Note to reader : Please note that the following text is intended to provide information on the existing signaling system in France. Although the basics are the same in most countries regarding the Stop and Clearance positions of signals or the management of turnouts, it may be interesting for you to understand how French signaling works and to see how it differs from the one applied in your country.


The rail system is based on a brilliant design, apparently contradicting the laws of physics, which consists in running vehicles equipped with steel wheels on rails themselves made of steel, the contact surface of the wheel being limited. to the bare minimum. This results in a displacement system with very low frictional forces, thus making it possible to transport heavy loads with a minimum of energy expended. This system was used especially in mines where ore wagons could be pushed by human force alone.

However, this system raises 2 major problems with regard to train safety:

  1. The convoys being guided by the rails are made prisoners.
  2. The low adhesion (steel of the wheels on steel of the rails) drastically extends the braking distance. The longer the train will be and the faster the speed will be.

Faced with these two problems, it was necessary on the one hand to design track devices such as switches, crossings-junctions for guiding trains and to develop a cantonment system that is generally called block, making it possible to space the trains on the same track with a sufficient safety distance between them.

These two traffic management systems require the installation of signals to ensure perfect safety.

This will seem obvious to you, but it is useful to recall them in order to understand the signaling as it exists on the French railway network in order to be able to reproduce it realistically in EEP.

However, this article can not constitute an exhaustive reference in the field of French railway signaling for it is particularly complex. Developing it here fully would be of no interest to the needs of the model maker. We will therefore limit ourselves to a study limited to the most useful aspects for the construction of EEP networks equipped with the most common SNCF signals. ( Société Nationale des Chemins de Fer =  National Society of Railways)

The dangers of rail traffic

In view of the two major problems, mentioned above, three major risks arise in the movement of trains :


Figure n° 1

The nose to nose

Figure n° 2

Side swipes

Figure n° 3

The three figures above speak for themselves. They are easy to understand.

In addition to the dangers we have just seen, there are also risks of derailment for several reasons. In this area we can distinguish, among others, 3 main causes:

  1. Poor positioning of the switch blades in relation to the direction of train travel
  2. The high speed for crossing a switch on a diverted track
  3. Excessive speed in curves

Therefore, faced with all these risks, the ever-increasing circulation of trains very quickly necessitated the establishment of a regulation system to ensure the safety of convoys both for crossing points at crossings and spacing of trains following one another on the same track. Thus we ended up with the installation of visual signals. Originally mechanical, signaling with technological development has become electric with illuminated lights. Today we have even come up with on-board electronic systems that allow signaling to be displayed on board locomotives. This is the case with TGVs.(high speed trains)

In EEP, a totally virtual universe, the risks are mainly limited to the catching up, nose-to-nose and side swipes that we saw above. The risk of derailment does not exist. It is therefore possible to cross a deviated turnout or a very tight curve at high or even very high speeds, without any risk. However, such an option would not be realistic and the virtual model maker, very often concerned with realism, will be keen to represent in his networks a railway universe as close as possible to the real world.

Thus the signaling that can be installed in EEP not only contributes to the safety of trains between them but also to visually make the virtual universe conform to the real railway model.

This article therefore aims to provide the reader with precise information on France signals, on the one hand, and to see its main applications in EEP, on the other hand.

We will therefore deal with the signaling of automatic blocks ensuring the spacing of trains and that of safety in crossing points and crossings which will be very useful for the creation of routes. (See articles on itineraries).

Illuminated railway signals

Block safety

The block manages the spacing of trains and prohibits any risk of overtaking. It can be perfectly rendered in EEP.

There are three block systems in the SNCF network: 

  1. The automatic luminous block or BAL
  2. The automatic block with restricted permissiveness or BAPR
  3. The manual block or BM

We will limit ourselves in our article to the 2 types of traffic exploitation in automatic mode in so far as they require the presence of visible signals.

The manual block or BM that we will not deal with here requires human intervention in reality. This type of block is available in several versions such as telephone block (CT) or computer-assisted block (CAPI).

In addition, we will make a distinction between automatic block signals intended to manage only the spacing between trains and those which ensure safety for crossing points and turnouts which we will call route management signals, including for a protecting signal. a single switch on a track because a switch implies the de facto management of 2 routes, the one in the direct track and the one in the deviated track.

Indeed, the automatic block responds to a logic of spacing of trains that follow one another while the management of the routes responds, for its part, to a security requirement between convoys traveling on different tracks but likely to end up at one point. given time on the same switchgear. (See the diagram of the side swipe above).

However, everyone will understand, and we will see it better later with concrete examples, that automatic blocking and signaling of transit on the routes do not constitute two independent universes and strictly separated from each other. Their nesting in a network, even simple, often poses programming problems for the virtual modeler to allow simultaneous consideration of the automatic block and the route.

The automatic luminous block

The automatic light block or BAL is the traffic operation system that ensures the spacing of trains following one another on the same track. It prohibits any risk of overtaking one train by another. This operating system is used on lines with heavy rail traffic (Paris – Lyon – Marseille for example).

The line is cut into blocks varying in length from 1.5 to 2 kilometers.

The light signal used in the BAL system is a 3-light signal that protects the entrance to each block and regulates the speed of the train:

  1. Green = Clear path
  2. Yellow = Warning
  3. Red = Semaphore or stop
Figure n° 4

In addition, the 3-light BAL signal is fitted with an F plate (Franchissable = passable) on the mast indicating that this signal can be crossed at a red light under certain conditions.

Each of the BAL signal states determines the action of the driver:

  1. Green / Clear : The following 2 blocks are not occupied by a train. The driver maintains his maximum authorized speed or resumes it, if, for example, he had reduced his speed as a result of a warning light displayed on the previous signal.
  2. Yellow / Warning : The next signal is closed or red. The mechanic must therefore slow down in order to be able to stop at a red light.
  3. Red / Semaphore : The next block is occupied by a train. The mechanic comes to a complet stop and then resumes at a maximum 30 km / hour and should be able to stop immediately.

The four figures below show the sequence of events as a train passes through each of the blocks represented:

Phase 1 - Figure n° 5
Phase 2 - Figure n° 6
Phase 3 - Figure n° 7
Phase 4 - Figure n° 8

These figures are self-explanatory in themselves and do not require special comments.

In certain field configurations the semaphore may be flashing red. This signal authorizes the driver to pass the red light without stopping. The maximum authorized speed will however be 15 km / hour. This particularity applies in particular to sections of track with a high ramp (upward slope) which would induce restarting difficulties.

The route of a line obviously includes stations but also switches which will require lights with specific conditions.

The first of these signals is the “carré = square”. It has the same states as those of the simple BAL signal but can also display a 2 red light signal called a square.

Figure n° 9

Intended to protect critical points, the square can not be crossed under any circumstances. This is why it has an Nf (Non franchissable = Non-passable) plate on the mast.

In addition, the signal is provided with a eyecup white light which is lit for all states except precisely when the signal displays the square. This device is a security in addition to the Nf plate to avoid any confusion with the semaphore in the event that a red bulb is burnt out and suggests that it is a semaphore therefore passable.

Thus, the mechanic seeing a single red light accompanied by a lit eyecup white light knows that he is indeed dealing with a semaphore and can therefore continue on his way.

Figure 10 on the right shows a semaphore with the eyecup on, located inside the yellow circle.

The diagrams below show examples of the classic layout of a type B signal on a railway route.

Figure n° 10
Figure n° 11

In figure n ° 11, the type B signal protects train n ° 1 stopped at the station and prohibits any overtaking by train n ° 2.

Figure n° 12

Figure 12 above shows us 3 type B signals, the first providing protection for turnout 1 and the other two on track 1 and 2 providing protection for switch 2.

In this case, the speed at which turnout 1 is crossed is not specified. However, a speed indicator board will have displayed the speed upstream of signal 1. However, the SNCF signals may include speed indications for crossing a switch or a turnout zone. These signals have limitations of 30 or 60 km / hour depending on the angle of deviation of the switch.

The following figure shows us a junction with upstream the slowdown signaling (Signal 1 with type F panel) and slowdown reminder (Signal 2 with type G panel).

The train approaching Sig 1 is programmed for a direct crossing towards block 2. No train presence, the signals are therefore green.

Figure n° 13

It should be noted by the way that even if block 2 bis is occupied by a train, the signing does not change as long as the route remains strate. The 2 signals behave as BAL signals in the same way as the 3-light BAL signal.

Figure n° 14

Conversely, if in this same configuration train 1 must be routed to block 2a in other words, take the junction in the deviated track, we would then have a slowdown (here at 30 km / h) materialized by the 2 horizontal yellow lights . As block 2 bis is occupied by the train, signal 2 is closed to the square since we are in a switch area:

Figure n° 15

As a result, the signal F displays, in addition to idling 30 km / h, the warning which warns the driver that he must slow down to stop before the next traffic light and we see in this configuration that the signal F displays at the same time a double signaling: a warning within the framework of the automatic block and an idle speed 30 km / h for the crossing of the switch.

The configuration shown in the following figure shows the signing normally displayed in the absence of the train for a diverted track route to block 2 bis. Signal F announces slowing down to 30 km / h. The train driver must therefore slow down in order to pass signal G at the same speed. In this case, the signaling does not work in BAL mode, but in turnout crossing mode.

Figure n° 16

Let us suppose that the route or block (canton) 2 and 2 bis are in the station zone with signals at the exit of the station. In this case the signals are closed and the train must stop at the station. Signals 1 and 2 behave as BAL signals with a yellow warning indicating that the next signal is in the closed state.

Figure n° 17

On a deviated path towards block 2bis, the state of signals F and G would be as follows: signal F displays the idle speed announcement at 30 km / h since the switch is in the diverted position and the idle speed recall is also at 30 km / h. However, as the next signal (G) is squared, it additionally displays the warning. This signal combines simultaneously a display in BAL mode and a display in transit mode.

Figure n° 18

We guess from these examples that programming the signals in EEP in a way that is real is not a simple matter due to the interlocking of the BAL signaling and the route signals. We will see in another article how to do this. The use of the Lua language is almost imperative, but the reader unfamiliar or even without any knowledge of this computer language can be reassured. It is easy to build small programs with a few Lua basics which I will explain to you later.

The automatic block with restricted permissiveness

Like the automatic light block, the automatic block with restricted permissiveness or access ensures the spacing of trains. This system, which therefore does not differ from BAL in principle, never the less stands out in its application in the field by the presence of cantons or blocks of significant length (from 15 to 20 kilometers). Obviously, this separation can only be applied on lines with low traffic density in so far as a train has to wait until the convoy in front has passed the block signal located downstream about twenty kilometers. Waiting times would be unacceptable on heavily trafficked lines with trains following each other very closely.

A block in BAPR is therefore of little interest in an EEP network because of the length of the blocks. Moreover, a modeled network is all the more spectacular as the rail traffic is important there. The BAL is therefore imposed as a priority. However, one can imagine a network with a Y bifurcation with the first branch continuing in BAL and the second in BAPR, which makes it possible to implement the signals specific to the BAPR such as the warning disc.

At this time in the EEP signal library, there are no signals for BAPR. As soon as they are modeled and available, a complementary article will be published giving more details on BAPR signaling.

The next text will be entirely devoted to the construction of an automation in rigid transit. At the end of this tutorial, everyone can then embark on the creation of an automation on their own networks.

See you soon !

Article written by François. Contact

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This article was translated by Pierre for the English side of the EEP-World from the article written by François for the French side of the EEP-World.

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