Diridon Delusions

San Jose is striving to redesign and expand its Cahill Street station, named for the (still living) former Santa Clara County board of supervisors chair Rod Diridon, to meet the needs of future rail service including BART and high-speed rail. The station's context was discussed here in 2017.

The process led by the Joint Policy Advisory Board, made up of representatives from the city and relevant transportation agencies, has now reached the key juncture of presenting a small number of alternatives to the public. Before we dig into this, let's pause to consider an alternate plan.

The HSR Environmentally Cleared Project

This design is already
environmentally cleared.

The California High-Speed Rail Authority, as part of its San Jose to Merced project, has already obtained full federal and state environmental clearance to build the simple Diridon station concept shown at right. This plan adds a couple of overpass mezzanines above the existing platforms, and rebuilds two of these platforms for compatibility with high-speed trains, using the newly established standard height of 48 inches above top-of-rail and lateral offset of 73 inches from the track center. The 48" x 73" platform standard was agreed in June 2023 between the Authority, the FRA, and other prospective high-speed rail operators such as Brightline West. Due to budget pressures, the HSR project took a rather minimalist approach to this station, electing to build it at grade within the footprint of the existing facility, but pledged to work harmoniously with other agencies on more ambitious concepts. Think of it as a minimum viable product that has already cleared CEQA and NEPA, before we turn to what is now brewing for San Jose.

The Diridon JPAB Alternatives

In any public alternative evaluation process, it is important to carry a sacrificial alternative. This serves the same role as an unlikable character in a movie, whose demise is heavily foreshadowed and brings relief to the viewer when it occurs. The sacrificial alternative can be eliminated in an overt display of due diligence, reassuring the public that the authorities are being thrifty and mindful of the interests of riders and taxpayers. In this case, the "stacked" alternative seems to serve this purpose, and warrants no further discussion because it will shortly be eliminated.

Note similarity of elevated and at-grade options.

This leaves a choice between two alternatives known as "at grade" and "elevated," actually a distinction without much difference. Both designs are driven by an overarching requirement to create an expansive concourse level below the tracks and platforms, purporting to imitate grand European train stations but far more likely (this is America!) replicating the airport experience for train passengers. Early architectural renderings show this as an open and airy space resembling an Apple Store, paying no heed to the fact that the sky will be completely obstructed by tracks and platforms built on a dense forest of beefy concrete columns. No matter how pretty the architects try to make it, this will be a heavy elevated structure built on alluvial soils near seismically active faults. The light-filled and soaring station canopy will be enjoyed by nobody for any length of time, since all waiting areas will be in the basement.

Things to Watch For

The effectiveness of a station modernization project should be measured by its operational efficiency. The primary focus should be on shaving seconds off travel times, to include:

• Removing slow zones in the station approaches. On the north side, this means removing the CEMOF double reverse curve, a self-inflicted obstacle added in 2005 that limits all trains to 40 mph over a mile before the station. Main tracks MT2 and MT3 should be restored to their former alignment on the west side of the maintenance facility, with a flatter curve allowing trains to pass the facility at higher speeds. On the south side, this means greatly increasing the speed limit between San Jose and Tamien, currently just 35 mph, and providing at least two electrified tracks.
   
  
• Re-configuring the layout of north and south station interlockings (a.k.a. "station throats") to enable swift and parallel train moves into and out of the station, on turnouts rated for much higher speeds than 15 mph of the current layout. Nobody in Europe or Asia would accept a train crawling slowly along a platform while dinging insistently; trains arrive and depart swiftly and quietly.
  
  
• Ensuring that all Caltrain traffic will shoot through on just two platform tracks and one island platform. Despite the "south terminal" school of thought still prevalent at Caltrain headquarters, San Jose Diridon should become just another intermediate stop on the way to further destinations in the greatly under-served but densely populated southern parts of the city, which the BART-fixated county agency seems to have completely forgotten about. A great way to sell this extension would be as a "South San Jose to BART Regional Connector Project." Cutting Caltrain's footprint to just two tracks and one island platform will free up ample space for other operators.
  
  
• Providing excellent vertical circulation, which means short vertical circulation. This is one benefit of putting the concourse under the tracks: people are shorter than trains. Architects should resist the urge to make the ceilings in the passenger concourse vault too high because this needlessly extends the reach of stairs, escalators and elevators. Likewise, structural engineers should resist the urge to put the tracks on top of enormous concrete box girders. The early concept renderings show 15-foot ceilings with 9-foot structure depth, while 12-foot ceilings and 3-foot structure depth (using through-girders) would bring the entire structure 9 feet down. This saves every single passenger ten seconds of vertical transport, worth an hour per year for each commuter! Don't go for drama, go for ruthless efficiency: form must follow function.
   
  
• Providing a straight-shot escalator / elevator ride from the north end of the Caltrain platform to the west end of the underground BART platform. This simple shortest-path connection avoids a long and circuitous walking detour through the main BART entrance, located outside and east of the station footprint. Please don't let agency turf lead to lengthy and confusing transfers.
  

The unifying theme here is to save passengers time, whether on the train or in the station. Every second of the San Jose travel experience matters. A counter-intuitive fact about high-speed rail is that the best way to save time is to relentlessly focus on speeding up the slowest bits, like station approaches and escalator rides. In terms of capital costs, those are by far the cheapest seconds to save. California has already committed to the enormous expense of building a 220 mph system, and San Jose is not the place to wastefully undo those hard-won time savings.

If operational efficiencies are not realized in San Jose, and the opportunity to bring the station into the 21st century is not captured, then we'll end up with a new multi-billion dollar train basement that does little to improve regional transportation.

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.

The Blend, HSR Style

The California High-Speed Rail Authority recently published a memo (requested by Kathy Hamilton and CARRD) justifying the oft-questioned claim that the Phase 1 "blended system" presented in the 2012 Business Plan is consistent with the trip-time requirements built into section 2704.09 of Proposition 1A, the HSR bond.  The trip times are in the bond language to prevent funds from being disbursed for projects that are not high-speed rail.

The memo states that the blended system will enable 30 minute non-stop trip times between San Francisco and San Jose.  In support of this claim, the memo provides the speed graph below, to which blue annotations have been added for clarification.  The annotations are necessary because the memo authors evidently did not go out of their way to explain the graph to non-engineers.

San Francisco to San Jose (southbound) speed versus distance graph, annotated.
Notches in the speed profile represent curve speed restrictions.

An independent calculation of the speed profile (using the output of a Train Performance Calculator that numerically integrates the differential equations of motion of the train, taking into account traction, braking, and drag forces) shows that an AGV train limited to 110 mph can travel from San Francisco 4th & King to San Jose in 33 minutes, under a slightly different set of assumptions where the train is slowed by a curve at Palo Alto, uses the existing 45 mph San Jose station approach, and makes an actual stop in San Jose.  After the differing assumptions are reconciled, the math does check out and the calculations are correct.

Those Pesky Assumptions

As for any computer simulation, the results are predicated on a set of input assumptions.  As the saying goes, "garbage in, garbage out"--bad assumptions will lead to bad results.  While the CHSRA's time of 30:22 is reasonable under the particular assumptions they made, the assumptions themselves are questionable.  They include:

1. The train starts from San Francisco 4th & King, not Transbay.  Starting from Transbay, with its notoriously slow approach, would add about another 3 minutes.
2. No Caltrain service is allowed for, or in their words, "Caltrain train service will allow for high-speed express train to run unimpeded between SF and SJ".  In Caltrain's blended operations analysis, all HSR services during rush hour make a two-minute stop at Millbrae, which has the effect of reducing the speed differential between HSR and Caltrain.  If HSR were to attempt a 30-minute run during rush hour, it is likely that Caltrain would be impacted by reduced rush hour track capacity, from six Caltrains per hour per direction to four or five.  The stop at Millbrae adds 3.5 minutes to the SF-SJ run.  Such is the nature of compromise.
3. No padding is included.  In the real world, timetables include a small amount of padding (5 to 7 percent) to allow for the occasional unplanned delay.  Over a half-hour SF - SJ run, a real-world timetable would add at least 1.5 minutes.
4. The train does not stop in San Jose, so no penalty is taken for the time lost as it slows down.  This alone is worth at least half a minute from 75 mph.
5. The train uses the least energy-efficient, pedal-to-the-metal driving style.  Brakes are applied fully and at the last moment, and acceleration is at full throttle.  In the real world, where energy and maintenance do cost money, a smoother and more energy-efficient traction and braking profile would add about 1 minute.
6. No speed restriction is present at Palo Alto, where a double reverse curve limits train speeds to 90 mph.  Slowing from 110 mph would add about 20 seconds.
7. The train approaches San Jose on an elevated viaduct leading into the proposed upper level at San Jose Diridon, maintaining a speed of 75 mph (as opposed to the slower 45 mph limit practiced on the existing alignment).
8. Timetables show departure times.  Departure from San Jose would be two minutes after arrival.

In the real world, all those assumptions add up.  In a blended scenario at rush hour, if a passenger picks up the HSR timetable, entries for SF Transbay and San Jose will be no less than 42 minutes apart (30.5 minutes express run time + 3.5 minutes Millbrae stop + 3 minutes Transbay + 1.5 minutes padding + 1 minute energy efficiency + 0.5 minutes slowing for San Jose + 2 minutes dwell at San Jose.)

While a special one-time midnight Cannonball Express run could be achieved in 30 minutes and 22 seconds without violating any speed limits or laws of physics, this figure is not operationally feasible in everyday service and boils down to nothing more than a stunt.  Under the same stunt assumptions, a decrepit old Caltrain diesel could rush from SF to SJ in just 39 minutes.

As the HSR project is litigated, the distinction between a one-time high-speed stunt and a robust every-day train timetable will be important to keep in mind.

The Shape of Palo Alto

Several years ago, the city of Palo Alto commissioned a public art work entitled The Color of Palo Alto. At considerable expense ($75,000), artist Samuel Yates set out on a techno-artistic quest to determine the exact shade of Palo Alto. In a similar vein, and bearing in mind that artistic form is more than just color, we set out to determine the shape of Palo Alto.

Why does the shape matter? While the area around the tracks in Palo Alto is pretty flat, small variations in the terrain do have an effect on how the high speed rail project will be configured as it crosses through town. The vertical alignment of the tracks must not only conform to the surrounding grade, but it must be routed over or under every creek, road, pedestrian or bike crossing while conforming to acceleration limits imposed by passenger comfort as well as train stability and performance.

There have already been strong hints as to what shape this vertical alignment might take, as previously discussed in Focus on Palo Alto. As part of its program-level EIR/EIS, the California High Speed Rail Authority produced a set of maps of the Caltrain corridor that fueled a firestorm of controversy in Palo Alto, with residents worried that raised tracks would form a Berlin Wall and divide the city. While the CHSRA now professes to consider all vertical alignment options for its project-level EIR/EIS, ranging from tunnels to elevated tracks, there aren't that many feasible and affordable ways to design the vertical alignment of HSR tracks through Palo Alto-- and it turns out that the shape of Palo Alto can tell us a lot about what those are.

Working from Caltrain track survey data, here is the shape of Palo Alto, with the vertical scale greatly exaggerated: (click to expand)

 Note a few salient features:

• Palo Alto isn't as flat as you might think. Who knew that the University Ave station is nearly 40 feet higher than the California Ave station?
  
• There are only four grade crossings in all of Palo Alto
  
• Including overpasses, underpasses and grade crossings, there are only nine places where pedestrians and bikes may cross the tracks in all of Palo Alto, and only seven places where roads cross the tracks
  
• The entire southern half of Palo Alto has only two places where pedestrians can cross the tracks, and both of them are very busy intersections.
  
• Four creeks cross under the tracks

As we consider various grade separation options, keep this in mind: while grade separations are a sine qua non condition for high speed rail, they could also become necessary in other non-HSR scenarios for the peninsula. For example, if Caltrain traffic increased to the point that grade crossing gates blocked rush hour traffic for too long (such as if HSR were to terminate in San Jose), or if BART were to connect Millbrae to Santa Clara, as originally planned in the 1960s. Grade separated tracks are by no means a unique requirement of HSR; they are likely to be required in Palo Alto within the next few decades, HSR or not.

Constraints on Vertical Alignment

Before evaluating various vertical track profile options in Palo Alto--especially if you're going to have a charrette--it's important to lay out a few simple, fundamental design rules that govern what you can and can't make the tracks do.

• The maximum grade (how steep the tracks can be) will be limited. High speed trains and electric commuter trains can easily climb 2% or 2.5% grades. Freight trains can't climb as steeply, and work best at 1% or maybe 1.5%.
  
• The radius of vertical curves (humps and sags) is constrained by maximum train speed. The vertical curves have to be gentle, unlike a roller coaster, to keep passengers comfortable and keep the train stable on the tracks as it crests over a hill. For 125 mph (200 km/h) operation, here are some typical track design standards:
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Standard (at 125 mph)	Typical Radius	Minimum Radius
  European Technical Standard of Interoperability	14 km (9 mi)	10 km (6 mi)
  Germany	16 km (10 mi)	10 km (6 mi)
  Sweden	17 km (11 mi)	10 km (6 mi)

  
  
  
  Some standards do allow vertical curves with a radius barely over 6 km (4 mi), but only in exceptional circumstances. For the peninsula, using the minimum value of 10 km is probably a good starting point. This radius results in a vertical acceleration of 0.3 m/s2, or about 1/3 to 1/4 of the acceleration you might feel in a typical elevator--infinitely smoother than a roller coaster!
  
• To the extent possible, the vertical profile should avoid obstacles like creeks or existing overpasses and underpasses. While earthworks and concrete can be used to solve any such puzzle, the cost may be prohibitive.
  
• Where roads cross under the tracks, the vertical distance between the road surface and the top of the rails must be 20 feet to clear trucks and buses.
  
• Where tracks cross under roads, the vertical distance between the road surface and the top of the rails must be 30 feet to clear freight trains and overhead electrification.

The chart at right shows vertical track profiles for various combinations of these parameters. On the top half of the chart is a 20-foot elevated grade separation, with representative 1% or 2% grades and 10 km or 16 km vertical curve radius. On the bottom half is a 30-foot depressed grade separation (trench), with the same variations of grade and vertical curve radius. The chart gives you an idea of how long these structures need to be, based on how high (or deep) they are.

The Elevated Scenario

Elevating the tracks over Palo Alto's few remaining grade crossings is one scenario being proposed by the California High Speed Rail Authority, and is likely the cheapest.

Taking a step back: the only reason to elevate track that isn't already elevated is to lift the track over a road or pedestrian underpass, also known as a grade separation. The only place where that might happen is in the vicinity of grade crossings. Elevating the track anywhere else would serve no purpose and is not being contemplated.

Here's what the elevated scenario might look like:

• All vertical curve radii are 10 km (6 miles)
  
• At Charleston and Meadow, the tracks are raised by 7 feet and the road sunk by 13 feet. This embankment height was given in the CHSRA's program EIR/EIS maps.
  
• At Churchill, the tracks are raised by 15 feet, with 1.5% ramps. The CHSRA's program EIR/EIS maps showed the embankment starting well north of Palo Alto high school, presumably to avoid dipping down and back up; however, there is absolutely no harm in the hilly profile shown here. The only people who might dislike it are freight train operators, not HSR, because of slack action. Speaking of freight trains, this embankment could be made even shorter and steeper if it didn't have to be designed with the gentle grades required for freight trains.
  
• Alma (a.k.a. Palo Alto Ave) is lowered to cross under the existing track level.
  
• As evident in the diagram, any claims of a continuous 20-foot wall bisecting Palo Alto from one end to the other are exaggerated.

The Depressed Scenario

With respect to the outcry over the community impact of raised embankments, it's worth looking at another scenario... and it doesn't involve tunnels! While tunnels are often contemplated as the only possible alternative to embankments, it is possible to grade separate the Palo Alto crossings by depressing the tracks into trenches. Trenches are preferable to tunnels because they can be narrower and involve far less earth moving and concrete works... although still far more work than embankments.

Here is what the depressed scenario might look like:

• Note the length of the grade separations increases considerably, since they must dive a full 30 feet under street level and do so with gentle, train-friendly grades. The excavation itself would be even deeper, since the red curve is drawn at the top-of-rail level. Do note that accommodation of freight trains requires an extra 3 feet of vertical clearance.
  
• The trenches are shown with 1.5% ramps. Shallower ramps are not possible, since the natural grade is already nearly 1% near the Churchill crossing. Steeper ramps (2% or 2.5%) would be possible if it weren't for those freight trains. (Do we see a pattern yet with those pesky freight trains?)
  
• At Churchill, the northern ramp would not clear the existing Embarcadero grade separation. This complication might be solved by locally depressing Alma to match the track level, and rebuilding Embarcadero as a low overpass rather than an underpass--but as always, the devil is in the details.
  
• At Charleston and Meadow, the trench would encompass the existing location of the Barron and Adobe creeks. Grade-separating the creeks is possible, but it involves lots of concrete, pumps, and ongoing maintenance expenses.

While the depressed trench scenario introduces several challenges, they pale in comparison (and cost) compared to building a full-fledged tunnel.

The Big Picture

Despite the recent controversy in Palo Alto, the city is not even close to being the most difficult to build high speed rail. There are far more challenging puzzles up and down the peninsula, for example downtown San Mateo. Many of the same design principles apply to any location on the peninsula, and as time allows we'll start discussing some more of these puzzles. As for Palo Alto, the squeaky wheel gets the blog grease!

San Bruno Done Right

As previously noted in Focus on: San Bruno, Caltrain has already spent $10 million on plans to rebuild the San Bruno station with new grade separations for downtown streets. These detailed plans (refer to plan views and cross-sections) were completed several years ago, and are now dormant for lack of construction funding. The recent economic downturn is creating renewed interest in the San Bruno project, because it is technically "shovel ready" with environmental clearances, community buy-in, and preliminary design work completed. The California High Speed Rail Authority, in its drive to carve out a slice of the $8 billion of high speed rail stimulus funding, has identified the San Bruno project as one of the few "shovel ready" items it can fund before the expiration of stimulus funding in 2012. The project, estimated to cost $300 million, is likely to appear on the list to be discussed at its May board meeting. San Bruno may not know it yet, but it is definitely on the fast track.

Quick Links (discussed extensively below)

• San Bruno Done Right dimensioned plan view PDF (224kb)
• San Bruno Done Right 3D model (1.1mb) for Google Earth

Not So Fast

Caltrain's design for the San Bruno station was conceived for commuter rail operations, with two extra tracks added ostensibly for HSR but equally useful for Baby Bullet express service. Whatever they may claim, Caltrain's old design is not compatible with high speed rail and threatens to lock in two disastrous design decisions before the conceptual engineering for HSR is complete.

First, the exceedingly sharp 60 mph curve at San Bruno would delay each HSR service by about 40 seconds; this curve was previously singled out as the worst curve for HSR on the peninsula corridor. This curve is so sharp that it needs flange greasers (shown at left) to squirt lubricant on train wheels, to mitigate wear and noise. Nevertheless, Caltrain officials have expressed ambivalence about straightening San Bruno curve, believing that the few seconds it would save are insignificant. A few seconds here, a few seconds there, and pretty soon it ain't high speed rail anymore... But why should they care, indeed? Straightening the curve for 100+ mph provides zero operational benefit to Caltrain. Any why would the CHSRA care, as they are tripping all over themselves to get something--anything--funded, and shovels turning dirt? Unfortunately, jerking a high speed train through a sharp 60 mph curve is very energy intensive and environmentally wasteful, and fundamentally at odds with modern train control software which seeks to minimize energy consumption. Assuming a realistic, environmentally appropriate, energy conservative speed profile, the San Bruno curve threatens to cost HSR far more than the 40 seconds lost in a lead-foot acceleration scenario.

Second, Caltrain's new station design at San Bruno puts the platforms on the outside, with the express tracks in the center. As was discussed in Slow Traffic Keep Left, this is probably not the best arrangement for a corridor shared with HSR, mainly because Caltrain service disruptions can propagate to HSR and disrupt service state-wide. Where to put the express tracks, and thus where to place Caltrain station platforms, is one of the most fundamental design decisions to be made on the peninsula, and it should be decided by a rigorous trade study. Such a momentous, corridor-wide decision should not default to five-year-old plans drawn up outside the high speed rail project.

San Bruno Done Right

Since a picture is worth a thousand words, a 3D model may be worth a thousand pictures. Here is the future San Bruno station and grade separation done right: with the curve straightened out for 100 mph operation, and a central island platform for Caltrain.

Download Google Earth model, enable the Terrain checkbox, and click on Tour. Make sure to fully explore the details of the station area, including stairways and platform canopy. (The necessary viewer, Google Earth, is free and easy to install.) At the new San Bruno,

• All pedestrian access paths lead to the correct platform.
  
  
• High speed trains, running on the outside tracks furthest away from the platform, save at least 40 seconds by avoiding the need to slow down for the sharp curve. That doesn't sound like much, but it's nearly half a percent of the entire express run from San Francisco to Los Angeles. Savings like this are too good to pass up.
  
  
• A continuous viaduct can be built across both San Bruno and San Mateo avenues, resulting in easy pedestrian access from anywhere in the vicinity of the station.
  
  
• The changes affect only the station area and adjacent curve. The remaining grade separations are identical to those proposed by Caltrain.

To be fair, this San Bruno design does have a few drawbacks. Straightening the curve requires taking a few residential properties on Montgomery Ave. by eminent domain--politically not very savory, considering this will likely be one of the first HSR construction sites on the peninsula. Nevertheless, such takings are kept to an absolute minimum by careful design of the curve, and amount to a tiny fraction of the project's $300 million price tag. The area allocated to station parking is also reduced somewhat, although an equivalent amount of parking could be recovered on the west side of the tracks.

For the track geometry junkies out there:

• The vertical track profile is similar to Caltrain's (see Appendix B page 4).
  
  
• The new horizontal alignment (see dimensioned plan view PDF) features a 1200 m (3900 ft) radius curve, good for 109 mph at 12 inch total equivalent cant or 100 mph at 10 inches.
  
  
• The 210 m (700 ft) long by 9 m (30 ft) wide platform is very slightly tapered to minimize the area consumed by track slews at each end of the platform; the radius of the southbound platform face is 6000 m (20,000 ft) and produces a less than 1 cm (3/8 inch) ADA-friendly platform gap, with a benign, ADA-friendly 25 mm (1 inch) superelevation, as demonstrated by the Bombardier cars placed in the 3D model.
  
  
• It is likely that all four tracks can fit under the I-380 viaduct without moving any support columns. Even if this were not feasible, and supposing that it became necessary to relocate one row of six columns, the CHSRA has already demonstrated a willingness to move freeway supports in their design for the north end of Tunnel #2 under I-280 in San Francisco. If it makes sense there, it makes far more sense in San Bruno.
  
  
• In recognition of the tight clearances under I-380, accurate Bloss spiral transition curves are shown. The tracks and station foundations do not interfere with existing BART tunnel, and the curve is configured so as to fit between the I-380 support columns while minimizing excursions from the existing right of way boundaries. These improvements are likely feasible without major re-engineering of adjacent civil structures.

On the whole, this proposed configuration would be a highly effective update of Caltrain's plans for San Bruno, making them fully compatible with High Speed Rail. Can we hope San Bruno will be done right?

Many thanks to Richard Mlynarik for his 3D modeling skills and advice on track geometry.

Peninsula Rail Traffic: 2030

How much rail traffic can we expect on the peninsula by the year 2030? Both the California High Speed Rail Authority and Caltrain have projected ridership figures that allow us to estimate overall traffic levels on the peninsula corridor. Ridership figures are used to sell transportation projects to the public; more often than not, they are slightly overstated. Accordingly, consider the analysis below to be an upper bound.

Caltrain Capacity

Today, Caltrain runs 98 trains per weekday, with a peak rush hour capacity of 5 tph (trains per hour) per direction, or 6400 seats per peak hour, counting both directions. Off-peak capacity is 2 tph per direction, and weekend capacity is just 1 tph per direction.

Caltrain has about 37,000 boardings per weekday. At 98 trains/day x 640 seats/train, this figures to a 58% load factor (the average proportion of occupied seats) assuming all trips go the full length of the line. In practice, the average load factor is likely under 50%, although the most popular rush hour trains do approach 100% (i.e. standing room only).

Caltrain plans to grow its ridership, independently of high speed rail, by using electric rolling stock that can operate faster and more frequently. Their Caltrain 2025 plan calls for a peak capacity increase from 6400 seats/hour to 11000-16000 seats/hour by the year 2025. Assuming trains remain at the same seating capacity, this implies an increase in peak traffic from 5 tph to 9-12 tph per direction. Total capacity would roughly double, to about 200 trains per weekday.

Is this a reasonable estimate? It is useful to compare with BART's current traffic through the transbay tube. At peak times, BART runs about 20 tph in each direction, in 10-car trains that seat 700 and often carry crush loads of over 1000 people. Considering that BART serves a much greater geographical area than the peninsula, their 28000 seats/hour peak capacity in 2009 seems at least consistent with Caltrain's lower bound of 11000 seats/hour, achieved 15 years later. The verdict on Caltrain ridership projections: plausible (update: see comments section for a dissenting verdict: highly optimistic)

High Speed Rail Capacity

The California High Speed Rail Authority has published various ridership estimates over the years, the latest of which is contained in their 2008 business plan. The chapter on ridership and revenue estimates that by 2030, the peninsula corridor will see 8 - 10 tph per direction during six peak hours (6-9AM and 4-7PM) and about 6 tph per direction off-peak. That's a total of roughly 220 trains per weekday or 1300 trains per week.

Interestingly, there are no trains that skip San Jose or terminate at San Jose, which neatly sidesteps the rivalry between San Francisco and San Jose for the title of most important Bay Area destination.

If you assume the average HSR train seats about 400 people, that amounts to 27 million seats a year. That compares to 20 million seats a year currently offered by airlines between the Bay Area and the LA basin. (Southwest Airlines alone flies nearly 100 flights daily each way, although each one seats only about 130 people). Compared to airline traffic alone, the HSR figures sound optimistic, although most of the ridership is claimed to come from automobile traffic on the 5, 99 and 101 freeways, rather than airline traffic. Accounting for traffic growth between 2009 and 2030, which would double in that time span at an annual growth rate of just 3.5%, the verdict on HSR ridership projections is: plausible. (update: see comments section for a dissenting verdict: ludicrous)

Peninsula Traffic in 2030

Let's add it all up. Since peak hours for Caltrain and HSR will coincide with morning and evening rush hours, it is conceivable that peak traffic on the peninsula could reach 20 tph in each direction by the late 2020's (9-12 tph Caltrain and 8-10 tph HSR). Off-peak traffic would be closer to 10 tph in each direction (4 tph Caltrain and 6 tph HSR). Total weekday traffic would be about 420 trains (including both directions), an increase of four times over today's traffic levels over a span of two decades. To an observer at any given place along the peninsula corridor, there would be a train passing by on average every 1.5 minutes at rush hour, and every 3 minutes off-peak.

While the 20 tph figure is similar to that achieved by BART on two tracks, the peninsula corridor will be very different: it will support five different classes of service, each running at a different average speed.

• HSR express, SF-SJ in 30 minutes (non-stop)
  
• HSR limited, SF-SJ in 34 minutes (1 intermediate stop)
• Caltrain Baby Bullet, SF-SJ in ~45 minutes (4 intermediate stops)
• Caltrain limited, SF-SJ in ~55 minutes (10 intermediate stops)
  
• Caltrain local, SF-SJ in ~66 minutes (15 intermediate stops)

Mixing these different classes of traffic requires frequent overtaking, which explains the requirement for four tracks throughout most of the peninsula corridor.

In San Francisco, there is a different implication to this 20 tph peak figure: since all trains must run at the same speed in the final approach to San Francisco, as dictated by the tight curve radii in this area, they would no longer need to overtake each other. Theoretically, running 20 tph through this speed-restricted area could be done on fewer than four tracks-- possibly just two! With homogeneous speeds, BART does it every day through the transbay tube, meshing together trains from four far-flung lines into a 20 tph trunk with just two tracks. Similarly, Amtrak and New Jersey Transit run up to 24 tph each way on the two tracks under the Hudson river. In both cases, there are efforts underway to increase the number of tracks, but it does give you a feel for the maximum throughput of two tracks when traffic is perfectly homogeneous.

Terminal Turnback Capacity

When a train reaches the end of the line in San Francisco, it needs to be cleaned, serviced and provisioned for its next trip. From arrival to departure, these operations typically take about an hour on other rail systems. If time is of the essence, which it will be in San Francisco, the turnback time might be reduced to about 30 minutes, very low by rail standards and commensurate with airline operations. The Transbay Transit Center is planned to have just six platform tracks shared by HSR and Caltrain, a very small number by international rail terminal standards. If a train occupies a platform track for just 30 minutes at a time, the maximum turnback capacity of a six-track terminal is 12 trains per hour.

This highlights another interesting feature of San Francisco rail operations: overall capacity into and out of the city will be constrained by terminal turnback capacity, and not by track capacity. You could build a six-track approach into San Francisco, but you still couldn't squeeze more trains in and out of the city.

Solutions to this Transbay turnback constraint include:

• Turning some trains, most likely Caltrain services, at another station. The existing Caltrain terminal at 4th & King streets might be retained for this purpose.
• Turning some HSR services at San Jose. This has the added benefit of reducing traffic on the peninsula.

Whatever happens between now and 2030, it is likely that the peninsula corridor will be hardly recognizable when compared to its current state.

The Top 10 Worst Curves

The peninsula corridor was laid out in the mid 19th and early 20th centuries, for train speeds of that period. It is the oldest passenger line west of the Mississippi. Needless to say, rail technology has progressed enormously in the last 100 years. The California High Speed Rail Authority is now planning to run trains on the peninsula at a top speed of about 125 mph. Sounds great, but what about all the curves? (Bayshore curve photo by Michael Patrick)

Minimum Curve Radius

To allow HSR operation at 125 mph, just how wide does a curve need to be? This is an elementary calculation of railway engineering, and is determined by safety and passenger comfort. Without going into details, speed can be increased in a curve by banking the track into the turn, like a turning airplane or a freeway exit ramp. The outside rail can be canted or super-elevated a maximum of 7 inches (178 mm) higher than the inside rail. Trains can go even a bit faster than the speed that balances this banking, causing passengers to feel a sideways push to the outside of the curve. The technical term for this is cant deficiency, and under current FRA regulations it is limited to 3 inches. Within those limits (7 inches cant + 3 inches cant deficiency), physics dictates the following curve radii:

Speed	Minimum Radius	(Recommended Radius)
160 km/h (100 mph)	1200 m (4000 ft)	1800 m (5900 ft)
200 km/h (125 mph)	1900 m (6300 ft)	2800 m (9200 ft)
215 km/h (135 mph)	2200 m (7300 ft)	3200 m (10500 ft)

The recommended radius is preferred, in the absence of trackside constraints such as houses and roads, to keep passengers comfortable and reduce wear and tear on the trains and the track. Wherever curve clearances are constrained (i.e. pretty much anywhere on the peninsula), the minimum radius becomes the quantity of interest.

The Cost of Slowing Down

Slowing down from 125 mph to take a curve, and accelerating back up to 125 mph costs several seconds of travel time, compared to an uninterrupted run at 125 mph. It's just a few seconds, but if every curve eats a few seconds out of the schedule, pretty soon HSR starts losing its "high speed." So exactly how many seconds are too many? Maybe the answer lies in the cost of a second. If you assume:

• HSR annual ridership will be 60M passengers / year (considerably less than the CHSRA's estimate)
• About one third of all HSR passenger trips will include the peninsula segment
  
• The average passenger (leisure and business) values their time at $12/hour (an approximate value based on time value studies)
  
• The cost of straightening a curve is amortized over 15 years of operation (the continuing benefit beyond 15 years is free)
  

Then each second of delay costs about $1 million of lost time to HSR passengers, and could be worth about $1 million in construction costs to remediate. That does not include the ancillary benefit to Caltrain Baby Bullet passengers. One can take issue with the exact assumptions and accounting methods, but the point of this exercise is to gain a very rough order of magnitude understanding for the cost of a second: on the order of a $1 million.

Using a typical deceleration / acceleration rate of 0.5 m/s^2, the cost of temporarily slowing down for a typical curve from a cruise speed of 125 mph goes as the square of the speed difference:

Curve Speed (mph)	Time Penalty (s)	Delay Cost
115	3	$3M
105	7	$7M
95	13	$13M
85	21	$21M
75	31	$31M
65	43	$43M

The square relationship means that it's not necessary to straighten curves all the way up to 125 mph. Arbitrarily setting our threshold of diminishing returns at 5 seconds of penalty, 110 mph curves can be considered "good enough" unless they can be straightened to 125 mph within the existing right of way, essentially for free. The reconstruction of any curve below 110 mph should be weighed against the dollar cost of time lost.

While this author is not versed in the fine art of estimating construction costs, we now have enough information to at least prioritize the worst curves where something should be done, short of deciding which ones are actually cost-effective to rebuild.

Existing Curves on the Peninsula

All major sub-125 mph curves in the Caltrain corridor from San Francisco to San Jose are shown in the chart below. Milepost is plotted along the bottom, and the curve's maximum speed is plotted on the vertical axis. The maximum speed is derived from the curve radius by assuming the aforementioned 10 inches of equivalent cant, except for reverse curves where different constraints apply. (Note, these speeds are not possible today; the maximum cant on Caltrain is 5 inches to accommodate freight trains, and the signaling system allows only 79 mph.)

Click for Larger View. First, there are quite a few curves that interfere with a 125 mph speed limit, as indicated by the blue dotted line.

• Several curves fall above the 110 mph "good enough" threshold, indicated by the green dotted line, although they should still be candidates for realignment if they are easy to fix. Recall these speeds are absolute maximum speeds, with 3 inches of cant deficiency (passenger discomfort).
  
• Some curves are very tight, but would be impossibly expensive to straighten; an example is the Sierra Point curve, which runs around the base of San Bruno mountain. There are other sharp curves in the San Francisco and San Jose terminal areas that fall into this category.
  
• One curve will be avoided entirely by HSR: the infamous CEMOF double reverse curve in San Jose, where the most expensive way to avoid a curve is planned, namely a tunnel.

Leaving aside these "impossible" curves and the "good enough" curves, we can examine the remaining curves and construct a list of the worst curves for HSR on the peninsula.

The Top Ten Worst Curves

Here's a Google map, although it is much more accurate and instructive to view the KML file directly in Google Earth.


View Larger Map

#10 (Honorable Mention) CEMOF Double Reverse Curve - Milepost 46.5 - While the CHSRA plans a tunnel under this area, you really have to wonder what Caltrain was thinking when they dropped this turd on the approach to San Jose. That's why it gets an honorable mention.

#9 Belmont - San Carlos Reverse Curve - Milepost 22.4 - While we're adding another two tracks here, the incremental cost of straightening this curve to 125 mph ought to be near zero, since it can probably be done within the existing ROW. Savings: 10 seconds.

#8 San Antonio Curve (see curve detail map) - Milepost 34.3 - Great potential for straightening to 125 mph, again within the existing ROW. Savings: a couple of seconds, but it's free!

#7 Bowers Curve (see curve detail map) - Milepost 41.9 - Already OK for nearly 110 mph, but could use as much flattening as practical because of the proximity of Lawrence curve.

#6 Lawrence Curve (see curve detail map) - Milepost 40.6 - This shallow 100 mph curve can easily be straightened all the way up to 125 mph by purchasing a narrow strip of office parking lot (which Sunnyvale has plans to redevelop anyway). This is low-hanging fruit, well worth the 10 second savings.

#5 Hayward Park Curve (see curve detail map) - Milepost 18.8 - This curve was already straightened in the year 2000 by moving the rails by 20 ft. It might now support 95 mph. Would be better at 110 mph, saving about 10 seconds.

#4 Millbrae Curve (see curve detail map) - Milepost 13.9 - An unfortunate consequence of the last Quentin Kopp extravaganza, the BART airport extension. Challenge: BART tail tracks occupy the inside of this 90 mph curve. BART would have to give up one of three tail tracks to straighten for 100 - 110 mph operation. This ought to be feasible: two of the tail tracks were built in anticipation of a BART extension south of Millbrae, which no longer makes sense. Savings: about 15 seconds.

#3 Palo Alto Station - Milepost 30.1 - Already discussed in Focus on Palo Alto. While the existing curve radii are gentle, the problem at Palo Alto is a double reverse curve, which requires long spiral easements to reverse the curvature and prevents the speeds you might deduce from the radius alone. The southbound track is good for just under 90 mph. Challenge: reconfigure the Alma St. overpass; on the plus side, JPB already owns all the required land. Savings: about 25 seconds. A must-do, regardless of whether Palo Alto becomes an HSR station.

#2 Bayshore Curve (see curve detail map) - Milepost 5.1 - Just north of the Bayshore station at the mouth of Tunnel #4, this curve is a piece of cake to straighten to 125 mph, provided Bayshore station is redone. This will probably happen anyway to make room for the approaches to the planned new tunnel bores on each side of the existing tunnel. The new tunnel bores could even have curved ends. Savings: about 20 seconds. Cost of new platforms: $10M tops. Low hanging fruit, just waiting to be picked!

#1 Worst Curve: San Bruno Curve (see curve detail map) - Milepost 10.9 - previously discussed in the San Bruno article. This curve, currently 65 mph, should be straightened to 110 mph minimum. Savings: a whopping 40 seconds. Challenges: well-advanced plans by Caltrain for a new station, locking in the existing curvature; eminent domain for ~$5M worth of houses on the inside of the curve; six I-380 viaduct pillars would need to be moved. If this curve can be fixed even for $30-40M, JUST DO IT!

The total time saved from straightening these 10 curves is about 2 minutes, not including the savings from straightening the other 110 mph+ curves not listed here. These time savings add up to ~7% of the non-stop travel time between San Francisco and San Jose, expected to be around 30 minutes.

The CHSRA and its engineering contractors should not resign themselves to the existing curvature of the peninsula corridor. A rigorous study of curve remediation should be undertaken before the new track alignments are finalized.

Update - 02 Feb 09

It was brought to my attention that the CHSRA published in its considerable (if un-navigable) body of work a series of run simulations. This is what the pros do, instead of the back-of-the-envelope calculations detailed here. A sample San Jose to San Francisco run is detailed below. The train used in the simulation is a Siemens ICE 3. It does not stop in San Jose in this particular example. Total time from San Jose (running start) to San Francisco is a few seconds short of 30 minutes (1793 seconds, to be precise)

This simulation reveals a couple of interesting assumptions on the part of the CHSRA's analysts:

• Total cant is 12 inches (vs. 10 inches assumed in the calculations above) allowing 10% higher curve speeds. This is not outlandish: 12 inches is practiced today on the NEC.
  
• The Palo Alto and Bayshore curves are evidently straightened out, with a curved platform at Palo Alto
  
• None of the other bad curves appear to be straightened, as revealed by the three deep notches in the speed profile at Hayward Park, Millbrae and San Bruno.
• The train's throttle is used heavily, and the regenerative brake will certainly get a good workout. Whether this lead-footed driving style is realistic is open to discussion.
  

While these assumptions are self-consistent and do not violate any laws of physics, they are somewhat optimistic. This is another reason to straighten San Bruno curve: then you could do SF to SJ in 30 minutes with margin.

Judging a Train By Its Nose

One of the recurring themes emerging from public comments about HSR on the peninsula, at scoping meetings or on community bulletin boards, is the notion that HSR on the peninsula merely duplicates existing Caltrain service at astronomical expense and disruption to communities. The reasoning goes like this: why bother with HSR running at "half speed" on the peninsula if passengers can just catch a Baby Bullet in San Jose that whisks them into San Francisco? We've already got a bullet, so why do we need another one? If HSR is only running at "half speed" why not use the existing tracks? Those are good questions.

One thing is certain, Caltrain has scored a marketing home run with their Baby Bullet brand, borrowing the aura of high speed rail and pointy-nosed aesthetics to convey an image of speed and efficiency. Unfortunately, there are a couple of problems with confusing the Baby and its namesake.

Myth #1: Speed

"We already have a bullet. We don't need another one!"

Baby Bullets look sleek, and they impress when they blast by, horn blaring. However, they are nowhere near as fast on average as the proposed high speed trains. Timings from San Jose to San Francisco:

• Caltrain local: 96 minutes - max speed 79 mph - average speed 29 mph
  
• Caltrain Baby Bullet: 57 minutes - max speed 79 mph - average speed 49 mph
  
• HSR: 30 minutes - max speed 125 mph (a.k.a "half speed") - average speed 94 mph
  

HSR at "half speed" is still nearly twice as fast as the Baby Bullet. Suppose HSR were terminated in San Jose, and that passengers transferred to Caltrain. Accounting for transfer time in San Jose, the effective speed of the Baby Bullet ride would approach three times slower than a single-seat HSR peninsula ride. The overall trip from LA to SF would increase from 2:38 to 3:15, an increase of about one quarter. If we compromise that much on the peninsula, why even bother with 220 mph in the central valley? Indeed why bother with high speed rail at all?

Ridership is very sensitive to total trip times and changing trains. Every second counts. That is the reason for terminating HSR in San Francisco, which has a large catchment area of potential riders.

Myth #2: Track capacity

"If HSR is running at half speed, let them just use the existing two tracks!"

Mixing trains with different average speeds on the same track reduces track capacity, measured in units of trains per hour (tph). A slow train must be given plenty of time to clear the tracks ahead of a fast train that follows; otherwise, the fast train will catch up to the slow train and get stuck behind it. While modern signaling systems allow 15 tph when speeds are homogeneous, today Caltrain can only manage 5 tph at rush hour because Baby Bullets and locals operate at very different speeds. Add HSR to the mix, and what little track capacity we have would collapse.

More tracks are needed along much of the peninsula to allow trains with vastly different speeds to overtake each other, thus freeing track capacity. This ultimately has benefits for local Caltrain service as well: with Baby Bullets allowed to operate on the new HSR tracks, local track capacity will increase, enabling more rush hour service to under-served stops like California Ave or Belmont or South San Francisco.

Never judge a book by its cover. Likewise, never judge a train by its pointy nose.

Focus on: Palo Alto

Palo Alto was founded in 1887, several decades after the railroad tracks were first laid between San Francisco and San Jose. The town grew and filled in around the railroad tracks, and now has one of the busiest stations on the Caltrain line (shown at right; credit cdent), second only to San Francisco. Palo Alto today handles nearly 50% more riders than San Jose's Diridon Station, vaunted as tomorrow's "Grand Central of the West." Palo Alto is also a major stopping and transfer point for Caltrain's Baby Bullet express trains. That is why Palo Alto, along with Redwood City, is under consideration by the CHSRA as the possible location for a mid-peninsula high speed rail station.

Whether or not this new station is located in Palo Alto, the CHSRA's choice of the Pacheco Pass alignment via San Jose means that high speed trains will run through the town along the Caltrain right of way, which will be widened to four tracks and electrified.

The following sections of this article consider HSR impacts to Palo Alto roughly from north to south. With no further introduction, let us scroll southwards:

San Francisquito Creek

The CHSRA's environmental impact documents describes the tracks crossing into Palo Alto at grade over the San Francisquito Creek, with two tracks on the existing historic (relic?) truss bridge, and two new tracks added to the west. The famous El Palo Alto tree, California Historical Landmark Number 2 and the landmark for which the town is named, is thus spared any direct impact. Perhaps an even better idea would be a new 4-track deck bridge, to get rid of the truss that crowds out the historic tree. (By the way, the San Francisquito creek area was also where ground was broken for the peninsula railroad on May 1st, 1861.)

The Palo Alto Ave. (a.k.a. Alma) crossing right after the bridge would become an underpass, and perhaps not an easy one to build considering the proximity of the San Francisquito aquifer.

The right of way is 100 to 120 ft wide in the area of the creek crossing (see ROW map), leaving plenty of room for four tracks.

Palo Alto Station Area

The existing Palo Alto depot, with its distinctive "Streamline Moderne" style, was opened in 1941. It is the third depot building that has existed at this location. The station once had three tracks running through it; today, the middle track has been dismantled, leaving a wide space between the two platforms. The platforms and pedestrian underpass were recently renovated by Caltrain, as part of a $35 million improvement project.

The impact of high speed rail on the Palo Alto station area will depend on whether or not the town becomes the mid-peninsula HSR stop. However, regardless of this outcome, the station area will require some reconfiguration to accommodate high speed trains passing through the station at speeds of 125 mph (200 km/h), as planned by the CHSRA.

The Palo Alto Chicane

The existing 1940s station, along with the underpass for the town's main street, University Avenue, were built alongside the tracks that previously existed there, presumably to allow uninterrupted service during construction. As a result, the entire station is offset laterally to the west of the straight alignment of the peninsula tracks; the northbound track is offset by 60 feet, and the southbound track by 85 feet (shown in the photo at right by ibison4). While this arrangement is fine for the speeds practiced today, it will look like a chicane to an approaching high speed train. At speeds of 125 to 150 mph (200 to 240 km/h), curves must have radii of at least 1 to 1.5 miles (1800 to 2300 m), with adequate spiral easements entering and leaving each curve. While there is enough room to run such curves through the present footprint of the Palo Alto station (see map below for approximate property limits), it will require a total reconfiguration of the tracks through the station.

At 150 mph, the maximum lateral track offset comfortably achievable within a run of 1500 ft (about the room available on each end of the existing station) is about 20 ft. At 125 mph, it is about 30 ft. Both of these values are much lower than the present lateral offset of 85 ft (on the southbound track), which would require a train to slow to about 85 mph (135 km/h). It may seem easy to slow down a bit through Palo Alto, but it would cost about a minute (over half a percent) on the overall SF - LA run times. If every trouble spot from San Francisco to Los Angeles cost a minute, HSR would never be possible; therefore, just like San Bruno's sharp curve, today's Palo Alto station alignment should be considered a serious obstacle to HSR on the peninsula.

To reconfigure the station for higher speeds, it is possible to (a) straighten the station by shifting the tracks closer to their ancestral straight-through alignment, as depicted in an effortless hand sketch in the CHSRA's "station fact sheet", or (b) make the tracks bow out westward on a smooth and continuous curve, which requires building gently curved platforms. Due to the overall width required for four tracks and two platforms, parking will need to be moved elsewhere from the east side of the station, and the Alma St. overpass that runs parallel to the tracks will need to be completely reconfigured. (This overpass, as it exists today, is built on railroad land.) The existing northbound platform would have to be demolished; however, the money recently spent to rebuild it is but a drop in the HSR bucket.

With the track alignment issue taken into consideration, there are basically two scenarios for the Palo Alto station area, where railroad land is abundant (see ROW map).

HSR Station Scenario

If Palo Alto chooses to become the mid-peninsula stop for high speed rail, the impact to the station area will obviously be greater. However, an expanded station would also create opportunities for more frequent and efficient Caltrain service, in addition to long-distance HSR service. It would become possible to operate timed, cross-platform connections between Caltrain local and express trains.

The CHSRA shows in its station fact sheet that Palo Alto would be rebuilt with two island platforms located between the inner and outer pair of tracks, a configuration that is favorable to cross-platform transfers. One is left to wonder why this configuration was not chosen for Millbrae as well. The basic cross-sectional dimensions from this station fact sheet are reproduced in the map below, with curved tracks bowing out such that the curve apex coincides with today's southbound track. The two island platforms are curved as well, but their radius of 3.5 miles (yes, miles!) might as well be straight for purposes of platform boarding and alighting. A more accurate version of this map is also available by downloading the original KML file into Google Earth. Note that if the existing depot building were demolished or moved, it would in principle be possible to shift the curve apex a further 15 meters (50 feet) west of the existing southbound track, possibly relieving some of the design constraints on the Alma / University road overpass.


View Larger Map

The station would require a new parking garage, with easy access from El Camino Real. The nearby El Camino Park would not be affected.

No HSR Station Scenario

If the mid-peninsula HSR station is built in Redwood City instead of Palo Alto, the station would be expanded to four tracks flanked by two outside platforms, with no platforms on the center high-speed tracks. Since there is only enough room for three tracks through the existing station, the northbound platform would most likely be moved (i.e. demolished and rebuilt), providing room to straighten the center express tracks and add the fourth track.

One design consideration, among many, is whether or not to preserve the existing three track alignments over the University Ave. underpass, only two of which are currently in use (as shown in map above). Shifting these track alignments may have impacts on the load-bearing structure of the underpass. (Update: there are actually four track ways across the overpass... one of them sits under the southbound platform, and it's unclear if it was ever used.)

No matter what happens at the Palo Alto station, expect a big rearrangement on the east side of the station, with serious impact to the Alma St / University Ave overpass. Given that major reconstruction will be required either way, Palo Alto ought to give serious consideration to "biting the bullet" and building the HSR station.

Bike Path

An existing bike path along the west side of the tracks, from the Palo Alto Medical Foundation to the Churchill Ave. crossing, is partially built on a revocable easement of Caltrain land (see ROW map). Widening to four tracks will require the bike path to be removed from this location. The existing bike tunnel would also have to be reconfigured. From approximately this location until California Avenue, the Caltrain right of way is narrower than 100 feet. From the station to Churchill Ave, the ROW is 85 feet wide.

Churchill Ave Grade Separation

The CHSRA plans a split grade separation for the existing Churchill Ave grade crossing, located behind Palo Alto High School. Refer to Volume 2, Appendix D, page 5 of the Bay Area EIR/EIS. The preliminary concept for this split grade separation would raise the tracks by 15 feet (4.6 m) on a retained embankment (i.e. an embankment with vertical walls) to pass over Churchill Ave, with the latter lowered by about 6 feet (1.8 m). It is difficult to lower Churchill further due to the proximity of the intersection with Alma St.; the impact of lowering the intersection must be traded off with the impact of the retained embankment.

Due to constraints on the vertical curvature of the tracks for planned operation at 100-150 mph, the approaches for a 15-foot raised embankment would necessarily be long, on the order of 400 m (1/4 mile) on each side of the overpass. Shorter approaches would make passengers feel uncomfortable as the train crested over the top. This is why the area behind Palo Alto High School as well as a good portion of Southgate would be affected by the long Churchill grade separation embankment described in the CHSRA's documents (although the 3% ramps described in Volume 2 Appendix D are not feasible).

Architect and local resident Jim McFall has produced video renderings of what this grade separation might look like, although he modeled it a full 21 feet higher, rather than the 15 feet assumed in CHSRA documents. It is likely that Churchill could be depressed ~6 feet from the current track level.

Southgate

Southgate is a neighborhood that abuts the western edge of the tracks, just south of the Churchill Ave crossing. This area is one the narrowest portions of the railroad right of way owned by Caltrain (see ROW map). The overhead view at right, superimposed with a scale ruler, shows about 75 feet of horizontal clearance between the back fences of houses on Mariposa Street and the Alma Street curb on the other side of the tracks. Eminent domain takings, even for as little as 10 feet into these properties, might be necessary to build four tracks through the area without constraining Alma St. This would be in addition to the impact of the raised embankment used to cross Churchill Ave.

As was described in a post about electrification, it would in principle be possible to squeeze the four-track right of way into an overall width of 75 feet, where no additional clearance exists. Whatever happens, it's a tight fit.

Peers Park

The railroad right of way is a mere 60 feet wide alongside Peers Park. Four tracks will likely require an encroachment of at least 15 - 20 feet into Peers Park, and the removal of all the mature trees along the railroad edge of the park. Immediately after the park, the railroad right of way returns to a more generous width of 95 feet.

California Avenue Station

The HSR tracks are expected to pass the California Ave. area at grade level. The station was recently rebuilt by Caltrain, under the $35 million Palo Alto stations project. The platforms and underpass would have to be partially demolished and rebuilt to make room for four tracks.

South of California Avenue, the right of way has a width around 100 feet or more. For details, see ROW maps for mileposts 31-32, 32-33, and 33-34.

Meadow and Charleston Grade Separations

While Palo Alto has just four grade crossings that are not yet grade separated, two of them, Meadow Drive and Charleston Road, are located just 1/3 of a mile (500 m) apart at the south end of town. (see also ROW map). The CHSRA documents describe a 7 foot (2.1 m) retained embankment at this location. This would require lowering each road by 14 feet, with the consequence that the nearby intersections with Alma St. would be lowered as well. Ramps for a 7-foot embankment would need to be about 1000 feet (300 m) long on each end for operation at 125 - 150 mph.

The tracks would return to grade level before San Antonio Ave.

Vertical Track Profile

The vertical track profile is the level of the tracks (raised above grade, at grade, or below grade). Working from Caltrain track survey data, here is the profile of Palo Alto, with the vertical scale greatly exaggerated: (click to expand)


HSR will significantly modify this profile. A detailed discussion of the vertical profile options for Palo Alto, including what can and can't be done with the tracks, is written up in the Shape of Palo Alto.

The Tunnel Idea

Some members of the Palo Alto community have suggested putting the tracks underground through most or all of Palo Alto, removing the barrier formed by the existing tracks and opening up the former railroad land to development of housing and parks. This idea was the subject of a cover story by the Palo Alto Weekly. The proponents of the idea suggest that HSR funding might be used to build such a tunnel. However, since the benefits of the tunnel would be solely to local residents (and not to users of HSR) it is probable that Palo Alto would need to foot most of the bill for a project that promises to cost hundreds of millions, if not billions, of dollars--especially if Alma St. traffic and Caltrain continue to operate during construction.

In conclusion, it will be interesting to watch Palo Alto's reaction to HSR impacts. The majority of residents voted for Proposition 1, and the city council supports HSR in principle, but the impact on affluent neighborhoods and the famed "Palo Alto Process" should make this an interesting show to watch.

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