Risk and Opportunity in Redwood City

Lowe, a major real estate development firm, is preparing to redevelop Redwood City's Sequoia Station, an outdated strip mall adjacent to the Caltrain station, into a 12-acre mixed-use project with towers up to 17 stories tall.  If that is eye-opening to residents of Redwood City, consider that few people yet know that a greatly expanded Redwood City station is the keystone transfer node to enable the growth envisioned in Caltrain's business plan service vision. This new station will require slightly more land than the railroad already owns, and can only be located in Redwood City, the sweet spot that lies halfway between San Francisco and San Jose at the connection point to the Dumbarton rail corridor.

This creates a risk: if a commercial development project is allowed to proceed without respect to the future real estate needs of the railroad, then Caltrain will be constricted and unable to build the optimal infrastructure to support future growth.

Additional Land Needed For Caltrain

Caltrain and Samtrans have extensive land holdings at the Redwood City transit center. Still, just a bit more is needed to build a high-functioning piece of infrastructure, and be could traded for other parcels. Click to expand the map:

Land needed for future expanded station in Redwood City (shaded green)

Design Principles

The absolute worst way to build it.
Existence of this city rendering is
reason enough to be concerned.

To ensure that the Sequoia Station project becomes an exemplar transit-oriented development, rather than relegating Caltrain to the role of development-oriented transit, the rail agency and the developer should agree on some broad design principles.

• Think Big. Redwood City is one of the few stops on the peninsula rail corridor not surrounded by a sea of low-density single-family housing. Intensive land use and transportation must fit together to achieve a dynamic yet sustainable low-carbon future.
   
• Form follows function. No amount of architectural flourish or amenity can make up for a poor station design. Optimize for convenient access, easy transfers between trains and buses, short walks, direct and intuitive routes.
   
• Put the station at the center of the action, right over Broadway. Don't shove it to the north, out of the way of the development. The city rendering at right shows precisely what NOT to do.
   
• Configure the station as two island platforms to facilitate cross-platform transfers, without time-consuming vertical circulation or platform changes. The Caltrain business plan's staff-recommended service vision relies entirely on these Redwood City cross-platform transfers; every single train that pulls into Redwood City will make a timed transfer to another same-direction train docked at the opposite edge of the same platform. Denoting express tracks as 'F' for Fast and local tracks as 'S' for Slow, the optimal layout is FSSF with two islands, resulting in F-platform-SS-platform-F. Again, the city rendering shows precisely what NOT to do: passengers would not only have to change platforms, but also cross the tracks at grade.
   
• Elevate the train station to reconnect the street grid and make the railroad permeable to pedestrians, bikes, and other traffic. A busy four-track station is fundamentally incompatible with at-grade railroad crossings, and the only reasonable way to grade separate at this location is by elevating the entire station. Obstacles to pedestrian circulation such as the Jefferson Avenue underpass would be removed. Once again, the at-grade city rendering shows what NOT to do.
   
• Use four-track approaches from the north and the south. Cross-platform transfers are most efficient if trains do not have to arrive and depart sequentially using the same track, which adds about 3 minutes of delay. The best transfer is one where the two same-direction trains can arrive and depart simultaneously on their own separate tracks. Temporal separation is efficiently established by having the local train stop one station away from Redwood City (southbound at San Carlos or northbound at a new Fair Oaks station at Fifth Avenue) at each end of a new four-track segment that will ultimately measure four miles. In this arrangement, the express trains naturally gain on the local trains without a single passenger being delayed at Redwood City.
   
• Include turn-back tracks. Preserve room in the right of way north and south of the station for turn back pocket sidings, between the central slow tracks. Dumbarton rail corridor trains may not necessarily "interline" or continue on the peninsula rail corridor, so it's important to give them a convenient place to transfer and turn around without fouling other train traffic on the express tracks (hence FSSF arrangement). Same thing for a possible San Mateo local, which could serve the more densely spaced stops north of Redwood City.
   
• Don't be constrained by discrete city blocks. It could make sense to build structures or connect them over and across the tracks, more tightly knitting the station complex into surrounding mixed-use neighborhoods. This has some surmountable safety and liability implications, but buildings on top of busy stations are a common feature of successful cities around the world.
   
• Plan for long 400-meter platforms, not Caltrain's standard 700-foot platform length (again as seen in the city rendering of what NOT to do). While statewide high-speed rail plans currently do not include a stop in Redwood City, it is becoming enough of a destination and a regional transportation node that it makes sense to build a station large enough to future-proof it for service by long high-speed trains, regardless of what the California High-Speed Rail Authority might have to say about it.
   
• Think ahead about construction sequencing. Redwood City should be grade separated in one project from Whipple to Route 84, including the elevated station, taking advantage of Caltrain's land holdings to minimize the use of temporary tracks. A shoo-fly track would have to be built on Pennsylvania Avenue (within the railroad right of way) to make room for construction of the western two-track viaduct. Trains would begin using the elevated station while a second eastern two-track viaduct is constructed. Pennsylvania Avenue could re-open later, under the new four-track viaduct. Construction sequencing may drive how much extra land is needed for the railroad, so it's important to think it through up front.

If these design principles are respected, the re-development of Sequoia Station will present not a risk but an amazing opportunity to enhance Redwood City by realizing its full potential as the fulcrum of the Caltrain corridor and of a new regional express network reaching across the Dumbarton bridge and beyond.

On Width

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

Original Post: When we reviewed just how wide the Caltrain corridor is, we assumed a 75-foot minimum width for a four-track rail corridor, measuring from fence to fence. New figures, obtained from reliable sources, indicate typical dimensions will be quite a bit more:

• 15' (4.6 m) Caltrain track spacing (measured center-to-center)
  
• 16'6" (5 m) HSR track spacing, or between HSR and Caltrain tracks
• The kicker: 23'6" to 28'6" between the outer track center line and the boundary fence, to allow for third-party utility easements (as already exist in many places along the Caltrain corridor), overhead electrification poles, maintenance walkways, drainage structures, etc.

Worst case, that adds up to 28'6" + 16'6" + 16'6" + 16'6" + 28'6" = 106'6" (32.5 m). The best case, with Caltrain tracks in the middle, adds up to 23'6" + 16'6" + 15' + 16'6" + 23'6" = 95' (29 m). Both figures are measured fence-to-fence, presumably for a situation where all four tracks run at ground level.

Time to Panic?

Well, maybe not quite yet.

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

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

The minimum legal side clearances in California are dictated in CPUC General Order 26-D. The absolute minima are 14' between track centers and 10' side clearances to the edge of the right-of-way. Caltrain's engineering standards reflect these constraints in a clearance drawing. None of these standards envision trains running at 125 mph and above, since those have never existed in California. Better numbers can be gleaned from foreign standards, for example the German Eisenbahn, Bau- und Betriebsordnung (EBO). That particular standard requires the following side clearances:

• A danger zone (free of any obstructions such as poles, walls, etc.) of 2.5 m (8'2"), measured from the track center line, for train speeds less than 160 km/h (100 mph) and 3.0 m (10') for greater speeds.
• Outside of the danger zone, a 0.8 m (2'6") space for rail personnel to take refuge at a safe distance from trains
• The danger zones of neighboring tracks may overlap, with tracks spaced 4 m (13') for speeds less than 250 km/h (150 mph) and 4.2 m to 4.5 m (14' to 15') above. Since European trains are about a foot narrower than ours, that's roughly consistent with the 15-foot minimum already in use on the peninsula.
  

Where the Caltrain corridor is too narrow (such as in certain sections of San Mateo or Menlo Park), technical and political considerations make it probable that the HSR project will prefer adapting to the local constraints before seizing property and revving up the bulldozers.

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

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

Focus on: Atherton

If the term wealthy enclave means anything, Atherton (per capita income about 20 times population) is it.

The leafy town of Atherton abuts a mere 0.8 mile of the peninsula rail corridor, and yet may turn out to be the greatest friction point for HSR on the peninsula--and possibly anywhere in California. This is not because of technical difficulty, but rather because the town is more willing and able than most to employ legal means to get its wishes: as a first priority, a routing of HSR that is not through Atherton (namely, via the Altamont Pass), and as a last resort, the construction of a tunnel to put Caltrain and HSR completely out of sight.

In an 11-page letter sent to the CHSRA in late 2007, the Town of Atherton detailed its concerns about the HSR project. Refer to Chapter 22, p. 101 of the Bay Area to Central Valley Program EIR/EIS. The letter includes the following claims:

1. properties will need to be condemned to build HSR through Atherton;
2. partially condemned properties are subject to remainder damages "easily in excess" of the value of the entire property, to compensate owners for noise and visual impacts in perpetuity;
3. the remainder of the property may not be condemned unless it is actually needed for the project; condemnation to limit remainder damages is not sufficient to support the taking.
   

In short, Atherton warned that running HSR through town would entangle the project in an expensive and drawn-out legal battle. That battle has already begun: Atherton was a co-plaintiff in a partially successful legal challenge brought by environmental and transit activists against the above-mentioned EIR, forcing it to be revised. Doubtless this is only the beginning.

Horizontal Alignment

Despite the controversy around the issue of eminent domain, the Caltrain right of way (see maps for mileposts 27 and 28) is 80 - 85 feet wide and straight as a ruler everywhere along the 0.8 mile section that falls within Atherton town limits. In principle, this is sufficient space to accommodate four tracks, although temporary construction easements may still be required to build the grade separation structures at Atherton's two grade crossings, Fair Oaks Lane and Watkins Avenue.

Trees are highly prized in Atherton, and many large volunteer trees growing on the railroad right of way would have to be removed. Caltrain's electrification EIR identified 80 trees that would need to be removed for a two-track at-grade electrified configuration; a wider four-track arrangement would likely result in even more tree removals.

Vertical Alignment

The existing tracks slope down at a gentle (less than 0.5%) grade to the north, and cross a drainage ditch known as the Atherton Channel at Watkins Ave. The vertical alignment of the tracks through Atherton is intimately linked to the choices made in neighboring Menlo Park, which has several closely-spaced crossings that would require a consistent vertical alignment to be used through both cities. The existing alignment is shown in the figure below, created from Caltrain track survey data.


Even with the program EIR in legal trouble, project-level environmental work is continuing, with the CHSRA's preliminary design alternatives including elevated, at-grade and below-grade variations of the vertical alignment through Atherton.

An elevated alignment, as originally suggested in the program EIR/EIS and as previously studied in neighboring Menlo Park, would raise the tracks about 15 feet and lower the roads by about 5 feet. Pedestrian sidewalks would stay at grade. The tracks would have to be elevated over all six crossings in Menlo / Atherton, as shown in the figure below. Note, the 1% grade specified for freight trains considerably lengthens the northern approach to such an elevated structure.



Putting the tracks in a trench would require lowering the rails by 30 feet, to accommodate tall freight cars under overhead electrification. The solid red line in the figure below shows a trench alignment. The tracks must rise back to grade at the existing Fifth Avenue grade separation to the north, so trains, tracks, poles and overhead wires would be out of sight for only a portion of Atherton. Again, freight-friendly 1% grades are shown.


Atherton's Folly

In the analysis of alternatives process for the San Francisco - San Jose project EIR, the CHSRA requested each city to state its preferred design alternative. Atherton's position is still that the Pacheco Pass HSR routing through Atherton is ill-advised, wasteful, expensive, and adds no transportation value. Should this route be built, however, Atherton proposes a tunnel concept that is ill-advised, wasteful, expensive, and adds no transportation value. An eye for an eye...

A letter from Atherton (see p. 5) states a preference for an unusual two-level stacked tunnel arrangement, with two HSR tracks in a tunnel on the lower level and two Caltrain / UPRR tracks in a trench on the upper level, as diagrammed in the notional cross-section at right. All roads would remain at grade, and the horizontal clearances would "fit well within" the 80 - 85 foot right of way, purportedly allowing trees to be preserved. The vertical alignment for such a tunnel is shown in the vertical profile (above) as a dotted red line. Accounting for the minimum vertical clearances, the HSR tunnel would bottom out about 75 feet below grade, well below sea level. The extensive ventilation head houses, emergency evacuation stairwells and pump houses required to operate such a tunnel are not shown in the diagram.

The claimed benefits of such an arrangement include:

• No property takes and little loss of property value
• No barrier or visual impact, little noise
• Less cost than a twin-bore four-track tunnel
• Upper level usable by diesel freight trains
  

The concept was originally proposed by Redwood City resident James Jonas, who calls it the Hat Trench. Jonas was invited to present the concept to Atherton's rail committee in summer 2009.

It remains unclear who would pay for such a pharaonic tunnel structure. While the price of property in Atherton is high, it remains small in comparison to a tunnel. Less easy to quantify is the price of a view and the price of peace and quiet. Are those truly worth $10,000 per linear inch? Atherton should have plenty of MBA's to figure it out.

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

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.

Why They Chose the Caltrain Corridor

A lot of peninsula residents now becoming aware of the California High Speed Rail Authority's plans are concerned that HSR will require extensive eminent domain takings along the Caltrain corridor, and suggest that HSR be routed instead via the existing (pre-blighted) corridors of highways 101 or 280. Those options were studied and formally eliminated in the CHSRA's Bay Area to Central Valley Final Program EIR/EIS, certified in July 2008. It's worthwhile to examine why the CHSRA chose the Caltrain corridor.

The simple answer: there's a lot more room in the Caltrain corridor than most people realize.

Right of Way Statistics

Average width: 112 ft (34 m)
Percentage 75 ft or wider: 94%
Percentage 80 ft or wider: 88%
Percentage 85 ft or wider: 80%
Percentage 90 ft or wider: 77%
Percentage 95 ft or wider: 70%
Percentage 100 ft or wider: 68%

The chart at right shows a graph of the width of the railroad right of way (in feet) versus milepost, constructed from official Caltrain right of way maps.

CHSRA documents indicate that the minimum width required for four tracks is about 75 feet; this is shown by a dotted red line in the chart. A comfortable width (allowing access roads and landscaping) is about 100 feet. The results:

• Along the two thirds (68%) of the peninsula rail corridor that are wider than 100 feet, HSR is an easy fit within the existing right of way.
• For another quarter (27%) of the corridor that is between 75 feet and 100 feet wide, HSR is a tighter fit, but possible without eminent domain
• For the remaining 5% of the corridor that is narrower than 75 feet, some eminent domain is necessary to achieve a minimum width of 75 feet.

How Much Eminent Domain?

One can calculate the area of land required to bring the entire corridor to 75 ft minimum width. Again some corridor length statistics, straight from the chart above:

50 (minimum) to 55 feet wide: 0.38 miles (needs 25 feet extra)
55 to 60 feet wide: 0.09 miles (needs 20 feet)
60 to 65 feet wide: 0.59 miles (needs 15 feet)
65 to 70 feet wide: 0.06 miles (needs 10 feet)
70 to 75 feet wide: 1.75 miles (needs 5 feet)

Adding up the series of strips with the dimensions above, the grand total amount of land required to widen the entire peninsula corridor to a minimum of 75 feet is less than four acres.

To put that figure into proper perspective:

• the entire corridor is about 700 acres, so the required land is about half a percent more.
• the CHSRA has a budget of $4.2 billion for the San Francisco to San Jose segment. At Atherton prices ($4 million per acre), the required land is worth about a third of a percent of that budget.

(Disclaimer: this analysis is based on Caltrain corridor maps, which are not official survey documents. Your mileage may vary; discrepancies of several feet have already been noted in some 100+ year old property lines. Also, temporary construction easements are not included.)

At the turn of the 20th century, the Southern Pacific secured enough land to expand the railroad to four tracks, precisely what is now envisioned for high speed rail. Is it any wonder that the California High Speed Rail Authority considers the Caltrain corridor a slam-dunk?

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.

Caltrain Right Of Way Maps

The table below contains maps of the Caltrain right of way, with key dimensions like ROW widths and the approximate boundaries of property owned by the Peninsula Corridor Joint Powers Board (Caltrain), the Union Pacific Railroad, local transit agencies, and others. This information will be useful in discussing the impact of HSR on peninsula communities.

The maps date mostly from March 2007. This public information was provided by Caltrain upon request; thanks to Brian Fitzpatrick (Manager Real Estate & Development) as well as Martha Martinez (PCJPB Secretary). The files are provided as-is; I decided against consolidating a large PDF to spare server bandwidth and allow linking to individual areas of concern along the line.

Milepost	City	Station	PDF Map
0 to 1	San Francisco	4th & King	00-TCCM-200-B.pdf
1 to 2	San Francisco	22nd Street	01-TCCM-200-B.pdf
2 to 3	San Francisco		02-TCCM-200-B.pdf
3 to 4	San Francisco		03-TCCM-200-B.pdf
4 to 5	San Francisco		04-TCCM-200-B.pdf
5 to 6	San Francisco / Brisbane	Bayshore	05-TCCM-200-B.pdf
6 to 7	Brisbane		06-TCCM-200-B.pdf
7 to 8	Brisbane / South San Francisco		07-TCCM-200-B.pdf
8 to 9	South San Francisco		08-TCCM-200-B.pdf
9 to 10	South San Francisco	South San Francisco	09-TCCM-200-B.pdf
10 to 11	South San Francisco / San Bruno		10-TCCM-200-B.pdf
11 to 12	San Bruno	San Bruno	11-TCCM-200-B.pdf
12 to 13	San Bruno / Millbrae		12-TCCM-200-B.pdf
13 to 14	Millbrae / Burlingame	Millbrae	13-TCCM-200-B.pdf
14 to 15	Burlingame		14-TCCM-200-B.pdf
15 to 16	Burlingame	Broadway	15-TCCM-200-B.pdf
16 to 17	Burlingame / San Mateo	Burlingame	16-TCCM-200-B.pdf
17 to 18	San Mateo	San Mateo	17-TCCM-200-B.pdf
18 to 19	San Mateo		18-TCCM-200-B.pdf
19 to 20	San Mateo	Hayward Park	19-TCCM-200-B.pdf
20 to 21	San Mateo	Hillsdale	20-TCCM-200-B.pdf
21 to 22	San Mateo / Belmont	Belmont	21-TCCM-200-B.pdf
22 to 23	Belmont / San Carlos		22-TCCM-200-B.pdf
23 to 24	San Carlos	San Carlos	23-TCCM-200-B.pdf
24 to 25	San Carlos / Redwood City		24-TCCM-200-B.pdf
25 to 26	Redwood City	Redwood City	25-TCCM-200-B.pdf
26 to 27	Redwood City / Unincorporated		26-TCCM-200-B.pdf
27 to 28	Unincorporated / Atherton	Atherton	27-TCCM-200-B.pdf
28 to 29	Atherton / Menlo Park	Menlo Park	28-TCCM-200-B.pdf
29 to 30	Menlo Park / Palo Alto		29-TCCM-200-B.pdf
30 to 31	Palo Alto	Palo Alto	30-TCCM-200-B.pdf
31 to 32	Palo Alto	California Ave.	31-TCCM-200-B.pdf
32 to 33	Palo Alto		32-TCCM-200-B.pdf
33 to 34	Palo Alto / Mountain View		33-TCCM-200-B.pdf
34 to 35	Mountain View	San Antonio	34-TCCM-200-B.pdf
35 to 36	Mountain View		35-TCCM-200-B.pdf
36 to 37	Mountain View	Mountain View	36-TCCM-200-B.pdf
37 to 38	Mountain View / Sunnyvale		37-TCCM-200-B.pdf
38 to 39	Sunnyvale	Sunnyvale	38-TCCM-200-B.pdf
39 to 40	Sunnyvale		39-TCCM-200-B.pdf
40 to 41	Sunnyvale	Lawrence	40-TCCM-200-B.pdf
41 to 42	Sunnyvale / Santa Clara		41-TCCM-200-B.pdf
42 to 43	Santa Clara		42-TCCM-200-B.pdf
43 to 44	Santa Clara		43-TCCM-200-B.pdf
44 to 45	Santa Clara		44-TCCM-200-B.pdf
45 to 46	Santa Clara / San Jose	Santa Clara	45-TCCM-200-B.pdf
46 to 47	San Jose		46-TCCM-200-B.pdf
47 to 48	San Jose	San Jose Diridon	47-TCCM-200-B.pdf
48 to 49	San Jose		48-TCCM-200-B.pdf
49 to 50	San Jose	Tamien	49-TCCM-200-B.pdf
50 to 51	San Jose		50-TCCM-200-B.pdf
51 to 52	San Jose		51-TCCM-200-B.pdf
77 to 78	Gilroy	Gilroy	77-TCCM-200-B.pdf
78 to 79	Gilroy		78-TCCM-200-B.pdf

Slow Traffic Keep... Left?

In all the existing plans for running high speed rail up the peninsula to San Francisco, the additional pair of tracks required for HSR traffic is invariably shown in the center of the right of way, with Caltrain local service running on the outside pair of tracks. The typical Caltrain station would still have two outside platforms, except there would now be four tracks through the station, like the existing Bayshore and Lawrence stations.

Intuitively, it's easy to accept this configuration without questioning it for even a second, because we are all familiar with freeways, where slower traffic keeps right and faster traffic passes on the left. (photo credit: mojoey) That paradigm is so deeply ingrained in our minds that we tend to think high speed trains should obviously operate the same way, right?

Not so fast-- with nearly every Caltrain station from San Jose to San Francisco about to be totally redesigned from a blank sheet of paper, it's worthwhile to question all assumptions, and in particular the assumption that HSR should run on the inside pair of tracks, i.e. slow-fast-fast-slow when enumerating the tracks from one side to the other. (Credit to Richard M for raising most of the following ideas in previous comments).

What if Caltrain local service ran on the center pair of tracks, with HSR and express trains on the outside tracks, i.e. fast-slow-slow-fast? What would be the pros and cons of each approach? For HSR? For Caltrain? For communities abutting the tracks?

Operational Flexibility

Anyone who commutes on Caltrain knows that periodically, an incident occurs that puts one track out of service for a few hours. While it is tempting to ascribe this to grade crossing accidents and equipment breakdowns, both of which would be alleviated by electrification and grade separation, the fact remains that service disruptions can and will happen on occasion.

When one track for local commuter trains is shut down, service is typically cut over to the other commuter track for a short stretch around the incident area. Caltrain has the option of switching tracks at over a dozen crossovers, spaced every few miles along the peninsula. Trains can temporarily run the "wrong" way and make their usual station stops on the other platform track. To the extent possible, this minimizes delays and inconvenience to passengers.

With HSR in the mix, it gets more complicated. If HSR runs down the middle pair of tracks, cutting over local commuter trains from one platform track to the other platform track requires crossing over both HSR tracks and thus waiting for, or delaying, traffic on those center tracks. Temporarily running on the "wrong" platform track would involve a complex, coordinated sequence of moves that disrupt service on all four tracks. In addition, waiting passengers would have to dash to the opposite platform in order to catch their train.

If HSR ran on the outside pair of tracks and Caltrain commuter service on the inside pair, a disruption on one of the commuter tracks would not conflict with HSR service. To switch to the other platform track, locals would simply cross over to the adjacent commuter track. Under this scenario, Caltrain stations would have a single island platform in the middle of the right of way, located between the center pair of tracks. Passengers would not have to switch platforms to catch their train on the other platform track, since the platform tracks would serve each side of the same platform.

What happens if instead, one of the express tracks is disrupted? It's not nearly as bad: a train can simply be routed to the adjacent track. Unlike local service, platform access is not required for HSR and Caltrain express services, which would stop only at key stations with four (rather than two) platform tracks. Therefore, the requirement to switch to the other platform track does not apply; any track will do.

In short, the fast-slow-slow-fast track configuration provides great flexibility for dealing with service disruptions on any given track. On the other hand, the slow-fast-fast-slow configuration causes a big mess that disrupts all four tracks, whenever one of the local tracks is knocked out of service.

One other interesting fact is that in certain locations along the peninsula, Caltrain service could theoretically run in both directions on a single track without trains ever conflicting with each other. (Hello Atherton! Take note!) This naturally depends on the density and scheduling of Caltrain traffic, but it opens up the possibility of having only three tracks in certain locations, as dictated by the operational service pattern (Hello Atherton! Service pattern, not your back yards!) Switching to a three-track configuration from a four-track configuration is much simpler if you go from fast-slow-slow-fast (4) to fast-bidirectional-fast (3)... a simple turnout, and presto. On the other hand, trying to neck down from slow-fast-fast-slow (4) to any combination of 3 tracks invariably requires expensive flyovers to avoid frequent fouling of HSR traffic by local trains.

Operational Flexibility - advantage: fast-slow-slow-fast

Turnbacks (added 18 Jan)

The option of turning some commuter service back in the other direction before reaching either end of the line provides additional flexibility to tailor service patterns to passenger demand. This falls under the broad umbrella of operational flexibility, but merits a brief mention. For example, some Caltrain service could be turned back at Mountain View, heading back north where most of the ridership demand currently exists. Similarly, future Fremont service could be turned back at Redwood City. When a train is turned back, it needs to switch from one local track to the other local track. In a slow-fast-fast-slow configuration, this move requires fouling all four tracks in both directions. The fast-slow-slow-fast configuration, on the other hand, allows turnback tail tracks to be placed in the center of the right of way between the local tracks, with turnback moves having zero operational impact on any other track.

Turnbacks - advantage: fast-slow-slow-fast

Station Design

For the slow-fast-fast-slow track configuration, commuter (Caltrain local) stations would have two outside platforms, like the existing Bayshore and Lawrence stations. For the fast-slow-slow-fast configuration, commuter stations would have a single island platform, like the existing Belmont station.

A single platform has several advantages for passengers: there is no choice of which platform to use, making station access less confusing. A single platform is more pleasant, because it is typically about 30 feet wide rather than 15 feet. It is safer, because there are fewer opportunities to be isolated from other people. It is cheaper to provide all the station amenities, such as benches, shelters, ticket vending machines, elevators, information signs, platform lighting, etc. since they are shared for both service directions.

Ease of Station Access - advantage fast-slow-slow-fast
Platform Comfort - advantage fast-slow-slow-fast
Platform Safety - advantage fast-slow-slow-fast
Cost of Station Furnishings - advantage fast-slow-slow-fast

Impact to Abutters

On stretches of track between stations, both track configurations require about the same amount of land. The fast-slow-slow-fast configuration puts high speed traffic 15 to 20 feet closer to abutters' back fences. Whether this makes a material difference to noise levels remains to be evaluated, since high speed trains are generally quieter than any other train type at speeds of just 125 mph.

The fast-slow-slow-fast configuration also requires more land for the approaches to commuter stations, because the outside fast tracks must slew aside to clear the center platform in the station. On tracks built for 150 mph operation, tracks can be slewed by the necessary amount (about 15 feet) in a run length of about 1200 feet before and after the platform itself. These dimensions require an extra four triangular strips of land, 15 x 1200 feet, at each of four corners of the station area; in total, just shy of 1 acre.

Noise Impact - no clear advantage
Land Impact - advantage: slow-fast-fast-slow

Passenger Comfort

In a slow-fast-fast-slow track configuration, HSR trains would run straight down the peninsula without care for Caltrain infrastructure. In the alternate scenario with fast-slow-slow-fast island platforms, HSR must jog around each and every one of about twenty Caltrain station platforms. However, comfort for HSR passengers would not be adversely impacted even with the somewhat frequent twisting and turning of the high speed tracks. The key to comfort in curves is managing the lateral acceleration and its time derivative (also known as "jerk"), and the dimensions mentioned above account for suitably benign track geometry.

HSR Passenger Comfort - no clear advantage

Freight Service

Union Pacific runs freight trains over Caltrain's peninsula tracks, to serve various industrial customers as far north as the port of San Francisco. There are roughly two round trips per night. Service to industrial branch lines could continue essentially unchanged under the slow-fast-fast-slow track configuration. If the local tracks were moved to the center for a fast-slow-slow-fast configuration, the occasional freight train would have to cross over the outside HSR track to reach the customer. Given the massive difference in axle loading and speed, it is unlikely that running freight trains over any HSR tracks would even be feasible.

Freight Service - advantage slow-fast-fast-slow

Impact to Caltrain Stations (added 02 Jan)

HSR on the peninsula will require the vast majority of Caltrain improvements made in the last decade to be demolished and rebuilt. Dozens of platforms, buildings, etc. will have to be moved to make way for four tracks. However, Caltrain has two stations, Lawrence and Bayshore, which could be used essentially as-is for slow-fast-fast-slow operations. Converting these two stations to fast-slow-slow-fast would require demolishing and rebuilding the platforms, modifying the pedestrian access, and realigning the tracks. On the other hand, the Belmont station is in the opposite situation: it could be used as-is for fast-slow-slow-fast operations, but would have to be entirely rebuilt for slow-fast-fast-slow. Whatever approach is chosen, there will be nearly total reconstruction of every Caltrain station, and the issues with Bayshore, Lawrence and Belmont will be lost in the noise.

Impact to Caltrain Stations - no clear advantage

Future Infill Stations (added 13 Jan)

Commuter stops that are added at a future date, as development fills in around the tracks, are termed infill stations. With a slow-fast-fast-slow configuration, they are easy to build by simply adding a pair of outside platforms and suitable pedestrian under/overpasses. With fast-slow-slow-fast, realignment of all four tracks is necessary to provide clearance for the new central island platform. Communities along the Caltrain right of way are already well developed, so future infill stations are unlikely to be numerous.

Future Infill Stations - advantage: slow-fast-fast-slow

Conclusion

To pull together all these pros and cons, it is useful to pause first and remember that Caltrain's most valuable asset is its land. As such, HSR ought to be considered a tenant on Caltrain's property, which means giving proper consideration to Caltrain's need to provide effective commuter service. That is why operational flexibility should be weighted heavily. Putting all the factors together in a table, and assigning weights, one can build a trade study to identify the optimal solution. The nice thing about a trade study table is that arguments about the best solution can be reduced to arguments about the factors, and the weights assigned to each.

Factor	Weight	Score (S-F-F-S)	Score (F-S-S-F)
Operational Flexibility	35%	0	1
Ease of Station Access	4%	0	1
Platform Comfort	4%	0	1
Platform Safety	4%	0	1
Cost of Furnishings	4%	0	1
Noise Impact	10%	0.5	0.5
Land Impact	15%	1	0
HSR Passenger Comfort	5%	0.5	0.5
Freight Service	10%	1	0
Impact to Caltrain Stations	5%	0.5	0.5
Future Infill Stations	4%	1	0
Weighted Total		39%	61%

One can quibble with the weights assigned to each factor, but the conclusion seems pretty emphatic: the Caltrain tracks should be placed in the center, flanked by HSR on the outside. In short, Slow Traffic Keep Left!