Last week was National Child Passenger Safety Week, a nationwide campaign to educate drivers and to raise their awareness of the appropriate use of car seats. The campaign is part of the National Highway Traffic Safety Administration’s efforts to reduce the number of children injured or killed in car accidents. The NHTSA and other organizations have good reason to pursue the goal: Research has shown that motor vehicle accidents are among the most common causes of death for children between the ages of 1 and 13.

Put those kids in car seats, though, and the risk of serious and fatal injury falls by 71 percent for infants and 45 percent for kids in grade school. The Center for Disease Control and Prevention put it in more heartwrenching terms last year: From 2002-2011, an additional 800 children’s lives could have been saved if car seats were used by 100% of 0-4 year olds. Just as seat belts save the lives of adults, car seats and booster seats save children’s lives—but child restraint systems have to be used right to be effective.

There are four basic types of restraints for children: rear-facing car seats, front-facing car seats, booster seats and seat belts. If you are trying to figure out which one to buy, remember that your child’s age is just one factor in choosing the right system; weight and height should be considered as well. The manufacturers’ instructions should specify height and weight restrictions for the particular model. Sites like offer materials about choosing the right system for each stage of a child’s development.

Age is just one factor: Height and weight must also be taken into consideration.

For example: Most sources, and some state laws, say that an infant—that is, children from birth to 12-months-old—should be in a rear-facing car takes it a step further: Kids should be in rear-facing car seats as long as possible, because the seats offer extra protection to the child’s neck and spinal cord. In a crash, the seat (if installed and used properly) will move with the baby.

When your child outgrows the rear-facing seat, the next step is a front-facing car seat. Again, pay close attention to the manufacturer’s instructions and restrictions. Generally, kids between 1- and 7-years-old use front-facing seats. The major safety difference here is that the seat limits forward movement in a crash — it doesn’t offer the same level of protection to the whole body that the rear-facing seat does.

The next step is a booster seat. As usual, the transition is only appropriate if your child has met the front-facing car seat’s height and weight limits. The age range for booster seats is about 7 to 12 years old. The primary function of a booster seat is to make sure the seat belt is placed appropriately: The lap belt should be snug across the upper thighs, and the shoulder belt should be snug across the shoulder and chest; the shoulder belt should not impinge on the child’s face or neck.