16 December 2018

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.

08 December 2018

Grade Crossing Trouble Ahead

Grade crossing in Denver (photo: RTD)
Denver's RTD has been operating a new 25 kV electrified commuter railroad since 2016. There's a big problem with it: the grade crossings gates are down for too long, which the FRA and Colorado PUC consider hazardous because impatient motorists frustrated by a longer-than-expected wait may drive around the gates just as the train finally shows up. The problem has festered, with  millions spent on human flaggers to supervise traffic at each grade crossing, contractual acrimony leading to lawsuits, and in recent days a threat by the FRA to shut down the entire railroad until the issue is resolved.

What does any of this have to do with Caltrain? The peninsula corridor electrification project uses the same electrification technology installed by the same contractor (Balfour Beatty), uses the same positive train control technology installed by the same contractor (Wabtec), must contend with more than three times as many grade crossings, and therefore, faces the same looming grade crossing problem. For months, the issue has topped the list of risks that threaten the project, and the search for a viable solution is causing the electrification contractor to fall significantly behind schedule.

How grade crossings are supposed to work

The simplest way to activate a grade crossing is for the train to shunt a track circuit at some set distance before the crossing. This is known as a conventional track circuit warning system, and doesn't work well if different trains arrive at different speeds. The point where the crossing activates must be set far enough ahead to give the required warning time before the fastest train arrives at the crossing; this makes the gates stay down too long for slower trains.

The usual solution to this problem is a Constant Warning Time (CWT) system, which uses electrical signals sent through the track to sense the distance and speed of the approaching train. The grade crossing controller can then predict when to activate the crossing such that the warning time is approximately constant regardless of train speed. This is the type of warning system installed today on the many grade crossings of the peninsula rail corridor.

The FRA provides a nice overview discussion of how various types of grade crossings work. The applicable federal regulations are under 49 CFR Part 234.

What happened in Denver

Because the Denver system is electrified, there are large 60 Hz AC traction return currents (at safe low voltage!) commonly present in the rails when a train is nearby. These currents interfere with and prevent the use of a traditional Constant Warning Time system.

The contractor came up with a "smart" solution: the crossings have a traditional track circuit warning system overlaid with a wireless crossing activation system (WCAS) that interfaces with the positive train control system. Software sends wireless messages back and forth between the train computer and the crossing controller. The train and crossing enter into a contract: the train predicts when it will arrive at the crossing and promises not to get there any sooner, and the crossing commits to activate at some fixed time interval before the appointed arrival, staying closed until the train passes. Depending on the circumstance, the train may arrive at the crossing later than anticipated when the contract was entered into, resulting in extended gate down time. When WCAS is inoperative, the old-school track circuit takes over, also resulting in extended gate down time when a train is operating at less than maximum speed.

In early 2016, before the Denver train opened for revenue service, FRA and PUC inspectors found that the crossings activation times were inconsistent, with frequent occurrence of long gate down times and erosion of what is known as "credibility" of the warning system. Things went gradually downhill from there:
  • So as not to delay the much anticipated start of revenue service, the regulatory agencies granted a temporary waiver to allow RTD to begin operating without WCAS, on the condition that human flaggers supervise traffic at each affected crossing, at the expense of the contractor.
  • The contractor tried to tweak the WCAS software to make warning times more consistent. A fudge factor known as the "Approach Condition Adjustment Factor" (ACAF, so known because every fudge factor needs an acronym to sound legitimate) was applied based on the observed statistical distribution of warning times at each crossing.
  • In September 2017, the FRA gave RTD relief in its interpretation of the consistency required for gate downtime, relaxing its unofficial consistency criterion from +/-5 seconds or +/-10% of programmed warning time to +15/-5 seconds for RTD's system.
  • Performance of WCAS failed to satisfy the increasingly picky regulatory agencies. RTD began to penalize the contractor for failing to deliver a working grade crossing solution. FRA inspectors kept writing up excessive downtime violations.
  • The FRA forbade the start of revenue service on a newer rail line that has since been completed. The original plan to create quiet zones, where train horns are not used at grade crossings, was delayed indefinitely to the continuing aggravation of neighboring residents.
  • In September 2018, the contractor decided that the regulatory agencies had invented and enforced new consistency requirements that were not in the official regulations, and sued RTD claiming "force majeure" of a regulatory change. The complaint makes a fascinating read.
  • In October 2018, the FRA provided the latest inspection report (of many) showing continuing non-compliance with the -5/+15 second consistency tolerance.
  • On November 15th, 2018, the FRA fired off a letter indicating that it was fed up with the continuing grade crossing non-compliance, among other things, and threatened to shut down the entire commuter rail system by revoking the 2016 waiver.
  • RTD is lawyering up against the FRA, and submitted a strongly worded legal memorandum with numerous exhibits effectively claiming that the grade crossing problem exists solely in the imagination of the regulators. RTD provided evidence that other railroads (including Caltrain!) commonly experienced long gate down times in violation of the criteria imposed on RTD.
Whatever happens next is sure to be dramatic. The entire saga can be reviewed under docket FRA-2016-0028, which organizes all the documents exchanged between RTD and the FRA relating to the temporary operating waiver.

Some Observations
Measured distribution of 38255 grade
crossing activation times in Denver.
  1. Denver solved the wrong problem. They tried to invent a better mousetrap, something more sophisticated than a constant warning time grade crossing predictor. All they needed to do was to provide the same simple function with a substitute detection method that didn't rely on traditional audio-frequency AC circuits, which are incompatible with electrification. Instead, they decided to invent a better mousetrap involving lots of software, GPS, and wireless messaging, which naturally attracted regulatory scrutiny.
  2. Complexity is bad. Multiplying the number of interfaces and creating dependencies between elements of the system leads to expensive aerospace avionics-like hardware and software that is cumbersome to deploy, test and maintain. System complexity leads to a proliferation of strange and unanticipated corner cases and failure modes.
  3. Software can anticipate when to activate a crossing and prevent a train from showing up too soon, but there is no software in the world that can make a train show up on time.
  4.  Grade crossing activation times naturally follow a statistical distribution that arises from random environmental factors beyond the control of the warning system. The low end of the distribution must never be shorter than the mandated 20 seconds, but the long end of the distribution will inevitably have some outliers. The diagram above shows the measured distribution of 38255 crossing activation times on RTD. Notice the long tail.
  5. Even traditional "constant" warning time systems have this statistical tail. If the FRA inspectors applied the same regulatory zeal to Caltrain as they did to RTD, Caltrain would certainly be found in non-compliance. This isn't idle speculation: RTD gathered the data to prove it.
  6. The criteria for non-compliance, namely a "significant difference" from the prescribed warning time, are subjective. Guidance from the FRA acknowledges as much: "Thus, prudent judgment must be exercised when reviewing the results of warning time testing to determine whether the actual warning time provided during testing was compliant with the standard."
  7. The regulators painted themselves into a corner. They imposed a strict -5/+15 second criterion, which is easy to verify for an inspector with a stop watch and a clip board, but makes the long tail of the activation time distribution an automatic violation that is almost impossible to avoid. In recognition of the environmental factors beyond the control of the warning system, the regulators should have used controlled test conditions or applied a different criterion, such as X% of activations within Y% of programmed warning time. This is harder to verify for an inspector with a clipboard, but the grade crossing controller ought to be able to maintain these statistical records across a very large number of crossing activations.
  8. While electrification is relatively rare in the US, there are numerous railroads abroad that have solved the constant warning time problem in electrified territory. This probably isn't rocket science. The mousetrap already exists.
Lessons for Caltrain
With the grade crossing warning system already at the top of the Caltrain electrification project's risk list and the contractor falling behind, this problem is already getting a lot of attention. The people involved hopefully already realize:

Keep it simple - the job is to come up with a grade crossing predictor that works in the presence of traction return currents. It will be tempting to come up with a more sophisticated custom solution that uses lots of software, but we learned from the CBOSS project, and Denver's travails, that complexity usually leads straight to disaster. The dumber the better.
Document existing conditions - a large database of activation time statistics should be assembled for each crossing as it exists today, to head off a conflict over the subjective nature of the FRA warning time consistency criteria. In the event of a Denver-like disagreement with FRA or CPUC, Caltrain would be in a position to quantify precisely how much more (and hopefully not less) consistent the new warning solution will be, regardless of the selected criterion. Caltrain enjoys the advantage that it isn't building new crossings like Denver, so there is an existing system performance baseline that is already accepted by regulators. That baseline will only be useful if it is thoroughly documented.
Plant the goal posts firmly - Work with FRA towards mutually agreed verification criteria that don't repeat the mistakes made in Denver of specifying a rigid range and then testing in the uncontrolled conditions of revenue service. The activation time distribution will always have a statistical tail. If the consistency criterion can't be met by today's existing grade crossing system, then it's probably a bad criterion.
Make sure we aren't paying for Denver - the contractor needs to be held accountable for the extent to which Caltrain electrification funds (and schedule delays!) are accruing to the Denver project's benefit, if the same grade crossing solution is ultimately pursued in both projects.

21 October 2018

Thinking Big in Redwood City

The architecture of Amsterdam Bijlmer
(photo by tataAnne) could represent
the future Redwood City station.
In a seamless transportation network that runs on a regular clockface schedule with timed, well-coordinated transfers, connecting nodes play a key role. Redwood City has natural potential as a connecting node, being located approximately at the midpoint of the peninsula rail corridor, serving as a logical transfer point between local and express trains, serving as the entry point to the peninsula from the future Dumbarton rail corridor, and being in of itself a significant destination with extensive connecting bus service and a willingness to grow.

With Redwood City currently renewing its interest in grade separations, it's important to think big and to re-imagine the station as a key node in the Bay Area's transportation network.

Start with a good timetable

Using our handy service pattern generator, let's see what we could do if we organized a blended system that made Redwood City a key transfer node. When you make a business plan, the first thing to be crystal clear about is: what is your product? In Caltrain's case, the timetable is the product, and all these stations and tracks should only be built as long as they contribute directly to delivering a quantifiably better timetable for the ordinary rider. Building a major new station in Redwood City isn't about trite superlatives like "Grand Central of the West," but simply about efficient and seamless coordination of timely and reliable ways to get from point A to point B.

Let's set some ground rules for our timetable:
  • Caltrain expresses will operate every 10 minutes on a regular clockface schedule. A base 'takt' of 10 minutes reduces gracefully to 20 minutes or 30 minutes in the off-peak.
  • In Silicon Valley, there will be no skip-stop service because the population and jobs are evenly sprawled. Every station in Silicon Valley needs to be served frequently, doing away with the ridership distortions induced by the Baby Bullet effect.
  • In San Mateo county, where stop spacing is closer, slower local trains will operate every 20 minutes. These local trains will meet the express at Redwood City, before turning back north.
  • Dumbarton service will operate every 20 minutes, meeting the express at Redwood City with little or no wait to transfer to trains on the peninsula corridor, before turning back towards the East Bay.
  • Because the overall pattern repeats every 20 minutes, HSR will operate 3 trains per hour rather than the planned 4. Otherwise, there is a harmonic mismatch between the HSR frequency and the Caltrain frequency. 4 HSR trains per hour in a clockface timetable forces the base 'takt' to increase to 15 minutes, which is not desired.
  • If we're going to make Redwood City a major node, it certainly rates HSR service, so we will create a new mid-peninsula stop for HSR.
This is the resulting timetable (see also additional data on service pattern), shown here for one hour in the southbound direction only (the northbound side is symmetrical). Colors denote the 10-minute Caltrain express, the San Mateo local, Dumbarton service, and HSR.

Notice the express arriving at Redwood City at 7:43 meets the Dumbarton train departing at 7:44, and the local arriving at Redwood City at 7:52 meets the next express at 7:53. Every ten minutes there is a cross-platform transfer, alternating between express-to-Dumbarton and local-to-express. Counting both directions, a cross-platform transfer occurs at Redwood City every five minutes!

Implicit in this timetable are a number of other capital improvements besides a new Redwood City station, such as overtake tracks in various locations along the corridor (highlighted in yellow in this view of the timetable... and while we're here, look how much less yellow is needed if HSR uses the Dumbarton corridor via Altamont Pass). It's important to remember that there is no formulation of the blended system that avoids the need for overtake tracks, unless one is willing to push slower trains into station sidings to sit for at least five minutes while a faster train catches up and pulls ahead. If you are a Caltrain rider, you should be wary of the cheapskates at the HSR authority who want to do this to your commute.

Deriving the functional requirements for the Redwood City node

To enable this timetable, we need the Redwood City station to have the following attributes:
  1. Four platform tracks serving two 400-meter long island platforms to facilitate both northbound and southbound cross-platform transfers of very long, high-capacity trains.
  2. Platforms centered on the best cross-town corridor, namely Broadway, for convenient access to and from local destinations on foot, by bike or scooter, by bus, or using the planned Broadway Streetcar.
  3. A turnback track that enables certain Dumbarton corridor trains to originate and terminate in Redwood City, without fouling other train traffic, long enough for an EMU-8 train.
  4. A turnback track that enables the San Mateo local to turn back in Redwood City, without fouling other train traffic, long enough for an EMU-8 train.
  5. Elevated grade separation of all downtown Redwood City crossings, enabling free flow of pedestrians, bikes and vehicles under the rail corridor and including the re-connection of streets currently cut off by the existing configuration (e.g. Hopkins and James).
  6. Bus facilities placed directly under the train platforms for seamless connections without the need for an umbrella. Same for an eventual Broadway Streetcar.
  7. No mezzanine level. Mezzanines needlessly drive up the size and cost of stations, and impede and complicate vertical circulation. Street level can fulfill all the functions of a mezzanine, including ticket sales, wayfinding, waiting, retail, and dining.
  8. The shortest and fastest possible vertical circulation (stairs, escalators, ramps, and elevators) using a U-shape viaduct cross section to avoid deep and vertical-space-wasting bridge structure. This helps with transferring quickly between the two island platforms, as would be needed for example to continue from the Dumbarton corridor south to Silicon Valley.
The footprint of such a station is not small. However, Redwood City has plentiful available railroad and transit district land, and the street level interface of such a station can be integrated into the city's street grid, opening up cross-corridor access and avoiding a wall effect. The aging Sequoia Station shopping center, with its wasteful surface parking, can be demolished and redeveloped to make room for an expanded station. Station parking can be moved underneath the approach structures, protected from the elements.

One possible station layout
An optimal station layout has four tracks, with the outer tracks for HSR and express commuter trains. The middle tracks are for commuter trains, and allow both northbound (Dumbarton) trains and southbound (San Mateo local) trains the opportunity to turn at Redwood City without impeding the flow of express traffic. The width of the structure is about 130 feet, as shown in the cross section below:
The northbound express track (Track 3) is tangent. The northbound island platform is 400 x 10 m. The center commuter tracks (Tracks 1 and 2) have curves that are not laid out in detail; this detail does not matter since any train that uses these tracks would slow and stop at Redwood City, using standard trackwork and turnouts. The southbound express track (Track 4) is the tricky one: it wows around the station, passing the southbound island platform on a 7500 m radius curve with approximately 1.5 inches of superelevation (not enough to matter for platform lateral tolerances). This track consists of a double reverse curve with six spiral transitions (tangent, spiral, curve, spiral, tangent, spiral, platform curve, spiral, tangent, spiral, curve, spiral, tangent). The curve is necessary to fit a pair of 400-meter island platforms (long enough to berth a double-length high-speed train) without bulldozing too much real estate.

Here is how this all fits (admittedly just barely) in downtown Redwood City:

The sacrificial victim is the Sequoia Station shopping center and associated surface parking crater, which can be redeveloped as part of the station complex with direct access from El Camino Real. Access for high-rise fire apparatus around the viaduct structure might also be a concern for the new condo buildings to the south, although this can be mitigated.

The station includes two pocket sidings to turn commuter trains. The siding south of the station can turn Caltrain locals at Redwood City, while the siding north of the station can turn Dumbarton service. Each siding is sized to store an eight-car EMU. Track center spacing is 15 feet throughout, and platform setback is 6 feet from track center. All viaducts are made from low-profile U-shaped sections that minimize the required height of the tracks and also double as sound walls, reducing the noise of up to 30 trains that would serve the station every peak hour.

Redwood City's slogan, "climate best by government test" would also become "transfer best" with timed, well-coordinated transfers to a variety of destinations. The impending start of designs for grade separations in Redwood City needs to factor in this future, and the city ought to think big.

27 September 2018

Growing Caltrain into an 8-Lane Freeway

Caltrain can and should become an eight-lane freeway. Not like an ugly concrete scar tearing loudly through the landscape, but in terms of throughput capacity in people per hour. Today, Caltrain already carries the equivalent of nearly 3 freeway lanes, and more than doubling the system's capacity is hardly a moonshot. For perspective, BART's Transbay Tube carries up to 27000 people per hour, almost double the entire capacity of the Bay Bridge with its ten freeway lanes.

More than doubling Caltrain's capacity has been proposed before and is now being studied by the agency itself, after a decade of not thinking much past electrification.

Capacity calculations can be controversial and rely on many details and assumptions, so the suggested path to expand Caltrain ridership from 3 to 8 lanes of freeway-equivalent is provided in the form of a spreadsheet, embedded below. You can dig into all the numbers and assumptions for each capacity increase and see the underlying formulas for yourself, down to the detailed number of seats in each train car, to understand how it all adds up.

This is a living document, and feedback is appreciated!

08 September 2018

Still Dithering on Level Boarding

EMU low door configuration
Recent documents seeking regulatory relief from certain FRA requirements for Caltrain's new EMU fleet reveal details of the interface between the train and a station platform.

The lower doors of the EMUs will feature a deploying step at 15 inches (measured above the top of the rail), halfway between the 8-inch platform and the 22-inch train floor. The resulting step arrangement, when deployed, is similar to the existing Bombardier cars, although the floor height of the Bombardiers is 3 inches higher.

So far, so good.

A closer examination of the step mechanism (see Stadler engineering drawing, as submitted to FRA) shows that the step module retracts upward from its 15 inch deployed height, using a cam mechanism, and stows with the step tread 2.5 inches below the door sill. This makes the step unusable for an ADA-compliant level boarding interface, where it might have been configured to close the gap with a 22" platform, at the same height as the train floor. Recall that ADA regulations for unassisted level boarding require a platform gap less than 3 inches, with vertical discontinuity less than 5/8".

One faction of Caltrain staff evidently envisions level boarding using the low doors of the new EMUs, but the engineering drawing proves this is out of the question without a complete redesign and replacement of the door step mechanism. Even then, there are serious questions about the feasibility of a gradual transition to level boarding where the train fleet must serve a slowly evolving mix of 8-inch and raised level platforms.

As per usual with level boarding, the end goal is clear, but getting there is the hard part and often involves lots of hand waving.

Consultant Still Doesn't Get It

Not only is the lower level door step mechanism unsuited for future level boarding, but Caltrain's vehicle engineering consultant, LTK Engineering Services, states that low platforms will be used indefinitely. On page 1 (PDF page 5) of the recent FRA waiver application, we read:
Initially, Caltrain will utilize only the lower level doors to serve their existing 8-inch platforms. Once CHSRA service begins in the corridor, there will be a station or two that will have high level platforms and will be served by the Caltrain EMUs via the intermediate level doors. Other Caltrain stations will remain low level and will be served by the lower level doors.
No! Continued use of 8-inch platforms means long dwell times and time-consuming conductor-assisted boarding for persons of reduced mobility using a manually emplaced bridge plate. This antiquated state of affairs cannot be allowed to persist. Blithely ignoring the minutes that can be saved while the train is at rest is unacceptable, especially after spending two billion dollars to save minutes while the train is in motion.

It is time to adopt a policy on level boarding, and to push Caltrain's staff and consultants to reach agreement on the technical approach to get there. Here we are in 2018 and there is still obvious disagreement about whether to implement level boarding at all (a no-brainer if you look at the big picture) and at what height, using what doors on the new EMU fleet. Stop dithering and do it!

Footnote: there are multiple waiver petitions relating to EMU design details.
FRA-2009-0124 Tier I Alternative Vehicle Technology crashworthiness (approved)
FRA-2017-0104 Position of bathroom car emergency exit window (approved)
FRA-2018-0003 Use of upper doors in lieu of emergency exit windows (denied)
FRA-2018-0067 Emergency brake handles, grab irons and steps, clearances (pending)

25 August 2018

Over-Promising on Electrification

Numerous recent Caltrain materials include the following quantitative claims (see slide at right) about the service benefits of the electrification project:
  1. A baby bullet train making 5-6 stops will make the SF - SJ trip in 45 minutes, down from 60 minutes today.
  2. A train making the SF - SJ trip in 60 minutes will be able to stop 13 times, up from 6 stops today.
Both of these claims are greatly inflated. They are easy to verify using a computer program known as a train performance calculator, which numerically integrates the differential equations of motion of a train based on the known characteristics of the track (vertical profile, curve, speed limits, station stops, etc.) and of the train (power, weight, tractive effort, drag, etc.) Physics and math can predict timetable performance quite accurately.

Myth #1: the 45-minute Baby Bullet express

Today's diesel performance
(pure run time, no padding)
Here is what a typical baby bullet run looks like today, with an MP-36 diesel locomotive, six Bombardier coaches, and a load of 600 passengers. There are five stops in this example, each lasting (very optimistically, as riders will attest) just 60 seconds. The pure run time from San Jose to San Francisco 4th and King is 52:22 under ideal conditions, without any margin or padding that is added to a real timetable; compare to the weekday northbound timetable at 64 to 67 minutes, or up to 25% longer (!) than the pure run time. Note that the weekday timetable has been extensively padded lately due to crowding; in 2012, the same run was timetabled at 59 minutes with 12% padding.

Tomorrow's EMU performance
(pure run time, no padding)
All other things being equal, let's substitute an EMU train for our slow diesel. The same run drops to 48:15, just four minutes quicker. This isn't surprising: baby bullet trains spend most of their time cruising near the speed limit, where the faster acceleration of EMUs doesn't provide a benefit. With all other things being equal (including crowding and long dwell times--why would electrification resolve these?) we can expect the timetable for our five-stop baby bullet to drop by the same four minutes, or 60 to 63 minutes. That is a full 15 to 18 minutes slower than claimed by Caltrain! Even if you remove the copious 5-8 minutes of extra padding present in today's timetable and compare to the 2012 timetable, we're still 10 minutes slower than claimed, at 55 minutes.

EMU performance at 110 mph
(pure run time, no padding)
How could you possibly get to 45 minutes? One approach is to raise the speed limit to 110 mph, which is planned in the long term but clearly outside of the scope of the electrification project. Changing only that variable, and slowing down as needed where curves limit the speed to below 110 mph, our EMU now makes the same San Jose to San Francisco run in 41:32, almost seven minutes faster. However, we're still 7 to 10 minutes slower than Caltrain's 45-minute claim, or 2 minutes slower when using 12% padding. Again, the reasons for having such enormous amounts of timetable padding will not suddenly disappear after electrification!

The best way to get there is with level boarding, which alleviates Caltrain's crippling dwell time problem. Level boarding has two benefits: the primary benefit is in the form of reduced dwell time during each stop, and the secondary benefit is in the smaller amount of timetable padding that is needed, thanks to the improved schedule adherence that is possible when the occasional wheelchair lift deployment no longer threatens to inject random three-minute delays. Padding could conceivably be cut to 7%, and dwell time to 30 seconds. No new simulation runs are required-- our five-stop 79 mph EMU makes it in (48:15 - 2:30)*1.07 = 49 minutes on the timetable; the 110 mph EMU makes it in (41:32 - 2:30)*1.07 = 42 minutes.

Caltrain's claim of a 45-minute baby bullet is readily attainable only after three major improvements are made. These are not included in the scope of the electrification project and are currently unfunded:
  1. Conversion of the baby bullet fleet from diesel to EMU
  2. Implementation of system-wide level boarding
  3. Curve realignment, track upgrades and grade crossing safety upgrades for 110 mph
To promise a 45-minute baby bullet run in the short term is at best misleading and at worst a flat-out lie. Once the electrification project is complete, we can expect approximately zero improvement in baby bullet performance, with timetabled runs in the range of 64 to 67 minutes. If the initial slight increase in capacity of the electrification project relieves crowding (but will it, enough to offset the performance loss from dragging a seventh Bombardier car?) then we could return to the 2012 timetable performance of 59 minutes.

Myth #2: the one-hour, 13-stop limited

Let us assume for the moment that padding returns to the 2012 level of about 12%. Assuming 60-second dwells and a 79 mph speed limit, how many intermediate stops can a limited train make between San Jose and San Francisco before the timetable hits one hour?  Subtracting 12% pad from one hour, we need to make a pure run time of 53:34.

With today's diesel bullet performance, Caltrain's claim of six stops in one hour checks out reasonably closely at 54:57 or just over one hour including padding, i.e. close enough. Let's change the assumptions, one by one:

Simulation CasePure Run TimeTimetable
Case A, Diesel, dwell 60, 6 stops, 12% pad0:54:571:01:33
Case B, EMU, dwell 60, 6 stops, 12% pad0:50:100:56:11
Case C, EMU, dwell 60, 7 stops, 12% pad0:52:040:58:19
Case D, EMU, dwell 60, 8 stops, 12% pad0:53:581:00:27
Case E, EMU, dwell 30, 8 stops, 7% pad (level boarding)0:49:580:53:28
Case F, EMU, dwell 30, 9 stops, 7% pad (level boarding)0:51:220:54:58
Case G, EMU, dwell 30, 10 stops, 7% pad (level boarding)0:52:460:56:28
Case H, EMU, dwell 30, 11 stops, 7% pad (level boarding)0:54:100:57:57
Case I, EMU, dwell 30, 12 stops, 7% pad (level boarding)0:55:340:59:27
Case J, EMU, dwell 30, 13 stops, 7% pad (level boarding)0:56:581:00:57
Case K, EMU, dwell 30, 13 stops, 7% pad (level boarding), 110 mph0:53:080:56:51

Simulation Case K
(pure run time, no padding)
Case D shows that the maximum number of stops permissible under post-electrification conditions is at most 8, just two more stops than today, and not 13 as claimed by Caltrain. Only after level boarding does the number of stops increase to 13 as shown by Case J, but once again, level boarding is not included in the scope of the basic electrification project. Case K illustrates the diminishing returns from increasing the speed limit to 110 mph; the more stops a train makes, the less benefit there is from the higher allowable speed. Case K (see diagram at right) shows the train almost constantly accelerating and braking, which is not how one would choose to operate given the cost of electricity in the real world.

The takeaway message to Caltrain is this: don't over-promise and under-deliver on the modernization project. Your electrification project reduces time in motion and establishes a foundation for further improvements, but is not sufficient by itself. To deliver the service benefits promised in your public presentations, you absolutely need level boarding to reduce time at rest.

(do I sound like a broken record?)

11 August 2018

New SF Caltrain Terminus Opens at 0 tph

Zero trains per hour (tph) is the inaugural Caltrain service level at San Francisco's new Transit Center, which opened to the public today after a decade of construction. The grand opening of the center, with its expansive $400 million basement featuring ghost tracks, ghost platforms and a ghost passenger concourse will no doubt crystallize the increasingly urgent transportation need for the downtown extension (DTX) of the peninsula rail corridor. Only then will train service increase beyond the current level of zero tph.

Huge opening day crowds at the Transbay Transit Center. Photo by Adrian Brandt.
Why build DTX?

Simple. Within a half mile radius of the Transit Center, there are more jobs than within a half mile radius of every station along the peninsula rail corridor from San Francisco 4th and King all the way to Gilroy, COMBINED! Even before high speed rail shows up, this is a piece of infrastructure that makes perfect sense. Or does it?

An epic opportunity for transit funding extortion

The clear (and, as of today's opening, agonizingly present) need for the DTX sets up a deliciously fat and juicy prey for the transportation-industrial complex, which you can think of as a hungry snake. Here we are, in a strong economy, in one of the richest cities on Earth, facing a specific and obvious transportation need: they can name just about any price. The latest estimate for the biggest meal that the snake can swallow is six billion dollars, and that's only the start. Scope creep, dizzying amounts of contingency cushioning, and construction change orders are sure to drive it far higher. Civil engineering megafirms, labor unions, and complacent and poorly coordinated government agencies are salivating at the prospect of feasting on the DTX. The bigger it gets, the more sated and comfortable everyone will be, with the notable exception of the suckers who pay taxes and ride trains.

The DTX project needs a major cost cutting exercise

"It is difficult to get a man to understand something, when his salary depends on his not understanding it." This insight by Upton Sinclair applies to any attempt to reduce the scope or optimize the cost effectiveness of the DTX project. There isn't and probably won't be a true will to do it, but in a pretend world where the interests of taxpayers and riders came first, where might you start cutting scope?
  1. Delete the Pennsylvania Avenue tunnel extension. There is a perfectly serviceable tunnel already available. Engineering acumen should be brought to bear to overcome the (otherwise delightfully profitable) constraints of building a new trenched grade separation by figuring out how to shore up I-280 during excavation; how to cross the SFPUC's giant new sewer; how to duck under 16th street using a steeper 2.5% grade than the train people would prefer; and how to build temporary "shoo-fly" tracks under I-280 during construction now that the area is hemmed in by fresh UCSF construction. The usual paint-by-numbers engineering that deploys freight train design standards as "constraints" shows this to be categorically impossible, but is it really? Sharpen your pencils.
  2. Delete the mezzanine level at 4th and Townsend. Station mezzanines are a knee-jerk (and delightfully profitable) design feature of every recent piece of rail infrastructure in the United States. Wedged above the tracks, underneath, in the sky or in a cavern, mezzanines tend to sprout everywhere. In this case, a mezzanine makes passenger access more circuitous and pushes the track level much deeper, increasing the depth of excavation. The mezzanine and station become an enclosed underground space, triggering an avalanche of fire safety requirements that greatly increase cost and complexity, with all manner of vent structures and evacuation shafts. The right answer is simple, direct and free-flowing access from platform to street, and an open station ceiling that vents to the street through a slot built into a raised median on Townsend Street-- as wide as necessary to treat the structure as an open station under fire safety regulations.
  3. Daylight as much of the shallow Townsend Street portion of the alignment as possible, with a central median vent slot (just like in Los Angeles on the Alameda Corridor, where three of the nation's busiest diesel freight tracks are concealed beneath the street with a vent slot as narrow as six feet). This configuration has the potential to simplify the engineering considerations and costs related to fire safety, and even improves rail operations: without the onerous fire safety requirement of having only one train at a time occupy each tunnel ventilation section, operation of the entire DTX becomes less constrained.
  4. Slim down the three-track tunnel, another one of Sinclair's salary considerations, to two tracks instead of the planned three. The Rail Alignments and Benefits (RAB) operations analysis, carried out by a premier Swiss rail operations consultancy, concludes on page C-68 that "Under normal conditions, only two tracks are required in the tunnel leading up to the TTC to operate the analyzed service plans. More detailed analysis is recommended to identify the most effective approach to provide infrastructure redundancy (e.g. the proposed third tunnel track) to help mitigate the potential effects of major service disruptions." The clear implication here, artfully worded so as not to upset Sinclair's salary men, is that a third track is not necessarily the best or only approach to achieve infrastructure redundancy.
  5. Add three 400-meter underground storage tracks, feeding in towards the Transit Center instead of the peninsula, along the northwest edge of the existing 4th and King station footprint. The fire safety requirements for this underground infrastructure would be less stringent because it would not be occupied by passengers. With beefy foundation columns bored down to bedrock to straddle this yard, the entire footprint of the site can still be redeveloped above grade, safeguarding San Francisco's desire to use "value capture" from this increasingly coveted parcel to finance DTX construction. The resulting train storage capacity is far more conveniently located than the remote yard sites currently proposed at Oakdale or Bayshore, reducing long-term operating costs. Even skyscrapers can be built on top of train storage: see Hudson Yards.
  6. Rationalize the Transit Center approach tracks to speed up train movements. The throat of the station has been identified as a key bottleneck for train movements (see RAB operations analysis page C-96, "Key Findings of Conceptual Planning"--and recall that you read it here first). An optimal layout has been identified that better enables concurrent arrivals and departures of two trains (see page C-117 of same). Precious seconds saved in the station approach can increase the traffic capacity of the DTX and make it more resilient to disruptions.
  7. Don't use exotic and expensive tunneling methods when their sole purpose is to keep businesses along the DTX route healthy during construction, by avoiding cheap but disruptive cut-and-cover methods. The intent is noble, and the recent impact of Central Subway construction in Chinatown is painful and fresh in our minds, but this sort of thing rarely pencils out for anyone but Sinclair's salary men.
Only after a draconian cost cutting exercise might it begin to make sense to build the DTX. At a price point of six billion dollars for a couple of miles of tunnel, we regretfully should keep service levels at zero trains per hour.

03 May 2018

Fleet of the Future

Not bad in blue, huh? This parody of the fragmented state of Bay Area transit is based on an image by Stadler Rail. There should be plenty in this image to offend almost everyone!

24 February 2018

The End of CBOSS

The rosy view, from 2011
Caltrain's troubled positive train control solution, known as CBOSS, has now been completely abandoned, to be replaced by the de-facto standard freight PTC technology known as I-ETMS. That's mostly good news, since Caltrain will no longer be stranded with a globally unique PTC system. I-ETMS is being deployed by numerous other commuter rail operators in the U.S., allowing some economies of scale and standardization.

Notwithstanding, CBOSS easily rates as the most spectacular contract failure and biggest lawsuit in Caltrain's entire history, since the Peninsula Corridor Joint Powers Board was formed in 1985.

Project expenditure history, by fiscal quarter. Fluctuations in
recent quarters are unexplained, presumably related
to termination of the Parsons contract in 2017 Q2.
Gap reflects two missing quarterly reports.
The sums expended are staggering, especially when considering that just 52 route-miles are to be fitted with PTC. To date, according to the latest quarterly capital projects report, Caltrain has expended $201 million out of $240 million budgeted for the project.

The March 2018 board packet includes a new item awarding a $49.5 million contract to Wabtec to deploy I-ETMS on the peninsula rail corridor, presumably re-using some of the hardware and communications infrastructure already installed under the CBOSS contract. The "owner's cost," borne by Caltrain to cover program management and testing, has averaged $1.2 million/month over the past five years, and should stretch well into 2019 until PTC is fully deployed and activated. (Note the December 2018 statutory deadline only requires a "revenue service demonstration" over a limited portion of the corridor). Caltrain staff estimates that owner's costs will grow the I-ETMS deployment to $59.5 million, pushing the PTC project total to at least $261 million. The board packet hints at additional future program costs, beyond the $59.5 million "switching cost" from CBOSS to I-ETMS.

How much money did Caltrain waste on CBOSS?

To estimate how much money Caltrain wasted on CBOSS, we can examine the PTC project finances of other commuter rail systems deploying I-ETMS, but without the wasteful detour into research and development of globally unique alternative solutions. These PTC-related expenses are variously reported to each operator's board of directors, in press releases, or to the FRA.

OperatorCityRoute Miles EquippedVehicles EquippedPTC Cost
MetrolinkLos Angeles249112$216M
CoasterSan Diego6017$87M
ACESan Jose06$10M

A linear regression analysis on three variables (cost per route mile, cost per vehicle, and a fixed cost allowance for control facilities) for these five commuter rail I-ETMS installations reveals that equipping one route mile of track costs on average $0.36M, equipping one locomotive or cab car costs $1.0M, and the fixed cost is $21M. These are simplistic approximations, but they do give a reasonable ballpark estimate for the underlying cost of a commuter rail I-ETMS deployment.

We then apply these estimated regression factors to Caltrain. With 52 route miles and 67 vehicles, the cost of I-ETMS deployment for Caltrain, had this solution been pursued from the beginning, would have been approximately 52 x 0.36 + 67 x 1 + 21 = $107M. This tells us two things.

First, we can infer from the $59.5M switching cost to I-ETMS that 107 - 60 = approximately $50M or just one quarter of the CBOSS sunk cost (including the fiber communications backbone and a subset of the control facilities and wayside/vehicle hardware) is salvageable for I-ETMS.

Second, since the total cost of Caltrain's PTC project is expected to reach at least $261M, we can infer that Caltrain wasted 261 - 107 = approximately $150 million on the egregious failure that was CBOSS.

$150 million flushed down the toilet. Heckuva job, Caltrain!

19 January 2018

CalMod 2.0: Three Things to Watch

UPDATE, from Caltrain TIRCP funding application
  • CalMod 2.0 is now formally known as EEP or Electrification Expansion Program
  • 100% state-funded through cap and trade program (TIRCP)
  • Consists almost entirely of option buys of 96 EMU cars for $600M
  • 17 x 8-car EMU fleet planned for start of electric service (if $$ awarded)
  • No 4-car EMUs (this is super important for future off-peak service)
  • No third bike cars.  Extra money for station bike parking
  • No level boarding.  Can kicked down road
  • Broadband internet on the EMUs at start of electric service, for a cool $14M
  • Diesel bullets redeployed to SJ - Gilroy - Salinas in unspecified future project

Caltrain was recently reported to be seeking another $630 million grant from California's cap and trade program to eliminate diesel trains entirely and to increase the passenger capacity of the new EMUs a decade earlier than previously envisioned. A previous board agenda alluded to a $756 million program known as CalMod 2.0, consisting of:
  • Full conversion to 100% EMU + capacity increase ($440M)
  • Broadband ($30M)
  • Maintenance facility improvements ($36M)
  • Level boarding and platform extensions ($250M)
While the amount reported in the press doesn't match the CalMod 2.0 tally, there may be other funding sources on tap and we are probably looking at the same package of improvements. The EMU fleet expansion is an exercise of the fully priced option for 96 additional EMU cars under the existing contract with Stadler.

There will be three important issues to keep an eye on:

1) Level Boarding

Level boarding is the logical next step after electrification, and a perfect complement: where electrification reduces time in motion, level boarding reduces time at rest. Every second of trip time saved is equally valuable, which is why cutting station dwell times is enormously important.

Not all level boarding solutions are created equal, and it's not enough for the height of the platform to equal the height of the train floor. To enable dense "blended" traffic on the peninsula corridor, what Caltrain needs is unassisted level boarding where persons of reduced mobility can board without the help of a conductor across an ADA-compliant gap. That means NO bridge plates, NO exterior lifts, and NO conductor assistance.

While the new EMUs will have the ability to dock at 51" platforms, staff and consultants evidently do not agree on a path forward towards system-wide level boarding. With a nine-figure amount being contemplated for platform extensions and level boarding under CalMod 2.0, the approach and transition strategy needs to be straightened out, and soon, to avoid enormous "do over" costs. And we should not let Caltrain claim that platform extensions for 8-car trains will cost a lot: the real price tag for that is in the range of $25 million.

2) Short EMUs for Frequent Off-Peak Service

Base order (blue) and option order
(orange) show fleet composition
for 100% electric service
The sort of service that Caltrain wants to run in the future, currently being discussed in the context of a nascent business plan, will determine the specific composition of the 96-car option order, i.e. how many of what EMU car type to buy. The wrong fleet decision could very well preclude service patterns that may be deemed preferable once the business plan effort concludes, which is why CalMod 2.0 needs to be carefully considered not to overtake or conflict with the business plan effort. That being said, you don't need an army of consultants to figure out what fleet Caltrain will need.

Use case #1: during rush hour, to run a 70 minute SF Transbay - South San Jose schedule at 6 tph per direction with 20 minute turns at each end, you need (70+20)/60 * 6 * 2 = 18 trains in service, plus one extra train available at each end of the line to protect against cascading delays, or 20 trains available for service. Allowing for a couple of trains to be down for maintenance, we need 22 trains total @ 8 cars each.

Use case #2: off-peak service running at 80 minutes SF Transbay - South San Jose at 3 tph per direction with 20 minute turns at each end, you need (80+20)/60 * 3 * 2 = 10 trains in service, plus one extra train at each end, or 12 trains available for service. Throwing in another two trains down for maintenance,  we need 14 trains total. Because it's very expensive to haul around empty seats, these must be short 4-car trains.

Supporting both of these use cases within the overall size of the Stadler order (96 cars base order + 96 cars option) requires the option order to consist primarily of 4-car EMUs, as shown in the figure at right. At peak times, 4-car EMUs would operate in pairs, mixing with the rest of the 8-car subfleet. If needed in the long term, EMUs could be extended to 12 cars by coupling 8 + 4 cars.

3) Just Say No to a Third Bike Car

Bringing a bike on Caltrain is one of the finest ways to commute; your author has done it hundreds of times. The bikes-on-board community is already gearing up to pressure Caltrain into adding a third bike car to the future 8-car EMUs, deeming the two bike cars in the base order 6-car EMUs to be inadequate. The typical argument goes that any bike "bumped" is a paying customer left behind, which is a logical argument when spare capacity is available. However, with trains at standing room only peak loads (by design!) there are plenty of potential non-bike passengers left behind. They are not "bumped" in the literal sense, since they don't even show up at the train station. Here's why: when the cost of enduring a crowded train trip becomes unbearable, the invisible hand of supply and demand pushes more and more potential riders to drive instead.

Under SRO conditions, every free bike space on the train displaces a paying passenger, a sort of "reverse bumping" effect that explains quite elegantly why, for example, the Paris RER does not and should not have dedicated bike cars. Caltrain has gone quite far enough in providing free bike space on board, and should not have a third bike car in 8-car EMUs, in everyone's interest of maximizing peak passenger capacity. In the long term, bike commuters will benefit more from world-class bike parking.