This invention provides an aerodynamic structure attached to the rear cargo body, having doors that swing open, or a single, full-width door, which rolls upwardly. The embodiments provide an aerodynamic structure attached to the rear in a manner that would obscure access to the door(s) in a deployed position, in which the structure reduces drag, yet enables access to the door(s) in a folded position. The folded position allows access to the rear for loading and unloading, and in the case of swinging, hinged doors, allows the doors to be folded through a 270-degree arc, with a minimal sideways projection. The various embodiments also enable relatively rapid and easy transition between the folded position and the deployed position using actuators and/or linkages that tie the folding and deployment of panels of the structure together. This allows selective folding and deployment of the structure without undue effort or strength.