Do you remember to always validate your metrocard, or to buy a ticket when boarding a bus, train or tram? If so, Adelaide Metro like you and in this series of ads, which have been posted at various tram stops, train stations and bus stops around Adelaide, they want to call you a "fare player". (This poster pictured above hangs on a fence at Noarlunga Interchange, looking east toward the railway line.) Presumably, the thumbs up means that they think you are doing a good deed, but I would not be surprised if a tourist or two may have been a bit offended by that signal.
Apparently, the opposite of a fare player is a "fare bludger" and they too have their own poster, which comes completely with a small, white figure giving the thumbs down signal.