FYI it is literally required by law that, to maintain a trademark, the company with the trademark must actively enforce it on an ongoing basis. Even if this side-project was benign, Waffle House must send cease-and-desist letters to maintain their trademark generally under US law.

That said, if the author had posted a tracker of Waffle House closures descriptively, without using their marks or branding, that would be fine, in the same way that google maps is fine to list which restaurants are open/closed. The key being that "google maps" is referencing the brand of google, their own trademark, and could not be confused for something authored by any of the restaurants featured on the map. Trademark is designed to avoid anyone being confused with who was the author, it's a "feels like" definition with a rubric, not a specific technical definition.

My suggestion would be to rename a site "disaster indices" and include the waffle index as one index. Even batter (yes) if you add other similar indices, like theme park closures or other.