Transbay Joint Powers Authority / Will Truettner via Unsplash
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Senior Staff Writer
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February 23, 2026
San Francisco’s Salesforce Transit Center has a busy bus deck and a stunningly futuristic rooftop park, earning an evocative nickname as the “Grand Central of the West.”
But below the surface lies an empty, two-story rail station waiting to be connected to Caltrain and the future California High-Speed Rail line.
That missing link is a new 1.3-mile tunnel project called The Portal, an enormous underground effort that will take place out of sight beneath our feet.
Here’s a closer look…
Engel Ching / Shutterstock
A hidden station waiting for trains
The six-level Salesforce Transit Center building opened in Downtown San Francisco in 2018, living up to its ambitious rendering with a verdant rooftop garden and sleek interiors. And while its upper bus deck and ground-level plaza are already serving AC Transit, Greyhound, Muni, and Amtrak Thruway buses, there’s more to look forward to over the next, well… several decades.
The transit center is planned as the northern terminus for California’s long-awaited bullet train to Southern California, A.K.A. California High-Speed Rail (CAHSR), which will share infrastructure with Caltrain.
While the two-story “train box” is already built, it’s still missing a tunnel to connect it to the future rail line. The Downtown Rail Extension, now called The Portal, is a 1.3-mile tunnel that will link Caltrain’s current terminal at 4th & King to Salesforce Transit Center. This will ultimately create a connection to 11 transit systems from the Bay Area and Southern California.
The project already has federal environmental clearance and is in the process of advancing design and funding agreements. According to a project schedule on the Transbay Joint Powers Authority (TJPA) website, tunnel construction will begin in 2028-29, and the tunnel should be ready for service in 2035.
Courtesy of California High Speed Rail Authority
What’s going on with California’s bullet train?
Once The Portal is constructed, it will carry Caltrain — and later California High‑Speed Rail (CAHSR) trains — straight into the underground station beneath Salesforce Transit Center.
We’re nearing a major milestone in the CAHSR project, as 2026 is the year when work will finally transition from civil construction to high-speed track laying. The past 11 years of construction have been focused across 119 miles of the 171-mile Initial Operating Segment (IOS) in the Central Valley, which connects the Merced and Bakersfield extensions. You can read our article to learn more about the next steps for this section, projected to open in 2032.
Due to current funding and planning restrictions, there’s still no firm projected opening date for the San Francisco-to-Los Angeles route, which would cover the distance between the two cities in 2 hours and 40 minutes.
🌐 Learn more: California High-Speed Rail Authority