text: Hi Richard,
  I've re-worked the highways in this area when adding detailed land cover. Many single-track tertiary are now tagged as unclassified, and small access tracks to single farms/ homesteads are service. 
  Ways with explicit ref=C* have been left tertiary, although I suspect several are more lanes=1 unclassified.
  I hope this addresses your concern about the previous tertiary default.
  Happy Mapping,
  
  James