External human-machine interfaces (eHMIs) may be useful for communicating the intention of an automated vehicle (AV) to a pedestrian, but it is unclear which eHMI design is most effective. In a crowdsourced experiment, we examined the effects of (1) colour (red, green, cyan), (2) position (roof, bumper, windshield), (3) message (WALK, DON’T WALK, WILL STOP, WON’T STOP, light bar), (4) activation distance (35 or 50 m from the pedestrian), and (5) the presence of visual distraction in the environment, on pedestrians' perceived safety of crossing the road in front of yielding and non-yielding AVs. Participants (N = 1434) had to press a key when they felt safe to cross while watching a random 40 out of 276 videos of an approaching AV with eHMI. Results showed that (1) green and cyan eHMIs led to higher perceived safety of crossing than red eHMIs; no significant difference was found between green and cyan, (2) eHMIs on the bumper and roof were more effective than eHMIs on the windshield, (3) for yielding AVs, perceived safety was higher for WALK compared to WILL STOP, followed by the light bar; for non-yielding AVs, a red bar yielded similar results to red text, (4) for yielding AVs, a red bar caused lower perceived safety when activated early compared to late, whereas green/cyan WALK led to higher perceived safety when activated late compared to early, and (5) distraction had no significant effect. We conclude that people adopt an egocentric perspective, that the windshield is an ineffective position, that the often-recommended colour cyan may have to be avoided, and that eHMI activation distance has intricate effects related to onset saliency.

外部人机界面 (eHMI) 可能有助于将自动车辆 (AV) 的意图传达给行人，但尚不清楚哪种 eHMI 设计最有效。在一项众包实验中，我们检查了 (1) 颜色（红色、绿色、青色）、（2）位置（车顶、保险杠、挡风玻璃）、(3) 信息（步行、不要步行、将停止、获胜）的影响'T STOP，灯条），(4) 激活距离（距行人 35 或 50 m），以及 (5) 环境中视觉干扰的存在，对行人在让行前过马路的感知安全性和非收益 AV。参与者 ( N = 1434）在使用 eHMI 观看接近的 276 个视频中的 40 个随机视频时，当他们感到安全时必须按下一个键。结果表明：（1）绿色和青色 eHMI 比红色 eHMI 带来更高的穿越安全感知；在绿色和青色之间没有发现显着差异，(2) 保险杠和车顶上的 eHMI 比挡风玻璃上的 eHMI 更有效，(3) 对于让 AV，与 WILL STOP 相比，WALK 的感知安全性更高，其次是灯酒吧; 对于非屈服 AV，红色条产生与红色文本相似的结果，（4）对于产生 AV，与晚期激活相比，红色条在早期激活时导致较低的感知安全性，而绿色/青色 WALK 在晚期激活时导致更高的感知安全性与早期相比，和（5）分心没有显着影响。我们得出的结论是，人们采用以自我为中心的观点，