Which safety feature must be installed and operational in all vehicles?

Seat belts are a critical safety feature that must be installed and operational in all vehicles because they protect occupants in the event of a collision. They work by restraining the body's movement, reducing the chance of injury by preventing occupants from being thrown forward or ejected from the vehicle. The use of seat belts is supported by numerous studies showing that they significantly decrease the risk of fatal injuries in traffic accidents.

While airbags, brake lights, and windshield wipers are also important for vehicle safety and functionality, they do not have the same mandatory requirement across all types of vehicles. In many jurisdictions, seat belts must be present and operational in cars, trucks, and other vehicles as part of road safety laws. This universal requirement emphasizes the role of seat belts as a fundamental safety measure for everyone traveling in a vehicle.