The current French railway signalling system is in force on the Réseau Ferré de France (now SNCF Réseau) since 1930, when the code Verlant was applied.
History Historically, each private railway company designed and used its own signals. However, during the First World War the interpenetration of trains between networks had increased, so that it became necessary to create a new unified signals specification. A commission was set up in May 1926, directed by Eugène Verlant of the PLM.
The Verlant commission submitted its report at the end of 1927. The new code of signals received the approval of the Ministry of Public Labour on 1 August 1930. Conversion to the Verlant code was completed only at the end of 1936, except on the network of Alsace-Lorraine where it was completed later, because of the unusual pre-existing signalling.
The Verlant code was very innovative, based on simple principles: Mainly based on color light signalling, which thereafter simplified the installation of the automatic block signalling. Light signals used three basic colors: red (stop), yellow (to announce stop or limited speed), green (clear). This color code was already applied by many foreign companies. It was also used for traffic lights. Simplification: it presented only the most imperative indications (except in special cases).
Placement of signals Signals are normally placed on the side of the line: on the left if the trains run on the left. However, in the Départements of Bas-Rhin, Haut-Rhin and Moselle, trains normally run on the right and so signals are placed on the right. This area was part of Germany from 1870 to 1918; trains run on the right in Germany and the railways were built during that period. When the area became French again in 1918, the railway network was almost complete, and trains ran on the right. Reversing the direction would be too expensive, in particular for interlocking, so circulation and signals remained on the right.
In several stations and on several line sections, when the local layout requires it, signals can be set on the right. They are then equipped with a white arrow indicating the way to which they are addressed.
On some double-track line sections equipped with "permanent counter-track installations" (IPCS), signals are placed normally on the right for counter-track circulations. No white arrows are used. In fact, entering the wrong way is confirmed by a luminous counter-track entrance board (TECS), which, when lit, indicates that the following signals are placed on the right (on the left for Alsace and Moselle). Similarly, a counter-track exit board (TSCS) indicates the return to normal running, with signals placed on the normal side.
Where trains run on the left, the hand-held stop signals (red flag, stop marker or lantern with red light) are presented on the left or at the center of the relevant track. If there is a platform by the track, they can be presented on the side of the platform.
If ground space is limited or risk obstructing trains, the signal can be mounted on a gantry. Additionally, if there isn't enough space on the left, it can be placed on the right side with a white arrow pointing to the track that it serves. This scenario is also possible with gantry signals, in which, the signal on the gantry has an arrow that points to the track that it serves, equivalent on ground.
Permissiveness and aspects
In automatic block signalling, the signalling device is generally one of three categories: Non-permissive signals are absolute signals; they protect routes or points, or delimit sidings. Such signals can be recognized by their "Nf" (, Non-passable) plate. In their most restrictive aspect, they cannot be passed except under exceptional circumstances; Permissive signals regulate traffic to prevent trains from rear-ending the next one ahead. They bear plates such as "F" (, Passable) or "PR" (, Restricted Permissiveness). Non-permissive signals can also temporarily become permissive, in such case their "Nf" plate is accompanied with a small white light (). The most restrictive aspect of a permissive signal allows the train to proceed after a certain number of conditions have been met. Distant signals only display deferred orders and require the driver to adapt their speed in order to be able to safely stop at the next point or signal. "A" (, Warning) or "D" (, Disk) plates are example of distant signals.
In general, the signalling device comprises: a 'block free' signal (green), meaning that the next block is clear or, in the case of a distant signal, that the next signal is also green; Warning signals or speed limits (yellow) requiring the driver to slow the train and especially to be able to stop before the next stop signal; Stop signals (red) require the train to stop.
These signals are supplemented by "indicator signals" (signaux indicateurs) showing speed limits, slow-down orders and reminders to go slow on a diverging route, various indications about the track layout (number, dead ends or garage) the signs of electrical section, numbers of radio channels.
Mobile and temporary signals (e.g. construction), are used to complement permanent fixed signals.
Some signals are specific to manoeuvres. These include various types of signals: Hand signals, Mechanical signals, Lights, Acoustic signals Signal board.
Respect of signals is an imperative condition sine qua non of safety. The first section of the safety regulations of the SNCF indicates that "any official, whatever his rank must obey passively and immediately any signals that are presented."
Appearance Mainline or home signals, also known as those capable of displaying four aspects, such as carré, voie libre, avertissement, and sémaphore (under special conditions detailed below), are also known as Type C signals. They typically use a standardized vertical oblong chassis shape (châssis-écran) made from aluminum or other composite materials painted matte black to maximize visibility at far distances. This panel features a distinct shape known by flat vertical sides capped by semi-circular arcs at the top and bottom. The perimeter of the chassis is outlined by a highly reflective, 40 millimeter wide white border, letting the physical target remains highly visible to drivers in low-light or unlit conditions.
For a standard four aspect configuration, the chassis houses a single vertical column containing four lens units arranged vertically from top to bottom as red, 230 mm gap, green, red, and yellow, each measuring 160 millimeters in clear diameter and spaced exactly 230 millimeters center-to-center. Type C signals are known by their gap between their upper carré light and Voie libre gap. While that gap can house a shunting lamp, doing so invalidates its type of being a C signal.
The sémaphore aspect (detailed more closely below again) is used for block or traffic management when the current block is occupied. Entry is permissible under strict rules, which require maintaining a speed no more than 30 km/h (marche à vue) and remaining prepared to stop short of any obstacle within the driver's line of sight until the next signal (or 15 km/h in some cases). This aspect is displayed by illuminating only the lower light of the lower red lamp, along with a small secondary light module (not part of the chassis) called the peephole (œilleton), usually located to the left or right of the avertissement (warning) lamp at the bottom of the signal. If the upper light of the carré fails, the œilleton serves as a backup system by remaining illuminated during these types of events. Although the carré signal is commonly vertical, they are sometimes shaped horizontally, (a square shape) to fit tight spaces. Examples contain like the platforms of Paris-Est and Paris-Saint-Lazare. In these stations, the vertical space underneath the station roofs and low bridges is simply too tight to house a full-sized vertical signal without risking a collapse of the whole station.
Unlike a standard vertical signal, a horizontal carré displays its stop aspect at the top, illuminating the top left and top right lights and leaving the bottom left and right lights non-illuminated (square shaped signal). In tight spaces where vertical clearance is slightly less constrained but still insufficient for a standard mast, the configuration shifts to illuminate the upper and lower right lights instead and leaving the upper left and right lights non-illuminated (oblong but not rounded-ish rectangle shape).
Block systems
The block system is based on breaking a line into block sections. The block sections on a line between two stations are part of the block system.
Non interlocked manual blocks: For safety reasons, non-interlocked manual blocks are used only on double track.
Interlocked manual blocks: In the case of a single track, interlocking is used in manual blocks to avoid an error resulting in a head-on collision.
Automatic blocks: Two types of automatic block are in common use in France. BAL (Bloc Automatique Lumineux, Automatic Luminous Block) is used on high traffic lines with block lengths of about 1500 m and BAPR (Bloc Automatique à Permissivité Restreinte, Automatic Block with Restricted Permissiveness) is used in low traffic areas with block lengths up to 15 km, usually accompanied with a distant signal up to 1 km away from the BAPR signal for sufficient braking. In both cases they are similar to the UK automatic block signalling.
Normally a train can only enter a block if it is free. The block is a track section delimited by signals, whose length depends on the distance needed for a train to stop or slow down, in the worst conditions on the portion of line under consideration. When traffic density is low, the blocks may be longer.
In future, the blocks may be mobile and follow the progress of the train (virtual blocks, not materialized on the ground and calculated continuously by an integrated onboard system). This will optimize the use of the line and reduce the distance needed between successive trains. This moving block system is already in use on the central section of the RER line A between Nanterre-Préfecture and Vincennes. The trackside signals are still in place but are turned off at the approach of a train whose mobile system signalling (SACEM) is confirmed in operation. They are turned on if problems arise.
The current signalling system has already reduced the spacing between trains from 3 to 2 min. But this is still too long on the busiest lines (suburban, and high-speed lines). In comparison, the moving blocks of the RER A allow a separation of only 90 seconds between trains at full speed.
Wayside signals
Here are some examples of signals used on the French network.
Signals and signs give information and special instructions to train drivers. For simplicity, only the most common elements are presented here.
Stop signals and warning signals
Example light signals Description Mechanical signals Carré (two red lights, aligned either horizontally or vertically): stop. The carré orders an absolute stop and must not be passed under any circumstances except upon a written order from the signaller. It is a protection signal used to protect points, crossovers, stopping places, etc.
This signal is also known as a square. As its name, carré, suggests, it was originally displayed as a square in mechanical signalling. Sémaphore (one red light): stop.