Keep it Simple with Midge's Delight: Part 2 Analyzing the Transbay Alignments

Last week we looked at the Lindsay Boxer Discovery option, with its distinctive BART line up Fifth St past many new developments. Today we look at the simplest option for San Francisco in our series on Transbay Alignment choices.

Here we have the shortest BART alignment possible, while the Caltrain/HSR DTX line follows the already environmentally approved path up Townsend and 2nd Street. The only "flourish" is calling for a 4-bore tunnel. The four tracks would include two BART tracks plus two Caltrain/HSR tracks east between Howard and Mission Streets out of the Transbay Transit Center.

The simplicity? This option would include the fewest new downtown BART stations (2 instead of 3 or 4); build the shortest BART tunnel (only 0.8 miles to Market St unlike Lindsay Boxer's 1.5 miles). Yet Midge's Delight gets folks to the Financial District directly, and a to Mission Bay directly via Caltrain or with a single transfer if from BART.
The two new towers rising in the Transbay District: Salesforce Tower and 181 Fremont as seen from Howard at 1st St. Image: Brian Stokle / Urban Life Signs
As noted before, the options will be names of people. In San Francisco they are names of fictitious characters from stories that took place in San Francisco. Also, the orientation of the map has east at the top, "looking" to Oakland.

  • BART
    • Arrives under the bay at Howard Street in SoMa.
    • Runs under Howard Street to 2nd St.
    • Turns west to go under O'Farrell Street and on to Geary Street to a terminus to be decided later
  • Caltrain/HSR 
    • The Downtown Extension DTX follows the Pennsylvania and 7th Street alignment from Potrero Hill to SoMa
    • Continues under Townsend St, then turning north under 2nd Street to the Transbay Center
    • Continues east out of the Center and on under the bay through a 4-bore 2nd Transbay crossing (2 tracks BART, 2 tracks 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.
    • Optional Geary St Muni Metro could loop around Transbay Transit Center and then turn back southwest along Folsom back to the Mission. (not mapped)
Midge's Delight option. Source: Brian Stokle / Urban Life Signs

Aerial view of SoMa and the Transbay District. Caltrain runs under 2nd St. Muni's T-Third runs under of 4th St. BART comes from East Bay under Howard St. Transfers possible between all three.  Fremont Transbay Station under Howard has easy transfers to the Transbay Center. 4th & Townsend Station within walking distance of AT&T Park, Chase Center Warriors Arena, and Mission Rock development,.
Image: Brian Stokle / Urban Life Signs. Base image: GoogleEarth
  • BART
    • Transbay Transit Center at Howard: The station on Howard between Fremont and First streets provides great access to the quickly developing and densifying Transbay District, while still being within walking distance of much of the Financial District north of Market. In addition a short pedestrian tunnel under Fremont would link to the Transbay Transit Center with its Caltrain, HSR, and bus services. The transfer through the tunnel would take less than a minute.
Looking west on Howard Street at Fremont Street. A BART station here would run between Fremont and First and only be a 1 minute walk to the Transbay Transit Center in a pedestrian tunnel. Image: Brian Stokle/Urban Life Signs
    • Union Square Powell Station (under O'Farrell Street) provides access to the Union Square shopping and cultural area in addition to providing transfers between the new BART line to the T-Third Muni Metro in the Central Subway, as well as existing Market Street BART and Muni Metro lines. Transfers from the new station could be made by connecting to the concourse under Stockton St. An optional additional pedestrian tunnel could directly link the two BART lines by going under Powell Street between O'Farrell and Market Street. 
The Union Square area already will have the new T-Third station that connects to the Powell St BART and Muni Metro station. Adding the 2nd Transbay BART station under O'Farrell create a major regional rail hub at this important shopping, culture and tourist neighborhood.  Image: Google Maps / Brian Stokle
  • Caltrain / HSR
    • Fourth and Townsend Station gives access to the same area as the current 4th & King station, with close proximity to AT&T Park, and the planned growth area in the Central SoMa plan. In addition, access to the new Chase Center Warriors Arena would be a short walk away. Transfers to Muni T-Third and the N-Judah would be important.
    • 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, pedestrian tunnels under Beale Street connecting Embarcadero Station and under Fremont Street to the new BART line under Howard would all connect to the Transbay Transit Center for passengers wishing to transfer from Caltrain and HSR to reach points throughout the Bay Area via BART and Muni.
Transbay Transit Center (center bottum) with its white patterned skin. The Salesforce Tower under construction rises center right with its glass exterior not yet complete.  Image: Brian Stokle / Urban Life Signs

The Cons
  • The new BART line does not provide direct access to Mission Bay, which continues to grow with the Mission Rock development, UCSF Mission Bay expansion, and the planned Chase Center Warriors Arena. A transfer from the new line to Caltrain or the Muni T-Third line would be required at:
    • Transbay Center Howard (BART to Caltrain) and then Caltrain to 4th & Townsend station.
    • Union Square Powell (BART to Muni) and then on Muni to Mission Rock or UCSF Mission Bay station.
  • Some of the BART tunnels pass through low lying areas vulnerable to sea level rise of five feet and under. SoMa, east of the Transbay Center where Yerba Buena Cove once existed, is vulnerable to 5 feet of sea level rise. If no mitigations or protections like a sea wall along the Embarcadero are created, the area could experience some flooding in the latter half of the century..
  • The DTX tunnel under Seventh and Townsend streets pass through low lying areas susceptible to sea level rise of 4 to 7 feet. The location of the station at Townsend and 4th would be the primary risky location for sea rise unless its station entrances and ventilation shafts were designed to adapt to higher seas and/or a raised ground level.
  • Parts of the alignment would require going under private property, especially between Howard St and O'Farrell Street. At a distance of 0.3 miles, this would be technically easy for engineering, but possibly complicated from an easement, building and structural point of view. Luckily, the path does not pass under any tall buildings.
  • 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 new BART line provides direct access to the Financial District with the Howard Transbay Station. With a station inside the neighborhood with the greatest concentration of current BART ridership, and where the highest concentration of employment exists, the Midge option means that passenger demand on the first Transbay Tube (TB1) will likely go down. .
  • The BART lines two stations stop at two major transportation hubs:
    • Transbay Transit Center
    • Union Square / Powell St Station
  • The BART line is shorter than other options, and quite straight with only a slight bend, making operations efficient, and making travel times shorter.
  • Muni Metro T-Line can be reached via BART at both Powell/Mission and via Caltrain at the 4th & Townsend station.
SF Planning Dept RAB Study looks at possible Downtown Extension alignments. Via Socketsite
Image: Pelli Clark Pelli

After the Downtown Extension is built, the four-bore crossing with BART and Caltrain could come next with other San Francisco projects added later.

In Summary
This option has a lot to like. It's very easy to read on a map. Connections between rail systems is quite easy, stops where highest demand currently exists, and would require the least amount of tunnels compared to any other options. The main downside of the option is that it provides little to no access to new or prospective development areas like Mission Bay and South SoMa, although Caltrain does offer one station in this area. However, transfers from BART to Caltrain on the 2nd Crossing would be relatively seamless at Howard and Transbay Transit Center. In addition the option provides a Financial District station for the 2nd BART line, which would greatly reduce crowding on the existing line, while also providing the option for all-night train service without forcing many to transfer far. 

Overall qualitative score: 4.0 / 5


  1. Love these posts.

    Throwing out my rough/incomplete/half-baked(?) "idea" of an alignment. Conventional rail from the Richmond Dist. connecting to Caltrain/HSR at DTX and Across the Bay, forming a new wye in SF. Lines could go all directions from the wye.

    The Richmond District Terminus would have a level below ground seamless transfer to GGT and Muni buses. Is fare integration with buses and trains possible/beneficial?

    In the East Bay, the new lines would "interact" with the existing BART to provide "Express" service from the far reaches of the BART system. There could be a level transfers at select BART stations on the Fremont line (where it roughly parallels a little used conventional freight line). Service from the Tri-valley could someday be integrated with an upgraded ACE service. From East Contra Costa, express service could be provided as well, probably using existing freight alignments with significant upgrades and seamless connections at existing BART Stations.

    1. I like the conventional rail from Richmond District to Transbay Center idea and on to Peninsula. I've thought of that too, but not pursued it much.

      Fare integration would be great.

      Do you suggest where the new rail should go in Downtown Oakland, or just that it should follow one of the existing freight rail corridors with a transfer at possible stations like San Leandro, South Hayward and Union Square?

    2. My initial feeling is it should bypass downtown Oakland. Existing BART lines already provide ample service.

      The transfers should be located at stations where they provide optimal transfer points for express service to SF and where there is local destinations/demand. This should be an option for "long" commuters to get a faster trip to SF.

      In addition to the options you mentioned, ideally there would be possibilities for Richmond Line (Solano via Capital Corridor), Antioch Line, and Dublin/Pleasanton (ACE?) riders as well. These present additional challenges.

    3. Remove the 680, run Bart through it, put caltrain where bart is now?

  2. The problem with this route is cutting under the buildings between the Transbay Transit Center and Market St. That's a lot of acquisitions & demolition...

  3. Going under buildings can be more complicated but doesn't necessarily require acquisition and demolition, especially if the tunnel is deeper. The Central Subway goes under 2 Stockton (XXI Forever building) but didn't require demolition or acquisition due to going about 90' deep.

    The Howard to O'Farrell BART tunnel under buildings would have to be about 120' deep to get under DTX (-60'), BART Market St Subway (-65'), and the Central Subway (-90').

    Of course a geologic and engineering analysis would be required for this tunnel or any to ensure it is safe and wouldn't affect any above buildings. Going under shorter buildings would likely not affect the foundations of the 2-6 story buildings on the route, so it should be considered as an option at this early stage.

  4. Nice post. A couple of comments:

    1) The original Transbay Terminal plan called for tail tracks down Main St. with possible extension to a loop track. I guess this turn is too tight for HSR, but I think an alignment that doesn't work for HSR should still be considered if it means not demolishing multiple high-rises. Loop track for Caltrain via Townsend/Embarcadero and/or an extension to the east bay via Pier 32/33 would be possible with this alignment. It's probably the cheapest option for heavy rail.

    2) Have you read the recent draft DEIR for Phase 2 of the BART to San Jose extension? It looks like they are seriously considering a deep single-bore tunnel downtown with 2-level stations built mostly within the tunnels. The thinking is that deep tunnels avoid utilities and the stations don't involve excavating the ROW which is disruptive. Access to the station is provided by excavating in sites adjacent to the ROW, which is easy in San Jose as there are lots of vacant lots. Would be trickier in SF, but choosing this method could have some impact on alignment choices.

    1. 1) Are you suggesting keeping the new Transbay Transit Center as a stub station? or make a loop track for Caltrain only down Main/Embarcadero/Townsend? Sounds like either way you suggest the Townsend tracks lead east to Oakland at Pier 30/32 or thereabouts. Hard to be sure with only text, but that's what it sounds like.

      2) I have not read the DEIR for Phase 2 of BART Silicon Valley. However, I am familiar with the single bore idea that includes station platforms. I believe it was used for a regional rail line through the center of Madrid built 5-15 years ago. I support this idea if it keeps costs down and still provides great service.

    2. Sorry for the slow reply.

      1) Two platforms (4 tracks) of the TBT would remain a stub terminal for HSR with access via 2nd St DTX alignment. I'm thinking that one platform (2 tracks) of the Transbay terminal would become a through station for Caltrain, with 2 tracks down Main St. to Pier 30-32 where there would be a Wye to either return to 4th/King along Embarcadero/Townsend. or go to the East bay via a new tube. Maybe it's also possible to extend up Main St. under Market to Drumm St. and have another platform there dedicated to East bay service. Could even be BART if a joint BART/Caltrain tunnel up Main st, is possible.

      2) If San Jose is successful in choosing this approach, I could see it being very attractive in SF as there is a lot less surface disruption. However, the need to excavate adjacent the ROW means station locations need to have open/underutilized lots nearby, which would be tricky in some places.

    3. Fascinating ideas about doing ONLY Caltrain down Main from the Transbay Center and possibly on to Oakland (or just looping back). I'd love to get HSR to Oakland, but maybe the cost and politics of taking towers down is too high. (I always thought that if they were taken down, the owners would get to build back new taller towers.)

      I have thought of BART (and Caltrain) coming into San Francisco via Pier 30/32. A BART line up Main and/or Beale is possible. If it were Main, a BART line could turn west down California, while a Beale line could turn west down Pine. Going north on Drumm or Davis is possible, but where would the line go?

      Great ideas. Any chance of mapping them?


  5. Is it ever going to be feasible to extend Caltrain beyond Transbay? My understanding is that demolishing all the buildings in front of Transbay Transbay terminal as this alignment requires, or doing a loop (described in many of these plans: will be expensive as heck. The former moreso than the latter. I'm also curious why none of the City's proposals for a rail alignment beyond Transbay all use a loop unlike the one in this post.

  6. I like this alignment. I've thought about a similar one for BART that would have stations at Transbay and Van Ness like this one, but instead of Powell would stop at Montgomery and a Union Square station on Geary. This would provide better access to the Financial District and a connection to a Geary subway. The only downside would mean no direct connection to the Central Subway, though there could be a pedestrian corridor between the Union Square station and the Central Subway station.

  7. Can you analyze an alignment via 3rd St, with stops at AT&T Park, Transbay/Montgomery/Yerba Buena-Moscone and Powell/Union Square?

    1. Funny you ask. I'm working on a 3rd St alignment post right now. It will have a bit of a twist to it, but cover much of what you list. Stay tuned.

    2. Great. Thanks. It's definitely my preferred alignment.
      PS. I particularly like your 4th/King to N-Judah MUNI LRT line. It's something I've been wanting for a while, but I haven't seen it online unitl here.

  8. As far as the Oakland side of a Transbay tunnel goes, what do people think about the following alignment? It would give all travelers a direct train to central Oakland, and the simplified network would maximize frequency and minimize delays.

    1. I really like it, under the assumption that a conventional rail station isn't built in the 680 ROW, in which case it would need to connect with that.


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