What is one of the key components of a personal fall arrest system?

A safety harness is a key component of a personal fall arrest system because it is designed to securely attach the worker to an anchorage point and helps distribute the forces experienced during a fall. This system is crucial in preventing injuries or fatal accidents when working at heights by providing a way to catch and hold an individual in the event of a fall. A properly fitted safety harness ensures that the worker remains in a safe position while allowing for mobility and functionality on the job site. The other options listed, while important for overall safety, do not serve the specific purpose of arresting a fall. Reflective vests enhance visibility, hard hats protect against falling objects, and gloves provide grip and protection, but none are equipped to secure an individual against the risks associated with falling from elevated surfaces.