Odd Stacking

The odd stacked alternatives shown in the figure at right (ripped out of a recent technical working group presentation) make little sense, for a number of reasons that were previously discussed.

Recall that track stacking, besides entailing very intensive and profitable construction of complicated earthquake-resistant civil structures on the taxpayer's dime, is intended to reduce the right-of-way width required to build a four track corridor, presumably to appease neighbors and minimize residential property takes. A brief glance at the above drawing (which should also reinforce fears of a separate-but-equal approach that is disastrous for Caltrain) necessarily leads to ONE of the following two conclusions:

1. The planners have lost sight of what they were trying to achieve, in effect destroying our village in order to save it. The stacked solution on the left requires "only" 87 feet of ROW width, while the one on the right requires 119 feet of ROW to make room for a Caltrain platform down in the trench. These elephantine structures, making use of enormous amounts of concrete, seem to miss the whole point of stacking: to save space. If you were to nibble back just 4 feet out of the 13 feet (thirteen!) devoted to drainage and third-party utility easements, you could simply stick all four tracks down in that trench on 15-foot centers. Dear peninsula communities: do you prefer 13 feet for drainage and utilities, and oh, by the way, a viaduct that looms 30 feet above ground level (16 feet of road vehicle clearance, 10 feet of viaduct box + rails, and 4 feet of sound wall) with another 30 feet of overhead wires towering above that? Or would you rather we cut back to 9 feet for drainage and utilities, and the viaduct disappears entirely? Let's think it over, for about a microsecond.
   
   
2. The planners are not so subtly trying to sand-bag the stacked options to gain community buy-in for property takes. Making the stacked alternative look this bad on paper fulfills the dual goal of giving it environmental due diligence under CEQA and ensuring that public opinion will be "stacked" against it, setting it up for being "not carried forward" in a way that is impervious to future litigation. These are the lengths to which we must go to take 5 feet of somebody's back yard.
   

Since one would prefer to assume that planners are not stupid, and that they don't take peninsula residents for idiots, #2 seems more likely. Stay tuned for the answer: the supplementary alternatives analysis report for the peninsula high-speed rail project is scheduled to be revealed to the public on Thursday, August 5th in San Francisco.

Stacked Nonsense

A preview of the alternatives analysis provided to Palo Alto residents reportedly included several stacked track alternatives. In a Palo Alto Weekly article, track stacking is described thusly:

Tim Cobb, whose firm HNTB is performing engineering work for the Peninsula segment, said the alternatives analysis is also considering stacking train tracks in sets of two. This could entail keeping the two existing Caltrain tracks in their current alignment and building two new high-speed-rail tracks either above or below them. This appears to be a particularly viable option at areas where the right-of-ways are narrow, such as Churchill Avenue, rail officials said.

Track stacking is a design that communities should beware. While it may solve the problem of threading four tracks through narrow right-of-way pinch points without taking adjacent properties, it has many disadvantages.

1. If the tracks are stacked, one pair of tracks (Caltrain's) will remain at grade. This will result in continued noise from grade crossing bells and train horns (especially from freight trains, which will operate between midnight and 5 AM), and continued accidents and service disruptions caused by the occasional trespasser or stalled car. The impact will only get worse as Caltrain traffic increases from the current 90 trains/weekday.
   
   
2. Grade separations can provide important community benefits such as reduced noise, smoothed traffic flows across the tracks, and a safer environment with a lower risk of accidents. Track stacking not only precludes these benefits, but it permanently prevents the future grade separation of Caltrain.
   
   
3. If the HSR tracks are stacked above the Caltrain tracks, they will need to clear tall freight trains and high-voltage overhead electrification. That means the free clearance underneath such a structure must be ~25 feet, with the HSR tracks ~30 feet above ground level rather than ~16 feet for a conventional overpass grade separation. Sound walls and overhead electrification poles would raise the overall height of such a viaduct to a neighborhood-blighting sixty feet (as shown in the figure above, with a viaduct taken from TM 1.1.21). The noise and visual impact could spread far beyond the immediate vicinity of the crossing, affecting several blocks on either side of the tracks.
   
   
4. If the tracks are sunk, all the surface disruption and expense of tunnel construction will be incurred with none of the benefits. After the dust settles, trains will still make noise, grade crossings will still close a hundred times a day, the tracks will still form a barrier through the community, and crossing accidents will still occur. The tunnel plus at-grade solution is now favored in Anaheim, where there is a 1.5-mile stretch of 50-foot right of way, far narrower than anywhere on the peninsula.
   
   
5. Building stacked tracks will require land takes anyway, since stacked tracks cannot be built directly over or under active Caltrain tracks. Any stacked scenario would require temporary shoofly tracks to keep Caltrain operating during construction, and those shoofly tracks might require the very same land takes that stacked arrangements are intended to avoid in the first place. Whether temporary (for construction) or permanent, such land takes have the same legal and material impacts to residents.
   
   
6. Stacked tracks are a waste of taxpayer money. For roughly the same cost and the same level of disruption, a simpler and functionally more effective four-track grade separation can be built instead. The only people who benefit from the tens of millions of dollars spent to stack the tracks are (a) the engineering and construction firms who build these complex structures, and (b) a handful of property owners immediately adjacent to the tracks, who get to hang on to their land in somewhat of a Pyrrhic victory.

One might reasonably conclude that stacked tracks are a badly overwrought solution to the perceived problem of residential takes.

Bloated Requirements

Taken for granted in this crazy talk about stacked tracks is an assumption that a 100-foot wide swath is required if all four tracks run on the same level. That 100-foot peg won't fit in some of the 60 or 75-foot holes that dot the peninsula corridor.

As it turns out, this 100-foot figure includes expansive margins for cable ducts, utility easements, maintenance walkways and drainage structures. In a pinch, the tracks can be spaced just 15 feet center-to-center. So are we going to build a 60-foot tall structure just so drainage trenches will fit and AT&T can run some fiber optic cable on the right of way? No, we shouldn't. With some creative engineering, four tracks can and do exceptionally fit within a 75-foot right of way, even with drainage and utilities. It makes no sense to build tall viaducts or tunnels because we're short a few feet for these ancillary items.

Which brings us to land takes, a.k.a. eminent domain... the third rail of peninsula HSR politics.

Destroying the Village In Order To Save It

With growing opposition to HSR on the peninsula, program managers are walking on eggshells, especially when it comes to taking any residential land. What they fear most in eminent domain proceedings is neither cost nor delay (both would likely be minimal), but the political fallout and galvanized opposition to the project.

Seemingly bending over backwards to avoid residential land takes at all possible costs, HSR designers are now contorting themselves into these stacked design alternatives possibly as a veiled signal to the communities. Perhaps it is their calculation to elicit such a negative response that the communities themselves will suggest far more reasonable solutions--solutions that may involve a residential take here and there. Whatever the underlying motives might be, peninsula cities should be suspicious of stacked tracks, and weigh the relative community benefits of carefully optimized and very limited residential takes. And communities will need to take the initiative on this, because the HSR project politically can't and won't.

In some cases, eminent domain is not just a last resort: it may be part of the "best" and overall lowest-impact design solution.

San Bruno Done Right

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

Quick Links (discussed extensively below)

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

Not So Fast

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

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

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

San Bruno Done Right

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

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

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

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

For the track geometry junkies out there:

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

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

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

The Joy of Tunnels

There's a lot of talk among peninsula communities about the virtues of tunneling certain portions of the peninsula rail corridor that run through residential neighborhoods, in order to mitigate the potential above-ground impacts of increased traffic, faster speeds, noise, vibration, visual blight of overhead electrification and grade separations, etc.

Tunnel advocates evoke visions of tunnel boring machines silently toiling underground, leaving the land above all but untouched. These visions need to be tempered with some basic facts about tunnel engineering.

1. A four-track tunnel is too wide (~80 ft) to be excavated using a tunnel boring machine. At a minimum, two tunnel bores would be required, driving up tunnel costs.
   
   
2. Boring a tunnel in soft soil under the water table is difficult because hydrostatic pressure increases with depth, making the tunnel more vulnerable to leaks and flooding.
   
   
3. Boring a tunnel in soft soil often causes subsidence. While this settling of the soil can be predicted and mitigated to some extent, the foundation of a house can be severely damaged by very small strains, curvatures or tilts of the underlying soil.
   
   
4. Once it is decided to build a tunnel, the method of construction is up to engineers and accountants. In peninsula communities where a shallow tunnel would suffice to mitigate noise, vibration and visual impacts, it is unlikely that they would select a bored tunnel, using massive tunnel boring machines. A far more likely approach is a cheaper cut-and-cover tunnel, where a trench is excavated and a roof built over it.
   
   
5. For reasons of fire safety, and possibly to accommodate the occasional diesel train, long tunnels must have extensive forced ventilation systems with large head houses constructed above ground. These structures contain powerful fans that are anything but quiet.
   
   
6. In a fire, a tunnel becomes an oven filled with toxic smoke. A four-track tunnel would have to be divided into at least two separate hermetically sealed sections to allow for emergency evacuation of hundreds of passengers. These fire-proof partitions add width to the tunnel.
   
   
7. Tunnel evacuation walkways need to be provided, adding some width to the tunnel. These walkways need frequent access to the surface along the length of the tunnel, for passenger evacuation as well as emergency access.
   
   
8. Running trains at 125 mph in a tunnel requires ample aerodynamic clearances to prevent strong pressure waves from forming between trains and tunnel walls. Pressure waves can cause intense discomfort (ear popping) and may even threaten the stability of a train on the tracks. For 125 mph operation, a typical clearance is 12 to 15 feet between the track center line and tunnel wall.
   
   
9. Digging a cut-and-cover tunnel while Caltrain continues to operate will probably require temporary shoofly tracks around the construction site. These tracks occupy about 30 feet of right of way, in addition to the width of the tunnel construction site.
   
   
10. Cut-and-cover tunnels of the size required for Caltrain and HSR will have concrete walls about 3 feet thick, to give them the structural integrity and seismic stability that the surrounding soils lack.
    
    
11. The overall width of a four-track cut-and-cover tunnel structure (accounting for 3-foot wall thickness, 15-foot track spacing, 12-foot side clearances for aerodynamics and evacuation, and two separate tunnel sections separated by a central wall) comes to 87 feet.
    
    
12. The overall depth of a cut-and-cover tunnel structure (accounting for 4-foot base slab, 2-foot trackbed depth, 20 feet of vehicle loading gauge, 6 feet of overhead contact system high voltage clearances, a 3-foot roof slab and a 5-foot soil layer) comes to 40 feet. The soil cover might be thinner or thicker than 5 feet according to local topography; 5 feet is a realistic average.
    
    
13. Building a 40-foot deep, water-tight barrier in an area with a high water table, extensive underground aquifers and surface creeks running perpendicular to the railroad is likely to cause changes in the water table, possibly leading to localized subsidence or flooding. Continuous pumping of surrounding aquifers may be required to prevent hydrostatic pressure buildup and excessive flotation (and cracking) of the sealed tunnel structure.
    
    
14. The amount of excavation for a four-track cut-and-cover tunnel is about 700,000 cubic yards per mile (330,000 cubic meters per km). A five-mile tunnel would require the removal of enough dirt to equal the volume of the Great Pyramid of Giza.
    
    
15. Including shoofly tracks and additional construction easements required to build the vertical walls, the overall right of way consumed by a cut-and-cover construction site could easily exceed 120 feet.
    
    
16. Some of the dirt excavated for tunnels may be contaminated by underground toxic plumes containing chemicals known to the state of California to cause cancer and birth defects or other reproductive harm. Such dirt would have to be treated and disposed of according to state and federal environmental regulations.
    
    
17. The primary criticism of tunnels has been cost, which can be roughly extrapolated from other Bay Area tunnel projects currently being planned. The BART extension to San Jose includes a five-mile, two-track, three-station tunnel for $3 billion ($9,500 per inch). The Caltrain extension to San Francisco's Transbay Terminal includes a 1.8-mile, three-track, two-station tunnel for $2.1 billion ($18,000 per inch). Based on these estimates, we can reasonably expect construction costs to be on the order of $10,000 per inch, give or take a factor of two.

Of course, tunneling conditions will vary according to each specific location. The California High Speed Rail Authority's consultants and geotechnical experts will certainly do a more detailed job of evaluating feasible tunneling options, as their project-level environmental impact process gets underway. In the meantime, this layman's overview is intended to put tunneling back in perspective among the other configuration options for portions of the peninsula corridor.

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.

Focus on: Palo Alto

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

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

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

San Francisquito Creek

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

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

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

Palo Alto Station Area

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

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

The Palo Alto Chicane

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

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

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

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

HSR Station Scenario

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

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


View Larger Map

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

No HSR Station Scenario

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

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

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

Bike Path

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

Churchill Ave Grade Separation

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

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

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

Southgate

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

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

Peers Park

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

California Avenue Station

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

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

Meadow and Charleston Grade Separations

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

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

Vertical Track Profile

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


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

The Tunnel Idea

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

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

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

Focus on: San Bruno

San Bruno is the point of departure for the "Bayshore Cutoff" to San Francisco, built in the early 1900s by the Southern Pacific Railroad. The rail line to San Francisco originally went straight through San Bruno and detoured around the west side of San Bruno mountain, where BART runs today. The cutoff was built around the east side of the mountain, then through a series of tunnels, as a shortcut into San Francisco. This is the alignment used by Caltrain today and planned for HSR.

San Bruno Curve

One important consequence of this history is that San Bruno is left with one of the sharpest curves on the peninsula, where the cutoff formerly diverged from the old main line. The radius of the curve is 1800 feet (550 meters), giving it a maximum safe speed of about 70 mph (115 km/h). Caltrain has a speed limit of 60 mph at this location. Slowing down a high speed train from a peninsula cruise speed of 125 mph (200 km/h) to take the existing San Bruno curve would cost more than a minute, or over half a percent of the entire SF to LA running time. Considering how much investment is being made to shave seconds off run times for the entire system, a 1-minute penalty in San Bruno for a single curve should raise some red flags at the CHSRA.

Consider the "San Bruno Curve" a significant obstacle to HSR on the peninsula.

To run trains safely at 110 mph through the curve, it would have to be straightened to a radius of 1200 m. This is shown as a blue outline in the map to the right (see the Top Ten Worst Curves for more information on curves). Straightening the San Bruno curve for HSR is complicated by several factors:

• The houses along Montgomery Ave, on the inside of the curve, would likely have to be taken by eminent domain. According to zillow.com these houses are worth a combined $6 million, a relative drop in the bucket compared to the $4200 million to be spent on the peninsula alone. The tracks would also pass on the site of the former lumber yard on the inside of the curve, recently torn down.
  
• The viaduct for I-380 (named, irony of ironies, the Quentin L. Kopp freeway) crosses over the tracks at the north end of the curve, supported by a forest of beefy concrete pillars.
• Caltrain has planned a 4-track grade separation in this location (see below) that essentially preserves the existing sharp curve. (The radius was planned to increase slightly from 1800 ft to a still-tight 2000 ft, staying within the existing Caltrain right-of-way.) However ill-conceived, these planning errors have a sneaky way of perpetuating themselves, especially after the $10 million spent to date on engineering this project.

The next significant curve, 2.5 miles to the north, around the base of San Bruno mountain at Sierra Point, has a radius of about 2600 ft (800 m), giving it a maximum safe speed of about 85 mph (140 km/h). This curve cannot be straightened due to the local topography, but is sufficiently distant from San Bruno to allow trains to accelerate to 125 mph (200 km/h) by the time they reach San Bruno curve.

Grade Separations

San Bruno has grade crossings at Angus Ave, Scott St, and San Mateo and San Bruno Avenues. The latter is known as one of the most dangerous crossings on the peninsula, because San Mateo Ave crosses the tracks at an acute angle and the nearby curve limits visibility for trains, auto traffic and pedestrians.

Caltrain and the city of San Bruno have long-standing plans to grade-separate the crossings in San Bruno. These plans have been delayed several times due to funding issues, most recently until 2012. Caltrain has produced a detailed Grade Separation Study Report, from which the preliminary track layout is of particular interest. The city of San Bruno is developing a downtown and transit corridors plan that includes the Caltrain station area. The San Bruno Caltrain station would be rebuilt to the north of its current location with four tracks, elevated over the San Mateo Ave / San Bruno Ave crossings. The streets would be sunk to pass under the new station. The Scott St. crossing would be closed to auto traffic, with a pedestrian / bike underpass built instead. The proximity of the BART tunnel, which passes under the Caltrain tracks just south of San Mateo Ave, is a complicating factor discussed in the report.

With the passage of proposition 1A, Caltrain's plans for San Bruno should be thoroughly re-evaluated, regardless of the studies, $10 million of preliminary engineering, committees, public input and debate of the last several years. With high speed rail in the mix, the requirements have changed, and the biggest problem with the existing plans is the San Bruno curve.

HSR Plans

The California High Speed Rail Authority's Bay Area EIR / EIS, Appendix D, shows the alignment through San Bruno as a 15-foot tall retained fill embankment with split grade separations (exactly as planned by Caltrain, except with four tracks all the way through town). The rails dip down briefly to grade level as they pass under the I-380 viaduct.

The CHSRA gives no indication of an intention to straighten San Bruno curve; their plans show the tracks following the existing Caltrain right-of-way.

San Bruno Done Right

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

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

For more details on this proposed design for the San Bruno station, see San Bruno Done Right.

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