Abstract: A streamlining appendage for the rearward end of a vehicle having a generally flat upright rearward surface includes a rearwardly tapering peripheral body defining and surrounding a rearwardly open plenum chamber. An opening is provided through the peripheral body for delivery of air into the plenum chamber for ejection through the open rearward end thereof to dissipate the partial vacuum which forms behind a forwardly moving vehicle. Air may be ducted to the appendage opening from higher pressure zones toward the forward end of the vehicle or from a forced air blower on the vehicle.