There seems to be a lot of interest in the "snake" trains in Paris. They are called the "Boa" type - which is of course Feench for snake. Here are some photographs of it, in French I am afraid. There are different car connections by different manufacturers - ANF is one, Faiveley is another, titles to the photos. The train type is MF88, this indicates it has been around since 1988. The prototype shown here has now been followed, after some years of tests, by definitive production trains here. You find them on lines 1, 5 and 14. 1 and 14 have rubber tyres, another French difference, whereas 5 has regular railway wheels. 14 has no driver's compartment so you can see forward up the tunnel as well as back down the train. It is also the fastest (and newest) line in Paris.