Proposal for highway classification revision

Great to hear, it’s definitely a work in progress and I am happy to improve it over time based on your input.

I have updated the workflow accordingly and added a couple of important footnotes:

Note: A "traffic through road" means vehicles passing through an area whose destination is elsewhere.
The next destination could be a village, a temple, an estate, or joining a road of equal or greater importance.

Note: If a road qualifies for multiple tag classifications (e.g. different highway, surface...), it should be split 
into separate segments. e.g. The first 100 meters of an agricultural track may be paved and have permanent houses along. 
First part could be tagged as a paved residential, while the rest stay as an unpaved track.

Is it ok to use tertiary for main links between villages including unpaved roads in mountainous areas?

How would you describe where a service road can be found in a few words?

Where would you classify such a road in the decision tree?

The road surface should not have an impact on its importance in the road network, thus if it is qualified, it can be a tertiary.
The issue is that I’m not sure if all of the village links qualified for tertiary. Perhaps it must show that it is more significant than a general unclassified or residential road, such as connecting two villages, each with its own residential road grid, and some residential road branches off along the way.

Maybe “A road that leads to a single building or property.”

Perhaps above all of them, “is the road usually only for pedestrians?”

P.s. IMO “does the road have no other function other than for residential purposes?” is too strict, because many residential roads may also serve some little other purposes. If it is mainly for residential it should be qualified.

I don’t think that’s accurate or precise enough. Official wiki says “Generally for access to a building, service station, beach, campsite, industrial estate, business park, etc. This is also commonly used for access to parking, driveways, and alleys.”

The road doesn’t have to be leading to a building, it can be lanes inside some parking, campground, park, or factory.

I think it has really to do with the fact service roads are not part of the general public network and are maintained by owners. They (should) come with access restrictions. Renderers show services as thinner lines and routers usually avoid them even if you can go through.

The owner of the land could technically be the government so public/private distinction does not really work. Anyone has a suggestion?

Added on top:


- is the road mainly or exclusively for pedestrians ?
  - yes: highway=pedestrian

Added:


- yes: is it the main link between 2 towns/villages/hamlets/settlements ?
  - yes: is the surrounding network large enough (a few unclassified, residential) to justify a more significant road ?
    - yes: highway=tertiary
    - no: highway=unclassified

I agree it was too strict, but it should not be too loose either. Traffic-through or agricultural tracks should not be tagged residential even if some permanent houses can be found along. I have changed the condition to:

- `no`: is the main purpose of the road access to permanent residences?

btw, how should housing for workers within an estate/facility be tagged? e.g. factory, government facility, industrial estate…

Ah… I think your original criteria, which distinguishes it with public/private distinction, is good enough and cover most of them (some government-owned roads are also private if they are gated behind a state agency’s fence). What I mean is for some of the public roads that should be service.

IMO, this differs from residential housing, in which land ownership is divided among the owners of each house. Because the majority of these land are owned by a single owner, highway=service should be appropriate.

P.s. I see you added a service=alley. I think most cases in Thailand are not in a private area. Most of what comes to mind is a road running through the gap between the rowhouses, or a road for the rowhouse’s rear access (not for main access). Also, I think that function is more important than width, because many residential roads in Thailand are narrower than an alleyway.

Ok. I removed it since it’s a special case, and it’s been used wrong in many places.

I improved the wording a little: “is the road inside a private property/estate/facility ?”

Ok. What would be the use-case for this?

Curious about this, can a road inside a large estate/facility really be something else than service?

It could be something technical, a road leading to a private estate is sometimes not part of the estate and is a public road. There is also a service road in the highway area, such as at 15.147637, 100.254418 . Anyway, these might be the rare case and, for rough guidance, can be ignored.

There is a discussion in https://forum.openstreetmap.org/viewtopic.php?id=68434 . A road within a large estate that is frequently used for through traffic could be unclassified.

Makes sense. I see the need for it. I added it to the decision tree.

What about dirt tracks to access fields/gardens inside a research center/farm/property, can these also stay as track or should they be service?

I think it is still track.

I’ve already made changes to the wiki. cmoffroad’s decision tree has also been added.

Regards

FYI, I have improved further some of the minor road classifications wiki definitions to reflect the current general consensus:

https://wiki.openstreetmap.org/wiki/WikiProject_Thailand#Urban_and_Local_Road_wide_enough_for_motor_cars

Please feel free to refine the wording, and refer to the topics below if you have any concerns or feedback.

highway=footway

Topic: https://forum.openstreetmap.org/viewtopic.php?id=73864

highway=service + service=alley

Topic: https://forum.openstreetmap.org/viewtopic.php?id=73799,

highway=living_street

Topic: https://forum.openstreetmap.org/viewtopic.php?id=73799, https://forum.openstreetmap.org/viewtopic.php?id=19316

Made a few small improvements to the minor road classification decision tree in the wiki:

https://wiki.openstreetmap.org/wiki/WikiProject_Thailand#Rough_guidelines_for_minor_highway_tag_decision-making_.28useful_in_most_cases.29

A) removed the possibility for the main link between two settlements to be tertiary without a reference

This is to ensure that only roads with a reference can be considered major (primary/secondary/tertiary) as per the wiki table:
https://wiki.openstreetmap.org/wiki/WikiProject_Thailand#Highway_classification

It used to be a topic of conflict in the past where some mappers would prefer to tag major roads based on their current usage instead of refs.
We want to avoid this again so no ref means unclassified.

B) Make highway=unclassified only possible for road through traffic without refs.

unclassified roads are essentially “quaternary” roads (tertiary without refs) and represent the lowest level of the interconnecting road grid network.
Below, minor roads can only be classified as service, residential, or track. If the mapper is unsure of the classification, highway=road should be chosen until others figure out the right one.

This is to ensure that unclassified is not incorrectly used for minor roads (happens often).

If you have any concerns about these changes or would like to request a change, please let me know.

It’s fine, but I have some concerns.
A) More and more local roads (maintained by the local administrative organization, green sign) are now referenced, implying that nearly all of the main link between two settlements is already referenced. The issue is that some are well signposted while others are not, and this is due to the budget and duty of each local administrative organization, not their importance. I’m not sure if this could lead individuals who are unfamiliar with the system to think the unsignposted road is unreferenced.
Furthermore, the ref classification in the table is intended to be used only for intercity highway tagging, not for urban and local road.
B) Though most unclassified roads are used for through traffic, some are as minor as residential roads, according to https://wiki.openstreetmap.org/wiki/Tag:highway%3Dunclassified, such as a short dead-end public road outside a residential area.

There are unclassified roads with ref number. Will show examples later.

Ok great, so unclassified may have an optional local reference, but when they do, how do we differentiate them from tertiary roads? Would the reference come in a different format? Also, can we assume tertiary roads must always have a reference?

Common issues I am trying to solve:

  • tertiary roads without reference tags in a strange location, is it safe to change these to unclassified?
  • new mappers changing existing primary classifications, can I refer them to the wiki table as a bulletproof way to find out correct classification based on existing reference format ?

I do not find the reference you mention in the highway=unclassified page. Could you please highlight it?

As far as I understood, the term through traffic does not exclude dead-end roads, if it leads traffic somewhere (temple, resorts, facilities).
But if it’s a very short minor road, leading traffic nowhere, and it’s not residential or within a property/estate, then surely it is an agricultural or forestry track, what else?

Unfortunately, there is no hierarchical format for local road references, and the referenced/unreferenced state has no link to importance, only registration. (Ideally, all public roads supervised by the local administrative organization should be registered.)

I understand your worry, and I agree that we should make it obvious for tertiary/unclassified decisions. I’m reconsidering, and I agree with you that upgrading to tertiary road should not be based solely on the “main link between two settlements”. For example, the main link between two settlements in a rural area where only tracks branch off is weird to be tertiary. Now, instead of focusing on “settlements”, I’d like to suggest focusing on “road network”. In general, when creating a map, road classification is used for route selection for navigation purposes which means that choosing a classification for each road is something relative, not absolute. To make the road network make sense, the number of high-ranking roads should be less than the number of low-ranking roads, respectively. In this sense, it’s fine if there are still less tertiary roads than unclassified roads, and it’s good for some dense areas with a lot of unclassified/residential roads that we have a main road over there designated as a tertiary road to make the map easier to read.

So, IMO, the definition of tertiary in the Urban and Local Road table is reasonable: “Roads that are more important than regular unclassified or residential roads, or roads that connect several unclassified or residential roads.” To make it clearer, we can say something like “it connects 5 secondary or higher roads, or 20 unclassified/residential roads.” It may be difficult to determine the appropriate number, and it may be necessary to conduct some study in several different areas throughout the country. BTW, I don’t think we should be too tight on this, but offering a number to give mapper an idea may be helpful (with caution stated).

“minor public roads, typically at the lowest level of whatever administrative hierarchy is used in that jurisdiction.”
“not residential streets or agricultural tracks”
“The value unclassified is indeed a classification, meaning ‘very minor road’.”
etc.

The statement in each section of the page emphasizes that unclassified roads are not more important than residential roads; they simply serve different purposes. BTW, if the term “through traffic” can refers to any route that leads somewhere, it is logical. However, I concern that using this term may mislead mappers into thinking it is used to connect to another road. And, sure, a very short minor road leading to nowhere is unlikely to be unclassified.

I do not see any statements in the wiki supporting this.

Unclassified roads are “minor public roads at the lowest level of interconnecting grid network”, residential roads are not. And for this reason, OSM end-user applications will always render unclassified roads more important than residential ones. To me, unclassified roads are more similar to tertiary roads than residential roads.

Excerpts from https://wiki.openstreetmap.org/wiki/Tag:highway%3Dunclassified:

  • “Public access road, non-residential.”
  • “Residential roads, primarily for access to properties, should be tagged highway=residential instead.”
  • “not residential streets or agricultural tracks”
  • “roads used only for local traffic”
  • “roads of low importance within town and cities (if not residential)”

The only similarity with residential roads I found is that they both are considered “minor” (so are service and tracks) and often it’s difficult to decide if a long dead-end road is residential or unclassified (see below)

I completely agree that the term may be misleading and need to be rephrased.

https://en.wikipedia.org/wiki/Glossary_of_road_transport_terms

  • “Thru traffic Road users passing through an area whose destination is elsewhere.”

https://wiki.openstreetmap.org/wiki/Tag:highway%3Dunclassified

  • “the road is frequently and legally used as a through route or to reach a (non-farm) workplace or tourist attraction”

Possible rewording for the decision tree:

A)


- no: is the road frequently used as through traffic or to reach a non-residential/farming destination (attraction, hotel, temple...) ?
  - yes: highway=unclassified
  - no: is the main purpose of the road access to forestry/agricultural fields?
    - yes: highway=track
    - no: is the main purpose of the road access to permanent residences?
      - yes: highway=residential
      - no: highway=road

B)


- no: is the main purpose of the road through traffic?
  - yes: highway=unclassified
  - no: is the main purpose of the road access to forestry/agricultural fields?
    - yes: highway=track
    - no: is the main purpose of the road access to permanent residences?
      - yes: highway=residential
      - no: is the road used to reach another destination (hotel, temple, tourist attraction...)
        - yes: highway=unclassified
        - no: highway=road 

The wiki definitions would be similar to solution B) but I find it a bit puzzling that a long residential or agricultural track road ending at a tourist attraction (e.g. waterfall or temple) should be not unclassified and I would normally tag as A).

what do you think?

They use the phrases “less important than tertiary roads” and “not residential streets or agricultural tracks”, rather than “not tertiary roads” and “more important than residential streets or agricultural tracks”. IMO, this seems to me that, in terms of importance, unclassified is more similar to residential or track than tertiary and I believe this is why osm-carto rendered unclassified and residential road the same size.

Anyway, this isn’t much of a topic to debate, and I agree with you that option A is superior owing to its simplicity and ease of understanding. Of course, exceptions can happen at any time, but since we specified “(useful in most cases)”, it’s fine.

I was not aware of this. Thanks for the clarifications!

PS: I have updated the Thailand wiki according to (A)

I am slightly unhappy with the final state of the table to suggest tagging highway=road.
This tag is sort of a temporary tag. Like you derive road geometry from aerial imagery, but not yet applied classification.

https://wiki.openstreetmap.org/wiki/Tag:highway%3Droad

So that state is more like a “ask other mappers/do further on the ground survey to get a proper classification”

Ending at that state in your decision tree might indicate that based on the available details it is a tricky situation. So maybe ask to get further details. What is the road actually used for? Who is using the road?
Also adding the physical properties of that road might help with future tagging. Like surface, width, weight limits and so on.

Happy to remove highway=road from the decision tree, but what would be the alternative if a mapper cannot decide what should be the correct classification?
A) to not map it?
B) to fall back to another classification that may be wrong?

If the questions in the decision tree are not clear enough to make a decision based on the purpose of the road, how would you reformulate to make it clearer?

At least in northern Thailand, most new road additions are based only on satellite imagery, and it’s often not possible to know if a road is used as through traffic (unclassified) or is mostly used for farming or residential access, this is where highway=road could come handy for unsure mappers to let others on the ground verify and tag it according to the local context.

Providing more tags through a ground survey is always welcomed but the initial goal of the decision tree was to provide a simple reference covering most use-cases, to avoid conflicts with other mappers (e.g. GrabOSM) due to different classification interpretations