Southern Automatic Signalling

[6Gman]

Can anyone explain the history and operation of the signalling installed on the ex-LSWR main line (I think between Woking and Basingstoke)?

It's described as "air-operated block signalling".

When was it installed (I've seen c.1903 quoted) and how did it work?

Thanks.

 

[Gloster]

My books are downstairs, but roughly it was brought in to service in stages 1904-1907. It was semaphore signals which were worked by compressed air carried through pipes from the box, which had an air tank/reservoir nearby. I think that even the early ones automatically returned to danger. Most signals consisted of a distant and a stop signal on the same post. There was no rapid movement, just a gentle movement to Off and a gentle return to On. (I know, I operated them in my first box.)

 

[mike57]

I found this description of a system used in the USA and described in 1890, is it similar? http://www.catskillarchive.com/rrextra/sdbk.Html

 

[Taunton]

Compressed air operation was a common reliable predecessor when electrics were unreliable, and also allows something electricity cannot do, which is to build up a force slowly, in advance, and hold it pressurised, to use it in a snap, like moving a signal, or more heavyweight still, like points.

The Woking-Basingstoke section came in I think with the 4-tracking. It did go in early in the 20th century. Originally it was lower quadrant, and look old-fashioned, then the signal arms were later replaced by contemporary upper quadrant arms. I don't know again when that was replaced by colour-light, but I suspect at the 1967 Bournemouth electrification. It handled both the automatic signalling between stations, and also the junctions and crossovers at the latter, for which normal signalboxes were retained, with power levers which operated, electrically, the air valves. I think when first installed the distants, which were universally provided as an effective 3-aspect approach for the main signalling, showed red lights when on at night, as standard then, so the lights showed red/red for stop, green/red for caution, and green/green for clear.

 

[ac6000cw]

Can anyone explain the history and operation of the signalling installed on the ex-LSWR main line (I think between Woking and Basingstoke)?

It's described as "air-operated block signalling".

When was it installed (I've seen c.1903 quoted) and how did it work?

Thanks.

As I understand it, on the plain line sections it was basically electro-pneumatic automatic block signalling, electrically controlled via track circuits, using compressed air to move stop and distant semaphore arms normally mounted on the same post (stop arm at the top, distant below it). Operationally, it was the equivalent of modern 3-aspect colour light automatic block signalling, so the signals would normally display 'clear' and only go to danger/stop or caution behind a train.

I believe the equipment was supplied by the British Pneumatic Railway Signal Company (see https://www.gracesguide.co.uk/British_Pneumatic_Signal_Co ), who were a pioneer of pneumatically operated signalling in the UK.

(US railways used similar semaphore automatic block signalling on a larger scale, either with lower-quadrant stop & distant arms or later using 3-position upper-quadrant arms. I think that's all gone now, but a few isolated bits on single-track routes survived in use until quite recently).

 

[Taunton]

Between about the 10 and the 15 minute mark of this video are shots of this signal section in 1966, shortly before replacement, including the signal arms moving:

It seems the signals were mounted almost wholly on gantries over the lines. Are they still in use nowadays for the colour light replacements? It also shows that a mixture of upper and lower quadrants lasted until the end.

 

[30907]

It seems the signals were mounted almost wholly on gantries over the lines. Are they still in use nowadays for the colour light replacements? It also shows that a mixture of upper and lower quadrants lasted until the end.

On a random photo sample, no.

The LSWR made extensive use of the low pressure pneumatic system, starting with Grateley and Salisbury E/W,and the latter lasted till resignalling in the 80s; from memory, the two Salisbury boxes each had slightly different systems (I visited East - or A - around 1971), and were all upper quadrants by then.

The 1960 Sectional Appendix describes the Farnborough-Basingstoke section as Auto and Semi-Auto block, so functionally the same as 3-aspect colour lights.
There was by then no signalbox at Fleet (was the goods yard closed, or was there a ground frame?), but the other stations had them to control sidings and main/local crossovers (not sure if Hook had the last?)

 

[Dr Hoo]

There is some description and illustrations in Two Centuries of Railway Signalling by Geoffrey Kichenside and Alan Williams (OPC, 1998).

 

[6Gman]

Thank you for all the comments which cover much of the subject. I'm still left wondering how it operated in practice (I'm thinking in railway operating terms rather than the technical details).

Woking to Basingstoke is about 23 miles; There was a junction at Pirbright and - I think - three stations where there are currently crossovers, so presumably these locations would have had signalboxes. But did this mean that between these points trains were signalled automatically? And if so, how? I'm puzzled how stretches of automatic signalling could be combined with conventional offer, acceptance arrangements?

I can see that a fully automatic system could offer capacity but not sure the technology was available.

 

[30907]

Thank you for all the comments which cover much of the subject. I'm still left wondering how it operated in practice (I'm thinking in railway operating terms rather than the technical details).

Woking to Basingstoke is about 23 miles; There was a junction at Pirbright and - I think - three stations where there are currently crossovers, so presumably these locations would have had signalboxes. But did this mean that between these points trains were signalled automatically? And if so, how? I'm puzzled how stretches of automatic signalling could be combined with conventional offer, acceptance arrangements?

I can see that a fully automatic system could offer capacity but not sure the technology was available.

AIUI the line was fully track circuited and signals defaulted to "off" just like colour lights. The various crossovers were low-speed and not much used in normal operation. What I don't know is which boxes had oversight of which intermediate signals, and whether any could be switched out.

 

[Taunton]

Thank you for all the comments which cover much of the subject. I'm still left wondering how it operated in practice (I'm thinking in railway operating terms rather than the technical details).

Woking to Basingstoke is about 23 miles; There was a junction at Pirbright and - I think - three stations where there are currently crossovers, so presumably these locations would have had signalboxes. But did this mean that between these points trains were signalled automatically? And if so, how? I'm puzzled how stretches of automatic signalling could be combined with conventional offer, acceptance arrangements?

I can see that a fully automatic system could offer capacity but not sure the technology was available.

This style of operation was not unknown in the former companies. The LNER installed similar, I believe by Westinghouse, in the early 1930s on the 4-track between York and Northallerton, apart from using colour lights instead of semaphores, with just a couple of new intermediate signalboxes, having closed most of the previous ones. Mostly the main lines ran on automation, and the boxes just intervened for the odd crossover move if instructed by control, and observed passing traffic and recorded it. I believe trains were still belled between signalboxes so you knew what was coming, though obviously not with traditional acceptance etc as there could be multiple trains between the two. In those times they still liked to have a look at passing freights every 10 miles or so, for hot boxes and other mechanical issues.

A lot of the automatic signalling concepts (in fact worldwide) came initially from the USA, who however had some unusual approaches of their own, such as Automatic Block Signalling on single lines, where it was effectively a safeguard, actual operation being by traditional train orders handed up.

 

[Gloster]

From the relevant volume of Pryer’s Signal Box Diagrams it seems that it was originally low-pressure pneumatic, but converted to electro pneumatic around 1932. It was track circuited throughout and most boxes except Brookwood had switches (I am not sure about Winchfield). It was bell block, i.e. TCB.

Fleet box closed in February 1960 and Ground Frames released by Farnborough and Winchfield were provided.

There were one or two accidents in the 1930s and 1940s and I think that in at least one telephones were involved. I think the report is on railwaysarchive.

EDIT: There are three accidents on railwaysarchive.co.uk listed under Farnborough.

 

[Pinza-C55]

The North Eastern Railway also had electro pneumatic signals between York and Darlington but they were removed by the LNER in the early 1930s. They were made by Hall & Co and looked nearly identical to American signals.

 

[Springs Branch]

The North Eastern Railway also had electro pneumatic signals between York and Darlington but they were removed by the LNER in the early 1930s.

Another pioneering electro pneumatic installation in Britain was the L&YR's 1903-vintage Bolton West Junction.
Of course, this one controlled a triangular junction outside a busy station (Bolton Trinity St), rather than automatically signalling open line.

I remember in the 1960s & 70s, when using the lengthy iron footbridge which passed right above the Bolton West triangle, I always noticed a continuous slight hiss when close to the signalbox. Unfortunately, at the time I never knew what that sound was (leaking compressed air presumably) or the unusual nature of the operation of signals & points there - the signals themselves looked identical to standard BR upper quadrant semaphores. I believe the electro pneumatic kit at Bolton West lasted until December 1985 (some years after that iron footbridge had been consigned to the scrap yard).

They were made by Hall & Co and looked nearly identical to American signals.

Speaking of American-style signals (not entirely OT because it still relates to automatic semaphores on the LSWR or SR): I have half a memory that for a time there was a stretch of three-position upper quadrant semaphores on the section between Waterloo and Clapham Jn.

Presumably these would have been replaced when the Southern Railway went into colour light signalling in earnest in the 1930s. But I can't easily find any reference to these (presumably automatic and electrically-operated) American-style semaphores with Google. Was I dreaming?


[EDIT] I've now realised the reason I found no search results for 3-position semaphores on the LSWR into Waterloo is because these were actually installed by the South Eastern & Chatham in the vicinity of Victoria!

 

[zwk500]

From the relevant volume of Pryer’s Signal Box Diagrams it seems that it was originally low-pressure pneumatic, but converted to electro pneumatic around 1932. It was track circuited throughout and most boxes except Brookwood had switches (I am not sure about Winchfield). It was bell block, i.e. TCB.

I hadn't heard of bell block, was this controlled from a central 'box, with the others switching in as required, or did it function in a similar way to intermediate block?

 

[Gloster]

I hadn't heard of bell block, was this controlled from a central 'box, with the others switching in as required, or did it function in a similar way to intermediate block?

Off the top of my head, I think that this means that there was no offering and acceptance of trains, merely using the bells to describe the train forward from box to box. Very much the same as could operate in the 1980s if there wasn’t a train describer on TCB.

 

[Pinza-C55]

Another pioneering electro pneumatic installation in Britain was the L&YR's 1903-vintage Bolton West Junction.
Of course, this one controlled a triangular junction outside a busy station (Bolton Trinity St), rather than automatically signalling open line.

I remember in the 1960s & 70s, when using the lengthy iron footbridge which passed right above the Bolton West triangle, I always noticed a continuous slight hiss when close to the signalbox. Unfortunately, at the time I never knew what that sound was (leaking compressed air presumably) or the unusual nature of the operation of signals & points there - the signals themselves looked identical to standard BR upper quadrant semaphores. I believe the electro pneumatic kit at Bolton West lasted until December 1985 (some years after that iron footbridge had been consigned to the scrap yard).

Speaking of American-style signals (not entirely OT because it still relates to automatic semaphores on the LSWR or SR): I have half a memory that for a time there was a stretch of three-position upper quadrant semaphores on the section between Waterloo and Clapham Jn.

Presumably these would have been replaced when the Southern Railway went into colour light signalling in earnest in the 1930s. But I can't easily find any reference to these (presumably automatic and electrically-operated) American-style semaphores with Google. Was I dreaming?


[EDIT] I've now realised the reason I found no search results for 3-position semaphores on the LSWR into Waterloo is because these were actually installed by the South Eastern & Chatham in the vicinity of Victoria!

Up until York station was resignalled in 1989 it used electro pneumatic point motors and it always added a dramatic note to the approach of a Deltic hauled train when you heard the hiss and bang of the points changing. There's an article on the NER Hall signals in the book "Britains Railway Super Centres York" by Ken Appleby and he relates that (as per a previous post) the trains were simply "belled" forwards between signalboxes although block instruments were retained for fog and snow conditions. The base of each signal contained 2 cylinders of CO2 gas and each was sufficient to power 7000 arm movements. The spectacle plates were heavier than the arms to make them normally horizontal and thus they were "powered down" to show Line Clear.

There's a nice pamphlet on the Hall signals here http://rrsignalpix.com/pdf/Hall_10_OCR_SEC.pdf

 

[Taunton]

Yet another pioneer automated pneumatic system was installed by Westinghouse on the Mersey Railway when it electrified in 1903, both signals and points. Apparently George Westinghouse himself came over from the USA to see the completion of it. Points were pneumatic, notably those at the shunting neck at Liverpool Central station, which operated completely automatically. The hiss-slam of them operating for each movement could be heard right through the station. This all lasted right until the Loop opened in 1977.

 

[30907]

From the relevant volume of Pryer’s Signal Box Diagrams it seems that it was originally low-pressure pneumatic, but converted to electro pneumatic around 1932. It was track circuited throughout and most boxes except Brookwood had switches (I am not sure about Winchfield). It was bell block, i.e. TCB.

Completing my note in #7, the appendix has TCB all lines Sturt Lane Jn to Farnborough and Up Local only Sturt Lane to Brookwood.

Fleet box closed in February 1960 and Ground Frames released by Farnborough and Winchfield were provided.

Thanks, much as I had guessed (except the date).

 

[Gloster]

Completing my note in #7, the appendix has TCB all lines Sturt Lane Jn to Farnborough and Up Local only Sturt Lane to Brookwood.

From Pryer’s diagrams, I think it had been TCB from Woking to Basingstoke West on the Down and from Worting Junction to Woking on the Up. Will check.

 

[matchmaker]

The biggest EP installation in the UK was the 1908 installation at Glasgow Central with 374 levers/slides. Remarkably, it lasted until 1960.

 

[Cricketer8for9]

Was air also used to move London Underground points?

 

[Snow1964]

Thank you for all the comments which cover much of the subject. I'm still left wondering how it operated in practice (I'm thinking in railway operating terms rather than the technical details).

Woking to Basingstoke is about 23 miles; There was a junction at Pirbright and - I think - three stations where there are currently crossovers, so presumably these locations would have had signalboxes. But did this mean that between these points trains were signalled automatically? And if so, how? I'm puzzled how stretches of automatic signalling could be combined with conventional offer, acceptance arrangements?

I can see that a fully automatic system could offer capacity but not sure the technology was available.

Originally there were more junctions, there were 2 branches from Brookwood (Bisley and Necropolis cemetery lines), Pirbright junction, Sturt Lane junction (to Frimley), a short branch that curved south from Farnborough plus crossovers and yards at the stations. Earthworks for 2 other spurs near Farnborough North were built, but not sure if tracks were ever connected to the mainline.

The intermediate signals were fully automatic (effectively 3 aspect, as had home and distant arms), the semi-automatic had a switch that stopped them clearing after train had passed if crossovers needed to be used (they could work as automatic if junction was set straight ahead).

Need to dig out some books, but I think there was a form of automatic train describer, basically a big rotary dial (like a double size old telephone dial) that had common train categories. Maybe this was added in 1930s (or I am mixing it up with some 1930s Southern power boxes). This took the place of normal bell codes to pass the train.

 

[edwin_m]

Was air also used to move London Underground points?

They certainly had them at Aldgate East until fairly recently when the SSL re-signalling reached there, and they may survive elsewhere.

 

[TSG]

It seems the signals were mounted almost wholly on gantries over the lines. Are they still in use nowadays for the colour light replacements? It also shows that a mixture of upper and lower quadrants lasted until the end.

No. Woking (covering the line as far as Deepcut) was re-signalled around 1997 with all structures replaced. Basingstoke (the rest) was re-signalled somewhere around 2005 I think, again with all structures replaced. Before that I don't remember any full gantries but there were some old and rickety cantilevers over the up or down pairs. I don't know, but by the look of them I can believe some of them were older than the '60s re-signalling works.

 

[Taunton]

Was air also used to move London Underground points?

There used to be a great working full size example of this in the London Transport museum in Covent Garden, shame it has gone now. They must have had a compressor in there. Right in front of you, over a bar, with a little operating button at child height. Do so, and the complete Hiss-Slam, right in front of your nose, which made many jump. Audible all round the museum.

 

[TomCrame]

They certainly had them at Aldgate East until fairly recently when the SSL re-signalling reached there, and they may survive elsewhere.

The point equipment wasn't replaced at resignalling - still air operated.