Signal Failure

[Deleted]

I ask this question as a humble passenger,and will be interested to see the replies,if not covered elswhere.
Out of all the many reasons for service disruption the dreaded ''signal failure at ......'' seems to occur most.
Why is this so prevalent ?It can cause major problems eg on the Picc.just yesterday when there was a big footie match at Arsenal.
Is it ancient equipment? Lack of maintainence? or whatever else.?

[upfast]

May 11, 2009 17:19:21 GMT @landau1945 said:

I ask this question as a humble passenger,and will be interested to see the replies,if not covered elswhere.
Out of all the many reasons for service disruption the dreaded ''signal failure at ......'' seems to occur most.
Why is this so prevalent ?It can cause major problems eg on the Picc.just yesterday when there was a big footie match at Arsenal.
Is it ancient equipment? Lack of maintainence? or whatever else.?

I'm told that yesterdays problem was down to a broken rail which caused a Signal Track Circuit Failure.

There are so many things that could go wrong with signalling equipment that may cause a delay. Some of it could be reduced by maintenance and some cannot be predicted at all. It may be a blown fuse, umbrella on the track, signal lamp gone out, defective train stop, broken track wire.

The important thing (though that then causes the delay) is that it fails safe.

[Chris M]

"Broken rail" was certainly the reason given at Victoria and on the Victoria Line train I took from there at ~19:50 yesterday.

[citysig]

In theory, you should rarely hear the terms "points failure," "track failure" or anything other than "signal failure."

First and foremost, many of the variants of failure end up causing a "signalling failure" no matter how they are caused. For us, the service operators, how that failure is caused is for the technical staff to ascertain. So we embrace it under the one term we know to be true.

Secondly, many of the other reasons have been withdrawn to avoid causing any undue alarm. Track failure conjures up visions of track simply crumbling away, and points failure, particularly when related to certain incidents on National Rail in recent years, tends to draw images of disasters caused by point structure failure - when in fact the real cause is probably one of London's numerous free papers jammed in the blades, preventing it from throwing fully.

[railtechnician]

May 11, 2009 21:56:07 GMT @citysig said:

In theory, you should rarely hear the terms "points failure," "track failure" or anything other than "signal failure."

First and foremost, many of the variants of failure end up causing a "signalling failure" no matter how they are caused. For us, the service operators, how that failure is caused is for the technical staff to ascertain. So we embrace it under the one term we know to be true.

Secondly, many of the other reasons have been withdrawn to avoid causing any undue alarm. Track failure conjures up visions of track simply crumbling away, and points failure, particularly when related to certain incidents on National Rail in recent years, tends to draw images of disasters caused by point structure failure - when in fact the real cause is probably one of London's numerous free papers jammed in the blades, preventing it from throwing fully.

Yep, it doesn't take much to cause trouble and a great deal of it can be laid squarely at the feet of passengers who bring things onto the system and leave them. Soft drinks cans are notorious for causing all sorts of problems as well as newspapers and other carelessly discarded rubbish. It's not unknown for points failures to be caused by such things as squashed hedgehogs in outside locations.

As for maintenance it is done regularly to a maintenance schedule, nevertheless as rails wear points and trainstops can go out of adjustment, weather is also a factor especially in the winter months when rainwater or snow freezes in and around equipment that works to close tolerances. As all signalling equipment is designed to fail safe there is more chance of failure than not in order to protect the travelling public when a potentially dangerous situation arises.

Surely all would agree that it's better to get to work or home late than not to arrive at all!

[Deleted]

but your correct old age is another factor and maintenance is done to a required level points are done every 6 weeks and signals and the rest of the equipment is 10 weeks apart from the interlocking machine which is done every year but usually gets done every 6 months