Automated Vehicles (AVs) are being developed rapidly and tested on public roads, but pedestrians’ interaction with AV is not comprehensively understood or thoroughly investigated to ensure safe operations and the public’s trust of AVs. In this study, we aimed to provide another research evidence to enhance such understanding with the use of external interfaces for facilitating the interaction between pedestrians and AVs. We developed five external interfaces, including text, symbol, animated-eye, a combination of text and symbol, and speed. These interfaces communicated five types of information, including (1) intent of AV; 2) advice to pedestrians of what to do, (3) AV’s awareness of pedestrians, (4) combination of intent and advice, and (5) vehicle movement (i.e., speed). We tested the interfaces through two field studies at uncontrolled intersections with crosswalks. The Wizard of Oz method was used, in which an experimenter worked as a driver in an instrumented vehicle and wore an outfit to be invisible to the pedestrians, thus rendering the set-up to simulate an AV interacting with a pedestrian. The interfaces were displayed on an LED panel mounted on the AV. Results showed that the AV’s external interface did not change pedestrians’ response time in comparison with the baseline without any interface. There was no statistically significant difference in response time among the external interfaces either. According to the post-experimental interview, vehicle movement pattern (e.g., vehicle speed) continued to be a significant cue for pedestrians to decide when to cross the intersections. Participants perceived the communication of the AV’s intent and vehicle speed as more beneficial than the communication of AV’s awareness. The subjective ratings showed positive effects of those interfaces that were easy to understand (e.g., text interface and speed interface), which also helped pedestrians feel safer when interacting with the AV.

自动驾驶汽车（AVs）正在迅速开发并在公共道路上进行测试，但是并未对行人与AV的交互进行全面了解或彻底调查，以确保安全操作和公众对AV的信任。在本研究中，我们旨在提供另一项研究证据，以通过使用外部接口促进行人和AV之间的交互来增强这种理解。我们开发了五个外部界面，包括文本，符号，动画眼，文本和符号的组合以及速度。这些接口传达了五种类型的信息，其中包括：（1）AV的意图；2）向行人提供行事建议，（3）AV对行人的意识，（4）意向和建议的结合，以及（5）车辆行驶（即速度）。我们通过两个人行横道在人行横道的非受控交叉点上对界面进行了测试。使用了绿野仙踪（Wizard of Oz）方法，在该方法中，实验人员在仪表车辆中担任驾驶员，并穿着行人看不见的服装，从而渲染了设置以模拟与行人交互的AV。接口显示在安装在AV上的LED面板上。结果表明，与没有任何接口的基线相比，AV的外部接口不会改变行人的响应时间。外部接口之间的响应时间也没有统计学上的显着差异。根据实验后的采访，车辆的行驶方式（例如，车速）仍然是行人决定何时穿越十字路口的重要线索。与会者认为，传达AV的意图和车速比传达AV的意识更为有益。主观评分显示了那些易于理解的界面（例如，文本界面和速度界面）的积极影响，这也帮助行人在与AV互动时感到更加安全。