You are not logged in.

#26 2022-01-09 15:21:40

nitinatsangsit
Member
From: Bangkok
Registered: 2020-04-03
Posts: 83

Re: Proposal for highway classification revision

cmoffroad wrote:

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?

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).

cmoffroad wrote:

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

"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.

Last edited by nitinatsangsit (2022-01-09 15:22:23)

Offline

#27 2022-01-15 03:23:11

cmoffroad
Member
Registered: 2021-07-15
Posts: 49

Re: Proposal for highway classification revision

The statement in each section of the page emphasizes that unclassified roads are not more important than residential roads; they simply serve different purposes.

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 … classified:

- "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)

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.

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

https://en.wikipedia.org/wiki/Glossary_ … port_terms
- "Thru traffic Road users passing through an area whose destination is elsewhere."

https://wiki.openstreetmap.org/wiki/Tag … classified
- "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?

Offline

#28 2022-01-15 05:15:21

nitinatsangsit
Member
From: Bangkok
Registered: 2020-04-03
Posts: 83

Re: Proposal for highway classification revision

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.

Last edited by nitinatsangsit (2022-01-15 05:16:12)

Offline

#29 2022-01-15 06:48:40

cmoffroad
Member
Registered: 2021-07-15
Posts: 49

Re: Proposal for highway classification revision

nitinatsangsit wrote:

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.

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

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

Offline

#30 2022-01-16 16:51:02

stephankn
Moderator
Registered: 2010-05-04
Posts: 635

Re: Proposal for highway classification revision

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.

Offline

#31 2022-01-17 05:14:49

cmoffroad
Member
Registered: 2021-07-15
Posts: 49

Re: Proposal for highway classification revision

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.

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

Offline

#32 2022-01-17 19:54:12

stephankn
Moderator
Registered: 2010-05-04
Posts: 635

Re: Proposal for highway classification revision

I personally typically opt into not mapping something if it is not clear from available imagery.

I understand that this might conflict with the benchmark metrics used by some organized mappers/paid mappers. Map more for better score/payment.

So if not mapping is no option, then a highway=road is maybe the next best thing. Still not optimal, as a better approach would be to clarify the situation on the ground.

The consequence of a highway=road is that it won't show up on some maps and it is likely ignored in routing.
Positive thing is that it will show up quite prominent in quality assurance tools. But then someone else might re-classify it as "unclassified". Not sure we are winning much with this approach. And in most areas are not that many local mappers whop are keen on cleaning up highway=road left by others.

How about promoting the option to not map it unless a survey provides more clarity?

Offline

#33 2022-01-20 03:58:46

cmoffroad
Member
Registered: 2021-07-15
Posts: 49

Re: Proposal for highway classification revision

Very good points @stephankn,

In fact, organizations will never use highway=road because it will not be rendered for their own purposes.

highway=road is a special case, and the decision tree is only meant to cover the most common use-cases.
So to keep things simple especially for new mappers, I have replaced the highway=road reference with:

no: best to not map it you are not sure of its classification

Offline

Board footer

Powered by FluxBB