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Theatre Display or Feathers?

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Theatre Display or Feathers?

Unread postby luckymucklebackit » Wed Sep 10, 2014 10:26 am

Hi - looking for advice on whether a signal I am planning for the layout would be correct practise. The signal would be three aspect and control the approach to a station which has three platforms, Platforms 1 and 2 are loops mainly used mainly by terminating trains, platform 3 is the through line with a platform face, trains stop in this platform but also run through this platform non-stop.
I was thinking of having the signal show a "1" or "2" in the theatre display along with a yellow aspect for trains taking the loops, but no theatre display indication and just a green aspect for trains running through or calling at platform 1, would this be prototypical, or should I try to rig up two feathers (more difficult).

Thanks

Jim
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Re: Theatre Display or Feathers?

Unread postby davidwoodcock » Wed Sep 10, 2014 11:37 am

It depends on the speed limit on the through road, although I a not sure whether there should be a theatre display no matter what route is set - the practice may have varied between companies/regions but I believe that SR versions always positively displayed the route set (which had the advantage that the display didn't have to be proved "alight").

I think the maximum permitted speed in modern practice is 40mph but suspect that it used to be 25mph.
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Re: Theatre Display or Feathers?

Unread postby Mike Hodgson » Wed Sep 10, 2014 6:08 pm

This document gives the industry's party line :
http://www.rgsonline.co.uk/Railway_Grou ... ss%203.pdf
The web site also contains a number of other relevant guidance papers.

But as David said, speeds will determine what you should do.
You would only use theatre type indicators at low to medium speed since they are not readable at high speed.

If the through route is fast (typically needing a "stand behind the yellow line" warning on the platform) you would use feathers, officially called Position Light Junction Indicators (PLJI); normally no feather is used for the main route, but there are exceptions where it makes for greater clarity.

If the speed over crossovers into the lesser platforms is much lower than the main, the signal into those platforms might be approach released from red, that is, it only clears as the train gets near it, limiting the preceding signal to single yellow and forcing trains to slow expecting to stop at the junction signal. This could be necessary if you are using theatre type indicators, so that trains are made to slow sufficiently to be able to read the indicator.

Whether the junction signal clears to yellow or green will depend on the platform's departure signal, which must obviously be Yellow or Green if a Green is to be displayed on the 3-aspect junction signal. If permitted speed through the loop platforms is much the same as on the main, the signal into the loops would also clear to green provided the signal back onto the main is showing a proceed aspect. All three departure signals could also have approach controls if necessary for speed limiting purposes. If any of the platforms were a terminal bay rather than a loop, the signal leading into it can only clear to yellow at best (since the Moorgate accident).

Different rules applied at earlier dates, so if your model is historical, you would need to specify approximate date and company.
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Re: Theatre Display or Feathers?

Unread postby luckymucklebackit » Wed Sep 10, 2014 7:02 pm

Thanks for that link Mike, I will read the document fully later. The era that the station is set is mid 1960s, with the signalling having been recently installed (I am thinking Perth as signalling installation that is closest to what is modelled)

Cheers

Jim
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Re: Theatre Display or Feathers?

Unread postby Pete2320 » Thu Sep 11, 2014 11:01 pm

It certainly was the practice on the North Eastern Region to use theatre route indicators with no indication for the main route, presumably where the main route was for higher speed than permitted for a theatre indicator. However, as it was also NER practice to provide a rear indication on theatres the rear indication would be displayed for all routes, presumably to avoid anyone working on the line from being misled into thinking that the signal was "on" if no route indication was displayed.

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Re: Theatre Display or Feathers?

Unread postby Mike Stone » Fri Sep 12, 2014 6:39 pm

Lack of any indication for trains preceding from p.11 or p.12 at Crewe has lead to at least one Anglo-Scot heading for Chester in error. I must say I am surprised to hear that it was NER practice - I thought it only came in at Crewe because of the use of theatre indicators to provide "feathers" meant that when the main route was set there would be no route that could be indicated
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