Thailand Road Classification and Tagging

I’ve started updateing the highway tag of roads in South Thailand. Most changes were “upgrades”, only a few “downgrades”.

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Bernhard, I’m a bit unhappy about the tag changing.

What classifies a road for an “upgrade”. Just you thinking it is “more important” than others?
I kindly ask you to suspend tag changing until we have agreed and documented a set of objective criteria for road classification.

The old one was very objective. Simply count number of digits. Everyone could verify it on the ground.

How should other mappers now verify your tagging? Maybe they disagree with your feeling of “importance”.

The possibility to check OSM data by every other mapper willing to do so is the foundation of OSM. I not want to let it go that easy.

So before (!) re-tagging we need to have a common understanding of the tagging. At least inside Thailand this MUST be consistent. It’s certainly not desirable to have different criteria for tertiary/secondary in the South and in the North.

The wiki page the highway tag lists come criteria used for example in Germany where you should be familiar with the mapping:
http://wiki.openstreetmap.org/wiki/DE:Tag:highway%3Dsecondary

It lists criteria when a lower category can be upgraded. I’m not aware of examples when some road category gets downgraded. Do we really want this as well?

We should have such a definition for Thailand first.

It should also take into account intra town highways.

Stephan

Hi,

Mostly I agree with Stephan.

However,

I can give you some examples where this is appropriate.

1: ID 78388648 - last time I rode through here it was labelled ‘1’. It’s an average local road that happens to be a shortcut from h’way 1 to 105. I made it into a tertiary, but I see somebody has now changed that to trunk_link. I don’t think it fits that definition, either and the Thai authorities have since changed the number to 1351. Accordingly I am changing it back to tertiary.

2: Just a little N is Ban Tak. Passing through here a few years ago I saw to my great surprise a milestone ‘1’. (way 77572641) This is a dual carriageway that loops through the little town. It’s hardly a trunk road and one could argue for any classification up from tertiary, so I made it primary. Unfortunately, no Bing images here, so I could only map what I had tracks for, but you can see it clearly in GM and the junctions in Streetview.

3: Going down h’way 1 you come to Nakhon Sawan. The 1 goes through the middle of the town, traffic lights, chaos and all, while the newer 121 goes around the outside as a dual carriageway (and happily is marked as trunk). Since nobody passing through would consider going through the city I vote to downgrade this section to primary.

4: Continuing on S the road splits. AH1 and all traffic for Bkk continue straight on, while the 1 meanders like a river through Chainat and Takhli, where it turns into a little country road, eventually making it to Lopburi. Most of this should be no more than primary: nobody going from A to B will follow this road for any distance and there is little traffic. I would bet that anybody going through the history of these roads will find that the 1 was built first and there were reasons why it meanders. Modern day traffic bypasses this bit, so it’s less significant.

5: In the deep South near Chumphon h’way 4 loops West as a country road, while AH12 and all long-distance traffic follow the 41, which is DC right through to Malaysia. When I drew this a few years back it was primary, but I see most, but not all of it is now trunk, “because it has only 1 digit”. The 41 is a trunk on the map, as it should be.

6: Diagonally between the two runs the 44, which is in the process of being re-classified as we speak, judging from the colour changes when I zoom in and out. This is a big DC and I imagine it carries a lot of the traffic from Bkk to Phuket, Krabi, etc.

7: Hat Yai, same story as 4, it seems.

There are a couple of local roads that have 4-digit numbers right here where I’m staying now. They don’t, however, have any of the standard road signs. That didn’t stop somebody from changing them to tertiary.

I think nobody should re-classify roads s/he has not seen in person, just because of a number. (Unless it’s an obvious beginners error, like primary roads in the back blocks…) We should have some guidelines for classification (based on the numbering scheme, obviously), but allowing for deviations where it is appropriate. Size of the cities or areas connected, size of the road, traffic volume, etc. should all be regarded.

Otherwise (and I am repeating myself here) we will create an administrative map that will end up sending people down the wrong way.

Kind regards,
Peter.

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It still must be possible to spot tagging mistakes. I know the definition in the wiki was never great but does this justify not to write a better definition on what classifies a highway “upgradeable”?

@RocketMan: Does the affecting section of 3462 really has a sign giving the 4 digits? I’ve never been there but can’t believe people give 4-digits to ways which can’t be used by a vehicle. Or are you exaggerating? It might also be something planned for extensions which has not yet be done. There is tagging to describe this. And maybe this is the “one exception to the rule” which is always there.

Still I really want definitions which match in the vast majority of cases. If we do classification by “gut feeling” we’re steering right into edit wars and inconsistent tagging all over.

Let’s keep a minute with the city bypass roads: Do we want to upgrade the bypass? Or downgrade the major highway? If downgrade: How many levels? Only in towns? Only if the numbering does not change?
There are bypass roads which share the same highway number. In these situations we might want to downgrade the intra-town part.

But what about not so clear cases:
Sukhumvit 3 is going strait through Rayong. Using 364 and 36 it would be possible to bypass town. Would this justify to downgrade the Rayong section?
http://thaimap.osm-tools.org/?zoom=14&lat=12.6811&lon=101.26325&layers=B00T

Stephan

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Quite a few upgrade/downgrade cases appear to be that of a newer two-digit route overtaking an older one-digit route in importance. What do you think of my old suggestion of merging the two classes into the same tag? This would eliminate the problem of upgrading individual two-digit routes. (Most seem to deserve the upgrade, I think.) This could also open up a separate class for the rural highways.

If this is done, we could still make the case of downgrading certain portions of old one-digit routes which have been completely superseded, where appropriate.

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The road network of Thailand was projected several decades ago. The major roads went thru most of the villages along the road, of course (not different from Western countries). Later on, some bypass roads were built.
And that’s the point where the difference in the numbering system comes from: in Thailand, the old road keeps its (typically one-digit) number and the bypass road receives a new number (often 4 digits). In Western countries, the bypass road becomes part of the old road and receives its number. The old route thro town loses its former number, it may get a new (tertiary etc.) number or none at all.
When you stick to the number for classification, the bypass is then a tertiary, while the former road thru town a trunk.
By the way, Phetkasem road is just a minor road in Phattalung. I do not remember exactly which of the roads leading South showed a road sign with that name, I think it was http://www.openstreetmap.org/browse/way/151510987 - also take a look at Google Earth for that place, where you’ll find Phetkasem road to be just a road in town…

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I think it’s rather obvious that that section is no longer maintained as a national highway. It’s not strange for a numbered route to be divided into non-continuous sections like this. This is much the exception rather than the norm, anyway.

The actual road conditions should be tagged using their respective tags: lane, width, surface, etc. As stephankn demonstrated, renderers can take those tags into account. We still need, though, to determine the proper default class for the routes, in terms of importance to the network.

This also falls into the above problem of tagging physical properties of the road, but at any rate, those are very inclusive criteria. There are many dual carriageways which aren’t that important on a national level. Then there’s the problem of routes which have separate carriageways for only some sections of their length.

I think downgrading the intra-town part for bypasses which share the same number seems reasonable. Not sure about Rayong, but Saraburi is another example. Heading northeast from Bangkok, most motorists would take the old junction in town rather than the route 362 bypass, which is actually much lengthier and has more traffic lights. Probably for these cases we should leave the old sections the way they are, unless local knowledge confirms that nobody really takes the route through the town any more.

I could hardly believe how dangerous that point is. But just a few days after changing the classification, I traced from Bing and found a road tagged “too low”. I thought I had forgotten that one. But a look into the history revealed: someone else had already changed it back.
OK, I do not want to engage in edit wars. I do not change that other mapper’s tag.
As for the Garmin map I will use during my holidays, I will use my own style file, and I’ve previously shown that I can cope with many problems of the present weird tagging scheme.
It is too bad that we’ve lost Willi after an edit war. No further losses needed!

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Actually, the default speed limit for cars is 120 km/h on motorways 7 and 9, 90 km/h on rural highways, and 80 km/h in municipal areas (plus Bangkok and Pattaya) and 90 km/h elsewhere for all other roads. With the exception of Bangkok, no municipalities currently have their areas tagged, so applying even the default speed limits properly will be tricky.

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