Ah, please forgive me for over-explaining something you were already well acquainted with! Yes, the tag I used specifies the source for the route. So you're saying that other mappers only link GTFS data to stops with stop_id and stop_name? And they don't link anything to route or route_master relations? Because I have found routes in and around Seattle (King County Metro and Sound Transit networks) with the older style gtfs:feed=* and gtfs:route_id=*.