What safety unit is classified as supplemental in a vehicle?

Airbags are classified as a supplemental safety unit in a vehicle because they are designed to work in conjunction with primary safety features, such as seat belts, to enhance occupant protection during a collision. Unlike seat belts, which are the primary restraint system that actively holds passengers in place, airbags deploy during a crash to cushion and protect occupants from impacting hard surfaces within the vehicle. This supplementary role is critical in reducing the risk of injury, particularly in moderate to severe accidents.

In contrast, other options like seat belts are essential for holding passengers securely, while brakes are critical for stopping the vehicle safely, and child safety locks serve to keep rear doors secure, especially for young passengers. While all these components play significant roles in vehicle safety, airbags specifically serve as an additional layer of protection that activates in response to the conditions of a collision, reinforcing their classification as a supplemental safety feature.