Backless booster seats: advantages and disadvantages of ISOFIX

The backless booster seat has gone from being seen as a basic element to being considered the most suitable child restraint system for a range of heights between 125 cm and 150 cm. This evolution is closely related to the development of UN Regulation 129, which incorporates side impact in its approval tests, forcing manufacturers to figure out how backless booster seats fit into a regulation that imposes safety standards in the event of a side collision.

The solution to this dilemma was provided by a car manufacturer in 2012 when it demonstrated that, in the event of a side impact, the window airbag in vehicles had head protection levels equal to or even higher than those provided by booster seats with backrests. Since then, legislation has been developed to ensure that the child’s head interacts with the car’s window airbag, thereby ensuring a level of safety similar to that of adults in the event of a side impact.

This is why, if we compare a backless booster seat approved by UN Regulation 44 (old standard) and one according to Regulation 129, we will see that the booster seat is almost twice as high. This is what guarantees the proper contact between the child’s head and the airbag in the car window.

WITH OR WITHOUT ISOFIX?

Having made this brief introductory explanation, we should mention that both ISOFIX and non-ISOFIX backless boosters are available to buy.

The ISOFIX system was designed to facilitate the installation of integral child restraint systems (with harnesses) that did not require the car’s seat belt.

At the beginning of the 2000s this system was also used in booster seats with a backrest, since they offered the option to recline. But there was no improvement in terms of safety, since the child was restrained by the car’s seat belt.

For the product we are talking about (the backless booster seat), ISOFIX connectors provide neither the possibility of reclining, as backless boosters do not tilt backwards, nor improvements in terms of how easy the system is to attach.

Furthermore, as there is no regulatory relationship between the ISOFIX position and the seat belt position (seat belt and ISOFIX attachments have no established positions, as their combined use is not provided for in the regulations), the seat belt may be too far away or too close to the child’s chest, with no way of moving it sideways.

In addition to this, the rotational movement of the booster seat, when connected to ISOFIX anchors, increases the risk of the child “submarining”. The rotation around a fixed point (the ISOFIX anchor) means that the booster seat can only move downwards, whereas with NON-ISOFIX systems, there is a translational movement that accompanies the child’s pelvis, and a somewhat smaller rotational movement.

In short, the use of ISOFIX connectors in boosters has become widespread due to the belief that the ISOFIX system is generally safer, but ignoring the reasons behind its invention and applying it to a child restraint system that does not need it to function properly.

Using it for no reason, such as being able to adjust the height of the booster seat or dissipate the energy from the impact, does not mean that it is a safety improvement.

Nevertheless, one positive aspect of booster seats fitted with the ISOFIX system is the fact that, in the event of a collision where the child is not present, the device would not be thrown around, although this could also be avoided by fastening the seat belt around a NON-ISOFIX booster seat or by storing it in the trunk of the car.