Mental workload accumulation effect of mobile phone distraction in L2 autopilot mode

Zhao, Hongfei; Ma, Jinfei; Zhang, Yijing; Chang, Ruosong · 2022 · openalex

DOI: 10.1038/s41598-022-17419-1

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Summary

This study investigates the mental workload accumulation effects of mobile phone distraction during Level 2 (L2) autonomous driving, addressing a gap in regulatory frameworks regarding secondary task usage in automated vehicles. While L2 systems require continuous driver monitoring, existing laws do not clearly define permissible mobile phone use. The research aims to determine how driving mode, call complexity, and driving duration interact to influence cognitive load, providing a theoretical basis for distraction detection systems. The researchers employed a 2 (driving mode: manual vs. automatic) × 2 (call content complexity: simple vs. complex) × 6 (driving stage: 10-minute intervals over 60 minutes) mixed experimental design. Fifty-eight novice drivers participated in a driving simulator study. Mental workload was assessed using a multimodal approach: Detection Response Task (DRT) performance (reaction time and accuracy), pupil diameter measurements via eye-tracking, and EEG alpha band power across five brain regions (frontal, temporal, parietal, occipital, and prefrontal). Simple call tasks involved naturalistic conversation, while complex tasks required logical reasoning and arithmetic. The results indicated that mental workload levels converged between manual and automatic driving modes as driving duration increased, regardless of call complexity. Specifically, DRT analysis revealed a significant interaction between driving stage and mode; initially, manual driving showed different response times compared to automatic driving, but these differences diminished over time. By the later stages (around 60 minutes), task performance in the automatic driving group deteriorated to match the manual group, with slower reaction times and decreased accuracy. EEG data supported this convergence, showing that alpha wave power values, which correlate with mental load, did not significantly differ between autopilot and manual groups after 60 minutes. Pupil diameter measurements similarly showed no significant difference between groups at the 60-minute mark. The findings suggest that mobile phone conversations disrupt the cognitive resource balance in L2 autonomous driving, increasing mental workload and impairing brain functions related to cognitive control, problem-solving, and judgment. Contrary to the hypothesis that secondary tasks might mitigate passive fatigue in automated driving, the study demonstrates that prolonged phone use leads to a cumulative negative effect, compromising driving safety. These results imply that current assumptions allowing drivers to engage in secondary tasks during L2 driving may be unsafe, highlighting the need for precise regulations and EEG-based intervention systems to monitor and limit mobile phone use during automated driving phases.

Key finding

Drivers' mental workload levels converge between manual and automatic driving modes as driving duration increases, regardless of mobile phone conversation complexity.

Methodology

simulator

Sample size: 58

Provenance

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

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• cognitive
• mobile phones
• manual
• mental demand
• temporal
• auditory

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: physiological data
• Theoretical Contribution: theory or model, conceptual framework