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

[Ken H]

Structures mate

thanks

 

[Brush 4]

So Christian Wolmar was right then. Those trees looming over the lines between the A30 and the tunnel must be doomed. I'm surprised they haven't been cleared already, unless they are protected. Honiton tunnel, Whiteball and others had been cleared a while back, although I don't know if they have been maintained since or just abandoned again. I hope NR are emboldened by this to clear away more vegetation, on safety grounds. Complaining residents in Bournemouth and other areas seem to have caused a reduction of lineside work, or so it seems from casual observation.

 

[alxndr]

Here's a 2015 cab ride available of the area from the same route as the SWR (second) train which might be of interest to people trying to orientate themselves with the area.

Pertinent timestamps:
37:55 - pass under SY31, the signal protecting Laverstock Junction.
38:18 - pass Laverstock Junction.
38:21 - SY27, the signal protecting Salisbury Tunnel Junction just comes into view (this may not be an accurate representation of the current sighting point depending on vegetation growth).
38:23 - pass over the TPWS OSS grids for SY27, the signal protecting Salisbury Tunnel Junction.
38:24 - pass over the AWS for SY27, the signal protecting Salisbury Tunnel Junction.
38:34 - pass SY27, the signal protecting Salisbury Tunnel Junction.
38:47 - reach the conflict point at the junction.

Edit: corrected timestamps!

 

[Adversane]

The full BBC report

 

[357]

Here's a 2015 cab ride available of the area from the same route as the SWR (second) train which might be of interest to people trying to orientate themselves with the area.

Pertinent timestamps:
27:55 - pass under the signal protecting Laverstock Junction.
28:18 - pass Laverstock Junction.
28:21 - the signal protecting Salisbury Tunnel Junction just comes into view (this may not be an accurate representation of the current sighting point depending on vegetation growth).
28:23 - pass over the TPWS OSS grids for the signal protecting Salisbury Tunnel Junction.
28:24 - pass over the AWS gor the signal protecting Salisbury Tunnel Junction.
28:34 - pass the signal protecting Salisbury Tunnel Junction.
28:47 - reach the conflict point at the junction.

All your time stamps are ten minutes early

 

[Horizon22]

No. Yellow and double yellow aspects are there to give drivers the braking distance they need to stop at a red signal ahead. They do nothing to increase the separation between trains.

In a way it does though - otherwise we'd just have red and green. Of course that's the actual reason but in reference to the comment it has a side effect of increasing separation because the driver won't be going at line speed the whole time under cautionary aspects.

 

[Horizon22]

I am not a signalling specialist but my understanding is that four aspect signalling is more a requirement because of the higher line speed and therefore longer stopping distances.

Indeed that's a part. My initial - slightly tongue-in-cheek - reply was in reference to the "leave more than a red" comment which was made earlier. It also useful for congested routes in urban areas, to allow trains to still continue to move, albeit at low speeds. Many drivers in a London & SE TOC at peak time on a metro service will barely see a green aspect!

 

[Efini92]

If, and I stress IF, it was caused by Leaf Fall, what is in place to try taking it into account? Do drivers drive differently regarding technique in Autumn?

Yes drivers tend to brake earlier and lighter. If the line is exceptionally poor though, their just a passenger.
This case sounds like the perfect storm, falling gradient in a cutting surrounded by vegetation, storm to bring more leaves down and the Rail head treatment train not running for 2 days.

 

[Signal Head]

Yes drivers tend to brake earlier and lighter. If the line is exceptionally poor though, their just a passenger.
This case sounds like the perfect storm, falling gradient in a cutting surrounded by vegetation, storm to bring more leaves down and the Rail head treatment train not running for 2 days.

It doesn't really become a cutting until after passing SY31, quite a lot of the approach is on a low embankment, judging from the cab video posted above.

 

[bramling]

Waiting for this rather critical bit of information could have saved 28 pages of speculation and this info would have been with Network Rail from the point of the incident.

I really, really, don't see why we need to have this constant bleating on about "speculation", whatever that is.

The definition of speculation is "the forming of a theory or conjecture without firm evidence". No one here has attempted to provide a theory as to what happened.

What people have done is had a mature and informed discourse about elements of how a railway works, which might have been contributory to the incident. This is the whole point of a discussion forum, and I'm sure people have learned things from this thread (I certainly have).

As it happens the gist of the thread has essentially from the outset pointed to the SWR train passing a signal, and correctly identified a number of indicators which pointed to that early on - the position of the points on the junction, what was seen in the TD berths, and the timings of another train having just passed over the junction.

There has been a much wider discussion played out in the news media regarding the initial reports of the GWR train having derailed and signalling having been "knocked out". This information came from Network Rail itself, it did not originate from this thread. People did ask what might be the consequences of signalling being "knocked out", and a relevant discussion was had. It is quite legitimate for people to discuss these things, and as long as no one passes off their thoughts as fact (no one has) then there is no problem. If news media were to be snooping around then they would find themselves reading discussion which has been reasonably well informed, balanced, unsensational, and relevant.

These posts which keep coming up moaning about "speculation" are adding nothing to this discussion.

 

[Meole]

What has signalling failure to do with wheelslip ?

 

[Llama]

Now we know that it was a SPAD I'm wondering if the preceding signal (presumably a yellow) had a TPWS speed limit? I know that all this will be examined in forensic detail by RAIB but I will be interested to know how long the train was sliding for with the brakes on.

Any TPWS fitted at the preceding signal SY29 (itself a junction signal protecting the chord so most likely fitted with TPWS overspeed and train-stop loops) would not have been active if that signal showed a proceed aspect.

The train would be unlikely to be 'sliding' as in all wheels locked up. The WSP system on 158/159 units isn't supposed to let that happen and usually doesn't, the best analogy would be driving a car with ABS on an ice rink.

 

[alxndr]

All your time stamps are ten minutes early

Oops, thanks, corrected them now!

 

[Efini92]

Good question. From what has been said elsewhere, my understanding is that 158/159 sets with sanding fitted automatically apply sand if the brake is in step 2 or above and wheelslip is detected by the WSP system.

Yes they do on 158’s. not sure about 159’s as I have never signed them, I’m guessing they are the same though.
I’ve known trains to come off depots without any sand. If it turns out to be the case, it highlights the importance of checking the hoppers on a prep.

Am I right then in that with 3 aspect signalling in 125 MPH areas headways will need to be longer as signals will need to be further apart to allow for longer stopping distances.

Yes the sections are massive. I braked to hard when I first encountered it. The instructor was having a chuckle when we eventually got the the red (which was by then a green)

 

[GC class B1]

I really, really, don't see why we need to have this constant bleating on about "speculation", whatever that is.

The definition of speculation is "the forming of a theory or conjecture without firm evidence". No one here has attempted to provide a theory as to what happened.

What people have done is had a mature and informed discourse about elements of how a railway works, which might have been contributory to the incident. This is the whole point of a discussion forum, and I'm sure people have learned things from this thread (I certainly have).

As it happens the gist of the thread has essentially from the outset pointed to the SWR train passing a signal, and correctly identified a number of indicators which pointed to that early on - the position of the points on the junction, what was seen in the TD berths, and the timings of another train having just passed over the junction.

There has been a much wider discussion played out in the news media regarding the initial reports of the GWR train having derailed and signalling having been "knocked out". This information came from Network Rail itself, it did not originate from this thread. People did ask what might be the consequences of signalling being "knocked out", and a relevant discussion was had. It is quite legitimate for people to discuss these things, and as long as no one passes off their thoughts as fact (no one has) then there is no problem. If news media were to be snooping around then they would find themselves reading discussion which has been reasonably well informed, balanced, unsensational, and relevant.

These posts which keep coming up moaning about "speculation" are adding nothing to this discussion.

Well said. I have also learnt from the threads. Also I hope some of the media have read the corrections to their rather worrying and sensationalist untruths.

 

[Peter Sarf]

And of course the longer it goes on the likelihood of the mainstream media ever going back and correcting their earliest stories decreases even more.

For many people out there in the non railway world they will never see the corrections and they will remain forever mis-informed.

I really, really, don't see why we need to have this constant bleating on about "speculation", whatever that is.

The definition of speculation is "the forming of a theory or conjecture without firm evidence". No one here has attempted to provide a theory as to what happened.

What people have done is had a mature and informed discourse about elements of how a railway works, which might have been contributory to the incident. This is the whole point of a discussion forum, and I'm sure people have learned things from this thread (I certainly have).

As it happens the gist of the thread has essentially from the outset pointed to the SWR train passing a signal, and correctly identified a number of indicators which pointed to that early on - the position of the points on the junction, what was seen in the TD berths, and the timings of another train having just passed over the junction.

There has been a much wider discussion played out in the news media regarding the initial reports of the GWR train having derailed and signalling having been "knocked out". This information came from Network Rail itself, it did not originate from this thread. People did ask what might be the consequences of signalling being "knocked out", and a relevant discussion was had. It is quite legitimate for people to discuss these things, and as long as no one passes off their thoughts as fact (no one has) then there is no problem. If news media were to be snooping around then they would find themselves reading discussion which has been reasonably well informed, balanced, unsensational, and relevant.

These posts which keep coming up moaning about "speculation" are adding nothing to this discussion.

I agree. Furthermore if the sort of informed thinking I have seen in this thread was to have been suppressed then I believe less informed opinion would have filled the vacuum. I too have learnt a few things. It is nice to be able to ask questions or suggest thoughts without being shot down. Albeit I admit this accident is a delicate subject.

I can imagine that, for some on this forum who might be involved in the accident or its investigation, the course of this thread could be quite frustrating - especially if their position means they cannot say what they know and have to watch silently !.

Also - Looking at one of the later photos of the front of the 159 the damage seems to go quite a long way back past the cab. So I imagine there must be some damage of equal severity to the 158 ?. The driver of the 159 must have been through quite an ordeal.

It is fortunate that no deaths or very serious injuries have occurred. I hope the driver makes a full recovery and is able to resume his/her career.

 

[Signal Head]

Well said. I have also learnt from the threads. Also I hope some of the media have read the corrections to their rather worrying and sensationalist untruths.

I doubt they have, or care. Sensationalism sells papers.

...

It is fortunate that no deaths or very serious injuries have occurred. I hope the driver makes a full recovery and is able to resume his/her career.

Wholeheartedly seconded.

 

[norbitonflyer]

Also - Looking at one of the later photos of the front of the 159 the damage seems to go quite a long way back past the cab. So I imagine there must be some damage of equal severity to the 158 ?.

Wasn't it said earlier that some of the damage to the 159's cab was caused by rescuers cutting the driver free?

 

[Peter Sarf]

Wasn't it said earlier that some of the damage to the 159's cab was caused by rescuers cutting the driver free?

Oh. I must have missed that. But makes sense. It just seemed as though a lot of the adjacent 158 was visible where I would expect to see the 159. Cannot find the photo now but it was one of the last from in the tunnel.

Found the photos - looks like an awful lot of the right side of the 159 is missing/caved-in. I mean not just the front few feet.

The below is a post by @Annetts key I have not been able to copy it in properly so it is not appearing as a quote.

Here are some pictures of one of the GWR 158 units in the tunnel:

View attachment 105037
View attachment 105038

 

[Dan17H]

Initial findings suggest SPAD caused by poor rail head condition, alongside leaf fall problems.

 

[neonison]

A point not made, though implicitly understood by professional railway staff is that following an adverse distant signal a train still proceeds towards the next signal but is prepared to stop.
The driver neither stops as soon as possible after the distant as it’s likely that the next signal will be out of sight, neither does the driver continue at line speed until the next signal can be seen.
A train therefore will always be moving when the red signal comes into view and the only things which can bring the train to a halt are the brakes or arising gradient.

 

[MarkyT]

Concerning early comments about the signalling being affected, there is a world of difference between the most likely type of fault manifested and wild speculations of wrong side failure etc. To be clear, damage to lineside equipment cabinets and cables from the wreckage were most likely to cause a loss of control and indications in the local area and eastward toward the boundary with Basingstoke somewhere between Grately and Andover. In that case signals will either revert to or stay at red and points should stay in the position they were in at time of failure. Significant movement of the track in the tunnel shown in some photos may have crushed or otherwise damaged cables laid in the cess and I think someone mentioned the likely damage to equipment cabinets around the junction. Tunnel Junction and the Laverstock Junctions are all part of the main station interlocking at Salisbury ASC. The panel also remotely controls another local interlocking for the passing loop at Tisbury, the cabling for which goes west from Salisbury station so would be unlikely to have been affected.

 

[50002Superb]

Does anyone know when the units are likely to be moved (?) and, if so, will this be road?

also where will they get moved to?

 

[farleigh]

I really, really, don't see why we need to have this constant bleating on about "speculation", whatever that is.

The definition of speculation is "the forming of a theory or conjecture without firm evidence". No one here has attempted to provide a theory as to what happened.

What people have done is had a mature and informed discourse about elements of how a railway works, which might have been contributory to the incident. This is the whole point of a discussion forum, and I'm sure people have learned things from this thread (I certainly have).

As it happens the gist of the thread has essentially from the outset pointed to the SWR train passing a signal, and correctly identified a number of indicators which pointed to that early on - the position of the points on the junction, what was seen in the TD berths, and the timings of another train having just passed over the junction.

There has been a much wider discussion played out in the news media regarding the initial reports of the GWR train having derailed and signalling having been "knocked out". This information came from Network Rail itself, it did not originate from this thread. People did ask what might be the consequences of signalling being "knocked out", and a relevant discussion was had. It is quite legitimate for people to discuss these things, and as long as no one passes off their thoughts as fact (no one has) then there is no problem. If news media were to be snooping around then they would find themselves reading discussion which has been reasonably well informed, balanced, unsensational, and relevant.

These posts which keep coming up moaning about "speculation" are adding nothing to this discussion.

Very good post

 

[Cowley]

Very good post

Yes I’d agree with that too. I know that some of my colleagues on here have put an awful lot of work into sifting out things that haven’t added anything of value to this discussion over the last few days and what has been left has hopefully been relevant and informative.
This isn’t a section that I personally monitor, but I know for a fact that it’s taken a fair amount of work by the other staff members to keep things on an even keel and I’m sure that we all appreciate what they’ve done here even though it’s subtle enough that we might not realise what goes on behind the scenes always.

 

[Horizon22]

Does anyone know when the units are likely to be moved (?) and, if so, will this be road?

also where will they get moved to?

Probably won't be until the end of the week before any sort of recovery can be made. Not sure about the rest of the questions.

 

[Nicholas Lewis]

I really, really, don't see why we need to have this constant bleating on about "speculation", whatever that is.

The definition of speculation is "the forming of a theory or conjecture without firm evidence". No one here has attempted to provide a theory as to what happened.

What people have done is had a mature and informed discourse about elements of how a railway works, which might have been contributory to the incident. This is the whole point of a discussion forum, and I'm sure people have learned things from this thread (I certainly have).

As it happens the gist of the thread has essentially from the outset pointed to the SWR train passing a signal, and correctly identified a number of indicators which pointed to that early on - the position of the points on the junction, what was seen in the TD berths, and the timings of another train having just passed over the junction.

There has been a much wider discussion played out in the news media regarding the initial reports of the GWR train having derailed and signalling having been "knocked out". This information came from Network Rail itself, it did not originate from this thread. People did ask what might be the consequences of signalling being "knocked out", and a relevant discussion was had. It is quite legitimate for people to discuss these things, and as long as no one passes off their thoughts as fact (no one has) then there is no problem. If news media were to be snooping around then they would find themselves reading discussion which has been reasonably well informed, balanced, unsensational, and relevant.

These posts which keep coming up moaning about "speculation" are adding nothing to this discussion.

Bramling excellent response and much appreciate you taking the trouble to write it and I will endorse that ive learnt a number of things around GSMR emergency calls and how the braking system behaves once tripped by TPWS.

 

[45669]

Probably won't be until the end of the week before any sort of recovery can be made. Not sure about the rest of the questions.

One of the TV reports said that they would be moved by road. But he didn't say where to.

 

[rebmcr]

Yes I’d agree with that too. I know that some of my colleagues on here have put an awful lot of work into sifting out things that haven’t added anything of value to this discussion over the last few days and what has been left has hopefully been relevant and informative.
This isn’t a section that I personally monitor, but I know for a fact that it’s taken a fair amount of work by the other staff members to keep things on an even keel and I’m sure that we all appreciate what they’ve done here even though it’s subtle enough that we might not realise what goes on behind the scenes always.

I realised there had been some cleanup when I got to the end of Page 32 just now, clicked the link to Page 33, and got taken to halfway down a re-jigged Page 32!

 

[yorkie]

I realised there had been some cleanup when I got to the end of Page 32 just now, clicked the link to Page 33, and got taken to halfway down a re-jigged Page 32!

The missing posts can now be found in various spin-off threads, such as:

• Signal spacing and where 4 aspects are needed
• Can fireworks cause poor railhead conditions?
• Network Rail's vegetation problem
• West of England line current service provision
• Do heavy locos cope with poor railhead conditions better than lightweight units?
• Was the Cowden crash due to cost cutting?
• Unnerving experience on 1803 from Paddington
• Do class 158's/159's have forward facing cameras?

If we missed posts, feel free to use the report button