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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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