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CBTC - General Discussion

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On 12/8/2018 at 12:10 PM, RR503 said:

A quick methodological note from my earlier sheet: the square footage data was not lifted from NYMTC; their stats are unreliable. I instead subtracted 3' from all car lengths to account for couplers, anti-climbers, end doors, etc, and set the widths to 8.5' for IRT and 9.9' for B div. I am well aware this fails to account for cabs, seats, etc, but without knowledge of car assignments, those stats are impossible to know. Here's the sheet on which I did those calcs; do point out any errors you see. 

UF30U9p.png

Isn't he the guy who did this?

https://www.newcivilengineer.com/moving-block-signals-finally-go-ahead-on-jubilee-line/796921.article

Am I reading this correctly how many trains via 14th street tubes 19 TPH with CTBC? 

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Hey @Union Tpke, I found something interesting while looking through the (MTA)'s website, and I found something relating to CBTC Installation for the Culver Line on the (F)

http://web.mta.info/capitaldashboard/allframenew_head.html?PROJNUM=t7080332&PLTYPE=1

 

Quote

New York City Transit

 

Project: T7080332

Description: Install Communication-Based Train Control (CBTC) from Church Avenue to West 8 Street on the Culver Line

Category: Signals & Communications

Element: Signals & Communications

xxxxxxxxxx

...

This project will install Communications-Based Train Control ( CBTC) signal equipment on the Culver Line in the borough of Brooklyn from Church Avenue to West 8 Street. 

Apparently, it also has this info right here which I couldn't copy and paste: 

Design Start - April 2016

Design End - November 2018

Construction Start - December 2018

Construction End - January 2022

Percent Complete - 0%

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6 hours ago, LaGuardia Link N Tra said:

Hey @Union Tpke, I found something interesting while looking through the (MTA)'s website, and I found something relating to CBTC Installation for the Culver Line on the (F)

http://web.mta.info/capitaldashboard/allframenew_head.html?PROJNUM=t7080332&PLTYPE=1

 

Apparently, it also has this info right here which I couldn't copy and paste: 

Design Start - April 2016

Design End - November 2018

Construction Start - December 2018

Construction End - January 2022

Percent Complete - 0%

Thanks, but I am already aware.

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https://stevemunro.ca/2015/03/30/the-evolution-of-ttc-signaling-contracts/

 

Reading this article, and knowing TTC and NYCT share the exact same fixed block system and operating rules. The "SCS" overlay for TTC, NYCT never tried it, why? SCS would eliminate all grade timers with an "alerter".

It sounds to me like TTC installed https://en.wikipedia.org/wiki/Punktförmige_Zugbeeinflussung for permanent speed restrictions/psuedo-cab signals but the transponders have no anti-collision function, only overspeed derailment or preventing suicidal notch 8 a train after an ST clears or notch 8 into bumper blocks after last GT clears.

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5 hours ago, bulk88 said:

Reading this article, and knowing TTC and NYCT share the exact same fixed block system and operating rules. The "SCS" overlay for TTC, NYCT never tried it, why? SCS would eliminate all grade timers with an "alerter".

SCS is, I guess, Canadian speak for ATC, or pulse code signalling. NYCT actually was going to do something along these lines in the '70s, but then the financial crisis happened. That's why the 44s were geared for such high speeds; they expected a performance boost from ATC. 

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Specifically, it was planned to be done on 2nd Avenue and the Queens Blvd bypass.

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23 hours ago, RR503 said:

SCS is, I guess, Canadian speak for ATC, or pulse code signalling. NYCT actually was going to do something along these lines in the '70s, but then the financial crisis happened. That's why the 44s were geared for such high speeds; they expected a performance boost from ATC. 

I cant tell from TTC's PDFs and contracts if TTC's/Thales "SCS" is PRR <200 Hz metronome pulse code (#1 purpose anti-collision, PSR secondary purpose) or no electricity, no relays, no track circuits, magnetic indusi transponders (no anti-collision function, only PSR). PDFs hint its unenergized baise with a wheel counter, maybe GPS, and PSR DB in a VOBC (ACSES over dark territory without ATC/ATP/cab signals). No radio link, no track loop link. TTC states "SCS" has "blue light" MOW function in its contract spec, but still, that would be an un-energized Balise clamped in the track bed temporarily by MOW in the simplest implementation.

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Quote

ATC [CBTC] enforces a minimum safe separation between trains based on the safe braking distance from the last verified location of the rear of a preceding train or any other obstruction such as disturbed switches. This technology allows trains to travel closer together than the traditional fixed block system currently employed on the YUS line. This ability to travel closer together increases the throughput of the service and therefore allows more trains to be scheduled and more passengers to be carried.

This is a quote from the TTC report that was referenced by Mr. bulk88, above. It's a misconception. 

Let's calculate the headway between trains, with the follower traveling at the minimum safe distance. 

Let's assume the leader and follower are traveling at the same velocity V. If the follower's emergency braking rate is a, then the follower's emergency braking time is (V/a). This is the minimum time between the rear of the leader and the front of the follower.

Let an observer at a point witness the time interval between the passing the front of the leader and the front of the follower. That time is the headway, T. It consists of the time for the leader of to pass the point plus the emergency braking time. If the leader is traveling at velocity V and has length L then

T = (L/V) + (V/a)  

where (L/V) is the time for the leader to pass the point and (V/a) is the minimum safe braking time for the follower.

This expression for the headway has a minimum when V = SQRT(aL).

The headway at this velocity becomes T = 2 * SQRT(L/a).

Plugging in the nominal values of 3 mph/sec for a and 600 ft for L, yields an optimum value of V = 51.4 mph and a minimum value T = 23.3 seconds.

Thus, the strategy of operating speeds slower than 51.4 mph with shorter distances between trains is not an effective strategy for decreasing the headway between trains. 

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Thales is one of the suppliers the MTA has considered, right?

Quote

Commuters face another day of MTR service delays after ‘unacceptable’ signal failure causes unprecedented train crash

  • Software system allowed two trains to pass through crossing at same time, says MTR managing director Jacob Kam
  • Extra services on public transport put on as trains on Tsuen Wan line between Central and Admiralty remain suspended

Hong Kong commuters are facing more confusion, delays and long waits on crowded platforms on Tuesday, with the city’s railway operator unlikely to restore services that were knocked out between two major stations by an unprecedented train crash on Monday morning.

The MTR Corporation blamed the first collision in its 40-year history on a signalling software failure as it warned passengers taking the Tsuen Wan line from the Kowloon side to Hong Kong Island that upon arriving at Admiralty station they would either have to walk down to a lower level to change platforms or find alternative modes of transport to continue their journey to Central station. Services between the two busy stations were suspended for all of Monday after the collision between a Central-bound train and another train heading for Tsuen Wan at around 3am at a crossover junction.

There were no passengers on board the two trains during the trial run for the MTR’s new signalling system, but a 31-year-old driver suffered minor leg injuries.

MTR operations director Adi Lau Tin-shing said around 120 staff had been deployed for repair work at Central station. "But they need to wait until after midnight before they can remove the two damaged trains from the station tracks to another siding area. They only have two to three hours to carry out this work,” he said. “Also, we need some time to repair the damaged tracks and the related facilities. We may not be able to resume service between the Central and Admiralty stations for the Tsuen Wan line [on Tuesday].”

Photos of the wrecked trains released earlier by the MTR Corp showed badly damaged compartments with several doors unhinged and shattered glass strewn across the floor. One train was seen tilting on its side, having completely jumped the tracks. MTR Corp managing director Jacob Kam Chak-pui said initial investigations suggested the crash was caused by a software flaw in the new signalling system, which had been undergoing testing for more than a year. The software for the HK$3.3 billion (US$423 million) system was supplied by French multinational Thales. 

Kam said the system had failed when railway staff were switching to a second backup computer. The current system that will be replaced has only one backup. He explained that the two trains were assigned the same route because of the error, resulting in their passing through the same crossing simultaneously. “This scenario, in terms of safety, is unacceptable,” Kam said.

Thales had identified the same issue through a computer simulation in its Toronto laboratory, he added. “It confirms that their software was problematic,” Kam said, noting that Thales would send four or five experts to Hong Kong soon to follow up.

The investigation was complicated and could take two to three months, he said. All trials of the new signalling system would be suspended for now.

Thales released a statement on Monday evening saying it was “deeply sorry” that a driver had been hurt in the accident, and that it would support the ongoing investigation. “We fully remain at the disposal of [the MTR Corp] and the authorities to bring the appropriate assistance and information,” it said.

MTR operating chief Alan Cheng Kwan-hing said the two trains had dealt glancing blows to each other, rather than crashing head-on. “It was not a head-on collision,” he said. “Our initial findings showed the trains sideswiped each other when they were travelling towards each other at the crossover junction … I’ve never come across this kind of incident on the MTR.”

Director of Electrical and Mechanical Services Alfred Sit Wing-hang said the government was concerned about the incident and would conduct an independent investigation. “We will run a careful, in-depth and complete investigation to ensure the new signal system is operating in a safe and reliable manner before it is implemented,” he said. Sit said the government would check the repairs on the Tsuen Wan line section of Central station, including rail damage, before services could be resumed. He said the government would also ask the corporation to submit a report.

Lawmaker Michael Luk Chung-hung, vice-chairman of Legislative Council’s railways subcommittee, called on the MTR Corp to thoroughly investigate the incident. “The MTR Corp needs to make compensation claims against this contractor,” he said.

The accident is another damaging blow to the MTR Corp’s reputation, which has taken a beating over the past year because of a series of constructions scandals that have prompted a top-level management reshuffle.

Article edited for brevity and relevance. Full article here: https://www.scmp.com/news/hong-kong/transport/article/3002174/bus-tram-and-ferry-operators-put-rush-hour-alert-after

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A really interesting presentation on work train CBTC compliance in Toronto. 

https://www.apta.com/mc/rail/previous/2017rail/presentations/Presentations/Palmer, Mike.pdf

Toronto’s legacy signal system was essentially a copy of NYC’s and their original CBTC plans paralleled ours in waste. Their successful redesign of installation processes to minimize the need for AWS and the fact that Tomlin/Byford are at NYCT now gives me hope...

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I think everyone forgot what was actually presented to the public.

transform_map.png?format=1000w

First 5 Years

4, 5, 6 – 149 St-Grand
Concourse to Nevins St

E, F, M, R – Jamaica 179
St and Jamaica Center
Parsons Archer to 50 St

F – Church Av to West 8
St NY Aquarium

A, C, E – Columbus Circle
to Jay St MetroTech

G – Court Sq to Hoyt
Schermerhorn

7 – Flushing Main St to
34 St-Hudson Yards COMPLETE

 

Next 5 Years 

1, 2, 3 – Jackson Av to
Atlantic Av – Barclays Ctr

B, D, F, M – 59 St Columbus Circle and 21 St Queensbridge to Dekalb Av and Jay St MetroTech

A, C – Jay St MetroTech to Ozone Park Lefferts Blvd

A, S – Rockaway Blvd to Far Rockaway Mott Av and Rockaway Park Beach 116 St

N, Q, R, W – Queensboro Plaza to Dekalb Av

 

In none of this is CPW included, and CBTC on Broadway will be completed at around the same time as 6 Av CBTC. In fact, according to Cuomo, we might even use UWB, and like @VIP said we don't know if this plan will change or not. 

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Posted (edited)
3 hours ago, subwayfan1998 said:

I think everyone forgot what was actually presented to the public.

<image>

First 5 Years

4, 5, 6 – 149 St-Grand
Concourse to Nevins St

E, F, M, R – Jamaica 179
St and Jamaica Center
Parsons Archer to 50 St

F – Church Av to West 8
St NY Aquarium

A, C, E – Columbus Circle
to Jay St MetroTech

G – Court Sq to Hoyt
Schermerhorn

7 – Flushing Main St to
34 St-Hudson Yards COMPLETE

 

Next 5 Years 

1, 2, 3 – Jackson Av to
Atlantic Av – Barclays Ctr

B, D, F, M – 59 St Columbus Circle and 21 St Queensbridge to Dekalb Av and Jay St MetroTech

A, C – Jay St MetroTech to Ozone Park Lefferts Blvd

A, S – Rockaway Blvd to Far Rockaway Mott Av and Rockaway Park Beach 116 St

N, Q, R, W – Queensboro Plaza to Dekalb Av

 

In none of this is CPW included, and CBTC on Broadway will be completed at around the same time as 6 Av CBTC. In fact, according to Cuomo, we might even use UWB, and like @VIP said we don't know if this plan will change or not. 

Why are you copying and pasting my post? lol

edit: not to mention posting it in multiple threads...

Edited by Bay Ridge Express
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What they are not saying are: the service (TPH) levels that CBTC will make possible; the service levels they plan to operate with CBTC; the service levels they currently operate; the service levels that are possible with the existing signal system; and the service levels predecessor agencies actually operated with this signal system.

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1 hour ago, Stephen Bauman said:

What they are not saying are: the service (TPH) levels that CBTC will make possible; the service levels they plan to operate with CBTC; the service levels they currently operate; the service levels that are possible with the existing signal system; and the service levels predecessor agencies actually operated with this signal system.

You're missing a crucial element.

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2 hours ago, Stephen Bauman said:

What they are not saying are: the service (TPH) levels that CBTC will make possible; the service levels they plan to operate with CBTC; the service levels they currently operate; the service levels that are possible with the existing signal system; and the service levels predecessor agencies actually operated with this signal system.

You know I generally agree with you, but the degree of modification to existing signalling that would be required to bring it into compliance with modern signal design standards (MAS through stations, absolute protection when facing potentially dangerous track characteristics, 135% safety margin on a 1.4mphphs assumed emergency braking rate, etc) in some areas tips the cost scale towards doing CBTC -- remember that NYC CBTC installs are ridiculously and unnecessarily costly. 

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4 hours ago, Bay Ridge Express said:

Why are you copying and pasting my post? lol

edit: not to mention posting it in multiple threads...

dude, some people don't understand that if G trains get NTTs, NTTs will be displaced off the N/W and Q Line and blah blah blah.

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On 4/25/2019 at 10:45 PM, RR503 said:

You know I generally agree with you, but the degree of modification to existing signalling that would be required to bring it into compliance with modern signal design standards (MAS through stations, absolute protection when facing potentially dangerous track characteristics, 135% safety margin on a 1.4mphphs assumed emergency braking rate, etc) in some areas tips the cost scale towards doing CBTC -- remember that NYC CBTC installs are ridiculously and unnecessarily costly. 

There is a theoretical maximum TPH, that depends on the emergency braking rate. How close does CBTC approach this limit? How close does the existing block system approach this limit? 

There's a difference between an algorithm and its hardware implementation. Digital logic's modern hardware implementation does not use relays nor the railroad industry's perverse vital circuits concept for reliability. It uses programmable logic controllers (PLC). The PLC's are commodities whose cost varies directly with the number of I/O ports rather than logic complexity. Thus, adding ubiquitous, accurate logical timers is a nominal extra expense.

There are approximately 16,000 signals in the system. This comes to a $2.5M replacement cost per signal with the projected $40B Fast Forward budget. The railroad industry's rule of thumb is about $1M per signal, using vital relay technology. It would probably be half that, if PLC's were used.

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1 hour ago, Stephen Bauman said:

There is a theoretical maximum TPH, that depends on the emergency braking rate. How close does CBTC approach this limit? How close does the existing block system approach this limit? 

There's a difference between an algorithm and its hardware implementation. Digital logic's modern hardware implementation does not use relays nor the railroad industry's perverse vital circuits concept for reliability. It uses programmable logic controllers (PLC). The PLC's are commodities whose cost varies directly with the number of I/O ports rather than logic complexity. Thus, adding ubiquitous, accurate logical timers is a nominal extra expense.

There are approximately 16,000 signals in the system. This comes to a $2.5M replacement cost per signal with the projected $40B Fast Forward budget. The railroad industry's rule of thumb is about $1M per signal, using vital relay technology. It would probably be half that, if PLC's were used.

The issue isn’t so much the viability of incremental fixed block upgrade, but of the fixed block system itself. Over time, the design principles for our block system has changed — the guaranteed emergency braking rate has been reduced, we’ve begun to assume that curves/switches whose geometric speed limit is more than x away from area maximum attainable speed must be protected with GTs, we’ve begun to design signals around the assumption that trains maintain maximum speed through stations rather than assuming they slow to 15 at the leaving end as done before, our chosen safety margin has changed, and finally the acceleration performance of equipment has changed. This is to say that bringing some (extra stress here — large swaths of the system are compatible) areas of our fixed block system into compliance with current design standards without reducing capacity would necessitate a complete resignalling — an effort which, given the complexity of fixed block systems, would be exceedingly expensive. 

There is of course a sleight of hand in the above: I’m taking current signal design standards as unchangeable, which they shouldn’t be — those standards need to be constantly reviewed. But while I imagine some revisions could be made, I doubt they’d be extensive enough to allow full reuse of older installations. So there’s that.

Now, the cost issue. I think we first must keep in mind that FF isn’t just CBTC — it’s a whole bunch of other things, too, like elevators, bus upgrades, etc, all of which cost money. I’d imagine that CBTC makes up a good chunk of that figure, but I don’t think it’s the entire 40 billion. The holistic lack of transparency in that figure makes it hard to determine what the exact brakedown is, alas, so it’s difficult to provide a CBTC estimate.

Then I think we need to factor in NYC’s approach to CBTC install. It’s been our policy to, in installing CBTC, create an auxiliary wayside signal system (AWS) that allows operation when CBTC is not functioning and when CBTC non-compliant trains are in the area. The infrastructure intensive (to say nothing of track access-intensive) nature of installing fixed block signals adds (per the FTA) about 30% to the cost of installation. Getting rid of AWS would require wider car fleet compliance and work train CBTC compatibility, but both of those are achievable/have been achieved elsewhere. With AWS gone, installation costs go down, but so do maintenance expenditures. There is an order of magnitude fewer components involved in a pure CBTC system than in a fixed block system — that means there’s less to inspect, repair and troubleshoot, which translates into reduced lifecycle costs, and (generally) increased signal system uptime. While those benefits pay off over a long timeframe, they’re not insignificant, and certainly should be taken into consideration when making decisions about replacement. 

All of this is to say that we need nuance when talking resignalling. Completely with you that the ahistorical ‘CBTC absolutism’ that has been adopted by many isn’t all that constructive of a point of view, but I don’t think the opposite is, either. 

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Wanna append a corrollary to the above: signals aren’t the only thing that drive capacity. Dwell times, interlocking performance, operator variability and terminal operations all play huge roles during the peak, and flagging an even larger one in the off peak. Those variables can, to some extent, be adjusted independent of signal systems, and certainly should be — they are low/zero cost ways to improve system performance, especially given the degree to which they’re poor today. Something else to think about when making decisions about signal investment...

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10 minutes ago, Enjineer said:

According to a (7) operator on Reddit, ATO is now active on all trips, other than when it's disabled for track maintenance in certain blocks. Thread: https://www.reddit.com/r/nycrail/comments/bm6o4w/a_7_express_flying_through_90_st_at_just_about_50/emxf9sz/

Could you ask where speed limits were reduced?

Thanks.

 

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12 minutes ago, Union Tpke said:

Could you ask where speed limits were reduced?

Thanks.

 

Sure thing. 

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1 hour ago, Union Tpke said:

Could you ask where speed limits were reduced?

Thanks.

Alright, got a quick response: I was told that they lowered some speeds in the Steinway Tubes, as well as heading southbound (Manhattan-bound, I assume) into 52nd Street and 33rd Street. For 52nd and 33rd, I'd assume it's for safety regarding the curves past both stations. 

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