Poorly-documented tags

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

The department of a university, organization, business, etc. that is responsible for, associated with, or relevant to the feature being mapped.

The wiki does have some mention of this tag, but it is woefully incomplete and ill-defined.

ex.

• https://wiki.openstreetmap.org/wiki/Tag:operator=Appalachian State University
• https://wiki.openstreetmap.org/wiki/Tag:operator:type=public
• https://wiki.openstreetmap.org/wiki/Tag:department=Department of Philosophy & Religion

Undocumented tags

https://wiki.openstreetmap.org/wiki/Key:scenic-related tags

https://wiki.openstreetmap.org/wiki/Key:scenic:name

The name of a way designated as a scenic way by some sort of authority, assuming this name is different from the usual/common/most signed name of it.

There’s one way using https://wiki.openstreetmap.org/wiki/Key:name:scenic, which is also not a documented tag, but https://wiki.openstreetmap.org/wiki/Key:scenic:name I feel makes more sense. scenic_name is also an option, but I think it’s better to use https://wiki.openstreetmap.org/wiki/Key:scenic:name as it makes the name be more obviously contingent on the scenic designation of the way.

ex.

• https://wiki.openstreetmap.org/wiki/Tag:scenic:name=New River Valley Byway
• https://wiki.openstreetmap.org/wiki/Tag:scenic:name=US 421 Scenic Byway

https://wiki.openstreetmap.org/wiki/Key:scenic:authority

The authority that designated this way as being notably scenic.

ex.

• https://wiki.openstreetmap.org/wiki/Tag:scenic:authority=NC Scenic Byways Program

Uncommon sources

https://wiki.openstreetmap.org/wiki/Tag:source=NC Scenic Byways 4th Edition

The North Carolina Scenic Byways Program’s handbook. You can get it for free, it’s a public domain work of the state government that allows for you to add the byway into OpenStreetMap purely based on the (very clear) directions given for each byway. Can’t recommend it enough. Buy the book itself too if you can, the program needs the money.