I ran some tests the last couple of days. I downloaded the whole Greek road network (even unclassified roads) and I tried to simulate the next 3 cases. After that, I ran some routing tests for each case. (Testing cases was only for provincial roads)
Case 1: tertiary: all provincial roads.
Result: A vast network of tertiary roads, very confusing to the eye, and even worse on islands. Many routing problems.
Case 2: secondary: primary provincial roads and tertiary: secondary provincial roads.
Result: Better looking map than case 1, less confusing to the eye. Some routing problems solved.
Case 3: secondary: all provincial roads.
Result: Good looking map, minor roads to villages were distinctive. Islands were looking very good too. Almost all routing problems solved.
To define what I mean by “routing problems” i will give just an example that caught my eye, among many others. At the map below there are 2 provincial roads. ΕΠ7 (primary provincial road) and ΕΠ30 (secondary provincial road ).
In the above cases 1&2, to go from Κεντρικό village to Δεσύλλας village, routing was going through the small tertiary road that connects these two villages directly.
In case 3, routing was going though the secondary roads. (as it should be)
Map is here http://www.openstreetmap.org/#map=14/37.2951/21.9784
So my conclusion is that all provincial roads must be tagged at least as secondary roads.
Other minor roads to villages and other priority roads must be tagged as tertiary, as they are now.
Of course secondary national roads must be tagged as primary
Please give me some time to study what we can do about tertiary national roads.
(Greek road network is really a pain in the ass :))
I also think that mtraveller’s opinion, about downgrading some roads to tertiary, must be taken into account as it adds some flexibility to the system. But keep in mind that by downgrading roads, routing problems can emerge easily. Anyway, we can discuss about exceptions later.
PS. I think that voting system is too confusing. (or is just me?).