Stages of Seat Safety - Stage 3


Booster Seats

install a booster seat

When a child has outgrown the forward facing, harnessed car seat, it’s time to use a booster. Children should never go into a booster before a minimum weight of 40 lbs AND before age 4. Both milestones must occur before boostering. We recommend that children stay harnessed until between age 5 and 6.

Boosters provide “artificial hips” for children who do not yet have them. Between ages 5 and 6, there are some developmental things that happen in the pelvis which makes using a seatbelt much safer. In adults, the seat belt rides on part of the hip, called the iliac crest. It holds the belt out of the soft tissues of the stomach and prevents the belt from hurting internal organs in a crash. (Seat belt syndrome) In order to be born and make it thru the birth canal, children have very narrow hips. This crest doesn’t begin to flare or widen until about age 5-6. When it does, it makes boosters safer to use. Children at this age also have better control over their behavior, allowing for maintained correct belt use.

Boosters position the adult belt so that it fits the child properly. If the child moves the belt behind his back, the belt is not positioned correctly and will not work to restrain the child. This is when injury occurs.

Booster must always be used with the lap and shoulder belt; NEVER with a lap only belt.

Why? Take a look at these two crash tests:

With a lap only belt.

With the lap shoulder belt.

Notice how much head movement the child in the lap only belt has? That’s what the shoulder belt prevents. Here in New Hampshire, Children must ride in a booster until two things happen.

  1. The child turns 8 years old, AND
  2. The adult belt alone fits them correctly.

If either milestone is missed, the child must stay in a booster. Also note, different cars have different layouts. A child who fits into the adult belt without a booster in one car may not fit into another. Test every time.



To judge if the adult belt fits, take the 5 step test.

  1. Does the child sit all the way back against the auto seat?
  2. Do the child's knees bend comfortably at the edge of the auto seat?
  3. Does the belt cross the shoulder between the neck and arm?
  4. Is the lap belt as low as possible, touching the thighs?
  5. Can the child stay seated like this for the whole trip?

If you answered "no" to any of these questions, your child still needs a booster seat. Your child will be more comfortable, too! This last video is sad, but demonstrates clearly why children should remain in boosters.

Children should remain in a booster until this test can be passed. This may be 8, 9, 10, 11, 12 or even 13!

install this seat
seat belts
install a different seat

new hampshire office of highway safety
children's hospital at dartmouth-hitchcock
new hampshire office of highway safety
children's hospital at dartmouth-hitchcock
safe kids new hampshire
safe kids new hampshire