Reduced-drag trailer

A transportable hauling container, such as a trailer of a tractor-trailer combination, has a rear portion that is configured in or convertible to a wedge shape. Movable portions are located at the rear sides of the trailer that can pivot inward toward a longitudinal centerline. Movable flaps also are located at the rear top of the trailer, which can pivot downward in alignment with the movable portions. The movable portions and flaps can be secured relative to each other in various combinations, thereby providing a more aerodynamic configuration of the trailer rear end. The container or trailer can be configured in such an arrangement, or be convertible from a standard configuration which also includes doors at the rear of the trailer, to a more aerodynamic configuration. A method is also disclosed, which includes operations for converting such a convertible trailer between the standard and aerodynamic configurations.