Billions of Seconds Wasted

The latest tweaks to the design of the San Francisco Downtown Extension (DTX) rail alignment can be seen in a March 2018 track plan and profile drawing. Because it largely follows the street grid, it's no secret that the alignment is full of sharp curves, which can only be traversed at slow speed. However, compared to a 2012 drawing, speed limits have dropped in several places from 40 mph to just 30 mph, because train speed evidently isn't a design priority when civil engineers get a blank check.

Back in 2012, the speed profile sort of made sense: starting from the basement of the Transbay Transit Center (left end of the diagram) the train would screech at about 20 mph through the sharp curve towards 2nd Street, speeding up to 35 mph along 2nd and through the curve towards Townsend. On that mostly straight bit along Townsend, speeds could pick up to 40 mph before dropping back briefly to 35 mph through the curve to 7th Street, then exiting along 7th Street at 40 mph (right end of diagram). If only one criticism were allowed, it wasn't clear why that final curve should be limited to 35 mph; there was plenty of space at Townsend and 7th to flatten it out to 40 mph, resulting in a simple and efficient stepped speed profile for the approach to Transbay.

Fast forward to 2018, and things are much worse. There is a new kink in the alignment where it connects to the existing tracks. The new underground 4th and Townsend station, at the city's request, has been shoved into the Townsend Street right of way in the hope of freeing up the existing rail terminal parcels for high rise redevelopment (where the 2012 alignment might have clashed with new building foundations). The rigid requirement for a straight island platform has resulted in a series of 30 mph kinks in the track. Elsewhere, the speed limit along Townsend has dropped by 5 mph.

The designers might argue this is only a few seconds lost, so no big deal, right?

How many seconds are wasted?

A train traversing the DTX will have to observe the speed limits not just for the length of each speed restriction, but for the added length of the train itself, as the limit applies from the moment the head end of the train enters a speed restriction until the tail end leaves the speed restriction. High-speed trains will be up to 400 m long, so this can really add up. We can simulate the time needed for a train to travel from a standing start at the end of a Transbay platform to a 40 mph entry into the existing Tunnel 1, a distance of about 2.2 miles. The results depend on the train type, and whether a stop is made at 4th and Townsend:

• 2012 alignment, single-length HSR: 4:04
• 2012 alignment, double-length HSR 4:17
• 2012 alignment, 8-car Caltrain EMU, no stop at Townsend 4:06
• 2012 alignment, 8-car Caltrain EMU, 30-second stop at Townsend: 5:04
   
• 2018 alignment, single-length HSR: 4:25 (+21 sec)
• 2018 alignment, double-length HSR 4:42 (+25 sec)
• 2018 alignment, 8-car Caltrain EMU, no stop at Townsend 4:27 (+21 sec)
• 2018 alignment, 8-car Caltrain EMU, 30-second stop at Townsend 5:19 (+15 sec)

To summarize and simplify, we can assume that every Caltrain will stop at Townsend, so the performance loss is 15 seconds per Caltrain movement, and roughly 20 seconds per HSR movement. That doesn't sound like much, but consider that trains are carrying hundreds of passengers, each of whom are individually delayed. The collective waste of time can be measured by multiplying the train delay by the expected ridership.

Today Caltrain has about 15,000 weekday boardings in SF, a number that Caltrain says could eventually quadruple. Let's say it only triples, and that 35,000 of those weekday boardings occur at Transbay and 10,000 at 4th and Townsend (which we won't count) making for 70,000 trips through the DTX approach. That's 70,000 trips x 15 seconds/trip = a million seconds wasted every weekday, or about 3 person-years of productive labor time per month of DTX operation. Over a year, about a quarter billion seconds would be wasted!

HSR eventually expects 18 million annual trips originating in the Bay Area, of which maybe half might involve Transbay. Combine that with a similar number of HSR trips terminating at SF, and you get 18 million annual HSR trips through the DTX approach. That would be a waste of another third of a billion seconds.

Every year then, about half a billion seconds would be wasted due to careless DTX alignment design.

How do we fix it?

Fixing it involves realizing that

1. every second matters, a lot
2. the marginal cost of the next second saved is more expensive than the last
3. saving seconds is most efficiently and cheaply done in the slow parts of a system

Making up 20 seconds through minor fixes to the DTX track alignment design, before any concrete is poured, is far cheaper and easier and more productive than trying to make up 20 seconds somewhere faster, for example in the Central Valley by running trains at 220 mph instead of 215 mph.

What ought to still be possible is an alignment that starts at 20 mph through the screecher to 2nd Street, rises to 35 mph along 2nd Street, then rises to 40 mph along Townsend continuing without slowing around the curve to 7th Street. With this improved speed profile, train run times from Transbay to Tunnel 1 (relative to the 2018 alignment plans) would be:

• Single-length HSR: 4:02 (23 seconds faster)
• Double-length HSR 4:14 (28 seconds faster)
• 2018 alignment, 8-car Caltrain EMU, no stop at Townsend 4:04 (23 seconds faster)
• 2018 alignment, 8-car Caltrain EMU, 30-second stop at Townsend 5:02 (17 seconds faster)

The combined annual time savings would exceed half a billion seconds per year. As we watch the cost of the DTX project reach ever more dizzying heights, we should at the very least expect to get more transportation value out of the project. Careless and inexcusable engineering of a rail alignment that wastes so much of everyone's time only adds insult to the injury.

San Bruno Out To Bid

Caltrain's San Bruno grade separation project is out to bid as of March 11th. The final engineering drawings reveal the HSR-hostile curve radius of 2387 feet, good for 75 mph (see details at right). While Caltrain has been exercising eminent domain in preparation for construction, they never seemed interested in acquiring the run-down houses on the inside of the curve to straighten out what is, has been, and will now forever be the #1 worst curve on the peninsula.

Caltrain officials continue to spread the falsehood that the curve is HSR-ready and that the design speed is 90 mph. Unfortunately, at an aggressive total cant of 12 inches (6 inches superelevation plus 6 inches unbalance) this curve will forever be restricted to a bit over 80 mph. Total cant would approach a drink-spilling 15 inches to run a train through the inside curve at 90 mph, something the FRA will never allow.

HSR trip time penalty: about 25 seconds, or 1/4 percent of the entire SF - LA run.

That may not sound like much, but when you consider that trip time is the foundation of high-speed rail, and that the next second saved always costs more than the last second saved, San Bruno is a terrible way to start off on the HSR path. Those 25 forsaken seconds will have to be recovered elsewhere, likely at far greater incremental cost than just doing San Bruno right with a 100 mph curve.

(we'll say nothing of the doomed-to-do-over 8 inch station platforms to be constructed right in the path of the future HSR alignment... that's just the cherry on this cake!)

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.

Freight on the Peninsula

UPDATE (3/18) Thanks to Martha Martinez, PCJPB Secretary, for providing the full text of the 1991 trackage rights agreement that governs freight access on the peninsula.

Freight trains operate daily along nearly the entire length of the Caltrain corridor (San Jose photo at right by Michael Patrick), and make up less than 5% of train traffic on the peninsula. The freight trains move mostly at night, when Caltrain traffic is sparse.

Freight trains have always been part of the traffic mix on the peninsula. The corridor formerly belonged to freight operator Southern Pacific, which sold the 51.4-mile railroad right of way to the Peninsula Corridor Joint Powers Board (Caltrain) in 1991 for $219 million.

Existing Freight Traffic

Thanks to Kevin Hecteman for the following description of freight traffic patterns on the peninsula:

Union Pacific currently operates three freight trains per weekday, all based out of the yard next to the South San Francisco Caltrain station.

1. SOUTH CITY SWITCHER: Goes on duty early in the morning: switches industries between South City and Pier 96 in San Francisco. Shippers include Granite Rock, Central Concrete and Pacific AgriProducts in SSF; Sierra Point Lumber near the Bayshore station; Dean's Refrigerated Trucking off Carroll Avenue in SF; Darling International, a rendering plant near Pier 96; and the Waste Solutions Group dirty-dirt concession at Pier 96. Famous for being the last freight train serving San Francisco. A sizable photo archive detailing this operation can be found here.
   
   
2. BROADWAY LOCAL: Goes on duty at 5:30 p.m.; switches industries between SSF and San Jose, such as the Port of Redwood City, after the evening rush hour ends. (One such industry is the Unilever plant in Sunnyvale, as seen here.)
   
   
3. MISSION BAY HAULER: Goes on duty at 6:30 p.m.; gathers up all the outbound cars brought in by the other two locals and hauls them to the UP yard in Milpitas, then returns with the inbound cars for distribution by the locals. This train can easily see 60 to 90 cars.
   

Freight in the Peninsula's Future

All existing plans for improving the Caltrain corridor (namely, Caltrain's 2025 Plan, including electrification, as well as California high speed rail) explicitly preserve the capability to carry freight up the peninsula, and allow for a possible expansion of freight traffic.

Whether this is justified by existing traffic levels (less than 5% of train movements) is open to debate. If freight service on the peninsula were discontinued, some traffic would likely move by truck over Highway 101, and the rest of it, and associated jobs, might disappear altogether from San Francisco and the peninsula.

Regardless of actual demand, the peninsula freight operator, Southern Pacific (and its successor, Union Pacific) retained trackage rights from Caltrain when the latter acquired the tracks, giving UP the right to operate a certain quota of freight trains on the peninsula. Such agreements are administered by the Surface Transportation Board, and would likely be difficult to terminate not only because of the bureaucratic process, but because UP (no supporter of the HSR project) might attempt to use their rights as a bargaining chip against the high speed rail authority.

So, while freight accounts for only a tiny minority of train movements that is likely to become infinitesimal when Caltrain service is expanded and HSR service begins, all agencies involved are proceeding under the firm assumption that freight trains will be accommodated for all time--regardless of whether or not this makes sense from an economic or technical standpoint.

STRACNET: A Military Twist

The Department of Defense designates a nationwide network of rail links critical to national defense, known as the Strategic Railroad Corridor Network, or STRACNET.

This network provides the readiness to ship materiel from military depots to ports of embarkation in the event of a war emergency. STRACNET was established in the 1970s, when freight railroads were falling into disrepair, and sets rock-bottom minimum standards for:

• operating speed, with a minimum desired track speed of 40 mph
  
• clearance profile, to ensure that track side obstructions do not foul the DOD load clearance requirements defined in MIL-STD-1366
  
• weight capability, to allow M-1 tanks to be carried in pairs on 140-ton flat cars.
  

Why would we care about this Cold War relic? As it turns out, the peninsula corridor is part of STRACNET, or at least it was according to the 1998 update (see California map on page 30), presumably to access the mighty port of embarkation known as San Francisco--never to be outdone by its far bigger rival across the bay. The makeup of STRACNET is updated every few years by the DOD and FRA; there is no guarantee that the peninsula corridor will retain its military designation.

Because the Caltrain corridor already accommodates daily freight trains (see Caltrain's clearance standards, also drawn as a green outline in the figure at right), Caltrain more or less meets the STRACNET requirement (red outline). Its track maintenance standards exceed the operating speed and weight requirements. Beyond the loading clearances shown at right, available structural clearances are much wider than required by the DOD because Caltrain already complies with the draconian clearance requirements of the California Public Utilities Commission.

Bottom line: STRACNET is a yawner, although that is unlikely to stop HSR opponents from making an issue out of the grievous omission of STRACNET from CHSRA environmental impact documents.

Implications of Freight for Caltrain and HSR

Freight service (in addition to HSR) has a few important implications for the future of the peninsula corridor, none of which are likely to be welcomed by neighbors.

1. More Tracks. The 125 mph speed envisioned for HSR on the peninsula requires tracks to be banked in curves (see the Top 10 Worst Curves for more technical details), with the outside rail raised as much as 6 inches higher than the inside rail. This steep banking is incompatible with slow and top-heavy freight cars and can lead to derailments excessive rail wear. The CHSRA's plan for four tracks along the entire length of the peninsula is likely to be driven just as much by the perceived need to accommodate freight trains (by having one pair of tracks banked, and the other pair not) than any service pattern considerations to allow trains of differing speeds to overtake each other. The need for four tracks may be somewhat alleviated without freight trains.
   
   
2. Taller Electrical Poles. Track improvements are being designed to increase Caltrain's clearances from AAR Plate F to the much taller AAR Plate H. This would allow "excess height" freight cars such as autoracks and double stack container cars--never mind for which supposed customer on our dead-end peninsula! Expanding from the existing Plate F condition to Plate H requires another 3 feet of vertical clearance, which will force the overhead electrification of the tracks to be built at least 3 feet taller, thus increasing visual blight.
   
   
3. Higher Embankments. Freight trains are much heavier than high speed trains or the "non-compliant" EMU trains coveted by Caltrain. In fact, the very high speed trains of the type required to run at 220 mph in the Central Valley are some of the lightest trains anywhere. On the other hand, heavy weight requirements lead to beefy bridge decks, further inflated by seismic requirements. For grade separations where a road crosses under the track, every additional foot of bridge deck thickness adds an additional foot to the height of the rail embankment (or an additional foot to the depth of the underpass excavation, with attendant increase in the length of the approach ramps.)
   
   
4. More Noise. Freight trains are generally not maintained to the same high standards as high speed passenger equipment. Freight trains with diesel locomotives and wheel flat spots banging along the track will be much louder than electric trains, even after horn-blowing is obviated by grade separations. Accommodations that are now being made for freight operations may lead to an increase in noisy freight traffic.
   

From the point of view of civil engineering companies who will design and build HSR infrastructure on the peninsula, every additional cubic yard of concrete and every design complication is a potential path to extra profit. To this end, the requirements arising from Union Pacific freight service and STRACNET may indeed be quite welcome. After all, if it's profitable, why not let the tail wag the dog?

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.