Incident at Chalfont & Latimer (21/06/20)

[Taunton]

I seem to recall the Chalfont Up Home signal is way back, even before the Bell Lane overbridge. You would be doing well to be even up to line speed by there from an Amersham start. And then a good long distance before the points.

Regarding the Southall accident, there was a regulating decision, the freight needed to access sidings on the south side but had been unable to be crossed at previous points; it already had two passenger services delayed behind it on the Down Local. However, let us not get distracted by a different event.

 

[philthetube]

on the 165's are there clear indications to the driver when the Trip is cut out and are they left in or out when away from LUL metals?

Also will they run at line speed with the trip cut out?

I am wondering if it could have been a spad with the driver unaware?

 

[Mojo]

Looking at diagrams - there is around 600-700 metres between the signal and the set of trailing points, around 900 metres to where the train stopped.
If the signal was red and the tripcock was activated, I can't see how it would take a 2 car 165 900m to stop from 60mph in emergency.

It didn’t.

 

[357]

on the 165's are there clear indications to the driver when the Trip is cut out and are they left in or out when away from LUL metals?

I would hope they are treated the same as any other safety system on prep - if it is cut out (authorised) then it should be on the prep slip and measures taken to ensure the unit does not run on LUL lines, or similar. My stock has a light that illuminates whenever any safety system is cut out, I suspect a 165 would too. I would hope that Chiltern would also print and place a notice in the drivers cab to state that the tripcock is isolated, or even better degrade the unit and ensure the cab is buried.

 

[Mojo]

I think one of the valuable things about this forum is that we don’t just shut down threads that are considered controversial or prohibit reasonable discussion about recent incidents that are newsworthy. However I fear some of the posts made in this thread could possibly be overstepping the mark, therefore I shall close this thread until any new information is published.

If anyone does have anything relevant to add, please report a post in this thread with the details and the forum staff team will consider unlocking it.

 

[ainsworth74]

An update from the RAIB which I think clarifies quite a few aspects of what happened and also lays out their broad terms of referrence for their full investigation:

At around 21:45 hrs on 21 June 2020, a Chiltern Railways passenger train travelling southbound on the Metropolitan line of the London Underground network, passed a signal at danger (red) without authority. The signal was protecting a junction through which a route was already set for a northbound train, waiting in Chalfont & Latimer station, to cross in front of the southbound train. Passing the signal at red resulted in an automatic brake application which stopped the southbound train around 310 metres beyond the signal. Shortly afterwards, the train driver reset the automatic brake equipment and the train continued towards Chalfont & Latimer station, around 620 metres away. As a result of the position of the points at the junction, its route towards the station took it onto the northbound line. The northbound London Underground train on this line was stationary because the signal in front of it had changed to red as a result of the southbound train passing the red signal. The two trains stopped about 23 metres apart.

There were no reported injuries but some track components were damaged as the southbound train had proceeded through a route that was not set for it.

Our investigation will identify the sequence of events which led to the signal being passed at danger and the subsequent near-miss. It will also consider

1. the actions of the people involved
2. Chiltern Railways’ arrangements regarding the training, competence and fitness of its train drivers
3. Chiltern Railways’ management of risk associated with its drivers operating on the London Underground network
4. how risk associated with signals passed at danger by non-London Underground trains is managed on the London Underground network
5. any relevant underlying factors

Our investigation is independent of any investigation by the railway industry or by the industry’s regulator, the Office of Rail and Road.

We will publish our findings, including any recommendations to improve safety, at the conclusion of our investigation. This report will be available on our website.

[Withdrawn] Signal passed at danger and subsequent near miss at Chalfont & Latimer station

Investigation into a signal passed at danger and subsequent near miss at Chalfont & Latimer station, Buckinghamshire, 21 June 2020.

www.gov.uk

 

[2HAP]

Can anyone tell me what ranking the SPAD has been given please? Is it over 20?

 

[Lewlew]

Can anyone tell me what ranking the SPAD has been given please? Is it over 20?

What does this mean?

 

[lonogrol]

Can anyone tell me what ranking the SPAD has been given please? Is it over 20?

What does this mean?

S.P.A.D Risk Ranking only applies on Network Rail controlled infrastructure. As this is London Underground track this is not applicable.

 

[chiltern trev]

I seem to recall the Chalfont Up Home signal is way back, even before the Bell Lane overbridge. You would be doing well to be even up to line speed by there from an Amersham start. And then a good long distance before the points.

Regarding the Southall accident, there was a regulating decision, the freight needed to access sidings on the south side but had been unable to be crossed at previous points; it already had two passenger services delayed behind it on the Down Local. However, let us not get distracted by a different event.

Rickmansworth to Amersham is up hill ( about 1 in 105 - http://www.trainweb.org/districtdave/html/_applying_the_rule_.html ) so the 165 is going downhill and would probably have no trouble reaching line speed.

 

[2HAP]

S.P.A.D Risk Ranking only applies on Network Rail controlled infrastructure. As this is London Underground track this is not applicable.

Thank you, I didn't realise that. Just trying to assess exactly how serious this one is compared to (e.g.) Wootton Bassett. It will all come out in the report, no doubt.

 

[MarkyT]

I seem to recall the Chalfont Up Home signal is way back, even before the Bell Lane overbridge. You would be doing well to be even up to line speed by there from an Amersham start. And then a good long distance before the points.

Rickmansworth to Amersham is up hill ( about 1 in 105 - http://www.trainweb.org/districtdave/html/_applying_the_rule_.html ) so the 165 is going downhill and would probably have no trouble reaching line speed.

The up home signal is about 700m clear of the first conflict point at the junction, which should be at least a full emergency braking distance overlap at the line speed and local gradient, as per the usual LU signalling practice.

 

[EnriqueEspaña]

Seems like a tea no biscuits situation. Am i misremembering or is has this reset and proceed happened before with chiltern?

 

[jumble]

Assuming the protocol in post 86 is correct then someone appears to have completely ignored safety procedures which has seriously compounded the original problem.
If true the RAIB are likely to take a very dim view

"Following a Spad the Chiltern driver is required to contact the signaller for permission to proceed, as they cannot make contact by radio this would have to be at a signal phone, so would involve the driver walking back to it so if this happened a minimum delay of five mins would follow, and I would expect much longer. "

 

[bramling]

Assuming the protocol in post 86 is correct then someone appears to have completely ignored safety procedures which has seriously compounded the original problem.
If true the RAIB are likely to take a very dim view

"Following a Spad the Chiltern driver is required to contact the signaller for permission to proceed, as they cannot make contact by radio this would have to be at a signal phone, so would involve the driver walking back to it so if this happened a minimum delay of five mins would follow, and I would expect much longer. "

A plausible scenario is that the driver wrongly had it in his mind that he was clear through to Chalfont, and then somehow completely missed the red aspect on JT6. Having then experienced an unexpected tripcock activation he might have looked ahead to see a yellow or even green aspect on the starting signal ahead, leading to forming a conclusion that the tripcock activation had been spurious. It's not unheard of for trains to be tripped because of something like a dead fox or football on the track.

LU's rules are actually a little vague on this. Drivers are required to report when they've passed a signal at danger, there isn't actually anything laid down to say that a tripcock activation *must* be reported -- unless there's anything in Chiltern's TOC-specific instructions, professional driving policy, or whatever. This differs from Network Rail where anything like a TPWS activation *must* be reported before moving.

 

[DerekC]

A plausible scenario is that the driver wrongly had it in his mind that he was clear through to Chalfont, and then somehow completely missed the red aspect on JT6. Having then experienced an unexpected tripcock activation he might have looked ahead to see a yellow or even green aspect on the starting signal ahead, leading to forming a conclusion that the tripcock activation had been spurious. It's not unheard of for trains to be tripped because of something like a dead fox or football on the track.

LU's rules are actually a little vague on this. Drivers are required to report when they've passed a signal at danger, there isn't actually anything laid down to say that a tripcock activation *must* be reported -- unless there's anything in Chiltern's TOC-specific instructions, professional driving policy, or whatever. This differs from Network Rail where anything like a TPWS activation *must* be reported before moving.

Interesting and plausible scenario. No doubt RAIB will have some recommendations for change to LU's rules if that is the case.

 

[MotCO]

An update from the RAIB which I think clarifies quite a few aspects of what happened and also lays out their broad terms of referrence for their full investigation:

[Withdrawn] Signal passed at danger and subsequent near miss at Chalfont & Latimer station

Investigation into a signal passed at danger and subsequent near miss at Chalfont & Latimer station, Buckinghamshire, 21 June 2020.

www.gov.uk

"The northbound London Underground train on this line was stationary because the signal in front of it had changed to red as a result of the southbound train passing the red signal." Am I reading this that, as a SPAD had occurred, all lights in the area revert to Red? In which case, that is pretty smart, and I had not realised this previously.

 

[Mojo]

"The northbound London Underground train on this line was stationary because the signal in front of it had changed to red as a result of the southbound train passing the red signal." Am I reading this that, as a SPAD had occurred, all lights in the area revert to Red? In which case, that is pretty smart, and I had not realised this previously.

In order for a signal to display a proceed aspect for a certain route, a number of conditions would have to be met. One of these would be that the track circuit must be "up" (ie. unoccupied). When the Chiltern train crossed the blockjoint, the track circuit would no longer have been up, and thus the signal would revert to danger. It is less of a case of being "smart" and more an integral part of the reason for the signalling system to exist!

 

[Taunton]

In order for a signal to display a proceed aspect for a certain route, a number of conditions would have to be met. One of these would be that the track circuit must be "up" (ie. unoccupied). When the Chiltern train crossed the blockjoint, the track circuit would no longer have been up, and thus the signal would revert to danger. It is less of a case of being "smart" and more an integral part of the reason for the signalling system to exist!

Although of course it is only a more recent signalling feature. In the days of mechanical interlockings the route only needed to be clear at the point the levers were swung, any subsequent overrun did not cause the levers to move back. As a result there were a few, apparently, specific warning bells etc linked to track circuits where an overrun might be anticipated. I think Adrian Vaughan wrote about this in one of his old-days signalling books. I wonder if the overrun here caused an immediate alert in the Underground signalbox.

 

[edwin_m]

In order for a signal to display a proceed aspect for a certain route, a number of conditions would have to be met. One of these would be that the track circuit must be "up" (ie. unoccupied). When the Chiltern train crossed the blockjoint, the track circuit would no longer have been up, and thus the signal would revert to danger. It is less of a case of being "smart" and more an integral part of the reason for the signalling system to exist!

Not familiar with LUL practice, but quite often on main line signaling track circuits not directly on the line of route are brought into the aspect controls for a particular route, so if that route is set and a SPAD occurs that could lead to a conflict, the signal will go back to red.

Although of course it is only a more recent signalling feature. In the days of mechanical interlockings the route only needed to be clear at the point the levers were swung, any subsequent overrun did not cause the levers to move back. As a result there were a few, apparently, specific warning bells etc linked to track circuits where an overrun might be anticipated. I think Adrian Vaughan wrote about this in one of his old-days signalling books. I wonder if the overrun here caused an immediate alert in the Underground signalbox.

When I was involved in IECCs back in the 90s, they were just implementing a system that would monitor state of track circuits and signals, possibly by intercepting the data logger feed. If a SPAD was detected it would light up a red alphanumeric LED display on the workstation giving the signal number.

 

[Ex LT]

Although of course it is only a more recent signalling feature. In the days of mechanical interlockings the route only needed to be clear at the point the levers were swung, any subsequent overrun did not cause the levers to move back. As a result there were a few, apparently, specific warning bells etc linked to track circuits where an overrun might be anticipated. I think Adrian Vaughan wrote about this in one of his old-days signalling books. I wonder if the overrun here caused an immediate alert in the Underground signalbox.

The signal lever would not move if a train spadded signal JT6, the conditions for the Met train having been shown a proceed aspect would then cease and the circuits not being correct signal JT80 would return to danger. Someone more technical will correct as needed.

 

[Dstock7080]

The signal lever would not move if a train spadded signal JT6, the conditions for the Met train having been shown a proceed aspect would then cease and the circuits not being correct signal JT80 would return to danger. Someone more technical will correct as needed.

Amersham is a totally push button frame.

 

[Ex LT]

Amersham is a totally push button frame.

I thought that Amersham was a push bitton desk which controlled the V frames at Amersham and Chalfont or have these been replaced.

 

[bramling]

I thought that Amersham was a push bitton desk which controlled the V frames at Amersham and Chalfont or have these been replaced.

Yes the desk is push button, which remotely controls the IMR frames, Amersham is IIRC located in the basement of the signal box, and Chalfont IMR is on the end of the platform.

 

[Tetchytyke]

the RAIB are likely to take a very dim view

RAIB are not there to apportion blame, they're there to ensure lessons are learned and it doesn't happen again. No doubt the ease with which a SPAD-and-reset can happen will be of interest, rather than the fact a driver easily did a SPAD-and-reset. RAIB are not there to hang people out to dry.

 

[PG]

Would I be correct in thinking that had the LU service departed Chalfont & Latimer some time earlier (possibly even seconds) then the LU driver would not have seen the signal revert back to danger and thus would not have had any indication of anything being amiss until they spotted the Chiltern service heading towards them?

If so I'd imagine RAIB may well comment on this possibility and the good fortune that it hadn't already departed.

 

[philthetube]

Looking at the images I struggle to work out how the Chiltern stopped where it did, had it being doing any sort of speed it would have travelled further than that, assuming that the driver realised his error when he saw the way the points were set.

My gut feeling is that had the Chesham service moved then the Chiltern service would have had time to stop.

I also suspect that the signal would revert to red immediately following the spad, and if I am correct this would also have mitigated any risk as the chiltern driver would have loads of time to see the other train moving and act accordingly.

Once the Chiltern train had the spad it would enter the signalling section which the Chesham train was going to use causing the signal to go back.

It could be (arguably) said that the Chiltern driver was unlucky as had the Chesham train moved he would have realised his error and acted differently.

 

[357]

The Chesham train had started moving, but had not passed the signal when the road went back on the driver and emergency brakes were applied

I can't see the logic in saying if the trains were closer together (Chesham having passed the signal) then it wouldn't have been so bad? It's likely that had the Chesham passed the signal there would have been a head on collision possibly even fatalities. The Chiltern driver would most likely assume the LUL train was heading to Amersham on a non-conflicting move until it crossed the points. The LUL driver would more likely notice something is wrong but as far as I'm aware the S stock does not have hazard lights like mainline trains do, and has a whistle and not a horn. Also, as far as I am aware, LULs Connect radio does not have a facility to stop other trains like GSMR does.

 

[Dstock7080]

The LUL driver would more likely notice something is wrong but as far as I'm aware the S stock does not have hazard lights like mainline trains do, and has a whistle and not a horn.

S Stock do have hazard warning lights.

 

[edwin_m]

From RAIB:

The northbound London Underground train on this line was stationary because the signal in front of it had changed to red as a result of the southbound train passing the red signal.

This suggests the original SPAD was what caused the signal to go to red. If the Underground train had passed the signal before that happened then it would probably have got clear onto the Chesham branch in the time it took the Chiltern train to stop, restart and reach the crossover. Also the Chiltern driver would probably have braked earlier if they had seen the Underground train crossing in front.