Investigating the Impacts Caused by Manual Secondary Tasks on Drivers’ Visual Behavior

Driver distraction induced by drivers concurrently executing multiple tasks has become a central issue for traffic safety. It is crucial to understand how different demands of secondary tasks affect driver visual behavior. This study employed a simulator-based experiment to assess the discrepances of manual and non-manual secondary tasks on drivers’ eye movements. Twenty five subjects performed oral calculation quizzes in different types and levels under dual-task conditions. Results suggested that drives had the smallest visual search area, the largest pupil area, and the most dispersed gaze points in manual-task conditions with regard to others. Subjective ratings and reaction time showed the similar variation. The more difficult the task was, the more degradation of main tasks and secondary tasks showed. These results revealed secondary tasks cause mental workload and the impact appeared to be greater when the driver performed manual tasks. The interface design would follow a rule to reduce manual tasks.