ScotRail HST derailment at Dalwhinnie (10/04/2021)

[gnolife]

The actions of the driver seem short of the mark from the psychometric slant: situational awareness and fast reactions?

Not sure where you're getting that from - the report seemed to have nothing to comment on for what the driver did?

 

[GC class B1]

Not sure where you're getting that from - the report seemed to have nothing to comment on for what the driver did?

The issue here is that the report did not appear to consider the driver’s actions. I am neither a driver nor a signaller but have over 50 years experience in this industry. I am surprised that the driver didn’t stop the train as soon as he/she realised that the train had been incorrectly routed but instead appears to have accelerated. I note from the report that there is only one signal (DW3) at the crossover so I would expect if the points were set to crossover to the down line then this signal would be held at red until the driver had contacted the signaller as the speed through the crossover is much lower than line speed on the up line. Perhaps signallers and drivers will correct me if I am wrong.

 

[43096]

The issue here is that the report did not appear to consider the driver’s actions. I am neither a driver nor a signaller but have over 50 years experience in this industry. I am surprised that the driver didn’t stop the train as soon as he/she realised that the train had been incorrectly routed but instead appears to have accelerated. I note from the report that there is only one signal (DW3) at the crossover so I would expect if the points were set to crossover to the down line then this signal would be held at red until the driver had contacted the signaller as the speed through the crossover is much lower than line speed on the up line. Perhaps signallers and drivers will correct me if I am wrong.

But this was a wrong-side failure which meant signal DW3 was cleared to a proceed aspect even though the points were reversed. The points are a bit further on, and this was 3am in the middle of nowhere so even with an HST’s headlights it’s unlikely the driver would see how the points were set.

 

[BRX]

The report says

The driver, who had started to reduce power, felt a lurch as the train moved
across onto the down line. He applied the emergency brake as the train stopped.
The rear of the train came to a stand around 35 metres beyond the toes2 of 13B
point end. The driver then alerted the signaller.

also

The driver checked DW3 signal and, after acknowledging the conductor team
manager’s permission to start, applied power and the train began to move. It was
now 03:00:28 hrs. From analysis of the OTDR, the front of the train passed over
the toes at 13A point end around 25 seconds later, travelling at around 25 mph
(40 km/h). It was dark and the driver realised the train had been wrongly diverted
onto the down line when he felt it lurch. Shortly afterwards, the OTDR registered a
loss of brake pipe air pressure, and the train started to slow.

The driver applied the emergency brake as the train came to a stand. He then
called the signaller on the Global System for Mobile Communications-Railway
(GSM-R) radio.

Don't think it says anything about him "accelerating".

The only thing that's a little unclear is the time between noticing the wrong direction and the emergency brake being applied.

When it talks about "a loss of brake pipe air pressure" does that imply a loss related to a pipe becoming detached as a result of the derailment, or just a loss from a normal application of the brake?

(It's unusual for an RAIB report not to be completely clear about a sequence of events)

 

[John Bishop]

The issue here is that the report did not appear to consider the driver’s actions. I am neither a driver nor a signaller but have over 50 years experience in this industry. I am surprised that the driver didn’t stop the train as soon as he/she realised that the train had been incorrectly routed but instead appears to have accelerated. I note from the report that there is only one signal (DW3) at the crossover so I would expect if the points were set to crossover to the down line then this signal would be held at red until the driver had contacted the signaller as the speed through the crossover is much lower than line speed on the up line. Perhaps signallers and drivers will correct me if I am wrong.

The report once again shows NR sadly lacking when it comes to procedures and policy and as the RAIB have stated, I can’t bear to imagine what would have happened if the train was at line speed or another one on the down line.

 

[matchmaker]

The report makes very disturbing reading!

 

[computerSaysNo]

I note from the report that there is only one signal (DW3) at the crossover so I would expect if the points were set to crossover to the down line then this signal would be held at red

I would imagine that if the system was incapable of detecting that one turnout was still set incorrectly (while the other was correct) that would therefore directly prevent the protecting signal being automatically held at red.
In very basic technical terms it sounds like it could be described as a logic gate being set to OR when it should have been AND.
E.g.

if ((turnout1.isSetStraight() == true) OR (turnout2.isSetStraight() == true)) { setRouteIsSafe(true); // route is safe protectingSignal.clear(); //clear signal/set to green } else { setRouteIsSafe(false); // route is not safe protectingSignal.block(); // block signal/set to red. }
when the condition should have been
if ((turnout1.isSetStraight() == true) AND (turnout2.isSetStraight() == true))

Edit: actually, after consideration, it's not. I guess what I'm describing would be more a processing error whereas what happened seems to be a detection error.

I am surprised that the driver didn’t stop the train as soon as he/she realised that the train had been incorrectly routed

It takes quite a long time for the brakes to apply on a HST, even with striking the Big Red Button the brakes will take at least a couple of seconds to go from fully released to fully applied.

 

[niggill617@gma]

Not sure where you're getting that from - the report seemed to have nothing to comment on for what the driver did?

Precisely, the report fails to mention what the driver should have done.

 

[4069]

DW3 is a wire-worked semaphore, and is visible, still at 'clear', in the background of figure 8, taken after the derailment. The locking and the (incorrectly wired) detection permitted the signaller to clear it, as the report explains.

 

[Railsigns]

DW3 is a wire-worked semaphore,

No; DW3 is a motor-operated semaphore.

 

[4069]

No; DW3 is a motor-operated semaphore.

My apologies- corrected

 

[MadMac]

It takes quite a long time for the brakes to apply on a HST, even with striking the Big Red Button the brakes will take at least a couple of seconds to go from fully released to fully applied.

The other thing that needs to be considered is the driver's "suspension of disbelief" time: they have to process that something that shouldn't be happening is actually happening and react to that.

 

[skyhigh]

I am surprised that the driver didn’t stop the train as soon as he/she realised that the train had been incorrectly routed

If you're making a signalled move there is no requirement to make sure the route is correctly set - you just trust the signalling.

 

[GC class B1]

Don't think it says anything about him "accelerating".

The train was travelling at 25 MPH when it reached points 13A and 33 MPH when they moved under the train.

== Doublepost prevention - post automatically merged: 26 Sep 2022 ==

It takes quite a long time for the brakes to apply on a HST, even with striking the Big Red Button the brakes will take at least a couple of seconds to go from fully released to fully applied.

I have calculated the stopping distance from the driver hitting Emergency to stopping from 25 MPH to be no more than 75 metres. The train length was about 155 metres and the train stopped 35 metres from the toe of points 13B. This suggests that the train travelled at least a 190 metres from the point the driver felt the lurch. Had the driver make an Emergency brake application at the point that the train lurched across the crossover the train may not have derailed.

== Doublepost prevention - post automatically merged: 26 Sep 2022 ==

If you're making a signalled move there is no requirement to make sure the route is correctly set - you just trust the signalling.

My point here is that if my surmise is correct that the signal would be held at red until the signaller had told the driver that the move was over the crossover, then I think the driver should have realised there was a problem and made a Full Service brake application as soon as the lurch was felt.

== Doublepost prevention - post automatically merged: 26 Sep 2022 ==

When it talks about "a loss of brake pipe air pressure" does that imply a loss related to a pipe becoming detached as a result of the derailment, or just a loss from a normal application of the brake?

(It's unusual for an RAIB report not to be completely clear about a sequence of events)

The loss of Brake Pipe pressure will have occurred when the brake pipes between vehicles parted at about the time of the derailment.

 

[AVK17]

My point here is that if my surmise is correct that the signal would be held at red until the signaller had told the driver that the move was over the crossover, then I think the driver should have realised there was a problem and made a Full Service brake application as soon as the lurch was felt.

Your surmise is totally wrong. You need to actually take the time to read the report (paying particular attention to paragraphs 41, 42 and 43) because what you’ve written shows you have completely picked up the wrong end of the stick about the sequence of events. It is very unfair to try to pin this on the driver as it had nothing to do with their actions.

 

[43096]

My point here is that if my surmise is correct that the signal would be held at red until the signaller had told the driver that the move was over the crossover, then I think the driver should have realised there was a problem and made a Full Service brake application as soon as the lurch was felt.

Before you dig yourself into a bigger hole, go and actually read the report. It's clear that you have failed to grasp what has happened - as I said in post #123 it was a wrong-side signalling failure: the train wasn't supposed to be using the crossover to the down line, it was supposed to be carrying straight on along the up line.

 

[GC class B1]

Your surmise is totally wrong. You need to actually take the time to read the report (paying particular attention to paragraphs 41, 42 and 43) because what you’ve written shows you have completely picked up the wrong end of the stick about the sequence of events. It is very unfair to try to pin this on the driver as it had nothing to do with their actions.

To explain my point. It seems to me that the driver would have read the clear signal to indicate that the route was set for the train to proceed on the up line. On reaching the crossover and feeling the lurch it seems the driver realised the train had been wrongly routed but instead of braking he accelerated. I can’t understand why a driver being route incorrectly over a 15MPH crossover would accelerate to 33 MPH.

 

[Dieseldriver]

Your surmise is totally wrong. You need to actually take the time to read the report (paying particular attention to paragraphs 41, 42 and 43) because what you’ve written shows you have completely picked up the wrong end of the stick about the sequence of events. It is very unfair to try to pin this on the driver as it had nothing to do with their actions.

Indeed, a few seconds during the event picked apart by people with hours and hours to consider the sequence of events. We’re all human and as a Driver, I’d imagine in the event of a wrong side failure (the impossible occurring to a Driver who is preconditioned to trust the signalling system because I have to, otherwise I’d never have the bottle to drive a train at linespeed) there would be a fair amount of reaction time for me to comprehend the ‘impossible’….

 

[43096]

To explain my point. It seems to me that the driver would have read the clear signal to indicate that the route was set for the train to proceed on the up line. On reaching the crossover and feeling the lurch it seems the driver realised the train had been wrongly routed but instead of braking he accelerated. I can’t understand why a driver being route incorrectly over a 15MPH crossover would accelerate to 33 MPH.

No, the train continued to accelerate - he was already accelerating after leaving the platform having seen a signal telling him he was heading on the up line. Once the power controller is knocked off the train will still continue to accelerate until the power ramps down. If the RAIB had seen anything on the OTMR download they would no doubt have investigated further.

 

[43096]

Indeed, a few seconds during the event picked apart by people with hours and hours to consider the sequence of events. We’re all human and as a Driver, I’d imagine in the event of a wrong side failure (the impossible occurring to a Driver who is preconditioned to trust the signalling system because I have to, otherwise I’d never have the bottle to drive a train at linespeed) there would be a fair amount of reaction time for me to comprehend the ‘impossible’….

And it was at 3am in the morning, in the middle of nowhere - not much light around!

 

[Purple Train]

To explain my point. It seems to me that the driver would have read the clear signal to indicate that the route was set for the train to proceed on the up line. On reaching the crossover and feeling the lurch it seems the driver realised the train had been wrongly routed but instead of braking he accelerated. I can’t understand why a driver being route incorrectly over a 15MPH crossover would accelerate to 33 MPH.

1) The crossover having a limit of 15mph has absolutely nothing to do with it. The rough figure of 25mph as the train's speed at the toe of the points does have something to do with your point.
2) Your point about the driver "accelerating" is misleadingly worded - it implies that the driver felt the lurch and then made a conscious decision to accelerate. The train was already accelerating out of Dalwhinnie station, well before it encountered the points. As other members have said, naturally there would be some reaction time required to process what was going on and brake accordingly. It was also dark, so visual clues would have been greatly reduced as well.
It's also possible that the lurch the driver felt was as the train ran through the trailing points, which were not set for his train/the rear of the train derailing, whichever came first - in which case the train's speed would be higher than the rough 25mph figure quoted as the train's speed at the toe of the facing points.

(EDIT: @43096 beat me to it, but their post weirdly didn't show up until now for me!)

 

[MadMac]

Indeed, a few seconds during the event picked apart by people with hours and hours to consider the sequence of events. We’re all human and as a Driver, I’d imagine in the event of a wrong side failure (the impossible occurring to a Driver who is preconditioned to trust the signalling system because I have to, otherwise I’d never have the bottle to drive a train at linespeed) there would be a fair amount of reaction time for me to comprehend the ‘impossible’….

Precisely the point I made a few posts ago re "suspension of disbelief".

 

[skyhigh]

On reaching the crossover and feeling the lurch it seems the driver realised the train had been wrongly routed but instead of braking he accelerated. I can’t understand why a driver being route incorrectly over a 15MPH crossover would accelerate to 33 MPH.

You seem incorrect in that assumption.

The train was travelling at 25 MPH when it reached points 13A and 33 MPH when they moved under the train.

So you have a HST potentially accelerating at full power. 25mph when it reaches the points, a few seconds more until the leading wheelset reaches the points and makes the train lurch, a few seconds for the driver to realise what's happening and by that point you could easily be doing 33mph before you have a chance to even cut power.

I think it's almost insulting the way you seem to suggest the driver knew they were going over a 15mph crossover and deliberately chose to accelerate!

 

[SamYeager]

I have calculated the stopping distance from the driver hitting Emergency to stopping from 25 MPH to be no more than 75 metres. The train length was about 155 metres and the train stopped 35 metres from the toe of points 13B. This suggests that the train travelled at least a 190 metres from the point the driver felt the lurch. Had the driver make an Emergency brake application at the point that the train lurched across the crossover the train may not have derailed.

== Doublepost prevention - post automatically merged: 26 Sep 2022 ==

It's not possible for a human being to instantaneously react to something going wrong. It takes a certain amount of time for the brain to (a) recognise that something's not normal and (b) initiate action as a result of that.

 

[skyhigh]

I am neither a driver nor a signaller but have over 50 years experience in this industry.

Out of interest, what is your 50+ years of experience in?

 

[GC class B1]

Out of interest, what is your 50+ years of experience in?

My 50 years experience has included technical and managerial roles in Traction and Rolling Stock, Overhead Line and Plant including on track plant. I have been involved with the investigation of incidents and been an incident investigation panel member in BR days. I have devised and audited Traction and Rolling Stock maintenance and overhaul specifications and processes including safety systems. I have also worked in an overseas railway organisation.

 

[alxndr]

Ironically the explanatory diagrams at the end of the report are incorrect.

Figure B3 has the contacts in 13A in the incorrect position. The contact should be made between D2 and D3, not D1 and D2. This is shown correctly in Figure B4.

Figure B3 also labels the relays as incorrectly energised. They are in fact correctly de-eneegised. The caption is correct, but the annotation within the diagram is not.

Figure B4 also shows a link appearing in 13A between D7 and D8 that is not present in Figures B1 and B3. From a quick look it appears that it should have been there, otherwise obtaining reverse detection would be impossible, but it implies that there was an error in that machine as well. The report does not mention any work done to 13A, or wiring errors there, so I assume the error is with the diagram and not representative of what was on the ground.

 

[eman_resu]

My point here is that if my surmise is correct that the signal would be held at red until the signaller had told the driver that the move was over the crossover, then I think the driver should have realised there was a problem and made a Full Service brake application as soon as the lurch was felt.

Bearing in mind that the geometry of the points can be skewed by the lens of the camera, figure 8 and figure 9 in the report would seem to indicate that the crossover from the up to the down isn't particularly tight.

Is it possible that the 'lurch' the driver felt was only slight enough to confirm the wrong routing, (hence the reduction in power once the driver realised the wrong routing) as opposed to a significant sideways movement to alert that the train was derailing.

There is much talk of the actions of the driver, however given the dark conditions, the relatively low speeds and the geometry of the crossover, (and the inherent faith that the being given the clear signal meant that the points were set correctly), I would suggest that the actions of the driver were commensurate with the realisation of taking an incorrect route, as opposed to an impending derailment.

After all, it looks like the train would have remained entirely on the rails had 13A not operated under coach E.

I was under the impression that the point machine controls are normally inhibited if the track circuit over them is occupied though (clearly not, as this would have been raised in the report)

 

[matchmaker]

There is also that up line to down line is not a signalled movement, whereas down line to up line is. As already pointed out, this is a very remote location and very dark!

 

[niggill617@gma]

The other thing that needs to be considered is the driver's "suspension of disbelief" time: they have to process that something that shouldn't be happening is actually happening and react to that.

The train took 25 seconds to accelerate up to 25 mph, so about 8 seconds to reach 33 mph, from the start of the points, to the moment the brake pipe fractured, and derailment. The red button should surely have been pressed, along with brake lever to emergency position, before the train actually stopped.

Playing the Monday morning quarterback is easy for sure, but lessons need to be learnt.