[OSM-talk] Should Bridges be independent of their ways?

[Anthony]

On Mon, Sep 21, 2009 at 6:31 PM, Martin Koppenhoefer <dieterdreist at gmail.com
> wrote:

> 2009/9/21 Anthony <osm at inbox.org>:
> > Right now, like it or not, ways are being used essentially in the manner
> I'm
> > suggesting we keep using them.  We don't combine everything that crosses
> a
> > bridge into a single way, and we don't break apart every lane into a
> > separate way.  Those saying that we should do one of these two things are
> > the ones trying to reinvent the wheel, and the burden of proof is on them
> to
> > prove that their new wheel is superior.
>
> It is needed for several situations that currently cannot be mapped
> completely (different surfaces, different maxspeeds, different
> turn-restrictions, etc.)


It is possible to represent different surfaces and different maxspeeds
without using more than one way.  "maxspeed:lane=130;110";
"surface:lane=asphalt;concrete".  That's not necessarily the best solution,
but it beats having two ways and some not-yet-proposed method of showing
that you can switch between them.

Different turn-restrictions is already possible.  If you have a three lane
way with two lanes going straight and one turning right, you join three ways
at one node: one with three lanes, one with two lanes, one with one lane.
If you have a three lane road with two lanes going straight and one lane
going straight or turning right, ditto, except the way going straight has
three lanes instead of two.  Which lane is which is determined by the
geometry of the ways as they come out of the node.

but I also see the pros:
> - is easier to understand and more intuitive to edit: better
> maintenance: you see what is there
>

That's an editor consideration.  You can make it *look* like you're editing
three separate ways when you're really editing one way with three lanes.


> - is more precise in terms of positional accuracy
>

I'm assuming the lanes are parallel.  If not, then yes, you need to use
multiple ways.


> - can better represent stuff like ramps for motorways (parallel ways
> that currently are mapped like intersections), cyclelanes, ...
>

Why are they being mapped like intersections?  They shouldn't be.  You mean
a gradual merge is being mapped at a right angle?  That's wrong, and there's
no good reason for it (other than didn't have the time to get it right,
anyway).
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