If two ways enter a roundabout at the same point, you can turn from road A into road B instantly, but going from B to A will require going around the entire roundabout. For a router to detect this, it would have to check (for every encountered node): 1) is this a part of a roundabout? 2) if yes, which of the turns I can make here would require going around the roundabout?
Note that 1) is a query for all ways using that node and 2) requires geometry data (instead of just network) While this is doable (or could be solved with turn restrictions), it makes roundabouts a much more of a special case. The current tagging of a one-way circular way is much easier for routing software to deal with and is conceptually "cleaner". Also, having the intersection directly on the roundabout is potentially also a valid way of drawing a regular intersection directly next to the roundabout. (I would not be surprised to see such a crazy construction somewhere) On 14 February 2018 at 23:04, Mateusz Konieczny <matkoni...@gmail.com> wrote: > On Wed, 14 Feb 2018 19:23:39 +0100 > Johan C <osm...@gmail.com> wrote: > > > The present tagging (used since 2005 or so, and all around the globe) > > is fine. > > I agree, I see no problem with this recommendation. > > _______________________________________________ > talk mailing list > talk@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk >
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