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Alternatives to time release of locking

You are here: Home > Forum > Miscellaneous > The real thing (signalling) > Alternatives to time release of locking

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Alternatives to time release of locking 18/10/2021 at 01:44 #141910
flabberdacks
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Have just been thinking about a couple of scenarios in New South Wales and got curious to see what is out there in the rest of the world.

Some power signal boxes in NSW had a number of routes or signals where returning the signal to stop with a train on approach does not incur the usual time release of approach locking - the signal will return to stop but the locking is maintained indefinitely (signal flashes red forever) unless another condition is met which requires human involvement.

1) Strathfield signal box had a 'key release' arrangement for many years. If certain signals became approach locked, they would never release the route unless the signal electrician was summoned from downstairs. The electrician would first agree with the signaller that it was safe to do so (a form was required), and then they would insert their key into the back of the panel which immediately dropped all locking applicable to that route (route locking, overlap, approach locking, everything).

While time releases were provided for some signals, there were many key releases. For such a busy corridor, it really punished poor decision making. One 'old hand' who I spoke to had some very colourful language about the key releases when trains became delayed.

2) On the NSW 'south coast' line, the large area controlled by Wollongong signal box has something like 45 kilometres of continuously bidirectional signalling, one of the first areas in New South Wales to be signalled in this way. Where crossovers between the two bidi lines are provided, the 'home' signals immediately protecting the points are provided with driver's pushbuttons. I believe that the intent of these pushbuttons is, when a signal is clear but returned to stop with a train on approach, designed to prove that the train is at a stand by the driver getting out and pushing the button before approach locking is released. (If I'm wrong about that please let me know).

Are there other creative risk controls when it comes to release of locking that the signaller can't do by themselves? Anywhere in the UK, or elsewhere in the world?

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Alternatives to time release of locking 18/10/2021 at 08:42 #141916
kbarber
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The 'L' frames between Clapham B. New Cross Gate and South Croydon had backlocks with no time release. The S&T were specially authorised to release the backlock on the signalman's request (no paper involved). The one time I saw it done, I reckon it was about 30 seconds from realising a wrong 'un had been pulled to the lever back in the frame and pulling off the intended route.

I should perhaps add that, as far as I recall, the locking took effect as soon as the signal cleared and regardless of how far away the train was. On the above occasion, the wrong 'un was pulled at Clapham B for the next train expected (up the Through to Vic), then the description came in from Balham for one to the West London. The correct route was cleared before he ever got a sniff of a double yellow (and if memory serves that was one of the suburban areas where it was authorised to pull off for diverging routes without checking an approaching train).

Last edited: 18/10/2021 at 08:48 by kbarber
Reason: Additional information

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Alternatives to time release of locking 18/10/2021 at 14:18 #141923
flabberdacks
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Amazing, that's rapid!
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Alternatives to time release of locking 18/10/2021 at 16:34 #141928
GeoffM
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In the UK, at least, the concept of a route never releasing doesn't exist (disclaimer: it's the railway, there are bound to be a few rogues). So a key release is not required and I don't recall ever seeing provision for one in hundreds of panel diagrams and relay drawings I've seen.

However, if the interlocking did get into some irrecoverable state then, as I understand it, all trains in the affected interlocking and possibly in immediately adjacent interlockings too would need to be stopped ("all wheels stop"and the interlocking unpowered and repowered. After this, both relay and CBIs have a kind of startup timer - something like 2-4 minutes - where very little can be done.

ESOC (Emergency Signals On Controls) were provided for SSIs way back because British Rail (or the inspectorate) were terrified of losing control of these new fangled CBIs. But they kill the power to the SSI so in the event of an incident, you'd have a complete blackout of indications and no logging would happen - not ideal in an accident!

So then SGRC (Signal Group Replacement Controls) were introduced. These just pull a group of aignals in a small area - under the hood it literally just pulls all the routes and operates emergency replacements so your original scenario of a route never cancelling would not be solved with SGRCs.

I do like the idea of a "I'm stopped" button on the signal though!

SimSig Boss
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Alternatives to time release of locking 18/10/2021 at 23:47 #141937
flabberdacks
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GeoffM in post 141928 said:
In the UK, at least, the concept of a route never releasing doesn't exist
Just like how 'subroute locked in opposite direction' doesn't exist here, the differences are subtle but very interesting.

I wonder if the key release came about because comprehensive time release was more expensive, or if it was a risk control for something else

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Alternatives to time release of locking 19/10/2021 at 00:35 #141939
kaiwhara
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kbarber in post 141916 said:
The 'L' frames between Clapham B. New Cross Gate and South Croydon had backlocks with no time release. The S&T were specially authorised to release the backlock on the signalman's request (no paper involved). The one time I saw it done, I reckon it was about 30 seconds from realising a wrong 'un had been pulled to the lever back in the frame and pulling off the intended route.

I should perhaps add that, as far as I recall, the locking took effect as soon as the signal cleared and regardless of how far away the train was. On the above occasion, the wrong 'un was pulled at Clapham B for the next train expected (up the Through to Vic), then the description came in from Balham for one to the West London. The correct route was cleared before he ever got a sniff of a double yellow (and if memory serves that was one of the suburban areas where it was authorised to pull off for diverging routes without checking an approaching train).

Interesting that, the four L frames that I worked did not have that issue with backlocks!

Sorry guys, I am in the business of making people wait!
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Alternatives to time release of locking 19/10/2021 at 08:53 #141942
kbarber
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kaiwhara in post 141939 said:
kbarber in post 141916 said:
The 'L' frames between Clapham B. New Cross Gate and South Croydon had backlocks with no time release. The S&T were specially authorised to release the backlock on the signalman's request (no paper involved). The one time I saw it done, I reckon it was about 30 seconds from realising a wrong 'un had been pulled to the lever back in the frame and pulling off the intended route.

I should perhaps add that, as far as I recall, the locking took effect as soon as the signal cleared and regardless of how far away the train was. On the above occasion, the wrong 'un was pulled at Clapham B for the next train expected (up the Through to Vic), then the description came in from Balham for one to the West London. The correct route was cleared before he ever got a sniff of a double yellow (and if memory serves that was one of the suburban areas where it was authorised to pull off for diverging routes without checking an approaching train).

Interesting that, the four L frames that I worked did not have that issue with backlocks!
I think it was very much that locality and railway (although it was British Railways by then the installation was to the standards of the old Southern Railway, including indication of all 4 aspects - see https://www.wbsframe.mste.co.uk/public/Clapham_Junction_B.html - and a lever for each route from a junction signal, to name two). Part of the frame from Cannon Street (originally owned by the LMS, loaned to the Southern Region when the original Cannon Street box was burned out) was later installed at Bedford North as part of the West Hampstead stageworks. That installation was to LM standards, including one lever for each signal with the junction indication according to the route set and the LM standard Red/'OFF' indications in the box. It also had standard 2 minute time-outs on the approach locking.

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Alternatives to time release of locking 19/10/2021 at 10:31 #141944
jc92
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Keith - presumably such an arrangement required S&T to be on standby in rush hour to effect such a release, otherwise theres the risk of everything backing up while they're sat in traffic for instance? Or was it pure luck in the example you gave that they were on hand?.
"We don't stop camborne wednesdays"
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Alternatives to time release of locking 19/10/2021 at 23:55 #141953
kaiwhara
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kbarber in post 141942 said:
kaiwhara in post 141939 said:
kbarber in post 141916 said:
The 'L' frames between Clapham B. New Cross Gate and South Croydon had backlocks with no time release. The S&T were specially authorised to release the backlock on the signalman's request (no paper involved). The one time I saw it done, I reckon it was about 30 seconds from realising a wrong 'un had been pulled to the lever back in the frame and pulling off the intended route.

I should perhaps add that, as far as I recall, the locking took effect as soon as the signal cleared and regardless of how far away the train was. On the above occasion, the wrong 'un was pulled at Clapham B for the next train expected (up the Through to Vic), then the description came in from Balham for one to the West London. The correct route was cleared before he ever got a sniff of a double yellow (and if memory serves that was one of the suburban areas where it was authorised to pull off for diverging routes without checking an approaching train).

Interesting that, the four L frames that I worked did not have that issue with backlocks!
I think it was very much that locality and railway (although it was British Railways by then the installation was to the standards of the old Southern Railway, including indication of all 4 aspects - see https://www.wbsframe.mste.co.uk/public/Clapham_Junction_B.html - and a lever for each route from a junction signal, to name two). Part of the frame from Cannon Street (originally owned by the LMS, loaned to the Southern Region when the original Cannon Street box was burned out) was later installed at Bedford North as part of the West Hampstead stageworks. That installation was to LM standards, including one lever for each signal with the junction indication according to the route set and the LM standard Red/'OFF' indications in the box. It also had standard 2 minute time-outs on the approach locking.
The latter of those two is pretty much what the Kiwi's ended up with, although the length of the approach locking did vary depending on what the signal was protecting and the approach speeds, with a mix of electrical and mechanical timers, the former favouring main line signals.

Sorry guys, I am in the business of making people wait!
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Alternatives to time release of locking 20/10/2021 at 07:58 #141958
kbarber
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jc92 in post 141944 said:
Keith - presumably such an arrangement required S&T to be on standby in rush hour to effect such a release, otherwise theres the risk of everything backing up while they're sat in traffic for instance? Or was it pure luck in the example you gave that they were on hand?.
There was an S&T messroom on the ground floor of the box. There was even a direct line from the box concentrator, so no need to spend time dialling. And I get the impression from some of the things Mark Adlington says on the L Frame website https://www.wbsframe.mste.co.uk/public/index.htm that, when the gang went out on a job, someone stayed behind just in case a release was needed.

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Alternatives to time release of locking 20/10/2021 at 14:02 #141963
flabberdacks
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kbarber in post 141958 said:
when the gang went out on a job, someone stayed behind just in case a release was needed.
I feel like this would have been widespread at busy locations. At Strathfield, we knew the times when the electricians' roster meant that there wasn't likely anyone downstairs, and even the mouse-and-keyboard computer boxes have a systems technician on duty 24/7.

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