Child safety harnesses
A child safety harness or 'H harness' is an extra piece of equipment used with a child restraint or seat belt.
Using child safety harnesses is not recommended.
A child safety harness (sometimes called an ‘H harness’) is an extra piece of equipment that is sold separately to a child restraint. It is not the same as an in-built harness on a child restraint.
Child safety harnesses attach to anchorage points and are used with booster seats or lap-only seat belts.
They are difficult to use and are often fitted incorrectly. Incorrect use of the child safety harness can cause the seat belt to ride up onto a child's stomach area. In a crash this could cause injury or death to a child.
When and how to use child safety harnesses
Do not use a child safety harness if there is a lap-sash seat belt available.
Only use a child safety harness when there is a lap-only seat belt and it is not possible to replace it with a lap-sash seat belt.
If you cannot replace the lap-only seat belt with a lap-sash seat belt, you will need to use a child safety harness with a booster seat. In this case, you should use a booster seat with an 'anti-submarining' device. This holds the lap part of the seatbelt down low on your child’s hips.
Make sure the shoulder straps are not too tight and that you check the harness is fitted correctly every time you use it.

Pictured: Anti-submarining device on a belt