Caltrain's 2021 peak hour timetable achieves a score of only 96, meaning the service is slightly worse than the taktulator's baseline, the 2011 peak hour timetable, which a decade ago earned our reference score of 100.
Why so mediocre?
It's mostly in the padding. Caltrain service planners have evidently given up on trying to run a tight timetable while also dealing with the debilitating variability in station dwell times inflicted by the lack of level boarding. The right way to solve this problem was and remains to plan for and implement level boarding, a system upgrade that (on a per dollar basis) has even greater service benefits than electrification. The lazy way is what we see here: about 20% of extra padding is baked into the station-to-station run times, allowing a train to easily make up time and arrive "on time" in the event of a dwell time delay along the way. In the absence of a delay, trains can dawdle along even more slowly than the ancient diesel fleet could manage, and just sit at stations until the clock says it's time to go.
Back in 2005, a baby bullet express with five intermediate stops was timetabled at 59 minutes. In 2015, it was up to 61 minutes. Today, the same express runs in 66 minutes. This follows a pattern noted by Alon Levy on the deterioration of speed.
Another factor that explains the lower score is one fewer train per peak hour, resulting in longer intervals between trains. This helps with fleet size, where only 16 train sets (+2 spares) are needed to operate the 2021 timetable where 18 (+2) were needed before. Two more train sets are freed up for maintenance downtime, a vital bit of breathing room as Caltrain's older diesel fleet is breaking down more often. The fleet is well past its expiration date due to the multi-year delays in the electrification project.
Is it optimal?
Can a timetable be devised that uses no more than 16 (+2) train sets and scores better than 96? Why yes it can. Here is a Silicon Valley Express timetable that uses just 14 (+2) train sets with four trains per peak hour per direction, and scores 102.
Why is it better? First, it follows census patterns and puts the stops where they link the most residents and jobs, not where there is the most parking. It is more regular and has fewer gaps with long waits. While this does not figure into the service score, it makes far better utilization of the train fleet (83% of the time in revenue service, versus 70%). More efficient fleet utilization leads to fewer trains and fewer crews being needed to provide the same service, reducing labor and maintenance costs per passenger mile. All this is done without any magic: 15-minute equipment turns, comfy 40-second station dwells and a slightly less absurd padding level of 15%. There are zero overtakes, so fewer opportunities for cascading delays. Finally, this timetable is much simpler to understand for a rider, having just two service patterns.
One can only hope that despite this interim state of mediocrity, Caltrain will successfully implement its "moderate growth" service vision, which scores an impressive 240. Getting there will require reliable 30-second dwells for which level boarding is a must.
Credit to Richard Mlynarik who did the time-consuming part of this analysis.
Posts
The best thing about the new timetable is mid-day limited service. Also, I am glad they are bringing back the bullet service at peak hours. There is a psychological barrier at 1hr(ish) SJ-SF time as competetive with driving. The Silicon Valley Express pattern makes sense for reverse commute, but not for commuters to SF. It's just too slow from SJ until we get EMUs.
ReplyDeleteThe downside of the bullet is that the local has to hang around at Lawrence for an extra 3 minute for the overtake. I always thought it would make sense to extend the 4-track overtake further south and add a new station near San Tomas Expressway. There's plenty of ROW all the way to Lafayette and I'd bet a station at San Tomas would look pretty good from a census-driven perspective. There are tons of jobs nearby and accessible by bike via the San Tomas Aquino trail. Those extra 3 minutes of dwell could be spent serving this station and would be especially helpful for the 6/4 HSR EIR service pattern.
The moderate growth plan is a great dream, but needs a lot of new infrastructure, including quad-tracking in Palo Alto (good luck with that!) to be compatible with HSR.
"The best thing about the new timetable is mid-day limited service."
DeleteNo it isn't, not really. It's less-than-hourly headways to some stations that's ... less-than-terrible.
The typical-Caltrain-whackjob limited-stops thing is they're running is just stupid, because nobody's taking Caltrain (at all) and especially not at 11am in order to arrive anywhere at all in a speedy manner, but it is literally the only thing they know how to do, so they just keep churning out random nonsense assortments of skip-stop service patterns. (I'm not joking about "literally" -- Interim Executive Director Bouchard has never worked anywhere on anything except at Caltrain post-"Baby Bullet" and look where we are.)
It's not even an efficiency gain, as they waste an entire train and crew on a 65 minute smoke break in SF every single hour -- eight trains/crews to operate just 2tph, with 1tph to many stations Caltrain 202109 mid-day (takulator score 83; 74% fleet utilization)
In contrast, with the same glacial 15 minute turnbacks, elephantine 15% padding and pokey 40 second station dwells as in the "Silicon Valley Express" to which Clem linked, 30-minute every-station service (think: BART!) can be run with the same trains/crews (83% utilization, taktulator score 90 in case anybody's asking; headway is king -- hourly or worse truly is "why even bother? / why are you trying so hard to fail?" territory, always has been, always will be.)
(Purely as a reference, dialing the "Silicon Valley Express" back to 1tph limited 1tph local is also 8 trains 73% utilitization but score 86 because, duh, increased number of stations with marginally-better-than-hourly service.)
"The Silicon Valley Express pattern makes sense for reverse commute, but not for commuters to SF. It's just too slow from SJ until we get EMUs."
DeleteYou know what? You'll say the same thing whatever decade EMU service is running!
The fundamental facts are that the stop penalties are worse for closely-spaced stops (ie San Mateo County, ie north of Redwood City) and that ridership is crap south of Mountain View anyway.
Stop the trains -- the time penalty is basically negligible, even with crap diesels and crap dwell times --, serve stations more than once a goddamned hour and let people get on and off the trains and don't leave people to decide that "miss the train and wait an hour? Nah, nobody needs that."
Better service for more people always beats an insane hour-headway monomaniac focus on one or at most two peak-of-peak commuters-only runs.
"I always thought it would make sense to extend the 4-track overtake further south and add a new station near San Tomas Expressway."
I think "expressway" tells you everything you need to know about ridership. (See also crap-ridership Lawrence "Expressway" Station and San Antonio "Expressway" station.)
There's, sadly, no there there, and a snowball's chance of that changing.
Any nearby-ish office park sprawl ridership isn't going to be pedestrian, regrettably, and Lawrence and Santa Clara already exist, in their own variously hellish ways, for bike/scooter/shuttle "last-mile".
Anyway, Caltrain doesn't have a service need for this track, so nobody should be wasting a penny on it.
The only track amplification Caltrain service needs (starting 20 years ago!) are San Carlos to Redwood City.
I used to be wrong about this way back in the 2000s and wanted Hillsdale as a midline overtake; but that's clearly wrong and this is the only service plan that makes sense. Even Belmont can wait; four track centre-island FSSF San Carlos and four-track two-island FSSF Redwood City turn back are absolutely everything we need (... DTX aside.)
"The moderate growth plan is a great dream, but needs a lot of new infrastructure, including quad-tracking in Palo Alto (good luck with that!) to be compatible with HSR. "
Caltrain service always has been and always will be incompatible with the HSR-via-Los Banos scam, and with every passing year (no passing tracks anywhere no grade separations anywhere never never no) it only gets more so.
PS I think -- of course I do -- that their "moderate growth plan" is a steaming pile of useless random-skip-stop shit, driven entirely by insularity and ignorance.
We know what to do, the data show what to do, and we can just copy what other, successful transportation operations do ... and that isn't a hundreds random limited-stop "blended" patterns.
Thanks as always Richard for your insightful comments. I still disagree with you about both of these points though,
DeleteFirstly, while I'm sure that there are better and more efficient service patterns, having all-day limited service is a big improvement. Saving 25 minutes on the otherwise interminable 1.40 SJ-SF time is a game-changer and makes mid-day trips to SF from SJ on Caltrain somewhat competetive with driving to San Bruno or Colma and taking BART.
Secondly, while I am a huge fan of your takulator, the metrics it uses to evaluate the quality of the service pattern are, frankly, pretty arbitrary. It dramatically overweights the ridership benefit of adding more stops at suburban SMC stations vs. increased travel time from places far more people actually live and work.
Since almost all Caltrain riders own cars, the real competition is with driving. If you want to expand ridership beyond the 2 places on the line that are expensive/inconvenient to park at (SF and Stanford), you need to offer competetive travel times to driving. This is pretty obvious when you consider the huge impact the baby bullet introduction had on ridership.
Lastly, my proposed San Tomas station fills a 3.5 mile gap in the line, is walking distance from NVIDIA HQ which employs thousands, and is right on the San Tomas Acquino trail which provides bike access to many other huge employers such as Intel. While land use is less than optimal in this area, this station provides a lot more utility than proposed suburban SMC stations like Broadway and North Fair Oaks while adding zero additional run time when served as part of the bullet/HSR overtake
Aha! This is just the kind of discussion we need to be having, about the metrics that underlie the taktulator scores. You have some gut feeling or intuition about how various timetables compare that is violated by the way the scores come out.
DeleteWhile Richard implemented and hosts the code, the underlying metrics are mine. That you describe them as "frankly, pretty arbitrary" suggests that you might not have read about the method behind the madness. It's not secret, it's not arbitrary, and a lot of thought went into it.
If we are to have an intelligent discussion, it should center on what we are missing in the scoring algorithm. Try to reduce your intuition or gut feeling into a rule or weighting calculation. Then we can have a meaningful exchange on what makes a good timetable.
You suggested parking abundance should factor into it, something I know Caltrain planners are very attuned to.
As they are, the scores are indeed weighted by the number of residents and jobs in the vicinity of each stop, so you will see lower scores contributed by extra stops at low-density stops. Where people live and work is fundamental to the scores.
It sounds as if you might also disagree with my weighting by distance, which discounts very long trips that are kind of outliers in the origin and destination mix of Caltrain riders. Remember the average Caltrain ride was 22.9 miles in 2019, and hasn't budged very much in a long time.
Clem, I did not mean to suggest that the scores are poorly thought out and I have read your excellent methodology on this in the past (though its been a while). However, there are many aspects, such as the relative weighting of max and mean trip times and distance from stations that are somewhat aribrary and could be argued differently yielding quite different takulator scores.
DeleteThe reason I mentioned it is that, as Richard points out, a 2ph lccal midday schedule would have a better score than the 1 local + 1 limited current schedule. That does not make sense to me as the all-local service is too slow for anything other than a short trip, which is why the all-local midday service in the past has had such low ridership. Increasing it to 2tph without improving trip time is unlikely to help that. Maybe midday trips are not a good match for the commute-based takulator score, but there are other issues as well.
As I mentioned, the takulator score can be easily boosted with lots of stops at closely-spaced suburban SMC stations since these stations seem to be weighted similarly without accounting for distance to neighboring stations. The distance-to-station weighting which (I think) is currently 1/R^2 capped at 0.25mil min, is probably not a perfect model and a better model would take into account distance to neighboring stations, especially above 0.5miles walking distance when most will switch to driving. Maybe weight any job/home above 0.5miles by the distance to the nearest neighboring station? Between 0.5 and 0.25 miles weight as 1/R^2 . The switch of modes from walking to driving will correspond to a big drop I think, but then be 1/R^2 again, but with a different scale factor accounting for nearest alternative station.
Regarding parking, I don't think that should be part of the service score, but probably factors into price sensitivity. I'm guessing SF passengers are less price sensitive as the alternative involves paying for parking in many cases. I do think that charging for parking in more destinations and workplaces would yield increased Caltrain ridership so there is definitely a correlation there.
I wonder if the fact that the average Caltrain trip length has not got longer over time is that Caltrain has not got any faster or offered better/faster service down to places like Blossom Hill. Car commutes seem to be getting longer and longer, so I think the demand is there if the service was quick enough to compete with driving.
Just a quick note, in the population and jobs weighting, each census tract is assigned to only one station. There is no overlap or double counting, and no undue benefit from stopping at Hillsdale AND Hayward Park.
Delete@Clem, does that note mean that if a train does not stop at Hayward park, the people living/working around that station are not counted as potential riders for Hillsdale? That would seem to overestimate the impact of not stopping there as many potential passengers would use Hillsdale instead.
DeleteAfter reading over Clem's methodology again, I think the biggest difference between how I think of a "good timetable" and the takulator score is the weighting by distance. The score weights potential trips by a Raylegh distribution with a peak at 25miles, essentially weighting SMC-SF trips as more likely than SCC-SF trips. This makes some sense if you are trying to optimize for number of passenger trips regardless of distance. A different optimization for number of passenger-miles, which one could argue is a more important metric, would additionally weight each potential trip by trip distance. I suspect this would yield a very different tabulator score that emphasizes the importance of limited/bullet service.
DeleteNot saying that the methodology should be changed, just trying to explore what causes the difference between the takulator score and my feeling for what constitutes a good timetable.
I'm not intimately familiar with local geography, but I think a stop at San Tomas as jpk122s suggests warrants more consideration than the quick dismissal it received from Richard and the non-acknowledgement it got from Clem.
DeleteIt fills a big gap, distance-wise - and the bike trail seems like it would be a significant game changer in a way that just measuring population inside a circle around the station doesn't adequately capture. ACTUALLY SAFE bike routes - meaning something that normal humans, not just MAMILs, will use, are unicorns: far less common along the Caltrain corridor than billion-dollar startups. Cycling as a means to access train stations is extremely popular in other countries with better trains and better bike infrastructure. The better trains are already being planned on Caltrain, so the missing ingredient is the bike infrastructure. Bike-to-train can easily be predicted to work fine here, too - if (and where) actual safe bike infrastructure (like the San Tomas Aquino Creek trail) exists.
Beyond the trail, though: Even if the low density housing to the south is considered off-limits, there is certainly plenty of mundane, low-density, obsolete office space to the north that could be a ready target for redevelopment, *if* Santa Clara would entertain it, which they probably would, at least to some degree.
My question about the methodology is what about connecting transit? this can drastically alter the actual amount of jobs/residents that have access to a certain caltrain stop. It's not as simple as a buffer around each station. People also follow the transportation network, they don't travel 2 miles or whatever as the crow flies. It's half-baked.
Delete@Anonymous I think that the only stations with significant transfers to fixed transit connections are Millbrae+SF. I agree it would be good to account for this, as otherwise stopping so many trains at Millbrae makes little sense for this suburban wasteland. However, the bus/shuttle connections at other stations largely cancel out and I don't think they would impact the scores very much. They can also be changed in response to service levels at the station so are probably not a good thing to base the service pattern on.
DeleteRe Taktulator scoring:
DeleteMy perspective is that there is definitely some wrongness in the algorithm implemented, which one can find and exploit when trying to achieve a "gamified" high score. I thought that a decade ago when I implemented the algorithm in the crappy code for the Taktulator, Clem and I have exchanged plenty of email over this lost decade of Caltrain decline and waste and off-the-scales contractor fraud, and nothing at all as changed (including the crappy PHP code.)
I further pissed away a ton of time exploring this 18 months ago, but, as usual for everything connected with trying to improve anything on this shitty planet, I eventually just gave up in despair and depression and pointlessness, with dozens of options not reported. (I still have about 80 browser tabs sitting around with different scenarios of this junk! ±DTX; ±Oakdale; ±Hayward; ±Antonio; ±Lawrence; 20/30/45s dwell; 7%/10%/15% padding; Belmont/RWC/PA/CalAve/MV/Lawrence/Sunnyvale turn backs; 2/4tph RWC shuttle; 2/4tph Tamien; etc; etc; etc; etc.)
One of my bigger beefs is that potential ridership from non-stop stations doesn't seem to redistribute to close-by adjacent stations in a what I perceive as a realistic way. So when gaming the Taktulator score, it's crazily valuable to stop at Broadway (for which many excellent arguments for permanent closure, or at least 15+ year deferral of reopening, can be made) or Hayward Park (which should be closed, without any question at all -- it's within sight of Hillsdale, for God's sake.) 4tph to Burlingame "has got to" beat 2tph Burlingame combined with 2tph Broadway, right?, right??? ... but it doesn't. Lawrence has to be overweighed. Oakdale crazily so.
So bat-shit-insane "service" patterns with a pissload of stupid skip-stop patterns with 1tph or 2tph between marginal station pairs can end out out-game-scoring rational local/limited patterns -- those used by everybody else with any actual ridership everywhere in the world.
I don't buy it, which is why I don't enter a game I don't want to win with a pissload of stupid skip-stop patterns.
In the real world of actual successful transit operations, frequency and dependability are kings, and actual human beings will and do trade 10 minutes of travel time (either on-service or connecting-to-service) for 15 vs 30 minute headway. And in the real world, hourly (or worse!) local or regional transit headway is "fuck you this isn't service we're just a welfare operation, mostly welfare for our agency staff, suckers", no anything anybody should offer to anybody unless they're asking to have their face punched. (Missing an hourly service is a catastrophe for real people living real lives; missing a 20-minute one hugely irritating but not necessarily relationship-ending.)
Re "That does not make sense to me as the all-local service is too slow for anything other than a short trip, which is why the all-local midday service in the past has had such low ridership."
DeleteI don't know what you think you're remembering, but I doubt you're remembering reality. (Hey, I hacked up that timetable HTML as a freebie for Caltrain in 2004!)
Caltrain's never offered regular 2tph all-station service at any hour of the day at any time in its history.
But you go off, I guess, as teh kids say.
@Richard, I was talking about the hourly 1tph all-local midday service that Caltrain has offered in the past. Adding a second local train to me does not make it much better, compared to adding adding a limited train. It's not like 2tph is show-up-and-go frequency anyway. I think we can disagree on this, but that's just my perspective as a potential SJ-SF rider.
DeleteRegarding the takulator scores, I agree with you that trying to "gamify" the Takulator score, while quite fun, does not result in what anyone would consider the best real-world timetable. However, the score is still a useful benchmark and I appreciate your efforts in coding it up.
Off topic, but I wonder if you have been tracking the recent tweaks to the DTX configuration as a result of DB operational analysis. It seems to be driven by real-estate interests rather than optimal operations (as usual in SF). The latest attempt to analyze it a through-running station really demonstrated the deficiencies of the proposed configuration that I have seen you describe many times in the past.
Through Running Operations Analysis
"San Tomas station fills a 3.5 mile gap"
DeleteRight. A gap.
On the map.
Same energy, as the kids say.
I've been there, I worked there for two decades, I've done that, I'm done with that. Nice map, sorry about the terrain.
@Richard, serving all of Silicon Valley with just 4 tph is going to take some very long trains, probably longer than 8 cars. Another consideration not captured in the scoring.
ReplyDeleteThis is a chopped moderate growth scenario with the locals turned back at Redwood City and all the expresses turned into Silicon Valley locals. It scores 233 and requires 18 trains, compared to 240 with 19 trains for Caltrain's plan.
I don't share your dislike of Caltrain's "moderate growth" plan. The two local patterns make every stop in Silicon Valley, every 15 minutes. It's not random skip stop shit as you claim, and I think the taktulator scores proves it.
"serving all of Silicon Valley with just 4 tph is going to take some very long trains, probably longer than 8 cars."
DeleteWe've exchanged email about this forever! It's nonsense.
BART took decades to crush-fill 210m single-deck trains at 4tph running to multiple stations directly serving the actual by-far most important regional CBD (not "some office parks 2 miles from where Lawrence Expressway crosses the tracks").
The idea that 4tph to the blasted wastelands of Silicon Valley is going to immediately exceed decades-to-be-established ridership on BART Richmond-SF or Fremont-SF or Concord-SF is laughable. Totally laughable.
I mean the BART Concord line had 6tph (including short-run turnbacks, imagine!) in 2019, but that's with massive Bay Bridge and Caldecott tunnel road congestion, and without 101 + 280 + SMCTA + VTA endless freeway "improvements". 4tph is fine, just fine, and will be for decades
And and by the way I completely agree -- in the medium, 15-20+-ish-year, timeframe -- about "probably longer than 8 cars". I've claimed for two decades or so now that Caltrain should be planning for 300m (12 "car") platforms based around coupled 150m+150m peak-of-peak trains, with 150m (6 "car") being both an excellent off-peak service length and a unit that can be readily double-berthed at 400+m long platforms with mid-platform crossovers, which will end up being super-important at constrained locations locations like Transbay, Redwood City and Cahill Street San Jose. Pro-actively extending platforms to 300m costs approximately nothing now, and will pay off in spades around 2040, by which time I hope to be dead. So yeah, run somewhat longer (but not crazy-long eg Zürich-Luzern) trains every 15 minutes when you need to 15+ years from now, but until then, just run some fucking trains.
In the meantime, run trains, and run them on non-laughable headways, and run them without stupid fucking deadweight sub-alternate-assistant-conductors torpedoing the budget and revenue. You know, what even BART does. Not fucking skip-stop 1tph bullshit.
PS Clem your various "moderate growth scenario" links don't include a "fleet" designation for some of the innumerable service patterns, meaning the full in efficient horror of skip-stop-stop-stop-skip-skip-stop isn't made clear.
Sure, the padding is less than ideal but nonetheless, I'm celebrating. 2 trains per hour off peak (to some stations)! Clockface scheduling! I mean still terrible by the standards of any modern halfway competent railroad, but still twice as good as it was before. So rarely does one see Caltrain making decisions that don't elicit audible groans.
ReplyDeleteDoes Caltrain ever leave early or do they actually stick the padded schedule? The mid-day limited I took today had some short dwell times, the limited I took back, less so.
What's stopping Caltrain from exceeding 79mph on the grade-separated portions? My quick google did not turn up the FRA requirements for class 5 track.
Grade crossings can be traversed at 90 mph (as they are on parts of the LA-San Diego LOSSAN corridor) and more, so those aren't preventing Caltrain from exceeding 79 mph. As I understand it, after some horrible wreck(s) someplace way back when, the FRA (or its predecessor) made a rule that says trains must have in-cab signaling to go 80 mph or more. RRs without it top out at 79 mph regardless of track class and/or how great and straight their trackbeds are.
DeleteWhat I don't know and have been wondering, is whether PTC — which Caltrain now has — qualifies as in-cab signaling for purposes of this rule?
"Sure, the padding is less than ideal but nonetheless, I'm celebrating. 2 trains per hour off peak (to some stations)! Clockface scheduling!"
DeleteOh hello, 2005 just called and wants its futuristic far-future back
OK, just as terrible as it was before and still extra shit on the weekends, with multiple train sets idling on very expensive real estate at either end.
DeleteCaltrain electrification shakeup: Caltrain Announces New Leadership for Electrification Project
ReplyDelete"... Caltrain Modernization (CalMod) Chief Officer John Funghi will be leaving at the end of this year. Funghi will be working until October 15, 2021 and then plans to take a well-deserved leave to the end of this year. The agency is transitioning the project to new leadership to ensure a successful outcome resulting in passenger service with high-performance electric trains by 2024.
"The agency is pleased to announce the appointment of Pranaya Shrestha as the Interim Chief of the Caltrain Modernization Program. Shrestha has 30 years of rail experience, including experience with 25kV AC commuter rail and DC light rail systems, and design-build project delivery successes with federal recognition. He has finished 19 major transit projects totaling more than $9 billion, and has worked on transit projects in Denver, Los Angeles, San Francisco, Portland, Orlando, and Seattle."
Over Funghi’s 43-month tenure, this $2B project has progressed 18 months closer to revenue service. Heckuva job.
DeleteFunghi did a heckuva job on the Muni Central Subway contractor-welfare 100%-fraud disaster, too.
DeleteThe system is working exactly as intended.
What next? CHSRA? WSP? WSP=CHSRA? AECOM? NYMTA? The sky's no limit! (Just don't try to get a job outside the USA.)
(PS I recall our long-sufferering blog host deleting a years-ago comment I made about the competence and professional achievements of of America's Finest Transportation Planning Exemplar John Funghi as unwarranted and unhelpful. Probably true, but also, you know, it was and is true.)
This new guy was at at RTD from 1996-2021. Hmmm... I wonder where I've heard of them recently... oh yes right here on this blog!
DeleteGrade Crossing Trouble Ahead
I guess he will be well versed in the "constant warning time" grade crossing issues that seem to be one of the biggest risks to the CalMod project.
Yes, he'll get to deal with the inelegant and bog stupid dual (or two) speed check (aka "2SC") replacement for Caltrain's existing AC electrification incompatible CWT grade crossing circuits. My PRA request to the CA PUC of last year has still not been responded to, but I believe 2SC is implemented with standard old fixed DC track circuits. These are used decide whether to treat each approaching train as either going the maximum authorized speed (e.g. 79 mph) or one other intermediate speed (e.g. 59 mph). That's the meaning of "dual" or "two" in 2SC: all trains are put into one of two speed buckets!
DeleteAnd, to take possible train acceleration after the point of speed assessment into consideration and to guarantee that the actual provided warning time never falls below the statutory minimum of 20s, trains that are measured at anything over, say, 40 mph are put into the 79 mph bucket and the rest are in the 59 mph bucket. So unless the trains are either already going 79 mph or accelerating like mad, the actual provided warning times will go way up in proportion to how much slower the train's actual speed is than its assigned speed bucket, as shown in this CWT vs. Dual Speed Check (2SC) chart and graph.
Of course, a different maximum authorized speed (MAS) and intermediate speed can be chosen for each crossing ... but the linked PDF illustrates the general idea.
Unless the fixed DC crossing circuits are already being installed to be long enough to accommodate speeds above 79 mph (e.g. the 110 mph HSRA says it plans to run over quad-gate equipped grade crossings), the crossing circuits will have to be lengthened for future speed increases. And because the FRA's CFRs for train horn quiet zones say that crossings are to be CWT-equipped, it may also may also mean future quiet zones are precluded. I'm not even sure if Atherton gets to keep Caltrain's first and only existing QZ at Fair Oaks Lane.
@RealityCheck The last update I saw on this from Caltrain said that the long-term plan is to develop a wireless CWT system and use the 2SC system as a backup for freight. Who knows how long that will take though and there will definitely be some traffic impacts in the interim period when only 2SC is available.
DeleteLPMG - Grade Crossing Activation System Update
@jpk122s: having 2SC as a future wireless fallback sounds remarkably similar to the Denver RTD's wireless (GPS) scheme for constant warning time: downloads.regulations.gov/FRA-2011-0106-0028/attachment_1.pdf
DeleteQuick! Hire the Denver program manager to get on top of it!
Delete