[Talk-us] State Route relations (was: Highway Tagging ConsensustoImprove OSM (and address some of 41 latitude's concerns))

Peter Budny peterb at gatech.edu
Sat Oct 16 16:17:53 BST 2010

"Mike N." <niceman at att.net> writes:

>> One thing I /haven't/ seen addressed yet is whether single relations are
>> preferred, or one relation for each way with a super-relation.
>> Currently both are in use, but I think it would be a lot easier for
>> future code if we pick one and move towards it from now on.
>  I don't see any advantage for a relation per way; a single relation
> with roles for each direction has all the information needed by a
> relation-user, and it's one less thing to keep track of when editing
> or updating. 

The potential problem I see is when you have a road that alternates
frequently between single- and dual-carriageways (which many state
routes do, and even a lot of US highways).  How do you represent this in
a single relation?

1) Put single-carriageways in once, with no role.  Or, with
"role=north/south".  Either way, this is difficult to recognize and
parse automatically.  And aren't members of a relation ordered inside
the relation?  (I know JOSM shows icons for whether a way is connected
to the ways before and after it in a relation.)  The ordering loses any
meaning under this method.

2) Put single-carriageways in twice, once with "role=north" and once
with "role=south".  This is allowed, and fixes the problem, but don't
most editors complain when the same object appears more than once in a

In my view, having separate relations for each direction, and a
super-relation to hold them solves this problem.  But maybe there's some
argument against them that I've missed.

Peter Budny  \
Georgia Tech  \
CS PhD student \

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