Monday, 5 December 2011

Bordeaux trams: underground power feeding the overground trains

One of Bordeaux mayor Alain Juppé’s proudest achievements is the city’s tram network, a project which he championed when entering office in 1995, going against thewishes of his predecessor Jacques Chaban-Delmas (who had dug up the last of the first-generation tram rails back in 1958). 

The greater Bordeaux local authority - the Communauté Urbaine de Bordeaux - rubber-stamped Juppé’s plans two years later, construction work began in 2000 and by 2005 the initial phase was complete, with three lines crisscrossing the city centre. 

One of the most innovative aspects of the Bordeaux tram system is the complete lack of overhead cables for significant portions of the network. This is thanks to the use of a technique that was conceived and perfected for the Bordeaux project, first by Spie-Innorail then by Alstom: ground-level power supply (or, in French, APS, Alimentation Par Sol). 


The 750 volts needed to power the trains is provided via a central rail. The central rail is split into 8-metre sections, each section being separated by neutral segments which are 3 metres long (visible in the foreground above). As the train moves, an antenna sends a signal to underground control units which are 22 metres apart. These, in turn, switch on the power supply in the sections of the rail which are located underneath the moving train, i.e. the third rail is only ever “live” when the train is travelling over it. At all other times, the rails are harmless and of no danger whatsoever to pedestrians. 

However, the system is costly, adding an estimated €100,000 to the price of the trains, as well as generating a three-fold increase in infrastructure costs. APS is therefore only used in central Bordeaux and, at specific points on each line (such as the one pictured below on Rue des Frères Bonie), trams raise their overhead masts and switch back to more conventional means of power supply for the remainder of their journey. But the aesthetically-pleasing "look-no-cables" APS has been adopted for tram projects in Angers, Reims (both of which opened in 2011) and Orléans (on a new line being added to the existing network).  


After grinning and bearing the purgatory of five years of roadworks, not to mention a few painful and well-publicised teething problems for the APS system, people living in Bordeaux were quick to embrace the new network. Around 350,000 people hop on and off the trams every day, with many also making good use of the new park and ride car parks dotted around the suburbs. 

The network will continue to develop in the years to come, most notably with the creation of a whole new line running from Place des Quinconces into the north-western suburbs, finishing up in Eysines, and the extension of line C to the Bordeaux Lac exhibitions centre (and where a brand new sports stadium is soon to be built). 

One final thing: the trams have all been given the names of towns or cities that are twinned with communities in greater Bordeaux, so keep an eye out for Norton Radstock (twinned with Ambarès), Burgos (Pessac), Kalambaka (Le Haillan), Munich (as pictured above, twinned with Bordeaux itself) and many more as they glide effortlessly and overhead cable-free through the streets… There are currently 50 names for tram-spotters to look out for!

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