With automated vehicles (AVs), the absence of a human operator could necessitate external Human-Machine Interfaces (eHMIs) to communicate with other road users. Existing research primarily focuses on pedestrian-AV interactions, with limited attention given to other road users, such as cyclists and drivers of manually driven vehicles. So far, no studies have compared the effects of eHMIs across these three road user roles. Therefore, we conducted a within-subjects virtual reality experiment (N=40), evaluating the subjective and objective impact of an eHMI communicating the AV's intention to pedestrians, cyclists, and drivers under various levels of distraction (no distraction, visual noise, interference). eHMIs positively influenced safety perceptions, trust, perceived usefulness, and mental demand across all roles. While distraction and road user roles showed significant main effects, interaction effects were only observed in perceived usability. Thus, a unified eHMI design is effective, facilitating the standardization and broader adoption of eHMIs in diverse traffic.

翻译：随着自动驾驶车辆（AVs）的出现，人类操作员的缺失可能需要外部人机界面（eHMIs）来与其他道路使用者进行通信。现有研究主要关注行人与自动驾驶车辆的交互，而对其他道路使用者（如骑行者和手动驾驶车辆的驾驶员）的关注有限。迄今为止，尚无研究比较eHMIs对这三种道路使用者角色的影响。因此，我们进行了一项被试内虚拟现实实验（N=40），评估了在不同分心程度（无分心、视觉噪声、干扰）下，一个传达自动驾驶车辆意图的eHMI对行人、骑行者和驾驶员的主观及客观影响。eHMIs对所有角色的安全感知、信任度、感知有用性和心理负荷均产生了积极影响。虽然分心程度和道路使用者角色显示出显著的主效应，但交互效应仅在感知可用性中被观察到。因此，统一的eHMI设计是有效的，有助于eHMIs在不同交通场景中的标准化和更广泛采用。