Downtown Rail Extension (DTX)

Phase 2

Phase 2 of the Transbay Transit Center Program includes construction of the Downtown Rail Extension, including a new Fourth and Townsend Street Caltrain station; completion of the Transit Center’s train station, including a pedestrian connection to BART and Muni; and a new intercity bus facility.

The Downtown Rail Extension

The Downtown Rail Extension (DTX) will extend Caltrain commuter rail from its current terminus at Fourth and King streets to the new Transit Center. It will also deliver the California High-Speed Rail Authority’s future high-speed rail service to the Transit Center.

The 1.3-mile rail extension (1.95 miles of total construction length) will be constructed principally below grade using cut-and-cover and mined tunneling methods underneath Townsend and Second Streets. The project includes an underground station at Fourth and Townsend streets, six structures for emergency exit, and ventilation along the alignment, utility relocation and rail systems work.

Click here to view the Train Operations Analysis of Two versus Three Mainline Tracks for DTX.

Fourth and Townsend Street Station

The new underground station at Fourth and Townsend Streets will serve Caltrain commuters. The station entrances along the north and south sides of Townsend Street will lead to two levels below grade: a concourse mezzanine and a train platform. The concourse will accommodate passenger amenities such as ticketing; maps and schedule information; and restrooms. It will also house mechanical and electrical rooms and Caltrain staff areas. The Train Platform will feature a center platform with one passing track on the south side.

Transit Center Train Station

The two below-grade levels of the Transit Center, the Lower Concourse, and Train Platform level will be built out and opened in Phase 2.

The Lower Concourse will house rail ticketing, passenger waiting areas, and support spaces. At its east end, it will connect to the intercity bus terminal and a pedestrian tunnel leading to the Embarcadero BART/Muni station, approximately one block north of the Transit Center. Along with ticketing and passenger waiting areas for rail and support spaces, the Lower Concourse will contain retail space.

The Train Platform will contain six tracks and three platforms for Caltrain commuter and high-speed rail service. Back-of-house support spaces will also be built on the Train Platform level to support rail service.

BART/Muni Pedestrian Connector

The BART/Muni Pedestrian Connector will connect the east end of the Transit Center’s Lower Concourse with the BART/Muni Embarcadero Station. The block-long pedestrian tunnel will provide passengers with a direct connection between the two stations. The tunnel will run beneath Beale Street, entering the Embarcadero Station at the mezzanine level.

Intercity Bus Facility

The Intercity Bus Facility, across the street from the east end of the Transit Center between Beale and Main Streets, will be dedicated to intercity bus services such as Greyhound and Amtrak. The main public entrances will be located along Beale and Natoma Streets, and the building will include a bus canopy on its north side where a bus parking and passenger-loading zone are planned. The facility will house a passenger waiting area, ticketing counters, retail space, transit agency operations space and mechanical space. An escalator and elevator located in the lobby will lead to the Lower Concourse of the Transit Center, giving passengers direct access to rail ticketing and waiting areas. An exterior escalator on Beale Street will also descend to the Transit Center’s Lower Concourse.

Getting Started

The Metropolitan Transportation Commission (MTC) and the Association of Bay Area Governments (ABAG) jointly approved a Regional Transportation Plan (RTP) that designates the DTX as a regional priority for the federal New Starts program. New Starts is the federal government’s primary financial resource for supporting this type of transit capital investment. As a regional priority for New Starts, the project will begin working with the U.S. Department of Transportation (DOT) towards a Full Funding Grant Agreement that would allow fo the construction of the DTX.

DTX Operators


Caltrain already serves as a vital regional link by connecting San Francisco to the Peninsula, Silicon Valley and San Jose, but it currently ends 1.3 miles from downtown San Francisco. The DTX will extend the Caltrain rail line into the new Transit Center, the heart of San Francisco’s new downtown. Extending Caltrain into downtown will directly save commuters almost an hour a day in travel time, and will result in less driving and more people taking the train into the City from the Peninsula.

For additional information on Caltrain, please visit Caltrain’s website at:

California High Speed Rail

The DTX will accommodate California’s High-Speed Rail service which will connect the mega-regions of the state, contribute to economic development and a cleaner environment. By 2029, the California High-Speed Rail Authority projects that the system will run from the Transbay Transit Center in San Francisco to the Los Angeles basin in under three hours. California High Speed Rail will eventually extend to Sacramento and San Diego, totaling 800 miles with up to 24 stations. The system is expected to transport up to 32 million intercity passengers annually and another 10 million commuters. It will connect with existing rail, airway, and highway systems, allowing intercity commuters and long distance travelers easier access to metropolitan regions and other transit options, improving traffic conditions and air quality by taking people out of their cars and off our freeways. This will help address traffic congestion in California cities, projected to continue to be among the nation’s worst by 2029. According to the California High-Speed Rail Authority, the system will result in an estimated 4 to 8 million metric tons of CO2 saved by 2030, making a significant contribution to California’s greenhouse gas reduction goals in AB 32 and SB 375.

For additional information on California High Speed Rail, please visit the California High Speed Rail Authority’s website at:

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