Abstract: A drag reducing device utilizing sealed aft cavities designed to limit interference with existing truck and trailer designs is described. The invention comprises one or more sealed aft cavities affixed to the rear of a traditional commercial straight truck or trailer, or any other blunt (or mostly blunt) aft faced vehicle. A capability is provided by which the device is stowed to allow normal operation of the straight truck, trailer or vehicle. Drag is reduced by the streamlining of the rear of the vehicle, postponing and narrowing the flow separation downstream of the trailing edge as well as increasing the pressure on the back of the vehicle with the open to the rear, sealed aft cavity. The concept described focuses on the utilization of sealed aft cavities) to limit the effects of blunt body drag and the means for attachment and stowage for loading and unloading cargo.