Impact of Highly Automated Vehicle (L4/5 AV) External Communication on Other Road User Behaviors

The advancement of SAE Level 4+ Automated Vehicles (L4/5 AVs) has led numerous stakeholders to develop external communication systems for these vehicles. Most research on vehicles emulating these displays has been conducted using one vehicle. However, it is vital to understand how communication to vulnerable road users (VRUs) is affected when multiple L4/5 vehicles are present. This study examined how L4/5 AVs can best communicate their intentions (e.g., turning, stopping, yielding) to VRUs and drivers of conventional vehicles. Subjective and objective data was collected to assess road user responses to two vehicles emulating L4/5 displays, from both a passenger and pedestrian perspective. Participants with no prior knowledge of the experiment’s design or intent experienced three light patterns that provided information regarding L4/5 AVs’ intent to slow/stop, begin, and travel with simulated automation active. Overall, participants were overwhelmed by multiple vehicles with different light bars in their crossing vicinity and found it difficult to prioritize attention. These results have implications for future design of external communication displays on L4/5 AVs. Training may be necessary for road users, given the relatively low percentage of participants who understood the meaning of these displays after multiple exposures and participants’ confusion in where to look and how to interpret the intention of the displays when multiple vehicles were present.