Thailand Road Classification and Tagging

Stephan, that’s a great offer!
From my point of view, the “trunk” roads deserve better attention. I know the situation in the South only, things might be different elsewhere.
Phetkasem road (#4) is tagged with highway=trunk even where it is just a “normal” road with two lanes, even when it is a narrow winding road (e.g. between Phang Nga and Thap Put). I’d prefer to “downgrade” it to a primary there.
On the other hand, there are some good dual-carriage highways tagged as primary (#41 from Krabi to Surat Thani), or secondary (#415 from Pang Nga to Thap Phut, or #403 to Nakhon Sri Thammarat), even tertiary (#4103 West of Nakhon Sri Thammarat), generally in accordance with the “administrative” tagging scheme described in the wiki.
Those roads have lanes=2 and oneway=yes, and I added dual_carriage=yes for ease of detection to many of them.
How easy/complicated is such an upgrading/downgrading action in Maperitive?

Hi Bernhard,

I hope I made it clear: I vote against changing road classifications based on the condition of the road. I vote for a change of the rendering to consider attributes like lanes for the rendering.

Changing in Maperitive it quite easy and straightforward. This is an example of what I changed in Maperitive on the style which comes together with maperitive:
I made a new define for oneway with two lanes:

highway lanes2oneway : highway=residential AND lanes=2 AND oneway=yes

and later style it according to a higher category road with colors of residential:


		elseif : *lanes2oneway
			define
				min-zoom : 13
				line-color : white
				line-width : 10:1;13:2;15:10;18:12
				border-style : solid
				border-color : white black 25%
				border-width : 15%
			for : tunnel=yes
				define
					border-style : dot
			for : bridge=yes
				define
					border-color : #000
			draw : line
			define
				min-zoom : 10
				max-zoom : 13
				line-color : white black 25%
				border-style : none
			draw : line
			define
				min-zoom : 15
				max-zoom : 20
			draw : text

For a change of the official style or thaimap a patch against mapnik styles is needed:
http://svn.openstreetmap.org/applications/rendering/mapnik/

I forgot: it the tag dual_carriage not a bit strange used in combination with oneway=yes?

Seeing it on a way I would have suggested it means the way is dual carriage but not yet separated into two ways having oneway=yes set each.

I think in most cases physical characteristics should be tagged independently without bearing on the classification. I agree that the distinction between soi and thanon can be rather arbitrary, but at least it’s something objective which can be easily recorded, and it usually does give a rough indication of a road’s “importance” to non-local traffic.

It seems to have been down for a while. Loads fine for me now.

Rendering/routing software taking physical characteristics into consideration would be very useful, but in some instances number of lanes alone won’t be adequate. Off the top of my head there’s Soi Ari Samphan (Rama VI Soi 30). Despite having two lanes (one in each direction), it (together with Soi Ratchakhru (Phahon Yothin 5)) serves a lot of non-local traffic travelling between Phayhon Yothin and Rama VI Roads.

As for Thailand in general, there’s also the issue of rural roads (those maintained by the DRR) not currently being distinguished from four-digit national highways (which are maintained by the DOH). I’m inclined to think that the difference between DRR and DOH highways should be more important than that among DOH highway classes. Any thoughts on this?

I still think that 1- and 2-digit DOH highways are usually of similar enough “importance” that their classes could be merged, leaving a different classification for DRR highways. But others may have better ideas.

Another important point for rendering are non-paved highways. Not all roads have an asphalt or concrete layer, look very similar to tracks, but are public roads connecting villages. I think it is important to see that difference also on the map.

@Stephan: of course, that “upgrading/downgrading” is done only locally for rendering purposes, not in the official database. E.g. I do

highway=trunk & (oneway!=yes) {set highway=primary}
highway!=motorway & (oneway=yes & lanes>1) {set highway=trunk}
highway!=motorway & (highway=* & lanes>2) {set highway=trunk}
highway!=motorway & dual_carriage=yes {set highway=trunk}

so that “trunks” which are not oneway roads are rendered like primaries; and secondary/tertiary etc. which have more than two lanes, or are oneways with more than one lane per direction, are rendered like trunks.
I think that’s similar to your “define” above, just for all previous classifications - mapnik can use more different styles than Garmin.

Sorry, I’m with Bernhard here. I have said it before and I’ll say it again: blindly adhering to the numbering scheme when classifying roads creates an “administrative” map, which is not very useful to anybody. The map should reflect the reality and not just some arbitrary numbering scheme.

As such, I have tagged sections of h’way 4 down South as primary, just like those kinks in the middle of h’way 1 should be (at most) primary, as these sections are of not a great significance in the network. H’way 32, on the other hand, is definitely a trunk road. It links (almost) Bkk to Chiang Mai.

In fact, the project page already states that roads should be ‘upgraded’ where appropriate and I suggest we also ‘downgrade’ roads in the same manner.

I have been mapping a lot of minor roads and tracks, mostly in the N. Some of these happen to have 4-digit ref numbers, but I doubt they are part of any classification scheme we know of. I was dismayed to find that people go and ‘upgrade’ these single lane dirt tracks to tertiary roads to “fill gaps in the road network”.

Regards,
Peter.

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Can you elaborate on this? Since I’ve started mapping in Thailand, I’ve been baffled as to why this highway type is considered inappropriate for any road in Thailand. Certainly from a routing perspective, it seems like a useful classification. In my opinion, there are many minor roads that are typically “less” residential, or typically used as “through-roads” more often than other more residential roads. According to the OSM wiki (http://wiki.openstreetmap.org/wiki/Routing#Highway-type) the default routing priority of unclassified is higher than residential. It seems to me we are leaving a valuable classification unutilized. I think its incorrect to assume that every road in every city (that is not considered at least a 4-digit highway) is of equal importance, and all considered residential (even if its not really residential).

Seems like there is some discussion on these matters, and I just wanted to add my opinion, thanks.

Also agree strongly with Beddhist. The reality of the road system is very different than the official classifications. I definately think that the “reality” of the individual road size, construction, traffic flow, and route should be the primary consideration of classification. The “official” designations often do not reflect the actual “priority of use” of the road. I certainly would trust the opinion of a local mapper over the goverments official designation.

And you are exactly correct about the bypasses, RocketMan. Absolutely daft of us to blindly follow the numbering system in situations like this! Often times, the bypass route around a city would be the preferred method of travel (due to traffic and traffic controls), and yet due to the guidlines in-place, you are invariably routed directly through the city. I think these situations could be handled similarly to the US “business route” system (where the old route through the city is downgraded in classification). Even though there is no official designation for business route here in Thailand, I don’t think we should wait around for the government to change its road classifications in order for us to have better maps - we’re not making maps for the government are we?

Anyway, just needed to vent and throw my 2 cents into the fray.

Please do not forget that almost all of the roads in Thailand with numbers are tagged according to their numbers now. Changes may cause inconsistencies.
I’d like to suggest to take a closer look at other usability criteria, e.g. width of the road (directly in meters, or indirectly by e.g. presence/absence of a central_line, existence of a shoulder), surface and smoothness, number of lanes, speed limits, …
Such criteria can be used for creating the maps instead of the “highway” tag.

Having the physical properties of every road surveyed and tagged would of course be the ideal solution. However, it is also unrealistic to expect this, at least in the short term. While it would be great to have renderers based on the roads’ actual characteristics, we should also be able to make the most of the default fallback when such information isn’t available, which is the highway tag. Having the highway tag reflect the number of digits in the ref 100% of the time would render it redundant. I agree that when local knowledge/experience is available, such information should be taken into consideration.

At any rate, we still need a good set of default classifications, for when detailed knowledge isn’t yet available. As noted above, the current scheme in the Wiki is inadequate as it leaves out / fails to distinguish many types of roads.

I see that my prevoius post could be mis-understood. I did not say: “do not chnage the highway tag”. Rather I’d like to say: “when you change the highway tag, do it with care”.

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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