Strange SPAD at Chalfont & Latimer?

[Jeremy Cumberland]

5 minutes ago, w124bob said:

I've seen a diagram which seemed to show the LT unit signalled across the path of the 165, what struck me was why. The safer mode of operation looked to, be get the 165 into the station then set the route for the LT. Whats the normal operational set up here, was one of the trains late or do LT take priority and is it signalling with no TPWS but LT tripcock or both? I'm not familiar with the area but am ex footplate, somethings just don't add up here. Error on the part of the Chiltern driver seems to be look like mulitple failures of operating procedures. 

I don't see how you can say that at all. Two trains each require to use the same piece of track at about the same time. One of them has to be signalled in front of the other, and the other one has to stop and wait. Stopping/holding one train is no safer or more dangerous than holding the other, and the whole of railway signalling in Britain for well over a century is based on this premise. Of course, a fast-moving train requires a considerable stopping distance, and a stationary train requires none, but this is built into the signalling and line speeds.

 

It might be more expedient, in terms of the least delay to the least number of passengers, for a particular train to be given preference over the other, but this is not a safety consideration. In this case, the Chiltern train (presumably the 21:18 Aylessbury - Marylebone) would have been scheduled to stop at Chalfont and Latimer, a little over 900 metres beyond the signal, and the RAIB announcement implies that the Metropolitan train was ready to depart when the SPAD occurred. We aren't given any reason for the Metroplitan train having been given priority, but it is not an obviously wrong decision; in fact, it seems to be perfectly normal to me.

[PaulRhB]

52 minutes ago, w124bob said:

The safer mode of operation looked to, be get the 165 into the station then set the route for the LT.

Train planning rules of the route assumes the interlocking and overlap provides the safety so the order is dictated by the wider timetable.
As you noted it may have been late running but signalling the LT service out first might put 2-3 minutes into the other train that causes conflicts elsewhere. We have very tight regulation that would benefit from being eased on the Cardiff - Pompey route but as the services cross other mainlines in three other locations you’re stuck with it due to the knock on effect. 

 

52 minutes ago, w124bob said:

somethings just don't add up here

Yes, as I noted earlier there are several details missing but that’s probably restricted due to legalities until the why has been established. 
Even incidents on a patch you know well can be confusing until one or two details are revealed, I’ve seen that locally.
Like I said in an earlier post I can see why people make the assumptions on what’s released but it needs to be balanced against the holes obvious to those of us that work in the industry. That’s no doubt true of any job where there’s an enthusiast interest and while we are used to sitting back to wait for the facts to creep out these interim reports understandably create speculation in the wider public domain!

Fortunately the whole safety system probably has worked in part in that after the initial stop the train arrived at the conflict point at a much lower speed meaning no one got hurt. 

Edited July 12, 2020 by PaulRhB

[caradoc]

59 minutes ago, w124bob said:

I've seen a diagram which seemed to show the LT unit signalled across the path of the 165, what struck me was why. The safer mode of operation looked to, be get the 165 into the station then set the route for the LT. Whats the normal operational set up here, was one of the trains late or do LT take priority and is it signalling with no TPWS but LT tripcock or both? I'm not familiar with the area but am ex footplate, somethings just don't add up here.If there are errors on the part of the Chiltern driver, it seems to be look like mulitple failures of operating procedures.

 

Perhaps one or both trains was late, perhaps the Chiltern was early, perhaps the LT train was booked and signalled first but was then delayed in the station, perhaps there was another service behind it so running it first caused less overall delay, perhaps the turnround of the LT train at Chesham was tight. Regardless, trains are signalled on conflicting paths every hour of every day, with the signalling ensuring safety, and if a train does pass a signal at danger it will be stopped - As happened here. What happened thereafter is the key question.

 

[stewartingram]

I would have thought that the Met train would normally have priority, considering the frequency of service on the mEt. A delay to the Chesham branch train could (theoretically) delay services behind it all the way from central London, including beyond Baker Street and the the Circle. A delay to the inbound Chiltern train would be minimal as it should have been slowing anyway for the Chalfont stop, with many fewer Met services behind it (only 1 stop from the end of the Met!).

[martin_wynne]

Can a signaller give permission for a train to pass a red signal (or continue after having passed it), without any check that the route is set for it?

 

In this case, after the SPAD occurred, it might have been entirely reasonable to allow the train to continue into the station -- it might not have been possible to clear the signal for the LT train again until that had been done?

 

Martin.

Edited July 12, 2020 by martin_wynne

[Jeremy Cumberland]

8 minutes ago, martin_wynne said:

In this case, after the SPAD occurred, it might have been entirely reasonable to allow the train to continue into the station -- it might not have been possible to clear the signal for the LT train until that had been done?

The signal had aleady been cleared for the Metropolitan train.

the signal in front of it had changed to red as a result of the southbound train passing the red signal

 

I very much doubt the signaller is allowed to exercise any discretion at all following a SPAD. In any case, there is no mention of the signaller in the RAIB announcement, which suggests (although it is no more than a suggestion) that the Chiltern driver did not contact the signaller at all.

[martin_wynne]

Thanks. Yes, I meant clear the signal again.

 

there is no mention of the signaller in the RAIB announcement, which suggests (although it is no more than a suggestion) that the Chiltern driver did not contact the signaller at all.

 

On the other hand, it also carefully avoids saying that the driver had any part in the train continuing. The wording is very puzzling.

 

Martin.

Edited July 12, 2020 by martin_wynne

[Grovenor]

33 minutes ago, martin_wynne said:

Can a signaller give permission for a train to pass a red signal (or continue after having passed it), without any check that the route is set for it?

No, not if the signaller is following the rules, to give an instruction to pass a red requires the signaller to secure the route to be used, and needs the signal to have failed for some reason

 Once there is a SPAD then there is a lot more to be done before that driver can be allowed to drive any more.

Yes, if the signaller ignores the rules as permission is given verbally and there is nothing technical to prevent it. The conversation should be recorded.

[meil]

The one aspect that is niggling me as that when the train started to move after the SPAD it is clear (and this is stated in the report) that it went through a set of points set against it. Obviously they were trailing points otherwise the train would have followed the set route, and in doing so damaged the point. The driver should have been able to clearly see they were adversely set against him yet it appears he carried on regardless. I find the whole issue of the: SPAD, continuing after the SAPD and then passing through adverse set points as bizarre quite frankly.

[martin_wynne]

5 minutes ago, meil said:

Obviously they were trailing points otherwise the train would have followed the set route, and in doing so damaged the point. The driver should have been able to clearly see they were adversely set against him yet it appears he carried on regardless.

 

It may have been a switch-diamond?

 

Given that the driver failed to see a red signal, there may have been an issue with his vision, or forward visibility from the cab.

 

Martin.

[melmerby]

20 minutes ago, martin_wynne said:

 

It may have been a switch-diamond?

 

Given that the driver failed to see a red signal, there may have been an issue with his vision, or forward visibility from the cab.

 

Martin.

It looks like a ladder where the Northbound Met crosses to the Southbound and then to the branch.

So the SB Chiltern train would have gone through the branch turnout in a trailing direction against the setting and then crossed onto the NB line as the crossover was already set for the NB Met train

Edited July 12, 2020 by melmerby

[martin_wynne]

19 minutes ago, melmerby said:

It looks like a ladder where the Northbound Met crosses to the Southbound and then to the branch.

 

Yes:

 

 https://www.google.co.uk/maps/@51.6687256,-0.5633651,194m/data=!3m1!1e3!4m5!3m4!1s0x4876661e322881ff:0x6efe85b8763d8e70!8m2!3d51.6297828!4d-0.577213

 

(I should have looked at that first.)

 

Martin.

[martin_wynne]

At that time and date, the sun would have been low and directly behind the driver, and full on the red signal. Might this be relevant?

 

Martin.

[Jeremy Cumberland]

48 minutes ago, martin_wynne said:

At that time and date, the sun would have been low and directly behind the driver, and full on the red signal. Might this be relevant?

 

Martin.

It is entirely possible, I would have said. At Ladbroke Grove, low sun behind the driver reflecting off one of the yellow lenses of SN109 was conjectured as being a possible reason for the driver not seeing the illuminated red; I can easily imagine the sun's reflection being brighter than a signal lamp. The signal at Chalfont and Latimer (unless it has been replaeced in the last two years) has three aspects, so presumably this, too, has a yellow lens.

 

There is a video of this route here, with the signal being passed at 2:18:

 

Edited July 12, 2020 by Jeremy C

[big jim]

One thing just do know is if you push the speak to signaller button on the GSM-R on the met it puts you through to Baker Street control not the relevant signal box maybe that’s caused some confusion, who can say? 

 

when you Have to pass a signal at danger with signallers authority on the met they just say “obey the rule” which is them basically telling you to pass the signal, I only ever did it once and I got him to use proper protocol before I moved such as confirming the signal number, repeating the message etc better safe than sorry! 

 

 

[Jeremy Cumberland]

Just now, big jim said:

when you Have to pass a signal at danger with signallers authority on the met they just say “obey the rule”

Only for automatic signals, surely, which this was not.

[DY444]

2 hours ago, martin_wynne said:

On the other hand, it also carefully avoids saying that the driver had any part in the train continuing. The wording is very puzzling.

 

Someone drove it forward and, unless there was a technical glitch causing it to reset by itself, someone in the cab of the Chiltern unit reset the trip cock before it was driven forward.  We don't know how many people were in the cab but you can understand why people are jumping to the most obvious conclusion. 

 

Obviously the RAIB report will set out the precise series of events and sometimes this turns out to be not at all what you expected.  Sometimes however it turns out to be exactly what you expected.

Edited July 12, 2020 by DY444

[big jim]

30 minutes ago, Jeremy C said:

Only for automatic signals, surely, which this was not.

 

been a while since I’ve done met rules so I’ll be totally honest I really can’t remember the exact rule.

 

 

[St. Simon]

2 hours ago, meil said:

The one aspect that is niggling me as that when the train started to move after the SPAD it is clear (and this is stated in the report) that it went through a set of points set against it. Obviously they were trailing points otherwise the train would have followed the set route, and in doing so damaged the point. The driver should have been able to clearly see they were adversely set against him yet it appears he carried on regardless. I find the whole issue of the: SPAD, continuing after the SAPD and then passing through adverse set points as bizarre quite frankly.

Hi,

 

’Run-Throughs’, whilst not common, are usually only spotted by the signalling see the points flash out if correspondence or by patrolman checking the lines. From the reports of run throughs that I have seen, it is very rare that a driver notices a run through and reports it.

 

In this case, it is entirely plausible that the driver may have been busy to pay really close attention to the state the of points (after all, the driver may have assumed that there is no reason as to why any of the points may be against them)

Simon

[jim.snowdon]

4 hours ago, martin_wynne said:

Thanks. Yes, I meant clear the signal again.

 

 

 

 

On the other hand, it also carefully avoids saying that the driver had any part in the train continuing. The wording is very puzzling.

 

Martin.

That is simply a consequence of the fact that the RAIB's role is to establish what happened and, if necessary to identify any shortcomings and make recommendations. It is specifically barred from apportioning any blame; that is the responsibility for the safety authority, ie HMRI, as part of the ORR.

 

Jim

[jcarta]

4 hours ago, big jim said:

One thing just do know is if you push the speak to signaller button on the GSM-R on the met it puts you through to Baker Street control not the relevant signal box maybe that’s caused some confusion, who can say? 

 

when you Have to pass a signal at danger with signallers authority on the met they just say “obey the rule” which is them basically telling you to pass the signal, I only ever did it once and I got him to use proper protocol before I moved such as confirming the signal number, repeating the message etc better safe than sorry! 

 

 

 

The LUL Signaller at Amersham can not speak to any Chiltern Line / other railway companies directly whilst they are in the cab, the GSM-R radio only goes to the Line Controller (not the signaller) whom is now based at Hammersmith SCC, although from Harrow-on-the-Hill through to Amersham the signal post telephones are kept operational and these are two way, signaller to signal and vice versa.

 

The signaller can communicate with LUL stock as this utilises the Connect radio system. 

 

Jim

Edited July 12, 2020 by jcarta

[phil-b259]

On 10/07/2020 at 23:03, PaulRhB said:

I don’t know about that one but there have been rule changes to clarify the difference between temporary and full isolation and the conditions that apply. Temporary isolation for authorised passing a signal and associated TPWS only lasts a short period and automatically resets. 

 

The incident happened on London Underground Infarstructure which does not use TPWS - it uses air powered mechanical Tripcocks (system dating from before WW1 I believe) to slam the brakes on if trains pass red signals.

 

Likewise the rules governing passing signals at danger will be those in use by London Underground, and thus all Chiltern Train Drivers which operate via Amersham are required to be fully conversant with the LU rulebook in exactly the same way as they do as regards the NR one.

Edited July 12, 2020 by phil-b259

[PaulRhB]

57 minutes ago, phil-b259 said:

 

The incident happened on London Underground Infarstructure which does not use TPWS - it uses air powered mechanical Tripcocks (system dating from before WW1 I believe) to slam the brakes on if trains pass red signals.

 

.

Phil that was in response to this post about TPWS directly above mine not the RAIB report

 

Quote

 

wasnt there an incident on Chiltern when a driver isolated TPWS?

 

 

Edited July 12, 2020 by PaulRhB

[big jim]

1 hour ago, phil-b259 said:

 

The incident happened on London Underground Infarstructure which does not use TPWS - it uses air powered mechanical Tripcocks (system dating from before WW1 I believe) to slam the brakes on if trains pass red signals.

 

Likewise the rules governing passing signals at danger will be those in use by London Underground, and thus all Chiltern Train Drivers which operate via Amersham are required to be fully conversant with the LU rulebook in exactly the same way as they do as regards the NR one.

 

 

you can see the signal tripcock in action in the video linked to further back in the thread, ill see if i can get the time mark and edit this post accordingly

 

something else to consider, not only no TWPS on the met, there is also no AWS either! 

 

the chiltern ‘Met rules’  are a watered down version of the full LUL rules dealing with issues you may encounter on the ‘fast lines’ north of harrow on the hill, no point learning rules applicable to the slows which have different types of signals, or south of harrow into the tunnels as chiltern drivers dont work over there, they only sign the conventionally signalled  (bar the tripcocks) EX GCR fast lines from neasden jn  to amersham 

 

one thing that does apply to both sets of rules though, if you pass a signal at danger you dont make any futher moves until you gave spoken to the signaller and have permission to proceed!

 

EDIT: tripcock arm in action at 38:55 on the linked video

Edited July 12, 2020 by big jim

[big jim]

On 10/07/2020 at 22:55, johnofwessex said:

Going back a few years wasnt there an incident on Chiltern when a driver isolated TPWS?

 

been racking my brain to think what you are refering to, do you mean the incident at greenford where the driver went past the section signal onto the single line toward south ruislip?