Oh Tube, Oh Second Tube

...take me north on a numbered street to GearyLand.

Folks heavily preferred 2nd Street and 3rd Street in this year's poll on Transbay Tube alignments. At least that's what the poll results of the Second 2nd Transbay Tube Alignment through SoMa Poll find. Nine months ago, I polled several 2nd Tube alignments when the Townsend and Folsom alignments virtually tied for first place. For this year's poll, "East-West" alignments (Folsom and Townsend) duked it out with the new upstart "North-South" alignments (3rd St and 2nd St). A bonus choice for Pier 70 and Potrero Hill was given modest attention.

Possible Mission Bay/Third St station location for a 2nd St/Post alignment. Image: Google StreetView
On the face of it, the 3rd St - Union Square alignment won the poll with 30% (14 votes) of the 47 responses. However, with 27% (13 votes), the 2nd St - Post Mission Rock alignment was virtually tied with 3rd St - Union Square. Potrero Pier 70 - Van Ness came in third place with 17% (8 votes), while Folsom - Powell, and Townsend - Division tied for last with 13% each (6 votes each).

With 47 total votes, the poll was a success. However, this year's poll (2015) only received about half as many votes as the 2014 poll, which received 93 votes. Does that mean anything significant? Probably only that I promoted the 2014 poll much more than the 2015 poll. The bigger the outreach, the more feedback. Lesson learned.

Analyzing the 2015 poll data more, we find some interesting elements. If we combine the votes for the north-south alignments (2nd St & 3rd St), and we separately combine the east-west alignments (Folsom and Townsend), we find that 2nd & 3rd St overwhelmingly won the poll by earning a combined 57% of the votes, while Folsom and Townsend only combine for 26% of the votes.

Unfortunately I didn't poll the 2nd or 3rd St alignments in the 2014 poll so we don't have any direct comparisons to make. The major changes between the polls are that the new Warriors Arena is coming to Mission Bay, the Giants won a third World Series, and a lot more residential and office towers have been built or are under construction in SoMa and Mission Bay. Possibly the most important element is the high crowding on BART and that BART has started discussing the idea of a second transbay tube. Maybe this all adds up to supporting the 3rd and 2nd St alignments. Or maybe it's just the persuasively vague map BART produced on the topic.

Using the same analysis summary from last time we get the following summaries for 2015 and 2014:


2014What's striking is the change in preference away from Folsom and Townsend to 2nd and 3rd streets.Let's look at the pros and cons of each alignment again based on criteria laid out in the initial 2014 poll and some newer criteria. I have used a point system ranging from -1 to +2 to demonstrate how each alignment succeeds or fails in each criteria.
+2 = strongly achieves criteria+1 = achieves criteria0 = only partially achieves criteria-1 = fails to achieve criteria

The scoring analysis shows clearly why the 2nd St - Mission Rock alignment is so popular and would meet most of the needs in a new Transbay Tube. With the 2nd Street - Post Mission Rock alignment passing through southern Mission Bay via Mission Rock past the new arena, near the Giants Ballpark in South Beach, and on past the Transbay Terminal Transit Center, the Financial District and on to the Tenderloin, this alignment is hard not to like. To make the difference between 2nd Street and 3rd Street alignments more clear, I'll be calling the 2nd St alignment the "2nd St - Mission Rock" alignment from now on. The 3rd St - Union Sq is virtually the same except it doesn't pass Mission Rock and does not allow for a direct transfer to the Transbay Center. And that is why 2nd St-Mission Rock scores a 10 instead of a seven. There are a few drawbacks. The route is longer and has more stations, which would cost more. In addition, it is a little bit less straight and requires a southern approach from the East Bay. A four-bore 2nd Transbay Tube would likely not work with this scenario.As I've mentioned before, any planning for the 2nd Transbay Tube should be planned in concert with the Caltrain DTX tunnel, and connecting the Transbay Center (HSR, Caltrain, etc.) with the East Bay. This could mean there is a single 4-bore tunnel or two separate 2-bore tunnels. In the end a cost/benefit analysis is necessary to examine each alignment for costs, benefits, station locations, time to build, and many other factors.Now if we could just find a way to finance the construction of this. Anybody know where $12 billion can be found?


  1. Of course, how you set up your scoring system has a big impact on how the final scores stack up. I have a couple questions on that front.
    "Service to new areas": You only use scores 1 & 2, ignoring scores -1 and 0. I suggest you grade harder on this scale, and more fully use the score range. This is measure that should take into account distance from existing lines, and length of that line in new areas. By this measure, Townsend-Division, Pier 70-Van Ness, and 16th-7th should far outrank the other choices, which align very closely to existing lines in the financial district. My rankings would be: Folsom -1; 3rd 0; 2nd 1; Townsend 2; 16th 2; and Potrero 3. (If the argument against higher scores for these routes is poor connectivity, that's what the "Interconnections" category is for.
    "Interconnections" and "High job growth" should similarly have a wider range of scores.
    "Line Redundancy": What's this? Isn't this captured by "Allows for Transbay1 Closure?
    "Allows for Transbay1 Closure" category: It's a binary choice, so seems odd to have -1 and +2 as scores. Did you set it up as a 3-point swing because this criteria is so critical to the design?

    Thanks for the analysis - very interesting stuff. I wonder how the scores would stack up with fine-tuning the grading system.

    1. Scoring systems are not perfect. You raise some good points. I will clarify the scoring at some point... which could adjust some of the scores. The one other big element not included in the scoring is cost. I don't have enough knowledge to address costs. However I do know that the more stations you have the much greater your cost - often much more than the distance of your tunnels (or els if we ever look at that).

      Just to review, under your scoring it appears you would adjust the final scores to:

      Folsom: 4
      Townsend: 4
      16th/7th St: 3
      Third: 6
      Second: 9
      Potrero Pier 70: 2

      Second street still scores the highest.

      Fine tuning coming.

  2. No more BART. Build a normal electric and high-speed rail tunnel. Tailor it to go to under-served towns that already have rail rights-of-way. Make it fast, quiet, and electric. Make BART transfer stations, in fact, it could be part of the BART-branded system, but it would cost a small percentage of what it costs to build BART and BART trains.

  3. Please add a 24 Hour Bart alignment to your next survey:

    1. Run 2nd tube along the 1st
    2. Convert Muni Underground to Bart from 2nd tube to West Portal
    3. Drill two tracks from 2nd tube to MacArthur

    Results: You would have 4 tracks between Civic and Macarthur, allowing a main artery to run 24 Hour Bart around early morning track maintenance. You would also get longer Bart trains on the East-West Muni underground.

  4. Brian,

    Very interesting analysis. I've been reading all over the internet and thinking about this issue myself. How important do you think a standard gauge transbay rail connection is? How would it be implemented with the 2nd St - Mission Rock alignment, assuming God forbid we don't build a third tub?.

    1. Standard Gauge,

      Thanks for writing. There are two pieces to your question, although you may have only intended one. I'll cover both in case you were thinking of both.

      1) Subway/BART service Tube vs. Regional Rail/HSR Tube
      Connecting Oakland and SF could should someday include both some sort of subway rail and some sort of regional intercity rail. Some folks have suggested building a four-bore tunnel so as to accommodate two tunnels for BART, and two tunnels for regional rail (e.g. Caltrain) and intercity rail (Amtrak and HSR). The 2nd St - Mission Rock alignment is principally for a subway alignment, not regional rail. It is also not close enough to the Transbay Center, for a four-bore tunnel to make sense, so the 2nd St-Mission Rock alignment would only be for BART, or some time of subway/metro service. It's possible to extend a rail from Transbay to this alignment, but it doesn't seem to make economic or service sense due to going so far south from the Transbay service. That said, it could be a great subway/metro service.

      2) Subway/Metro Service: standard gauge or BART gauge
      A new subway service along a 2nd St-Mission Rock alignment could be operated by BART, a separate agency, or a new agency. The alignment could also be either gauge.
      Standard Gauge:
      Pros: lower capital and operating costs. Standard gauge rail means traincars, equipment, and other supplies can be purchased and a lower cost and "off the shelf" unlike BART gauge which is much more customized due to it's near-unique rail gauge.
      Cons: a standard gauge rail would not be able to interline with existing BART lines in SF or Oakland. Location of rail in East Bay may not reach the large markets a subway would need to reach to make it cost effective, unless a major new route were created in Oakland (in addition to and SF Geary line).

      BART gauge:
      Pro: Allows for interlining service with existing BART rail lines into the new 2nd Transbay Tube. Allows more flexible service, and can have trains diverted if one tube is out of service (accident, repairs, etc.).
      Cons: Costs more

      Wild cards:
      Driverless trains. Could the new route, whether BART or standard gauge be made driverless? Probably. This would significantly reduce operating costs.
      Converting BART gauge to Standard on one route. Could converting, say the Yellow line, to Pittsburg Bay Point, to standard gauge allow for a viable standard gauge service? If the conversion could be made during service by BART gauge trains, then this should be considered and studied.

      The long term cost savings of having driverless trains and a Yellow Line with standard gauge may outweigh the initial capital costs, and construction inconveniences, and prove better than using BART gauge on a new Transbay Tube.


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