Methods of and devices for providing naturally driven routing of air bleed derived from the external air pressure field typically developed about a moving vehicle were conceived. By design, internal duct ways to be used for providing an open flow path from relatively higher air pressure sources (such as that in the undercarriage region of a driven car) into lower base pressure regions (typically developed aft of blunt trailing body regions) as are generally found on road and ‘airdrop” cargo delivery air vehicles having open rear doors. Low energy air bleed flow injected into the vehicle's separated afterbody region acts to replenish entrained base flow and its base drag reduction is thereby, achieved.