Future Proofing Hillsdale

The next big grade separation project on the peninsula rail corridor will be at 25th Ave in San Mateo, a logical next step in the decades-long process to grade separate the corridor.  This grade separation will establish a 6.5-mile stretch of 100% grade separated right of way, laying the groundwork for a future four-track mid-line overtake facility that will allow express trains to overtake slower commuter trains under the "blended system" jointly planned by Caltrain and the HSR authority.

Preliminary rendering of new
Hillsdale station with island platform

The latest plans presented to the Caltrain board of directors show a split-grade elevated solution, built sufficiently wide for four tracks but initially only fitted with two tracks spaced on approximately 48-foot centers.  The Hillsdale station is moved north by a quarter mile to straddle 28th Ave, and fitted with a central island platform sized approximately 36 x 700 feet and built 8 inches above the rails.

Vertical circulation to this island platform is provided at the north end (two stairways connecting to the sidewalks on each side of the new 28th Ave underpass) and the south end of the station (a new pedestrian tunnel with one stairway and one wheelchair ramp).  In cross section, the new Hillsdale might look like this:

Of course, the accelerated schedule for its completion is closely linked to electrification, so quite soon thereafter it might look like this, with mixed diesel and EMU service.  Note that per Caltrain plans, the overhead contact system is 22 feet above the rails. plenty to clear even the tallest freight cars.

It's not too difficult to guess what happens when the blended system overtake tracks are built: the new platform and all associated vertical circulation (stairs and ramp) will be demolished, to be replaced by a pair of new express tracks right down the middle of the corridor.  A first phase of this "New New Hillsdale" station would like this, hopefully with level boarding platforms.  Note the new portal configuration of the overhead electrification, to span across four tracks and two platforms without placing poles close to the edge of the new platforms:

After demolition of the "New Hillsdale" island platform, the original 48-foot track centers allow for two additional overtake tracks and a central fence (track spacing 15 + 18 + 15 feet) to prevent passengers from crossing between the two new side platforms of the "New New Hillsdale."  Including stairs, the "New New" station is 106 feet wide and looks as much as possible like any station on Amtrak's Northeast Corridor.  It could almost be mistaken for Princeton Junction:

While it's a fine idea to build the new grade separation sufficiently wide for four tracks, demolishing the "New Hillsdale" station only to replace it so soon with a "New New Hillsdale" seems terribly wasteful. Perhaps this is another case of "why build it right when you can build it twice?" Surely there is a better way.

Rebuilding Hillsdale Once and for All

There's a much better way to build the New Hillsdale once and for all.  It initially looks like this:

Note the central island platform is a full-height level boarding platform, disguised for now as an 8-inch platform by raising the track bed by 51 - 8 = 43 inches using a thicker-than-usual layer of ballast. The final footprint of this station, which will ultimately have the HSR overtake tracks on the outside, is less than 100 feet wide at the platform. The footprint will never change; all the concrete has been poured and not another cubic yard is needed in the future. Soon after electrification, mixed EMU and diesel service would look like this:

The overhead contact system is built in its final configuration 22 feet above the eventual height of the tracks; because the tracks are raised by 43 inches, the vertical clearance is temporarily reduced to 18' 5" which still safely accommodates Plate F freight cars, the tallest that have historically been used in this part of the corridor.  Therefore, there is no constraint to freight service.  This electrification will never change, with all the portals in their final configuration.

When all the diesels are gone and it's time to transition to level boarding, a track maintenance project takes place over a weekend.  43 inches of ballast are removed from under the tracks, using standard track maintenance machines.  The rails are never even disconnected.  (Not to be too flippant, this is still a major track maintenance operation that would require sophisticated planning and modern high-capacity machinery; but it is certainly within the realm of what Caltrain has done before.) Minor lateral adjustments are made to track and overhead contact system alignment, yielding this for the Monday morning rush:

Not a single cubic yard of concrete is required either to convert to level boarding, or to add the overtake tracks once HSR service begins on the peninsula.  The final blended system configuration is ultimately this:

Built once, and built right!

That FSSF Thing

Placing the express overtake tracks on the outside, in a fast-slow-slow-fast or FSSF configuration, as opposed to the traditional slow-fast-fast-slow or SFFS configuration inspired by road design, is a key architectural decision for the blended system.  The forces of traditionalism will argue strongly for SFFS because that's how it's "always" done, yielding nice straight express tracks down the middle of the corridor-- but clear exceptions to this "rule" exist, with examples of FSSF corridors in these videos from Sweden (with 125 mph express trains!) and Australia.

The fatal operational flaw of traditional SFFS corridors is that when a track must be taken out of service, either accidentally or intentionally for maintenance, commuter trains either must cut across the express tracks (fouling express traffic) to reach the opposite platform, or use super awkward bridge plates to board from the fouled express track.  In contrast, an FSSF island platform is operationally flexible: the train simply crosses over to the opposite side of the island, without ever getting in the way of express traffic.  For the peninsula "blended system" where Caltrain and HSR share the corridor, the operational headaches of SFFS could prove unworkable in the long run as the rail corridor is maintained.

One argument systematically trotted out against FSSF is this: wowing express trains around the outside of every island platform will make for a slalom "barf ride" that will give HSR passengers motion sickness, if not downright whiplash.  This argument intuitively rings true, but turns out to be patently false when you run the numbers.  In reality, an express train blasting around the Hillsdale island platform at 125 mph will do so on curves with a radius greater than four miles, requiring just 2 inches of superelevation to be rendered imperceptible to passengers.

Download FSSF island platform plans
for every station on the Caltrain corridor
(3.3 MB PDF, see page 9 for Hillsdale)

Another argument leveled against FSSF is that the island platform arrangement requires additional right of way compared to a traditional SFFS outside platform arrangement.  The footprint of a FSSF station can be made nearly as compact as a SFFS station, especially if the central island platform (shown in the above diagrams at 33 feet wide) is slightly tapered at its ends, yielding an imperceptibly curved platform that is for all practical engineering purposes the same thing as a tangent (straight) platform. In any case, the available right of way at the Hillsdale location is a generous 150 feet wide, making such footprint considerations moot.

The Takeaways

• DON'T rebuilt infrastructure multiple times.
• DO build it once and build it right, in its final configuration
• DON'T build station platforms that are not compatible with level boarding, where this can be avoided.
• DO create the Caltrain engineering standards for level boarding.
• DO build the new Hillsdale station with a level boarding platform, years before the transition to level boarding occurs, by temporarily raising the track bed to make the platform only 8" tall.
• DO build the new Hillsdale station as an island platform, even after high-speed overtake tracks are added
• DO put the high speed tracks on the outside, in the FSSF configuration, for operational flexibility.

Optimizing the Midline Overtake

The most important piece of infrastructure required for "blending" HSR with Caltrain on the peninsula rail corridor is an overtake facility, basically a several-mile long stretch of up to four tracks that will enable faster trains to overtake slower trains.  Caltrain studies have shown that the best performance (measured by robustness to cascading delays) can be achieved with a midline overtake  from San Mateo all the way through Redwood City.  Preliminary engineering and environmental clearance for this infrastructure is now resuming, with the recent award of a $36 million contract by the CHSRA to engineering firm HNTB.

The baseline configuration for this overtake is described in Caltrain's blended operations analysis, and assumes rebuilt stations at Hayward Park, Hillsdale, Belmont, San Carlos and Redwood City with four tracks and outside platforms in the tried and true style of the 1930s Pennsylvania Railroad. High-speed trains would use the center pair of tracks to overtake slower trains on the outside pair of tracks, as shown below (click figure to enlarge):

For comparison, the figure also shows a better solution that ensures the highest level of punctuality for all trains using the corridor.  This optimized overtake configuration differs from the baseline configuration as follows:

• The slow trains run in the middle, so that disruptions to local commuter service (for example, when an incident blocks a track for hours) do not disrupt high-speed service when commuter trains are re-routed around the incident location.  This track configuration is known as Fast-Slow-Slow-Fast (FSSF) as opposed to the traditional SFFS.  Real world examples of FSSF can be seen in train cab videos from Sweden and Australia.
   
• All commuter stations are built with central island platforms.  This allows commuter trains to use either platform face without confusing passengers, and requires only one set of station amenities (shelters, elevators, escalators, stairs, ticket vending machines, PA systems, train arrival screens, lighting, benches, etc.) because there is only one platform.
   
• A major new interchange station at Redwood City, with four platform tracks and additional train storage sidings.  This station (described below) would serve as a transfer point for HSR, Caltrain and future Dumbarton trains, as well as non-rail transportation modes.
   
• A carefully planned future-proofed high-speed rail junction where the Dumbarton rail corridor meets the peninsula rail corridor, preparing for the inevitable arrival of passenger rail service across the Bay.

Here's how it would ideally play out.

Short Term: the San Mateo Grade Separation

Preliminary rendering of new
Hillsdale station with island platform

The next step in the decadal process of grade separating the peninsula rail corridor will soon begin in San Mateo.  A new $180 million grade separation project is in the final stages of planning for 25th Avenue (currently a grade crossing) as well as 28th and 31st Avenues (currently not connected).  Concurrently with this project, the busy Hillsdale station will be moved a bit north of its current location and turned into an island platform.

This project is caught in an interesting political bind.  There is on one hand a rush to complete it by 2019 before Caltrain's electrification project, to minimize disruptions to Caltrain service.  On the other hand, due to its strategic location, this project will form a key building block of the blended system with HSR, which still needs to be environmentally cleared.  It is a near certainty that this portion of the corridor will require four tracks to enable trains to overtake each other, but any attempt to design and build it as such is likely to run afoul of HSR opponents who will accuse the CHSRA of advancing their project through CEQA piece-mealing.

The southern San Mateo grade separation design will have to be very carefully considered to preserve the ability to add two additional tracks with as little disruption as possible.  Road underpass profiles and bridge abutments should be designed for four tracks, as should the elevated structure that will support the tracks.

The choice of an island platform configuration for the new Hillsdale station is either a sneaky way to build a wide four-track embankment in preparation for yet another new station with SFFS outside platforms, or is an excellent choice for FSSF because it allows future tracks to be added without rebuilding the station for a second time.  One hopes the station access (stairs, ramps, etc.) will be designed to allow the platform height to be raised easily from 8" to 50".  An intelligently designed San Mateo grade separation would atone for the terrible failures of the San Bruno grade separation, designed with great hostility towards higher speeds or additional tracks.

Medium Term: Redwood City HSR Station

Amsterdam Bijlmer (photo by tataAnne)
could just as well be the future
Redwood City train station.

While the CHSRA's plans for a mid-peninsula stop have been shrouded with ambiguity for several years, Redwood City stands out as a more optimal location for a new HSR station than Palo Alto or Mountain View, the other two locations in the running.  Unlike its neighbors to the south, Redwood City favors strong urban growth, has a large amount of railroad land available, and is reasonably well-connected to the existing road and transit network.  Redeveloping the antiquated but popular Sequoia Station shopping center would enable the construction of an elevated four-track station with plenty of capacity to support not just HSR but also Caltrain cross-platform connections and future Dumbarton service.

The station complex would feature two shared (HSR or Caltrain) 400-meter island platforms centered between Broadway and Brewster, easily accessible from both streets.  Bus connections would be conveniently located under the station. To the north of the platforms, a pocket turnback track would allow Dumbarton trains to reverse without fouling other traffic.  Similarly, to the south of the platforms, another pocket turnback track would allow southbound Caltrain locals to terminate in Redwood City before turning northwards again to serve the densely-spaced stations of San Mateo County, allowing Caltrain to serve more passengers with fewer trains and crews.  Thanks to the FSSF configuration, all this to-and-fro by commuter trains would stay well out of the way of HSR.

This would be a large train station and quite a tight fit (if you're curious about exactly how large and how tight, download this KML file into Google Earth to view the station footprint and track layout).  It would be a big change for Redwood City, but with a huge payoff: the tracks would no longer form a barrier through town, and the Sequoia Station shopping center would be merged with the station to form a gateway and a destination in its own right that is connected to downtown.  HSR service could make the city a very desirable location for business.  The new station could become the centerpiece of the ambitious revitalization strategy described in Redwood City's downtown precise plan.  But this idea is not without pitfalls, as the size of the station could be compared to plonking a couple of Nimitz-class aircraft carriers in the middle of town.  To use the tired slogan, it needs to be done right.

Medium Term: a New Fair Oaks Station

Approximate location of new Fair Oaks
station island platform, view to northeast.
Overtake would extend just beyond
platform to the right (south).

The key to reliable overtaking on a multiple-track railroad is to ensure that the average speed of the slower train being overtaken is sufficiently slower than the average speed of the faster overtaking train.  One of the ways of ensuring a good speed differential is to have the slower train make station stops that the faster train doesn't; each station stop is worth about 2.5 minutes.  Therefore, locating stations on the four-track overtake section is helpful.

This brings us to a lemon of a station immediately south of the midline overtake: Atherton.  Located in an area of very sparse population and jobs density, Atherton should be permanently closed.  This closure would come not only as a show of appreciation commensurate with the town's support of Caltrain modernization, but especially because census data shows clearly that Atherton is precisely where you would never place a train station.

To replace Atherton, a new Fair Oaks station should be built just 0.6 miles to the north, at the 5th Avenue grade separation.  The overtake section would be extended a bit southwards, just beyond the station, enabling locals to be passed while stopped at the central island platform that can be accessed from either side of 5th Avenue.  The new Fair Oaks stop would be equidistant from Redwood City and Menlo Park, and located in an area with very high population density that could support thriving ridership, in contrast to Atherton.

Longer Term: a Seamless Dumbarton Connection

Dumbarton rail has been an uncertain prospect for decades, with some political backing but insufficient funding.  While it may take another few decades for the money and the will to finally materialize, large concentrations of employment and the need for additional transbay corridor capacity make some form of passenger rail service inevitable.  The Dumbarton corridor also happens to be ideally suited for high-speed rail.

The key node is Dumbarton Junction, which should be reconfigured in such a way that trains can enter and leave the peninsula rail corridor swiftly and seamlessly.  This will likely involve a flyover track, enabling southbound trains to enter the Dumbarton corridor without crossing (and therefore blocking) any of the northbound tracks.  To minimize the altitude of the flyover, the Rte 84 / Woodside Road overpass would be turned into an underpass.  As for the Redwood City station, the fit would be quite tight with a 90-foot corridor width where the flyover track begins.

While the flyover may seem like an expensive solution to a problem we don't yet have, planning for it now (if not actually building it) will save money in the long run when passenger rail service grows.

Design Values

No matter how the midline overtake is ultimately configured, it must reflect design values that are clearly articulated.  One of these values should be compatibility between Caltrain and HSR.  It's not enough to talk about the "blended system" without actually taking the steps to make the two systems seamlessly interoperable, allowing any train to use any track to serve any platform.  This means no tracks can be dedicated to one operator at the exclusion of another.  Everything must be shared, including the platforms at the new mid-peninsula station.  This sharing contributes to another important value, robustness to service disruptions.  The fast-slow-slow-fast track layout is the key to ensuring that a commuter train delayed in Belmont won't create a statewide domino effect that eventually makes a train late in Los Angeles.  A third important value is future-proofing.  Infrastructure like the midline overtake will define what is possible (and not) for generations to come.  It would be short-sighted not to plan for a fast and seamless connection to the Dumbarton corridor, even if its future use isn't well-defined today.

The midline overtake is the key to an effective blended system.  When evaluating its design, ask yourself: is it compatible?  Is it robust?  Is it future-proof?

Grade Separation: The Decadal View

For the last few years of debate around the issue of high-speed rail, grade separating the peninsula rail corridor was often cast as an all-or-nothing proposition.  This extremist view clouded two important facts: first, the corridor is already mostly grade-separated (in 2013, only 40 road crossings out of 104 between San Francisco and San Jose will remain at grade); and second, grade separation is a slow and inexorable process that takes place over many decades.

If we assume the next several decades will be like the last several decades, we can take an educated guess about how and in what order grade separations will be built.  The criteria for prioritizing each project could be:

• creating long, uninterrupted stretches of grade separated right of way to enable higher train speeds without compromising safety
• creating a four-track mid-line overtake facility to increase the capacity of the corridor, to support initial HSR service
• separating crossings that rank highest in the CPUC's Section 190 Grade Separation Priority List
• delaying the most expensive and politically costly projects until last

Phase I is simply the completion of the San Bruno grade separation in 2013.  The San Mateo / San Bruno grade crossing being replaced was once rated #7 statewide on the CPUC's priority list.

Phase I: San Bruno Grade Separation

Phase II consists of four projects in San Mateo County, opening up two long stretches free of crossings by the early 2020s, including 14.8 miles free of crossings north of Burlingame, and 6.5 miles south of San Mateo.  This enables the future construction of the "short" mid-line overtake envisioned in Caltrain's corridor capacity analysis, and leaves only a few dense clusters of crossings within San Mateo County.  The new grade separations, in order of priority, are:

1. 25th Ave in San Mateo, the only grade crossing that remains between San Mateo and Redwood City.  Along with new grade separations already planned at 28th and 31st, this project enables the future 4-track mid-line overtake.
2. Broadway in Burlingame, an extremely congested crossing that has been slated for grade separation since the 1970s.  It rates #11 statewide on the latest CPUC priority list.
3. Linden Ave in South San Francisco, originally planned as part of the San Bruno project, but dropped from the final design in 2007.  Grade-separation at Linden is accompanied by the closure of Scott St, which becomes a pedestrian tunnel.
4. Center Street in Millbrae, a grade separation that will require a U-shaped elevated ramp due to the nearby BART subway tunnel box.  Such are the consequences of bad planning.

Each of these projects is independent and can be negotiated on a case-by-case basis with the four affected cities.  Starting in San Mateo County allows at least another decade for the Pacheco vs. Altamont debate to run its due course, legally and politically; these four projects are useful either way.

Phase II: San Mateo County Grade Separations

Phase III occurs mostly in Santa Clara County, creating a new stretch free of grade crossings from the southern half of Palo Alto all the way to San Jose in the late 2020s, assuming the routing of HSR over Pacheco survives as currently planned.  The last two grade crossings in San Francisco are also eliminated as part of the downtown extension project.  This phase includes the following six discrete projects:

1. Mary Ave in Sunnyvale, the corridor's busiest grade crossing in this county, with more than 25,000 daily vehicles
2. Sunnyvale Ave
3. Rengstorff in Mountain View, with about 18,000 daily vehicles
4. Castro in Mountain View, with about 9,000 daily vehicles
5. Charleston and East Meadow in Palo Alto, with a combined ~30,000 daily vehicles plus numerous pedestrians and bicyclists
6. 16th and Common in San Francisco, as part of the DTX project

Together, these six projects create a new 16-mile stretch of track that is entirely free of grade crossings.  The corridor is now left with just three dense clusters of grade crossings, in San Mateo / Burlingame, Redwood City, and PAMPA (Palo Alto - Menlo Park - Atherton), highlighted in orange in the figure below.  Note that these three dense clusters contain 27 crossings, and that to get this far, only 12 existing crossings were newly separated.

Phase III: Santa Clara County Grade Separations

Phase IV is the Great Redwood City Grade Separation.  This project, potentially for the early 2030s, would prolong the four-track mid-line overtake by three miles, by removing six grade crossings in downtown Redwood City.  Removing this cluster first makes sense from the standpoint of increased corridor capacity, the lowest number of new structures, the short mileage, and the entire project being politically simplified by virtue of its containment within Redwood City limits.

Phase V is the Great San Mateo / Burlingame Grade Separation.   This is a tougher project because it involves some of the most highly constricted portions of the corridor.  It also involves political and technical coordination between two neighboring cities, adding an additional challenge.  The sheer quantity of crossings (13 grade crossings + 4 obsolete grade separations within 2.4 miles) is also a complicating factor.

Phase VI is the Great PAMPA Grade Separation.  This project is left for last because it lies in the most expensive real estate on the corridor, involves coordination between three different cities, and is liable to cause the fiercest political and legal backlash anywhere on the peninsula.  Delaying it until last, perhaps into the late 2030s, allows the customarily long planning process to run its course without undue haste in all three affected communities.

We didn't arrive at today's state of grade separation (more than half) overnight.  It resulted from a slow and steady process that began in earnest in the 1940s.  The future is likely to be similar, and the peninsula rail corridor can reach a far improved state by separating just 12 more crossings over the next couple of decades, as described in Phases II and III.  This dozen should be prioritized for construction, before any of the crossings in the remaining dense clusters are touched.

Primarily Two Tracks

Figure 4 from Caltrain's study, showing several possible locations for new overtake tracks.  Not all would be built.

In recent days, the high-speed rail Draft Revised 2012 Business Plan as well as the Caltrain Blended Operations Analysis were released to the public.  Both of these documents refer to the peninsula blended solution as a "primarily two-track" system, in the hope of allaying fears of massive eminent domain takings of homes and business-- fears that are largely unfounded, but fanned relentlessly by the local press and project opponents.

The confusion continues over what "primarily two tracks" precisely means, because neither agency seems ready to come out yet and state it in crystal clear terms.  The process still needs to unfold.  Luckily, enough data has already been published to allow a reasonably good reading of the tea leaves, down to the nearest tenth of a mile.

Phase 1 will be electrification, according to the memorandum of understanding currently being put in place by MTC and other parties.  This project already has federal environmental clearance and is very close to state environmental clearance, although a strong push will be made by opponents to subsume Caltrain's electrification EIR into the peninsula HSR project EIR, a document that will not be finalized (let alone litigated!) until 2015.  This phase of the project will not add any tracks, so the total length of quadruple track will stay as it is today (2 miles in Brisbane; 1 mile in Redwood City; 2 miles in Sunnyvale).

• Purpose: improves Caltrain, enables future peninsula HSR
• Time frame: 2013 - 2019
• Total miles of quadruple track: 5
• Grade-separated fraction: 61% (64 of 104 road crossings)
• Trains per peak hour per direction: 6
• Cities impacted by construction: none

Phase 2 will be a concrete viaduct through Santa Clara, completed at the same time as HSR reaches San Jose sometime in the mid-2020's, enabling a one-seat ride to San Francisco under the so-called "Bay-to-Basin" scenario.  If the CHSRA's grandiose plans (described in an October 2011 report to the legislature) are to be believed, this will entail building a massive double-decker station complex at San Jose.  A new four-track HSR station will hulk over the existing Diridon Station, perched on massive concrete straddle bents.  A more than 3-mile-long, 60-foot-tall viaduct will be constructed northwards, joining the existing corridor at approximately milepost 44.5, north of the Santa Clara Caltrain station.  Overpasses at Hedding and De La Cruz will be demolished and rebuilt as underpasses to make room for the new double-deck rail right of way.  Note that Caltrain's study considers this phase as part of the "baseline infrastructure" and therefore does not count it as additional tracks.

• Purpose: enable single-seat HSR ride to San Francisco
• Time frame: mid 2020's
• Total miles of quadruple track: 8
• Grade-separated fraction: 61% (64 of 104 road crossings) 
  
• Trains per peak hour per direction: 8 (6 Caltrain + 2 HSR)
• Cities impacted by construction: Santa Clara

Phase 3 will be the "short" mid-line overtake from 9th Ave in San Mateo (milepost 18.3) to Whipple Ave in Redwood City (milepost 24.8), which enables HSR service to increase from 2 to 4 trains per hour during the peak.  The data tables in Caltrain's study show that this overtake facility provides nearly all the benefits of the "full" mid-line overtake that extends southwards through Redwood City, but presumably at far lower cost.  The transportation-industrial complex's approach to the short mid-line overtake might very well entail demolishing the entire Belmont - San Carlos grade separation and replacing it with a four-track viaduct on concrete stilts.  A more realistic implementation will likely be to tack on another 15 feet of width on each side of the existing grade separations to accommodate new overtake tracks, something that should have been done in 1999 (but why do it right when you can do it twice?).  In San Mateo, new four-track grade separations will be built at 25th, 28th and 31st Avenues.

• Purpose: increases HSR peak capacity from 2 to 4 trains per hour per direction
• Time frame: late 2020's
• Total miles of quadruple track: 14.5
• Grade-separated fraction: 63% (67 of 106 road crossings) 
  
• Trains per peak hour per direction: 10 (6 Caltrain + 4 HSR)
• Cities impacted by construction: San Mateo, Belmont, San Carlos

Phase 4 will be the "full" mid-line overtake, also known as the Great Redwood City Grade Separation, creating a new mid-peninsula HSR stop at Redwood City and grade-separating a dense cluster of six grade crossings.  The four-track mid-line overtake will be extended southwards to milepost 26.3, merging with the existing four-track section.

• Purpose: adds mid-peninsula HSR stop
• Time frame: late 2020's
• Total miles of quadruple track: 16
• Grade-separated fraction: 69% (73 of 106 road crossings) 
  
• Trains per peak hour per direction: 10 (6 Caltrain + 4 HSR)
• Cities impacted by construction: Redwood City 

Beyond that, it gets murkier.  Presumably, the 33 remaining grade crossings that are not removed under Phases 1 - 4 will be addressed on a case-by-case basis, with grade separations designed and built in consultation with the respective cities.  San Francisco's downtown extension to the Transbay Transit Center may finally be built.  Additional passing tracks may be constructed where it's relatively easy and cheap, for example the remaining 2.5 miles from Lawrence to Santa Clara and the "north overtake" in Caltrain's study, an additional 8.2 miles of quadruple track from Brisbane south into Burlingame.

Only one thing is quite certain: the peninsula rail corridor will categorically NOT remain a two-track operation, even if it might still use "primarily" two tracks.  At a minimum, approximately 16 miles or over a third of its length will be quadruple-tracked.  As the process unfolds, it will become apparent that the cities of Belmont, Redwood City, San Carlos, San Mateo and Santa Clara will be the first to suffer the construction impacts.

Elevated Blight in San Mateo

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

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

Threading the San Mateo Narrows

Downtown San Mateo as previously discussed is one of the most difficult bottlenecks on the peninsula corridor, with some of the narrowest right of way anywhere on the peninsula (see mini map at right, extracted from Milepost 17 map). The following is an expanded discussion of horizontal alignment options in the downtown area.

Assuming one needs to build four tracks through this area (an assumption we will later revisit), the inescapable mathematics of right of way width and track clearances dictates that the railroad will expand significantly beyond its current boundaries. The figure below shows a cross-section elevation at Third Avenue looking "north". The building on the left is the cinema, built partially on former railroad right-of-way and completed in 2003. To the right is Railroad Avenue, providing access to several blocks of downtown business frontage. Railroad Ave becomes a residential street north of the train depot.


The cinema, along with other recently built projects such as the Main Street Parking Garage and the new train depot, have greatly restricted horizontal alignment options for the railroad. While they would only cost a few million to tear down and redevelop, these buildings are the source of considerable civic pride, so it is likely that the city will bend over backwards to preserve them--potentially at many millions of dollars of additional cost to the high speed rail project, and possibly with additional impact to residences in North Central San Mateo. Such is the sad reality of cost-benefit analysis when other people's money is involved.

The figure below shows the city's preferred vertical alignment, with the tracks relocated below grade in a four-track trench, with side clearances appropriate for safe 125 mph (200 km/h) operation. The avenues would cross the tracks on bridges.


As is readily observable, a four-track trench (the narrowest possible below-grade solution) could not be built without impacting structures on one side or the other of the right of way. Constructing the side walls of the trench would require even greater clearances than shown, approximately 110 feet by the city's own estimates--to accommodate wall tie-backs as well as temporary tracks to keep Caltrain operating during construction. More importantly, the trench obliterates Railroad Avenue, the only access to several businesses and residences. Those would have to be acquired under eminent domain.

An outright tunnel would allow continued access to Railroad Avenue, along with exciting new land uses on top of the tunnel. However, a tunnel isn't just a trench with a lid: it requires a vertical divider for fire safety and to support the roof, which further increases the side clearances. (The reasoning behind the resulting dimensions was discussed in the Joy of Tunnels.) Building an underground station would consume even more space for platforms, stairs, escalators and elevators, as will be shown later. The figure below shows how a tunnel compares to the available space: it simply won't fit without causing even greater impact than a trench.


About the only option that is possible to construct (a) without "taking" several buildings and (b) without permanently removing Railroad Avenue and its frontage is an elevated viaduct. The diagram below shows what such an elevated might look like. It could be built in halves, in order to keep Caltrain operating during construction. While an adorable little sketch by city staff (reproduced at right) shows a single concrete column supporting the entire four-track bridge deck, it is likely that seismic codes and the requirement to support massive freight trains would lead to four rows of columns, placed directly under each track. Parking is probably the only reasonable use for the concrete forest resulting underneath. The ambiance would be just like other parking garages in downtown--and might even replace other parking structures entirely, freeing up those locations for redevelopment. Driveway access to Railroad Ave businesses could be preserved.


The elevated option is also likely to be far cheaper to build than a trench or tunnel: it involves about the same amount of concrete, but far less earth moving or road closure logistics. Furthermore, an elevated does not require the permanent closure of several residential cross-streets north of downtown, as contemplated in Focus on San Mateo. Despite the visual blight and noise, look for this alternative to be ultimately favored by the California High Speed Rail Authority... and possibly also by the city, once all the trade-offs are fully understood. While the elevated may not be a desirable solution, on the whole it may be the best solution.

Station Placement

The foregoing musings do not take into account the configuration of the downtown San Mateo train station. By far the most important consideration is the location of Caltrain platforms--both their location with respect to the tracks (outside platforms vs. island platform), as well as their location along the tracks. Recall that the new depot was squirreled away to the north of First Avenue, on the outskirts of downtown, to minimize the impact of lowered grade crossing gates on rush hour traffic. If the tracks are grade-separated and grade crossings are eliminated, this concern evaporates, enabling some options for a more centrally located station closer to 3rd and 4th Avenues, which form the main east-west artery of downtown San Mateo. Such central locations would be far more accessible for both pedestrians and motorists.

In a four-track scenario, the resulting station widths are shown in the diagram below, not including the width of any ramps, stairs or escalators that might be required to access the platforms. These widths bear a direct relationship to the horizontal alignment of the tracks, since the station will be constrained on at least one side by existing structures.

The island platform requires about 6 feet more width than the outside platforms, and the tracks sit 23 feet further apart. The CHSRA might use this as an excuse not to implement island platforms, despite their significant operational advantages.

Let us consider the below-grade option favored by the city, with the station remaining at its current 1st Avenue location. The existing station is shown below in a cross section at 1st Avenue looking "north":

A below-grade station would be built in a trench, with 1st Avenue on an overpass. For all the talk about San Francisco's Transbay "train box", San Mateo's very own train box would be nothing to sneeze at, as readily observed in the following diagram.


Whatever horizontal and vertical location is ultimately selected, none of these four-track station options will fit in downtown San Mateo without very significant property impacts. So you might consider...

Solutions with Three Tracks

So far, we have assumed that four tracks would be absolutely necessary throughout downtown San Mateo, with potential property impacts that go along with that. In practice and with a little bit of creativity, the envisioned levels of Caltrain and HSR service could be achieved on just three tracks, by consolidating the two southbound tracks for a brief stretch through downtown. The goals of such an approach are:

• To reduce the property impacts to downtown businesses and residents by minimizing excursions outside the existing right-of-way
• To increase the range of configuration options for the downtown Caltrain station, for example an island platform that maximizes station access from 3rd and 4th Avenues
• To reduce property impacts along the narrow right of way in the North Central neighborhood, immediately to the north, such that residences do not have their driveway under an elevated.

Naturally, such real-world engineering involves compromise. The drawback is that local and express trains must all share the same southbound track through downtown. Scheduling trains around this operational constraint involves coordinated HSR and Caltrain timetables, which can probably be done reliably because all southbound trains originate from nearby San Francisco and are unlikely to build up significant delays in the space of just 17 miles. (The northbound tracks do not benefit from this proximity to a terminal, and would be difficult if not impossible to schedule reliably; for example, a delay in Bakersfield could later result in a northbound conflict at San Mateo. That's why two northbound tracks are still required.)

Two of the most interesting three-track configuration options are shown in the figure below (linked to annotated PDF file), as designed by Richard Mlynarik. Both assume an elevated, for the reasons described above, and stay confined to the existing right of way between Monte Diablo Ave and the San Mateo Creek to reduce impact to residences along those blocks. There may be more design options with three tracks, but these two convey what is possible.
Option 1 is a three-track station with outside platforms. This can be built either just north of the parking garage and cinema, at the existing location of the San Mateo station, or just south of the offending buildings. The southbound track skirts the cinema as tightly as possible. The northbound platform is built over Railroad Ave, which complicates access by ramps, stairs, escalators or elevators. Railroad Ave would have to be shifted underneath the elevated to free up room under the platform, and station access might interfere with business frontage.

Option 2 is a better three-track station with a central island platform built over Third and Fourth Avenues. The same layout from the PDF file is overlaid on an aerial photo below.


The central island platform enjoys easier access from below, since stairs and elevators would have ample space to touch down under the elevated, with direct pedestrian access from both sidewalks of 3rd and 4th Avenues. It doesn't have to be an oppressive structure: it could look like this amazing photo of Amsterdam's Bijlmer station, a model of pedestrian access.

The difficulties in downtown San Mateo will be great, but so is the potential for an elegant solution that better integrates the station with the city.

Focus on: San Mateo

The city of San Mateo was incorporated in 1894, 30 years after the railroad began operating. Along the 4.5 miles of rail through the city, there are today three Caltrain stations, two of which (Hillsdale and San Mateo) are Baby Bullet stops. The three stations in San Mateo generate greater combined Caltrain ridership than San Jose, a city with ten times San Mateo's population.

San Mateo is among the most treacherous areas on the peninsula to expand to four tracks for high speed rail because the existing Caltrain tracks run through dense residential neighborhoods and downtown blocks where the available right of way width is significantly less than 100 feet. The city is a "ground zero" of future grade separations: it is home to one-fifth of the grade crossings on the entire peninsula rail corridor (9 out of 46). To improve safety and traffic circulation, the city has long had plans to grade-separate all of its rail crossings; high speed rail will only hasten this process. The San Mateo County Transportation Authority has been carrying out a series of preliminary grade separation footprint studies in support of these plans.

San Mateo finalized a Rail Corridor Transit-Oriented Development Plan in April 2008, covering the vicinity of the Hillsdale and Hayward Park Caltrain stations and including the re-development of the Bay Meadows racetrack site.

Station Area and Downtown

The San Mateo Caltrain station was rebuilt in 1999-2000 to alleviate auto traffic congestion. The new $11 million station with underground parking (photo above by ibison4) replaced a sparse older station a few blocks to the south. Every time a train stopped at the old station's center boarding platform between 3rd and 4th Avenues, auto traffic on 2nd through 5th Avenues was paralyzed, exacerbating rush hour congestion.

With some foresight, albeit a bit fuzzy, the new station's underground garage and surrounding structures were reportedly built so as to allow the tracks to be relocated underground. This would not only grade-separate the tracks through town, but also accommodate a future BART subway, as was envisioned in the late 1990s while construction of the SFO extension was underway.

Plans change.

The problem is now this: the new station building and underground parking encroach on the railroad right of way and do not leave the necessary clearance for four tracks, as likely required for Caltrain and HSR, whether at, above, or below grade. Worse, a couple of blocks south of the station, San Mateo's new downtown cinema and Main Street parking garage were completed in 2003 and encroach on what was once railroad right of way, leaving just 50 - 60 feet for the tracks (see Caltrain right of way map).

There will be no easy or cheap solutions to these constraints. In discussions about a preliminary grade separation footprint study for downtown, city staff makes the following key observations:

• The vertical alignment of all the downtown rail crossings must be consistent, since their close spacing does not allow sufficient space for rail grade changes;
• Any grade separation alternatives with the tracks at grade or near grade is infeasible because of the need to lower or raise downtown streets in a manner that severely impacts frontage on both sides of these streets;
  
• The two remaining vertical alignment alternatives leave the streets at grade, with the rails either fully elevated or underground--the latter being the city's stated preference;
• The right of way required to build a four-track underground trench is 110 feet wide, far more than the 50 - 60 ft available;
  
• Moving the horizontal alignment of the tracks to the east (with impact to Railroad Ave and frontage) is preferable to impacting the new train station, Main Street parking garage and downtown cinema;
• The underground alignment presents significant technical complications, with residential property impacts just north of downtown where the tracks would ramp down, possible street closures, as well as the technical difficulty of crossing San Mateo Creek underground.

While no decisions have yet been made, and despite the city's stated preference for a depressed alignment, the elevated alignment may present the least physical impact to property adjoining the tracks, although the visual impacts are worst. The city is considering options to mitigate the Berlin Wall effect, including building the track on a viaduct instead of retained fill. Contrary to San Mateo's official preference, the California High Speed Rail Authority shows an elevated track profile with 15-foot embankments through San Mateo in their program EIR/EIS; this may or may not be the preferred alternative once they complete the project EIR/EIS.

The issue of track alignment through downtown San Mateo is discussed in much greater detail in Threading the San Mateo Narrows. That discussion includes diagrams showing various track configuration options such as the elevated shown below.
For more details, read all about Threading the San Mateo Narrows.

North Central San Mateo

North of downtown, the tracks curve through dense residential blocks on right of way that ranges from 60 to 90 feet wide, less than the ~75 feet required to run four tracks on a retained embankment, and certainly less than the ~110 feet required to excavate a trench or tunnel. The tracks cross four residential streets (Poplar, Santa Inez, Monte Diablo and Tilton avenues) on low-clearance bridges that have long been slated for refurbishment.

The key question for downtown and the North Central neighborhood will concern the vertical alignment of the tracks. The close proximity of these residential blocks to downtown, combined with the gentle track gradients required for freight trains (yes, freight trains), will require that these areas be considered as one.

Vertical Alignment Considerations

The vertical profile of the existing tracks in San Mateo is shown in the figure below. This figure was created from Caltrain track survey data, with the vertical scale greatly exaggerated. The grade level of cross streets is estimated from the known vertical clearance at each location; the level of creeks is likewise estimated.


We make a few assumptions (for more background on where these came from, read about The Shape of Palo Alto):

• Vertical track radius is constrained to a minimum of 10 km
• Gradient limit of 1 to 1.5% for freight trains, 2.5% for passenger trains
• 20-foot clearance from underpass road surface to top-of-rail (to clear trucks)
  
• 30-foot clearance from overpass road surface to top-of-rail (to clear freight trains)
  
• Tracks must be close to level for 750 feet north of First Ave, for Caltrain platforms
• Tracks are elevated at Peninsula Ave., an area with adequate clearances and commercial frontage that would favor this minimum-cost solution.
  

Scenario #1: track elevated throughout. With a 1% gradient limit and a 10 kilometer vertical radius constraint, this is what San Mateo would look like. We assume each road is depressed by 5 feet (something that can be done with little impact to adjoining frontage), with the rails raised by 15 feet. It is likely that a viaduct structure would replace the existing embankments, possibly making room for a rebuilt Railroad Ave. All vehicle height restrictions in North Central would be removed. Worth noting, the elevated alternative does not require the closure of any crossings, unlike depressed alternatives.


Scenario #2: trench through downtown. To shorten the sloping approaches and reduce the depth of the trench, we assume each road is raised by 5 feet (something that can be done with little impact to adjoining frontage), with rails depressed by 25 feet. Even this 25-foot trench penetrates below the water table and will require constant pumping to keep dry. With the 1% gradient limit desirable for freight trains, this design would require the closure of Villa Terrace, Bellevue, Poplar, Santa Inez, Monte Diablo and Tilton avenues, unless those streets were either raised or depressed with considerable impact to frontage on either side of the tracks.


Scenario #3: trench through downtown, with steep approaches. With a less stringent gradient limit just a shade over 2%, difficult for freight trains but easily handled by high speed trains and Caltrain, the approaches to the trench are much shorter. This allows underpasses at Villa Terrace, Bellevue and Poplar and reduces the need to close cross-streets. Santa Inez, Monte Diablo and Tilton would likely still be closed.


Scenario #4: tunnels. While this alternative will no doubt be studied by the CHSRA, it is unlikely to be implemented due to a host of disadvantages, not the least of which is the astronomical cost. The sloping approaches to a tunnel diving under downtown are likely to present even greater interference with cross-streets than the depressed trenches described above.

Whatever alternative is ultimately favored, one must keep in mind that the biggest constraints on the vertical alignment of the tracks come from freight trains, which don't handle steep grades well and require very high vertical clearances. The more nimble electric trains used by HSR and Caltrain would easily handle steep gradients up to 2.5%, and would require about 3 feet less vertical clearance. In short, freight trains may have a direct impact on San Mateo neighborhoods.

Southern San Mateo

The southern half of San Mateo is an area currently slated for extensive re-development. It does not have nearly as much access across the tracks as northern San Mateo, and the available right of way is far less constrained, generally greater than 100 feet (see maps for mileposts 18, 19 and 20). The area encompassing the Hayward Park and Hillsdale Caltrain stations (and the former Bay Meadows race track) is slated for redevelopment as described in San Mateo's Rail Corridor Transit-Oriented Development Plan.

Hayward Park includes a reverse curve in the tracks (curving right, then left). The northern curve at milepost 18.8 has a radius of just 1100 meters, good for about 95 mph. This curve made #5 on our list of Top Ten Worst Curves on the peninsula. While it was already flattened by shifting the tracks 20 feet westwards in the year 2000, this curve may need to be straightened some more so that high speed trains don't need to slow down as much in this area. This may not please residents of South Boulevard.

The Hayward Park Caltrain station was rebuilt in 2000 and moved slightly to the south of its former location. The original station provided convenient pedestrian access across the tracks at 16th Ave; the City is now considering a new pedestrian underpass at this location to restore the access that was lost after the move. The new Hayward Park station was built for three tracks, although it currently has only two tracks. The southbound platform already includes a cut (see photo at right) allowing it to be trimmed back to make room for a third passing track. Whatever the original intent of this configuration, the station will likely be entirely rebuilt when high speed rail comes through town.

The Route 92 overpass (actually two side-by-side bridges, seen in the background of the photo) provides ample clearance for four tracks.

The Hillsdale Caltrain station is already planned for relocation to the site of the former Bay Meadows station, and will be located between newly constructed grade separations at 28th and 31st avenues, connecting the west side of El Camino to the newly developed Bay Meadows area. The tracks will be elevated over 25th, 28th and 31st, linking up to the existing grade separation at Hillsdale Ave. These long-standing plans by the Caltrain JPB and the City are unlikely to be altered by the HSR project, except for quadruple tracking; for a detailed description, refer to Chapter 4 of San Mateo's Rail Corridor Plan. The resulting vertical profile is shown in the diagrams above.

South of Hillsdale, the frontage along the east side of El Camino Real is already owned by Caltrain, Samtrans or Union Pacific; while businesses on that narrow strip of land will likely be displaced, plenty of land is available for expansion of the tracks.

San Mateo promises to be one of the biggest design challenges on the peninsula. The CHSRA certainly has its work cut out for it, with a 50-foot right of way threaded through dense city blocks surrounded with residential neighborhoods, with a creek thrown in for good measure.

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

Caltrain Does the Right Thing: Nothing

For a few months after the passage of Proposition 1A in November 2008, it seemed as if Caltrain was conducting business as usual on its capital improvement program. They are finally showing signs of waking up to HSR and its implications for the numerous capital projects in their pipeline. (photo by PBO31)

In April, Caltrain placed the renovation of the South San Francisco station on hold. This $50 million project, fully funded and at the 90% design stage--the shovel doesn't get any readier--was shut down at the last minute over uncertainty in the plans for HSR and the future configuration of the Union Pacific freight yard located there. The project will resume when more is known about detailed HSR plans for the area, probably within the next two years.

Further south and for the better part of the decade, Caltrain had plans to replace century-old, seismically unsafe, low-clearance bridges just north of downtown San Mateo. These antiquated bridges, crossing over Poplar, Santa Inez, Monte Diablo and Tilton avenues, are so low that even the Google Street View camera car nearly crashed into one. The work on this $27 million project was to start this summer. Not only would these four bridges need to be rebuilt and expanded for HSR, but they are also located in an area where the future vertical alignment of the tracks is highly uncertain, depending on how the new tracks are routed through downtown San Mateo. A San Mateo resident rightly complained about the disconnect. Recently, Caltrain announced they were opting for a better approach, consisting of a basic seismic retrofit and continued maintenance to extend the lifetime of the bridges just long enough to find out what will happen with HSR.

As part of their announcement, they stated: Caltrain is assessing its extensive capital program to better coordinate with high-speed rail and to make certain that today’s investments are not deemed obsolete in the near future.

Better do it right than do it twice.