Hi Gerd,

Here's a patch to hide abandoned highways in the default style. Abandoned highways have some evidence of their former existence but are no longer used. I made a separate rule for this change to highlight that abandoned highways could be useful in topographical maps.

https://wiki.openstreetmap.org/wiki/Key:abandoned:

The rule also matches highway=abandoned. While not an official OSM rule, it is being used in the US an Europe:

https://taginfo.openstreetmap.org/tags/highway=abandoned#map

I also found a German wiki page for it but not a page in English:

https://wiki.openstreetmap.org/wiki/DE:Tag:highway%3Dabandoned

Let me know what you think.

Thanks, Ben