How the system worksHow the system works  - Lane change assist feature - Audi side assist - Controls - Audi A4 Owner's Manual - Audi A4

When other vehicles are detected, the side assist system registers their distance and how fast they are approaching. The warning lamp on the relevant exterior mirror will light up whenever the side assist calculates that the distance and the speed differential of approaching vehicles would be critical in the event of a lane change.

The warning lamp may light up when you are being overtaken and when you are overtaking another vehicle.

If you are overtaking slowly, with a speed differential of less than 15 km/h, the warning lamp will light up as soon as the other vehicle enters your blind spot and is detected by the sensors. If you are overtaking with a speed differential which is greater than this the lamp will not give a warning.