Final answer:
Children under 8 years old or under 4' 9" tall must be secured in a booster seat to ensure their safety during car travel.
Step-by-step explanation:
All children under 8 years of age (unless they are taller than 4' 9") must be secured in an appropriate booster seat. This requirement ensures the safety of children who are too large for a baby carrier but too small for a standard seatbelt to offer proper restraint during a car trip. While a bicycle helmet is essential for protection when riding a bike, it is not the correct safety equipment for vehicular travel for children within the specified age or height range. For children ages 0 to 2.5 and ages 2.5 to 6, the use of a car seat or booster is especially critical to prevent injuries during transit.