BART mulls second Transbay Tube

Bay Area Rapid Transit (BART) has begun early planning for a potential second Transbay Tube connecting San Francisco and Oakland, California.

BART's board last week heard a presentation outlining plans for a second rail connection between the cities. It's still too soon to say whether the new structure will  be an underwater tunnel like the existing Transbay Tube or some other kind of rail crossing, BART officials noted in a news release.

The companion structure could include both standard-gauge tracks and BART's wider ones. Including the standard-gauge track would present some "important opportunities," agency officials said. For instance, it could allow for connections with any standard-gauge rail operator in the area, such as Caltrain or the Capitol Corridor Amtrak line.

Those connections would provide a way to link the San Francisco region with one-seat rides between the peninsula, Silicon Valley, the East Bay and Sacramento, BART officials said.

BART aims to use a feasibility study to narrow multiple alternatives for the second crossing to a list of two to four options. Next steps would include awarding a contract for the study in mid-2019, BART officials said.

Construction on the second crossing may not begin for another 10 years, although BART officials said "there's little time to waste."

"Despite BART's plan to increase capacity through the existing Transbay Tube, planners project demand for Transbay transit will outpace capacity by 2040 in medium or high demand growth scenarios," agency officials said.

BART's board presentation, which was released online, contained no cost estimates for the new structure.