Railway routes - part 2

Practical realization

Routes in rigid transit (classic solution known as mechanical)


After having treated in tutorial Railway routes part 1, the theoretical and general approach on railway routes, we now get to the heart of the matter with a tutorial  devoted to the practical realization of an automatic route management system in EEP. The proposed model will be called a “classic solution” because it will not make any use of programming in Lua language so as to allow as many people as possible to be able to build it without too much difficulty. Users familiar with the Lua language will certainly be able to write a program from the data which will be explained here. For those who do not master this computer language but who would like to get started in programming, it is planned to publish tutorial on this site at a later date in order to allow them to build a digital automation.

In the first tutorial we learned that the life of a route takes place in 5 stages if the route can be executed immediately or in 6 stages in the case of a hold.

Let us recall these stages:

  1. The calling of a  route 
  2. Compatibility check with other routes
  3. Putting on hold
  4. Initiation and establishment of a route
  5. Execution of the route
  6. Destruction of the route (Canceling of a route).

We will see later the importance of clearly distinguishing these stages when constructing automatisms in EEP. This allows us :

  • To perfectly design the automation according to the route you want to automate,
  • To greatly facilitate the construction and programming of routes in EEP,
  • To quickly identify the causes of operating anomalies.

On this last point I would like to stress the fact that errors are frequent despite all the vigilance that can be exercised. The contact windows to fill are numerous and an oversight, an inadvertent error quickly happens. We will be able to locate them all the more quickly when we know in which phase the error occurs, which will restrict the work of searching among the many contacts concerned by this same stage.

We will see all these points from the next tutorial when it comes to moving to the concrete realization of the routes in EEP. In the meantime, this tutorial will show us how to prepare a good installation of a route system. This step is particularly important because it will allow you to clearly visualize the routes.

The preparation consists of 3 stages:

  1. The construction of the OCP or optical control panel,
  2. Establishing of the itinerary table,
  3. Establishing of the incompatibility table.

The screenshots above (Figs 1 and 2) show us respectively the East and West rail works which surround the transit station of our network. Very readable as is, they can be used directly to establish the route table. It is therefore not necessary to draw up a OCP. However, we will build it for the purposes of this tutorial for educational purposes.

On the other hand, if I consider my “Lugdunum” network, the eastern rail works at the entrance to Lyon-Perrache station looks like this in 3D view (Fig 3):

Transposed in the 2D window (Fig 4) such a network is not readable. The track plan is difficult to use as shown in the view below :

In this case the establishing of a OCP becomes imperative. The optical control panel is a schematic representation of a network that allows the dispatcher to monitor traffic and plan the programming of routes.

The OCP that I am offering you here is inspired by real models for a better understanding of my tutorial, but in your work to develop the route table a simple sheet of paper, a pencil and an eraser will suffice. They will allow you to trace the paths by following the same principle of diagramming, the main thing being that your diagram is easy to use and that you can find your way around.

This step may seem tedious to you but in the end you will save a lot of time by clearly identifying the routes. The methodology that I am suggesting to you indeed limits errors in the construction of automation systems and makes it easier to identify and resolve operating anomalies.

Construction of the Optical Control Board

You should now be familiar with Figure 5 below. It is more or less the global representation of Figures 1 and 2 above:

  1. Route signs (S…) have been numbered in purple.
  2. The routes are numbered in red with the additional indication of origin or destination.
  3. Turnouts (A…) are numbered in green.
Figure n° 5

With such a diagram, even elaborated in a more rudimentary way, the visualization of the routes with the signals and track equipment becomes much easier. As an example, figure n ° 6 below provides direct reading information on the ITN (Itinerary) Paris – Marseille route via track 3, which is materialized by an orange dotted line. This route uses the following equipment points and crossings:

TJD 1 – A 302 – A 303 – TJD 2.

Translation TJD = DSS (double slip switch),      A or Ag = turnouts.  

This same route is protected at its entrance by the signal S 32 doubled at the exit of the station by the signal S 34. In this case as we are only dealing with rigid transit S 32 and S 34 must be opened to allow the passage of the train. Already I see observers rightly making some criticisms of such a device, especially if we consider that trains are likely to stop at the stations. They should be reassured in the configuration that I am proposing to you, the flexible transit is obvious. We will therefore review our station in the tutorial which will deal with flexible transit and we will then see that it is much more suitable for ensuring smooth management of rail traffic in a station.

Figure n° 6

Fig. 7 below gives us a 3D window preview of the eastern entrance to our transit station so that everyone can better visualize our configuration.

We can easily identify on the left the passenger building (BV) with from left to right, in order, tracks 1, 2 and 3 without forgetting the slip track which crosses track 2.

In the foreground on the right of track 2 the signal controlling the entry of ITNs 1 – 2 – 6 used for the identification of these routes. This is a combined SNCF signal ( France, signal abbreviation ) which presents a slowdown reminder indicating in this case that the train will be switched to track 3.

Establishing the itinerary or route table

Figure n° 8

Figure n ° 8 above shows the table of possible routes. The left part does not call for any particular comments. On the other hand, the right part is by far the most important. It must be filled in with the greatest care. First of all at the top of the columns are designated all the switches and crossings from TJD1 to TJD 2 likely to be used. In my example 12 routes are listed. Each time an ITN uses a rail equipment, this is mentioned in the concerned box.

Once completed this table becomes very explicit. In vertical reading of the columns we immediately see which routes are incompatible with each other. Thus, reading the TJD 1 column shows that ITN 1 is incompatible with ITN 2 – 3 – 4 – 5 – 6 –7 but the TJD 2 column also reveals that this same ITN 1 is incompatible with ITN 9.

From this first table we can now build a second table, which will be much easier to use, when we approach the practical construction phase of the automation controlling our network in the station. In the meantime, the work we have just done allows us to state the fundamental rule that defines incompatibilities:

Two routes are said to be incompatible as long as they have at least 1 turnout or rail equipment in common.

It follows from this fundamental principle that railway routes which have in common a switchgear (switch or crossing-junction) and a fortiori several switches can in no case be executed at the same time by several convoys.

Over time, two concepts or two different modes have emerged allowing the regulation of rail traffic in complete safety:

  1. Rigid transit in which routes are defined by an entry point, turnouts on the route and the exit point. In this mode of operation, in strict application of the principle of prohibition between incompatible routes, a route is only made free when the running train has passed the exit point.
Figure n° 9

The diagram shows us 2 ITNs in conflict: the 1st Marseille – Paris by track 3 (Turquoise) and the 2nd Paris – Marseille track 2 (Red). Assume that ITN Turquoise is running and ITN Red is requested. In rigid transit ITN Rouge can only be executed when the train on ITN Turquoise has passed point S towards Paris. For the duration of ITN Turquoise, train 2 will be blocked at signal ITN S 21.

  1. Flexible transit : this concept has emerged with the increase in rail traffic to allow greater fluidity in train traffic. Thus, when 2 routes have several switches and crossings in common and are therefore incompatible in the rigid transit mode, they can nevertheless run simultaneously in flexible transit as soon as the first route started no longer includes switches and crossings. together with the second on hold, even though the convoy traveling the first route has not yet passed the exit point.
Figure n° 10

Let’s take the same routes as before and observe in the diagram above what happens in flexible transit. Train 2 is stopped at S 21 as for rigid transit but where things differ significantly when train 1 has passed TJD 1 on the Turquoise route. In fact, there is no longer any cause for conflict between the 2 routes since, from the moment train 1 has crossed point < S’ > there is nothing to prevent the execution of the Red route. ITN Rouge is then engaged at this time without having to wait for train 1 to pass S, the exit point.

Flexible transit therefore makes it possible to reduce waiting times linked to incompatibilities. The time saved will be all the more considerable as the bundle of tracks has a large number of routes and the circulation involves heavy traffic of trains in both directions of travel. This is the case of the large Parisian stations where the circulation of suburban and mainline traffic can be done on hundreds of possible routes at the level of the entry-exit beam of the station.

In application of these two principles, the SNCF designed, at the time, two types of control stations:

  1. The fully automatic relay station or PRA ensuring the management of transit in rigid mode,
  2. The any relay station with flexible transit or PRS.

The PRA and PRS substations, named after electromagnetic relay technology, are now obsolete with the advent of digital management. However, these acronyms, even if they are obsolete, are often still used in model making because they correspond to route operation regimes whose principles are perfectly transposable and applicable in a world of virtual model railroading such as EEP.

Establishing the incompatibility table

The table below is the one that will be used for the installation of the track contacts ensuring incompatibility between the routes. The red crosses obviously indicate incompatibilities. The work that we have just carried out shows that on a fairly simplistic configuration (nothing to do with the entrance rail work of Dijon station or that of Lyon-Perrache) the realization of an automatic and secure management of routes has despite everything proven to be a complex and meticulous job. But the result is equal to the trouble we took. The movement of trains on a large station network with heavy traffic gives a spectacular result.

Figure n° 11

Recommended methodology for establishing the incompatibility table.

From a strictly practical point of view to limit errors, Table 10, below gives you the best procedure to follow. As I indicated above with the example of ITN 1 it is necessary to start with the horizontal reading of a route line. In the example below we are taking an inventory of routes incompatible with ITN 2.

If at all possible for the realization of tables 8 and 9, get help from someone around you. This helps to limit errors.

Given the significant risk of reading errors, it is necessary to be very methodical in drawing up the table of incompatibilities. Orderly exploitation is therefore essential. Here is an example from the Paris-Marseille route track 3 (ITN 2).

To do this we start with a horizontal reading of the ITN 2 Paris – Marseille line. From the first column (TJD 1) we see that it is entered ITN 2. We must now check the incompatibilities with the other routes by a vertical reading of the TJD 1 column.

This vertical reading indicates to us that ITN 2 is incompatible with ITN 1, ITN 4, ITN 5, ITN 6, ITN 7. We therefore mark with an X the corresponding boxes in the table of incompatibilities.

Once step 2 has been completed, we resume the horizontal reading of the ITN 2 line. The columns Ag 101, Ag 102 and Ag 301 are not filled in. There are therefore no incompatibilities for ITN 2 in relation to these track equipment. Arriving at the Ag column 302 we observe that it is filled in. There are therefore incompatibilities. We must therefore proceed as in step 2 by performing a vertical reading of this column.

This step shows us no less than 9 incompatibilities ranging from ITN 4 to ITN 12 inclusive. Since ITN 4 to ITN 7 incompatibilities have already been checked in step 2, we only need to report the ITN 8 to ITN 12 incompatibilities on ITN 2 line by checking the corresponding boxes with an X as before.

Once the report has been made in the incompatibility table, we take again in step 5 the horizontal reading of the ITN 2 line. We immediately note that the following column Ag 303 is filled in. We must therefore proceed to a vertical reading on this column as for the previous columns. This well be the subject of step 6.

Vertical reading and reporting of incompatibilities as for steps 2 and 4.

Continu horizontal reading of the ITN 2 line.

The TJD 2 column being filled in, we report the incompatibilities in the table 9.

This step ends the operation of the ITN 2 line. We will have to continue this procedure in the same way up to the ITN 12 line so that the incompatibilities table is completely filled out.

Note : The incompatibility of an ITN with itself should be entered on the incompatibility table. This may seem odd considering that the train, when it acts on the contact of the approach and route call relay, can only be on its own. Certainly, but once this train has entered the route, a second train can arrive just behind it on the same line and request the same route. Not considering an ITN as incompatible with itself would in this case lead to authorizing the second train to enter a route already occupied by the first train, which is an aberration unless it is, for example, to a locomotive in operation which must come to couple with a train waiting at the station. We will see subsequently (in an other tutorial)  how to deal with this scenario which for the moment is outside the scope of our study.


This tutorial has shown you the necessary preparatory work to be carried out  if one does not want to expose oneself to insoluble problems of cascade operation.

Happy reading and do not hesitate to contact me on the forum if some points of this tutorial does not seem clear to you.

The next tutorial will be entirely devoted to the construction of an automation in rigid transit. At the end of the 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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