From Driver to Supervisor: Comparing Cognitive Load and EEG-based Attention Allocation across Automation Levels

With increasing automation, drivers' role progressively transitions from active operators to passive system supervisors, affecting their behaviour and cognitive processes. This study aims to understand better attention allocation and perceived cognitive load in manual, L2, and L3 driving in a realistic environment. We conducted a test-track experiment with 30 participants. While driving a prototype automated vehicle, participants were exposed to a passive auditory oddball task and their EEG was recorded. We studied the P3a ERP component elicited by novel environmental cues, an index of attention resources used to process the stimuli. The self-reported cognitive load was assessed using the NASA-TLX. Our findings revealed no significant difference in perceived cognitive load between manual and L2 driving, with L3 driving demonstrating a lower self-reported cognitive load. Despite this, P3a mean amplitude was highest during manual driving, indicating greater attention allocation towards processing environmental sounds compared to L2 and L3 driving. We argue that the need to integrate environmental information might be attenuated in L2 and L3 driving. Further empirical evidence is necessary to understand whether the decreased processing of environmental stimuli is due to top-down attention control leading to attention withdrawal or a lack of available resources due to high cognitive load. To the best of our knowledge, this study is the first attempt to use the passive oddball paradigm outside the laboratory. The insights of this study have significant implications for automation safety and user interface design.