A couple of quick comments:
There is a 4wd tag already in use - 4wd_only:yes|recommended (with no
being a pointless value)
http://wiki.openstreetmap.org/wiki/Tag:4wd_only%3Dyes There's about 1000
instances of this tag in use in Australia.
There was a proposal kicking around ages ago that was trying to define
some improved classification for unpaved roads (as unpaved roads come in
all sorts of varieties). I think the discussion got pretty acrimonious
and petty, but the thought was there. There are roads I've been on where
the surface would be OK for a normal car, but the road is a series of
sharp humps that would easily ground a standard clearance vehicle.
Seasonal closure is another area where I don't think the tagging is
complete/useful. The current tag is dry_weather_only=yes or
access=dry_weather_only, which is valid for any road that is impassable
in the wet due to surface condition or creek/river crossings, but there
are also tracks with explicit closures (usually mid may to the first
weekend in September or October) - generally marked as 'SSC' in the
VicMap series of maps. Don't have a solution, but it something that
might need working on as there are a lot of SSC roads in Victoria and NSW
Anyway, I'm all for improved tagging of dirt roads - it's my favourite
kind of mapping (usually cos it turns out to involve a couple of days of
camping and getting out into the bush
Matt
On 21/10/2012 12:03 PM, dban...@internode.on.net wrote:
Hi Folks, recent I have been going over parts of OSM mapped some time
ago, following up on the infamous redaction. One thing that jumps out
at me is the inconsistent tagging of dirt roads. Even, I must say,
ones I have done myself but over a several year time span.
So I started to write some notes for myself and thought that maybe I
should add them to
http://wiki.openstreetmap.org/wiki/Australian_Roads_Tagging I don't
think this is inconsistent with whats there now, just more detailed.
However, I do suggest that we need consider what the rendering engines
do with our data and I know that is a bit naughty. But, in this case,
I'd suggest to do otherwise is negligent as it can have quite serious
safety issues.
So, would people like to comment on what I say here ? If we can reach
consensus, I'll graft some of it onto the OSM wiki.
Unmade roads
These are typically forestry and remote tracks, while they may have
been cut initially by a bulldozer they are not regularly maintained
and, importantly, are not domed and don't have good run off gutters on
the side. Such roads might or might not be single lane, 4x4 only,
might be dry weather etc. Be careful about deciding on such
restrictions, some people are often surprised at how well a carefully
driven conventional vehicle can use these tracks. Highway=track will
typically render to a dashed line.
highway=track
surface=unpaved
lanes=[1; 2]
4x4_only=[recommended; yes]
source=survey
Made but unsealed roads.
Many rural roads fit here. There is no asphalt but the roads are
'made' and regularly maintained by, eg, the local council. These roads
often have a gravel base, always have dome shape, the middle is
somewhat higher than the sides and there is some sort of gutter at the
edge. The gutter will usually have "run offs" to drain water away from
the road. Such roads are almost never 4x4_only nor dry weather only.
highway=[unclassified; tertiary, secondary]
surface=unpaved
lanes=[1; 2]
source=survey
Use of the highway tag on dirt roads.
While the selection of tags should not be defined by how current
rendering engines display, we cannot ignore the final outcome. In
Australia, a lot of dirt roads are quite important and sometimes its
necessary to compromise a little to achieve a useful result. So the
correct highway tag may be determined by a combination of the purpose
of the road and its condition. Tracks are often rendered as dashed
lines and most people would understand that means some care may well
be needed. Unclassified would indicate a purely local function and is
typically rendered as two thin black lines with white between
Tertiary roads usually are rendered with two black lines and a
coloured fill and many people (incorrectly) interpret that as meaning
a sealed road, so maybe mappers should ensure they apply that tag only
to dirt roads that are reasonably well maintained. Secondary roads are
shown as wider and a different colour than tertiary and are definitely
presented as viable routes for people passing through the area. Some
care needs be exercised if a dirt road is to be classified as 'secondary'.
Discussion
Sometimes its hard to balance the description of a road against its
purpose. A good example might be the Plenty Highway. This road is
probably a track from a road condition perspective, rarely maintained,
sections of sand, corrugations and ruts. However, its pretty long and
a major link between some (admittedly small) communities. As a 'track'
it would not show up on a map until you zoom in way past where you can
get any idea of where it starts and ends. At time of writing, its
highway=primary (and, I might note, incomplete), that's possibly
dangerously misleading. Conventional vehicles routinely use it but I'd
probably give it a 4x4_only=recommended tag. However, none of the
mainstream rendering engines observe that tag, it is no real
protection for a visiting tourist.
Similarly, even on the east coast, its not unusual to see dirt roads
defined as 'tertiary' or even 'secondary'. Thats probably quite
correct from a purpose view but a lot of (especially city based)
drivers get quite nervous when they find themselves on a dirt road. If
they have got there by following a OSM map showing a road with
coloured fill, maybe they have a case ? Most printed maps here in
Australia show unsealed roads without a coloured fill.
And this does, of course, highlight the need to survey roads.
David
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