From OpenStreetMap Wiki
|Part of a classification scheme for hiking trails, but can be used for any type of paths.|
|Used on these elements|
|Tools for this tag|
This is part of a classification scheme for hiking trails.
This key describes attributes regarding trail visibility (not route visibility) and orientation.
and its shortcuts
|trail_visibility=excellent||Unambiguous path or markers everywhere||None, orientation unproblematic, no map required|
|trail_visibility=good||Next marker always visible, but sometimes has to be searched for.||Basic sense of direction, map recommended|
|trail_visibility=intermediate||Track mostly visible||Good sense of direction, map required|
|trail_visibility=bad||Path sometimes invisible, route partly pathless||Basic skills in orientation|
|trail_visibility=horrible||Often pathless||Advanced orientational skills|
|trail_visibility=no||Mostly pathless||Excellent orientational skills|