DescriptionDescription  - Audi braking guard - Adaptive cruise control (ACC) - Controls - Audi A4 Owner's Manual - Audi A4

Audi braking guard warns you in case of an impending collision with a vehicle in front.

Instrument cluster: Display

Instrument cluster: Display

Audi braking guard is active at speeds above approximately 30 km/h and operates within the system limitations even when the adaptive cruise control is deactivated.

The radar sensor is fitted at the front of the vehicle, fig. 137. 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.

Once the system has measured the distance, it can assess a dangerous situation where a vehicle in front brakes suddenly or you are driving fast and approach a vehicle travelling at a much slower speed. The system warns you as soon as it anticipates that a potential collision with the vehicle in front can only be avoided by hard braking or by taking evasive action.

The system has a preset response time so that it can warn you in time. In certain situations, the system response time will be reduced dynamically, e.g. when you are accelerating onto a motorway. Braking, lateral acceleration and steering angle are other factors which can shorten the system response time. The warning will be deactivated if you press the accelerator pedal right down in order to overtake.

The system draws the driver's attention to two different hazardous situations:

Distance !

A distance warning will be given if you travel too close to the vehicle in front for longer than 5 seconds. For example, if the distance is less than 9 m at 80 km/h, a message will appear in the instrument cluster display, fig. 156.

If the vehicle in front were to brake hard, a collision would no longer be avoidable, even if you reacted immediately. In this case, you should leave more room between your car and the vehicle in front.


If the vehicle in front of you is travelling in the same lane at a much slower speed or if it brakes hard, the Audi braking guard will calculate the time at which a collision can be avoided only by emergency braking or evasive action. When the system warns you, it is possible to avoid a potential collision with the vehicle in front by braking or changing lane. There are two warning levels:

  • Х Early warning: A message will appear in the instrument cluster display and you will also hear a warning tone.
  • Х Acute warning: The second (acute) warning will be triggered if you do not react to the advance warning. There will automatically be a short dab of the brakes to remind you to concentrate on the traffic. If you brake hard, the brake assist system helps you to achieve the optimum braking effect.

Please always direct your full attention to the road, even when the Audi WARNING

Please always direct your full attention to the road, even when the Audi braking guard is activated. It is always you who is responsible for determining your speed and for keeping a safe distance to the other vehicles on the road.

  • Х Always maintain the statutory minimum safety distance to the vehicle in front (risk of accident).
  • Х Due to the system limitations, the Audi braking guard will not react in certain situations, for example when approaching a stationary obstacle (such as the end of a traffic jam or a brokendown vehicle).
  • Х Please note that the Audi braking guard is subject to limitations in tight bends on account of the radar sensor's field of vision. This means that obstacles may not be detected in certain situations.
  • Х The radar sensor's "field of vision" can be impaired by rain, snow or a lot of water on the road. This results in vehicles not being reliably recognised or, in some circumstances, not being detected at all. Always keep the road ahead within your field of vision.
  • Х Reflecting objects, such as crash barriers or the entrance to a tunnel, could impair the function of the radar sensor.