Child car seat reviews: Features explained
Child car seats with integral harness
Group 0 and Group 1 car safety seats for younger children generally have a 3- or a 5-point harness built into the seat.
Booster seats (or group 2 and 3 seats) don't usually have this; instead they use the car's normal 3-point adult seat belt to secure the child in the seat.
In general, a 5-point harness is more effective at restraining a child because, with a 3-point belt, the shoulder belt can slip in a crash if it's not correctly positioned.
We check for this, and take it into account in the child car seats' test scores.
Child car seat as part of a travel system
Some child car seats can be removed from the car and placed in a travel system, such as a pram or carrycot.
Group 0 and 0+ car seats are most commonly sold as part of travel systems.
Some child car seats have a detachable back, so you can convert them into a booster seat once the child gets older. However, most booster seats don't offer the same level of side-crash protection as full child car seats.
Isofix car seats
If you have an Isofix car safety seat and Isofix mounts in your car, you can forget about messing about with seat belts to secure your car seat.
Isofix is the standard system for all new cars and seat manufacturers, designed to make installing your child safety seat quick and easy. Many parents worry about fitting their car seat correctly, but with Isofix you simply ‘plug in’ a compatible car safety seat to mounting points in the car.
Isofix seat crash protection
The concept of using Isofix attachments is that seats should be easier to install than when using the belts. However, there can be a trade off between this easy installation and the energy absorbing capacity of the seat, which our testing shows can lead to the child being exposed to slightly higher loads in crashes than the same seat with a belted installation.
With Isofix mounts the 'joint' between the seat and the car is relatively stiff, creating a rigid path for force transmission. When a seat is installed using a seat belt, there is compliance in the belt which means slightly more movement of the seat in a crash, but the forces transmitted to the seat (and hence the child) are often lower, because of the energy absorbed as the belt flexes.
2-point and 3-point Isofix
Most cars made since 2002 have 2 fixing points, but many cars now have 3, where the third (top) tether attaches to a mount behind the rear seat to stop it tipping forward in an accident.
The 3-point fixing should work even better than 2-point fixing, because it holds the child car seat even more securely. However, the 2-point fixing is still generally more secure than using seat belts to secure car safety seats.
Another way of providing a third constraint to resist tipping in a front crash, is to have a support leg between the child seat base and the floor of the car. Using a support leg is usually easier than attaching a top tether, but such seats can only be used in cars where the floor is solid. They aren't suitable if there is hollow storage space where the foot contacts the floor. Always check with the car maker to ensure the seat can be used in your car.
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If you're buying a new car, make sure it comes with Isofix mountings - sometimes they're a 'no-cost' option.
Based on past crash-test results, Which? has found most carry cots unsuited to use in cars, as they offer inadequate protection in crashes. Only one carry cot we've tested (the Britax Baby Safe Sleeper) protects the baby well enough, and is a Best Buy. If you already own a carrycot, we suggest you buy an alternative 0+ category child safety seat for use in the car. But if you have a carrycot and there’s nothing else you can use, it’s better than nothing at all.
If you have to use a carrycot, place it across the back seat, as close to the middle as you can. This may use up more space, but it means the baby is less vulnerable in a crash. Place the baby’s head as far from the door as possible, to try to avoid contact with the door in a side crash.