The driving style of a highly automated vehicle has major influence on acceptance and trust ratings of passengers. Studies show that a defensive driving style is preferred over a dynamic one in highway and rural road scenarios. However, there are only few findings on driving style perception in urban areas. To fill that research gap, an exploratory driving simulator study with 42 subjects was conducted. Subjects experienced four highly automated drives with 9 different driving situations. For each experimental condition, the Ego-vehicle performed either a dynamic or a defensive driving style. During each test drive, subjects gave continuous feedback on their discomfort level via handset controller and filled in questionnaires regarding acceptance, trust and subjectively experienced driving performance of the automation. For a detailed assessment of the two driving styles, a final interview was conducted at the end of the study. Overall, a significantly better evaluation of the defensive driving style was found. Subjects submitted significantly higher acceptance, trust and subjectively experienced driving performance ratings for the defensive driving style. Due to the continuous evaluation of the discomfort level, every situation could be examined separately afterwards. The situation-based analysis showed high discomfort ratings for driving situations with cross-and oncoming traffic, especially in the dynamic driving style. In contrast, situations with longitudinal traffic resulted in low discomfort ratings. In these situations, the dynamic driving style was rated as positive as the defensive driving style and in two situations was even desired. The interviews confirmed the results and showed also subjects wishes for a situation-specific adjustment of the automated driving style. The vehicle should behave differently depending on the traffic situation and personal preferences. The findings of the study help to develop accepted and trustworthy driving styles by providing recommendations for driving behaviour in specific urban situations. © 2022, VDI Verlag GMBH. All rights reserved.
