Anna Noyd-Dryver wrote:
Robert wrote:
Evening all,

https://www.bbc.com/news/uk-england-london-53150748

It will be interesting to see what happened here.

"Passengers narrowly avoided a collision when a train travelled the
wrong way on a London Underground track.

The Chiltern Railways service stopped a few metres in front of a Tube
train at Chalfont and Latimer station in Buckinghamshire.

An image from the scene shows the two just metres apart on the
Metropolitan line on Sunday night.

No casualties were reported and the Rail Accident Investigation Branch
(RAIB) is investigating.

The train caused damaged to points and parts of the track, according to
BBC London Transport and Environment Correspondent Tom Edwards."


I'll choose this one of the two threads to reply to as it seems to have the
most posts. I don't particularly want to get into a discussion about this,
but I can confirm some of the speculation as correct and some as being
false.

What I know about the incident is as follows:

The trains involved were an Up Chiltern, and a Northbound LU to the Chesham
branch. The LU train was timetabled across the junction first, if the
Chiltern unit had been slowing appropriately for the signal aspects
received, it likely wouldn’t have had to actually stop before being routed
into the station (where it was booked to call).

For reasons currently unknown to me, the Chiltern train spadded the signal
(which is around 700m-1km from the station, its shadow is clearly visible
on google maps near a footbridge around halfway between the station and the
divergence of the two lines), apparently at some speed (the track-mounted
tripcock equipment was damaged). It had received YY, Y, fog-repeater Y (ie
an additional single yellow aspect in the sequence) then the red. No AWS or
TPWS is fitted to the line because LU use tripcocks; all Chiltern stock
which uses the line must be tripcock-fitted.

The driver then reset the tripcock and carried on, for reasons unknown. The
signal went back to danger in front of the LU train before it moved from
the station; the Chiltern ran through and damaged the trailing points (bent
the end of the point blade and broke parts of the mechanism), then ran
across the facing crossover (which is presumably when the driver applied
emergency braking) ending up 23m from the LU train.

Points to bear in mind are the differences between LU and NR signalling and
procedures. This was a controlled signal so the following rule doesn't
apply, but its existence needs to be considered, I think: LU auto signals
aren’t allocated to a signaller as NR ones are; you contact the Line
Controller for any problems at them (eg signal failure, etc). As used to
apply at NR automatic signals, if you can’t contact anyone you can pass
them at danger and proceed at caution. The additional rule is that if you
spad one, and can’t contact anyone within two minutes, you can proceed at
caution up to a suitable location. This being a controlled signal that rule
didn’t apply, of course.

Also, after tripcock operation, most LU stock has a feature which limits it
to 10-15mph for 2 minutes; the Chiltern stock does not have this feature.

Personally I wonder whether the lack of AWS (a great tool for focusing the
attention of a distracted driver to something out of course) will be
considered by the investigation.

For clarity: there was no fault with any signalling equipment, no wrong
route was set or taken, and no fault with either of the trains.

From the signal the Up Chiltern train spadded, only one route can be set -
straight on into the southbound platform at C&L. There's no signalled route
across the crossover in that direction.

Thanks for the confirmation and extra details. So it sounds like the
Chiltern driver made multiple mistakes (travelling much too fast, spadding,
perhaps wrongly proceeding after resetting the tripcock, running through
and destroying the facing points…). It sounds like a spectacular way to end
a driving career.

Do you know how Chiltern trains will be adapted for the new Met signalling,
or will conventional signals and tripcocks be retained for them?

This raises another question in my mind: in the modern era, are there any
other places where national rail trains run in routine passenger service on
some other railway's tracks, with a different signalling system? I think
the shared Richmond line is NR, and the Wimbledon line is run to NR
standards.