Self-Driving Vehicles and Pedestrian Interaction: Does an External Human-Machine Interface Mitigate the Threat of a Tinted Windshield or a Distracted Driver?

Abstract

With self-driving vehicles (SDVs), pedestrians lose the possibility of making eye contact with an attentive driver. This study investigated whether an external human-machine interface (eHMI) displaying the automated driving mode (a. without eHMI vs. b. with eHMI) affects how pedestrians respond to different driver’s states: (1) attentive driver, (2) tinted windshield, (3) distracted driver (within-subject design). At a test site, N = 65 pedestrians crossed a pedestrian crossing while a Wizard-of-Oz SDV approached. We assessed perceived safety and crossing onset times after each trial. Findings reveal that without an eHMI, pedestrians felt significantly less safe if the windshield was tinted or the driver was distracted as compared to an attentive driver. With an eHMI, pedestrians did not differ in perceived safety with regard to the driver’s state. We observed no significant differences in pedestrians’ crossing onset times. We conclude that an eHMI helps pedestrians to not consider the driver’s state.