Abstract
As autonomous systems become more prevalent, understanding how humans interact with varying levels and reliability of automation is critical. This study investigates the effects of automation level and automation reliability on performance, mental workload, and situation awareness in hybrid automation systems. Using OpenMATB, 45 participants completed a multitasking simulation under different automation levels (manual to fully automated) and reliability conditions (50%, 70%, 99%). Results indicated significant effects of both automation level and reliability on task performance, situational awareness, and heart rate variability, with higher automation and reliability generally improving performance but lowering physiological markers of workload. Participants also showed a tendency to prefer lower automation levels when system reliability was low. Findings highlight the importance of designing adaptive systems that account for user preferences and reliability expectations. Future work may focus on modeling user transition behavior to inform adaptive automation strategies that support performance while maintaining engagement and situational awareness.
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