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Which car seat?

i-Size child car seats explained

By Olivia Howes

Article 3 of 6

What are i-Size child car seats? How are they different from other car seats? Are they safer for my child? Here's all you need to know. 

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What is i-Size?

All car seats are approved to a regulation, meaning they must pass certain tests before they can go on sale. The new European standard for child car seats, known as i-Size, forms part of regulation ECE R129.

The idea behind i-Size is that all car seats will fit in all cars. Your car and your car seat must have Isofix, a fitting system that attaches car seats directly to the frame of your car using connectors. 

We've tested and reviewed several i-Size seats. See how safe they are in our child car seat reviews.

More and more new cars that come on the market will be i-Size ready. For now, you can buy an i-Size seat if you want to, but you'll need to check the list of approved vehicles that fit the seat and check the fitting in your car.

One of the big improvements that i-Size should bring about is a reduced risk of fitting your child car seat incorrectly. Generally, Isofix seats are simpler to fit than ones that use the vehicle’s seat belt.

Key differences between the old regulation (R44/04) and i-Size child car seats
R44/04 i-Size
Frontal and rear-impact tests but NO side-impact tests Frontal, rear and side-impact tests
Seat can fixed to car using seat belt or isofix Isofix-only fixing
Baby must be rear-facing until 9kg (approx 10 months) Baby must stay rear-facing until 15 months
Classification of seat based on weight Classification of seat based on height

Rear-facing car seat for longer

The i-Size regulation keeps your child rearward-facing until they are at least 15 months old.

Rearward-facing travel is advisable until this age or longer because of the relative size of babies’ heads compared with their bodies, and the weakness of their neck muscles. In a frontal impact in a forward-facing seat, the forces placed on a baby’s neck by their head can be too great to withstand. But in a frontal impact in a rear-facing seat, the child is pushed further into the seat, supporting the head and back and limiting the movement of the head on the neck.

Height is what matters, not weight

The weight of your child will no longer tell you when they need the next-stage car seat.  The old system of groups will completely disappear, and instead your child's height determine which seat they need. This could vary from seat to seat.

Your child will outgrow the seat once they exceed the maximum height stated on the car seat’s label.

If you're not sure how tall your child is, look at the labels on their clothes. You’ll probably find a height band printed somewhere on them. But you'll need to measure your child properly to make sure you are buying the right seat for their size. Some child car seat retailers have height charts in store.

i-Size and Isofix

i-Size currently requires the use of Isofix to fit your car seat. Not seat belts. 

Isofix is designed to make installing your car seat quick and easy. We know from our research that parents and retailers regularly make errors when fitting seats into the car. In Spring 2014 we asked 42 major stores from all the major baby product retailers to fit two car seats. Most made mistakes, some of them worrying ones. Using an Isofix child car seat removes the potential to make many of these mistakes.

Isofix is a child car seat attachment system which uses metal bar connectors built into the chassis of the car to connect to the child car seat. The connectors are often hidden within the car's seat padding. Once the connectors are clicked together with these anchorage points, the child car seat is secured by a third point, either a support leg which comes built-in into the seat or seat base, or a top tether (a strap that attaches to a mount somewhere behind the rear seat). Both of these work to stop the car seat tipping forward in an accident.

i-Size car seats fit all i-size-ready vehicles. 

Do I need to buy a new car seat?

At the moment, i-Size is running in parallel with the old regulation, ECE R44/04. This is expected to continue until at least 2018, but the date that ECE R44/04 is phased out is not fixed.

This means that while there are some i-Size seats on the market, you don't have to buy a new car seat.

All car seats display a label that tells you they comply with a relevant regulation. As more i-Size seats come on the market, you'll find car seats that display either the i-size/ECE R129 label or the ECE R44/04.

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

You'll see the logo above. Many of the models of i-Size seat will also have an 'i' in their name or include the word 'i-Size' in their name.

Why has i-Size been created?

The old regulation has been in place since the 1980s. Child car seats – and cars – have come a long way since then in terms of the safety they offer children. The new i-Size tests are more up to date.

For a long time Which? has been putting pressure on the industry to improve their car seats by carrying out tests that are far more stringent than the old standard. The new i-Size test has incorporated some of the aspects Which? has been testing for years, including a side-impact test. Read more about how Which? makes child car seats safer.

Side-impact accidents make up around 25% of collisions, but the old regulation doesn't test how a child car seat and its occupant will react in this type of accident.

The new tests also use more technologically advanced dummies, known as the Q-series, which behave far more like real people in a crash scenario.

As the moment i-Size includes only Isofix car seats that can be used from birth up to 105cm (approximately four years old). More changes for older children are expected in 2016.

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