Here is a current example, trying to make use of most of the tagging suggestions made so far. Zoom in and take a look around. https://www.openstreetmap.org/way/146238242#map=12/49.0034/-55.9194
Tertiary: An unclassified road carrying through traffic.
Unclassified: An unpaved road that can carry regular automobile traffic (usually 2 lanes but sometimes 1 with shoulder).
Track, tracktype=grade1: Not applicable, as paved tracks are not found in these areas.
Track, tracktype=grade2: Prepared roadbed. Can carry most automobile traffic without major issues. May shows sign of vegetation.
Track, tracktype=grade3: Prepared roadbed, mainly dry and hard, but overgrown or in the process of. Can carry automobile traffic.
Track, tracktype=grade4: Prepared roadbed, mainly soft or wet. Can carry automobile traffic but not recommended.
Track, tracktype=grade5: Roadbed same as surrounding terrain. Does not support automobile traffic, but can support ATVs.
Service: Roads leading to quarries or small groups of buildings (usually 1 lane with no shoulder).
And some examples:
Tertiary: https://imgur.com/jeuC9f3
Unclassified: https://imgur.com/qrMrIkH
Track grade2: https://imgur.com/5pwTNP1
https://imgur.com/InOJHqk
Track grade3: https://imgur.com/wbIQhYu
Track grade5: https://imgur.com/DBD81l8