3 aspect distant signal

[Lee Rambo]

Where would you find a 3 aspect distant signal?
Please explain possible layouts and sequence.

 

[brad465]

Where would you find a 3 aspect distant signal?
Please explain possible layouts and sequence.

On the Southeastern Network there's one at the end of Higham station on the up platform (1), which I believe is around the area of transition from 3 to 4 aspect signalling, and on the approach to Hoo Junction, so may help control Freight trains heading for the yard (the next stop signal is relatively close behind it). There's also one at the end of Shortland's junction on the up line towards Beckenham Junction, which appears to be somewhere a stop signal would foul the junction, but the 4-aspect sequence needs to be maintained along that line.

Further afield I recall there being a 3 aspect distant signal on the Settle-Carlisle line between Dent and Ribblehead just before Blea Moor tunnel, which appears to be to help approach control on the approach to Blea Moor loop and ultimately Ribblehead viaduct (this is in an area of 2 aspect operation).

(Happy to be corrected if the reasons for the above examples existing are different)

 

[Tomnick]

Examples:

- Where one signal in an otherwise typical run of four aspect signals isn’t capable of displaying a red aspect (perhaps it’s in a tunnel).

- In the transition from three-aspect to four-aspect signalling, where the last three-aspect stop signal is R/YY/G and followed by a three-aspect (Y/YY/G) to provide the correct aspect sequence and braking distances for the first couple of four-aspect stop signals.

- Approaching a four-aspect stop signal from an AB section or a long TCB section (either a single three-aspect distant signal or an outer and an inner distant).

- Where it’s necessary to provide an outer and an inner distant signal approaching a two- or three-aspect stop signal (e.g. the outer, YY/G, is needed to provide the braking distance, but a station intervenes and its desirable to have an inner distant to allow the level crossing beyond the stop signal to be kept open to road traffic for longer).

...and probably more besides!

 

[King Lazy]

From memory (I may be wrong and it may have changed) Workington on the down is a good example in an absolute block area.

2 signalboxes close together (a remnant from a much more complex layout. One at each end of the station basically)

On approach the 1st signal encountered is a 3 aspect colour light capable of displaying Green, 2 yellows or 1 yellow.

Signalboxes are No2 then No3.

Signals encountered are as follows.

3-Aspect colour light with no red.
3-Aspect Stop signal (Box No2)
Semaphore Home signal (Box No 3)
Semaphore section signal (Box No 3)

-If Box 2 has its stop signal at danger the distant shows 1 yellow.

-If Box 3 has any of its Semaphore stop signals at danger but Box 2 has cleared its stop signal the distant shows 2 yellows and the Box 2 stop signal shows 1 yellow.

-If both boxes have cleared all signals the distant shows green (as will all the other signals).

As a distant can only show clear when all associated stop signals are clear in this case it can only show clear when all associated stop signals of 2 signalboxes in close proximity are clear. Otherwise it displays a yellow.

Hope I’ve made this clear enough?

 

[MrEd]

Where would you find a 3 aspect distant signal?
Please explain possible layouts and sequence.

I seem to recall that there was one on the up main approaching Diss from the Norwich direction- this could show Y/YY/G depending on the aspects of the signals ahead. A 3-aspect R/Y/G signal protected the northern end of Diss station, and the Diss up platform starter was a 2-aspect R/G. When initially converted (mid-1980s, coinciding with electrification) to Track Circuit Block controlled from Colchester PSB, the northern end of the Great Eastern Main Line between Haughley and Norwich used a mixture of 2-aspect and 3-aspect signals. I’m not sure if this is still the case as the line might since have been re-signalled.

 

[swissrailpassion]

Down trains approaching Hunmanby encounter a yy/g distant then a r/y followed by the station and a r/g.

 

[Flange Squeal]

One example I can think of is on a stretch of single line, on the approach to a junction. The reason why the distant in question can show either a single or a double yellow is because there are two main aspects protecting the junction. I have made a simple diagram to try and explain it. The signal closest to the junction is very close to it, but is presumably located there (as opposed to further back) due to there previously being a signal box opposite it. As a result, I assume there is not deemed to be sufficient overlap between it and the junction for a train to be brought down to a stand at it from linespeed.

[TOP PIC - SINGLE YELLOW AT DISTANT] If the route has been set for a train on the mainline to travel across the junction in front of a train coming off the single line (TRAIN A), Train A will receive a single yellow at the distant signal and have to reduce its speed towards the outer home, which will be at red. This signal will then change from red to a single yellow on approach and allow the now-slow train to proceed as far as the home signal close to the junction.

[BOTTOM PIC - DOUBLE YELLOW AT DISTANT] If a train on the mainline has already crossed the junction and stopped in the platform (TRAIN B), then Train A can receive a double yellow on the distant, a single yellow on the outer home, and proceed as far as the home signal close to the junction.

 

[Phillipimo]

Travelling from Hedge End to Eastleigh the signals are:

3-aspect distant (YGY) -> 3-aspect (GYR) -> 2-aspect (YR) with theatre route indicator for platform number.

This must be because there is insufficient braking distance between the final two signals so there must be prior warning. Otherwise the sequence could be GY, GYR, YR.

 

[DorkingMain]

If I remember correctly there is a 3 aspect repeater just outside Malden Manor on the up, as one signal protects the junction and another protects the level crossing outside Motspur Park.

Y - Junction not cleared
YY - Junction cleared, level crossing not cleared
G - Route cleared through to Motspur Park

 

[Eccles1983]

On the approach to Astley crossing on the Chat Moss, Down direction, and Gobowen in the down direction.

The one in Gobowen is odd, outer distant > 3 colour stop> semaphore stop.

 

[Colin1501]

On the approach to Astley crossing on the Chat Moss, Down direction, and Gobowen in the down direction.

The one in Gobowen is odd, outer distant > 3 colour stop> semaphore stop.

I suspect the reason at Gobowen is that there is insufficient braking distance between the 3-aspect home and the semaphore starter. If the starter is 'on', the 3-aspect home will show single yellow, and the distant double yellow, thus providing adequate braking distance.

 

[30907]

Another regular use is (or more likely was) at a transition from semaphore to 4-aspect MAS, with a 3-aspect distant under a semaphore starter/section signal: this was not uncommon on the SR, I can remember examples at West Croydon (Up to Gloucester Road Jn) and Tulse Hill (Down), and I imagine Esher (Up) and Selsdon.
No light was displayed when the semaphore was "on."

PS from another forum I've discovered New Beckenham had one for the spur; no doubt there were others!

 

[EvoIV]

There's one on the Down Cherwell Valley line approaching Aynho Junction. I'd assume to do with maintaining braking distance when there are line speed increases.

 

[Scotrail84]

Pretty sure theres one near Rosyth heading towards Edinburgh on fife circle.

 

[DennisM]

If I remember correctly there is a 3 aspect repeater just outside Malden Manor on the up, as one signal protects the junction and another protects the level crossing outside Motspur Park.

Y - Junction not cleared
YY - Junction cleared, level crossing not cleared
G - Route cleared through to Motspur Park

Just to add a little more detail as to why this one exists;
The signals down the line toward Chessington are all 2 aspect and the signal ahead protecting the junction is 4 aspect.
The previous signal being a 2 aspect stop signal (R/G) therefore means this one cannot be capable of displaying a red.

 

[21C101]

There is also one on the (preserved) Great Central.

I dont think there is a semaphore equivalent though for this, only colour light.

 

[The Planner]

There's one on the Down Cherwell Valley line approaching Aynho Junction. I'd assume to do with maintaining braking distance when there are line speed increases.

That one is also to smooth out the approach incase something is coming off the Chilterns.

 

[Tomnick]

There is also one on the (preserved) Great Central.

I dont think there is a semaphore equivalent though for this, only colour light.

The semaphore equivalent is just a standard distant signal, with route knowledge telling you what it applies to. There’s examples of that on the GCR (Rothley on the Up and Swithland on the Down, subtly different) too, and still a few (well at least one that I can think of!) on the national network too.

 

[driver9000]

There is one on the end of Curriehill Down platform which leads to a red at Wester Hailes protecting the level crossing at Kingsknowe. The previous signal to Curriehill is a 2 aspect red/green which is the set up for much of the route from Carstairs (with the exception of the Midcalder Junction area).

You will also find one (SH101R) between Eccleston Park and Thatto Heath on the Up just before the cutting and the steep falling gradient towards St Helens Central. This signal was also in place when the line was worked by Absolute Block.

 

[175001]

One on the approach to Chapel Lane LC for the crossing and then Parbold on the Wigan-Southport line.

1 yellow, you're stopped at Chapel Lane LC.
2 yellows, you're stopping before Parbold.
A Green and you're into Parbold and beyond.

 

[TSG]

I know of an example at the edge of an area that was resignalled from 3 to 4 aspect. The aspiration was to resignal the adjacent area to 4 aspect as well eventually so passive provision was made in the shape of 4 aspect signal with a blanked red. There wasn't the braking distance from the last 3 aspect to the 2nd 4 aspect's red. This now all 4 aspect so the red has been put in. See simplistic layout below (no sighting/overbrake etc)

 

[Deepgreen]

Where would you find a 3 aspect distant signal?
Please explain possible layouts and sequence.

This sounds like an exam question - please show your workings.

 

[satisnek]

Kidderminster used to have one approaching from the Birmingham direction, followed by a colour light (3 aspect) outer home (by the cricket ground). The idea was that terminating trains had a clear run into the platform without being checked by the outer home.

 

[MarkyT]

I know of an example at the edge of an area that was resignalled from 3 to 4 aspect. The aspiration was to resignal the adjacent area to 4 aspect as well eventually so passive provision was made in the shape of 4 aspect signal with a blanked red. There wasn't the braking distance from the last 3 aspect to the 2nd 4 aspect's red. This now all 4 aspect so the red has been put in. See simplistic layout below (no sighting/overbrake etc)

That's the preferred method for such a 3 to 4 aspect transition in modern schemes.

 

[bluesfromagun]

Pretty sure theres one near Rosyth heading towards Edinburgh on fife circle.

Spot on, hadn't even thought of that one and I pass it pretty often!

On the routes I sign, there's the above signal on the up line approaching Rosyth which can display DY, SY, G. The reason for this one is because there is a diverging approach controlled junction at the next signal (Inverkeithing North Jn), for Inverkeithing East Jn.
Also, Montrose up distant which can display DY, SY, G. The reason for this one is just a bastardisation of absolute block signalling - the home signal has been changed to a three aspect colour light, so the whole sequence allows you to approach the section signal (if its at danger) much faster. A single yellow would have you stopped at the home signal, before the station. The section signal in this case is at the end of the up platform and protects the single line to Usan.
The first 'proper' Aberdeen signal on the down line at Torrie, approaching Craiginches, can display DY or G. The reason for this is, I think, braking distance for freight trains going into Craiginches.

 

[Chris Hamilton]

GMC426RR and its next signal, GMC426R on the Up Midcalder approaching Carstairs are three aspect distants as it is a transition point between a two and four aspect signalling area, and also because there are three potential points to be stopped ahead. GMC426 as a controlled signal protects Carstairs East Jcn , where a train can be brought to a stand, but also the next two signals protecting Carstairs South and Carstairs Station can also be used to bring trains to a stand. So having the extra caution aspects allows a better regulation of speeds on their approach, keeping Carstairs East and the single line chord to the Station moving faster.

 

[Colin1501]

That's the preferred method for such a 3 to 4 aspect transition in modern schemes.

Interesting to read your reference to 'modern schemes', as I believe it wasn't always the case. Take the situation at, say, Winchfield under the 1967 Bournemouth electrification/resignalling. There were facing crossovers fast to slow and slow to fast either side of the station. The 3-aspect signals controlling these crossovers (let's call them A and B) had insufficient braking distance between them, so the next signal in rear (C) was a 4-aspect. If A was red, then the driver got single yellow on B and double yellow on C. However, because the signal in rear of C (D) was only a 3-aspect, full braking distance was provided between C and B, which meant that when A was red, the driver actually got one and a half times the required braking distance from C to A. Transition 3-aspect distants, as described above, avoid this situation. Apologies if this is confusing - perhaps a diagram might have helped!

 

[godfreycomplex]

F274 at Sunnymeads is a 2 aspect
F272R at Moor Farm is a 3 aspect
F272 at Staines Oil Terminal is a 4 aspect

 

[8stewartt]

Few around the Peak District:

-1 in Bradway tunnel toeards Dronfield.
-1 in Bradway tunnel towards Dore
-1 in Totley tunnel towards Dore
-1 in Disley tunnel towards Hazel Grove

 

[Snow1964]

There used to be one at Lymington Junction.
it protected a 4 aspect signal when the line via Sway was 2 aspect signalled. It would show double yellow when level crossing gates were up. It was the only 4 aspect signal in the area as all others in Brockenhurst-Lymington Jct area were 3 aspect