[TSR :D]

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?

[AlexS]

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]

Originally Posted by TSR :D

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]

londonist.com/2006/06/signal_failures.php

A little bit of information

[Jordy]

The title has been improved (although it wasn't that bad!)

[Cherry_Picker]

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

[jonmorris0844]

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]

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]

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]

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

http://www.nationalrail.co.uk/servic...hy/signal.html

Originally Posted by National Rail Enquiries

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]

Originally Posted by Bill EWS

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]

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]

Originally Posted by Tiny Tim

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.

[OuterDistant]

Originally Posted by Ferret

And what is known to generally bollocks up anything of an electrical nature?

My Uncle Colin!

[DarloRich]

Originally Posted by TSR :D

Electricity powered things are usually known for very reliable.

I wonder why does this happen?

Often because some little scroat pinches the cable!