ACC is the new technology being available with few BMW models which means an Active Cruise Control or sometimes called the Adaptive Cruise Control. It’s a technology of automatically controlling speed taking in consideration the proximity of nearby vehicles.

ACC is a system based on radar sensors which calculates the distance of nearby vehicles up to a range of 120 meters. Depending upon the relative speed and distance of a nearby vehicle, the system may slow down the engine or brake softly to adjust own speed. To monitor the road ahead, a radar sensor with three beams is used.

When you have a vehicle within 120 meter of your car, it is immediately picked up by the ACC radar eye. It takes subsequent readings to estimate the target vehicles relative speed, distance and future positions depending upon the present factors. With all these information available to the processor of the ACC, it will take actions like slowing down the engine or applying a mild brake. Thus it will keep your car at a safe distant constantly till the front vehicle is cleared. Once the ACC finds that the vehicle ahead poses no threat or has been cleared, it will regain its original speed by accelerating at its own.

The apart from the radar signals from the sensors, the ACC also takes consideration of other data inputs form on board systems like the ASC+T, ABS or DSC (Dynamic Stability Control) . Thus the system’s computer has data on the revs (wheel revolution), centrifugal force (while turning), etc. So, it can calculate difficult conditions like target vehicle estimation even while turning on a curve.

However, if the driver himself applies brakes or accelerates to avoid any situation, while ACC was taking action. However, when you are running freely and accelerate normally, the ACC is not deactivated. The system operates normally if you run at a speed over 30 kmph. The ACC is also very useful while going down a slope as it can keep a speed constant at its own.

Though ACC is designed to operate in inclement weather, like rain, fog or storm, you may not depend upon the automatic system fully to remain safe. Moreover, the ACC is not able to pick up static objects, like a jam or parked car. So, at all times the sole responsibility is on the driver.