How to assess situation awareness while driving with automation? Impact of visual attention during AD mode on measures of situation awareness.

A variety of objective and subjective methods is used to assess situation awareness (SA) in automated driving (AD). In fields like aviation, established methods like SAGAT are used as state of the art for assessing SA, whereas in AD, there is less consensus on the most valid measures. In a driving simulator study with N = 41 participants, four different levels of SA were experimentally created by manipulating visual attention during AD. Different methods for assessing SA were logged during AD-mode and during takeover situations including subjective ratings, gaze behaviour, performance and probe measures. The impact of the manipulation of visual attention during AD mode on the different measures of SA as well as their relation to each other is analysed, reported and discussed. Results show pronounced differences between levels of attention during AD-mode in subjective SA, gaze behaviour and performance measures while preventing visual processing of the driving scenery completely while during AD mode caused surprisingly little impact. A relation between measures of SA and performance can be shown for specifically designed takeover scenarios with increased demands on SA. On the one hand, this implies that there can be a critical impact of SA on performance in takeover situations but it also highlights the robustness and efficiency of drivers' visual processing that enables safe takeover responses even in situations with only little visual processing before a takeover. The implications of the results for assessing SA as well as the processes behind SA in AD are discussed.