Feather vs Theatre Box

[TheEdge]

What decides if a signal will get a feather or a theatre display. I can understand why station approaches are more suitable for theatres than feathers but what about where both are equally suitable?

Lets say you had a through station with a starter with three possible routes. What would dictate which type of direction indicator it got?

 

[swt_passenger]

Whatever answers come up in other replies, I shall hereby add fuel to the fire by pointing out that feathers and letters are used at the same time at the London end of Reading West.

 

[SPADTrap]

If there are numerous more routes than a feather can display?

 

[IrishDave]

Linespeed is a major factor - feathers are much more easily visible than theatres, so feathers must be used over a certain speed (75mph, maybe?). At Coventry, for example, the home signals from Rugby and Birmingham both have feathers, not theatres, because the linespeed is 80mph for non-stopping trains, IIRC.

 

[LNW-GW Joint]

Isn't there a limit on the number of feathers allowed these days?
There used to be a signal at Reading before the resignalling which had 6 feathers.
I think that would have to be a theatre signal today using modern standards, to improve readbility.

 

[TheEdge]

If there are numerous more routes than a feather can display?

Thats the obvious one but given a feathered signal can display 7 routes (in theory) I doubt there are all that many applications where that would be a limiting factor.

 

[Railsigns]

Isn't there a limit on the number of feathers allowed these days?

Yes, six, although certain combinations are non-preferred.

There used to be a signal at Reading before the resignalling which had 6 feathers.

I don't believe there has ever been a signal in the UK with six feathers.

 

[ComUtoR]

Junction Indicator - Category 1 (long range)
Standard Alphanumeric Route Indicator - Category 2 (medium range)
Miniature Alphanumeric Route Indicator - Category 3 (short range)

Long Range - Readable between 300-800m
Medium Range - Readable up to 250m
Short Range - Readable up to 100m

That's the basics. There is a whole document with all the nitty gritty and the minutae of sighting. The only speed caveat I can find is if the speed is greater than 60mph but other conditions also apply.

 

[Railsigns]

By current standards, junction indicators cannot be used for routes into, or out of, terminal platform lines. They cannot be provided on any signal where all trains start from rest.

 

[NSEFAN]

They cannot be provided on any signal where all trains start from rest.

This is interesting, what is the reasoning for this rule?

 

[ComUtoR]

By current standards, junction indicators cannot be used for routes into, or out of, terminal platform lines.

I know a Junction indicator into a terminal platform.

 

[Railsigns]

I know a Junction indicator into a terminal platform.

So do I. Large parts of the network were signalled to earlier standards.

 

[ComUtoR]

I have found some more speed criteria too. It's a very verbose document :/

So do I. Large parts of the network were signalled to earlier standards.

The earliest colour light standard I have is 1992


A Good description I just read.

The signalling associated with a junction shall provide the train driver with clear, unambiguous indications of the route that the train is to travel in such a manner that he can safely control the train speed whilst at the same time not unnecessarily slowing the train

 

[Railsigns]

The earliest colour light standard I have is 1992

I have the original BR Standard Signalling Principles from 1960 - three pages of foolscap and two graphs.

S.S.P.7 concerned "Route Indicators on Running Signals".

 

[ComUtoR]

By current standards, junction indicators cannot be used for routes into, or out of, terminal platform lines.

I can't find this rule under the current standards. (or at least the most current version I have)

 

[Railsigns]

I can't find this rule under the current standards. (or at least the most current version I have)

Which standard are you looking at? It's in the Network Rail standard on junction signalling.

 

[ComUtoR]

That is what I'm looking at. Maybe I'm reading it wrong.

Using the flow chart it allows the provision of a junction indicator if the only diverging route is a bay platform. If it isn't then you provide a theatre box for the bay and you can still provide junction indicators for the rest of the diverging routes.

The signal I'm thinking of certainly conforms to being the only diverging route.

Unless there is another standard somewhere with a more overarching rule. I have noticed with group standards that they constantly refer to other standards. The junction one I'm reading also refers to signal sighting standards so there possibly may be some overlap ?

I hate trawling through group standards at the best of times but they are often an interesting read.

 

[Railsigns]

Using the flow chart it allows the provision of a junction indicator if the only diverging route is a bay platform. If it isn't then you provide a theatre box for the bay and you can still provide junction indicators for the rest of the diverging routes.

The first question in the 'divergences' flowchart (figure C2) asks "Is the route into a terminal platform?". Answering 'yes' takes you to either "MAR + SI" or "MAF + SI", so a standard alphanumeric route indicator is the only option available. Section 6.1 a) of the text says the same thing in words.

As you say, it is permissible for the same signal to have both an SI and a JI, each applicable to different routes, but any route(s) into terminal platforms must use the SI.

 

[ComUtoR]

Sent a PM to prevent going back and forth. Your usually pretty reliable with standards etc. So I'm gonna defer.

 

[t0ffeeman]

Used to be six feathers from on approach from say Coleshill to Nuneaton. Dunno if its still there though

 

[swt_passenger]

Used to be six feathers from on approach from say Coleshill to Nuneaton. Dunno if its still there though

A discussion in the signalbox forum a few years back suggested it only had five. Picture here: http://www.roscalen.com/signals/WestMids/7309/0156.jpg

 

[Class 170101]

Used to be six feathers from on approach from say Coleshill to Nuneaton. Dunno if its still there though

Some signals at Colchester have six routes because there an additional Position Light Signal to allow movements to the Goods Roads due to insufficient routes available to signal it I believe.

 

[Lockwood]

How come Platform 1 at Havant has letters rather than feathers after the resignalling?
Not all trains stop there (freight, XC, ECS)
There are AIUI only 2 options from there. Certainly 2 normal options.

 

[gimmea50anyday]

There "Havant" been any XC services from there since 2002......

 

[455driver]

There "Havant" been any XC services from there since 2002......

What about the daily ECS from Guildford to Eastleigh?

 

[Bigfoot]

Anyone else thinking BOOM? I am.

 

[swt_passenger]

How come Platform 1 at Havant has letters rather than feathers after the resignalling?
Not all trains stop there (freight, XC, ECS)
There are AIUI only 2 options from there. Certainly 2 normal options.

There's a relatively slow speed through Havant, 40 I think.

 

[physics34]

Sutton station.... you can leave towards london from any platform.

Platform 1 and 3 have feathers
platform 2 and 4 have theatre boxes. (displaying W for wallington and P for Portsmouth.)

Platform 1 and 3 are up platforms and are not reversible.

Platform 2 and 4 are down platforms with the ability of down services to "turn around" there, but trains cannot arrive from the south (unless they have travelled wrong road.)....

therefore the rule above about the platforms not being allowed to have feathers for trains that "start from rest" there applies in this instance too.

 

[ComUtoR]

therefore the rule above about the platforms not being allowed to have feathers for trains that "start from rest" there applies in this instance too.

I still cannot find where the current standards require that or the terminal platform requirements. I've had a good look. The latest standard I'm reading is 07/03/2015.

From the Guidance Notes

When deciding which type of route indicator to provide, it is important to take an holistic approach to the readability of the combined signal aspect and route indication

 

[Lockwood]

There's a relatively slow speed through Havant, 40 I think.

I have had to take SWT to Guildford and then change onto an XC that had gone fast from Fareham via Havant. In 2013. Probably on diversion.

Anyway. RailUK pedantry aside... How come a signal at a station where there are two routes gets a theatre? (I think that they can't go wrong road to Brighton or Waterloo)