Συμφωνώ κι εγώ. Η πρόταση του Ρικ Σάντσεζ φαίνεται η πιο ταιριαστή. Συν η γενική πτώση, ακριβώς για οποιονδήποτε επαρχιακό δρόμο είναι αναγνωρισμένος και αριθμημένος με ΦΕΚ (η λίστα αυτών των δρόμων στο wiki είναι καλύτερο υπάρχει σε ταξινομημένη λίστα ανά περιφέρεια και νομό για εύκολη αναζήτηση).
Rick Sanchez C-137 is almost correct.
Whether National Roads are “highway=trunk” or “highway=primary” depends on whether they are part of the main E-road network (Class A only).
I would keep things simple and make Provincial Roads “highway=secondary” by default, and other roads to towns, villages or hamlets should be at least “highway=tertiary”, depending on how important it is.
It is tempting to downgrade roads for not being asphalt/concrete, but I would resist the temptation, and use surface=* and smoothness=* to provide detailed surface information.
I would downgrade such roads if motor vehicles cannot legally use it (like in Hydra), or the surface is so poor that motor vehicles cannot use it for at least 3 months per year (e.g. https://www.openstreetmap.org/way/794828975)). In such cases, we need to use note=* to explain why, to avoid confusion in the future.
I would also be careful not to overuse highway=track: we do not need to pave every local road with asphalt/concrete, even if we had all the money in the world. jimkats recently express concern about Kaart members overusing highway=track outside cities.
I think that trying to make the classification system dependent on the surface has made the debate more complicated than it should be, especially with the availability of surface=* and smoothness=*.