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RR503

Subway Capacity Thread

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6 hours ago, RR503 said:

It’s the dwell times and to a lesser extent the reluctance to use ST that kills there. In Lower Manhattan, the latter issue becomes the primary issue, and you can throw in Bowling Green congestion in too. 

Just imagine that the second platform was added to Bowling Green.

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7 hours ago, Union Tpke said:

Just imagine that the second platform was added to Bowling Green.

I always wondered if it were possible to extend the shuttle track and platform and use that for terminating (5) trains...

so something like this:

--------------------------------

[ drop off only (5) ]

--------------------------------

[     brooklyn (4)    ]

--------------------------------

[uptown & bronx (4)(5)]

Brooklyn bound (4) trains would have to use both sides but idk if that's a huge issue or not.

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This feels like a situation where we’re letting operational incompetence cloud our vision of need. We really shouldn’t have (5) short turns — they exist largely to relieve Rogers — and if we are gonna have them, just schedule uptown service so that the terminating (5) can immediately re-enter service northbound. Then you can operate just like City Hall.

On weekends, no decently operated railroad would have issues running (5)s through. 

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4 hours ago, Around the Horn said:

I always wondered if it were possible to extend the shuttle track and platform and use that for terminating (5) trains...

so something like this:

--------------------------------

[ drop off only (5) ]

--------------------------------

[     brooklyn (4)    ]

--------------------------------

[uptown & bronx (4)(5)]

Brooklyn bound (4) trains would have to use both sides but idk if that's a huge issue or not.

Here is what @CenSin came up with several years back that I saved:

29063193521_df62d0e6f3_o.pngHRiWITh by Union Turnpike, on Flickr

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Posted (edited)
13 minutes ago, R68OnBroadway said:

How much TPH could we gain by redoing the Astoria switches? 

Current limit is 15; you could probably get to 24-26 before you need tail tracks.

Edited by RR503
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50 minutes ago, RR503 said:

Current limit is 15; you could probably get to 24-26 before you need tail tracks.

Are there any other factors limiting along Broadway? 

Also, could you maybe add some switches to turn some trains at Astoria Blvd’s center track?

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24 minutes ago, R68OnBroadway said:

Are there any other factors limiting along Broadway? 

Also, could you maybe add some switches to turn some trains at Astoria Blvd’s center track?

On the local, the big one is the curve at City Hall. I’ve heard figures as low as 24 for that area, though luckily you have Canal/City Hall Lower to short turn trains. 

I’ve heard both ways on Astoria Boulevard, but I’d generally err on the side of it not being possible. Getting switches onto that hump would be difficult in the best of conditions. 

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Posted (edited)
6 hours ago, RR503 said:

Current limit is 15; you could probably get to 24-26 before you need tail tracks.

Can you ELI5 this? 

I know from playing Bahn that terminal stations hold trains until the appointed departure time, and its logical that with rail tracks you could have 4 trains holding - one on the platform to depart; two waiting on the tails for that platformed train to depart, and one on the incoming platform waiting for space on the tail tracks.

But what goes into limiting train capacity at a terminal? All I can think of is waiting for crew to board and depart (including rest breaks), train service intervals (ie it can’t depart 2 minutes after arriving if the interval is 6 minutes between trains), etc?

To me, seems the problem is easily solved by having the next crew board as soon as the terminating train platforms, but I’m sure that’s not the only factor.

Edited by Deucey

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Posted (edited)
1 hour ago, Deucey said:

Can you ELI5 this? 

I know from playing Bahn that terminal stations hold trains until the appointed departure time, and its logical that with rail tracks you could have 4 trains holding - one on the platform to depart; two waiting on the tails for that platformed train to depart, and one on the incoming platform waiting for space on the tail tracks.

But what goes into limiting train capacity at a terminal? All I can think of is waiting for crew to board and depart (including rest breaks), train service intervals (ie it can’t depart 2 minutes after arriving if the interval is 6 minutes between trains), etc?

To me, seems the problem is easily solved by having the next crew board as soon as the terminating train platforms, but I’m sure that’s not the only factor.

There’s a lot that goes into it. In the most specific terms, what determines terminal capacity is the rate at which you can cycle conflicting moves through the terminal interlocking, which is more easily thought of through the lens of total terminal cycle  time, or the time from when an inbound train enters the terminal interlocking to when it leaves it going back out.

Therein, on the end of “things that you can’t change” there is the time it takes to reverse a consist. In NYC, unlike really everywhere else in the work, you cannot ‘pass the air,’ or reverse a train without dumping the brakes. That’s a minute or so of fixed pocket dwell. 

Beyond that, pretty much everything is situational or competency-based. At Astoria, the big killer is the combination of a long terminal interlocking (so conflicts are prolonged) and slow terminal entrance speeds owing to the lack of tail tracks—trains have to be slowed WAY down so there’s no chance of anyone gunning it into the bumper, or worse, over it onto the street below. Other common issues are slow switch speeds (so again, prolonged conflicting moves) and, as you point out, poor crewing arrangements. 

It’s worth noting that the above applies largely to turnback terminals, where trains reverse at the last station platform. At relay terminals, your limit (in NYC, at least) is almost always the operation in/around the last stop rather than in the delays themselves. In a well operated system, this wouldn’t be the case — the last stop before a relay would be treated like any other stop, and the relays themselves like a platformless turnback terminal — but NYC is not a well operated system. Train clearing, poor signaling decisions and lag in swapping crews slaughter cap.

Does this somewhat make sense? I realize I’m pretty crap at explaining things and I’m multitasking here

Edited by RR503
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31 minutes ago, RR503 said:

There’s a lot that goes into it. In the most specific terms, what determines terminal capacity is the rate at which you can cycle conflicting moves through the terminal interlocking, which is more easily thought of through the lens of total terminal cycle  time, or the time from when an inbound train enters the terminal interlocking to when it leaves it going back out.

Therein, on the end of “things that you can’t change” there is the time it takes to reverse a consist. In NYC, unlike really everywhere else in the work, you cannot ‘pass the air,’ or reverse a train without dumping the brakes. That’s a minute or so of fixed pocket dwell. 

Beyond that, pretty much everything is situational or competency-based. At Astoria, the big killer is the combination of a long terminal interlocking (so conflicts are prolonged) and slow terminal entrance speeds owing to the lack of tail tracks—trains have to be slowed WAY down so there’s no chance of anyone gunning it into the bumper, or worse, over it onto the street below. Other common issues are slow switch speeds (so again, prolonged conflicting moves) and, as you point out, poor crewing arrangements. 

It’s worth noting that the above applies largely to turnback terminals, where trains reverse at the last station platform. At relay terminals, your limit (in NYC, at least) is almost always the operation in/around the last stop rather than in the delays themselves. In a well operated system, this wouldn’t be the case — the last stop before a relay would be treated like any other stop, and the relays themselves like a platformless turnback terminal — but NYC is not a well operated system. Train clearing, poor signaling decisions and lag in swapping crews slaughter cap.

Does this somewhat make sense? I realize I’m pretty crap at explaining things and I’m multitasking here

So I looked at your capacity map, and found out that the (N) can only do 6 tph at Coney Island which was shocking to me. This means some trains have to terminate at 86 right? Although I don't really understand the reason behind it, other than what you just stated about dumping, which can be applied to any terminal.

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Posted (edited)
4 minutes ago, Bay Ridge Express said:

So I looked at your capacity map, and found out that the (N) can only do 6 tph at Coney Island which was shocking to me. This means some trains have to terminate at 86 right? Although I don't really understand the reason behind it, other than what you just stated about dumping, which can be applied to any terminal.

Ah, the map shows current capacities, not maximum capacities — (N) only runs 6tph to CI. It could probably do 15 or so given the length/complexity of that terminal interlocking. 

Edited by RR503
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19 minutes ago, RR503 said:

Ah, the map shows current capacities, not maximum capacities — (N) only runs 6tph to CI. It could probably do 15 or so given the length/complexity of that terminal interlocking. 

Can the (N)’s tracks turn the most amount of trains given the lack of a curve and bumper block? (West End crawls with the bumper, Brighton has a slow curve and Culver is only a little better)

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1 hour ago, RR503 said:

Does this somewhat make sense? I realize I’m pretty crap at explaining things and I’m multitasking here

You asked...

1 hour ago, RR503 said:

In NYC, unlike really everywhere else in the work, you cannot ‘pass the air,’ or reverse a train without dumping the brakes. That’s a minute or so of fixed pocket dwell.

Why is it NYC trains have to bleed while other systems’ don’t? Something to do with how the subway is designed; cheapness of contractors, or something else?

 

1 hour ago, RR503 said:

Other common issues are slow switch speeds (so again, prolonged conflicting moves) and, as you point out, poor crewing arrangements.

By slow switch speeds, are you referring to train speed limits, or the actual rate of speed for the switch to orient itself towards a particular track? And is that dependent upon how quickly someone in the tower flips a switch or is that an automatic thing (like alternating switches based on if a train tripped a sensor that affects the routing of its follower)?

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1 hour ago, Deucey said:

Why is it NYC trains have to bleed while other systems’ don’t? Something to do with how the subway is designed; cheapness of contractors, or something else?

I'm honestly unsure of the reasoning here. I know that there were concerns about unattended trains rolling away back in the day and about T/Os reversing on the road (which compromises the failsafe nature of fixed-block systems), but I'd assume that foreign systems have figured those things out.

1 hour ago, Deucey said:

By slow switch speeds, are you referring to train speed limits, or the actual rate of speed for the switch to orient itself towards a particular track? And is that dependent upon how quickly someone in the tower flips a switch or is that an automatic thing (like alternating switches based on if a train tripped a sensor that affects the routing of its follower)?

Both, really. As we've converted switches from pneumatic to electric actuation, they've slowed down, which loses us a few seconds. That loss of course pales in comparison to delays in issuing lineups at manned terminals (IINM some terminals are now operated automatically), and slow train speeds over the switches themselves. 

1 hour ago, R68OnBroadway said:

Can the (N)’s tracks turn the most amount of trains given the lack of a curve and bumper block? (West End crawls with the bumper, Brighton has a slow curve and Culver is only a little better)

I wouldn't be surprised if this were the case, but the difference would be marginal. Stillwell was absolutely slaughtered during the rebuild, what with (F) and (Q) trains now essentially having to AK into the station, GT10s everywhere, and no consideration given to the potential to mitigate some of those impacts by moving crossovers closer to the terminal platforms. That complex, to be fair, is intrinsically hard to signal because trains entering on the (F)(Q) and (N) are running from complex trackwork or sharp curves towards an interlocking (meaning you have to provide absolute protection for home signals and keep people at reasonable speeds through curves/complex trackwork), while the (D) comes from complex trackwork into a stub...but I've gotta believe that they could have done better. 

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18 hours ago, RR503 said:

It’s worth noting that the above applies largely to turnback terminals, where trains reverse at the last station platform. At relay terminals, your limit (in NYC, at least) is almost always the operation in/around the last stop rather than in the delays themselves.

I feel like the one exception to poor crewing, etc. that I've noticed is 34-Hudson during rush hours. They really seem to have crews always board immediately after a train platforms and dumps the brakes, and will have it ready to head back out towards Queens in a minute or two. It's the one terminal I've witnessed trains running in and out like clockwork. 

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5 hours ago, Enjineer said:

I feel like the one exception to poor crewing, etc. that I've noticed is 34-Hudson during rush hours. They really seem to have crews always board immediately after a train platforms and dumps the brakes, and will have it ready to head back out towards Queens in a minute or two. It's the one terminal I've witnessed trains running in and out like clockwork. 

Yes, as always, you cannot paint with a broad brush. Some terminals -- like 34 -- operate really well, while some, uh, do not.

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On 5/26/2019 at 7:36 PM, Deucey said:

Why is it NYC trains have to bleed while other systems’ don’t? Something to do with how the subway is designed; cheapness of contractors, or something else?

Most, if not all terminals, have a bumper block in place designed to indicate where the train has to stop. The Port Authority Trans Hudson may be an exception, due to the presence of relay tracks in all but two terminals, which are 33rd Street and Hoboken.

There are a few NYC terminals that do not have the requirement for lifting up the Master Controller lever or the power lever prior to reversing, and those terminals are inside the Interborough Rapid Transit. The Brooklyn Bridge, Bowling Green and South Ferry loop stations are perhaps the only three terminals that can pass the air.

Stillwell is unique in its own.

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On 5/27/2019 at 12:23 PM, Enjineer said:

I feel like the one exception to poor crewing, etc. that I've noticed is 34-Hudson during rush hours. They really seem to have crews always board immediately after a train platforms and dumps the brakes, and will have it ready to head back out towards Queens in a minute or two. It's the one terminal I've witnessed trains running in and out like clockwork. 

I commend Flushing for doing just that. Dyre and Bronx Park thru local conductors are poor in doing that. Van Cortlandt keeps its doors open during peak hours.

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On 5/26/2019 at 11:31 AM, R68OnBroadway said:

Also, could you maybe add some switches to turn some trains at Astoria Blvd’s center track?

You know I really like that idea. Most of the pax along the line still get served by those trains, and even those headed for ditmars - its only a 7 minute walk away, or if they can't/don't want to, the next train won't be far behind. 

Switches really shouldn't be that hard to add...

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24 minutes ago, itmaybeokay said:

You know I really like that idea. Most of the pax along the line still get served by those trains, and even those headed for ditmars - its only a 7 minute walk away, or if they can't/don't want to, the next train won't be far behind. 

Switches really shouldn't be that hard to add...

As long as the slope doesn't get in the way...

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9 hours ago, LaGuardia Link N Tra said:

Since this is a thread about subway capacity, I am working on a new map that lists out all bottlenecks that exist in the subway system. Feel free to inform me of any bottlenecks that I might've missed. 

DeKalb

E 180

34

There are many more.

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