[talk-au] tagging 4WD and dirt roads - want it ?

Andrew Harvey andrew.harvey4 at gmail.com
Sat Nov 10 03:54:19 GMT 2012

On 10/11/12 12:33, David Bannon wrote:
> Righto folks, I have not had a lot of feedback about the drafted
> proposal to tidy up how 4x4 tracks (and other) are described. I added a
> bit about what happens when tags conflict after Li queried that but
> thats all !
> http://wiki.openstreetmap.org/wiki/User:Davo#Draft_4x4_road_proposal
> Its fair to say that we'll need Australian votes to get this approved.
> Can you please indicate that you will vote, either yes or no, before I
> go to the trouble of formally putting the proposal up ?
> Suggestions are also obviously very welcome.

Hi David,

To be honest I haven't been following the discussion but I agree that it
is important to sort this out so I'm going to provide my thoughts.

Among other things OSM in interested in mapping the location and
topology of thoroughfares which exist on this planet. Accompanying this
is attributes which provide more details about the through fare.

These attributes include,
* nomenclature of the thoroughfares (name, *name, name:lang, ref, etc.)
* legal regulations on the use of the thoroughfares (access, maxspeed,
  maxheight, maxweight, turn restrictions)
* type of use
  *  highway classification (residential, primary) describes for which
     purpose the road is mainly used for
  * which vehicles is it primarily intended to support (in OSM inferred
    by the key and sometimes value, such as railway=, highway=,
    highway=footway, bicycle=, maxheight:physical=, etc.)
* physical attributes (surface, bridge, tunnel, width, lanes)
  * make up of the surface's top layer
    * what is the top layer material covering this thoroughfare
      concrete, asphalt, clay, grass, soil, rock
    * what is the form of that material covering this thoroughfare
      pavers (large 25m2 slabs, medium 0.25m2 blocks, small bricks),
      rubble (large bear sized boulders, head sized rocks, or grape
      sized pebbles), compacted/solid
    * what is the stability/friction of the surface (do I need a 4wd to
      prevent sliding out?), perhaps can be implied by surface x form.

These attributes need to be non-subjective so that they can be applied
universally, collaboratively and consistently across the globe. They
also need to be truthfully representations of what actually exists on
the ground.

I think it is best to describe the real world with attributes like
these. It is an accurate representations yet allows users to decide
higher lever questions like "I only have a standard 2wd car, not a 4wd
one. Should I take road A or B?" by looking at the attributes which are
important to them, be it traction of the road surface (ice, clay,
dirt...), smoothness (frequency and amplitude of the surface profile).

This way both a 4 wheel drive Ferrari and a 4wd Jeep can make a good
determination of whether they should take route A or B.

Furthermore, the current tracktype grades although not well defined
essentially measure the "compactness" of a surface. If you try to bring
4wd only into the mix it could become complicated as you can very well
have paved track or heavily compacted hardcore but so uneven and with
large gaps that you would need the large wheels and ground clearance of
a 4wd to traverse; yet have another unpaved uncompacted track with lack
of hard materials with the same requirement on a 4wd due to uneven
ground. This isn't as you suggest, "bad data that needs to be fixed by

In summary, I would ask you to pull out attributes of a thoroughfare
which make it 4wd only and tag those instead.

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