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

[the sniper]

4) Emergency Protection of the line - imho something that is not always given enough briefing or training time these days, it (thankfully) being such a rare necessity, more so since GSM-R.

Generally speaking, I don't think the basics are kept at the forefront of peoples minds anymore, unfortunately. In GSM-R we trust...

 

[21C101]

With respect, I’m not sure much of what you put can be assumed either.

I think what I put can be reasonably stated based on the evidence freely available (such as photos of the east end of the tunnel taken this morning in daylight).

But the point I was trying to make is that there is much unknown and even official/semi official statements put out in the immediate aftermath of the event have to be treated with great caution.

We will know more within a few days when the investigators have done their job. I fear it may make for uncomfortable reading though.

In the meanwhile we must be thankful for what so easily could have happened but didn't happen, which could have been truly awful.

 

[81097]

C

They're not switch diamonds, so shouldn't have played a part in proceedings. I'd suggest that the fact that the facing points on the Up can be seen to still be set towards Romsey is, though, significant.

Correct, that was my thinking if they were set for Romsey then the Down signal should never have cleared towards the Junction.

 

[bramling]

Correct, that was my thinking if they were set for Romsey then the Down signal should never have cleared towards the Junction.

It's also of some value that we can see the TD doesn't appear to have stepped forwards for the SWR train.

 

[Gloster]

C

Correct, that was my thinking if they were set for Romsey then the Down signal should never have cleared towards the Junction.

If they are not switch diamonds (they weren’t in my day there, but I assumed that some of the other posters on this thread had more recent knowledge) then it looks a though the London hit the rear of the Bristol, which was still on the sharp curve, partially side-on and was then diverted to the right, rather than hitting it straight on. If the Up line points were set for the Romsey line then, barring a major wrong-side signalling favour, the protecting signal on the Andover line would be at red and the previous one at yellow.

 

[mcmad]

I don't think anything further can be assumed than:

The GW train came to a stand with the rear carriage outside the tunnel fouling tunnel junction.

The GW train rear was then struck by the SWR train shortly afterwards and due to the position of the rear of the GW train, rather than a full impact, it sideswiped and was deflected/derailed onto the up side through the tunnel, with the tunnel wall and GW train acting like the side walls of a bobsleigh run to "guide" the SWR train while it came to a stand.

The derailed SWR appeared to progress a considerable distance into the tunnel before stopping.


Anything else, whether illicit reports or early official/semi official statements has to be treated with great caution.

In the meanwhile we should be truly thankful that the GW train wasn't fully in the tunnel (as had it been the SWR train would have full on rammed it) and that there wasn't an up train in the tunnel at the time, otherwise we could have been looking at something akin to Lewisham.

I'm not sure, based on the BTP statement, that you can assume point 1 on your list any more. The second part is realistically all that can be assumed to be accurate so far.

 

[jfollows]

They're not switch diamonds, so shouldn't have played a part in proceedings. I'd suggest that the fact that the facing points on the Up can be seen to still be set towards Romsey is, though, significant.

1F27 16:58 Bristol Parkway to Portsmouth Harbour passed over the up facing points towards Romsey at fractionally before 18:42, according to RTT

 

[bramling]

It is taken from the BTP statement: https://www.btp.police.uk/news/btp/...nt-at-fisherton-tunnel-salisbury---statement/

The points are very close to the tunnel mouth, so this is splitting hairs really.

 

[reddragon]

Daily Telegraph have posted an update:
- Train 1 didn't hit an object and derail
- Both trains travelling in same direction, train 2 crashed into side of train 1 in the tunnel
- Driver left with 'life-changing' injuries
- Total of 44 people assessed for injuries
https://t.co/KwGShGNR19?amp=1

Well that kills off 90% of the speculation on this thread!

 

[JN114]

I'm not sure, based on the BTP statement, that you can assume point 1 on your list any more. The second part is realistically all that can be assumed to be accurate so far.

Put much more succinctly than I would have managed, thank you.

 

[Ianno87]

I'm not sure, based on the BTP statement, that you can assume point 1 on your list any more. The second part is realistically all that can be assumed to be accurate so far.

Yep. All we can be certain of at this point is the final resting positions of each train.

 

[MarkyT]

Correct, that was my thinking if they were set for Romsey then the Down signal should never have cleared towards the Junction.

Indeed. Standard flank protection. Unless the points have been moved after the event. Maybe as part of some post-incident testing of the signalling. Most if not all interlockings of all types include comprehensive event logging today, so the changing states of all the primary relays during the incident should be clear from this.

 

[backontrack]

In the meantime, I think the best thing to do would be to sit tight and hope that what happened at Fisherton Tunnel was due to chance, rather than mechanical error. If it's a foreign object or entity fouling the line (e.g. Great Heck) rather than a points failure, then that's something at least.

 

[Signal Head]

The points are both trailing ones. The switch diamonds may well have still been set for the Bristol-Portsmouth which had just passed, but, presuming the Portsmouth-Bristol was correctly signalled, the London-Honiton should not have been there. It looks to me as though it is possible (I do not know enough to be certain) that the London may have been deflected towards the other line by the switch diamonds and so did not hit the rear of the Bristol straight on. It also looks as though the rear vehicle of the Bristol was still on the sharp curve coming off the Romsey line, which would also mean that the London did not hit it straight on. It could be either or both or neither, but I do not know definitely.

Note to Mods: there is an element of speculation here, but it is about the course of the accident, not its causes.

Including the speculation about 'switch diamonds', which don't exist.

As stated by someone earlier the junction has a fixed diamond.

 

[TheEdge]

Generally speaking, I don't think the basics are kept at the forefront of peoples minds anymore, unfortunately. In GSM-R we trust...

Don't get me started on the presumed "infallibility" if GSMR. Its a slippery slope...

 

[TT-ONR-NRN]

To hear that the driver has life changing injuries is so very sad Poor guy, just doing his job like a normal person it’s horrible

Also, I read on I think BBC that the GWR driver was less badly hurt but has suffered a broken ankle.

 

[paul1609]

They're not switch diamonds, so shouldn't have played a part in proceedings. I'd suggest that the fact that the facing points on the Up can be seen to still be set towards Romsey is, though, significant.

I don't disagree with your conclusion but if you've seen the network rail photos the springs of the SWR leading bogie are by the rear car of the GWR train and the tunnel wooden sleeper track has been totally destroyed so the wrong side points may have been moved under the collision.

 

[Ianno87]

As stated by someone earlier the junction has a fixed diamond.

And are quite clearly visible as such in the picture on the BBC News Article.

 

[bramling]

Yep. All we can be certain of at this point is the final resting positions of each train.

I'd say we can also be pretty certain that the route wasn't set for the SWR train.

 

[Suraggu]

Widely reported does not necessarily mean an actual, factual report.

Considering myself and others who are in the industry have quoted further down this thread that an initial message from control of an incident such as this are reported to what they have been informed about.

At that time I imagine those in the Basingstoke ROC the last thing they were thinking about was are we sure there is a train is on its side, rather than we need to publish the information given at that time from what would of been an official source.

For example I remember the initial message of a derailment during the Waterloo blockade, within a couple of hours the facts were more laid out than just a train derailment.

 

[backontrack]

Widely reported does not necessarily mean an actual, factual report.

Especially as we know one of the trains did strike an object (that object being the other train).

I wouldn't trust anything coming out of @PoliticsForAlI. It's a pretty disreputable twitter aggregator being run out of a uni student's bedroom. (At least I've bothered to sit down in the kitchen before writing this!)

 

[Peter Sarf]

I saw in one photograph that the track is somewhat moved/deformed near the diamond. Presumably as a result of the collision. Would it be possible that the point ends on the up line could have moved as a result of the collision and so do not reliably indicate any route set just prior to the collision ?.

 

[westcoaster]

If you read the BTP statement it says the GWR hit the SWR unit.

 

[bramling]

Don't get me started on the presumed "infallibility" if GSMR. Its a slippery slope...

The lesson of not legging it down the line to protect the train was learnt, with tragic consequences, in the 1995 Ais Gill accident. It may well also turn out to be the case that the subject of emergency protection may be something of relevance during last year's Carmont accident (where there was certainly considerable scope for a secondary collision). It seems unlikely to have been a salient factor yesterday though.

 

[backontrack]

I saw in one photograph that the track is somewhat moved/deformed near the diamond. Presumably as a result of the collision. Would it be possible that the point ends on the up line could have moved as a result of the collision and so do not reliably indicate any route set just prior to the collision ?.

If we are going to speculate, then this is a very good point, I think.

 

[Suraggu]

Especially as we know one of the trains did strike an object (that object being the other train).

I wouldn't trust anything coming out of @PoliticsForAlI. It's a pretty disreputable twitter aggregator being run out of a uni student's bedroom. (At least I've bothered to sit down in the kitchen before writing this!)

It's certainly a disreputable account along with NewsForAll etc.

 

[QueensCurve]

RAIB report will be interesting on this one when a following train has received a proceed aspect allowing an initial accident to be worsened. Delighted to here the injuries are minor as this is most important fact currently.

That is speculation.

 

[backontrack]

The lesson of not legging it down the line to protect the train was learnt, with tragic consequences, in the 1995 Ais Gill accident. It may well also turn out to be the case that the subject of emergency protection may be something of relevance during last year's Carmont accident (where there was certainly considerable scope for a secondary collision). It seems unlikely to have been a salient factor yesterday though.

What is really tragic about Ais Gill is that the one fatality appears to have been the person who was doing the most to protect the train and its passengers.

It's certainly a disreputable account along with NewsForAll etc.

Indeed, I wouldn't touch it.

 

[MarkyT]

I'd say we can also be pretty certain that the route wasn't set for the SWR train.

I don't think it's possible to draw that conclusion for certain. The timing of the second movement so close behind the first suggests a signalled move. A verbal proceed past a red would probably have taken longer, and the protecting signal is also TPWS fitted, so a SPAD should have resulted in emergency braking which would have brought the train to a stand before the junction conflict point.

 

[Bacon_BMW]

I saw in one photograph that the track is somewhat moved/deformed near the diamond. Presumably as a result of the collision. Would it be possible that the point ends on the up line could have moved as a result of the collision and so do not reliably indicate any route set just prior to the collision ?.

Points can “banana” where they’re run through in the straight direction while they’re set for a diverging route. Not sure if there is an equivalent for the other direction.