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

[skyhigh]

I dispute the dynamic brake masked the isolation of the 8 coaches. If the driver had received continuation training, he would of identified the earlier error. The whole concept of running brake tests is called into question here.

I don't quite understand what you're saying. Are you suggesting that if the driver had been able to calculate the rate of deceleration the incident wouldn't have happened?

 

[GC class B1]

Thank you for your input.

With consideration to the running brake test re RAIB report 5/2020 Edinburgh Sleeper. In my interpretation from the time trace, the brake application lasted about 26 seconds, with about 50 percent selected, 11 mph reduction in speed, level gradient. Therefore a deceleration of about 0.189 m/s/s. Had the coaches been providing braking effort the rate would be about 0.45 m/s/s. The speed reduction would be around 23 mph.

I dispute the dynamic brake masked the isolation of the 8 coaches. If the driver had received continuation training, he would of identified the earlier error. The whole concept of running brake tests is called into question here. The drivers feel or sense of inertia failed.

Looking forward to constructive polite counter debate, and happy to be corrected.

I have looked at your calculations and the RAIB report. I have had difficulty reading the trace so I have taken your values. The speed when the running brake test commenced was 70 MPH (31.1m/s). The speed at the end of the running brake test was 59 MPH (26.2m/s). I have used a retardation time as 24 seconds assuming 4 seconds to achieve the selected brake cylinder pressure. This has been calculated in accordance with the principles in BS/EN14531 part 1. This gives a deceleration rate of 5/24 which is approximately 0.2m/s/s. I would expect a Full Service retardation rate of no more than 8 to 9%g (0.81 to 0.92m/s/s) so my calculated value of 0.21m/s would suggest the brake application was about 25% of Full Service. You read the graph to be a 50% brake application so there do appear to be some anomalies.

if only the locomotive friction brake was braking the train, I would have expected a maximum retardation rate of 0.25 m/s in Full Service. With the dynamic brake (rheostatic for the class 92) when the dynamic brake is established the friction brake is reduced to a very low level. As a result the retardation rate achieved with the dynamic brake and the locomotive friction brake may be very similar to that experienced if the friction brake on the coaches was initially applied and then reduced to a low value as designed. This would explain why the driver on the incident train had to make a higher than normal application but perhaps this was within what he believed to be acceptable. The dynamic brake appears to have only partly masked the issue with the friction brake on the coaches.

 

[niggill617@gma]

I don't quite understand what you're saying. Are you suggesting that if the driver had been able to calculate the rate of deceleration the incident wouldn't have happened?

Thanks for the polite post.

When I drove class 800, I would select about 30 percent on the gauge. This is 30 percent of 1.2 m/s/s or approximately 12 percent g. So .3 times 1.2 = .36 m/s/s. This rate would take about 12 seconds to slow by 10 mph, with established retarding force on level gradient outside of severe wsp. The brake performance is proved. The same principle applies to consists with dynamic brakes. The dynamic retarding force builds quicker than friction and will of course be taken into consideration. This will become evident during my interaction with GC class B1 who is very informed. If I was driving within appendix C signalling I would do a further brake test using about 60 percent. If the time was say 18 seconds I would be concerned.

The driver would not calculate while driving. The parameters are known before you even key in.

 

[Peter Sarf]

Thanks for the polite post.

When I drove class 800, I would select about 30 percent on the gauge. This is 30 percent of 1.2 m/s/s or approximately 12 percent g. So .3 times 1.2 = .36 m/s/s. This rate would take about 12 seconds to slow by 10 mph, with established retarding force on level gradient outside of severe wsp. The brake performance is proved. The same principle applies to consists with dynamic brakes. The dynamic retarding force builds quicker than friction and will of course be taken into consideration. This will become evident during my interaction with GC class B1 who is very informed. If I was driving within appendix C signalling I would do a further brake test using about 60 percent. If the time was say 18 seconds I would be concerned.

The driver would not calculate while driving. The parameters are known before you even key in.

== Doublepost prevention - post automatically merged: 12 Mar 2022 ==


Have you ever heard of evolution.

In the case of wheel slip. Do you believe this can be avoided by the driver taking into account your calculations above ?.

 

[Need2]

Thanks for the polite post.

When I drove class 800, I would select about 30 percent on the gauge. This is 30 percent of 1.2 m/s/s or approximately 12 percent g. So .3 times 1.2 = .36 m/s/s. This rate would take about 12 seconds to slow by 10 mph, with established retarding force on level gradient outside of severe wsp. The brake performance is proved. The same principle applies to consists with dynamic brakes. The dynamic retarding force builds quicker than friction and will of course be taken into consideration. This will become evident during my interaction with GC class B1 who is very informed. If I was driving within appendix C signalling I would do a further brake test using about 60 percent. If the time was say 18 seconds I would be concerned.

The driver would not calculate while driving. The parameters are known before you even key in.

Instead of showing everyone how clever you are with your in-depth knowledge of this subject please, could you tell me in easy to understand English, what exactly you would like trainee drivers to learn and what benefits it would bring?

 

[GC class B1]

In support of the views of niggill617@gma although I am not a driver, my view is that because the braking performance of different types of rolling stock, and within classes of the same type of rolling stock varies as a result of in-service degradation and unnoticed faults, understanding what deceleration to expect should help to identify potential problems. I know from personal experience that deterioration in the performance of cars can be gradual and not noticed until it becomes a problem. It is natural to brake a bit harder each time to compensate without realising you are doing so until it becomes too late to stop in time. Also I believe understanding the way a system works will make it more likely that people who understand why something works the way it does will understand why rules exist and be more likely to follow rules that make sense and question those that do not.

Although this is not entirely on topic, your post has prompted me to loook again at the sleeper incident report. Investigation of the circumstances around the closed headstock Brake Pipe isolating cock and its effect is thorough and well documented in the report. However when I look at the trace from the locomotive OTDR, it seems to me that the running brake test commenced when the train had reached 80MPH and the speed reduced to about 68 MPH which is different to the speeds stated in clause 82. I have noticed apparent errors in other RAIB reports and this is a concern. The fact that the running brake test did not identify the closed cock does not appear to have been given sufficient consideration or a specific recommendation made to address this.

 

[seagull]

The "running brake test" is the standard method used by drivers to assess the braking performance of the train they are driving, carried out (ideally) before they need the brakes for any other situation.
However, even if it were possible to select a wayside marker to commence the test, and determine whether speed had reduced by "x" amount by the next preset marker, the practicalities of such do not work, as a running brake test can be required at a multitude of locations, and have to be carried out a variety of speeds depending on signal aspects, rail condition and traction ability.
Therefore I would opine that there is no obvious improvement over the current method of "driver feel" for brake testing.

 

[Need2]

The "running brake test" is the standard method used by drivers to assess the braking performance of the train they are driving, carried out (ideally) before they need the brakes for any other situation.
However, even if it were possible to select a wayside marker to commence the test, and determine whether speed had reduced by "x" amount by the next preset marker, the practicalities of such do not work, as a running brake test can be required at a multitude of locations, and have to be carried out a variety of speeds depending on signal aspects, rail condition and traction ability.
Therefore I would opine that there is no obvious improvement over the current method of "driver feel" for brake testing.

100%

 

[GC class B1]

The retardation rate achieved (I.e. the percentage g) in the running brake test would indicate the effectiveness of the brake and could be judged (or calculated) by the speed reduction in a set time. I don’t think it needs to be distance based.

 

[Peter Sarf]

In support of the views of niggill617@gma although I am not a driver, my view is that because the braking performance of different types of rolling stock, and within classes of the same type of rolling stock varies as a result of in-service degradation and unnoticed faults, understanding what deceleration to expect should help to identify potential problems. I know from personal experience that deterioration in the performance of cars can be gradual and not noticed until it becomes a problem. It is natural to brake a bit harder each time to compensate without realising you are doing so until it becomes too late to stop in time. Also I believe understanding the way a system works will make it more likely that people who understand why something works the way it does will understand why rules exist and be more likely to follow rules that make sense and question those that do not.

Although this is not entirely on topic, your post has prompted me to loook again at the sleeper incident report. Investigation of the circumstances around the closed headstock Brake Pipe isolating cock and its effect is thorough and well documented in the report. However when I look at the trace from the locomotive OTDR, it seems to me that the running brake test commenced when the train had reached 80MPH and the speed reduced to about 68 MPH which is different to the speeds stated in clause 82. I have noticed apparent errors in other RAIB reports and this is a concern. The fact that the running brake test did not identify the closed cock does not appear to have been given sufficient consideration or a specific recommendation made to address this.

I think what many are arguing about is around the case of the accident resulting from wheel slip. No matter how accurately the driver could calculate/determine the expected rate of retardation it is TOO LATE to do anything about it if the driver perceives the retardation is below what is expected. The train is sliding already. It might have been possible to react and then select a lower level of braking as a result of experiencing the initial slip but how long would the driver have and how effective would it be. Unlike a car where taking pressure off the brake pedal results in immediate reduction in braking effort I get the impression that in the case of a train there is some reaction time before the brake effort requested actually takes effect.

A rough analogy would be a car driver encountering black ice. They only notice the black ice when they apply the brake. All they can do is avoid panic, steer and hope for the best. They can try cadence braking (I have successfully done that). In the case of a train steering is not an issue furthermore you cannot swerve to avoid a collision. In the case of a train it is drop sand and hope the Wheel Slip Prevention copes. I think different trains have different types of Wheel Slip Prevention so do not expect all trains to cope to the same level.

I write the above with all due respect to actual drivers of trains, I am not a train driver.

Note the driver does not appear to have experienced much degradation in retardation for any of the journey beforehand. If the driver had then how cautious would a driver be at the place where the serious slip happened ?.

 

[GC class B1]

This thread is general and not related to any specific incident. The sleeper train incident has been mentioned where there is some evidence that the running brake test could possibly have identified the issue with the friction brake.

== Doublepost prevention - post automatically merged: 12 Mar 2022 ==

As an indication, a speed reduction of 10MPH with a step 2 (or 6%g) retardation should take about 10 seconds or less allowing for brake build-up time.

Another incident where it is possible that an effective running brake test and a greater driver understanding of the principles of train braking systems is the SPAD at Loughborough South detailed in RAIB report No. 10/2020. It is possible that the 200 metres signal overrun could have been avoided even though the train was travelling considerably faster than the permitted speed. It appears that the locomotive braking system was set to the Goods timings position as the brake build up time was reported by RAIB as 15 seconds. A train with a maximum speed of 75 MPH should have the brake timings set to passenger and the application time should be 3-5 seconds. At 75 MPH the train would have travelled at least an additional distance of 330 metres in the extra ten seconds brake build up time against the correct passenger timings. I also suspect from calculations I have performed that the brake mechanical equipment on the locomotives involved was not performing satisfactorily. I am fairly confident that if the locomotives had been set to the correct passenger timings and the locomotive brake equipment had been in good order the SPAD would not have occurred.

 

[O L Leigh]

The "running brake test" is the standard method used by drivers to assess the braking performance of the train they are driving, carried out (ideally) before they need the brakes for any other situation.
However, even if it were possible to select a wayside marker to commence the test, and determine whether speed had reduced by "x" amount by the next preset marker, the practicalities of such do not work, as a running brake test can be required at a multitude of locations, and have to be carried out a variety of speeds depending on signal aspects, rail condition and traction ability.
Therefore I would opine that there is no obvious improvement over the current method of "driver feel" for brake testing.

I think I would have to subscribe to this view also.

I would not be able to use the arithmetic method espoused by @niggill617@gma but I believe that I would be able to spot a brake that is below-par, either through the running brake test or through normal service braking. A lot of this is down to experience and route knowledge, and is one of the reasons why driver training and route learning requires so many hours. I have certainly found units with defective brakes and even been able to diagnose an inaccurate speedo this way.

 

[niggill617@gma]

In the case of wheel slip. Do you believe this can be avoided by the driver taking into account your calculations above ?.

Wheel slip on power take up, is a well known indicator of possible wheel slide, during braking. If a driver reports severe wheel slip, the signaller will be contacted and report. So the driver approaching the same location will brake as required. I appreciate your context of slip.

No , but mu does form part of the calculation, (static friction). One of the methods used to alert drivers re adhesion, uses a colour code. This divides down into numbers and a short narrative, if I remember correctly. If the system was changed to a format, that just stated " locations ABC may have levels of mu 0.03". I would simply know step 1 not step 2, for a 3 step brake, or percent gauge equivalent. The braking efficiency is checked with a meaningful running brake test.

If a signaller contacted me and required a running brake test, because someone had had an issue. I would request at what rate of braking would you like the test . If I went skating through at 6 percent g, I would report mu as less than 0.06. The current system does not really have a direct correlation, or does it? Is it dimensionless. This is in addition to the drivers normal skills, not a replacement.

== Doublepost prevention - post automatically merged: 13 Mar 2022 ==

The "running brake test" is the standard method used by drivers to assess the braking performance of the train they are driving, carried out (ideally) before they need the brakes for any other situation.
However, even if it were possible to select a wayside marker to commence the test, and determine whether speed had reduced by "x" amount by the next preset marker, the practicalities of such do not work, as a running brake test can be required at a multitude of locations, and have to be carried out a variety of speeds depending on signal aspects, rail condition and traction ability.
Therefore I would opine that there is no obvious improvement over the current method of "driver feel" for brake testing.

Deceleration equals speed reduction divided by time, meters per second and seconds. So a 10 mph reduction, that takes 12 seconds thus 0.37 meters per second every second. Rule of thumb, from 75 mph the time in braking is 90 s. The distance to stop is one mile with 3 seconds freewheel. This assumes uniform deceleration. This is not a procedure just a parameter. Again additional to the drivers normal skill of driveability. The understanding simply adds dimension.

== Doublepost prevention - post automatically merged: 13 Mar 2022 ==

Instead of showing everyone how clever you are with your in-depth knowledge of this subject please, could you tell me in easy to understand English, what exactly you would like trainee drivers to learn and what benefits it would bring?

My level of education is ordinary, nothing clever. This level of mathematical physics is what I remember from secondary modern aged 15. When this debate is over people will make up their own mind re worth. I still believe the industry is non-compliant to the Statutory Instrument. The ORR stated the calculation element is only for freight drivers, and some EU member states, utter nonsense. This legislation should not be spun into nonexistence.

== Doublepost prevention - post automatically merged: 13 Mar 2022 ==

I have looked at your calculations and the RAIB report. I have had difficulty reading the trace so I have taken your values. The speed when the running brake test commenced was 70 MPH (31.1m/s). The speed at the end of the running brake test was 59 MPH (26.2m/s). I have used a retardation time as 24 seconds assuming 4 seconds to achieve the selected brake cylinder pressure. This has been calculated in accordance with the principles in BS/EN14531 part 1. This gives a deceleration rate of 5/24 which is approximately 0.2m/s/s. I would expect a Full Service retardation rate of no more than 8 to 9%g (0.81 to 0.92m/s/s) so my calculated value of 0.21m/s would suggest the brake application was about 25% of Full Service. You read the graph to be a 50% brake application so there do appear to be some anomalies.

if only the locomotive friction brake was braking the train, I would have expected a maximum retardation rate of 0.25 m/s in Full Service. With the dynamic brake (rheostatic for the class 92) when the dynamic brake is established the friction brake is reduced to a very low level. As a result the retardation rate achieved with the dynamic brake and the locomotive friction brake may be very similar to that experienced if the friction brake on the coaches was initially applied and then reduced to a low value as designed. This would explain why the driver on the incident train had to make a higher than normal application but perhaps this was within what he believed to be acceptable. The dynamic brake appears to have only partly masked the issue with the friction brake on the coaches.

The dynamic brake would have started to slow the consist after say 1 or 2 seconds re inertia, cylinder fill time is not relevant, isolated. By using time and not distance to assess the braking efficiency, the isolation is easy to realise. If a running brake test fails to catch this situation what is the point. Luckily these issues are few and far between. I could list about 6 or so incidents over the last 8 years how lucky is that. The ORR also mentioned cost risk analysis; all for the sake of some elementary physics of motion understanding. All illustrated within RGS and the SI.

The loco produces 63 tonnes brake force and all up consist mass say 480 tonnes. Newtons Second Law (mentioned as ludicrous) produces 0.167 m/s/s. 50 percent selected ?


Part of the consist may have been on the gradient, during the running brake test.

== Doublepost prevention - post automatically merged: 13 Mar 2022 ==

I think I would have to subscribe to this view also.

I would not be able to use the arithmetic method espoused by @niggill617@gma but I believe that I would be able to spot a brake that is below-par, either through the running brake test or through normal service braking. A lot of this is down to experience and route knowledge, and is one of the reasons why driver training and route learning requires so many hours. I have certainly found units with defective brakes and even been able to diagnose an inaccurate speedo this way.

I totally agree: intuition/ driveabilty, NTS, and finally underpinning Knowledge. This knowledge would of saved a number of very experienced drivers, from some nasty incidents, I wonder if they would rewind and take onboard. Your natural accelerometer is well calibrated by experience, that is respected. The calculation stuff is not difficult to understand. All in all it just comes down to parameters, based on some logical theory. Surely 3 is better than 2.

 

[GC class B1]

Wheel slip on power take up, is a well known indicator of possible wheel slide, during braking. If a driver reports severe wheel slip, the signaller will be contacted and report. So the driver approaching the same location will brake as required. I appreciate your context of slip.

No , but mu does form part of the calculation, (static friction). One of the methods used to alert drivers re adhesion, uses a colour code. This divides down into numbers and a short narrative, if I remember correctly. If the system was changed to a format, that just stated " locations ABC may have levels of mu 0.03". I would simply know step 1 not step 2, for a 3 step brake, or percent gauge equivalent. The braking efficiency is checked with a meaningful running brake test.

If a signaller contacted me and required a running brake test, because someone had had an issue. I would request at what rate of braking would you like the test . If I went skating through at 6 percent g, I would report mu as less than 0.06. The current system does not really have a direct correlation, or does it? Is it dimensionless. This is in addition to the drivers normal skills, not a replacement.

== Doublepost prevention - post automatically merged: 13 Mar 2022 ==


Deceleration equals speed reduction divided by time, meters per second and seconds. So a 10 mph reduction, that takes 12 seconds thus 0.37 meters per second every second. Rule of thumb, from 75 mph the time in braking is 90 s. The distance to stop is one mile with 3 seconds freewheel. This assumes uniform deceleration. This is not a procedure just a parameter. Again additional to the drivers normal skill of driveability. The understanding simply adds dimension.

== Doublepost prevention - post automatically merged: 13 Mar 2022 ==


My level of education is ordinary, nothing clever. This level of mathematical physics is what I remember from secondary modern aged 15. When this debate is over people will make up their own mind re worth. I still believe the industry is non-compliant to the Statutory Instrument. The ORR stated the calculation element is only for freight drivers, and some EU member states, utter nonsense. This legislation should not be spun into nonexistence.

== Doublepost prevention - post automatically merged: 13 Mar 2022 ==


The dynamic brake would have started to slow the consist after say 1 or 2 seconds re inertia, cylinder fill time is not relevant, isolated. By using time and not distance to assess the braking efficiency, the isolation is easy to realise. If a running brake test fails to catch this situation what is the point. Luckily these issues are few and far between. I could list about 6 or so incidents over the last 8 years how lucky is that. The ORR also mentioned cost risk analysis; all for the sake of some elementary physics of motion understanding. All illustrated within RGS and the SI.

The loco produces 63 tonnes brake force and all up consist mass say 480 tonnes. Newtons Second Law (mentioned as ludicrous) produces 0.167 m/s/s. 50 percent selected ?


Part of the consist may have been on the gradient, during the running brake test.

Using the class 92 brake force 63 Tonnes you have quoted and a loco weight of 126 Tonnes, I have calculated the Full Service retardation force for the locomotive to be about 8.2 Tonnes. The retardation rate for this locomotive alone is therefore about 6.5%g. This seems very low - do you agree with this figure? As the class 92 has cast iron brake blocks, the actual retardation will be different to this figure as the brake force quoted in TOPS is for reference only.
Taking a consist weight of 480 Tonnes and 50% brake force with the retardation force of around 4 Tonnes for the loco friction brake only (using the TOPS value of brake force) the deceleration rate would be about 0.08 m/s/s and 0.8%g.
As a check on the validity of my calculation, the weight of the unbraked trailing coaches is about 3 times the weight of the locomotive. If the Full Service deceleration rate for the locomotive is 8% which I would expect from 70MPH, then half this will be 4%. The locomotive weight is about a quarter of the total train weight therefore the deceleration rate for the train with only then locomotive friction brake will be about 1% (0.1m/s/s). I understood that the train was on fairly level track when the running brake test was carried out.
As the deceleration rate when the running brake test was carried out was about 2%g, the dynamic brake was making a significant contribution to the braking effort.
I agree however that at 50% braking, I would have expected a retardation rate at least 4%g (the sleeping cars should brake to about 9%g), which supports your view that the running brake test could have indicated a problem.

With regard to the brake build up time, the friction brake should reach 95% of Full Service value in 3-5 seconds. This would mean that retardation should be felt in about 2 seconds, similar to your suggestion for the dynamic brake.

 

[niggill617@gma]

Using the class 92 brake force 63 Tonnes you have quoted and a loco weight of 126 Tonnes, I have calculated the Full Service retardation force for the locomotive to be about 8.2 Tonnes. The retardation rate for this locomotive alone is therefore about 6.5%g. This seems very low - do you agree with this figure? As the class 92 has cast iron brake blocks, the actual retardation will be different to this figure as the brake force quoted in TOPS is for reference only.
Taking a consist weight of 480 Tonnes and 50% brake force with the retardation force of around 4 Tonnes for the loco friction brake only (using the TOPS value of brake force) the deceleration rate would be about 0.08 m/s/s and 0.8%g.
As a check on the validity of my calculation, the weight of the unbraked trailing coaches is about 3 times the weight of the locomotive. If the Full Service deceleration rate for the locomotive is 8% which I would expect from 70MPH, then half this will be 4%. The locomotive weight is about a quarter of the total train weight therefore the deceleration rate for the train with only then locomotive friction brake will be about 1% (0.1m/s/s). I understood that the train was on fairly level track when the running brake test was carried out.
As the deceleration rate when the running brake test was carried out was about 2%g, the dynamic brake was making a significant contribution to the braking effort.
I agree however that at 50% braking, I would have expected a retardation rate at least 4%g (the sleeping cars should brake to about 9%g), which supports your view that the running brake test could have indicated a problem.

With regard to the brake build up time, the friction brake should reach 95% of Full Service value in 3-5 seconds. This would mean that retardation should be felt in about 2 seconds, similar to your suggestion for the dynamic brake.

Yes the locomotive rate of deceleration is correct I would say. I was of the opinion that TOPS uses braked weight percentage, Lambda? The light engine would stop in around 1000 m from 75 mph. That is ok for appendix A signal spacing, the min being 1258 m level. It may be limited to 60 mph.

The running brake test should be based on parameters, from previously understood principles. On level track select 50 percent, this would yield 0.45 m/s/s. Wait for 5 seconds, within this time the dynamic brake would produce a minor deceleration, ignore it. From this point time a 10 mph deceleration. The time should be around 10 seconds. If it was 26 seconds as in this case, the consist is brought to a stand. There will be some minor empirical error.

At this point get out reset, and blame the delay on a big badger.

 

[dk1]

Good job a Physics exam doesn’t form part of driver training. It bores me senseless & I drifted off doing it at school.

 

[martin2345uk]

If we had to know some of the stuff in this thread I'd never have passed out...

 

[GC class B1]

Yes the locomotive rate of deceleration is correct I would say. I was of the opinion that TOPS uses braked weight percentage, Lambda? The light engine would stop in around 1000 m from 75 mph. That is ok for appendix A signal spacing, the min being 1258 m level. It may be limited to 60 mph.

The running brake test should be based on parameters, from previously understood principles. On level track select 50 percent, this would yield 0.45 m/s/s. Wait for 5 seconds, within this time the dynamic brake would produce a minor deceleration, ignore it. From this point time a 10 mph deceleration. The time should be around 10 seconds. If it was 26 seconds as in this case, the consist is brought to a stand. There will be some minor empirical error.

At this point get out reset, and blame the delay on a big badger.

The GB brake force is different to the value for lambda braked weight percentage. It may be that TOPS uses Lamba values but the working manual which is used to calculate the maximum speed of freight trains uses GB brake force. Lambda value are a percentage and are calculated from the stopping distance at a specified speed using the formula in GM/RT2045 issue 4 Appendix E.
Appendix A of GM/RT2045 curve B1 i believe is applicable to the sleeper trains and specifies a maximum stopping distance from 80 MPH in Full Service to be 1082 metres. This should include an allowance for tolerance and performance variation so I would suggest a stopping distance of less than 1000 metres is reasonable. With an application time of 3-5 seconds and a deceleration rate of 8%g, the sleeper train should stop in less than 900 metres.
The light locomotive would stop from 80 MPH in about 1100 metres so as you suggest it would need to be restricted to less than 80MPH. However as mentioned previously the actual performance will not be as suggested by the GB brake force as the coefficient of friction of cast iron varies with the speed at which the brake application is made and the forces on the brake blocks.

In my opinion although I am not a driver, I would not expect drivers to be able to calculate stopping distances, however understanding what deceleration rate to expect for the trains they are driving seems reasonable and if the running brake test does not achieve that it would be helpful to understand why that may be the case. Understanding the braking principles would help with that understanding.

Calculation of the designed deceleration rate for a particular type of rolling stock involves detailed knowledge of the braking system design. Calculating the expected slowing time for a specific speed reduction and the stopping distance using the designed/expected deceleration rate for the rolling stock being driven is straightforward and the formuale used are relatively simple.

For the sleeper train running brake test I calculate that for 50% brake application the deceleration rate should be about 0.4m/s/s. This is about double the rate achieved by the incident train.

 

[43066]

The drivers feel or sense of inertia failed.

And that would have almost certainly been the case even if he’d been able to answer friction maths problems.

I would not be able to use the arithmetic method espoused by @niggill617@gma but I believe that I would be able to spot a brake that is below-par, either through the running brake test or through normal service braking. A lot of this is down to experience and route knowledge, and is one of the reasons why driver training and route learning requires so many hours. I have certainly found units with defective brakes and even been able to diagnose an inaccurate speedo this way.

Absolutely. Of course some stock has a brake % gauge driven from an accelerometer which gives you an idea of deceleration rate, but of course “seat of the pants” feel is more important.

I still believe the industry is non-compliant to the Statutory Instrument. The ORR stated the calculation element is only for freight drivers, and some EU member states, utter nonsense. This legislation should not be spun into nonexistence.

With respect that might be your interpretation, but it means nought when the industry and its masters evidently don’t agree with you. For the record freight drivers don’t have to learn to do these calculations either.

however understanding what deceleration rate to expect for the trains they are driving seems reasonable and if the running brake test does not achieve that it would be helpful to understand why that may be the case.

Agree with this and it does seem that something went wrong in the case of the Caledonian sleeper, for whatever reason. I’m just not remotely convinced the OP’s suggested approach would have made the blindest bit of difference. Quite honestly if a train is relying on a running brake test to determine that most of the brakes are disconnected, it’s already too late (RBTs are to gauge railhead conditions rather than checking the brakes are working!)

The most useful learning point from that incident was the importance of ensuring adequate training on new stock.

 

[niggill617@gma]

And that would have almost certainly been the case even if he’d been able to answer friction maths problems.



Absolutely. Of course some stock has a brake % gauge driven from an accelerometer which gives you an idea of deceleration rate, but of course “seat of the pants” feel is more important.



With respect that might be your interpretation, but it means nought when the industry and its masters evidently don’t agree with you. For the record freight drivers don’t have to learn to do these calculations either.



Agree with this and it does seem that something went wrong in the case of the Caledonian sleeper, for whatever reason. I’m just not remotely convinced the OP’s suggested approach would have made the blindest bit of difference. Quite honestly if a train is relying on a running brake test to determine that most of the brakes are disconnected, it’s already too late (RBTs are to gauge railhead conditions rather than checking the brakes are working!)

The most useful learning point from that incident was the importance of ensuring adequate training on new stock.

Thanks for your participation, it is of course respected. You know as well as I do the elementary physics is not that difficult, yet is relevant. The ORR did have some sympathy, and stated the Driver Academy would comply. The legislation compliance date for new drivers 2016 and 2018 for existing, as I read it. The world of corporate governance is just an enigma. The Edinburgh driver must of thought his time was up. The theory would surely of alerted him, same for the guys regards the other incidents.

 

[Need2]

The Edinburgh driver must of thought his time was up. The theory would surely of alerted him, same for the guys regards the other incidents.

You just can’t give in can you?
I cannot believe that you honestly think that the driver in the incident(s) would not of had the said incident(s) if they had a basic theory in friction and how to estimate de-acceleration whilst driving!
Utterly unbelievable.

 

[niggill617@gma]

You just can’t give in can you?
I cannot believe that you honestly think that the driver in the incident(s) would not of had the said incident(s) if they had a basic theory in friction and how to estimate de-acceleration whilst driving!
Utterly unbelievable.

It is you that has missed the point. That is utterly unbelievable. Thank you for proving me correct. No one is doing calculation while driving. Understand the theory and have parameters.

 

[Need2]

It is you that has missed the point. That is utterly unbelievable. Thank you for proving me correct. No one is doing calculation while driving. Understand the theory and have parameters.

So what is your point if it not the one you gave in your previous post?
You quite clearly state that if drivers had a knowledge of elementary physics (and your continual rubbish about friction in even earlier posts) then the driver would have realised something was wrong.

 

[niggill617@gma]

So what is your point if it not the one you gave in your previous post?
You quite clearly state that if drivers had a knowledge of elementary physics (and your continual rubbish about friction in even earlier posts) then the driver would have realised something was wrong.

Define for me what deceleration is with reference to units of deceleration? I will take it step by step with you. I'm not a qualified teacher, some of the readership will be, so this will be interesting.

 

[Need2]

Define for me what deceleration is with reference to units of deceleration? I will take it step by step with you. I'm not a qualified teacher, some of the readership will be, so this will be interesting.

My point is that as a driver I do not need to know elementary physics or deceleration or friction to be able to drive (or stop) a train safely.
You, on the other hand seem to think it would stop incidents.
I fail to see this, perhaps you will tell my how and why?

 

[niggill617@gma]

The knowledge would reduce incidents, not necessarily stop them. Refer back to #54 and all will be revealed, you Need2 make yourself a little more informed first.

 

[Need2]

The knowledge would reduce incidents, not necessarily stop them. Refer back to #54 and all will be revealed, you Need2 make yourself a little more informed first.

I do not need to be more informed on your say so. My employer telling me to do so maybe.
Please explain exactly how you think it would reduce incidents.

 

[niggill617@gma]

As per #54 and we will move forward. The example will be the Edinburgh Sleeper incident, and brake performance understanding. Friction will have to wait, I don't want to pre-empt the Salisbury RAIB report.

 

[GC class B1]

I am not a driver however I have studied the Edinburgh sleeper incident report and from the best interpretation I can make of the OTDR trace in the report at the time of the running brake test it appears that the deceleration rate was about half what I would expect. This was probably because the friction brakes on the sleeping cars did not apply along with the dynamic brake. The incident was caused by the brake pipe isolating cock between the locomotive and the first sleeper car being left closed. This is not the only incident of inadequate brake force on a train resulting in a SPAD or similar incident that has been the subject of an investigatio.
Whilst I appreciate that the brake system should be expected to perform as intended, problems occasionally occur that are not seen before the train is in service and I understand that the purpose of the running brake test is to check that the brake system performance is adequate before it is necessary to make a brake application to reduce the speed for a speed restriction or to stop the train within the required distance. Understanding the expected deceleration in the running brake test should help to identify whether the brake system is performing satisfactorily or not.

 

[Need2]

As per #54 and we will move forward. The example will be the Edinburgh Sleeper incident, and brake performance understanding. Friction will have to wait, I don't want to pre-empt the Salisbury RAIB report.

I have not said I understand it but, I do not need to. Nor does any train driver, infact any driver of any vehicle does not need to know it.
A driver knows his brakes and knows the conditions he is driving in and reacts accordingly.
What you are spouting, near enough solely, is not needed and never will be.
So back to the thread title that includes the words ‘basic physics’ (not friction and deceleration calculations).
Do I think it’s necessary, absolutely not
Do you think it’s necessary, obviously.
Good luck in your quest in getting the ORR and TOC’s to take up your baby.