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Major signal systems failure at Brimsdown, 24/11/2025

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700007

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In the last hour or so a major signal systems failure has apparently taken place at Brimsdown in North London that has taken out virtually the entire West Anglia network including all London Overground services out of Liverpool Street. This has also impacted the London Overground route from Gospel Oak to Barking Riverside. What's happened for it to virtually suspend all services including on routes that do not serve the Brimsdown locality?
 
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QueensCurve

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In the last hour or so a major signal systems failure has apparently taken place at Brimsdown in North London that has taken out virtually the entire West Anglia network including all London Overground services out of Liverpool Street. This has also impacted the London Overground route from Gospel Oak to Barking Riverside. What's happened for it to virtually suspend all services including on routes that do not serve the Brimsdown locality?
This comes days after the major failure at Stafford? Is anyone investigating the possibility of cyber attacks?
 

Deepgreen

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I'm sure/hope cyber issues are part of the investigations, but even if there is no interference, it is a fact that today's huge signalling areas have the potential for more widespread disruption than ever before.
 

D1537

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This now appears to have been fixed, though of course there will be residual disruption for the rest of the day.
 

Nicholas Lewis

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Despite its age Liv Street IECC is very reliable. Invariable these wide area failures are often down to data transmission issues.
 

Lucy1501

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Signalling systems are completely airgapped. Anything sent to outside systems such as TD berths are on read only connections. The suggestion of a cyber attack being responsible is practically impossible.
 
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Air gaps can sort of be breached, but within the realm of social engineering along with negligence or insider threats. I think if you were a sophisticated enough to bridge an air-gap you'd probably do something more subtle than just turn everything off, which is probably much easier achieved by going round cutting up wires. I suppose the idea is that of a rather post-modern cold-warfare of just causing minor havoc across a range of things within a country to undermine their belief in national systems of all kinds since they keep falling apart semi-regularly. Of course, the symptoms of this kind of long-term attack are the same as that of serial underinvestment.
 

Bald Rick

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It wasn’t a major signalling system failure. It was one small thing, unfortunately at a critical place.


Despite its age Liv Street IECC is very reliable. Invariable these wide area failures are often down to data transmission issues.

The signalling concerned is 22 years old.


Must be not far short of 40 years old for the oldest parts?

36, but the newest is much less than that although there is an element of Trigger’s broom about it. The control kit has all been changed, at least twice, im that time. I’m fairly sure the interlockings have too. And the data links transferred. And much of the ground equipment will have been changed through failures and renewals.
 
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Class 170101

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The signalling concerned is 22 years old.
That part commissioned as part of WARM, so 2003/4 then. Time flies.
36, but the newest is much less than thatbbAlthough there is an element of Trigger’s broom about it. The control kit has all been changed, at least twice, im that time. I’m fairly sure the interlockings have too. And the data links transferred. And much of the ground equipment will have been changed through failures and renewals.
Must be interesting getting spare parts for the 'computer' parts though. Never had a computer at home last anywhere near that long.
 

najaB

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Must be interesting getting spare parts for the 'computer' parts though. Never had a computer at home last anywhere near that long.
I don't have any direct knowledge about NR's plan for dealing with obsolescence, but typically organisations facing situations like this will buy up the last remaining stock of spare parts when the manufacturer announces the end-of-life. That, and buying up equipment that's recovered from upgrade projects elsewhere.
 

Harpo

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Anyone want to explain how that failure at Brimsdown managed to effect the Gospel Oak to Barking line?
Given that both the Lea Valley and the Southbury Loop have junctions connecting them to the T&H, it’s highly plausible.
 

Bald Rick

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Must be interesting getting spare parts for the 'computer' parts though. Never had a computer at home last anywhere near that long.

That’s the point - every so often a complete new box is installed. I can’t remember the detail of what has been replaced in Liverpool St, but it is quite straightforward to replace the ‘box’ with the interlockigns in it. The interlocking is, after all, data.


Anyone want to explain how that failure at Brimsdown managed to effect the Gospel Oak to Barking line?

It wasn’t at Brimsdown.
 

321362

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Anyone want to explain how that failure at Brimsdown managed to effect the Gospel Oak to Barking line?
The GoBLin stock is stabled at Ilford, so if everything out of Liv St was struggling then that would be difficult
 

greatkingrat

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The GoBLin stock is stabled at Ilford, so if everything out of Liv St was struggling then that would be difficult
No trains on the Gospel Oak - Barking route stable at Ilford, and the incident happened in the middle of the day, so everything would already have left the depot.
 

Annetts key

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That part commissioned as part of WARM, so 2003/4 then. Time flies.

Must be interesting getting spare parts for the 'computer' parts though. Never had a computer at home last anywhere near that long.
I know of an SSI system that has been operational for 32 years and most of it is original. Ironically some of the newest modules are the most unreliable.

Even older, there are some electronic TDM (Time Division Multiplex) communication systems the are late 1960s designs that are still in use in some places (or were three years ago).

The key is that where possible, defective units / modules / systems are repaired.

But yes, spares is a problem. And as the manufacturing lifespan of modern semiconductors keeps reducing, there comes a point where a sub-system, module etc. has to be be replaced with a new design. Or the entire system replaced.

Off topic, but there are computers that were made in the 1980s that are still work but are not in use continuously like a signalling system. It was only in 2024 that Zilog ended production of the Z80 microprocessor. The original design having been made in 1976. But many other semiconductor chips have long ago become obsolete.
 

najaB

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But yes, spares is a problem. And as the manufacturing lifespan of modern semiconductors keeps reducing, there comes a point where a sub-system, module etc. has to be be replaced with a new design. Or the entire system replaced.
One thing that's becoming increasingly common in other areas, so likely also in the railway industry, is emulating old hardware in virtual machines running on modern equipment. This can be quite challenging as sometimes they have to replicate the bugs undocumented features of that older hardware since programmers took advantage of them.
 

Annetts key

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One thing that's becoming increasingly common in other areas, so likely also in the railway industry, is emulating old hardware in virtual machines running on modern equipment. This can be quite challenging as sometimes they have to replicate the bugs undocumented features of that older hardware since programmers took advantage of them.
Yes, that is one possible work around. But in order to fully and accurately emulate an existing system, you need to know that system in a very great level of detail. And trying to do that if the original documentation is not available is time consuming, expensive and finding any problems (bugs) can be difficult. Plus as you say, there is the issue of undocumented issues. Some of which may have been happy coincidences, such as subtle timings that results in the original system working but screws up a modern recreation or emulation.

For example, some 1980s computers don't work correctly if a current production part with the same part number is fitted. Because although the logic function is the same, there are slightly different signal characteristics.
 

Class 170101

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Anyone want to explain how that failure at Brimsdown managed to effect the Gospel Oak to Barking line?

Given that both the Lea Valley and the Southbury Loop have junctions connecting them to the T&H, it’s highly plausible.

TFL reported the Gospel Oak to Barking line was suspended due to an issue at Brimsdown.
That will be the workstation name at Liverpool Street IECC which interfaces with the workstation covering the T&H route at South Tottenham.
 

najaB

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Yes, that is one possible work around. But in order to fully and accurately emulate an existing system, you need to know that system in a very great level of detail. And trying to do that if the original documentation is not available is time consuming, expensive and finding any problems (bugs) can be difficult. Plus as you say, there is the issue of undocumented issues. Some of which may have been happy coincidences, such as subtle timings that results in the original system working but screws up a modern recreation or emulation.
One way around this is by designing a VM that replicates the actual behaviour of the system as implemented rather than as designed. Basically, you hook existing hardware up to a system that allows them to send every possible combination of inputs and record the outputs and then replicate them.
 
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