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Collision and derailment near Salisbury (Fisherton Tunnel) 31/10/21

Horizon22

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Your first paragraph makes the point that maybe the interpretation of each driver to reportable rail conditions is different; just remember that many times the next train through that same section will be running on a railhead that has been sanded by the train experiencing reportable conditions. That sanding between the wheels and railhead will alter the retardation characteristics for the next train.

I’ve been asked to do controlled brake stops due to the previous train experiencing low adhesion, I’ve braked as specified in the rule book and each time I’ve stoped ok which I’ve reported back. I didn’t brake more cautiously than I would have for normally for that station stop and the time of year. Slippery rail can clear up as quick as it starts. Ask any driver whose immediately following the RHTT how terrifying that can be trying to stop normally.

Indeed it does - there's a lot of factors at play as to how and why a train just a few minutes later might have a different experience entirely. Obviously the signaller should treat the report as genuine and therefore further trains will need to test the site but as you say, the actual initial report may prevent any further problems. The same is also true - sometimes to a more extreme degree - with icy rails. Circumstances can combine together to cause significant problems and indeed this was a major factor that caused the start of the Lewisham incident in 2018.
 
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Greybeard33

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[SY29] is a 3 aspect, but its Distant signal (29R) is also 3 aspect (Y/YY/G), and so acts as an outer Distant for 31 at Tunnel Junction. With 31 at Red therefore, the first warning is a double yellow aspect at 29R.
There is getting on for 2 miles of braking distance for 31 signal.

Probably a good thing there is a double yellow at 29R. Trains can rattle down the bank at quite a speed: in those days it was 33s and the first 50s.

Yes, it's 90 MPH virtually up to Laverstock North. There's no way you'd have sufficient braking distance using just 29.
The RAIB preliminary report seems to say that the driver commenced braking on approach to signal SY29 (single yellow) at Laverstock North:
Preliminary analysis of data downloaded from the On Train Data Recorder (OTDR) fitted to train 1L53 shows that the driver initially applied service braking to slow the train on approach to the caution signal before signal SY31.
The report does not mention the preceding distant signal SY29R, which would have shown a double yellow. Nor does the report say if the train was travelling at the 90mph linespeed before braking, or some lower speed.

I suppose "on approach to" might mean that braking commenced at SY29R or shortly after passing it.

Presumably we will have to wait for the final report to fill in these details.
 

bramling

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The RAIB preliminary report seems to say that the driver commenced braking on approach to signal SY29 (single yellow) at Laverstock North:

The report does not mention the preceding distant signal SY29R, which would have shown a double yellow. Nor does the report say if the train was travelling at the 90mph linespeed before braking, or some lower speed.

I suppose "on approach to" might mean that braking commenced at SY29R or shortly after passing it.

Presumably we will have to wait for the final report to fill in these details.

I'm not sure we can read too much into this. RAIB can be surprisingly sloppy on detail points, especially in their preliminary reports.

It has to also be remembered that the RAIB are a bit of an "arm's length" body, and are also quite small. Somewhere like this forum has a big enough clientele that there will pretty much always be someone who is able to post some local knowledge or dig out diagrams or supporting material, and be able to readily interpret it. RAIB's expertise is a lot broader, whereas on here we tend to be quite operationally focussed.
 

MarkyT

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The RAIB preliminary report seems to say that the driver commenced braking on approach to signal SY29 (single yellow) at Laverstock North:

The report does not mention the preceding distant signal SY29R, which would have shown a double yellow. Nor does the report say if the train was travelling at the 90mph linespeed before braking, or some lower speed.

I suppose "on approach to" might mean that braking commenced at SY29R or shortly after passing it.

Presumably we will have to wait for the final report to fill in these details.
The 90mph line speed reduces to 50mph at milepost 82, 5 chains (about 100m) before reaching Laverstock N Jn, which is after SY29. Even on greens all the way all trains would be braking for the restriction between the distant and first stop signal.
SW115-003.jpg
 

Annetts key

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The RAIB preliminary report seems to say that the driver commenced braking on approach to signal SY29 (single yellow) at Laverstock North:

The report does not mention the preceding distant signal SY29R, which would have shown a double yellow. Nor does the report say if the train was travelling at the 90mph linespeed before braking, or some lower speed.

I suppose "on approach to" might mean that braking commenced at SY29R or shortly after passing it.

Presumably we will have to wait for the final report to fill in these details.
Keep in mind that the signalling and the distances between signals is designed for the rolling stock with the worst braking performance. It’s up to the driver and his/her knowledge of the performance of their train and the locality (as in route knowledge) including any inclines or downward slopes to determine when how hard to brake. The driver will also take into account their current speed, current weather conditions, the rail conditions (based on their journey so far) and the actual performance of their train (again based on their journey so far).

Hence where a driver in a disc braked three car DMU starts braking is going to be different to that of a faster train, or a loco hauled train. And very different to the driver of a heavy freight train.

Further ‘crunching’ of the train data and interviews with the driver will hopefully clear this point up.
 

30907

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The report does not mention the preceding distant signal SY29R, which would have shown a double yellow.
To add to the previous replies: surely 29R showing YY is a "caution signal" in normal parlance (and railway usage too)? It cautions that 31 is (potentially) at danger.
 

rd749249

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Sounds like TPWS+. If you could get hold of the signalbox special instructions for the location and check the TPWS appendix, or maybe a yellow peril, that'd clear it up which signal the OSS is related to but I'd say it's almost certainly going to be the red, not the yellow.
This is the Anglia route and specifically the up electric outside of Maryland. I am told there is no TPWS+ here. Speeds are 50 down to 40 but the signals are so close to one another that whilst I agree that it may not be the SY that triggers OSS, it is within the platform of Maryland and before what would be at SY. Drivers have been caught by this exact scenario by not reacting in time to the DY just before Maryland.

If there’s a third explanation then I’d be interested to hear what that could be.

Mods: feel free to move this if you think I have strayed off topic.
 

Annetts key

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The following only applies to colour light signals in track circuit block (or equivalent) areas.

The distance between signals is determined by the braking curve of the type of trains the route is designed for, the line speed and the capacity (frequency) of service. Gradients are also taken into account.

The system has be designed so that the train with the worst braking characteristics can come to a stop at a red signal after seeing the previous signal(s) showing a caution aspect.

If the line is not expected to have a much traffic, two aspect signalling will be used (because it’s cheapest). With the ‘distant’ colour light signal (which can only show a green or yellow aspect) positioned at normal service braking distance from ‘stop’ signal (which can normally only show a green or red aspect) it is associated with. The distance between the ‘stop’ signal and the next ‘distant’ signal can be many miles.

The next step up, for lines that have a more frequent service, is three aspect signalling. Here a ‘stop’ signal is combined with the ‘distant’ signal. All the signals are spaced apart at a minimum of normal service braking distance.

Where faster trains are used, or where the frequency of trains is higher, or where there is mixed traffic (fast and slower passenger trains, or a mix of passenger and freight trains), then four aspect signalling may be used. Because the signal spacing is now less than the normal service braking distance of some train types, a train driver needs to know to start slowing down before the train comes into view of a signal showing a single yellow aspect. Hence the previous signal is provided with a second yellow aspect (also called preliminary caution or top yellow), and becomes a four aspect signal.

The sequence is now green, double yellow, single yellow, red. Drivers of trains that therefore require the maximum stopping distance can apply the brakes when they see a signal showing a double yellow, and in normal circumstances, the train should stop before it gets to the red signal.

But if the train is not travelling at line speed, or the train has better braking characteristics, the driver may not need to start slowing at the point that they see a double yellow. In some cases they may not need to brake until they are much closer to the signal showing the single yellow.

Sometimes, one or two four aspect signals (or a three aspect ‘distant’ that can show green, double yellow and single yellow) may be provided on approach to busy junctions so that there is less delay in getting trains over the junction because they have less distance to travel once the junction signal is cleared to a proceed.
 
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Dieseldriver

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I can 100% confirm that if SY31 is at danger, SY29R will display a double yellow and SY29 will display a single yellow.
 

MOONY

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HPSS is a type of point operating equipment (i.e. the thing that makes the switch blades move). That wasn't what was installed here, from the photographs I'd say it looks like standard clamplocks with mechanical backdrives.

I've added two images of examples, the big yellow kit is HPSS, the other is a standard clamplock.
Many thanks!
 

Signal Head

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One detail which had been unsettling me, was that from the outset it appeared the driver had remained in his cab throughout, and this now appears to have been confirmed. Serious respect for that.
I can't understand how he's still alive considering the state of the very part of the cab in which he would be sitting. It looks completely demolished.
 

Julian Atkins

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Can I just say how interesting and informative this thread has developed by most posters. And well done to the Moderators.

Cheers,
Julian
 

Mawkie

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Forgive me if it's been posted already, but the provisional RAIB report is live


"RAIB’s preliminary examination has found that the movement of train 1F30 across the junction was being protected from trains approaching on the Down Main line by signal SY31, which was at danger (displaying a red aspect). Train 1L53 passed this signal, while it was at danger, by around 200 metres, immediately prior to the collision occurring. Preliminary analysis of data downloaded from the On Train Data Recorder (OTDR) fitted to train 1L53 shows that the driver initially applied service braking to slow the train on approach to the caution signal before signal SY31. Around 12 seconds after service braking started, the driver made an emergency brake demand. As the train approached signal SY31, and with the emergency brake still being demanded by the driver, a second emergency brake demand was made by the train protection and warning system (TPWS). These emergency brake demands did not prevent the train from reaching the junction, where the collision occurred. OTDR analysis indicates that wheel slide was present both when the driver applied service braking and after emergency braking was demanded. This was almost certainly a result of low adhesion between the train’s wheels and the rails."
 
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alexl92

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One detail which had been unsettling me, was that from the outset it appeared the driver had remained in his cab throughout, and this now appears to have been confirmed. Serious respect for that.
I felt this too. Huge respect for him.

Hope this isn't in appropriate to ask, but hypothetically, if the driver had chosen to leave the cab once he had applied the emergency brake and it was clear the train wasgoing to be involved in a collision (i.e. there was nothing futher he could do), would he have been disciplined for leaving the controls?

Also, how does the emergency brake differ from a full brake application? In poor adhesion what difference is an emergency brake application supposed to make?
Thanks!
 

ashkeba

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Hope this isn't in appropriate to ask, but hypothetically, if the driver had chosen to leave the cab once he had applied the emergency brake and it was clear the train wasgoing to be involved in a collision (i.e. there was nothing futher he could do), would he have been disciplined for leaving the controls?
And where could he go? I remember reading of locomotive drivers being told to leave cabs and secure themselves in the engine framework, but that is not an option in a multiple unit. Is the middle of a motor carriage the strongest place on a unit?
 

Dai Corner

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And where could he go? I remember reading of locomotive drivers being told to leave cabs and secure themselves in the engine framework, but that is not an option in a multiple unit. Is the middle of a motor carriage the strongest place on a unit?
In this case the driver was the only person seriously injured so he'd clearly have been better off going back into the passenger area.

Edit: if possible. I'm not sure if the layout in a 159 allows that.
 

AidanCKY

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Hope this isn't in appropriate to ask, but hypothetically, if the driver had chosen to leave the cab once he had applied the emergency brake and it was clear the train wasgoing to be involved in a collision (i.e. there was nothing futher he could do), would he have been disciplined for leaving the controls?

I was thinking the same, to me I feel like you could so easily get crushed to death this way, for no benefit - if the emergency brake is on, is there any benefits to staying in the cab?
 

ainsworth74

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And where could he go? I remember reading of locomotive drivers being told to leave cabs and secure themselves in the engine framework, but that is not an option in a multiple unit. Is the middle of a motor carriage the strongest place on a unit?
The passenger saloon which on trains of that vintage is not part of the crumple zone unlike the cab is!

To be clear I'm not suggesting the driver in this incident was anything other than brave in remaining at the controls as whether or not they was anything they could do staying at controls was clearly a very brave act indeed as they must have known some seconds before the collision what was coming.
 

alexl92

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And where could he go? I remember reading of locomotive drivers being told to leave cabs and secure themselves in the engine framework, but that is not an option in a multiple unit. Is the middle of a motor carriage the strongest place on a unit?
I was thinking futher back into the carriage to take himself out of the direct line of impact (though obviously still wouldn't be 100% safe).
 

ashkeba

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Edit: if possible. I'm not sure if the layout in a 159 allows that.
The cab door is in the vestibule, not external, based on memory and wikipedia pictures. These are gangway units, I think, but I am not sure I have ridden a doubled up one.
 

thejuggler

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Imagine you are a passenger on a 158/9 and you see the driver exit the cab (which is into the vestibule) whilst the train is moving and walk into the passenger cabin!

What is the driver then supposed to do which won't instill instant panic in dozens of people in a confined space?
 

320320

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I felt this too. Huge respect for him.

Hope this isn't in appropriate to ask, but hypothetically, if the driver had chosen to leave the cab once he had applied the emergency brake and it was clear the train wasgoing to be involved in a collision (i.e. there was nothing futher he could do), would he have been disciplined for leaving the controls?

once the emergency brake is applied and it‘s evident you’re going to be involved in a collision there’s nothing more you can do. I’ve always been told if you find yourself in that position and you have time, then get into the coach and sit, if possible, your own safety is paramount and no, you wouldn’t be disciplined for leaving the controls.

Also, how does the emergency brake differ from a full brake application? In poor adhesion what difference is an emergency brake application supposed to make?
Thanks!

It provides additional braking force. A full service application will give 3-3.5 bar of brake force and an emergency application will give 4-4.5 bar of brake force.

I don’t know how much of a difference it would make in a slide like that but you’re instructed to use the emergency brake whenever it becomes apparent you’re unlikely to stop at the intended place using normal braking procedure. If the driver didn’t use the emergency brake and subsequently collided with another train he probably wouldn’t drive again.
 

TheEdge

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It provides additional braking force. A full service application will give 3-3.5 bar of brake force and an emergency application will give 4-4.5 bar of brake force.

I don’t know how much of a difference it would make in a slide like that...

In a full wheel slide where everything is locked up, nothing. The emergency brake could increase it to 500 bar but it still wouldn't make a difference.
 

AdamWW

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Imagine you are a passenger on a 158/9 and you see the driver exit the cab (which is into the vestibule) whilst the train is moving and walk into the passenger cabin!

What is the driver then supposed to do which won't instill instant panic in dozens of people in a confined space?

In general, if I saw someone in uniform walk from the front cab into the saloon I'd assume there had been more than one person in there.

If I was on a train where the braking had clearly gone into emergency I might come to a different conclusion but I don't think I'd criticise the driver for doing so.

Maybe I'm getting muddled up but my recollection is that SWR have modified 158's with the leading vestibule out of use for passengers. I assume that's to ensure a quick exit for the driver if required, though maybe there's some other reason I've missed. (It's not very convenient from a passenger point of view).
 

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