  eHMIs refers to a novel and explicit communication method for pedestrian-AV
negotiation in interactions, such as in encounter scenarios. However,
pedestrians with limited experience in negotiating with AVs could lack a
comprehensive and correct understanding of the information on driving
intentions' meaning as conveyed by AVs through eHMI, particularly in the
current contexts where AV and eHMI are not yet mainstream. Consequently,
pedestrians who misunderstand the driving intention of the AVs during the
encounter may feel threatened and perform unpredictable behaviors. To solve
this issue, this study proposes using the pre-instruction on the rationale of
eHMI to help pedestrians correctly understand driving intentions and predict AV
behavior. Consequently, this can improve their subjective feelings (ie. sense
of danger, trust in AV, and sense of relief) and decision-making. In addition,
this study suggests that the eHMI could better guide pedestrian behavior
through the pre-instruction. The results of interaction experiments in the road
crossing scene show that participants found it more difficult to recognize the
situation when they encountered an AV without eHMI than when they encountered a
manual driving vehicle (MV); in addition, participants' subjective feelings and
hesitations while decision-making worsened significantly. After the
pre-instruction, the participants could understand the driving intention of an
AV with eHMI and predict driving behavior more easily. Furthermore, the
participants' subjective feelings and hesitation to make decisions improved,
reaching the same criteria used for MV. Moreover, this study found that the
information guidance of using eHMI influenced the participants' walking speed,
resulting in a small variation over the time horizon via multiple trials when
they fully understood the principle of eHMI through the pre-instruction.
