Abstract: A wind deflector having a movable fairing is mounted on the tractor cab of a tractor-trailer combination to allow for the reduction of wind resistance during movement of the vehicle. The deflector which may be mounted directly to the cab or a stationery wind deflector has a fairing which pivots between operative positions which direct the air to reduce wind resistance and the rest position where the fairing has no substantial effect on wind resistance. Alternative methods are provided to move the fairing from its rest position to its operative position, including use of an air bag inflated by wind generated during movement of the vehicle or an air cylinder. The deflector is designed to be deployed during movement of the vehicle and may include the ability to change its operative position during movement of the vehicle.