Semaphore Signalling

[YorkshireBear]

Hope someone can help, how do you signal a loop off of a main line when it comes to semaphores? Ie not a passing loop on a single track section a double track with a passing loop to put a slow train out of the way on.

I presume you've got Junction Distant, Junction Home, TURNOUT, then would each line then have a single distant and single home before the loop comes back in?

 

[SteamontheMet]

Correct, ofcourse the mainline take priority and will have a longer bracket/Gantry on which the semaphore rests.

As regard to the single Distant, it depends on the length of the loop.

This website may help:

http://www.roscalen.com/signals/

 

[Tomnick]

It depends - is the loop controlled entirely by one signal box, or does it form an additional running line between two signal boxes?

Assuming the former, you'd first come to - most likely - a single distant (maintained at Caution for the move into the loop), then the home signal protecting the turnout into the loop (with the arm controlling movements into the loop on a shorter doll - might even be a miniature arm if it's a goods loop), and finally* a stop signal on each line at the outlet. This stop signal wouldn't have its own distant signal - the initial one, before the loop, would normally apply to all stop signals within station limits unless there's any funny stuff going on.

* - there could well be an additional stop signal beyond the loop connection, and equally there could well be an outer home signal in rear of that signal protecting the turnout into the loop...all in the name of increased flexibility.

If the outlet from the loop is controlled from the next signal box, then the signal (on the main) protecting that end of the loop, and any subsequent stop signals worked by that box, will have a distant signal in rear - depending on the length of the loop, probably co-located with (i.e. on the same post as, and slotted with) what's now the section signal at the box in rear: the one protecting the turnout into the loop.

Tom

 

[YorkshireBear]

Thanks for replies. It is a short loop yes controlled entirely by one box ( this is for my model layout but I am also interested in the wider knowledge hence putting it here) with a level crossing just before the loop too it makes sense to have a single distant.

 

[Tomnick]

Are there any other connections (crossovers etc.) to consider? That sort of thing, and the need to provide shunt routes to run round or start back from the loop, can make a difference too...even little details like ensuring that the Signalman can confirm that the train's complete with tail lamp (no problem if the box is in rear of the loop).

 

[YorkshireBear]

Are there any other connections (crossovers etc.) to consider? That sort of thing, and the need to provide shunt routes to run round or start back from the loop, can make a difference too...even little details like ensuring that the Signalman can confirm that the train's complete with tail lamp (no problem if the box is in rear of the loop).

Nothing like that this is all the box looks after,plus the line in opposite direction but this just goes over crossing nothing fancy. Its just to loop stuff no need for running round or shunt moves and by chance box is at rear of loop.

 

[TDK]

There is this scenario at Abergele where there is a colour light distant and 2 semaphores on one gantry. One is slightly higher than the other and this is for the main the lower one is for the loop. I think it would be accurate to use one distant for both routes even if a semaphore.

On the exit you have one semaphore for the loop (Home) and one semaphore for the through (home). The section is after the lines merge and is a single section signal.

If it is a goods loop you will sometimes find a smaller semaphore arm for the goods.

 

[Tomnick]

At Abergele, presumably the distant doesn't clear for moves into the loop?

 

[Ploughman]

If in the case of a junction then there is the added inclusion of Splitting Distants etc.
As used to be in place at Apperley Junction between Leeds and Shipley. Only removed as part of the Electrification and resignalling project.

 

[Tomnick]

Splitting distants are rare beasts though, especially in later years - that's not to say one couldn't be used in this case, of course, but I reckon it'd be unlikely (and would need something extra to avoid the suggestion that the road's set out of the far end of the loop too!).

 

[John Webb]

If this is a loop simply to allow a goods train to be put in the loop to allow a faster train to overtake, then the move into the loop will almost certainly have to be done at reduced speed compared to the straight-through run. It is very unlikely, therefore, that there would be a splitting distant prior to the loop/straight signals. The distant would be held at caution by the loop being selected to remind the driver that he needed to reduce speed.
In some cases the signal into the loop was 'approach controlled', that is, it could not be cleared until the train had occupied a track circuit for a certain minimum time which thus proved the train had slowed down enough.
Splitting distants were usually used only on the approach to a junction used by passenger trains where the speeds on the two lines were fairly similar. If for some reason the diverging line had a significantly lower speed then only a distant for the 'straight-through' would be provided. Again this was to ensure that trains taking the diverging route were reduced in speed appropriately.

 

[Parham Wood]

The stop semaphore signal giving entrance to the loop would not normally be cleared by the signalman until the train had slowed to the loop entry speed limit and was seen to be under control.

 

[1018509]

One for the old railway buffs:-
I was travelling on the M3 the other day and on the left (towards London) or right (away from London), I noticed a semaphore signal. This may have been on the Hockley Viaduct as some sort of memorial but I am not sure.
Anyone know where I mean?

 

[TDK]

At Abergele, presumably the distant doesn't clear for moves into the loop?

That is correct
--- old post above --- --- new post below ---

The stop semaphore signal giving entrance to the loop would not normally be cleared by the signalman until the train had slowed to the loop entry speed limit and was seen to be under control.

This is not the case at Abergele with the line speed from 75mph to 15mph if this was converted to colour light then it would certainly be track approach, I am not certain but I think there are TPWS overspeed loops at this location!

 

[Tomnick]

Thanks for confirming that one - 'tis as I'd expected!

Regarding approach control for diverging routes at junctions - it's often not enforced by the locking (although the miniature arm controlling entry into our Up Goods is), and the signalling regs only require the approaching train to be brought under control if it's not booked to take that diverging route (hence the situation at Abergele where it seems they happily - and correctly - pull off for anything booked into the loop without checking it).

 

[Bedpan]

One for the old railway buffs:-
I was travelling on the M3 the other day and on the left (towards London) or right (away from London), I noticed a semaphore signal. This may have been on the Hockley Viaduct as some sort of memorial but I am not sure.
Anyone know where I mean?

Yes, there is a semaphore signal on the Hockley Viaduct. It can be seen at 01:05 on http://www.bbc.co.uk/news/uk-england-hampshire-21592576

Also listen carefully, the commentary provides some astonishing news at this point which I bet nobody was aware of......."The viaduct was originally used for the West Coast main line railway". What a load of absolute tosh!!

The signal is also shown again at 01:29, when it is explained (more believably) that it originated from Kew East Junction.

 

[dysonsphere]

If you want more info go to http://www.signalbox.org/forum/ and enquire there you will get chapter and verse there.

 

[matchmaker]

If in the case of a junction then there is the added inclusion of Splitting Distants etc.
As used to be in place at Apperley Junction between Leeds and Shipley. Only removed as part of the Electrification and resignalling project.

The last ones were at Larbert. removed in 2007.


http://www.railbrit.co.uk/imageenlarge/imagecomplete.php?id=9245

 

[Tomnick]

In response to dysonsphere - that is indeed a good forum - but the knowledge on here is far from exhausted, so I'm sure we could answer any further queries here rather than shifting the whole discussion elsewhere...