What's required for children under age four weighing less than 40 pounds?

• They must use a rear-facing child seat with a five-point harness in the back seat.
  Explanation:

  "Children under the age of four and weighing less than 40 pounds must be secured in a federally approved, rear-facing child passenger restraint system with a five-point harness, positioned in the vehicle's rear seat."
• They can sit in the front seat with a regular seat belt.
• They don't need any special seat if sitting with an adult.
• They must sit in a booster seat in the front seat.