Platform starter signal

[daryll]

We are talking coloured light signals.

in  absolute block signalling on a terminus station , are the platform starters 2 or 3 aspect , and  , if 2 aspect are they red/green or yellow / green or another combination .

If 3 , what are the colours , a Minories type layout

[Joseph_Pestell]

There has to be a red so trains can not pass unless the route is set.

 

Could be 2 aspect or 3 aspect depending on the supposed track layout ahead (including anything off-scene and not modelled). 

[bécasse]

Colour light signals as platform "starters" are unlikely to have been erected in isolation but as part of a scheme. Even if that scheme generally used wide-headway colour light signals (effectively replicating the distant+home approach of semaphores but without individual signal boxes) there is likely to be a further "starter" signal ahead of the platform starters, if only to facilitate shunting from one platform to another, and that would mean the platform starters would have G/Y/R three aspect heads. If it was a multiple-aspect-scheme, they might well have Y/G/Y/R four aspect heads. The rule for the colour positions was that the red aspect was always the closest to the driver's eyeline, but for platform starters that almost invariably meant the lowest.

 

In recent years LED signals have come to the fore and two- or three-aspect LED signals actually only have a single lens which can display the three colours (obviously not at the same time), while four-aspect signals have a second lens spaced out above the multicolour one which, when lit, can only display yellow as one part of the double-yellow aspect.

[dave55uk]

10 hours ago, bécasse said:

... they might well have Y/G/Y/R four aspect heads...

Terminus platform starters would be 3 aspect (R/Y/G) as the double yellow is used to give an increased braking distance, something not necessary from a terminus.

 

 

[St. Simon]

12 hours ago, bécasse said:

Colour light signals as platform "starters" are unlikely to have been erected in isolation but as part of a scheme.

 

Hi,

 

Quite legitimate for Platform Starters to be Colour Light in a semaphore area.

 

1 hour ago, dave55uk said:

Terminus platform starters would be 3 aspect (R/Y/G) as the double yellow is used to give an increased braking distance, something not necessary from a terminus.

 

Again, legitimate for Terminal stations to have 4-aspect starters.

 

There are a couple of books that explain all about Colour Light Signalling 👇

 

Simon

[Michael Hodgson]

The OP has specified absolute block signalling, not a more modern multiple aspect scheme.  So the original semaphore platform starter would have shown red or green lights at night. 

 

It could be replaced a 2-aspect colour light, G/R from top to bottom to show the same aspects, EXCEPT where was either a further ("Advanced") Starting signal before leaving the area or a distant arm for the next box below the starter.  In that case it would be 3-aspect G/Y/R, only capable of showing G if the advanced starter/ lower distant arm was off.  A "searchlight" signal could alternatively be used, which had a single lamp with movable coloured lenses to show the same aspects.

 

It is perhaps worth noting that at night a semaphore stop arm over a distant shows red over yellow, or green over yellow, or two greens - and the early Paddington scheme had colour lights which followed this practice using two searchlight signals.  See https://www.railsigns.uk/sect2page6.html  2.109 to 2.111

 

Rarely applicable to a starting signal at a terminus, but 4-aspect signals were not necessarily Y/G/Y/R.  Earlier schemes favoured G/Y/R/Y.  There was always another lamp between the two yellows to space them out, as it could be difficult to tell from a distance whether you were seeing single or double yellow if they are too close together.

 

The final signal inbound to the terminus would these days only show red or yellow (with a subsidiary call-on provided for use if the platform was partly occupied); before the Moorgate accident on the Underground, green rather than yellow was usual.

 

 

Some urban systems (London Underground, Tyne & Wear Metro etc) only use two-aspect G/R signalling, although G/Y repeaters may also be provided.

 

 

[RailWest]

>>>>...EXCEPT where was either a further ("Advanced") Starting signal before leaving the area or a distant arm for the next box below the starter.  In that case it would be 3-aspect G/Y/R, only capable of showing G if the advanced starter/ lower distant arm was off.....

 

However, I think you will find that the two C/L Starting signals at Portishead were R/G only. Stationmaster might know more....:-)

[Grovenor]

6 hours ago, dave55uk said:

Terminus platform starters would be 3 aspect (R/Y/G) as the double yellow is used to give an increased braking distance, something not necessary from a terminus.

See http://www.norgrove.me.uk/signalling/plans/Euston-a.gif

[dave55uk]

44 minutes ago, Grovenor said:

See http://www.norgrove.me.uk/signalling/plans/Euston-a.gif

Thats hardly a minority type layout though :-)

[The Stationmaster]

As noted by 'Railwest'. the colour light platform starting signals at the new (1954) Portishead station were 2 aspect colour lights showing red or green; the next signal in advance was a semaphore stop signal.  

 

The platform starters at Glasgow Queen St - until the platform extensions and resignalling in, I think, the early years of this century - were also 2 aspect although I'm not sure what colour the proceed aspect was but memory suggests that it too was probably green (It's along while since I saw them).

 

The 1938 insrtallation at Hull Paragon had 2 aspect  r/g platform starters while the installation at Leeds from a similar time period had 3 aspect signals.  As ever the decision was influenced by layout factirs and the spacing of successive signals.

 

The platform starters at Liverpool Lime St were 2 aspect (R/Y) with the introduction of the Westinghouse power frame and remained so at the time of resignalling in connection with electrification work.  The location was however very unusual with successive signal very closely spaced.

 

Also in Glasgow illustrated below is one of the platform starters at Glasgow Central reading to the next signal only a short distance in advance of it again 2 aspect r/y (I think).  Similar sort of arrangement to Lime St with a two aspect signal protecting points  between it and, in this case, the signal which would serve for a longer train.

 

 

 

Illustrated below is the two aspect r/g bay platform starter at Twford with a draw-ahead subsidiary although in the most recent resignalling this has become a 3 aspect signal with no sub.

 

 

 

 

Over the years  there have, of course, been numerous example of 4 aspect terminal platform starting signals and some no doubt still exist.  St Pancras and Euston were  probably for many years the best known examples in London.   The reason for using 4 aspect signals in such situations is veru logical because with potentially closely spaced signals in complex track area they create for a Driver the opportunity to accelerate to a higher speed than would be possible if only 3 aspect signals were used.

Edited March 28, 2023 by The Stationmaster

[phil-b259]

On 27/03/2023 at 07:41, dave55uk said:

Terminus platform starters would be 3 aspect (R/Y/G) as the double yellow is used to give an increased braking distance, something not necessary from a terminus.

 

 

 

Not so!

 

Having a 4 aspect starting signal will mean the signals further ahead are closer together and therefore the quantity of trains which can be run will be grater.

 

Now while a small two platform location is unlikely to have a service frequency high enough to warrant it, larger termini with significantly more platforms but constrained approaches can easily require them

[5BarVT]

3 hours ago, The Stationmaster said:

Also in Glasgow illustrated below is one of the platform starters at Glasgow Central reading to the next signal only a short distance in advance of it again 2 aspect r/y (I think).  Similar sort of arrangement to Lime St with a two aspect signal protecting points  between it and, in this case, the signal which would serve for a longer train.

 

Hi Mike et al,

All the ‘platform starters’ at Glasgow Central were 3 aspect RYG reading up to Gantry A where the 4 aspect started.  There were then inner signal 2 aspect RG which protected conflicts ‘inside’ the starter.  The Inner signals required the starter off before they could show green.  So in the photo above, G44 is a 2 aspect RG, 69m to G54 3 aspect and another 57m to G86 4 aspect on Gantry A in the background.

 

In the past, when there was engineering works requiring the sleeper to run with both portions from Glasgow, it was too long to fit inside the platform starter (G54) so was started from Gantry A.

 

Paul.

[The Stationmaster]

13 minutes ago, 5BarVT said:

Hi Mike et al,

All the ‘platform starters’ at Glasgow Central were 3 aspect RYG reading up to Gantry A where the 4 aspect started.  There were then inner signal 2 aspect RG which protected conflicts ‘inside’ the starter.  The Inner signals required the starter off before they could show green.  So in the photo above, G44 is a 2 aspect RG, 69m to G54 3 aspect and another 57m to G86 4 aspect on Gantry A in the background.

 

In the past, when there was engineering works requiring the sleeper to run with both portions from Glasgow, it was too long to fit inside the platform starter (G54) so was started from Gantry A.

 

Paul.

But don't forget that plenty of trains star away from in rear of the 2 aspect signals hence as far as the Rule Book is concerned they were;are the signals required to show a proceed aspect before the Driver could be given the signal to start,.  And in at least one case because of the platfirm curvature and structures the 2 aspect signal is the only one a Driver can see before starting away so, again in accordance with the Rules, that is the one that allows him to start away unless an Instruction in the Sectional Appendix gives him authority to do otherwise.