Bay Area Rapid Transit expansion

Bay Area Rapid Transit
Company type	Public transit agency
Industry	Public transportation
Founded	1962
Area served	San Francisco Bay Area, California, United States
Products	Rapid transit services

Throughout its development, Bay Area Rapid Transit has envisioned multiple expansions to broaden its network coverage.

History

The initial 1962 BART system maps featured several routes beyond the main network labeled as Potential Future Extensions. Over time, some of these have been incorporated into the operational system:

The extension from Concord to Antioch was introduced in stages: North Concord / Martinez in 1995, followed by Pittsburg / Bay Point in 1996, and the eBART branch commenced service in 2018.
A line reaching Livermore extended service to Dublin/Pleasanton by 1997, with additional development planned through Valley Link.
Expansion southward beyond Fremont is anticipated to connect San Jose and Santa Clara by 2030, partially utilizing the Caltrain corridor. Extensions arrived at Warm Springs in 2017 and Berryessa in 2020.
The Daly City to Millbrae route was implemented progressively: Colma Station opened in 1996, with Millbrae and a spur to San Francisco International Airport following in 2003. Electrification of the former Southern Pacific (now Caltrain) corridor has been carried out independently to support frequent mainline operations.
The proposed Marin Line along Geary Boulevard was abandoned after Marin County exited the planning district due to financial and engineering obstacles. Proposed alignments included integrating rail into the Golden Gate Bridge structure or tunneling from Fort Mason to Sausalito along previous rail paths.

A separate corridor not included in the 1962 blueprint is the automated guideway transit spur connecting BART with Oakland International Airport, which began operation in 2014.

San Jose subway extension (Phase 2)

The initial plan for the Silicon Valley extension intended to extend service through downtown San Jose and Santa Clara via a subway. However, due to sales-tax revenue falling short of projections, the Santa Clara Valley Transportation Authority (VTA) scaled back the project in February 2009, terminating it at the Berryessa/North San José station and deferring downtown tunneling to a later phase. The full extension from Fremont to Santa Clara was estimated at $6.1 billion, while Phase 1 reaching Berryessa carries an estimated cost of $2.3 billion.

Downtown alignment includes a subway portal beneath US 101, featuring stations at 28th Street/Little Portugal, a consolidated Downtown San Jose station (merging earlier Civic Plaza/San Jose State University and Market Street stops), and Diridon/Arena. After passing under I-880, the line would emerge and conclude at a Santa Clara BART station adjacent to the existing Santa Clara Depot. Independent proposals by San Jose International Airport include a people mover linking either Santa Clara Depot or Diridon Station.

To reduce disruption within downtown San Jose, VTA plans to employ a tunnel boring machine for most of the subway construction, reserving cut-and-cover methods exclusively for station areas. This approach contrasts with the cut-and-cover excavation used for BART subways in San Francisco and Oakland. Construction of cut-and-cover stations downtown will cause temporary but significant impacts such as closures on Santa Clara Street and interruptions to the VTA light rail line operating there. Pending funding approval, this downtown extension could open by 2026. As of April 2018, designs called for a single-bore tunnel beneath Santa Clara Street with cut-and-cover limited to stations. Utility relocation commenced in February 2019, with construction expected to start in 2022.

Electoral decisions and financing (2000–2008)

When Santa Clara County chose not to join the BART District at its establishment, responsibility for extending BART within the county boundaries was assigned to the Santa Clara Valley Transportation Authority (VTA). The initial capital originated from a sales tax measure approved by local voters in 2000. In December 2002, VTA acquired an $80 million freight rail corridor from Union Pacific Railroad, securing the necessary right-of-way for the Warm Springs and San Jose extensions.

In 2004, the Federal Transit Administration (FTA) postponed funding due to uncertainties regarding BART's operational financing for the extension. The San Jose project received a "not recommended" evaluation from the FTA, placing federal funding at risk because of concerns about sustainable long-term operation and maintenance funding.

Measure B was approved by Santa Clara County voters in 2008, increasing the sales tax by one-eighth of a cent. Independent analyses supported by the FTA confirmed that this revenue boost would adequately cover ongoing operation and maintenance expenses for the extension. This approval was essential in securing local funds critical to advancing the project.

Subsequently, in 2016, San Jose voters passed another Measure B, which provided final financial backing for constructing the downtown subway segment.

Extension toward Livermore: I-580/Tri-Valley Corridor

A planned expansion aims to extend service eastward from Dublin/Pleasanton station to Livermore utilizing either standard BART infrastructure, diesel multiple unit technology akin to eBART, or enhanced bus transit. This extension might further progress through the Altamont Pass toward Tracy and into the Central Valley via I-580, or alternatively head north through Dublin, San Ramon, Danville, and Alamo before reaching Walnut Creek station along the I-680 corridor.

Currently, the Altamont Corridor Express (ACE), a diesel-powered commuter rail line, serves Livermore. A complimentary shuttle bus connects ACE’s Pleasanton station with BART’s Dublin/Pleasanton station.

In July 2010, a preferred route alignment was chosen with initial endorsement from Livermore City Council, proposing stations in downtown Livermore and near Vasco Road adjacent to national laboratories. However, by July 2011, the Council shifted its preference toward stations located at I-580 interchanges with Isabel Avenue and Greenville Road. BART’s Environmental Impact Report published in 2012 recommended a single station at I-580 and Isabel Avenue complemented by express bus services and park-and-ride facilities at Greenville Road. Land use plans anticipated completion by 2026.

Although additional funds were allocated in late 2016 for consulting and planning efforts, BART released its Draft Environmental Impact Report in July 2017. The prospect of a direct connection between BART and ACE was examined within broader ACE expansion initiatives.

In 2017, citing a lack of sufficient interest from BART leadership, Livermore City Council advocated for establishing a local agency to oversee planning and construction efforts—an initiative supported by the California State Assembly Transportation Committee. That same year saw the creation of the Tri-Valley–San Joaquin Valley Regional Rail Authority tasked with developing an affordable transit link connecting BART and ACE within the Tri-Valley region. On May 24, 2018, BART’s board declined proposals for full rapid transit or bus rapid transit extensions eastward from Dublin/Pleasanton station. Responsibility and funding for the new service, named Valley Link, were transferred to this Authority. Funds previously designated for BART’s extension were relinquished by July 1, 2018.

BART Metro Vision

The primary objectives of BART Metro Vision include increasing station capacity, boosting train frequency to enable convenient "show up and go" service within the system's central area, and improving operational reliability. The most recent revision emphasizes essential upgrades such as enhancements to the rolling stock, improvements at the Hayward Maintenance Complex, and modernization of the train control system to ensure long-term viability.

Second Transbay crossing

In celebration of its 50th anniversary, BART proposed constructing a new Transbay Tube beneath San Francisco Bay, positioned parallel and to the south of the current tunnel. This project envisions a four-bore passageway featuring two tracks dedicated to BART and two tracks for conventional and high-speed rail services. It would connect directly to the Salesforce Transit Center, facilitating seamless integration with Caltrain and California High-Speed Rail (CAHSR). Due to differences in rail gauge and safety requirements between BART and traditional rail systems, separate tracks are necessary.

Transit advocates in the Bay Area, including SPUR, have long championed expanding BART through initiatives like this second tunnel to enhance capacity and regional connectivity. In 2018, BART commenced a feasibility study for this additional crossing. By 2019, a partnership formed with the Capitol Corridor Joint Powers Authority to investigate a multimodal tunnel that could extend Capitol Corridor and San Joaquin trains into San Francisco.

The Link21 program, funded by Regional Measure 3 and launched in 2021, initially proposed a four-track transbay crossing accommodating both BART and commuter rail; however, this was later scaled back to two tracks. In November 2024, Link21 staff recommended utilizing standard gauge tracks for commuter rail rather than BART’s broader gauge for the tunnel, enabling electrified Caltrain service with potential future extensions for Capitol Corridor and CAHSR.

eBART extension

Expanding the DMU-operated eBART network presents a more cost-effective alternative per mile compared to traditional wide-gauge BART infrastructure. Potential service extensions could reach Oakley, Byron, or Brentwood.

Geary Subway

Initially conceived prior to Marin County’s exit from the BART District, plans called for a subway beneath Geary Street extending northward toward the Golden Gate Bridge. Following Marin’s withdrawal, proposals shifted toward a Geary-only subway but were eventually abandoned. In 1995, the San Francisco Municipal Railway evaluated constructing a BART subway underneath Geary paired with surface light rail, estimating $1.4 billion in construction costs (1995 dollars) reaching Park Presidio Boulevard. Forecasted daily boardings were approximately 18,000, with potential extension into Marin County. Opposition from local merchants and residents concerned about construction disruptions led to shelving these plans. Current analyses continue examining this corridor for possible future BART service, potentially linked to an extension of the second Transbay Tube.

wBART extension

The Richmond line remains unique as the sole original BART branch without any extensions. Studies conducted in 1983, 1992, and 2017 explored northbound expansion possibilities using either new wide-gauge electrified rail or existing freight corridors with standard gauge trains. Proposed stations include Hilltop Mall, Pinole, and Hercules Transit Center. Extending mainline BART to Hercules was estimated at $3.6 billion in 2017 with projected ridership reaching 21,980 by 2040. The proposed extension is contentious: supporters advocate for direct service from El Cerrito del Norte BART station, whereas Richmond opposes this alignment. Furthermore, most members of Hercules’ city council resist the extension due to concerns it may conflict with their development plans surrounding Hercules station.

I-680 Corridor

Earlier considerations for service within the Tri-Valley region involved diesel multiple units operating between Walnut Creek and Tracy. In alignment with BART's vision for its 50th anniversary, planners suggested a new East Bay route commencing at Warm Springs station and following Interstate 680 to the Martinez Amtrak station, thereby linking the existing stations at Dublin/Pleasanton and Walnut Creek.

Menlo Park extension

In 1999, the San Mateo County Economic Development Association (SAMCEDA) put forward a proposal to extend BART from Millbrae station to Menlo Park. This extension would run parallel to Caltrain tracks up to Broadway station in Burlingame, then continue along the Bayshore Freeway median with stops planned in San Mateo, Belmont/San Carlos, Redwood City, and Menlo Park. The projected cost was approximately $2.5 billion in 1999 dollars, intended to be financed through a proposed half-cent sales tax increase within San Mateo County. However, BART leadership assessed that the timing was not appropriate for further southward expansion, leading SAMCEDA to withdraw the proposal by mid-1999.

Infill stations

Infill stations refer to new stations constructed on existing rail segments between current stops. Currently operational infill stations include (opened in 1976) and (opened in 2011). The Doolittle Maintenance and Storage Facility, originally designed as a full station on the Oakland Airport Connector, holds potential for future conversion to passenger service.

A proposed 30th Street Mission station in San Francisco was estimated to cost $500 million as of 2003. A plan for a Jack London Square station in Oakland was dismissed in 2004 due to complications with track geometry; alternative solutions such as a stub line and other transit options were explored. In 2007, BART evaluated additional infill station possibilities at Albany, Calaveras, Irvington, and 30th Street Mission. By 2014, candidate locations had expanded to include 30th Street/Mission, one site between and , plus four Oakland sites: Children's Hospital Oakland, San Antonio/Brooklyn Basin, Melrose, and Elmhurst.

The city of Fremont revisited the environmental impact report for the Irvington station in 2017; subsequently, a station area plan was adopted by the Fremont City Council and received approval from BART's Board in 2019. As of January 2019, construction was anticipated to commence in 2022 with service projected to begin in 2026.

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