Signalling question: Intermediate block signals on the former Southern Region

[Islineclear3_1]

Please could a signaller explain the raison d'etre of such signals. Are they worked from a box, or are they automatic. What aspects can they display?

 

[zwk500]

Are these different from normal Intermediate Block signals in Absolute block areas?

 

[Islineclear3_1]

Are these different from normal Intermediate Block signals in Absolute block areas?

I don't know. Is there a difference? Are intermediate block signals only found in AB areas? These are the ones I would like more info. From memory, if a signalbox closed down and the block section between the other signalboxes was too long, my understanding was for an IB signal to be installed (to split the long block section into two) which was supervised from the box in advance. I also thought they were automatic, and thus, colour light capable of displaying a red or green aspect. However, I could be wrong...

 

[Gloster]

In Absolute Block areas an Intermediate Block Signal is in many ways the same as having a signal box and iit often replaced a former box. If you have signal boxes A, B and C you can close B by putting in an IBS instead: this could be in both directions or just in one. The line from A to B is track-circuited through out and a Stop Signal with own Distant is put up. These are operated by A: the Distant may be individually controlled or be operated automatically by the aspect of the Stop Signal.

For a train the signalman at A will operate the signals at A normally and also the switch or lever for the IBS: the Line Clear release from C releases the IBS. A puts his signals at A back to normal after the train has passed, but waits until the train passes the IBS before returning that to normal; most automatically return to danger. Once the track-circuit to the IBS is clear, a second train can be allowed up to the IBS, but the IBS will/can not be cleared until C has given Train Out of Section for the first train and given another Line Clear.

They allow a signal box that is only required to reduce headways and has no other purpose to be closed. Normally, the Stop signal has red and green aspects, and the Distant yellow and green. I don’t know of any major differences, operationally at least, between the SR types and the other regions.

In some ways, and I hope I am not confusing things here, they are like an Advanced Starter that is so advanced that it has its own Distant.

They are worked in much the same way as any other signal in AB areas that reverts to Danger automatically, but can only be cleared by the signalman each time a train is to proceed.

 

[Islineclear3_1]

Thank you, Gloster, that's a very good description and is vaguely what I remember.

However, I thought the signalman at C had the switch, rather than A because only C would know if the train from A has passed his box and as you say, C would have to inform A by giving the Train Out of Section or Line Clear codes

I understand the need for an IBS to have its own Distant, but could there be more than one IBS signal on the same running line, such as if the section was really long?

 

[Tomnick]

Thank you, Gloster, that's a very good description and is vaguely what I remember.

However, I thought the signalman at C had the switch, rather than A because only C would know if the train from A has passed his box and as you say, C would have to inform A by giving the Train Out of Section or Line Clear codes

I understand the need for an IBS to have its own Distant, but could there be more than one IBS signal on the same running line?

There were examples of IB signals in the rear section, i.e. controlled by C in this example, but they weren't common and I don't think there are any left now. If you have it worked by the box in rear, you can work Absolute Block normally with C sending 'train out of section' once the tail lamp has been directly observed. If it's worked by the box in advance, i.e. C, you have to have the section track-circuited throughout as there's then no way of C knowing that it's complete once it's cleared the Absolute Block section.

 

[Gloster]

I am fairly sure I have seen cases where there are (effectively) two IBS in a row, each with their own Distant. They would still be controlled by A, but whether the first one really is an IBS is arguable as it is not released by Line Clear. The point is that the line is track-circuited throughout from A to the IBS, so A knows whether the train has passed the IBS or not.

It is very unusual for a signal box to control a signal outside of its Distant. I think I have seen one or two special arrangements, but these might have been more of an emergency replacement type of arrangement.

 

[MadMac]

I understand the need for an IBS to have its own Distant, but could there be more than one IBS signal on the same running line, such as if the section was really long?

Good example of that is between Blair Atholl and Dalwhinnie, where there are two IB sections on each line. One thing that hasn’t been mentioned is that if the IB signal fails (e.g. lamp out), the Line Clear Release transfers back to the “regular” starter effectively “switching out” the IB section. On a side note, I think this example may be the last IB section(s) in Scotland.

 

[matchmaker]

I don't know. Is there a difference? Are intermediate block signals only found in AB areas? These are the ones I would like more info. From memory, if a signalbox closed down and the block section between the other signalboxes was too long, my understanding was for an IB signal to be installed (to split the long block section into two) which was supervised from the box in advance. I also thought they were automatic, and thus, colour light capable of displaying a red or green aspect. However, I could be wrong...

IB signals need not be colour light, although I suspect that any remaining ones are. At one time there were IBs between Dalmeny Junction and Saughton Junction which were motor operated semaphores.

 

[Tomnick]

IB signals need not be colour light, although I suspect that any remaining ones are. At one time there were IBs between Dalmeny Junction and Saughton Junction which were motor operated semaphores.

Elmton & Creswell has a colour-light IB home signal on the Up, but its associated distants (outer and inner) are both semaphore, co-located with the home and starter respectively.

 

[D6130]

As stated above, it was/is normal practice for an IBS to be controlled from the box in the rear, but I can think of at least one exception to that rule, which was the Down semaphore IB home signal between Hampden Park and Eastbourne, which was controlled by Eastbourne box and mounted on the same post as the Eastbourne Down Distant.

The Up colour light IB home signal between Settle Junction and Hellifield - situated on the approach to Long Preston station - has its distant signal combined in the same three aspect signal head as the Settle Junction Up section signal, due to the relatively short distance between the two. As far as I am aware the new colour light IB signals installed on the Settle-Carlisle line in 1997 to allow closer headways for the then burgeoning coal traffic from Scotland to the Yorkshire and Nottinghamshire power stations, were the last new IBs to be installed on the network but, as always, I am open to correction.

 

[Highlandspring]

On a side note, I think this example may be the last IB section(s) in Scotland.

There’s still an IB section on the Up line between St Fort and Leuchars, controlled by Tay Bridge South.

 

[MadMac]

There’s still an IB section on the Up line between St Fort and Leuchars, controlled by Tay Bridge South.

Yeah, I’d forgotten about that one. From a quick look at the Sectional Appendix, no others in Scotland apart from Blair Atholl-Dalwhinnie.

 

[Islineclear3_1]

So, I have a specific example (now historic) relating to the section between Cooden Beach and Pevensey & Westham.

From Collington (heading west), there was CCW5R followed by CCW5 at Cooden Beach. (Pevensey signal code). I believe CCW5 was an automatic signal but was its repeater officially a Distant? Was CCW5 an intermediate block signal?

Then there was CCW1 (and it's repeater) just east of Pevensey Bay. I presume this was a normal worked signal and at one point, been a semaphore

I don't remember ever seen an SRS diagram of this line as I'm also interested in the signalling arrangements between Bexhill and Stone Cross/Hampden Park and the Willingdon triangle

 

[matchmaker]

Yeah, I’d forgotten about that one. From a quick look at the Sectional Appendix, no others in Scotland apart from Blair Atholl-Dalwhinnie.

Stirling North - Dunblane? Don't know if that has changed with the new Cornton full barrier crossing, as that involved signalling changes.

 

[MadMac]

Stirling North - Dunblane? Don't know if that has changed with the new Cornton full barrier crossing, as that involved signalling changes.

It’s gone now. There’s one at St. Fort (as mentioned above) between Tay Bridge South and Leuchars and another which still “Technically Exists” at Mossgiel between Hurlford and Mauchline, although Hurlford has been switched out for over 10 years.

 

[matchmaker]

It’s gone now. There’s one at St. Fort (as mentioned above) between Tay Bridge South and Leuchars and another which still “Technically Exists” at Mossgiel between Hurlford and Mauchline, although Hurlford has been switched out for over 10 years.

Has the signalling between Stirling and Dunblane changed from Absolute Block?

 

[Gloster]

So, I have a specific example (now historic) relating to the section between Cooden Beach and Pevensey & Westham.

From Collington (heading west), there was CCW5R followed by CCW5 at Cooden Beach. (Pevensey signal code). I believe CCW5 was an automatic signal but was its repeater officially a Distant? Was CCW5 an intermediate block signal?

Then there was CCW1 (and it's repeater) just east of Pevensey Bay. I presume this was a normal worked signal and at one point, been a semaphore

I don't remember ever seen an SRS diagram of this line as I'm also interested in the signalling arrangements between Bexhill and Stone Cross/Hampden Park and the Willingdon triangle

I don’t know the area and can’t really help with the specific arrangements there, but it wouldn’t surprise me if it was one of those areas where the standard arrangements were altered to suit local conditions. One point is that there was a CCTV crossing (controlled from Pevensey) at Pevensey Bay and Havensmouth manned crossing at Norman’s Bay. The former would require a controlled signal to protect it in both directions, which would be operated by Pevensey. The latter would also, almost certainly, have a controlled signal in each direction, which would probably be operated by the Pevensey signalman after the gatekeeper had confirmed the gates closed.

 

[Islineclear3_1]

Yes, both crossings had protecting signals on the Down which were controlled. But it's the Up Direction that I am asking about in this instance. I now know that CCW1 was a controlled signal and I assume, it's repeater (or Distant?) could not display a green unless CCW2 and CCW3 were cleared.

So, it still leaves me with my original example, that being of CCW5 and it's repeater or Distant. Was this an intermediate block home signal?

 

[Gloster]

My sources say that Pevensey was CCV and Bexhill was CCW. I managed to find a photo of Bexhill’s diagram and this shows 5 with a Distant D5, so it was probably an IBS. It appears to have had a control from Pevensey and a slot, possibly in connection with Pevensey Sluice AHB or Havensmouth Crossing.

As CCV 1 had a red and yellow lever it seems that the Distant was controlled off the same lever; such economies were necessary in a short frame. Based on the signal indicators in the only interior photo I can find, CCV 1 was three aspect which only cleared to green when 2 was showing a proceed aspect. (Be warned: some of this is based on deduction from partial information.)

 

[Islineclear3_1]

Yes you're right, sorry, I meant CCV for the Pevensey signals duh...

CCW5 only showed a red or green aspect, so as you say, this was an IB signal whilst D5 only displayed yellow or green and was a Distant. Presumably then, the switch to lock CCW5 to red during engineering possession was in Bexhill signal box rather than Pevensey & Westham?

Further along, I wonder if BK41 at Glynde was an IB signal when Glynde box was abolished. I remember a switch in Berwick signal box

 

[Tomnick]

So, it still leaves me with my original example, that being of CCW5 and it's repeater or Distant. Was this an intermediate block home signal?

CCW5 was shown on Pevensey's diagram as an IBH signal, with Havensmouth crossing having a slot on it too (Pevensey didn't have any direct control over it though). An IBH signal can't be an automatic signal - Bexhill would have to clear it for every train, as you'd expect for any signal reading into an Absolute Block section. The section in that direction was continuously track circuited, presumably to allow 'train out of section' to be sent once an Up train had arrived at Pevensey Bay rather than waiting for it to pass the box a few minutes later (as long as Bexhill was switched in?).

 

[Gloster]

As Berwick-Lewes was TCB, BK 41 was probably not an IBS. It may have been a semi-automatic.

The relevant signal box register says that Bexhill did not have a block switch.

 

[Tomnick]

The relevant signal box register says that Bexhill did not have a block switch.

The only thing that made me think differently was a note on the diagram at Pevensey that stated "Telephone at signal CCW5 connected only when Bexhill Central closed", which presumably is also why Pevensey had an indication for Havensmouth's slot on Bexhill's IBH. Whether the block switch was removed at some point is, of course, a different question!

BK41 was shown on Berwick's diagram as an automatic signal, with a replacement switch and a "fog switch", whatever one of those is. As you suggest, you can't have an IBH in a TCB section!

 

[Freightmaster]

Has the signalling between Stirling and Dunblane changed from Absolute Block?

Yes - work was carried out a couple of months ago:

Cornton level crossing

I've received a "Neighbour Notification". Work commences 30th April to convert the existing AHB crossing to full barriers with object detection. Works will continue to 31st May, with the B832 road closed from 30th April to 10th May.

www.railforums.co.uk

MARK

 

[Gloster]

The only thing that made me think differently was a note on the diagram at Pevensey that stated "Telephone at signal CCW5 connected only when Bexhill Central closed", which presumably is also why Pevensey had an indication for Havensmouth's slot on Bexhill's IBH. Whether the block switch was removed at some point is, of course, a different question!

BK41 was shown on Berwick's diagram as an automatic signal, with a replacement switch and a "fog switch", whatever one of those is. As you suggest, you can't have an IBH in a TCB section!

The Register was from 2009, although (by the nature of things) some of the information may have been collected a year or two earlier. It does say that a block-switch had never been fitted, but perhaps one was installed in the period before closure.

 

[matchmaker]

Yes - work was carried out a couple of months ago:

Cornton level crossing

I've received a "Neighbour Notification". Work commences 30th April to convert the existing AHB crossing to full barriers with object detection. Works will continue to 31st May, with the B832 road closed from 30th April to 10th May.

www.railforums.co.uk

MARK

I assume it's now TCB

 

[LowLevel]

As stated above, it was/is normal practice for an IBS to be controlled from the box in the rear, but I can think of at least one exception to that rule, which was the Down semaphore IB home signal between Hampden Park and Eastbourne, which was controlled by Eastbourne box and mounted on the same post as the Eastbourne Down Distant.

The Up colour light IB home signal between Settle Junction and Hellifield - situated on the approach to Long Preston station - has its distant signal combined in the same three aspect signal head as the Settle Junction Up section signal, due to the relatively short distance between the two. As far as I am aware the new colour light IB signals installed on the Settle-Carlisle line in 1997 to allow closer headways for the then burgeoning coal traffic from Scotland to the Yorkshire and Nottinghamshire power stations, were the last new IBs to be installed on the network but, as always, I am open to correction.

Leigh signalbox on the North Staffs closed 12/06/1999 and was replaced by IB sections between Caverswall and Uttoxeter in either direction. Not sure if there were any after that.

 

[Tomnick]

The Register was from 2009, although (by the nature of things) some of the information may have been collected a year or two earlier. It does say that a block-switch had never been fitted, but perhaps one was installed in the period before closure.

Is the item in the foreground of the linked photo below a block switch? The box diagram (on the next photo) suggests that there's one fitted!

Bexhill Signal Box 03 Sept 10122 | dav_88 | Flickr

It also helpfully confirms that Pevensey does have a control on CCW5 signal in addition to the slot from Havensmouth crossing and I've found another photo showing it (a replacement switch) on Pevensey's block shelf. A very interesting - and unusual - arrangement indeed!

 

[Gloster]

Is the item in the foreground of the linked photo below a block switch? The box diagram (on the next photo) suggests that there's one fitted!

Bexhill Signal Box 03 Sept 10122 | dav_88 | Flickr

It also helpfully confirms that Pevensey does have a control on CCW5 signal in addition to the slot from Havensmouth crossing and I've found another photo showing it (a replacement switch) on Pevensey's block shelf. A very interesting - and unusual - arrangement indeed!

It definitely looks like the pictures of SR types of switch that I have seen, or rather two linked together for simultaneous operation. The box diagram does say that a switch is fitted, so perhaps there was less need for the box to be open all the time in its later years.