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

[niggill617@gma]

Thanks I will amend.

 

[TheEdge]

Statutory instrument 1798 , the text is clear "understand performance calculation"

Seeing as this is your favourite bit of paperwork ever I thought I'd better have a look at it.

"understand braking systems and performance calculation" in a section titled "In relation to trains, their composition and the technical requirements for traction units, wagons, coaches and other rolling stock". To me reading it and in conjunction with the other points of that section it's nothing to do with the maths of deceleration or any pure physics. It's about a working understand of different brake systems in use and understanding the different performance and behaviours of those systems.

Then the section about "basic principles of physics" and "forces at the wheel". You would no doubt claim I need to be able to understand the whole process and maths behind the wheels turning. I'd understand that as if I apply work to the wheels with adhesion I'll move. If I apply some sort of retardation to those wheels I slow down. And then the rails guide the flanges laterally to keep me upright. What more do I need?

 

[AlbertBeale]

The understanding of friction or rail adhesion is mu, a coefficient with no units of measurement.

Your wording seems rather confused - perhaps your understanding of physics is a bit rusty! The coefficient of friction (usually referenced by a lower case Greek letter mu) is - as with many such coefficients in physics - a function of the specifics of the equipment or materials whose coefficient is being measured. Depending on how they're defined, a coefficient might be in some unit or other (eg a coefficient of viscosity can be in newton-seconds per metre squared); or, as in the case of a coefficient of friction (because it's defined as the ratio of 2 forces), it can be "dimensionless", ie a pure number. I guess that's what you mean by "with no units of measurement"?

 

[niggill617@gma]

yes correct, the two forces being normal reaction and static frictional force. Understand forces at the wheel.

Seeing as this is your favourite bit of paperwork ever I thought I'd better have a look at it.

"understand braking systems and performance calculation" in a section titled "In relation to trains, their composition and the technical requirements for traction units, wagons, coaches and other rolling stock". To me reading it and in conjunction with the other points of that section it's nothing to do with the maths of deceleration or any pure physics. It's about a working understand of different brake systems in use and understanding the different performance and behaviours of those systems.

Then the section about "basic principles of physics" and "forces at the wheel". You would no doubt claim I need to be able to understand the whole process and maths behind the wheels turning. I'd understand that as if I apply work to the wheels with adhesion I'll move. If I apply some sort of retardation to those wheels I slow down. And then the rails guide the flanges laterally to keep me upright. What more do I need?

your opinion with no real evidence, in my opinion. No point in protracted debate.

 

[XAM2175]

The consist took about 31 seconds to slow by 11 mph with about 50 percent selected, it should of [sic] been about 12 seconds simple maths, not "feel the force force the Luke" (inertia). The dynamic brake masking performance; utter folly. I mean 8 carriages of unbraked mass. Could of [sic] been the worst disaster this side of Paddington. The driver was let down by non-compliance of Rail Authorities regards continuation training.
...
Remember its knowledge not necessarily a procedure.

I feel I should point out to you that the colloquial terms "should've" and "could've" are contractions of "should have" and "could have", not "should of" and "could of".

In fairness, it's an easy misapprehension to acquire if you rely on the procedure of using the spelling that sounds 'right' rather than objective knowledge of this aspect of the English language.

 

[Randomer]

yes correct, should be lower case. the two forces being normal reaction and static frictional force. Understand forces at the wheel.

Putting aside the Physics discussion for a moment is your case that the driver of the train concerned in the Salisbury Incident required different or additional training on what the brake application would have done in terms of slowing the unit?

Or is it a more general one that drivers are being insufficiently trained in the idea of "my train weighs about this much today when I put in X amount of brake I should slow down by about Y amount in Z seconds?"

The former seems a more pertinent issue and is already being discussed e.g. slow gentle vs emergency. The latter doesn't seem particularly pertinent to the discussion at hand (although I do accept that it is relevant in other accidents or near misses e.g. the Sleeper issue you have mentioned.) As other posters have mentioned as long as you have a good idea of what should occur the precise knowledge of why seems not particularly relevant.

To give an example when I descend on a static rope made to the relevant standard at work I know by the end of the descent my body mass will elongate it about 80cm for that particular length of rope in use. There is a relatively simple rule of thumb for knowing this which serves perfectly well for routine jobs. Can I do the full calculation, yes, but it isn't a necessity or going to cause me or others additional risk if I don't (and its not a requirement of the standards I work to.) It would seem to be the same case here, as long as a driver knows roughly how much they should slow by for a particular brake application and in what time where is the necessity of knowing how to calculate exactly why that occurs?

 

[niggill617@gma]

I feel I should point out to you that the colloquial terms "should've" and "could've" are contractions of "should have" and "could have", not "should of" and "could of".

In fairness, it's an easy misapprehension to acquire if you rely on the procedure of using the spelling that sounds 'right' rather than objective knowledge of this aspect of the English language.

Thank you for being fair. Perhaps you could mark the rest of the forum, good luck.

Putting aside the Physics discussion for a moment is your case that the driver of the train concerned in the Salisbury Incident required different or additional training on what the brake application would have done in terms of slowing the unit?

Or is it a more general one that drivers are being insufficiently trained in the idea of "my train weighs about this much today when I put in X amount of brake I should slow down by about Y amount in Z seconds?"

The former seems a more pertinent issue and is already being discussed e.g. slow gentle vs emergency. The latter doesn't seem particularly pertinent to the discussion at hand (although I do accept that it is relevant in other accidents or near misses e.g. the Sleeper issue you have mentioned.) As other posters have mentioned as long as you have a good idea of what should occur the precise knowledge of why seems not particularly relevant.

To give an example when I descend on a static rope made to the relevant standard at work I know by the end of the descent my body mass will elongate it about 80cm for that particular length of rope in use. There is a relatively simple rule of thumb for knowing this which serves perfectly well for routine jobs. Can I do the full calculation, yes, but it isn't a necessity or going to cause me or others additional risk if I don't (and its not a requirement of the standards I work to.) It would seem to be the same case here, as long as a driver knows roughly how much they should slow by for a particular brake application and in what time where is the necessity of knowing how to calculate exactly why that occurs?

Non-compliance regards General Professional Knowledge. No criticism of the driver, only the absence of continuation training. The fact you can do the rope calculation is General Professional Knowledge.

 

[The Ham]

Putting aside the Physics discussion for a moment is your case that the driver of the train concerned in the Salisbury Incident required different or additional training on what the brake application would have done in terms of slowing the unit?

Or is it a more general one that drivers are being insufficiently trained in the idea of "my train weighs about this much today when I put in X amount of brake I should slow down by about Y amount in Z seconds?"

The former seems a more pertinent issue and is already being discussed e.g. slow gentle vs emergency. The latter doesn't seem particularly pertinent to the discussion at hand (although I do accept that it is relevant in other accidents or near misses e.g. the Sleeper issue you have mentioned.) As other posters have mentioned as long as you have a good idea of what should occur the precise knowledge of why seems not particularly relevant.

To give an example when I descend on a static rope made to the relevant standard at work I know by the end of the descent my body mass will elongate it about 80cm for that particular length of rope in use. There is a relatively simple rule of thumb for knowing this which serves perfectly well for routine jobs. Can I do the full calculation, yes, but it isn't a necessity or going to cause me or others additional risk if I don't (and its not a requirement of the standards I work to.) It would seem to be the same case here, as long as a driver knows roughly how much they should slow by for a particular brake application and in what time where is the necessity of knowing how to calculate exactly why that occurs?

Which is akin to car drivers knowing that when wet they should allow 3x the stopping distance and when icy 10x the stopping distance.

Some take it onboard, as typically when the roads are wet cars are recorded as being 2 to 3mph slower (85th percentile free flow speed), which reduces their stopping distance a little from maintaining their normal speed.

However that doesn't stop people from driving poorly for the conditions.

Yes knowing the maths isn't going to make you undertake the calculation, however for some understanding the theory allows them to understand why driving their car driving a little slower is benefitting in that it will reduce their risk of a collision. However even if it doesn't avoid it, the impact speed would be lower and therefore more likely to be survivable (either for them or the person they hit).

An ex colleague (a former traffic cop) would often say, you can teach any monkey to go fast in a straight line the skill is going fast round corners and safely.

Chances are you can do so without understanding the maths to the minutiae, however it certainly can help.

Often the issue is that, in the case of car drivers, people are lucky 99.9% of the time and they don't encounter a problem which puts them beyond their driving skills. In that last 0.1% of times they could have improved their chances of either avoiding trouble or being within the limit of their driving skills by going slightly slower.

Far too many car drivers see a speed limit as a target and not a limit, often meaning that they are going too fast for the conditions. Even slowing down by a few miles an hour in wet conditions when it's likely that the rate of breaking will be impacted can mitigate against a significant amount of the risk.

For instance a car doing 70 rather than 80 (yes I know 80 is too fast for the UK road network, but it highlights the point that fairly small percentage change in speed can make a reasonable difference) which tries to stop in wet conditions will stop in 76% of the distance of the faster car (even though the speed reduction is 12.5% the distance reduction is nearly double that at 24%) which will stop about 70m further along the road. If it's icy then the faster car keys going for a further 230m (that extra distance is about twice the normal stopping distance).

Now those distances may not feel significant to a car driver. Until you realise that going even 1m further could mean the difference between you stopping before hitting something. Whilst in a car most things you're likely to hit aren't going to end in your death, that doesn't mean that you aren't going to ruin your life or someone else's.

Obviously whatever speed someone is doing there's always the argument that they could have been going slower to reduce the likelihood of an incident (except in some very rare cases). As such I'm not criticising anyone (and certainly not the driver in question) however knowing that slowing a little more than you perhaps "need" to (even if that only by 5mph) well in advance of where you would normally consider slowing down when there's a higher than normal risk of poor breaking conditions it could be a useful thing to consider as it could reduce the chance of something going wrong and even if it doesn't it is likely to reduce the harm caused.

That's useful for those in control of most ground based modes of travel where surface conditions can have significant impacts on their ability to control their vehicle.

 

[TheEdge]

your opinion with no real evidence, in my opinion. No point in protracted debate.

Ah yes, the ultimate answer when trying to discuss an issue, refuse to engage with those who disagree.

 

[jfollows]

The Edinburgh sleeper service incident is a classic example amongst others. Running brake test what a farce; the brakes on 99.999999 % of stock are well maintained and designed by very talented people. The time when the brake test should count failed to yield.

You reminded me that I alluded to this on this forum when the report came out: ( #397 )

For me, and I'm not any railway expert, I wonder about the process of the running brake test here.

....

I wonder what the point of the running brake test is, if it's not able to ascertain that the brakes on the entire consist are working as they should, since clearly all it did here was to ascertain that the locomotive's brakes were working.

The report covers this in more detail in paragraphs 80 to 84, but doesn't really go on to say much more than this. Clearly the running brake test did not enable the driver to be sure that the brakes were operating effectively, to paraphrase the Rule Book slightly (paragraph 81).

....

I'm just a little surprised that this point isn't made more significant in the report than it is.

 

[niggill617@gma]

Ah yes, the ultimate answer when trying to discuss an issue, refuse to engage with those who disagree.

I have engaged no end. Having spears thrown on grammar, and non-applicable measurement of fluid dynamics, well best not to engage, in the name of economy of effort.

 

[TheEdge]

I have engaged no end. Having spears thrown on grammar, and non-applicable measurement of fluid dynamics, well best not to engage, in the name of economy of effort.

Where did I do that?

What I questioned is that you are reading a few select lines in your document and equating them to the requirement for drivers to be taught, understand and calculate all these braking parameters and performances in the style of theoretical physics. But when these few points you are reading are read in conjunction with the entire document they read far more like a basic practical understanding is all that's needed as opposed to being able to calculate and present the expected deceleration in m/s/s.

 

[niggill617@gma]

You reminded me that I alluded to this on this forum when the report came out: ( #397 )

Edinburgh is not the only event, I cite non-compliance of elementary principles of motion as a contributing factor. This is not criticism of the unfortunate drivers concerned, I believe they have been let down and than blamed.

Where did I do that?

What I questioned is that you are reading a few select lines in your document and equating them to the requirement for drivers to be taught, understand and calculate all these braking parameters and performances in the style of theoretical physics. But when these few points you are reading are read in conjunction with the entire document they read far more like a basic practical understanding is all that's needed as opposed to being able to calculate and present the expected deceleration in m/s/s.

See upload from former ORR (Regulation).

 

[TheEdge]

See upload from former ORR (Regulation).

Assuming you mean the letter attached to post #1448 I still can't agree that it demands drivers start being able to calculate this kind of thing at a theoretical level. "check and calculate that a trains braking power is sufficient as required for the railway line", that is something that is going to vary with every train in differing conditions and doesn't correlate to being able to present the ideal m/s/s deceleration in step 2 with mathematical proof.

The guidance from the RDG you've uploaded is the same, it just doesn't scream "get the calculators out", more a basic working understanding of what happens and why, not the mathematics going on behind that. It mentions "general understanding....e.g. friction, kinetic energy" and "why it can take so long to stop a train". That doesn't demand a driver start learning the friction coefficient of wheel on rail or the amount of joules a train has and how that impacts driving. More that a driver understand metal on metal has poor grip anyway, can be very easily degraded and an object the weight of a train thrown in will take a while to stop, even more if you lubricate that surface.

 

[172007]

Problem with this friction calculation whilst driving is that I know that each carriage is 44 tons thereabouts. What I don't know is the weight of the passengers and their luggage and how that will affect the change in mass of the train hence how much kinetic energy there is. I don't know how much extra brake pressure is being supplied via the variable load valve and how this affects the breaking power per brake step in meters per second and whether there is enough friction to sustain this. The other snag is I don't know how much sand is in each hopper and whether each sander is sanding correctly which can of course modify the friction available to assist in slowing down.

 

[Annetts key]

Problem with this friction calculation whilst driving is that I know that each carriage is 44 tons thereabouts. What I don't know is the weight of the passengers and their luggage and how that will affect the change in mass of the train hence how much kinetic energy there is. I don't know how much extra brake pressure is being supplied via the variable load valve and how this affects the breaking power per brake step in meters per second and whether there is enough friction to sustain this. The other snag is I don't know how much sand is in each hopper and whether each sander is sanding correctly which can of course modify the friction available to assist in slowing down.

I think the point has been lost here.

I feel that a driver should have a practical understanding of the system including the relevant basic principles of physics. By the system, I mean, the whole train including the braking system and how it works. By practical, I do not mean just the “learning while driving”, but also the basic theory. I don’t think anyone expects a driver to try to actually calculate the train mass or to work out the theoretical available braking force or theoretical traction.

Outside driving, these are requirements in other disciplines. You would not want the person working on the track to just judge it by eye, would you?

Anyway, as mentioned a number of times now, this discussion should really continue in the other topic, not here.

 

[niggill617@gma]

Problem with this friction calculation whilst driving is that I know that each carriage is 44 tons thereabouts. What I don't know is the weight of the passengers and their luggage and how that will affect the change in mass of the train hence how much kinetic energy there is. I don't know how much extra brake pressure is being supplied via the variable load valve and how this affects the breaking power per brake step in meters per second and whether there is enough friction to sustain this. The other snag is I don't know how much sand is in each hopper and whether each sander is sanding correctly which can of course modify the friction available to assist in slowing down.

Listen to the podcast by Tim Davies Fast Jet Performance.com re Shoreham. The pilot Andy Hill was never going to calculate energy, but I bet he could. Unfortunately in this case due to cognitive impairment, he failed to appreciate the energy state of the Hunter, both kinetic speed, and potential height. The same is true when landing, 5 knots fast and 40 ft high on approach could put the jet through the fence at the end of the runway.

I will post up a document re post 1455. After that I will only engage on the physics thread.

 

[43066]

Non-compliance regards General Professional Knowledge. No criticism of the driver, only the absence of continuation training. The fact you can do the rope calculation is General Professional Knowledge.

Surely you aren’t seriously suggesting that the incident wouldn’t have happened if the driver had been trained in calculating braking coefficients?

What would he have done differently? Can you point to part of any RAIB report ever where they suggest the ability to calculate braking coefficiencies would have made a difference?

Which is akin to car drivers knowing that when wet they should allow 3x the stopping distance and when icy 10x the stopping distance.

Some take it onboard, as typically when the roads are wet cars are recorded as being 2 to 3mph slower (85th percentile free flow speed), which reduces their stopping distance a little from maintaining their normal speed.

I’d suggest most car drivers speed, or drive too fast for the conditions, not because they aren’t aware of this knowledge, but simply because there are almost invariably no consequences to doing so. Train drivers who speed or drive in a manner which causes them to regularly overshoot stations will soon loose their livelihoods.

Can I do the full calculation, yes, but it isn't a necessity or going to cause me or others additional risk if I don't (and its not a requirement of the standards I work to.) It would seem to be the same case here, as long as a driver knows roughly how much they should slow by for a particular brake application and in what time where is the necessity of knowing how to calculate exactly why that occurs?

Precisely.

You have a rough expectation of braking performance based on prior experience and traction knowledge (confirmed at the start of each trip by RBT). The skill of the job is remaining situationally aware and knowing the conditions they might give rose to low adhesion, and braking accordingly (and according to the driving policy). Every so often unusual conditions occur in which case you report to the signaller so that other drivers can be warned. This subject is regularly trained for and re briefed, sometimes including simulator training.

However much background knowledge you might have, braking is ultimately done by eye and feel. Station overruns and SPADs aren’t caused by drivers lacking the ability to brake, they’re caused by loss of situational awareness, for example focussing on restrictive signal aspects and “forgetting” to stop! The main tool to counter this kind of incident is training is non technical skills.

General Professional Knowledge. No criticism of the driver, only the absence of continuation training.

I have double award gcse science and was quite happy to leave it there! I don’t know much about friction coefficients. However I have made twenty odd station stops today, probably a hundred in the last couple of weeks. As I metro driver I’d often do eighty to one hundred stops per day. In common with others on this thread, over the last few years, I’ve stopped at literally tens of thousands of stations, without once overshooting (or SPADDING). Are you seriously suggesting we lack sufficient training in stopping trains safely?

Unfortunately in this case due to cognitive impairment, he failed to appreciate the energy state of the Hunter, both kinetic speed, and potential height.

Do you mean kinetic energy and potential energy? As someone noted upthread, your use of language suggests you don’t have a good grasp of these topics yourself!

Pilots certainly don’t have to do complex calculations, in fact you might be surprised how how little is actually required. Principles of flight ATPL theory (which, incidentally, I’ve sat and passed) is a multiple choice exam, requiring a reasonable grasp of aerodynamics, but nothing that would trouble a mediocre GCSE maths student. An ability to rearrange triangular equations is about all you need.

 

[Wyrleybart]

I am struggling to comprehend some of the stuff in this thread.
Every train is slightly different in terms of handling which is why drivers are trained to perform running brake tests to establish how the trains react. Train drivers tend to be practical people and use their knowledge training and experience to do their job every day. From what I understand the SWR driver had been at Salisbury depot for years, which is where the class 159s were based from new, so the driver was totally in his natural surroundings in terms of cab environment, geography and skillset. In the more elderly age profile you might describe the driver as possessing significant train driving experience in all railhead conditions. That is how train drivers are , and how they accumulate skills and experience.

I have been on the railway for 44 years and I believe that SWR driver is somewhat older than me. I have been involved with train drivers for most of my career but I have to say that in all my time I have never known one to comment on or discuss the physics of steel wheel on steel rail in such technical detail as is mentioned by some on this thread.

 

[Cowley]

This thread hasn’t been going too well this afternoon has it..?
From now on any in depth physics discussions need to be in this thread thanks:

Should Train Drivers sit a basic physics examination as part of their training?

It's possible that there's a key detail that I've missed. In the incident you cite, your analysis disagreed with the official findings in that the incident could have been avoided. Presumably this means that you felt that, had the driver held the brake in Step 5, the train would have stopped on...

www.railforums.co.uk

 

[GC class B1]

You reminded me that I alluded to this on this forum when the report came out: ( #397 )

The sleeper incident running brake test is a special case. The dynamic brake operates by initially applying the friction brake on the whole train and when the dynamic brake takes effect to slow the train the friction brake is backed off to a very light application to allow the dynamic brake to be the means of slowing the train. This means that the coaches can have a braking shock as they start to push the locomotive.
In British Rail InterCity days the dynamic brake on locomotives operating sleeping car services was isolated to avoid the sleeping passengers being woken. The driver of the Caledonian sleeper train involved in the incident was aware of this problem with braking shocks hence braked very gently for the running brake test. As a result the running brake test masked the problem with the friction brake.

 

[Cowley]

Now that everyone has had a good chance to discuss the interim report we’re going to lock this until the main report comes out.

Thank you all for your contributions over the last couple of weeks.

 

[ainsworth74]

There's been a short update from the RAIB regarding their report which you can find below:

RAIB’s draft investigation report into this accident is currently being reviewed prior to the start of the consultation. RAIB expects to publish the final investigation report before the end of the year. RAIB issued an interim report in February 2022, which discussed our initial findings, and has continued to liaise with stakeholders, including the rail industry, as the investigation has progressed.

[Withdrawn] Collision between passenger trains at Salisbury Tunnel Junction

Investigation into a collision between passenger trains at Salisbury Tunnel Junction, Wiltshire, 31 October 2021

www.gov.uk

 

[ainsworth74]

There has been a further update from the RAIB which they've not called a delay but considering the first version of this was "published by the end of the year" which has now become "the Spring" it feels like a delay:

RAIB’s draft investigation report into this accident is currently being reviewed prior to the start of consultation. RAIB expects to formally consult the parties involved in March 2023 and to publish the final investigation report in the Spring. RAIB issued an interim report in February 2022 and continues to liaise with stakeholders on our findings and any arising safety issues.

[Withdrawn] Collision between passenger trains at Salisbury Tunnel Junction

Investigation into a collision between passenger trains at Salisbury Tunnel Junction, Wiltshire, 31 October 2021

www.gov.uk

 

[Mag_seven]

A further update from the RAIB dated 27th June:

RAIB’s draft investigation report into this accident has now been sent to interested parties as part of the statutory consultation process. RAIB expects to publish the final report shortly after the consultation process is completed.

[Withdrawn] Collision between passenger trains at Salisbury Tunnel Junction

Investigation into a collision between passenger trains at Salisbury Tunnel Junction, Wiltshire, 31 October 2021

www.gov.uk

Thread will remain locked until the final investigation report is published.

 

[Mag_seven]

Thread will remain locked until the final investigation report is published.

Thread now unlocked as RAIB final investigation report has now been published.

Report 12/2023: Collision between passenger trains at Salisbury Tunnel Junction

RAIB has today released its report into a collision between passenger trains at Salisbury Tunnel Junction, Wiltshire, 31 October 2021.

www.gov.uk

RAIB has today released its report into a collision between passenger trains at Salisbury Tunnel Junction, Wiltshire, 31 October 2021.

 

[Daytona]

Final RAIB report released, no surprises -
"The level of wheel/rail adhesion was very low due to leaf contamination on the railhead, and had been made worse by a band of drizzle that occurred immediately before the passage of train 1L53. This leaf contamination resulted from the weather conditions on the day of the accident, coupled with an increased density of vegetation in the area which had not been effectively managed by Network Rail’s Wessex route. Network Rail’s Wessex route had also not effectively managed the contamination on the railhead with either proactive or reactive measures."

Report 12/2023: Collision between passenger trains at Salisbury Tunnel Junction

Collision between passenger trains at Salisbury Tunnel Junction, Wiltshire, 31 October 2021.

www.gov.uk

 

[75A]

Well worth a read.

 

[43096]

Final RAIB report released, no surprises -
"The level of wheel/rail adhesion was very low due to leaf contamination on the railhead, and had been made worse by a band of drizzle that occurred immediately before the passage of train 1L53. This leaf contamination resulted from the weather conditions on the day of the accident, coupled with an increased density of vegetation in the area which had not been effectively managed by Network Rail’s Wessex route. Network Rail’s Wessex route had also not effectively managed the contamination on the railhead with either proactive or reactive measures."

Report 12/2023: Collision between passenger trains at Salisbury Tunnel Junction

Collision between passenger trains at Salisbury Tunnel Junction, Wiltshire, 31 October 2021.

www.gov.uk

Exacerbated by some frankly strange logic and decision making by the driver.

 

[MotCO]

What immediately struck me was this paragraph:

The causes of the accident were that wheel/rail adhesion was very low in the area
where the driver of train 1L53 applied the train’s brakes, that the driver did not apply
the train’s brakes sufficiently early on approach to the signal protecting the junction to
avoid running on to it, given the prevailing low level of adhesion, and that the braking
systems of train 1L53 were unable to mitigate this very low adhesion.

Does this imply criticism of the driver?