East Midlands Railway Trust/GCR (Nottingham)

The description of the loop being three quarters of a mile long was rather interesting... And seems rather unnecessarily long. Hell, there are several preserved railways who have running lines shorter than the length of that loop.

From an operational point of view I feel a crossover between the up and down main beyond number 10 points, basically opposite the signal box itself would be more useful for running round trains at the halt.

Unless the GCR is still thinking gypsum trains might be a thing, in which case a run round loop that long might be useful?

 

I assumed it was in relation to getting line speeds up. If you have a longer loop can you approach it that bit more quickly as you've got longer to stop in?

 

It should not be difficult to lay out a turnout suitable for the 25 mph line speed.

 

Might part of the thinking be in relation to tours coming off the midland main line, a long loop will enable an engine to run round and head for Leicester north, because the lack of signalling will restrict anything running towards Nottingham to one engine in section, which might affect timetabled operations,

 

Even so a 1/4 mile would accommodate even the longest charter train ?

 

Yes, but is that the critical factor? Surely if you enter a loop, you need to be able to stop before the other end of it. With a long loop, both trains can enter at line speed and not be at risk of not being able to stop in time?
(What is the allowed braking distance of a the slowest-braking train likely to be on the line?)

Where was the gypsum loaded? Could it be you can then "hide" a gypsum train at one end of the loop, receive a terminating train, and have a through train? (Or is this signalling WIBN?)

 

Assuming that the single-line sections are controlled by Staff or Token the distance walked by the Signaller to collect / issue same is going to dictate station dwell times, and thus the timetable. ¼ mile seems a lot.
Pat

 

If both trains enter at line speed that is a closing speed of 50 mph if something goes wrong. The required overlap would also be much greater. It is also not normal to allow both trains to enter a loop at the same time on a single line railway. I doubt anyone would agree to that.

 

It seems odd to me on operational grounds to have the loops any longer than you need to pass the longest trains you expect to run. (For example, at 3/4 mile, running a train round could take up to ten minutes if you are restricted to 10mph; it’s going to be a long time in any event). It will also make passing trains much slower if you don’t have simultaneous arrivals on each loop.

I did wonder if the justification is more visual than operational, since, with the loop points well out of site, the visual appearance will be a pseudo twin track line, not a single track with passing loop. That may be a consideration, and was sort of hinted at in the video.

Tom

 

As I understand it, having two trains entering a loop at the same time from opposite ends is an absolute no-no. Current practice is to have one train enter the loop, come to a halt, and then have the opposite train enter the loop and either pass straight through or come to a halt to allow the other train to leave.

True, but this could also be achieved by having a second set of points closer to the station to allow a shorter run round, plus continuing the line further and having a second set of points where the line then reduces to single track. Obviously that's an additional expense and complexity, but solves the issue of very long times waiting for run rounds, while also maintaining the double track appearance.

 

Yes, I think that is a better operational solution, but I guess adds to the signalling complexity and therefore cost - an additional pair of points and associated dummy signals, plus the extra interlocking. But I think it would give the best of both worlds.

Tom

 

An odd statement considering how, for example, this is the way the Central Wales line and the far north RETB lines have operated for many years.

 

As I said, it was only from my understanding based on my observation of heritage lines. Perhaps the main line is different.

 

There are quite a few differences where RETB and NSTR methods of operation are in use otherwise the system wouldn’t work. They are in effect compromises in safety considered necessary to make them work, mitigated by the provision of TPWS but not totally fail safe as happened on the Cambrian recently. Normal practice on signalled lines pretty much universal on heritage railways is for only one train to enter a loop at a time and signalling to be interlocked to make this happen.

 

How long does a loop need to be before it is considered a section of double track rather than a loop?
Presumably in that scenario, different rules would apply.

 

When it's got a block post at either end?

Sent from my PGT-N19 using Tapatalk

 

So did it work that way when it was normal to have signalboxes at both ends?

 

My understanding is that there has to be an overrun distance, so one approaching train must not pass a point short of the loop before the other train has come to a stop at the loop. One place where I believe trains can approach at the same time is Horsted Keynes, providing the train approaching platform 3 from the south is routed via the loop to the south which rejoins the single line beyond Leamland Bridge - this provides the overrun going north and the southbound train is routed into Platforms 4/5 with the points set for the carriage yard headshunt - providing the overrun going south. Disclaimer - I am not an S&T person so happy to be corrected if I have got this wrong.

 

The RAIB is still investigating contributory causes, but essential cause of the Cambrian incident was a failure of braking. I don't see that any other signalling system would have made any difference.

 

Agreed; the incident happened when the first train to arrive at the loop overran. There may be questions about whether additional protection against overruns should have been installed, but the signalling system per se was not at the heart of the incident.