What do seat belts on a school bus help to do?

Seat belts on a school bus are primarily designed to reduce the risk of injury during braking or an accident. When a bus is involved in a sudden stop or collision, seat belts help to restrain passengers, preventing them from being thrown from their seats and minimizing the impact forces that they would otherwise experience. This is particularly important in a school bus scenario where children, who may not have the same physical capabilities as adults, are more susceptible to injury.

While the other options mention potential benefits, they do not capture the primary safety function of seat belts. For instance, while seat belts might marginally reduce noise levels or provide some level of comfort, these are not the main purposes of seat belts. Protecting passengers, especially children, during unexpected events is the critical role that seat belts play in enhancing safety on school buses.