07 May 2016

Caltrain Has a Dwell Time Problem

Actually, Caltrain has two dwell time problems. The first is that station dwell times are too long, and the second is that station dwell times are too unpredictable.  Both of these problems will prove fatal to the blending of Caltrain and HSR services on "primarily two tracks."

To help visualize why, let's use position-versus-time string diagrams, often discussed on this blog.  Imagine trains following each other on a single track that runs from San Jose to San Francisco (ignore the other direction for now).  This red line is a local train making a lot of stops.  It leaves San Jose, and a while later arrives in San Francisco.  If you looked really closely you might see the individual station dwells, small horizontal kinks that occur whenever the train is stationary and time passes, but when you squint, it looks pretty much like this:
Every once in a while, this local train comes to a station where Jane, a wheelchair user bound for San Francisco, would like to board.  Because we don't have level boarding, getting Jane on board the train involves manually deploying lifts or ramps to ascend the several steps from the platform into the train.  Conductors must help Jane through the mechanics of the boarding process, which can easily take several minutes but feels like an eternity, even for Jane.  Timetable planners allow for riders like Jane by making sure that no other trains are scheduled right behind each other, to absorb these randomly occurring super long dwells without causing a train traffic jam.  They call it padding.  Here's what padding looks like, in pink:
This being a blended system on "primarily two tracks," we've got express trains and even high-speed trains using the same track as Jane's local.  A faster train looks like this blue line:
The blue line is steeper because the express train can cover the same distance from San Jose to San Francisco in much less time.  Here comes the express behind the local:
The timetable planners don't want the express to be delayed.  That's why they left a big gap between the trains, giving the local a good head start out of San Jose so that the express won't catch up to it before San Francisco.  Alternately, here is the local departing San Jose right behind the express:
Once again, a big gap opens up behind the express because the local is so much slower to arrive in San Francisco.  Now it's rush hour, and this is what "blending" soon looks like (not to scale):
In one hour, six trains can arrive in San Francisco.  Our string diagram is full of gaps, which means we are making very poor use of the capacity of our single track.  How do you fix this?

First, you electrify Caltrain.  While this isn't cheap, one of the main advantages of electrification is that EMUs start and stop much more quickly, so that on average, a local can get to San Francisco several minutes sooner while still making the same station stops.  The local will have a higher average speed than it did before.  Compare:
See how the new EMU local train shows up as a steeper line?  That's because it spends less time moving between stations.  (Note to Atherton: electrification is not just an emissions thing.  Tier IV diesel trains can't pull off this neat trick like an EMU can.)  Now this is what the "blended" rush hour looks like:
If you compare it carefully to what we had before, we can now fit eight trains in the span of one hour, instead of six, because those dreaded gaps are shorter.  By increasing the average speed of the locals, we were able to squeeze in more trains (and more passenger capacity).  Caltrain seems content to declare victory and live like this happily ever after.  This is what they envision as the "blended system".  Whenever Jane decides to ride the train, the pink padding still ensures that following trains aren't delayed too badly.

It's better, but still kind of mediocre.  Especially for Jane.

What if the local train could spend less time standing still at each station?  Dwell time can be reduced by level boarding, a step-free and gap-free configuration where you simply walk on or walk off the train, just like when you ride BART.  For a given number of passengers getting on and off the train, level boarding shaves off about 1/3 of the station dwell time since they can all shuffle on and off more quickly and seamlessly.  The magic of reducing dwell times is that while the train's actual speed is no higher, it still gets to San Francisco sooner, because it saved a few seconds during each station stop.  A few seconds here, a few seconds there, and pretty soon you're talking several minutes.  The average speed went up without the actual speed increasing!  The string for an EMU local with level boarding now looks like this:
If the local arrived in San Francisco ten minutes earlier thanks to electrifying Caltrain, it can arrive another five minutes earlier than that by having level boarding at all stations.  Electrification saves time between station stops, and level boarding saves time during station stops.  The two work together as perfect complements to each other.

The diagram above is actually wrong, and here's the second amazing thing about level boarding: Jane can get on and off the train like everybody else.  Not only does this give Jane the dignity and equal treatment that she deserves, but it saves everybody else the grief of those randomly occurring Jane delays.  Because dwell times are now predictable, timetable planners can get rid of the padding they applied in case Jane wanted to ride before.  Like this:
If you like probability distributions, here is the effect of level boarding on the probability distribution of dwell time:
Caltrain commissioned a study of station dwell times, which found that across a sample of 5149 station dwell observations, the median duration from wheel stop to wheel start was 49 seconds.  The median excludes abnormally long dwells, such as those occurring when Jane wants to ride.  The average dwell time does account for Jane and is 58 seconds, practically an eternity.  That was back in 2010.  Today, with the system bursting at the seams, average dwells are getting so long that the timetable was recently adjusted to make chronically late trains into slower on-time trains.  With level boarding, typical dwell times could easily be cut to 30 seconds.

Level boarding really improves the situation for rush hour:
We're really cooking now.  We can squeeze 12 trains through in one hour on the same track.  That represents a massive capacity increase, with the combined effect of reduced and predictable dwell times providing a similar benefit as electrification alone did.

Caltrain staff just doesn't seem to get this, and they are certainly not helping their board of directors understand the issue. They think of level boarding as primarily an optional comfort feature. Here is their view of level boarding, from a recent board meeting quarterly update:

First of all, they don't even call it level boarding. Dual doors!  What a pain!  Requested by interloping stakeholders, or imposed by those annoying HSR people!  Ew, it's so complicated!  It costs $30 million to equip the new fleet!  It's almost as if they are disowning the very idea of level boarding, and reluctantly trying "not to preclude" some unspecified future decision because this stuff is just too hard to think about.  Presented this way, you couldn't blame the board or the public for thinking this is a stupid idea.  Where's the upside?

The upside is this: dual doors are the only realistic path for Caltrain to achieve level boarding, and level boarding is the only way that the blended system can work on "primarily two tracks."

This issue cannot be taken lightly, because the next opportunity to start a Caltrain conversion to level boarding will not occur until 2050, when the new fleet reaches the end of its useful life.  That's because the new fleet, as about to be ordered, cannot provide level boarding at a platform height of 25 inches.  The entire system would have to be shut down for the trains to be modified and all platforms to be rebuilt at that height.  So, doing nothing today and blindly kicking the can down the road until 2050 is not an option.  A prudent and strategic $0.03 billion down payment for a gradual transition to level boarding is minuscule as a fraction of the $2.2 billion modernization budget, and unlocks great potential for quicker and more punctual commutes as soon as the next decade.

Dual doors are a customization that amounts to less than 5% of the price tag for new trains ($30 million out of $648 million bid price).  They can hardly be used as an excuse for the massive increase in the cost of Caltrain modernization.  They will help to address Caltrain's dwell time problem.

Caltrain has a dwell time problem.  The first step is for everyone (staff, board and public) to understand it.

53 comments:

  1. As you likely know, Caltrain does not run locals all the way up/down the peninsula during peak hours, so I don't quite get the point of the first half of this post. I know the odd stop patterns are subject to much ridicule here and elsewhere, but that is how they avoid having the huge gaps you picture. Baby Bullet, short gap, limited that runs local halfway, then expresses the rest of the way, short gap, limited that expresses halfway, then runs local the rest of the way, etc. The main reason they only run 5 peak trains per hour each way is that they can't afford enough trains or crews to run more.

    I've been riding Caltrain daily during peak hours for the past decade. The recent delays (and timetable adjustments) have nothing to do with "Jane", they are due to the slow orders caused by seemingly endless random construction projects along the line. Throw in aging locomotives that fail halfway through a run, doors that fail to close properly, wheel chair lifts that don't retract, engineers who overrun stations and have to back up (really!), bicyclists who can't figure out which car to get on, cars taking out crossing gates (necessitating slow orders until fixed), drunken Giants fans holding doors open for their friends who can't figure out the ticket machines, and of course, the occasional car or person strike, it's a wonder that Caltrain ever runs on time.

    What news do you have (aside from that presentation) that suggests that dual height doors have been dropped?

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    1. BTW, I'm very much in favor of level boarding, I'm just suggesting that "Jane" isn't the only problem these days, I tend to blame the bikers ;^)

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    2. Good points, thanks.

      I over-simplified to illustrate the issue. I believe the basic point is sound: running trains of different average speeds wastes valuable track capacity, and level boarding can significantly increase Caltrain's average speeds. This is crucially important if you plan to run HSR over the entire SF - SJ distance on the same tracks. (I know, crazy!)

      Faster average speeds also enable more frequent peak service for a given fleet size, or a smaller fleet for the same peak frequency.

      I have no information that indicates that dual (a.k.a. level) boarding might get de-scoped, but listening to the presentations and comments at the recent board meeting made me wonder why, this late in the process, the concept is so half-heartedly described.

      Level boarding won't end world hunger but it ought to be the next major strategic push after electrification.

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    3. Level boarding would also help a lot with getting bikes on and off the train.

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    4. Nope. Level boarding would make things worse for bikes. To off-board, bikes would (most likely) have to go up the stairs from the lower level to exit the upper door. This is yet another reason why the dual-door solution is such a bad idea.

      For comparison, BART schedules 25s dwell time. Generally they are able to do that, except during peak hour in downtown SF where it can be as long as 50s (at least until they get the 3-door trains).

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    5. If a better solution exists with HSR platforms at 550 or 760 mm, how goes the search for a TSI and ADA compliant high-speed train that can be sourced competitively from multiple vendors?

      The HSR people have legitimate reasons to aim for world-standard 50 inch floors.

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    6. Right now, people with bikes have to carry them up much steeper stairs onto and then later down off of the train. Explain to me how this current situation of dealing with extremely steep staircases (on gallery cars) is better than dealing with a smaller set of internal stairs (that can also be navigated while the vehicle is in motion)?

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    7. Nobody is talking about getting more gallery car relics, so your comparison is irrelevant. The correct comparison is dual-height car (with internal stairs) vs. TSI-compliant rolling stock (i.e. something similar to current Bombardier cars) with entrance always on the lower level.

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    8. This has been rehashed many times… For bi-level cars, it is common understanding that a low-floor configuration is the optimum; it allows level boarding at 55 cm platform heights (76 cm would not be such an issue with the bigger loading gauge in the US). For single-level cars, you are better off with 120 cm floor and platform height. Actually, bi-levels with triple-wide doors at 140 cm (or so; the space for the trucks gets cramped even at this floor level) would provide the shortest dwelling time. For all that, several vendors could reach out to their vehicle kit and build something with ease.

      On the other hand, single-level HSR with low-floor does not exist (the fastest one, I am aware of, under construction right now) is in the 250 km/h league.

      On a different note: shaving off another 5 seconds per stop could be accomplished with a "technology-supported departure control system" (in other words, automatically closing doors, with force-closure by the driver). Ah, yeah, no conductor needed for that.

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    9. If bikes on board become a problem, then we will do as the Dutch. They are way ahead of us. They don't do bikes on board, and they have outstanding off-board bike parking. Just look at Delft for an example.

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    10. I fully agree; when bikes are a problem, the have lost nothing on a train. Period. The first measure to deal with the bike situation would be to charge for them; even have a monthly pass, at the price of a regular monthly pass. That probably would reduce the number of bikes on board by 80 percent…

      Yes, safe station bike parking would then be a good cost-effective alternative (and it could be priced so that for a monthly pass, it would cost less to have two bikes in the parking stations than a "bike" pass.

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    11. And what about the strollers, airport luggage, elderly, and wheelchairs -- ban those too? Removing bikes from the train won't erase the self-inflicted access problems.

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    12. Where are you going with this? Are you saying that gap-free, step-free level boarding creates a "self-inflicted access problem?"

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    13. @Drunk Engineer: I a not quite sure whether I understand the "self-inflicted access problems"… what does that mean?

      With bikes, I have made the experience that bikes per se are not such a problem (except that they use up a lot of space); the main problem is their operator. Let's say it like this… "smart" and "considerate" are two attributes you have to search quite far with the typical bike rail customer.

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    14. If they were smart they would leave the bike at the station and get around at their destination like all the other people on the train do.

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    15. @Clem: it is not step-free. All that is being done is to relocate the steps and lift from outside to inside the train. Compare to the current Bombardier car with legacy platforms, where it is a relatively small step up from the platform. The new solution appears to add more steps, so arguably worse access. Quite a dismal result considering the $1+ billion being spent on new railcars and platforms.

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    16. Well, one could use ramps instead of steps … nickname for those cars would be "covered hopper"…

      just kidding… The advantage to keep steps and lifts in the train is that they can be used while the train is in motion. And that allows to keep the dwell time reasonably short.

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    17. @DrunkEngineer: The Bombardier cars have two steps up, not one, with a total rise of seventeen inches. To me that's not "relatively small."

      I think I'm beginning to understand what you mean: you assume there will be no room for priority seating on the middle level above the wheels. That remains to be seen, doesn't it?

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    18. Utah Frontrunner uses same Bombardia Car but have level boarding. So, Caltrain can make level boarding with Bombardia car even before the electrification. Why not?

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    19. Because Utah FrontRunner complies with ADA by using bridge plates to span the horizontal gap between the platform and the rail car. They also don't run past platforms at full speed.

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    20. Clem, Thank you for picture. Is this bridge plate for wheelchair or everyone? What do you mean " They also don't run past platforms at full speed"? Is there any clearance issue with platform?

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    21. Yes, there are clearance issues with platforms. Typical suspension sway (or even suspension failures) cannot safely be accommodated at speed without a wider gap than the 3" maximum levied by ADA.

      Systems like BART, SMART or the Denver A line deal with this by limiting speeds past platforms.

      Your questions serve as an excellent illustration of the deceptive complexity of level boarding. A lot of seemingly obvious solutions just don't work. Caltrain's dual level solution does work.

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    22. "deal with this by limiting speeds past platforms" Is it possible to implement in San Francisco, Bayshore, Lawrence, San Jose and Tamien? All train stop at these station (or there is bypass track).
      In addition, "Express stop" stations like Milbrae, Hilsdale, Redwood City, Palo Alto, Mountain View and Sunnyvale can implement this configuration by making all train to stop there (or speed limit), if it provide better dwell time control.

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  2. Morris Brown08 May, 2016 12:10

    12 trains per hour each way! The crossing gates will for the most part be in the down position, causing unacceptable traffic chaos on surface streets.

    This can only be mitigated by installing above or below grade crossings installed at all current at grade crossings. Where is the money? $4 to 7 billion needed?

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    1. God forbid that even one single elite SUV or BMW driver be slightly inconvenienced by "dirty public transit". The horror.

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    2. 12 is just a number I used to illustrate the issue, but it's not crazy.

      The corridor is already 60% grade separated, and there are always more grade separations in the pipeline. We will get to 100% some day, in "small" chunks of a hundred million here and a hundred million there.

      Meanwhile, the light on Ravenswood at El Camino is red for far more than 50% of the time. Nobody complains!

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    3. BART runs 24 train/h with 2-tracks. Why Caltrain not?

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    4. ...because of the whole point of the article - that multiple speed trains consume frequency potential

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  3. Would it be possible to do a full level boarding blitz over a long weekend? Perhaps by using temporary platforms to raise the station height. The temporary platforms could be prebuilt, staged, and then dropped into place. Over time more permanent platforms, if needed, could be installed.

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    1. Not really over a weekend, but maybe over two weeks. However, it would be quite expensive and had to be extremely well coordinated. In that period, platforms had to be raised, the electrification fully activated, the signalling system updated or changed, and the whole line tested and approved. There would be not much time for mess-ups, and it had to be finished in time.

      Comparing the extra cost for a "Big Bang" changeover with the extra cost for dual level boarding rolling stock might lead to some interesting results.

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    2. RFF rebuilt 1300 platforms at a cost of 50 million euros.

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    3. It's not quite correct to think of this only in terms of the platforms. For trains to be able to (a) pass platforms at speed without touching them and (b) remain compliant with the ADA maximum gap of 3 inches, the trains have to be fitted with deployable gap-filler steps. These devices are included on the high doors (384 of them!) in the $30M quoted by Caltrain.

      These devices are NOT optional, and to think that a 25 inch low floor train can simply dock at a platform after it's raised to 25 inches is incorrect.

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    4. How about having different horizontal gap (train-platform) between local stop and express stop?Local stop uses manually operated device to handle wheel chair like Utah front runner. Express stop to have narrow gap. Current ridership data well justify which station to be express stop.

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    5. This problem can be solved and has been solved without resorting to operational constraints that are literally cast in concrete.

      The solution is gap-filler steps that deploy automatically from the train. These are in wide use around the world, and were required for the "high doors" in Caltrain's RFP.

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  4. morris brown08 May, 2016 18:19

    @ Clem

    Who writes:

    "Meanwhile, the light on Ravenswood at El Camino is red for far more than 50% of the time. Nobody complains!"

    NOBODY COMPLAINS! You have got to be kidding. It is horrible and tons of people complain. I go by there at least 4 times a day.

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    1. Certainly nobody suggests that we grade separate El Camino. So just like people suck it up and wait for that red light, they will wait for that crossing gate that's down more than they would like. Especially now that CEQA criteria for traffic impacts are changing...

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    2. It's a hilarious double-standard: Drivers at any almost any major intersection (with turn lanes, etc.) face more "gate down (red light) time" than at any Caltrain grade crossing either now or in the conceivable future ... and yet they talk of how grade separations are absolutely necessary to avoid the outrageous/unacceptable "impact" of waiting for a train with up to a thousand riders aboard to pass -- far more than are allowed to pass in motor vehicles while waiting for a red light at ordinary road intersections.

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  5. If Caltrain and HSR don't share the platform, Caltrain don't have to adjust platform height same as HSR. If HSR and Caltrain really want to share the platform, Caltrain should choose 50" single floor EMU and use longer train as capacity needed.
    BART is moving to 3-door car, as their ridership increase. Caltrain may need same 3-door single floor EMU too. Ridership density of Caltrain system becoming similar to BART if they provide frequent services. Population near Caltrain station within walking distance is much more than BART. So, ridership density of Caltrain may surpass the BART system.

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    1. Better yet, go to three-door bi-level cars like the Paris RER. But we're a long way from needing that.

      Besides which it would be counter-productive not to share platforms!

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    2. Majority of high speed rail system have fare gate, except continental Europe. If HSR decided to use fare gate, it is difficult to share the platfrom unless Caltrain to implement same system.

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    3. Majority of high speed rail system have fare gate, except continental Europe. If HSR decided to use fare gate, it is difficult to share the platfrom unless Caltrain to implement same system.

      Ah yes, the solution to such a trivial difference in fare collection is ... more concrete!

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  6. "With level boarding, typical dwell times could easily be cut to 30 seconds" - With more passenger, Caltrain need more and/or wider door for faster passenger flow at station. Line-up is also useful. BART knows this fluid mechanics.

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  7. Your diagrams don't show any overtakes. Isn't that what that whole four track section they're building in the middle is for? So that expresses can overtake locals?

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    1. That's what it would be for, if it was built optimally. However, the latest documents and statements from the HSR people indicate that the four-track overtake section being contemplated is quite short (Hayward Park to Hillsdale) with a new emphasis of "station overtakes" which essentially means the commuter train sits for at least 5 minutes to let the express pass it. If the express is even on time, that is. Overtakes help, but they don't solve the basic challenge of operating trains with different average speeds on the same tracks. Level boarding helps lift Caltrain's average speed.

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  8. Clem, Current local-express overtake at Bayshore and Lawrence adds 3~4 minutes penalties but with very poor signal system and slower acceleration. Electrified Caltrain with very short signal spacing will not need 5 miniutes penalties for overtake.

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  9. Why not just have two levels at the railway station. Similar to what we have these days for A380s. There is one galley that serves for 1st floor, and other on 2nd. You still can go up and down internally. That could speed up the boarding process too. Again, just throwing an idea out there. No idea about the cost/feasibility/performance. But I think if there are companies who are designing hyperloops, this should be anything far stretched of an idea.

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    1. From time to time, Talgo suggests such a concept. So far, it dit never get to very serious consideration, because of practical reasons. For one, the decks would be maybe 2 meters apart, which would create very cramped conditions in the stations, and it would require gated platforms, which in itself requires the capability to stop at a precision of more or less one inch, something which is possible with automatic (driverless) operation on subways, but rather questionable for an application like Caltrain.

      In the current situation (Caltrain / HSR), it would not solve anything, as the question is low-level platform (for bi-level Caltrain) and high-level platform (for single-level HSR). The important thing is in any case, as the main message of the article, level boarding; the height above rail top is not really relevant, as long as there are no steps between the platform and the vestibule of the train.

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  10. Los Banos-area farmers seek voice in High-Speed Rail Project
    "Although the San Francisco line crosses Los Banos on its way to Merced, there is no proposed station near the city. Farmers say they would bear the economic cost of their land being divided without seeing the benefits because residents still would need to drive west to Gilroy or east to Merced to board the train.

    Others, such as Los Banos farmer Gene Vierra, said the plans presented a personal cost, taking land that has been farmed by generations of family members."

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  11. Regarding Caltrain's priority for level boarding, I asked a staff member. She said that the board presentation that the slide above was taking from was focusing on the decisions before the board relating to the first phase of electrification. Level boarding is not yet included, so it wasn't mentioned in that presentation. Level boarding is a goal and priority to be funded and implemented separately. The good news there is that Caltrain asked for, and VTA included, funding for the investments in capacity increases and level boarding (longer platforms, changed platform height, longer trains), for the upcoming 2016 ballot measure. In a separate presentation that covered the proposed investments for the ballot measure, delivered to VTA's advisory committees in the last few weeks, level boarding is mentioned in a bullet point, and the staff member who delivered it said that she briefly mentioned the benefits. I suggested adding a few more words on the slide so that people who were not at the meeting could also see why level boarding is being included for funding.

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  12. Reality Check27 May, 2016 10:45

    Interesting news: at this week's SF-SJ EIR scoping meeting in Mountain View, CA HSRA's Northern California Regional Director Ben Tripousis stated (more than once) that in their modeling for mid-Peninsula passing track designs for blended operation with Caltrain, they are assuming Caltrain will be operating with the same 110 mph top cruising speed as HSR. In answer to an audience question, he clarified that post-electrification Caltrain will operate with the same 79 mph top speed it does today, but that once various system improvements for 110 mph HSR blended operations are completed, Caltrain's top cruise speed will increase to 110 mph.

    Another point made at the meeting was that while they will be modeling mid-Peninsula passing track configurations, if none of those work for the needs of both agencies, they will continue to "iterate" until they find one that does ... AND that while they do hope to stay inside the current ROW footprint, depending on what track designs their modeling shows they need, some property takes may be necessary.

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    1. Reality Check27 May, 2016 11:02

      Here's the presentation showing the three passing track configurations to be modeled (see page 22):
      Caltrain/HSR Blended Service Plan Operations Considerations Analysis (June 2013) Available on Caltrain’s Website

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  13. Reality Check27 May, 2016 11:06

    Trying this again.

    Here's the presentation showing the three passing track configurations to be modeled (see page 22):
    San Francisco to San Jose Project Section Open House Meeting Presentation – May 2016

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  14. I like the graphs with the shading indicating variability. However, I always that shading is better used to show the limitation of the signal system. It might be hard to make such a graph unless one knows the exact locations of signals, but would be great to show how longer passing sidings improve throughput over the current situation where Baby Bullets catch up and slow down as they prepare to pass.

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