When air bags are installed in a vehicle:

1. It is unnecessary to install seat belts in that vehicle.
2. Correct answer: The seat belts must be fastened at all times when the vehicle is in motion.
3. If the airbag system malfunctions, seat belts should not be worn.
4. The seat belts should only be worn when the air big system malfunctions.

WhyEven with airbags you must always buckle up. An airbag is designed to work together with the seat belt.