The present invention relates to a method for determining a vehicle operator's visual input of an object in the operator's surroundings, which method comprises receiving an object position signal indicative of the position of at least one object, receiving an operator motion input signal indicative of operator physiological data comprising information relating to body motion of the operator, estimating an operator eye-gaze direction, and determining a visual input quality value representative of level of visual input of the at least one object received by the operator, based on the object position signal and the estimated operator eye-gaze direction.