How does the distance control work?How does the distance control work?  - Speed and distance control system - Adaptive cruise control (ACC) - Controls - Audi A4 Owner's Manual - Audi A4

Vehicles in front are detected by a radar sensor.

Area covered by radar sensor

Area covered by radar sensor

The adaptive cruise control uses a radar sensor ⇒ fig. 137 which is integrated in the front of the vehicle and is subject to certain system limitationsgggggg 140. Stationary objects are disregarded. The system requires reflecting surfaces in order to be able to measure the distance. If the ACC is unable to measure the distance it will not respond.

No vehicle in front

When there is no vehicle in front, the adaptive cruise control works like a speed control system. It maintains a constant target speed specified by the driver.

Vehicle in front

If you catch up with a vehicle driving in front, the adaptive cruise control will reduce the speed accordingly (within the limits set by the system, Driver intervention prompt and, System limitations) and adapt it to the speed of the vehicle in front. Then the system will try to adjust the distance to the car in front according to the settings selected. During the adjustment process the system may temporarily not be able to adhere to the distance you had specified ⇒in Description on page 128. If the vehicle in front accelerates, the adaptive in Description on page 128. If the vehicle in front accelerates, the adaptive cruise control will also accelerate, up to the target speed you have specified.

Driver intervention prompt

In some situations, it is necessary for the driver to brake the vehicle with the foot brake in order to keep a safe distance to the vehicle in front or to avoid a collision. In this case, a warning message will appear in the display and you will also hear a warning tone.

When overtaking

When you move into the overtaking lane and no vehicle is detected in front, the adaptive cruise control will accelerate up to the target speed and then maintain it.

Overriding

You can still use the accelerator pedal at any time to increase speed in the normal way. The previously programmed speed will be resumed when the accelerator pedal is released.

Note

  • Please note that acceleration will vary depending on the preset programme. If you have, for example, selected Distance 1 and the driving programme dynamic, acceleration will be more "sporty". However, if you have set the system to Distance 4 and driving programme comfort, acceleration will be more gradual. For a detailed description please refer to, Setting the distance.
  • No vehicle in front, Vehicle in front and a Driver intervention prompt will be indicated by an indicator lamp, Indicator lamp and display in the speedometer.