Low-speed, empty stock derailment at Bletchley (26/06)

[westcoaster]

It seems strange that the train didn’t follow the fully signalled path north from Bletchley from the US along BR1, then through the double slip onto the DS. The photos of the points at the derailment seem to indicate that the latter part of this route was set, as does the screenshot of the head code on the signalling. Perhaps the signaller assumed the diamond at the derailment point was also a double slip, or he confused it with the double slip at the exit from BR1?
View attachment 182702

Silly question time does the route from BR1 have 2 available routes onto the down slow.
1 via the diamond (turn left)and straight out on to the down slow.
2. Straight through the diamond onto the up slow, then via Denbeigh hall north jn onto the down slow.

 

[Bald Rick]

But why on earth is it being allowed to affect services today? I couple of years ago we took the train from Guayaquil to Quito and spent a lot of time in the open balcony car at the back. At one point this carriage derailed - it was very bumpy and unpleasant for a few seconds until the brakes were applied. I thought, based on British Rail practice, that it would take a day to fix it, but not at all. The crew got a metal frame out of storage behind the loco and manhandled it on the track in front of the derailed wheels, used their radio to get the driver to move the train extremely slowly forwards so the affected wheels slowly mounted the steel channel up over the rail and back down into place. So we got back under way in not much more than 30 minutes. Admittedly this was light rail, but surely there must be a fast way of getting a carriage back on the track?

The train is back on the track, and will be moved shortly once declared safe to do so (if that hasn’t already happened). The track is in a mess and will need some fixing before it is safe to use (especislly with the forecast weather). I have no idea how long it will take to fic the track to open the slow lines, but in my experience it coudl be quite quick - probably with the junction taken out of use.

 

[jfollows]

Silly question time does the route from BR1 have 2 available routes onto the down slow.
1 via the diamond (turn left)and straight out on to the down slow.
2. Straight through the diamond onto the up slow, then via Denbeigh hall north jn onto the up slow.

I think your penultimate word was meant to be “down”.
But, no, a switch diamond has moveable point ends to make the crossing smoother, especially at higher speeds, but the crossing can only be used as a diamond crossing. You can’t turn left or right.
Physically there is a route via TK263 shown on the plan earlier, though.

 

[zwk500]

Silly question time does the route from BR1 have 2 available routes onto the down slow.
1 via the diamond (turn left)and straight out on to the down slow.
2. Straight through the diamond onto the up slow, then via Denbeigh hall north jn onto the up slow.

The Traksy drawing is somewhat misleading as it simplifies the exact nature of the connections. The actual track layouts are visible a few posts further down from the post you quoted.

 

[westcoaster]

I think your penultimate word was meant to be “down”.
But, no, a switch diamond has moveable point ends to make the crossing smoother, especially at higher speeds, but the crossing can only be used as a diamond crossing. You can’t turn left or right.
Physically there is a route via TK263 shown on the plan earlier, though.

Sorted and thank you.

 

[SCDR_WMR]

WMT is a mess. Nothing calling at MKC for ages and they dropped the MKC call from the fast Northampton relief.

Late boarding of everything causing concourse congestion.

Absolutely shocking performance. Not sure what happened to the old contingencies like dropping the Tring semi fasts and breaking the service at Northampton both of which would have helped a lot.

And once again the presence of the transverse displays caused congestion in the platform tunnel.

Possibly fallen under the trainees at Rugby ROC, not fully operational

 

[zwk500]

Sorted and thank you.

The actual track layouts are shown in Post #86, the Traksy layout is slightly compressed and is slightly misleading.

 

[jfollows]

The actual track layouts are shown in Post #86, the Traksy layout is slightly compressed and is slightly misleading.

The map at Open Train Times, https://www.opentraintimes.com/maps/signalling/r1_1, is a bit more prototypical. That’s not a criticism of Traksy, it’s a great resource, and it deliberately simplifies a lot of things to present a higher level view.

 

[zwk500]

The map at Open Train Times, https://www.opentraintimes.com/maps/signalling/r1_1, is a bit more prototypical. That’s not a criticism of Traksy, it’s a great resource, and it deliberately simplifies a lot of things to present a higher level view.

Absolutely, it's all part of the tradeoffs these sites choose to make.

 

[RiponHall]

But why on earth is it being allowed to affect services today? I couple of years ago we took the train from Guayaquil to Quito and spent a lot of time in the open balcony car at the back. At one point this carriage derailed - it was very bumpy and unpleasant for a few seconds until the brakes were applied. I thought, based on British Rail practice, that it would take a day to fix it, but not at all. The crew got a metal frame out of storage behind the loco and manhandled it on the track in front of the derailed wheels, used their radio to get the driver to move the train extremely slowly forwards so the affected wheels slowly mounted the steel channel up over the rail and back down into place. So we got back under way in not much more than 30 minutes. Admittedly this was light rail, but surely there must be a fast way of getting a carriage back on the track?

Your experience of re-railing a simple derailment, where a couple of wheelsets have left the rails but have not been laterally displaced by too much is one thing (especially with rolling stock that is relatively light). However, re-railing multiple coaches of stock built like a heavily armoured tank with with 5-7 bogies (10-14 wheelsets), and with lateral displacement meaning that at least some of the rails have moved over the opposite running rail (in this case, almost getting to the point where they are on the adjacent running line!) is something else entirely!

15-20 years ago, I was involved more often than I would have liked in having to rerail vehicles on non-running lines - and, so long as it only involved a couple of wheelsets that were not to far away from the rails they needed to be on, the re-railing could be complete within an hour. Often we had agreement with RAIB within that time so that operations could resume as soon as any track repairs had taken place.

The issues here will have been the task of rerailing, and then the work required to rectify damaged trackwork (a particular issue with S&C involved). With so many wheelsets derailed and significant lateral displacement, I would assume this has meant using heavy lifting equipment. Once the stock has been removed, there is then the issue of replacing track (that the photos available indicate has been seriously distorted by the forces of the derailment). If the pointwork is bespoke to the location, it is likely that new pointwork will need constructing - with the quickest way to reopen the lines being replacement of the pointwork with plain track until this can be done. However, that brings with it operational implications of taking the junction out of use for some considerable time...

 

[800001]

But why on earth is it being allowed to affect services today? I couple of years ago we took the train from Guayaquil to Quito and spent a lot of time in the open balcony car at the back. At one point this carriage derailed - it was very bumpy and unpleasant for a few seconds until the brakes were applied. I thought, based on British Rail practice, that it would take a day to fix it, but not at all. The crew got a metal frame out of storage behind the loco and manhandled it on the track in front of the derailed wheels, used their radio to get the driver to move the train extremely slowly forwards so the affected wheels slowly mounted the steel channel up over the rail and back down into place. So we got back under way in not much more than 30 minutes. Admittedly this was light rail, but surely there must be a fast way of getting a carriage back on the track?

The train was rerailed between midnight and 5am this morning.
There is track damage including at the points which needs replacing.
Until that is repaired the wcml is a 2 track railway last that area. So that is why it is affecting services today.

 

[GadgetMan]

Going from the left, thats the Down Fast, Up Fast, Down Slow, Up Slow. That layout seems to suggest the move from Up Slow (in down direction) to Down Slow is impossible.

 

[MarkyT]

Despite what traksy implies, the exit from BR1 is a set of back-to-back turnouts, not a double-slip. https://maps.app.goo.gl/7NDLa9ZDXJepg2Et5

The Open Train Times map gives more precise fine detail. Note no US down signal protecting Denbigh Hall Jn parallel with 3225/7 which suggests the line is signalled in the up direction only. This incident may be more the result of an operational misunderstanding than a technical issue. If the train was proceeding without interlocking protection wrong road on the US with no clear destination, then how that came to be is important. Note the switched diamond actually arrested the movement before going any further on the US perhaps prevented a head on. A route from 5228 to receptions, sidings or high level might have been set and in use at the time, for example.

 

[66701GBRF]

How did the train description end up where it did? Usually they only move with a signalled move or manual interpose.

 

[MarkyT]

Two motors are visible on Google maps https://maps.app.goo.gl/p2KF6teX9ULaKs3h8, but in Signalling diagrams the two ends of the switched diamond are listed as TK262A and TK262B indicating they are controlled as a pair (the turnout on the down slow is also TK262C).

Apologies I'm not a signalling engineer so don't know if that answers your question.

All point ends with the same number, suffixed A, B, C, etc, are operated by a single IPS.

 

[RiponHall]

The Open Train Times map gives more precise fine detail. Note no US down signal protecting Denbigh Hall Jn parallel with 3225/7 which suggests the line is signalled in the up direction only. This incident may be more the result of an operational misunderstanding than a technical issue. If the train was proceeding without interlocking protection wrong road on the US with no clear destination, then how that came to be is important. Note the switched diamond actually arrested the movement before going any further on the US perhaps prevented a head on. A route from 5228 to receptions, sidings or high level might have been set and in use at the time, for example.
View attachment 182727

When looking at the wider area, signal 9821 seems to signal moves in the down direction on the Up Slow - the next signal is 9753. It is not unusual to have more widely spaced signals for opposite direction moves on a line where the traffic is predominantly in one direction. Other examples can be found between Lincoln and Peterborough (on the GN&GE) and between Eastliegh and Basingstoke (on the Bournemouth mainline):

Live map of Peterborough (exc.) to Retford Low Level and Doncaster (exc.)

See trains move in real-time on our live map of Peterborough (exc.) to Retford Low Level and Doncaster (exc.)

www.opentraintimes.com

Live map of Micheldever to Southampton and Hinton Admiral

See trains move in real-time on our live map of Micheldever to Southampton and Hinton Admiral

www.opentraintimes.com

 

[NSEWonderer]

Looks like 1Z99 is about to rescue the re-railed units. I assume it will do a wrong direction move to get to 5Y26 from the Down Fast.

 

[Vexed]

How did the train description end up where it did? Usually they only move with a signalled move or manual interpose.

My records show an interpose into 5231 at 12:25:58 after being cancelled from 5222 at 12:03:11.

I can't find any intermediate descriptions.

 

[66701GBRF]

Thanks

 

[louis97]

When looking at the wider area, signal 9821 seems to signal moves in the down direction on the Up Slow - the next signal is 9753. It is not unusual to have more widely spaced signals for opposite direction moves on a line where the traffic is predominantly in one direction. Other examples can be found between Lincoln and Peterborough (on the GN&GE) and between Eastliegh and Basingstoke (on the Bournemouth mainline):

There is no signalled route from signal 9821 to 9753.

Also one of your examples is incorrect, there isn't any signalled routes between the signals not in the normal direction of traffic between Lincoln and Peterborough. The routes from those signals are to cross to the other line or another local move dependent on the signal. The only exception is on the Sleaford avoiding line allowing an up train to travel along the down line between Sleaford North and Sleaford South.

 

[Jimini]

1Z99 is parked up on P2 at Milton Keynes. Rescue loco?

 

[MarkyT]

When looking at the wider area, signal 9821 seems to signal moves in the down direction on the Up Slow - the next signal is 9753. It is not unusual to have more widely spaced signals for opposite direction moves on a line where the traffic is predominantly in one direction. Other examples can be found between Lincoln and Peterborough (on the GN&GE) and between Eastliegh and Basingstoke (on the Bournemouth mainline):

It's possible certainly the route exists and they're easy to add in processor-based interlockings, as at Bletchley now. The distance from signal to switched diamond concerned me however, as in traditional signalling principles, the signal to furthest facing point in route distance should be no more than 800m. In this case, 9821 to the diamond is ~1400m. That's still not a complete deal breaker, as a non-compliance can be permitted in some cases.

== Doublepost prevention - post automatically merged: Friday at 13:53 ==

There is no signalled route from signal 9821 to 9753.

Thanks for the clarification.

 

[zwk500]

Looks like 1Z99 is about to rescue the re-railed units. I assume it will do a wrong direction move to get to 5Y26 from the Down Fast.

View attachment 182735

Based on this image, 1Z99 crossed over to the Down Slow and would then have used the shunt signal to move back towards 5Y26. Generally, if a signalled move exists to allow the movement, it will be used.

 

[Silverlinky]

The units have been split with the loco rescuing the north end unit and 5B99 (a 350) to take the south end unit back.

 

[Harpo]

The distance from signal to switched diamond concerned me however, as in traditional signalling principles, the signal to furthest facing point in route distance should be no more than 800m. In this case, 9821 to the diamond is ~1400m.

A divergent route isn’t (normally, anyway ) available at switched diamonds so would they be treated as facing points?

 

[RiponHall]

There is no signalled route from signal 9821 to 9753.

Also one of your examples is incorrect, there isn't any signalled routes between the signals not in the normal direction of traffic between Lincoln and Peterborough. The routes from those signals are to cross to the other line or another local move dependent on the signal. The only exception is on the Sleaford avoiding line allowing an up train to travel along the down line between Sleaford North and Sleaford South.

So does 9821 just read for a route to line R1? Would one approach 9753 from lines R1/R2 via the crossover that is immediately prior to the junction with the US?

My direct knowledge is based on the resignalling of the Bournemouth line, but I am sure that flexibility on the GN&GE was mentioned during a tour prior to the commissioning of the resignalling at Lincoln - I must have misunderstood the exact flexibility they were referring to (it is some time ago now!).

 

[zwk500]

So does 9821 just read for a route to line R1?

Correct.

Would one approach 9753 from lines R1/R2 via the crossover that is immediately prior to the junction with the US?

Also Correct.

 

[Supercoss]

More on switch Diamonds -
and specifically for site comcerned
you can go A to B up slow to Up slow
or
D to C down Bletchley (Flyover) to Down slow or return
No route from A to C through Switch Diamond

 

[MarkyT]

A divergent route isn’t (normally, anyway ) available at switched diamonds so would they be treated as facing points?

Yes. Two of the switches of a diamond could divert and likely derail, due to the dog leg turn, if misaligned. Limiting the distance limits the running time from the moment the last check of the mechanism was conveyed to the driver when passing the clear signal to encountering the facing switches.

 

[zwk500]

5B99 has now moved into the Carriage Sidings so looks like the south unit has been recovered. 1Z99 has just been given the signal from platform 2 at MKC so hopefully the north unit will be recovered soon.