Filmed 40 years ago, in August 1976, in one take, with director Claude Lelouch at the wheel, zipping through Paris, this is a high-concept, but high-reward film.
It was a bit of a goof. The director, having just acquired a high-tech camera mount for use in his new feature, decided to try it out in a short film. The whole thing was done very quickly, as you'll see. Rumors persist that he was later arrested. It is not known if these are true. It certainly was dangerous and irresponsible. But also pretty cool.
There is a Wikipedia article about the production here.