16 December 2018

Billions of Seconds Wasted

The latest tweaks to the design of the San Francisco Downtown Extension (DTX) rail alignment can be seen in a March 2018 track plan and profile drawing. Because it largely follows the street grid, it's no secret that the alignment is full of sharp curves, which can only be traversed at slow speed. However, compared to a 2012 drawing, speed limits have dropped in several places from 40 mph to just 30 mph, because train speed evidently isn't a design priority when civil engineers get a blank check.

Back in 2012, the speed profile sort of made sense: starting from the basement of the Transbay Transit Center (left end of the diagram) the train would screech at about 20 mph through the sharp curve towards 2nd Street, speeding up to 35 mph along 2nd and through the curve towards Townsend. On that mostly straight bit along Townsend, speeds could pick up to 40 mph before dropping back briefly to 35 mph through the curve to 7th Street, then exiting along 7th Street at 40 mph (right end of diagram). If only one criticism were allowed, it wasn't clear why that final curve should be limited to 35 mph; there was plenty of space at Townsend and 7th to flatten it out to 40 mph, resulting in a simple and efficient stepped speed profile for the approach to Transbay.
Fast forward to 2018, and things are much worse. There is a new kink in the alignment where it connects to the existing tracks. The new underground 4th and Townsend station, at the city's request, has been shoved into the Townsend Street right of way in the hope of freeing up the existing rail terminal parcels for high rise redevelopment (where the 2012 alignment might have clashed with new building foundations). The rigid requirement for a straight island platform has resulted in a series of 30 mph kinks in the track. Elsewhere, the speed limit along Townsend has dropped by 5 mph.
The designers might argue this is only a few seconds lost, so no big deal, right?
How many seconds are wasted?
A train traversing the DTX will have to observe the speed limits not just for the length of each speed restriction, but for the added length of the train itself, as the limit applies from the moment the head end of the train enters a speed restriction until the tail end leaves the speed restriction. High-speed trains will be up to 400 m long, so this can really add up. We can simulate the time needed for a train to travel from a standing start at the end of a Transbay platform to a 40 mph entry into the existing Tunnel 1, a distance of about 2.2 miles. The results depend on the train type, and whether a stop is made at 4th and Townsend:
  • 2012 alignment, single-length HSR: 4:04
  • 2012 alignment, double-length HSR 4:17
  • 2012 alignment, 8-car Caltrain EMU, no stop at Townsend 4:06
  • 2012 alignment, 8-car Caltrain EMU, 30-second stop at Townsend: 5:04
  • 2018 alignment, single-length HSR: 4:25 (+21 sec)
  • 2018 alignment, double-length HSR 4:42 (+25 sec)
  • 2018 alignment, 8-car Caltrain EMU, no stop at Townsend 4:27 (+21 sec)
  • 2018 alignment, 8-car Caltrain EMU, 30-second stop at Townsend 5:19 (+15 sec)
To summarize and simplify, we can assume that every Caltrain will stop at Townsend, so the performance loss is 15 seconds per Caltrain movement, and roughly 20 seconds per HSR movement. That doesn't sound like much, but consider that trains are carrying hundreds of passengers, each of whom are individually delayed. The collective waste of time can be measured by multiplying the train delay by the expected ridership.
Today Caltrain has about 15,000 weekday boardings in SF, a number that Caltrain says could eventually quadruple. Let's say it only triples, and that 35,000 of those weekday boardings occur at Transbay and 10,000 at 4th and Townsend (which we won't count) making for 70,000 trips through the DTX approach. That's 70,000 trips x 15 seconds/trip = a million seconds wasted every weekday, or about 3 person-years of productive labor time per month of DTX operation. Over a year, about a quarter billion seconds would be wasted!
HSR eventually expects 18 million annual trips originating in the Bay Area, of which maybe half might involve Transbay. Combine that with a similar number of HSR trips terminating at SF, and you get 18 million annual HSR trips through the DTX approach. That would be a waste of another third of a billion seconds.
Every year then, about half a billion seconds would be wasted due to careless DTX alignment design.
How do we fix it?
Fixing it involves realizing that
  1. every second matters, a lot
  2. the marginal cost of the next second saved is more expensive than the last
  3. saving seconds is most efficiently and cheaply done in the slow parts of a system
Making up 20 seconds through minor fixes to the DTX track alignment design, before any concrete is poured, is far cheaper and easier and more productive than trying to make up 20 seconds somewhere faster, for example in the Central Valley by running trains at 220 mph instead of 215 mph.
What ought to still be possible is an alignment that starts at 20 mph through the screecher to 2nd Street, rises to 35 mph along 2nd Street, then rises to 40 mph along Townsend continuing without slowing around the curve to 7th Street. With this improved speed profile, train run times from Transbay to Tunnel 1 (relative to the 2018 alignment plans) would be:
  • Single-length HSR: 4:02 (23 seconds faster)
  • Double-length HSR 4:14 (28 seconds faster)
  • 2018 alignment, 8-car Caltrain EMU, no stop at Townsend 4:04 (23 seconds faster)
  • 2018 alignment, 8-car Caltrain EMU, 30-second stop at Townsend 5:02 (17 seconds faster)
The combined annual time savings would exceed half a billion seconds per year. As we watch the cost of the DTX project reach ever more dizzying heights, we should at the very least expect to get more transportation value out of the project. Careless and inexcusable engineering of a rail alignment that wastes so much of everyone's time only adds insult to the injury.


  1. Besides consuming more time, the 2018 plan is consuming more energy.

    And I have my doubts that drivers would do the necessary "nervous" driving.

    Question: do the diagrams with the color codes take into account the train lengths? I could see at least one segment where the 35 mph limit is useless because when the train has cleared one of the 30 mph segments, the next one follows a few seconds later.

    Finally, it can never be repeated too many times: The first fundamental law in motion engineering is that when something is time critical, you MUST keep the slow sections as short as possible. (FWIW, I learnt that law with stacking devices in the glass bottle manufacturing… when your stacker is too slow, up to 50% of your bottles end up on the floor…)

    1. The diagrams do not show train lengths, but the simulation times do account for it. I also assumed perfectly-timed acceleration and braking, which is not likely in practice.

      I love the idea of "motion engineering," which equally applies to the inefficient vertical circulation design of the 4th and Townsend station. These civil engineers think they are providing a fantastic passenger experience by funneling everyone through a useless and cumbersome mezzanine level. In reality they are wasting 30 valuable seconds of every passenger's time each way.

      Don't get me started on the design of that station: the station box and platform are only long enough for an 8-car Caltrain EMU, pouring into concrete a permanent operational constraint on a system that will eventually have to grow to 10 or 12 car trains.

    2. OK, thanks for the clarification.

      I am trying to think of a station in Europe where they have a mezzanine level. Actually, Zürich HB does. However, this level is the main circulator between the various "sub"-stations (there are 3 underground and 1 on-ground "sub"-stations in Zürich HB). And this level is the main shopping/grazing area, only interrupted by the Sihl river crossing the station at mezzanine level.

      I don't think it is the civil engineers who made this mess, but the planners. And I guess those types are brainwashed from airport design and/or from the (to me typical for the US) "stockyard people flow" model.

      Sorry that I always refer to my greater hometown system… tell me to stop doing so… It has shown to become a serious flexibility issue that certain lines of the Zürich S-Bahn are limited to 200 m train length, while the standard is 300 m. The only way to overcome this capacity-limiter is to increase the frequency. …looks to me like a serious lack of long-term planning (probably "thanks" to relying on too many consultants).

      About the motion engineering… well, I was impressed when I first saw the device I was writing the documentation for in use (fabrication of glass bottles), and the idea of half of the bottles ending on the floor instead of the cooling oven. And the principle is soo simple.

  2. Hey Clem, great writeup. 500 million seconds is clearly a ton. But what about analyzing the tradeoffs more fully? You brush off the benefits of the high rise development. That railyard site "could accommodate between 1.05 and 2.43 million square feet of commercial [development] and up to 1.46 million square feet of residential space based on current zoning in the area" per Socketsite.

    How many seconds would be saved every year by having thousands of people living on 4th and Townsend and walking to work instead of using Caltrain? How many millions of dollars of new tax dollars would be generated every year via property and payroll taxes, which could in turn improve infrastructure in other ways? How many meaningful companies or meaningful jobs could develop from 2M square feet of commercial space?

    I'm not involved with the project in any way, simply a local urban planning aficionado. I loved your analysis, but to truly assess the situation requires understanding what you'd be giving up in order to save all of those seconds.

    1. I don't think that fixing the alignment (these are really minor tweaks) will preclude high rises on the old terminal parcels, so this is a case of "and" not "or". I agree that providing housing near jobs is a higher priority than providing more and more mobility.

      What you would probably have to give up to save these precious seconds is the perfectly ramrod straight platform at Townsend. Straight platforms are one of those paint-by-numbers engineering constraints that ultimately result in bad designs. Slightly curved platforms are not the plague!

      Tapering the ends of the Townsend platform just a bit could also enable it to be lengthened to 12 cars from the present inadequate length of 8 cars.

      And lose that mezzanine already! Make an island in the street above the platform, and have all the vertical circulation go straight to the surface.

  3. Think of how many lives those seconds represent! Reminds me of this Steve Jobs story:


  4. Clem writes:

    "because train speed evidently isn't a design priority when civil engineers get a blank check."

    Not that anybody seems to care, Prop 1A reads:

    2704.09. The high-speed train system to be constructed pursuant to this
    chapter shall be designed to achieve the following characteristics:
    (a) Electric trains that are capable of sustained maximum revenue operating
    speeds of no less than 200 miles per hour.
    (b) Maximum nonstop service travel times for each corridor that shall not
    exceed the following:
    (1) San Francisco-Los Angeles Union Station: two hours, 40 minutes.
    (2) Oakland-Los Angeles Union Station: two hours, 40 minutes.
    (3) San Francisco-San Jose: 30 minutes.

    1. .....and 4th and Townsend is San Francisco Morris. Better check your map.

    2. Yes, but Prop. 1A also specified that HSR Phase I is to run from the S.F. Transbay Terminal (now the Transbay Travel Center) to L.A. Union Station. In 2015, the judge handling the HSR litigation - in response to the HSRA arguing that travel times could be measured from 4th & Townsend - ruled that Prop. 1A required travel times to be measured starting at the TBT/TBTC.

    3. The best way to get fast travel times is to speed up the slow bits of the system, as described in this post. Whatever the law or the judge may say.

  5. Try this alignment instead (80 MPH all the way, Ba-By!!!) https://youtu.be/v-QYQJYDTt4?t=4

    - No encroachment on the old railyard
    - No encroachment on Townsend
    - No vent shafts every 400 feet
    - Bye-bye 20 MPH $1/2B screecher (straight shot into tracks 6 and 1 Ba-By!!!)
    - 6 double-length through tracks (same storage capacity as 4th & King Ba-By!!!) => no need for off-peak "turnback"
    - $4B saving (even after including the PAX, Ba-By!!!)
    - No need to take down the entire Rincon Center (and countless other SF high rises) to get to Emeryville (another $2B saving).
    - 2704.09 compliant => $500M in Prop1A bonds (Ka-ching!)

    Are we having fun yet?

    1. With regards to the 7th Street station
      - Muni at grade
      - Concourse (what else would you propose 30 feet below the surface??????)
      - Caltrain/HSR/CC/standard gauge BART (PAX/DTX)
      - Classic BART to Alameda (and the Richmond)

    2. I should have stated that I was pre-supposing that it would be politically impractical to completely change the DTX alignment. I don't dislike your idea, but the DTX peer reviewers rejected it for the following reasons:

      - No TBM big enough for the obligatory 3-track tunnel
      - impact to midrise buildings at curve from 7th to Minna / Natoma
      - underground conflict with Central Subway tunnel, requiring deep dive
      - SF MOMA razed (!!!) to make room for jog into train box
      - may still be too deep to enter the train box

      Some of these may be valid concerns, others not so much.

    3. 1) One cannot help but wonder if the "political impracticality" of a 4-5 year $1/2B crater on Second Street may somehow be related to the "temporary" suspension of funding for the "advancement" to 30% "engineering".

      2) The DTX peer review panel were TOLD by the TJPA "stakeholder" (Parsons) that 7th Street had been rejected in prior studies (the Peer Review panel WERE NOT ASKED to peer review the alignment). Adding insult to injury, none of the 7th Street alignment "studies" ever considered the only possible design: SEPARATE BORES under Minna (southbound) and Natoma (northbound).

      2) The rest of the "concerns" have been refuted by multiple independent firms ("Buy America" need not apply).

      - The 3-track BORED tunnel is INCONSTRUCTIBLE (C&C all the way Ba-By!!!). BTW, did you ever consider that THE 3RD TRACK MAY BECOME REDUNDANT the day the new Transbay tunnel connects the TTC to the East Bay (does BART need 3 tracks between Montgomery and Embarcadero???)
      - There are no issues transitioning from 7th to Minna/Natoma because that section of the alignment can dive down to over 120 feet IF REQUIRED (very unlikely). Oh and BTW, what about the "impacts to midrise buildings at curve from Townsend to second street" with FORTY feet of ground cover (C&C all the way, Ba-By!!!)
      - No problems crossing the Central Subway (confirmed by TWO independent firms)
      - Please elaborate on "SF MOMA razed"???
      - "May still be too deep to enter the train box": 100% FUD. While on this subject, please account for the de facto decelaration/acceleration as trains approach/depart the TTC at +/- 3% grade in your timing estimates.

    4. I get you're upset, but you have to realize what you're up against here. The transportation industrial complex can smell six billion and it is NOT in their interest to make major changes that set the environmental review clock back years. If you are to succeed, it will take a lot of technical resources to offer fully-baked alternative plans, and to persuade a large array of stakeholders using phrases other than "Ba-By!!!"

  6. Notice that they still have the platform height at 25" (which won't work with the trains caltrains already ordered.)


  7. Mission Bay alignment with long smooth curve from Third starting under Mission Rock site and under AT&T park outfield aligning perfectly with Second. The Giants can find another park to play home games in for a season if need be. It is worth it and is a better DTX than Pennsylvania/Townsend.

    1. I think what killed Mission Bay (using Third instead of 7th to Townsend) was the impossibly expensive station imagined under Third by the new arena. At this stage of analysis, the tunnel length or alignment didn't.

  8. Does anyone know if CHSRA is still building the stations only for a max train length of 10 cars?

    1. Notice to Designers No. 13 reduced the required station platform length from 1410 feet (430 meters) to 800 feet (240 meters) at new-build HSR stations. This rule does not apply to shared stations like Transbay, so the train box extension is still planned as part of the DTX project.

    2. The author of Notice to designers No. 13 was fired in November 2017.

    3. @Anon

      How is that relevant to the question of whether they were still designing for 800 ft platforms, what basis do you have for that claim, and what business is that of yours?

  9. Among the headaches Gavin Newsom will inherit as governor: California's troubled bullet train project

    One possibility is that the high-speed rail in the Central Valley would connect in Merced with the Altamont Corridor Express commuter rail system that runs through the Altamont Pass to San Jose. In fact, the commuter system’s executives are quietly positioning for that very possibility.

    It would operate far slower and with less capacity than a high-speed system and it could require awkward connections, but it would be a system that the state could improve in the future.

    The San Joaquin Regional Rail Commission, which operates the Altamont system and the Amtrak system in the Central Valley, is extending the commuter rail system to Merced in a $300-million project, a more modest plan than the rail authority’s idea of connecting the Central Valley through a $10-billion-to-$12-billion tunnel under the Pacheco Pass east of Gilroy. The authority’s 2018 business plan acknowledges that it cannot afford the tunnel.

    “No matter how you look at it, Merced will be the northern point of high-speed rail for quite some time,” said Stacey Mortensen, Altamont’s executive director. “So we need to get there. We are trying to be part of the solution.”

  10. Transbay update:

    - "A WAH is not a Weld Access Hole."
    - "Cutting material out of flanges is not a smart thing to do.”


  11. Fun stuff! Media is head-lining articles as "high-speed rail". Brightline's high-speed rail plans get two boosts and High-speed rail from St. Louis to Chicago faces more delays

    However, within the articles, they usually correctly refer to "higher-speed rail".

    So in all likely-hood when trains start running on the Central Valley part, media will headline "'High-speed rail' starts running" even if they aren't operating at 200kmh.

  12. Talking about saving precious seconds of runtime .... I just saw this possibly good news on FB:

    Caltrain-hostile Atherton may decide it has "outgrown" its need for train service. (We can only hope so! ... ridership had dropped to under 150 per day when weekday service was suspended in 2005.)

    Some have predicted that bills such as Sen. Scott Wiener's SB 827 to prohibit banning taller, denser housing near transit stations may actually cause density-averse, affluent areas to oppose new (or close existing) transit stations.

    (Low-density Atherton, population 7,238, has an average household income of $443k and the most expensive zip code in the US with a median home value of $6.75m.)

    Atherton to discuss future of Caltrain service in town

    1. Atherton service should be discontinued. With great prejudice.

    2. But they need to keep the station! Where else are the nannies (or mothers & fathers less typically) going to take the kiddies to see the trains pass by especially after grade separation?

    3. From a demographic perspective, it makes a lot of sense to delete Atherton and add a new Fair Oaks stop approximately halfway between Menlo Park and Redwood City. Such a stop could faciliate overtake since located in a 4-track section. I wrote about it in this post from 2015, near the bottom. An aerial view of a Fair Oaks station would look somewhat like this.

    4. Congratulations!!!

      You discovered the location of the PAMPA northern tunnel portal 4 years after the fact!!!