Making Pick-up Maneuvers at Virtual Stops More Transparent for Following Drivers Through Rear eHMIs

In future mixed traffic scenarios, manual drivers are likely to struggle to anticipate flexible curbside stopping maneuvers of demand responsive automated shuttle buses (ASB) at virtual stops (vStops), which lack of infrastructure cues. This experimental study investigates how ASBs could use rear external human-machine interfaces (eHMI) by combining conventional and novel light signals to explicitly inform following drivers in order to improve safety in on-demand pick-up scenarios. Therefore, an online video study (N = 97) investigated rear eHMI light signals regarding perceived information quality, perceived criticality, trust, preparing for action, and user experience (UX). The results underline the effectiveness of novel eHMI designs and reveal that incorporating a displaying a bus stop symbol into eHMI designs significantly improved the understanding of following drivers compared to communicating with conventional light signals (turn indicator, brake lights) alone. Furthermore, findings of this research advise for the utilization of the well-known turn indicator as form of explicit communication at the rear of ASBs to improve interaction with following drivers at vStops. Consequently, this research contributes to a better integration of ASBs in mixed traffic environment.