Comparisons between upright and reclined seating positions in autonomous vehicles

In highly automated vehicles (SAE level 3 and up), the relinquishing of control allows its passengers to engage in non-driving-related tasks, including resting. Consequently, seat positions like a reclined seat may become more prevalent, which can in turn impact the passenger. The current study explored possible effects on comfort perceptions and the evaluation of the autonomous system in a driving simulator study. Here, 37 participants were seated on an off-the-shelf driver's seat inside the RODOS driving simulator. They experienced three short driving scenarios that each included a swerving manoeuvre with noticeable lateral accelerations and yaw rotations in three different seating conditions: (1) an alert condition, with their hands on the steering wheel; (2) a hands free condition, where they were still seated upright, but were no longer monitoring the autonomous driving system; (3) a reclined seating condition, where they lay back in a reclined seat. They evaluated their experience with regard to overall comfort, the localisation of discomfort feelings, their trust in the autonomous driving system, and their perceived safety. Significant differences were found in comfort ratings and trust between the alert and hands free conditions, but not between the upright and reclined seating conditions.