Commissioned from 1967 - 1974 the CC 72100 locomotives for the SNCF were the most powerful diesel electric locomotives in Europe. A total of 92 machines were built to haul fast Intercity trains across the non-electrified portions of the French network as well as being capable of moving heavy freight trains.
The class could be seen throughout France for many years, but with the increase of the TGV network, and the replacement of many loco-hauled trains with units their work has declined. By the mid 2000's many locomotives had been withdrawn, but there was still one line with a medium term requirement for the machines, the old Line 4, from Paris Gare de l'Est to Mulhouse and on to Basel in Switzerland.
Known for their noise and pollution, residents in Paris had long campaigned against these locomotives, and so it was that between 2002 and 2004, 30 examples of the class were rebuilt with new engines and silencing to become the CC 72100's. These locomotives soon replaced all of the original 72000's on the route, and by 2010 were the last of the class working regular passenger trains, Just a handfull- (2 at the time of writing) of original CC 72000's remaining in traffic on freight and special duties.
All now carrying the latest 'En Voyage' livery in place of the classic blue and white colour scheme the 72100's working out of Paris Est are still impressive machines offering good diesel runs on what is now France's last all diesel trunk route. While the service was hit with the opening of the TGV Est in 2007- direct services to Basel being withdrawn, and many other services truncated and no longer reaching Mulhouse, this line is still worth riding.
You will, however have to be quick. The death nail for Line 4 is fast approaching with the TGV Rhin-Rhône route to Belfort and Mulhouse due to open early 2012. While it is unclear exactly what fate will befall the loco hauled trains, it is clear that the service will be severely hit, and likely that the remaining trains on the classic Line 4 will be worked by DMU's. Whether the 72100's will be re-deployed elsewhere remains to be seen. In the meantime it certainly does feel that winter of 2011 may be the final swansong of the classic CC 72100 diesels on the SNCF.