Driver visual attention is crucial for the safe transition of control from higher levels of automation to manual driving. Without efficient visual sampling of their surroundings during the transition process, drivers have an increased risk of collisions, due to reduced situation awareness, imposed by automated driving. The use of directional auditory warnings has been proposed as an effective way for guiding drivers' attention to the right place at the right time, during transitions of control that require a lane change for obstacle avoidance. Here, directional auditory warnings either direct drivers' attention towards a free lane (i.e., towards-free-lane warnings) or towards a hazard (i.e., towards-hazard warnings). Whilst studies have demonstrated that the towards-hazard warnings facilitate faster hazard detection, relative to non-directional warnings, little is known about the effects of towards-free-lane auditory warnings on gaze behaviours. Studies have also shown that temporal separation of auditory warnings and visual information can improve the effectiveness of warnings, by attenuating the visual dominance effect. However, the impact of this temporal separation on drivers' gaze behaviour during transitions from automation remains unknown. Using a driving simulator study with forty-eight participants, we investigated how directional auditory warnings and asynchronous presentation of auditory warnings and visual information affect drivers' gaze behaviour during transitions from a hands-on SAE L2 driving system. Results showed that, compared to non-directional warnings, directional auditory warnings reduced the probability of fixation to wing mirrors. Towards-hazard and towards-free-lane warnings effectively guided drivers' visual attention to the hazard location and the free lane, respectively, and also led to faster fixations on these areas. However, under towards-hazard warnings, drivers still adhered to their habit of checking the free lane wing mirror during lane changes with these warnings. Finally, longer stimulus onset asynchronies (SOA) were associated with faster fixations to the wing mirrors and quicker hazard detection, suggesting that longer SOAs attenuated visual dominance effect, leading to an increase in the effectiveness of directional auditory warnings in guiding drivers' visual attention. Findings from this study provide valuable insights for the design of in-vehicle warning systems in automated vehicles.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)