The "classic" Harry Beck London tube map is widely considered by design experts to be a masterpiece of map design, and it appears in design contexts, not just in the context of a map on the tube.
Over time this has caused TfL to attract people interested in designing for users of public transport, and they created a design system that is now licensed, and they do consultancy, so you will see "TfL style" design in other cities. The tube "roundel", map and advertising poster archive is all considered key commercial IP assets.
Many other public transport entities try to mimic TfL as a result, either by licensing directly (Dublin buses do this IIRC), or trying to look a bit similarly abstract and "clean" but with their own vibe. Weirdly this just makes the TfL design system even more recognisable to some people.
Another transport related design system from the UK that's worth looking into if you are interested in such things is the road signage system that was overhauled in the 1960s. It also highly regarded in the international design community: https://www.bbc.co.uk/news/magazine-15990443
Thank you for the answer (that is not a semantic discussion /end-of-rant)
I had no idea that the London map inspired so many others (among them - the Paris one I mentioned in my question), I thought that the design was rather a typical one for maps of underground services the same way as ground maps look more or less the same (at lest in their raw design). TIL.
Over time this has caused TfL to attract people interested in designing for users of public transport, and they created a design system that is now licensed, and they do consultancy, so you will see "TfL style" design in other cities. The tube "roundel", map and advertising poster archive is all considered key commercial IP assets.
Many other public transport entities try to mimic TfL as a result, either by licensing directly (Dublin buses do this IIRC), or trying to look a bit similarly abstract and "clean" but with their own vibe. Weirdly this just makes the TfL design system even more recognisable to some people.
Another transport related design system from the UK that's worth looking into if you are interested in such things is the road signage system that was overhauled in the 1960s. It also highly regarded in the international design community: https://www.bbc.co.uk/news/magazine-15990443