[OSM-talk] turn restriction relations: via

Nic Roets nroets at gmail.com
Sun Mar 29 19:51:00 BST 2009


Hi Tobias & Marcus

On Sun, Mar 29, 2009 at 8:06 PM, Tobias Knerr <osm at tobias-knerr.de> wrote:
>
>
> I'm not exactly sure what the semantics of an "only_*" with several via
> members would be, though. Should it require that you use at least one
> via member or every via member?


I implemented "only_*" as something that's disallowed i.e. a restriction.
The "obligation" interpretation only came later.

Perhaps we can specify that complex vias may not have "only_*"'s and require
people to implement their ideas with no_'s ?


>
>
> Despite via splitting not being necessary for proper relation handling,
> I still think that "a relation using via nodes will always contain all
> nodes as via nodes one would travel along" is essential. Otherwise,
> there would inevitably be some problems:
> If, in your example, the via information was represented by via nodes on
> S instead of via way(s), that restriction would also forbid turning left
> from A onto S, following S without turning into B, then using other
> roads to return to the double carriageway and following B back to the
> restriction's "to" part. This is obviously not intended.
>
> Tobias Knerr
>

I think we should require that complex vias must always include all the ways
that are traveled.

>One question,
>does anyone have an implementation of turn-restrictions that
>have "via" as more then an optional specifier for a list of nodes
>to limit the effect of the restriction to only intersections where
>"from" and "to" meet at one of the "via"-nodes?
>(either "via" being a start- , end- or middle- node of "to" and "from")?

Not me.

Regards,
Nic
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