A method and a system for automatically detecting unintended lane departures of vehicles are described. A lane departure warning system comprises a lane departure recognition unit (10), an alarm generation unit (12), and a driver activity monititoring unit (14). The driver activity monitoring unit (14) is configured to monitor one or more vehicle-related parameters like the steer angle that change continuously in response to a control intervention of a driver. The alarm generation unit (12) generates an alarm if an actual or forthcoming lane departure is detected and if additionally an evaluation of the one or more parameters indicates a low or no driver activity.