Main FAQ about i-Size


1. What is i-Size?

i-Size (also known as UN legislation - R129) is the latest standard for maximum child car safety. Whereas ECE R44/04 compliant child car seats offer great safety, i-Size takes it to the next level. Besides improved safety i-Size also helps parents to choose the right product. Following pillars differentiate i-Size from ECE R44/04:

- Improved protection :

Using state-of-the-art ‘Q-dummies’ and performance criteria

Rearward facing up to 15 months

Improved protection on side impact

- Better adjustment to child :

Classification using child size (cm) instead of weight (kg)

- Better compatibility with cars :

Isofix solutions Better compatibility with each car.


2. Why is i-Size developed?

i-Size is developed to further increase the safety level of children when travelling in a car. Technical know-how is evolving every day, which implies that test protocols become more advanced. For example, the current legislation ECE R44/04 does not provide performance standards for side-impact collisions, i-Size does.

Also, i-Size helps parents to choose the right car seat:

- Group classification within i-Size is based on length (cm) and not on weight (kg) like ECE R44/04.

- Thanks to an intense collaboration between the child car seat industry and automotive industry i-Size car seats result in better fitment in most cars.


3. Why does Maxi-Cosi support the new i-Size legislation?

We support the new i-Size legislation because we believe that i-Size approved child car seats are even safer than ECE R44-04 approved child car seats. Because of this new legislation, the safety level for children transported in cars will further increase.


4. Which age groups are covered by i-Size?

The introduction of i-Size consists of different phases. In the first phase of i-Size, only Baby (Gr 0+) and Toddler (Gr 1) car seats were covered. This legislation came into place in 2013.

During the summer of 2017, the second phase of i-Size will come up. This will be another major step, because for the first time ever i-Size safety will also apply to Child (Gr 2/3) car seats.


5. As of when is the i-Size legislation effective? What are the different phases of i-Size?

The development of the i-Size legislation is an ongoing process and consists of three phases.

- Phase 1: effective since the summer of 2013 :

Applies to Baby (Gr 0+) and Toddler (Gr 1) car seats

- Phase 2: will become effective in the summer of 2017 :

Will apply to Child (Gr 2/3) car seats – 100 to 135cm

- Phase 3: introduction date unknown (likely to be 2018-2019) :

Will apply to belt installed Baby (Gr 0+) and Toddler (Gr 1) car seats.


6. What does i-Size mean for Baby (Gr 0+) and Toddler (Gr 1) car seats? (Phase 1 of i-Size)

Phase 1 of i-Size is in force since July 2013 and applies only to Baby (Gr 0+) and Toddler (Gr 1) car seats. Whereas ECE R44/04 car seats offer good safety, i-Size car seats take it to the next level:

- Improved protection at higher forces for side and front impact and much better protection for head and neck.

- Rearward facing travelling mandatory up to 15 months old.

- I-Size requires the use of ISOFIX, which decreases the risk of incorrect installation significantly (compared to belted car seats).

- Better fitment in ISOFIX-cars

- Age groups defined on length (cm), not on weight (kg).


7. What does i-Size mean for Child (Gr 2/3) car seats? (Phase 2 of i-Size)


Currently, all European Child car seats are ECE R44/04 compliant. Once Phase 2 of i-Size becomes effective (in the summer of 2017), it will also be possible to have i-Size Child car seats for children above 100 cm.

Just like Phase 1 of i-Size, the tests and criteria have improved significantly compared to ECE R44/04 by using more precise dummies and adding side-impact testing to the existing frontal impact tests.

Additionally, the classification of the car seats has changed from kilograms to centimetres. Often parents know better how tall their child is versus how heavy their child is, and therefore they are more likely to choose the correct car seat.

Another improvement of R129 over R44/04 is the better fitment in cars, thanks to agreements between car seat manufacturers and vehicle manufacturers.

On the use of ISOFIX anchorage points, there are no changes. Car seats for children from 100 to 150 cm can use ISOFIX anchorage points for installation, but this is not mandatory.

When phase 2 of R129 will be in force (summer 2017) the existing R44/04 legislation for these products will not end, but both legislations will continue to exist side-by-side. As a result, consumers might choose to use the latest and highest standard for car seats in Europe. Phase 2 of i-Size will not allow booster car seats without backrest to be sold; all i-Size booster-type car seats sold after the summer of 2017 must have a backrest.

Depending on the country, national legislation still defines if a child needs to be in a car seat until 135 or 150 cm – this is not going to change.


8. Why is it safer to transport a baby/toddler rearward facing instead of forward-facing?

The neck of a child matures with age, and not when it reaches a certain stature or mass. Up until 15 months, the baby’s neck is not yet developed enough to withstand the impulsive force of an average frontal collision because of its relatively heavy head. The excessive pressure on the neck of the baby might lead to serious neck injuries. When travelling rearward facing, the forces of a frontal collision are better spread over a greater area of the body of the baby, which leads to less pressure on the head and neck.


9. What are i-Size cars? And how do they affect the fitting of child car seats in cars (Car Fitting Lists)?

i-Size cars are cars that meet all needed specifications to have an i-Size car seat correctly installed. As from July 2013, the automotive industry is able to homologate their cars according to the i-Size standard. i-Size though is not mandatory for car manufacturers, while ISOFIX is.

One of the advantages of the i-Size legislation is that both the child car seat and the automotive industry are involved. The result is that the fit between car seats and cars is further improved: all i-Size car seats will fit all i-Size cars. i-Size car seats can also be used in cars with ISOFIX positions, and you can consult the fit in a compatibility list (Car Fitting List).


10. Can I use an i-Size homologated car seat in my ISOFIX car?

The vast majority of ISOFIX equipped cars are suitable for an i-Size car seat. i-Size car seats have always been intended to be backwards compatible with ISOFIX cars. However, we strongly advise checking upfront with your shop attendant or online – using our Car Fitting List.


11. Why the name i-Size?

i-Devices are generally seen to be intelligent, convenient and well thought-out. These are the characteristics of this new safety standard. The word “Size” appears in the name because the length primarily determines how to choose a child restraint system, more so than age or weight.


12. What are Q-dummies?

‘Q-dummies’ are state-of-the-art dummies used in crash laboratories. In comparison to the previous generation of ‘P-dummies’ crash test results can be measured much more precise.

A very important improvement in the ‘Q-dummies’ is the use of sensors in the abdominal body parts. Before, the abdominal impact was not precisely measured because crash dummies were not able to.

As from January 2017, all newly homologated i-Size products are being tested using ‘Q-dummies’.


13. Can I keep using the current ECE R44/04 car seats?

Yes, you can. I-Size runs parallel with the current safety regulation ECE R44/04. Car seats complying with ECE R44/04 can still be used or sold until decided differently.


14. Is i-Size a new regulation or legislation (law)? Does it replace the current ECE R44/04 legislation?

i-Size is introduced as a new legislation next to the current ECE R44/04 legislation. This means that, for now, new car seats can still be homologated as ECE R44/04 and consumers can remain using the ECE R44/04 products.

Both i-Size and ECE R44 are laws. Meaning that manufactures such as Maxi-Cosi can choose to make either i-Size or ECE R44/04 car seats. Likewise, consumers can choose to either buy an i-Size car seat (safest) or an ECE R44/04 car seat (safe).


15. Who has been involved in defining the i-Size legislation?

A multi-disciplinary task force was set up by the European Union to create the i-Size legislation. All parties below were involved:

- Dorel Juvenile Europe

- Britax-Römer






- European Commission

Dorel Juvenile (Europe) is the holding company of Maxi-Cosi. As a long-time and leading manufacturer of child car seats, Dorel Juvenile has established an advanced Technical Centre in France. This center encompasses everything necessary to conceive, build and test car seats in a modern, state-of-the-art facility. This facility, along with Dorel Juvenile’s expertise in child seat designing and manufacturing were deployed by the UNECE to help develop and define the i-Size standard.


16. What is the effect of side-airbags on travelling rearward facing longer?

Side-airbags have no negative effect on child restraint systems, also not in rearward facing mode. In some but not all cases of a side-impact collision, the side-airbag will provide additional safety for the child. This effect of side-airbags does not differ whether the child is travelling forward or rearward facing.

Frontal airbags do have a negative impact on the safety of rearward facing children. Therefore frontal airbags have to be switched off at all times when travelling rearward facing on the passenger seat.


17. Longer rearward facing travelling is safer, does this mean current ECE R44/04 car seats like Pearl or Axiss are not safe anymore?

No, all Maxi-Cosi car seats are safe and meet all current safety standards and requirements. These products are also tested by independent test institutes like STIWA, ADAC, ANWB, ÖAMTC and TCS. Many of these tests also include side-impact parameters.

In addition, Maxi-Cosi has established an advanced Technical Center in France which also includes a crash sledge for crash testing. In this centre, all products are being tested extensively on safety performance by Dorel, also on frontal and side- impact and misuse.

The current R44/04 car seats are totally safe while the newer i-Size car seats that allow rearward facing longer can be called even safer.


18. Why does the legislation not use minimal length for rearward facing but 15 months instead?

This is because research has shown that on average the neck of a 15-month-old child is developed enough to withstand the forces of a forward collision. This is based on the child’s age and not his stature or weight.

Although transporting rearward facing is required to at least until 15 months, Maxi-Cosi recommends transporting children rearward facing as long as possible.


19. Why until minimally 15 months rearward facing? Why not 4 years?

i-Size legislation dictates to travel rearward facing up to minimum 15 months because, until this age, the baby’s neck is not yet developed enough to withstand the impulsive force of an average frontal collision because of its relatively heavy head.

As from 15 months on, the neck is sufficiently developed and thus withstands the forces in forward-collision better. The biggest leap in safety enhancement can be achieved by prolonging rearward facing travelling until 15 months (compared to 9 months in many cases).

This being said, it is important to know that Maxi-Cosi strongly recommends using car seats as long as possible in a rearward facing mode. Many of Maxi-Cosi’s newest car seats allow rearward facing travelling up until 4 years!


20. Why is longer rearward facing travelling more common in Scandinavia compared to the rest of Europe?

This is mainly due to cultural differences. In Scandinavian countries, the level of safety is a crucial factor. Compared to Scandinavia other European countries also value other elements like comfort and ease of use.

Also, Scandinavian people tend to drive bigger cars, implying they have more space to install rearward facing solutions.


21. What will Maxi-Cosi do to enable longer rearward facing travelling?

Maxi-Cosi has been highly active in establishing the new i-Size legislation. Thereby, all manufacturers will be obliged in the future to enable longer rearward facing travelling with their products.

At the same time, the product development teams are working on solutions that allow for longer rearward facing travelling.


22. While ECE R44/04 uses weight, i-Size uses length as the reference to change age-groups for car seats. Why not use the child’s age?

The child’s age might seem the easiest solution, but it is not because children with the same age differ significantly in length (small/tall) and weight (light/heavy). Children are known to grow differently, as they can have growth spurts at different times.

Length is the main denominator since it tells best if a child fits a seat well and when a parent should switch to the next car seat. Age and weight can be used as a secondary indication.

It is also easier for parents because they rather know the length of their child – not the weight. The reason for this is that length is also used for clothing sizes.


23. What is ISOFIX?

ISOFIX is an international standardized fitting system, which provides a safe, easy and quick way to install a child car seat without the need for car seat belts. The name ISOFIX stands for ISO (International Standardization Organization) plus FIX (Fixation). ISOFIX car seats make use of two standard attachment points at the base of the seat in the car, plus an anti-rotation device to prevent forward pitching: this can be either a support leg or top tether.

From 2006, most new cars are equipped with ISOFIX and a top tether anchorage point. ISOFIX is also fitted in a large number of car brands built prior to 2006.


24. Why do parents currently up-size too soon?

There are different reasons why parents tend to switch too soon from rearward to forward facing travelling:

- It enables the baby to interact more with other car passengers. A common misinterpretation is the 9 kg limit for forward-facing that is often mistakenly understood as 9 months.

- They think that the child has outgrown its car seat once the child’s feet stick out of it. Only when the baby’s head sticks out of the top of the baby shell, it is the right time to switch to a consecutive car seat.

Basing seat type advice on specific child length ( and not weight) helps to avoid giving in to the temptation of premature upsizing and premature switch from rearward to forward facing.