Supplementary data for the paper 'Augmented reality for supporting the interaction between pedestrians and automated vehicles: An experimental outdoor study'

Communication from automated vehicles (AVs) to pedestrians using augmented reality (AR) could positively contribute to traffic safety. However, previous AR research for pedestrians was mainly conducted through online questionnaires or experiments in virtual environments instead of real ones. In this study, 28 participants conducted trials outdoors with an approaching AV and were supported by four different AR interfaces. The AR experience was created by having participants wear a Varjo XR-3 headset with see-through functionality, with the AV and AR elements virtually overlaid onto the real environment. The AR interfaces were vehicle-locked (<em>Planes on vehicle</em>), world-locked (<em>Fixed pedestrian lights</em>, <em>Virtual fence</em>), or head-locked (<em>Pedestrian lights HUD</em>). Participants had to hold down a button when they felt it was safe to cross, and their opinions were obtained through rating scales, interviews, and a questionnaire. The results showed that participants had a subjective preference for AR interfaces over no AR interface. Furthermore, the Pedestrian Lights HUD was more effective than no AR interface in a statistically significant manner, as it led to participants more frequently keeping the button pressed. The <em>Fixed pedestrian lights</em> scored lower than the other interfaces, presumably due to low saliency and the fact that participants had to visually identify both this AR interface and the AV. In conclusion, while users favour AR in AV-pedestrian interactions over no AR, its effectiveness depends on design factors like location, visibility, and visual attention demands. In conclusion, this work provides important insights into the use of AR outdoors. The findings illustrate that, in these circumstances, a clear and easily interpretable AR interface is of key importance.

自动驾驶汽车（Automated Vehicles, AVs）借助增强现实（Augmented Reality, AR）向行人传递交互信息，有望对道路交通安全产生积极增益。然而，过往面向行人的AR相关研究，大多通过线上问卷或虚拟环境实验开展，而非真实场景下的实地实验。

本研究招募28名受试者，在户外场景中开展针对即将驶来的自动驾驶汽车的交互试验，共采用四种不同的AR交互界面。受试者佩戴具备透视功能的Varjo XR-3头显，将自动驾驶汽车与AR元素虚拟叠加至真实环境中，以此构建完整的AR交互体验。

四类AR交互界面分别为：车辆锁定式（<em>Planes on vehicle</em>，即车辆平面标记）、世界锁定式（<em>Fixed pedestrian lights</em>，即固定行人信号灯；<em>Virtual fence</em>，即虚拟围栏）以及头部锁定式（<em>Pedestrian lights HUD</em>，即行人信号灯平视显示器（Head-Up Display, HUD））。

试验过程中，受试者需在确认可安全横穿道路时持续按住按钮，研究通过评分量表、访谈与问卷收集受试者的主观反馈与实验数据。

研究结果显示，受试者主观上更倾向于使用AR交互界面，而非无AR辅助的场景。其中，行人信号灯平视显示器的交互效果显著优于无AR辅助状态，该差异具备统计学显著性，且该界面使受试者更频繁地保持按钮按压状态。而固定行人信号灯界面的得分低于其余三类界面，推测原因为其视觉显著性较低，且受试者需同时识别该AR界面与真实的自动驾驶汽车。

综上，尽管用户在自动驾驶汽车与行人的交互场景中更青睐AR辅助方案，但其实际交互效果取决于界面的位置、可视性与视觉注意力需求等多项设计因素。整体而言，本研究为户外场景下的AR应用提供了重要的研究洞察，研究结果表明，在此类真实交互场景中，清晰易懂的AR交互界面是保障交互体验与安全性的核心要素。