OpenStreetMap
On the German mailing list one mapper recently asked how to tag a dirt road:
http://lists.openstreetmap.org/pipermail/talk-de/2011-October/089483.html
There are many dirt roads with local importance which should be tagged as tertiary due to their importance, but also as track due to their road condition:
Let's take the Mosquito Pass in Colorado - it is a major connection between Fairplay and Leadville that looks like presented in these videos:
http://www.youtube.com/watch?v=sOOzE2_qrNg
http://www.youtube.com/watch?v=4owzKpG4JPU
I wish we had a tagging mechanism for dirt roads combining importance (highway=*) and road condition (tracktype=* or 4wd=easy/moderate/difficult).
Any suggestions?
Discussion
stevageಅವರಿಂದ 23:39 ರಲ್ಲಿ 10 ಅಕ್ಟೋಬರ್ 2011ರಂದು ಅಭಿಪ್ರಾಯ
Interesting question. I'd ask on help.openstreetmap.org.
z-dudeಅವರಿಂದ 01:27 ರಲ್ಲಿ 11 ಅಕ್ಟೋಬರ್ 2011ರಂದು ಅಭಿಪ್ರಾಯ
If you can't use a normal car, then I'd tag it as a track. You don't want people in normal cars getting stranded because their GPS told them to drive on a dirt road. http://www.torontosun.com/2011/10/04/stranded-woman-recounts-tale-of-survival
If you can use a normal car, then tag it as a road, surface = gravel or surface = dirt (potlatch has this in the simple editor)
There's some proposed 4wd tags.
osm.wiki/Proposed_features/4WD_Only
osm.wiki/Tag:4wd_only%3Dyes
Panಅವರಿಂದ 05:28 ರಲ್ಲಿ 11 ಅಕ್ಟೋಬರ್ 2011ರಂದು ಅಭಿಪ್ರಾಯ
Here in DRC, even most of the primary roads are dirt tracks. it is difficult to know how to tag them.
Diomasಅವರಿಂದ 06:53 ರಲ್ಲಿ 11 ಅಕ್ಟೋಬರ್ 2011ರಂದು ಅಭಿಪ್ರಾಯ
highway=track doesn't tell us anything about accessibility - it can have excellent smooth surface, it just mean that the road leads to "nowhere": road in the forest to some single hut or a road in the field to some lake. So it's just about the status of the road.
In other words, if the road has a name/number, or if it's the only way to get to some hamlet/village/town, then it can't be highway=track whatever surface it has. Otherwise it should be at least highway=unclassified.
You can also do some check: if removing highway=track cause some highway=unclassified|residential etc way to be not connected to other roads, then the road you just removed is not a highway=track.
To define a surface there is a "surface" tag - it can be applied to any highway: from highway=trunk to highway=footway.
To define a physical accessibility of the road there are many tags can be used:
tracktype (for tracks only),
smoothness,
and different proposals like 4wd, 4wd_only, surface:grade etc
Richardಅವರಿಂದ 07:09 ರಲ್ಲಿ 11 ಅಕ್ಟೋಬರ್ 2011ರಂದು ಅಭಿಪ್ರಾಯ
highway=tertiary, surface=unpaved | gravel | dirt | what-have-you.
maxolasersquadಅವರಿಂದ 15:27 ರಲ್ಲಿ 11 ಅಕ್ಟೋಬರ್ 2011ರಂದು ಅಭಿಪ್ರಾಯ
Richard ++
marscotಅವರಿಂದ 19:29 ರಲ್ಲಿ 12 ಅಕ್ಟೋಬರ್ 2011ರಂದು ಅಭಿಪ್ರಾಯ
I would tag them highway=track but they are as you say tertiary tracks, maybe this points to a new type of track that needs to be drawn
Highway=track
track_type=tertiary_grade1or 2 or 3 or 4
Jean-Marc Liotierಅವರಿಂದ 09:31 ರಲ್ಲಿ 14 ಅಕ್ಟೋಬರ್ 2011ರಂದು ಅಭಿಪ್ರಾಯ
Richard's "highway=tertiary, surface=unpaved | gravel | dirt | what-have-you" is the correct answer. Here in Europe we are not used to anything but pavement, whereas in Africa I have often seen tertiary and even secondary dirt roads. The place of the road in the network hierarchy is the primary indicator for the highway tag - road surface is less important.