Adaptive Cruise Control is an optional feature on the 2009 A4, A5, S5, A8 and Q7. This feature uses radar to sense forward moving vehicles in front, to maintain a predetermined distance and speed. Adaptive Cruise Control will apply both brake and throttle as needed to keep your desired speed while maintaing a safe distance with the vehicle ahead of you. If there is no traffic in front of you the Adaptive Cruise Control will simply maintain your speed. Adaptive Cruise Control will not react to stationary objects such as animals in the road. Audi braking guard will react and a chime will be heard and the brakes will be applied (however not at full force) to alert the driver. Also, if the weather conditions are poor, such as heavy fog or snow, the Adaptive Cruise Control will be disabled. It goes with out saying that the driver of the vehicle should always have full control and only use this system as a suplementry comfort device.
2009 Audi A4 with Adaptive Cruise Control
2009 Audi A4 without adaptive cruise control
On the A8 and Q7 the Radar system is not visable unless the front bumper is removed. However as pictured above on the 2009 A4 the Radar system is exposed and visable in the lower right front grill. This goes for the A5 and S5 as well.