Effects of Display-Control Modality on Workload During Non-Driving Related Tasks in Autonomous Vehicles

With the advancement of Level 3 autonomous vehicle (AV) technology, passengers frequently engage in cognitively demanding non-driving-related tasks (NDRTs). However, increased cognitive workload from these tasks may negatively affect takeover performance when drivers are required to resume control. Identifying interface designs that minimize workload is critical for enhancing safety and user experience in AVs. Despite extensive research on stimulus-response compatibility, its effects on workload in an in-vehicle N-back task context remain unexplored. This study investigates how display-control modality influences workload during N-back task performance in an AV setting. A within-subject, on-road experiment was conducted with four interface conditions: visual-manual, visual-speech, auditory-manual, and auditory-speech. NASA-TLX scores revealed significant differences in total workload, physical demand, and frustration across conditions. These findings highlight the need for workload-efficient interface design to support safer automated driving environments.