Booster seats are used to position a child or toddler in a car seat that's designed to fit an adult. Without a booster seat, the child may not be in the correct position to allow a seat belt and shoulder harness to protect him in the event of an accident. Booster seat height, age and weight requirements vary by each state. When in doubt, it's usually best to go with the most stringent safety requirements.
Booster seats are required for children who have outgrown their car seats. States often set age, weight and height requirements for booster seats. Rear-facing infant seats are usually required until a child is 1 year old or 9kg. in weight. Forward-facing car seats are usually required until a child is 18kg. to 36kg. Car seats are required for height of less than 90cm (36 inches) in Texas, 100cm (40 inches) in Kentucky, 137cm (54 inches) in Rhode Island and 144cm (57 inches) in Hawaii. After these specifications have been exceeded, most states require the use of a booster seat.
A booster seat is usually a specially designed bottom support to "boost" the child to a level where the seat belt and shoulder harness are effective in the event of a crash. Some booster seats also have side protection that encompasses the child's torso, neck and head. Maximum age for required booster use varies from four years in Alaska, five years in Florida and Texas, to six to eight years in most other states. Note that the minimum age for not using a booster seat doesn't relieve the requirements for minimum height or weight to use adult restraints.
Children must use a booster seat until they exceed a height of 50 inches in Kentucky, 139cm (55 inches) in New Hampshire, and 144cm (57 inches) in most other states. Not all states have a height requirement for booster seats. For combined height, weight and age requirements, see Resource 1.
Many states are turning toward a minimum safety standard for adult passenger restraints. These are widely accepted as eight years' minimum age and 36kg. or more in weight. Following a more stringent standard is the safest path to follow when deciding if your child should be in a booster seat or not.
Check with your state's Department of Motor Vehicles for current regulations regarding child seats. These laws are changing frequently with pressure for more stringent safety for our children. After a child has passed the age, weight and height specifications for a car seat, he is usually required to use a booster seat. The booster seat must be used until the child reaches a minimum height, weight or age. Beyond that point, it's permissible to allow the child to use the standard adult safety belt and shoulder harness.