5. Outlook

What are the prospects for the future? A few observations:

• higher TGV speeds can only be achieved if the aerodynamic phenomenon of ballast flight is controlled, as for the world record (at the design stage, through maintenance and cleaning operations, etc.), in order to limit the degradation of wheel and rail surfaces, and hence rolling noise, both for the environment and for acoustic comfort. A slab-mounted design is obviously another solution;

• the development of lighter motorization, such as permanent magnet motors distributed throughout the bogies, increases the number of seats for equivalent length, and improves equipment reliability thanks to the greater number of motors. This architecture (difficult to implement on a 2-storey TGV, although see the record trainset) may, however, present the aforementioned...