DOI: 10.4121/8887ca18-53df-49dd-a7df-991219edaf15.v1
title: Supplementary material for paper: "Exploring the Effects of Interior Design Elements on the Uncertainty of Passengers of Fully Automated Cars"

description: <strong>Abstract</strong>Humans are masters in predicting each other’s behaviour and acting relatively appropriately in ambiguous and uncertain situations. Although road accident statistics show a slight decrease in the number of road traffic deaths, these numbers are still very high. Fully automated cars are said to offer the potential to bring everyone everywhere, avoid accidents, and save parking spaces. This does not mean that the objective benefits of fully automated cars are also perceived this way by society. We may feel uncertain about the intentions, behaviour, and reliability of these fully automated cars. Our perceived psychological uncertainty influences our behaviour and the way we interact with them. Psychological uncertainty can alter our mental state and, thus, our behaviour. Psychological uncertainty further shapes perceptions of and interactions with fully automated cars. People should not feel uncertain about the capability of the fully automated car to prevent misuse, feelings of unsafety and discomfort. Interior design could play a role in mediating the perceived psychological uncertainty that passengers of fully automated cars perceive. A study was conducted to explore the effects of interior design elements on the perceived psychological uncertainty of passengers of fully automated vehicles. Results of the conducted study, with 113 participants, indicate that factors such as familiarity, trust, and perceived control are significant considerations when addressing perceived psychological uncertainty through interior design. Furthermore, the introduction of unfamiliar design elements and perceived loss of control may lead to an increase in feelings of psychological uncertainty.<br><strong>Procedure</strong>Participants were presented with photo-realistic images showcasing various interior designs of the same fully automated car in random order. They were required to evaluate their perceived psychological uncertainty towards these different interior designs. All participants were above the age of 18 years old and digitally agreed to informed consent prior to participation. This study procedure was approved by the Ethical Review Board of the Eindhoven University of Technology. Participants did not receive compensation for their contribution and participated voluntarily.<br>The survey was presented through Microsoft Forms and was accessible on multiple devices, such as phones, tablets, and desktops. Participants first provided demographic information, including their age group, gender, residential country, driving experience, opinions on automated vehicles and general perceived psychological uncertainty level. Subsequently, participants commenced the survey and were shown 25 images depicting different interior designs of the same fully automated car. The images were presented in a randomised order, but with the baseline image always being the first and repeated randomly once among the remaining images. After viewing each image, participants were prompted to rate their level of perceived psychological uncertainty on a scale from 0 to 10, where 0 indicated ‘absolutely not uncertain’ and 10 indicated ‘absolutely uncertain’. Additionally, an open-ended question asking participants to describe the elements they were uncertain about the previously shown images, was interspersed three times among the images.