i-Size Regulations

Everything You Need to Know About i-Size Car Seats

I-Size is the new buzz word in car seats but what does it mean and do you need to do anything? The myriad of technical details can be confusing but our car seat experts have deciphered the jargon and highlighted the important points.
Currently all car seats are tested and legislated under a regulation called ECE R44. This is being superseded by the new i-Size (R129) regulation over a period of time. The transition period will be staggered so there’s no need to panic about changing your seat immediately. Here we have reviewed the key points of i-Size, why it’s being introduced and how it might affect you.

Why Size?


Some of the car seat weight ranges are encouraging parents to move their children up to the next stage seat too early. For example changing from a rear facing infant carrier at 9kg when baby might be less than one! Staying rear facing as long as possible is much safer and the low weight limit for forward facing seats was only designed for the very small percentage of children that grew very tall and thin without adding significant weight. Now i-Size (R129) will mean seats are classified on the size and height of a child rather than his/her weight. Plus it will mean the absolute minimum age to change from rear facing will be 15 months.


Can you believe that in the R44 regulation there is no requirement for side impact testing! Many manufacturers including Diono carry out the optional testing but it is great news that all car seats will have to pass side impact limits in the future


Up to 85% of car seats are fitted incorrectly so the new i-Size regulation will standardise fitting procedures making it much easier for parents.

What are the main changes?

Currently only the initial phase of i-Size has been launched. This covers the first car seat parents buy – infant carriers. i-Size for these seats is running in tandem with ECE R44 for the time being so there will be both car seats legislated under R44 and i-Size available in shops. All other types of car seat for older children must still only be regulated under ECE R44. Here we have listed the new areas covered by the i-Size regulation and applicable to infant carriers.

Rear facing for longer

The most frequently occurring accidents are frontal impacts (because this is the normal direction of travel) so the safest position for babies is rear facing because the back of the seat supports the head and entire body in the event of a collision. When forward facing, the only support for children is the 5 point harness so much more force is exerted on the neck leading to a higher risk of injury. This is why the new i-Size regulation mandates rear facing use of the car seat until at least 15 months of age.


All i-Size R129 infant carriers must fit into the car with isofix and have a support leg or tether strap to prevent any rotation in a collision. The maximum weight which can be placed on the isofix is 33kg. This can be any combination of car seat and child weight. For example if the car seat weighs 10kg, the maximum child weight using the isofix is 23kg

Car compatibility

Many seats regulated under R44 won’t fit into all cars but the new i-Size regulation will change this. Car seats certified under R129 must fit into one of nine envelope sizes. In order to be considered a universal seat (i.e. will fit in every i-Size ready car) they must fit into one of two specific sizes (one rearward and one forward facing). Seats that fit within one of the other seven envelope sizes can be approved under R129 as vehicle specific and will have a list of cars that the seat fits into.

Side impact protection

Side impact is not currently tested despite 28% of fatalities occurring from a side collision. The i-Size regulation will test seats with an intruding door which moves into the internal car space.

Size instead of weight

Each group of seats tested under R44 have to accommodate a certain weight range. With i-Size this will change to ensure a car seat fits a child’s heights and width and there will be no predetermined groups e.g. 0, 0+,1,2/3. So for example a car seat which can be used for a child from birth to 2 years must be large enough to accommodate the height and width of children at birth as well as at 2 years. Obviously there is some variation in how quickly children grow so car seats will have to be made to accommodate the upper height and size at the maximum age range. This will make it much easier for parents to know if a seat is suitable for their child and how long it will last!

i-Size Frequently Asked Questions

Does it mean R44 seats aren’t safe?

Car Seats legislated under R44 still meet all the legal requirements and can be used without any issues. It is not necessary to throw away your current seat for a new model. It is important to note that any group 1 and group 2/3 (including the Diono Monterey and Cambria) seats are not yet included in i-Size, so you will only find ECE R44 seats on the market.

How do I know if my car seat is i-Size?

If your car seat has been tested to i-Size Regulations, you will see this mark on the product.

How long until all car seats are i-Size?

I-Size is currently running alongside ECE R44 so both regulations are applicable. This will continue for some time because a transition period is required for car seat manufacturers to make the necessary changes . The next stage will be to introduce i-Size for seats after the infant carrier stage. This is expected to happen in 2016. At this point there could be both i-Size and R44 seats available for parents to buy in all categories.

Around the end of 2016 no more infant carrier approvals under ECE R44 will be made. The seats with R44 classification will still be sold for a period of time. Other groups of seats for older children will stop being classified under R44 around 2018 but again they will still be sold through shops for a period of time afterwards.

These dates are not firm because of the work that still has to be done with car manufacturers, child seat restraint manufacturers, testing laboratories and regulatory bodies. We will keep you updated with all the changes as and when they happen.

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