03 July 2017

The Overtake That Won't Be

In its renewed environmental review process for the San Francisco to San Jose project, the high-speed rail authority is considering the alternatives for the peninsula rail corridor. The outlines of the new draft EIR are emerging, and this is where politics meets engineering.

Interested stakeholders keep asking about how the blended system will actually work, with Caltrain and high-speed rail sharing the scarce resource that is track capacity. The issue is being studied in some detail behind closed doors by an entity known as the Joint Scheduling Working Group (JSWG), consisting of experts from HSR and Caltrain aided by their respective consultants. As of the end of 2016, the JSWG had produced a first report on its work, which was shaken loose by a public records request from CARRD. Before digging into this, let's take a look back at how we got here.

2012 Blended Operations Analysis (Caltrain/LTK)

While the original four-tracks-all-the-way HSR plan was collapsing in a firestorm of community opposition, Caltrain commissioned a study of blended system operations (8 MB PDF) from consultant LTK Engineering Services, to see if blending Caltrain and HSR primarily on the two existing tracks was viable. The 2012 study concluded that without any additional tracks, the corridor could support up to 6 Caltrain + 2 HSR trains per hour per direction, increasing to 6 Caltrain + 4 HSR with overtake tracks.  Key results were:
  • With speeds limited to 79 mph, the most reasonable option with 6 Caltrain + 4 HSR was a "short middle overtake" between Hayward Park (San Mateo) and Whipple Ave (Redwood City).
  • A "long middle overtake" all the way through Redwood City provided only marginal performance improvements.
This study legitimized the blended system, which has ever since been the favored approach to bringing HSR to the peninsula rail corridor. The study contained numerous disclaimers to the effect that no official decisions had been made regarding future service levels, programmed overtakes, stopping patterns or scheduled trip times... all the important considerations that feed into a railroad's product, namely its timetable.

2013 Additional Blended Operations Analysis (Caltrain/LTK)

A short while later, LTK published another report (2MB PDF + 14MB Appendices) that can best be characterized as an expansion and refinement of the 2012 analysis, considering additional options. Key results were:
  • Unlike the 2012 study, the "long middle overtake" performed significantly better than the "short middle overtake."
  • A new option, the "middle 3-track overtake" (between San Mateo and Palo Alto) performed almost as well in simulation, although it assumed all HSR trains entered the corridor on time, unlikely in practice.
  • Other overtake track options did not fare as well.
The disclaimers continued, with the conclusions of the study being described as "educational."

2016 Joint Schedule Working Group Report (HSR/SMA)

The key chart in the SMA study
(PDF page 62 / slide 48)
The JSWG was established in April 2016, a while after HSR had engaged the services of Swiss rail consultancy SMA. To avoid a standoff between dueling agencies and consultants, Caltrain/LTK and HSR/SMA are now comparing notes on their respective plans for the blended system. The JSWG's 2016 draft year end report (10 MB PDF) provides important context to the decisions now being made to select a "preferred alternative" for the HSR blended system EIR. This study is interesting for three reasons: it is the first blended system study led by HSR, it offers insight into the evolving ideas of the JSWG, and it is not sugarcoated because it wasn't intended for wide public distribution. Key results were:
  • The "no additional passing tracks" case is shown to support 6 Caltrain + 4 HSR per hour per direction, unlike in the LTK studies, provided that headways are tightened and Caltrain passengers don't mind sitting in a siding for 6 or 7 minutes during these overtakes.
  • The "short middle 4-track overtake" degrades Caltrain trip times, since overtakes don't naturally tend to occur there.
  • The "middle 3-track overtake" performs better than any other option, thanks to allowing bidirectional operation through almost its entire length, unlike in the LTK study where half the length of the overtake track was dedicated to each direction.
Tea Leaf Reading
The grotesque station-in-the-sky
proposed for San Carlos under
the short middle 4-track option
The constant refrain that nothing has been decided yet continues to this day, but the tea leaves are becoming quite readable. Here is some informed speculation:
  1. The HSR team really, really doesn't want to build the "short middle 4-track overtake," generally because they have no money and specifically because the SMA analysis has shown this scenario to be a poor performer operationally.
  2. However, the HSR team is reluctant to withdraw any alternative this late in the preparation of an EIR, after it was carefully introduced to the public through countless outreach meetings, workshops and open houses. Sudden change scares people.
  3. In order not to build the "short middle 4-track overtake," the HSR team has engineered it into a straw man alternative, using the prospect of grotesquely massive concrete viaducts towering fifty feet over San Carlos and Belmont to strategically elicit vigorous public opposition. It's working, but unbeknownst to them, San Carlos and Belmont have little to worry about.
  4. Due to having no money, the HSR team strongly favors the "no additional passing tracks" alternative. The mediocrity of the resulting Caltrain timetable, and the amount of time spent by Caltrain passengers waiting to be overtaken, is of little concern to them. But that's okay, since San Carlos and Belmont made them do it.
  5. The HSR team probably dreads resistance from Caltrain stakeholders who don't want the peninsula rail corridor being taken over to Caltrain's detriment. Strong resistance could force the HSR team to revive the "middle three-track" alternative that had previously been eliminated from the EIR process (see slide 15 in this outreach presentation), setting back the environmental review schedule.
  6. If the assumptions in the SMA analysis stand up to closer scrutiny, the "middle three-track" scenario could actually be a viable compromise for the blended system. It would no doubt be expensive due to the number of new grade separations, but the result (if one believes SMA) would be fast and robust service for both HSR and Caltrain, with reasonably-sized grade separations in every town from San Mateo to Palo Alto. In the last year, the winds of public opinion have turned more favorable to grade separations in Menlo Park and Palo Alto.
One thing is sure: the "middle three-track" alternative should be added to the HSR EIR and studied in detail, with an eye towards designing the future blended system timetable. The timetable is the product, and it will soon be time to decide on one.