[OSM-talk] Changed highway=*_link meaning?!

[Dermot McNally]

On 3 July 2010 11:37, John Smith <deltafoxtrot256 at gmail.com> wrote:

> Personally I don't see a point for anything but motorway_link, but
> what is the difference between what you said and what others are
> suggesting for other *_link roads?

Firstly, I haven't suggested anything for *_link roads, I've simply
disagreed with your assertion that our use of the highway tagging
represents tagging for the renderer. On balance I tend to prefer links
that know what type of road they belong to. As noted, this is
indispensable for motorways, because:

* Many (most?) countries support the concept of motorway regulations
and we need to mark the point from which they apply
* We want our navigation apps to be able to give instructions about
entering the motorway

And it so happens that having that tag also does the right thing for
renderers too.

I think the concept works well for other road classes too - a trunk link is:

* one that leads inescapably to a trunk road -or-
* One that diverges from a trunk road and can only be reached by the trunk road

And so on for other road classes. I'm concerned here more with access
ramps - roundabout avoidance lanes and suchlike probably could, in
many cases, be sufficiently catered for by a generic highway=link tag.
This could be used by mappers who feel there's no obvious ownership of
the link by one road or the other and renderers could be permitted to
colour it according to whichever of the above-argued logics proves
most compelling.

But sneaky wiki changes to subvert established tagging practices one
newbie at a time just isn't big or clever - so don't do that.

Dermot

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