A method for deriving a fatigue score which is indicative of a current drowsiness state of an operator, the method comprising steps of - measuring, by means of a first sensor, at least one machine control signal which is indicative of a control input from said operator to a machine, - determining an operator identification signal for uniquely identifying said operator and for taking personal characteristics of said operator into account by means of a personalized fatigue model for improving a precision of the derivation of said fatigue score, - in response to having uniquely identified the operator, loading from a local memory and/or receiving via a wirebound or wireless link from a remote database at least one generic signal which is indicative of said personalized fatigue model for said uniquely identified operator as identified by said operator identification signal, - deriving, using said machine control signal, said operator identification signal, and said generic signal said fatigue score which is indicative of said current drowsiness state of said operator, - measuring, by means of a second sensor, at least one operator signal which is indicative of a physiological state of said operator selected from the group of * a pupil diameter, * a blood pressure, * a pulse rate, * a body temperature, * an electroencephalogram, * a skin conductance level, and * a blood glucose level of said operator, and/ or wherein said at least one operator signal is indicative of a behavioral state of said operator selected from the group of * an eyelid closing state, * a mouth closing state, * a viewing direction, * a head orientation, * a focal point position, * a body posture, and * a distraction level of said operator, and said operator signal is used for deriving said fatigue score which is indicative of said current drowsiness state of said operator. - measuring, by means of a first sensor, at least one machine control signal which is indicative of a control input from said operator to a machine, - determining an operator identification signal for uniquely identifying said operator and for taking personal characteristics of said operator into account by means of a personalized fatigue model for improving a precision of the derivation of said fatigue score, - in response to having uniquely identified the operator, loading from a local memory and/or receiving via a wirebound or wireless link from a remote database at least one generic signal which is indicative of said personalized fatigue model for said uniquely identified operator as identified by said operator identification signal, - deriving, using said machine control signal, said operator identification signal, and said generic signal said fatigue score which is indicative of said current drowsiness state of said operator, - measuring, by means of a second sensor, at least one operator signal which is indicative of a physiological state of said operator selected from the group of * a pupil diameter, * a blood pressure, * a pulse rate, * a body temperature, * an electroencephalogram, * a skin conductance level, and * a blood glucose level of said operator, and/ or wherein said at least one operator signal is indicative of a behavioral state of said operator selected from the group of * an eyelid closing state, * a mouth closing state, * a viewing direction, * a head orientation, * a focal point position, * a body posture, and * a distraction level of said operator, and said operator signal is used for deriving said fatigue score which is indicative of said current drowsiness state of said operator. * a pupil diameter, * a blood pressure, * a pulse rate, * a body temperature, * an electroencephalogram, * a skin conductance level, and * a blood glucose level * an eyelid closing state, * a mouth closing state, * a viewing direction, * a head orientation, * a focal point position, * a body posture, and * a distraction level