Using a High Back Booster Car Seat Correctly and Safely

The last stage Child Car Seat, High Back Boosters, is the easiest type of car seat to install but they are still prone to being used incorrectly and unsafely.

Weight / Height Limits
High Back Boosters either have a weight or height limit, depending on the EU Regulation that they were approved for use under.

R44 approved HBB have a weight limit of 15 kg to 36 kg.
R129 i-Size HBB have a height limit of 100 cm to 150 cm.

*We recommend rear facing for as long as possible.*

Legal Requirements in Ireland
In Ireland, a child must be in a car seat restraint until 150 cm or 36 kg. This is approximately age 11 / 12, depending on a child. Car 3 point belts are designed for adults over 150 cm so high back boosters are so important to use until a child reaches either the height or weight limit as they aid in correct belt positioning and provide side impact protection. We know it can seen as uncool by some kids to be in a high back booster seat but they need to be used for as long as possible.

Head Rest Position
The headrest on a HBB needs to be set to the correct position and adjusted upwards as a child grows. Your car seat manual will detail what this correct position is and it can differ between car seats. We have listed the correct headrest position for all the HBBs that we stock at below.

BeSafe iZi Flex Fix: Make sure that the shoulder belt is level with your child’s shoulder. 

Axkid Bigkid 2: The correct height of the headrest is when there is 1 cm between the child’s shoulder and the lower edge of the Axkid Bigkid 2 headrest.

Britax Kidfix III S: The headrest must be adjusted so that there is a space two fingers wide between the headrest and your child's shoulders.

Britax Kidfix i-Size: Two Finger width between the bottom of the Kidfix i-Size headrest and the top of a child's shoulder (as pictured below).

Britax Kidfix i-Size car seat

Shoulder Belt Guide
It is very important that the shoulder part of the car 3 point belt is put correctly into the shoulder belt guide (closest to where the car 3 point belt is positioned in the vehicle) and that it runs through and retracts smoothly through this belt guide.
If it doesn't retract smoothly this will hinder the shoulder belt from working properly in the event of a collision. You may need to move the HBB to a different vehicle seat position to see if it will work better there, if not you will need to change to another HBB that allows smooth retraction of the shoulder belt with the headrest in all height positions.  
The shoulder belt will run diagonally across the seat once the car 3 point belt is buckled into place and it should not be next to a child's neck. If it is then the headrest is not positioned correctly or the shoulder belt guide is not being used properly.

Britax Kidfix i-Size car seat

Belt Guides at side of the HBB
Another common error in HBB use is the incorrect positioning of the lap part of the car 3 point belt.
Every HBB will have guides on both sides to indicate where the car 3 point belt should go through, these are either red or green.
If a HBB has side horns both the lap and shoulder parts of the car 3 point belt needs to go underneath these, not on top (the shoulder belt will only be under one side horn, on the side diagonally across from the shoulder belt guide that you are using).

Car Seat Buckle Side

Britax Kidfix i-Size car seat

Opposite side

Britax Kidfix i-Size car seat

The lap part of the belt needs to lie low on the child’s hips and contacting the thighs as opposed to the abdominal area as this can cause serious internal injuries in the event of a accident otherwise.
If your HBB has a Lap Belt Holder it is important that it is used as it aids in the correct positioning of the lap belt as above also (shoulder belt does not go into the lap belt holder).

Britax Kidfix i-Size car seat

Some HBB have an isofix installation, otherwise they are installed with car 3 point belt only. An isofix installed HBB can also be installed with car 3 point seat belt only.

If the HBB is not installed with isofix it is very important that it is still installed with car 3 point belt when then HBB is not being used by a child. This will prevent the HBB becoming a projectile in the event of a collision.

Sitting on Vehicle Buckles
A HBB must not be sitting on top of a vehicle car seat buckle and it must be easy for the child sitting in the HBB to release the car 3 point belt in an emergency.

Making contact with the vehicle seat back rest.
Your HBB car seat manual will detail the requirement to make contact with the vehicle seat backrest. In some cases it is necessary to move up the vehicle seat headrest to allow a HBB to make contact, another alternative is to turn the vehicle headrest around and use it backwards (in this case you need to ensure that it is locked into place and that is turned to the correct position when the vehicle seat is being used without the HBB).

Car 3 Point Belt
The car 3 point belt should have no twists and it must be tight with no slack to allow the belt to perform safely in the event of a collision.

Side Impact protection
Refer to the car seat manual for directions on how to use the side impact protection and the spacing required between the side impact and the vehicle door. It is important that you can close the vehicle car door and that it is not pushing against either the side impact protection or the high back booster itself  (if no side impact protection) to allow for the correct HBB positioning on the vehicle seat.

Impact cushion
If your HBB comes with an XP Pad or Pad+ it is important that you follow the instructions in the car seat manual for proper usage.

Britax Kidfix i-Size car seat

"Sit Up Properly"
This is the refrain heard in our car every time we travel, even though our eldest is now aged 10. When a child travels in a HBB they need to sit up straight without slouching, sit within the seat and keep the car 3 point belt tight also.  

Different Users
If there is more than one child using a HBB at different times please remember to adjust the headrest to the correct height each time.

Britax Kidfix i-Size car seat Collection of the Safest High Back Booster Car Seats

BeSafe iZi Flex Fix
Axkid Bigkid 2

Britax Kidfix i-Size

We provide all our customers with installation support and if you did not purchase a seat from us but you are not sure if it is installed correctly, just contact us and we would be more than happy to help.