An unmanned aerial vehicle (UAV) is disclosed that includes a retractable payload delivery system. The payload delivery system can lower a payload to the ground using an assembly that secures the payload during descent and releases the payload upon reaching the ground. The assembly can also include a bystander communication module for generating cues for bystander perception. While the assembly securing the payload is being lowered from the UAV, the bystander communication module can generate an avoidance cue indicating that bystanders should avoid interference with the assembly. The assembly also includes sensors that generate data used, at least in part, to determine when the descending assembly is at or near the ground, at which point the assembly releases the payload. The bystander communication module can then cease the avoidance cue and the UAV can retract the assembly.