B Line Improvements

Matthew said:
Oh, I was making a list for the entire Green Line, not just the "B". And my understanding is that the Type 9 design and order is being funded through the GLX, at least, enough for the new branches to use.

This is somewhat of a "transit pitch" but if they got the money somehow, where to put it for best effect?

  • POP infrastructure (ticket/vending/validation machines)
  • Power system upgrades to central subway
  • Add more Type 9 cars to order
  • Traffic signal upgrades where needed
  • Fund design and study of modern signalling system in central subway
  • Reconstruction of BU Bridge/Comm Ave intersection (in conjunction with MassHighway)
  • Reconstruction of Packard-Warren (centering ROW)

On the topic of CBTC, my understanding is that computer-based moving block safety systems can achieve upwards of 36 TPH, maybe more in practice (and in theory). The GL is currently scheduled for nearly 48 TPH on the most central section. But GL vehicles are much easier to stop than most other railroad vehicles. Does this really require a whole new design, or is it just an incremental improvement to existing ones?
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The basic design would be CBTC. Which can either have moving blocks or fixed blocks. Since the blocks are mostly software-based and virtual, it can be whatever you program it to be. Moving blocks probably are not going to work in the Central Subway, so they would have to implement it with fixed blocks more or less the same as the current setup. And surgically fine-tuned to not decay headways under computer guidance vs. line-of-sight/human judgement. That's hard. Not impossible, but really really hard. And they have to get it right on the first try, so they can't proceed with haste.

IF such a setup can be designed it wouldn't increase throughput, but would bring all the other compelling advantages advantages of CBTC: safer operation with auto stop enforcement, vastly less track-mounted hardware to maintain, far less reliance on human dispatching. But, again, Central Subway capacity isn't the issue so much as unpredictability of branch schedules causing clogs where they intermix. So half the battle of making it run smoother is getting the branches all reliably on-schedule. Fix the surface clogs on the B and C first. Then a more conventional CBTC setup on the D and GLX to manage those headways. At a purely traffic management level the Central Subway can thrive as-is if the pen-and-pad guesswork were reduced to just the Kenmore-North Station stretch with more accurate branch arrival times. After all, it handled many more branches than this a half-century ago and lots of 3-car operation back then too. The main argument for CBTC downtown is purely safety: preventing operator-error incidents like the Gov't Ctr. crash. With secondary considerations for lowering maintenance burden and preventing crippling signal downtime like there was for months after the '96 flood shorted out everything from Kenmore to Copley. All of that's worthwhile enough to keep plugging away at the studies for due diligence.


Type 9's have a +30 car option order to the 24-car base order. So there already is pretty generous flex for piling up enough cars to initiate all-day 4-car ops on the subway, D, and GLX co-mingled with all-day triplets on the B, C, and E.
 
Well, another benefit of an upgraded signal system would be to finally get rid of those idiot "dead stops" in the middle of tunnels. With a proper signal system, trains should be able to run at full speed between stations under normal schedule conditions (ie. when they don't bunch up).

Speeding up round-trip times can result in operational savings -- fewer cars needed to satisfy headways -- and make people happier.

The current fixed-block system relies on line-of-sight to cover for its inadequacies, so I don't see why a future signal system ought to use the same blocks.
 
Matthew said:
Well, another benefit of an upgraded signal system would be to finally get rid of those idiot "dead stops" in the middle of tunnels. With a proper signal system, trains should be able to run at full speed between stations under normal schedule conditions (ie. when they don't bunch up).

Speeding up round-trip times can result in operational savings -- fewer cars needed to satisfy headways -- and make people happier.

The current fixed-block system relies on line-of-sight to cover for its inadequacies, so I don't see why a future signal system ought to use the same blocks.
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It's the fucking-with-headways thing. And every one tweak having 3 unintended consequences. This is so difficult...and so difficult to do as open-heart surgery during active service...that you can't assume there will be any improvements whatsoever. The block locations may shift slightly, but it is far-fetched to see how this will result in headway enhancement. It may take 10 years to design something that even meets the do-no-harm standard, and there will be compromises. It is entirely possible that a 'tolerable' level of headway limitations will prove acceptable for installing CBTC if counteracted with 4-car trains and other enhancements compensating for a new headway cap. Enhancement is not the reason they'd be considering CBTC on the Central Subway. Safety, safety, safety. Because there are questions about how safe an operation line-of-sight is with that kind of density and such hugely heavy modern LRV's.

It's not a magic bullet. It's not intended to be one. And it doesn't do the same thing here that it would do on Red/Blue/Orange or D/GLX. Where they have to thread the needle is finding the do-no-harm compromise point, or as close as they can get to it. You are not getting throughput enhancements. The only way to do that is by biting the bullet and constructing parallel subway trunks: Huntington to Brookline Village, South End-Back Bay-Huntington, and Grand Junction LRT between Lechmere and a BU Bridge subway extension. Route the traffic on different circuits for exponential capacity increases. No Jetsons shit is going to do that on signals alone in a 115-year-old continuously operating trolley subway.


You can, however, make the whole thing run properly by getting trains into the subway on-time. That's a known-known, because that's how it all worked when there were more branches to juggle. That's what the current means of dispatching is predicated on. Fixing the B bottlenecks, streamlining the C, and re-signaling the D and GLX do that job. Do it well enough that you can still fit in other extensions. That's where the crux of the problem is. That's where the solution has to come from. Downtown doesn't make the branches operate better. The branches make downtown operate better.
 
Why does the Central Subway have to be a test case for light rail CBTC?

The Central Subway has the B, D, and E on 6-minute headways and the C on 7 minutes during rush hour - an average of one train every 1.56 minutes. San Francisco's Muni Metro runs the J, K/T, L, M, and N with a nominal average of one train every 1.66 minutes (with the S shuttle and a few peak-of-the-peak extras dropping it to about every 1.5 minutes). Like the Green Line, Muni runs surface routes into a branched two-track tunnel.

Muni Metro is fully signalled, with the SelTrac automatic moving-block system (one of the world's gold-standard systems, widely used for both light rail and heavy rail). The system is fully automated - operators only have to close the doors in the tunnel. Muni has been running CBTC Seltrac since 1997, and Docklands Light Railway (also a heavily branched network) has been since 1995.

What's different with the Central Subway?
 
The EGE said:
Why does the Central Subway have to be a test case for light rail CBTC?

The Central Subway has the B, D, and E on 6-minute headways and the C on 7 minutes during rush hour - an average of one train every 1.56 minutes. San Francisco's Muni Metro runs the J, K/T, L, M, and N with a nominal average of one train every 1.66 minutes (with the S shuttle and a few peak-of-the-peak extras dropping it to about every 1.5 minutes). Like the Green Line, Muni runs surface routes into a branched two-track tunnel.

Muni Metro is fully signalled, with the SelTrac automatic moving-block system (one of the world's gold-standard systems, widely used for both light rail and heavy rail). The system is fully automated - operators only have to close the doors in the tunnel. Muni has been running CBTC Seltrac since 1997, and Docklands Light Railway (also a heavily branched network) has been since 1995.

What's different with the Central Subway?
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~50 trains per hour is higher than MUNI Metro, and stop spacing downtown is tighter here. It doesn't have to be a particularly big difference in headways to account for the difference in the Green Line functioning well vs. functioning at all. If a CBTC installation lowers the cap too much...the Central Subway doesn't function at all.

But that's still beside the point. The Central Subway gets exacerbated by arrivals into the subway from the branches being such a schedule crapshoot. Bunching kills when headways have to be that tight. The difference today vs. when the subway handled more branches is that the arrivals into the subway weren't such a crapshoot. And they aren't such a crapshoot on MUNI. To fix this, you have to fix the branches. Do that and the Central Subway's got a lot of life left in it. Don't fix the branches...it doesn't matter what gold-standard signaling you come up with for the subway, crapshoot branch schedules are still going to make it all perform like ass. Computers won't help much if you still have no idea whether a train departing Harvard Ave. is going to make it into Kenmore without blowing its slot.


And yes, CBTC on the D and GLX can help with that quite a bit. Those branches with those easier-to-program headways are the next place to start after B, C, E surface signal priority and other surface bottleneck fixes.
 
The EGE said:
Why does the Central Subway have to be a test case for light rail CBTC?

The Central Subway has the B, D, and E on 6-minute headways and the C on 7 minutes during rush hour - an average of one train every 1.56 minutes. San Francisco's Muni Metro runs the J, K/T, L, M, and N with a nominal average of one train every 1.66 minutes (with the S shuttle and a few peak-of-the-peak extras dropping it to about every 1.5 minutes). Like the Green Line, Muni runs surface routes into a branched two-track tunnel.
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Except for intervals where they are supposed to throw in three car trains, the B and D headways are 5/6. The C headway is 6/7, and the E line briefly has a 5 minute headway for part of both peaks. The scheduled service between 4:30 and 5:30 PM westbound between Government Center and Copley is 43 trains for the hour, 11 B, 9 C, 11 D, and 12 E. The combined average headway is one every 84 seconds or 1.39 minutes. MUNI also has the advantage of all high platforms/level boarding in the subway, with shorter dwell times on the platform, which results in less back-up in the subway.
 
The EGE said:
Winston, that is contrary to the schedule documents published by the MBTA. Until at least late 2012 they claimed 6 minutes on everything but the C; now they have downgraded it to 7 minutes on everything except 6 on the C. Where are you getting your much lower numbers from?
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Copies of the employee schedules from a friend (not something on line I can link to). The public headway tables are always conservative and round up. If a headway is every 5.5 minutes, the table will say 6 minutes, if it is every 6.5, it will say 7. The E Line operates the 5 minute headways for only part of each peak, so the public tables rounds it up for the average of the entire peak.

Also, as I mentioned, when they schedule a three-car train, the headway in front of the three-car trip goes up to 7 (and that's what they display in the public table for B and D). So if you stand on the platform at say Copley westbound for 1-hour from 4:30-5:30, you will probably see 40 trains vs 43 trains. But for multiple 15-20 minutes periods, when there are no gaps for 3-car trains, the trains per hour rate remains at 43.

Additional edit:
I've transcribed the scheduled westbound departure times from trip origin points for each branch from 4:30 to 5:30 PM:

Scheduled B-line departures from Government Center
4:34
4:38
4:46
4:51
4:57
5:03
5:09
5:16-three car
5:22
5:28

Scheduled C-Line departures from North Station
4:33
4:39
4:46
4:52
4:58
5:05
5:11
5:18
5:24

Scheduled D Line departure from Government Center
4:34
4:40
4:45
4:51
4:56
5:03-three car
5:08
5:13
5:19
5:24

Scheduled E Line departures from Lechmere
4:30
4:35
4:40
4:45
4:50
4:55
5:00
5:05
5:10
5:15
5:20
5:27
 
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Schedules mean jack shit on the T. Those E headways? Yeah right. Try 10 minutes if you're lucky during the peak.
 
datadyne007 said:
Schedules mean jack shit on the T. Those E headways? Yeah right. Try 10 minutes if you're lucky during the peak.
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I would say the most important thing the MBTA could do short-term to improve the Green Line is make sure they have enough crews and enough cars available each day to actually run the service that is already scheduled. If you drop just one round-trip because of lack of either, that will result in a 10-12 minute gap in the peak, and that will result in heavy loads and delays.

In the long run, if you are talking about the theoretical capacity of new or improved signals, you have to make assumptions that they will have enough crews/trains to run what is scheduled now.
 
I would rather see them make changes to lower dwell times (all-door boarding) and mitigate the unpredictability of traffic signals on the surface. That would be much cheaper than adding more crews.
 
Without changing any infastructure, I would like to see this happen at peak:
A: Washington St - Government Center (8 min)
B: Boston College - Park St (8 min)
C: Cleveland Circle - Kenmore (6 min)
D: Riverside - Government Center (6 min)
DX: Reservoir - Lechmere (7 min)
E: Heath St - North Station (6 min)
S: Blanford St - Lechmere (6 min)

The headways I picked are somewhat arbitrary, but relative. They would have to be adjusted to whatever the cap is on downtown throughput.

Eventually a turnback or pocket track should be installed between Harvard Ave and Griggs for the A. The T NEEDS to bring back SCHEDULED and signed short turns, especially on the B. I would rather have the B turn at Kenmore instead of the C, but since its not set up that way the least trafficed line gets the cut in favor of a downtown shuttle. Really the cross platform transfer wouldn't be too bad anyway, you've got a train coming in every 2 mins or so. The DX would also add some additional service from Cleveland Circle to mitigate inconvenience on the outer part of the line.

The best thing about forming a shuttle train is that they can load up Lechmere and Blanford with a few spare sets, so if headways start to suffer on any branch line they can dispatch another shuttle to take its slot, and turn the underperforming branch asap. The shuttle could also be four cars long, preferably type 7-8-7-7 so it would eat crowds.
 
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The limit right now is from number of cars available, so if you feel like it, you might try counting how many your plan requires.

Also, I'm not really sure that Washington Street is set up to handle turnbacks at rush hour. Whenever they do it for maintenance, it is typically very slow.
 
I think the biggest fix that can be made to all the branching surface st. Green Lines (especially the B) is to consolidate stops and eliminate street intersections. There are many places where the road should not cross over the tracks and trains could blow through those areas. There is no need for stations to be on every block, it is completely ridiculous. Eliminate those station or consolidate them into a more practical location, maybe between current stations, and that would cut down on lost time spent waiting for lights to change or having to stop between station.

If those two things were done, I think the GL would deserve to be included on the map that states "rapid transit lines".
 
c_combat said:
I think the biggest fix that can be made to all the branching surface st. Green Lines (especially the B) is to consolidate stops and eliminate street intersections. There are many places where the road should not cross over the tracks and trains could blow through those areas. There is no need for stations to be on every block, it is completely ridiculous. Eliminate those station or consolidate them into a more practical location, maybe between current stations, and that would cut down on lost time spent waiting for lights to change or having to stop between station.

If those two things were done, I think the GL would deserve to be included on the map that states "rapid transit lines".
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I agree. Unfortunatly stop consolidation isn't happening as long as BU is helping to pay for the rebuilding of Comm Ave, plus whatever other influance they are throwing around behind the scenes. East of the BU bridge, you can close the Silber Way and Cummington St crossings, but St Mary, Granby and Carlton/Mountfort are vital (although the mess at Carlton/Mountfort needs to be reconstructed badly, but that's a road issue).
West of the bridge, you can't really do much. St Paul, Pleasant and Babcock are major streets. You might be able to get away with closing Pleasant if they allow left turns at Babcock (you need to be able to access the shaws). You can't close Babcock because of the fire house, they are always responding to calls in Allston. St Paul you just can't close, its too major. West of Packards corner, Linden st is HUGE and you can't close it, and then once you're past Harvard Ave conflicts aren't really an issue.

The biggest help would be signal priority. First, the T. Needs to pay the 14k or whatever stupidly small number it is to install the sensors on the C like brookline wanted them to. Then once that is proved to be the resounding success it will be, upgrade all the signals on comm ave west of Harvard Ave.

Also, all door boarding again. My god, worst experiment ever. No one gives a shit about fare evasion when they can't physically get on and off a train, and every stop takes five minutes with everyone trying to squeese to the front to get off. The B used to be a sort of funny "were all in this together" overcrowding situation, but now people are just pissed off.
 
Learned that MassDOT is designing some kind of replacement for the BU bridge intersection/clusterfuck, maybe for 2016. Apparently they've convened officials from surrounding cities and towns about it, but no public meetings. Supposedly there may be public meetings next year.

Comm Ave Phase IIA from Amory to Malvern Street is set for 2015. It needs an infusion of state money to get it going, though. BU is not paying for it.

Last month, BTD posted notices of a tree removal hearing along Comm Ave on the Phase IIA section. That hearing took place a week or so ago. The Tree Warden rejected their request for the time being, asking them to come back with a better plan. The removals would be necessary for sidewalk narrowing, because BTD wants to create left-turn lanes and bring all the platforms up to AAB standards. Nothing wrong with that, but it seems to me that station consolidation would be a much more sensible solution, and would avoid unnecessary sidewalk narrowing, and make for better Green Line operations.
 
Sidebar question: I'll soon be moving to the Aberdeen neighborhood of Brighton to be 2 minutes from the B, 5 minutes from the C and maybe 8-10 minutes from the D. Coming home I'll take whichever train comes first (which is awesome) but which train would you head towards in the morning?
 
I'm sure you'll get good answers from people who live over there, but most everyone I know who lives within 10 minutes of the D goes for that over the B or C.
 
Shepard said:
Sidebar question: I'll soon be moving to the Aberdeen neighborhood of Brighton to be 2 minutes from the B, 5 minutes from the C and maybe 8-10 minutes from the D. Coming home I'll take whichever train comes first (which is awesome) but which train would you head towards in the morning?
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D > C > B. Although the C isn't too bad, EXCEPT when they run a single car train near rush hour, which screws up everything. Don't even bother with the B between 7am and 10pm.
 
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