People exiting a Caltrain vehicle

Photo: Sergio Ruiz, Flickr


The Downtown Rail Extension project will extend Caltrain and future California High-Speed Rail service from the existing 4th and King railyard to the newly constructed Salesforce Transit Center. The project will construct a new station at 4th and Townsend streets and bring rail service to the underground train station that was built as part of the construction of Salesforce Transit Center.

The Transbay Joint Powers Authority is responsible for the Downtown Rail Extension project.

In 2019, the Transportation Authority Board accepted the final report of an expert Peer Review Panel, which was convened to conduct an assessment of the project’s governance, oversight, funding, and delivery strategy. In 2020, the Transportation Authority led development of a six-agency memorandum of understanding to implement most of the recommendations of the Peer Review Panel and to support the Transbay Joint Powers Authority in advancing the Project to ready-for-procurement status.

The Downtown Rail Extension project will be designed to connect to a future project to continue a tunneled alignment south from 4th and Townsend along Pennsylvania Avenue. This future project, known as the Pennsylvania Avenue Extension, will avoid conflicts with 16th Street, a major east-west travel corridor serving Mission Bay. This route was also endorsed by Mayor London Breed following completion of the San Francisco Planning Department’s Railyard Alignment and Benefits Study. The Transportation Authority is currently leading conceptual design study work for the Pennsylvania Avenue Extension.

See a January 2021 presentation about the project.

Public Meetings

The Transportation Authority participates on the Executive Steering Committee of the San Francisco Peninsula Rail Program. The Executive Steering Committee holds public meetings and oversees activities related to the development of a comprehensive work program, master schedule, project phasing plan, and risk assessment for the Downtown Rail Extension.

Public meetings are listed on the TJPA website


  • 2018-2019

    Transbay Joint Powers Authority and Federal Transit Administration provided local and federal environmental approvals. (The Pennsylvania Avenue Extension will be the subject of a separate subsequent environmental review process.)

  • 2020

    Transportation Authority allocated half-cent sales tax funds to the Transbay Joint Powers Authority to support development work for the project.

  • Early 2030s

    Transbay Joint Power Authority completes project, pending funding.

Project Partners

The Transbay Joint Powers Authority is leading the development of the Downtown Rail Extension project, in partnership with:

  • California High-Speed Rail Authority
  • Caltrain
  • City and County of San Francisco
  • Metropolitan Transportation Commission
  • Transportation Authority

Cost and Funding

The cost of the Downtown Rail Extension project was estimated in 2016 at approximately $3.9 billion.

The Transportation Authority has allocated or appropriated about $75 million in half-cent transportation sales tax funds toward the Project. The Transportation Authority also provides oversight for the project. 

The project is in the early design phase and faces a significant funding gap. The Transportation Authority is working with all project partners to develop an updated funding plan for the Downtown Rail Extension, including federal, state, regional, local, and private sources.



Transbay Joint Powers Authority at info@tjpa.org

Key features
Map showing the potential Downtown Rail Extension running from the current Caltrain station at 4th & King, along 2nd St to the Salesforce Transit Center

The Downtown Rail Extension will:

  • Close the regional rail connectivity gap from the Peninsula to downtown San Francisco, enabling the Salesforce Transit Center’s full potential
  • Create an essential link in the mega-region and state’s rail network to improve mobility 
  • Be a linchpin for realizing the New Transbay Rail Crossing; DTX would be the first phase of a standard-gauge connection
  • Improve sustainability and environmental quality

Passenger benefits

  • Will allow California High-Speed Rail to provide a one-seat ride between San Francisco and Los Angeles 
  • Promotes seamless transfers between transit services at and near the transit center, including BART, Muni, and buses serving the East Bay, North Bay, and other regional and long distance destinations 
  • Increases access to public transportation in an area of the city with highest expected population growth over the next 30 years

Environmental and Economic benefits

  • Improves air quality and reduces vehicle miles travelled VMT on US 101, one of the most congested corridors in the Bay Area 
  • Builds two new rail stations in areas targeted for investment, new affordable homes, and job growth  
  • Enhances access to retail, entertainment and employment, improving opportunities for disadvantaged communities 
  • Contributes to a better coordinated statewide rail /air transportation system 
  • Creates jobs for underrepresented groups through small business enterprise, disadvantaged business enterprise, and veterans' programs

Related programs


The Salesforce Transit Center is San Francisco’s new regional transit hub.

The Caltrain Electrification project will bring fully electrified service to Caltrain.

San Francisco's voter-approved Transit-First Policy states that decisions regarding the use of our public streets and sidewalks shall prioritize public rights of way for pedestrians, bicyclists, and public transit.

The Pennsylvania Avenue Extension project will support future uninterrupted passenger rail service through San Francisco.