On a Group 0 seat, the time to move your child from that to the next stage is when the child has the ability to sit up unaided. This means when the child is sitting and gravity starts to pull them over, they have the ability to correct themselves and sit up again. That tells us they are physically strong enough to move forwards into the next seat.
The thing that often gets asked is if the child’s feet reaches the end of the seat, have they out grown it? If they haven’t attained the weight and the sitting up ability, they are still perfectly safe in the seat. Most Group 0 seats are Group 0+ which takes them all the way through to 13kg. There are still some Group 0 seats that take them through to 10kg, that’s a minimum of 22lb or 28lb as a maximum. Child can remain in that seat until it reaches the maximum weight.
Frequently asked if when the child head gets to the top of the seat, have they outgrown it? Until the child’s eyes get level with the top of the seat, they are safe still remaining in that seat. Just need to take into account the front seat or dashboard, making sure there is sufficient distance between the child and those obstructions.
With a Group 1 seat, keep the child in to the maximum weight of 18kg, we would only move them early if they were so tall that their shoulder is level with the top harness position. That would mean they are at the limit of that particular product. Must ensure the child is a minimum of 15kg before moving onto the Group 2/3 seat.
The majority of Group 2/3 seats today are merged together, so maintain the back and head protection all the way through to 36kg, or on average 12 years. Some Group 2/3 seats separate out at 25kg, the end of Group 2, to become a booster cushion. If at that point the diagonal seatbelt isn’t sited at the edge of the shoulder and the centre of the chest, it is well worth looking at a new style high back booster that maintains the head and body protection, as well as the guide to keep the seatbelt in the correct position.
If a child meets the legal requirement 135cm or 12 years old, but the diagonal belt still isn’t sitting in the correct position, then continue to use the safety device until they are tall enough to sit there like an adult.