OK, so I'm a bit late in the game on this one, but I've just come back
from mapping some 4WD tracks around Mt Stirling, and I thought I'd throw
in my 2 cents here (also, the 4WD_Only tag is the one and only tag I've
ever proposed in OSM, so I have a sentimental attachment to it).
If a track seems to be 2WD for a bit, and then 4WD for a bit, then back
to 2WD (and so on), then the entire section between other track
junctions really does need to be marked as 4WD.
Eg:
Section A Sec B Sec C Sec D Sec E
2WD 2WD 4WD 2WD 2WD
---------------|--------=============---------|----------------------------------
road A
| |
| road B:2WD | road C:2WD
| |
| |
|
|
So, if you are travelling on road A, and there is a section of 4WD in
there, then instead of marking just that section as 4WD, then entire
road between the junctions (ie: sections B, C and D) would need to be
marked as 4WD, while sections A and E could remain as not marked for 4WD
access.
It's all very well to say only mark the section that is 4WD, but from a
routing perspective, it's pretty important that you don't end up in a
2WD vehicle stuck (ie: sections B and D might be 2WD navigable with a
bit of effort going forward, but if there's no place to turn around,
then trying to navigate them while driving in reverse gear could end in
serious tears (especially if the area is remote, there are some steep
ascents/descents, the weather turns nasty etc.)
As for the signage/marking of tracks, DSE and Parks Victoria are
trialling a new track classification system for 4WD tracks. There are
only a handful of roads in the state that have been classified so far,
but rather than just having 4WD-only=yes, we might also be able to tag
the roads with their classification (there are four categories, easy,
medium, difficult and very difficult - see
http://parkweb.vic.gov.au/__data/assets/pdf_file/0006/318768/4WD_Recreational_Track_Classification.pdf).
Parks Vic are apparently going to start signing the tracks with these
classifications apparently, so we might need to work up some tagging
structures for this I guess (I think I spotted one at the base of the
track to Craigs Hut, but not sure).
There's also an interactive (but pretty slow to load) map
http://nremap-sc.nre.vic.gov.au/MapShare.v2/imf.jsp?site=forestexplorer
that shows the 4WD trails they have trialled the classification, which
gives you a better idea of what I mean (turn on the Recreation/Four
Wheel Driving layers)
Matt
On 5/01/2012 10:11 PM, Ross Scanlon wrote:
On 05/01/12 18:47, Sam Couter wrote:
Ross Scanlon<[email protected]> wrote:
To me this is really odd. If the track is 30km long and there is
1km of 4wd only then is not this track all 4wd_only. As without a
4wd you will not be able to go from one end to the other in a 2wd.
Only if the track has no other access. Said access may not yet be mapped
in OSM. 2WD can also be used to get from one end of the track to the 4WD
section, even if it can't be used to traverse the 4WD section.
Ok so if your mapping every 10m and the first 10m is 2wd and then the
next is 4wd the remainder of the track becomes 4wd_only.
Read the wiki:
http://wiki.openstreetmap.org/wiki/Tag:4wd_only%3Dyes
It's quite specific as to what constitutes a 4wd.
And all your's below has been discussed before.
Cheers
Ross
Also any track sign posted as 4wd only should be marked in it's
entirety as 4wd_only=yes.
What's the difference between "NPWS sign states 4WD only" (You can be
fined real money for disobeying these signs), "You'd be crazy to drive
a Commodore down here" and "Holy shit, how'd that Commodore get here?!".
The tagging guidelines page isn't clear about this and people in general
have no idea about how far you can really drive a 2WD if you're
determined and skilled. Conversely, people in general have no idea how
easy it is to get stuck in a 4WD if you are not skilled.
Also, contrast tricked-out Toyota Landcruiser with Subaru Forester with
2WD rally car. These vehicles, ignoring driver skill, have vastly
differing off-road capabilities. The 2WD rally car will go places the
4WD Forester won't. Clearly the Forester isn't a serious 4WD like the
Landcruiser, but the rally car isn't 4WD at all. How to indicate that
the Forester isn't suitable for a particular track?
The 4wd_only tag lacks any of the expressiveness needed to solve the
problem and the tagging guidelines don't address it either.
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