use-case: a section of a major road has become recently obsolete most likely due to a landslide and a new section has been built to replace it:
The old section is still visible on all imagery, while the new one is not.
If you remove the old section, someone else may add it again using imagery
What valid/documented tag should be used instead to mark the old section taking into account rendering/routing support?
abandoned:highway=secondary + smoothness=impassable ?
I’d keep the old way adding tags like https://wiki.openstreetmap.org/wiki/Key:disused etc. and add a note about the landslide.
disused: “features that are in a reasonable state of repair but which are currently unused”
In this context,
disused would not fit since the landslide is most likely permanent and the road is not in a “reasonable state of repair”. I feel abandoned life cycle tag would be more appropriate here.
The old road is still visible? I would also consider the razed prefix + note=*
that is for road where remains are still existing
I would use
note=destroyed by landslide in XYZ, still visible in aerial imagery such as Bing, please remove once no longer visible in standard imagery
razed prefix or
was … that is anyway for humans)