Tagging tertiary highways

I want to again discuss the tagging of tertiary highways in Thailand. When I first started mapping I followed what I thought were hard rules about tagging highways the way it was specified in the Thailand Wiki. That tagging scheme is imperfect and leaves a lot to be desired in my opinion. The Wiki says tertiary highways:

  • connect two or more villages/hamlets
  • are often 4 digit roads maintained on province level, blue sign.
  • most of them are paved, but unpaved roads are possible

There have been some recent changes in this convention effectively making these definitions looser and it is now no longer unusual to see a highway without a provincial designation tagged as a tertiary highway. Which brings me to my question. I want to tag some local residential highways as tertiary. The type of highway I am discussing is common in Chiang Mai and, while it has no designated route or ref number and does not always connect two towns, it does experience high traffic volumes and is important because it’s a well used and efficient means of getting from point A to point B.

Two good examples from my neighborhood are Patan Road (Way: ถนน ป่าตัน (20262778) that runs along the west side of the Ping River and its east side counterpart, an unnamed residential road, Way: 20267994. Both are smooth, wide highways that connect ชม.3029 and the Superhighway and consequently carry much traffic. Both were at one time probably smaller residential highways that have, over the years, been joined, straightened, and improved so they look continuous.

Tagging them tertiary would give them more visibility and indicate their usefulness, and popularity, as a route despite having no official number designation.

Opinions please. Is this something we can live with? Is it a good idea?


I think this is pretty much an issue of urban road classification, which so far hasn’t really been given much consideration. Most roads and streets in urban areas are looked after by local governments, and thus don’t fall under the wider national and provincial classification schemes. However, in larger cities, they often serve considerable amounts of traffic and are quite important to the network. It’s natural that the map should reflect these roads’ importance, even if they are locally administered.

I’ve previously asked on the help forum for advice on the subject, and the responses indicated that without official sources as a guide, classification will mostly have to depend on local knowledge of the roads’ importance. This probably means each city will need its own discussion, but we could probably come up with some general guidelines.

The answer given to your question on OSM Help suggests, to me at least, that the highways in question here could be tertiary. If we were to reword the Wiki slightly that might be a good first step:

  • is a connector, that is, it connects two or more villages/hamlets or larger highways

and possibly add:

  • carries larger amounts of traffic at higher speed than nearby residential highways

In reality, I think the definition has already changed but this has not been done systematically nor reflected in the Thailand Wiki.

I’ll wait to see if any other comments emerge before doing anything else.

Thanks again, Paul.



That’s what I’ve decided as well. I guess I’m guilty of wanting to map for the renderer to some extent because when I’m browsing my Garmin maps while creating routes, I sometimes want to locate the faster, smoother highways. The plain fact is, tertiary highways grab my attention while unclassified ones do not.

Plus, the definition of unclassified leaves a lot to be desired. Not specific enough to make a decision IMO :

At any rate, if a highway has tertiary characteristics as outlined above and in the Wiki, that’s the deciding factor. I’ll be tagging those tertiary regardless of what the Thai Highway Department does, or doesn’t do.