Supplementary data for the paper 'External human-machine interfaces: Gimmick or necessity?'

The last few years have seen a wealth of research on external human–machine interfaces (eHMIs). It has been argued that eHMIs are vital because they fill the social interaction void that arises with the introduction of automated vehicles (AVs). However, there is still much discussion about whether eHMIs are needed. The present article surveys arguments for and against eHMIs. We list three arguments against eHMIs: (1) Implicit communication dominates pedestrian-AV interaction, and there is no social interaction void to be filled, (2) There is a large variety of eHMI concepts and a lack of standardization and consensus, and (3) eHMIs may elicit various negative effects such as distraction, confusion, and overreliance. Next, we present five reasons why eHMIs may be useful or required: (1) eHMIs can make planned actions of the AV visible, thereby increasing the efficiency of pedestrian-AV interaction, (2) Participants value an eHMI compared to no eHMI, (3) eHMIs do not have to be limited to showing instructions or the AV’s planned actions; showing the AV mode or the AV’s cooperative or detection capabilities are other uses of eHMIs, (4) Recent research shows that driver eye contact is important in traffic, and a social interaction void thus exists, and (5) A large portion of pedestrian-vehicle accidents in current traffic is caused by unclear implicit communication, suggesting that pedestrians may benefit from explicit eHMIs. It is hoped that this article contributes to the critical discussion of whether eHMIs are needed and how they should be designed.

过去数年，学界围绕外部人机交互界面（external human–machine interfaces, eHMIs）开展了大量研究。有观点认为，外部人机交互界面（eHMIs）至关重要，因为它们填补了自动驾驶车辆（automated vehicles, AVs）普及后出现的社交互动空白。然而，学界目前仍围绕eHMIs是否有必要存在这一问题存在诸多讨论。本文梳理了支持与反对eHMIs的各类论点。我们列出了三项反对eHMIs的理由：（1）行人与自动驾驶车辆的互动以隐性沟通为主，不存在需要填补的社交互动空白；（2）eHMI的设计概念繁多，缺乏统一标准与共识；（3）eHMIs可能引发多种负面影响，例如分散注意力、造成认知混淆以及过度依赖。随后，我们阐述了五项支持eHMIs具备实用性或必要性的依据：（1）eHMIs可使自动驾驶车辆的规划动作可视化，从而提升行人与自动驾驶车辆互动的效率；（2）相较于无eHMI的场景，参与者更青睐配备eHMI的交互模式；（3）eHMIs的应用范畴不必局限于展示指令或自动驾驶车辆的规划动作，展示自动驾驶车辆的运行模式、协同能力或感知检测能力也是其可行用途；（4）近期研究表明，驾驶员的眼神交流在交通场景中至关重要，这意味着自动驾驶车辆普及后确实存在社交互动空白；（5）当前交通场景中，很大一部分行人-车辆事故源于隐性沟通不清晰，这提示行人可从显性的eHMIs中获益。本文希望能为eHMIs是否必要、以及应如何开展设计的批判性讨论贡献参考价值。