Which component is primarily responsible for tightening seat belts upon impact?

The seat belt pre-tensioner is designed to tighten the seat belt during a collision, helping to secure the occupant in their seat and minimizing movement. This component works in conjunction with the airbag system; however, the primary function of the pre-tensioner is to ensure the belt is snug against the body as the crash occurs, effectively reducing the risk of injury.

Upon impact, the pre-tensioner's mechanism activates, often using a small explosive charge or a pyrotechnic device, which retracts the seat belt to remove excess slack. This action effectively secures the occupant by holding them in place, reducing the likelihood of contact with the vehicle interior during a crash.

The airbag system, while crucial in providing additional protection, deploys after the pre-tensioner activates and serves a different function by cushioning the occupant upon impact. The vehicle frame and the steering column do not have a direct role in the function of tightening seat belts during an impact; rather, they contribute to the overall crash safety of the vehicle by absorbing energy and maintaining structural integrity.