What is the primary purpose of a vehicle's safety chain when towing a trailer?

The primary purpose of a vehicle's safety chain when towing a trailer is to provide an emergency attachment. Safety chains are designed to catch the trailer in the event that it becomes unhitched from the towing vehicle. This feature serves as a critical safety measure, preventing the trailer from completely detaching and potentially causing an accident or hazard on the road.

In the scenario where the primary hitch fails, the safety chains help to keep the trailer connected to the towing vehicle, allowing for some control until the vehicle can come to a safe stop. The proper installation and condition of these chains are vital for safe towing practices.

The other potential purposes mentioned in the incorrect options do not align with the actual function of safety chains. For example, enhancing fuel efficiency, supporting the trailer's weight, or improving the vehicle's turning radius are not related functions; instead, they pertain to other aspects of towing and vehicle dynamics. Safety chains are specifically about safety and maintaining control in emergency situations.