  In comparison to conventional traffic designs, shared spaces promote a more
pleasant urban environment with slower motorized movement, smoother traffic,
and less congestion. In the foreseeable future, shared spaces will be populated
with a mixture of autonomous vehicles (AVs) and vulnerable road users (VRUs)
like pedestrians and cyclists. However, a driver-less AV lacks a way to
communicate with the VRUs when they have to reach an agreement of a
negotiation, which brings new challenges to the safety and smoothness of the
traffic. To find a feasible solution to integrating AVs seamlessly into
shared-space traffic, we first identified the possible issues that the
shared-space designs have not considered for the role of AVs. Then an online
questionnaire was used to ask participants about how they would like a driver
of the manually driving vehicle to communicate with VRUs in a shared space. We
found that when the driver wanted to give some suggestions to the VRUs in a
negotiation, participants thought that the communications via the driver's body
behaviors were necessary. Besides, when the driver conveyed information about
her/his intentions and cautions to the VRUs, participants selected different
communication methods with respect to their transport modes (as a driver,
pedestrian, or cyclist). These results suggest that novel eHMIs might be useful
for AV-VRU communication when the original drivers are not present. Hence, a
potential eHMI design concept was proposed for different VRUs to meet their
various expectations. In the end, we further discussed the effects of the eHMIs
on improving the sociality in shared spaces and the autonomous driving systems.
