A steep technical road for 4WD or MTB - highway=path or highway=track?

General talk
1

We have a hilly forest near where I live, which has this pattern of normal roads circling a hill, and “roads” (which are just gaps in the forest) descending a steepest line down the hill:

http://www.openstreetmap.org/#map=17/32.58477/35.02262

These steep “roads” are used by 4WD vehicles and mountain-bikes; one of them is partly an official hiking path.

http://imgur.com/3Cdlnxp

Which value of the “highway” key should I use for marking them?

highway=track? (because it’s used by motorized vehicles)

highway=path? (because it can only be used by special vehicles, and I don’t want these ways to be used for any automatic routing)

If there are several (5-10) of these “roads” in the area, and some of them clearly are not (and I guess cannot be) used by 4WD vehicles, should this influence the value of their “highway” key?

One of these “roads” has a sign “entrance for vehicles is forbidden”; should this influence the value of its “highway” key?

In addition, if I use highway=track (like I think I should), which keys should I add to set them apart from “normal” roads?

2

highway=track is the correct tags for vehicles that leave separate tyre tracks and highway=path is only suitable for walking hiking, biking, etc and not for 4 or more wheeled vehicles that leave a ‘tracked mark’, though the image you have uploaded could be either and I would be guided by the look of the way where it goes over ground instead of the large rocks. And certainly add surface= tags.
There is a 4WD tag for special road conditions conditions
https://wiki.openstreetmap.org/wiki/Tag:4wd_only%3Dyes
There is also the track type
https://wiki.openstreetmap.org/wiki/Key:tracktype
Also the Australian tagging guidelines may be useful info
https://wiki.openstreetmap.org/wiki/Australian_Tagging_Guidelines#Unsealed_and_4wd_Roads_.28Dirt.2C_Gravel.2C_Formed.2C_etc.29
You could use the access tags to define the ones where vehicles are forbidden/allowed but I don’t think this should influence the highway tag (in most cases?).
https://wiki.openstreetmap.org/wiki/Key:access

3

Agreed, if it is possible to take a car and it does happen from time to time, it should at least be a track. In less developped countries, a road like this might actually connect major towns, so in that case it could even be rightfully tagged as secondary or even primary.

4

To make the suggestions in the replies above more concrete:

highway=track (as suggested by the users above)
motor_vehicle=no (where it’s forbidden by a sign)
surface=unpaved (to override the default “paved”)

Also, after some digging, I found the following that seems appropriate:
smoothness=very_horrible

5

I was unaware that the default surface of a track was “paved”. The wiki at https://wiki.openstreetmap.org/wiki/Tag:highway%3Dtrack says:

“This tag represents roads for mostly agricultural use, forest tracks etc.; usually unpaved (unsealed) but may occasionally apply to paved tracks as well, that are suitable for two-track vehicles, such as tractors or jeeps.”

In the mapping I’ve done I have left off the surface tag unless it was paved.