The Rolling Robot and the Human Brain: Handover of the Driving Task in Automated Vehicles

Roessger, Peter; Acevedo, Cristi; Bottesch, Miriam; Nau, Samuel; Stricker, Tobias; Diederichs, Frederik · 2024 · Crossref

DOI: 10.54941/ahfe1005467

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Summary

This study addresses the critical challenge of designing effective Human-Machine Interfaces (HMI) for the handover of driving tasks in partially automated vehicles. As automation shifts from secondary functions to core driving procedures, clearly delineating responsibilities between the human driver and the automated system is essential for safety and user experience. The research, conducted within the KARLI project, aims to identify which icon designs and handover procedures maximize user comprehension, acceptance, and trust, thereby mitigating risks associated with mode confusion and situational awareness deficits. The researchers conducted a laboratory study with 20 participants (aged 20–59, 55% female) with varying experience in advanced driver assistance systems. The study comprised two phases. First, the comprehensibility of eight animated icons was tested, comparing "detailed" versus "holistic" representations for actions such as removing hands from the steering wheel or feet from pedals. Second, four distinct handover procedure designs (A–D) were evaluated using 10-second looping video clips. These designs varied by icon type (detailed vs. holistic), location (parallel to road, horizontal, vertical, or single central), roadmark style (line vs. carpet), and animation effects. Data were collected via direct questioning, Net Promoter Score (NPS), the meCUE user experience questionnaire, design rankings, and semi-structured interviews. Results indicated that detailed icons were significantly more understandable than holistic ones. The "feet off pedal" detailed icon achieved 95% correct recognition, whereas "eyes off road" icons were poorly understood, with recognition rates below 40% and frequent misinterpretations. Among the handover procedures, Design D—featuring a single, centrally located detailed icon with action and bubble animations—was ranked highest by 55% of participants. Design D also achieved the best scores in NPS and overall meCUE ratings. However, age influenced preferences: younger participants (18–29) strongly favored Design D, while no participants aged 50+ ranked it first. Despite Design D’s superiority, all designs received negative NPS scores, indicating room for improvement. Interview feedback highlighted a preference for clarity and simplicity, with some users desiring indicators for completed versus upcoming handover steps. The study concludes that user-centric design is vital for automated driving systems, specifically advocating for detailed icons over holistic ones to enhance information transfer efficiency. Design D is recommended as the basis for future HMI development in the KARLI project. However, the authors emphasize the urgent need to redesign the "eyes off road" icon, suggesting alternatives like closing eyelids or a brain symbol to better convey cognitive relief. The findings underscore that while current designs are understandable, they lack strong user endorsement, highlighting the need for further refinement to ensure safe and intuitive human-automation interaction.

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Topics

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• automation
• ehmi external hmi
• takeover transitions
• mode awareness
• automation surprise
• situational awareness

Information type

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• Applied Guidance: design guidelines
• Methodological Resource: measurement protocol
• Theoretical Contribution: conceptual framework