[OSM-dev] Renderer issue: highway=service and service=driveway?

[Greg Troxel]

Pierre Béland <pierzenh at yahoo.fr> writes:

> In this particular case, if there was a hierarchy of roads, it would
> be less a problem if the rule that I proposed was followed. See
> https://wiki.openstreetmap.org/wiki/Highway_Tag_Africa

I think the notion of having primary/secondary be about importance makes
sense.  It may be better to try to tag with a characteristic distance to
avoid quantization and arguing.

First, set motorway aside.  We know what the motorway rules are, and all
motorways are important (to first order).  Then, in a non-motorway
world, you can ask "what is the shortest typical distance for which many
routes will use this road".  Essentially, I'd argue that (if one decides
to not use motorways), primary highways are likely to be the roads
chosen for distances of 200km or more.   Secondary for perhaps 50 km,
and many of the roads that feel like they should be tertiary are used to
get to the next town, or next next town, but not 10 towns (except as
local feeders, not a through route).  So that's more like 20 km.

However, this breaks down in the city (calling only those roads
tertiary); consensus is to have far more tertiaries.  My sense is that a
road is properly tertiary if it takes you from one place of 5000 people
to another place of 5000 people.

However, this population-based argument is a) not really important in
the areas we are talking about and b) not related to showing roads at
low zoom.

So maybe roads should be tagged with a typical_distance tag, inferred
From class, and that can be used to render.

I realize this needs a lot more thought.


> An automatic rendering rule will not take care of these particular
> contexts. Distance could be one rule, or absence of roads.

I don't follow the "will not take care of".  We are basically talking
about automating the judgement of the cartographer.
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