The history of French railway signalling can be divided into three eras: (1) innovative variety, until 1885; (2) the unified signal code, 1885 until 1934; (3) after the Verlant reform, 1934 to present. The fundamentals of French signalling practice were established in the first period, and the general course of development is clear. Gernigon gives many examples of pre-1885 practice. Lineside bells, the Lartigue semaphore, and the beginnings of block working and interlocking were introduced in the latter part of this first period. The best practice of the railway companies was collected in the Code des Signaux of 1885 (see The 1885 Code for the complete text in English). Although the 1885 Code achieved uniformity, it was at the expense of free innovation. There were still small variations between companies, but French signalling presented a generally consistent appearance. The Verlant committee, whose chairman was Eugène Verlant (1867-1958) of the PLM, attacked the problem of replacing white with green for Safety, and eliminating green for any other use, replacing it with yellow. The Code Verlant came into effect in 1934, resulting in even greater uniformity throughout the country.
The areas corresponding to the six main line companies are shown schematically at the right. The routes are approximately those of the Chappe télégraphe aerien of 1794-1856, except that the telegraph took the high ground, the railway the low. The regional monopolies were all but complete. The Orléans railway is usually abbreviated P-O, the Paris-Orléans. The PLM is the Chemins de Fer de Paris à Lyon et à la Méditerranée, the largest of the companies. The Nord served the coal-mining and industrial region around Lille, was a link in the Paris-Bruxelles-Amsterdam main line, and was always technologically innovative. The Nord also served Liège in Belgium. The Est's lines east of Nancy and Metz passed into German ownership in 1871. After 1918, the ex-Est lines in Alsace-Lorraine were operated independently and retained their German practices. The État began in the west of the Ouest's region to operate bankrupt local lines, but in 1909 absorbed the Ouest itself. The Midi, an early user of electrification, offered four crossings of the Pyrenees into Spain, where there was, of course, a break of gauge. The main crossings were the sea-level ones at east and west. These companies merged in the Societé Nationale de Chemins de Fer Francais, SNCF, in 1938. These areas correspond in general to the operating regions of the SNCF.
This article concentrates on fixed signals. Several particular aspects of French signalling are treated in separate articles on this site, to which links are given. This is a large field with an extensive literature, most of which is not easily accessible to readers outside of France. The best interpretations possible with limited resources are given in this article, but may not be adequate or correct. The idea is to give the reader a feel for French signalling, and to allow him or her to make sense of the signals that may be seen while travelling. The author is eager to find out about his errors and misconceptions! A vocabulary of French railway terms will be found in French Railway Vocabulary.
Railway signalling has two provinces, that of hand or mobile signals and that of fixed signals. Hand signals, using flags and lamps, appeared at the birth of railways and for some time were sufficient. Indeed, the United States relied on hand signals almost exclusively until the 1870's. Many early fixed signals were just flags or lamps displayed on a post or other fixed support. In Britain, the necessity of giving signals at certain important locations, such as at stations and junctions, led to the supplementation of hand signals with fixed signals, that were usually rotating vanes or targets. At first the vanes were painted boards, rotating through 180° about a vertical axis, that showed one side or the other to the approaching train. Though the vane was perhaps red on one side and white on the other, under some conditions it was difficult to perceive the colour at a distance. After the error of using colour in this way was appreciated, shape was adopted to identify signals. The vane was rotated through 90°, and displayed different shapes in the two settings. Although many such signals displayed vanes of two different shapes, as in the Great Western Railway disc-and-crossbar signals (both vanes the same colour, red), most displayed a vane or target perpendicular to the track in one position, indicating a restriction, and parallel to the track in the other, indicating clear track. Of course, when the target was parallel to the track, it effectively disappeared when viewed from a distance.
It is ironic that the country where the Chappe brothers invented the semaphore optical telegraph, and in which it was still in use during the early development of railways, never used the semaphore as an important part of railway signalling. Semaphores were only used for block signals, and for direction indicators. In most countries, rotating vanes were nearly completely superseded by semaphores by the 1870's, but in France rotating vanes survived to the last days of mechanical signalling.
In Britain, and later in the United States, the absence of a positive clear signal was deprecated. E. C. Carter, Signal Engineer for the Chicago and North Western Railway in the 1890's, observed that anxious enginemen peered into the gloom of night looking for the white signal lights that meant the way was clear, and were reassured as each was sighted. When the clear signals were absent, doubt arose, and the engineman ran cautiously until the situation was evident. Indeed, in Britain and the United States, the absence of a signal where one is usually displayed is in itself a Stop signal. Carter's observation is an important principle and shows that enginemen do not simply run freely until stopped, but depend on positive reinforcement to proceed. The French 1885 Code, however, states clearly that "Dans tous les cas, l'absence de signal indique que la voie est libre." This imperfect theory is stoutly maintained in French signalling practice. It is unsettling for an Anglo-Saxon observer to observe the brighly coloured French mechanical signals, so clearly visible, and then when the signals are cleared for a train, to note their astonishing disappearance! However, it was never suggested to display a red light for Stop by night, and then no light at all for Proceed (which is the logical consequence of the principle).
Consequently, French signals generally display two aspects. When the more restrictive aspect is displayed, the signal is said to be closed (fermé), and when the less restrictive aspect is displayed, as open (ouvert). The track beyond the signal in the direction the train is moving is said to be en aval (English: in advance), and the track on this side is said to be en amont (English: in rear). Signals are placed to the left of the track, since trains run on the left on double track, and the driver's post is on the left of the locomotive.
Observers often state that French signalling is "speed" signalling, not "route" signalling. Actually, speeds are always given by subsidiary aspects, not the main ones, and often by additional signs. Route indications are also commonly given, again by subsidiary signals placed above the main signals in the case of light signals. These have the same significance as "directional feathers" in Britain (though speeds are sometime explicitly shown). The main signal aspects do not present speed information, as they do in the United States. Therefore, French signals are sui generis, and cannot be classified as "speed" or "route".
The original method of operating trains was conceived in Britain, and spread to all places with the introduction of railways. On double track, trains ran with the current of traffic according to time tables that ensured that fast trains preceded slow, and that trains were adquately spaced. The spacing was monitored by employes along the line. The usual French interval was 10 minutes. A train stopping out of course was protected by the rear guard using hand signals (using the ten minutes to take his position). Trains generally stopped at all stations, where they were naturally vulnerable to following trains. Running through stations at speed was definitely discouraged. Fixed signals were consequently first used at stations, which were points of constant danger. Although a single signal could show when it was safe to enter the station, or for a train to depart, it soon became general to use at least two signals. One signal, at the entrance, allowed a train to enter a station when its track was clear, and protected its rear from following trains. Another, at the exit, authorized a train to proceed, after its route had been set. These signals clearly replaced earlier hand signals. They were more visible, uniform and displayed at fixed locations, all desirable characteristics.
It was soon realized that a train waiting outside the entrance signal to enter the station should be protected against following trains. This was accomplished by an advance signal operated by a wire from the station. Trains had to approach this advanced signal prepared to stop, since it was indeed considered to be a Stop signal. After stopping, the train could proceed at restricted speed (marche à vue) looking out for a train ahead, or the closed entrance signal to the station. When express trains not stopping at every station were introduced, this was very inconvenient. Consequently, the rule was changed to prescribe that a train encountering a closed advance signal must immediately be brought under control, and thereafter proceed at restricted speed. This eased the problem, but the fundamental duty of an advance signal to protect a train waiting ahead was not changed. The braking distance in advance of the advance signal was marked by a small round or square sign or poteau bearing the legend "limite de protection". A train pulled within this post was effectively protected against following trains.
The operation of the advance signal was considered so important that a device was invented to operate the signal automatically by the train. When a train arrived at a station, an employe covered the train by operating the lever that closed the advance signal by means of a wire and a counterweight (the wire was pulled against the counterweight to open the signal). If the signal operated correctly, it closed a contact that rang a trembling bell at the station. Let's suppose a train passes an open advance signal. When the first wheels of the train pressed down the pédale Aubine, the signal was released and went to stop under the action of a local counterweight. The pedal stayed down so it would not be battered by the following wheels. Quite purposely, the bell at the station was not rung, as it would have been if an employe had operated the signal. When the operating lever was used by an employe at the station in the usual way, the pedal was raised again and the bell began to ring. The advance signal could be operated as if the Aubine were not there. Aubine worked for the PLM, and the pedal was first installed between Paris and Dijon in 1883.
Observance of the advance signal by wakeful drivers was also essential to safety. The crocodile was introduced by the Nord around 1872 to ensure this observance. The crocodile is an electrical contact between the rails that repeats the position of the advance signal in the locomotive cab. For a complete explanation, see The Crocodile. In practice, the driver acknowledges a closed advance signal before reaching the crocodile to demonstrate his alertness. This acknowledgement and the state of the advance signal are recorded on the speed recorder tape as evidence of the driver's vigilance. The crocodile was the first widely used cab signal in the world. Later, with government encouragement, it spread throughout France.
The introduction of the block system meant that the main purpose of the advance signal was made unnecessary. A train that had not yet exited the block would not be followed by another, unless the following train was admitted on the understanding that the block was occupied and a lookout for the preceding train was necessary. However, the subsidiary job of ensuring that a Stop signal ahead would not be encountered unexpectedly remained. The advance signal became a distant signal, in British and American parlance, and was placed the stopping distance in the rear of the stop or home signal. In French, such a signal is called an avertisseur, a "warner," or earlier, an annonce d'arrêt.
At the exit signal of a station, where alternate routes may be available, the driver must not only be instructed when it is safe to proceed, but must know the appropriate speed and possibly the route to be taken. If the speed of the route is less than the line speed, this should be announced in advance so that the speed can be reduced as necessary. A signal called a ralentissement gives this information. At the point of divergence, the driver is reminded of the speed restriction by another signal called a rappel de ralentissement. The route is given by an Indicateur de Direction. In French signalling, the warning and the route information are separate from aspects of the main signal.
At this time it seems best to explain the mechanical signals used after the Verlant reform of 1936, which are shown in the figure at the right. Many of these signals still exist, and were very common until recently. The target signals rotate 90° about a vertical axis in the open position. The night aspects are shown below the targets (all lights on to show what colour is there). When open, the green light is displayed in all cases. If no green light is shown, none is displayed. When oil lamps were used, all double lights were produced by reflection.
French signalling was characterized by the continued use of rotating targets. The earliest railway signals were of this type, with a board painted different colours on its two sides that could be rotated by 180° to display one side or the other. This proved very unsatisfactory since the colours could not be distinguished under bad lighting. They were succeeded by signals that gave one indication when the board was displayed, and were rotated 90° so the edge of the board was presented removing the signal. The signal was then effectively invisible, as in a three-position semaphore at Clear when its arm was inside the post. This was soon deemed unsatisfactory, and a positive Clear signal was demanded. In France, open ("Ouvert") signals continued to disappear as long as they were used.
The Verlant reform ensured, however, that the shape of the aspect expressed its meaning. A square was an absolute stop signal; a disc was a deferred stop signal; a lozenge (square on a point) was a warning, a triangle with point upwards indicated a reduced speed ahead, and a triangle with point down indicated that reduced speed was immediately required. These indications were independent of the painting, which of course was also distinctive. This correspondence did not exist before the Verlant reform. For example, there had been green, yellow and blue discs in addition to the red one, all meaning different things.
The carré is the stop signal used as an entrance and exit signal at stations (for example). The driver must stop just short of the signal. Passing a closed carré was an extremely serious offence. In French signalling, no considerable clearance is provided in advance of a signal. The capital letter "C" is the symbol for this signal and its aspects; there is a similar letter for each of the other signals. The disque rouge is the advance signal mentioned above, and it can be passed when closed. The carré violet is also an absolute stop signal, but is used on secondary lines normally not used by passenger trains. It is not preceded by a warning, since the speed on such lines is low. The yellow square on its point is the distant signal. When closed, it implies that a stop is required the stopping distance ahead. Normally, the avertissement is placed above the carré:, but it can also be placed below. The carré was originated by Robert of the Nord around 1850, and was adopted by all companies, becoming the most familiar example of French signalling. The counterchanged border shown was typical of the Est. The Ouest and the Etat used a rectangular board, the larger dimension horizontal.
By night, the carré displayed two red lights horizontally. One light was the direct light of the lamp, the other reflected, and they were coloured by the tinted glass in the target. The red and white squares of the carré were painted so that the reflected red light always appeared in a white square. The upper right corner square appears generally to have been red, but since different light arrangements were used on the PLM, sometimes it was white.
The ralentissement appears at the distant signal. When closed, it displays two yellow lights in a horizontal line. Unless otherwise provided, the speed indicated is 30 km/h. When open, it shows a single green light and indicates that there is no speed reduction at the junction immediately ahead. At the junction itself, the rappel de ralentissement will be displayed if the diverging route is set, showing two yellow lights in a vertical line. When open, the target is not visible and no lights are shown by night.
At the left are shown semaphore directional indicators, indicateurs de dirction. The PLM signal is typical of pre-Verlant practice, with violet arms and lights of violet and white. The arm for the route set is depressed. The signal shown indicates that the rightmost route of two is set. At the right is the post-Verlant signal. The arms are now white, and in the horizontal position screen the lunar-white lights. The uppermost semaphore arm is permanently depressed and shows a lunar-white light. If the lower arms are horizontal, this indicates that the left-hand route is lined. For each route more to the right, an additional arm is depressed. This semaphore ID was rare and has probably vanished by now. It easily suggests the equivalent light signal, which is shown below.
Two block semaphores are shown. The upper one is typical of the PLM, while the lower is typical of the Nord and other companies that used the Lartigue block. The Lartigue block is described in The Lartigue Electrosemaphore. The PLM semaphore is pivoted near the middle, while the Lartigue arm is pivoted at the right-hand end. The block semaphore differs from the carré in that the stopping point is not specified. The block semaphore may be at some arbitrary place on the platform, and arms for both directions may be on the same mast. A horizontal arm indicates that the train may not proceed into the block in advance. An inclined arm, or the Lartigue arm hanging nearly vertical, indicates that the block is free. Before the Verlant reform, semaphore arms displayed red and green when closed, and two white lights when open. It should be remembered that green meant Caution at that time. The display of red and green distinguished them from the carré, which was two reds. There was, of course, only one lamp, the second light obtained by reflection.
Paulin Talabot of the PLM invented a three-aspect semaphore in 1855 that was widely used by that company, especially for the manual block system. Originally, it displayed Stop when horizontal and a red light. At 45° the aspect was Caution, with a green light. When the arm was nearly vertical, the aspect was Voie Libre and a white light was shown. Later, the Caution aspect was suppressed, and the signal showed red and green when at Stop, two white lights when open. It was generally operated by a small lever at the base of the signal. The signals illustrated display red for Stop and green for Voie Libre, in agreement with the Verlant code. Note the provision for raising and lowering the lamp on a track. This signal was announced by a disque rouge, which also covered a train stopped at it. A block post in a Tyer block system would have a semaphore with two arms, one for each direction, near the station, protected by a disque rouge at 800 m or more in either direction.
At the left, a semaphore is shown that was developed by the Est in 1922 for the purpose of subdividing a block. It was electrically operated, and announced by a green-and-white chequerboard, also electrically operated. When closed, it showed red and red/green lights, and when open two white lights and was depressed 70°. Like the usual block semaphore, it could be passed when at stop. The arm returned to horizontal by gravity; when open, it was maintained by a reduced current. Its purpose was stated as protecting, or covering, a train stopped at a block signal ahead, instead of a disque rouge. After the Verlant reform, it displayed a red light when closed, and a green light when open instead, and was announced by an avertissement. The last was replaced in 1978.
French colour-light signals (signaux lumineux) are easy to understand if you know the mechanical signals, since they display the night aspects of these. Four common forms are shown in the diagram, with the colours of the lights. The basic signal has three lights, and is shown at the left. Since it has only one red light, it cannot display the carré. The next form has added a red light at the top for this purpose. The third form adds the lights for a ralentissement, and the fourth form those for a rappel de ralentissement as well. Light signals appeared in the 1920's on the Est, État and P-O as panneaux lumineux in a variety of forms, not illustrated here. These underwent many revisions, with the final result after Verlant as shown.
At the left, it is shown how these signals each can display Voie Libre. The green light replaced two white lights. A flashing green light warns a train moving faster than 160 km/h to reduce to that speed. A voie libre cannot be followed immediately by a stop aspect.
Similarly, at the right we see avertissement, shown by a single yellow light. If the yellow light is flashing, as shown in the figure below, the indication is the same as a British double yellow, or an American Approach Medium or Advance Approach. Before 1975, there was a five-light signal that added a green light at the top to indicate this with a green-over-yellow aspect.
In French, the indication of this signal is: "Be prepared to stop before the stop signal announced at reduced distance by the following avertissement". A flashing red indicates: "Proceed at restricted speed without stopping, but without passing the signal at above 15 km/h."
The stop aspects are shown at the right. The significance of one or two red lights is maintained. Every stop signal has a plate with white letters on black, bearing "F" if the signal is franchissable (can be passed after a stop), or "Nf" if not. There may be a lunar white light below and to the left of the signal, called an oeilleton. If this is lighted, the signal may be passed even though bearing an Nf plate, provided the aspect has only one red light. This permits the same signal to display C and S. A signal with blank main aspect may be passed if it bears an "F" plate, or if the oeilleton is lighted and it bears an "Nf" plate. Absolute stop signals are typically supported by detonators, automatically placed and withdrawn. These may be electrical, instead of pyrotechnic.
The disque rouge is represented in colour-light signals by a signal with a round background. This signal displays three indications, the closed disque rouge, avertissement and voie libre. Additional yellow lights can be installed to show ralentissment.
The ralentissement and rappel de ralentissement are displayed as shown at the right. The small yellow lights at the top of the signal are used for these aspects. If the lights are flashing, the speed restriction is 60 km/h instead of 30 km/h. These speeds correspond to American medium and slow speeds. Other speeds may be prescribed by signs or illuminated panels, showing speeds in units of 10 km/h. Note that the ralentissement is a warning, while the rappel marks the point of restriction.
Direction indicators are shown at the left. They may also have three lights if there are three directions. Compare with the semaphore direction indicators illustrated above. These are very commonly found above exit signals at stations. Colour light direction indicators are used with mechanical signals as well.
Colour-light shunting signals are shown at the right. These have the same significance as the carré violet. They display a violet light when closed, lunar white when open. They authorize shunting movements past a signal at stop, even a carré, but not past another stop signal or a limit-of-shunt sign, consisting of the white letters "LM" on a black background. A flashing white light on a signal also allows shunting ahead.
An unusual PLM signal is shown at the left. This was the sémaphore queue d'aronde or swallowtail signal, displaying a blue light by night when closed, and a white light when open. It was called a signal d'embranchement and allowed a train to be taken apart at a yard and classified. Apparently, when open, it guaranteed that signals were set against conflicting movements.
Some pre-Verlant signals are illustrated at the right, with the initials of the companies that used them. After the 1885 Signal Code, all companies used signals that were basically similar, though with small differences in design and location of the lights. Note that the green checquerboard (damier vert) was used instead of the yellow square on point for avertissement (then called "annonce d'arrêt). This green chequerboard on point indicated that the braking distance was less than normal (less than 800 m). In such cases, the train already had received a restricting signal. The green disc was used for ralentissement, and there was no rappel de ralentissment. The speed prescribed was 30 km/h for passenger trains, 15 km/h for freight. The carré violet did not yet exist, a yellow square or disc serving its function. The Est and the Nord did not use the disque jaune. The carré and the disque rouge were preserved in the Verlant reform. The P-O did not use the disque rouge. The Est, Nord, État and P-O used the Lartigue lattice semaphore, while the PLM used its bar (shown) and the Midi a unique aspect for the PD block (not shown). The carré and disques were 3.8 to 7.0 m high to their centres. Typical disques were 1000 to 1200 mm in diameter, and carrés 800 to 1000 mm on a side. The point indicators showed their targets when the switch was set for the divergence.
The disque bleu was placed about 500 m in advance of the crossover used for backing onto a service track (refoulement). It was normally parallel to the track. When perpendicular to the track and showing a blue light by night, it authorized a reverse movement onto the service track, showing that the crossover had been lined for this movement. There was usually a disque jaune at the crossover, which was parallel to the track when the crossover was reversed. This signal governed exits from the service track. The point indicators were various colours, but the double-fishtail shape was usual. They could be high or low, rotated through 90°, and a lamp of one lens showing the same colour was located above them. A high lamp showed its light at an elevation of about 1500 mm. Some low point indicators also showed an acute angle pointing in the direction of divergence, using an illuminated box with translucent sides. These point indicators were intended for the station staff, not trains. The typical sequence of signals approaching a junction was disque rouge, damier vert and carré.
A point indicator used on the Midi is shown at the left. It was used at stations on single track. The target was displayed when the points were reversed. Note that it showed a green light.
The post-Verlant night aspects have electric lights in a framework usually below and near the signal. The illustration shows several cases of illumination with oil lamps. In this case, the target held coloured lenses in front of a stationary white lamp. In some early cases, the lamp moved with the target, but only until t he patent for the stationary lamp expired. When the target rotated, the coloured lenses were removed, and the white lights of the lamps displayed. Always, when there were two lights, one was created by reflection from the other. When a carré was open, it displayed two white lights in a horizontal row by night, as did the annonce d'arrêt. The open disque rouge showed only a single light. Direction indicators used the fishtail semaphore blades, but they were usually painted violet pre-Verlant.
Hall enclosed disc automatic signals (banjo signals) from the U.S. were used on the Midi and on the Métropolitaine de Paris. They were installed Bordeaux--Langon and Bordeaux--Lamothe in 1902 with normal-stop track circuits. The intermediate signals had a round case with a central aperture, those equivalent to the carré a square case. The light aperture was at the top. When the square "disque d'entrée" used at larger stations was at Stop, a red silk disc was displayed and a red light was shown. These signals displayed a "G" plate. When at Voie Libre, the disc was withdrawn and a white light was displayed. The "sémaphore de cantonnement" displayed red and green when at Stop, two white lights when at Voie Libre. Incidentally, sémaphore was the general word for a block signal, whether or not it was actually a semaphore. The large aperture was at a height of 2.5 to 5.0 m to its centre. The apertures were covered by glass. Eventually these signals protected the whole line Bordeaux--Montauban. These signals were replaced beginning in 1907 by those designed by the Midi, called PD (Paul and Ducousso) signals, presenting square aspects and preceded by round disques. They were called sémaphores, but were not of that form. Rather, they were glass enclosures that seem to have had screens that opened outwards to reveal the interior. The Bloc PD eventually covered Bordeaux--Sète and Bordeaux--Dax. It survived until 1983-84.
Signals with a limited viewing distance are preceded by mirlitons at intervals of 100 metres. There are signs, usually elevated, that can be permanent, or rotating (effaçable), consisting of an abbreviation in white letters on a black background giving information on the route that has been set. The letters may be translucent and illuminated by night from behind. The letters are: "G"- lined for a service track, implying proceed prepared to stop unexpectedly; "D"- lined for a dépôt, "SAS" - lined for a track where there is not the usual stopping distance to the next carré. It is the word for a canal lock, recalling the short distance between the lock gates, "H" with Heurtoir spelled out, and a distance in metres - lined for a buffer stop, "Imp"- lined for a dead end, an impasse. A rotating V.I (voie en impasse) sign indicated lined for a dead end, but could be removed when lined for a through track. H.I (heurtoir impasse) means the same. A "Stop" sign means stop and proceed if the way is clear; an "Arrêt" sign means stop and proceed only on verbal instructions. "LM" is a shunting limit, "MV" prescribes marche à vue in advance of that point. A white "S" (sifflez) means to whistle. If accompanied by a black "J" on a white background, do not whistle between 20.00 and 07.00 except in emergency.
Speed limit signs consist of a TIV-D (tableau indicateur de vitesse á distance) giving the speed in km/h in black digits on a white background in a square. If the square is on point, the restriction is monitored by a crocodile. A white "Z" on a black background marks the beginning of the restriction, a white "R" its end. A rotating sign (TIV-R) gives the speed limit at points where there are routes with different speeds. There are some other signs applying to trains of different sorts. An upper semidisc applies to motor cars, a lower semidisc to trains with allowable speed greater than 140 km/h. These have black figures on a white background. A black "P" on a white background is a preannonce of a TIV.
At the right are shown some illuminated signs. The TIDD is a tableau indicateur de direction à distance, displayed on the ralentissement announcing the junction. The TECS is a tableau d'entrée à contresens, while the TSCS is a tableau de sortie de contresens, placed at the start and the end of a stretch of running on the right-hand track.
The chevron pointing down indicates that a turnout at the location is covered by a speed restriction previously announced. This sign is also found 100 m before the siding turnouts at the entry to a station on a line with signalisation simplifiée, commanding marche à vue. It is preceded at 800 m by a "GARE" sign. The chevron pointing up is used at tracks with a common exit signal. The train must wait at that point until a signal is received to proceed. The signal may display the track to which it applies when it clears. The rightmost sign warns that a point of limited clearances is approaching. Not covered above are a few details with respect to speed limit signs, electric traction signs, hump yard signals, and special signalling for LGV, lignes de grande vitesse. These are not of major importance, or are similar to signs described elsewhere, and I await further information on them.
Single track was much more common in France than in Britain. It was operated somewhat differently than double track. The general method of operation was to send trains from station to station on the basis of telephone messages (earlier, telegraph messages) between stationmasters, very much like the later block téléphonique. As a supplementary safety measure, lineside bells were introduced from Austria. For a complete discussion of these bells, see Austrian Bells. Operation by "one engine in steam" (en navette) was sometimes used on secondary branches, but the use of train staffs and tokens was quite rare. The train staff existed only on the Ouest, and had disappeared by 1950.
When signals began to be used, the disque rouge was typical, announced by a disque vert. Two station layouts were used. The voie de gauche was in effect a short length of double track, while the voie directe had a through track and a siding. The voie de gauche was appropriate when trains stopped at the station, facilitating crossings, when spring switches were used at each turnout. The voie directe allowed expresses to pass at speed, but required facing point locks. The Nord, Est and Midi had only voie directe, while the Ouest, P-O and PLM had both, mainly voie de gauche. The voie de gauche station of the P-O in 1880 had three disques in each direction. One preceded the station, one was at the facing point, and one was at the heel of the trailing point. For one train to pass another at a voie de gauche station, it was simpler for one train to move through the station and reverse.
Later signalling, after Verlant, is shown at the right. A new signal, the voyant de talon, literally the "heel target," was introduced to show when the leaving turnout could be used. This was earlier a simple blue disc. The approach carrés were later replaced by diques rouges, and the carrés at the turnouts by downward chevrons. The target with two black lines replaced the exit carré in some cases, placed opposite the voyant de talon. For the voie de gauche, the avertissment and ralentissment were permanent, but for the voie directe, the avertissements could be opened, of course. In general, there was a great variety of signalling for stations on single track.
Two examples of signalling stations on single track are shown in the figure. Note that the levers are shown and identified by letters. Point and lock levers are located near the turnouts, signal levers near the station. The spring-switch turnouts at the PLM station have point indicators. The semaphores, near the station building, are block signals. The disques rouges of the Midi station are 1000 m from the limit of protection signs. After Verlant, ralentissement triangles would be put on top of the disques rouges, replacing the green discs, and the blue lozenges would be replaced by downward chevrons.
The guidon d'arrêt is a curious signal that is used when it is necessary to stop a train at a particular point, in the fashion of a hand signal. There are light and mechanical versions, shown in the diagram. When the signal is open, it has no significance at all, as if it were not there. It is always preceded by a disque rouge, so is approached only at low speed whenever it would be displayed.
R. Lemon, An Introduction to French Signalling (Signalling Record Society Signalling Paper No. 13, 1995).
A. Gernigon, Histoire de la Signalisation Ferroviaire Française (Paris: La Vie du Rail, 1999).
Les différents types de blocks automatiques à la S.N.C.F., La vie du Rail no. 1534, 14 March 1976, pp. 10-12.
D. Wurmser, Signaux Mécaniques (Grenoble: Presses and Editions Ferroviaires, 2007)
Composed by J. B. Calvert
Created 8 July 2004
Last revised 11 March 2008