How widespread was Lock and Block?

[FelixM]

I am trying to find information about how widespread lock and block signalling was. The internet has some info about specific types of block instruments or signaboxes but I don't get the full picture from this.

 

Was it in operation on main lines only? Was it in use by specific companies only? Was it mandatory to install on passenger lines? Also a timeline would be interesting too.

 

Lock and block to my knowledge means that signal levers can only be pulled in dependance of the position of the block Instrument, and that the three block positions can only be passed in a specific order and in dependance of a pulled signal lever and that cancelling an offered train needs co-acting of both signalmen on their instruments. Were there any deviations?

 

Felix

[david.hill64]

A complex subject.

 

In UK Lock and Block was often used as a shorthand reference to the 1889 Regulation of Railways act that required railways (other than industrial lines) to:

• Use Block Signalling
• Interlock Signals and points and
• Fit Automatic Continuous Brakes on Passenger Trains

In a mechanical signal box I believe there was no link between the indications on the Block Signalling Instruments and the ability to pull a lever. The UK usually used route signalling. The levers that could be pulled depended though on the position of other levers so that it was not for example possible to set signals for a particular route if the points were set for another.

 

Once train vacancy detection (track circuits) and electric signal boxes arrived, things become more complicated............Now routes could be locked by the presence of trains

 

 

[meil]

17 minutes ago, david.hill64 said:

In a mechanical signal box I believe there was no link between the indications on the Block Signalling Instruments and the ability to pull a lever.

 

 

The Starting or section Signal was linked to the Block Instrument or Token Machine (for single line) following the Abermule accident.

[The Stationmaster]

22 minutes ago, FelixM said:

I am trying to find information about how widespread lock and block signalling was. The internet has some info about specific types of block instruments or signaboxes but I don't get the full picture from this.

 

Was it in operation on main lines only? Was it in use by specific companies only? Was it mandatory to install on passenger lines? Also a timeline would be interesting too.

 

Lock and block to my knowledge means that signal levers can only be pulled in dependance of the position of the block Instrument, and that the three block positions can only be passed in a specific order and in dependance of a pulled signal lever and that cancelling an offered train needs co-acting of both signalmen on their instruments. Were there any deviations?

 

Felix

The normal understanding of 'lock & block' in UK signalling practice is basically as you describe but there were some subtle, and sometimes radical variations on the principles involved.  The most radical fully integrated the operation of the signals with the block instrument and treadles operated by the passage of trains and it is what most people would think of when 'lock & block working' is mentioned - it was used, in particular, on various of the lines south of London whrre it normally allowed safe operation of intensive services.  Use the link below and download the PDF to for an excellent description of how Sykes Lock & Block system worked (and how it could go wrong)

https://www.railwaysarchive.co.uk/docsummary.php?docID=294

 

However some people, as already exampled, also use the term in connection with the standard UK  system of Absolute Block system working but in the case of it the signals might not necessarily be interlinked with the block instruments and there might not be any physical (electrical) link between the block instrument and the passage of trains such as existed in the Sykes Lock & Block system.  Various controls between the block instrument and certain signals were gradually added over the years commencing, really, in the early part of the 20th century (so already well behind Sykes Lock & Block) but linking the block instrument with evidence of the passage of trains didn't properly come until the devising of what is known as 'Welwyn Contriol' which was developed following a collision at Welwyn in 1927.

 

But, and it is a BIG BUT, numerous mechanical signal boxes working Absolute Block never had Welwyn Control installed before they were either closed or succeeded by more modern signalling - for example in the latter half of the 1970s I had 15 signal boxes working double line Absolute Block on my then patch and only one of them had Welwyn Control but all of them had various running line signals linked to the block system.  On another area I was managing in the late 1970s none of the 'boxes had Welwyn Control.

 

Even more worrying (perhaps?) was that well into the 1960s there were still signalboxes on rural lines (including some on the at times very busy Somerset & Dorset Joint) where signals were not interlinked with the block system which made it quite possible to v clear the signal into the next block section while there was a train already in that section.  All such lines were worked on the Absolute Block system but the signals remained free of any control by or over the block system!

[Guy Rixon]

The original Lock and Block, capitalized, was a Sykes product. It was first fitted, IIRC, by the LCDR in their Metropolitan area and then fairly quickly, over all their main lines. It was a rare examples of the LCDR getting ahead technically. Adoption on the neighbouring SER came later, and I don't know if it was completed over the SER lines before the formation of the SECR.

 

I don't know how widely the product was sold. I suspect that the patent ran out and the basic idea was copied by other signalling suppliers.

[Compound2632]

Re. train detection, before track circuits became widespread, Rule 55 provided an effective form of protection (when carried out correctly) as the physical presence of the fireman in the box acted as an indicator that the line was occupied; one hopes that most firemen would be bright enough to shout out if they saw the signalman accepting a train that would run into their own!

[The Stationmaster]

10 minutes ago, meil said:

The Starting or section Signal was linked to the Block Instrument or Token Machine (for single line) following the Abermule accident.

It was only a recommendation - not a requirement although it was generally applied when other work took place or one busy lines.  but according to some sources there were single line railways closed c.40 years after the Abermule collision where the section signals were still not linked to and controlled by token etc instruments.

[Guy Rixon]

1 minute ago, Compound2632 said:

Re. train detection, before track circuits became widespread, Rule 55 provided an effective form of protection (when carried out correctly) as the physical presence of the fireman in the box acted as an indicator that the line was occupied; one hopes that most firemen would be bright enough to shout out if they saw the signalman accepting a train that would run into their own!

True, but Lock and Block was also combined with train detection via treadles and lock bars. One presumes that Rule 55 made a big dent in the efficiency of working urban lines.

[RailWest]

>>>but according to some sources there were single line railways closed c.40 years after the Abermule collision where the section signals were still not linked to and controlled by token etc instruments....

 

Indeed. In fact, is it not the case that many GWR lines did not have 'token out'  locks fitted until BR days ? :-) 

 

As you mention the S&DJR, although eventually they had 'tablet out' releases for all the single-line sections on their main line, the evidence suggests that provision (if at all) on the various branches was intermittent until well into the 1950s. Most of the main line  section kept 'free' section signals right up until closure, although a small amount of 'Line Clear' releases was added in the 1930s for the Down line only from Evercreech Jcn South to Templecombe No2 Jcn.

 

Although Sykes is probably the best known of the various Lock & Block systems, others patented their own version.

 

As regards the L&SWR, apart from the main suburban areas around London there were 'pockets' of it at other places (eg Exeter Central and the branch to Topsham) until replaced by more modern controls, and it remained at Pottington (for the swing bridge) until 1967.

[micknich2003]

The Hull & Barnsley Rly used Syke's Lock and Block but without treadles, the block was effectively controlled by the "Back Stroke" of the starting signal lever.  I have a c1895 description here, and also the Block Regulations.

[Guy Rixon]

Perhaps the HBR adopted this on Mr. Kirtley's advice?

[micknich2003]

William Kirtley was prior to the appointment of Mathew Stirling the locomotive and C&W consultant to the H&BRly. The L&B was the influence of James Staats Forbes, Managing Director of both the Metropoitan Rly and the  L C & D Rly.

[Grovenor]

The block controls used on the LMS can be found here http://www.norgrove.me.uk/signalli-LMS.htm

Rgds

[Edwin_m]

4 hours ago, Guy Rixon said:

True, but Lock and Block was also combined with train detection via treadles and lock bars. One presumes that Rule 55 made a big dent in the efficiency of working urban lines.

Rule 55, and the local track circuiting that replaced it in some places, were about ensuring the signalman remembered that he had a train standing at one of his signals and therefore avoiding collisions (almost always) within the station limits of the box.  The various interlocks between signals and block instruments were more to do with avoiding collisions in the block section itself caused by signaling a second train into an occupied section.  So they were essentially separate developments addressing different hazards.  

[The Stationmaster]

20 minutes ago, Edwin_m said:

Rule 55, and the local track circuiting that replaced it in some places, were about ensuring the signalman remembered that he had a train standing at one of his signals and therefore avoiding collisions (almost always) within the station limits of the box.  The various interlocks between signals and block instruments were more to do with avoiding collisions in the block section itself caused by signaling a second train into an occupied section.  So they were essentially separate developments addressing different hazards.  

In some respects yes but collisions could, and did, just as readily occur in rear of the outermost Home Signal if the engine crew had not carried out Rule 55 and the Signalman had accidentally accepted a second train into the section.  Hence one of the specific sites for track circuiting from quite early on (i.e. pre 1914) was to provide a track circuit in rear of the outermost Home Signal which had the dual advantage of not only reminding a Signalman of the presence of a train standing at that signal but it could also be combined in various ways (including, in later years,  Welwyn Control) with controls in the block circuit.

[Edwin_m]

1 hour ago, The Stationmaster said:

In some respects yes but collisions could, and did, just as readily occur in rear of the outermost Home Signal if the engine crew had not carried out Rule 55 and the Signalman had accidentally accepted a second train into the section.  Hence one of the specific sites for track circuiting from quite early on (i.e. pre 1914) was to provide a track circuit in rear of the outermost Home Signal which had the dual advantage of not only reminding a Signalman of the presence of a train standing at that signal but it could also be combined in various ways (including, in later years,  Welwyn Control) with controls in the block circuit.

Indeed, and what I was thinking when I added "almost always".  Being (almost always!) at least a quarter mile from the box, Rule 55 from the outermost Home was particularly time-consuming with a correspondingly greater risk of collision before the fireman had reached the box.  So a track circuit here would have been particularly beneficial for safety as well as avoiding the long walk to the box and (though it wasn't seen as a hazard at the time) the driver being alone on the footplate when drawing forward to pick up the fireman.  

[RailWest]

4 hours ago, Grovenor said:

The block controls used on the LMS can be found here http://www.norgrove.me.uk/signalli-LMS.htm

Rgds

Regarding Proposal No 9....

 

Assuming that you have accepted a non-stopping train from the box in rear, got TES, then got LC from the box in advance, how then can you pull off all your stop signals to clear your distant if the berth TC at the Home needs to be occupied first 'cos you have not yet pulled the Starting signal?  Or do you have to pull in reverse order from section signal back to distant in order to circumvent this?

 

[The Stationmaster]

15 hours ago, RailWest said:

Regarding Proposal No 9....

 

Assuming that you have accepted a non-stopping train from the box in rear, got TES, then got LC from the box in advance, how then can you pull off all your stop signals to clear your distant if the berth TC at the Home needs to be occupied first 'cos you have not yet pulled the Starting signal?  Or do you have to pull in reverse order from section signal back to distant in order to circumvent this?

 

As I read it you would have to pull in reverse order. (not a process I've ever really encountered, it always struck me as an odd way of doing the job).

 

16 hours ago, Edwin_m said:

Indeed, and what I was thinking when I added "almost always".  Being (almost always!) at least a quarter mile from the box, Rule 55 from the outermost Home was particularly time-consuming with a correspondingly greater risk of collision before the fireman had reached the box.  So a track circuit here would have been particularly beneficial for safety as well as avoiding the long walk to the box and (though it wasn't seen as a hazard at the time) the driver being alone on the footplate when drawing forward to pick up the fireman.  

I wouldn't necessarily agree that the outermost Home Signal would  be that far from the 'box - in fact I can't immediately call to mind very many 'boxes I knew where that was the case but my experience is of course mainly on the Western.

 

Interestingly looking at a GWR minute from October 1913  it lists three situations where it proposed that the early installation of more track circuiting should take place in the following order -

 

'a. Home Signals where they are situated 300 yds or more from the 'box or less than 300 yds if there is a bad sight from the 'box or if there is difficulty or risk to guards or firemen in carrying out the provisions of Rule 55

b.  At junctions where trains are shunted from the main line to a branch for other trains to pass.

c.  Starting and Advanced Starting Signals situated 440 yards or more from the signal box (or less than 440 yards if there is a bad sight from the 'box).

 

In addition to the track circuiting mentioned the provision of push reply bells at about 1,000 Starting or Advanced Starting Signals situated at a distance varying from 200 to 440 yards from the signal boxes has also been recommended and this work should be pushed forward with the utmost despatch'

 

It should be noted that not only was this discussed in the context of the aftermath of the Hawes Jcn and Ais Gill collisions on the Midland Rlwy but the GWR was in any case already advanced in the provision of track circuiting and the above minute largely confirmed, albeit with a small variation in respect of outermost home signals, principles for the application of track cicuiting which had been laid down in a minute of July 1911.   A sum of £30,000 was requested to be voted for the new track circuiting work, as outlined in the above minute, although I don't know if this was actually approved and in addition lists were to be produced of all the locations where the work was required (there is no record of them).   It seems most likely that the advent of war in 1914 brought an end to such an extensive programme and the money for it simply didn't exist in subsequent years although I am aware of some of it showing on early signal box diagrams reflecting the above principles,  

 

I don't know what happened about the push reply bells but they seem to have vanished from the scene

[Martin Shaw]

17 hours ago, RailWest said:

Regarding Proposal No 9....

  

Assuming that you have accepted a non-stopping train from the box in rear, got TES, then got LC from the box in advance, how then can you pull off all your stop signals to clear your distant if the berth TC at the Home needs to be occupied first 'cos you have not yet pulled the Starting signal?  Or do you have to pull in reverse order from section signal back to distant in order to circumvent this? 

 

 

Unfortunately the wording of the proposal doesn't fully explain the situation, it should have added "if the train has not been accepted by the box in advance and line clear given on the block instrument". The effect of the LC release overrides the berth track circuit occupation release on the home signal lock allowing it to be pulled before the starting signal. Given the propensity of the LMS for sequential locking it has to be this way. It was presumed that given a clear run a signalman would have no need to not pull off all the signals, which is the slight loop hole still present.

 

One manufacturer of Lock and Block systems not mentioned was Tyers and although not as common as Sykes was much used by the Caledonian Rly especially in the Glasgow area.

Regards

Martin

[Compound2632]

1 hour ago, The Stationmaster said:

It should be noted that not only was this discussed in the context of the aftermath of the Hawes Jcn and Ais Gill collisions on the Midland Rlwy

 

It's also noteworthy that the Hawes Junction collision - in which failure to carry out Rule 55 by the crews of the light engines held at the down advanced starter was a major contributory factor - took place only a few months after the North and South boxes had been replaced by the single box on the down platform that exists to this day. It was a longer walk to the new box than it had been to the old North box...

Edited October 25, 2019 by Compound2632

[The Stationmaster]

23 hours ago, Compound2632 said:

 

It's also noteworthy that the Hawes Junction collision - in which failure to carry out Rule 55 by the crews of the light engines held at the down advanced starter was a major contributory factor - took place only a few months after the North and South boxes had been replaced by the single box on the down platform that exists to this day. It was a longer walk to the new box than it had been to the old North box...

Not necessarily as it really depends whose evidence you believe about the position pf the light engines before they started away northwards when the Down Advanced Start was lowered.  On the balance of evidence from other people Col Pringle estimated the two engines were standing about 270 yards north of Hawes Jcn signal box, i.e they were not standing at the Advanced Starter.  According to an online source which states it used official MR records, and quotes chainages, the former North Box was 550 yards north of the new 'box.  Interestingly Col Pringle states that it had been 50 yards north of the new 'box which looking at the track layout actually makes a lot more sense as it would have placed the North Box at the major concentration of pointwork at that end of the station.

 

So wherever the North Box had been the distance to it from where the Colonel concluded the engines were actually standing was either slightly less (50 yards according to his Report) or slightly more (10 yards according to the online information) than the 270 yards distance which Pringle concluded was the position of those engines in relation to the signal box.  (The Inquest jury had different ideas on that but they were of course not professionals in the matter of railway opetation or the investigation of collisons on the railway.)

[Compound2632]

17 minutes ago, The Stationmaster said:

According to an online source which states it used official MR records, and quotes chainages, the former North Box was 550 yards north of the new 'box.  Interestingly Col Pringle states that it had been 50 yards north of the new 'box which looking at the track layout actually makes a lot more sense as it would have placed the North Box at the major concentration of pointwork at that end of the station.

 

 

Plate 82 in V.R. Anderson and G.K. Fox, Stations & Structures of the Settle & Carlisle Railway (OPC, 1986) shows the North Box at the end of the down platform, which fits with 50 yds, although a bit to the south of the crossover etc. The South Box was opposite the water tower (plate 78).

[johnofwessex]

On 24/10/2019 at 11:37, The Stationmaster said:

It was only a recommendation - not a requirement although it was generally applied when other work took place or one busy lines.  but according to some sources there were single line railways closed c.40 years after the Abermule collision where the section signals were still not linked to and controlled by token etc instruments.

 

I gather that the WSR is gradually rolling out interlocking the starting signals with the token instruments

[RailWest]

11 hours ago, johnofwessex said:

 

I gather that the WSR is gradually rolling out interlocking the starting signals with the token instruments

To the best of my knowledge the WSR has always had 'token out' releases on its section signals every since it introduced  EKT to its various sections.

[beast66606]

On 24/10/2019 at 11:28, The Stationmaster said:

Even more worrying (perhaps?) was that well into the 1960s there were still signalboxes on rural lines (including some on the at times very busy Somerset & Dorset Joint) where signals were not interlinked with the block system which made it quite possible to v clear the signal into the next block section while there was a train already in that section.  All such lines were worked on the Absolute Block system but the signals remained free of any control by or over the block system!

 

There existed a free pull at Ellesmere Port No.2 (iirc) until the mid 1970s, and this on a (double track) line with passenger trains and Stanlow tank trains !