A vehicle or trailer assembly is disclosed comprising at least one fan positioned on an exterior of the vehicle or trailer, wherein the at least one fan redirects or accelerates air moving over, around, or through the exterior of the vehicle or trailer. Also disclosed is a fan assembly comprising a manifold configured to be positioned on an outside surface of a vehicle, along an axis transverse to a direction of travel of the vehicle. The fan assembly also includes a plurality of motorized fans rotatably mounted along the axis of the manifold, such that the motorized fans are configured to accelerate air passing along the outside surface or within an exterior of the vehicle, in the direction of travel of the vehicle.