HMI-based Communication Methods for Negotiation between a Manually Driven Vehicle Driver and an Autonomous Vehicle in an Ambiguous Traffic Scenario

Autonomous vehicles (AV) are considered to be applicable in a predictable future, especially in urban areas. Generally, two human drivers in manually driving vehicles (MVs) can negotiate the right-of-way through communications when they encounter in ambiguous traffic scenarios, e.g., equal narrow passage with an obstacle on each side. However, a human driver may face some communication issues when he/she needs to negotiate with a driver-less AV. To convey the intention of AV to MV drivers, a highly comprehensible communication strategy is necessary. This work proposed three types of HMI: a) internal HMI (iHMI) based on vehicle-to-vehicle communications; b) external HMI (eHMI) on AV and c) using both of them synchronously (iHM+eHMI). Participants experienced three HMIs through online survey videos and performed subjective evaluations. We found that the iHMI was significantly more effective for the communication between AV-MV driver than the eHMI and iHM+eHMI. Besides, although there were no significant differences among the three HMIs in the other subjective evaluation items, iHMI provided better evaluations of understanding, safety, and stress, while eHMI had the lowest evaluation of trust.