Signal Passed at Danger (SPAD) and near miss at Sileby Junction 05/05/2021

[XAM2175]

Part of the problem with UKs very basic cab warning and protection systems (AWS/TPWS) is, if you successfully pass a magnet or grid without being tripped (after acknowledgment in the case of AWS), they impose no ongoing control on speed, so after an AWS warning you can go on to increase your speed. ... Even some fairly old systems in other countries can provide ongoing protection after similar events. 'Indusi' (or PZB (Punktförmige Zugbeeinflussung) in Germany applies ongoing restricted speed conditions for a fixed distance after getting a distant warning or passing under an OSS equivalent transponder on approach to a red.

Interesting thought. I guess a modern system could remember the speed at passing the OSS and the time difference between the loops to deduce the set speed, and restrict the train to that speed for a certain period afterwards.

That was also my thinking. Running under PZB90 in these circumstances;

1. The driver would have needed to acknowledge the caution aspect displayed by the preceding signal (LR473) without being prompted to do so by any in-cab warning. Failure to do so within approximately four seconds of passing the signal would have resulted in an emergency brake demand.
2. Had the driver successfully acknowledged the caution aspect, they would then need to have reduced the train's speed to be below the supervisory speed limit* of 70 km/h (approx 43 mph). Failure to make this speed reduction within approximately 30 seconds of successfully acknowledging the caution aspect would also have resulted in an emergency brake demand.
3. Had the driver successfully made the initial speed reduction, they would then need to control their speed so as to be travelling at no more than 35 km/h (22 mph) when they passed the 500 Hz beacon placed 250 metres ahead of the signal at danger. Failure to do so would have resulted in an emergency brake demand. This particular feature is replicated by the TPWS OSS arrangement where installed, but is standard at all signals under PZB.

* = the supervisory limit is chosen from three options - the others being 85 and 55 km/h (53 and 34 mph) - based on the individual train's braking performance.

 

[GC class B1]

In clause 60 of this report it is stated that design of TPWS OSS loops whilst not able to prevent a SPAD are intended at this location to bring a train to a stand before the conflict point is reached. I have calculated that the present location of the OOS loops for signal LR 477 will not achieve the design requirement. I have concluded therefore that the OSS are incorrectly positioned and are closer to the signal LR 477 than required to ensure that a train running at 10MPH above the line speed will be stopped before the conflict point. A sprinter train running at 75 MPH will require at least 650 metres to come to a stand with a 9% g Emergency brake applocation being initiated at the OOS loops. The conflict point is 262 metres beyond LR 477 and with the present OSS loops initiating an Emergency brake application about 250 before the signal, the conflict point will be overrun by about 150 metres. I note that the design assumes a braking rate of 12% g in Emergency, however sprinter and AFAIK Class 170 dmu trains have a braking rate in Emergency of 9% g.
Placing the OSS loops 500 metres in advance of signal LR 477 would have prevented the Railgrinder reaching the conflict point and therefore would achieve the objective for all trains operate over this line.

 

[deltic]

Points I noted from the report were that the driver wasn't aware that it was fine to have a nap, that not eating or drinking for a whole shift was a reasonable thing to do, that sitting around doing nothing all night was a strange way to run a shift and its not surprising that someone would not be alert after doing that something that has been noted in other RAIB reports.

Daft question but why doesn't the driver who brings the grinder to the site not also operate it when there.

 

[Signal Head]

I am not an expert in signalling however having carefully considered the content of the report and document RIS-0775-CCS issue 3, I am of the opinion that had the OSS loops beeen positioned about 475 or 500 metres before the red signal the conflict may have been avoided. In summary I believe that the existing TPWS technology, although not able to prevent the SPAD may have prevented the conflict.
There may of course be a reason why the OSS loops were positioned much closer than 475 metres from the signal.

I am not an expert in signalling however having carefully considered the content of the report and document RIS-0775-CCS issue 3, I am of the opinion that had the OSS loops beeen positioned about 475 or 500 metres before the red signal the conflict may have been avoided. In summary I believe that the existing TPWS technology, although not able to prevent the SPAD may have prevented the conflict.
There may of course be a reason why the OSS loops were positioned much closer than 475 metres from the signal.

These TPWS fitments are most likely to date from the original rollout about 20 years ago. At the time, the loop positioning was dictated by a fairly simple set of tables, and was (from memory) based on 12%g in Emergency.

Since that time, a lot of experience has been gained, and the design process refined. It is usual when carrying out alterations, or even renewals, to reassess the effectiveness, and to alter the arrangements if practical to do so, and also to attempt to achieve effectiveness at 9% too.

A couple of instances from my own experience -
TPWS found not to be effective at 9% for a Warning approach (signal in rear released R-Y on approach) to a signal with a 50m Restricted Overlap (ending almost exactly at the conflict point). No issue with the full overlap, which extended past the conflicts. In this instance it was found difficult to position loops to work for both without being overly restrictive, and adding extra loops would have been complex. It was found that the approach release on the outer signal wasn't to current standards, and barely provided any 'incentive' to reduce speed, as the signal cleared with the train a long way back, basically in many cases it would already have been displaying a Y when sighted. The solution was to adjust the time release to bring the train much closer to the Red. This achieved (theoretical) effectiveness at 9%.

Another instance - the OSS loops were positioned a greater distance from the signal than the current calculation standard required. This actually decreased effectiveness as the set speed was higher than the TSS alone could cope with, so the train 'flies under' the OSS, arrives at the TSS with no further retardation, and exceeds the available Safe Overrun Distance. The loops were moved inwards, reducing the set speed and improving the effectiveness at both 12% and 9% (12% stopped before the conflict, 9% got better but couldn't be made to work without more loops).

A current example being looked at has an OSS+ already, but this is so far from the signal that, again, a train can get past it, and still be going too fast for the inner OSS to handle. This is compounded by the presence of a conflict actually within the overlap, ie the extremity of the overlap is foul of a conflicting move the interlocking does not prevent, which is an unusual situation. Calculations indicate that, with the current SOD, three OSS loops would be required to achieve 12% effectiveness (with the outermost loop moved inwards), but even then 9% still fails.

 

[E27007]

Whilst having a SPAD on your record shouldn't automatically mean instant dismissal or disqualification from applying for a driver role, clearly this driver did not have the required skills, or perhaps qualities, to be operating trains safely. As proven by the fact they now have two RAIB reports to their name!

There's also a worrying accountability gap here because, as with many RAIB reports, we are again reminded that decade-old recommendations have still not been fully implemented. It's no good having the RAIB simply make recommendations if they don't have the power to force companies to comply.

It's frankly astonishing that the rail network doesn't have more incidents, with so many holes in the Swiss cheese just waiting to line up...

The figures by the industry is a SPAD risk per Driver of 1 SPAD per 8 years, This Driver worked over 20 years , his record is better than the 1 per 8 risk.
You also wrote the driver lack required skills, you have ignored the fact that his company pushed him way beyond recommended limits in his shift lengths and shift patterns.Have you considered his company may not have the necessary skills or resolve to manage their operation in a safe manner?

 

[Signal Head]

It already exists in some areas and there's no fundamental technical reason why it couldn't be implemented everywhere (albeit modifying old mechanical or relay based interlockings would be "interesting").

The reason why it's not done everywhere is that it would significantly reduce capacity and would essentially break a lot of timetables. You'd have to completely rewrite them with higher junction margins and in many cases that would necessitate reducing frequencies.

A 'solution' without TPWS+:
Approached control before final protecting signal.
Ie: GR, YY, Y, R (turns Y from approach control), R = Protected Junction. And if this already exists, why isnt put into practice at every junction where there is even the remotest possibility of a collision.

"Two Reds Rule" (AKA 'Double Red'). This was introduced, for new work at least, around 20 years ago, and has also been implemented on existing interlockings for alterations, including Line Speed Enhancements.

As it's an interlocking alteration, it is generally more invasive and therefore costly than just providing another OSS.

Done 'properly', it works at 'interlocking level', and requires only that the 'forward route' (through the junction) is set, and therefore the conflict is removed.

It is generally simpler to do it at 'aspect level' , but this then requires that the junction signal has cleared, which of course requires the line ahead clear to the end of the overlap of the signal *after* the junction signal as well, way beyond the actual conflict you're trying to protect, with a much greater impact on line capacity, particularly on busy lines where trains are running at close spacing.

 

[GC class B1]

These TPWS fitments are most likely to date from the original rollout about 20 years ago. At the time, the loop positioning was dictated by a fairly simple set of tables, and was (from memory) based on 12%g in Emergency.

Since that time, a lot of experience has been gained, and the design process refined. It is usual when carrying out alterations, or even renewals, to reassess the effectiveness, and to alter the arrangements if practical to do so, and also to attempt to achieve effectiveness at 9% too.

A couple of instances from my own experience -
TPWS found not to be effective at 9% for a Warning approach (signal in rear released R-Y on approach) to a signal with a 50m Restricted Overlap (ending almost exactly at the conflict point). No issue with the full overlap, which extended past the conflicts. In this instance it was found difficult to position loops to work for both without being overly restrictive, and adding extra loops would have been complex. It was found that the approach release on the outer signal wasn't to current standards, and barely provided any 'incentive' to reduce speed, as the signal cleared with the train a long way back, basically in many cases it would already have been displaying a Y when sighted. The solution was to adjust the time release to bring the train much closer to the Red. This achieved (theoretical) effectiveness at 9%.

Another instance - the OSS loops were positioned a greater distance from the signal than the current calculation standard required. This actually decreased effectiveness as the set speed was higher than the TSS alone could cope with, so the train 'flies under' the OSS, arrives at the TSS with no further retardation, and exceeds the available Safe Overrun Distance. The loops were moved inwards, reducing the set speed and improving the effectiveness at both 12% and 9% (12% stopped before the conflict, 9% got better but couldn't be made to work without more loops).

A current example being looked at has an OSS+ already, but this is so far from the signal that, again, a train can get past it, and still be going too fast for the inner OSS to handle. This is compounded by the presence of a conflict actually within the overlap, ie the extremity of the overlap is foul of a conflicting move the interlocking does not prevent, which is an unusual situation. Calculations indicate that, with the current SOD, three OSS loops would be required to achieve 12% effectiveness (with the outermost loop moved inwards), but even then 9% still fails.

I have suggested that the OSS loops should be positioned about 475 metres from signal LR 477 as in accordance with the standard at this distance in advance of the signal, the set speeds are 55 MPH for passenger and 44MPH for freight trains. I have calculated that in order to stop in advance of the signal at red, a passenger train braking in step 2 I.e. 6% g would need to be travelling no faster than 51 MPH at the OSS loops and a freight train braking at about 3.5 to 4% g would need to be travelling at no more than 40 MPH. I would expect that in order to come to a controlled stop the train speeds would in any event be less than these and therefore the OSS would only be likely to initiate an Emergency brake application if the train was at risk of passing the red signal.

 

[Railsigns]

I have suggested that the OSS loops should be positioned about 475 metres from signal LR 477 as in accordance with the standard at this distance in advance of the signal, the set speeds are 55 MPH for passenger and 44MPH for freight trains.

The maximum permitted distance between a signal and its closest OSS is 450 metres. An OSS can be positioned at a greater distance from a signal, but there must be another one in between.
Also, OSS loops tend to be more effective when they're located in rear of the relevant signal.

 

[Surreytraveller]

I have suggested that the OSS loops should be positioned about 475 metres from signal LR 477 as in accordance with the standard at this distance in advance of the signal, the set speeds are 55 MPH for passenger and 44MPH for freight trains. I have calculated that in order to stop in advance of the signal at red, a passenger train braking in step 2 I.e. 6% g would need to be travelling no faster than 51 MPH at the OSS loops and a freight train braking at about 3.5 to 4% g would need to be travelling at no more than 40 MPH. I would expect that in order to come to a controlled stop the train speeds would in any event be less than these and therefore the OSS would only be likely to initiate an Emergency brake application if the train was at risk of passing the red signal.

In advance of the signal or in rear of the signal? Normally you'd want a train to stop in rear of a signal, otherwise its a SPAD

 

[GC class B1]

In advance of the signal or in rear of the signal? Normally you'd want a train to stop in rear of a signal, otherwise its a SPAD

By in advance I mean before the signal is reached. I used this term because I am not a signalling engineer or driver, but I am a car driver and remember before the advent of electronic ignition control, the petrol engined car spark ignition was advanced by vacuum as the engine speed increased. This brought the firing point earlier in the cycle and a greater distance before the piston reached top dead centre.

 

[edwin_m]

By in advance I mean before the signal is reached. I used this term because I am not a signalling engineer or driver, but I am a car driver and remember before the advent of electronic ignition control, the petrol engined car spark ignition was advanced by vacuum as the engine speed increased. This brought the firing point earlier in the cycle and a greater distance before the piston reached top dead centre.

Highway engineers use the term "in advance of" as you describe, but it's the other way round in traditional railway practice. Possibly for this reason it's no longer favoured, the official term now being "on the approach to".

 

[Surreytraveller]

By in advance I mean before the signal is reached. I used this term because I am not a signalling engineer or driver, but I am a car driver and remember before the advent of electronic ignition control, the petrol engined car spark ignition was advanced by vacuum as the engine speed increased. This brought the firing point earlier in the cycle and a greater distance before the piston reached top dead centre.

Railway definition of 'in advance of' is once you've passed the signal. Before you get to it is 'in rear of'. But these terms are disused now due to people's confusion of them

 

[43066]

Railway definition of 'in advance of' is once you've passed the signal. Before you get to it is 'in rear of'. But these terms are disused now due to people's confusion of them

AIUI “I’m advance of” and “in rear of”used to be the other way around to the sense you’ve described above. That is the usage that has fallen out of favour.

 

[niggill617@gma]

The figures by the industry is a SPAD risk per Driver of 1 SPAD per 8 years, This Driver worked over 20 years , his record is better than the 1 per 8 risk.
You also wrote the driver lack required skills, you have ignored the fact that his company pushed him way beyond recommended limits in his shift lengths and shift patterns.Have you considered his company may not have the necessary skills or resolve to manage their operation in a safe manner?

I believe there are around 20,000 U.K. train drivers. The industry experiences about 280 Spads per year.

The incident driver was exposed to increased fatigue risk for all of his career. We all know drivers are only as good as the next turn of duty. He may well be good at what he does, when not knackered.

 

[TheEdge]

AIUI “I’m advance of” and “in rear of”used to be the other way around to the sense you’ve described above. That is the usage that has fallen out of favour.

Understandable because its a really stupid clunky use of English that is about as clear as mud. Only slightly less terrible than the old terms for exceptional rail head conditions.

 

[Efini92]

AIUI “I’m advance of” and “in rear of”used to be the other way around to the sense you’ve described above. That is the usage that has fallen out of favour.

In advance of was always after the the signal, in rear was before it. It did seem to confuse some people though.

 

[Sonik]

The incident driver was exposed to increased fatigue risk for all of his career. We all know drivers are only as good as the next turn of duty. He may well be good at what he does, when not knackered.

I'd say that fatigue risk is particularly high for OTP operations, due to the work pattern.

Surprising that RAIB did not not address this, especially since this was the second such incident for the same driver, but at a different employer.

 

[Surreytraveller]

AIUI “I’m advance of” and “in rear of”used to be the other way around to the sense you’ve described above. That is the usage that has fallen out of favour.

I have been trying to find the old Rule Book definition, but so far without success. But I have found this rule using both terms

 

[Signal Head]

[...]
Also, OSS loops tend to be more effective when they're located in rear of the relevant signal.

Understandable because its a really stupid clunky use of English that is about as clear as mud. Only slightly less terrible than the old terms for exceptional rail head conditions.

I've never had a problem with it, it's 'written' from the perspective of a train - in advance of is a point ahead the train that it has yet to reach, in rear of is a point behind the train which it has already passed.

 

[Sheridan]

I've never had a problem with it, it's 'written' from the perspective of a train - in advance of is a point ahead the train that it has yet to reach, in rear of is a point behind the train which it has already passed.

I think the confusion arises because we use ‘advance’ to describe things in both time and space. ‘In advance of’ in time terms means something that happens earlier or before something else, so a moving train encounters an over speed loop which is ‘in rear of’ a signal in location terms, ‘in advance of’ reaching the signal in terms of time (if that’s not worded too confusingly!).

Personally I’m fine with its use in railway terms now but it took a while. I would still say ‘on approach to’ more readily though.

 

[niggill617@gma]

The maximum permitted distance between a signal and its closest OSS is 450 metres. An OSS can be positioned at a greater distance from a signal, but there must be another one in between.
Also, OSS loops tend to be more effective when they're located in rear of the relevant signal.

450 m is just good practice , not absolute, what is your reference?

 

[Railsigns]

450 m is just good practice , not absolute, what is your reference?

It's an amber requirement within TI022 Appendix A, Appendix C:

"To minimise the risks associated with trains accelerating having passed an OSS, the distance between consecutive OSS loops or OSS and TSS shall not exceed 450m, unless fitment on an Outer signal."

 

[GC class B1]

I have searched the RSSB website and a search for T1022 doesn’t return any results. Is this the correct identifier please.

 

[Railsigns]

I have searched the RSSB website and a search for T1022 doesn’t return any results. Is this the correct identifier please.[?]

That's TI022, with an I for India, not the digit 1.

It's a Network Rail standard, so you won't find it on the RSSB website.

 

[GC class B1]

That's TI022, with an I for India, not the digit 1.

It's a Network Rail standard, so you won't find it on the RSSB website.

Thank you.

 

[niggill617@gma]

It's an amber requirement within TI022 Appendix A, Appendix C:

"To minimise the risks associated with trains accelerating having passed an OSS, the distance between consecutive OSS loops or OSS and TSS shall not exceed 450m, unless fitment on an Outer signal."

Thanks for that.
The distance between LR473 and LR477 is 2580 m. The line speed is 65 mph, with 1 in 508 falling gradient. Appendix A with 1 in 400 falling states, minimum signalled braking distance of 1220 m. Why is this location in excess of the normal 50 percent excess signalled braking distance. I always thought derogation was required, if indeed still the case?

It seems like the OSS loops are generically placed, rather than tailored.

Oh no, here we go again.

As has been gone over on this point with you countless times, there is a difference between the forensic reconstruction of an incident or the application of theoretical physics and the day to day judgements a driver makes when braking.

Another report into an incident where fatigue has played its role yet again. Yet NR, TOCs and FOCs are constantly after "productivity" which invariably translates as longer shift, shorter breaks and tighter rostering.

Also, impressive record of the driver managing to get his own old incident investigation referenced as a "similar occurrence" in his new RAIB report

What you and your cohort fail to understand, is understanding underpins judgement.

 

[Watershed]

The distance between LR473 and LR477 is 2580 m. The line speed is 65 mph, with 1 in 508 falling gradient. Appendix A with 1 in 400 falling states, minimum signalled braking distance of 1220 m. Why is this location in excess of the normal 50 percent excess signalled braking distance. I always thought derogation was required, if indeed still the case?

Because, as the report explains, the SL signals are placed at the same spacing as the FL signals. Presumably because this was cheaper to do and the resultant headway was considered acceptable.

 

[niggill617@gma]

Because, as the report explains, the SL signals are placed at the same spacing as the FL signals. Presumably because this was cheaper to do and the resultant headway was considered acceptable.

Of course cheaper, so ignore best practice. Regarding Loughborough report paragraph 51 suggests the same? The spacing is 1320 m. ( this distance is not compliant to 110 mph minimum signalled braking distance ) Paragraph 51 makes no sense, as I see it. Please explain.

 

[Signal Head]

Of course cheaper, so ignore best practice. Regarding Loughborough report paragraph 51 suggests the same? The spacing is 1320 m. ( this distance is not compliant to 110 mph minimum signalled braking distance ) Paragraph 51 makes no sense, as I see it. Please explain.

It's not necessarily that it's cheaper, there are are risks if Fast and Slow line signals are positioned separately - drivers on one line will encounter signals for the other line with no signal visible on 'their' line, at a distance it may not be clear which line the signal applies to, particularly in the dark when other positional cues are not as apparent. So, generally, signals are positioned parallel so they always appear in pairs.

There are long stretches of the 4-track ECML which are signalled this way, but often the Fast lines have 4-aspect signals, with 3-aspect on the Slows, which reduces the braking distance as a double yellow on the Fast equates to a green on the Slow, for the same stopping point. And of course the southern WCML is similar, but with 4-aspect on both, though perhaps not with a large speed difference.

Where there is a wide disparity in speeds, there will be unavoidable excess braking distances which under current standards are subject to risk assessment for new or altered signalling. Leicester area signalling was designed around the mid 80s, when I don't think risk assessments were the big thing they are now.

 

[niggill617@gma]

It's not necessarily that it's cheaper, there are are risks if Fast and Slow line signals are positioned separately - drivers on one line will encounter signals for the other line with no signal visible on 'their' line, at a distance it may not be clear which line the signal applies to, particularly in the dark when other positional cues are not as apparent. So, generally, signals are positioned parallel so they always appear in pairs.

There are long stretches of the 4-track ECML which are signalled this way, but often the Fast lines have 4-aspect signals, with 3-aspect on the Slows, which reduces the braking distance as a double yellow on the Fast equates to a green on the Slow, for the same stopping point. And of course the southern WCML is similar, but with 4-aspect on both, though perhaps not with a large speed difference.

Where there is a wide disparity in speeds, there will be unavoidable excess braking distances which under current standards are subject to risk assessment for new or altered signalling. Leicester area signalling was designed around the mid 80s, when I don't think risk assessments were the big thing they are now.

I appreciate your explanation thanks.

I would say driving appendix C is absolute to the cautionary signal, and appendix A is more intuitive. Is the Loughborough incident location ( class 57 times two and class 710) 4 aspect on the fast line? If not 1320 m is out of limits.