"TPWS Activation: A Driver's Reflection"

[Moterman31]

Saw this on LinkedIn today and thought it was such a good reflection. It’s so easy to get caught up in being hard on ourselves when things go wrong, but this is a great example of taking a step back and looking at what can be learned. We all get annoyed at ourselves sometimes, but it’s worth remembering to focus on the lessons rather than just beating ourselves up.

I like to think that I’m always a conscientious driver however I recently had the unfortunate experience of a TPWS activation - totally through my own misjudgement and delayed reaction to the signalling conditions at the time. Naturally I was initially berating myself after the activation and having gone through the reporting procedure. I started to question myself how could someone with considerable experience have such an incident? If I’m being totally honest I would say it even knocked my confidence. After further reflection the incident highlighted just how easily as humans we are designed to occasionally fail particularly when performing a repetitive routine. It also leads to question what the consequences could have been had a safety system not been in place or had been isolated. I can fully appreciate the effectiveness of the system in place. Other questions I’ve tried to self-analyse: Were my priorities correct at the time? Did I have a personal protection strategy in place and if so why did I not use it? Are my strategies robust enough? What external influences (if any) could have prevented me from applying these strategies? Am I able to actively recognise situations where I need to be more focused? No driver reports for duty with the intention of having an incident. But I welcome the outcome of the post-incident investigation and look forward to further discussions with my manager and fellow drivers, applying any recommendations in order to maintain the high level of professionalism the role deserves.

Link to profile: https://uk.linkedin.com/in/mark-watson-aciro-489716160

 

[coxxy]

The second we stop analysing our actions, we become a danger. The driver here is bang on!

 

[dctraindriver]

Absolutely spot on. I drum this into my trainees.

 

[Economist]

Fair play to the driver for being so open about the incident. I wish the railway had more of a "just culture" where errors such as his weren't punished and only violations were. I was speaking with some friends who are pilots and they were very surprised when I said the first thing recruitment look at when applying for a qualified driver vacancy is your safety record. As much as the railway seems for the most part a very good industry to work in I think there are things we can learn from just culture being implemented elsewhere.

 

[12LDA28C]

Saw this a few days ago. He is spot on although I'm not a huge fan of TPWS - it's a fairly dumb system in which everything is black or white, i.e. the train is either within the required speed profile or it's not, and if it's not then the control is removed from the driver and a brake application is initiated. It would be better in certain circumstances if the driver was given a warning before the brake applies, for example on the approach to a TSR although I fully appreciate that if a SPaD is likely then it's only right that TPWS should intervene.

 

[DMckduck]

Fair play to the driver for being so open about the incident. I wish the railway had more of a "just culture" where errors such as his weren't punished and only violations were. I was speaking with some friends who are pilots and they were very surprised when I said the first thing recruitment look at when applying for a qualified driver vacancy is your safety record. As much as the railway seems for the most part a very good industry to work in I think there are things we can learn from just culture being implemented elsewhere.

Doesnt help when you've got management whether that's local or senior, looking for patterns in incidents and hyper analysing everything in post incident fact finding.

For example, here driver we strongly believe the fact you haven't eaten this morning played a factor in this incident occurring.

But I fast until midday every morning??

It's drummed into new drivers so hard that they are all petrified to even make a slight mistake, which I believe factors into more mistakes occurring.

 

[Twotwo]

It's drummed into new drivers so hard that they are all petrified to even make a slight mistake, which I believe factors into more mistakes occurring.

There's also a high correlation between drivers having an incident and then having another in close proximity which I believe is for the same reason you've listed.

 

[skyhigh]

Saw this a few days ago. He is spot on although I'm not a huge fan of TPWS - it's a fairly dumb system in which everything is black or white, i.e. the train is either within the required speed profile or it's not

Personally I find it pretty odd. Where I've worked, most of the set speeds seem to have been treated as a state secret meaning most drivers are totally unaware of what speed will actually trigger the TPWS - or even what the TPWS loops are actually in position for.

A couple of the speeds were briefed out, because they were either such a distance from the speed change or set at questionably high speeds.

It just means we end up in a situation where someone triggers the TPWS because they normally brake down to 45mph for the grids, but on one occasion misjudge it and go over at 47mph when they're set at 46mph. If you knew they were set at that speed, you would aim to go over with more of a margin!

 

[12LDA28C]

Personally I find it pretty odd. Where I've worked, most of the set speeds seem to have been treated as a state secret meaning most drivers are totally unaware of what speed will actually trigger the TPWS - or even what the TPWS loops are actually in position for.

A couple of the speeds were briefed out, because they were either such a distance from the speed change or set at questionably high speeds.

It just means we end up in a situation where someone triggers the TPWS because they normally brake down to 45mph for the grids, but on one occasion misjudge it and go over at 47mph when they're set at 46mph. If you knew they were set at that speed, you would aim to go over with more of a margin!

Exactly this. If there was a facility for TPWS to warn a driver they are outside the braking curve and give them a chance to apply more brake, rather than simply dumping the brake and bringing the train to a stand, surely that would be beneficial? Essentially incorporating some of the features from ATP into an improved version of TPWS.

 

[800301]

Just like the ceiling speed on ETCS which hopefully gains traction on being rolled out ASAP everywhere

Exactly this. If there was a facility for TPWS to warn a driver they are outside the braking curve and give them a chance to apply more brake, rather than simply dumping the brake and bringing the train to a stand, surely that would be beneficial? Essentially incorporating some of the features from ATP into an improved version of TPWS.

I totally agree that TPWS is a ‘dumb’ system but that’s what we get when money doesn’t want to be spent, in a lot of places where we have ATP, it’s common that TPWS will trip before an ATP intervention making it a redundant safety system in some situations

 

[Fragezeichnen]

Exactly this. If there was a facility for TPWS to warn a driver they are outside the braking curve and give them a chance to apply more brake, rather than simply dumping the brake and bringing the train to a stand, surely that would be beneficial? Essentially incorporating some of the features from ATP into an improved version of TPWS.

Personally I find it pretty odd. Where I've worked, most of the set speeds seem to have been treated as a state secret meaning most drivers are totally unaware of what speed will actually trigger the TPWS - or even what the TPWS loops are actually in position for.

It just means we end up in a situation where someone triggers the TPWS because they normally brake down to 45mph for the grids, but on one occasion misjudge it and go over at 47mph when they're set at 46mph. If you knew they were set at that speed, you would aim to go over with more of a margin!

The problem with drivers knowing exactly the speed which will trigger an emergency brake application is the tendency they will treat it as a "target" speed, which it isn't. If 47mph is truly worthy of an emergency brake application, then 46mph is also far too fast.

I am not a train driver so I can't assess this, but I can understand that in reality the TPWS may sometimes be set unreasonably low speeds that are not actually dangerous

The Indusi system used in Germany(and Newcastle?) uses a different approach - the supervised speeds are known and fixed according to the train brake performance, but they only take effect some time after passing an induction magnet and deliberately no countdown timer is provided to the driver.

More sophisticated systems like ETCS have multiple braking curves, including a target speed, warning speed, service brake intervention speed, emergency brake intervention speed and this enables clear guidance to be given to the driver, but that's obviously a far more complex(and expensive!) system.

From what I know in Germany, interventions from Indusi are not considered a calamitous matter. However the nature of the system means they are more likely to occur due to technical problems, and that they can also occur due to user error rather than an actual overspeed.

 

[DMckduck]

The problem with drivers knowing exactly the speed which will trigger an emergency brake application is the tendency they will treat it as a "target" speed, which it isn't. If 47mph is truly worthy of an emergency brake application, then 46mph is also far too fast.

The only issue with this is timetables in the UK are based on the train travelling at linespeed so in this case if 46mph would be deemed to fast, what should the speed over the grids then be?

Then the next question would be, why aren't the grids set at just above that speed?

 

[Fragezeichnen]

As I understand it TPWS is used to check if the train is slowing down for a signal or an upcoming speed restriction, not to check if it is travelling at the line speed. So the line speed is not relevant.

 

[12LDA28C]

The only issue with this is timetables in the UK are based on the train travelling at linespeed so in this case if 46mph would be deemed to fast, what should the speed over the grids then be?

Then the next question would be, why aren't the grids set at just above that speed?

Timetables are not all based on trains travelling at line speed all the time, there is often recovery time and similar built into train schedules.

In the situation described above 46mph does not relate to linespeed. This would be a TPWS trigger speed on the approach to a signal at danger or a PSR. Clearly a train running under restrictive signals would not be travelling at line speed.

 

[PudseyBearHST]

The problem with drivers knowing exactly the speed which will trigger an emergency brake application is the tendency they will treat it as a "target" speed, which it isn't. If 47mph is truly worthy of an emergency brake application, then 46mph is also far too fast.

This is often what drivers are told when they ask why can’t they be given a list of TPWS trip speeds which I think is nonsense. If the grids are set at 46mph, saying that drivers may treat that as a target speed is insulting. Drivers are professional enough to create their own margins and should be trusted to do so. E.g. a driver may choose to aim for 35-40mph over the grids in this example.

 

[Ducatist4]

One of the big differences between railways and aircraft is that mistakes on the railway can have almost instant consequences. SPAD'ing could result in an accident there and then. Mistakes whilst flying tend to cascade and the swiss cheese model eventually lines up and something bad happens.

 

[TurboMan]

The problem with drivers knowing exactly the speed which will trigger an emergency brake application is the tendency they will treat it as a "target" speed, which it isn't. If 47mph is truly worthy of an emergency brake application, then 46mph is also far too fast.

There is at least one TOC I know of that published TPWS trip speeds only to find that some drivers did exactly that. The list of speeds was withdrawn very soon after.

I am not a train driver so I can't assess this, but I can understand that in reality the TPWS may sometimes be set unreasonably low speeds that are not actually dangerous

It's reflection of the fact that it's a relatively simple system that can only differentiate between 'passenger trains' and 'freight trains', so all passenger trains are treated the same regardless of braking capabilities - from an old DMU with tread brakes to a brand new traction with highly efficient dynamic braking. This is unlike ETCS or BR-ATP where braking curves are calculated based on the braking performance of the specific train, which is why ETCS and BR-ATP are so much more expensive to implement.

 

[AverageJoe]

Some areas on my routes I have been told to “watch out for these grids” and “get your speed right down for these ones”.

Which results in me and others crawling towards the speed change.

No one seems to know what these grids are set to but people are scared of tripping them.

If there was no grids we would all safely brake later with zero concern of braking heavy or missing the speed change.

Generally I try not to pay attention to over speed grids and drive at a pace I’m happy with and willing to back myself on if the chat with the managers happened.

However on those few locations I’ve had the fear of god put in to me it would be handy to know the trigger speed.

 

[Zontar]

This is often what drivers are told when they ask why can’t they be given a list of TPWS trip speeds which I think is nonsense. If the grids are set at 46mph, saying that drivers may treat that as a target speed is insulting. Drivers are professional enough to create their own margins and should be trusted to do so. E.g. a driver may choose to aim for 35-40mph over the grids in this example.

The same way in which most grids in bay platforms are set at 10mph.

Most drivers don't see that as a target and will aim for between 6- 8mph.

 

[AverageJoe]

There is at least one TOC I know of that published TPWS trip speeds only to find that some drivers did exactly that. The list of speeds was withdrawn very soon after.

It's reflection of the fact that it's a relatively simple system that can only differentiate between 'passenger trains' and 'freight trains', so all passenger trains are treated the same regardless of braking capabilities - from an old DMU with tread brakes to a brand new traction with highly efficient dynamic braking. This is unlike ETCS or BR-ATP where braking curves are calculated based on the braking performance of the specific train, which is why ETCS and BR-ATP are so much more expensive to implement.

Although I’m sure those drivers would still comfortably got their speed down in time if the TPWS didn’t intervene.

It’s a shame it can’t take in to account whether or not the driver is making brake application once travelling over the grids to show he is responding to the change in speed.

 

[Zontar]

I tend to treat the grids as you would a speed camera. You know what speed will get you caught on a camera, but grids it's guess work

 

[AverageJoe]

The same way in which most grids in bay platforms are set at 10mph.

Most drivers don't see that as a target and will aim for between 6- 8mph.

I find them frustrating at times.
Especially if coming on to a bay platform you haven’t used before.

Come in at 15mph on a long bay and you don’t want to slow too early, but also don’t want to be overly focused on looking for grids on a busy platform that while approaching buffers. Personally I think they should be set at 15mph.

Sometimes getting down to 8 like most of us do can be a right crawl to the buffers, and if it’s on an uphill gradient you may need to take power again which is worse if you ask me, I’d prefer to never take power towards a buffer.

 

[PudseyBearHST]

I find them frustrating at times.
Especially if coming on to a bay platform you haven’t used before.

Come in at 15mph on a long bay and you don’t want to slow too early, but also don’t want to be overly focused on looking for grids on a busy platform that while approaching buffers. Personally I think they should be set at 15mph.

Sometimes getting down to 8 like most of us do can be a right crawl to the buffers, and if it’s on an uphill gradient you may need to take power again which is worse if you ask me, I’d prefer to never take power towards a buffer.

I don’t know about having them set at 15 especially considering most bay platforms are only 15mph linespeed. But I know what you mean, 12mph would probably be more ideal.

 

[AverageJoe]

I don’t know about having them set at 15 especially considering most bay platforms are only 15mph linespeed. But I know what you mean, 12mph would probably be more ideal.

I personally don’t see how 12mph is much different to 15mph.

I understand you are showing a reduction in speed, but that has already happened when approaching the platform edge.

For me it just means I can have my eyes ahead being prepared for any potential issues on a busy platform and also keeping my eye on the buffers.

There’s no rule to be doing 10mph when approaching a train on a permissive platform so the 10mph seems a little micromanaging to me.

There has to be some element of trust in the driver.

 

[TurboMan]

If there was no grids we would all safely brake later with zero concern of braking heavy or missing the speed change.

You seem to be suggesting that TPWS is superfluous/unnecessary - or have I misunderstood you?

== Doublepost prevention - post automatically merged: 16 Jan 2025 ==

There has to be some element of trust in the driver.

It's not about trusting or mistrusting drivers, it's about the fact that human error is inevitable, therefore TPWS acts as an engineering control to mitigate the risk associated with human error.

It's quite clear from the data (at least in terms of SPADs, as this is the data that RSSB have analysed in depth), that we have reached the limits of human performance and there is little to no more that can be done from a human factors point of view to reduce the SPAD risk even further - hence we have engineering controls. Not just that, but in the hierarchy of risk control measures engineering controls should always be implemented in preference to training etc., which should only ever be a 'last resort' to manage any residual risk that remains once engineering controls are in place.

 

[AverageJoe]

You seem to be suggesting that TPWS is superfluous/unnecessary - or have I misunderstood you?

== Doublepost prevention - post automatically merged: 16 Jan 2025 ==


It's not about trusting or mistrusting drivers, it's about the fact that human error is inevitable, therefore TPWS acts as an engineering control to mitigate the risk associated with human error.

It's quite clear from the data (at least in terms of SPADs, as this is the data that RSSB have analysed), that we have reached the limits of human performance and there is little to no more that can be done from a human factors point of view to reduce the SPAD risk even further - hence we have engineering controls. Not just that, but in the hierarchy of risk control measures engineering controls should always be implemented in preference to training etc., which should only ever be a 'last resort' to manage any residual risk that remains once engineering controls are in place.

You misunderstood me.
I’m saying a driver would naturally reduce his speed for the PSR. The grids often demand a great reduction in speed than necessary likely by basing the speed on heavier trains that use the line also.

Did you read the rest of my post on trusting in drivers part?
I didn’t say remove tpws on approach to buffers, I just feel 15mph grids at the beginning of a platform would still work nicely but also remove the negatives I also mentioned.

 

[12LDA28C]

I personally don’t see how 12mph is much different to 15mph.

I understand you are showing a reduction in speed, but that has already happened when approaching the platform edge.

For me it just means I can have my eyes ahead being prepared for any potential issues on a busy platform and also keeping my eye on the buffers.

There’s no rule to be doing 10mph when approaching a train on a permissive platform so the 10mph seems a little micromanaging to me.

There has to be some element of trust in the driver.

Actually, some TOCs mandate exactly that instruction to their Drivers as part of a Professional Driving Policy, or similar document.

 

[AverageJoe]

Actually, some TOCs mandate exactly that instruction to their Drivers as part of a Professional Driving Policy, or similar document.

Fair enough, but that as you say is a toc by toc situation and nothing set out by NR or RSSB, whereas we HAVE to be doing 10 or below at buffer grids to avoid a brake application.

 

[Railsigns]

The same way in which most grids in bay platforms are set at 10mph.

Most buffer stop loops are set at 12.5 mph. 10 mph was originally the standard set speed for buffer stop loops, but this was increased to 12.5 mph after a few years.

 

[AverageJoe]

Most buffer stop loops are set at 12.5 mph. 10 mph was originally the standard set speed for buffer stop loops, but this was increased to 12.5 mph after a few years.

I wasn’t aware of that. But the idea of ‘most’ of them being 12.5 doesn’t make me want to test any of them just in case.