Hi Joost! I'm not sure that there is much to do in OSM if the route is really broken on the ground, except document it more clearly in the changeset comment.

In theory, routes are really broken when an unforeseen event happens: landslide, broken bridge; it takes some time for the local operators to plan a replacement route. But it often happens that it is planned in advance, and in that case there is already a replacement route proposed. Did you see anything?