What does a shoulder belt primarily protect in the event of a crash?

A shoulder belt primarily protects the head and chest in the event of a crash. During a collision, the forces exerted on the body can be immense, and without proper restraint, the upper body is at significant risk of injury. The shoulder belt is designed to keep the upper body, including the head and chest, securely positioned in the seat. This maintains proper alignment and reduces the likelihood of the occupant being thrown forward or sideways, which can lead to severe injuries such as whiplash or impact injuries to the vital organs.

In the crash scenario, the shoulder belt works in conjunction with the lap belt (if used) to distribute the force of the impact across the strongest areas of the body, helping to prevent these injuries. While the other choices mention protection for different body parts or comfort, the primary purpose of the shoulder belt is centered on securing the upper torso, thus ensuring the safety of the head and chest during a crash.