Great Western Coffee Shop

Apparently there was a serious operating incident at Chalfont and Latimer station last night (21 June 2020).  Details a bit scant at the moment but apparently a Chilterns Turbo was close to head on collision with an Northbound MET Train stood in the platform.  The Turbo stopped not more than a carriage length from the MET Train.  Trying to search out some more details.

Edit to add. Found a photograph here: https://twitter.com/BBCTomEdwards/status/1275110168104239110

There is currently (10h00 23-06) no service between Chalfont and Latimer and Chesham due to reported track damage at Chalfont and Latimer. Looking at the layout, I suspect the Met was routed to Chesham as the incident unfolded. The rest I can imagine, and it could have been a whole lot worse. I believe Turbos are trip-cock fitted on this line.

These picture I took a couple of years ago shows the layout looking south (with a bit of heat haze!).  It is quite possible the northbound train was waiting to cross over onto the Chesham branch (as the tube train in the picture has just done). 

As you can see, there is a signal just before the junction protecting moves from the branch (left hand track) onto the main line.  The Chiltern service would not have been on that line.  The signal protecting the junction from the line the Chiltern service would have been located on (centre track) is by the bridge the photo was taken from, which is over half a mile away from the station.

Presumably GSM-R isn't an option there as it's within the area controlled by TfL signalling, so I wonder why a tripcock didn't automatically apply the brakes before it got as far as it did?  It would (if being driven normally) be going quite slowly at the set of points as it would have been slowing for the station stop.

It's obviously an unusual set of working rules at Chalfont (national rail trains running under TfL signalling), so it will be very interesting to see what happened and the recommendations.

The Metropolitan Line between Harrow-on-the-Hill and Amersham is signalled to normal main line practice, using three or four-aspect signals.  As its TfL infrastructure there is no TPWS fitment, and as standard LU trainstops are fitted to the signals, the Chiltern trains are fitted with tripcock apparatus instead.  The Chesham branch (to the left in the photographs taken by II) is signalled with two-aspect signals to LU standards as the line is not used by 'Mainline' services.

I think I have a good idea what might have happened in this instance, but won't speculate on here.  The RAIB report will make interesting reading though (well, for me at least).

For me too. I am interested to know how many holes there were in this particular cheese. Never a single cause.

Edited to ask S+T-E: In addition to trainstops, are there AWS ramps on this part of the route?

No.  Not on the TfL/LU owned part of the route.  There is AWS between Marylebone and HotH (exclusive) and north of Amersham (exclusive).

Thank-you. The challenges of inter-running heavy and metro rail. I foresee some material changes ahead between Mantles Wood and Harrow-on-the-Hill.

Mantles Wood. Now there's a place name I haven't heard mentioned for over 50 years now.  I helped errect some of the last new railway telegraph poles there at the begining of my railway career. ;D

Just had a look, as far as I can see, nothing on the RAIB website yet.

Although potentially this could have seen loss of life or serious injury, no one was harmed in this incident.  The rail authorities (TfL, NR, ToC) will have advised the ORR, RAIB, BTP the ORR is the organisations that has the statutory powers under the 1974 Health and Safety at Work Act to investigate the incident, BTP involvement is where a suspected criminal act has been involved, the RIAB operate separately to these.

The ORR, BTP and RIAB may have chosen to all TfL and NR to investigate this operational incident 

Should be treated as a precursor. Not swept under the carpet.

It will not be swept under the carpet, the ORR, RAIB and BTP will all have their investigations on the books.  Not every operational incident is published to the public by the ORR or RAIB.

I was part of an internal investigation team investigating a serious electrical fire that injured 2 staff disrupted train services for days, it was never publicised on the ORR or RAIB websites and that incident will incur a hefty financial penalty on NR

The RAIB has picked this up.  Their announcement states:

“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 ... [etc[ ”

I don’t think any of us who had privately speculated on the cause of this incident expected the sequence of events to be as stated above..

If it's a 'reset and continue' then that makes the job of recommendations to stop it happening again much more straightforward.

Straightforward?  As RAIB say, they will need to look at:

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

As is often the case with incidents which RAIB investigates, the direct cause may be straightforward, but the underlying causes and contributory factors may not.

Point taken.  Though that's straightforward compared with a scenario where the incident could happen without rules and procedures being broken.

It'll be interesting to see the conclusions.

Is there working cab radio for both Chiltern and TFL trains on this stretch of line?

Which begs the question, was the signalman (ler0 involved?

We must wait for the RAIB report.  Just for a start, what category of SPAD was it?  And whatever category it was, you would normally expect the signaller to be involved before the train starts moving again.  I can think of several scenarios, but like SandTEngineer earlier I will keep them to myself.

edit later - I'm aware that the old SPAD categories have been superceded, but the drift of what I'm saying stands.