Lane departure warning system and a method for a lane departure warning system

A lane departure warning system (2) for a vehicle (20), comprising a lane monitoring unit (4) adapted to delivering a location signal (6) which indicates the vehicle's position relative to the lane markings (22) of a road, a lane deviation unit (8) adapted to calculating on the basis of said location signal (6) the vehicle's current deviation and prospective deviations from its lane, and the direction of deviation relative to the vehicle, and to generating on the basis thereof one or more deviation signals (10). The system further comprises an alarm unit (12) adapted to generating on the basis of said deviation signals (10) one or more alarm signals (14,16) to the vehicle's driver, comprising a first alarm signal (14) arranged to be generated if the vehicle's current deviation exceeds a first threshold value (T1,T1') which represents an impermissible deviation, and a second alarm signal (16) arranged to be generated if said deviation signal (10) indicates that the vehicle will impermissibly deviate from its lane. The second alarm signal (16) is an acoustic signal which indicates the direction of prospective deviation relative to the vehicle.