What is the primary function of seat belts in a vehicle crash?

The primary function of seat belts in a vehicle crash is to safely secure passengers in their seats, minimizing the risk of injury. By keeping passengers firmly in place, seat belts are designed to prevent them from being ejected from the vehicle during a collision. This retention greatly reduces the likelihood of severe injuries or fatalities.

Each of the other choices reflects different aspects of passenger safety, but the essential role of seat belts revolves around securing individuals within the vehicle. While slowing down passengers would indeed result from the physics of how seat belts function during a crash, their main purpose is not solely to decelerate but to hold occupants in position. This anchoring allows crumple zones and other safety features of the vehicle to effectively absorb the energy of the crash, rather than the passengers experiencing that force directly.

It's also important to note that seat belts are not primarily designed to protect against side impacts or to serve as a mechanism to prevent ejection alone, even though these are significant safety benefits. The overarching design principle of a seat belt is to provide restraint and mitigate movement during an accident, which enhances overall passenger safety in the vehicle.