Are Signalling Faults Becoming More Common?

[SpacePhoenix]

With two mainlines having had major signalling faults in the last week or so (GWML & WCML), it got me wondering, are signalling faults becoming more common? Over the last month or so when I've flicked through the rail travel news, the number of times that I've seen signalling faults mentioned.

Is it just something about warmer weather that makes signalling systems more prone to failure?

 

[thecrofter]

Not at all. As signalling becomes more telecoms reliant (the digital railway) faults on either system invariably get quoted as a signalling failure.

 

[Tio Terry]

With two mainlines having had major signalling faults in the last week or so (GWML & WCML), it got me wondering, are signalling faults becoming more common? Over the last month or so when I've flicked through the rail travel news, the number of times that I've seen signalling faults mentioned.

Is it just something about warmer weather that makes signalling systems more prone to failure?

Mechanical Signalling was always prone to problems with temperature, expansion and contraction of things like point rodding and signal wires have always had their difficulties. But reliance on mechanical signalling has significantly reduced over the past 30 years or so.

Modern electronic signalling systems do require some form of temperature management system to ensure they don't overheat and sometimes this fails, when you think about it, we go to great lengths to ensure dual power supplies to important locations, the systems themselves have duplication built in, but in the end we rely on a single air conditioning unit!

Points are mechanical and will always have problems with extremes of temperature, both high and low, the temperature ranges within the UK are some of the most extreme - that's not to say other countries don't have higher extremes at either end of the scale, but few have the breath of change that we have.

Also, a lot of our signalling systems are quite old, Wimbledon, which covers Waterloo out past Clapham is almost 30 years old and there are plenty in the same ball park, in terms of the "bathtub" effect they are approaching the end of their reliable life.

 

[Bald Rick]

There was some analysis done about 10 years ago (no source, sorry) that showed when the air temperature got above 23C, signalling faults started to go up also. Some faults are immediate - block joint and points failures being classic, whereas some faults develop some time after the warm weather or after a prolonged hot spell.

Since then a lot of cash has been spent on hot weather protection, e.g. Aircon / fans / shades on signalling equipment boxes.

To answer the original question, the general rend in signalling failures is not increasing, but the current hot spell (down south) may well have caused a short term 'blip'.

 

[MarkyT]

Focusing on GWML, much of the route is being resignalled currently or has been within the last few years ready for electrification. That means a lot of new systems still 'bedding in' and being managed down the leading edge of their bathtub reliability curves. While the electrification digging continues, the risk of construction activities disturbing active communications systems that carry signalling links also remains.

 

[3141]

Is a "signalling fault" likely to affect a wider area than in the past? If it was the rodding to a single signal previously, it seems to me that now it's at least an "area" before and after a junction

 

[noddingdonkey]

Isn't it also the case that renewal projects in recent years have tended to remove rarely used crossovers and the like which mean that there is less flexibility to work around problems so the effects are more noticeable? Traincrew route knowledge policies can mean there are fewer viable diversations than previously.

 

[MarkyT]

Isn't it also the case that renewal projects in recent years have tended to remove rarely used crossovers and the like which mean that there is less flexibility to work around problems so the effects are more noticeable?

Rarely used crossovers etc can also be the cause of signalling failures so it's not as simple as that.

 

[30909]

I'm a complete novice on this subject but one thing does appear to happen, certainly where the equipment is ageing, is what I will term "a wave effect". An example is the good old Portsmouth Direct between Guildford and the Petersfield area boundary with Havant. Regularly there are track circuit failures at one or more locations. When fixed often there is another fault in an adjacent section.
So I ask if an electrical component is breaking down it probably absorbs more power and when replaced does it cause overloads near by?

 

[LAX54]

As the smaller boxes, including PSB's go, and are replaced by bigger boxes, and of course cover a wider area, they are now I.T based, and you will tend to find, that one small bit of I.T can cover quite a few locations !
So maybe not as many failures per se, but will affect a much larger area

 

[snowball]

Signalling has always been information technology.

 

[alxndr]

Faults on the more modern signalling systems can affect larger areas than previously.

For example, if one relay fails in a Route Relay Interlocking the issue is limited to just what is controlled by that contact, or whole relay, and the amount of equipment that is controlled by one relay is generally fairly limited. In a Solid State Interlocking area though, there might be a couple of things controlled by one signal or point module.

The fact that the equipment is more spread out can cause problems with the speed of fault finding too, and issues are more likely to be reported publically where they cause significant delays. A track circuit is limited in length, so all the fault finding is generally limited to one small area. With an axle counter fault it's often a case of going one place to carry out a diagnostic download, and then back to the next town to investigate the equipment out on the ground, which obviously takes time.

Maybe I'm biassed slightly though. I'd much prefer to be working on old stuff any day, and it strikes me as more solid and resilient; hefty, reassuring lumps of metal, wood and bakelite. Now it's plastic and fiddly bits that wouldn't look too out of place in a toy box.