What is required on passenger vehicles concerning seat belts?

Passenger vehicles are required to have seat belts for all front seats, which is why this answer is correct. The regulations typically ensure that the driver and front seat passengers are protected by seat belts, as these seats are most directly involved in the operation of the vehicle and are generally positioned at the front of the vehicle where the impact of a collision is most significant. This requirement is crucial in enhancing safety for the occupants of the vehicle.

In many jurisdictions, although there are standards for front seat belts, there may be different regulations regarding the rear seats, such as whether all seats must have seat belts or if they are optional. Options related to only needing a seat belt for the driver's seat or treating rear seat belts as optional do not align with the broader safety requirements that prioritize passenger protection.