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

Peter Budny peterb at gatech.edu
Sat Oct 16 17:43:18 BST 2010

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

>> 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.
>  The way I've done this, and seen it done, is to put single
> carriageways in once with no role.     I'm not sure I understand the
> difficulty of parsing it automatically - please elaborate.

Here's one instance where this doesn't work as well as I'd like:
Michigan 3 (which I picked randomly off a list) alternates between
single- and dual-carriageway.

Because the analyzer doesn't understand that the unlabeled roles actually
belong with both north /and/ south, it shows a bunch of gaps that aren't
actually there.

If this is the tagging format we're going to use, we need to fix the
tools to handle this correctly.

Adding a single-carriageway to the relation twice, once for each role,
would solve this problem instantly, as would using two separate
relations.  Neither requires much (if any) code changes to support it.
But in any case, I'm much more in favor of consistency, even if the
format we choose isn't the one I would prefer.
Peter Budny  \
Georgia Tech  \
CS PhD student \

More information about the Talk-us mailing list