[TRIVIA] - Shortest Signal Block

_toommm_ · 8 May 2019

I remembered reading somewhere that the line from Leeds to Lancaster features one of the longest signal blocks in the UK so it got me thinking: what is the shortest signal block in the UK?

I suspect somewhere like Leeds station with its intermediate platform signals..
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RailUK Forums

Kite159 · 8 May 2019

Stratford P5?

(As over the weekend I saw some C2C services draw up to the platform end when a TfL Rail/GA service was in the platform)

Maybe on the Thameslink core? I.e. at Blackfriars where you can sometimes see a 700 coming out of the tunnel from City Thameslink, pausing near the gateline when another 700 is on the southbound platform

jawr256 · 8 May 2019

Could the eastbound signals at Manchester Oxford Road P3/4 (possibly also 2?) be considered separate blocks? There are mid-platform and platform-end signals around 70m apart; because the lines merge so close to the platform end, trains often have to stop at the mid-platform signal in order for the signal on the adjacent platform to be cleared.

Belperpete · 8 May 2019

New Street has got some very short sections where lines join near the platform end (e.g. platform 8 I think). But I suspect that some of the shortest sections will be the near-platform-end running-in signals on LU, e.g. at Baker Street on the east-bound H&C platform that allows a train to enter the platform while a Met train is blocking the junction beyond the platform end. These running-in signals are often only yards in rear of the platform-end signal.

driver_m · 8 May 2019

Belperpete said:
New Street has got some very short sections where lines join near the platform end (e.g. platform 8 I think). But I suspect that some of the shortest sections will be the near-platform-end running-in signals on LU, e.g. at Baker Street on the east-bound H&C platform that allows a train to enter the platform while a Met train is blocking the junction beyond the platform end. These running-in signals are often only yards in rear of the platform-end signal.

I know what you mean. The platforms with 3 signals along them rather than two. However we can’t depart from one if the intermediate signals showing only a yellow (basically end signal being a red. There are 3 wherever there is pointwork at the ends of platforms such as 3, or where a middle road exists such as 6. 11 car pendos must have the line all the way to the last signal on these platforms otherwise we cannot open the doors.

Llanigraham · 8 May 2019

Thought it was between Edgeley 1 and 2 in Manchester

Peter C · 8 May 2019

Waterloo is definitely a station where two trains can use one platform. I've never seen any signals halfway down the platforms, however, so whether this is the shortest signal block I don't know. Maybe the terminus station with the shortest platforms has the shortest signal block, as there are always signals at the ends of the platforms? Just a thought.

-Peter

Ianno87 · 8 May 2019

jawr256 said:
Could the eastbound signals at Manchester Oxford Road P3/4 (possibly also 2?) be considered separate blocks? There are mid-platform and platform-end signals around 70m apart; because the lines merge so close to the platform end, trains often have to stop at the mid-platform signal in order for the signal on the adjacent platform to be cleared.

Now... this depends how you define a block section. At Oxford Rd, I understand the interlocking does not permit running up to the 'outer' (Piccadilly end) signal unless the onward route to the Piccadilly home signal is clear. Hence why the Deansgate starter (2 signals in rear) is three aspect, so/as it can't display Double Yellow in any circumstances.

My money would be on one of the New St examples.

Iskra · 8 May 2019

Wouldn’t it be a head shunt or specifically designed stabling point for something like a thunderbird loco, controlled by a ground signal? Or is that not a block section?

ASharpe · 9 May 2019

Outside of a station the shortest I can think of is protected by 3631 On the approach to Leeds. A 4 car train just about fits but I doubt anything longer would.

I think it's just really for allowing units in the bay platforms a slightly quicker reverse back to Neville Hill and means they don't get in the way as much.

I wonder if they will have to do anything with it for fancy new 6 car trains I hear are coming to the Airedale line.

westcoaster · 9 May 2019

P1 at Redhill must only be 10-20m between signals.

Bigfoot · 9 May 2019

P1 up slow at Surbiton is split for wrong direction, wk543 to wk545 signal is probably a candidate.

bramling · 9 May 2019

_toommm_ said:
I remembered reading somewhere that the line from Leeds to Lancaster features one of the longest signal blocks in the UK so it got me thinking: what is the shortest signal block in the UK?

I suspect somewhere like Leeds station with its intermediate platform signals..
.

If one includes LU there are some very short distances between signals on the remaining conventionally signalled lines, especially at locations where a station has multiple home signals. And some of the block marker boards on the Central Line are very close together.

Sunset route · 9 May 2019

westcoaster said:
P1 at Redhill must only be 10-20m between signals.

It used to be, but now sadly done away with after platform 0 was brought into use.

Ploughman · 9 May 2019

Would Selby Swing Bridge be a short block?

apinnard · 9 May 2019

Up and down Electric between Maryland and Stratford?

Scotrail84 · 9 May 2019

Queen street high level station and tunnel?

Tomnick · 10 May 2019

Ianno87 said:
Now... this depends how you define a block section. At Oxford Rd, I understand the interlocking does not permit running up to the 'outer' (Piccadilly end) signal unless the onward route to the Piccadilly home signal is clear. Hence why the Deansgate starter (2 signals in rear) is three aspect, so/as it can't display Double Yellow in any circumstances.

It does allow it. The mid-platform signal in each case is approach released from red in that situation, though, which is why the platform starters at Deansgate can never show double yellow.

The outlet signal from Mayfield Loop in the Down direction is very close to the next signal on the Down Slow, and this one *does* require that next signal clear as I understand it. Does that rule it out in the context of this question?

Ianno87 · 10 May 2019

Tomnick said:
It does allow it. The mid-platform signal in each case is approach released from red in that situation, though, which is why the platform starters at Deansgate can never show double yellow.

The outlet signal from Mayfield Loop in the Down direction is very close to the next signal on the Down Slow, and this one *does* require that next signal clear as I understand it. Does that rule it out in the context of this question?

Ah, thanks.

There are a few of those signals around Piccadilly; e.g. the Platform 12 'inner' starter is a Red/Green two aspect, and can only clear if the 'common' signal shared with Platforms 10 & 11 is also clear. Liverpool Street also has some examples (e.g. Platforms 9/10)

Tomnick · 10 May 2019

Ianno87 said:
Ah, thanks.

There are a few of those signals around Piccadilly; e.g. the Platform 12 'inner' starter is a Red/Green two aspect, and can only clear if the 'common' signal shared with Platforms 10 & 11 is also clear. Liverpool Street also has some examples (e.g. Platforms 9/10)

A slight correction at Man Picc - all of platforms 9 to 12 have such a signal, all “shared” with the signal at the end of platform 9 which can be used as a platform starter in its own right if there’s a train occupying the full length of 9 (which also blocks access to 10-12). I’m pretty certain that the distance between these signals (not sure about those at Liverpool Street) is still longer than that example at Oxford Road - it’s barely 30m between the signals on platform 3!

RichJF · 10 May 2019

Are the signal sections on approach/on Blackfriars station treated as signal blocks? Extremely short sections between Elephants & City Thameslink.

bionic · 10 May 2019

Platform 2 at (London) Victoria must be a contender... or indeed any of the higher number platforms that route over to it.

driver_m · 10 May 2019

Tomnick said:
A slight correction at Man Picc - all of platforms 9 to 12 have such a signal, all “shared” with the signal at the end of platform 9 which can be used as a platform starter in its own right if there’s a train occupying the full length of 9 (which also blocks access to 10-12). I’m pretty certain that the distance between these signals (not sure about those at Liverpool Street) is still longer than that example at Oxford Road - it’s barely 30m between the signals on platform 3!

They’re all 2 aspects and I remember taking a pendo into 9 regularly when I was at Manchester. Once they’d gone 11 though I think this stopped as it would guarantee to stitch up all the platforms as it would be sat in front of the 2 aspect signal on 9. 9 cars used to have to draw right up to the buffers to prevent this IIRC.

driver_m · 10 May 2019

If you want a short ‘conventional’ signal section that’s not on a platform, there are two signals on the down fast at West London Junction adjacent to Willesden Depot that are very close together. Get two yellows just after Kensal Green Tunnel and we really have to be bringing the train’s speed down quickly. There have been a number like this in the past but as resignalling occurs, they’ll be less common. I’d say for sheer closeness, and forgetting other rules, Oxford Road’s are the closest together.

Llama · 11 May 2019

Probably nowhere near the shortest signal section per se, but must be one of the shortest in three aspect TCB signalling on a 90mph line - Vitriol Works' VW29 (5m 1419yds) to VW31 (5m 243yds). I make that 1176yds, and that's on a 1-in-152 falling gradient.

Islineclear3_1 · 11 May 2019

How about the 1/4 mile or so between Newhaven Harbour No 39 signal to Nrwhaven Town CCO1578 signal controlled by their respected signalboxes under AB regulations? Even shorter prior to 2013 between Harbour's NH39 signal and Town's CCO37 when it existed

dk1 · 11 May 2019

As Absolute Block Sections go Norwich to Trowse Lower Junction (2mins timing today) used to have up to four back when I was a box lad. They where Passenger Yard - Thorpe Junction - Trowse Swingbridge - Trowse Yard - Trowse Lower Junction. Trowse Yard however was only switched in 0800-1600 weekdays. Also switched in similar hours was the next box at Trowse Upper Junction if heading towards Diss & this was just over a mile away up the bank at Lakenham.

Crossover · 11 May 2019

Would the DLR count? As I understand it, the appearance of a moving block on there is actually lots of short signal blocks to allow the trains to run close to each other

Ianno87 · 11 May 2019

driver_m said:
If you want a short ‘conventional’ signal section that’s not on a platform, there are two signals on the down fast at West London Junction adjacent to Willesden Depot that are very close together. Get two yellows just after Kensal Green Tunnel and we really have to be bringing the train’s speed down quickly. There have been a number like this in the past but as resignalling occurs, they’ll be less common. I’d say for sheer closeness, and forgetting other rules, Oxford Road’s are the closest together.

There are a number of signal sections on the Great Eastern Main Line around Stratford/Forest Gate that are less than braking distance between what would be the Double Yellow and the red. So non-standard aspect sequences of two or three consecutive double yellows at successive signals can be displayed to counteract this.

dk1 · 11 May 2019

Ianno87 said:
There are a number of signal sections on the Great Eastern Main Line around Stratford/Forest Gate that are less than braking distance between what would be the Double Yellow and the red. So non-standard aspect sequences of two or three consecutive double yellows at successive signals can be displayed to counteract this.

And thank goodness they are :lol:

Many more on the EL further back too.

[TRIVIA] - Shortest Signal Block

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