Part 4
Routes and Automation in EEP

Flexible transit in EEP

Note : that the writer of the article is from France and therefor uses French themes, signals, and equipment. The names and initials used in the pitchers and diagrams are kept the same for practical reasons but are explained in English through out the article


Presentation of the support network

We have seen in the articles devoted to rigid transit (parts 1 , 2 and 3) that this mode of traffic operation precisely lacked flexibility because an engaged route blocked all other incompatible routes as long as it was not released at the end of the route. This is why engineers very quickly, with the development of rail traffic, developed flexible transit allowing much faster flow of traffic in a switch area.

This article therefore proposes to transpose the operating regime in flexible transit mode into EEP.

The support network

As support for our study, here is a very simple little network. First, let’s define the operating rules for this mini-network: train traffic is one-way. In other words, all trains enter either through the entrance to track 1 or to the entrance to track 2, and exit at exit 1 or 2 depending on the route assigned to them (Fig 1).

Figure n° 1

Important : No train are running in the opposite direction !

In this network, entrance 1 and 2 are each protected by a route entrance signal. On track 1, the signal defined here as SIG ITN A is of the 4-light type with unified panel type B while on track 2, we are dealing with a signal with a slowdown reminder mounted on a unified panel type G. On our network this signal is called SIG ITN B.

We will see below why we have installed a different signal at each of the entrances. However, they both have one essential point in common, namely that they display in the closed state the square (double red light … France stop signal) that can not be crossed. This non-passable stat is confirmed by the Nf (non franchissable ) plate affixed to the middle of the mast.

The square is imperative here because we are entering a switch area which requires total safety to avoid any risk of collision between two trains.

The itineraries present

For the purposes of the tutorial and in order not to lengthen  the explanations, we have limited are selves in figure 2 to only two routes, called ITN 1 (by the entrance track 1) and ITN 2 (by the entrance track 2).

Figure n° 2

The ITN1 (blue) route is straight from end to end and therefore does not require slowing down to cross a switch on a diverted track. On the other hand, the ITN2 route (red) crosses A2 and A3 on a diverted track. A slowing down of 30 or 60 km / hour is necessary which explains the presence of the signal with slowdown reminder. The choice of deceleration speed will depend on the angle of the deviated track. If this angle is important, it will then be advisable to choose a slowing down to 30 km / h.

Moreover, the observation of the above network shows us that from the entrance to track 1 two other routes are possible, as for track 2 we have a second route possible.

So these are 3 other routes that we did not list in our study, so as not to overload it as we mentioned above. The reader can take over this network at will and build it by programming all of the routes. It would also be an excellent exercise for those who are not familiar with so-called “mechanical” programming (exclusive use of logic signals or used as such and track contacts without any Lua script). I called this programming mode “mechanical” because it draws heavily on the electromechanical management used in the past with the use of track contacts.

Figure 3 is a right sided view of our demonstration network. It allows us to visualize the lines of the routes from another angle revealing us that the A2 and A3 switches (circled in yellow) are common to the ITN1 and ITN2 routes. This means that these two routes are incompatible to each other with respect to these two switches.

Figure n° 3

In rigid transit management, the ITN2 route (red line) will only authorize the initiation of the ITN1 route when the rear of the convoy has passed the BAL signal downstream of A4.

In flexible transit, the engagement of the ITN1 route can be operated as soon as the rear of the train in ITN2 has passed A3.

The table below (fig 4) summarizes the essential characteristics of these two routes ITN 1 and ITN 2:

Figure n° 4

The question now arises of knowing how to differentiate flexible transit from rigid transit in its practical application. The answer to this question is the subject of Chapter II below.

Building a flexible transit in EEP

The switch engagement relays

We have seen in rigid transit that the use of an invisible 2-state signal (stop – clear), called route interlock signal or SEI, locks a route thus preventing any execution of another incompatible route. with this one. The Clear state indicated that the route was not engaged (therefore free) and conversely, the stop state prohibited any engagement.

In flexible transit, the engagement is no longer done at the route level as a whole but more finely at the level of the switches and crossings used.

For this, let’s see in 2D view the switch area of ​​our network with turnouts A1, A2, A3 and A4.

Each switch is backed by an invisible signal that acts as a turnout engagement relay (REA). So we have the following correspondences:

  1. A1 and REA 9
  2. A2 and REA 10
  3. A3 and REA 11
  4. A4 and REA 12
Figure n° 5

The 4 turnout engagement relays have been placed in the closed position for better readability against the green background.

In reality, looking at the table in Figure 4, we obtain by deduction the table below, with for each switch the invisible signal ensuring the function of the turnout engagement relay.

Figure n° 6

So for ITN 1 we know that REA 9, 10 and 11 will have to be engaged to ensure that the route is locked. For ITN 2, REA 10, 11 and 12 will be requested.

Important : in the present case where we only have 2 routes, we note that A1 and A4 are not points common to the 2 routes. In this case we can do without REA 9 and REA 12 so not to overload the file. If we had built the 5 possible routes as I indicated above, we absolutely would have had to place an REA for each switch.

Operation of turnout interlocking relays

Closing relays

The REA signals are closed when the route is initiated by the action of the mobile switch on the route programming line. We will see this point below when we deal with the structure and operation of the Itinerary Management Automation or AGI (see paragraph 2.2.2.).

At the moment as we are in the 2D window lets look at the opening of the turnout engagement relays.

Opening Relays

The turnout engagement relays are released after the train has passed. Let us first study the case of our network with only one direction of circulation.

Figure n° 7

The REA signal contacts are placed at the turnout exit so that they can be actuated from behind the convoy when it has left the turnout area. Thus in circle A3 we note the presence of 2 contacts, ie 1 per exit way. On the other hand, for switch 4, a single contact is sufficient since there is only one direction of movement.

I stress that we are dealing here with signal contacts (in this case REA 11 for A3 and REA 12 for A4).

As in the switch areas, traffic is usually done in both directions, especially at the entry and exit beams of the station, I indicate in figure 8 what the placement of the contacts should be at the exit of the switch area. (Switches circled in pink). Not really rocket science here. It’s just a matter of common sense.

Figure n° 8

Each direction of movement is indicated by an arrow with an appropriate color. We find the REA signal contacts on the tracks, marked with circles of the same color as the direction of travel. As a simple turnout has 3 exits, we will also have 3 REA signal contacts per turnout. Here it is important to clearly define the direction of circulation for each REA contact, otherwise it will inevitably have untimely operations.

Programming each contact on the track does not pose any particular difficulty.

Figure n° 9

As an example, let’s look at the programming of the REA 11 signal contact coupled with the A3 turnout of our network.

The information inside the 2 red boxes must be programmed. The direction of circulation should be defined as I mentioned above. It must be triggered by the tail of the train (end of vehicle) and the automatic mode activated.

As this involves programming a opening of the switch engagement relay, the position mentioned in the lower box must be ‘Clear‘(or open or free depending on the signal used), which will make the turnout available, if necessary, for engagement. from another route

The automatic route management system

Schematic diagram principal

All of  the components of a route mechanism are important, the fact remains that the heart of the device lies in the automation itself, which acts like a brain receiving information from the rail network and transmitting back to the track the orders necessary to ensure the proper exploitation of the traffic.

So that everyone can remember the general articulation of a route management system, I reproduce the principle diagram as I had inserted it in the third part on rigid transit but in this case adapted to flexible transit.

Figure n° 10

The general articulation remains the same except that the interlocking and destruction are done by means of the switch interlocking relays coupled to the switches and crossings.

In general, we can consider that the data coming from the network is information that will be exploited by the automation which will send back orders to the track.

Structure and operation of the automation


Figure 11 below shows us the configuration of the automation built as part of our support mini-grid. Those who have read the articles devoted to rigid transit will find an air of déjà vu in this mechanism.

Figure n° 11

you find the same structure as a whole. At first glance, the only notable difference is the disappearance of the route initiation signals (SEI) which were placed to the right of the route calling signals (SAI) which have not disappeared. In fact, since the interlocking is carried out at each turnout thanks to the REA signals, the presence, in theory at least, of SEIs is no longer justified in flexible transit. However, I will come back to this point at the end of the article because it may be wise to keep SEIs in certain cases.

Those who are familiar with the articles on rigid transit will observe some modifications which are not functional but which are only intended to bring more clarity in the study of the mechanisms. So I chose the term route establishment rather than route execution in so far as, strictly speaking, the automation establishes a route by adequately positioning the switches  and opening the signal. ‘route entry. Execution, on the other hand, takes place after the route has been established when the train executes the same route in the direction in which it is going to travel.

We will not dwell too much on the design of the automation, which has been explained at length in the previous tutorials. I will limit myself to a simple reminder to save the reader from going back and forth.

In this case, the first route line corresponds to ITN 1 and the second to ITN 2. Each line is made up of segments each corresponding to a specific phase in the life of a route.

A mobile vehicle called “Schaltauto” in German, a term we translate as mobile commutator (CM), is constantly running the automation system. The segments are linked together using the virtual connection feature in EEP. The lines are connected to each other in the same way. Thus the mobile commutator traverses the line ITN 1 from 1 to 2, then jumps via the virtual connection from 2 to 3 to traverse the line ITN 2. At the end of this line a virtual connection in 4 allows it to return to 1. This cycle is permanently ensured at approximately 400 km / h which allows rapid processing of information and orders between the track and the automation itself.

The internal operating principle of the automatic system is based on a permanent exchange between the mobile commutator and the contacts placed on the route lines, working in particular on the route selection of the switch.

Figure n° 12

The vehicle control panel in the 3D window, called the EEP control window, displays in automatic mode the route selection as shown in figure 12.

Here the commutator displays the state ‘0 NEUTRAL‘.

In the present case, we should not consider the routes of the mobile commutator (CM) as routes in the literal sense of the term but as ‘states’ which will act on the contacts placed on each route line. This is why we will henceforth retain the term ‘state’ by reserving that of route only for the different routes that trains must take on a network.

For the proper functioning of the automation, we have defined 7 states:

  • 1 CALL
  • 6 HOLLDING     

We note that these states correspond to the different phases in the life of an itinerary from the request to open or call until its destruction

These states are saved the same as all routes created by you in the route editor

We will see in detail the function under taken by each of these states in the following paragraph.


The operation of the automation is based in particular on the states displayed by the mobile commutator. In the following paragraph, let us now analyze, from the programming of the different phases, the internal workings of a route line.

Programming each phase

We will take the ITN1 route as a reference to explain the programming of each of the phases.

Figure n° 13

The call segment has 2 vehicle type contacts here marked with numbers 1 and 2.

Figure n° 14

Vehicle contact n ° 1 : Once the SAI is closed, the mobile commutator (CM) must take the state of 1 CALL ITN (french 1 appel) regardless of its state at the it’s entrance. However, we will see that the CM will be systematically assigned the 0 NEUTRAL state (red box 1 french 0 NEUTRE) each time it exits a route line.

Box 2 conditions the change for the state of the CM. If the SAI (provided here by signal 13) is at the stop position, in other words closed, this means that the ITN1 route is requested by a train on track 1.

The mobile commutator (CM) then takes the 1 CALL ITN state to be able to act thereafter. If there is no route request the SAI 13 will be in the clear state and therefore the CM will keep the same state (0 Neutre) as at the entrance and will have absolutely no action on the route line.

Figure n° 15

Vehicle contact n ° 2 : The second contact on the call segment is limited to switching the state of the CM to (french 2 VERIFICATION)  2 VERIFICATION state. Everyone will note here that if the mobile commutator is in 0 NEUTRAL state, nothing will happen.

2 - The Verification process
Figure n° 16

At first glance, the second segment has only two contacts but in reality it has many more due to the presence of a group  contacts (in black numbered 1 on the diagram) depending on the number of relays switch’s (REA) to be checked.

By opening the contact group we see here that it contains 2 vehicle contacts. Each contact verifies  whether a turnout engagement relay is not already closed. This phase is particularly important because it will be decisive in the initiation or not of the requested route.

Figure n° 17

We saw above that only switch’s 2 and 3 were common to the ITN1 and ITN2 routes. These switch’s being coupled respectively to the REA 10 and to the REA 11, the verification phase will consist in ensuring that neither the REA 10 nor the REA 11 are already engaged.

So let’s open a vehicle contact to see its programming.

Figure n° 18

The mobile commutator being in state 2 VERIFICATION phase it verifies through red box 2 the position of REA 10. If signal 10 is not ‘Clear’ then the CM takes state 6 HOLDDING, which will neutralize any action on the rest of the route line as we will see below.

As the incompatibility concerns points 2 and 3, the verification applies to the REA coupled to these 2 switches, namely signals 10 and 11.

It is obvious that the contact group contains as many vehicle contacts as there are REA to check . Here we have deliberately opted for a simple scheme but in a complex bundle we could have routes with 10 switches in common with other routes. In this case, there would be 10 vehicle contacts programmed like that of FIG. 17, obviously with a specific number for each REA signal verified.

On leaving the contact group if no REA signal was triggered, the CM will have retained the initial state displayed at the entry of the verification segment. On the other hand, a single closed REA is sufficient to set state to 6 HOLDDING.

It is at the exit of the contact group that the vehicle contact 2 intervenes.

Figure n° 19

One of two things: either the CM exits in state 2 VERIFICATION, which indicates that nothing is opposed to the engagement and establishment of the requested route, or conversely it exits at the ‘state 6 WAITING for having detected 1 or more REA in closed position.

We see here that if the CM is in state 2 VERIFICATION it thereby takes on state 3 INITIATION since no other condition is imposed except the original state.

Figure n° 20

Segment 3 of the route line  INISIATION segment has 3 contacts or more precisely 1 group of contacts and 2 separate contacts (in red the SAI contact and purple, the vehicle contact). As one can imagine the group of contacts 1 will bring together all the REA contacts to allow the immediate engagement of these signals. So even before the establishment of the route our ITN 1 in this case will be locked and protected.

Figure 21 shows a view of the  group contact window n ° 1 of the INITIATION segment.

Figure n° 21

This shows the signal contacts 9, 10 and 11 corresponding to the REA ensuring the protection of switches 1, 2 and 3.

In so far as only turnouts 2 and 3 are involved in the conflict between ITN 1 and ITN 2, one might rightly be surprised by the presence of a REA contact 9 ensuring the engagement of switch 1. I ‘ve intentionally inserted the REA 9 contact to allow me to check the correct layout of the route in the radar window. However, the presence of this contact in the programming of the INISITAION has no effect since the verification for the opening of the ITN 2 route does not take into account the REA 9 as shown in the figure below.

Figure n° 22

Figure 22 taken from the group contacts on the verification segment of the ITN 2 route clearly shows us that this same verification does not take any account of the REA 9. Only the REA signals 10 and 11 linked to the switches 2 and 3 common to the 2 routes from our network.

Thus, closing the REA 9, specific to the ITN 1 route, has no impact on the programming of the ITN 2 route.

Figure n° 23

Programming REA contacts is easy. The only condition is that the CM must be in state 3 INISIATION. It will be remembered that this same CM keeps state 0 NEUTRAL if no call request is detected in the first segment or, on the contrary, takes state 6 HOLDDING if an incompatibility is detected during the verification phase.

These 2 states neutralize the mobile commutator which can not then exert any particular action here. Forgetting to program this contact, for example inadvertently left in the “all routes (cartridge 1)” state, would systematically close the REA 10 and very quickly lead to a blockage.

Of course, all the REA contacts of the turnouts common to several routes will be grouped together and programmed in the same way.

Still on this line segment ‘INISIATION’ we then find the signal contact of SAI 13 actuated and closed by the approaching train. As the route has been validated, the closed position of the SAI is no longer necessary. On the contrary, keeping it in the closed state would lead to requesting the programming of ITN 1 again each time the CM goes to the CALL segment.

Figure n° 24

Figure 24 shows us which programming parameters should be displayed in boxes 1 and 2 to trigger the return of the SAI to the idle state (Clear).

We have seen above that if route ITN 1 could not be initiated, the CM would switch to the verification phase in state 6 HOLDDDING. Then passing here on this contact he could not drop the SAI which will remain closed for a new call to the next passage on the call segment of route line A.

We have here rigorously the same mechanism as for the rigid transit.

Third and last contact on the engagement segment, the vehicle contact thus positioned controls the change to state ‘4 ESTABLISHMENT’.

Figure n° 25

Figure 25 shows us that only state 3 INITATION of the mobile COMMUTATOR allows the transition to state 4 ESTABLISHMENT. Any other programming of the route in box 1 would induce untimely operation in the execution of a route.


This phase consists of creating the requested route by properly positioning the switches placed on the route and opening the route entry signal. Concretely in our mini network the turnouts 1, 2 and 3 will be positioned in direct route then the signal (SIG ITN 1) n ° 5 will be open to Clear.

Figure n° 26

The ESTABLISHMENT segment has 3 contacts. Let’s open the group contact 1 as shown in figure 27:

Figure n° 27

The group contact  contain all of the turnouts involved in the ITN 1 route.

Do not forget here switch 1. We have seen that A1 is not shared with ITN 2 and that consequently it is not necessary to include REA 9 in the verification phase of ITN 2, nor necessarily to program it in the initiation. On the other hand, turnout 1 does figure in the establishment of the ITN 1 route and must therefore be taken into account.

There is no difficulty in programming each switch.

Figure n° 28

It is obviously important that each switch be programmed as indicated here by figure 28. The box 1 must obligatorily display ‘4 ESTABLISHMENT‘ under penalty of untimely operation.

The position of the switch in box 2 depends of course on the line of the route.

Contact 2 in figure 26 activates the route entry signal 5 on the track.

Figure n° 29

Box 1 tells us that this is indeed signal 5, titled SIG ITN 1 in our network as we saw at the beginning of the article in Figure 1.

The mobile commutator must always be in state 4 ESTABLISHMENT as it appears in box 2.

box 3 specifies the appearance of the light. In our network signal 5 is in the ‘Clear’ state.

Here again, the programming will depend on the layout of your route. Thus for ITN 2 signal 6 is programmed in the state ‘Warning signal, recall idle 60 km / h’.

Figure n° 30

The last contact in the ESTABLISHMENT segment changes the mobile commutator to the ‘5 DESTRUCTION‘ state. One should logically expect to find in box 1 the mention of the route ‘4 ESTABLISHMENT’, the phase which precedes the destruction.

This apparent logic is, in fact, not good. Indeed, it is only when the route is established that the train will enter and travel it. It will take some time, given its speed and the length of the route.


This means that when the train acts on the dropout contact of the REA linked to the last incompatible turnout (here REA 11 with switch 3) the mobile commutator which, let’s not forget, runs along the route lines at close to 400 km / h will be in a place that can not be defined in advance.

With respect to time, the destruction of a route is therefore not immediately following that of the establishment.

Also, the condition of the CM for the destruction of the route is not of any kind before entering the last segment of the route line.

5 - Destruction

In fact, the destruction phase is carried out as the train travels its route, dropping the REAs from the rear of the convoy. So when the train on ITN 2 has dropped REA 11 / switch 3, the ITN 1 route can then engage and run even if switch 4 has not been released before.

In absolute terms, this means that the destruction phase is not necessary and that in this case the DESTRUCTION segment is superfluous, to say the least.

So why did you schedule it if it turned out to be useless?

Here it is important to take into consideration the existence or not of a route initiation signal (SEI) as in the case of rigid transit. I indicated above (paragraph Structure) that in the context of flexible transit, the SEI is not absolutely necessary.

This is the reason why SEIs do not appear at the end of the route lines in Figure 11. However, I installed them on my network which justifies the presence of the destruction segment.

We will not go into the scope of this article on the usefulness of the presence of SEIs in flexible transit. Let’s just say that its presence allows for better management of flexible transit at the station entrance beams. This will be the subject of an article specially devoted to transit at a station, as this takes into account station stops which may be shorter or longer.

Let us nevertheless see the programming of the destruction.

Figure n° 31

The destruction segment has three contacts as we can see in figure 31.

Let’s take a look at Group Contact 1 first.

Figure n° 32

Figure 32 tells us that 3 vehicle contacts are included in the group contact. We see in the right part that the contacts exert a control on the signals 9, 10 and 11 which are the REA engaged to lock the route ITN 1.

Figure n° 33

Let us now examine vehicle contact number 2 in figure 31. It controls signal 10 (REA 10 / switch 2) as indicated by box 2.

The ‘5 DESTRUCTION’ state is the imperative for the control to take place.

Here the condition is at ‘is not‘ condition. If the REA 10 is not in the Clear stat, this means that the switch 2 which is associated with it is still engaged. If this condition is met, the CM will then take the “6 HOLDING” state, which will prevent it from taking any action on the next contact.

It suffices that the ‘is not‘ condition occurs only once, regardless of the total number of vehicle contacts in the group, for the state of the CM to be switched to ‘6 HOLDDING’.

Figure n° 34

Contact 2 in the DESTRUCTION segment is a route start signal (SEI) 14 contact.

The fallout from all REAs kept the ‘5 DESTRUCTION‘ state alive. This state now acts on the SEI which falls back to the CLEAR position. In other words, the route is no longer engaged.

We have reached the end of route line ITN 1. Before the mobile commutator jumps to line ITN 2, it should be reset to the ‘0 NEUTRAL‘ state.

Figure n° 35

Vehicle contact 3 in the DESTRUCTION segment performs this function. As it may, when arriving on this contact, be in different states, no route condition appears in cartridge 1, which implies that the CM will always exit in the neutral state.

We have come to the end of the study of flexible transit using a simple network model implementing 2 routes, which is already more than sufficient to allow a good understanding of the subject.

In a future article, we will complete this study by showing how to establish a table of route incompatibilities by taking into account the switches of each route.

In addition, we will see the management of routes with SEI in the station area. Rest assured, this particular point will not call into question what we have studied throughout this article on the structure of automation and its internal programming. It will simply give full justification for the presence of the destruction segment on the route lines.

To conclude...

Until then, I can only encourage you to build a network similar to the one we have used here for support or to create your own. Don’t be greedy at first. Make a simple network with 3 or 4 routes at most. This is enough to learn but also to make mistakes. I do it every time because it’s almost inevitable. You yourself will make mistakes. This happens systematically taking into account the number of parameters to be established for each of the contacts. The greater the number of routes, the more switches there will be and consequently the greater the number of contacts to be configured. The most difficult will then be to locate the error in order to correct it, especially when you are a beginner. With experience we come to identify more often the location and nature of the error, but sometimes finding it remains a difficult task. This is the reason why I recommend that you work on a modest network at the start.

Good luck everyone and 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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