SNCF has completed a €33·5m programme to convert a TGV Réseau trainset for inspecting track, overhead electrification, signalling and telecommunications systems at speeds up to 320 km/h. Laurent Charlier reports

SNCF'S INFRASTRUCTURE division now has a new inspection tool at its disposal, which promises a real 'leap in performance' as then SNCF President Louis Gallois enthused during the unveiling of Iris 320 on June 12.

Originally conceived as MGV (Mesures à Grande Vitesse), Iris 320 brings together in a single, self-propelled train capable of operating at up to 320 km/h, or even 350 km/h under certain conditions, the complete range of infrastructure inspection and recording functions. These were previously undertaken by a whole fleet of specialised vehicles with different, and much lower, operating speeds.

SNCF manages the maintenance of the French national rail network on behalf of RFF. Iris 320 will simplify infrastructure inspection on the high speed lines and part of the conventional network, some 7500 track-km in total. Because it performs a wide range of functions at the maximum line speed, the new train will also free up train paths for commercial services. Another benefit is that inspection of the high speed lines no longer has to be undertaken within maintenance possessions.

More frequent and more rigorous inspection of track, electrification equipment, signalling and telecommunications should also help to improve the efficiency of maintenance operations, and encourage a general move from a reactive to a preventative maintenance regime.

Higher operating speeds and the ability to undertake in one pass operations previously divided between a number of vehicles enable more frequent inspections to made, which through data analysis should enable defects to be more readily prevented. Iris 320 will inspect between 3 500 km and 5 000 km every week, or 200 000 km every year. One week every three months has been reserved for maintenance of the train and its onboard systems. The train is staffed by two drivers and seven inspection technicians, and is equipped with a kitchen, dining area, sleeping accommodation and showers.

Holistic infrastructure management

Systematic inspection of the rail infrastructure using this new tool should enable SNCF to build up a complete picture of the state of the French rail network. Detailed local information on the condition of track, electrification equipment, signalling and telecommunications systems will now be available to the respective maintenance teams. Project Manager Jean-Marie Descusses stresses SNCF's desire to 'exploit the synergies between the different parameters measured to improve data analysis and the understanding of physical phenomena'.

The total number of parameters measured in a day by Iris 320 represents between 60 Gb to 100 Gb of data. The results are presented in real time and assessed on board, enabling data to be accepted or rejected depending on the quality and usefulness. This means that the results can be made available without the need for extensive analysis or processing off the train, and they can easily be compared with the results of previous inspection runs.

Classified as normal, urgent or critical, the inspection data is also transmitted by GPRS (with a slight time delay) for storage on a national server with a capacity of 80 Tb and an archiving capability of 20 years. On board Iris 320, the IT hardware comprises six redundant servers linked to measurement sensors and 12 workstations via a local area network with 20 km of optic fibre cabling, capable of transmitting data at a rate of 4 Mb/sec.

Maintenance teams should now be able to call up data captured by Iris 320 wherever they require it. Data is presented in the same format as used previously, but changes are likely to be made over time accompanied by appropriate training.

In-house solution

SNCF says that designing and building Iris 320 in-house has ensured that the performance of the new inspection train has been closely matched to the requirements of its infrastructure division. In addition, making good use of its own expertise has helped keep costs under tighter control; the railway reckons that recourse to an external supplier would have cost five times as much as the €33·5m spent on the project.

Of this total, €21·2m was needed to purchase a TGV Duplex trainset to replace the TGV Réseau set which was converted into Iris 320. No 4530 was the last three-voltage (25 kV 50Hz AC, 1·5 kV and 3 kV DC) Réseau set to be built, and was converted for its present role by SNCF's Hellemmes workshops in Lille, under the direction of the rolling stock division and its engineering centre at Le Mans. On December 9 2005 the train was delivered to Le Landy depot in Paris for final modifications and installation of the monitoring equipment.

Although it is a world-class inspection tool, and SNCF is keen export its expertise in this field, Iris 320 is unlikely to be seen much beyond the frontiers of its home country. 'The French inspection programme is already very full and will become even more so with the opening of new lines such as TGV Est and TGV Rhin-Rhône' said Descusses. In theory Iris 320 is currently capable of operating in Spain and as far as London, although its pantographs are not configured for the Channel Tunnel. In practice it is only expected to cross the French border to reach Brussels.

Iris 320 in profile

Car and Use

  1. OHLE observation post, track geometry monitoring
  2. OHLE and signalling monitoring, OHLE research area
  3. Positioning system, IT system with six redundant servers, telecommunications monitoring, research area, audio and video systems
  4. Workshop, spare parts store for monitoring equipment, office, meeting room with video display screen for group assessment of data
  5. Meeting rooms, buffet and food storage
  6. Kitchen and dining room
  7. Six sleeping compartments for onboard staff and drivers
  8. Four sleeping compartments, two shower compartments, OHLE observation post

Measurement capabilities of Iris 320


Geometry under load Measured by video camera, laser and inertial sensors. Replaces Mauzin track recording cars.

Vehicle/track interaction Measured at the front, middle and rear of the train, allowing ride comfort to be assessed. Replaces high speed test car Mélusine.

Rail tread defects Analysed on the basis of images captured by linear cameras.

Axlebox acceleration New measurement parameters enabling intermittent Wheel noise defects to be categorised

Overhead line equipment

Contact wire dynamics To meet the requirements of the programme to assess contact wire condition, due for completion by the end of 2006. Also research into fault recognition through signature analysis.

Arc detection To meet the requirements of the programme to identify major arcing sites, due for completion by the end of 2006.

Contact wire wear and To be introduced following reliability trials. Suppliers currently geometry unable to meet SNCF specification.

Shape of supply frequency Abandoned due to lack of suitable sensors.


UM track circuits for TVM Measurement of short-circuit strength at the front and rear cab signalling on high of the train. Measurement of transversal impedance. Replaces speed lines recording car Hélène and IES signalling inspection vehicles.

Traction current return Measurement of the difference in current between the two rails

KVB ATP system used on conventional lines.

Height and voltage of Conventional lines, replacing IES vehicles.track ramps

Phase jump loops and TVM 300 and TVM 430 cab signalling on high speed lines.EPI loops

ERTMS In preparation for deployment from 2007.


Analogue 400MHz Two systems are used to assess network quality and the track-train radio coverage of railway and private (Orange, SFR and

GSM-R, GSM, EDGE and Bouygues) networks: Carmen for analogue radio and UMTS (3G) digital networks Romes for digital.The latter meets ERTMS requirements.


Position location and GPS Systems linked to databases to ensure maximum precision and identify the relative position of defects.

Ancillary measurements Including energy of crossing trains, temperature, humidity. To assist with the interpretation of primary measurement data.

  • CAPTION: Iris 320 staff pose with then SNCF President Louis Gallois at the launch on June 12
  • CAPTION:A catenary measurement workstation
  • CAPTION: Iris 320 is seen here between Sainghin and Fretin junctions during a test run on TGV Nord from Oignies to Calais-Fréthun on June 21
  • CAPTION: Iris 320 Project Manager Jean-Marie Descusses (left) demonstrates the video screen installed in the train's main meeting room
  • CAPTION: Track geometry is one of the main parameters measured by Iris 320