# [OSM-talk] zones for motorway/in town/outof town?

Cartinus cartinus at xs4all.nl
Thu May 21 00:01:22 BST 2009

```On Thursday 21 May 2009 00:30:13 Radomir Cernoch wrote:
> However it's important to notice that two polygons can never overlap
> (unless there is a futuristic city with zone-30 area flying in the air
> above a 130 km/h highway).
>
> > Now we have an urban area, with a circular road with maxspeed=50, and
> > streets and cul-de-sacs left and right of that road with maxspeed=30
> > zones. And that is just a simple example. The polygons are going to be
> > complex in some cases.
> >
> > > I can imagine a situation, where a normal 50 km/h road goes through the
> > > middle of a zone-30. Then there are two options:
> > > 1) You split the zone-30 polygon into 2 polygons.
> > > 2) You tag the 50 km/h road with "maxspeed=50".
> >
> > Right, exactly the scenario I mentioned at the top of this msg.
>
> I agree that the polygons are going to be complex. As complex as current
> 'landuse=residental' polygons or administrative border polygons or...
> I know it's pain to work with them, but the solution is to learn JOSM to
> split map into layers, not to adjust the data-model.

You are still missing the point!

The road network is a 3D network. Your 2D polygons can't model the fact that
traffic zones are not 2D, but chunks of that 3D network.

It is completely possible for a village ringroad on a bridge (highway=primary
or secondary) to have a maxspeed of 80 km/h due to being outside the build-up
zone, not because there is a sign on it that says 80 km/h. It is also
possible at the same time for the road under that bridge to have a maxspeed
of 50 km/h due to being inside the build-up zone. The point of the bridge has
one lat/lon, but the roads are vertically separated. This will never fit in
any 2D model.

--
m.v.g.,
Cartinus

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