The interaction between perceived safety and perceived usefulness in automated parking as a result of safety distance.

Improved safety and traffic efficiency are among the proclaimed benefits of automated driving functions. In many scenarios, traffic safety and efficiency can be somewhat contradictory, especially in the perception of a user. In order for potential users to accept the automated system, it is necessary to find the optimal system configuration. Therefore, it is important to understand how the factors underlying acceptance develop and interact. In this study, seven safety distances of an automated parking system were implemented resulting in parking manoeuvres of varying efficiency (in terms of required moves). Participants experienced each configuration twice and rated their perceived safety and perceived usefulness. The results show that maximizing safety distances results in high perceived safety, yet also a diminished perceived usefulness due to reduced efficiency. On the other hand, maximum efficiency leads to a lower perceived safety and thus, a reduced rating of perceived usefulness. Furthermore, in some participants, perceived safety increased gradually, while for others, a threshold effect could be observed. The results demonstrate that the specification of a sole system characteristic can have multiple effects. These have to be considered to maximize acceptance.

Cross-cultural differences in the acceptance of decisions of automated vehicles.

Automated vehicles are expected to enhance driving safety and comfort. In order to fulfil these expectations, they have to be widely accepted and used. Implementing an acceptable driving style is therefore a must. Previous research on automated vehicle acceptance has largely concentrated on the effects of driving dynamics. This study takes a different approach and focuses on the effects of the driving decisions. To assess the effects of driving decisions on acceptance, an online experimental study was conducted in China, Germany, Japan and the US. Four overtaking scenarios, in which the automated vehicle took a decision, were presented as short texts. The situations differed with regard to the action (overtaking vs. stay in lane) and potential consequence (high or low hindrance of another driver). Participants then rated their acceptance. The results indicate that acceptance is dependent on the driving decisions and is further influenced by cultural background. Chinese drivers show high acceptance to the decisions and there were no significant differences between the presented scenarios. In the US and Germany, decisions leading to high hindrance of others are rejected, whereas in cases of low hindrance, overtaking is preferred. Japanese participants reject decisions, which lead to hindrance of others.