Is it me or are signal failures common?

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TSR :D

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Even though they're operated by electricity with very little to no moving parts? Electricity powered things are usually known for very reliable.

I wonder why does this happen?
 
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AlexS

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Signal failures are very rarely down to the actual signal head failing - although it can happen. Usually something like a track circuit failure/point detection failure or interlocking fault is to blame causing the signals to be stuck (correctly) at danger. 'Signalling failures' are just a general term for the whole system. You might get a burned out component/relay, cable theft etc.
 

Ferret

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Even though they're operated by electricity with very little to no moving parts? Electricity powered things are usually known for very reliable.

I wonder why does this happen?

And what do we get a lot of in this country? And what is known to generally bollocks up anything of an electrical nature?


 

ole man

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londonist.com/2006/06/signal_failures.php

A little bit of information
 

Cherry_Picker

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Discounting damage & delay caused by theft I would say that signalling is more reliable than ever these days.
 

jon0844

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Love this bit;

So according to LU, signal failures are just a natural part of life. Like taxes and awful television on ITV.

(Although I don't mind watching Die Hard when they show it on ITV2 every other week)
 

E50019

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Given the state of the railway signalling in this country i surprised we have so few failures.

And yes i do work on the railways so my experience is first hand.
 

Bill EWS

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E50019, I had 42 years railway experience as a fireman and driver and can't quite work out what you mean by "Given the state". Are you saying that the UK signaling system is unsafe in some way. Remembering that signalling is designed to fail in the 'safe' position the fact is that most failures are due to outside sources, such as has been mentioned, weather, general wear & tear and/or theft and vandalism.

I can see how the general public can see 'signal failure' as sounding more dangerous than in reality. Perhaps a better term should be used for such situations. I never, ever experience a signal failure that you would ever say put my train or myself in any real danger. In most cases simply an annoyance and inconvenience. I would be interested in knowing just what you meant by "Given the state", thanks.
 

yorkie

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There is more to it than the opening post suggests....

http://www.nationalrail.co.uk/service_disruptions/why/signal.html

National Rail Enquiries said:
Signal failure

What is a signal failure?

The signalling system is used to control the running of trains throughout their journey and ensure that trains are on the correct route at the right time to complete their journey safely.
The signalling system includes:

  • The signal centre - where staff use the signalling system to regulate train running, including changing the colour of the signals and operating points to set the correct route for trains
  • The signals – the red, yellow and green lights, similar to traffic lights, seen at stations, on overhead gantries and at the track side
  • Track points – the moveable sections of track, and the method of moving the points, that allow trains to move from one track to another
  • Signal cabling - the cables used to connect the signals and points to the signal box to allow staff to use the signalling system
  • Track circuit – a simple electrical system used to detect the precise location of trains on the rail network
A signal failure may occur because:

  • Signal cabling is damaged or stolen
  • Track points fail to operate correctly
  • Track circuits become faulty so that the precise location of trains cannot be correctly identified
  • The electrical supply to the signalling system fails
The smooth operation of the signalling system is essential to ensure that trains run safely and on time.
A signal failure means that trains cannot run correctly and delays to trains will occur whilst the problem is identified, corrected and/or an alternative method of moving trains through the affected area is put in place.

Also can I ask that if people have concerns about a post for any reason (including spelling, grammar and punctuation) it is reported using the report button (
) so we can make any corrections and/or send a polite but assertive message to the OP (original poster) via PM (private message), rather than an insult being posted on the forum please? Thanks :) (We really do appreciate all reports and will handle them in confidence)
 

MarkyT

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E50019, I had 42 years railway experience as a fireman and driver and can't quite work out what you mean by "Given the state". Are you saying that the UK signaling system is unsafe in some way. Remembering that signalling is designed to fail in the 'safe' position the fact is that most failures are due to outside sources, such as has been mentioned, weather, general wear & tear and/or theft and vandalism.

I can see how the general public can see 'signal failure' as sounding more dangerous than in reality. Perhaps a better term should be used for such situations. I never, ever experience a signal failure that you would ever say put my train or myself in any real danger. In most cases simply an annoyance and inconvenience. I would be interested in knowing just what you meant by "Given the state", thanks.

Well said Bill. Age of underlying assets alone is rarely an indicator of system safety, as robust maintenance procedures should continually check the integrity of sub-systems and components. In all generations of signalling almost all 'failures' are 'right side'; for instance sensor systems detect a point switch going out of adjustment, or a track circuit detects a failing insulator or damaged cable - the end result is a signal maintained at or replaced to red. The main drivers for renewal of systems are the costs and difficulty of effective maintenance, particularly obsolescence issues with respect to spares and skills. Also becoming more important are capacity issues and compatibility with further control centralisation; it is not practical to control a old mechanical lever frame remotely from a modern control centre, whilst it is becoming fairly routine to transfer control of late 20th century relay interlocking areas from contemporary panels to the newer VDU systems. Finally as each new generation of signalling technology is introduced, it's safety must be carefully judged against the previous generation as a baseline; hence the apparent slow pace of development compared to some less safety critical areas of engineering.
 

Tiny Tim

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Signalling systems are, as has been said, designed to fail safe, I don't think that's the issue here. Modern signalling is extremely complex in comparison to previous technology, presumably meaning there's more to go wrong. The question seems to be: Have signalling faults increased leading to more delays? This information should be available from NR.
 

MarkyT

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Signalling systems are, as has been said, designed to fail safe, I don't think that's the issue here. Modern signalling is extremely complex in comparison to previous technology, presumably meaning there's more to go wrong. The question seems to be: Have signalling faults increased leading to more delays? This information should be available from NR.

New systems are supposed to be specified at least as reliable as those they replace. However, sometimes the modern control architecture leads to greater time to overcome individual failures, even if each system element is actually more dependable. For instance with a manned signalbox at every junction, a set of points can be clipped up securely and trains authorised to pass danger signals quite quickly. Once control became more centralised, there was a delay incurred whilst an operations agent or technician drives to the problem site before movements can recommence. An unlucky spate of simultaneous failures at opposite ends of a duty area or road congestion can lead to significant delays.
 

E50019

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i fully understand the principles of fail safe signalling, as a signalling designer of 14 years.

What i mean is the general run down condition of the equipment, lineside equipment cases that you can't access due to tree growth yet hold vital relays and batteries. Yet when a new signal is put up the structural steelwork seems fit to support a bridge.

Lineside cables not kept neat and tidy inviting theft, the infrastructure owner only wanting the bare minimum work taking place to 'keep the job running' and so on. Projects get funded by different pots of money, there are plenty of projects that didnt quite do everything. The patch and make do mentallity is alive and well on the railways. Cronic under-investment since WW2 is a major factor some very poor decisions in the past, some good but not nearly enough.

Countless projects i have worked on have renewed signalling but never 100% of the installation, you can have a brand new crossover and point machine installed but still driven by the 35 year old location case wiring. Modern circuitry introduces so many more potential failure points, in the 1970s a crossover would have typically had 3-5 control relays, in 2011 this can be upto 12 with an increase in associated equipment.

Failures are generally compunded as massive delays as all companies involved have their own processes and control rooms, and have to arrange things separately, privatisation has not worked in so many aspects.

I wont talk about the LU infrastructure as from personal experience i'm amazed it manages the service levels it does given the amount of hammer the network gets from so many trains. Its a credit to all those guys who work permenant nights to keep it running, well done chaps.
 

Robsignals

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Many delays described as due to Signal failure aren't. Both point and track circuit failures may be down to the Civil Engineer but all too often now it's cable theft and I don't know why they aren't better announced. When lots of track circuits suddenly go Occupied and points flash Out of Correspondence it's obvious a cable has been cut. Can't be totally sure it's theft straight away but almost certainly will be so why not say "...due to cable damage"? Regular travellers will soon recognise the underlying meaning.

Long Track circuits are affected by the level of moisture in the ballast and may require Summer/Winter adjustment, this years weather extremes must be causing problems. Axle-counters are weather immune, touch wood, which is one of the main reasons for their adoption.

One other factor is there are more trains than ever on most lines so any problem soon causes a queue, a perverse sign of the railways success!
 
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