A transit tangle. Illustration by Matt Petty

Link21’s marquee project is a new train tunnel between Oakland and San Francisco — described in a separate article on the rationale of the region’s epic infrastructure push — but it is by no means the only project included in this regional rail program. Reports on Link21 from BART and the Bay Area Council identify 13 projects across Northern California as part of the overall vision to connect the region by train. Some projects, like Caltrain electrification, are nearly complete, while others, like the Altamont Corridor Vision, are pretty fantastical at this point. Below, we describe each of these projects, including their estimated costs and timelines for completion, when possible. 


All 13 of the projects associated with the Link21 program. (Bay Area Council)

There’s no denying this is an epic infrastructure wishlist, whose total price tag stretches into the twelve figures. (Though, as transit advocates are wont to point out, California is set to spend about $20 billion maintaining and expanding state and local roads, and paying for highway patrol, this year.) In all likelihood, not every project enumerated below will get built. Indeed, not all of them should: Even as planners get more ambitious, they also need to make sure they get as much bang for their buck as possible. In some cases, simple fixes, like transit-only lanes, or increasing frequency on existing bus and train lines, can be nearly as transformative as major infrastructure projects.

Read More: An ambitious plan to connect NorCal by rail is gaining steam.

But for any of these mega-projects to even have a shot at becoming a reality, there needs to be a comprehensive plan detailing why they are important, and how they will enhance transportation, the environment, housing affordability, and economic opportunity in Northern California. If Link21 is to succeed, it will have to make that case to voters and the federal government.   

It wouldn’t be a novel concept, either. LA, Seattle, and Austin have all recently passed detailed regional transportation plans, in the hopes that the federal government will someday be willing to step in and help out in a major way. LA, in particular, has really big plans. We won’t bore you with the details of our rival region’s rail network here, but suffice to say, if the Bay Area doesn’t get its act together, LaLa Land’s transit system will put our own to shame in a decade or two. And no self-respecting Northern Californian wants that.

Downtown Extension 

The Downtown Extension, which the stylish among us call “DTX,” is a train tunnel planned to connect the existing Caltrain terminus at 4th and King in San Francisco to the unfinished train station in the basement of the Salesforce Transit Center. Upon completion, the SFTC will serve both Caltrain and High Speed Rail trains. The project will also bury the train tracks between the 22nd Street station and 4th and King — eliminating all “at-grade” Caltrain street crossings in San Francisco — and include a pedestrian tunnel between SFTC and the Embarcadero BART and Muni station. 

The DTX project is being led by the Transbay Joint Powers Authority (TJPA), although Caltrain, California High Speed Rail, SFCTA, MTC and the city of San Francisco are all involved in planning. Planners are currently working on phasing the project and developing an updated cost estimate. The project’s $3.9 billion price tag, from 2016, will likely go up, says Eric Young, a spokesperson for SFCTA. With about $1 billion in funding secured so far, planners will need to find additional funds in order to get the project started by 2023 or ’24 and complete it by 2030 or ’31, as planners hope. DTX planners are coordinating with the Link21 team to get regional rail trains out of the SF Transit Center and into the second transbay rail crossing. The station is being envisioned as a “through-running,” as opposed to a “terminus” station, with trains entering and exiting from two ends. After leaving the SFTC from the east, trains have a number of potential paths to get to the Bay, including heading straight out paralleling the Bay Bridge, or heading south along Main or Spear before hitting the water near the Giants Ballpark, according to a January presentation by TJPA. This raises additional questions about the siting of a new BART line through San Francisco: Should BART and regional rail trains continue to share a tunnel once they’ve alighted in San Francisco?

Caltrain Electrification and Modernization

Caltrain is currently in the midst of a transformative electrification project that will ultimately make the service more like BART in terms of speed and frequency, and allow the rail service to eventually share tracks with high speed rail trains. Electrified trains can travel much faster than the current diesel trains — up to 110 miles per hour, keeping pace with high speed rail trains — and run closer together. In order to sustain travel at these speeds, the corridor is ultimately slated to receive other upgrades, like new passing tracks and other safety features. These elements will be necessary for Caltrain to fulfill its 2040 service vision of providing eight trains per direction, per hour, along with four high speed rail trains per direction per hour, during peak commute times. 

While electrified service was initially projected to begin in 2022, the pandemic has caused “interruptions in the supply chain” that could have an impact on the project’s opening, according to SamTrans spokesperson Dan Lieberman. He expects the agency to provide an update on the project timeline at their June board meeting. 

BART to San Jose 

With little fanfare, BART actually made it into Santa Clara County in 2020. But the new stations, in Milpitas and the Berryessa neighborhood of San Jose, represent only the first step towards the much more significant extension into downtown San Jose. That project is well on its way, however, with 75 percent of its funding secured and the rest expected to come in the form of a federal grant to be announced this summer. (All the brouhaha about “Pelosi’s Subway” during the debate of the American Rescue Plan was basically moot, as the Trump Administration had all but guaranteed funding for the project already.) The project is slated to break ground in 2022, and be largely completed by 2028, with service beginning in 2030, according to Bernice Alaniz, a spokesperson for the Santa Clara Valley Transit Authority. VTA is funding and planning the extension, which will ultimately be operated by BART.

Together with electrified Caltrain service, the BART extension to downtown San Jose will create a mass transit ring around the Bay, connecting the region’s three major cities with fast and frequent trains. 

California High Speed Rail

California’s high speed rail system, which officials pledge will eventually link San Francisco and Los Angeles in 2 hours and 40 minutes, is currently under construction in the Central Valley. The nearly $100 billion project has been plagued by financial, logistical, and political problems for years, many of them related to difficulty acquiring land and shoddy work by consultants. And there are lingering frustrations among rail advocates about the system’s route — namely, the fact that it will travel through the Pacheco and Tehachapi Passes, rather than the more direct path through the Altamont Pass and the Grapevine. On the other hand, advocates also contend that the project has received unfair criticism from Republican lawmakers as well as the LA Times. 

Things could be turning a corner now, though, with an administration that has explicitly embraced high speed rail. “After a couple years of mostly radio silence we now have basically daily contact with the federal administration,” says Boris Lipkin, Northern California Regional Director for California High Speed Rail. 

Here’s the current project status, laid out in the latest California High Speed Rail business plan: The under-construction Merced to Bakersfield segment is expected to be running by 2029, with connections to Sacramento and the Bay Area provided by Amtrak’s San Joaquins and Valley Rail, described below. In the first half of 2022, the final piece of the “Valley to Valley” segment, connecting Silicon Valley to the Central Valley via the Pacheco Pass, is expected to be environmentally cleared. That paves the way for final design and construction of this tricky mountain crossing to get underway, with an estimated 2031 opening date. Finally, the full Phase 1 system, connecting the Bay Area to L.A. and Orange County, is expected to be complete by 2033. Of course, those opening dates are contingent upon securing additional funding for the project, whose total price tag is now approximately $98 billion.

That’s not including Phase 2, which envisions high speed trains going out to San Diego and Sacramento. The High Speed Rail Authority has asked the state legislature to allow it to use the rest of the funds from its 2008 voter-approved bond measure in order to complete the segment in the Central Valley. It will then pursue other funding sources for the rest of the line.

Meanwhile, Brightline West, a privately funded high speed rail line connecting Southern California and Las Vegas, is set to break ground this year. That rail line could link up with California High Speed Rail in Palmdale, north of L.A., meaning San Franciscans might someday be able to take the train to Vegas in the neighborhood of 5 hours and 19 minutes, according to one estimate.   

Valley Link  

For years, BART had plans to extend its Dublin-Pleasanton line east to Livermore and perhaps beyond, along the 580 corridor. But BART cancelled those plans in 2018, leaving a pot of money to the Tri-Valley San Joaquin Valley Joint Powers Authority, helpfully abbreviated as TVSJVJPA. That group has been quickly working on the development of a new rail plan for the corridor called Valley Link, which will proceed from the existing BART terminus at Dublin-Pleasanton, down the 580 median to Livermore, before traversing the Altamont Pass and travelling through the Central Valley to Tracy and Lathrop. 

Unlike the Altamont Commuter Express (ACE) rail service, which runs just a few trains per day during peak commute hours, Valley Link would offer frequent, all day service providing timed transfers to BART. In theory, it should work much like the existing E-BART service linking Pittsburg and Antioch — except Valley Link is being built and operated by a separate agency, creating new complications. 

While few people outside of the communities immediately surrounding the line have likely heard of it, this project is remarkably far along. Michael Tree, executive director of TVSJVJPA says the project is poised to receive environmental clearance this week, and then promptly begin final design work with an eye towards an early 2028 opening. The project has approximately $700 million in funding secured, about a third of what it will need for completion. Depending on the availability of additional funding sources, Valley Link could begin service with smaller initial operating segments, out to Livermore or just beyond the Altamont Pass at Mountain House. The construction of the segment within the 580 median will require the freeway to be widened, although Tree emphasizes that existing lane configurations, including the newly installed express lanes, and exit interchanges will be kept intact. 

The San Joaquin Regional Rail Commission, operator of ACE, is the “presumed” operator of Valley Link. (This relationship could be tricky, if the rail service begins its initial operating segment out to Livermore, which would not cross into San Joaquin County.) ACE and Valley Link services are “working together on the potential” to share tracks over the Altamont Pass, Tree says. In the future, the slow journey among the windmills for both train services could be replaced by a 3.5 mile tunnel, as part of the Altamont Corridor Vision, described below.

Valley Rail

Valley Rail is an expansion of the existing ACE service — which currently runs between Stockton and San Jose — south to Merced and north to Sacramento. The first phase of the southward extension, out to Modesto and Ceres, is under construction and expected to be complete by the end of 2022, according to Valley Rail spokesperson David Lipari. The rest of the extension, to Merced, is expected to be complete in 2025. Once there, ACE trains, as well as existing Amtrak San Joaquins trains are expected to provide a transfer to high speed rail trains. While the agencies involved are all coordinating, the specifics of how that will happen remains unclear. In all likelihood, high speed rail trains will terminate at Merced, and offer a transfer to other services, rather than continuing along the Valley Rail tracks into the Bay Area. That concept was studied, but deemed less practical than a cross-platform transfer, California High Speed Rail’s Boris Lipkin says. 

The northward extension to Sacramento, which will also serve San Joaquins trains, is under construction and should be complete by 2023, according to Lipari. That extension will include a new station in Midtown Sacramento, walking distance from the State Capitol, as well as new stations near the Sacramento Airport, Sacramento City College, and Elk Grove.   

Altamont Corridor Vision

Altamont Corridor Vision proposes a train tunnel under the Altamont Pass, drastically improving train speed and reliability through the corridor. The 3.5 mile tunnel, estimated to cost $1.9 billion and designed to enable trains to travel up to 125 miles per hour, would be shared by ACE and Valley Link trains. The vision would also include track improvements along other parts of the old rail line, in order to provide a one-hour long, one-seat ride between Stockton or Modesto and San Jose, Redwood City or Oakland. The connection to Redwood City would be contingent upon the Dumbarton Rail Crossing (described below) being built for regional rail trains.

Phase 1 of the Altamont Corridor Vision would include the Altamont tunnels and other improvements in that area, benefitting both ACE and future Valley Link trains. That phase is estimated to cost $1.9 billion. All of the envisioned improvements along the corridor are estimated to cost $9.7 billion. Lipari of ACE emphasizes that this a long-term vision that has not been funded, and that ACE is pursuing shorter-term improvements to the tracks over the Altamont Pass.

Dumbarton Rail Crossing

The Dumbarton Bridge is probably the least dramatic of the Bay Area’s bridges, spanning the narrowest, flattest part of the Bay, between Fremont and Menlo Park. It is, however, one of the key gateways to Silicon Valley from more affordable points east. Right next to the car bridge, there’s already a rickety old one track rail bridge that’s been out of commission since the 1980s. 

In recent years, SamTrans, San Mateo County’s public transit agency, has been studying the possibility of restarting rail service across the Dumbarton corridor. The project is currently in a pre-design phase, studying potential alternatives that include traditional regional rail technology, light rail, or autonomous vehicle transit. The project’s very early cost estimate is about $3 billion, with a proclaimed completion date of 2028.

Funding, of course, is yet to be sorted out. However, Facebook, whose headquarters is right off the west side of the corridor in Menlo Park, has contributed $15 million for initial planning, and continues to be involved in the project, according to SamTrans spokesperson Tasha Bartholomew. The Plenary Group, a transportation planning firm that leads public-private infrastructure projects, is also involved. Bartholomew says SamTrans has had “preliminary conversations” with ACE about “coordinating their service with future service on the Dumbarton Corridor.” Whether that means direct service, with ACE trains crossing the bay, or transfer to another rail technology, remains to be seen.

The latest presentations on the Dumbarton Corridor have given autonomous vehicle transit the highest marks in terms of ridership and affordability. Adina Levin, a transit advocate who runs the blog Green Caltrain, believes these estimates neglect the corridor’s potential for regional transportation. Levin also points out that proposed technology, eight-person autonomous vehicle pods from a company called Glydways, is unproven at this scale. The SamTrans board will continue to discuss which transportation technology to pursue this summer

SMART Extension

Sonoma Marin Area Rapid Transit (SMART) opened in 2017, with their cute little green trains paralleling the 101 between San Rafael and Santa Rosa. In 2019, the train service was extended south to Larkspur, enabling passengers to transfer to ferries bound for San Francisco. Now, SMART needs to make its way further north to Cloverdale via Windsor and Healdsburg to fulfill the terms of its voter-approved plan. Those plans have been pushed back, however, due to the legal challenges against the Bay Area’s 2018 voter approved bridge toll increases, which prevent that money from flowing to transit agencies.  

The Windsor extension began construction last year, but was halted as the lawsuit against the 2018 bridge toll increase makes its way through the court system. SMART spokesperson Matt Stevens says the agency will provide updates on the extensions to Windsor and beyond after the California Supreme Court rules on the case.  

North Bay Connection 

While SMART works to complete its original line, the agency, along with regional and state rail planners, are hoping to eventually connect it to the rest of the statewide rail network. The simplest, and likely cheapest, solution would be to make use of existing freight tracks between Novato and Suisun City, near Fairfield, which is home to a Capitol Corridor station. That was the subject of a 2019 SMART study, which envisioned potential stations along the way near Infineon Raceway, Schellville (just south of the town of Sonoma) and American Canyon. Preparing those tracks and stations for passenger service would cost between $700 million and $1.2 billion. 

That option is not the only one for a North Bay Connection. Notoriously congested Highway 37, which rings the top of the Bay between Vallejo and Navato, is likely going to be underwater in a couple of decades, prompting calls to rebuild the route, potentially with adjoining rail service. The Richmond Bridge might need to be rebuilt in the near future as well, due to seismic issues, creating another possibility for new rail infrastructure. 

There have also been studies about establishing rail service into the Napa Valley, which is currently only served by the tipsily slow Wine Train. 

Monterey Bay Rail 

Construction is currently underway to prepare for an extension of Caltrain into Monterey County. The route will follow existing freight rail tracks from Gilroy south to Salinas, where the historic train station is being modernized for passenger service. However, a number of hurdles remain in terms of coordinating service with Caltrain and Union Pacific, the freight rail company that owns the tracks. The earliest the four-train-per-day service could begin is 2024, according to Christina Watson, a planner with the Transportation Agency for Monterey County (TAMC). 

Amtrak has also identified this corridor, from San Jose to Los Angeles — which is currently served by the three-trip-per-week Coast Starlight — for increased train service in the near future. 

In the future, TAMC hopes to build passenger stations on the existing tracks at Pajaro, near Watsonville, and Castroville. The Pajaro station would connect to a state-owned rail right of way that could provide service to Santa Cruz, and the Castroville station would connect to a proposed bus rapid transit line connecting to Seaside and Monterey. These destinations would be linked to the statewide high speed rail system via the Gilroy station.  

Capitol Corridor Vision 

In 2016, Capitol Corridor, the rail service connecting the Bay Area and Sacramento, laid out an extensive long term plan called the Capitol Corridor Vision. It includes electrifying the diesel rail service, adding tracks to get freight trains out of the way of passenger trains, and building lots of new infrastructure, like a tunnel for the tracks that currently run through the middle of Oakland’s Jack London Square — which could be all the more important if the A’s get approval to build their new ballpark. 

Capitol Corridor’s farthest along “Vision” project is South Bay Connect, which will move Capitol Corridor trains to new tracks close to the bay, south of San Leandro, reducing road crossings and scheduling conflicts with freight trains. The project will eliminate the existing Hayward and Fremont stations, and add a station at Ardenwood, next to the Dumbarton Bridge. The Ardenwood station will provide improved access to buses going to and from the Peninsula, which would be sped up by bus-only-lanes planned in MTC’s Dumbarton Forward program. Capitol Corridor is “in discussion” with SamTrans about their plans for the Dumbarton Crossing, which is a longer-term project, Capitol Corridor spokesperson Karen Bakar says. South Bay Connect is in the environmental review phase, and is slated to begin construction in 2024.

Another project underway will add a new track between Sacramento and Roseville, allowing Capitol Corridor to increase service to the growing Sacramento-area suburb.

Benjamin Schneider is a staff writer at SF Weekly. Twitter @urbenschneider