Guiding Drivers’ Visual Attention during Transition from Vehicle Automation

Modern vehicles increasingly communicate with drivers through a wide range of messages and warnings. While these systems are intended to improve safety, the growing number of in-vehicle signals can sometimes overwhelm drivers, compete for attention, or create confusion—particularly in safety-critical situations. This challenge becomes especially important in automated driving, where drivers must rapidly regain control of the vehicle during transitions from automation to manual driving. In these moments, drivers need to quickly identify relevant hazards and make appropriate control decisions. However, it remains unclear how warning design can best support drivers’ visual attention and takeover performance during these transitions. The research conducted in this thesis examined how to guide drivers’ visual attention to safety-critical areas on the road environment during transitions from vehicle automation, with a particular focus on the effects of directional auditory warnings under audiovisual asynchrony conditions. This work addressed questions related to (i) providing a comprehensive understanding of how directional takeover requests (TORs), compared to non-directional ones, influence drivers’ gaze behaviour during transitions from automated driving, (ii) whether directional auditory warnings, particularly under audiovisual asynchrony conditions, can guide driver’s visual attention to the right place at the right time, (iii) how such attentional guidance affects takeover performance (i.e., takeover time and quality).
To address these questions, a systematic review and meta-analysis synthesised existing evidence on the effects of directional TORs on drivers’ gaze behaviour. Additionally, a driving simulator experiment (N = 48) examined the effects of directional auditory warnings and audiovisual asynchrony in modulating their impact on visual attention allocation and takeover responses in a lane-change scenario.
By quantitatively aggregating gaze-related metrics across studies, the review clarified the overall effects of directionality and identified key moderators contributing to previously inconsistent results. Meta-analyses revealed that directional TORs significantly alter drivers’ visual attention allocation compared to non-directional ones. Specifically, incorporating directionality into the visual interface increased both number and duration of fixations on the TOR display. Moreover, directional TORs that indicated hazards’ location led to faster fixations on them. Interface modality and location were also identified as moderating factors influencing the effectiveness of directional TORs.
The driving simulator experiment demonstrated that directional auditory warnings effectively guide drivers’ visual attention to the right place (i.e., safety-critical areas), at the right time (i.e., faster fixation). These attentional benefits translated into performance improvements: directional warnings reduced first steering reaction times, improved steering accuracy, and lowered maximum lateral acceleration compared to non-directional warnings. Furthermore, increasing audiovisual asynchrony—presenting the auditory warning before the appearance of visual information—enhanced both attentional and behavioural outcomes. Longer Stimulus Onset Asynchronies (SOAs) reduced drivers’ tendency to prioritise visual information over auditory warnings (a phenomenon known as the Colavita visual dominance effect), facilitated faster visual orienting, reduced takeover time, and improved steering response accuracy.
Overall, by demonstrating that directional warnings—particularly auditory warnings that precede the visual information—can effectively guide drivers’ visual attention during transitions from vehicle automation, this thesis provides valuable insights for designing effective in-vehicle warning systems for AVs.