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Frequently Asked Questions


What is Link21? Open accordion Close accordion

Link21 is a program of system improvements for BART and Regional Rail (including commuter, intercity, and high-speed) that will transform the Northern California Megaregion’s passenger rail network into a faster, more integrated system, providing a safe, efficient, equitable, and affordable means of travel for all types of trips. 

Link21 will include a new transbay rail crossing between Oakland and San Francisco that will increase BART’s transbay capacity and connect Regional Rail service across the Bay. 

Additional improvements will be included in Link21 to address issues that affect system performance and the passenger experience, such as travel time, reliability, and capacity in high-demand corridors. 

Link21 aims to create better connections, improve ease of travel, promote sustainability, support the Megaregion’s economy, and advance equity.

When is Link21 going to be built? Open accordion Close accordion

Link21 is in the early stages of planning and development. Construction of new rail facilities will begin once planning, engineering, and environmental approvals are complete and funding is secured. Schedule details will be refined and updated as the Program progresses and we develop program alternatives.

Where will Link21 go? Open accordion Close accordion

Link21 will study options to improve passenger rail service for many areas within the Northern California Megaregion. While specific locations have not yet been determined, the Link21 Program will include a new transbay rail crossing between Oakland and San Francisco. Market analyses, along with public input, will help us identify where Link21 improvements can be the most effective.

Who is leading Link21? Open accordion Close accordion

BART and Capitol Corridor have partnered to advance Link21, building on the existing planning work done by many regional partners to identify the need for an integrated rail network. Both agencies are regularly engaging key stakeholders.  

Why are BART and Capitol Corridor leading Link21? Open accordion Close accordion

Solutions that improve both San Francisco Bay Area Rapid Transit (BART) and Regional Rail (including commuter, intercity, and high-speed rail) will likely be the most impactful in addressing the Northern California Megaregion's long-term transportation challenges. 

BART is the primary way that people move across the San Francisco Bay during peak commute hours. BART’s 2016 voter-approved Measure RR provided funding to begin the study and development of Link21.   

A second transbay crossing could be an important solution to reducing congestion throughout the transbay corridor and may also enable expanded BART service hours and other possible system projects.   

Capitol Corridor Joint Powers Authority’s (Capitol Corridor) role in the Link21 Program is to provide a regional and intercity rail perspective to the Program on a day-to-day basis, as well as support the implementation of the California State Rail Plan. The California State Transportation Agency (CalSTA) is Capitol Corridor's funding partner for this Program. Other rail operators in our region are also active partners in the Link21 Program. 

A popular travel itinerary on Capitol Corridor is between Sacramento and San Francisco, which currently requires riders to transfer to a bus in Emeryville or to BART in Richmond. Having to transfer makes the trip slower and less convenient for travelers. A new transbay passenger rail crossing between Oakland and San Francisco would allow for a seamless ride between the Sacramento Area and San Francisco. 

In addition, a new transbay passenger rail crossing could allow new connections between rail systems that are currently separate. For example, passengers from points along the Peninsula could more easily and quickly travel by rail to the East Bay, Sacramento Area, or Northern San Joaquin Valley. Providing Regional Rail access across the Bay could attract riders throughout the Megaregion and reduce vehicle congestion. 
Because BART is a member agency to Capitol Corridor, these two agencies are primed to collaborate effectively and efficiently. 

Why is Link21 needed? Open accordion Close accordion

Although the Northern California Megaregion has grown into one of the nation’s largest economies over recent decades, not everyone has benefited from this growth and prosperity. Due to the region’s difficult geography, the rail network has not kept pace with the growth and complexity of the region.

The inability of the existing transportation network, in particular the transbay corridor, to meet the needs of the 21-county area leaves many residents struggling to live affordably and within each reach of work, school, shopping, and recreation.

Link21 will help alleviate many of the transportation challenges that residents of Northern California face daily, including overcrowded trains and buses, increased freeway congestion, and unreliable travel times. These challenges restrict the Megaregion's ability to forge a path to a vibrant future.

As the Megaregion continues to grow, Link21 will be an important part of a sustainable transportation network to tie communities and economies together.


Link21 is a program. How is this different than a project? Open accordion Close accordion

As an overarching program, Link21 will identify a set of rail projects throughout the 21-county Northern California Megaregion that improves passenger rail. These improvements will be grouped into separate projects that each provide independent benefits. 

One key project within the Link21 Program will be a new transbay rail crossing between Oakland and San Francisco.

What is Regional Rail? How is it different from BART? Open accordion Close accordion

Within the Link21 Program, "Regional Rail" refers to commuter (e.g. Caltrain, Altamont Corridor Express [ACE], Sonoma-Marin Area Rail Transit [SMART]), intercity (e.g. Capitol Corridor and San Joaquins), and high-speed rail (e.g. California High-Speed Rail) service and operators.

BART is referred to separately since its unique gauge (width between the wheels/rails) requires separate infrastructure. 

What is the Northern California Megaregion? Open accordion Close accordion

The Northern California Megaregion is a 21-county area covering the San Francisco Bay, Monterey Bay, Northern San Joaquin Valley, and Sacramento regional areas. These 21 counties increasingly face shared transportation, housing, environmental, and economic challenges. Taking a megaregional approach helps the Link21 Team identify the most comprehensive and effective solutions.

Counties in the Megaregion are:

  • Monterey Bay Area: Monterey, San Benito, Santa Cruz
  • Northern San Joaquin Valley Area: Merced, San Joaquin, Stanislaus
  • Sacramento Area: El Dorado, Placer, Sacramento, Sutter, Yolo, Yuba
  • San Francisco Bay Area: Alameda, Contra Costa, Marin, Napa, San Mateo, San Francisco, Santa Clara, Solano, Sonoma

What is the Transbay Corridor? Open accordion Close accordion

The transbay corridor refers to the travel routes between Oakland and San Francisco. This includes the existing BART Transbay Tube, Oakland-San Francisco Bay Bridge, and the San Francisco Bay Ferry. The transbay corridor has some of the highest vehicle congestion and transit crowding in the Megaregion.

A New Transbay Rail Crossing

Are you considering transbay rail crossings between places other than Oakland and San Francisco? Open accordion Close accordion

Every alternative we analyze will include a new transbay passenger rail crossing between Oakland and San Francisco. Prior work, such as the Metropolitan Transportation Commission’s (MTC) Crossing Study, Horizon, and Core Capacity Transit Study, as well as the 2018 California State Rail Plan, identifies a crossing in this location as key for improving the Northern California Megaregion’s transportation network.

Is the new transbay passenger rail crossing going to be a bridge? Key system trains used to run across the Bay Bridge. Open accordion Close accordion

No. One of the biggest constraints for a bridge crossing is the need to maintain enough overhead clearance for the shipping channel. We would need a lot of space on both sides of the Bay to make a climb high enough to provide that clearance—that’s too much for modern trains to handle. Given these constraints, a tunnel or another underground option is more feasible.

Where will the new transbay rail crossing go? Open accordion Close accordion

The new transbay rail crossing will connect Oakland to San Francisco. Exact locations are still under study. We will be asking the public for input in the near future.

Why is a new transbay rail crossing so important to Link21? Open accordion Close accordion

The existing transbay corridor is a critical chokepoint for BART and a gap in the Regional Rail system. The California Department of Transportation (Caltrans) and the Metropolitan Transportation Commission have both rated the transbay corridor as the most congested corridor in the region.

Creating a new transbay rail crossing, with associated improvements, is expected to be the first major project within Link21 because addressing this chokepoint and gap first will increase the effectiveness of any future Link21 projects.

Will the new transbay passenger rail crossing use dual or standard gauge? Open accordion Close accordion

Rail gauge is the distance between the inner edges of two parallel rails on a train track. Standard gauge used by Regional Rail is 4 feet 8½ inches (1,435 millimeters). BART gauge is 5 feet 6 inches (1,676 millimeters). Dual gauge refers to tracks with three or four parallel rails that allows trains of two different gauges to share the same track.  

The Link21 Program is in the early stages of defining what a more unified rail network will look like for the Megaregion. The Program will consider a variety of options, including the use of BART-gauge and standard gauge tracks as well as 2-track and 4-track versions. 

Travel Mode

Shouldn’t we be looking to improve the existing BART and Regional Rail systems instead of building something new? Open accordion Close accordion

Link21 will make key investments that leverage the existing rail network, increase capacity, and system reliability. One of the key benefits of Link21 is the positive impact it will have on existing systems. Link21 will build on the continued investment in the existing rail network.

New infrastructure is also necessary to better connect the 21 counties. Improvements are needed at the core of the system (the transbay corridor) to be able to support better service systemwide.

What services will use Link21? Open accordion Close accordion

At this early stage of development, we are studying options that could allow BART and multiple Regional Rail operators (including commuter, intercity, and high-speed rail) to take advantage of the improvements from Link21, including a new transbay rail crossing.

Who decided that Link21 should be a BART and Regional Rail program? Open accordion Close accordion

Link21 is a program supported by the public and backed by data. When voters approved BART’s Measure RR bond and Metropolitan Transportation Commission's Regional Measure 3, they mandated that funds support the development of a second transbay crossing.  

BART's Measure RR and Regional Measure 3 were both developed with extensive community and regional planning input. 

Public outreach from recent efforts like MTC’s Plan Bay Area 2050, the Bay Crossings Study, Horizons, Core Capacity Transit Study, and San Francisco’s ConnectSF have also shown the public's desire for transformative investments in BART and Regional Rail (including commuter, intercity, and high-speed rail), particularly through the transbay corridor.

Why aren’t you considering light rail? Open accordion Close accordion

Light rail is a great solution to transportation challenges in more local settings. However, at a megaregional scale, options like BART and Regional Rail (including commuter, intercity, and high-speed rail) provide capacity and speed that better meet the needs of long-distance riders.

Link21 will look at all rail systems within the Megaregion as part of an integrated network.

Why aren’t you looking at options for cars? Open accordion Close accordion

It is clear that traffic on the Bay Bridge is worsening. However, transportation planners have long known that we can't build more and more highways to solve our congestion issues.  

MTC’s Crossings: Transformative Investments for an Uncertain Future study demonstrates that the most cost-effective and sustainable way to address transbay congestion is through new BART and Regional Rail infrastructure (including commuter, intercity, and high-speed rail).

Wouldn’t improving bus and ferry service, especially through the transbay corridor, be a less expensive and quicker solution to our transportation challenges? Open accordion Close accordion

Buses and ferries are essential transportation options. Important improvements to bus and ferry systems are planned and underway. Link21 will compliment these efforts. Major investment in BART and Regional Rail (including commuter, intercity, and high-speed rail) is also necessary to help address our transportation challenges in the long term.

BART and Regional Rail have the ability to move larger numbers of people more quickly and serve longer-distance trips than buses and ferries. 

MTC’s Core Capacity Transit Study considered bus and ferry improvements. In the study, MTC noted that, while buses and ferries do provide modest increases in transbay capacity, they do not provide the capacity needed to meet long-term demand. MTC’s Crossings: Transformative Investments for an Uncertain Future study also concluded BART and Regional Rail are the most effective long-term solutions.  


Does Link21 offer any benefits beyond transportation? Open accordion Close accordion

Due to its size and geographic reach, Link21 has the potential to bring many positive changes to the Northern California Megaregion. Benefits outside of transportation include reducing greenhouse gas emissions, helping to address housing issues, and encouraging the spread of economic and social prosperity through all 21 counties.

Because BART and Capitol Corridor are transit agencies, they are working closely with partners in state, regional, and local government organizations to make sure these benefits can be realized.

Does this mean BART is going down Geary Boulevard? Open accordion Close accordion

No alternatives or alignments have been chosen yet. Link21 will look comprehensively at the full 21-county Northern California Megaregion. This could include studying possibilities to bring BART to the western parts of San Francisco.

What will Link21 do to make it easier for me to travel by train? Open accordion Close accordion

Link21 will provide a variety of benefits to people moving throughout the Northern California Megaregion. Possible benefits include:

  • Faster travel times
  • Fewer transfers
  • Reduced crowding
  • Longer service hours
  • More frequent service

A new transbay rail crossing for Regional Rail (including commuter, intercity, and high-speed rail) could also provide direct service by train to more parts of the Megaregion.

What would the future look like without Link21? Open accordion Close accordion

Studies indicate that the Northern California Megaregion's population is expected to grow by nearly 3.5 million people over the next 30 years. Without transformative investment into our transportation system, the mobility issues we face today will only worsen. 

In the Core Capacity Transit Study, MTC estimates that by 2040, travel demand in the transbay corridor could be nearly double what current capacity allows. To provide mobility options that work for all — without impacting our ability to meet greenhouse gas and pollution reduction goals — we need major investment in BART and Regional Rail (including commuter, intercity, and high-speed rail).

Who will build Link21? Open accordion Close accordion

Link21 is still years away from construction and the issue of who will build any part of the Program or its individual projects is yet to be determined. The Link21 Program will create many high-quality construction jobs for residents of the Northern California Megaregion.

Will I be able to afford the ride? Open accordion Close accordion

Link21 does not want fares to be a barrier to riders using the rail system; however, any changes to transit fares will require a collaborative effort among the different operators in the Megaregion.

Will Link21 only benefit people who commute to San Francisco and Silicon Valley? Open accordion Close accordion

Link21 will provide benefits to people taking all types of trips throughout the Northern California Megaregion, including train trips that were not practical or feasible before. 

The improvements advanced by the Link21 Program will connect populations and key markets that are not currently connected. The improvements will make it easier to travel throughout the 21-county Megaregion for school, work, play, and all other types of journeys. As the project alternatives are developed, we will articulate the benefits of each so that they can be compared. 

Will this create 24-hour BART and Regional Rail service? Open accordion Close accordion

A major benefit from Link21 may be the ability to provide extended hours on BART and Regional Rail (including commuter, intercity, and high-speed rail). The Link21 Team is currently evaluating what improvements are needed to allow for extended service hours, especially on BART.

Will you be doing work in all 21 counties? Open accordion Close accordion

BART and Capitol Corridor are conducting a detailed market analysis for the entire Northern California Megaregion to determine where the program will yield benefits. Although there may not be shovels in the ground in every county, Link21 is intended to improve rail access to most, if not all, 21 counties. 

Furthermore, work in any area will have a ripple effect across the Megaregion, generating $145 billion in economic benefits and enabling future passenger rail improvements.


How are we going to pay for it? Open accordion Close accordion

BART’s voter-approved Measure RR has provided funding to begin the study and development of Link21. The Measure RR funding is augmented by funds from the California State Transportation Agency. The Link21 Team is working to identify additional funding sources to carry the project into future phases.

How much is this going to cost? Open accordion Close accordion

Link21 is still in the early phases of planning. Preliminary costs estimates have not yet been developed.  

However, Link21, listed as "New Transbay Rail Crossing," in the Metropolitan Transportation Commission's regional transportation plan, Plan Bay Area 2050, is listed at $29 billion (2040 dollars). This amount is subject to change as the development of program alternatives allows for a more detailed estimate.


How are you considering equity? Open accordion Close accordion

Equity is an essential consideration in the development of all major transportation programs such as Link21. Link21 will seize the opportunity to address many of the Northern California Megaregion’s challenges in access to jobs, housing, education, health, and safety.

Equity is a core component of our evaluation framework in determining how each alternative will maximize benefits to the public, particularly to historically disadvantaged communities. 

Work is currently underway to learn from the public, cities, and other agencies on how to build an inclusive equity platform to define and measure, listen and learn, focus and deliver, and train and grow.

How will the Program impact land use? Will it lead to displacement? Open accordion Close accordion

A program of this magnitude can be a catalyst for transformative land use policy changes, creating an opportunity for our cities, counties, and state to address the biggest problems facing the Northern California Megaregion.

By working with local jurisdictions early on, we will begin planning, designing, and creating vibrant, equitable, and transit-oriented communities in those areas around Link21 improvements. We will also seek to avoid negative impacts on local communities.  

If you’re taking equity seriously, why isn’t it one of the four goals in the Link21 Goals and Objectives? Open accordion Close accordion

Equity is a central and core principle of Link21, which will integrate equity goals and concepts throughout the Program.  

The Link21 Team felt that having a separate equity goal could "silo" it and therefore diminish the importance of including equity as a fundamental and integral part of the entire Program. 

The Link21 goals and objectives will be evaluated using quantitative metrics that consider equity, allowing a thorough consideration of equity through all analyses.

Program Development

How are you considering sea level rise? For some projects, won’t the existing railroad tracks be flooded? Open accordion Close accordion

BART, Capitol Corridor and other transit partners are looking critically at the impact of environmental changes like sea level rise on their systems. 

Resiliency to the effects of extreme weather and sea level rise is one of the Link21 objectives. Link21 will consider sea level rise projections when recommending improvements that improve the passenger rail system.

How are you deciding what alternatives will be environmentally reviewed? Open accordion Close accordion

We are using a Business Case process to develop and evaluate a shortlist of alternatives that maximize public benefits, economic benefits, financial viability, and deliverability.

One or more preferred alternatives may be carried into the CEQA/NEPA environmental process that will culminate in environmental review of a final preferred alternative. Extensive public outreach will be conducted during the Business Case and environmental review to ensure that people have ample opportunity to provide input. 

How does a Business Case work? Open accordion Close accordion

Link21 is using a Business Case process to help screen and evaluate program and project alternatives to ensure that only the most beneficial and feasible possibilities are brought to environmental review.

Performing this more in-depth screening up front will help limit the number of alternatives that go through the detailed analysis required for environmental review, which saves taxpayers money. In addition, it builds in public input right from the start.  

Link21 is a megaregional program, but only two agencies are leading it. How are other agencies and cities involved? Open accordion Close accordion

Our partners from transit, funding, regulatory, city, and county agencies are valued stakeholders as we develop Link21. We meet regularly with an expanding group of partners to get their input on Link21. 

As the Link21 Program evolves and specific projects are defined, other agencies may take on additional responsibilities in the development and delivery of this transformational rail program.

The Northern California Megaregion is a large area. How are you identifying program alternatives for Link21? Open accordion Close accordion

The initial list of program alternatives will be developed with information from three sources: existing studies, the Link21 Market Analysis, and public input. 

What role does the public play in shaping Link21? Open accordion Close accordion

Public input is essential to Link21. We look forward to receiving your input on the direction of the Link21 Program. 

The Link21 Team is following state and local health mandates related to the COVID-19 pandemic. We hope to be able to get out and meet you face-to-face. In the meantime, keep an eye on this website and social media channels for opportunities to weigh in and get involved. You can also use our comment form or leave a voicemail at 855-905-Link (5465).

When can the public weigh in? Open accordion Close accordion

Intensive public outreach will begin in 2021 and will continue through all phases of Link21. Please sign up to stay informed for more information here on the website.

Why does the planning and development process take so long to finish? Could the Program be implemented sooner than 2040? Open accordion Close accordion

Link21 is a generational investment that will provide benefits far into the future. Taking time up front to consider the options and address potential challenges is prudent and important.

There are many planning and engineering challenges inherent in implementing such a large program, requiring full consideration of how projects might affect communities, cities, the business community, and the environment.

Although it will take a long time, careful work in planning, environmental analysis, design, and construction will ensure that Link21 meets the needs of the Northern California Megaregion's residents.

Link21 will be considering innovative delivery methods, alternative financing mechanisms, and phasing. These ideas will emerge as the Program progresses.

Impact of COVID-19

How can you do a market analysis when COVID-19 has altered travel behavior so significantly? Open accordion Close accordion

The Link21 Market Analysis is based on prepandemic data that reflects "normal" conditions. We plan to address the potential long-term impact of COVID-19 on travel patterns by modeling future scenarios with different assumptions for population, jobs, telecommuting, and travel growth. 

Is Link21 still necessary, when many more people are working remotely? Open accordion Close accordion

The pandemic has caused dramatic changes to travel patterns in Northern California. At this point, we cannot predict whether the changes will be temporary or permanent.

Regardless, BART and Capitol Corridor are moving forward with early-stage analyses for Link21. The Link21 Team is looking at a range of possible postpandemic travel patterns, including the possibility that more people will be working from home.

Early data also shows that, since the pandemic became apparent in March 2020, more people are moving to less expensive parts of the Northern California Megaregion. As population spreads more evenly across the 21 counties, it becomes more important for people to have fast, convenient, and environmentally friendly ways to see family and friends, visit cultural and recreational centers, and access health care, jobs, and education.

The decision to construct Link21 project(s) will not be made for several years. This gives BART and Capitol Corridor time to continue to understand travel patterns and the need for Link21.

Even in the face of the pandemic, MTC considers Link21 an important program for the Bay Area. MTC adopted a Final Blueprint for Plan Bay Area 2050 on September 23, 2020 that includes Link21.

Shouldn’t we be focused on current challenges caused by COVID-19, including operating budgets for transit? Open accordion Close accordion

BART and Capitol Corridor are both working daily to address the challenges of COVID-19. At the same time, BART and Capitol Corridor understand that they must also continue to plan for the future. The public agrees.  

In a June 2020 survey of residents across the Northern California Megaregion, 79% of voters said that even as we deal with the impact of the COVID-19 pandemic, we still need to develop plans to help fix our Megaregion’s long-term challenges with traffic and transportation. This result held in each area of the Megaregion and across demographic splits. 

The Megaregion's many transit operators are facing severe financial difficulties in sustaining short-term operations. The funds that support Link21 are dedicated for use on capital projects and cannot be used to fund operations. 

Therefore, planning work on Link21 can move forward without impacting the operating budgets of our region’s transit operators.