I think vehicle is explicitly defined in Alabama Code 32-1-1.1 Part 82
Does that answer your question(s)?(81) VEHICLE. Every device in, upon or by which any person or property is or may be transported or drawn upon a highway, excepting devices moved by human power or used exclusively upon stationary rails or tracks or electric personal assistive mobility devices; provided, that for the purposes of this title, a bicycle or a ridden animal shall be deemed a vehicle, except those provisions of this title, which by their very nature can have no application.
So, quite simply, you need a license to carry concealed and you are covered. Other than that, without the gun unloaded, covered, and secured; there is no open carry in a vehicle in Alabama.