SNCF signals?

[JeffP]

Can any kind person explain the system of colour light signalling on French lines, please?

I've recently had quite s few cabrides, courtesy of You-tube, and noticed they seem to have two red lights?

And some signals seem to have lights horizontally aligned?

Also, in some yards, I've seen what appeared to be purple lights?

[Andy Hayter]

Purple lights are used in sidings and I suppose the closest UK equivalent would be a shunting signal. 

[Suzie]

Wikipedia has a good page for this:-

 

https://en.wikipedia.org/wiki/French_railway_signalling

 

But to answer your specific points two reds will be found on an absolute signal protecting a junction and means stop and do not pass, whereas a single red may be permissive depending on the specific signal type such as a block signal. The purple is equivalent to two reds and is used in a similar way to the way a ground signal would be used here to protect the exit from a yard (purple equivalent to two horizontal reds, white equivalent to two inclined whites).

[Pacific231G]

This is obviously a fairly huge subject, especially when it comes to which signals are used in what situations. However, the basic indications shown to drivers are fairly simple and are still based on the Code Verlant  introduced in about 1930 following difficulties experienced during WW1 when drivers often had to work over "foreign" company's lines. In times of "National Emergency", a single national code enabled drivers to operate on lines without proper route knowledge. It also brought French signalling into line with agreed international standards where green replaced white for line clear and yellow replaced green for caution. 

 

The basic principles are that protection signals, block signals and speed restriction signals are different and have their own indications and that the indications displayed by colour light signals should be the same as those displayed at night by mechanical signals. The names of colour light signals, such as disque rouge, carré, carré violet and sémaphore generally reflect the mechanical signals that they have almost entirely replaced though a colour light signal head can include several indications. 

These are the main Code Verlant indications From a chart issued around the the time of their introduction.

With mechanical signals, to avoid the constellation of different coloured lights facing drivers at night,  only the most restrictive aspect was supposed to be shown but that depended on the lighting being electrical rather than oil (Think of the equivalent of a British junction signal with a main stop showing green, main distant yellow, branch home red and branch distant yellow)  so it didn't happen immediately.

Colour light signalling later added a few additional indications - by flashing the lights- and there are a couple of others such as the Guidon d'Arret - a horizontal red bar often used to protect level crossings from shunting moves- that is an absolute stop signal when lit but deemed to not exist at all when it isn't (It's supposed to represent a manual signal flag)

 

Taking them in order,

The disque (as a colour light often on  a round signal head) is a deferred stop signal requiring drivers to slow down immediately to a speed where they can stop on sight and to stop, unless signalled forward, at a defined pont, often the first set of points coming into a station. It tends to be found on more lightly used lines and, with an open block system, protects activites within a station or on a private siding between stations.

The carré (meaning square from its mechanical shape) is an absolute stop signal indicated by two red lights (arranged horizontally or vertically) that protects junctions or multiple routes out of a station.

The carré violet (mauve square) is also an absolute stop signal that mostly protects running lines from exits from voies de service (sidings. depots, yards  etc) but they can also be used to signal reversing moves on voies principal (on which passenger trains can run) . Making it a different colour meant that a driver proceeding through a station at speed wouldn't be faced with so many red signals that didn't apply to him.  Normally, as a shunting signal, its clear aspect is white meaning that it doesn't  clear a train  to proceed on its onward journey onto the main line until it has passed a green indication from a Carré or Sémaphore. Sometimes though, an open  carré violet may clear trains from a voie de service to proceed onto the open main line and these will display a green aspect when clear 

The Sémaphore is a block signal displaying a single red light when closed that controls whether or not a driver can proceed into the next block section. They're normally mounted at the start of each block and can be passed for shunting moves but some were mounted near the centre of a station and could also be passed by a train that was stopping in the usual place on a platform.

The avertissement ,  with a single yellow light when closed is roughly equivalent to a distant signal and gives warning of a stop signal ahead, either a sémaphore or a carré and also of certain speed reductions.

Not shown here as it only applied to colour light signalling is the Signal de préavertissement  

showing green over yellow when closed that gives advance warning of an avertissement at reduced distance from the stop signal.

The other two signals are ralentissement (reduce speed)- two yellow lights side by side -and rappel de ralentissement (reminder to reduce speed) with two yellow lights one above the other. They are normally closed when a junction is set for the branching road and indicate a speed reduction to 30 km/h,  typically before a set of points when the junction road is to be taken. The ralentissement is set at a suitable braking distance before the points and the rappel immediately before them to show from where the speed limitation applies. It is these signals that give colour light signal heads some of their odd shapes. For junctions that can be take at higher speeds these signals are replaced  by T.I.V.s (Tableaux indicateurs de vitesse limite)  with the max. speed in km/h indicated (at a suitable braking distance) by black letters on a white diamond, followed by the rappel   with white letters on a square black background. These are either mechanically turned towards the driver when the points are set to diverge  and illuminated separately or simply self-illuminated with whilte lights.  

 

Most of this is based on the 1960 SNCF rule book but, though there may have been some changes, French trackside signalling still follows the Code Verlant. 

 

 

 

 

 

 

 

 

 

 

 

[Gordonwis]

Horizontal lights can also be the equivalent of UK 'junction feathers'

[JeffP]

Thanks to all.

I can now enjoy my cabrides without having to puzzle out why the driver went through a red signal, etc.