The **headrest** is a **passive safety** device that protects the neck and cervical spine in the event of a sudden impact. It is crucial to adjust it correctly to reduce the risk of injury in a collision. The top of the headrest should be at the same height as the top of the passenger's head, and the distance between the head and the headrest should be four centimeters or less. This helps minimize neck movement during an impact, thereby reducing the risk of injury.

In comparison, although the **seat belt** and **ABS brakes** are important for safety, they are not specifically designed to protect the neck in a collision. The seat belt prevents the body from moving forward, and ABS brakes help maintain control of the vehicle during sudden braking, but neither of these elements has the specific function of protecting the cervical spine as the headrest does.