It would also be interesting to see the distribution of `bus_stop`'s with shelter and seat (full service) verses just a pole. Maybe amenity=shelter or covered=yes - I'm unsure if they're usually on the same node or a separate node (within x many metres).

In Australia there's a considerable variation of bus stop quality. There might be some interesting insights into where the minimum effort bus stops are (council/gov boundaries? transit deserts? who knows.)