Signalling a move from Fast to Slow lines

[Steadfast]

1 minute ago, beast66606 said:

 

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

A nice touch!

 

Jo

[Ken.W]

On 29/12/2023 at 08:40, eatus-maximus said:

 

If the signaller has set the junction for the train to pass AND it will be clear to proceed (no conflicting movements), the process will start four 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 and finally a red aspect before the junction. As the train approaches (distance may vary by junction), the final signal will change to an appropriate proceed aspect (single yellow if the next one is red for example) and a route/junction indicator.

 

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.

 

 

No, Flashing Yellow aspects indicate that the the junction signal is cleared, but, for a lower speed diverging route, as the purpose is to allow the driver to brake according to the diverging speed at the turnout, instead of to stop at the junction signal. You do not get flashing yellows and then approach control. The sequence will be G - FYY - FY - Y With Junction indicator which can clear up on approach to YY or G if the line ahead is clear to permit.

 

A junction equipped for flashing yellows will operate as traditional approach control if the routes not clear to allow the junction signal to be cleared. The junction signal will then clear on approach if the route is then clear but the driver would be prepared to stop if it didn't.

A common example of this is Platform 1 Southbound at Darlington. Approach speed is 125, reducing to 90 on Up Main past the station. Speed for Pl.1 is 50 Main to Main then 40 into platform. Flashing yellows are provided, so normal sequence would be FYY - FY - Y+Position 4 feather - R at platform end. However, if a unit is departing from No.2 Bay this conflicts with the overlap beyond the Pl.1 end signal preventing the flashing yellows and normal approach control operates.

 

5 hours ago, Goodnight Sweetheart said:

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.

 

The fifth aspect signaling on the ECML - actually just Peterborough / Stoke Summit - is a flashing green aspect not an additional one, so the sequence is FG - G - YY - Y - R. For a diverging route with flashing yellows the normal sequence after the G follows, there isn't an additional steady YY aspect.

The FG permitted 140 mph running, for test running of the 91s when being introduced only, and a steady G meant reduce to 125. For the reason you gave it was never used for normal service, though we did* take a steady green as an early warning of a YY ahead where the next signal ahead couldn't be seen.

They do, mostly, still operate*, though there are some where the flasher unit has clearly failed and hasn't been replaced

 

* l last saw these 4 years ago now

 

All incidental really, unless you happen to be fortunate to be signaling Mr Waterman's Making Tracks layout, as these signals should be around a mile, and at least 3/4 mile apart. The OP referred to 125 running, and at that speed a train takes a full mile stop - and even that's with a full emergency application

[Mike_Walker]

11 hours ago, Goodnight Sweetheart said:

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.

No, it's a flashing green followed by steady green then double yellow, yellow, red.  This allowed a standard 4-aspect head to be used.

[eatus-maximus]

5 hours ago, Ken.W said:

 

No, Flashing Yellow aspects indicate that the the junction signal is cleared, but, for a lower speed diverging route, as the purpose is to allow the driver to brake according to the diverging speed at the turnout, instead of to stop at the junction signal. You do not get flashing yellows and then approach control. The sequence will be G - FYY - FY - Y With Junction indicator which can clear up on approach to YY or G if the line ahead is clear to permit....

 

I did say I was going from memory, which is going back 20 years, and to be fair I thought it was implicit that we were talking about a lower speed diverging route. I have adjusted my post though.