I really don’t know if this is feasible or not, but regardless I would like to share my thoughts with you. This is not even a proposal, because you are the ones which spent most of your time mapping these roads and I am really not familiar with the whole road network in Greece. These are just my thoughts which hopefully might help you to reach a consensus. If you like it, then do take it under consideration or propose it and/or modify it yourself as you see fit :). JayCBR please don’t include this on proposals unless someone else does so, and once again, thank you for taking the time to organize all this (sorry for another long post, I guess I should start blogging instead).
If ΦΕΚ 664B/1995 and ΦΕΚ 735Β/1995 extends ΠΔ401/1993, which was issued for the the implementation of ΒΔ 465/70 as it was modified by articles 2 and 3 of Ν3155/55, which states that «Αι οδοί της χώρας διακρίνονται σε α) Εθνικάς, β) Επαρχιακάς και γ) Δημοτικάς ή Κοινοτικάς», it seems that we basically have three different types of roads, with two of them having some sub-categories. To put it on other words, National Roads are basically our primary network (most important ones), Provincial Roads are our secondary network (less important) and Municipal Roads are our tertiary network (least important) (don’t confuse this with either OSM values for the highway key, or sub-classes of each type of road). Now, if OSM only had 3 different types of highways, then national roads would be highway=national, provincial roads would be highway=secondary and municipal roads would be highway=tertiary. Of course, motorways are clearly defined, therefore they should go to highway=motorway. Now, by definition (see wikipedia), trunk roads are “strategic roads”, therefore they are indeed the most important national roads which connect major cities. In other words, these are the primary national roads as defined by 1995 ΦΕΚs and roads planned to become motorways. This leaves highway=primary for secondary national roads AND for tertiary national roads. If tertiary national roads are in a bad shape they could also be downgraded to highway=tertiary. This leaves the highway=secondary clear for Provincial Roads. All of them. If they are indeed bad, they could also be downgraded to highway=tertiary. Again, this leaves the highway=tertiary more or less clear for Municipal Roads, which are by definition tertiary roads and priority roads ( In fact, just by checking municipal archives, almost all of the current priority roads seem to be the main municipal roads, which are already tertiary on OSM, as they can be easily be distinguished due to their importance.
In other words, how about something like…
Disclaimer: This is not a proposal but merely a thought:
motorway - motorways (under ΦΕΚ 253ΑΑΠ/2015)
trunk - primary national roads AND roads planned to become motorways (under ΦΕΚ 253ΑΑΠ/2015)
primary - secondary national roads AND tertiary national roads (tertiary national roads could be downgraded to tertiary based on their actual condition and importance).
secondary - primary provincial roads AND secondary provincial roads (secondary national roads could be downgraded to tertiary based on their actual condition and importance).
tertiary - main municipal roads and other priority roads, downgraded tertiary national roads, downgraded secondary provincial roads.
unclassified or residential - every other public-access highway
To make this easier, we could have a page on the wiki with all the national roads, their class as defined by ΦΕΚs, their relation on OSM, and their actual highway value on OSM. Later, this could be extended for provincial roads. By default, most of the roads would be on their default highway value, UNLESS, tertiary national roads or provincial roads are downgraded according to their actual conditions - and those roads should be noted on this page. You could also add a note at their OSM relation (ΦΕΚ for classification and reasons for downgrade if applicable). I think that this covers almost everything: a) JayCBR’s concern that provincial roads are less important than national roads. b) JayCBR’s concern that some provincial roads are in a bad shape, c) Amaroussi’s and my own concern that municipal and priority roads should be tertiary ones d) nikospag concern about having too many tertiary roads. This also stays true to the actual definitions of our road network based on the previously mentioned ΦΕΚs AND is helpful for routing AND follows the verifiability rules of OSM.
Now, as I said, I don’t really know if something like this is feasible or not, but at least I believe it’s somehow logical.