BART passengers could someday see a second route across the San Francisco Bay, with a parallel but totally new alignment and crossing points on the either side of the bay.

"BART officials are starting to study a second Transbay Tube," reports Michael Cabanatuan. That news follows "years of supposition and pie-in-the-sky conjecture from planners and passengers alike," according to Cabanatuan, but now the real planning can finally begin.
"Much of the talk about a new rail tunnel has centered on its location, or alignment, including where the BART lines would head once they emerge from the tube, and how they could connect with jobs and housing," according to Cabanatuan. The project could eventually cost $12 billion to $15 billion, and the possibilities for crossings and alignment are still wildly speculative, but lots of fun for fans of BART and The Bay Area, or public transit and metropolitan areas more generally.
As for the expected cost just to study the idea, "BART plans to pay for a variety of studies and some early engineering with some of the $200 million set aside in Measure RR, its $3.5 billion system modernization bond. Regional Measure 3, the Bay Area toll increase proposal on the June ballot, would set aside $50 million to further study the new tube, and Caltrans and the state Transportation Agency have said study money should be available as well, reports Cabanatuan.
Oddly enough, there's been renewed talk of a second Bay Bridge span in recent weeks—mostly speculative talk originating from the office of U.S. Senator Diane Feinstein that stands in obvious juxtaposition of the BART plan.
The source article includes a lot more detail about the various regional organizations and powers that will partner on the planning process and could eventually sway the final alignment of the second Transbay Tube.
FULL STORY: BART gets serious about a 2nd East Bay-S.F. Transbay Tube

Alabama: Trump Terminates Settlements for Black Communities Harmed By Raw Sewage
Trump deemed the landmark civil rights agreement “illegal DEI and environmental justice policy.”

Study: Maui’s Plan to Convert Vacation Rentals to Long-Term Housing Could Cause Nearly $1 Billion Economic Loss
The plan would reduce visitor accommodation by 25% resulting in 1,900 jobs lost.

Planetizen Federal Action Tracker
A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

Wind Energy on the Rise Despite Federal Policy Reversal
The Trump administration is revoking federal support for renewable energy, but demand for new projects continues unabated.

Passengers Flock to Caltrain After Electrification
The new electric trains are running faster and more reliably, leading to strong ridership growth on the Bay Area rail system.

Texas Churches Rally Behind ‘Yes in God’s Back Yard’ Legislation
Religious leaders want the state to reduce zoning regulations to streamline leasing church-owned land to housing developers.
Urban Design for Planners 1: Software Tools
This six-course series explores essential urban design concepts using open source software and equips planners with the tools they need to participate fully in the urban design process.
Planning for Universal Design
Learn the tools for implementing Universal Design in planning regulations.
Caltrans
Smith Gee Studio
Institute for Housing and Urban Development Studies (IHS)
City of Grandview
Harvard GSD Executive Education
Toledo-Lucas County Plan Commissions
Salt Lake City
NYU Wagner Graduate School of Public Service