Speed signalling in GB

[fwsmVor]

Has there ever, on some obscure isolated branch or tramway, been a speed-signalled railway in GB? (and did the ECML flashing greens count?)

 

[jfollows]

Yes, at Mirfield, see https://signalbox.org/signals/lms-speed-signalling/

One sole installation of speed signalling was made in Yorkshire by the LMS in 1932. This was installed on a three-mile stretch of quadruple line between Heaton Lodge Junction and Thornhill LNW Junction which included a junction and station at Mirfield. The scheme was for the signals alone, and whilst a little sensible thinning-out of signal boxes occurred, the control remained from mechanical frames and the Absolute Block system continued in use.

It was replaced by standard signalling in May 1970.

 

[Elecman]

Mirfield and covered on a recent thread on here
jfollows above beat me to it

 

[Railsigns]

As well as at Mirfield, a small amount of speed signalling was implemented in the resignalling of the Camden - Watford New Line in 1932/33, but this was replaced by route signalling in 1953. Both schemes were designed by the LMS's Signal Engineer Arthur Bound, and both were a mix of route signalling and speed signalling depending on speed of divergence.

 

[jfollows]

Mirfield and covered on a recent thread on here
jfollows above beat me to it

Recent thread at https://www.railforums.co.uk/threads/mirfield-resignalling.253043/ with more information than in my post above.

 

[zwk500]

Has there ever, on some obscure isolated branch or tramway, been a speed-signalled railway in GB? (and did the ECML flashing greens count?)

There is the current installation of TVM-430 on HS1.
ETCS (Cambrian and Thameslink) and CBTC (Crossrail Core) also contain elements of Speed Signalling but not sure if they count as 'proper' speed signalling.

The ECML Flashing Greens are not speed signalling - the flashing green indicates only that the signal ahead is showing a steady or flashing green and conveys no information about the permitted speed specifically.

 

[eldomtom2]

The ECML Flashing Greens are not speed signalling - the flashing green indicates only that the signal ahead is showing a steady or flashing green and conveys no information about the permitted speed specifically.

So when flashing greens were used, you could theoretically pass a double yellow at 140mph as long as you could stop in time?

 

[357]

So when flashing greens were used, you could theoretically pass a double yellow at 140mph as long as you could stop in time?

No, or at least not designed as such.
The sequence is flashing green - solid green - double yellow - single yellow - red
So you'd start slowing when you see the solid green.

 

[Gerald Fiennes]

Jubilee line/DLR moving block? The speed is what is controlled, to ensure the train can stop at the end of the block (stationary or moving...)

 

[zwk500]

So when flashing greens were used, you could theoretically pass a double yellow at 140mph as long as you could stop in time?

No, because the signal spacing is almost certainly not going to allow the service braking to stop a train from after the double yellow in time. Although not tied to a specific speed (unlike in the Netherlands, where single yellow = 40kph), it is still required that drivers control their train and approach cautionary aspects appropriately. It's just that Double Yellows might be passed at a range of speeds because they mean 'expect to find next signal at Yellow' rather than 'reduce speed to Xmph'. But any driver who went through a Steady green at 140mph has already broken the rule by not reducing the speed of their train when receiving a 'expect to find next signal at preliminary caution' aspect (which would be the meaning if receiving a Green on a 5-aspect section).

Jubilee line/DLR moving block? The speed is what is controlled, to ensure the train can stop at the end of the block (stationary or moving...)

Given this is ATO does it count as either Speed or Route Signalling?

 

[DerekC]

Jubilee line/DLR moving block? The speed is what is controlled, to ensure the train can stop at the end of the block (stationary or moving...)

Depends on your definition. To me the essence of speed signalling is about transmitting the speed information to the driver visually. Electronic transmission as part of a CBTC system is a different thing. No doubt others will disagree, though.

 

[Taunton]

Yes, at Mirfield, see https://signalbox.org/signals/lms-speed-signalling/

It was replaced by standard signalling in May 1970.

It's arguable whether the Mirfield installation gave any indication of speed. It was given that designation by the LMS, and by its USA manufacturer, but did little new. On open line it was similar to UK 4-aspect signals, with two lights just telling how many signals ahead were clear. For junctions an additional light, and combinations of colours, showed whether it was clear to the main line (termed "high speed") or any turnout (termed "medium speed"). No indication of actual speed was given. There was advance signal indication given of a turnout, compared to UK practice of only showing the feather at the actual junction signal, but that was a marginal difference.

 

[D6130]

One of the Mirfield speed signals is preserved in the museum at Oxenhope on the Keighley & Worth Valley Railway, should anyone wish to examine it in close-up.

 

[fwsmVor]

It's arguable whether the Mirfield installation gave any indication of speed. It was given that designation by the LMS, and by its USA manufacturer, but did little new. On open line it was similar to UK 4-aspect signals, with two lights just telling how many signals ahead were clear. For junctions an additional light, and combinations of colours, showed whether it was clear to the main line (termed "high speed") or any turnout (termed "medium speed"). No indication of actual speed was given. There was advance signal indication given of a turnout, compared to UK practice of only showing the feather at the actual junction signal, but that was a marginal difference.

Reading through the website, although it must have seemed foreign at the time, it doesn't look like speed signalling. It seems like it's more "what if the ECML in the 90s had splitting distants".

 

[Taunton]

One of the Mirfield speed signals is preserved in the museum at Oxenhope on the Keighley & Worth Valley Railway, should anyone wish to examine it in close-up.

There's another in the NRM at York (unless it's the same one moved around).

 

[eldomtom2]

It's arguable whether the Mirfield installation gave any indication of speed. It was given that designation by the LMS, and by its USA manufacturer, but did little new. On open line it was similar to UK 4-aspect signals, with two lights just telling how many signals ahead were clear. For junctions an additional light, and combinations of colours, showed whether it was clear to the main line (termed "high speed") or any turnout (termed "medium speed"). No indication of actual speed was given.

The question is whether or not "medium speed" and "low speed" actually had defined speeds. The Signal Box website does not say they did, but American practice would definitely be to define "medium speed" and "low speed" as specific speeds - see this diagram of aspects on their Southern Railway for an example:

There was advance signal indication given of a turnout, compared to UK practice of only showing the feather at the actual junction signal, but that was a marginal difference.

Were there feather indicators in use in the 1930s?

 

[Taunton]

I think the Southern were the first users of a feather - 3 lights instead of five.

Regarding "speed", I understood the LMS interpretation was high = through line, medium = turnout, slow = siding. Bear in mind when installed at Mirfield, hardly any (possibly no) locomotives had speedometers.

 

[QueensCurve]

The ECML Flashing Greens are not speed signalling - the flashing green indicates only that the signal ahead is showing a steady or flashing green and conveys no information about the permitted speed specifically.

There was an element of speed signalling in the flashing green in so far as the maximum speed was 125mph on green and 140mph on flashing green.

 

[eldomtom2]

Regarding "speed", I understood the LMS interpretation was high = through line, medium = turnout, slow = siding. Bear in mind when installed at Mirfield, hardly any (possibly no) locomotives had speedometers.

Well that's inherent to the concept of speed signalling at junctions. The question is whether precise speeds were defined - there certainly were plenty of definite speed limits around in the 1930s despite the lack of speedometers.

 

[zwk500]

There was an element of speed signalling in the flashing green in so far as the maximum speed was 125mph on green and 140mph on flashing green.

It's inevitable given the relationship between speed and safe stopping distances that as systems get more sophisticated they will take on elements of speed signalling. As the line becomes blurred it's harder to say something is definitely not speed signalling.
A case in point is ETCS - It issues a movement authority to a specific marker board (is the destination/route indicated to the driver?), but also displays the calculated speed profile according to the braking curves and ESR/TSR/PSRs to the driver.

 

[eldomtom2]

As the line becomes blurred it's harder to say something is definitely not speed signalling.

These are the definitions I personally use:
Route signalling - signals at junctions indicate which route the train is being routed on
Speed signalling - signals at junctions indicate the speed limit for the upcoming junction
Progressive speed signalling - signals warning of an upcoming stop signal impose speed limits on trains passing them

 

[Ken H]

What about approach control? (This is where a junction signal wont clear till the signalling is sure speed has been reduced)
Yeah I know its a bit different but I thought it was worth a shout.

 

[D6130]

I think the Southern were the first users of a feather - 3 lights instead of five.

The first use of three lamp directional route indicators ('feathers') by the Southern Railway was in the Waterloo-Hampton Court Junction resignalling in 1936. However the LNER used five lamp feather route indicators in the Thirsk resignalling - the first British route-setting panel installation - in 1933.

 

[Railsigns]

However the LNER used five lamp feather route indicators in the Thirsk resignalling - the first British route-setting panel installation - in 1933.

The Thirsk resignalling of 1933 contained not a single feather. There was however a trial at Thirsk that year where a signal was fitted with neon-tube type feathers (including one in the vertical position for the straight route). The LNER's 5-lamp feathers didn't appear until about 1938.

 

[GC class B1]

I am following this thread with interest. I have always been interested in signalling and more recently in braking techniques to avoid SPADs. In my current part time role I calculate theoretical stopping distances for rolling stock to confirm compliance with GM/RT2045. My understanding is that there aren’t any lines with speed signalling on NR infrastructure. The definition of signals as indicating the limits of movement authority confirms that their purpose is the instruct the driver the point that they must not pass. It is therefore the driver’s role to ensure that the train is brought to a stand before the limit of authorised movement is passed. Understanding the braking technique drivers use to stop their train within the signal spacing has been an area where I didn’t have any experience. My understanding is that the minimum signal spacing for the applicable line speed is about 15 or 20% longer than maximum Full Service stopping distance mandated in GM/RT2045. As I don’t think it would be good practice to make a Full Service brake application at every restrictive signal aspect. My question is how do drivers ensure that as far as possible they don’t need to make a Full Service or Emergency brake application when encountering a restrictive signal aspect and are restrictive signal aspects in effect an indication of the maximum speed that the signal should be passed at I.e. a ‘speed signal’.

 

[Snow1964]

The Southern used to have various double banner repeaters, whilst not strictly speed signalling, they were to avoid trains having to slow excessively because they gave advance warning if a junction signal had been cleared before it could be seen.

There were also some locations with two banner repeaters, one of which had fishtail, so effectively pair could show a three aspect signal. These were normally before bridges where signal was obscured until quite close.

I know Midland also used splitting distants quite extensively, again not true speed signals, but one which gave indication of which route ahead when might have had different speed limits. But driver knowledge was expected to know the limits.

These days some banner repeaters seem to use coloured LEDs, but don't know if any are used as advance junction indicators or indication that signal after next is red.

 

[D6130]

The Thirsk resignalling of 1933 contained not a single feather. There was however a trial at Thirsk that year where a signal was fitted with neon-tube type feathers (including one in the vertical position for the straight route). The LNER's 5-lamp feathers didn't appear until about 1938.

Ah yes....further research shows that to be true. Slightly OT, but would I be correct in thinking that the first LNER five lamp 'feathers' were actually installed at Northallerton?

 

[12LDA28C]

I am following this thread with interest. I have always been interested in signalling and more recently in braking techniques to avoid SPADs. In my current part time role I calculate theoretical stopping distances for rolling stock to confirm compliance with GM/RT2045. My understanding is that there aren’t any lines with speed signalling on NR infrastructure. The definition of signals as indicating the limits of movement authority confirms that their purpose is the instruct the driver the point that they must not pass. It is therefore the driver’s role to ensure that the train is brought to a stand before the limit of authorised movement is passed. Understanding the braking technique drivers use to stop their train within the signal spacing has been an area where I didn’t have any experience. My understanding is that the minimum signal spacing for the applicable line speed is about 15 or 20% longer than maximum Full Service stopping distance mandated in GM/RT2045. As I don’t think it would be good practice to make a Full Service brake application at every restrictive signal aspect. My question is how do drivers ensure that as far as possible they don’t need to make a Full Service or Emergency brake application when encountering a restrictive signal aspect and are restrictive signal aspects in effect an indication of the maximum speed that the signal should be passed at I.e. a ‘speed signal’. they in effect read the preceding am interested in the real situation and how drivers would not be desirable braking techniques would and therefore the driving technique to stop within the minimum signal spacing distance for the maximum line speed has been an interest

Signals should be spaced so that trains can make a normal service braking application when encountering restrictive aspects in order to stop at a red. Normal service braking would be the brake step mandated in an operator's braking instructions which varies between companies but in any case would not be anything like Full Service brake.

Some TOCs have their own specific rules about what speed their drivers should attain by the time they pass a single yellow signal in four-aspect signalling sections for example, but that does not mean that there is speed signalling in operation.

== Doublepost prevention - post automatically merged: 28 Aug 2023 ==

These are the definitions I personally use:

Progressive speed signalling - signals warning of an upcoming stop signal impose speed limits on trains passing them

You could claim that any signal fitted with TPWS OSS does that, but that does not make it speed signalling.

 

[eldomtom2]

Some TOCs have their own specific rules about what speed their drivers should attain by the time they pass a single yellow signal in four-aspect signalling sections for example, but that does not mean that there is speed signalling in operation.

If there's a specific speed listed in the rules that drivers must always be under when passing all single yellow signals, I would call that progressive speed signalling.

You could claim that any signal fitted with TPWS OSS does that, but that does not make it speed signalling.

What are you defining as speed signalling?

 

[zwk500]

If there's a specific speed listed in the rules that drivers must always be under when passing all single yellow signals, I would call that progressive speed signalling.

What are you defining as speed signalling?

Speed signalling is where the signalling system conveys authority to the driver to proceed at a specified speed. Progressive Speed signalling sounds like another name for just 'driving properly'. The only 'true' speed signalling system in the UK is TVM-430. All other signalling systems indicate whether or not a track ahead is occupied and the driver is expected to modify their speed accordingly, but the signalling itself does not change the authority to move at a specified speed.
Think of it as the difference between caution signs or Advisory speeds and Mandatory Speed limits on the road. If you see 'Caution sharp bend' you are instructed to moderate your speed to avoid crashing but the legal speed limit is not changed by that sign alone.