History of proposals to fix highway=path ambiguity – and a wayforward?

General talk
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I don’t get the impression that highway=* values primarily refer to purpose or usage. One can infer a purpose or usage, but it isn’t inherent to the value.

Identity

Sometimes, the highway=* key is used as a thematic key, essentially a metonym for “transportation”, analogous to natural=*, emergency=*, or healthcare=*. The following values answer the question “What is it?” using plain-English nouns:

  • What is highway=motorway? It is a motorway.
  • What is highway=motorway_junction? It is a motorway junction.
  • What is highway=cycleway? It is a cycleway.
  • What is highway=footway? It is a footway.
  • What is highway=bridleway? It is a bridleway.
  • What is highway=raceway? It is a raceway.
  • What is highway=busway? It is a busway.
  • What is highway=bus_stop? It is a bus stop.
  • What is highway=crossing? It is a crossing.
  • What is highway=elevator? It is an elevator.
  • What is highway=rest_area? It is a rest area.
  • What is highway=living_street? It is a living street.
  • What is highway=via_ferrata? It is a via ferrata.
  • What is highway=path? It is a path.
  • etc.

Each of these answers is an identity; from that identity we can infer a purpose or usage. Up to this point, each answer can be found in a British English dictionary – even “path”. The dictionary definitions might not line up 100% with OSM’s, but at least one can explain any discrepancy as mere nuance. No matter how much circumlocution we require, a bevy of secondary tags are still incapable of stating the identity of a feature.

I don’t know if anyone ever uses “scramble” as a noun to refer to places where you have to scramble, but English has a tendency to nominalize verbs, so highway=scramble would still fit the pattern.

Classification

Other times, we presume that the key highway already means it’s a literal highway in the sense of a road or street. Instead of repeating that information, the following values answer the question “What kind of highway is it?” using adjectives that naturally form compounds with “road” or “street” in English:

  • highway=trunk is a trunk road highway
  • highway=trunk_link is a trunk road’s link road highway
  • highway=primary is a primary street highway
  • highway=secondary is a primary street highway
  • highway=tertiary is a secondary street highway
  • highway=unclassified is an unclassified street highway
  • highway=residential is a residential street highway
  • highway=service is a service road highway
  • highway=track is a track road highway

The use of highway=* can be slightly confusing, because “highway” is the word for a motorway in some dialects, but it hasn’t turned out to be a major issue. Instead, the main point of disagreement is often about whether these “kinds” correspond to functional classifications, legal designations, or something else. There are alternative keys for these aspects, such as designation=* and network=*, but no one seems to care as much about them as these highway=* classification values.

Something something

Recent discussions have mentioned values or definitions that don’t fit this pattern:

  • I always thought highway=road means it’s a road, even if we expect mappers to be more specific than that. But if the wiki is to be believed, it doesn’t literally mean a road; it could be a path instead.
  • highway=motorcycleway would coin a brand-new word that doesn’t exist in English, “motorcycleway”, to refer to a kind of path, by analogy with cycleway.
  • highway=pathless is an adjective, yet it doesn’t refer to a kind of highway. There’s no such thing as “a pathless”, and it isn’t a pathless road or street. A “pathless path”? That’s an oxymoron! No, it’s a pathless… something. In other words, it’s a not-a-path, a not:highway=path – or even a no:highway=path based on verifiability.

This would be far from the first time OSM keywords depart from standard English, but I think anyone who wants to promote further departures should tread with caution. What appears to be a mere linguistic quirk today might turn out to be a real headache for mappers and software developers in the future.

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