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 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 .