[OSM-talk] Turn restrictions ambiguity

David Lynch djlynch at gmail.com
Thu Apr 23 20:46:27 BST 2009


On Thu, Apr 23, 2009 at 14:45, David Lynch <djlynch at gmail.com> wrote:

> On Thu, Apr 23, 2009 at 14:25, SteveC <steve at asklater.com> wrote:
> >> If both from and to ways continue after the via point and neither is
> >> one-way, there's two possible ways to interpret it: the restriction
> >> could apply when coming from either of the ends of the from-way.
> >> This of course doesn't matter if there is similar restriction coming
> >> from both directions, but that's not nearly always the case. And
> >> even if there is symmetry in the real life restrictions, it's not
> >> appropriate in my opinion to map those with just one restriction.
> >
> > eh? don't you assign direction by saying 'from' and 'to' ?
> >
>
> To use a bit of ASCII art: (best viewed in monospace font)
>
>         (1)
>          |
>          B
>          |
> (2)--A--(3)--A--(4)
>          |
>          B
>          |
>         (5)
>
> A turn restriction from way A onto way B via node 3 of "no left turn"
> doesn't specify whether the left turn is from Node 2 towards Node 1, from
> Node 4 towards Node 5, or both.
>
> IMO, adding a "from_node" role for the last node before the intersection
> and a "to_node" for the first node after the intersection would be the way
> to get rid of the ambiguity without requiring a lot of splitting.
>
> --
> David J. Lynch
> djlynch at gmail.com
>
>


-- 
David J. Lynch
djlynch at gmail.com
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