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

[AlbertBeale]

I hate to prick the bubble of this tree bashing festival but if you look at the photo posted a few posts earlier

Link https://www.flickr.com/photos/96859208@N07/10873585803

you can see from the photo that by the time the SWR train had passed under the road bridge and entered the now tree infested cutting with junction and tunnel entrance, it will already have passed the red signal in question.

The mile or so that the train would have been braking on, from roughly the A30 overbridge at Hampton Inn to the signal in question is mostly embankment/level ground level and, as a look at google maps shows, not greatly tree or bush infested.

The RAIB have stated that wheelslide is a factor, but have not stated it is the root cause.

There are also other mitigations available for wheelslide other than a chainsaw orgy (see the clasp brakes on Thameslink class 700s for an example).

Yes - looking at the cab video posted since this message, that [ie a lack of significant tree cover before the signal] seems to be the case. In that video, is the signal protecting Laverstock North junction also where the distant signal would be giving advance warning of the signal protecting the junction by the tunnel? [Excuse my ignorance.] If so, then presumably that yellow before Laverstock North junction would mean the driver was braking, from then at least, ready to be able to stop at the expected red before the tunnel.

From that cab video, it seems that the lineside vegetation between those two signals is largely isolated scrub and so on; the significant tree cover is only in the cutting by the junction just before the tunnel entrance - ie, after the signal where the train was due to stop. The pictures of the immediate area of the collision, together with the many comments on this thread about the need to cut down lots of trees, led me to believe that everyone making those comments knew (or at least assumed) that there was tree cover like that all the way back to where the train was due to be slowing down.

If that was the assumption, then it appears not to be an accurate assumption. I'd appreciate comments about this point from those who were calling for a lot of tree culling...

 

[FOCTOC]

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

Well, they ain't going by road from where they currently sit. I suppose they'll be rerailed and tripped on to Salisbury depot, SWR. They can be hidden out of sight there until such a time as something else is arranged to shift them.

 

[Gloster]

Yes - looking at the cab video posted since this message, that [ie a lack of significant tree cover before the signal] seems to be the case. In that video, is the signal protecting Laverstock North junction also where the distant signal would be giving advance warning of the signal protecting the junction by the tunnel? [Excuse my ignorance.] If so, then presumably that yellow before Laverstock North junction would mean the driver was braking, from then at least, ready to be able to stop at the expected red before the tunnel.

The signal protecting Laverstock North Junction is (I think) a three aspect signal which would be displaying a yellow if the signal protecting Tunnel Junction is at red (unless it is approach controlled, in which case the first would be at red until the train has slowed down and only then would it change to yellow). The driver should start braking once he sees the yellow and, using his route knowledge, do so at a rate that can bring the train smoothly to a stand at the red, but not waste time crawling up to it. The distance between the two signals will be such that the train with the worst braking performance (longest braking distance) can come safely and smoothly to a stand between the point where the driver first gets a clear view of the yellow and the red. (It is rather different to my time there: Laverstock Curve didn’t even exist.)

 

[Signal Head]

The signal protecting Laverstock North Junction is (I think) a three aspect signal which would be displaying a yellow if the signal protecting Tunnel Junction is at red (unless it is approach controlled, in which case the first would be at red until the train has slowed down and only then would it change to yellow). The driver should start braking once he sees the yellow and, using his route knowledge, do so at a rate that can bring the train smoothly to a stand at the red, but not waste time crawling up to it. The distance between the two signals will be such that the train with the worst braking performance (longest braking distance) can come safely and smoothly to a stand between the point where the driver first gets a clear view of the yellow and the red. (It is rather different to my time there: Laverstock Curve didn’t even exist.)

It 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.

I doubt there is any approach control (except for the route to the east curve), as that would render the top yellow on its distant redundant.

 

[dastocks]

Yes - looking at the cab video posted since this message, that [ie a lack of significant tree cover before the signal] seems to be the case. In that video, is the signal protecting Laverstock North junction also where the distant signal would be giving advance warning of the signal protecting the junction by the tunnel? [Excuse my ignorance.] If so, then presumably that yellow before Laverstock North junction would mean the driver was braking, from then at least, ready to be able to stop at the expected red before the tunnel. From that cab video, it seems that the lineside vegetation between those two signals is largely isolated scrub and so on; the significant tree cover is only in the cutting by the junction just before the tunnel entrance - ie, after the signal where the train was due to stop. The pictures of the immediate area of the collision, together with the many comments on this thread about the need to cut down lots of trees, led me to believe that everyone making those comments knew (or at least assumed) that there was tree cover like that all the way back to where the train was due to be slowing down. If that was the assumption, then it appears not to be an accurate assumption. I'd appreciate comments about this point from those who were calling for a lot of tree culling...

I drove out of Salisbury along the A30 and A338 that runs parallel to that stretch of railway about an hour before the collision. There was a *lot* of debris and compacted leaves on the roads in the area at that time. The satellite views on Google maps show a significant amount of vegetation/tree cover along parts of the railway in that area as well, so it's not surprising that there would have been problems for trains.

<<https://www.google.com/maps/@51.0890643,-1.7700485,348m/data=!3m1!1e3>>

- these images probably date from earlier this year so are rather more recent than the linked cab video.

 

[Gloster]

It 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.

 

[theageofthetra]

Isn’t that a definition of a collision?

Were they running roughly to schedule? If so why would planning have allowed a conflict? This isn't a dense metro operation.

That RAIB interim statement, if the full report backs it up, is a game changer. I expect a whole raft of vegetation clearance is about to commence.

Usual railway, totally reactive, sadly.

 

[Signal Head]

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 sniper]

I drove out of Salisbury along the A30 and A338 that runs parallel to that stretch of railway about an hour before the collision. There was a *lot* of debris and compacted leaves on the roads in the area at that time. The satellite views on Google maps show a significant amount of vegetation/tree cover along parts of the railway in that area as well, so it's not surprising that there would have been problems for trains.

<<https://www.google.com/maps/@51.0890643,-1.7700485,348m/data=!3m1!1e3>>

- these images probably date from earlier this year so are rather more recent than the linked cab video.

And the '3D' view gives a better appreciation of them: https://www.google.com/maps/@51.0780721,-1.7814763,37a,35y,29.62h,79.2t/data=!3m1!1e3

Though the worst of the trees are obviously in the area of the signal protecting the junction.

 

[Juniper Driver]

It is a 3 aspect, but its Distant signal (29R) is also 3 aspect, 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.

I doubt there is any approach control (except for the route to the east curve), as that would render the top yellow on its distant redundant.

I'm not sure if I've ever seen 29R at single yellow, but I do see the point of having a (Y/YY/G).
Between 29 and 31 is not a lot of distance.

 

[ivorytoast28]

Were they running roughly to schedule? If so why would planning have allowed a conflict? This isn't a dense metro operation.

The GWR train was delayed by about 20 minutes so they arrived at the same time despite being scheduled 16 minutes apart arriving at Salisbury

Realtime Trains - 1F30 1708 Portsmouth Harbour to Tunnel Jn.

Realtime Trains is an independent source of live realtime running information for the Great British railway network.

www.realtimetrains.co.uk

Realtime Trains - 1L53 1720 London Waterloo to Andover

Realtime Trains is an independent source of live realtime running information for the Great British railway network.

www.realtimetrains.co.uk

 

[Snow1964]

Well, they ain't going by road from where they currently sit. I suppose they'll be rerailed and tripped on to Salisbury depot, SWR. They can be hidden out of sight there until such a time as something else is arranged to shift them.

There is a chalk quarry about 3 miles South at Alderbury junction (on the former line via Fordingbridge)

Some 4TC units were initially stored there when they were withdrawn, but it is possible the rarely used tracks have been taken up since then (although storing them off track probably won’t make any difference to those unlikely to be fixed)

There are a number of secure (military) sites in the area which might be alternatives if they want to keep away from prying eyes.

 

[Pete_uk]

I can't see the 159 leading carriage being reused as the front is pretty badly damaged.

Would it be a big problem for either TOC if both full units were scrapped?

 

[Towers]

I can't see the 159 leading carriage being reused as the front is pretty badly damaged.

Would it be a big problem for either TOC if both full units were scrapped?

It will be an issue for GWR to lose a 158 (which they almost certainly will, repair of the damaged rear unit of 1F30 is extremely unlikely). I would imagine less so for SWR, who always seemed to have plenty of slack with their allocation at Salisbury even pre-Covid.

 

[The Ham]

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'm sure many on here appreciate all the hard work that's done by you and the others that try and keep things in order around here (I certainly do), I imagine that at the very of times it's like playing wack-a-mole and threads like this only make such a task much harder and probably tie up a lot of time keeping on top of them.

Can you or @yorkie please ensure that the other staff and admins are aware that there's, at least some but probably lots, people on here who appreciate all that you do to keep this forum going and a place where people behave themselves.

 

[Ianno87]

I'm sure many on here appreciate all the hard work that's done by you and the others that try and keep things in order around here (I certainly do), I imagine that at the very of times it's like playing wack-a-mole and threads like this only make such a task much harder and probably tie up a lot of time keeping on top of them.

Can you or @yorkie please ensure that the other staff and admins are aware that there's, at least some but probably lots, people on here who appreciate all that you do to keep this forum going and a place where people behave themselves.

Also agree - with some sillier posts filtered out what is left I don't think is overly speculative, but is a good discussion around a wide number of factors that have been at play.

If a lay person came across this thread (as I'm sure many have), I think they would think "oh, actually, this could be more complicated than it first appears" rather than "X/Y/Z definitely happened and its clearly their fault"

 

[Towers]

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?

One of the images from within the tunnel shows a lump of the rear corner of the 158 has been torn off and is against where the 159 driver's side cab bulkhead should be - the small window and the signage for the cycle area can be clearly seen. That's clearly quite some damage to the 158.

Photos below; not mine.

(The first image shows a general view inside the tunnel, with the fronts of both trains alongside one another. The second picture is a zoomed version of the first, showing a section of class 158 bodyshell resting inside the damaged cab of the class 159).

 

[theageofthetra]

The GWR train was delayed by about 20 minutes so they arrived at the same time despite being scheduled 16 minutes apart arriving at Salisbury

Realtime Trains - 1F30 1708 Portsmouth Harbour to Tunnel Jn.

Realtime Trains is an independent source of live realtime running information for the Great British railway network.

www.realtimetrains.co.uk

Realtime Trains - 1L53 1720 London Waterloo to Andover

Realtime Trains is an independent source of live realtime running information for the Great British railway network.

www.realtimetrains.co.uk

Thanks for clarifying.

 

[reddragon]

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

I have been impressed in the way that you have managed this thread, it must have taken most of your time up!

That has certainly made the thread clearer and less off track.

 

[kwrail]

Big thank you to the mods, and to the vast majority of posters who have avoided baseless speculation and kept the discussion informative and civilised.

It's made it a really interesting read

 

[rd749249]

This time of year can be a nightmare to drive. Ordinarily I’m straight on the brakes for DY with at least a 50% reduction but in this weather, it’s more. And if it does go into a slide, well that’s my worst nightmare. Fortunately it’s only happened to me at a very low speed and it was contained, but it does shake you up. Being the first unit behind a RHTT isn’t a pleasant experience either.

I sincerely hope that the driver is ok in body and mind after this.

 

[theageofthetra]

This time of year can be a nightmare to drive. Ordinarily I’m straight on the brakes for DY with at least a 50% reduction but in this weather, it’s more. And if it does go into a slide, well that’s my worst nightmare. Fortunately it’s only happened to me at a very low speed and it was contained, but it does shake you up. Being the first unit behind a RHTT isn’t a pleasant experience either.

I sincerely hope that the driver is ok in body and mind after this.

I find it ridiculous that drivers are given no warning that they are going to be following the RHTT on their diagrams . Control will have this information, so there's no excuse.

I had this on Saturday and the adhesion was awful.

 

[Annetts key]

Ah, now you're asking me, I retired before such things came in.
As such not familiar with the intricacies of TPWS but I thought that at certain signals it can check the speed of approach of the train and if it's too fast will apply the brakes

Only with some signals and then only when a position light/calling on aspect is being shown (main aspect red, with two smaller diagonal white lights). When a main proceed aspect (green, double yellow or single yellow), is being shown, all the TPWS ‘loops’ are deactivated.

What has signalling failure to do with wheelslip ?

Nothing.

Were they running roughly to schedule? If so why would planning have allowed a conflict? This isn't a dense metro operation.

The GWR train was running late.

One of the images from within the tunnel shows a lump of the rear corner of the 158 has been torn off and is against where the 159 driver's side cab bulkhead should be - the small window and the signage for the cycle area can be clearly seen. That's clearly quite some damage to the 158.

(The first image shows a general view inside the tunnel, with the fronts of both trains alongside one another. The second picture is a zoomed version of the first, showing a section of class 158 bodyshell resting inside the damaged cab of the class 159).

We now know that this photo shows the front of the rear two car GWR class 158. There is two other photos that actually show the front of the leading two car GWR class 158, which is the real front of the train.

 

[backontrack]

Nice to see that the statement clearing up all the confusion and speculation about what caused the collision has only led to more confusion in the form of SPAD/SPAR or whatever terms exist for going past a red/danger signal.

Bit of undue cynicism there! I was only asking for clarification.

 

[USRailFan]

It will be an issue for GWR to lose a 158 (which they almost certainly will, repair of the damaged rear unit of 1F30 is extremely unlikely). I would imagine less so for SWR, who always seemed to have plenty of slack with their allocation at Salisbury even pre-Covid.

One thinkable outcome, I suppose, might be to repair the 158 with the undamaged endcar from the 159, and then either keep the 159 middle car for spares, or put it into another unit if needed?

 

[LAX54]

SPAR is for a signal reverting to red in front of the driver. Various categories depending on why the signal reverted (equipment malfunction, signalling reverting but driver unable to stop in time, or train runaway)

A train passing a "valid" red signal is a SPAD (cat A), regardless of why the train passed the signal. That doesn't mean driver is at fault

Correct, The Signal was Red for a reason, thus it was a SPAD regardless, as @Domh245 says, it does NOT mean the Driver is at fault.

Will there be any internal questions as to why a Network Rail spokesman apparently announced that the signalling system had been “knocked out”?

Assume at the start of the incident details were hazy for a while, and no doubt the signalling was affected, but after investigation once everyone on site, may have found that it may not have been that at all.

I find it ridiculous that drivers are given no warning that they are going to be following the RHTT on their diagrams . Control will have this information, so there's no excuse.

I had this on Saturday and the adhesion was awful.

Yet some drivers prefer following an RHTT, they say the adhesion is far better ! many times when we have had 'issues' and had an RHTT do some special runs, we speak to the Driver following, who normally says it's a lot better, if he says its just as bad......the RHTT will do another run !

 

[swt_passenger]

Assume at the start of the incident details were hazy for a while, and no doubt the signalling was affected, but after investigation once everyone on site, may have found that it may not have been that at all.

Yes that’s the reasoning we were discussing a few posts after my earlier question. Posts 934/935. The first announcements were being made when they still thought there had been two incidents a few minutes apart.

 

[RPI]

One of the images from within the tunnel shows a lump of the rear corner of the 158 has been torn off and is against where the 159 driver's side cab bulkhead should be - the small window and the signage for the cycle area can be clearly seen. That's clearly quite some damage to the 158.

Photos below; not mine.

(The first image shows a general view inside the tunnel, with the fronts of both trains alongside one another. The second picture is a zoomed version of the first, showing a section of class 158 bodyshell resting inside the damaged cab of the class 159).

I can't work out whether that is just a door from the 158. Though it looks a bit big for a 158 door, if not then logically that will be from the rear coach as the bike sign would be closest to the door and the small window is from the bike area. Could just be an easy (well, not easy, but you know what I mean) panel to weld back in dependent on how damaged the body shell is. Certainly losing 2 158's will have a huge effect as we're short of units as it is, again I'm speculating, but the front unit may be able to return to service as it doesn't appear from the limited pictures available that its too badly damaged, obviously though there could be some to the couplings from when the units came apart!

 

[Towers]

I can't work out whether that is just a door from the 158. Though it looks a bit big for a 158 door, if not then logically that will be from the rear coach as the bike sign would be closest to the door and the small window is from the bike area. Could just be an easy (well, not easy, but you know what I mean) panel to weld back in dependent on how damaged the body shell is. Certainly losing 2 158's will have a huge effect as we're short of units as it is, again I'm speculating, but the front unit may be able to return to service as it doesn't appear from the limited pictures available that its too badly damaged, obviously though there could be some to the couplings from when the units came apart!

Definitely not a door; you can see the green paintwork and the silver stripe, and as you say it's too big for a door.

I'm also hopeful that the leading set will make a comeback! I can't see that the damaged unit is likely to, from what can be made out in the pics it looks like the inner ends of both cars are pretty mangled. Time will tell, I guess.

 

[paul1609]

Were they running roughly to schedule? If so why would planning have allowed a conflict? This isn't a dense metro operation.

There is a major flow that relies on a connection between the GWR train and the SWR train. There are far more passengers from Southampton/Portsmouth/South Coast to the WofE line towards Exeter than from the WofE to the Bristol line. The Bristol line generally relies on Westbury for its London connection.