Open Street Map Thailand highway reference status

In order to gauge the status of Thai highways in Open Street Map it is useful to compare the difference between a list of highways in Open Street Map that have a reference number (eg. 3, 31, 301, สป.1005 etc.) associated with them already and the official highway registry.There are two main types of highways in Thailand, the National Highway managed by the Department of Highways with a list on Wikipedia and the rural highways now managed by their respective local governing bodies with a list scraped from the Department of Rural Roads. This gives us a master list of 13,408 highways.

With OSM a list was acquired by downloading a daily dump of Thailand from Geofabrik and getting a list of highways with the Key ‘ref’ in it. This got us a total of 3,026 highways. Relations weren’t taken into account because only a ballpark was needed and there are not that many relations.

We look for the reference numbers that exists in OSM that also exists in the master list. The result is that there are only 1,640. I have made a list of ways which exist in OSM but doesn’t exist in the master list available for further scrutiny. Some of these are trivial such as the usage of instead of or the use of xx notation in the rural road numbers, others will require further investigation.


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3 thoughts on “Open Street Map Thailand highway reference status

  1. I’d venture a guess that the majority of those are either malformed DRR refs (lacking or with incorrect prefixes) or old ARD (รพช.) refs from roads which have been transferred to local governments and are not recognised by the DRR.

    I’m rather curious about the five-digit DRR refs (all beginning with 7) in your master list, though. Don’t think I’ve seen them before.

  2. This are quite interesting numbers. Still it amazes me that over half of the highways in OSM should officially not exist.
    Given the way we acquire the number – by local survey, watching the sign – it should be far less errors.

    So I assume some sort of systematic problem which needs to be ruled out.
    Could it be that the “master list” itself is lacking some roads? For example there should exist a road ขก.1018. A web search for this reveals several references to it. So it’s likely it is existing.
    Why would it miss in the DRR list? I keep all my photo mapping pictures. If you can produce a list of “surplus” roads, I can try to match them with my pictures. So we can get an example of a road which is correctly missing in your master list.
    Is it expected to have huge gaps in the numbering?
    eg ขก.1011, ขก.1016, ขก.1023, ขก.1027

    Another thought:
    I remember a re-numbering effort of streets. Probably it’s either a forgotten sign with an old number or some old contributions to OSM which have not yet been updated.

  3. @Stephan:
    Searching for your example, ขก.1018, does indeed reveal that the road was transferred to the Khon Kaen PAO in 2003. That would explain why it is missing from the DRR’s data. Not sure if the PAO has assigned it a new ref number though.

    As for the apparent gaps in numbering, this is due to the way DRR refs are assigned. Only the last three digits serve as a running index number; the first indicates the level of the road it branches off from. When sorted, that would be ขก.1011, ขก.5012, ขก.2013, ขก.2015, ขก.1016, ขก.2017, ขก.3018, ขก.3020 etc. So the gaps aren’t as huge as they initially appear.

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