Method for warning the driver of a motor vehicle about an incipient dangerous situation due to inadvertent drifting into an opposing lane

The method involves determining (b,d) a virtual vehicle path directed in travel direction of own vehicle, and a lane marker which separates lane of own vehicle from opposing traffic lane. The position of own vehicle is determined in relation to the lane marker. A warning signal is output or an automatic driving mode intervention is performed according to the indication of entrance of oncoming vehicle into the virtual vehicle path and crossing of own vehicle from the lane marker when the sensor information indicates an absence of active steering operation by the driver. An independent claim is included for motor car.