Signalling a move from Fast to Slow lines

[jpendle]

Hi,

 

This is about colour light signals on todays railway.

Let’s suppose a Pendolino is belting along at 140mph in a 4 aspect signalling area.

The signal operator needs to send the Pendo into a loop or onto the slow lines, how is that done?
Clearly there’ll be a feather on the signal at the junction itself but how are earlier signals set to tell the driver that they’ll be taking a diverging route and will need to slow down?
 

Thanks,

 

John P

[Davexoc]

Flashing yellow aspect, only done on single I think. So slowed by the double yellow, flashing single yellow warns that the route diverges, then the junction yellow with feather...

Thinking Ledburn and Bletchley South on WCML....

Edited December 28, 2023 by Davexoc
added

[jpendle]

Smashing, thanks.

 

John P

[russ p]

Not always preceeded by flashing yellows often two yellow, one yellow and red which is approaching controlled which will clear to the appropriate aspect with a feather 

[Michael Hodgson]

54 minutes ago, jpendle said:

Hi,

 

This is about colour light signals on todays railway.

Let’s suppose a Pendolino is belting along at 140mph in a 4 aspect signalling area.

The signal operator needs to send the Pendo into a loop or onto the slow lines, how is that done?
Clearly there’ll be a feather on the signal at the junction itself but how are earlier signals set to tell the driver that they’ll be taking a diverging route and will need to slow down?
 

Thanks,

 

John P

It shouldn't be.  Pendolinos whilst capable of 140 are limited to 125 in the UK.  Only HS1 is authorised for very high speed (300  kph/186 mph Eurostars or 140 for Javelins).  There was an experiment on the ECML of 5-aspect signalling (flashing green allowing higher speeds than 125 for Class 91 only).  The signals still work that way, but the decision was taken that lineside signals were not good enough (drivers don't get long enough to see them clearly) so in-cab signalling is required for speeds in excess of 125.  Ultimately we probably won't have lineside signals.

 

The signalling for a crossover onto the slow would indeed normally be a feather over a proceed indication, but the details of how it operates would vary according to the speed difference between the main route and the divergence and complex cacluations may be involved in the design.  The junction signal (or in some cases the first signal after the junction on the divergent route) may be held at red to ensure that the diverging train runs through the usual sequence of YY, Y and reduces speed sufficiently for the junction, and clearing only when the train is proven to have slowed, probably reinforced by TPWS.  This can be measured by a timer on the occupation of a track circuit before the signal, the next track not yet having been reached.  These techniques - approach control (from red), approach control from yellow can be used,  or the flashing yellow signals mentioned could be used.

 

Another way of giving advance warning to drivers the route they are to take at a junction is the use of Preliminary Route Indicators (PRIs) - see 6.62 on this page https://www.railsigns.uk/sect6page5.html

[Mol_PMB]

For chapter and verse, this may be relevant, or may just be confusing...

 

https://www.gov.uk/raib-reports/report-06-slash-2023-train-overspeeding-at-spital-junction

[Mark Saunders]

3 minutes ago, Mol_PMB said:

For chapter and verse, this may be relevant, or may just be confusing...

 

https://www.gov.uk/raib-reports/report-06-slash-2023-train-overspeeding-at-spital-junction

The UK uses route signalling rather than speed signalling as on the continent.

[Michael Hodgson]

1 hour ago, Davexoc said:

Flashing yellow aspect, only done on single I think. So slowed by the double yellow, flashing single yellow warns that the route diverges, then the junction yellow with feather...

Thinking Ledburn and Bletchley South on WCML....

Full sequence would be green, flashing double yellow, flashing single yellow, yellow with a feather.  See 2.132/2.133 on this page  https://www.railsigns.uk/sect2page7.html

This gets complicated if 2 junctions are close together, as they have to restrict overlapping combinations of aspects that could otherwise arise. 

[Mol_PMB]

5 minutes ago, Mark Saunders said:

The UK uses route signalling rather than speed signalling as on the continent.

The link I posted is an investigation report into an incident in the UK, on the ECML approaching Peterborough, where a train was signalled from the fast lines onto the slow lines, and ended up significantly over-speeding over the junction.

The correct signal sequence was followed, but the driver misinterpreted the final aspect clearing to green and didn't see the feather, thinking they were proceeding on the main line. The distance from the signal to the crossovers, and the rapid acceleration of the train, allowed a very considerable overspeed.

[jpendle]

Thanks for all the replies.

 

I know that 140mph isn't done these days, pity!

 

Anyhow, the root of my question was in regards to signalling my WCML N Gauge layout.

 

I'm playing around with 4 aspect signals in iTrain and it's going to be a steep learning curve. iTrain's Automatic signals are based on German speed signalling rather than UK route signalling.

 

 

I currently have 1 working 4 aspect signal and a signal decoder. I doubt that I'm going to be buying any more stuff until I've been able to get head around signals in iTrain.

 

Regards,

 

John P

[Steadfast]

I've always been told the lowest speed divergence you'll get flashing signals for is 40 mph. Junction speeds elow that you'll get checked down double yellow, single yellow then red, and the red will then clear to a colour and a feather.

49 minutes ago, Michael Hodgson said:

Full sequence would be green, flashing double yellow, flashing single yellow, yellow with a feather.

You can also have that sequence but with a green with a feather. 

 

Jo

[russ p]

6 hours ago, Steadfast said:

I've always been told the lowest speed divergence you'll get flashing signals for is 40 mph. Junction speeds elow that you'll get checked down double yellow, single yellow then red, and the red will then clear to a colour and a feather.

You can also have that sequence but with a green with a feather. 

 

Jo

 

Used to be Jo but get flashing yellows at long Eaton for a 20mph junction 

[eatus-maximus]

On 28/12/2023 at 18:10, jpendle said:

....Anyhow, the root of my question was in regards to signalling my WCML N Gauge layout.

 

I'm playing around with 4 aspect signals in iTrain and it's going to be a steep learning curve. iTrain's Automatic signals are based on German speed signalling rather than UK route signalling.

 

 

I currently have 1 working 4 aspect signal and a signal decoder. I doubt that I'm going to be buying any more stuff until I've been able to get head around signals in iTrain....

 

In the UK, from memory, there are two ways that a 'high speed' junction could be approached.

 

If the signaller has set the junction for the train to pass AND it is clear to proceed (no conflicting movements), the process will start three signals away from the junction. The driver will see two flashing yellow aspects, followed by one flashing yellow aspect, then a steady single yellow aspect with route/junction indicator before the junction. The driver should expect the signal after the junction to be red. As the train approaches (distance may vary by junction), the signal may change to a less restrictive aspect.

 

If the signaller has NOT set the junction and/or it is NOT clear to proceed over the junction, the process starts three signals before the junction. The signal will show two steady yellow aspects, the next one yellow aspect, and then the final signal before the junction is red. It will stay red until the route is set and the route is clear to proceed.

 

As always, if the route clears and the junction is set whilst the train is approaching, a signal may change. For example, a double yellow aspect could change to a single flashing yellow.

 

A route/junction indicator is only shown on the final signal before the junction. The indicator will usually only show for a diverging route, but there are exceptions.

 

This process may change if there is a signal in the middle of 'a junction', see the Colwich accident (1986??) for more gruesome details on that!

Edited December 31, 2023 by eatus-maximus
Correction

[Steadfast]

8 hours ago, russ p said:

 

Used to be Jo but get flashing yellows at long Eaton for a 20mph junction 

Thanks Russ, always changing this railway of ours!

 

Jo

[WillCav]

There are five forms of modern junction signalling. In order of speed (slowest first)

 

1. MAR (Main aspect Approach released from Red)

4 aspect sequence is:

G - YY - Y - R stepping up to Y/YY/G with feather/standard indicator as appropriate.

 

2. MAY (Main aspect Approach released from Yellow)

Sequence is G - G - YY - Y with route indicator 

This is rare / non-existent on the Western where I work

 

3. MAY-FA (Main aspect Approach released from Yellow with Flashing Aspects)

Sequence is G - FYY - FY - Y with route indicator stepping up appropriate on Approach.

If the FYY  signal displays a route indication for a previous junction then the Sequence would be G - YY+route indication - FY - Y with route indication.

If the signal beyond the junction is at red then Colwich controls are generally implemented- the junction signalling is restricted down to MAR.

Flashing aspects and/or feathers are not permitted into bay lines. 

 

4. MAY-SD (Main aspects Approach released from Yellow with Splitting Distant)

Aspect Sequence is pretty complex with double headed signal(s) approaching the junction.

 

5. MAF (Main Aspect Free) no Approach control where divergent line is within 10mph of main line.

 

Hope this helps a bit!

 

Will (signal design engineer by trade)

Edited December 29, 2023 by WillCav
Typo

[Rugd1022]

There are lots of junctions on my route card where you'll be a given green, two flashing yellows, one flashing yellow then one yellow with the appropriate route indicator illuminated, in many cases the junction signal will step up to green just as you approach the AWS ramp if the route you're taking is already clear - a good example of this is Hanslope Junction on the WCML which is 70mph. The flashing yellows tell the driver that he / she is guaranteed to have at least a single yellow and the appropriate route indicator showing at the junction signal. This allows you to keep your momentum up which is easily lost if you're brought down to the junction without the flashing yellows.

Edited December 29, 2023 by Rugd1022

[Mike_Walker]

1 hour ago, WillCav said:

Flashing aspects and/or feathers are not permitted into bay lines.

Which is exactly what I was taught but I know of at least one exception.

 

Unless it's been altered in the last couple of years, signal ME137 approaching High Wycombe displays a flashing single yellow when ME139 is showing a yellow main aspect and position 1 route indicator to take you into the bay platform.  Always caused a comment from drivers.

 

[WillCav]

22 minutes ago, Mike_Walker said:

Which is exactly what I was taught but I know of at least one exception.

 

Unless it's been altered in the last couple of years, signal ME137 approaching High Wycombe displays a flashing single yellow when ME139 is showing a yellow main aspect and position 1 route indicator to take you into the bay platform.  Always caused a comment from drivers.

 

Mike,

 

What I should have said is that we're not allowed to do that for a new design.  There are lots of weird and wonderful arrangements that were put in at different times and regional variations.

 

I also should have said that a junction signal can have different junction signalling methods on different routes.

Eg.

MAR with a standard indicator to a bay and MAY-FA with a feather to a different through line.

 

Will

[The Pilotman]

On 29/12/2023 at 09:25, WillCav said:

Flashing aspects and/or feathers are not permitted into bay lines. 

Signal T2865 Newbury East Junction, the route from Down Westbury to Platform 3 (bay) is a position 5 junction indicator. Not flashing aspects but definitely “feathers.”

Edited December 30, 2023 by The Pilotman

[Mike_Walker]

6 minutes ago, The Pilotman said:

Signal T2865 Newbury East Junction, the route from Down Westbury to Platform 3 (bay) is a position 5 junction indicator. Not flashing aspects but definitely “feathers.”

Agreed.  I know of many locations where the route into a bay or other dead end line is indicated by a "feather" on schemes implemented over a wide period of time, from the 1960s into the 21st century although I know of no other situation with a flashing approach as at High Wycombe which is probably unique. 

 

@WillCav's assertion that feathers are no longer permitted into bays seems decidedly odd to me.  If this is the case what indication is given to the driver that he is going into a dead-end?  If it were applied at High Wycombe, for example, then would they see the same single yellow at ME139 for both the bay and continuing along the Down Main and platform 2 to ME151 if that were displaying red.  The distance from ME139 to ME151 is considerably further than to the blocks on the bay line so different braking would be required and the driver needs to know.

 

I have recently come across some new works where a standard alpha-numeric indicator (SI or "Theatre Box") is provided at some locations which remains dark unless a specific route is selected which is therefore presumably the new standard for situations such as High Wycombe and Newbury.  

 

By the way, before anyone asks, the dark indication is not an issue and cannot be mistaken for a failure just as in the case of a dark feather.  As part of the detection and interlocking, a signal will not clear to a proceed aspect if the system detects the required route indication has failed to display.  If you are fortunate enough to be observing a signal as it clears you will see the junction indication illuminates a second or so before the main aspect clears.

[Stoke West]

16 minutes ago, Mike_Walker said:

Agreed.  I know of many locations where the route into a bay or other dead end line is indicated by a "feather" on schemes implemented over a wide period of time, from the 1960s into the 21st century although I know of no other situation with a flashing approach as at High Wycombe which is probably unique. 

 

@WillCav's assertion that feathers are no longer permitted into bays seems decidedly odd to me.  If this is the case what indication is given to the driver that he is going into a dead-end?  If it were applied at High Wycombe, for example, then would they see the same single yellow at ME139 for both the bay and continuing along the Down Main and platform 2 to ME151 if that were displaying red.  The distance from ME139 to ME151 is considerably further than to the blocks on the bay line so different braking would be required and the driver needs to know.

 

I have recently come across some new works where a standard alpha-numeric indicator (SI or "Theatre Box") is provided at some locations which remains dark unless a specific route is selected which is therefore presumably the new standard for situations such as High Wycombe and Newbury.  

 

By the way, before anyone asks, the dark indication is not an issue and cannot be mistaken for a failure just as in the case of a dark feather.  As part of the detection and interlocking, a signal will not clear to a proceed aspect if the system detects the required route indication has failed to display.  If you are fortunate enough to be observing a signal as it clears you will see the junction indication illuminates a second or so before the main aspect clears.

The same way feathers illuminate prior to the aspect . If entering an occupied loop , feather with subsiduary illuminated

[Michael Hodgson]

2 hours ago, Stoke West said:

The same way feathers illuminate prior to the aspect . If entering an occupied loop , feather with subsiduary illuminated

The reason for the slight delay is that it takes time to prove the feathers alight.  This transient state is the only time you should see red plus feathers. 

 

The reason it must be lit is that that Y or G without feathers means proceeed on main route so would be a wrong-side failure if the diverging route were set.  It would be dangerous in some cases as the speed of the diverging route is often lower than for the main, and a driver could overspeed onto the branch having been signalled to proceed at the linespeed of the main route.

[Steadfast]

Well, I've just learned why the feathers light first when the signal clears. I'd often wondered why, and it's a distinctive feature. I don't think I've seen it modelled on a layout with colour light signalling.

 

Jo

[Goodnight Sweetheart]

On 28/12/2023 at 18:38, Steadfast said:

I've always been told the lowest speed divergence you'll get flashing signals for is 40 mph. Junction speeds elow that you'll get checked down double yellow, single yellow then red, and the red will then clear to a colour and a feather.

You can also have that sequence but with a green with a feather. 

 

Jo

UP Main to Line B (Leckwith North Junction m, Cardiff) is 25mph with flashers provided,

 

The added magic is if the route is set UP Main to line A 25mph to 15mph you won’t get the flasher a conditional single yellow only with the next red releasing once the track section has been occupied for X time.

 

Likewise the other side of Cardiff DN to UP Relief (25mph) can provide a flasher, and conditional release depending on how far in advance the route was called (3 sections to get the flasher).

 

The odd one is DN main cross Moorland Road isn’t flasher equipped (70mph) even with a q 40th PSR very very close after completing the crossing.

 

But, trying to answer the OP…

 

140 running on the ECML had a fifth aspect added to signals another green.

 

So you’ve get GG G YY Y R as a normal sequence of signals for a stop, or GG G YY FYY FY G + Feather for a crossing move, I think there was one junction up north somewhere set up for very high speed crossing so the sequence would be different probably with primarily route indicators in addition to the crossing sequence of signals.

[beast66606]

8 hours ago, Steadfast said:

Well, I've just learned why the feathers light first when the signal clears. I'd often wondered why, and it's a distinctive feature. I don't think I've seen it modelled on a layout with colour light signalling.

 

Jo

 

Widnes had this modelled - I wrote the software to control it