations and Systems. Both utility relocation contracts and the Tunnels contract have been completed, and work is underway on the Stations and Systems contract.

The Tunnels contract was awarded in June 2011, to the Joint Venture of Barnard/Impregilo/Healy. The $233.9 million contract consisted of 1.5 miles of twin-bore tunnels underneath Fourth Street and Stockton Street, from I-80 to North Beach. Its major components included tunnel boring machine (TBM) procurement, construction of the TBM launch box and cross passages, construction of extraction shaft and portal, and headwalls for the Union Square and Moscone stations, among other elements. The contractor procured the TBMs from The Robbins Company, headquartered in Solon, Ohio. With the completion of this contract in May 2015, on schedule and $16 million under the baseline budget, the Central Subway project achieved a major milestone. Reaching this milestone retired one of the major risks of the project.

The Stations and Systems contract was awarded in May 2013 to Tutor Perini Corporation. At $838 million, this is the largest single construction contract ever awarded by the SFMTA The contract consists primarily of the three underground stations and one surface station stations and their overall systems including track, overhead contact system, communications, signals, ventilation and fire protection among others. Other associated components include a connection between the existing Powell Street station and the new Union Square station.



As of March 31, 2016, the Central Subway Project was 59% complete. 

At the Chinatown station, excavation for the surface level slab and concrete placement at the station headhouse area has been completed. Excavation has begun for the entrance archway to the station platforms. At the Union Square station, work continues on the portion of Union Square that will become the station headhouse and on the station mass excavation, while deck and rebar installation continue on the North Concourse and Ellis Street Annex. At the Yerba Buena/Moscone station, roof slab construction and placement of the Fourth Street road base and pavement have been completed, allowing traffic to be restored to the street. At the surface station at 4th and Brannan Streets, installation of the cast-in-place drilled piles has been completed, while work on the Muni ductbank installation, the 78 inch sewer rehabilitation, 36 inch sewer force main, and Auxiliary Water Supply System installation continue. Installation of the tunnel invert slab—the precursor to rail installation—will begin in summer. As of March 2016, the Stations and Systems contract was 45% complete, with substantial completion anticipated by February 2018. 

The SFMTA continues with its construction outreach program, keeping the neighbors in the vicinity of the project informed about ongoing and upcoming construction activities, lane closures, and general project information. Transportation Authority staff and project delivery oversight consultants will continue to work closely with the SFMTA project team as the project progresses on the construction phase. Revenue service is scheduled for December 26, 2018.


  • Extend the north-south corridor of Muni's Metro System
  • Provide shorter travel times for passengers
  • Relieve congestion on the Stockton Street corridor
  • Provide connectivity to a future Geary line.


Date and Milestone

Conceptual and Preliminary engineering: Oct 2003–Dec 2009
Supplemental engineering: Jul 2005–Oct 2008
FTA Record of Decision: Nov 2008
Final Design: Jan 2010–Oct 2012
Full Funding Grant Agreement: Oct 2012
Right of Way Acquisition: July 2009–Dec 2012
Construction: Jan 2010–Feb 2018
Startup and Commissioning: Feb 2018–Dec 2018
Revenue service begins: Dec 2018


Download the latest Central Subway Fact Sheet.