Crossing in the dark: Investigating the effect of vehicle kinematics and eHMI on older pedestrians’ crossing behavior in a virtual reality experiment

INTRODUCTION: There has been a surge in interest in evaluating new forms of communication for Automated Vehicles (AVs), namely external human-machine interfaces (eHMIs). However, much of the research has focused on younger pedestrians' crossing behavior and experience while interacting with AVs and in daytime conditions with optimum visibility. Given that the AVs will interact with pedestrians of all ages, and at all times, there are still key knowledge gaps that need to be addressed. METHOD: Using a cave-based pedestrian lab, this study investigated the effect of AV kinematics (i.e., deceleration, speed, time gaps) and eHMI (a Slow Pulsing Light Band) on the crossing behavior of younger adult pedestrians (18-35 years old) and older pedestrians (64-77 years old), in both daytime and nighttime virtual environments. RESULTS: Results showed that older pedestrians adopted a different crossing strategy than younger pedestrians. If they decided to cross in the non-deceleration trials, they compensated for their longer crossing duration by initiating their crossing earlier than younger pedestrians. However, if they decided to wait until the deceleration was more prominent, they waited longer than the younger pedestrians. Generally, pedestrians reported feeling less safe and behaved more cautiously during nighttime crossings (i.e., less likely to cross, longer crossing initiation time (CIT) when there was no eHMI). eHMI decreased CIT for both age groups but was interpreted and used differently between younger and older pedestrians. Finally, an eHMI failure trial mainly affected younger pedestrians. CONCLUSIONS AND PRACTICAL APPLICATIONS: This knowledge should inform the design of effective communication for AVs for younger and older pedestrians.