What is the ISOFIX system?

ISOFIX, a system that hooks onto life

ISOFIX, a system that hooks onto life

The main aim of the ISOFIX  system is to  avoid errors when installing child restraint systems, which often occurs when they are installed with seat belts and the manufacturers’ instructions are not followed.These are the characteristics of this system:

  • There are two anchors or rings attached to the vehicle.These anchors engage with the child car seat by means of rigid bars which are pushed against the rings and locked with a simple click.
Instructions to secure a child seat properly using ISOFIX system
  • In addition, there is a top anchor point (top tether) or a bottom anchor point (support leg)  to prevent the seat from turning or tipping over. 

Top Tether:

What is Top Tether and how to use it
Support leg:
How to secure a child seat with a support leg
The smallest child seats are usually equipped with ISOFIX, i.e., those belonging to groups 0, 0+ and I or for children that are 40 to 105 cm tall. However, child restraint systems for taller children up to 125 cm can also be equipped with ISOFIX. In the case of larger car seats, this system can be combined with the seat belt.
ISOFIX label

In order to define the characteristics of CRSs we will first have to differentiate between universal and semi-universal seats.

Child car seats belonging to groups 0+ and I with an ISOFIX system are divided into universal and semi-universal, depending on where the third anchor point is located.If it is located at the top of the car seat (top tether), it is a universal seat. If the anchor point extends from the vehicle floor to the base of the seat (support leg), it is considered a semi-universal seat.A universal seat means that the child car seat can be used in any car that has the third top anchorage point while a semi-universal seat can be used in a number of vehicles, but not all of them.In this last case, the child restraint system manual includes a list of vehicles in which the car seat can be used with the ISOFIX system.

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