Nashville area anon here.
There is literally nothing of note along that stretch of 231 in Wilson County. It's a 3-lane stretch with an entrance to a state park and a roadside flea market is basically it. It's rural territory and extremely rocky. Cedars of Lebanon state park is there, but cedar trees are pretty much the only thing that grows among the rocks with shallow topsoil.
My guess - its merely a broken down truck.