Yielding Light Signal Evaluation for Self-driving Vehicle and Pedestrian Interaction

Abstract

An external Human-Machine-Interface (eHMI) signaling the vehicle’s intended movements facilitates pedestrians’ encounters with self-driving vehicles (SDV). However, there is no standard for automated driving system (ADS) lamps today. This study compares the efficacy of a steady, a flashing and a sweeping light signal to communicate an SDV’s intention to yield. The eHMI designs were evaluated at an unsignalized intersection with participants crossing in front of a yielding Wizard-of-Oz SDV. We analyzed crossing behavior and conducted questionnaires and structured interviews with N = 30 participants to identify eHMI design recommendations. Our research provides evidence that a steady and a flashing signal facilitate user experience, learnability and likeability more than a sweeping light. With a flashing signal, pedestrians tend to cross sooner compared to a sweeping signal, and thus improving traffic flow. Design adjustments to the present signals are proposed. This paper provides guidance in the development of a standardized yielding light signal.