DRIVER WORKLOAD AS A FUNCTION OF ROAD SITUATION, AGE, TRAFFIC DENSITY, AND ROUTE FAMILIARITY

This report describes a field experiment which addressed the effects of driver age, road situation, traffic density, and familiarity with the area of driving on visual and cognitive workload. The purpose of this experiment was to test the feasibility of an automatized Estimator and to obtain data for such a device. Subjects drove an experimental route with various characteristics and were supported by oral route instructions of the experimenter who acted as an optimal route guidance system. Workload was measured with two secondary tasks, a visual detection and an auditory addition task. The results showed clear differences in visual and cognitive workload in the various road situations (eg turning left at uncontrolled intersections, turning right at uncontrolled intersections, and straight ahead at rural roads). Workload in similar situations (eg the turning left situations) did not differ much suggesting that the workload obtained in one set of situations can be generalized to similar other situations. This opens up possibilities for workload estimation in any situation based on workload measured in only a limited set of road situations. In a standing-still condition auditory addition performance of younger subjects was somewhat better than of older subjects. More over, auditory addition performance deteriorated less for younger than for older while driving suggesting that older drivers are cognitively more loaded by driving than younger ones. No effect on workload was found of traffic density. Also, when unfamiliar subjects were guided they did not experience higher workload than subjects familiar at the experimental route. The report completes with implications of the results for the Workload Estimator. (A)