No Need for Speed? The Impact of Delivery Robot Speed on Passersby’s Perceived Comfort and Safety and Preferred Signaling Distance

Abstract Autonomous robots have the potential to assist us in various everyday tasks, including driving and package delivery. In the case of autonomous delivery robots, efficiency and safety need to be guaranteed in order for them to be deployed in real-world settings. The speed of the robot and its signaling distance emerged as crucial research focus points, greatly influencing the perceived efficiency and safety of delivery robots. This study therefore investigates the impact of different robot speeds on participants’ preferred signaling distance, perceived comfort, and safety during encounters. It also explores whether participants’ prior robot experience or pet ownership influences these factors based on the literature. We conducted an online study with 48 participants who watched videos of encounters with delivery robots at different speeds. Participants indicated when they would step aside from the robot, defining the signaling distance. An additional real-life interaction study involved 11 participants. As expected, results indicated that as robot speed increased, participants preferred a larger signaling distance and felt progressively less comfortable and safe with higher robot speeds. However, there were no significant findings related to pet ownership or robot experience. We provide a formula to calculate the most adequate distance for signaling depending on robot speed. In conclusion, careful consideration must be given to robot speed and signaling distance to ensure that participants can react in time and have comfortable, safe interactions with delivery robots in various contexts.