HSTs - Are they sufficently crashworthy now, should they be withdrawn?

[bramling]

You're missing my point. How and when (and on what grounds) you determine the point at which something becomes "unacceptable"? Bearing in mind where that bar is set has quite significant implications for the economics of the railway as a whole.

I'm not disagreeing that HSTs aren't "old hat" now. But it's a balance between keeping safety risk low and recognising that stock is designed (and accounted) for a 35+ year lifespan. Some level of non-compliance with the latest safety standards is inevitable in any legacy stock - what level of non-compliance is "acceptable" - how is that determined?

Although, frankly, HSTs should possibly always have had power doors, it wasn't exactly space age technology at the time!

It perhaps doesn’t help that the rolling stock situation has gone all over the place in the last few years. So we have perfectly decent, modern, recently refurbished, crashworthy and accessible 365s potentially up for disposal having completed less than 25 years in service, whilst at the same time ancient HSTs still going.

 

[Bletchleyite]

...but they were scrapped - deemed unfit for service - even if it meant some people would have to stand or use less safe means of transport

For reasons that were (a) political and (b) more related to PRM-TSI than safety.

Look at today's news about the 800/801/802s. A problem was found and they were taken out of service (as has happened in the past with various different types of stock - the 195/331s recently, but many unit classes had periods where they were taken out of service and some safety modifications were addressed)

Discovering cracks that could cause a serious incident if they failed without warning is quite different from running older stock that isn't quite as safe but met requirements when introduced.

For instance, many houses, mine included, still have older-style wiring installations. Indeed, as a new Edition of the Regulations has recently come out, most homes will presently have "not to current spec" installations. There is no need to replace such an installation, but if it was failing in some way you certainly would. You might consider, however, some minor safety modifications such as adding an RCD if not fitted, as this provides a considerable safety benefit.

And this is in the context that domestic electrical installation failures kill far more people than trains do.

The decision about the 800/801/802s wasn't based on whether people would have to stand on other trains or whether that'd encourage more people to take bigger risks by driving - it's a simple question of "is this train safe enough" - all of your discussion over people having to stand or cars being more dangerous is just whatabouttery

Safe enough. An HST is safe enough.

I think we sometimes forget on here that we are talking about people's workplaces - they should be as safe as reasonably possible

I'd say they are, to be honest. Perhaps some minor improvements to the cab might be economically viable, though. And they are planned for replacement within 10 years or so.

Remember "reasonably".

I don't know if HSTs are "safe" (that's for the RAIB to determine), but we can't base our railway safety on the grounds of "well, it's not as safe as it could be but at least it's better than on the roads, so we'll allow it" - this shouldn't be some Lowest Common Denominator thing, where we turn a blind eye to unsafe practices on the railway because it's still safer than roads - we need to be better than that

No, we don't necessarily, as we head down the route of diminishing returns if we spend huge sums on very minor safety improvements when it could be spent on other things which will have more effect. TPWS vs. ATP was a good example of a pragmatic - and in my view the right - decision on this matter.

Agreed - I'm surprised at some of the people on here shrugging safety concerns off by trying to compare Apples with Oranges

It's not comparing apples with oranges. It's saying "we have £X of taxpayer's money, what shall we spend it on? Saving 1 life every 10 years on the railway, or saving 10 lives a year on a dangerous road junction?" - the answer to me is obvious.

Which is as it should be (rather than ignoring reasonable improvements that could be made because we imagine that railway safety is some kind of "competition" against other modes of transport)

The railway is not an island and neither is its funding. If the railway was profitable within itself I would agree, but it's not. It competes for public funding with other things which are a much more pressing safety improvement need.

If you want to get an 80x order in now (which will only get you the HSTs replaced perhaps 5-6 years earlier than planned) that's going to cost some more subsidy. It is fairly likely, given the rarity of railway accidents, that it will save precisely 0 lives. Good value?

I'd expect that old stock still needed to meet some minimum standards (in terms of safety, emissions, accessibility etc) - it doesn't have to be the same as brand new stock but standards improve - what was acceptable in the past (sticking your head out of the window so you could reach the door handle, toilets that aren't accessible) becomes unacceptable in the future - there should be a period of grace in which we can decide whether to upgrade the old stuff or scrap it

That much is true.

Although, frankly, HSTs should possibly always have had power doors, it wasn't exactly space age technology at the time!

Because in line with Forum rules they have to be brought into any discussion, the Mk3 coach (LH and HST) should have been what the 442 vehicles were. Power doors, better (and safer*) seating, better lighting, no banging vestibule doors. Minor changes yet so much better.

Slam doors were a foolish choice - or at least if they were going for slam doors, they should have been UIC-type folding doors with autoclosers and locking.

* IC70s apparently have a habit, in a collision, of breaking up into large pointy bits of plastic.

 

[GlitterUnicorn]

It perhaps doesn’t help that the rolling stock situation has gone all over the place in the last few years. So we have perfectly decent, modern, recently refurbished, crashworthy and accessible 365s potentially up for disposal having completed less than 25 years in service, whilst at the same time ancient HSTs still going.

Perhaps as with the disabled accessibility regulations, there should be binding rules that stock in regular TOC service after a set date has to comply with certain safety standards or have certain features. That way older generations of stock that don't meet the standards can be phased out or upgraded. Obviously this would have to be done taking into account the practicality of these measures.

 

[Bletchleyite]

Perhaps as with the disabled accessibility regulations, there should be binding rules that stock in regular TOC service after a set date has to comply with certain safety standards or have certain features. That way older generations of stock that don't meet the standards can be phased out or upgraded. Obviously this would have to be done taking into account the practicality of these measures.

That doesn't sound unreasonable. However, it would be necessary to allow for reasonable replacement timescales, which with the HST means that you're not realistically going to be able to move replacement much earlier than the presently-planned 10 years. You might get them 5 years earlier, I suppose, but is that worth the rush and additional cost to save probably 0 lives?

If there wasn't already a reasonably short (in railway terms) replacement plan, then I think I'd be inclined to say one should be sorted out - but there is one.

 

[Ianno87]

It perhaps doesn’t help that the rolling stock situation has gone all over the place in the last few years. So we have perfectly decent, modern, recently refurbished, crashworthy and accessible 365s potentially up for disposal having completed less than 25 years in service, whilst at the same time ancient HSTs still going.

That's another example - 365s are less crashworthy than 387s/700s (GTR even said so when 387s were introduced - I recall from a news article.when they were explaining the slight reduction in seats per unit). But:

A) How much less?
B) Is that enough less to be "unacceptable"? Who decides and how?

(Leaving aside for now the 365s would probably be going for years if Covid had never happened)

 

[Bletchleyite]

That's another example - 365s are less crashworthy than 387s/700s (GTR even said so when 387s were introduced - I recall from a news article.when they were explaining the slight reduction in seats per unit). But:

A) How much less?
B) Is that enough less to be "unacceptable"? Who decides and how?

(Leaving aside for now the 365s would probably be going for years if Covid had never happened)

I'm not a driver. But if I was I'd rather be driving an HST (which at least has a hefty underframe even if the upper cab is fibreglass, and you sit a fair way back from the end) than a 150, 153, 156 or 158, personally. Wouldn't take much to completely stove one of those in, and indeed I've seen photos of a smashed-up 156 which in an end on collision barely did any better than that Pacer did.

And as a passenger I'm happy to travel in any rolling stock currently in operation on the railway, including Mk1s and Mk2s on a railtour, because the primary safety system - preventing trains hitting other trains - is pretty good these days. I do not expect that at any point in my life I will be in a train that hits another train, or indeed anything similarly hefty (though I have been on one, sadly, that hit a person who jumped in front of it).

Cycling to the station is many orders of magnitude more dangerous.

 

[GlitterUnicorn]

That doesn't sound unreasonable. However, it would be necessary to allow for reasonable replacement timescales, which with the HST means that you're not realistically going to be able to move replacement much earlier than the presently-planned 10 years. You might get them 5 years earlier, I suppose, but is that worth the rush and additional cost to save probably 0 lives?

If there wasn't already a reasonably short (in railway terms) replacement plan, then I think I'd be inclined to say one should be sorted out - but there is one.

I suppose in this case it's a moot point, though if it had been in place before it could well have prevented refurb HSTs being introduced as a new fleet for Scotrail.

 

[Bletchleyite]

I suppose in this case it's a moot point, though if it had been in place before it could well have prevented refurb HSTs being introduced as a new fleet for Scotrail.

Yes, true, and to be fair I would have favoured ScotRail getting 80x (or FLIRTs) instead myself, not specifically because they are safer, but because they aren't old junk, and because having bi-modes would have provided well for a progressive electrification programme without the need for changes to the service pattern, just as they have on GWR.

 

[GlitterUnicorn]

Yes, true, and to be fair I would have favoured ScotRail getting 80x (or FLIRTs) instead myself, not specifically because they are safer, but because they aren't old junk, and because having bi-modes would have provided well for a progressive electrification programme without the need for changes to the service pattern, just as they have on GWR.

I agree entirely. There are a lot of reasons why the HSTs were a bad idea and safety is by no means the greatest of these. My anger at the safety side is more related to it being basically an unintended consequence of what is essentially a ScotGov money saving scheme.

 

[fishwomp]

You believe wrong then. It's the bodyshell.

Apparently so. Was going on the R4 interview with r'Roger.

 

[edwin_m]

Fair point. Perhaps old-stock-on-new routes should be considered to need to comply to full standards, where old use is significantly changed. Or at least risk-assessed.

The operating regime of the HSTs is now much lower-risk than it was a couple of years ago. Most of them are running at lower speeds and in shorter formations, reducing the energy to be dissipated in any accident.

 

[bramling]

That's another example - 365s are less crashworthy than 387s/700s (GTR even said so when 387s were introduced - I recall from a news article.when they were explaining the slight reduction in seats per unit). But:

A) How much less?
B) Is that enough less to be "unacceptable"? Who decides and how?

(Leaving aside for now the 365s would probably be going for years if Covid had never happened)

I'd say the answer depends on whether we're talking about a specific design issue (perhaps even a flaw) versus simply being overtaken by incremental improvements in crashworthiness.

One could argue Mk1s had a flawed design with their separate underframes. Likewise one could argue HST power cars have a weak superstructure around the driver's cab. Both these issues essentially existed from day one. By contrast there doesn't appear to be anything fundamentally wrong with something like a Networker, just that it's probably not quite as good as an Electrostar (though, of course, fortunately the bolted construction hasn't been tested in a real-life accident).

 

[Annetts key]

I'd venture that a landslip (as happened here, I think?) may well now be the most likely thing for a train to crash into (because we've got quite good at preventing trains crashing into other trains), or on some lines a large, heavy vehicle on a level crossing, and that might well bring its own design considerations.

I disagree. All we have done in this regard (train vs. train) is to deal with the low hanging fruit. To try to reduce the likelihood of collisions at junctions. The vast majority of signals are not fitted with TPWS. So if a train is stopped at a station on plain line, or a train stops due to a failure or other reason, and the driver of the next train on that line fails to obey the signals, a crash is just as likely as 24 years ago (unless it’s an ATP fitted train on an ATP fitted line).

 

[najaB]

The vast majority of signals are not fitted with TPWS. So if a train is stopped at a station on plain line, or a train stops due to a failure or other reason, and the driver of the next train on that line fails to obey the signals, a crash is just as likely as 24 years ago (unless it’s an ATP fitted train on an ATP fitted line).

AWS will stop the train in time in the vast majority of cases. There will always be edge cases.

 

[yorksrob]

...but they were scrapped - deemed unfit for service - even if it meant some people would have to stand or use less safe means of transport







You may not like it, but this is the reality of the situation.

Look at today's news about the 800/801/802s. A problem was found and they were taken out of service (as has happened in the past with various different types of stock - the 195/331s recently, but many unit classes had periods where they were taken out of service and some safety modifications were addressed)

The decision about the 800/801/802s wasn't based on whether people would have to stand on other trains or whether that'd encourage more people to take bigger risks by driving - it's a simple question of "is this train safe enough" - all of your discussion over people having to stand or cars being more dangerous is just whatabouttery

I think we sometimes forget on here that we are talking about people's workplaces - they should be as safe as reasonably possible



Its like slam door stock IMHO - that was deemed "safe" when HSTs were being built but standards changed - they became seen as too dangerous - we then had to decide whether to introduce power doors or scrap them

That's how all stock should be - we can't allow people to keep sticking their heads out of windows just because it was acceptable once upon a time



I don't know if HSTs are "safe" (that's for the RAIB to determine), but we can't base our railway safety on the grounds of "well, it's not as safe as it could be but at least it's better than on the roads, so we'll allow it" - this shouldn't be some Lowest Common Denominator thing, where we turn a blind eye to unsafe practices on the railway because it's still safer than roads - we need to be better than that



Agreed - I'm surprised at some of the people on here shrugging safety concerns off by trying to compare Apples with Oranges



Which is as it should be (rather than ignoring reasonable improvements that could be made because we imagine that railway safety is some kind of "competition" against other modes of transport)



I'd expect that old stock still needed to meet some minimum standards (in terms of safety, emissions, accessibility etc) - it doesn't have to be the same as brand new stock but standards improve - what was acceptable in the past (sticking your head out of the window so you could reach the door handle, toilets that aren't accessible) becomes unacceptable in the future - there should be a period of grace in which we can decide whether to upgrade the old stuff or scrap it

At the heart of it though, the idea that comparing the safety of different modes of transport is "comparing apples and oranges" is emotional claptrap.

If turfing people off one form of transport because of "safety" results in them being shifted onto one where they are at greater risk of harm, then this should logically be considered in in terms of benefit/disbenefit..

 

[Class465pacer]

HSTs and especially cabs are pretty old and should be replaced but I’m even more concerned about the DVT cab. Disintegrated in Great Heck

 

[43096]

I’m even more concerned about the DVT cab. Disintegrated in Great Heck

It's not exactly surprising considering that it was in a 140mph collision. Rather difficult to design something that would survive that.

 

[Annetts key]

The simple TPWS interfaces both onboard the trains and with the trackside signalling not only reduced the cost significantly compared to any available full supervision ATP system of the time, but also allowed network-wide fitment at the highest risk junction locations in an extraordinarily short timescale, hence delivering the safety improvement much more quickly. ATP could easily have taken 3 or 4 times as long to roll out.

TPWS ties into the existing signalling system such that quite a lot of wiring changes are needed. The signal control circuitry needs changing. New equipment cupboards, new multicore lineside cables if the interlocking relays are not in the existing location cupboard for the signal. Alterations to the indication circuits that provide the signallers indications. And all this requires lots of installers and testing staff.

Whereas the Great Western Main Line (GWML) ATP system just needs the cable links in the feed to the signal head replacing with current transformers. Plus a power feed, a new (separate) cupboard, and a beacon (loop). A lot less staff are needed So actually GWML ATP is far quicker and easier to install. I don’t know about equipment costs though.

The real difference, is that you can’t just spot fit the occasional or odd signal with ATP. You need to do at least four or five signals on the approach to a junction signal. Unlike TPWS where you only normally fit the junction signal and maybe the signal in rear.

The other difference is that the in cab/on train fitment of TPWS was supposed to be quick and cheap. Remove some of the existing AWS equipment and replace with combined AWS & TPWS equipment. But because around 50% of the existing cabs were found to have a problem with the existing AWS equipment, a lot more work has to be done.

In comparison, to be fitted with ATP, a cab/loco/DNU had to taken out of service for a lot longer and required far more work.

However, if BR had been allowed to choose which ATP to use as standard after the two trial ATP installations had run for their original time frame. ATP would have been specified to have been fitted in all new trains. This is the most cost effective way of bringing in a new safety system. And we have had rather a lot of new trains since then.

Similarly, ATP would have become a requirement for any new signalling schemes or where major or significant changes were to be carried out to existing signalling systems. Again, this is the most cost effective way of doing it.

Would the roll out for ATP have been slower? I don’t know for certain, but most likely yes. Especially as the roll out of TPWS was made a very high priority.

But if BR had been allowed to choose back in the early to mid 1990s, the Southall crash and maybe Ladbroke Grove crash would not have occurred.

 

[43096]

TPWS ties into the existing signalling system such that quite a lot of wiring changes are needed. The signal control circuitry needs changing. New equipment cupboards, new multicore lineside cables if the interlocking relays are not in the existing location cupboard for the signal. Alterations to the indication circuits that provide the signallers indications. And all this requires lots of installers and testing staff.

Whereas the Great Western Main Line (GWML) ATP system just needs the cable links in the feed to the signal head replacing with current transformers. Plus a power feed, a new (separate) cupboard, and a beacon (loop). A lot less staff are needed So actually GWML ATP is far quicker and easier to install. I don’t know about equipment costs though.

The real difference, is that you can’t just spot fit the occasional or odd signal with ATP. You need to do at least four or five signals on the approach to a junction signal. Unlike TPWS where you only normally fit the junction signal and maybe the signal in rear.

The other difference is that the in cab/on train fitment of TPWS was supposed to be quick and cheap. Remove some of the existing AWS equipment and replace with combined AWS & TPWS equipment. But because around 50% of the existing cabs were found to have a problem with the existing AWS equipment, a lot more work has to be done.

In comparison, to be fitted with ATP, a cab/loco/DNU had to taken out of service for a lot longer and required far more work.

However, if BR had been allowed to choose which ATP to use as standard after the two trial ATP installations had run for their original time frame. ATP would have been specified to have been fitted in all new trains. This is the most cost effective way of bringing in a new safety system. And we have had rather a lot of new trains since then.

Similarly, ATP would have become a requirement for any new signalling schemes or where major or significant changes were to be carried out to existing signalling systems. Again, this is the most cost effective way of doing it.

Would the roll out for ATP have been slower? I don’t know for certain, but most likely yes. Especially as the roll out of TPWS was made a very high priority.

But if BR had been allowed to choose back in the early to mid 1990s, the Southall crash and maybe Ladbroke Grove crash would not have occurred.

Southall was all about the culture of the railway in running with safety systems isolated or staff not trained on them. Both track and train were ATP fitted.

 

[coppercapped]

I apologise for the flippancy of my remark.

I am simply saying that these vehicles are far from modern safety standards and as a driver you should be entitled to feel safe when doing your job. Clearly at least one does not.

I am purely an interested layman here. If anyone disagrees with any of my views I completely respect that.

Accepted.

The point I am trying to make is that the kinetic energy present in a train at any speed greater than about 50 to 60mph vastly exceeds the ability of any crumple zone in the nose of the train to absorb it. This is independent of the age of the train. The driver has to rely on others, track maintenance, signalling and so on, to keep him or her safe.

If a higher level of safety is required for the driver then the best bet would be to install high definition cameras at the front of the train and position the driver in a place where he or she cannot be involved in an accident and drive the train under remote control. I am being serious — the USAF drone pilots carrying out raids in Iraq and Afghanistan sit in offices in the US so the technology exists.

 

[Dai Corner]

Accepted.

The point I am trying to make is that the kinetic energy present in a train at any speed greater than about 50 to 60mph vastly exceeds the ability of any crumple zone in the nose of the train to absorb it. This is independent of the age of the train. The driver has to rely on others, track maintenance, signalling and so on, to keep him or her safe.

If a higher level of safety is required for the driver then the best bet would be to install high definition cameras at the front of the train and position the driver in a place where he or she cannot be involved in an accident and drive the train under remote control. I am being serious — the USAF drone pilots carrying out raids in Iraq and Afghanistan sit in offices in the US so the technology exists.

Or even let the signalling and train control systems talk to each other directly and do away with the biological interface.

 

[najaB]

Or even let the signalling and train control systems talk to each other directly and do away with the biological interface.

Oi, you! Take your driverless trains talk to a different thread.

 

[Dai Corner]

Oi, you! Take your driverless trains talk to a different thread.

Point taken. Apologies for going off topic.

 

[edwin_m]

TPWS ties into the existing signalling system such that quite a lot of wiring changes are needed. The signal control circuitry needs changing. New equipment cupboards, new multicore lineside cables if the interlocking relays are not in the existing location cupboard for the signal. Alterations to the indication circuits that provide the signallers indications. And all this requires lots of installers and testing staff.

Whereas the Great Western Main Line (GWML) ATP system just needs the cable links in the feed to the signal head replacing with current transformers. Plus a power feed, a new (separate) cupboard, and a beacon (loop). A lot less staff are needed So actually GWML ATP is far quicker and easier to install. I don’t know about equipment costs though.

The real difference, is that you can’t just spot fit the occasional or odd signal with ATP. You need to do at least four or five signals on the approach to a junction signal. Unlike TPWS where you only normally fit the junction signal and maybe the signal in rear.

The other difference is that the in cab/on train fitment of TPWS was supposed to be quick and cheap. Remove some of the existing AWS equipment and replace with combined AWS & TPWS equipment. But because around 50% of the existing cabs were found to have a problem with the existing AWS equipment, a lot more work has to be done.

In comparison, to be fitted with ATP, a cab/loco/DNU had to taken out of service for a lot longer and required far more work.

However, if BR had been allowed to choose which ATP to use as standard after the two trial ATP installations had run for their original time frame. ATP would have been specified to have been fitted in all new trains. This is the most cost effective way of bringing in a new safety system. And we have had rather a lot of new trains since then.

Similarly, ATP would have become a requirement for any new signalling schemes or where major or significant changes were to be carried out to existing signalling systems. Again, this is the most cost effective way of doing it.

Would the roll out for ATP have been slower? I don’t know for certain, but most likely yes. Especially as the roll out of TPWS was made a very high priority.

But if BR had been allowed to choose back in the early to mid 1990s, the Southall crash and maybe Ladbroke Grove crash would not have occurred.

BR and the nascent Railtrack did consider what should be installed in the early to mid 1990s - I was the humble minute-taker for one of the committees involved.

It was clear a full ATP system was unaffordable and unjustifiable on safety grounds, and TPWS was developed as a way to get most of the benefits of ATP at far less cost and also much quicker and easier installation. Knowledgeable people from both the rolling stock and the signalling sides were involved in this process - though at the time it was not intended to detect TPWS operation via the lamp proving circuit, which would have made it much simpler to install. The same committee came up with the Drive Reminder Appliance, which was predicted to pay for itself financially in reduced rolling stock damage, as long as everybody used it properly.

And I repeat my point that if ATP had been widely fitted in the 90s, we would now have had the headache of supporting an obsolescent system across the whole network, not just on two routes.

 

[Annetts key]

A question I have asked before.... what was the last fatal accident that could only have been prevented by ATP i.e. AWS/TPWS would have been ineffective?

That depends on how you categorise AWS/TPWS as being ineffective. And thank goodness, we don’t have many crashes with fatalities. So we don’t actually have much data.
The problem with AWS is threefold:
* the on train equipment is not fail safe, it’s not designed to bring the train to a halt in the event of the system failing, or detect when an input from the track side equipment has not been received.
* there is no distinction between a unlit (black) signal, a signal showing red, a signal showing yellow, a signal showing double yellow or a ESR/TSR speed restriction or advance warning board.
* the driver is able to cancel the warning, which is not normally a problem, but if the driver is not paying enough attention, it has been occasionally known for a driver to not respond to a yellow aspect, then when the next signal comes into view (which is showing a red aspect), find that they can’t stop the train before running past the red signal (one possible reason for a SPAD).
* we know that a faulty signal AWS (track mounted equipment) can go for days before a driver actually reports it, once one AWS was found to have been faulty for over ten years before the problem was discovered.
* we also know that in the past (I don’t have the data for the current situation) the train equipment has been unreliable
* not all signals are provided with AWS.

Nobody knows how many times a fully working AWS has prevented any incidents becoming accidents or crashes. AWS and it’s GWR version (ATC, but no relation to the modern meaning/system) has been in existence for a long, long time now.

TPWS also has problems:
* it’s not fitted to every signal, normally it’s only fitted to signals where there is a possible point of conflict ahead, such as on signals protecting junctions or level crossings.
* the standard installation only is officially effective for speeds up to 75MPH.
* for higher line speeds, to provide better protection, an additional installation is required, called TPWS+. This is just another TPWS installation, but fitted further away from the signal. This extends the effective protection up to speeds of 100MPH.
* not all signals with TPWS have TPWS+ fitted.
* TPWS (and TPWS+) are also not fail safe systems, the on train equipment is not designed to bring the train to a halt in the event of the system failing, or detect when an input from the track side equipment has not been received.
* the track mounted equipment and the control equipment in the lineside equipment cupboard is not fully fail safe, it can detect some failure modes and this results in the signal in rear (the previous signal) being returned and held at red, but it is a ‘dumb’ system in that it has no way of knowing if the trains are receiving its radio signal
* the on train equipment offers no protection if there is a fault with the track mounted equipment or the signal is not fitted.
* the track mounted equipment and the control equipment in the lineside equipment cupboard is less reliable than what you would expect for equipment of its age.
* it can restrict how a driver can drive their train, there are still plenty of nuisance trips where the train is travelling at less than the line speed, at a safe speed, but above the TPWS trip speed, causing it to activate and bring the train to a halt.

The Southall crash could have been prevented if any of these had been working: AWS, TPWS, ATP. The train was fitted with ATP but the TOC had many HSTs running with it isolated, including the HST that SPAD the signal.

However, AWS has not stopped the large number of SPADs that have occurred over the years. We have no idea how close to disaster the railway has come or how many near misses there have been.

The Ladbroke Grove crash illustrates what happens when AWS is not effective. Either TPWS or ATP would have prevented this crash.

But there are some important differences between TPWS and ATP. The very basic TPWS system is designed to apply the brakes AFTER the train has passed the red signal. Where the distance to the point of conflict (normally the points at the junction ahead) is too short for the brakes of a typical train to bring it to a halt just prior to the point of conflict, an extra item of TPWS equipment is fitted. This activates the train brakes on the approach to the red signal {not to be confused with TPWS+} so that there is just enough distance to stop the train just short of the point of conflict, but AFTER the red signal.

ATP does things rather differently. The objective with ATP is to prevent a train from ever (*) passing a signal at red. * apart from at a very slow speed or if the system is isolated, also ATP sometimes gets the distance travelled by the train wrong due to wheel slip/slide, so may get the actual location of the signal slightly wrong.

ATP monitors the speed of the train and continuously monitors the distance to the target. The target being the limit of the trains authority to proceed. So if you are approaching a signal showing a yellow aspect, the target is the red signal after the the yellow signal. If the driver does not control the speed of the train so that it is within the braking curve calculated by the ATP computers (so as to stop before the red signal), it will apply the brakes and bring the train to a halt.

ATP also enforces all permanent speed restrictions, all junction speed restrictions, all temporary speed restrictions and after it has been updated (*), any emergency speed restrictions. * - for an emergency speed, we have to wait for the restriction details to be supplied before the ATP can be adjusted, more details than just the speed are needed, as distance information is also required.

Because the intention is for all main signals to be fitted on a line, ATP provides protection throughout the trains journey while on a ATP fitted line, not just at where a point of conflict has been identified ar some time in the past.

ATP was proved to be very effective at every test thrown at it during the BR trials. The Great Western Main Line (GWML) system surprised many when a test train (a ECS HST) was found to stop from 125MPH in a distance a lot shorter that they expected during the tests to see what would happen if a signal went to red in front of a ATP fitted train.

So, there is no easy answer, but...
ATP would have prevented nearly all (if not all) of the crashes caused by drivers failing to control their trains where they either ended up passing a signal at red, or were travelling too fast for the speed of the line or junction.

TPWS is the next best, it would have prevented some crashes caused by a driver passing a red signal, and reduced the speed at the point of impact at some others where a driver passed a red signal. But it’s not as effective on high speed lines, and is totally ineffective if the signal is not fitted with TPWS. It is spot fitted to the infrastructure at some advance speed restriction signs, but does not continuously enforce any speed restriction or limit.

AWS is only effective if the driver takes full notice of it and it’s working.

Note that in the book Red for Danger, there is I think a couple of crashes due to drivers failing to stop at a signal at danger on plain line, and hence crashing into the back of a earlier train that has stopped. Of course, now we have much better colour light signals, and there has not been a crash like this in recent history. But this is the type of crash that could be nasty, which TPWS would not prevent (as currently fitted), but ATP definitely would prevent (if fitted).

A bit of speculation on my part, but at Ladbroke Grove it would have in theory stopped the Turbo within the signal overlap after it Spadded SN109.

At Southall (much higher speed approach), TPWS would have at least reduced the severity of the accident by intervening on the speed sooner than the driver did (I think - happy to be shot down by an actual TPWS expert on this)

ATP would have stopped both crashes, the trains would have been stopped before the red signal or well within the overlap.

TPWS most likely would have stopped the Turbo short of the points. For Southall, I would need to reread the accident details. TPWS+ would have done better than standard TPWS though.

At Ladbroke Grove the distance from SN109 to the convergence of the tracks was enough for a TPWS brake application to stop the train safely if both had been TPWS-fitted, as they would have been under the later programme.

Southall would have been prevented by a working AWS (very likely) or a working ATP (certainly) or a working TPWS (almost certainly if fitted). I suppose you can argue that if TPWS had been fitted it might not have been working either, given the attitude to train protection systems at the time. But it would be a stretch to say that Southall was ATP-preventable without also agreeing that it would have been prevented by AWS or TPWS under the same assumptions.

If, and it’s a big if, the ATP was no longer classed as a pilot/trial system, but as a essential safety system, then the TOC should have been maintaining it properly (the track and lineside equipment was being maintained properly) and for it to be in use rather than many HSTs having it isolated.

It was shocking learning that the train AWS equipment was often not operational, or often had faults and defects. Again, the track and lineside equipment was being maintained properly.

The closest "near-miss" I believe we've had (in terms of a SPAD that could have been a very serious accident has circumstances been slightly different) was the Wootton Basset SPAD - which only happened as severely as it did because the AWS (and as a consequence TPWS) had been isolated.

One thing to note though, is that there are rather too many incidents that are not in the public domain. For example, two trains ending up in a signal section because a driver saw the points ahead of him move shortly after a train passed over them. Said driver then moved his train forward and proceeded on to the main line. The signaller was about to report a wrong side failure of the track circuit (because it had gone clear) before realising what was actually happening. Later on the driver when asked, said he had a yellow at the signal. But that signal had no lamp in the yellow aspect, and had a black painted blanking plate instead of a glass lens, because it was not in use. The signal only needing to be a two aspect red/green.

AWS will stop the train in time in the vast majority of cases. There will always be edge cases.

AWS is useless if the signal is not fitted, the AWS on the train is faulty or isolated, or the train has already traveled over the AWS track mounted magnets (platform starter signals, or any other starting from having been stopped at a signal situation), or if the driver fails to react to the signal aspect.

At a junction near Bath, a driver had another two drivers in the cab because they were route learning. Because the driver in control got distracted discussing the speed restrictions, he missed the signal that was showing a yellow aspect. The AWS was working, it was acknowledged. The sighting of the signal protecting the junction is not very good, so by the time he saw it, it was far too late to stop his train. Hence it was passed at danger. Lucky for everyone, this did not result in a crash. But it could have been a lot worse as the junction ahead is a high speed junction.

How many other ‘near-misses’ happen?

Southall was all about the culture of the railway in running with safety systems isolated or staff not trained on them. Both track and train were ATP fitted.

Yes, but why just concentrate on the TOC. The whole system fails to remember the reasons why if it’s inconvenient to the powers that be or individuals at the time.

We appear to go though cycles. An accident happens. Everyone takes notice. Over time the memory fades, then a different accident happens. Years later an accident that should have been prevented because lessons were learnt, happens. Because the why got forgotten and hence system/procedures were not maintained because they were not perceived to be important enough or were inconvenient for some reason/excuse.

ATP significantly reduces the element of human error more than AWS or TPWS does.

It’s like comparing the safety of a 747 passenger jet with one from the 1940s.

Of course technology has moved on, and it would be foolish to fit an obsolete ATP system now. ERTMS (level 1, or level 2) should be widespread on the Network Rail Infrastructure, but it’s not.

At the very least, ERTMS should have been fitted as Network Rail was busy replacing conventional signal boxes and power signal boxes/Panels with ROCs. But no.

BR and the nascent Railtrack did consider what should be installed in the early to mid 1990s - I was the humble minute-taker for one of the committees involved.

It was clear a full ATP system was unaffordable and unjustifiable on safety grounds, and TPWS was developed as a way to get most of the benefits of ATP at far less cost and also much quicker and easier installation. Knowledgeable people from both the rolling stock and the signalling sides were involved in this process - though at the time it was not intended to detect TPWS operation via the lamp proving circuit, which would have made it much simpler to install. The same committee came up with the Drive Reminder Appliance, which was predicted to pay for itself financially in reduced rolling stock damage, as long as everybody used it properly.

And I repeat my point that if ATP had been widely fitted in the 90s, we would now have had the headache of supporting an obsolescent system across the whole network, not just on two routes.

I’m not saying that every single signal should have been fitted with ATP. And I am not saying that ATP fitment should have been a big expensive program on it’s own. I’m saying that provision should have been made for all new rolling stock to either have been fitted with ATP equipment or be designed with provision for retro fitment of ATP (or an equivalent system, such as ERTMS) to be easy to install.

And that for new signalling schemes, ATP to be provided as part of the scheme or provision to be made to enable ATP (or equivalent) to be fitted easily as soon as the rolling stock was available with ATP (or equivalent).

TPWS is a bespoke system where the U.K. railway is tied to a single supplier. Please name which other countries use it.

I agree that the existing ATP systems are old, and will become increasingly difficult to keep operational. But if it had been fitted across the network rather than two different systems on two different areas, demand for replacement equipment and parts may have made it worthwhile for companies to continue to manufacture spares.

As I said above, now, today, ATP is no longer the answer. But TPWS is not really suitable for a modern high speed railway either. TPWS is in my humble opinion, a not very cheap stop-gap.

 

[HSTEd]

TPWS is a bespoke system where the U.K. railway is tied to a single supplier. Please name which other countries use it.

Parts of Australia!

But the point is well made regardless

 

[XAM2175]

Parts of Australia!

Actually only one part, and even then only because it was considered preferable to fitting trip-stops to the regional fleet. I also believe it's sourced from the same UK supplier, so the use in Victoria creates no additional diversity in the supply chain.

 

[najaB]

As I said above, now, today, ATP is no longer the answer. But TPWS is not really suitable for a modern high speed railway either. TPWS is in my humble opinion, a not very cheap stop-gap.

Well, I guess that would make ATP an expensive stop-gap.

 

[edwin_m]

That depends on how you categorise AWS/TPWS as being ineffective. And thank goodness, we don’t have many crashes with fatalities. So we don’t actually have much data.
The problem with AWS is threefold:
* the on train equipment is not fail safe, it’s not designed to bring the train to a halt in the event of the system failing, or detect when an input from the track side equipment has not been received.
* there is no distinction between a unlit (black) signal, a signal showing red, a signal showing yellow, a signal showing double yellow or a ESR/TSR speed restriction or advance warning board.
* the driver is able to cancel the warning, which is not normally a problem, but if the driver is not paying enough attention, it has been occasionally known for a driver to not respond to a yellow aspect, then when the next signal comes into view (which is showing a red aspect), find that they can’t stop the train before running past the red signal (one possible reason for a SPAD).
* we know that a faulty signal AWS (track mounted equipment) can go for days before a driver actually reports it, once one AWS was found to have been faulty for over ten years before the problem was discovered.
* we also know that in the past (I don’t have the data for the current situation) the train equipment has been unreliable
* not all signals are provided with AWS.

Nobody knows how many times a fully working AWS has prevented any incidents becoming accidents or crashes. AWS and it’s GWR version (ATC, but no relation to the modern meaning/system) has been in existence for a long, long time now.

TPWS also has problems:
* it’s not fitted to every signal, normally it’s only fitted to signals where there is a possible point of conflict ahead, such as on signals protecting junctions or level crossings.
* the standard installation only is officially effective for speeds up to 75MPH.
* for higher line speeds, to provide better protection, an additional installation is required, called TPWS+. This is just another TPWS installation, but fitted further away from the signal. This extends the effective protection up to speeds of 100MPH.
* not all signals with TPWS have TPWS+ fitted.
* TPWS (and TPWS+) are also not fail safe systems, the on train equipment is not designed to bring the train to a halt in the event of the system failing, or detect when an input from the track side equipment has not been received.
* the track mounted equipment and the control equipment in the lineside equipment cupboard is not fully fail safe, it can detect some failure modes and this results in the signal in rear (the previous signal) being returned and held at red, but it is a ‘dumb’ system in that it has no way of knowing if the trains are receiving its radio signal
* the on train equipment offers no protection if there is a fault with the track mounted equipment or the signal is not fitted.
* the track mounted equipment and the control equipment in the lineside equipment cupboard is less reliable than what you would expect for equipment of its age.
* it can restrict how a driver can drive their train, there are still plenty of nuisance trips where the train is travelling at less than the line speed, at a safe speed, but above the TPWS trip speed, causing it to activate and bring the train to a halt.

These can broadly be classified as system integrity issues - you can't always rely on the system to fail in a safe way. This point was well understood in the discussions I was involved in back in the 1990s, but the counter is that drivers succeed in obeying signals in the huge majority of cases, so an accident only results if the system also fails to protect when the driver fails to stop. The chances of both these events at the same time are tiny, as long as "latent" failure modes are addressed - these are failures that aren't detected until the system is called on to do its job in an emergency. This may be one reason the TPWS was brought into the lamp proving circuit, but I don't know about that as I was no longer involved by that time.

ATP does things rather differently. The objective with ATP is to prevent a train from ever (*) passing a signal at red. * apart from at a very slow speed or if the system is isolated, also ATP sometimes gets the distance travelled by the train wrong due to wheel slip/slide, so may get the actual location of the signal slightly wrong.

ATP also has a "release speed" which allows a driver to start accelerating if the signal clears on approach but the system hasn't yet been updated by passing over a balise. The train will pass the signal if the driver approaches it at red at or below the release speed, but it is calculated so the train can stop within the overlap. This is similar to TPWS which aims to stop the train before any position of possible sidelong or head-on collision.

ATP would have prevented nearly all (if not all) of the crashes caused by drivers failing to control their trains where they either ended up passing a signal at red, or were travelling too fast for the speed of the line or junction.

TPWS is the next best, it would have prevented some crashes caused by a driver passing a red signal, and reduced the speed at the point of impact at some others where a driver passed a red signal. But it’s not as effective on high speed lines, and is totally ineffective if the signal is not fitted with TPWS. It is spot fitted to the infrastructure at some advance speed restriction signs, but does not continuously enforce any speed restriction or limit.

The programme I referred to was known as SPAD Reduction and Mitigation (SPADRAM). Part of the change in emphasis relative to ATP was to realise that the SPAD itself isn't the problem, there is only a risk of harm if the SPAD continues beyond a safe distance. The same applies to overspeeds as most restrictions can be passed at somewhat over posted speed with no major hazard. Another change was trying to address most of the risk rather than doing a lot more in an attempt to address all of it. As I say this was very well understood by the people round the table at the time. TPWS may also reduce the collision speed in accidents that it can't totally mitigate. Basing the analysis on casualties rather than accidents, "some" above for TPWS is about 80% of what it would be with ATP, remembering that some crashes aren't ATP-preventable either. That includes Hatfield, Ufton Nervet, Potters Bar, Great Heck and Carmont.

Of course technology has moved on, and it would be foolish to fit an obsolete ATP system now. ERTMS (level 1, or level 2) should be widespread on the Network Rail Infrastructure, but it’s not.

At the very least, ERTMS should have been fitted as Network Rail was busy replacing conventional signal boxes and power signal boxes/Panels with ROCs. But no.


I’m not saying that every single signal should have been fitted with ATP. And I am not saying that ATP fitment should have been a big expensive program on it’s own. I’m saying that provision should have been made for all new rolling stock to either have been fitted with ATP equipment or be designed with provision for retro fitment of ATP (or an equivalent system, such as ERTMS) to be easy to install.

And that for new signalling schemes, ATP to be provided as part of the scheme or provision to be made to enable ATP (or equivalent) to be fitted easily as soon as the rolling stock was available with ATP (or equivalent).

TPWS is a bespoke system where the U.K. railway is tied to a single supplier. Please name which other countries use it.

I agree that the existing ATP systems are old, and will become increasingly difficult to keep operational. But if it had been fitted across the network rather than two different systems on two different areas, demand for replacement equipment and parts may have made it worthwhile for companies to continue to manufacture spares.

As I said above, now, today, ATP is no longer the answer. But TPWS is not really suitable for a modern high speed railway either. TPWS is in my humble opinion, a not very cheap stop-gap.

What you are saying for ATP is now coming to pass with ERTMS. The big difference is that ATP would have been a bolt-on safety system with no other benefits, and in fact would reduce capacity and service reliability in some ways. There's no safety justification to do that today, because TPWS delivers so much of the benefit already. ERTMS replaces large parts of the signalling and gets rid of constraints imposed by signal position etc, so (if done rightly) will reduce cost and increase capacity. This makes it worth doing and the safety benefit is almost incidental.

As well as the obsolescence issue, the two BR ATP systems were each tied to a single supplier, as were all ATP systems before ERTMS. The railway would have had to go to a one supplier, unless they were prepared to fit much of the train fleet with multiple systems or limit it to certain parts of the network. So the railway would have been beholden to that supplier for ever, or had to face a huge task of migrating the network and all the trains over to a competitor.

TPWS may have delayed the widespread fitting of ATP on the British rail network by 20 years or so (remember ATP couldn't have been fitted everywhere at the drop of a hat if mandated in 1995). But so far and touchwood, in the 20 year period when TPWS has been the main train protection system, there have been no accidents that were preventable by ATP.