In the field of child seats there are always doubts about timescales, ages, weight and which seat is suitable for each child at every stage. The most frequent queries usually concern when to change the model and size of the seat, when to use a booster cushion and when to stop using one. The answers are very simple so long as you always remember the basic rules you need to follow in order to comply with the law and apply a little common sense.
The current legislation in Spain regarding the use of car seats for children, known as CRS or child restraint systems, states that all children must travel in a car using a seat that is specifically appropriate for their size and weight. Age is not a variable that needs to be taken into account: it is only the child's physique that is important.
Furthermore, a minor less than 135 cm tall may not travel in the front seat if there are places available in the rear. This is not strictly related to the subject of booster cushions, but we must bear in mind that a booster cushion is a CRS and that they are used by minors who may not have grown taller than 135 cm. We will return to the subject of this height shortly.
When should the seat be changed in order to use a booster cushion?
Possibly another of the most recurrent questions and another which, as you might imagine, has a very simple answer: whenever the current seat has become too small you immediately have to look for a better solution. If we are talking about a Group 1 seat i.e. a CRS with harnesses, the time to stop using it is when the child's shoulders grow to be above the highest point through which the harness passes, or else when they get to weigh more than 18 kilos, given that the harnesses don't usually support more than that weight in a collision. Of course, if their head is above the highest point of the seat it is time to change it.
The change will be to a Group 2 seat with a backrest and lateral support for the body and the head. Why? Despite the fact they weigh over 18 kilos, they are still little children who benefit greatly from such support in the event of a crash. The back rest and side support are extras that improve protection in any type of crash, but above all the sides.
These seats, that don't come with a harness, are held in place by the seat belt, and we need to understand that the seat belt must be properly positioned. In the article “Seat belt and CRS, life insurance” we explain in detail the correct positioning of seat belts on children.
Having reached this point, then the next question is inevitable: what about booster cushions? Why can't we use a booster cushion when we progress beyond Group 1 car seats? Once again the answer is simple: you can use a booster cushion, but the fact is that it is more advisable to use a seat with a backrest and side support. It is safer for the children. Additionally, remember that the more time they use them the safer they will travel. The law states that a CRS is not compulsory for children taller than 135 cm, but that it is highly recommendable. We cannot equate a law that establishes a compulsory minimum with safety recommendation. Without doubt, booster cushions are a legal form of CRS, but they are not as safe as seats with backrests and side protection.
Thus, the correct answer to the question we posed at the beginning is no, what we should use is the safest possible CRS appropriate to the physical features of our children, and we must use them for as long as possible before progressing to a simple booster cushion or seat belt.
Lastly, we recommend the report ‘Booster seats in cars: How long should we use them for?’ (Spanish), produced by Fundación MAPFRE, where you will find full information on the subject.