Friday, April 17, 2009

The Vexed DTX Tunnel

NOTE: We've moved! Visit us at the California High Speed Rail Blog.

Just a techie tidbit note today regarding the DTX tunnel that is at the heart of the engineering side of the dispute between CHSRA and TJPA on whether the current design meets CHSRA's future needs. I know we've been over this too many times already, but somehow the issue needs to be put to bed such that everyone can save face and focus on maximizing California's share of the $9.5 billion in federal dollars already on the table. Protracted tiffs don't do much for the confidence of the general public, let alone potential private investors, in either TJPA or CHSRA.

My objective for this post is to suggest a tunnel sharing and operations timetable strategy that might help bridge the gap. First, a quick recap of the saga so far.

Issues Related to Planning and Funding

TJPA has been planning the entire Transbay Terminal since SF voters approved prop H in 1999, with the objective of bringing not just Caltrain but eventually also HSR under the same roof as a large number of bus services. The old building dates to 1939, has seen better days and is anyhow no longer up to seismic code. The only part that will be re-used are the bus ramps that once allowed electric trolley cars to run across the lower deck of the Bay Bridge. The underutilized neighborhood south of the new building will also be redeveloped.

The DTX tunnel is the bit between Caltrain's existing terminus at 4th & King Street and the basement of the new terminal building. As designed, it features three tracks under Townsend and 2nd Streets and widens into a curved throat section to reach six platforms tracks accessed via an underground concourse level and three full-length wide island platforms. Of these, two will feature the level boarding height to be chosen by CHSRA and the other the one chosen by Caltrain. The outside tunnel tracks are to be shared by both services and are permanent as inbound and outbound tracks, respectively. The center track will apparently alternate between inbound and outbound traffic.

CHSRA has recently raised a red flag regarding the design, claiming it couldn't support the 12 HSR trains per hour (tph, meaning that number each way) during peak periods claimed in the most recent ridership forecast for 2030. There seems to be fairly broad agreement among the readership of this blog that this is a new and excessive demand made public only after TJPA decided to bypass CHSRA in seeking a slice of the HSR dollars in the recent stimulus bill. Quentin Kopp is concerned this would set a precedent and cause CHSRA to lose control of project cost.

TJPA claims its plans are based on a previous estimate of just 4tph and a minimum dwell time of a full hour. The latter is itself a highly questionable requirement, given that terminal stations in Europe manage to turn HSR trains around in 6-10 minutes. They are treated as through stations that happen to require trains to reverse direction, generally with a change of driver. Old-fashioned terminus stations are grand buildings providing small town folk with access to a metropolis, reached after many hours or even days on the move. Thanks to high speed, even San Diego-SF-San Diego will amount to just a single eight-hour shift for employees, so in that sense SF could indeed be considered a through station along out-and-back routes originating in SoCal and Sacramento.

The Authority would be on much firmer ground if it stuck to AB3034, which point blank requires that the entire network must support headways of no less than 5 minutes. This refers to the time interval between the nose of one train and the next one running in the same direction on the same track. The technically required minimum is a function of speed and emergency braking distance at that speed. For moderate speeds, experienced operators of modern train control infrastructure can make do with as little as 2.5 minutes, so the legal target set by the bill is conservative. As will become evident shortly, the link between short headway capability and system throughput is not always straightforward.

Technical Issues and Solution Concepts

The beef that Clem/Richard Mlynarik, BruceMcF and yours truly have with the current design of the DTX tunnel is twofold:

a) at just 500 feet, the two curves in the tunnel will prevent at least the HSR trains from running them at much more than bicycle speed. In addition, we expect screeching noises as the long wheelbase trucks needed for high speed stability are dragged kicking and screaming around the corner. Passengers on board and especially, anyone present on the platforms would hear a sound reminiscent of fingernails on a blackboard, just much louder. Special lubricants might help keep both the noise and the wear and tear down, but no brand-new design should need them. The radii are also too tight for off-the-shelf Japanese shinkansen designs, which need ~925 feet. Even for European designs, 500 is the number the marketing department made the engineers sign up to, not one they'd recommend for brand-new track.

b) the slow speeds combined with the tunnel layout combined with train lengths of 660-1320 feet mean that during peak periods, inbound and outbound trains of both operators will block each others' paths to such an extent that the "throat" between the tunnel proper and the platform tracks becomes the throughput bottleneck. It's highly unlikely that HSR could achieve 5 minute headways during Caltrain's rush hour with that design.

Both post authors and commenters have propsed a wide range of solution concepts on both this blog and Clem's. Here's a recap:

  • terminating some or all HSR trains at 4th & King
  • a central rail station at Market & 7th instead of the Transbay Terminal
  • redefining the Transbay Terminal to include a narrow two-level heavy rail station under Mission Street, reached via a short underground pedestrian passage and featuring moving walkways along the 1/2 mile concourse level
  • keeping the tracks in the basement, but redesigning the DTX tunnel as a one-way single-track loop through the building from east to west; any future second transbay link would then be BART down Mission Street
  • redesigning it to run up 3rd Street to increase curve radius for just two - possibly individual track - tunnels
  • minimally, some tweaking of the curve radii and the use of curved switches in the throat of the official three-track tunnel design

Dedicated Single Tunnel Tracks

In the vein of this last concept, I'd like to add one more suggestion to the list. Since HSR and Caltrain are supposed to get dedicated platforms and platform tracks anyhow, I figured why not give each of them a single, dedicated track in the DTX tunnel as well. That would at least get the operators out of each others' hair. A third track should be avoided to keep the tunnel engineering as straightforward as possible so the curve radii can be increased without breaking the bank.

The idea is really quite simple: each operator sets the signals in the tunnel track to outbound and runs a group trains out in quick succession. The timetable is arranged such that an equal number of inbound trains arrives at the mouth of the tunnel just as the last of the outbound trains clears it. The operator sets the signals in the opposite direction, the platforms tracks fill up again and the process repeats.

The advantage is that as long as traffic is guaranteed to be one-way, headways as small as three minutes are quite realistic. No outbound trains blocks any inbound one, no HSR train any Caltrain and vice versa. In other words, there is no throat in the classic sense, just two independent tunnel tracks that fan out to two resp. four platform tracks that are alternately used in one direction or the other for a well-defined period of time.

The disadvantage is that each operator's timetable would feature a number of trains in quick succession, followed by a period without service in that direction. Note that in each of these groups of trains, the fastest service classes (e.g. express) come first, followed by the slower ones (e.g. semi-express). This ensures headways do not decrease below three minutes in nominal operations. For two consecutive trains of a slower class, it may go back and forth from the minimum value to a higher one.

Spreadsheet Model

To get a better sense of the kind of timetable this would produce, I made a number of assumptions and plugged them into a spreadsheet. In addition to the three-minute headways, I assumed that the cumulative delay for an outbound group of trains would be no more than one minute. For inbound groups, I allowed a three-minute buffer and assumed a two-minute dwell time for trains making a stop between San Jose and SF. Finally, I assumed Caltrain's commuter EMU equipment would traverse the 1.3mi tunnel in two minutes (39mph average speed thanks to high acceleration and short wheelbase trucks), whereas HSR trains would take three (26mph average).

For service patterns based on half-length trains (660ft or less), the first inbound train would proceed to the end of the platform track. The second would stop before colliding with the first. However, since it's a terminal station, the later arrival would have to be the first one to leave, resulting in uneven dwell times. Also, I assumed a platform track would be cleared entirely before trains from the next inbound batch are admitted. This is how an operator would use the facility during rush hour. At off-peak periods, the ends of the platform tracks can be used for parking.

The results were as follows:
  • For HSR service based entirely on single trainsets, I assumed a group size of four trains occupying one track on each island platform. The first two were express, the second two semi-express trains on the SJ-SF segment. This affects the length of time the track needs to be reserved for inbound traffic. Note that I did not consider service class impacts south of San Jose for this preliminary analysis. Instead, I assumed appropriate service groups would be created via wait states in San Jose.

    After allowing four trains to leave, four new inbound ones would be admitted, followed by the other four trains still in the station and four inbound ones to replace them. The period for this pattern of 8 trains each way works out to exactly 60 minutes, i.e. 8 tph. The minimum dwell times for the trains in each group worked out to 38, 44, 36 and 42 minutes, respectively. Because of the buffers built into the schedule, they could be up to four minutes longer.

  • I also looked at HSR service based exclusively on full-length trains. With a group size of four, this also works out to 8 tph - but each of train would now have twice as many seats! The snag is that the minimum dwell times are down to just 11, 11, 9 and 9 minutes, respectively. As discussed above, that is considered enough for a terminal in Europe. However, if a large fraction of seats is actually occupied in SF, seat reservations and some pedestrian flow control would be highly advisable to avoid delays. Evidently, trainset utilization rates are much higher if full-length trains are used. Note that it's very easy to couple and uncouple HSR trainsets at stations, so operators could transparently switch to single trainsets during off-peak hours.

  • HSR service based on full-length trains and a group size of just two yielded a throughput capacity of 7.06 tph, with minimum dwell times of 21 minutes.

  • Separately, I looked at Caltrain local service based on 8-car trains that would be used during rush hour. With a train group size of four, throughput worked out to a very respectable 9.23 tph. Minimum dwell times were 6, 12, 6 and 12 minutes, respectively.
Fiddling with the parameters, it quickly became apparent that the minimum headway had the greatest effect on throughput, followed by the time required to traverse the DTX tunnel, dwell time at through stations down the line. Doubling the cumulative buffer period allowed for inbound Caltrain groups from 3 to 6 minutes resulted in a loss of only 1 tph in throughput.

Overnight Parking

Note that CHSRA still needs a solution for overnight parking of additional trainsets, as the first ones of the day will take some time to arrive from Merced and LA. The old Brisbane yard near Bayshore Caltrain would do nicely and could double as a transshipment center for High Speed Cargo trainsets that ride piggyback on single passenger trainsets during off-peak hours. Toward the end of the day, selected passenger trains would terminate at Millbrae/SFO.


Provided that inbound trains are grouped neatly and operators are willing to accept that consecutive trains in the same direction may run anywhere from 3 minutes to 13, 17 or even 21 minutes apart, aggregate throughput of over 17 tph is possible with this concept. For reference, a single loop track serving all six platforms with a minimum headway of 3 minutes would support 20 tph and provide more flexibility if CHSRA and Caltrain decide on a common platform height after all.

Cost Containment Opportunity

Just for kicks, I also looked at the possibility of saving some money in phase I by extending the dedicated single track for HSR beyond 4th & King to Bayshore. Caltrain already has four short tunnels in that stretch, CHSRA intends to bore new single track tunnels to either side of that. The CHSRA web site gives a time of 13 minutes for Transbay Terminal to Millbrae/SFO, so I figured it would take about 9 out to Bayshore. This longer single-track section caused HSR throughput to decrease from from 8 to 5.71 tph (4.14 tph for full-length trains with a group size of two but minimum dwell times of 33 minutes). For the single-trainset scenario with a group size of 4, minimum dwell times went up by 12 minutes. For full-length trains with the same group size and throughput number, they were unchanged.

In other words, it would be possible to shift some tunneling overheads south of 4th & King from phase I to phase II of the overall bullet train project, given that 4.14-5.71 tph will be enough for HSR operations for a while. Note that running northbound HSR trains east of Caltrain in that section would currently force UPRR trains to cross the HSR track. By the time HSR needs dual tracks between Bayshore and 4th & King, it's entirely possible the mighty Port of SF will no longer be served by UPRR's South City Switcher - a freight train running in streetcar mode.


Anonymous said...

Rafael: your plan is just plain... stupid. Instead of one point of conflict, you now have a nice extended mile-long bottleneck for both Caltrain and HSR. And the big problem with single track sections is not just the very severe limitation on capacity, but also the very poor reliability of the schedule as delays in one direction propagate to trains in the other direction until the whole service is a mess. To avoid that, you need to either run significantly below the bottleneck capacity, or put in a generous amount of padding. A proper terminal design (full ladder at the throat, plus outer crossovers at least 1-2 train lengths out) would allow for enough flexibility that the tracks wouldn't be the bottleneck. Look at how Penn Station is laid out, and realize that they push through 24 trains per hour in the peak direction via the Hudson River Tunnels together with reverse peak trains, LIRR trains in the East River Tunnels, and Amtrak Empire Service train, and it all more or less work out without too much delay, despite all the potential for conflicting movements all over the place.

BruceMcF said...

How does the headway between the fourth HSR train into the tunnel and the following HSR train into the tunnel work out? Five minutes or less? That's one magic bi-directional single track if that's five minutes or less.

A single central access track and two side egress tracks would untangle the TBT platform access with a relatively simple switching network ... though at the cost of a little additional work at the descent into the tunnel to untangle it, and requiring an island platform and two bypass tracks at 4th and Townsend ...

... but Richard's design for the DTX and TBT station throat layout promises to be substantially more cost efficient, since it only requires two tracks the length of the tunnel.

Clem said...

Hi Rafael, argh you lost me again halfway through.

I think the suggestion to operate the terminal as two separate mini-stations runs counter to the most basic principles of operational flexibility. Flexibility is at the root of efficient station operations. The mantra should be "any train, any track, any time".

In your scheme, if a service is even a little bit late, the entire timetable falls apart. Delay propagation is, once again, not desired. Neither is the tight coupling between HSR and Caltrain timetables.

More fundamentally, the tunnel itself isn't the bottleneck. As you point out, a two-track tunnel could easily support 20+ tph in each direction. The bottlenecks are in the station throat, and at the 3-track underground 4th & Townsend station. That is where you need to offer solutions, not in the tunnel.

HSR also doesn't need extra tracks for tunnels 1 and 2. They provide zero additional capacity or transportation value, since the terminal's turn-back capacity constrains the train throughput--kind of like a 4-lane freeway with a slow metering light.

Richard's plan is a far more realistic solution which promises to satisfy more stakeholder needs.

Anonymous said...

yesterday I was in both the 4th /king area nad the tbt area. Two things came to mind. One, doesn't is make more sense for hsr to partner with muni on the central subway under forth and tear up only one street to get the subway and the dtx done at the same time the way they did bart and muni under market street. That would give a better approach to tbt for hsr. Two, the tail tracks, will be located where the temp terminal is going in now. there is a full sqaaure block + of soace that will be open and available when tbt opesn and the temp is removed which mean they can have 2/4/6/8 tail tracks or more in a cut and cover a fill block wide in that open space. That should increase capacity/thoughput. I don't for the life of me know why we are going to tear up 4th street and 2nd street at the same time. it will make downtown a clusterfk for traffic.

Rafael said...

@ anon -

first, I'm not suggesting this is an optimal approach. It's just that I don't know how much flexibility TJPA still has at this point. Penn Station the current design most definitely isn't, given that the most critical section - the throat - is so severely curved.

Propagation issues are why there are buffers in the schedule, parameters that can be optimized. Note that JR manages to run its shinkansen trains such that they are typically less than a minute off schedule after hundreds of miles.

Since HSR would not share track with anyone at all north of Fullerton in this scenario, there is no good excuse for them to be late.

Similarly, Caltrain doesn't have to worry about UPRR during its peak periods. After grade separation and raising its platforms to level boarding, it also has no good excuse for significant delays.

@ BruceMcF -

perhaps I misunderstand you, but there is no need for a five-minute delay between the time the tail of the last outbound train clears the single track section and the time the nose of the first inbound one can enter it (and vice versa). The operator just flips a switch in the signaling system.

Any safety gap would be baked into the tunnel traversal time in my model. In addition, there's a minute of buffer time for the outbound group of trains and three minutes for the inbound group. No magic required.

@ Clem -

I completely agree with you that a design in which any train from any operator can go to any platform track would be preferable. The idea of a central station under Mission Street would achieve that, as would a single-track one-way loop tunnel.

In the concept described here, there is actually no connection between the HSR and Caltrain timetables at all. Neither service ever uses the other's track. It's just that both would have to deal with the issue of having to make do with a single-track tunnel.

If you stick with a three-track tunnel design, you could give Caltrain two of those so it can implement a smoother schedule - especially during rush hour. On the other hand, I believe the plan was anyhow to run some trains to 4th & King to leverage the Central Subway's reach beyond Market Street. I so, they might not want to run 9 tph into the Transbay Terminal anyhow.

Rafael said...

@ jim -

I don't know off-hand how much of the tunneling will be done using cut-and-cover and how much using strictly underground methods.

As for the tail tracks, last I heard CHSRA had decided it would rather have straight full-length platforms. The old Brisbane yard at Bayshore Caltrain would offer a lot more parking capacity at much lower cost.

Adirondacker said...

Why do the tracks and platforms have to run parallel to Minna and Natoma? They could run parallel to Main and Beale. Lots of space over that way including what looks like parking lots on Google's satellite views. You trade two 90 degree turns for two 45 degree turns if you run across Townsend or King to Embarcadero and then up Main to the station. Build a big station, lots of space for services coming in through the new tunnel to Oakland.

mike said...

As others have pointed out, this design is totally inflexible and very, very sensitive to delays. Can you give an example of any rail terminus in the entire world that operates like this?

To be honest, I don't think it's in the blog's self-interest to publish posts like this. If you want to impact policy (i.e., if you want CHSRA to pay attention to you), then you should project the image of informed citizens presenting reasonable suggestions. This type of post projects the image of "highly imaginative rail-fan with way too much time on his hands coming up with outlandish solution." That type of thing, repeated enough times, is going to dissuade CHSRA from paying attention to you.

BruceMcF said...

"perhaps I misunderstand you, but there is no need for a five-minute delay between the time the tail of the last outbound train clears the single track section and the time the nose of the first inbound one can enter it (and vice versa). The operator just flips a switch in the signaling system."

The fourth train of one group of four and the first train of the next group of four are "two consecutive trains". They have to have an operating headway of five minutes.

That is physically impossible with a single bi-directional track over a mile long.

As a non-engineer, I cannot answer the question of whether the TJPA can offer 5 minute headways to HSR when it is pooled with Caltrain traffic. I can only pose the question ... clued in that there was a serious unresolved problem by the testimony of TJPA at the California State Senate committee hearing and then finding Richard's critique of the TJPA design and his proposal.

However, its inarguable that this present proposal fails to comply with AB3034.

Al2000 said...

look, the 4 trains-in-each-direction-taking-turns idea does seem a bit off, but the loop idea, with the better curves shows some promise.. anyone have thoughts on that?

Anonymous said...

Clearly the simplest answer is to have hlaf the trains term at 4th and half of them term at tbt problem solved. I sill have to insist that 4th is a good if not better destination for at least half the people arriving in sf.. and to resond to a previous post comment bout mission bay being mostly low rise development. 99 percent of the entire residential population lives in low rise neighborhoods. Further, only 4th street corridor, mision bay and third street corridor have nay plans and any potential for increasing heights and density and the majority of any population gorwth in SF will be there. There is not a single neighborhood anywhere in the city that is going to alow any further growth. 4th street will srver a much larger future residential population than tbt and will also have much better freeway access to 80/280/101 As much as we want to believe that everyone is going to arive by BART. They aren't. They are going to drive and if they have a choice of driving and parking at oakland airport, versus no parking at sf hsr they will fly.

Clem said...

To be honest, I don't think it's in the blog's self-interest to publish posts like this.Strongly seconded. The stuff you can come up with using Excel!

Alon Levy said...

I would add the word "only" to any discussion of 20 tph. If Caltrain attracts a reasonable market share after electrification and the TBT extension, it will have 20+ tph on its own, without HSR. Terminating a few trains at 4th and King will really not solve the problem, since that's not where most people want to go. If SF leaves the main terminal at 4th and King then it can attract investment there and turn the area into a secondary CBD; if there's a stop at TBT, it'll never happen, and 4th and King will go the way of the various pre-Penn Station termini in New Jersey.

BruceMcF said...

Alex said...
"look, the 4 trains-in-each-direction-taking-turns idea does seem a bit off, but the loop idea, with the better curves shows some promise.. anyone have thoughts on that?"

In terms of castles in the sky, its one I like ... its probably the one I like the best ... but since its outside the frame of the EIR/EIS, and so loses a chance at the Stimulus funding, its in the nature of one more opportunity lost back when they were busy short-changing the design of the TBT train box, long before I ever heard of the TBT.

The options inside the frame of the EIR/EIS, and therefore politically realistic options to push for, are the train box that is compatible with Richard's design, and the TJPA design and ... well, that's it.

Now, the strongest leverage that the other stakeholders have on getting TJPA to fix their design post-haste is the requirement to get the signed support of the stakeholders if the TJPA is going to apply for the Federal stimulus money.

Of all the alternatives canvassed in this post, that leverage can only be applied with respect to getting a train-box that is compatible with Richard's layout.

That would still leave the battle over the layout at 4th and Townsend and the layout of the TBT train throat to be fought, but at least an improvement on those fronts and a reduction from three tunnel tracks to two tunnel tracks to avoid a gross waste of public funds would remain on the table as an option.

Everything else in Rafeal's list is "coulda / shoulda / woulda / but didn't".

And at that, he misrepresents the difference between Richard's design and the TJPA design. I presume that being busy creating dead-on-arrival alternatives does not leave enough time to look at the potentially viable alternative.

BruceMcF said...

Alon Levy said... "If SF leaves the main terminal at 4th and King then it can attract investment there and turn the area into a secondary CBD; if there's a stop at TBT, it'll never happen, and 4th and King will go the way of the various pre-Penn Station termini in New Jersey."

If only Caltrain locals go to the TBT ... and they of course all stop at 4th and Townsend, underneath 4th and King ... and all Express and Semi-Express services terminate at 4th and King ... clearly 4th and King would be the main Caltrain terminal.

Anonymous said...

4th and king is going to be a central location for the majority of residential growth in San Francisco for the next 20 years. how many times must a say it before it sinks in? It makes sense to have have half the trains term there if they can't all fit into tbt and for people who drive to and from the tbt to head south, 4th is a better location.... and people will be driving make no mistake. I know everyone want to believe that most people will use public transit to complete the trip but at least half the total are going to drive and park. They just are. And again - the vast majority of future residential growth in San Francisco is going to be in the corridors adjacent to 4h a king. Is anyone listening?

Brian Tyler said...

@ Adirondacker
The plan you propose, where: "[The tracks] could run parallel to Main and Beale" does not align the terminal for Transbay Tunnel. That is why that plan was not chosen, although that was the original plan. How a new Transbay would solve the capacity issue is discussed on the Switching Modes site.

Adirondacker said...

If only Caltrain locals go to the TBT ... and they of course all stop at 4th and Townsend, underneath 4th and King ... and all Express and Semi-Express services terminate at 4th and King ... clearly 4th and King would be the main Caltrain terminal.

Every LIRR train, except for the ones on the Port Washington branch, stop at Jamaica. Many of them terminate at Jamaica. Does that mean Jamaica is the LIRR's main station or does that mean that Penn. Station is the LIRR's main station? It's going to be even worse one they start running to Grand Central also. Hmmmm.

Most SEPTA trains stop at 30th Street Station, Suburban and Market East. Which one is the "Main" station?

Brian Tyler said...

The idea proposed here is called "convoying". It is used in BRT systems in Sao Paulo and Porto Alegre. It might just work, but that doesn't mean it's a good idea. (Still, it's great to see new ideas explored).

So, why is convoying a bad idea in the DTX?

1.) This proposal would inundate the TBT with passengers, rather than spread them out. The result would be packed escalators, elevators, ticket booths, taxi pick up lanes etc... The TBT is overbuilt, but it's not built for four or more trains arriving or leaving at once.

2.) Having only one tube available would be too risky. If a train broke down there it would clog the whole system all the way to San Diego.

3.) Under this idea the trains would have to run so close together it would require extensive IT. This is done with BRT buses when they are convoying in Brazil: the driver of the first bus has electronic control of the buses that follow it. So, it could be done... but I don't think it's appropriate here.

4.) For all of the trains to run as one train in a convoy they would have to be staged. This would take time, extra trackage and complicated logistics - you'd have to build more than just the tunnels.

5.) Also, the third bore is necessary for reliability and capacity.

Reducing turn radii is good; the sharp turns of the DTX aren't great. But are squeaky trains going to deter riders? Is there really going to be that much extra wear and tear from just two turns? Do we even want the Japanese trains that can’t make the corners? In short, the turn radii issue isn't that big of a deal, even if it not ideal.

A new Transbay Tube is the right way forward to increase capacity at the TBT, when increased capacity becomes necessary.

Alon Levy said...

A third bore will increase neither reliability nor capacity. HSR mainlines all over the world have two tracks; they experience so few breakdowns that it's not worth it to add a third track. CAHSR is planned to have two tracks for most of the system's length, as well; why three-track only a few kilometers at one end?

As for capacity, the only way to squeeze extra capacity out of a three-track tunnel is to run trains 2/1. This turns out side of the tunnel into either a massive source of trains, or a massive sink. This requires a very large number of station tracks to house all these extra trains. The Metro-North gets away with running trains 3/1 in Manhattan because Grand Central has 67 tracks; TBT won't have this privilege.

Unknown said...

4th and king is going to be a central location for the majority of residential growth in San Francisco for the next 20 years. how many times must a say it before it sinks in?Jim, I hear you. Everyone is perfectly happy with LA Union Station as the main LA terminus. Guess what? Union Station is sandwiched between the freeway, Chinatown, and the county jail, a good long walk from the main downtown financial district. Yet everyone seems to recognize that the shuttle bus, metro red line, or a stroll over the freeway is a workable compromise instead of spending billions to tunnel under Bunker Hill. Whereas Central subway is going to be a nice fast run from 4th and King to downtown SF.

If anything, 4th and King is a much more promising neighborhood than where LA Union Station is located, and would only come up faster if that was the main HSR terminal. There's this fanciful idea that Transbay is needed for connections to East Bay traffic. Guess what, it's still going to be more convenient for East Bay travellers to fly out of Oakland, whether HSR terminates at 4th and King or at Transbay. If they really want to take the train, they can take BART and catch HSR at Millbrae.

Maybe after peak oil hits flying out of OAK will become uneconomical, but surely by then there will be either a new transbay tube and/or a HSR spur from the South Bay to Oakland.

BruceMcF said...

Quoth I: "If only Caltrain locals go to the TBT ... and they of course all stop at 4th and Townsend, underneath 4th and King ... and all Express and Semi-Express services terminate at 4th and King ... clearly 4th and King would be the main Caltrain terminal."

Quoth Adirondacker: "Every LIRR train, except for the ones on the Port Washington branch, stop at Jamaica. Many of them terminate at Jamaica. Does that mean Jamaica is the LIRR's main station or does that mean that Penn. Station is the LIRR's main station?"

That would depend on destinations to Jamaica versus Penn Station. Having been to Jamaica (if not by train), I doubt that the destinations to Jamaica make it a dominant station.

No services terminate at Cityrail's Town Hall station at all, and all services that stop at Town Hall stop at Central, while all interurban services terminate at Central, and the Light Rail connects to Central (doesn't the existing light rail connect to 4th and King?) ... but Town Hall is co-equal as the main Sydney destination station.

Its the destinations in the immediate environs of the two that will determine which is the dominate mass transit terminal. The catchment of an HSR station is much wider than the catchment of a mass transit station, so the intermodal connections are more important for the HSR.

jim poses the argument that the 4th and King will be the more important of the two as a Caltrain destination, in which case what seems to be Caltrain's agreement to run only locals into the 4th and Townsend / TBT system, with all Express or Semi-Express services terminating at 4th and King, would make more sense.

Rafael said...

@ mike, Clem, BruceMcF -

I would be quite happy if TJPA were open to the sensible improvements put forward by Richard Mlynarik. I'm not claiming that convoy operations are optimal, but virtually anything is better than the current DTX design. To my mind, "DTX" includes the throat and the 4th & Townsend station, which I consider superfluous.

It's just that so far, TJPA's position appears to be that the only question left to be decided is if the trainbox should be built right away or later.

They haven't even acknowledged that the current design of the DTX tunnel is a fundamental problem because they desperately want to pretend their project is shovel-ready.

CHSRA isn't helping matters by suddenly asking for additional platform tracks that aren't needed.

@ BruceMcF -

by definition, headway refers to trains traveling in the same direction to ensure there is adequate distance for an emergency brake maneuver. The concept is not applicable when trains are anyhow moving away from one another.

Once the tail of the last train of an outbound group has vacated the tunnel track, there is no reason why the first train of an inbound group should not be given a green light right away.

@ Alon Levy -

20tph for Caltrain would mean 20 trains per hour in each direction. They are currently at 5 tph peak and hope to increase that to 10tph by 2025, using 8-car bi-level trains. Together, these measures would support 3x the current ridership.

Given that Caltrain only operates on the SF peninsula and down to Gilroy, it's not clear to me where they would get the passengers to support doubling that volume yet again.

Adirondacker said...

where they would get the passengers to support doubling that volume yet again.East Bay and North Bay commuter services, rapid rail to Sacramento and Stockton?

Clem said...

In short, the turn radii issue isn't that big of a deal, even if it not ideal.These curves are a HUGE deal, precisely because they would be so EASY to straighten before any concrete is poured. The turn from 7th to Townsend is entirely on railroad land and the turn from Townsend to 2nd would result in fewer property impacts if flattened a bit.

If we start excusing every sub-optimal feature of the TJPA design, we're going to end up with one turd of a station.

they desperately want to pretend their project is shovel-readyThis is a big problem. Putting on an appearance of shovel readiness is becoming more important than doing proper engineering... they want to build, build, build, whatever the hell it is, so as not to miss the funding opportunity. Watch for the same nonsense to happen in San Bruno, where HSR will be forever stuck with a 60 mph curve courtesy of Caltrain.

Schaufelbereitschaft ueber alles!

Rafael said...

@ adirondacker -

Caltrain will run three trains a day each way across the Dumbarton rail bridge to Union City once that is finally restored. That's the sum total of their expansion plans into the East Bay, which is already served by Amtrak CC, BART and ACE. Perhaps ACE will run some trains of its own up to 4th & King some day, but the passenger numbers won't be huge.

Marin would love to have either BART or Caltrain service but there's no way to run trains across the Golden Gate or the Richmond-San Rafael bridges.

Monterey county is trying to persuade Caltrain to run a handful of trains per day out to Salinas, but the number of commuters that will add to Caltrain's total is also small.

BruceMcF said...

@ Rafeal: "@ BruceMcF -
by definition, headway refers to trains traveling in the same direction to ensure there is adequate distance for an emergency brake maneuver. The concept is not applicable when trains are anyhow moving away from one another.

The thing is, AB3034 does not support your semantic game of treating the 10 minute, 15 minute or 20 minute long headway between a fourth inbound train and the next inbound train as "it doesn't count because I decided not to count it". You are pushing up the average HSR headway, by blowing out one in four of the HSR headways.

Which makes sense ... obviously a pair of bidirectional tracks have less capacity that a two way pair of track, so while you are "fixing" one bottleneck, you are imposing a bottleneck with even lower capacity.

Anonymous said...

Eric said...
4th and king is going to be a central location for the majority of residential growth in San Francisco for the next 20 years. how many times must a say it before it sinks in?Jim, I hear you. Everyone is perfectly happy with LA Union Station as the main LA terminus. Guess what? Union Station is sandwiched between the freeway, Chinatown, and the county jail, a good long walk from the main downtown financial district"

Exactly my point. What is the obsession with redesigning the TBT. First of all, it is going to be at least three decades before all that capaicty is needed at which time a transbay crossing can be considered. Not to mention the transbay crossing would be easier to line up with 4th and king that the tbt. It so happens that where the 280 extension lands at king st - that 280x was going to continue up king to the bay to become the southern crossing ( 2nd bay bridge ) Also access to 4th WIll be easier for a large portion of SFers because Muni also has plans to develope a transit corridor down 16th street, likely to connect with the n judah terminus at king which adds more downtown capacity outside the market street subway.

Alon Levy said...

Bruce: Jamaica is a secondary downtown in New York, and not even the largest. If I remember correctly it's third, after Downtown Brooklyn and Long Island City - and of course these are already far smaller than Manhattan's job centers.

Rafael: the San Mateo and Santa Clara Counties to SF commuter market is a lot larger than you think. It's about two thirds the size of the market served by Metro-North, which runs 50 tph, and a little more than half the Long Island to Manhattan market, where the LIRR runs 41 tph.

Rafael said...

@ BruceMcF -

ok, I see what you mean now. AB3034 specifies a minimum headway that must be supported by the signaling and train control system. It does not say that headway has to be used.

It would be perfectly possible to fill the gaps in the schedule with trains terminating either at Millbrae (to park them in the Brisbane yard) or else at 4th & King. I know AB 3034 sets a limit on HSR stations, but by the time this would become an issue, we'll be in phase II of the HSR project anyhow, long after the AB3034 funds were used up.

Besides, the two single-track tunnels would anyhow have a crossover X section underneath 2nd Street, as close as possible to the fan tracks, for emergency and maintenance purposes. It wouldn't normally be used in the operations regime I described, but it could be once the political dust has settled and FRA drops any objections it may have to HSR and non-HSR trains running on the same tracks. In effect, that would give you a regular throat.

Whether or not it has higher aggregate throughput capacity depends on the speeds the trains can achieve in the curved sections. Both services could operate a smoother timetable, but only after integrating their separate ones.

@ Alon Levy -

not everyone who lives in SM and SC county works in SF, the situation is comparable to New York. Silicon Valley actually employs a lot more people than SF does. Most of them live in the East Bay, which is why I-880, the San Mateo and Dumbarton bridges and 237 are every bit as packed as I-80 and the Bay Bridge every morning. That's the reason Caltrain will provide limited commuter services across the Dumbarton rail bridge once that is restored.

Plenty of Silicon Valley worker bees also live in SF and commute down. 101 southbound is very congested in the morning.

Ergo, Caltrain attracts a slice of the north-south commuter market in both directions, but the transit connections within SF to 4th & King and within Silicon Valley are fairly limited. Some of the larger employers offer corporate courtesy shuttles for employees who enroll in commute alternatives programs.

It's entirely possible more people will start using Caltrain after electrification, especially if electric folding bicycles become more mainstream. During the summer months at least, that combination would make for a nicer commute than sitting in bumper-to-bumper traffic for an hour.

Alon Levy said...

No, I specifically meant the number of people who live in SM and SC but work in SF. As of 2000, there are 80,000 such people, compared with 114,000 who live in the Metro-North counties and work in Manhattan, and 136,000 who live in Long Island and work in Manhattan. If Caltrain ever gets the same modal share to the central city as the LIRR or MNRR, it'll need about 24 tph in the peak direction, if we scale it to the LIRR, which also runs trains to destinations other than Manhattan. If we scale it to the MNRR, make it 35 tph instead.

So yes. It's going to need four tracks.

BruceMcF said...

@ Rafeal: "ok, I see what you mean now. AB3034 specifies a minimum headway that must be supported by the signaling and train control system. It does not say that headway has to be used."

This plan does not offer that assured headway. You are talking about bi-directional track, and the ruling headway with a single bi-directional track is the length of time between one train going one direction, then the traffic the reverse direction clearing the line, so that the next successive train can proceed.

Just deciding that the point where your plan blows the legal requirement completely out of the water, requiring double or triple or quadruple the legal maximum operating headway, by deciding to not call it "headway" when you reach the point that the trainbox is full and no more inbound trains can arrive on the single line until one or more outbound trains are cleared is playing a game with the semantics of the terms, but it does not change the actual throughput capacity.

And, fortunately, AB3034 is clear that it is talking about operating headways, so there is no ambiguity in the legislation to permit that semantic game.

Brandon in California said...

It's been a long, but great weekend. And I am finally catching up now. This post was another long one, but I finally read to teh end... whereas before I gave up.

That said, I agree with the first post by anon. I'd like to add that the idea has numerous downstream implications... and ask for a train ballet to occur for many. It does not work. Also, it's not rider friendly.

The objective for rail planning is to design a system up front with great flexibility. A system should not be built witha specific operating plan in mind... for fear of capping the ability of the system or creating undue constriants during speciual events or unusual/unplanned operating conditions.

In my opinion, I feel CHSRA should stop at 4th and King Street until a point in time when the TBT can accommodate the needs of the planned HSR system. That seems like a difficult thing to achieve right now... and I would not object to the TBT project being abandoned entirely in favor of a new HSR terminal serving the core of downtown AND connected to BART.

Question.. is Richard Mlynarik visiting and posting on this blog? Or on the other one? I hope he is... as he seems to be well informed on the constraints. His info is so detailed I suspect he is crazy or he is prevy to information first-hand.

Unknown said...

His info is so detailed I suspect he is crazy or he is prevy to information first-hand.Having dealt with a few engineering types with his particular style of communication, I assure you, while they can fool you for a considerable time into thinking that the latter situation is true, trust me, in the end, it is always the former.

Brandon in California said...

^^^ Yes, I know. Another angle... if he's prevy to information, he is risking that connection... which could possibly be his job. Unless financially well-off, that is short-sighted / crazy.

Adirondacker said...

His info is so detailed I suspect he is crazy or he is prevy to information first-hand.He hasn't said anything that needs "inside" information. The existing and proposed right of way is public information. Calculating curves, platform lengths etc. is a matter of looking up the right formula in the manuals railroad designers use.

lyqwyd said...

If the trainbox is funded and built immediately what sort of impact does that have on the alignment/design of the DTX? I would hope there is no direct impact on the DTX just because the trainbox is built. Of course I could be wrong about that. Is it that the EIR/EIS includes the DTX and could not be changed once funded? I would think a new EIR/EIS could be created even after the trainbox is built. Again I could be wrong.

If the DTX could be redesigned then I don't think it matters if the trainbox is built now. From what I've read there are no major operational problems with the trainbox itself (especially if no platforms/tracks would be built until actual service begins). If the TBT is operated as a through station it seems there should be no problem accomodating 5 minute headways.

In that case it seems that the DTX is the real issue, but one that can reasonably be redesigned, so I'm not sure why we are assuming we have to live with the existing design. Why not run run it up Townsend to Embarcadero, and then up Main or Beale? That will completely solve the curve radius issue. It will probaly be more difficult to engineer since it's so close to the water, but I can't believe it would be that much more difficult or expensive that it's worth choosing an operationally worse alternative.

Why can't we just have 2 tracks that allow a crossover and can have any train run in any direction? I imagine one would operate most of the time in 1 direction, but it could be used either way if necessary. Why do we need to dedicate 1 track to 1 type of train (Caltrain vs. HSR)?

It seems that headway in the DTX could be much lower than 5 min, since the trains will have to be going much lower than their highest possible speeds. If headways are 2.5 min the two tracks could support 24 tph in each direction (that would be for all combined traffic of course, Caltrain + HSR). IIRC BART operates at about 2 minute headways through the transbay tube at peek going about 60-70 mph

My assumptions could certainly be wrong, but can anybody put some concrete examples of why this wouldn't work?

lyqwyd said...

I agree with jim regarding the 4th and King station, I believe it will be much more popular than most think.

UCSF is in the process of building out a 55+ acre campus focused on biomedical research that is planned to have over 9,000 employees by 2020. I'm sure there will also be numerous business that serve that population and do related biomedical business.

SOMA is probably the fastest growing neighborhood in SF, with a little development going on even in the current economic conditions, and I expect it to pick back up quickly once the real estate market recovers. I wouldn't be surprised if 10,000 or more residences are built in the surrounding area over the course of the next decade or 2.

Once the Central Subway is build the 4th & King station will connect directly with Union Square, a huge tourist draw with lots of hotels. It will also connect with Chinatown, the most densely populated neighborhood in SF.

If the Central Subway connects with North Beach then the station will connect directly with the possibly second densest neighborhood in SF.

If the CS connects with Fisherman's Wharf 4th & King will directly connect with SF's biggest tourist area.

Once the CS is complete I think 4th & King will more convenient for many San Franciscan's leaving from home for HSR travel as every Muni Metro line (SF's light rail system) will be at most 1 transfer from 4th & King with at most a very short walk to the train station.

Brandon in California said...

@ Adirondacker...

Do you think those engineering drawings are publicly accessible? Or that he made originals?

I have doubts that one of those is the case.

Anonymous said...

@lyquyd - thanks for summing up the points Ive been trying to make about 4th . Itll be more useful, more flexible and more appealing to many people and has a lot of potential. There is no reason whatsoever that every train has to term at tbt other then the fact that some folks just have their mind set on it no matter what. As for the tbt itself - its not really up to outsiders. No one is going to be moving it or redesigning it or anything else. It was a major production to even get it through city hall and approved by the people of san francisco.

Adirondacker said...

Do you think those engineering drawings are publicly accessible? Yes. The filings all these government agencies have to make to other government agencies are public documents. Lots of them are a click... well a few clicks away.