Measuring Driver Electrodermal Activity when Exposed to HMIs Conveying Uncertainty in Conditional Automated Driving

The emergence of automated vehicles (AVs) introduces new challenges to human-vehicle interactions, especially in conditional automated driving. This study presents different head-up display designs as the human-machine interface (HMI) to convey uncertainty to AV users. It investigates the impact of such designs on drivers’ physiological responses–via electrodermal activity data–and subjective evaluations of cognitive workload during the automated drive. A between-subjects driving simulator experiment (N=187) was conducted to examine four conditions: baseline (no HMI), a progressive colour-based Guardian Angel display, a text-based interruption, and a combination approach. The results showed significant effects of the presence of the Guardian Angel display interventions on physiological arousal associated with cognitive workload. However, the subjective ratings showed no difference across conditions. These findings indicate that the designed displays can trigger physiological responses without affecting perceived workload. It offers insights into HMI design to balance driver awareness and cognitive demand in automated driving.