Analyzing the Transbay Alignments: Part I Lindsay Boxer in San Francisco

Talk of a 2nd Transbay Rail Crossing has gained a bit of a bump in the last few weeks due to a few new things:
  • BART's announcement that it will reduce service in the Transbay Tube for several months (VERIFY DETAILS) to seismically upgrade the tunnel.
  • The UC Berkeley Transportation Studio presented its findings on where a 2nd Tube, or as they put it, a 3rd Crossing, could go based on some robust analysis.
  • BART trains were either "stuck" in the tube Tuesday, December 20 due to mechanical problems (old system) plus there was a medical emergency that caused delays. Both cascaded delays through entire system.
So I've finally come to a very late annual edition of where a BART and Caltrain tube and tunnel (and maybe bridge) system should go. (Other editions happened in 2013, 2015, 2016) In I'll be looking at where they trains could go, the tradeoffs, the opportunities, the challenges, and the timing. In past installments, I've only looked at San Francisco, but I'll also be looking at Oakland too this time.

Rather than looking at all the alignments all at once (like I've done before I think taking a slower approach will give a chance to better look at each possibility on its own. This time around I'll be also trying a new approach - calling the alignments by unique non-geographic names. Because I'll be showing both BART and Caltrain/HSR and Muni, creating names by major streets would get really long and confusing. 

Rather, the options will be names of people. In San Francisco they'll be the names of fictitious characters from stories that took place in San Francisco. In Oakland it will be something else. I'm thinking it'll be famous East Bay sports figures, but maybe it will be something else.  

I've also oriented the maps a bit differently so as to jog my mind and perspective a bit to be open to new ideas and catch weaknesses I may haven't seen before. In San Francisco the perspective looks eastward with the bay at the top of the image, and Geary running up and down to the bottom of the image.

We begin with San Francisco and the "Lindsay Boxer Discovery". You can learn about the other options here: Midge's Delight (12/30)

  • BART
    • Arrives under the bay at Pier 50 in Mission Bay.
    • Runs under 5th Street.
    • Turns west to go under Geary Street to a terminus to be decided later
  • Caltrain/HSR 
  • Muni
    • Operates largely as today
    • Central Subway extended to North Beach and possibly Fisherman's Wharf
    • Optional extension of N-Judah Mission Bay line further west to Division Street.

Aerial view of Mission Rock Station in Mission Bay. Caltrain runs under 3rd St. Muni's T-Third runs on surface of 3rd St. BART comes from East Bay and turns north under 5th St. Transfers possible between all three.  Mission Rock Station within walking distance of AT&T Park, Chase Center Warriors Arena, UCSF Mission Bay, Mission Rock development,.
Image: Brian Stokle / Urban Life Signs. Base image: GoogleEarth

  • BART
    • Mission Rock: The station at Third and China Basin St provides great access to the growing Mission Bay neighborhood and transfers to Caltrain and the Muni T-Third.
    • Central Soma Brannan 5th provides stops in the center of planned new development in this part of SoMa that is far from current BART access. The Central SoMa Plan will bring 20 story hi-rises of offices here so getting access to more people will be important.
    • Mission Powell Station will be provide access to the Union Square shopping and cultural area in addition to providing transfers between the new BART line and existing Market Street BART and Muni Metro lines plus T-Third (for a second time).
  • Caltrain / HSR
    • Mission Rock station gives access to the same basic area as the current 4th & King station, with close access to AT&T Park, plus very close to the new Chase Center Warriors Arena. In addition, transfers to Muni T-Third and the new BART line are critical.
    • Transbay Transit Center: as planned this station will provide rail access into the heart of Downtown San Francisco providing service to the Peninsula, San Jose, as well as Fresno and eventually Los Angeles with the California High Speed Rail. In addition, a planned pedestrian tunnel under Beale Street will connect Embarcadero Station and the Transbay Transit Center for passengers wishing to transfer to the Caltrain and HSR from BART and Muni under Market Street.
Third and China Basin St where a Mission Rock Caltrain/HSR/BART/Muni Metro station would be placed.
Image: Google Streetview.

Central SoMa area with much future new dense office development planned at places like the Tennis Club, Flower Mart and even possibly the Caltrain railyard.  Image: Google Maps

The Cons
  • The new BART line does not provide direct access to the Financial District where the greatest concentration of current BART ridership exits, and where the highest concentration of employment exists. A transfer from the new line to the old BART line would be required at:
    • Mission Powell (BART to BART) and then to Embarcadero.
    • Mission Powell (BART to Muni) and then to Embarcadero.
    • Mission Rock (BART to Caltrain) and then on to the Transbay Center.
      • Transferring adds to a person's journey time. Transferring is also normally perceived to take longer than it actually does - sometimes reducing the number of people who would take transit.
      • Not reaching the Financial District directly might also mean that vast majority of people going to the Financial District will use the original Transbay Tube (TB1), possibly leading to continued crowding there due to the TB2 arriving to far away.
  • The BART line does not reach the Transbay Transit Center, which will be the primary long distance HSR train station in San Francisco.
  • Much of the BART route passes through low lying areas vulnerable to sea level rise of five feet and under. Mission Bay and SoMa near the Caltrain Railyard are vulnerable to 6 feet of sea level rise, if no mitigations like a sea wall are created.
  • Parts of the alignment would require going under private property, especially between Market St and Geary Street. At a distance of half a mile, this would be technically easy for engineering, but possibly complicated politically.
  • This DTX tunnel under Third Street would be longer than the currently approved tunnel under Townsend and Second. 
  • Much of the DTX route passes through very low lying Mission Bay, which is very vulnerable to sea level rise.
  • Tunneling east of the Transbay Center will require removal of some tall buildings (regardless of alignment chosen - which would be very expensive.
  • Tunneling east would require breaking through the sea wall due to having insufficient distance to clear below the sea wall.
The Pros
  • The BART lines three stations stop at three growing work centers:
    • Mission Bay - with expanded employment at the new Chase Center in addition to UCSF, Mission Rock development and biotech offices.
    • Central SoMa with the planned upzoned buildings near 5th and Brannan.
    • 5M project at Mission and 5th St, which will include much new housing and office space.
    • The DTX tunnel under Third Street would be relatively easy to build thanks to having no utilities to move. 
  • Both the DTX and the BART lines are quite straight and without many turns - making their operations efficient, and making travel times on shorter.
  • Muni Metro T-Line can be reached via BART at both Powell/Mission and at Mission Rock. In addition, other Muni Metro lines are accessed at Powell Station.
  • The New BART line has a transfer point to Caltrain at Mission Rock, while the current TB1 BART lines can transfer to Caltrain at Embarcadero to Transbay Transit Center.
SF Planning Dept RAB Study looks at possible Downtown Extension alignments. Via Socketsite
5M project will increase demand for transit access at 5th & Mission. Image: 5M

With two new crossings, the BART or Caltrain/Crossing could come first with the other crossing added later. Building the DTX would be first followed by a new crossing. Separating crossings could be well intended, but the 3rd crossing might take decades to build, or never be built.

In Summary
This option has a lot to like. It's easy to read on a map. Connections between rail systems is quite easy, and it has stops at many new developing areas where ridership will be high. The main downside of the option is that it provides a less than seamless transfer from BART to the Transbay Center (1000' tunnel under Beale from Embarcadero). However, transfers from BART to Caltrain on the 2nd Crossing would be seamless at Mission Rock. In addition the option does not provide a Financial District station for the 2nd BART line, which could risk not reducing crowding on the existing line. 

With the 3rd Rail Crossing of Caltrain/HSR from Transbay Transit Center, maybe a TB2 Transbay Center station is unnecessary. Of course having TWO new rail crossings that are separate would be significantly more costly than a single new crossing.

Overall qualitative score: 3.0 / 5


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