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

[alxndr]

Will the RAIB have even looked that closely into the time it took for the train to come to a stop? The movement of the train isn't particularly relevant to "improve railway safety by preventing future railway accidents or by mitigating their consequences." The key thing to preventing another incident like this would be to ensure that equipment is installed correctly and properly tested.

 

[GC class B1]

Will the RAIB have even looked that closely into the time it took for the train to come to a stop? The movement of the train isn't particularly relevant to "improve railway safety by preventing future railway accidents or by mitigating their consequences." The key thing to preventing another incident like this would be to ensure that equipment is installed correctly and properly tested.

I would expect the RAIB looked at the performance of the train, as a defective train would be considered a causal factor in the outcome. A thorough investigation would consider all factors and not just the immediate and obvious initial cause.

 

[computerSaysNo]

Just to clarify, I refer to the red button as being the GSRM emergency call facility

Ah.
When I was talking about the Big Red Button I was referring to the emergency brake plunger.
Oops.

 

[BRX]

I have also been a bit unclear about what the references to the "red button" mean.

In terms of danger to other trains, the time taken to stop the train wouldn't really have made much difference as far as I can see. As soon as the front had started moving onto the crossover, there would be a danger to anything coming the other way, and it wouldn't have been removed even with an instantaneous reaction from the driver.

But if there's a red button that sends a message to stop other traffic then clearly, the sooner it's pressed, the greater the likelihood of it preventing something.

RAIB reports are usually very thorough and they quite often go into some detail on aspects of what happened, even if they weren't "causal" or had no impact on potential outcomes - with some explanation of why the report decides they need not be considered further.

Also, sometimes they'll contain some discussion of something that happened, decide it had no impact in this case but nonetheless include a recommendation that's relevant to it, because it's been identified that it could be significant in other scenarios.

I read these reports as a complete layperson (and am always impressed with how well written they are) but this one feels like there's a part of what happened that has simply escaped discussion.

None of this needs to mean there's any criticism of the driver ... to me it's entirely understandable that it would take some time to realise that something's not right and react to it. But I might expect some discussion of things that could be changed to make it more immediately obvious to a driver that a wrong route has been taken.

Alternatively, perhaps the answer is that it doesn't actually matter too much because the system as a whole did virtually instantly detect something was wrong (there's a mention of multiple alarms going off in the signalbox) and the signaller had the means to stop other traffic. But it's not discussed.

 

[GC class B1]

I have also been a bit unclear about what the references to the "red button" mean.

In terms of danger to other trains, the time taken to stop the train wouldn't really have made much difference as far as I can see. As soon as the front had started moving onto the crossover, there would be a danger to anything coming the other way, and it wouldn't have been removed even with an instantaneous reaction from the driver.

But if there's a red button that sends a message to stop other traffic then clearly, the sooner it's pressed, the greater the likelihood of it preventing something.

RAIB reports are usually very thorough and they quite often go into some detail on aspects of what happened, even if they weren't "causal" or had no impact on potential outcomes - with some explanation of why the report decides they need not be considered further.

Also, sometimes they'll contain some discussion of something that happened, decide it had no impact in this case but nonetheless include a recommendation that's relevant to it, because it's been identified that it could be significant in other scenarios.

I read these reports as a complete layperson (and am always impressed with how well written they are) but this one feels like there's a part of what happened that has simply escaped discussion.

None of this needs to mean there's any criticism of the driver ... to me it's entirely understandable that it would take some time to realise that something's not right and react to it. But I might expect some discussion of things that could be changed to make it more immediately obvious to a driver that a wrong route has been taken.

Alternatively, perhaps the answer is that it doesn't actually matter too much because the system as a whole did virtually instantly detect something was wrong (there's a mention of multiple alarms going off in the signalbox) and the signaller had the means to stop other traffic. But it's not discussed.

I completely agree with your assessment and it is well presented. As a layperson your views are equally important and it is possible that a layperson will spot an important point that is missed by the professionals who may not be able to see the wood for trees.
With regard to your point about making the wrong move apparent to the driver there are two points in this respect that are not mentioned in the report but have been highlighted in this thread. The first point is that the unintended move across the crossover is not signalled and the driver presumably realised this when the train lurched. Signalled moves through crossovers are indicated to the driver by the signalling system. The other point not mentioned is that as the move is not signalled, then until the train either ran through points 13b or occupied a track circuit on the down line any trains travelling on the down line at the time would not be alerted to the potential conflict. The use of a Railway Emergency Call (REC) would have brought any trains at risk of becoming involved with the incident to a stop.

 

[Greybeard33]

I would expect the RAIB looked at the performance of the train, as a defective train would be considered a causal factor in the outcome. A thorough investigation would consider all factors and not just the immediate and obvious initial cause.

All the causal factors identified in the report relate to the incorrect configuration of the wiring in the 13B point machine.

Once signal DW3 was cleared with the 13A points mis-set, the derailment became inevitable, regardless of the driver's subsequent actions and the performance of the train in response to those actions. Therefore it would have been a waste of resources for the RAIB to investigate the derailment sequence in more detail.

 

[BRX]

With regard to your point about making the wrong move apparent to the driver there are two points in this respect that are not mentioned in the report but have been highlighted in this thread. The first point is that the unintended move across the crossover is not signalled and the driver presumably realised this when the train lurched.

Although it's not really clear in the report what the "lurch" was - was it at the first set of points, at the second, or was it actually the lurch felt when the rear of the train derailed?

 

[GC class B1]

All the causal factors identified in the report relate to the incorrect configuration of the wiring in the 13B point machine.

Once signal DW3 was cleared with the 13A points mis-set, the derailment became inevitable, regardless of the driver's subsequent actions and the performance of the train in response to those actions. Therefore it would have been a waste of resources for the RAIB to investigate the derailment sequence in more detail.

The purpose of investigating all factors involved in an incident (including near misses) is to ensure that all lessons can be learned and this is certainly the case with the excellent RAIB reports. The posts in this thread have suggested there may be further factors to consider in addition to the incorrect configuration of the points.

 

[Greybeard33]

The purpose of investigating all factors involved in an incident (including near misses) is to ensure that all lessons can be learned and this is certainly the case with the excellent RAIB reports. The posts in this thread have suggested there may be further factors to consider in addition to the incorrect configuration of the points.

But what safety lessons are you suggesting could be learnt from these "further factors"?

The RAIB was surely correct to focus on ways to reduce the risk of similar maintenance errors causing more wrong side signalling failures in the future.

 

[Wilts Wanderer]

Although it's not really clear in the report what the "lurch" was - was it at the first set of points, at the second, or was it actually the lurch felt when the rear of the train derailed?

I read it as being the ‘lurch’ of the train changing direction as it went through the points, not an unusually strong movement, just one that the driver was not anticipating.

 

[BRX]

I read it as being the ‘lurch’ of the train changing direction as it went through the points, not an unusually strong movement, just one that the driver was not anticipating.

Whatever any of us read it as ... the wording of the report does not make it clear.

 

[niggill617@gma]

Whatever any of us read it as ... the wording of the report does not make it clear.

RAIB have informed me that; the investigation only focuses on the wrong side signalling failure leading to derailment. Other factors are not necessary to consider.

 

[GC class B1]

RAIB have informed me that; the investigation only focuses on the wrong side signalling failure leading to derailment. Other factors are not necessary to consider.

I am a bit surprised by this in view of the depth and breadth of other investigations.

 

[4069]

If you can think of any other factors in the accident that could result in a recommendation for a safety improvement, and whose investigation would not give rise to accusations of wasting public money, then I'm sure RAIB would be pleased to hear from you.

 

[niggill617@gma]

Just to clarify, I refer to the red button as being the GSRM emergency call facility, stopping all trains. The driver clearly would have been subject to startle for a number of seconds, before realising a no route? When the brake pipe is vented the power is automatically cut. The cab operated emergency brake selection, is either by plunger or brake control lever. ATP data states 2 seconds for full rate of deceleration to establish. The truth is just less than 5 seconds for a 2 plus 8, and lessor for a 2 plus 5. This is proved by the timeline within the RAIB Didcot report 23/2008 page 59 and 60. There is definitely no further acceleration regarding any delay function.

Hopefully RAIB will answer the question regarding time and distance to stop from brake pipe vent. GC class B1 makes a very valid hypothesis. The RAIB report regarding stopping distance is not logical, unless 3 bogies in the ballast produces no resistance, which it certainty will.

I asked RAIB for some extra data. The time to stop from brake pipe vent, is confirmed as 11.5 and 9.7 seconds, the speed at vent was 33.3 and 34.4 mph, taken from each power car OTDR.

This calculates to a stopping distance of around 90 m. Therefore the consist was dragged with 3 bogies derailed, by around 75 m under power, notch 1 power is recorded at brake pipe vent, with the brake lever still at release.

Within the incursion the train accelerated from 25 to 34 mph for 15 seconds, before automatic brake application.

 

[Stathern Jc]

Just curious.
Does anyone know whether the crossover is likely to be reinstated?
Passenger convenience / mobility issues had been mentioned earlier. The derailment was quite a while ago.