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How we test baby car seats

By Lisa Galliers

We crash test every baby, toddler and child car seat we review to reveal which ones give the best protection in a crash, and which you should avoid.

Put us to the test

Our Test Labs compare features and prices on a range of products. Try Which? to unlock our reviews. You'll instantly be able to compare our test scores, so you can make sure you don't get stuck with a Don't Buy.

Our video shows you the huge difference between a good child car seat and a bad one, and talks you through how to find the safest seat for your baby. But what goes into our testing and how is the score for each seat generated?

Jump straight to:

Why our car seat tests are different

Which? is part of a European test consortium, consisting of International Consumer Research & Testing (ICRT) and the European car clubs. We've been testing car seats together since 2003. Which? has been testing child car seats since 1967.

We work together jointly to crash test child car seats in two specially designed crash scenarios, using state-of-the-art crash-test dummies and sensors. 

Each car seat goes through the same tests in our labs, so you can directly compare their strengths and weaknesses. Our crash tests are severe, and our experts feel that they more accurately reflect what happens in real crashes than the legal minimum standards.

Our baby, toddler and child car-seat test results reveal big differences between seats. Some protect babies and children well, but others expose them to the risk of serious injury or even death.

What are Which? Best Buys and Don't Buys?

The best child car seats will provide protection from both front and side-impact crashes – two of the most common types of crash. As of September 2019, a baby car seat (Group 0 or 0+) must score 79% or more to be a Best Buy. A baby and/or toddler car seat (Group 1/2/3 or any combinations of these groups) must score 74% or more. i-Size baby car seats must score 77% or more and i-Size toddler car seats must score 75% or more.

  • Best Buy car seats will tick the most important boxes – good or excellent safety scores, an easy installation process, and good ergonomics and comfort.
  • Don’t Buy car seats score 45% or less. Some car seats are Don’t Buys even if the crash test scores are good because they may be extremely difficult to fit into your car which could pose a safety risk if not installed properly. Car seats rated 0% will have performed so badly in parts of our crash tests that we will automatically downgrade the total test score to the lowest possible rating, and make it an automatic Don't Buy. This can be because the seat is not up to withstanding the forces of a crash in a particular set-up, or because part of the seat breaks or detaches during the crash tests.  A good result in any other part of the tests cannot compensate for such a poor result.

How is the Which? score calculated?

The Which? overall score is a percentage. This score only takes into account the results of our tests and ignores price completely. This means that all car seats are tested on exactly the same scale, so you can compare any car seat at any price and know how it measures up against its rivals in key areas. All car seats are tested in the same way, regardless of the manufacturers’ claims.

Weightings and star ratings

A Which? overall score is made up of dozens of individual tests and checks, from key factors such as safety and ease of use to how comfortable the seat is whether or the cover is easy to remove and clean.

Behind each of those ratings could be many more individual tests and checks. This means that the most important things – such as how well the car seat performs in front and side impact collisions, will more greatly impact a car seat’s score than whether or not the harness buckle is a bit fiddly.

To keep things simple, the most important scores are shown as star ratings out of five on each car seat’s Test Results page as an easy-to-compare list of strengths and weaknesses, so you can quickly work out whether this particular car seat is right for you.

Which? does not rate a car seat on the colour or pattern of the car seat cover.

How the overall car seat test score is calculated

Our key testing criteria

Below are the key testing categories and how we evaluate each one:

Car seat safety 

Key question: Is my car seat unsafe?

Our experts have specially designed the crash tests, making them more demanding than the legal minimum standard requires. They’re derived from tests by Euro NCAP, which carries out crash testing on cars to show how well they protect occupants in severe accidents. We do a similar thing for car seats, and feel this more accurately reflects what could happen in a real crash.

Crash test dummies are wired up with state-of-the-art sensors to record the crash forces on the most vulnerable parts of the body, to help accurately indicate the risk of injury to a real baby or child in a crash.

Each car seat we test endures a front crash, equivalent to a head-on collision at around 40mph, and a side crash, equivalent to two cars crashing into each other at 30mph. These are repeated again and again, with the seat installed in all the different ways it can be used.

We can go through as many as 15 samples of the same seat to get the final score for just one.

Which? gives car seats star ratings from one to five with the following meanings:
5 stars – excellent
4 stars – good
3 stars – satisfactory or average
2 stars – poor
1 star – very poor

If a car seat can be used in a number of different ways, and attached by different methods (Isofix or car’s seatbelt), we crash test it in the different ways it can be used and provide star ratings for each one.

The overall safety rating also takes into account the stability of the car seat in the car in case it seems loose or rickety, and how easy it is to thread the car’s adult seat belt around the car seat if this is an option.

Safety makes up 60% of the score for a car seat and considers front crash, side crash, seat design, stability in the car and belt routing.

Ease of use 

Key question: How easy is the car seat to fit?

It’s vital to ensure any car seat is fitted correctly. Any car seat, even a Best Buy, would be unsafe if it’s installed the wrong way.

Ease-of-use tests are not part of the legal requirements, but we conduct a whole range of tests on each seat to make sure that parents can fit them properly, without any risk of getting it wrong.

Parents get hands-on with the car seats to try to install them. These hands-on assessments give our experts an indication of the risks of installing a seat incorrectly, what could be forgotten, or how the seat could be misused.

We fit each seat in three different makes and models of car to see how easy it is to install. Experts consider both Isofix and seatbelt modes.

We scrutinise instructions and warning labels to see whether there is anything confusing, annoying or misleading.

Real children of different ages try out each seat, in all the cars. This helps to highlight any safety issues or problems with using the seat on a day-to-day basis – something our dummies can't tell us.

We also consider how easy the car seat cover might be to clean based on whether you can remove it easily and how it can be washed, and whether the seat has any signs of shoddy workmanship.

Our reviews point out potential issues you'll need to check before selecting your car seat, such as underfloor storage compartments or car headrests that could stop your seat working properly.

If a car seat is particularly heavy, we'll let you know in our review, so you can weigh up this information before you buy your car seat.

Ease of use makes up 30% of the score for a car seat and factors in installation, possibility of misuse, instructions, adjusting the seat, cleaning and workmanship.

Car seat ergonomics 

Key question: Is the car seat comfortable?

Our car-seat testing includes an ergonomic assessment of each seat to make sure your child will be in the best position when travelling. Any seats that hold your baby too upright, especially baby car seats, will have points deducted. 

Our car-seat experts check to make sure your baby or child will be held in a good position while travelling, which is especially important for small babies.

Experts check how roomy the seat is for your child and how much space they'll have to grow, as well as how the head support padding works.

The amount of space a car seat takes up is important, too. If it takes up too much, there may be none left over to safely transport other children, or it could impact space for the passenger in the front seat.

We look at the comfort for the child including how much support there is for the child's legs, the padding and their view from the seat, as you don't want children tempted to lean forwards out of their seat.

A flatter position is considered the best position for babies to travel in, especially those who are premature, newborn and young – not only for comfort, but also to help their breathing. 

Most people know of the two-hour rule – the guidelines recommending you don't keep your baby in a car seat for any longer than two-hours – but we advise you not to keep your baby in a car seat for any longer than absolutely necessary. 

The Baby Products Association advises parents not to use a car seat in the first four weeks of a baby's life for periods of more than 30 minutes. If it's essential to travel within the first four weeks, take regular breaks, at least every 30 minutes, and have an adult sit in the back to monitor your baby. Remove your baby from the seat for short periods before continuing with your journey.

Car seat ergonomics make up 10% of the test score and include posture, comfort, space for child, support, padding and view.

Fifty years of car seat testing

Which? has been helping to keep children safer in cars for more than 50 years. In 1966, almost 8,000 people were killed in road accidents in the UK. There was a huge push for better road safety, and the following year the motorway speed limit was fixed at 70mph, the breathalyser was introduced and the first Which? child car-seat reviews were published.

We constantly review the tests we carry out on car seats for babies, toddlers and children, and update them as required to keep them as thorough as possible.

In 2011 we changed the car body we use for testing to more accurately reflect the current seatbelt layout and design of a typical family car. 

In 2015, following the introduction of r129 car-seat regulations (which run alongside r44.04), we revised our testing procedures and assessments again to those detailed on this page.

This means you should be aware of the date tested when you read each review, and avoid direct comparisons between pre-2015 reviews and those since.

Watch our video below to see how things have changed between then and now, and see how our crash tests discover the best child car seats.

As well as being at the forefront of independent safety testing of child car seats, Which? has campaigned for decades to help families travel more safely in their cars. We’ve helped usher in stricter seatbelt laws, and raise the standard for child car-seat testing in the UK.

Join Which? to access all our in-depth child car seat reviews. Already a member? Log in to find your new car seat.


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