Which feature primarily protects passengers in the event of a rear-end collision?

Active head restraints are designed specifically to protect passengers in the event of a rear-end collision. Their primary function is to move forward and upward in response to a rear impact, which helps to limit the backward movement of the occupant's head. This mechanism reduces the risk of whiplash injuries by aligning the head more closely with the spine, absorbing some of the force of the impact and minimizing the potential for injury to the neck.

While adaptive cruise control, automatic emergency braking, and rear parking sensors enhance overall vehicle safety and assist in avoiding collisions, they do not provide direct protection to passengers during the impact itself. Instead, their roles involve preventing collisions or assisting in parking maneuvers, which does not address the immediate protection of occupants when a rear-end collision occurs.