31 December 2009

Focus on: Mountain View

Mountain View, home to some of the biggest names in Silicon Valley, is the third busiest Caltrain stop behind San Francisco and Palo Alto, and serves as a transfer point between Caltrain and the VTA light rail system. (photo by LazyTom.) The city has so far adopted a conciliatory attitude towards the high-speed rail project, unlike several cities to the north. In its scoping comments (p. 90), Mountain View first and foremost asks to be considered as a candidate for a peninsula HSR stop, citing its strategic location, transit connections, and easily accessible freeway network. The CHSRA's preliminary alternatives analysis for the first time featured Mountain View as a potential peninsula HSR station.

The railroad right-of-way through Mountain View parallels Central Expressway, a four-lane divided highway that is part of Santa Clara County's expressway network. This inherently gives the peninsula rail corridor a less residential character than in communities to the north, although several new housing developments have been built near the tracks in recent years, with more planned in the vicinity of the San Antonio Caltrain station. The latter station, opened in 1999, replaced the primitive stop formerly located at Rengstorff Avenue with what was billed as a model transit-oriented development.

Vertical Profile

The vertical profile of the existing Caltrain tracks is shown in the diagram below, created from Caltrain track survey data. The tracks slope gently, with the southern end of town a full 50 feet higher than the north. The slope is steepest (a bit over 0.6%) in the section between Castro St. and the Rte. 85 overpass, near the downtown station.

There are just two grade crossings remaining in Mountain View: Rengstorff Avenue and Castro Street.

The city has been planning a grade separation at Rengstorff Avenue since 2002, which is currently entering the environmental review process independently of high-speed rail. The city's preferred alternative (see feasibility study in PDF Attachment 2) calls for Rengstorff and the nearby intersection with Central Expressway to be depressed under the tracks. The $45 million plan already includes a corridor expansion to four tracks, as shown in the figure at right. Other design alternatives were eliminated: trenching the tracks at this location would have been complicated by the nearby Permanente Creek, and residents were concerned about the visual impact of elevated tracks. Nevertheless, the HSR scoping comments submitted by the city (see p. 95) ask that all vertical alignment alternatives be re-examined for the Rengstorff grade separation. Since the technical and community constraints have not changed at this location, the HSR alternatives analysis is likely to be consistent with the city's prior study.

That leaves the crossing at Castro Street in the downtown area, the most challenging design puzzle in Mountain View, where only one vertical alignment solution stands out as realistically feasible. The options that will probably not be practical are:
  • A deep bore tunnel. While technically feasible, such a tunnel would be prohibitively expensive and difficult to build because the entire Mountain View train station would need to be sunk below grade, including 1/4 mile platforms if the city is selected as an HSR stop.

  • A cut-and-cover tunnel or trench. The rails would need to be sunk 25 to 30 feet deep to pass under Castro Street, but the natural slope of the terrain to the south would require a steep 3% rise back to grade level at the Stevens Creek, potentially compromising the ability of freight trains to use the corridor. (This assumes re-routing the creek is not practical.)

  • An at-grade alignment. The high train speeds would require the permanent closure of Castro Street, or the construction of a bridge over the tracks with extensive impacts to the 100 block of the historic downtown and businesses on Moffett Blvd. Either way, Castro would no longer connect to Central Expressway.

That leaves just one reasonable option: a split grade separation with the tracks elevated about 15 feet above grade and Castro Street sunk by about 5 feet. Sidewalks could stay at the current grade level, and the station would be elevated, not unlike the existing design at Belmont. To the north, the tracks would require a 2% grade to duck under the bridge at Shoreline Blvd. To the south, the tracks could run level (which is of benefit for building a new train station) to meet the rising natural grade, returning to ground level at the Stevens Creek. The resulting vertical profile is shown in the diagram below, in green; compare to the infeasible below-grade alignment shown in red.

While Caltrain and high-speed rail would comfortably handle this vertical profile, a rigid adherence to a 1% grade limit for the benefit of freight trains would likely require Castro Street be closed entirely to road traffic.

Horizontal Alignment

The Caltrain right of way is quite wide throughout Mountain View, with 75 - 100 feet available to build out the corridor to four tracks. The relatively sharp curve at San Antonio (the #8 worst curve on the peninsula) just barely allows 125 mph operation, although it could be straightened within the confines of the right of way. Does that mean Mountain View will easily accommodate an expanded, four-track, high-speed corridor? Sadly, no.

In the late 1990s, Caltrain agreed to let VTA and the city construct a light rail extension on its right of way. The light rail system now runs alongside the Caltrain tracks for about one mile, ending at a 50-foot wide terminal with expansive storage tracks near Castro Street (photo by LazyTom). On the western side of the Caltrain tracks, the city built a "transit center" to replace the dingy asphalt strip that previously served as a Caltrain platform. This $20 million intermodal facility was completed in 2002 with a new plaza and modern-day replica of Mountain View's old train depot, which might have earned a spot in a register of historic places had it not been razed in 1959. All this recent construction consumed a large portion of the available right of way, where ample space to build four tracks existed as recently as 1998. Not surprisingly, the city clings to this new civic infrastructure and suggests among other options that HSR be routed via the Central Expressway median--never mind that $20 million is a relative pittance in the context of the peninsula HSR project.

Further south, one southbound lane of Central Expressway will likely be taken to route the VTA track east of the bridge support pillars at Rte. 85 and Whisman, freeing up space for the four-track peninsula corridor.

The light rail situation is further complicated by (a) VTA's inexplicable ambition to double-track the short section of single track that encroaches on the Caltrain corridor, (b) the possible need to maintain freight train access to the Moffett Drill Track (see docket FRA-1999-6254 ; the switch that connected the VTA tracks to the peninsula corridor was recently dismantled, but the Moffett spur is not formally abandoned), and (c) the difficulty of relocating the Evelyn VTA station--incidentally second-to-last in ridership on the entire light rail system, with roughly 60 daily passengers. All three of these factors need to be examined with a critical eye towards who will pay and who will benefit.

Further north, another pinch point exists near the San Antonio station, where the San Antonio Road overpass (a 1960s structure that Caltrans lists as a deficient bridge) does not provide sufficient horizontal clearance for four tracks. The nearby pedestrian underpass would also require modification, likely as part of its extension across Central Expressway to the planned residential redevelopment of Hewlett Packard's former Mayfield campus. It goes without saying that the San Antonio platforms will need to be rebuilt, just like anywhere else on the peninsula.

Downtown Done Right

To visualize downtown "done right," download Mountain View 3D Model (2.2 Mb) for Google Earth. All the illustrations in this section are taken directly from this model, built by Richard Mlynarik.

While Mountain View's transit center is billed as an intermodal, accessible facility, there is vast room for improvement in passenger circulation. The challenge of designing a rail alignment that overcomes the twin obstacles of Castro Street and the light rail tracks presents an opportunity to improve Mountain View's transit center by creating a modern, functioning gateway into downtown. While the construction impact would indeed be frustrating, especially so soon after the area was rebuilt, this would simply reflect the haphazard manner in which the existing facility was planned, with little regard to future HSR requirements or effective pedestrian circulation.

Currently, the light rail tracks end on an unpleasant concrete island hemmed in by Central Expressway and the Caltrain tracks, requiring a circuitous route for pedestrians to access the trains. Centennial Plaza, the faux-depot and the bus loop cut off the Caltrain platforms from downtown. All passengers wishing to transfer between buses and trains must use crosswalks.

There is surely a better way. One possible redesign of the Mountain View Transit Center is described below. It is an exercise to achieve the best possible transportation functionality, providing these specific benefits:

  • Keeps Castro open to all traffic
  • Provides direct, elevator-free access from Caltrain/HSR platforms to sidewalks on both sides of Castro, without circuitous detours
  • Places the VTA light rail terminus in Centennial Plaza, where it meshes intimately with the pedestrian fabric of downtown
  • Allows direct platform-to-platform, passenger-friendly transfers between light rail, Caltrain locals and expresses, HSR, buses and employee shuttles--without the need for an umbrella during the rainy season
  • Locates station amenities such as ticketing, bathrooms, snacks, etc. at the crossroads of pedestrian traffic
  • Provides station parking under the tracks, reducing the need for unsightly parking structures
  • Does not force bus passengers to use a crosswalk
The resulting configuration is a four-track, two-platform Caltrain / HSR station, elevated over Castro Street. The light rail station slants diagonally underneath the elevated tracks, with the trolleys pulling right up to the corner of Castro and Evelyn in a sunken Centennial plaza. (Light rail requires the same 16-foot vertical clearance as road traffic on Castro). The twin Caltrain / HSR island platforms are extended north over Castro, enabling direct access to sidewalks on both sides and a platform-to-platform transfer between all transit modes.

Centennial Plaza looking east
Evelyn looking north to Castro
Castro & Central looking south

View from northbound Central Expressway

For additional views and detail, download the 3D model for Google Earth.

What happened to the retro-faux-depot? Remember, this design is an exercise in form following transportation function. In 1895, the depot would have housed important functions such as mail and baggage handling, signaling staff, and a telegraph operator. Today, those functions are obsolete, so the depot building has no place or purpose. It's gone, for the greater good of functional 21st-century transportation. Architecturally, there are far more exciting possibilities that enhance rather than impede functionality.

Regardless of the details of how exactly HSR is integrated with Mountain View's transit center, one thing is clear: the high-speed rail authority's charter is to build HSR, period. Ensuring that the intermodal connections at Mountain View can live up to their potential will largely be up to the city and its citizens, who ought to take strong initiative to ensure it's done right--without letting their judgment be unduly clouded by the $20 million they spent this past decade.

NOTE: This post will be updated continuously, as warranted by additional information or new events relating to Mountain View.

20 December 2009

Constructions Methods Booklet

A neat little Constructions Method Booklet (2.8 MB PDF) authored by Peninsula Rail Program director Bob Doty was recently distributed at a community meeting. This booklet is currently undergoing an update, which will be posted under the Resources section as soon as it's available. In the meantime, the booklet provides some good general background for making sense of the draft Analysis of Alternatives document that will be published within the next couple of months. The draft AA will be the first time that peninsula residents are given specific design information resulting from the preliminary engineering work that has been underway since the summer.

As the caveat clearly states: This information is provided for discussion purposes only and includes data and assumptions representative of similar programs. The actual requirements for the Peninsula Rail Corridor have not been established.

17 December 2009

On Width

Update: a different reliable source indicates the land impacts along the corridor were determined (and minimized) by laying out an 87-foot wide corridor, measured over the fence footings on either side. That was a nominal value, with narrower design exceptions possible in highly-constrained locations.

Original Post: When we reviewed just how wide the Caltrain corridor is, we assumed a 75-foot minimum width for a four-track rail corridor, measuring from fence to fence. New figures, obtained from reliable sources, indicate typical dimensions will be quite a bit more:
  • 15' (4.6 m) Caltrain track spacing (measured center-to-center)
  • 16'6" (5 m) HSR track spacing, or between HSR and Caltrain tracks
  • The kicker: 23'6" to 28'6" between the outer track center line and the boundary fence, to allow for third-party utility easements (as already exist in many places along the Caltrain corridor), overhead electrification poles, maintenance walkways, drainage structures, etc.
Worst case, that adds up to 28'6" + 16'6" + 16'6" + 16'6" + 28'6" = 106'6" (32.5 m). The best case, with Caltrain tracks in the middle, adds up to 23'6" + 16'6" + 15' + 16'6" + 23'6" = 95' (29 m). Both figures are measured fence-to-fence, presumably for a situation where all four tracks run at ground level.

Time to Panic?

Well, maybe not quite yet.

These figures are quite likely quoted for the nominal situation, where plenty of land is available. Indeed, more than two-thirds of the peninsula rail corridor is 100 feet or wider, allowing generous side clearances. Caltrain's own environmental documents, drafted for the electrification project long before HSR came along, include the typical four-track section reproduced at right, with a nominal fence-to-fence width of 89 feet.

Then again, the HSR numbers are incredibly generous by international standards, and probably accommodate vehicular access along both sides of the right of way. (A Department of Homeland Security Crown Victoria is 6'6" wide, for reference.)

The minimum legal side clearances in California are dictated in CPUC General Order 26-D. The absolute minima are 14' between track centers and 10' side clearances to the edge of the right-of-way. Caltrain's engineering standards reflect these constraints in a clearance drawing. None of these standards envision trains running at 125 mph and above, since those have never existed in California. Better numbers can be gleaned from foreign standards, for example the German Eisenbahn, Bau- und Betriebsordnung (EBO). That particular standard requires the following side clearances:
  • A danger zone (free of any obstructions such as poles, walls, etc.) of 2.5 m (8'2"), measured from the track center line, for train speeds less than 160 km/h (100 mph) and 3.0 m (10') for greater speeds.
  • Outside of the danger zone, a 0.8 m (2'6") space for rail personnel to take refuge at a safe distance from trains
  • The danger zones of neighboring tracks may overlap, with tracks spaced 4 m (13') for speeds less than 250 km/h (150 mph) and 4.2 m to 4.5 m (14' to 15') above. Since European trains are about a foot narrower than ours, that's roughly consistent with the 15-foot minimum already in use on the peninsula.
Where the Caltrain corridor is too narrow (such as in certain sections of San Mateo or Menlo Park), technical and political considerations make it probable that the HSR project will prefer adapting to the local constraints before seizing property and revving up the bulldozers.

If one had to make an educated guess about the minimum allowable corridor width, as opposed to the typical width, it would likely be closer to the values in the German EBO and/or the European Technical Specifications for Interoperability (TSI). Using the 16'6" track spacing mentioned above, that comes out to 0.8 m + 3 m + 5 m + 5 m + 5 m + 3 m + 0.8 m = 22.6 m, or 75 feet. The actual minimum for the peninsula corridor is likely to be spelled out in the upcoming draft Analysis of Alternatives.

Those figures are only valid for an alignment at grade level, which is the narrowest option. Raising or lowering the tracks requires additional width for construction.

05 December 2009

Elevated Obsession

Another creative proposal (see also PDF brochure) has emerged from Palo Alto architect Joseph Bellomo, this time for an elevated high-speed rail line built down the middle of the Caltrain right of way, partially enclosed in a tubular structure with sound baffles, solar panels, and if one believes the sketches, optional LED lighting. More broadly, Bellomo is calling for an international design competition to come up with the best world-class design; he laments that the design has so far been dominated by teams of engineers working separately on each segment of the line.

Design is nice, but what about engineering function? For something as utilitarian as rail transportation infrastructure, function obviously trumps form. That inevitably leads one to ask the most obvious question about Bellomo's concept.

Why Elevate?

It is a useful exercise to identify the reasons for elevating the tracks.
  1. because it looks sexy and futuristic, just like the Disneyland monorail or other gadgetbahn concepts like maglev or Tubular Rail. These are so often depicted on elevated guideways that elevation itself has become associated with modernity and speed. The average American, who has little or no exposure to high-speed rail, is especially vulnerable to this pop-culture association--and it's a terrible reason to build elevated tracks.

  2. because it allows the tracks to collect solar energy, as envisioned by Bellomo. Solar panels sure are green and trendy, but they are far from proven as an optimal way to power a peaky and very high electrical load (a single accelerating train can draw about 10 megawatts). If renewable energy is used to power the trains, its source should be a choice that is not locked in by design of the infrastructure. The problem of powering the trains is adequately decoupled (through the electrical grid) from the problem of how to generate the power.

  3. because of a need to fit more tracks into a constrained right of way. If you can't spread out horizontally, then go vertical. Again, this is a solution to a problem that mostly doesn't exist on the peninsula: the vast majority of the railroad right of way, including the portion through downtown Palo Alto, has ample width for as many tracks as would ever be required to provide both commuter and HSR services. Even in those few locations that are constrained, acquiring additional land is far cheaper than the construction cost and ongoing maintenance cost of elevated structures or tunnels. That available width is why they chose the Caltrain corridor in the first place. Where Bellomo's renderings show an elevated across University Avenue, the railroad right of way is over 160 feet wide!

  4. because it provides unimpeded access from one side of the tracks to the other for pedestrians, bicycles and motor vehicles--something that is better known as grade separation. This is the only good reason ever to elevate the tracks. Unfortunately, the Bellomo proposal falls short on this as well: the existing commuter tracks stay at grade, forming the same community barrier that they already are today. Worse, elevating HSR over Caltrain would severely curtail the options for later removing grade crossings.
Of course, there are plenty of valid reasons not to elevate the tracks, including noise, shadow, visual blight, expense, safety (passenger evacuation) and operational flexibility.

Missing the Point

While Bellomo's HSR concept has obviously been polished from an architectural design standpoint, the basic premise of an elevated HSR is not rooted in any realistic functional or engineering need. That flaw makes Bellomo's complaints that engineers are in charge ring a bit hollow.

While he can be lauded for proposing fresh solutions, Bellomo clearly needs to review his concept with civil engineers who have direct experience with high-speed rail infrastructure. (Hint: there are precious few of them in California.) In the meantime, we can easily state...

The Three Rules of Elevation
  1. Don't elevate the tracks if you can avoid it.
  2. If you can't avoid it, then elevate solely to provide access from one side of the tracks to the other, i.e. grade separation, and return to ground level as quickly as possible.
  3. Keep all tracks at the same elevation, to provide operational flexibility--allowing trains to easily switch from one track to another as dictated by operational service needs.

01 December 2009

Earthquakes and Terrorists

The specter of derailments has been raised in scoping comments and through general opposition to the high-speed rail project in letters to the editor, online forums and blogs. Such comments generally express fear that a train could hurtle off the rails somewhere on the peninsula and smash into residential neighborhoods and schools. The recent train bombing in Russia seems to have renewed this concern. While HSR has a demonstrated safety record that compares favorably to any other mode of transportation, the risk of derailment is not zero, whether from track or equipment failure, track intrusion, terrorist attack, or an earthquake.

Chronologically, the few noteworthy accidents that took place at speeds of 200 km/h (125 mph) and above were traced to the following causes:
  • Track failure: on 21 December 1993, a French TGV derailed at over 290 km/h (180 mph) after a sink hole formed under the track. Deaths: 0.
  • Equipment failure: on 3 June 1998, a German ICE derailed at 200 km/h (125 mph) after a wheel failure and struck a bridge, which collapsed onto the train. Deaths: 101. The Eschede disaster remains the world's deadliest high-speed rail accident.
  • Equipment failure: on 5 June 2000, a Eurostar partially derailed at over 200 km/h (125 mph) after a piece of the train failed. Deaths: 0.
  • Earthquake: on 23 October 2004, a Japanese Shinkansen derailed on an elevated structure after a magnitude 6.8 earthquake struck nearby. The derailment dynamics are neatly illustrated by a simulated animation. Deaths: 0.
  • Track Intrusion: on 26 April 2008, a German ICE derailed in a tunnel after striking a stray flock of sheep. Deaths: 0. (not counting sheep.)
  • Terrorist Bomb: on 27 November 2009, a Russian conventional (not bullet) train derailed at 200 km/h (125 mph) after a bomb was detonated on the tracks. Deaths: 26. Note, a 1983 TGV bombing failed to produce a derailment.
Mitigation Measures

Preventing a derailment is always the first line of defense, but once it happens, there are design features that can mitigate the consequences. In all the zero-fatality high speed train accidents mentioned above, the train remained upright and was confined to the track area; those that 'escalated' by departing entirely from the track were deadly. Therefore, so-called Derailment Containment Provisions are an important passive safety feature, about which a study prepared for the Dutch HSL-Zuid project provides a good introductory overview. Such measures can include:
  • Crash barriers and wheel guides that are integrated into the trackway, keeping derailed vehicles upright and moving along the track even when off the rails.
  • Articulation - train cars that are semi-rigidly coupled together and cannot jackknife off the tracks.
  • Guide blocks on the underside of trains that slide along the rails.
In the United States, one can reasonably argue that our foreign policy could make high speed rail a more attractive target for terrorism than in any other country where HSR exists. Here in the Bay Area, big earthquakes are quite likely. Those real risks are often held against HSR on the peninsula as if they could not be mitigated--but they can. Some form of derailment containment is almost certain to be used on the peninsula corridor, if only in the most sensitive locations such as bridges, tunnels, curves, or schools.