Evaluating take-over requests with directional audio

Abstract

Taking over control from an automated vehicle may take a substantial amount of time if the driver is not engaged in the driving task. Take-over requests containing directional information of hazardous surrounding cars could aid the driver in taking over the vehicle faster. However, whether the directional information should be presented ipsilaterally or contralaterally is still inconclusive. In this study, 34 participants were presented with animated video clips of traffic situations on a three-lane road, ending with a near-collision in front after 1,3, or 6 seconds. In each video, one lane was free to maneuver to safely. Participants were instructed to make a safe lane-change by pressing the left or right arrow key. At the start of each video, participants were provided with verbal auditory feedback: (1) ‘Go left/right’ (ipsilateral), (2) ‘Danger left/right’ (contralateral), and (3) Non-directional beeps as a baseline. 80% of the trials provided valid auditory feedback (i.e., relevant to the video situation). 20% of the trials provided invalid auditory feedback (i.e., feedback opposite to the video situation, so left instead of right and vice versa). Auditory feedback ‘Go/Danger left’ was always presented from the left speaker, and ‘Go/Danger right’ was always presented from the right speaker, whereas the non-directional beeps were presented from both speakers. Participants’ keyboard responses and first gazes were recorded in each trial. It was hypothesized that when there was 1-second to respond, ipsilateral feedback (‘Go’) would lead to fastest responses because little time is available to detect the hazard. For 3 and 6-second-to-respond situations, it was hypothesized that contralateral feedback (‘Danger’) would lead to a faster detection time of the hazard, because it facilitates visual detection. The results showed that for 1 and 3-second videos, ipsilateral feedback led to significantly faster responses compared to the baseline, and for 3 and 6-second videos contralateral feedback ‘Danger’ led to significantly faster responses compared to the baseline. ‘Go’ and ‘Danger’ did not yield a significant difference in response time between each other in all videos. First fixations seem to be placed on the most salient visual stimuli, independent of the audio feedback. In 1-second time-to-respond videos this was the center of the road (the location where the potential collision is happening. In 3-seconds, this was the hazard coming from the left or right lane. And for 6 seconds the first fixations were more distributed. In conclusion, verbal auditory feedback ‘Go’ and ‘Danger’ can aid in taking over a vehicle, by reducing the take-over response time compared to baseline warnings. However, this may not be the result of facilitation of the visual detection of the hazard, because visual behavior seems to be influenced mainly by visual stimuli, independent of auditory stimuli.