Using Driver Performance Measures to Estimate Workload

This study evaluated the impact of the modality of distractor tasks and the difficulty of the driving task on driver control over a vehicle. Driving is a task with a close link between visual information processing and driver performance variables such as lane keeping. Consequently, compared to auditory distractors, visual distractors should have a larger negative effect on vehicle control, but mainly when the driving task also adds significant workload for the driver. In this study, drivers drove around either a curvy or a straight track while occasionally performing either an auditory or a visual secondary monitoring task. Performance of the secondary task was associated with deterioration in steering wheel control and lane keeping, but only on the curvy track and mainly when the secondary task required visual monitoring. These results are discussed in terms of their implication for developing workload managers in in-vehicle driver support systems.