How long do children need to use a car seat?

European and UK law states that children must use a car seat until they are 135cm tall (around age 12). The standard three-point seatbelts in a car are designed for people 135cm and over and will not effectively restrain your child in the event of a collision without the help of a car seat and/or high back booster from 105cm (around age four).

It is recommended that children remain rear-facing for as long as possible until they are four years of age. This is the safest way for young children to travel as it exerts the least amount of pressure on their spine and neck muscles in the event of a collision. However, this is not mandatory and currently, toddler and child car seats are still regulated under R44 legislation rather than the new R129 (i-Size) legislation introduced in 2013.

However, many manufacturers are already starting to reflect R129 regulation features in their toddler and child car seats, such as improved side-impact protection, allowing a rear-facing position for longer and Isofix installation as standard.

Confused by car seat regulations? Check out our guide to UK Car Seat Legislation in plain English for more information.

For children from 15 months old, there are two options: either a toddler car seat or a combination car seat, which will take your child from 15 months up to 135cm/age 12 (the maximum height/age a child is required to use a car seat to).

Some car seats suitable from birth will last your child up to age four and therefore may be a preferable option for now. Some of these are i-Size certified and many will allow your child to be rear facing for longer.

Car seat categories

  • Group 0/1 (from birth to 18kg, around age four)
  • Group 1 (from 9kg to 18kg, around nine months to age four)
  • i-Size infant and toddler seats (either from birth or 15 months/75cm to 105cm)
  • Group 1/2/3 (from 9kg to 36kg, around nine months to age 12/135cm)

Prices vary from £100 to £400.

Group 1/2/3 combination car seats

joie everystage

If you opt for what’s know as a Group 1/2/3 combination car seat, your child can use this from 9kg (around nine months old) to 135cm (around 12 years old). The seat is designed to expand from a toddler car seat to a high-back booster seat, keeping your child safe and secure throughout their childhood. This means that after your newborn car seat, you will only need to purchase a single piece of kit, which for most parents will also be more cost effective.

Please note: As of 1 March, 2017, under the new R129 (i-Size) regulations, children must be in a high-back booster seat until they are 22kg/120cm (around age seven), at which point they can move to a backless booster if you prefer. Group 1/2/3 combination car seats adhere to this new regulation.

Pros: These car seats are designed to expand with your child as they grow and last the whole of childhood. Most come with Isofix installation as standard and the majority also now include improved side impact protection (more commonly known as the ‘big, padded sides’).

Cons: Some reports suggest combination car seats aren’t quite as safe as car seats designed for a specific age range. (NB: this does not mean they are unsafe, it simply means they may not be as safe.) These are big pieces of kit and if you have more than two children, it can be a struggle to fit more than two in the back seat. Furthermore, once your child is 125cm or 22kg (around age seven) you may prefer to use a backless booster seat, which is far more portable and you can more easily fit three across the back seat.

Adjusting combination car seats

Combination car seats are designed to grow with your child, including various adjustable features. But always double check how easy it is to adjust these before you buy. It’s all very well having 10 different heights you can adjust the headrest to, but if it’s super stiff and requires you to take the seat out every time, this might feel more faff than it’s worth. But if your car seat is not configured to your child’s size, it may not be as safe for them to ride in as it could be. You want to make sure that the seat is adjustable to suit your child’s varying size over the years of use, and is also safe and easy to use.

Five-point harness or an impact shield?

A traditional five-point harness attaches above each shoulder, on both sides of the waist and between your child’s legs, restraining your child while they are in the car seat and in the event of a collision. Styles vary, with some manufacturers creating padded harnesses, automatically adjustable harnesses (when you extend the headrest) or removable harnesses, meaning you can use the car seat as a high-back booster when your child reaches four years of age. For a harness to be an effective restraint system, it must be buckled correctly and tightened so the straps are flat to your child’s chest. Some children will be able to wriggle their arms out from the harness, making it not as effective in the event of a crash.

An impact shield restrains your child by sliding into place in the seat and is held in place using the car’s standard three-point seatbelt. The child is restrained in the seat but their arms are less restricted as they are not held down in the same way as in a harness. In the event of a front or rear-end collision, the upper body curls over the shield, meaning the force on the spine and neck is significantly reduced in comparison to a five-point harness. As an added bonus, the top of the shield can even act as a little trap top table for the child to do colouring or balance toys on during a car journey. However, some children do not like feeling ‘pinned down’ by an impact shield and some parents report this can make it harder to fasten a squirming child into, especially in smaller cars.

Most combination car seats with a harness have planned ahead for when it converts to a high-back booster. Either the harness is entirely removable (just don’t lose it if you’re planning on using this seat with future children too!) or you can tuck it behind the car seat back cushion, meaning it’s out of your child’s way and doesn’t affect their comfort in the chair either.

Does it need to use Isofix?

Child car seats can be installed using Isofix or the car’s standard three-point seatbelt. Isofix installation minimises the chances of parents installing the car seat incorrectly. Most combination car seats have Isofix built in as standard and eventually non-Isofix car seats will be phased out.

How long should my child be rear-facing?

Some combination car seat models will allow your child to be rear-facing in their car seat until until they reach 105cm (around age four), but this is not currently standard for combination models. It is standard for children to be forward-facing from 105cm/age four at the latest.

What other features should I look out for?

Side-impact protection both creates a comfy seat for your child and protects them in the event of a side-on collision. The padding on the sides of the chair and headrest absorb the force of the impact, meaning less strain on your child’s spine, neck and muscles in the event of a collision. Some models also have a stabiliser that touches the door closest to the car seat, which helps absorb the force of impact as well.

Some models include a recline feature, allowing your child to dose more comfortably when in the seat. This feature is particularly common in seats with a rear-facing mode.

An adjustable headrest is essential for combination models to ensure the seat is safe and grows with your child’s changing height. This makes sure their head always remains within the safety of the padded headrest. Some models (such as the Cybex Pallas M-Fix) also have reclining headrests to ensure your child’s head doesn’t loll forward when they inevitably nod off.

Removable and machine washable covers can be handy , but you’ll want to check how easy it is to actually remove the cover. If it’s too much of a faff, you’re unlikely to take advantage of this feature.

If you’re hoping the seat will be used up until your child is 135cm, keep in mind that the cutesy, bright patterns they may like when they’re four, may stop them wanting to use the seat as they get older. No manufacturers yet have the option to purchase new seat covers separately (missing a trick!) so you’ll need to consider the longevity of the colour and pattern choice when purchasing a combination car seat.

Ready to dive in? Read our reviews of Mumsnet's five Best Toddler Car Seats.

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