Examples of drag reduction apparatuses and assemblies for land vehicles, and particularly for attachment to a door of a land vehicle operated by a cam lock bar, are described. A drag reduction apparatus may include a plurality of panels foldedly coupled together and automatically deployable into an unfolded configuration. The panels may be coupled to a base panel that is coupled to the door of the land vehicle by a double-hinge mechanism operated by the cam lock bar. The double-hinge mechanism may draw the base panel toward the centerline of the rear of the land vehicle to allow the door to fully open with the drag reduction apparatus attached. The apparatus may be attached to two adjacent doors of a land vehicle and a plurality of panels on one door configured to overlap with a plurality of panels on the adjacent door.