[Tagging] How to tag: Legally separated ways

Simone Saviolo simone.saviolo at gmail.com
Mon Oct 15 12:52:39 GMT 2012


2012/10/15 Tobias Knerr <osm at tobias-knerr.de>

> On 15.10.2012 10:56, Martin Vonwald wrote:
> > http://wiki.openstreetmap.org/wiki/File:Lanes_Example_2.png
> >
> > Only part 5 is relevant. Assume there is no physical separation just a
> > double line between the upper and lower two lanes. How would you tag
> > this:
> > a) One way with lanes=4
> > b) Two separate ways with lanes=2 each
> > c) Tell me!
>
> I would choose (a) and reserve separate ways for _actual_ physical
> separation.
>
> One practical reason for doing so is that there would simply be no
> possibility to distinguish legally separate ways from physically
> separate ways if we used the same mapping (splitting the way) for both.
>
> Splitting the way at that point could be considered "tagging for the
> router", in my opinion, and ignores the needs of applications that do
> use OSM for something else than navigation.
>

+1, BUT...

I agree with you that a long section of road with double solid lines would
have to be tagged as a single way. If not, an ambulance would be routed to
go to the end of the double solid lines and then go back, even though in
reality it just needs to cross the road (even though such an example sounds
silly, please consider that a route involving this situation would come out
all wrong because of weird paths).

However, if we found ourselves with the situation depicted in the image
(I'm talking about the full image here, not just section 5), then I'd say
that we start the way splitting as soon as it is topologically correct. If
the way splitting happens fifty metres ahead of where an actual physical
barrier begins, it should be no problem for any consumer, and we would
still get an acceptable model of reality based on our base concept of
drawing road by their centerline.

Regards,

Simone
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