@AlaskaDave sorry, If I continue with the topic. At least some aspects of the mentioned table in the wiki needs further discussions.
I know it is tempting to have a guide-book which exactly tells how to tag what. Unfortunately, due to the way OSM works, this is not possible.
We should not re-define established meanings of tags, but hint towards the specific situation in Thailand and how to apply the tagging here.
I added a hopefully introduction to the table:
Always check the main wiki pages for a detailed description of the tags and some examples on how to use them along with other useful tags to add to them as well. The below table gives some hints on the tagging to cover the specific situation in Thailand.
For the highway=track, I added a note as discussed above:
Especially for paved roads double check the function the road serves: Would you recommend this road to someone travelling from A to B? Then it is probably no track.
I think we all agree that the function of the road matters and not physical attributes like the surface. Still both comes together. The more important a road, usually the better the road.
When wondering about road classification, I usually ask: Would this be the road to take if you want to go from A to B?
Maybe the road I picked by luck above is a nice example to discuss this further. You can see that on one side of the road we have this small road with concrete pavement, while on the other side of the canal we have this wide asphalt road.
The small road is tagged as track: Way: 559237369 | OpenStreetMap
The wider road is unclassified: Way: 526559398 | OpenStreetMap
Unfortunately, no one had yet been on the ground to see the mile-stone which identifies the wider and nicer road as ref=สพ.4056 (Google Maps)
So we have exactly the typical problem. Roads had been added by some remote mappers (not important whether it was Facebook, Grab or a different party) and the classification was guessed.
If you are on the ground, then you would clearly say: everyone who wants to travel along the canal should use the road on the eastern side. That is the “main” road. The other side is only used by farmers to access the fields or by people who have houses there (guessing on farmers again).
This specific problem comes due to the remote mapping. Our wiki table can’t solve it. It requires “on the ground” survey (or recent street-level imagery).
We might now say: Yes, we need a tag to know that a road tagging was “guessed” by some machine or remote mapper. At least for the large-scale Facebook edit we have this. The roads above have the “import=yes” tags on them.
Exploring a bit the area with Google gives us an impression of how it might look on the ground.
In the west-side way along the canal, I already mentioned that it also has some houses along the canal. So the road also serves the purpose to access these houses. Maybe it is still mostly farmers using the road, it is also visitors to these houses.
These houses do not really form a settlement. So tagging the road as residential sounds wrong. It might still be “mainly” agricultural and the access to the houses is then the minor usage. Und having a paved road might lead people to build further houses there.
Or we could see that these roads are more used for “access”. Then it might justify highway=unclassified. This is where Dave’s initial point came in that a track is never paved in Thailand.
If we would tag the tertiary road correctly, then in this specific example we would have no issue with routing, as the travel cost used for calculation would lead to a clear preference of the tertiary only a few meters away.
But situation could be different. I came up with this road:
Imagine, you are travelling southwards on the 2012 and you want to continue north on the 4050. Currently, this paved road is tagged as “track”. This prevents routing for cars over this segment.
But what if we would tag it as “unclassified”, then we save some kilometers including traffic lights, so routing engines might consider this as the “shortest route” and guide you there. I tried routing on OSM data in Thailand before and I ended up being guided through such “shortcuts”. Since then I no longer “just use” OSM for routing but preview routes on aerial/Google, or simply use Google right away.
Check out the Streetview: You do not want to drive your city car this road and want to meet a truck on this narrow one: (Google Maps)
If the ground-survey looks like streetview, I clearly agree to tag this road as track, even having some concrete pavement. It only provides here access to rice fields. Certainly, the other aspects of this roud should be tagged as well, especially the width or maybe lanes=1 to clearly mark this as a minor road.
Trying to summarize it a bit: Function of the road is a good indicator for classification. And it is important to tag other road properties like surface and width to have the data available to make informed decisions when doing routing.
BTW: I did tag roads which only prove access to eg a forest temple as service. I feel this appropriate, but we can certainly discuss this as well. Maybe better then to open a specific thread for individual tagging where we could also collect real-world examples of the tagging.