Which safety device is essential for cranes?

The essential safety device for cranes is the horn. Horns serve a critical function in crane operation by alerting nearby workers and personnel of the crane's movements or potential hazards. This auditory warning helps prevent accidents by ensuring that individuals in the vicinity are aware of the crane's activity, especially during lifting operations or when the crane is in motion.

While safety harnesses, reflective tapes, and emergency lights are important for overall site safety, they do not directly enhance operational safety and communication in the same way a horn does during crane operation. Safety harnesses are more about fall protection for personnel working at height, reflective tapes primarily enhance visibility of structures or objects, and emergency lights provide illumination in emergencies but do not communicate the crane's operational intent to nearby workers. Thus, the horn is key to maintaining a safe working environment around cranes.