[OSM-talk] definition of the main highway-tag

[Greg Troxel]

  If the highway-tag was the only tag on a road, I would agree with this
  approach, but as we are meanwhile tagging physical attributes as
  supplementory tags (e.g. lanes, surface, traffic-lights), as we do for
  administrative classification (ref), I am in favour of changing the
  definition for highway (no longer mainly physical but mainly according
  to importance / logical position in the grid). The other properties
  and attributes will still persist (ref, lanes, dual-carriageways,
  surface, tracktype, ...) and describe the situation. Also there won't
  be many changes / tagging-modifications necessary, because bigger
  roads are generally more important roads.

  What do you think about this?

There are three separate concepts:

  physical structure

  administrative designation

  importance according to actual use


In the US we are more or less following:

  interstate => interstate class, so motorway

  trunk is physical, but tends to match importance

  among primary/secondary/tertiary, it's not really about physical any more

    US highways tend to be important, and get primary without scrutiny

    state highways tend to be somewhat important and get secondary by default

    after that, state highways get upgraded to primary if usage
    warrants, and other semi-important roads get marked tertiary

which blurs all three, but in a way that doesn't cause a lot of trouble.


I would be in favor of

  trying to move slightly to importance-based tagging

  using ref to mark administrative designation

  using motorway and trunk as the current rules state.  Here, the roads
  are so big physically that the importance more or less matches, and
  all such roads are important more or less by definition.

  using primary, secondary, tertiary without real regard to legal status
  or physical size, but according to usage:

     primary is typically used for long-distance travel, 100km or more,
     or for a road that until recently was still used for that and is
     still culturally important

     secondary is typically used for travel at least 25km (between
     multiple towns)

     tertiary is used to get to secondary roads (to get to the 'real
     road' in the next town)


This is more or less that I do around my town, and it mostly matches the
rules.
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