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.