Why Boosters Work

Posted in: Booster Seats

Boosters improve how the vehicle safety belt fits the child and how the child fits the vehicle seat.

The booster raises the child up, making the shoulder belt fit correctly.

The shoulder belt crosses the center of the chest and rests between the shoulder and neck. The child is comfortable – and therefore not tempted to place the shoulder belt behind the back or under the arm (both of which are dangerous)

girl on booster with captionsThe booster seat is shallow, eliminating the need to slouch.

The booster’s shallower seat allows the child’s knees to bend comfortably over the edge without having to slouch. The child’s back rests against the back of the vehicle seat (in a backless booster) or booster seat (in a high-backed booster), allowing the safety belt to tighten appropriately against the child’s upper body. The child is again more comfortable and of course safer.

The booster includes seat belt guides to prevent the seat belt from approaching the child’s abdomen.

The booster has either small handles, arm rests, guides or slots that help position the lap portion of the belt low and flat across a child’s upper thighs and prevent the lap belt from riding up onto the abdomen. This eliminates the risk of “seat belt syndrome.”

Boosters in Action: Booster vs. No Booster

Booster seats work in conjunction with lap and shoulder belts to restrict head movement during a crash. The farther forward the head moves, the more likely it is to be injured. These diagrams, which are courtesy of the Children’s Hospital of Philadelphia, show the difference in head movement in three different scenarios.

Lap and Shoulder Belt worn incorrectly, No Booster

In the first diagram, a child who should be using a booster seat is instead using just a lap-and-shoulder belt. However, he has put the shoulder portion of his seat belt behind his back, which means his upper body is not restrained. Look how far his head moves in a crash!


Lap and Shoulder belt worn correctly, No Booster

In the second diagram, a child who should be using a booster is instead using just a lap-and-shoulder belt, albeit correctly. His head still moves quite far forward during a crash.


Lap and Shoulder Belt worn correctly WITH Booster

In the third diagram, the child uses a booster correctly. His head barely moves forward and he will sustain much less serious injuries than the other two children in the above diagrams.


7 Responses to “Why Boosters Work”

  1. Laura says:

    What is the best spot in the car for britax frontier using 5 point harness with my 42 pound 6 year? She does not complain about the “baby” seat but my new vehicle 2014 honda pilot has center LATCH. Is that still the safest place in the car for her? Thank you!

    • She has outgrown the weight limit for using the lower anchors – so use the vehicle’s seat belt AND top tether to secure her seat. Center is a great choice, so long as you get a secure installation.

  2. Amy says:

    When using a high back booster or the backless booster, I have my daughter use the child-lock feature of the seat belt. This forces her to stay in the correct position, which is extremely important, but I cannot find any information on what happens in the event of a collision. What are your recommendations?

    • For kids riding in boosters (or bigger kids/adults not in boosters but just using the seat belt) it is not recommended to “lock” the seat belt as you are asking – as research shows that it changes how the body moves into the belt in a crash and can increase the chances of the lap belt ending up in the belly which is a really dangerous place for the lap belt to be. See here for more –

  3. Shawnelle says:


    We bought the Clek Oobr for our 6.5 year old, and while she really likes the seat, she gets carsick sitting on the side-we switched from a Britax seat that was in the center-forward facing. We have 2014 a Subaru Forrester and want to figure out how to place her safely in the center to avoid her getting nauseous. What would you recommend?

    Thanks so kindly,

  4. Elizabeth says:

    Some parents tell me they think it’s enough to have their child put on a seatbelt while sitting on top of a booster–and they don’t check to see if the booster itself is strapped in too. Can you please explain whether and why it’s necessary to secure the boosterin place with the seatbelt straps (under the armrests or through the guides or clips, depending on the design)? Many thanks in advance!

    • If the seat belt is not routed properly (according to the instructions for that booster) – the following can happen in a crash:
      1. The seat belt applies the crash forces to the wrong parts of the child’s body, causing injury (for example, putting the lap belt over an arm rest will put the lap belt on the child’s belly, which is the most dangerous place for it – rather than on the strong hip bones where it needs to be).
      2. The booster flies out from under the child in a crash, leaving the seat belt very, very loose and the child very much at risk for injury.

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