Effect of riding experience and HMI on users' trust and riding comfort in fully driverless autonomous vehicles: An...

The wide adoption of autonomous vehicles (AVs) or robot taxis relies on technological advancements and public acceptance, which can be influenced by users' trust in AVs and comfort during rides. Among the influential factors of riding comfort, motion sickness (MS) has attracted lots of attention in previous research, and both trust and MS have been found to be associated with human-machine interface (HMI) designs in AVs. However, previous research on trust and MS in AVs predominantly utilized driving simulations or "Wizard of Oz" methods, which failed to introduce risk and realistic vehicle motions, potentially introducing bias to conclusions. For the first time, our study investigated the impact of displaying the dynamic path trajectories of AVs on passengers' perceptions of system transparency, trust, and MS in a commercially running AV. The results from 16 participants and 32 rides revealed limited effects of the dynamic path trajectory on trust, and a discernible but statistically non-significant trend in MS alleviation. Further, we found that the initial riding experience was more important in trust enhancement than subsequent rides. These results provide insights into future HMI design in robot taxis and suggest directions for future research in trust enhancement and MS alleviation in AVs.