I am Nicolas Kuttler, a web developer, system administrator and IT consultant from France, currently living in Germany.
I have been working with various web-related technologies for more than a decade...
This makes it possible to have the taxonomy below some post type slug, e.g. the post type is at /cars/ and taxonomies are at /cars/manufacturer/, /cars/year-of-construction/ etc. You want to register the taxonomy with the same $slug.