An automatic gap closing system automatically moves a gap closing cover between an un-deployed and a deployed configuration to selectively cover a gap between two coupled vehicles (e.g., tractor-trailer combination) in response to an actual or expected speed of at least one of the vehicles, thereby increasing fuel efficiency at relatively high or fast speeds without hindering maneuverability of the coupled vehicles at relatively low or slow speeds. Indications of speed and/or location may come from speed sensors, on-board computers (i.e., black box), GPS receivers, or wireless receivers.