I am french. This video shows some tests. Actually, the way tgv is used is far less fast : around 300-320kph. It's very comfortable and allows me from time to time to come and see my family very quickly. The point is, it does not pollute very much, since it is powered by electricity (which is, in France, mostly provided by nuclear powerplants, so nothing in the air). In comparison, an airplane is very, very much more polluting.