Reasonable Transit Pitches

Ok here's another one: When the Green Line leaves North Station heading towards Science Park, there is a mandatory stop in the area of the crossover/storage area. This stretch of track is one of the newest parts of the system, installed when the Green Line moved from elevated track to underground. Was there really no way to design it so that every train doesn't have to stop here? What is the point of this stop? In case a T worker is standing on the tracks for some reason?

These mandatory stops basically just show to me that the T is more worried about liability and risk management than providing comfortable, reliable transit service. It's the same reason they refuse to allow for any new pedestrian/bicycle crossings of Green Line tracks, even though the whole aboveground system is crossed by numerous intersections. From my perspective, they are managing light rail like a freight rail system.
 
Ok here's another one: When the Green Line leaves North Station heading towards Science Park, there is a mandatory stop in the area of the crossover/storage area. This stretch of track is one of the newest parts of the system, installed when the Green Line moved from elevated track to underground. Was there really no way to design it so that every train doesn't have to stop here? What is the point of this stop? In case a T worker is standing on the tracks for some reason?

No. That one was because of the sunlight-to-tunnel transition. Viaduct faces due south with midday glare in the cabin, then immediately descends into the tunnel lighting 1 signal block's distance away from the North Station yard interlocking with crossing traffic. It's an eye adjustment pause.

Stand in the front of the front car on staring out all the way down the viaduct on a bright-sun day to get better grasp of the logic of that one. Wintertime better because of the lower sun angle. You're still fighting residual sun spots by the time that first tunnel signal comes up.

These mandatory stops basically just show to me that the T is more worried about liability and risk management than providing comfortable, reliable transit service. It's the same reason they refuse to allow for any new pedestrian/bicycle crossings of Green Line tracks, even though the whole aboveground system is crossed by numerous intersections. From my perspective, they are managing light rail like a freight rail system.
It's that one-in-a-million risk mitigation on a 100% human-controlled system that racks up million trips fast. We've seen with 2 bad wrecks in the last 10 years that perfectly functioning signals in low risk areas aren't foolproof, even if they pass the one-in-a-million odds under such heavy frequencies. The identified highest-risk spots need extra mitigation. And since there's no way to rig up ATC for only one spot and no guarantee that one operator on one trip once every XXX thousand trips won't do something stupid, they have to resort to doing road-style traffic calming a la a permanently flashing red light.

It's a kludge, but without a final-final safety net available within the signal system to override human judgement it's the last resort for mitigating the risk. This is the last subway-signaled LRT system left of comparable service density that still doesn't have ATC. Therefore some very old-time practices that were once commonplace on several high-density systems are still in effect here. Because designing ATC for the Green Line's frequencies is legitimately that hard.

They don't have much of a choice but to do it because the human-controlled system is not airtight enough. But it's going to take time. You will probably see CBTC get deployed on the D, North Station outbound to GLX, and Huntington subway years and years before they do brain surgery on the Central Subway. Once they get a system ID'd that they're confident can get scaled up to ATC on the tightest-of-tight headways they'll start the deployments on the grade-separated branches first where the max headways are a lot more 'conventional' to comparable systems. Even nipping at the fringes first will have very beneficial effects downtown. It'll raise the default speed limits on the D and GLX. It'll make the schedules on those lines into the subway much more precise. Combined with the regular traffic signal priority on the B, C, and E that's going to make for a huge improvement with the bunching problem and roll back the Central Subway's OTP closer to what it was before service reliability on the reservation branches decayed to what it is now. As well as ensuring safe computer-guided operation on the majority of Green's route miles with operator error largely eliminated.

If that means it takes a lot more time to design the Central Subway's resignaling in the highest-density stretch, so be it. It avoids the mistakes MUNI and SEPTA made not being precise enough. And it's enough of an improvement elsewhere that they can take their time to get it right.

That's the best non-emotional answer to how it's going to proceed going forward. They're not naive. One more rear-ender from operator error and the NTSB is going to slap them to install ATC whether it maims headways or not. So they might as well plan ahead to get it right.


These kludges too shall pass, because the technology is finally there to do this correctly if they're careful enough. It wasn't there beforehand. Legitimately wasn't there. That's not "NIH" syndrome, not T incompetence. You simply can't run the Central Subway at anything close to current throughput with direct signal intervention using a mechanical system like the Blue Line or a magnetic pulse system like Red and Orange. That's a pickle they've had to live with for decades, and deploy kludges around. Not because they're fearful, but because the alternatives were too draconian to maintain service levels.


Other shit...hell yes, they need to modernize. Proof-of-payment and all-doors boarding, signal priority on the surface, re-spacing stops more evenly with uniform-dimension platforms that can distribute crowds. And state-of-repair investment to the billions so stuff runs reliably. All of that matters. All of that which they DON'T do is no-holds-barred for criticism.


The stoplights have a reason behind them. The stoplights are the least of the Green Line's problems. You can find the stoplights archaic, and they are. But that's because ATC-based fixes for those hurdles have only recently come available, and whether commuters think those 10 seconds are a pain commuter convenience isn't enough to cut corners on risk abatement. If that's not a good enough answer, go strike up a conversation with a suitably friendly veteran Green Line operator on rear-car duty or an inspector and see if they'll give you the answer straight from the horse's mouth.

Anything but a purely from-the-gut emotional argument. That's not useful for solving a problem. Don't get mad; suggest a course of action looking forward, not backward. Piss and vinegar doesn't solve anything except spreading an acrid smell.
 
First words out of your mouth to first reply:



I think tenor of this "discussion" was pretty well established right then and there.

Yes: that's a pithy way to say "I think you're making excuses for something that's not right." The word "bullshit" encapsulates that sentiment. Is that what you're complaining about? The reason you won't actually answer any of my logical points? Or that you suddenly dismiss everything I say?

You know perfectly well that I am not some random guy on the Internet but someone who is very well informed about these matters -- despite being a complete outsider. I view that as an advantage, however, because I can safely say "The Emperor has no clothing" without fearing for my career or ability to put food on the table. I'm not beholden to special interests nor to institutional inertia.

I've also spent a hell of a lot more time organizing and advocating, in the real world, for improvements to the Green Line than you (I presume: since I would have met you by now if you were out there working on this stuff). It's nice to talk about technical matters online, and being an engineer at heart, I do enjoy that conversation, but it's also just words on a website. Really, a distraction from the true work at hand, which is largely political.

Some of you may remember that this thread "Reasonable Transit Pitches" began when I (and some others) wondered if we could talk about actually feasible things instead of the "Crazy Transit Pitches" in the other thread. We've had a lot of fun discussing all sorts of ideas for transit engineering over the years. But I would say that the most important, most fundamental obstacles to true transit improvement are not technical matters. The technical problems have solutions, largely, some more expensive than others. The real obstacles are political and organizational. Why does South Coast Rail keep getting money when it's truly atrocious from every technical perspective? Because politicians love to promise it. Why are Green Line riders forced to fight to get on and off through a tiny front door while train delays pile up? Because suburban voters always think some 'inner city person' might somehow, someway be getting away with fare evasion. Why must a train or a bus with potentially hundreds of people be forced to wait at a traffic signal for minutes while a handful of cars go by? Because political weight of the elites who might be driving in those few cars is much heavier than a trainload of MBTA riders.

Now here's a reasonable transit pitch to be made: how to fix the political and organizational problems with the T to get the most out of existing infrastructure, to prioritize riders, and also eventually to build new infrastructure that comes in at reasonable cost?

Sadly, not as fun as talking about tunnels or wires, or whatnot. But those physical improvements ("electronics and concrete") are virtually impossible to do well so long as the T remains the same old broken organization. And so it goes.
 
Is there any reason to believe or proof that any of these "nuisance" stops have actually prevented anything? Human error will always be a possibility until there is automated control of the system. And from what I've seen, the places where human error resulted in a crash were not locations of particularly high risk.
 
And as to the North Station stop, I was referring to the one on the other side of the underground yard, as you come around the curve from North Station, not the one at the tunnel portal.
 
Is there any reason to believe or proof that any of these "nuisance" stops have actually prevented anything? Human error will always be a possibility until there is automated control of the system. And from what I've seen, the places where human error resulted in a crash were not locations of particularly high risk.

You could make the same argument about traffic lights or stop signs...
 
Is there any reason to believe or proof that any of these "nuisance" stops have actually prevented anything? Human error will always be a possibility until there is automated control of the system. And from what I've seen, the places where human error resulted in a crash were not locations of particularly high risk.

There is no easy answer to that. The system isn't foolproof. A human can elude any of the safety warnings. A human can elude any of the safety warnings on any non-ATC system. That's the difference between having ATC and not having it. And they need to address that before another crash ties their hands and forces them to quickly implement an ATC solution without the lead time to figure out the headway management that maintains capacity. That is the true doomsday scenario: get the ATC off-shelf, lose 20% of the service levels because there's not enough time on-deadline to right-size it.


The resignal isn't going to make the Central Subway go faster. Best case for ATC is fighting to par. No "pointless" reds, but your trip thru-and-thru goes not gain one second on the stopwatch vs. what it does today in a non-FUBAR condition. The closest-packed Jetsons-shit ATC system is more inflexible than humans are at exercising discretion in very close spacing situations like when packing back-to-back trains into Park St. So the self-perception of "movement > non-movement" with elimination of those enforced reds gets counterbalanced--and then some--by throttling back to low speed or outright elimination of those on-platform back-to-backs. It's movement, but lower-speed movement. Wow. What...a...difference...that...isn't.

The target they have to aim for with the new signal system design is that any attrition from present conditions in the closest technologically allowable train spacing can immediately be offset by running 3-car trains everywhere all the time. And run 4-car trains to bank for future growth. This is deadly tricky because when Red was re-signaled downtown in 1988 from more permissive Blue Line-style mechanical trips to today's magnetic pulse ATO they gambled on overly cautious signal spacing being offset by lengthening of trains from 4 to 6 cars. And whiffed on their projections, which is why you get to pause and enjoy the view on the middle of the Longfellow in the morning at a pointless 'virtual' red unable to approach Park any closer. Stakes are way, way higher on a Central Subway than they were on Red. If they misfire the slightest on design they lose a crippling amount of capacity that extra cars won't solve. It has to hit nail square on the head: if headways are X seconds wider under computer-regulated ATC, it must be within margins that train capacity can offset at zero aggregate loss of service.

Godspeed with that engineering job. It's not an exaggeration to say that getting it right may take a cumulative 15 years from next survey to prelim engineering to full design to build. And a build that starts endpoints-in before it ever touches Kenmore-GC. That's how delicate and fraught with peril the brain surgery is.


And ATC still doesn't address the Green's main problem: branch bunching KO'ing the schedules before the trains ever descend on Kenmore or Copley and see their first subway signal. That's the real cause of the GL's precipitous decay the last 20 years. The Central Subway has always been a "garbage in, garbage out" operation. It gives you what you feed it. Always has. This current signal system, "pointless" reds and all, managed crush-load traffic just fine for decades upon decades until the branches stopped being functional. When the B chokes on its own bunching and takes the C's and D's down with it, there is nothing the Central Subway can do to restore order. Slotting's all fucked up before trains ever merge onto the same track, and when bunching's dragging an outbound branch schedule down you have crapshoots like "Three D's and two E's before the first B sighting" syndrome @ Park outbound. String up Jetsons-shit signaling all the way from Kenmore to North Station but leave the branches thrown to the wolves unchanged from current conditions and it's exactly the same: garbage in, garbage out.

The only way this gets meaningfully better is taking out the trash at its source: on the fucked-up branches. Like a broken record, all of the obvious B/C/D/E fixes go on the table:

-- Improvements to station dwell times: all-door boarding and PoP as the rule, security cams for random-sample fare enforcement, standardized platform dimensions so entering and exiting passengers don't have to squeeze by each other.
-- Transit signal priority on B/C/E. Now, now, now.
-- GPS tracking everywhere to aid dispatch with a live look at train position instead of intermittent snapshot through radio squawking. (They're almost there with this capability.)
-- Stop recalibration. Not just outright consolidation, but also things like re-spacing for more stops with offset platforms on either side of a traffic light when that makes the starting spots vs. a traffic light much easier to time.
-- Short-turns and alt-routing. Supplemental B turnbacks at a Harvard Ave. mini-yard for surging and throttling around the student-heaviest hours. C's extended to BC to infill the B slots that are turning. D-to-E on-street connection to Brookline Village. Low-cost infrastructure enabling greater elasticity in branch service patterns.
-- Electrical system and platform length upgrades so 3-car trains run as a default condition on all B/C/D and Medford trains all the time except for the far off-peak. Heath-Union Sq. the only deuces left since Heath Loop isn't big enough for triplets.


And the first and arguably most important deployment of Jetsons-shit tech. . .
-- CBTC first on the D and GLX. There is still a human inefficiency with the present-day dispatching on those grade-separated lines (and lines-to-be), with lower posted speed limit out in the open than the vehicles are rated for due to concerns about line-of-sight signal visibility. Get those D's all the way in from Route 128 to Kenmore within a minute of schedule target every time and let the computers auto-adjust the timings through Longwood and Fenway to time the GPS position of the next B or C heading for the portal that it has to slot between. That's what takes the trash out of the Central Subway. Computer brain smooths out still more bunching by leveraging precision dispatching of the full-signaled branch against the variable schedules of the mixed-traffic branches. Kenmore...and especially Kenmore inbound...is where the new tech improves capacity and throughput. Central Subway still takes what you feed it. You're just no longer feeding it a shit sandwich of schedule conflicts at the mouth.


The ATC business will work itself out. For proactive action and advocacy purposes, it's still the ^^fat targets^^ we've known all along. Get the branches and the roads they share debugged, get better operating/boarding practices on the branches, increase their flexibility and establish better elasticity with short-turn or alt route throttling options. Do everything that improves their OTP from endpoint to portal so the dispatching at the portal is more predictable. And repair those rolling ruins.

That's all. Take the garbage out and the Central Subway will do its thing. Keep stuffing garbage down those portals and the Central Subway vomits it back up. It's not hard to put 2 and 2 together on primary cause-effect.
 
FWIW, here's the official PowerPoints from the initial Green Line re-signal study establishing what's at stake here. (Note: they call it "PTC", but it's really CBTC...which is the computerized ATC for subways. Interchangeable acronyms FTW!)

http://www.wcvb.com/blob/view/-/177...Green-Line-Positive-Train-Control-Project.pdf

Decade-long, $¾B project. 13 different implementations to evaluate. And mitigations required for each of the study options in the form of 3-car trains, speed increases, or both to cancel out the unavoidable headway hit the technology imposes and keep total throughput at equal-or-better.

And that's just the signaling, not the fix for the "garbage in, garbage out" problem of the schedule variability of the three reservation-running branches. So make that a nice round billion total to get the whole to-do list done: B/C/E fixes to get the branch schedules running reliability, and the whole package of fail-safe signaling on the Central Subway + D + GLX. More than a billion if other state-of-repair prerequisites inevitably get added to the to-do list.
 
You could make the same argument about traffic lights or stop signs...

Well except we don't have stop signs and traffic lights to prevent us from hitting vehicles traveling the same direction as us and where there are no intersections or cross-traffic.
 
Reasonable pitch: replace the Beverly draw at maximum height, simultaneously eliminating the Congress St grade crossing, all while maintaining clearances at March St and School St overhead bridges.
 
Huh. It's actually possible to do all that within a 2% grade.

4RKMfEA.jpg
 
Nows the time for it too considering the whole thing is up for repair in 2017. Increased Beverly frequencies and decreased maint. costs will pretty much pay for themselves, seems like a no brainer.
 
Huh. It's actually possible to do all that within a 2% grade.

4RKMfEA.jpg

Wow, 50 ft above sea level? Could probably lower this and still not require a movable span in order to reduce the grades.

I wonder what current maritime traffic requires for height.
 
The adjacent road bridge has 50' (well 49' really) of clearance, and the maritime interests are probably going to scream bloody murder if that gets lowered.
 
Not new pitch, but some questions if anyone can shed more light, info on the messy ops behind organizing such a service:

Riverside-SS, Riverside-NS via GJ DMU. Let's assume that a) DMUs are FRA compliant. b) that the frequency ceiling on GJ is no lower than 20min headways, c) SSX is realized, and d) that West Station is realized.

Could the MBTA saturate the Riverside + Newton Stop with 10-15min DMU headways and split the tails at West. GJ-running NS service runs every 20-30 (per the W/F line GJ studies) from split at West, South Station bound DMUs offer similar (or maybe 2:1 ration on NS-bound DMUs) headways along the inside-Boston B&A trackage. I don't see it as a long-term plan, and the constrains on the GJ are such that I don't think anything lower than 20min headways in feasible. Would offer Newton-originating riders a potential one-seater to Kendall, offers a transfer to N-S busses at West, could be useful intermediate step in both readying the GJ for proper light-rail and start to soften the fairly rigid E-W Newton travel transit patterns.

Now there are problems galore, not the least of which would be the lack of RT frequency headways - especially during peak which is really the only time GJ service is useful/cost effective. That and the question to whether Newton needs this kind of service - Newton has a fairly lower transit modal share for towns with direct access to RT (12.7% transit, compare to Brookline - 29.3%, Medford - 17.1%, Arlington - 16.7%, Belmont - 13.3%, Hingham - 14.6%, Watertown - 14.8%, etc...). Is that more a function of lack of access, easy access to 128 jobs, or just a general preference for automobiles in a wealthy suburb? I guess I'm asking does the low transit ridership indicate that a Kendall connection is unnecessary or does it indicate that there's pent-up demand for improved service.
 
The problem with splitting your downtown frequencies is then it doesn't feel like rapid transit for the ride home. You'd be willing to walk up and wait 10-15 minutes inbound most days, but you're not going to wait 20-30 at either NS or SS, so you'd have to still treat it like commuter rail.
 
The problem with splitting your downtown frequencies is then it doesn't feel like rapid transit for the ride home. You'd be willing to walk up and wait 10-15 minutes inbound most days, but you're not going to wait 20-30 at either NS or SS, so you'd have to still treat it like commuter rail.

That's true - I don't think anything more frequent than 20min headways is achievable on the GJ under any circumstances (unless it's flipped to light-rail). My thinking was a) if they can achieve clock-facing schedules with DMUs, that may be help people mediate/adapt quicker to the less-than-RT frequencies and b) assuming the GJ-DMU moves forward, does it make sense to short-turn it at West or continue to Riverside via B&A. I don't think DMUs are particularly well-suited to West-Kendall-North, but it would appear that's the only service improvement the MBTA is even remotely considering so I wanted to flesh it out just for personal reference.
 

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