text: This is related to http://wiki.openstreetmap.org/wiki/Ireland/Roads which is (AFAIK) applied on the whole Isle of Ireland. Anything higher than tertiary just looks at the road reference, regardless of other aspects.
  
  If this scheme doesn't work well for NI, you should bring up the subject on https://lists.openstreetmap.org/listinfo/talk-ie so we can come up with something better and maybe distinguish NI from ROI in the wiki.