Slažem se, highway=primary wiki kaže:
Use highway=primary to tag a major highway linking large towns, but which does not satisfy the performance requirements of a highway=motorway or highway=trunk. Primary highways are generally specified by country road classification bylaws and assigned a ref=reference name.
(naglašavanje moje) dakle, za tagiranje u OSM-u primarno (no pun intended) je koje je funkcija te ceste , a iako su uglavnom uzete iz zakonske specifikacije, to nije kruto pravilo. (npr. v. Some questions about Srpskian objects - #4 by Mateusz_Konieczny)