On Wed, May 20, 2009 at 09:05:45PM +0100, Radomir Cernoch wrote: > By "traffic zone" you mean a tag "zone=XXX" on each individual road in > the city? I'm afraid that such system is very prone to forgotten tags. > > If you use a polygon around a city, you can also derive the source of > the speed limit. Rules 1) - 3) mean that being "on highway"/"in > city"/"outside city" is the main limitation. Applying rule 4) means > there is a physical sign that causes the regulation.
The problem with the polygon is that in Germany it perfectly possible
to have streets within the city above the normal city limit
and also below (very common). So once you put the polygon around the city
you implicitly bring all streets to city level e.g. 50 although
there might be loads of streets with 30 kph or 70 kph
> Yes, in the "polygon" system you would encircle the whole area and every
> road inside of it has automatically 30 km/h limit.
Which is IMHO a very dangerous behaviour - i wouldnt want any fact be set
without checking - so the limit explicitly set on every street is my favourable
way.
> Sorry, I maybe didn't make myself clear. "Polygon" rules do not apply
> for motorways. Is there any country, where a highway inside a city has
> different speed limit from the highway outside of the city? Even if yes,
> this can be specified in the set of country-specific rules...
>
> 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".
The problem with the polygon is that you set a default without checking every
individual street. Id rather check all the individiual streets and tag them
one by one when i am shure i have the correct fact.
Its not calculating Pi where 3.1 might be acceptable for the start and later
we calculate more digits.
Flo
--
Florian Lohoff f...@rfc822.org +49-171-2280134
Those who would give up a little freedom to get a little
security shall soon have neither - Benjamin Franklin
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