"Checkmate situation" meaning?

[Kilopylae]

Hi all. Last Sunday (14th December) my friend was on a delayed train from Reading (ex Paddington) to Exeter. He says the guard told all passengers that they couldn't hold the last train out of Exeter to Barnstaple, because it "creates a checkmate situation at Crediton".

I have no idea what this could mean. I am local to the area, so I know the trains pass to exchange tokens at Crediton. My best guess is that perhaps the driver from Barnstaple to Exeter is nearing the end of the maximum hours she can work, so if she has to wait at Crediton for the train which is being held, she might run out of hours, leaving herself and the train stranded? But that's total conjecture.

Can anyone shed any light on what the guard might have meant by "checkmate situation" here?

 

[LYradial]

Stalemate would have been a better word, they could have held the exeter bound train at Crediton but when you got there a Quick Look on realtime trains suggests there were three other Exeter bound trains all occupying the single track waiting to pass at crediton so you could have got no further without delaying them considerably

 

[Falcon1200]

'Mexican standoff' was the term we used in Glasgow Control. Not a common occurrence but I recall one such event on the then-new Borders Railway when, during disruption, we ended up with several trains stopped at various locations resulting in a deadlock. IIRC one had to return to Tweedbank to get things moving.

 

[norbitonflyer]

Didn't something similar happen at Mill Hill east in the early days of automated running? A train left Finchley Cebtral for the branch and got so far before the moving block detected a train ahead. But it was a train on the branch, waiting to leave the single track section.

I don't remeber the details, or how it was resolved. .

 

[AndrewE]

Only an anecdote, I admit, but (when working in Bath Rd depot in 1974) I was told that in the very early days of the Bristol Panel/Power Signal Box 2 locos came face to face either side of a signal on the single track between Bristol W Jct and N Somerset Jct!

 

[bramling]

Didn't something similar happen at Mill Hill east in the early days of automated running? A train left Finchley Cebtral for the branch and got so far before the moving block detected a train ahead. But it was a train on the branch, waiting to leave the single track section.

I don't remeber the details, or how it was resolved. .

Yes it did. The system as originally designed would allow two (or more) trains on the branch, even though the second would never be able to reach Mill Hill. However it would throw up an “Override automatic hold?” message, which would have to be responded with a yes in order for the second train to be routed. The signaller concerned chose the yes option without it dawning on him what the implication would be. The situation was entirely safe as all trains were fully supervised and protected by the signalling at all times, but clearly inconvenient, and scary for the drivers no doubt as they wouldn’t have been aware that the new system allowed this to happen. It was resolved simply be routing the second train back to Finchley Central, again all fully signalled. The system was modified in a subsequent software drop to prevent this happening, and the signaller IIRC got quite a telling off about it.

 

[brad465]

I'd be surprised if this situation hasn't happened of the West of England line before: the route is prone to disruption and has the absolute minimum in passing points, to the point that reduced timetables have had to be introduced in extreme weather impacts.

 

[Kilopylae]

The system as originally designed would allow two (or more) trains on the branch

Why? Is there a sensible reason why this would ever be a good idea? - my best incomplete guess is that if a train developed a fault at Finchley and needed to be emptied out it could go into the branch briefly to let another train past?

 

[Kite159]

I'd be surprised if this situation hasn't happened of the West of England line before: the route is prone to disruption and has the absolute minimum in passing points, to the point that reduced timetables have had to be introduced in extreme weather impacts.

It has, especially in the Gillingham area

 

[bramling]

Why? Is there a sensible reason why this would ever be a good idea? - my best incomplete guess is that if a train developed a fault at Finchley and needed to be emptied out it could go into the branch briefly to let another train past?

I don’t really know the answer to the question, but I *suspect* it lies in the fact that the system is designed primarily by software engineers rather than railway operators. Seltrac is an inherently fully bi-directional system, allegedly LU had to actually have this feature removed to suit their way of operation, so really this was just a relic of the “off the shelf” product that was left in.

There are exceptions to everything however, and one a day a year or two ago they actually had three trains on the Mill Hill branch, possibly for the first time ever. A 12-car train needed to be refuged somewhere so Mill Hill was chosen as the least disruptive option. As LU don’t generally like pulling defective trains, it was arranged for the 12-car to arrive at Mill Hill on top of a further train, with the 12-car being uncoupled and the defective train then coupled to the other 6-car so it could be pushed back to depot. As it happened, it was all somewhat academic as the defective train actually had full motors and braking so wouldn’t have been being pushed anyway. In this instance it was all done by unsignalled moves.