A control system/method, for controlling operation of a vehicle system, comprising one or more controllers. The control system is configured to receive image data 302 representative of at least one image of at least a portion of a vehicle occupants face and identify 403 from the received image data one or more Facial Action Units, e.g. a contraction or relaxation of one or more muscles of the face of the vehicle occupant. The control system determines 306 whether the one or more identified Facial Action Units correspond to Facial Action Units associated with an underlying medical condition and outputs a control signal 308 which is configured to control operation of a vehicle system in dependence on a determination that the one or more identified Facial Action Units correspond to Facial Action Units associated with the underlying medical condition. The control system may provide an audio/visual warning and the vehicle system may be a steering and/or a braking system. Reference is also made to computer software to perform the method.
