Lumo overspeed incident at Peterborough (17/04/2022)

[dk1]

Well, if we are going back in history, the comparable crossovers approaching Taunton in semaphore days were locked with the distants so they could not give a Clear, equivalent to an mas green, when set to cross over to the Relief platforms. Someone local can tell whether the current mas there does the same.

I honestly thought that TPWS would catch this one.

Sorry but I have no idea where you see the comparison. The arrangements at Peterborough are perfectly fine in the context of modern signalling. As a driver I cannot fault them.

 

[43096]

Can we remember there is a driver out there with a potentially career ending investigation over their head right now.

His, her, their whole life is at stake because of this mistake, maybe we can remember that for a moment…?

Either way there is someone’s life / future on the line.

It might also be as well to remember that this incident was only narrowly away from scattering five vehicles running at 75mph right across Peterborough station and the consequent literal risk to rather more people's lives.

 

[Watershed]

I honestly thought that TPWS would catch this one.

Unfortunately these sorts of incidents are where the caveat of "90% of the functionality for 30% of the cost" (or whatever the precise figures were) comes into play.

TPWS only acts as a control on the train's speed at specific points. It doesn't provide any continuous form of monitoring and doesn't stop overspeeds etc. before or after the grids.

Having slowed down sufficiently for the approach control to clear, the driver evidently expected to go through on the Fast Lines as normal, and drove accordingly. With the train likely still being at some speed when approaching the signal, and it then clearing before the train reached the signal, and the good acceleration of the 80x, that leaves plenty of room to reach 75mph.

I would be surprised if the concept of expectation bias didn't feature in the final report; it's been a consistent factor in many aviation incidents and remains one of the biggest human factors in accidents across all industries. There is only a limited amount that can be done to guard against this - really this has to come down to technical solutions.

 

[Davester50]

Having slowed down sufficiently for the approach control to clear, the driver evidently expected to go through on the Fast Lines as normal, and drove accordingly. With the train likely still being at some speed when approaching the signal, and it then clearing before the train reached the signal, and the good acceleration of the 80x, that leaves plenty of room to reach 75mph.

How could the driver know the signal would clear though? I'm just a layman, but I didn't think you drove to what you're assuming what it's going to do, just what it is doing.

 

[PG]

I don’t think it’s a coincidence the MD of Lumo stepped down just before this happened.

I fail to see it as anything other than a coincidence, unless you are able to elaborate?

 

[Watershed]

How could the driver know the signal would clear though? I'm just a layman, but I didn't think you drove to what you're assuming what it's going to do, just what it is doing.

What I'm saying is that when approaching the signal, they may well have expected to be routed onto the Fast line, as would likely have happened every previous time they went through Peterborough. And then when the signal stepped up, expectation bias may have kicked in, meaning they took the indication as "all ok, up to linespeed".

Obviously that's not what was actually happening, but expectation bias can be a powerful factor, even if it is difficult for an uninvolved third party to see how anyone could have thought that way.

 

[TheBigD]

I don’t think it’s a coincidence the MD of Lumo stepped down just before this happened.

Doubt it's connected. It's fairly common for a new company to have one MD during the initial/development phase and then a different one once day to day operations commence.

Different people different skills etc etc.

 

[edwin_m]

What I'm saying is that when approaching the signal, they may well have expected to be routed onto the Fast line, as would likely have happened every previous time they went through Peterborough. And then when the signal stepped up, expectation bias may have kicked in, meaning they took the indication as "all ok, up to linespeed".

Obviously that's not what was actually happening, but expectation bias can be a powerful factor, even if it is difficult for an uninvolved third party to see how anyone could have thought that way.

What I'm saying is that when approaching the signal, they may well have expected to be routed onto the Fast line, as would likely have happened every previous time they went through Peterborough. And then when the signal stepped up, expectation bias may have kicked in, meaning they took the indication as "all ok, up to linespeed".

Obviously that's not what was actually happening, but expectation bias can be a powerful factor, even if it is difficult for an uninvolved third party to see how anyone could have thought that way.

If the driver had approached the signal too fast when it was red, then the TPWS would have stopped the train before the end of the overlap. This theory (and it's only a theory but a plausible one) is that once the signal cleared, the driver was able to accelerate to an excessive speed before reaching the crossover. It's worth remembering that the signalling at Peterborough was designed in the era of Deltics - the increasing power to weight ratio of HSTs, then 225s, and now 80x units makes this type of incident more likely to happen.

Rather like the Bletchley incident where a light engine was given full power after the signal cleared, accelerated rapidly with no train behind it, and was going fast enough to derail on the crossover.

 

[Wilts Wanderer]

If Peterborough was last remodelled in the mid-1970s then that pre-dates the first flashing aspect sequences which I believe were mid-80s? Prior to that new concept, most station layouts and diverging junctions were only low speed crossovers because that was all you could achieve from the very restrictive ‘approach control from red’, which was basically the only design choice short of providing full linespeed turnouts and free aspects, not practical for most stations.

That being said, 105mph to 25mph is a significant speed reduction to still provide flashers for - does anyone know what the current best practice percentage reduction is? I’d thought it was 40% linespeed but might be wrong.

 

[paul1609]

If the driver had approached the signal too fast when it was red, then the TPWS would have stopped the train before the end of the overlap. This theory (and it's only a theory but a plausible one) is that once the signal cleared, the driver was able to accelerate to an excessive speed before reaching the crossover. It's worth remembering that the signalling at Peterborough was designed in the era of Deltics - the increasing power to weight ratio of HSTs, then 225s, and now 80x units makes this type of incident more likely to happen.

Rather like the Bletchley incident where a light engine was given full power after the signal cleared, accelerated rapidly with no train behind it, and was going fast enough to derail on the crossover.

When was the platform built on the Up fast? I would have said that at that time there should have been a comprehensive review of the infrastructure or that the fast line speeds should have been significantly reduced. A speed differential of 80 mph depending on which platform you are routed into is excessive.
Even on the much more modest SEML with its line speeds of 100mph, platform loop turnouts are generally 40 mph and in some cases 60 mph unless there is restricted space.

 

[takno]

If Peterborough was last remodelled in the mid-1970s then that pre-dates the first flashing aspect sequences which I believe were mid-80s? Prior to that new concept, most station layouts and diverging junctions were only low speed crossovers because that was all you could achieve from the very restrictive ‘approach control from red’, which was basically the only design choice short of providing full linespeed turnouts and free aspects, not practical for most stations.

That being said, 105mph to 25mph is a significant speed reduction to still provide flashers for - does anyone know what the current best practice percentage reduction is? I’d thought it was 40% linespeed but might be wrong.

It seems like the preceding train in this case led to the signalling operating more like approach control anyway. If you can accelerate heavily between the approach control and the controlled junction then it's not really going to help. Meanwhile the flashing yellows would (normally) have provided a clear indication that you hadn't got a nice fast route ahead of you

 

[D6130]

Meanwhile the flashing yellows would (normally) have provided a clear indication that you hadn't got a nice fast route ahead of you

The flashing single and double yellows only apply to the signal before the one controlling the turnout and the one before that. I would have thought that - given the severe speed restriction on the turnout - once the EMR train had cleared the Up Fast - the controlling signal (P468) would have cleared to steady single yellow with a position 2 route indicator, regardless of the clear state of the line ahead through platform 1. However, I didn't sign the route and I'm well aware that on the railway there are exceptions to almost every rule.

 

[Railsigns]

If Peterborough was last remodelled in the mid-1970s then that pre-dates the first flashing aspect sequences which I believe were mid-80s? Prior to that new concept, most station layouts and diverging junctions were only low speed crossovers because that was all you could achieve from the very restrictive ‘approach control from red’, which was basically the only design choice short of providing full linespeed turnouts and free aspects, not practical for most stations.

The first flashing yellow aspects were introduced in 1979. It was never the case that a particular range of junction speeds were impossible to signal. Apart from approach release from red, other available methods of junction signalling included approach release from yellow (without flashing aspects on approach) and the provision of a splitting distant signal.

Junction Signalling

That being said, 105mph to 25mph is a significant speed reduction to still provide flashers for - does anyone know what the current best practice percentage reduction is? I’d thought it was 40% linespeed but might be wrong.

For an approach speed between 125 mph and 80 mph, flashing yellows are permitted with diverging route speeds of 40 mph or greater.
For an approach speed between 80 mph and 40 mph, flashing yellows are permitted with diverging route speeds between 25 mph and 40 mph.

 

[D6130]

The first flashing yellow aspects were introduced in 1979.

Would I be correct in thinking that flashing yellow and double yellow aspects were installed retrospectively in some pre-1979 signalling schemes....Peterborough included perhaps?

 

[Watershed]

That being said, 105mph to 25mph is a significant speed reduction to still provide flashers for - does anyone know what the current best practice percentage reduction is? I’d thought it was 40% linespeed but might be wrong.

When Stafford was resignalled in 2015, it gained flashing yellow aspects for routes from the Up Fast and Down Fast to platforms 1 and 3, respectively.

In the Up direction that's a reduction from 110 to 40, though the limit is 125 EPS until just half a mile before the turnoff, and it reduces to 25 as soon as you enter the platform. So in a sense it's 125-25, although Pendolini would of course be subject to TASS intervention.

In the Down direction it's a reduction from 85 EPS/75 to 25.

Clearly this is permissible within modern signalling standards - just.

 

[Railsigns]

Would I be correct in thinking that flashing yellow and double yellow aspects were installed retrospectively in some pre-1979 signalling schemes....Peterborough included perhaps?

Yes; most of the early installations retrospectively applied the new aspects to existing signals.

 

[Wilts Wanderer]

The first flashing yellow aspects were introduced in 1979. It was never the case that a particular range of junction speeds were impossible to signal. Apart from approach release from red, other available methods of junction signalling included approach release from yellow (without flashing aspects on approach) and the provision of a splitting distant signal.

Junction Signalling


For an approach speed between 125 mph and 80 mph, flashing yellows are permitted with diverging route speeds of 40 mph or greater.
For an approach speed between 80 mph and 40 mph, flashing yellows are permitted with diverging route speeds between 25 mph and 40 mph.

Which is interesting as here we have 105 to 25mph with flashers although presumably the initial 30mph turnout is what it is calculated against. Possibly Peterborough was installed with some kind of derogation?

To my knowledge approach release from yellow (no flashers) is used predominantly south of the Thames in areas where the density of junctions prevents flashing sequences and linespeeds are generally low / rolling stock braking performance high.

 

[Steve Harris]

When was the platform built on the Up fast? I would have said that at that time there should have been a comprehensive review of the infrastructure or that the fast line speeds should have been significantly reduced. A speed differential of 80 mph depending on which platform you are routed into is excessive.
Even on the much more modest SEML with its line speeds of 100mph, platform loop turnouts are generally 40 mph and in some cases 60 mph unless there is restricted space.

From memory, around about 2014 (give or take a year).

 

[paul1609]

Which is interesting as here we have 105 to 25mph with flashers although presumably the initial 30mph turnout is what it is calculated against. Possibly Peterborough was installed with some kind of derogation?

To my knowledge approach release from yellow (no flashers) is used predominantly south of the Thames in areas where the density of junctions prevents flashing sequences and linespeeds are generally low / rolling stock braking performance high.

What will be interesting to know is if the 30/25 mph limits are actually for the type of turnout fitted or for signalling spacing/ sighting issues.

 

[edwin_m]

When was the platform built on the Up fast? I would have said that at that time there should have been a comprehensive review of the infrastructure or that the fast line speeds should have been significantly reduced. A speed differential of 80 mph depending on which platform you are routed into is excessive.

If you're stopping anyway, then surely the difference in speed into the platforms doesn't affect anything very much?

However, the new platform may have had the effect of making it more likely that a non-stopping train would be routed via the 25mph crossover, because a train calling at the new platform blocks the obvious route via the Up Fast.

The first flashing yellow aspects were introduced in 1979. It was never the case that a particular range of junction speeds were impossible to signal. Apart from approach release from red, other available methods of junction signalling included approach release from yellow (without flashing aspects on approach) and the provision of a splitting distant signal.

I'm surprised it was so late. I seem to recall seeing them discussed in a Modern Railways supplement "Intercity 125 into service" or similar, which would have been about 1976.

The same supplement explained that they were required because of the better braking capability of the HST. Approach control from yellow relies on the driver approaching at a speed at which they can stop at a red signal beyond the junction, but a driver of an HST with better brakes would be able to do so at a higher speed and therefore possibly exceed the junction speed. Flashing yellow gives a positive (albeit confusing) indication that the train is taking a diverging route and needs to respect the turnout speed.

 

[Railsigns]

I'm surprised it was so late. I seem to recall seeing them discussed in a Modern Railways supplement "Intercity 125 into service" or similar, which would have been about 1976.

The idea for flashing yellows certainly goes back as far as 1976 (I have a set of typical wiring diagrams originally dated 10.8.76, with later amendments), and the explanatory leaflet issued to drivers etc. was dated October 1978, but the first installation wasn't commissioned until 4 March 1979 (at Didcot East Junction).

Possibly Peterborough was installed with some kind of derogation?

Installed to an earlier standard probably.

 

[TheBigD]

I "think" that P468 signal at Peterborough used to be approach controlled for diverging routes. I also seem to remember that it used to be a double red approach but not 100% sure on that.
I think it was changed to flashing yellows when Peterborough was recontrolled and the new platform 3, and 6+7 were added.

Happy to be corrected.

 

[Taunton]

I would have thought that - given the severe speed restriction on the turnout - that once the EMR train had cleared the Up Fast - the controlling signal (P468) would have cleared to steady single yellow with a position 2 route indicator, regardless of the clear state of the line ahead through platform 1.

I thought so too, above, but was criticised. One suspects that an outcome of the event is that it will be modified to do so and give single yellow rather than green.

Given the line is pretty straight there, I wonder what the next signal ahead on the Up Fast was showing, and whether visible. Was that green too, although not for this train?

 

[D6130]

I thought so too, above, but was criticised. One suspects that an outcome of the event is that it will be modified to do so and give single yellow rather than green.

Given the line is pretty straight there, I wonder what the next signal ahead on the Up Fast was showing, and whether visible. Was that green too, although not for this train?

Hmm....a possible 'read through'?

 

[Snow1964]

So basically we know the train had been checked (following a slower EMR service), it is clear that the junction signal cleared from red before Lumo train passed it (nothing to indicate signal passed at danger)

There is unknown regarding how slow the train was going, or how far away from signal it was when it cleared, it obviously then accelerated, and then seems to have been doing at least 70mph by the points

It then sounds like a heavy brake application was made (but if this was before the points, or when lurching started) isn’t clear.

Then there is whole series of possible scenarios (which I will list but don’t want to speculate on, as RAIB will do this):

1) Signal didn’t show diverging route indicator due to fault
2) Driver misread (or didn’t register) the junction indicator
3) Driver forgot the junction speed (or thought it was higher)
4) Signs indicating junction speed were missing or obscured
5) Driver could see next signal, after passing P468 and registered that instead of the low speed points which came earlier
6) Approach control was designed for lower power trains (wasn’t expected they could accelerate so much between signal and points)
7) The next signal beyond the platform was green, so signal P468 might not have shown single yellow
8) There is a mix of point speeds and speed restriction signs were confusing (including the yellow border advance warning signs)
9) Some sort of train fault (something like equivalent of a jammed accelerator, including something wrong in control software)

 

[Clarence Yard]

For obvious reasons, I’m not going to comment on the actual incident but a word about P468 and what a driver sees once he is past that signal, just to correct/amplify a few things that have been said here.

If you are following right behind an EM train into Peterborough on the up fast you will most likely be on Greens or Double Yellows nearly all the way in and at P468 you will be on a red, which is to allow the EM to get out of the way. Therefore the route beyond P468 will not be set and you won’t get any flashing aspects. Once your route is set, you might well get a rapid progression through the sequence and could well be off on a green. If you are going into 1, the route indicator should be illuminated and therefore that diverging route would be indicated to you.

Beyond P468 you have just under half a mile to the actual set of points that take you to Platform 1, long enough to get speed up from a standing start on an 80x unit. If you are looking ahead, the next “signal” you will see on your usual route (if you think you are going UF) is the banner repeater for the next signal on the up fast. What that banner tells you depends on how the route has been set up beyond Peterborough and you will either brake accordingly or continue to accelerate up to 105 mph. The next thing you will notice is where the points are taking you.

The RAIB will tell us what actually happened.

 

[Efini92]

I fail to see it as anything other than a coincidence, unless you are able to elaborate?

Only rumours about incident rates.

 

[Nottingham59]

a word about P468 and what a driver sees once he is past that signal,

Thank you. That is very helpful.

Beyond P468 you have just under half a mile to the actual set of points that take you to Platform 1, long enough to get speed up from a standing start on an 80x unit.

Would a 80x be able to reach 75mph within that distance from a standing start? (If the rate of acceleration is 10%g, it could reach 90mph in 800m, but i don't know how fast 80x's accelerate.)

 

[Watershed]

Would a 80x be able to reach 75mph within that distance from a standing start? (If the rate of acceleration is 10%g, it could reach 90mph in 800m, but i don't know how fast 80x's accelerate.)

We don't even know that the train was at a standing start. It may well have been going 20mph when the signal cleared, and then started to accelerate before even reaching the signal.

 

[Nottingham59]

We don't even know that the train was at a standing start.

I know that. The question was to help me work out the minimum speed it must have been going when it passed the signal. Can anyone point me to a published acceleration curve for a Class 803?