R129 (i-Size) Car Seat Regulation

By law all children must travel in the car in a seat that is suitable for their weight, height and age.

There are two car seat regulations in Europe, ECE R129 which was introduced in 2013 and ECE R44 which has been around since the early 1980s (the last version was R44/04). R44 was discontinued in September 2024 and although you can continue to use any R44/04 seats that you already own, they are no longer available to buy. 

Why the change?

- In an R129 car seat all children must rear face until they are at least 15 months old and 76cm tall, regardless of their weight. R44 allowed forward facing from 9kg regardless of age.

- R129 car seats are mainly height based, although they do also have weight limits that must be adhered to. R44 seats had set weight limit groups and no height limits.

- R129’s advanced technology Q crash test dummies have 32 sensors to simulate a child’s fragile body more accurately. The P-dummies used for R44 only had sensors in the head and back. Please click here for more details.

- R129 car seats have all passed a side-impact test which was not compulsory in R44 testing.

- i-Size was the first phase of R129 which only applied to infant carriers and harnessed seats up to 105cm. These seats are guaranteed to fit in any i-Size approved vehicle. From 2016 onwards some, but not all, new cars have at least two i-Size compatible seats.

- R129 can seats can be no more than 44cm wide to increase the chance of being able to fit three seats across the back seat of the car. R44 seats have no width restrictions and can be as wide as 48cm.

- In most R44 combination seats the belt is routed differently for rear and forward facing. R129 seats only have one belt path for both travel directions, to avoid confusion and prevent mistakes.

- Belt fitted R44 seats have blue seat belt guides for rear facing seats, and red for forward facing. In R129 seats from 2020 all belt guides are green.

R129 car seats for older children come in four height categories

- i-Size Infant carriers up to around 75-85cm (these limits vary, so please check your instruction manual to check your seat's limit)
- i-Size seats up to 105cm, which is about four
- Belt fitted or ISOfix seats up to 125cm, around six or seven years
- i-Size high back boosters up to 150cm or twelve years

Infant carriers and harnessed seats up to 105 and 125cm also have a seat-specific weight limit which can be found on the orange sticker on the back of the seat, and this limit must not be exceeded.

Most infant seats have a base that can also be used for a bigger seat up to 105cm for older children.

There have been three phases of R129 so far:

- 2013: R129/01, also known as i-Size. These are harnessed ISOfix infant carriers and car seats up to 105cm. They fit into an invisible box known as an envelope, which is 44cm wide, 75cm long and 81cm tall. This means that i-Size seats are guaranteed to fit in any i-Size approved car.
- 2017: R129/02, high back boosters from 100-150cm.
- 2018: R129/03, belt fitted harnessed seats, either up to 105 or 125cm.

You should choose your child's car seat according to their height and weight, and use it up to its limits. All children are different and the age given is just a rough idea of how long you can expect a seat to last, based on an average 50th percentile child. Children only grow out of their car seat by weight or height, never by age. 

But the age at which they can start using a seat is important. The regulations' 9 and 15 months minimum forward facing ages are far too young. Regardless of how big or heavy they are, the bones in a child's neck and spine don't begin to fuse together until they are between two and three years old, and it takes about three years for this process to complete. So it isn't actually until they are six that their neck is strong enough to cope with the forces of a car crash. This is why it is important for children to travel rear facing for as long as possible.

The same applies to the move from rear facing seat to high back booster. Although according to the regulations a child can go into a booster seat at 15kg or 100cm, a lot of children reach that weight or height long before they are physically strong, and mentally mature enough to sit in a booster seat. We recommend rear facing until 125cm, which on average is between six and seven.

The orange sticker