The safety of our babies is every good parent’s priority, but when it comes to car seat safety, it can be an absolute minefield – particularly with ever-changing height and weight guidelines and car seat laws. UK legislation and regulations can be confusing – do new laws mean your existing car seat is no longer legal? And even if it is, is it unsafe to continue using it? Naturally, you don’t want to take any unnecessary risks with your child or baby’s safety, so being up to speed with current UK child seat laws and recommendations is crucial. This post covers the most recent 2017 updates to car seat regulations, including booster seat law (UK).

Car Seat Laws UK: Height and Weight Guidelines, & Legislation Changes Affecting Car Seats


Current car seat laws demand that babies weighing less than 9kg must be rear-facing, but a new law (i-Size) which currently sits alongside (and is set to replace it in due course), requires that infants remain rear-facing until at least 15 months. For everything you need to know about i-Size, take a look at the link above which details the changes and what they mean for your family.

Mother Putting Child Into Car
Child seat laws: UK legislation has changed to make your child safer.

Backless Booster Seat Law UK

These seats were previously sold as being suitable for children over 15kg, which is usually between the ages of three and four. New car seat laws which came into effect in February 2017 aim to prevent manufacturers from designing new backless booster seats for those a minimum of 22kg in weight, or 125cm in height – whichever comes first. As with i-Size, the new law does not condemn those with existing backless booster seats, and applies only to new models coming to market.

Types of Child Car Seat

The law states that children must use a car seat until they are twelve years of age or 135 cm tall – whichever comes first. There are many types available, both in terms of age/weight range, and restraint. For a full list of the different seat types available, check out this link.

Car seat laws and height and weight guidelines and safety can be a minefield. Here's a guide to current legislation and recommendations.

How to Choose the Safest Car Seat For Your Child

When it comes to selecting the seat you’re essentially entrusting your babe’s life to, we’re united in not wanting to take any chances. But how on God’s green earth do you choose when there’s such an abundance of possibilities? Is the market saturated with variations or what are basically the same seat, or are some genuinely safer than others?

Well, a little of both. Some aspects are non-negotiable, while many more nuances may only be aesthetic.

The following list sets out the basic criteria to ensure car seat safety, and legal compliance:

  • It conforms to the United Nations standard, ECE Regulation 44.04 (or R 44.03) or to the new i-size regulation, R129. (Look for the ‘E’ mark label on the seat.);
  • It’s suitable for your child’s weight and size;
  • It’s correctly fitted according to the manufacturer’s instructions.
  • If you can tick these points then you can be confident that the seat you’ve chosen when brand new and installed correctly meets current car seat height and weight guidelines.
Kids in a Car

Of course, these are the basic parameters. If you’re keen to make further assurances for your little rascals’ safety then there are additional recommendations too:

  • Only use a brand new car seat. Because it’s not possible to be certain of its history unless you’ve owned it from new, it’s not recommended to use a secondhand seat. Any impact on the seat may cause deterioration, and when the issue is so serious, it’s simply not worth taking that risk.
  • Use a rear-facing seat for as long as possible (see above information about the new i-Size legislation  for car seat height and weight guidelines coming into effect).
  • Never allow your child to wear bulky layers when travelling in the car – provide a blanket to go over straps rather than coat to go beneath.
  • As a guide for how tightly to restrain your little one, once strapped in, you should be confident enough to safely turn your baby upside down in their car seat.

Rearward-Facing Versus Forward-Facing

We all know that rearward facing seats are encouraged for as long as possible – but why?

Family Posing in Car Boot

Essentially, it’s to minimise impact on the neck, spine and internal organs in a head-on collision (sounds horrific, and it is, hence the imperative nature of knowing this stuff). Frontal collisions are the most dangerous because of the massive trauma they represent to those delicate areas of your infant’s vulnerable little body. Being flung forward with nothing to support the head means their neck is completely unprotected. I don’t have to spell out the potential consequences.

Conversely, when rearward facing, the child is forced backwards against their seat meaning the force of the impact is distributed across the whole back of the chair.

If you’re the kind of person who responds to numbers, here’s all you really need to know about head-on collisions: forward-facing, the neck is subjected to a force equivalent to 300kg-320kg; rearward facing, the force on the neck is equivalent to 50kg. Your child is up to 75% better protected in a rear-facing seat.

Britax Dualfix i-Size and Multitech III
Examples of rear-facing and booster car seats.

Of course, there are some disadvantages to using rearward facing seats, otherwise everyone would use them until it were no longer feasible… However those reasons are really kind of trivial:

  • As your toddler grows in height, their legs must be bent in order for them to fit in their seat;
  • You’re less able to ‘keep an eye’ on your sprog;
  • Your child would prefer to sit forward to see out of the window;
  • It’s easier to include your little one if they travel in the same direction as the family.

Legitimate reasons for it to be a pain in the bum, but given that the alternative could quite literally be the difference between life and death, annoyances absolutely worth persevering with.

How Do You Know When Your Baby Needs a New Car Seat?

Okay, so there are weight and age guides to assist here, and car seat laws and legislation to ensure nobody can inadvertently go way beyond what’s deemed safe – but how can you tell if your child has outgrown their seat early? What’s the criteria, beyond weight?

It’s a really simple test and most parents will be aware of this already: if your little moppet’s head is visible above the back of the car seat, then it’s no longer safe.

Child Sleeping in Car

Your Legal Responsibility, and Exceptions to UK Child Seat Laws

Legal responsibility for children being correctly restrained falls to the driver up until 14 years of age, after which time the individual becomes responsible for themselves.

There are some exceptions to these car seat laws, for situations such as being a passenger on a bus or in a taxi. See here for more information.

If you have any concerns, be sure to seek assistance, particularly when it comes to ensuring your child’s seat is correctly installed: there’s no point spending hundreds of pounds on a safe seat and then fitting it in such a way that it fails on impact.

It’s worth noting that a lot of car seat manufacturers will only sell to you once they can confirm that their seat has been satisfactorily tested in your model of car, and these safety assurances do just that: they reassure me.

Retailers selling car seats also tend to offer a fitting service free of charge. However, if you purchase online or otherwise acquire a seat in circumstances which prevent you from making use of this service, I understand that the safety officer at your local council can also assist if required.

If you found these height and weight guidelines and UK child seat legislation useful, please consider sharing!

An award-nominated blogger and author, Kate is a huge advocate of personal growth, focusing on journaling to increase positivity and facilitate mindful motherhood. With a wealth of experience in breastfeeding and CMPA, Kate is also an expert baby sleep chaser. Her writing has appeared on Mothercare, Huff Post, and BritMums.

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