St. Andrews signalling questions

No, the changed wording the the Sectional doesn’t mean SA47 is approachable at Red - and although it would open up that possibility in future, you don’t gain anything service-wise by permitting it with the current track layout.

Both SA2 and SA4 are 3 aspect. I have drawings, but no way of uploading them from work

JamesN in post 128804 said:

No, the changed wording the the Sectional doesn’t mean SA47 is approachable at Red - and although it would open up that possibility in future, you don’t gain anything service-wise by permitting it with the current track layout.

Both SA2 and SA4 are 3 aspect. I have drawings, but no way of uploading them from work

You should be working. *shakes head*

Whether SA47 can be approached at red, I don't know. I wouldn't have thought so given the linespeed, plus, as you say, it is mentioned in that document you linked to. SA47 is not approach controlled for either route. It wasn't me that said SA47's red aspect is for reversals, but it's a junction so it needs a red aspect. SA7 would not need to be off to get SA47 off. It's possible the now-gone SA9 signal James mentioned is the cause of this confusion: it wouldn't be the first time something is overly restrictive (SA47 being off for SA7 to be off) to avoid modifying an interlocking too much (see my earlier bodge comment).

Going back, a 1988 signalling notice shows 2/4/6 as capable of R/Y/G, while 2 and 9 (the latter outside the signalbox) as R/G, with 7 capable of Y/G. It doesn't show signal information around Holesmouth, though interestingly the oil terminal simply crossed the Severn Beach line with no connection, via a ground frame.

Signal SA.7 will be altered to show a Red or Green aspect only and will only show a green aspect when signal SA.47 also shows a green aspect

The inbound binliner reverses in the area does anybody know the move. Does it reverse at SA47 (which it seems it could do), or does it go all the way back to beyond SA7 to reverse?

If you look at the schedule (like todays for example), it looks a little convoluted, with three reverses shown. Not sure if it actually uses all of these - the diversions could access Avonmouth directly from the Hallen lines. I may have to go and have a look one day. It's often TnT I notice, so that may help....

Link to todays schedule, which will expire in a few days for interest:

https://www.realtimetrains.co.uk/train/H06052/2020-07-02/detailed

slugsix in post 128815 said:

The inbound binliner reverses in the area does anybody know the move. Does it reverse at SA47 (which it seems it could do), or does it go all the way back to beyond SA7 to reverse?

If you look at the schedule (like todays for example), it looks a little convoluted, with three reverses shown. Not sure if it actually uses all of these - the diversions could access Avonmouth directly from the Hallen lines. I may have to go and have a look one day. It's often TnT I notice, so that may help....

Link to todays schedule, which will expire in a few days for interest:

https://www.realtimetrains.co.uk/train/H06052/2020-07-02/detailed

https://www.opentraintimes.com/schedule/H06052/2020-07-02

I prefer OTT over RTT because the former is more pure, whereas RTT tend to "fill in" information it thinks should be there and is not always helpful.

Anyway, that shows the train coming in from Filton, running around opposite St Andrews Road station, heading back to Hallen Marsh where it reverses, and thence to St Andrews Road to reverse again in order to access the Severn Beach branch. I doubt it would go to SA7: it's unusual to be able to reverse direction on a single line with two or more signals because of directional locking.

Anyway, that shows the train coming in from Filton, running around opposite St Andrews Road station, heading back to Hallen Marsh where it reverses, and thence to St Andrews Road to reverse again in order to access the Severn Beach branch. I doubt it would go to SA7: it's unusual to be able to reverse direction on a single line with two or more signals because of directional locking.

I suspect the reason for a three aspect head on SA7 is simply that when SA9 was removed there was no economic value in replacing the signal head so the lamp would simply have been removed from the yellow aspect and the interlocking adjusted so that it could never be called.

Stephen Fulcher in post 128832 said:

I suspect the reason for a three aspect head on SA7 is simply that when SA9 was removed there was no economic value in replacing the signal head so the lamp would simply have been removed from the yellow aspect and the interlocking adjusted so that it could never be called.

Previously it was Y/G only.

Out of interest, is SA38 a 3 aspect or 2 aspect. The following signal is SA2R Y/G, which suggests SA38 only needs to be 2 aspect R/G.....

(From the cab ride, it looks like 2A but it's really hard to tell and I'm not sure!)

Another "unusual" thing I noticed is that the AWS magnets for SA4 and SA7 are co-located.

slugsix in post 128855 said:

Out of interest, is SA38 a 3 aspect or 2 aspect. The following signal is SA2R Y/G, which suggests SA38 only needs to be 2 aspect R/G.....

(From the cab ride, it looks like 2A but it's really hard to tell and I'm not sure!)

SA38 is a 2-aspect R/G

slugsix in post 129301 said:

Another "unusual" thing I noticed is that the AWS magnets for SA4 and SA7 are co-located.

This is actually very common.

GeoffM in post 129303 said:

slugsix in post 128855 said:

Out of interest, is SA38 a 3 aspect or 2 aspect. The following signal is SA2R Y/G, which suggests SA38 only needs to be 2 aspect R/G.....

(From the cab ride, it looks like 2A but it's really hard to tell and I'm not sure!)

SA38 is a 2-aspect R/G

slugsix in post 129301 said:

Another "unusual" thing I noticed is that the AWS magnets for SA4 and SA7 are co-located.

This is actually very common.

Thanks Geoff. Appreciate the help. Whilst you may be able to quote a number of co-located AWS magnets at me, it is by no means the norm, and it's the first one I've come across in the Bristol area. Not the norm = not the usual = unusual.

slugsix in post 129309 said:

GeoffM in post 129303 said:

slugsix in post 128855 said:

Out of interest, is SA38 a 3 aspect or 2 aspect. The following signal is SA2R Y/G, which suggests SA38 only needs to be 2 aspect R/G.....

(From the cab ride, it looks like 2A but it's really hard to tell and I'm not sure!)

SA38 is a 2-aspect R/G

slugsix in post 129301 said:

Another "unusual" thing I noticed is that the AWS magnets for SA4 and SA7 are co-located.

This is actually very common.

Thanks Geoff. Appreciate the help. Whilst you may be able to quote a number of co-located AWS magnets at me, it is by no means the norm, and it's the first one I've come across in the Bristol area. Not the norm = not the usual = unusual.

Examples can be found at:
Bedminster
North Somerset Jn
Filton Abbey Wood
Westerleigh Jn
Weston-super-Mare
Bristol Parkway
...to name a few. So yeah, quite normal on bi-directional lines.

It’s actually easier to co-locate them on BiDi lines than have them separate - less suppression circuitry and the like involved.