Car Seat Booster Safety – All You Need To Know

Car Seat Booster Safety - All You Need To Know

When it comes to moving your child onto a booster, there can be some confusion about when is the right time to do this and what type of booster to use. In this blog, we explain the differences between high back boosters and booster cushions as well as the guidelines you need to follow to keep your child safe.

When should my child use a booster?

Car seat harnesses last until 18kg on R44 restraints, and to 105cm on iSize restraints. Therefore, your child is safest staying in a harness until they have outgrown it. Your child can move into a high back booster when they meet the minimum limits for the booster

You child is then legally required to use an appropriate child seat until they’re 12 years old OR 135cm – whichever comes first.

High Back Booster, or a Booster Cushion?

Booster cushions and high back boosters are not the same, and offer very different levels of protection.  A booster cushion simply raises a child up, and provides no side impact protection. It also cannot route the shoulder belt correctly.  We recommend that your child travels in a high back booster seat, with deep, padded side wings, until it’s outgrown.

High Back Booster, or a Booster Cushion

It’s very difficult to protect children against side impacts. This is because there’s such little space between the child and point of impact. The lack of space means there’s very little time to absorb the energy from whatever has hit the door, away from the child. This is why, as well as having deep, padded side wings, we have developed Side Impact Cushion Technology (SICT), which can be found on our KIDFIX range.

SICT is an additional layer of side impact protection, which absorbs 25% of the energy forces away from your child. It also pushes the seat and child away from the force of impact.

Car Seat Booster Safety - All You Need To Know


When your child moves up to a high back booster, you have the choice of using ISOFIX to secure the booster to the vehicle, or a non-ISOFIX high back booster.

The benefit of using the vehicle’s ISOFIX points to secure the booster are:

  1. The seat belt only works to restrain your child in a collision
  2. When you are driving without your child, the seat is secured to the vehicle with the ISOFIX. As it’s not loose on the back seat, you don’t have to remember to strap it in when not in use!  A loose booster will become a projectile in a collision.

While both ISOFIX and Non-ISOFIX boosters are safe, ISOFIX boosters do offer better performance in a collision.

Correct Belt Routing

One of the biggest errors made on booster fitting, is when the seat belt is not placed over the child correctly or the child’s movement on a journey causes the seat belt to become mispositioned. On forward facing child seats, the guides for the seat belt are red. The lap belt should be placed over your child’s lap, against the red markers, and the shoulder belt should go through the shoulder belt guide.

A correct belt routing is:

1. The lap belt against the red guides, not over the armrests or behind the guides

2. The shoulder belt on the buckle side, sits on top of the lap belt, against the red guide

3. The shoulder belt then runs diagonally across your child’s torso, and must sit within the red belt guide

4. The headrest should be set at the correct height for your child. At the back of the headrest on Britax boosters, there is a handle. If you squeeze this handle up, you can lift the headrest up and increase the height to suit your child.

Car Seat Booster Safety - Correct Seat Belt Route
Correct Seat Belt Route

5. The SecureGuard on the Britax KIDFIX II models creates a fourth attachment point for greater safety and helps to ensure that the adult lap belt remains in the optimal position over the pelvic bones, even when a child moves during the journey.

Car Seat Booster Safety - Secureguard