Final answer:
Children under 4 years old or weighing less than 40 pounds must be secured in a safety seat in a vehicle. This is a legal requirement to ensure child safety during collisions, alongside other vehicle safety features like airbags.
Step-by-step explanation:
The question pertains to the safety regulations regarding children in vehicles. For a child under 4 years old or weighing less than 40 pounds, it is mandated they be secured in an approved safety seat while the vehicle is in motion. This requirement is a safety measure to protect young passengers from injury in the event of an accident. It's part of broader child protection laws which often include guidelines for different age groups, such as children ages 0 to 2.5, children ages 2.5 to 6, and so on. The use of car seats, along with other safety features like airbags, greatly reduces the risk of serious injuries during a collision, making it crucial for the child's well-being.