As autonomous vehicles enter public spaces, external human-machine interfaces are proposed to support communication with external road users. A decade of research has produced hundreds of studies and reviews, yet it remains unclear whether the field is converging on shared principles or diverging across approaches. We present a multi-dimensional analysis of 620 publications, complemented by industry deployments and regulatory documents, to track research evolution and identify convergence. The analysis reveals several field-level patterns. First, convergence on a safety-first core: simple visual cues that clarify intent. Second, sustained divergence in necessity and implementation. Third, a progressive filtering funnel: broad exploration in research and concepts narrows in deployment and is codified by regulation into a minimal set of permitted signals. These insights point to a shift in emphasis for future work, from producing new prototypes toward consolidating evidence, clarifying points of contention, and developing frameworks that can adapt across contexts.

翻译：随着自动驾驶车辆进入公共空间，外部人机界面被提出以支持与外部道路使用者的通信。十年的研究已产生数百项研究和综述，但该领域究竟是在向共享原则趋同，还是在不同方法间分化，仍不明确。我们对620篇文献进行了多维度分析，并结合行业部署与监管文件，以追踪研究演进并识别趋同趋势。分析揭示了若干领域层面的模式。首先，在安全优先的核心原则上趋同：即阐明意图的简单视觉提示。其次，在必要性与实施方式上持续分化。第三，存在渐进式筛选漏斗：研究与概念层面的广泛探索在部署阶段收窄，并通过监管被编纂为少量允许使用的信号。这些发现指出未来工作的重点应发生转变：从创造新原型转向整合证据、厘清争议点，并开发能够适应不同情境的框架。