See2Refine: Vision-Language Feedback Improves LLM-Based eHMI Action Designers

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Auteurs principaux: Xia, Ding, Gui, Xinyue, Colley, Mark, Gao, Fan, Zhou, Zhongyi, Li, Dongyuan, Jiang, Renhe, Igarashi, Takeo
Format: Preprint
Publié: 2026
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author Xia, Ding
Gui, Xinyue
Colley, Mark
Gao, Fan
Zhou, Zhongyi
Li, Dongyuan
Jiang, Renhe
Igarashi, Takeo
author_facet Xia, Ding
Gui, Xinyue
Colley, Mark
Gao, Fan
Zhou, Zhongyi
Li, Dongyuan
Jiang, Renhe
Igarashi, Takeo
contents Automated vehicles lack natural communication channels with other road users, making external Human-Machine Interfaces (eHMIs) essential for conveying intent and maintaining trust in shared environments. However, most eHMI studies rely on developer-crafted message-action pairs, which are difficult to adapt to diverse and dynamic traffic contexts. A promising alternative is to use Large Language Models (LLMs) as action designers that generate context-conditioned eHMI actions, yet such designers lack perceptual verification and typically depend on fixed prompts or costly human-annotated feedback for improvement. We present See2Refine, a human-free, closed-loop framework that uses vision-language model (VLM) perceptual evaluation as automated visual feedback to improve an LLM-based eHMI action designer. Given a driving context and a candidate eHMI action, the VLM evaluates the perceived appropriateness of the action, and this feedback is used to iteratively revise the designer's outputs, enabling systematic refinement without human supervision. We evaluate our framework across three eHMI modalities (lightbar, eyes, and arm) and multiple LLM model sizes. Across settings, our framework consistently outperforms prompt-only LLM designers and manually specified baselines in both VLM-based metrics and human-subject evaluations. Results further indicate that the improvements generalize across modalities and that VLM evaluations are well aligned with human preferences, supporting the robustness and effectiveness of See2Refine for scalable action design.
format Preprint
id arxiv_https___arxiv_org_abs_2602_02063
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle See2Refine: Vision-Language Feedback Improves LLM-Based eHMI Action Designers
Xia, Ding
Gui, Xinyue
Colley, Mark
Gao, Fan
Zhou, Zhongyi
Li, Dongyuan
Jiang, Renhe
Igarashi, Takeo
Human-Computer Interaction
Artificial Intelligence
Automated vehicles lack natural communication channels with other road users, making external Human-Machine Interfaces (eHMIs) essential for conveying intent and maintaining trust in shared environments. However, most eHMI studies rely on developer-crafted message-action pairs, which are difficult to adapt to diverse and dynamic traffic contexts. A promising alternative is to use Large Language Models (LLMs) as action designers that generate context-conditioned eHMI actions, yet such designers lack perceptual verification and typically depend on fixed prompts or costly human-annotated feedback for improvement. We present See2Refine, a human-free, closed-loop framework that uses vision-language model (VLM) perceptual evaluation as automated visual feedback to improve an LLM-based eHMI action designer. Given a driving context and a candidate eHMI action, the VLM evaluates the perceived appropriateness of the action, and this feedback is used to iteratively revise the designer's outputs, enabling systematic refinement without human supervision. We evaluate our framework across three eHMI modalities (lightbar, eyes, and arm) and multiple LLM model sizes. Across settings, our framework consistently outperforms prompt-only LLM designers and manually specified baselines in both VLM-based metrics and human-subject evaluations. Results further indicate that the improvements generalize across modalities and that VLM evaluations are well aligned with human preferences, supporting the robustness and effectiveness of See2Refine for scalable action design.
title See2Refine: Vision-Language Feedback Improves LLM-Based eHMI Action Designers
topic Human-Computer Interaction
Artificial Intelligence
url https://arxiv.org/abs/2602.02063