Comparison of External Human–Machine Interfaces for Presenting the Intention to Yield from an Automated Vehicle to a Driver

Drivers use turn signals and stop lamps to inform the surrounding environment of their intentions and behavior. However, these notifications are insufficient in reality; therefore, drivers also use gestures and eye contact to communicate with others, as necessary. However, automated vehicles that are currently being tested or put into practical use are not equipped with these communication functions. Therefore, we focus on communication methods using an external human–machine interface (eHMI). In this study, we conducted an experimental investigation using a driving simulator to examine the effect of an eHMI on a driver who intends to enter the main road from a parking lot of an off-road facility when an automated vehicle traveling on the main road presents an intention to yield. The results of a subjective evaluation indicated that the driver understanding of the eHMI was related to the number of contacts with it. When the text-display type eHMI presented specific information, drivers merging onto the mainline made their merging decisions earlier than in other conditions.