Integrating ETCS Level 2 with TVM430 on TGV Est
The Paris - Strasbourg TGV line is the first in France to be equipped with ETCS Level 2 for trains running through to Germany, but will also have the domestic TVM430 train control. Richard Hope explains how some complex system interface issues are being resolved
JUNE 2007 has been set for the start of commercial services on the 300 km first stage of TGV Est, or LGVEst Européenne, as it is officially known, between Vaires-sur-Marne 23 km from the Paris Est terminus and Baudrecourt, near Metz.
Given the delays elsewhere, it may yet turn out to be the first line in the world on which the standard operating speed is 320 km/h - although this speed is already permitted on short sections of TGV Méditerranée. The alignment will permit 350 km/h in the future. No firm date has been set for completion of the remaining 106 km to Vendenheim, on the edge of Strasbourg, but it is hoped that construction will get underway by 2010 at the latest.
The official name reflects the fact that TGVEst is destined to be a very important international route, even before the second section is completed. According to Alain Le Guellec, SNCF's Director responsible for TGV Est services, 30% of passengers using the fleet of 52 TGV sets allocated to this line will be travelling to or from Germany or Switzerland, and 70% on domestic services or those to Luxembourg. This made TGV Est the logical choice for the first ERTMS installation in France.
From June 2007, Frankfurt will be only 3 h 45 min from Paris via Saarbrücken and Mannheim, with five daily services each way from December 2007. Paris to München via Stuttgart and Strasbourg will take 6 h, and Zürich via Strasbourg and Basel 4 h 30 min.
RFF and SNCF reached the cost-effective decision that TVM430, the standard LGV signalling system, must also be available. Because the projected loadings do not generally justify double-deck stock, 33 TGV Réseau trainsets are being refurbished. These will not be equipped with ERTMS, and will operate over the new line using TVM430.
There will also be 19 TGV POS trainsets equipped specifically to operate the international services into Germany and Switzerland. Formed from new multi-system power cars and refurbished TGV Réseau trailers, they will be fitted with ERTMS and TVM430, with ERTMS used for preference on the TGV Est, and existing train protection systems such as Indusi and LZB when running in Germany. For operation in Switzerland they will be fitted with ZUB and Integra.
In addition, five of German Railway's ICE3M trains are being adapted to run through to Paris. These will be fitted with TVM430 for use on TGV Est and the French KVB automatic train protection needed to allow them to run on conventional lines; they will be equipped with ERTMS at a later date.
GSM-R already in use
A GSM-R radio network is already in use for works trains on TGVEst, and this will be used to support the ERTMS. This spring will see GSM-R brought into use for voice only along the existing line between Paris and Bar-le-Duc. Addressing the Institution of Railway Signal Engineers' convention in Strasbourg last September, Jean Cellmer of RFF explained that TGV Est would be 'totally immersed' in a larger area where GSM-R coverage would be in use on other lines from a total of 58 base stations, replacing obsolete analogue radio systems.
Cellmer said that each base station was being connected to both of the TGV Est switching centres from which the communications network is monitored. This is being done to create redundancy, and also to avoid any problems with handing over a train from one centre to the other. Whereas a TVM failure only affects about 20 km of track, which is manageable in terms of keeping trains moving using block markers and verbal orders, 'we face the risk of losing ETCS along the whole line' if the radio network breaks down, he explained.
In addition, RFF has decided to install solar-powered trackside 'phones' on TGV Est that are linked independently by radio to the traffic control centre at Pagny-sur-Moselle. These can be used to keep trains moving if there is a total failure of the ERTMS.
'One signalling system'
Olivier Pignal, SNCF's Director responsible for ERTMS, is at pains to emphasise that 'for signalling designers, for safety engineers, for signallers and TGV Est traffic controllers there is only one signalling system.' The block sections are the same.
In the case of the drivers, they must drive to ERTMS rules if the train is equipped with ETCS, but if not they must drive according to TVM rules. A train using TGV Est can be fitted with either system, or with both, in which case ETCS will normally be used.
One of the first safety issues to be addressed was the compatibility of the track-to-train transmission systems used by TVM and ERTMS. TVM430 relies on coded track circuits using a 2kHz carrier in the rails to provide continuous communication, and local loops transmitting at 62·5kHz and 125Hz. ERTMS sends data by GSM-R at 1800MHz, and the Eurobalise operates at 27MHz. No difficulties there.
Pignal noted, however, that there had been 'some problems of compatibility between KVB and Eurobalises' when ETCS-equipped trains used the conventional lines in France - but this had nothing to do with the use of TVM and ETCS Level 2 on the same line.
The basic signalling function on TGV Est is performed by Ansaldo SEI interlockings, which detect the location of trains from track circuit occupation and send instructions to the train via the TVM track circuit codes.
The Radio Block Centres collect the data they require from the SEI interlockings (Fig 1), and use it to generate movement authorities for transmission to those trains that are being driven in ERTMS mode.
One difficulty that had to be overcome was the fact that when TVM enforces a stop from 300 km/h it displays to the driver successive speed reductions, along with a target distances to the next reduction, until '000' appears. One block section is left as a safety overlap in case braking is not fully effective.
An ERTMS train, by contrast, calculates and enforces a smooth braking curve using data stored on board. It requires no overlap because that safety margin is built into the braking curve. This will permit any ERTMS trains with improved braking characteristics that may be introduced in the future to follow each other more closely without altering the signalling parameters, thus automatically reducing the headway.
The signaller should see no variation in the way he handles trains using ERTMS or TVM, even though the drivers may have to follow different procedures.
Pignal quotes the example of two trainsets starting from different locations that have to be joined at an intermediate stop for the journey to Paris. If the second train to arrive is running on TVM, the driver will stop it at the Nf03 marker board (Fig 2). After a short interval, he will take his train forward on sight to stop at the rear of the first trainset, where they are then coupled.
If ERTMS is being used, the second train arrives under a movement authority which ends close to the F05 marker. Having stopped here, the driver requests authority to drive on sight. When this is granted, an icon appears on his cab display and he can move forward.
As might be expected, the displays in the cab which tell the driver how fast he is going and indicate how fast he should be going are quite different for ERTMS and TVM (Fig 3). ERTMS uses an electronic dial to display the actual speed, the permitted speed, the target speed (which may be zero), and the distance to that target location.
The linear and digital TVM display shows the target speed, which must not be exceeded when passing the next lineside marker board, and the distance to go to the target. The actual speed is shown elsewhere on the desk.
As TGV Est is interoperable, all trains fitted with ERTMS must use the standard speed and target distance displays as laid down in the appropriate TSI. The Driver-Machine Interface that will be installed in the cabs of TGV POS therefore includes the standard ERTMS dial arrangement and other features mandated by the TSI (Fig 4). This display will also be installed in the Thalys TGV fleet for operating on high speed lines in Belgium and the Netherlands (p142).
Obviously, drivers of TGVs relying on TVM430 will have to know the normal rules that apply to high speed lines in France. However, the rules for driving ERTMS trains are standardised and mandatory on TGV Est for any train using ERTMS. In degraded modes, such as passing closed markers and driving on sight, the rules normally in force on TGV lines will apply. But to give an order to the train, the signaller will use European forms to ensure that the instruction is understood by the driver.
Validation at Valenciennes
In view of the complexities involved in using two train control systems on the same line, and the difficulties that arise from trying to validate them on a working railway, Pignal explains that the first stage of this process is already in progress in a laboratory at the Centre d'Essais Ferroviaires test centre near Valenciennes.
Two rooms are used, one representing the trackside equipment and the other representing the train (Fig 5). The first room contains two radio block centres supplied by Ansaldo which are actually receiving data in real time from interlockings controlling TGV movements between the stations at Aéroport Charles-de-Gaulle and Marne-la-Vallée.
The second room contains the Eurocab modules and the driver's display, which is connected by GSM-R modules to the RBCs. Simulators supply data on the movement of the 'train' being driven such as the speed and braking force. Eurocabs from different suppliers can also be tested here to demonstrate cross-acceptance.
The second test phase, which started in January, uses SNCF's ERTMS test train which runs around a loop inside the Valenciennes site at up to 80 km/h. The train exchanges data with the two RBCs in the laboratory (Fig 6). Tests that cannot be done in the laboratory but are possible on the test ring include movements at stations with points.
The next stage, planned for this spring, is to run the test train on an existing high speed line, and once again the TGV Ile de France between Charles-de-Gaulle and Marne-la-Vallée will be used for this purpose, still communicating with the two RBCs at Valenciennes.
Finally, the test train will move to the section of TGV Est which has been completed early, in readiness for validation of the complete system. Then it will be time to operate a TGV POS at 320 km/h in preparation for the start of commercial service in June 2007.
Picture caption: TOP: After commissioning tests at Velim, SNCF's pre-series TGV POS trainset is currently undergoing interoperability certification trials on the German Railway network
RIGHT: Fig 1. Overview of the combined ETCS Level 2 and TVM430 signalling installation being developed for TGV Est
Picture caption: Fig 2. ERTMS will allow portioned workings to be joined more efficiently by reducing the distance over which the second portion must be driven slowly on sight
Picture caption: BELOW LEFT: Fig 3. The ERTMS driver-machine interface (left) provides more information than the present TVM cab signalling display (below)
RIGHT: Fig 4. The driver-machine interface for the TGV POS trainsets is based on the ERTMS standards, and will also be retrofitted on the Thalys multi-system TGV derivatives
Picture caption: ABOVELEFT: Fig 5. The ERTMS validation tests at Valenciennes are based in two rooms, with one representing the lineside equipment and the other the trainborne systems
ABOVE: Fig 6. Once the tests at Valenciennes have been completed, SNCF's ERTMS test train will be used to validate real-time operations using a section of TGVIle-de-France, communicating with the twoRBCs at the test centre
Picture caption: SNCF's ERTMS test train is currently being used to validate the Level 2 equipment at Valenciennes, and will then start live testing on a section of TGVIle-de-France
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The 320 km/h Paris - Strasbourg TGV line will be the first in France to be equipped with ERTMS Level 2, but it will also have TVM430 train control for domestic TGV services. Richard Hope explains how SNCF and RFF are resolving some complex interface issues by ensuring that the two systems do not interfere with each other, and making their differences invisible to signalling staff even though the drivers must observe different operating rules.
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