Method for operating a driver assistance system on a motor vehicle outputting a recommendation related to an overtaking manoeuvre and motor vehicle

The method involves providing a camera (6) navigated in drive direction of the motor vehicle (1) and provided on or in an exterior mirror (4). The data from the camera is evaluated through the driver assistance system (2). From the data of the camera a length of the vehicle running ahead or a vehicle platoon running ahead is determined and is considered during the determination of the reference.