Age-based Differences in Pedestrians’ Feeling of Trust and Safety when Crossing in Front of a Real Communicating Self-driving Car During Daytime or Nighttime

Abstract: The introduction of self-driving cars (SDCs) onto public roads will raise challenging issues to ensure traffic fluency. One of these is to guarantee pedestrians feel safe and confident when encountering this new type of vehicle in order to promote pedestrian crossing in front of SDCs. Hence, the aim of the study was to investigate the impact of different types of external Human-Machine Interfaces (eHMIs) indicating the yielding behaviour of a SDC on pedestrians’ feeling of safety and trust. Thirty-four participants (19 young adults aged 22-41 and 15 older adults aged 63-80) volunteered to take part in the experiment. Participants were requested to cross in front of a real SDC which gave way to them on a crosswalk. The SDC was equipped with devices that could send different types of eHMI signals. In the hourglass condition, two displays located in front of the SDC were showing a luminous hourglass when the SDC yielded (daytime and nighttime tests). In the safety zone condition, projectors were sending a cyan light signal onto the ground around the SDC when it yielded (nighttime tests). In the no eHMI condition, none of the above-mentioned signals were shown. The participants were not informed in advance about the presence of the eHMI signals or their meaning. After each crossing, they were asked to rate their level of trust (on a Likert scale from 1- no trust at all to 7- totally in trust) and their level of safety (on a Likert scale from 1- not secure at all to 7- totally secure) during their crossing in front of the SDC. Finally, semi-directive interviews were lead in order to gather additional information such as the cues used by the participants in their crossing decision-making, other than the eHMIs signals. Our results showed high levels of self-reported trust and safety overall. Moreover, a significant main effect of the age group indicating a stronger level of trust during the crossing of the older adults as compared to the young adults was found. However, no significant effect of the age group nor of the type of eHMI signal were found on the participants’ feeling of safety during their crossing. In addition, no significant effect of the type of eHMI signal was found on the participants’ level of trust during their crossing. Yet, the analysis of the semi-directive interviews revealed that the young adults were likely to use more implicit communication cues exhibited by the SDC during the nighttime tests as compared to the daytime tests while the older had a more conservative crossing decision-making strategy during both daytime and nighttime tests. These findings provided understanding elements of pedestrians’ crossing experience with regards to communicating SDCs in realistic conditions.

Keywords: Pedestrian, Ageing, Self-driving car, External Human-Machine Interface, Crossing decision, Safety, Trust

DOI: 10.54941/ahfe1005468

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