[Tagging] Clarification on the role link in route relations

[Yves]

It's mentioned in the route=piste (winter sports) doc.
I'll have a look on its usage.
wiki.openstreetmap.org/wiki/Tag:route%3Dpiste

I wouln't be surprised if this role appears in hiking routes too.
Regards,
Yves 

Le 8 janvier 2022 22:02:15 GMT+01:00, Minh Nguyen <minh at nguyen.cincinnati.oh.us> a écrit :
>The wiki page for route relations lists an optional role "link" for highway=*_link ways leading to and from the route. [1] Under what circumstances should this role be used? Should we deprecate it?
>
>The "link" role was originally documented in 2009. [2] At the same time, the highway=motorway_link documentation was edited to state that all link roads should be members of route relations as "link" members. [3] I can't find any discussion about the changes. The requirement to add link roads to route relations was removed the following year [4], but the role remained documented on the route relation page.
>
>Since then, there have been occasional references to this role [5][6], but it seems to have gone mostly unnoticed. It goes unmentioned in other parts of the wiki that describe route relations. As of writing, the "link" role is used on 26,157 route relation member ways (0.06% of all route relation member ways). [7] This is a high enough number that it can't be dismissed as a mere tagging mistake, yet it falls far short of the 766,473 highway=motorway_link ways, let alone other highway=*_link ways. [8]
>
>Is there a particular route type, region, route network, or scenario in which the "link" role is more appropriate? Or is this is just a misunderstanding based on the residual description on the route relation page? Perhaps some mappers have misunderstood that this role is required in order for a router to announce "Take on the ramp toward ABC 123", even though that's what the destination:ref key and destination_sign relation type are for.
>
>At the current usage level, data consumers probably would be unable to depend on the "link" role for any practical purpose. There just isn't nearly enough coverage of it. Routers such as Valhalla are already capable of automatically determining connecting routes anyways.
>
>Meanwhile, the inclusion of "link" members causes problems for any editor, QA tool, or data consumer that lacks support for this role when determining the linear progression of a route. For example, iD has a known issue incorrectly ordering members of a nonlinear route relation when splitting one of its ways. [9] Renderers such as OsmAnd and openstreetmap-americana understand route relations but don't understand the "link" role, so they end up showing redundant route shields that can easily confuse the user. [10]
>
>I think we should qualify the documentation for the "link" role so that mappers don't misunderstand its purpose and feel obligated to use them for optimizing router guidance instructions. Perhaps we should even deprecate the role, since it seems redundant to the "connection" role for recreational route relations. [11]
>
>(There's also a note on the German E54 route relation [12] justifying a slightly different usage, apparently for keeping the route connected, but the "link" roles were removed last year. [13])
>
>[1] https://wiki.openstreetmap.org/wiki/Special:PermanentLink/2207268#Members
>[2] https://wiki.openstreetmap.org/wiki/Special:Diff/270172
>[3] https://wiki.openstreetmap.org/wiki/Special:Diff/270169
>[4] https://wiki.openstreetmap.org/wiki/Talk:Tag:highway%3Dmotorway_link#.22Link_roads_should_be_members_of_all_related_route_relations.21.22
>[5] https://lists.openstreetmap.org/pipermail/tagging/2010-June/002512.html
>[6] https://lists.openstreetmap.org/pipermail/tagging/2010-June/002512.html
>[7] https://taginfo.openstreetmap.org/relations/route#roles
>[8] https://taginfo.openstreetmap.org/tags/highway=motorway_link
>[9] https://github.com/openstreetmap/iD/issues/8578
>[10] https://github.com/ZeLonewolf/openstreetmap-americana/issues/79
>[11] https://wiki.openstreetmap.org/wiki/Special:PermanentLink/2185644#Tagging
>[12] https://www.openstreetmap.org/relation/6244657
>[13] https://www.openstreetmap.org/changeset/87072348
>
>-- 
>minh at nguyen.cincinnati.oh.us
>
>
>
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