This is an attempt to gather a range of opinions on the topic of how to get unsealed or unpaved roads rendered differently from 'normal' roads. It follows on from a long discussion on the Tagging mailing list and I suggested it was getting a bit hard to follow. But its no where near ready to be written up as a proposal yet. So, please feel free to hack away at what is here or, if you don't have a OSM Wiki logon, post to the list or directly to me and I'll make your changes.
Lets think of this as an informal vote, first we play a little with the questions, then record who is happy to line up behind what ?
Do we need a change ?
OK, at present, on the 'official' OSM map on the website, unsealed roads are indistinguishable from sealed ones. Some of us believe we must ask the renderers to correct this. If you think such a change is unnecessary, say so here.
- It would be very useful to have road surface/quality/smoothness somehow rendered in the 'official' map. Nillerdk (talk) 12:22, 10 January 2014 (UTC)
- This is a good idea and I support pushing for special rendering of such roads AlaskaDave
- Useful, and additional the lit tag should be rendered, especially on footways Osmonav
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 used those tags in there for a reason.
A New Tag ? sletuffe reminds us about http://wiki.openstreetmap.org/wiki/Proposed_features/usability If we do need a new tag, it could well be this. I'd prefer a touch finer grain but the idea is sound.
Maybe that for a Car Roadmap, Levels 1, 2 and 3 would be rendered 'normally', 4, 5 and 6 need to alert user of something to watch. Racing Bikes 1,2 and 4,5,6. 4x4 Club maps 1,2,3,4 and 5,6. Hmm, like it --Davo (talk) 00:55, 16 January 2014 (UTC)
- Use Existing Tags--Davo (talk) 10:39, 9 January 2014 (UTC)
- Use existing tags. I would focus on smoothness and surface. For smoothness, I would recommend the values (thin_rollers, thin_wheels, ...) but still allow the use of the corresponding (excellent, good, ...) as given on the Wikipage smoothness=*. Nillerdk (talk) 12:34, 10 January 2014 (UTC)
- Use mostly existing tags. But I think smoothness is not sufficient enough. Key surface_condition should be added Osmonav 14:48 12 January 2014 (UTC)
The existing tag options
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. "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." 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.
- The values of tracktype should be changed. It's not at all intuitive using grade1 - gradex. I would prefer values like 'sealed', 'skidmarks', 'hardly_visible'. Values like 'grass, plates, etc' can be added using surface=* Osmonav 12 January 2014 14:51 (UTC)
I agree with what Osmonav is saying about this value being non-intuitive but not the rest. My view about tracktype is that it should be reserved for unpaved tracks. Furthermore, the definition of grade1 should be revised to remove the use of the word "paved". Yes, I realize there are a huge number of ways that use the current tracktype values and I don't expect many of you will agree with me but I believe such changes would clarify the existing confusion. We can then go on to discuss the problem of how to fairly evaluate the usability of highways by redefining existing tags and/or creating new tags. AlaskaDave
I must say that I disagree here, roads vary far too much for us to be able to have descriptive tags IMHO. There are potentially hundreds of reasons why a particular road is unsuited to a normal car or a racing bike or what ever. An end user is not so much interested in if a road has soft sand or deep washouts, he wants to know if his vehicle is likely to be OK or not. So, while we also have tags that attempt to describe the surface, I believe we need a broad, "sure mate, you'll be OK" or not ! --Davo (talk) 10:46, 18 January 2014 (UTC)
Key:smoothness= has about 25 thousand ways. That's 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!).
- Note: According to taginfo, there are 200k ways using Key:smoothness. I do like the fact it is meant to be a rough guess scale from "all possible wheeled vehicles" to "no wheeled vehicles" with an explicit list of vehicles but like many others I find the values hard to remember when to use them if you don't have the wiki page under your eyes. Also, the distinction between value "good" and "intermediate" is a bit fuzzy (are there really roads where racing bike can't pass while city bike can ?). That is why I proposed the page Proposed_features/usability long ago, but numbers don't really make it easier to remember but at least makes it clear 3 is worst than 2. The idea of extended/replacing it with thin_wheels, high-clearance, ... is also a good idea, even if I think we should keep an explicit list of "wheeled vehicles" on the wiki because not only wheels matters, engine's power could also make a difference in steep/mud situations. sletuffe (talk) 17:52, 14 January 2014 (UTC)
Key:surface_condition= would be a new key to describe the state of the surface. Smoothness says nothing about the quality of the surface. A surface of real cobblestones has a smoothness of 'horrible' (old term) but may be in an excellent state or full of potholes. Values could be 'perfect', 'good', 'intermediate', 'damaged', 'demolished'. This tag could also be useful for showing need of repair to the administration.Osmonav 12 January 2014 14:52 (UTC)
Actually surface_condition is not new and has been used 2,200 times. I've used it myself. Unfortunately all of these tags are problematic because, as has been repeatedly pointed out above and elsewhere, they ask the mapper to evaluate the quality of the highway. And such quality assessment varies depending on the target vehicle, be it roller blades or wheelchair or a 4wd truck, and even on the personality of the person doing the assessment (daring, couch potato, etc.). AlaskaDave
One existing tag or a combination
Any one of the above, or a combination ?
- Lets keep it simple --Davo (talk) 10:42, 9 January 2014 (UTC)
- Those 3 are hardly replaceable "as is" by the others (given the current description and usage, none can be merged into another). IMHO surface+smoothness are enough and I don't use tracktype, but since many use it, I guess it make sense to keep it ;-) sletuffe (talk) 18:00, 14 January 2014 (UTC)
How to render it
OK, lets assume we have agreed on a way to make the roads that need rendering differently, now how to display them ?
For larger roads, ones normally shown with casement and infill, lets make the infill dashed. Smaller roads, show as single line, should be dashed.
Other suggestions ?
OK, so this is a hobby horse of mine, get on board if you want to. Its not tied to the paved/unpaved issue but is related.
Do we push to extend the tracktype= tag to have three additional classes of road, grade6 to grade8 representing 4wd Only = recommended, yes and extreme. We also push to have it acknowledged that this tag applies to other than highway=track. This tag is certainly the one most mappers have chosen around the world, used two and a half million times.
Good points - renderers such as OSM's website already note tracktype and render it accordingly. Its only an extension of what is in use, indeed, there are even a number of tracktype=grade6 tags in the database already.
Bad points - Without additional values, does not cover 4x4 roads. Its not currently totally clear that this tag can be applied to, eg, highway=[secondary, primary]. And that is important, we do have larger, longer 'highways' that need to be marked as being possibly suitable for 4wd only. And the changes do change the meaning of tracktype (does it ?), getting it past the OSM approval process will be no easy task.
Alternative - 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'.