Human-Machine Interface Evaluation Using EEG in Driving Simulator

Liu, Yuan-Cheng; Figalova, Nikol; Baumann, Martin; Bengler, Klaus · 2023 · Crossref

DOI: 10.1109/iv55152.2023.10186567

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Summary

This study addresses the critical need for objective evaluation methods for Human-Machine Interfaces (HMIs) in automated vehicles (AVs). While AVs promise improved safety, current HMI designs often confuse users regarding their responsibilities during automation transitions. Existing evaluation methods rely heavily on subjective heuristics, lacking standardized, objective metrics suitable for real-time assessment. The research investigates whether electroencephalogram (EEG) spectral power analysis can detect differences in mental workload across distinct HMI designs, aiming to validate EEG as a psychophysiological measure for HMI transparency assessment. The researchers developed three SAE Level 2 HMI designs varying in transparency: "Fog" (low clarity, poor system feedback), "Trans" (high clarity, clear system feedback), and "Trans-fog" (high interface clarity, poor system feedback). Twelve participants with valid driving licenses underwent trials in a static driving simulator. Each participant experienced all three designs in a counterbalanced order across four traffic layouts, totaling 12 trials. Mental workload was measured subjectively using the NASA-Task Load Index (NASA-TLX) and a subjective transparency questionnaire. Objectively, 32-channel EEG data were recorded and preprocessed using adaptive mixture independent component analysis. The study analyzed relative mean spectral power in the alpha (8–12 Hz) and theta (4–7 Hz) bands during L2 automation activation events. Subjective evaluations confirmed significant differences in mental workload and transparency among the designs. The "Trans" HMI yielded the lowest NASA-TLX scores and highest transparency ratings, indicating it was the easiest to understand. The "Fog" HMI resulted in significantly higher workload and lower transparency compared to "Trans." Notably, while "Trans" and "Trans-fog" showed no difference in subjective transparency scores, "Trans" had significantly lower mental workload, highlighting the importance of system transparency (feedback logic) alongside interface design. However, the EEG analysis failed to detect significant differences in relative alpha or theta power across the three HMI designs. Although the direction of the means aligned with literature expectations (higher alpha for lower workload), the statistical tests showed no significance. The study concludes that while the three HMI designs successfully elicited distinct subjective workloads, EEG spectral power analysis was not effective in distinguishing these differences in this experimental setup. The authors attribute this null result to low statistical power caused by a small sample size and the aggregation of EEG epochs, which may have averaged out subtle neural signals. The findings underscore that both interface and system transparency are crucial for reducing driver workload. The validated HMI designs serve as a basis for future research to refine psychophysiological measurement techniques, potentially by analyzing separated epochs or recruiting larger samples, to enable efficient, objective HMI evaluation in real driving scenarios.

Key finding

Subjective evaluations detected significant differences in mental workload among the HMI designs, but EEG spectral power analysis did not yield statistically significant results.

Methodology

simulator

Sample size: 10

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StageOutcomeToolModelPromptAttemptsCompleted
discover success Crossref 1 2026-06-05
archive success canonical_url 1 2026-06-06
extract success cached 3 2026-06-10
clean success clean 1 2026-06-07
chunk success chunk 1 2026-06-07
embed success embed Qwen/Qwen3-Embedding-8B 1 2026-06-07
enrich success semantic_scholar 1 2026-06-06
promote success 1 2026-06-05
summarize success llm qwen3.6-27b-prismaquant summ-v5 2 2026-06-10
tag success vector_similarity 15 2026-06-11
verify success 2 2026-06-10

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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