[OSM-talk] Turn restrictions ambiguity

Ed Loach ed at loach.me.uk
Fri Apr 24 10:01:20 BST 2009


> What is your problem with having way sections between each
> intersection
> instead of one long way?

I don't have a problem with splitting ways, as that is what I've
always done to add the relevant tags to the relevant section. But I
can understand that there is a bit of an issue with doing such a
thing. By so doing it isn't possible, currently, as far as I know,
to work out at any given junction which road has priority (if any).
If we didn't have to split ways, then a way could run as far as it
has priority. Ways crossing it that had to give way (yield for our
American readers) could end at the way to indicate they have lower
priority at that junction. At a 4 way stop (American again), you
could have 4 ways ending at the same node.

But we do have to split ways for many reasons and I don't know how
routing engines work out when one way at a junction has priority
over another (or whether they even bother - I guess the best
available at present is to compare names and/or refs).

I did read something about road relations somewhere. I felt at the
time that these, used carefully, could be used to indicate
priorities at junction - so if a road crossed a road which had
priority the lower priority would need a relation for either side
for example. But this is complex and road relations I feel currently
are probably unnecessary in most cases (I wouldn't want to create
one for each residential road, though having said that I (Karlsruhe)
tagged my first house numbers the other day and did an
associatedStreet thing, so perhaps such relations will come with
time).

Ed






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