Advice sought on a few signalling questions.

[phil-b259]

 

• The permanent red with shunt below at the platform ends is indeed a good solution. I have placed these. But what kind of main signal heads please?

 

As here - a single red aspect.

 

http://www.simplonpc.co.uk/BluebellRly2013/E-Grinstead_130326-1398.jpg

 

(Actually a 2 aspect head with one aperture blocked up)

[phil-b259]

 

• What solution for the end of service, when a second unit needs to enter the platform at the B end, while the platform A end already contains a stabled unit?

 

This is where a 'call on' signal is used.

 

In todays colour light signalled areas this takes the form of a position light shunt signal in outline, but it only has two white lights at 45 degrees. When the signalman sets the route, the main aspect STAYS at red and the two white lights illuminate so as to tell the driver they may proceed at caution (because they will be sharing a platform with something else).

 

See here for an example http://www.freefoto.com/images/23/70/23_70_63---Red-Railway-Signal_web.jpg

 

However if the signalling dates from the late 50s or 60s, then you could well have a 'floodlit disc' calling on signal (basically an motor worked semaphore style shunt signal the face of which was illuminated by a floodlight) in place of the position light signal.

 

See here for an example http://www.roscalen.com/signals/London/Victoria/7209/0105.jpg

 

You also need to remember that call on moves still require the driver to be given a route indication so the 'feather' / route indicator would still be lit just as if it was the main aspect that had changed to a proceed.

[phil-b259]

 

I have changed the feathers from 2B and 3B in to theatre indicatorboxes. These signals should remain 4-Aspect types?

 

What sort of indicator you use makes no difference to the type of aspects you use.

 

A 4 aspect signal MUST be followed by:-

 

Another 4 aspect

OR

A 3 aspect signal

 

In other word the next signal after a 4 aspect one must be capable of showing a single Yellow aspect so as to maintain the correct aspect sequence going downwards. Going from double yellow on a 4 aspect to a green on a 3 aspect is fine because that maintains the correct aspect sequencing as far as a driver is concerned - i.e. a driver is allowed to a signal step UP to a green from any colour but when going back DOWN a Green MUST be preceded by a double (for 4 aspect signalled areas) or a single yellow (in 3 aspect areas)

 

A real life example of the transition from 4 to 3 aspect signalling occurs at Three Bridges Station. The signals on the south ends of Platforms 2 & 3 are 4 aspect ones and behave accordingly if the route is set straight down to Brighton. However the line round to Horsham is signalled using 3 aspects so if that route is selected the platform signals will only display a Green or a single Yellow - NEVER a double.

 

-------------------------------------------------------------------------

A 3 aspect Red / Yellow / Green signal MUST be followed by:-

 

A 2 aspect red / green signal

OR

A 3 aspect Red / Yellow / Green signal

OR

A 4 aspect signal.

-------------------------------------------------------------------------

A 3 aspect signal not capable of showing a red (yes they do exist in certain places - i.e. it can show Green,/ double yellow / single yellow) MUST be followed by :-

 

A 3 Aspect Red / Yellow / Green signal

OR

A 4 Aspect signal

-------------------------------------------------------------------------

A 2 aspect Red / Green signal MUST be followed by either a

 

Fixed (as in cannot show anything else) single yellow signal

OR

A 2 aspect Yellow / Green repeater signal

OR

A 3 aspect Red / Yellow / Green signal

OR

A 4 aspect signal.

 

It MUST NEVER be followed by another 2 aspect Red / Green signal (unless the line is a very low speed freight line)

-------------------------------------------------------------------------

A 2 aspect Red / Yellow signal should be followed by:-

 

A fixed single red aspect (or a buffer stop lamp)

 

But may be followed by

 

A 2 aspect Red / Green signal

OR

A 3 aspect signal

OR

A 4 aspect signal

 

While technically these later 3 options don't break any signal sequencing rules - if the next signal after a  2 aspect Red / Yellow signal can show a Green, it sort of destroys the point of having a 2 aspect Red / Yellow signal in the first place.

[59004 ( was Shedcombe....)]

Hi Phil,

 

Thanks for this wealth of information. Of course all logical, but a lot to take in and grasp.

 

I have amended my signaling diagram and have also drawn the signals in on the layout trackplan.

 

Going by these two, I still have a few quenstions to get answers to.

 

Apologies if some or all should have been clear, from your information just given.

 

Going by the images :

 

• The two ground signals off the stabling are positioned on the gantry. What type of signals should they actually be on there?
   
• The starter signals from Platform 2B and 3B, are these logical to be 4 Aspect (with Theatre boxes), or rather 3 Aspect or even 2 Apect?
   
• The signal in to Platform 2 and 3, I've drawn in as 2 Aspect Y/R, with Theatrebox (for 2 or 3) AND Call On (for just 2B or 3B instead of 2 or 3). Is this correct?

 

Regards,

Michel

 

 

 

[ForestPines]

To my mind that 2-aspect signal looks a bit unnecessary. I'd think it more likely that coming from road C you would have a 4-aspect signal with 2 RH feathers (one pointing right and up and one pointing horizontally right) and call-on, and from road D, either an identical signal, or one with one LH and one RH feather.

 

The aspects for platforms 2 and 3 from road C would be a single yellow with feather if the platform was empty, and a call-on with feather if the platform was occupied. In both cases the aspect would be red until the train approached. The double yellow and green aspects would only show for the main route (and would depend on the following signal). Whether you allow a call-on route into the main platform depends on whether on not you think you need to be able to - but if you do, you should only be able to call-on if the signal at the other end of the platform is red.

 

If you had both LH and RH feathers on D, then you would show the LH feather for routes into the main platform and no feather for routes into P2. I don't think main aspects from this signal would need to be approach-released, because all routes would be the same speed, but call-on aspects would be.

 

You could have a theatre box on the P2/P3 departure signals, but I suspect - because you only have two routes from each signal - a single LH feather on each signal would be more likely.

 

The above is assuming a roughly late-70s installation designed purely for multiple unit working into P2/3. If your signalling was designed for loco-hauled workings it might well be more complex. In fact, if you envisage a need for a train to swap between P2 and P3 you would at the least need some ground shunt signals on roads A and B, facing for moves into the station, so a train can shunt out towards the tunnel and reverse back into the station. You may also want shunt aspects on the P2/3 departure signals, which would be for trains doing the same move via roads C and D. In this case there would be either "limit of shunt" boards or fixed red shunt signals for trains shunting out of the station on C or D, just over the maximum train length away from the signals for trains entering the station - so a train has room to shunt out of the station and reverse back in.

[phil-b259]

 

• The starter signals from Platform 2B and 3B, are these logical to be 4 Aspect (with Theatre boxes), or rather 3 Aspect or even 2 Apect?

 

Please have a re-read of my post and think about it.

 

While technically a 2 aspect can be followed by a 4 aspect it poses significant operational restrictions. Remember that if the two aspect (Red / Green presumably) is at Green the following signal MUST be:-

 

Double Yellow or Green if it is a 4 aspect

OR

Yellow at a 3 aspect.

 

You CANNOT have a two aspect Red / Green signal followed by a 4 aspect signal showing a red or single yellow aspect. Thus mixing 2 and 4 aspect signals simply doesn't happen - you either have 2 & 3 aspects mixed together or 3 and 4 aspects mixed together.

 

A 3 aspect on the other hand could be followed by a 4 aspect signal BUT if your signal governing the exit from platform 4B is a 4 aspect, then having a 4 aspect in the exit from platforms 2 & 3 is more logical as it makes things more straightforward for drivers.

 

 

 

• The two ground signals off the stabling are positioned on the gantry. What type of signals should they actually be on there?

 

 The same type as if they were on the ground - a mechanical floodlit disc signal (like the call on posted earlier by without the "C" on the disc basically) or a position light signal (he triangular shaped thing with three lights on it)

[The Stationmaster]

Please have a re-read of my post and think about it.

 

While technically a 2 aspect can be followed by a 4 aspect it poses significant operational restrictions. Remember that if the two aspect (Red / Green presumably) is at Green the following signal MUST be:-

 

Double Yellow or Green if it is a 4 aspect

OR

Yellow at a 3 aspect.

 

You CANNOT have a two aspect Red / Green signal followed by a 4 aspect signal showing a red or single yellow aspect. Thus mixing 2 and 4 aspect signals simply doesn't happen - you either have 2 & 3 aspects mixed together or 3 and 4 aspects mixed together.

 

A 3 aspect on the other hand could be followed by a 4 aspect signal BUT if your signal governing the exit from platform 4B is a 4 aspect, then having a 4 aspect in the exit from platforms 2 & 3 is more logical as it makes things more straightforward for drivers.

 

 

 

 The same type as if they were on the ground - a mechanical floodlit disc signal (like the call on posted earlier by without the "C" on the disc basically) or a position light signal (he triangular shaped thing with three lights on it)

But you can have a 2 aspect red/yellow followed by a 3 or 4 aspect.  However very unlikely in this scenario - the 'bay platform starters' would inevitably have been 3 or 4 aspect.

 

PS the discs were electrically worked - not mechanical

[phil-b259]

But you can have a 2 aspect red/yellow followed by a 3 or 4 aspect. However very unlikely in this scenario - the 'bay platform starters' would inevitably have been 3 or 4 aspect.

Erm, that's what I said - but in slightly different words

[phil-b259]

PS the discs were electrically worked - not mechanical

Badly worded on my part - the term mechanical was meant to indicate physical movement rather than different couloirs lights being illuminated as on the colour light equivalent.