LAUSR

In order to facilitate safe and efficient interactions between autonomous vehicles (AVs) and pedestrians, lighting communication functions through extended signal forms such as light patterns and pictograms are of particular interest to express AV intentions. Currently, there is no consensus on which signal form should be used for Autonomous Vehicle-to-Pedestrian (AV2P) communications. Considering that the understandability of signal forms is crucial for the effectiveness of AV2P communications and thereby for choosing the appropriate signal form, we conducted a controlled investigation, consisting of designing forty-nine signals in the forms of light patterns and pictograms to express the vehicle yielding intention, and evaluating their performance in terms of understandability through monitor-based tests with more than five hundred online participants. It is found that, with the blank background where no external influence existed, the light patterns performed badly for correctly expressing the vehicle yielding intention but they were able to convey a warning message. The pictograms performed relatively well for expressing the yielding intention, but the diverse types of confusion were observed for those which were not well designed. With the vehicle-pedestrian encounter scenario where the vehicle yielding behaviors were explicit, the light patterns and the pictograms all performed well and the difference between them became less evident. These findings add new insights on the difference of understandability between light patterns and pictograms as available signal forms for AV2P communication functions, and are discussed in terms of usage recommendations in future road systems.