The Bay Area Needs a
Second Crossing
Link21 is a once-in-a-generation opportunity to build a new transbay rail crossing connecting San Francisco, Oakland, and the entire Northern California megaregion. Here's why it matters and how to make it happen.
What Is Link21?
Link21 is a program to build a new passenger rail crossing between Oakland and San Francisco under the Bay. It's led by BART and the Capitol Corridor Joint Powers Authority (CCJPA), with support from CalSTA, MTC, and federal agencies.
The current BART Transbay Tube, built in 1974, is the only rail crossing of San Francisco Bay. Even after a $313 million seismic retrofit completed in September 2024, it remains a single point of failure. Transbay ridership is projected to double by 2050, and the current tube cannot handle that growth.
Think About This
Every major world city with a water crossing has multiple rail connections. New York has 20+ subway tunnels under the East River. London has numerous Thames crossings. The Bay Area - the economic engine of the world's 5th largest economy - has one.
In June 2025, both the BART Board and CCJPA Board voted to advance Link21 as a standard-gauge regional rail project. This is a landmark decision - it means the new tunnel will be compatible with Capitol Corridor, Caltrain, ACE, San Joaquins, and potentially California High-Speed Rail. One crossing connecting the entire Northern California rail network.
Possible Station Locations
Several alignment concepts are being studied. Potential stations include:
- San Francisco: Salesforce Transit Center (connecting to Caltrain/Portal)
- Alameda: Would receive rail service for the first time ever
- Oakland: Jack London Square, Oakland City Center, MacArthur (BART transfer)
- East Oakland: San Antonio neighborhood
Final station selections are being made NOW - your input matters.
Why We're Championing the Alameda Route
Three of four Link21 concepts route through Alameda - an island of 78,117 people with zero rail stations. Alameda lost its rail service when the Key System was dismantled in 1958 and was bypassed by BART. For 68 years, the island has been car-dependent, with 70,000+ daily vehicles crammed through aging tubes and a drawbridge. With 2,696 housing units planned at Alameda Point and 5,353 RHNA units required by 2031, rail transit isn't just nice to have - it's essential. Link21 is Alameda's once-in-a-century chance to rejoin the regional rail network.
Learn More: Link21 for Alameda →Why This Matters for You
Housing & Affordability
Fast rail connections let people live in more affordable areas (East Bay, Sacramento corridor) while accessing SF/Oakland jobs. This eases housing pressure across the region without building luxury towers in every neighborhood.
Jobs & Economy
A connected megaregion means a larger labor pool for employers and more job options for workers. Economic studies show transit investments generate $4-6 in economic returns for every $1 spent.
Resilience
The current transbay tube is a single point of failure. In earthquake country, having only one rail crossing is a serious vulnerability. A second crossing provides critical redundancy for the region's economy.
Climate
Transportation is the Bay Area's #1 source of greenhouse gas emissions. Getting people out of cars and onto trains is one of the most impactful things we can do. Link21 enables a future with far fewer car trips.
Equity
Better transit connections serve communities of color and low-income residents who are most dependent on public transit. Link21 is designed with equity as a core principle, connecting underserved areas to opportunity.
World-Class Region
The Bay Area competes globally with cities like London, Tokyo, and Singapore. Those cities have extensive, integrated rail networks. We need one too if we want to remain competitive and livable.
Link21 Is a Housing Project Too
California has a housing crisis. Cities must build hundreds of thousands of new homes. State law (SB 79, signed October 2025) now requires high-density zoning near transit stations. Every Link21 station automatically unlocks massive housing development potential.
What This Means
Under SB 79 (Senator Wiener, effective July 1, 2026), a Link21 station in Alameda would automatically enable thousands of new housing units within walking distance - at up to 120 units/acre. Combined with the 2,696 units already planned at Alameda Point, a Link21 station could help Alameda meet its entire state-mandated housing obligation. California's AHSC program has already invested $4+ billion funding 22,000+ affordable transit-oriented homes - a Link21 station makes Alameda eligible. Without rail transit, all those new residents just add cars to the already-overwhelmed tubes. You can't solve the housing crisis without solving the transit crisis. They're the same fight.
Link21 IS High-Speed Rail for the Bay Area
California's High-Speed Rail has been under construction in the Central Valley for over a decade. Cost estimates have grown from $33 billion (2008 Prop 1A) to $126 billion (2026 Business Plan) - a 282% increase. $13.8 billion spent, zero passengers carried, no track laid. The Trump admin pulled $4 billion in federal funding. The Bay Area extension (HSR reaching SF via Gilroy) is targeted for 2038-2039 at earliest - and the $5-6B San Jose-to-Gilroy segment is not funded.
Why Wait for HSR When Link21 Builds What HSR Needs?
Link21 chose standard-gauge specifically to be compatible with HSR, Capitol Corridor, Caltrain, ACE, and San Joaquins. Link21 terminates at the Salesforce Transit Center - the exact same station HSR plans to use. The tunnel Link21 builds is HSR infrastructure for the Bay Area. When HSR eventually arrives, it can plug right in.
This isn't about defunding high-speed rail. It's about delivering results now. Link21 gives the Bay Area fast, frequent regional rail service a generation before HSR arrives. And every dollar spent on Link21 is a dollar invested in California's complete rail future.
The Standard-Gauge Advantage
Building a Megaregion
Northern California is growing. New communities, new housing, new jobs. But growth without transit means growth with gridlock. Link21 is the backbone that makes sustainable regional growth possible.
Solano County & Beyond
The Solano Rail Hub project is upgrading the Suisun-Fairfield station into a multimodal hub - explicitly described as "a key station in the future Link21 Project." Proposals like the California Forever development (up to 400,000 residents in Solano County) highlight the demand for regional rail in the I-80 corridor. Whether that project is built or not, growth is coming to the corridor - and it needs rail, not more freeway lanes.
Sacramento Connection
Sacramento housing costs are 1/3 of San Francisco's. Link21 makes Sacramento a realistic commute option - fast, frequent trains instead of a 2-hour I-80 crawl. That's a housing solution that doesn't require building towers in every neighborhood. It requires building a tunnel.
Central Valley Access
ACE and San Joaquins already connect the Central Valley to the Bay Area. Link21 gives those riders a one-seat ride to San Francisco. For Central Valley residents priced out of the Bay, this is a lifeline to jobs without a soul-crushing commute.
Alameda Point TOD
Alameda Point's 878-acre development is the East Bay's biggest transit-oriented development opportunity. With 2,696 housing units planned and SB 79 enabling even more density near stations, a Link21 stop here creates a model community: rail + ferry + bus + housing + jobs in one connected hub.
Where It Stands
2019-2024: Concept Identification (Complete)
Program launched in 2019. Analyzed 60+ concepts, narrowed to viable alignments (Concepts A, B, E, F). Developed Preliminary Business Case (August 2024). Engaged thousands via Equity Advisory Council and community co-creation process with local CBOs.
June 2025: Technology Selection (Complete)
BART Board and CCJPA Board both voted to advance as standard-gauge regional rail. Day-to-day management transferred from BART to Capitol Corridor. Project included in California State Rail Plan. Now eligible for FRA Corridor ID Program ($1.8B federal fund).
Now: Project Selection Phase (In Progress)
Defining specific station locations and track alignments for the standard-gauge crossing. Preparing to launch formal environmental review (EIR/EIS). Developing federal/state funding strategy through the Corridor ID Program. Public input now directly shapes the final project.
Next: Environmental Review (EIR/EIS)
Formal CEQA/NEPA environmental review. Public comment periods. Alternatives analysis.
Future: Engineering, Funding & Construction
Detailed engineering. Securing federal (FTA New Starts, Corridor ID), state, and regional funding. Construction. Target for benefits: 2040.
The Economic Case Is Overwhelming
The Bay Area Council Economic Institute projects Link21 would generate 377,000 jobs and $145 billion in economic benefits. The Northern California megaregion's GDP is $875 billion (5% of US GDP). Market analysis shows 45% of all unmet travel demand involves crossing the Bay, and the current Transbay Tube will be at 107% over capacity by 2050. This isn't optional infrastructure - it's economic necessity.
The Risk: Delay and Death by Committee
The original target was 2040. It's already slipped - current documents suggest construction starting ~2039 with full completion in the 2050s. The Bay Area has a history of letting great transit projects stall (BART-to-San Jose took decades). $155M has been spent on planning with $125M to consultants. That money is wasted if the project dies in committee.
Every month of delay costs money (construction inflation) and lives (continued car dependence, emissions, traffic deaths). We need to push for urgency. Seamless Bay Area has warned that the current governance structure (two agencies with equal power) is "an unstable arrangement likely to contribute to years of delay."
Imagine the Megaregion
With Link21, Northern California becomes one connected region. Here's what that looks like:
Sacramento to SF
Fast, frequent trains connecting the state capital to the Bay Area. Live in Sacramento, work in SF. Or vice versa. That's the power of real regional rail.
Oakland to SF (New Route)
A new alignment could serve neighborhoods not currently on BART, opening up transit access for communities that have been underserved for decades.
One Seat to Anywhere
Connecting BART and regional rail in a unified system means fewer transfers, simpler trips, and a system that works the way people actually travel. One ticket, one system, one region.
How Other Cities Did It
London's Crossrail (Elizabeth line) transformed the city with a new east-west rail line. Despite cost overruns and delays, it now carries 700,000 daily passengers and generated billions in economic value. Tokyo's rail network, built over decades of sustained investment, moves 40 million people daily. These cities decided transit was worth investing in. We need to make that same decision.
Champion This Project
Link21 needs public support to stay on track and on schedule. Here's how you can help.
Submit Public Comment
The environmental review process is open for public comment. Your input directly shapes the project. Say you support it. Say you want it built quickly. Be specific about what stations and connections matter to you.
Submit comment at Link21 →Contact Your Elected Officials
Tell your state legislators, city council, and county supervisors that Link21 is a priority. Ask them to publicly support the project and push for state and federal funding.
Find your representative →Attend Community Meetings
Link21 holds regular community meetings (in person and virtual). Show up. The more people who attend, the stronger the mandate to build.
Upcoming meetings →Spread the Word
Most Bay Area residents don't know Link21 exists. Share this site, talk about it at dinner, post about it online. Awareness is the first step to momentum.
Push for Speed
The biggest risk is delay. Ask BART board members and MTC commissioners: what is the timeline? Can it be faster? What's the bottleneck? Public pressure for urgency matters.
Support BART Funding
Link21 needs a financially healthy BART as a foundation. Supporting BART's current funding needs helps ensure Link21 has a strong institutional partner to deliver the project.
Save BART info site →Common Questions
How much will it cost?
Current estimates: $18-30 billion for the crossing itself (2023 dollars), plus $15-25 billion for network connections - potentially $33-55 billion total. Yes, that's enormous. But consider: the Bay Area GDP is over $1 trillion annually. London's Crossrail cost $23 billion and now carries 700,000 daily passengers while generating billions in economic value. Federal funding through the Corridor ID Program and FTA New Starts could cover a significant share. Over 50+ years of service, the economic returns dwarf the investment.
When will it be built?
The target for delivering benefits is 2040. The project is currently in the Project Selection Phase, defining stations and alignments before launching formal environmental review. There is no specific construction start date yet - that depends on completing the EIR/EIS and securing funding. But every year of delay increases costs (construction inflation) and prolongs our vulnerability with a single crossing. Public pressure for urgency matters.
Where will it go?
Several alignments are being studied. The crossing would connect Oakland and San Francisco, but the exact station locations and route through each city are still being determined. This is why your input during the environmental review matters - you can advocate for specific stations and connections.
Isn't the current tube enough?
No. The current tube was built 50 years ago and is already at capacity during peak hours. It's also a single point of failure - one disruption and there's no alternative. Every major world city with a water barrier has multiple crossings. We're overdue.
Why not just build more highways?
Decades of research prove that adding highway lanes doesn't reduce congestion (induced demand). Rail moves far more people per dollar invested and per unit of land. A single rail track moves the equivalent of 10-16 highway lanes. Rail is the future; highways are the past.
Stay Connected
We track Link21 developments, community meetings, and political updates. Follow along.