Following the Bedford incident, should TPWS - or something providing an equivalent level of protection - be fitted to all remaining unfitted signals?

[Watershed]

Moderator note: Split from

Report of collision Bedford (Elstow) - 19/06/26

Hearing reports of a collision between two trains at Bedford with one train now derailed

www.railforums.co.uk

The likelihood of a signalling system error causing WH154 to display a proceed aspect always seemed incredibly remote. So as expected, this was a SPAD.

Obviously we must maintain an open mind to the circumstances but I think we can be fairly safe in saying that TPWS would have prevented the accident.

The question is whether this will provide sufficient impetus to roll out TPWS - or something providing an equivalent level of protection - to all remaining unfitted signals.

 

[Harpo]

The likelihood of a signalling system error causing WH154 to display a proceed aspect always seemed incredibly remote. So as expected, this was a SPAD.

Obviously we must maintain an open mind to the circumstances but I think we can be fairly safe in saying that TPWS would have prevented the accident.

The question is whether this will provide sufficient impetus to roll out TPWS - or something providing an equivalent level of protection - to all remaining unfitted signals.

ETCS would have determined the braking curve needed to the end of the movement authority (i.e. WH154) and would have warned if it wasn’t complied with, then intervened (brakes) if it was exceeded beyond specific levels. ETCS has to be the way forward.

 

[VP185]

Running at 76 mph after passing a single yellow in a four aspect area where you might expect 2Ys to be the braking point from linespeed.

That’s the risk which you crossover. You focus attention on the crossover speed, forget the previous signal was a single yellow and just power up once you know you’ve cleared the crossovers. That’s why TPWS should be installed at signals following a crossover.

Add to that, he’d probably done that move so many times, but never on a single yellow. Normally the fast trains would be well clear of the sections ahead.

 

[zwk500]

ETCS would have determined the braking curve needed to the end of the movement authority (i.e. WH154) and would have warned if it wasn’t complied with, then intervened (brakes) if it was exceeded beyond specific levels. ETCS has to be the way forward.

ETCS is quite a long way from being fitted to most areas though.
The question is whether this risk is high enough to justify an interim solution (noting that national rollout of TPWS was itself supposed to be an interim solution for ETCS)

 

[Signal Head]

That’s the risk which you crossover. You focus attention on the crossover speed, forget the previous signal was a single yellow and just power up once you know you’ve cleared the crossovers. That’s why TPWS should be installed at signals following a crossover.

Add to that, he’d probably done that move so many times, but never on a single yellow. Normally the fast trains would be well clear of the sections ahead.

I've had the same thought - fit TSS at signals following junctions where the aspect has been 'artificially' restricted, but where the following signal will in most cases be encountered at Green.

Similar fitments are already done at plain line signals in other circumstances, one being where there has been a change of aspect sequencing from three to four aspect and thus a driver will not have had a double-yellow, seen as an elevated SPAD risk.

 

[Harpo]

ETCS is quite a long way from being fitted to most areas though.
The question is whether this risk is high enough to justify an interim solution (noting that national rollout of TPWS was itself supposed to be an interim solution for ETCS)

But which signal gets a TPWS rack?. It only operates on a red doesn’t it? So TPWS would do nothing on the first two single yellows and at 76mph I suspect TPWS on WH154 might not have prevented a collision?

 

[Nicholas Lewis]

But which signal gets a TPWS rack?. It only operates on a red doesn’t it? So TPWS would do nothing on the first two single yellows and at 76mph I suspect TPWS on WH154 might not have prevented a collision?

It would have come close to stopping the train given that signal is c800yrds in the rear and arrested the speed considerably as its nearly 800yds in the rear. This is validated by the fact RAIB report the trains speeds being reduced by 27mph over the 9s from brake application to collision.

This is why all signals that can display a red should be fitted with TPWS train stop loops now.

 

[jfollows]

This is why all signals that can display a red should be fitted with TPWS train stop loops now.

I’m not saying I disagree, but who will pay for this? John Prescott?

 

[Nicholas Lewis]

I’m not saying I disagree, but who will pay for this? John Prescott?

ATP has been mandated after many accidents and supported by several governments. TPWS train stop loops (TSS) is an economical fix given all trains already carry the kit. The ECML project to install ETCS is already well over 1 Billion and is not yet in operational use and thats bough barely 100 route miles. Thats enough to equip c5000 signals with TSS. If nothing else a revisit of higher risk signals is now warrented.

 

[Mike395]

He means the approach control to the crossover - there may well be some learnings about approach control and the potential dual implication of a single yellow clearing onto a fast line which introduces a layer of risk.

Agree with this - there is definitely an argument that all signals immediately following crossovers in this scenario should get TPWS fitted.

 

[zwk500]

This is why all signals that can display a red should be fitted with TPWS train stop loops now.

Do you say this as a personal opinion/position or that it is now an industry standard?

 

[Watershed]

So TPWS would do nothing on the first two single yellows and at 76mph I suspect TPWS on WH154 might not have prevented a collision?

Class 360s are capable of 12%g emergency braking, i.e. around 2.6mph/s. That makes the stopping distance from 76mph around 465m. The distance from WH154 to the rear of a class 810 stood 20m before WH156 is around 1170m. So a collision would have been entirely avoided.

If the order of the trains had been the other way round, and the class 810 had been doing 125mph ,then TPWS even just at WH154 itself would have slowed the train down to 43mph - still less than the actual collision speed. Whereas an 810 that started braking 9 seconds before impact would still have been doing 100mph...

In reality, TPWS fitment would include 'overspeed' loops before WH154. Given the linespeed these would likely have been fitted the maximum 450m before the signal, thus avoiding a collision entirely as the stopping distance from 125mph is approx. 1350m.

It would have come close to stopping the train given that signal is c800yrds in the rear and arrested the speed considerably as its nearly 800yds in the rear. This is validated by the fact RAIB report the trains speeds being reduced by 27mph over the 9s from brake application to collision.

This is why all signals that can display a red should be fitted with TPWS train stop loops now.

 

[Nicholas Lewis]

Do you say this as a personal opinion/position or that it is now an industry standard?

Its a personal opinion however there remains no driver independent system to stop a train like that which the underground has used for over a 100yrs. Of course ETCS is the long term solution but thats very long term if ever affordable but TPWS provide a far more cost effective solution with faster rollout.

 

[MadMac]

That’s the risk which you crossover. You focus attention on the crossover speed, forget the previous signal was a single yellow and just power up once you know you’ve cleared the crossovers. That’s why TPWS should be installed at signals following a crossover.

Add to that, he’d probably done that move so many times, but never on a single yellow. Normally the fast trains would be well clear of the sections ahead.

Similarities to Colwich some 40 years ago: it always happens, until that one time that it doesn’t.

 

[68000]

TPWS TSS & OSS fitment at every signal to protect rear end collisions? That will cost an absolute fortune

== Doublepost prevention - post automatically merged: 24 Jun 2026 ==

It would have come close to stopping the train given that signal is c800yrds in the rear and arrested the speed considerably as its nearly 800yds in the rear. This is validated by the fact RAIB report the trains speeds being reduced by 27mph over the 9s from brake application to collision.

This is why all signals that can display a red should be fitted with TPWS train stop loops now.

You are assuming the train ahead is stopped at the signal ahead. It could be stopped anywhere in the signal section.

 

[thedbdiboy]

ETCS would have determined the braking curve needed to the end of the movement authority (i.e. WH154) and would have warned if it wasn’t complied with, then intervened (brakes) if it was exceeded beyond specific levels. ETCS has to be the way forward.

The Talerddig report covers a route with ECTS, one of the factors being that the ECTS calibration was not optimally set up for the Class 158 units when degraded braking conditions applied. So whilst a network where it is no longer possibly to 'miss' any red signal without active intervention is the obvious objective, no solution is a panacea - they all come with their own challenges.

 

[zwk500]

TPWS TSS & OSS fitment at every signal to protect rear end collisions? That will cost an absolute fortune

Although could be mitigated as @Signal Head suggests by requiring TSS & OSS fitment only at signals normally approached from routes using Approach Control/Release.

However, it is a 'when do you draw the line' question as you could argue similar risks would apply to signals protecting stations, or where the signal is not visible from a platform.

 

[68000]

Although could be mitigated as @Signal Head suggests by requiring TSS & OSS fitment only at signals normally approached from routes using Approach Control/Release.

However, it is a 'when do you draw the line' question as you could argue similar risks would apply to signals protecting stations, or where the signal is not visible from a platform.

True

 

[thedbdiboy]

TPWS TSS & OSS fitment at every signal to protect rear end collisions? That will cost an absolute fortune

== Doublepost prevention - post automatically merged: 24 Jun 2026 ==

Although could be mitigated as @Signal Head suggests by requiring TSS & OSS fitment only at signals normally approached from routes using Approach Control/Release.

However, it is a 'when do you draw the line' question as you could argue similar risks would apply to signals protecting stations, or where the signal is not visible from a platform.

Indeed, accidents of this nature often lead to a recalibration of the risk calculations, so one outcome short of fitting TPWS to every signal would be to extend the criteria, for example to include the first 'normal' signal after an approach controlled sequence

 

[Nicholas Lewis]

TPWS TSS & OSS fitment at every signal to protect rear end collisions? That will cost an absolute fortune

== Doublepost prevention - post automatically merged: 24 Jun 2026 ==

Im only proposing TSS.

You are assuming the train ahead is stopped at the signal ahead. It could be stopped anywhere in the signal section.

Yup but the probability of a train stopped mid section vs at the next signal ahead is 1000's of time less.

 

[zwk500]

Indeed, accidents of this nature often lead to a recalibration of the risk calculations, so one outcome short of fitting TPWS to every signal would be to extend the criteria, for example to include the first 'normal' signal after an approach controlled sequence

Indeed. But also it is important to wait until the RAIB have thoroughly investigated to understand whether this accident requires any changes to the risk calculations, and if so what they should be.

 

[Sorcerer]

Out of curiosity, will the rollout of ERTMS and ETCS eventually make TPWS redundant or can it simply not fulfil the same role? Even it can is the planned rollout simply too slow to not do anything in the mean time? That's the only question I have about whether it should all signals should be fitted with it.

 

[bramling]

That’s the risk which you crossover. You focus attention on the crossover speed, forget the previous signal was a single yellow and just power up once you know you’ve cleared the crossovers. That’s why TPWS should be installed at signals following a crossover.

Add to that, he’d probably done that move so many times, but never on a single yellow. Normally the fast trains would be well clear of the sections ahead.

This isn’t a total answer. Had the driver forgotten the single yellow and just powered up after the points, one would still expect there to have then be an emergency brake application at the red aspect, which - for whatever reason - didn’t happen.

That reason, or reasons, may well never be known with certainty, though no doubt there will be a range of factors explored.

Clearly TPWS would probably have prevented the accident, or very much reduced its severity, though not guaranteed if the 810 had stopped just past WH154’s overlap.

I think I’m right in saying this is the first actual accident where non-fitment of TPWS to certain signals has been a factor? Can anyone point to any others, or any known near-misses?

As things stand at the moment, there appears a somewhat unsettling similarity to Ladbroke Grove in terms of what the 360 did. Let’s hope there don’t turn out to be a massive list of contributory factors like in that accident which could have been reasonably foreseen.

 

[Harpo]

Out of curiosity, will the rollout of ERTMS and ETCS eventually make TPWS redundant or can it simply not fulfil the same role? Even it can is the planned rollout simply too slow to not do anything in the mean time? That's the only question I have about whether it should all signals should be fitted with it.

ETCS should make TPWS unnecessary as it constantly supervises unlike AWS and TPWS being intermittent.

 

[zwk500]

Out of curiosity, will the rollout of ERTMS and ETCS eventually make TPWS redundant or can it simply not fulfil the same role? Even it can is the planned rollout simply too slow to not do anything in the mean time? That's the only question I have about whether it should all signals should be fitted with it.

ERTMS/ETCS would make TPWS redundant as it covers the functionality of TPWS in a better way. The planned digital signalling rollout cannot possibly cover the entire country in one go (resources or money), nor would it be wise to do so.

Worth pointing out that there's ETCS Level 1, which is essentially just an ATP layer on conventional signalling, and ETCS level 2, which is the in-cab bit with Block Markers.
Level 1 would make TPWS redundant in covered areas, but Network Rail seem to try to be avoiding Level 1 as much as possible, presumably because it incurs significant cost in converting the interlocking but doesn't provide meaningful capacity upgrades.
Level 2 can be 'overlaid' on existing signalling (as is done on the GWML and Thameslink Core), which is usually provided when there's no plans to convert all trains to ETCS, or as an interim step to signals-away. In a L2 overlay situation, TPWS would still be required for trains not fitted with ETCS.
In a proper Level 2 situation, TPWS would be redundant (e.g. Moorgate-Drayton Park, although I've got no idea if they did recover the grids there.)

If you google 'Enhanced TPWS' you should be able to find various reports comparing the collision risk of ETCS, GW-ATP, normal TPWS and 'Enhanced TPWS' which is where it's fitted to most/all signals and potentially adding more loops at high-risk locations.

 

[bramling]

ETCS should make TPWS unnecessary as it constantly supervises unlike AWS and TPWS being intermittent.

This brings us back to the whole ATP argument though. There was some level of question as to whether TPWS should be fitted because the superior ATP system was being developed. Here we are 30 years on from when this was all a hot topic, and only a small proportion of the network has any form of ATP.

Had the view been taken on the early 2000s that we don’t need to bother with TPWS because ATP is just around the corner, who knows how many accidents would have happened that TPWS has successfully prevented.

Clearly there’s a discussion to be had about extending the scope of TPWS, though from a factual point of view we are looking at one fatality in 26 years (hoping and praying that the death toll from Friday’s accident doesn’t increase). Extending TPWS coverage will have an immense cost, and it is right to consider whether that cost can deliver better benefits if directed towards something else.

 

[zwk500]

This brings us back to the whole ATP argument though. There was some level of question as to whether TPWS should be fitted because the superior ATP system was being developed. Here we are 30 years on from when this was all a hot topic, and only a small proportion of the network has any form of ATP.

Had the view been taken on the early 2000s that we don’t need to bother with TPWS because ATP is just around the corner, who knows how many accidents would have happened that TPWS has successfully prevented.

Equally, had the view been taken in the early 2000's to focus on the ATP rollout because it provides a higher level of protection than TPWS can, we'd have prevented multiple overspeed incidents.

And potentially be a substantial way along the migration path to ETCS Level 1.

 

[HSTEd]

I'm of the view that TPWS and probably AWS should be replaced with an ETCS L1 Limited supervision installation.

Switched balises are available that would provide the same or more capabilities as the existing systems as 'drop in' replacements. Certainly for TPWS and more speculatively for AWS.

This accident combined with the over speed incidents that may have been exacerbated by the high power to weight ratios of modern stock suggests to me that simply waiting decades for ETCS L2 is not sufficient.

A drop in AWS replacement would at least be able to enforce speeds suitable for a caution signal without modifications to the main signalling system.

 

[rmHawk765]

Others have mentioned in the main thread that the GWML ATP is actually much easier to retrofit to the track than any other method. But of course, its obselence means it isn't going to be fitted anywhere else, and it would require train modifications anyway.

To me it seems ETCS Level 1/Limited Supervision is the best way to go for lines that don't necessarily need a capacity increase. ETCS L2 is easily upgraded to support moving block on running lines and so should be standard for future fitment on mainlines including the MML in my opinion (particularly to help alleviate the freight issues).

This is a political topic of course, but if you're asking who will pay, why not ask where all the government's money seems to go...

Agree with this - there is definitely an argument that all signals immediately following crossovers in this scenario should get TPWS fitted.

This is a 'halfway' solution and that's exactly why ATP wasn't installed. In my view the only acceptable option after that lesson was learned is to either fit ALL signals with TPWS, or to roll out ETCS LS nationwide.

 

[zwk500]

I'm of the view that TPWS and probably AWS should be replaced with an ETCS L1 Limited supervision installation.

The RSSB have looked at it: https://www.rssb.co.uk/research-catalogue/CatalogueItem/T1043

Not sure if the documents are available to non-registered people but the summary should be visible.

If ETCS LS mode was to be fitted alongside existing legacy systems to capitalise on the functionality of the ETCS fitted trains, it is likely that there would be an improvement in safety, but at a substantial cost, owing to the additional maintenance workload incurred by fitting a supplementary protection system.

The research therefore suggests that it is unlikely that the GB railway would benefit from the generic fitment of ETCS LS mode infrastructure on lines where the existing legacy systems are not life expired. Nor will ETCS LS mode fitment be appropriate on lines where the functionality provided by a Level 2 system offers a much greater performance enhancement, and therefore merits the much higher costs associated with ETCS Level 2.