Robotic Delivery Worker in the Dark: Assessment of Perceived Safety from Sidewalk Autonomous Delivery Robots’ Lighting Colors

Abstract

Sidewalk autonomous delivery robots (SADRs) share sidewalks with pedestrians and may affect their perceived safety. In outdoor nighttime environments, the color of the lights on SADRs serves as a noticeable form of communication that can influence human emotions. Therefore, this study investigated whether the perceived safety of SADRs varied with the colors of their lighting. In this study, an experiment (n = 30) was conducted where participants walked towards a robot from opposite directions to interact. The perceived safety of five different lighting colors (red, yellow, blue, green, and white) on SADRs was measured before and after the interaction using two perceived safety scales. The results showed significant differences in participants’ perceived safety for the robot’s red, green, blue, and yellow lighting before and after the interaction. Red lighting was rated the least perceived safe, while white and yellow lighting were rated the most perceived safe. Additionally, gender significantly influenced the perceived safety assessments, with females reporting lower perceived safety than males. These findings are valuable when designing SADRs that enhance pedestrians’ perceived safety, thereby facilitating their integration into broader environments in the future.