Proposal:Tag:highway=unknown

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unknown
Proposal status: Draft (under way)
Proposed by: CMoffroad
Tagging: highway=unknown
Applies to: way way
Definition: Road with unknown classification.
Statistics:

Draft started: 2024-09-17
RFC start: 2024-09-17

Proposal

This proposal aims to replace the existing highway=road tag, and expand its scope to include pathways.

The changes proposed are:

  • Approve the use of highway=unknown for roads and pathways of unknown classification that require surveying.
  • Deprecate the highway=road tag.

Rationale

Extend Coverage to Pathways

Although the wiki currently mentions that the "tag is used for a road/way/path/street/alley/motorway/etc. with an unknown classification," the initial highway=road proposal and early wiki changes specifically excluded pathways and footways.

Some may have thought that highway=path without additional tags could serve as an alternative solution for unknown pathways. However, this approach is controversial and misleading because highway=road is:

  • Not meant to be rendered or should be displayed with a distinct style
  • Not intended for routing
  • Considered a temporary placeholder until properly surveyed
  • Solely for this purpose

Conversely, highway=path:

  • Is typically rendered the same, whether or not additional tags are present
  • Is included in routing
  • Is not a temporary measure
  • Serves multiple purposes, such as multi-use pathways and recreational/outdoor trails

Renderers Do Not Follow Guidelines

I have observed that many renderers display highway=road the same as highway=unclassified. This:

  • Contradicts wiki guidelines, which state that such ways should either not be rendered or should have a distinct style different from other road types
  • Misleads users with unverified roads
  • Reduces the incentive for mappers to identify these roads visually in order to reclassify them

Additionally, the frequent emergence of new renderers—especially commercial startups—makes it difficult to keep them all updated.

Confusing Name for End-Consumers

After some limited success in convincing a few renderers to follow the guidelines, I’ve received numerous complaints[1] that highway=road is misleading, causing end-consumers to interpret it as some type of generic road.

Confusing Name for Mappers

The tags highway=road and highway=unclassified have been long-standing sources of confusion for new mappers. Introducing a new tag would help reduce future misunderstandings.

Lack of Usage and Lower Data Quality

The confusing nature of highway=road may also contribute to its underuse as a valuable feature. There’s a perception that we should steer clear of using this tag, so mappers often rush to reclassify it..

This trend could lead to poorer data quality, as mappers might reclassify highway=road (often mapped from imagery or GPS traces) without proper local knowledge.

Lack of Router Support

highway=road is currently not consistently excluded from routing profiles. A clearer, more specific highway=unknown tag would encourage routers to update their codebases accordingly.

Impact

Since most renderers don’t need to display these ways by default, the impact should be minimal:

  • Editors need to support the new tag, and most already have deprecation mechanisms in place, so the coding effort will be low.
  • Renderers who already display highway=road with a distinct style, such as openstreetmap-carto, will need to handle the new highway=unknown, which should be a straightforward change.
  • Renderers who wish now to follow the guidelines are welcome to display highway=unknown with a unique distinct style or hide it by default.

In the long term, the new tag will improve clarity, prevent confusion, and encourage mappers to use it more often for ways that have need to be surveyed.

Name Selection

I chose highway=unknown because it's currently labeled this way in iD’s presets ("Unknown roads"), but I’m open to alternatives such as `unverified`, or `unsurveyed'.

highway=yes, as previously suggested, feels too broad and is more commonly used for sub-tags.

Discussion

Further Reading

  1. ↑ https://github.com/osmandapp/OsmAnd/issues/20357#issuecomment-2306771982
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