NYCT - Bottlenecks Discussion Thread

[T to Dyre Avenue]

6 hours ago, Caelestor said:

As many have pointed out, the  needs to stay on the express tracks and run up 2 Ave. Merging onto the local tracks, whether at 34 St or 57 St, is undeniably a theoretical capacity decrease for the entire Broadway Line because one train effectively occupies both tracks as it uses the switch. Also, if the  isn't on time, it would only delay the  if it stayed on the express tracks vs the as well. That said, changing the  also requires changing the , which is currently scheduled as a branch of the . Basically the  trains have two different northern terminals at 96 St and Astoria, two southern terminals at Whitehall and 86 St / CI, and even two different routes through Manhattan (Broadway local vs express).

What really should happen is that the  should be scheduled together, as they would share the same trunk line (Broadway Express tracks) and terminals, albeit along a different branch in Brooklyn. Then the  from Forest Hills and the  from Astoria could be scheduled together down the Broadway local tracks, with varying southern terminals at Whitehall, Bay Ridge, or Gravesend during peak hours if the other 2 terminals can't turn 25 tph. If DeKalb deinterlining becomes a reality, then the  could even share the 4 Ave express tracks while the  get Brighton to themselves, and route consolidation can propagate throughout the entire B Division. 

Long story short, deinterlining reduces the effective number of services that conflict with each other and potential delays, benefiting operators and riders alike.

I was going to suggest simplifying things by swapping the  and  in Queens, but it’s still the same number of tph (though then it can be 15  and 10 ) and you’d still have to turn some ’s at Canal due to the sharp curve at City Hall limiting service to 21 tph, as @RR503 posted earlier.

As for deinterlining DeKalb, I’m not opposed to it, but the increased amount of transferring at Atlantic or DeKalb for Broadway or 6th Avenue service it would bring, is a concern I have with it. It’s too bad there’s no way to build a new infill station somewhere between DeKalb station and the interlocking with cross-platform transfers between  and . At least that would provide some relief for Atlantic and DeKalb. And provide additional service to the MetroTech area.

Edited November 6, 2019 by T to Dyre Avenue

[P3F]

4 minutes ago, RR503 said:

I would not be at all surprised if the rider mins equation favored deinterlining today; Broadway and 6th run within a block of each other north of 14 and Dekalb is...quite the dumpster fire. 

I would be surprised. During the majority of rush hours, DeKalb junction does not add a perceivable delay to runtime, beyond needing to stop at Myrtle. Even if something has to merge up ahead (which is not usually the case) that's usually no more than a minute or two added.

So, in my opinion, riders would simply see it as reducing convenience for no perceived benefit. 

[T to Dyre Avenue]

6 minutes ago, P3F said:

I would be surprised. During the majority of rush hours, DeKalb junction does not add a perceivable delay to runtime, beyond needing to stop at Myrtle. Even if something has to merge up ahead (which is not usually the case) that's usually no more than a minute or two added.

So, in my opinion, riders would simply see it as reducing convenience for no perceived benefit. 

Under the current service operations, northbound  and  trains arrive at Canal Street in groups of two, so you get an  followed right behind by a  (or vice versa), followed by a longer wait before the next two trains. Even if the schedule doesn’t call for it, I see it every day. This isn’t something that should be happening regularly, yet it does. There is a delay because you’ve got an  and a  getting to the junction at the same time on the Brooklyn side, therefore one has to stop and wait till the other is a “safe enough” distance ahead.   

Edited November 6, 2019 by T to Dyre Avenue

[Around the Horn]

Just now, T to Dyre Avenue said:

Under the current service operations, northbound  and  trains arrive at Canal Street in groups of two, so you get an  followed right behind by a  (or vice versa), followed by a longer wait before the next two trains. Even if the schedule doesn’t call for it, I see it every day. This is something that needs to be addressed. 

And in the reverse, I'm on trains that have to hold for trains to enter the 4th Avenue corridor practically every day.

Not to mention crowds at Canal Street (and to some extent Union Square nowadays) waiting for Brooklyn bound trains are legitimately dangerous and it's a minor miracle that someone hasn't fallen in the tracks yet with how damn narrow that platform is. Being able to take an or into Brooklyn and then switch at 36th if necessary would help reduce that dramatically.

[RR503]

10 minutes ago, P3F said:

I would be surprised. During the majority of rush hours, DeKalb junction does not add a perceivable delay to runtime, beyond needing to stop at Myrtle. Even if something has to merge up ahead (which is not usually the case) that's usually no more than a minute or two added.

So, in my opinion, riders would simply see it as reducing convenience for no perceived benefit. 

Dunno about that. The data I'm looking at for the  show a solid 2-2.5 min median PM peak runtime premium from Canal to Dekalb. When the *median* loss is that much, yeah, you're inconveniencing people. Given the interchangability of the 6th and Bway corridors, the fact that the only people who'd really lose full dual access are folks at Brighton express stops and 36 St, and that there may be people who want the corridor they don't have, I'd def say this is worth considering. 

Also the reasons @Around the Horn and @T to Dyre Avenue give. Capacity and schedule reliability are important!

[Jemorie]

9 hours ago, T to Dyre Avenue said:

Under the current service operations, northbound  and  trains arrive at Canal Street in groups of two, so you get an  followed right behind by a  (or vice versa), followed by a longer wait before the next two trains. Even if the schedule doesn’t call for it, I see it every day. This isn’t something that should be happening regularly, yet it does. There is a delay because you’ve got an  and a  getting to the junction at the same time on the Brooklyn side, therefore one has to stop and wait till the other is a “safe enough” distance ahead.   

It’s only like that so that loads are evenly divided (Sea Beach and Brighton customers respectively southbound, same goes for Astoria and SAS respectively northbound), although I don’t really review the  timetables much (they’re not my home lines anyway). I noticed this on the  as well, but then there are those times where trains do come evenly apart on every shared-track line. In my experiences, some people going to Flatbush will take the  rather than wait for the  behind it (say 5 minutes or more away) and ride the  to Nevins or Franklin. Same with how some people going to New Lots will take the  to Nevins or Franklin and catch the  there. Others on the other hand will wait solely for their designated line, even if it means waiting long.

I, personally, don’t mind the “back-to-back” structure, but I understand overall why this would be frustrating to some, especially off peak when service is way less frequent.

Edited November 6, 2019 by Jemorie

[T to Dyre Avenue]

On 11/6/2019 at 9:14 AM, Jemorie said:

It’s only like that so that loads are evenly divided (Sea Beach and Brighton customers respectively southbound, same goes for Astoria and SAS respectively northbound), although I don’t really review the  timetables much (they’re not my home lines anyway). I noticed this on the  as well, but then there are those times where trains do come evenly apart on every shared-track line. In my experiences, some people going to Flatbush will take the  rather than wait for the  behind it (say 5 minutes or more away) and ride the  to Nevins or Franklin. Same with how some people going to New Lots will take the  to Nevins or Franklin and catch the  there. Others on the other hand will wait solely for their designated line, even if it means waiting long.

I, personally, don’t mind the “back-to-back” structure, but I understand overall why this would be frustrating to some, especially off peak when service is way less frequent.

Southbound, leaving Canal, that may be the case, especially because the  doesn’t stop at DeKalb. But northbound, everyone crowds onto the first train that comes. Now if it’s the , then it might not be so bad because from what I’ve observed, northbound ’s tend to be noticeably less crowded entering Canal than ’s. I usually get a seat on the  at Canal. But if the  comes first, then it’ll be SRO leaving Canal (if it isn’t already).

Edited November 8, 2019 by T to Dyre Avenue

[RR503]

Back-to-back trains are yet another consequence of interlining. If you're trying to thread service at uneven frequencies through complex arrangements of merges, you sure as hell are going to get some ugly gaps in the schedule. Compare and contrast: 

...the 's scheduled headways at 125 St

...and the 's scheduled headways there:

[Jemorie]

@RR503, I don't really understand the data to be honest....are you generally saying that a  being scheduled to come followed by a  a minute or two behind it, most of the day and evening hours, in both directions, is what causes irregular service (trains being behind their schedules and all)?

What about the  and ? The former goes straight from Manhattan to the Bronx while the latter ends in Manhattan. Either way, both trains will get crowded, with the  being more so with all of its Bronx-bound passengers. In reality, based on my personal prescriptive, the  and  come evenly apart or the  comes right before the  in both directions between the 135 St interlocking and the Rogers Junction interlocking. It should always be the  coming first, followed by a  right behind it, for much of the day and evening in both directions. Remember, the  will pick up everyone traveling within Manhattan and will be emptying out as it heads further uptown while the  will be crowded all the way through since it serves the Bronx. This is common every afternoon all the way into midnight. Downtown wise (particularly every morning), the  will be picking up everyone traveling within Manhattan while the  will gradually empty out. So what is wrong with the "back-to-back" structure?

The major reason for the  delays are the East 180th Street/3rd Avenue-149th Street merge, 142nd Street Junction, and Nostrand Avenue Junction. A perfect scenario: a Manhattan-bound  express and a Manhattan-bound  local in the AM Rush can arrive just before the junction at East 180th Street, only for one of them to get held as the other proceeds first. The  can be delayed 2 minutes and will again can be delayed an additional 2 minutes by another Manhattan-bound  local departing Jackson Avenue on its way to 3rd Avenue-149th Street. It happens. It probably might end up being delayed by a Manhattan-bound  crossing over to the outer track from the middle track at 138th Street-Grand Concourse and again by a New Lots-bound  in Brooklyn after Franklin Avenue. So in total, 2 + 2 + 2 + 2 = 8 minutes behind schedule for the southbound  towards its Flatbush terminus.

All I'm saying is that if all of these IRT A Division at-grade level junctions were foreseen beforehand, the whole 3rd Avenue-149th Street and 149th Street-Grand Concourse would have been 3-tracks with two island platforms, and the junction at East 180th/Rogers Junction would have been designed differently so that AM Rush Hour southbound  express trains would experience little to no delays today.

As for as the ...the R62A's narrow doors, smaller seats, and end cabs resulting in a loss of 4 seats per car, are where the delays come from...

[RR503]

24 minutes ago, Jemorie said:

@RR503, I don't really understand the data to be honest....are you generally saying that a  being scheduled to come followed by a  a minute or two behind it, most of the day and evening hours, in both directions, is what causes irregular service (trains being behind their schedules and all)?

To a degree, yes. When you make that chart with the  and  together, the chart changes, but that's precisely the issue -- the complex interactions the  has with the  and  force it to run irregular headways to maintain a schedule that has any chance of being delivered, which force the  to run irregular headways, etc. Because trains don't generally line up into perfect windows between other trains, you're forced to do ugly shit like this, or schedule delays. 

25 minutes ago, Jemorie said:

What about the  and ? The former goes straight from Manhattan to the Bronx while the latter ends in Manhattan. Either way, both trains will get crowded, with the  being more so with all of its Bronx-bound passengers. In reality, based on my personal prescriptive, the  and  come evenly apart or the  comes right before the  in both directions between the 135 St interlocking and the Rogers Junction interlocking. It should always be the  coming first, followed by a  right behind it, for much of the day and evening in both directions. Remember, the  will pick up everyone traveling within Manhattan and will be emptying out as it heads further uptown while the  will be crowded all the way through since it serves the Bronx. This is common every afternoon all the way into midnight. Downtown wise (particularly every morning), the  will be picking up everyone traveling within Manhattan while the  will gradually empty out. So what is wrong with the "back-to-back" structure?

South of 96 St, the loading difference between  and  trains is relatively small, and there exists significant intra-segment ridership between 96 and Franklin. Scheduling the  unevenly creates load imbalances and increases the chance of dwell congestion related delays as you get further away from 135 St. Outside of Rogers, I don't see  scheduling as being nearly as much of a problem as some B div lines, but it's something worth keeping in mind when you try to estimate the impact of interlining on rider-experienced service.

30 minutes ago, Jemorie said:

The major reason for the  delays are the East 180th Street/3rd Avenue-149th Street merge, 142nd Street Junction, and Nostrand Avenue Junction. A perfect scenario: a Manhattan-bound  express and a Manhattan-bound  local in the AM Rush can arrive just before the junction at East 180th Street, only for one of them to get held as the other proceeds first. The  can be delayed 2 minutes and will again can be delayed an additional 2 minutes by another Manhattan-bound  local departing Jackson Avenue on its way to 3rd Avenue-149th Street. It happens. It probably might end up being delayed by a Manhattan-bound  crossing over to the outer track from the middle track at 138th Street-Grand Concourse and again by a New Lots-bound  in Brooklyn after Franklin Avenue. So in total, 2 + 2 + 2 + 2 = 8 minutes behind schedule for the southbound  towards its Flatbush terminus.

All I'm saying is that if all of these IRT A Division at-grade level junctions were foreseen beforehand, the whole 3rd Avenue-149th Street and 149th Street-Grand Concourse would have been 3-tracks with two island platforms, and the junction at East 180th/Rogers Junction would have been designed differently so that AM Rush Hour southbound  express trains would experience little to no delays today.

As for as the ...the R62A's narrow doors, smaller seats, and end cabs resulting in a loss of 4 seats per car, are where the delays come from...

Preaching to the choir here. Merges suck, and a delay at one generally leads to delays at the rest. I will say that E180 isn't much of an issue in the AM -- s use B lead to get around s crossing to the middle -- but the rest of them are crap. Rogers especially. But the infrastructure of today is what we're stuck with, so the task at hand is coming up with ways to mitigate these design issues as best we can. New switches and deinterlining at Rogers are at the top of my list for this very reason. 

[LGA Link N Train]

I have a certain question regarding Deinterlining. 

If certain lines were deinterlined (or interlined with one other line in the entire system) could you still increase the capacity limit to anything above 30 TPH given that the line has good signals in addition to having a strict schedule?

Edited November 9, 2019 by LaGuardia Link N Tra

[Jemorie]

1 hour ago, RR503 said:

Scheduling the  unevenly creates load imbalances and increases the chance of dwell congestion related delays as you get further away from 135 St.

I thought scheduling the  to come immediately followed by the  in both directions between the 142 St Junction and Rogers Junction would have been the perfect solution though. I thought it would make both lines run faster in terms of dwelling at stations. But I now see, well, partially anyway, of what you're saying. The former uses R62s, a fleet of cars that have a loss of 4 seats per car, smaller seats, and, more importantly, narrower doors, that create longer dwelling time. So any delay on the former also negatively impacts the latter as well. It's just that I was under the impression that when the  comes first, followed immediately right by a , all the Manhattan-inter borough crowds would go inside the former quickly at each station (with it eventually emptying out as it heads further uptown to 148 St), same with the Bronx-bound crowds going inside quickly on the latter. (Uptown  loads from Brooklyn are light in the reverse peak anyway until they gradually begin picking up at their first Manhattan stop, Wall St, until they have so many passengers each as they head further uptown). Downtown wise, I thought that when the  came first and picked up all the customers traveling within Manhattan, would have made it easier for the  immediately behind it to loose its customers from the Bronx (Downtown loads become lighter on both lines closer to Lower Manhattan, where, by then they are in Brooklyn considered "reverse peak" and are lightly loaded the rest of their routes to Flatbush/New Lots anyway).

In addition, from my perspective, every afternoon after school, southbound  trains are super crowded between Lower Manhattan and Eastern Brooklyn, until trains empty out through the New Lots Branch stations. Though loading does vary between the  (since they both serve the Flatbush Branch) and the  (since it only goes as far as Utica) during this time around. So I guess you are correct that the back-to-back structure being played out on the  would not sit well given the latter's fleet of cars having narrower doors that increase dwelling time. It's the main issue the  also faces nowadays.

Tbh, I was also under the impression, outside of rush hours, of having the  come right before the  in both directions between the 149-GC interlocking and the E 180 St interlocking, since more people on lower WPR want West Side than East Side, which is why during rush hours, the  runs express on that stretch in the peak direction anyway.

[RR503]

17 minutes ago, Jemorie said:

I thought scheduling the  to come immediately followed by the  in both directions between the 142 St Junction and Rogers Junction would have been the perfect solution though. I thought it would make both lines run faster in terms of dwelling at stations. But I now see, well, partially anyway, of what you're saying. The former uses R62s, a fleet of cars that have a loss of 4 seats per car, smaller seats, and, more importantly, narrower doors, that create longer dwelling time. So any delay on the former also negatively impacts the latter as well. It's just that I was under the impression that when the  comes first, followed immediately right by a , all the Manhattan-inter borough crowds would go inside the former quickly at each station (with it eventually emptying out as it heads further uptown to 148 St), same with the Bronx-bound crowds going inside quickly on the latter. (Uptown  loads from Brooklyn are light in the reverse peak anyway until they gradually begin picking up at their first Manhattan stop, Wall St, until they have so many passengers each as they head further uptown). Downtown wise, I thought that when the  came first and picked up all the customers traveling within Manhattan, would have made it easier for the  immediately behind it to loose its customers from the Bronx (Downtown loads become lighter on both lines closer to Lower Manhattan, where, by then they are in Brooklyn considered "reverse peak" and are lightly loaded the rest of their routes to Flatbush/New Lots anyway).

No, you're totally right that that's the optimal solution coming south from Harlem/Bronx in the AM peak. It's just that it has knock-on effects when extended to the rest of the line -- in Brooklyn especially, as you point out. That said, the determinants of  schedules are much more Rogers/142/149 than they are convenience. At Rogers, s have to be snaked between s and s; at 142, you have to make sure no conflicting moves are scheduled through the plant at the same time, and at 149, you have to take the result of the previous two interactions and make that 'mesh' with merging  service. Those three variables are a challenge enough; I doubt all that much thought is given to load balancing after managing them in the peak hours thanks to their complexity. 

 

[4 via Mosholu]

From my observation riding the train in the morning peak, there are no bottlenecks north of East 180th Street in the morning peak, as the and trains do not merge on each other from the Bronx. The point where it starts to get blocked are at Jackson Avenue and 138th Street due to the fact that the Bronx Park at that point becomes two tracks. Entering the direct junction immediately south of 149th Street has not been a problem, but getting to the Mosholu Junction has been. One early morning, when I got on an early train out of 238th Street that runs as the Bronx Park thru Express, there was not a train in the way at 138th Street; there have only been a few times where I have gotten them from 238th Street since I believe that those out of Dyre (the ones I've taken at more frequent levels being that its the main branch) have been rather problematic further south with merging.

The midday train is quite interesting; the junction issue at 138th Street is not as bad and the Jackson Avenue portion seems to run very well when both are local, but the 180th Street junction has an issue since it becomes local from Eastchester Dyre only. I don't really like to take it that often, as I have taken the Express out of Pelham Bay Park without much trouble with merging, even with the train when running local. The last one I took early in the morning hauled through two different crossovers at about twenty two miles per hour where it would normally run slowly at about fifteen (a direct one to the local being that it departed from the east track and the local to express one just before East 177th Street). It felt like I was riding on the train when it came to those two switches. The Local as well as the Grand Concourse Express are better at timing since there is deinterlining at play there.

[CenSin]

At DeKalb Avenue today, there was actually a self-inflicted delay: held in station while waiting for an to creep into the bypass track. At Church Avenue, there was a , so obviously that's was also a right behind us since the went first. Why didn't they send the into the junction since it would've cleared it before the even showed up? It just delayed the and the , and the was already 3 minutes late leaving the terminal!

[Jemorie]

21 hours ago, 4 via Mosholu said:

From my observation riding the train in the morning peak, there are no bottlenecks north of East 180th Street in the morning peak, as the and trains do not merge on each other from the Bronx.

Wrong.

https://www.nycsubway.org/perl/caption.pl?/img/trackmap/detail-e180th.png

[P3F]

34 minutes ago, Jemorie said:

Wrong.

https://www.nycsubway.org/perl/caption.pl?/img/trackmap/detail-e180th.png

The southbound uses a yard lead during the AM rush to avoid sharing trackage with the at E 180 St.

(I don't actually ride the line in the AM rush, but I remember that being noted in some thread several years ago.)

[CenSin]

26 minutes ago, P3F said:

The southbound uses a yard lead during the AM rush to avoid sharing trackage with the at E 180 St.

(I don't actually ride the line in the AM rush, but I remember that being noted in some thread several years ago.)

Need a better track map with color to show what tracks the trains actually use nowadays

[RR503]

24 minutes ago, CenSin said:

Need a better track map with color to show what tracks the trains actually use nowadays

S/b s diverge at the top arrow, run along the track pointed at by the middle arrow (called B lead), and rejoin at the lower arrow.

[Jemorie]

@P3F and @RR503, thanks. I see.

EDIT: @RR503, I was confused all this time because I thought S/B s do get in the way of S/B s just before E 180. 

Vanshnookenraggen's official website actually has the wrong track layout design. Same with the nycsubway.org one as well. That's what threw me off at first.

Edited November 14, 2019 by Jemorie

[T to Dyre Avenue]

5 hours ago, CenSin said:

At DeKalb Avenue today, there was actually a self-inflicted delay: held in station while waiting for an to creep into the bypass track. At Church Avenue, there was a , so obviously that's was also a right behind us since the went first. Why didn't they send the into the junction since it would've cleared it before the even showed up? It just delayed the and the , and the was already 3 minutes late leaving the terminal!

What time today? I heard announcements and saw on the MTA website that there were switch problems at Prospect Park. If it was during pm rush, perhaps it was trains the getting back on track after the problem cleared.

[Trainmaster5]

12 hours ago, Jemorie said:

@P3F and @RR503, thanks. I see.

EDIT: @RR503, I was confused all this time because I thought S/B s do get in the way of S/B s just before E 180. 

Vanshnookenraggen's official website actually has the wrong track layout design. Same with the nycsubway.org one as well. That's what threw me off at first.

nycsubway.org  used to be one of the sites I’d recommend to anyone who needed information about the history of the subway. Times have changed and I have cautioned folks to be careful about relying solely on the site. Track maps are probably reliable but I was going through the Line by Line pages and I was shocked to see 135th St- Lenox described as a two track station when my memory and track maps have a center track there. Even one of the thumbnails shows the center track. It seems that many thumbnails have been removed from the site over time covering all lines and some station descriptions have been modified. I wish everyone would take the time to look at the descriptions of stations that they know and point out any errors they encountered. I don’t get around the system as much as I did in the past so I gotta rely on the posters and my family to keep me informed. I’ve tried to contact the site through their contact list on the home page with no response except for a sometime poster to this site who couldn’t help me. Maybe someone on the site can get in touch with someone over there. BTW I didn’t respond to your post because even a decade ago s/b  trains used the yard lead during the am rush as SOP to avoid blocking the  Dyre trains arriving at the same time. I find myself more interested in the infrastructure of the system these days as well as scheduling and delays, probably due to my experience and training. Just my observations. Carry on.

[CenSin]

13 hours ago, T to Dyre Avenue said:

What time today? I heard announcements and saw on the MTA website that there were switch problems at Prospect Park. If it was during pm rush, perhaps it was trains the getting back on track after the problem cleared.

That was in the morning. The problem repeated itself this morning. The  was late again, due to there being no trains at the Coney Island terminal at 7:36 AM this morning. Again there was a  train on our tails after Parkside Avenue. The train didn't hold at DeKalb Avenue, but it did hold in the tunnel to let the  go ahead. There was no  train right behind that , but there was a  right behind our . What they could have done was send the  ahead so that the  behind wouldn’t be delayed. But instead, both the  and  became delayed.

[LGA Link N Train]

Not sure exactly where to put this question but;

If the  were to remove a few bottlenecks and deinterline in the process. How much money would they be saving right now?

[NBTA]

On 11/8/2019 at 8:43 PM, RR503 said:

Back-to-back trains are yet another consequence of interlining. If you're trying to thread service at uneven frequencies through complex arrangements of merges, you sure as hell are going to get some ugly gaps in the schedule. Compare and contrast: 

...the 's scheduled headways at 125 St

...and the 's scheduled headways there:

Where can I find graphs like this?