The aim of an active grille shutter (AGS) is to respond to the driving environment in order to reduce drag and improve fuel economy. During motorway driving, for example, the louvres would close thereby pushing the air around the vehicle to improve aerodynamics. If the car is towing a load or slow moving in traffic, the louvres would remain open to help maintain the best engine temperature.  Given that an increasing number of cars now have an AGS, here is our round-up of the market.