The right kind of car seat is as important for your child as it is for babies and younger children.
Once your child reaches the age of three or four, they'll need to move on to a group 2/3 or i-Size child car seat.
These are designed to last your child until they no longer legally need to sit in a car seat.
The very best ones will be comfortable, with a high back and sides to the seat that provide protection in front and side-on collisions.
This is a group 2/3 car seat that's approved to the older regulations (R44), so can be used with children weighing 15kg to 36kg. This is from age three or four up to around 12 years old.
It has a 12-position height-adjustable headrest, and the backrest can also be reclined slightly to provide a more comfortable position.
Cybex states that the seat has linear side-impact protection to help shield your little one in a side-on collision.
The Solution Z i-Fix is an i-Size-approved car seat and is suitable for children who are from 100cm to 150cm tall, which is around age four to 12 years old.
Your child and the seat itself are secured into the car using the vehicle's adult 3-point seatbelt. But it also has Isofix connection points to provide additional stability and to keep the seat in place if nobody is sitting in it during your car journey.
The Solution Z i-Fix has a few more features than the Solution B-Fix - find out if that makes for better protection and higher test scores.
The Maxi Cosi Kore Pro is another i-Size high-back booster seat that's approved for use with children measuring 100cm to 150cm.
It has an innovative light that detects when your child is in the seat and illuminates the buckle area to help you (or your child if they're old enough) to see when buckling up.
The travel-friendly MiFold HiFold is a high-back booster seat that's approved for use with children weighing between 15kg and 36kg.
It has an impressive 243 individual combinations for you to adjust the seat to as your child grows, including the seat width, body width, head width and the height.
It can be folded in on itself for easy storage (25×34.4×34.4cm), and it comes with a carry strap so you can sling it over your shoulder. This means it could be a great option if you're travelling abroad and want to bring your own car seat.
But can a seat such as this provide adequate protection in front and side-impact collisions?
The Chicco Fold & Go is another foldable high-back booster seat, although one that's approved to the latest car seat regulations (R129).
It's not as compact as the MiFold seat when folded, but does have a carry handle.
The seat has a belt positioner, similar in design to the crotch strap you'd get on a three- or five-point harness, and it's designed to help position the seatbelt across the hip bones and ensure that the delicate abdominal area is protected in a crash.
Our state-of-the-art crash test dummies use sensors to check whether a seat is protecting the various areas of a child's body in a collision.
UK law states that a child must use a car seat until they're 12 years old or 135cm tall - whichever comes first. However, safety experts recommend using a car seat until they're 150cm.
For older children, the best type of seat is a high-back booster seat. This is either one that's approved for children weighing 15kg to 36kg or measuring 100cm to 150cm.
High-back booster seats are better than backless booster seats because the padded wings provide protection during a side-on collision.
However, a recent Which? survey in March 2020 of 1,800 parents with a child under 12 revealed that 35% of parents incorrectly think that backless booster seats offer the same protection as high-backed booster seats.
Which? car seat tests are more severe than the EU and UK regulations - we test at higher impact speeds and in both front and side-on collisions, no matter which version of the regulations the car seat claims approval to.
With more than 50 years of car seat testing under our belt, manufacturers know that a good Which? test score is the hallmark of a great seat. It's what pushes them to develop seats that don't just meet the requirements of the legal regulations, but also succeed in the tougher tests that we put car seats through.
You can read more on this in the latest issue of Which? magazine (July), plus tips on how to ensure your baby or child is safely strapped into their seat.