[Tagging] Describe explicitly that values of highway tag do not imply anything about road quality (except highway=motorway and highway=motorway_link)

Mateusz Konieczny matkoniecz at gmail.com
Wed Aug 12 08:56:20 UTC 2015

What is below is supposed to document existing consensus rather than
introduce new rule. I am aware that there is significant majority
convinced that some road types universally guarantee or imply certain
values (like widespread usage of highway=track to mark all unpaved
roads and only unpaved roads, popular in some regions).

I am also aware that in some regions "dual carriageways are usually at
least highway=tertiary", "paved roads are at least
highway=unclassified", "highway=primary has at least 2 lanes in each
direction" or "paved roads passable for the entire year are
highway=trunk" are good approximations - but it does not make it
universally true or necessary requirement to use these tags.

proposed description to be added on
http://wiki.openstreetmap.org/wiki/Key:highway - maybe also on pages
about individual road types.

Only highway=motorway/motorway_link implies anything about quality.
Other road types, from highway=trunk through highway=tertiary to
highway=residential=residential/service or
highway=path/footway/cycleway/track do not imply anything about road
quality. In area with poor infrastructure road forming main road
network, of the highest importance in region should be tagged
highway=trunk - no matter whatever is is high-quality asphalt road or
unsurfaced tract unusable after major rains.

In absence of surface, tracktype and other tags describing quality of
road one may try to extrapolate this information from
value of highway tag. Note that this needs tuning for every region.
Typical highway=primary may be drastically different in various places
across the planet.

It is highly recommended to add and use tags describing road quality
like surface. In one region it may be obvious that all highway=tertiary
are paved and highway=track unpaved but no assumption like that will
work worldwide.

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