Abstract: A vehicle includes a vehicle body having a first body end configured to face oncoming ambient airflow when the vehicle is in motion relative to a road surface, and also having a second body end opposite of the first body end. The vehicle also includes an underbody portion configured to span a distance between the first and second body ends and define a space between the vehicle body and the road surface. The vehicle additionally includes an active diffuser assembly disposed at the second end and configured to control the airflow past the underbody portion through the space between the vehicle body and the road surface and out to the ambient. The active diffuser assembly includes a panel configured to selectively extend into and retract from the ambient airflow aft of the second end. The active diffuser assembly also includes a first device configured to extend the panel.