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About Link21

Link21 and its Partners Will Connect Northern California 

Together with partner agencies, Link21 aims to better connect the BART and Regional Rail (including commuter, intercity, and high-speed rail) train system in Northern California, as envisioned by the California State Rail Plan. The Program will include projects that help to improve train travel for people living and working in the 21-county Northern California Megaregion. 

A critical step in enhancing train service and better connecting the train system is the construction of a second underground train crossing of the San Francisco Bay. This crossing along with other projects will improve service reliability and provide riders easier access to destinations in Northern California that includes the greater San Francisco Bay Area, the Sacramento area, the Monterey Bay area, and the Northern San Joaquin Valley. 

Link21 will result in a more connected, equitable, and accessible train system by shortening travel times, improving transfers between BART and Regional Rail services, improving or adding stations to service new markets, and increasing service frequency, making train travel a more viable transportation alternative. A better train system will improve the quality of life for residents and visitors alike by growing ridership on zero-emission trains and taking automobiles off the congested roadways. Link21 will enable train service that will be:


Fast Train

RELIABLE: Depend on trains to get you where you need to go.


FREQUENT: Wait less and have more travel options.

Mesh Network

CONNECTED: Enjoy quick and easy train access to home, jobs, airports, healthcare, school, sports, and entertainment.

Cloud Blowing

GOOD FOR THE ENVIRONMENT: Help improve air quality by using zero-emission vehicles and providing alternatives to driving, which lowers greenhouse gas emissions.

Increasing Bar Chart

GOOD FOR THE ECONOMY: Benefit from a $145 billion economic boost to the Megaregion and creation of 377,000 jobs generated by the Program (2021 estimate).


EQUITABLE: Have more passenger rail options with better access to quality jobs and affordable housing.

Link21 is sponsored by BART and Capitol Corridor with support from the California State Transportation Agency (CalSTA) and other partners. Identification of train system enhancements and target projects to better integrate Northern California's train service involves close collaboration amongst many agency partners.

At The Core of Link21 – New Train Crossing Between Oakland and San Francisco 

For decades, transportation leaders have recognized the need for a new train crossing between Oakland and San Francisco. The State Rail Plan and the Metropolitan Transportation Commission’s (MTC) 2019 Horizon initiative include a new crossing in its vision for a more connected passenger rail network in Northern California.1, 2 
The existing transbay corridor includes BART, the San Francisco-Oakland Bay Bridge, buses, and ferry service and is one of the most congested transit routes in the United States. What could be a 15-minute journey can easily turn into an hour or more due to traffic or transit disruptions. 
Adding a second train crossing along with other improvements to both BART and Regional rail service will create service redundancy, reliability, and offer more travel options to move by train easily between destinations locally, throughout the region and Northern California Megaregion. 
Watch experts talk about the benefits of Link21 or read a report on how the new crossing will be a game changer for Northern California.

1California Department of Transportation (Caltrans), California State Rail Plan, 2018

2MTC, Horizon, 2019

A timeline beginning in 2007 shows the various state and regional plans that have identified the corridor and crossing as a key investment for the future.

The New Transbay Rail Crossing is critically important for the future of the Northern California Megaregion. It will literally transform the entire megaregional transportation network. I try not to use the phrase ‘game-changer,’ but that’s exactly what it is. A game-changer.

- Secretary David Kim, CalSTA in the webinar Bay Area Impact: The Megaregional Case for a New Transbay Rail Crossing


Why Link21 and Why Now?

Northern California's population is projected to reach 13.7 million by 2050. Travel demands across the Megaregion are expected to increase sharply in the coming decades. Without improving our public transportation system, traffic congestion and overcrowding will worsen, pollution will reduce air quality, transit will be strained, and economic stagnancy will diminish our quality of life.

Transit Agencies across the Megaregion are working to recover ridership and address new travel needs in this post pandemic time. While looking at near term solutions, agencies must also plan for a better future. Programs like Link21 are critical to our recovery, and meeting state and regional air quality requirements. Although infrastructure improvements may occur near the Bay Area, the improved service and connections that they allow benefit residents across the Megaregion. Link21 will facilitate new connections and open more possibilities for business and leisure travelers across Northern California.