Car seats are all about safety – and yet, it’s remarkably easy to get things wrong when it comes to installing the seat or fixing your child inside it. In fact, there are certain mistakes that many parents make over again without realising.


We’ve spoken with car seat expert Julie Dagnall, co-founder of Child Seat Safety, and Rebecca Needham, Road Safety Evaluation Officer at the Royal Society for the Prevention of Accidents (RoSPA). These road safety experts explain what to look out for and how to keep safe.

These are the 8 most common car seat safety mistakes and how to avoid them

1 Car seat not installed correctly or securely

Spot the mistake: Unfortunately this is a common error. The Child Seat Safety team carry out more than 4,000 child seat checks annually and each year they find that as many as 51% of car seats and children in them are not correctly fitted.

There are 2 ways that a car seat isn’t fitted securely:

  • The car seat isn’t compatible with the car
  • The car seat hasn’t been installed properly

A slightly loose seat may be an indication, but equally may not. The key thing is, it’s all about checking – before you buy, before you install and after it’s fitted.

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Why it’s important: “It’s vital to have a correctly installed seat to reduce the chance of injury if you are in a collision. Ultimately any car seat is only as good as the way it’s fitted – and it needs to be fitted exactly as the manufacturer states,” says Julie Dagnall of Child Seat Safety. “This is exactly the same principle whether it’s fitted with ISOFIX points or using a seatbelt.

How to fix it: Never ever try to guess how a car seat should be fitted. “Firstly do your own research by checking manufacturer websites for compatibility lists with your car,” says Julie. “Then read the manual for both your car and the seat.”

Joie Spin 360 car seat rear-facing

Joie offers an online vehicle fitting guide, which identifies which of their car seats will fit your car, and is the only one in the market that enables you to compare 3 cars.

Under normal circumstances, we’d always recommended getting the car seat fitted professionally the first time. Rebecca Needham of RoSPA explains, “When buying a child car seat, we recommend visiting a retailer with trained car seat fitters who will be able to check the compatibility of the seat and show you how to correctly fit it in your vehicle.”

However, during the current COVID-19 situation, if you’re not able to get the car seat fitted, many manufacturers have official videos on their websites showing parents how to correct install the seat. 

“We urge parents and carers to follow the manufacturer’s instructions on installation of the seat to the vehicle and how to secure your child in it,” adds Rebecca from RoSPA.

Many manufacturers also have trained car seat installation advisors who you can contact when you buy the seat. There are also listings on the Child Seat Safety website of car seat advisors based at different retailers across the UK.

2 Harness straps not tight enough

Spot the mistake: Harness straps need to be tightened or loosened carefully – you can use the pinch test to check.

One in three children ‘are at risk’ because they are strapped in their car seats incorrectly. Harnesses being too loose is something we see all the time
Julie Dagnall, co-founder of Child Seat Safety

Why it’s important: “If you have a perfectly fitted seat but a poorly fitted child there’s a risk they may be ejected from the seat if there is a crash,” explains Julie. “To ensure the car seat works properly and is safe enough then it’s vital to have your child restrained correctly. It really could save your child’s life.”

How to fix it: You can do a quick test, called the pinch test, to check that harness straps are correctly tightened. Julie explains the steps:

  1. Place your fingers on the harness, in the area of your child’s collarbone
  2. Try to pinch the harness strap (by this we mean is there enough slack to enable you to pinch the material together)
  3. If you can get a good pinch of the material between your fingers, that means the harness is not tight enough
  4. If you can’t get the strap to pinch between your fingers, that means the harness is tight enough, and your child is strapped in properly

Watch our video on how to do the pinch test correctly

3 Wearing bulky clothes in the car seat

Spot the mistake: Wearing bulky coats, scarves or padded clothes can mean you can’t tighten the harness effectively, adding slack to the straps.

Julie explains how to show this:

  • Pop your child in the seat with their coat on and strap them in securely
  • Now take them out, remove the coat and strap them in again
  • Don’t readjust the harness and it’s likely that you’ll see a big gap between your child and the harness

Why it’s important: “A jacket, unless it is very thin, is actually creating an unseen gap between the harness and the child,” says Julie. “So thick clothing like coats can make the harness less effective.”

It’s not something parents are necessarily aware of, especially in the winter. One mum in the MadeForMums Facebook community reveals, “I look back at old photos of my first child in padded coats in her car seat and thank goodness we were never in an accident where that could have jeopardised her!”

Child with woolly hat in car seat

How to fix it: Avoid any bulky clothes – take them off when seating your child in the car seat. “Even a hoodie could be an issue as it pushes your child’s head too far forward if the hood isn’t up,” warns Julie.

For children you could also lightly place a blanket over the top but be careful it doesn’t get in the way of any of the safety fastenings so they can still work properly.

Rebecca from RoSPA adds, “Clothing can affect how snugly the seat’s harness fits the child, so it’s important to check that the harness is snug on every journey. If in doubt, take any layers off.”

4 Switching from rear-facing to forward-facing too early

Spot the mistake: Many babies are put into a forward-facing seat at the age of 9 months or when they reach 9kg – because this is the minimum age suitability for many non-i-Size forward-facing seats.

Some mums worry their toddler will be bored if they just have to look at the back of a seat. Or they’re concerned they’ll feel sad as they become more aware and can’t see their parents but can hear voices.

“But you should keep your child rear-facing for as long as possible,” emphasises Julie, “until your child is at least 13kg.”

Why it’s important: “A young child’s neck, head and spine are very fragile and the reality is rear-facing seats offer more protection and can help to reduce potential injuries in a crash,” explains Julie. “Your child should stay in a rearward facing seat until they are at least 13kg and according to i-Size rules they should be at least 15 months before they go forward-facing.”

If you are in a collision, a rear-facing seat means the force of the crash is spread down more effectively into the seat rather than into the child
Julie Dagnall, co-founder of Child Seat Safety

How to fix it: “Keep your child in a rear-facing car seat for as long as possible as this is the safest seating position,” stresses Julie. “And this means longer than 15 months: some rear-facing seats go up to 6 years.

“For your own piece of mind and to entertain your child, think about buying a specially designed mirror so you can still see each other even though your baby or child is facing the other way.”

5 Shoulder straps not threaded at the correct height

Spot the mistake: Some parents might think harness straps are a set-it-and-forget-it task, but you need to adjust the harness height as your child grows.

Why it’s important: If the strap height is incorrect, it can increase how much your child's body can move during a crash. “Ultimately, proper harnessing ensures that your child is reaping the full benefits of both the car seat and the vehicle’s crash management features,” says Julie.

How to fix it: Regularly check the harness is at the correct height for your child’s shoulders. “On rear-facing car seats, the shoulder straps should come through the car seat slots AT or just BELOW your child's shoulders,” explains Julie.

“On forward-facing seats, the shoulder straps should be AT or just ABOVE the shoulders.

“The general rule is that if your child goes up a shoe size then you will probably need to re-adjust the harness too, as they will have grown.

“Make sure you check every few months and either look online or in your car seat manual to find out how to do it on your seat.”

6 Baby kept in upright car seat for too long

Spot the mistake: Your baby is cozy and fast asleep so, rather than getting them out of the seat for a stretch, you leave them in the seat to sleep a bit longer. Or you use an upright car seat as part of your travel system for long periods, rather than ensuring they’re in a lie-flat position.

One mum in our Facebook community can relate, saying, “With my first, I made the mistake of thinking it was safe to leave my daughter in her car seat for an extended amount of time. I remember letting her sleep in the seat once we got out of the car. I wouldn't dream of doing so now!”

Why it’s important: “When a baby is in a semi-upright position for a prolonged period of time it can cause strain on the baby’s spine and also restrict air-flow to the baby’s lungs,” says Julie.

“The chance of this can increase if a baby falls asleep with their head flopped forward. Plus growing bodies need to be stretched out.

Joie i-level car seat positions
Some car seats sit upright in the car but a lie-flat position when out of the car and used as part of a travel system, such as the Joie i-Level (above)

How to fix it: Follow the ‘2-hour rule’ – the safety recommendation that advises that babies shouldn't sit in a car seat for more than 2 hours at a time. “We would actually go further than this and say, especially for those first few months, your baby should be in their car seat for as little time as possible,” says Julie.

In summary, be sensible. Be sure to check on your child regularly during periods sitting in their car seat, and give them regular breaks so they can stretch out their growing bodies.

Find out more about the 2-hour rule

7 Moving to the next-stage-up seat too early

Spot the mistake: As children get older they may be eager to change up to the next stage car seat or sometimes as a parent you want to mark the development of your child with a bigger seat. But it’s vital to wait until your child is the right size for their car seat.

Why it’s important: “The more snug a child is in a car seat then the less they are likely to move in the event of a crash.” says Julie. “Bones are still developing and they need the protection that the seat offers.”

The current law states that all children travelling in a car must use the correct car seat appropriate to their weight or height, until they are either 135cm in height or 12 years in age.

How to fix it: The legislation is complicated with different regulations that can be based on height, weight or age measurements, but the key is to familiarise yourself with each stage requirement. “Also get your money’s worth out of a seat and resist the temptation to put your child in the next stage seat as soon as they reach the minimum weight,” says Julie.

“Compare it to opening a bottle of wine (or non-alcholic drink if you prefer!). You don’t want to only drink half before pouring the rest down the sink and opening a new one.”

The latest UK car seat laws explained

8 Not using the top tether if your car seat has one

Spot the mistake: A top tether is a fabric strap used on some ISOFIX car seats that secures the child seat to a tether point behind the rear seat of the car. It’s a safety attachment that can be easily overlooked. “All too often parents forget to attach it,” says Julie.


Why it’s important: “The tether stops the seat from pivoting and keeps it level. If you are in an accident, the strap really reduces the forward movement of your child and the seat,” Julie explains. “This therefore means you’re really reducing the risk of injury, especially to your child’s head.”

How to fix it: The tether is usually found at the back of the rear seat, the bottom of the boot or on the ceiling. “Check both the vehicle’s manual and the car seat manual to make sure you are securing it in the right place in the car and on the seat itself,” says Julie. “For most straps you will see a green indicator when you have it at the right tightness.”


About our expert, Julie Dagnall

Julie Dagnall is co-founder of Child Seat Safety along with Claire Waterhouse. Julie has more than  20 years’ experience in the road safety industry and specialises in child car seat fitting. Child Seat Safety is Road Safety Great Britain’s national advisors for child car seats and run the UK’s first and only IOSH accredited car seat fitting course.