[Tagging] Tags useful _SUMMARY_ for rendering of roads in poor conditions

David Bannon dbannon at internode.on.net
Fri Jan 10 10:12:39 UTC 2014

OK folks, I have moved a draft summary of the discussion on this topic
to my OSM wiki discussion page. Anyone with OSM Wiki credentials is
welcome to edit it to try and make the choices clearer.

if you don't have OSM credentials, feel free to post corrections or
additions to me and I will put them in on your behalf.

If we edit for a bit and then vote to determine what is the popular
solution to this problem.

We can then, if appropriate, turn it into a formal proposal and really

Please forgive me for being so late in getting this wiki page up and
ready, been some unrelated family issues...


On Sun, 2014-01-05 at 17:07 +1100, David Bannon wrote:
> OK, this discussion is huge and conducted in a great manner.
> But being so huge, I feel lost !  So, here is an attempt to summarize
> where we are and what the options seems to be. Maybe by identifying what
> we already agree on, we can see the way into the rest ?
> If people think its a good idea I could post a more evolved summary onto
> my OSM wiki page where we could all have a hack at it, might be more
> manageable than the mailing list ? If nothing else, we need to break
> this very complicated problem into manageable hunks.
> Think of this somewhat like a flow chart, I just have not drawn it up...
> Do we all agree that its important that significant maps, such as the
> one on the OSM website, shows some indication if the road may be in a
> state where some drivers are uncomfortable (right through to
> dangerous) ?
> If Yes, proceed, if No, please explain why not. You may like to address
> this -
> http://www.abc.net.au/news/2012-11-07/25yo-man-dies-of-thirst-in-outback-queensland/4357380
> There are lots more. Tourists from outside Australia are at particular
> risk.
> OK, assuming we agree we want 'something' ...
> We need some tag (or tags) associated with a way that tells a rendering
> engine this way is one that might need caution. We can try and use
> existing tags or invent a new one. 
> The "new one" option (such as BGNO's trafficability) could be tuned,
> based on experience, to do exactly what we want. On the other hand there
> are currently no ways in the database using that new tag. There are 3
> million surface= and 2.5 million tracktype= tags in there. Mappers put
> used those tags in there for a reason. 
> If you want a new tag defined, please say so, maybe with a new subject ?
> Continuing on, assuming we support using existing tags, which ones ? At
> lease three 'approved' candidates, four if you include 4wd_only.
> Surface= has about 3 million ways that are what we, in Oz, call
> 'unsealed', dirt, sand, gravel, unpaved and so on. This is not a bad fit
> but neither is it perfect. http://wiki.openstreetmap.org/wiki/Surface
> "To provide additional information about the physical surface of
> roads/footpaths...." However, my experience is that a precise statement
> about the surface does not necessarily relate to its
> "trafficability" (thanks for the term BGNO!). I have driven sandy roads
> that were so easy and somewhere else, spent a day with a shovel digging
> through sand. Similarly, hard packed clay can sometimes be preferable to
> a made gravel road that has developed severe corrugations. And a sealed,
> tarmac road that is breaking up is a nightmare.
> Tracktype= has about 2.5 million grade2 and beyond ways. "Tracktype is a
> measure of how well-maintained a track or other minor road is."
> http://wiki.openstreetmap.org/wiki/Tracktype
> Thats a lot closer to what someone (or a router) might be wanting to
> know. It can and should be applied to all sorts of highway= ways, not
> just =track and that seems to be a major problem. In some people's view
> (Malenki..), it should be used only when highway=track. I and several
> other people (and the wiki) disagree. The values of Tracktype are not
> intuitive. The values are linearly expandable, to cover more extreme
> road conditions, grade6 is already widely used but not approved.
> Smoothness= has about 25 thousand ways. Thats drawing the line at
> very_bad. But there are another 40 thousand 'bads' so its hard to call.
> http://wiki.openstreetmap.org/wiki/Key:smoothness
> I am personally convinced this tag would be used heaps more if the
> values did not seem to make some moral judgment ! As I said before, I
> could never label the pretty road I live on as "horrible".
> There is some support for making a new set of values and that would be
> cool (Fernando, Martin). But has the horse already bolted ? Surface= and
> tracktype each have more than 100 times more use.  Further, if we come
> up with new values, why not a new name ? Truth is, 'smoothness' is only
> a small aspect of trafficability (there, I used it again!).
> 4wd_only=yes.  Used 3 thousand times, more in Australia than elsewhere.
> In hindsight, maybe it could have done with at least three values,
> 'recommended', 'yes', 'extreme'. It does cut in somewhat beyond the spot
> we are talking about, I get the impression that people want a road
> labeled differently long before we get to 4wd_only=recommended.
> Any one of the above, or a combination ? Personally, I think a
> combination would be over complicating it. Just my view.
> Other Issues -
> How to render it ?  That can come later on I guess.
> Wolfgang, Peter, Janko, Gerald  warns about subjective tags. Truth is,
> almost everything we record is subjective to some degree. I'd take the
> legal approach where they talk about a "reason person's view". For a
> normal road, thats someone driving a conventional car. For a mountain
> bike track, its someone riding a mountain bike....
> Fernando pointed out that to make a truly objective assessment, we'd
> need many more tags and some elaborate technology to measure. Gerald
> suggested a smartphone app to do the measuring but is he allowing for
> variation of suspension in the vehicle in use ?
> David S and Dominic don't seem to want more detailed measures either.
> David S reminds us what highway= tag is about. Its to describe the
> purpose of a road, not in any way its "trafficability" (David S said
> "usability but I am starting to like trafficability...). he is right but
> the anomaly is highway=track, its use opens up, at present, the
> tracktype modifiers, wrong, wrong....
> One important effect of the highway= tag is "more important" roads get
> rendered at lower zoom numbers. Useful when you want to see how to get
> from A to B. Sadly, we hear of people taging important roads as =track
> so their usability can be described by tracktype. And then you cannot
> see them at all at sensible zoom levels. Sigh....
> Now, I have not mentioned everyone nor every view, impossible !  Thats
> why I think its time to move to the wiki, perhaps show a series of
> options and just see who really wants to vote for what.
> But, I really must thank Fernando for driving this issue, its very, very
> important and damn hard as well !
> David
> On Fri, 2014-01-03 at 21:10 -0200, Fernando Trebien wrote:
> >  a massive contribution...
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