The Prescriptive Framework: System Requirements

A System Requirement is a statement that identifies a necessary attribute, capability, characteristic, or quality of a system in order for it to have value and utility to a user. The entire engineering effort for the California high-speed rail system is prescribed by a long list of technical requirements, which taken together form the system specification. The requirements are prepared by the program management team at Parsons Brinckerhoff, and cover every detail down to the allowable shades of red for the train's tail lights.

The Palo Alto grassroots group CARRD recently made a public records request for this important material. Thanks to their persistence, the system requirements have now been made public:

• System Requirements Index by Subsystem (161 kB PDF)
  
• System Requirements Index by Package (161 kB PDF)
  
• System Requirements Text (770 kB PDF)
  

The document that is likely to be of most interest is the 961-page "kitchen sink" which also contains background information on how each requirement was developed:

• System Requirements - Full Details and Supporting Information (5.2 MB PDF)
  

A large portion of the requirements is a hodgepodge of existing FRA regulatory requirements (Title 49 of the Code of Federal Regulations), AREMA (U.S. industry) recommended practices, and TSI (European Technical Standards for Interoperability) requirements. The European requirements are featured prominently because there is no existing regulatory framework for very high-speed rail in the United States, and California must blaze the regulatory trail.

As the high-speed rail system comes under ever-increasing scrutiny, these requirements will reveal where and why the CHSRA and its prime contractor (Parsons Brinckerhoff Quade & Douglas) might resist design suggestions made by communities along the rail corridor.

Another Wheel Gets Squeaky

With the recent release of the Supplemental Alternatives Analysis for the peninsula high-speed rail project, Redwood City has found itself with only one design alternative carried forward: an elevated four-track viaduct through downtown. This does not sit well with the mayor, who fired off a sternly worded letter to the Peninsula Rail Program, as reported in the Daily Post.

The letter points out that trenches are being carried forward only in those cities that have vigorously opposed the high-speed rail project, unlike Redwood City. The squeaky wheel seemingly gets the grease, and Redwood City feels left out.

The letter is noteworthy because Redwood City has not been at the forefront of HSR opposition so far. Councilwoman Rosanne Foust, a former mayor, is a strong supporter of high-speed rail and serves as CEO of SAMCEDA, the San Mateo County Economic Development Association. One of SAMCEDA's initiatives is the Alliance for Sustainable Transit and Jobs, a pro-HSR lobbying group.

Long-Standing Plans For An Elevated Station

The cover page of Redwood City's controversial 2007 Downtown Precise Plan (set aside in 2009 after litigation) prominently featured the architectural rendering of a downtown elevated train station shown at the top, similar to what the HSR project now proposes. The plan stated that "the preference and assumption has been that the tracks will be elevated above grade, and a new train station will be centered on Depot Circle and the pedestrian connection to Sequoia Station and El Camino Real. This elevated railway will be carefully designed to become one of Downtown’s major assets." The draft New Downtown Precise Plan, published in March 2010, also assumes an elevated railway, as revealed in Book 2.3, which features the diagram of a railroad frontage lane shown at left.

Does that make Redwood City's new-found stance a bit disingenuous?

Alternatives Analysis Analysis, Part 3

The Supplemental Alternatives Analysis for the peninsula corridor reveals some key engineering choices being made. That tunnels would be taken off the table was never in doubt: tunnels are nothing but trouble. The only tunnels now left are those that have a mountain. Well, almost... as we'll see below.

• Freight grades: we were told all along that 1% is the limiting gradient for heavy freight. Not so in Palo Alto, where there is a 2% grade shown in the track profiles (page 15). Recall that the steepness of a grade has no impact on passenger comfort, frequent references to roller-coasters notwithstanding. (This question of dynamics seems to confuse civil engineers, who deal mostly with statics.) If a freight train can handle a 2% grade in Palo Alto, it can certainly handle a 2% grade anywhere else; that's the concept of ruling grade. Considering that steeper grades would greatly reduce the footprint of any elevated section, for example, the massive Mary Avenue rail overpass in Sunnyvale shown on page 18, why are 2% grades not the rule?
  
  
• Rail yard: the rail yard in Brisbane, the closest-available 100-acre parcel near San Francisco, is on a direct collision course with the redevelopment plans for this area. This may end up as the largest land transaction in the peninsula HSR project. Curiously, the yard is planned on the east side of the tracks, opposite the historical site of the Southern Pacific rail yard.
  
  
• Berms be gone: Belmont and San Carlos get their grade separation berms removed and replaced by a gratuitously tall viaduct, with the tracks 20 feet higher than today's berms. That doesn't go over well with the mayor of Belmont. Prediction: when all's said and done, Belmont and San Carlos will be begging for their berms to stay essentially as they are.
  
  
• Blank-check engineering: Millbrae gets some ridiculously massive civil works in order to shoe-horn a fourth track under the ill-configured station. The plan features a 2.5-mile long tunnel (see track profiles, page 8), diving 75 feet below grade in order to duck under the Hillcrest Blvd underpass. Cross sections are also provided (see pages 13 and 14). There are two design options that are likely to be far cheaper and less disruptive to construct:
  
  
  1. Convert the western-most BART track to Caltrain (see Option D in this diagram). While this requires minor surgery on the existing BART station, and may require an exception to side clearances (e.g. a steel crash barrier to separate BART from Caltrain), no digging would be required.
     
     
  2. Put the Millbrae BART platforms underground. The tunnel already exists, emerging right before the station.
  
  When the alternative is a 2.5-mile tunnel with an underground station mezzanine, which would likely require partial demolition of the existing station structure all in the name of leaving untouched the under-used BART parking tracks, one is left wishing that these issues had been thoroughly examined and addressed in the AA.
  
  
• Slimmer sections: Many cross-sections have gone on a diet, narrowing down from the previous elephantine proportions to more realistic dimensions. The four-track retained-fill berm is slimmed down to 78 feet (wall to wall), the elevated viaduct is down to 78 feet, the trench is down to 76 feet (fence to fence). The at-grade alignment remains at 93 feet (fence to fence), but only because the fences are set back 11 feet from the (perfectly safe-to-touch) overhead catenary masts. The eminent domain panic set off back in March was premature: the tracks will mostly fit within 80 feet, a width already available along 88% of the corridor.
  
  
• Fatter bridges: box-beam elevated structures have a depth of nearly 10 feet (measured from the bottom of the bridge deck to the top of the rails), compared to 5 feet as routinely practiced today, for example on the Belmont - San Carlos grade separations. That means future grade separations must lift the rails at least 25 feet above the road surface, compared to about 20 feet today, with attendant increases in the size of the bridge approaches. Five feet taller, especially when a sound wall will rise another 4 to 8 feet above rail level, makes a huge difference to visual impact.
  
  
• PAMPA sandwich: The finalized application for the next federal funding increment includes a description of the project phasing plan for the peninsula. Phase 1: 4 tracks Redwood City and north + PTC. Phase 2: 4 tracks Mountain View and south + electrification. That leaves Palo Alto - Menlo Park - Atherton (PAMPA) with a two-track at-grade gap, left until such a time as there develops overwhelming pressure to fill it in.
  
  
• VTA buried: The light rail spur in Mountain View is buried under the Stevens Creek, to make room for the expansion of the corridor. That doesn't strike one as the cheapest way to do things.
  
  
• Viaduct vengeance: A FIVE MILE, 60-foot tall viaduct is planned in Santa Clara, an area of the corridor that is (a) already fully grade separated and (b) mostly wider than 100 feet. These people don't do subtle: their vocabulary is reinforced concrete, shoring walls and outrigger bents. This area of primarily commercial and industrial properties is less likely to oppose such a gratuitous structure. Operationally, the HSR viaduct needlessly prevents Caltrain overtakes anywhere between the Santa Clara and Lawrence stations. All pain, no gain... or from their point of view, all profit.

Clearly, there is a long way to go before context-sensitivity is achieved.

Elevated Blight in San Mateo

The elevated structure spans across several blocks of San Mateo, like a gash through the heart of downtown. Its 67-foot width casts vast shadows onto downtown shoppers, like a freeway overpass, although women and children seem to pass underneath without being attacked. The concrete structure, strangely free of graffiti, provides a full 16 feet of free clearance underneath it for trucks. Three stories up above, the side walls of the elevated bridges loom a full 25 feet over the street. To add insult to this injury, metallic poles tower another 18 feet above the structure, bringing its overall height to an incredible 43 feet!

If you know San Mateo, you might have guessed this describes the Central Parking Garage, a structure with presence, visual impact, and context-sensitivity resembling the elevated, four-track high-speed rail corridor that residents fear.

Peninsula (Northeast) Corridor

It's official: as noted on page 7 of the latest program management team monthly progress report, the selected track arrangement for the peninsula corridor, a key architectural decision with extensive ramifications for Caltrain operations, is slow-fast-fast-slow (SFFS). That means the express tracks will be located in the middle of the right of way, with Caltrain local tracks flanking them on each side. This arrangement is similar to the Northeast Corridor throughout New Jersey (photo at right by theahnman). From the report:

While the June schedule does not show any change in the deliverables dates, in July there will be a change in the delivery of the 15% integration package from September 2010 to October 2010 to change the alignment of the Caltrain tracks to the outside and HST tracks to the inside tracks to reduce the footprint at Caltrain station locations (using side rather than center platforms).

The good news is that the previously-favored, segregated SSFF or FFSS arrangements seem to be off the table. Those arrangements would have prevented the express overtakes that are the key to an effective Caltrain timetable, and would have forced wrong-way movements whenever any one of four tracks went out of service. Wrong-way movements vastly diminish track capacity and exacerbate cascading delays, where one late train makes a mess of the whole timetable--as any regular Caltrain rider knows all too well. So that's the good news.

The bad news is that Caltrain will be stuck with side platforms. When a Caltrain track goes out of service, as it inevitably will, routing trains to the opposite platform will now require cutting across the HSR tracks, as shown in the diagram at left. No more central island platforms, which have undeniable operational advantages as well as simplified passenger access.

Given the choice between giving up island platforms (SFFS) or giving up overtakes (FFSS / SSFF), then SFFS wins by a mile because overtakes are key--but that's really a false choice, constrained by the menu of alternatives. The one alternative that is seemingly not being given due diligence is FSSF.

Their logic might go like this:

1. Caltrain design criteria (Chapter 3, paragraph 1.1.d) and HSR Technical Memo 2.2.4 (Station Platform Geometric Design, section 6.1.3) dictate that platforms must be perfectly straight.
   
   
2. Straight island platforms require a double-reverse curve "wow" around the platform at every station, conflicting with HSR Technical Memo 2.1.2 (Alignment Design Standards for High-Speed Train Operation, section 6.1) that prohibits more than four so-called direction changes per mile.
   
   
3. The reverse curve "wow" beyond each end of the island platform consumes an inordinate amount of land precisely where it is most valuable, in the denser suburban cores where train stations tend to be located.

That's a perfectly logical chain of reasoning, but it is unfortunately based on a poorly conceived requirement that prohibits curved platforms.

As discussed in Football Island, curved platforms allow the "wow" around the center island platform to be much more compact, using barely any more land than the side platform configuration. The diagram at right (do you see the football?) highlights the difference in green, amounting to about a half acre. With the exceedingly generous clearances likely to be used--the diagram shows a mere 75 feet of right of way width!--the difference would be even less. Now imagine a straight island platform, not shown in the diagram, where the green area would need to bulge out over a far greater length; the extra area would amount to the entire area of the platform, 30 x 750 feet or another half acre. That is indeed a waste of valuable land.

Fast-Slow-Slow-Fast isn't some far-fetched concept. It works in Sweden, and it would work here, far more efficiently and flexibly than a carbon copy of the Northeast Corridor. Why not give a careful second thought to curved platforms, unencumbered by rote compliance with ill-considered specification requirements?