SAFEST time to stop using the HBB

[StormzMe]

I know this isn't very 'Mumsnet' but my average height 11 year old is still in a HBB. He is about 143cm and skinny build. In my head I've always said he should stop using one when he hits 150cm, recently I was thinking maybe when he turns 12 but actually that should be about the same time. Then I was looking at him at the car the other day and realised he is completely content in there, he has never asked to stop using it. Maybe I will keep him in there til he outgrows it?? Is there any benefit above 150cm? I guess answering my own question that he should stay in until he fits the adult belt properly with. I'm at the back of seat, belt on lap not tummy etc. But that is sort of subjective and will vary by car - I'd like to have a specific height/number in mind!

We needed a booster seat (not hbb) for about 6 months in my car between shoulders getting to big for the hbb, and adult belt fitting. Straight from HBB to seat belt in DHs car.
It was pretty close to the 150cm, iirc maybe more like 145cm.

Unfortunately the problem is it IS subjective. It does vary by car and by the child's height, size, shape etc and the belt geometry. It's very possible that they fit some cars perfectly while others still need the booster and a third one is borderline (and you may choose to go without for short/occasional journeys).

If my understanding is correct, any add on including a booster seat adds (a very small) risk because it introduces a chance to use it incorrectly, because it's impossible to test every single configuration of every car model and child seat, and it adds extra belt routing plus it may diminish other safety features in the car - most HBB manufacturers tell you to remove the headrest, for example, even though a headrest secured by those metal bars is likely to give better head support in an accident than a plastic HBB headrest. It also lifts the child up higher and slightly more forward, whereas for best safety you want them to be low and further back.

Obviously, when the child is too short to use the proper seatbelt and they do not yet have the correct pelvis development to "catch onto" an adult seatbelt, then the booster improves safety by so much that these tiny things are outweighed, and why they are required by law up to 135cm/12 years (minimum).

So when we get between 135-150cm (or even taller) what then?

On a practical level the HBB can add body support - we did a very long drive when DS1 was 9 and had moved to a backless booster and when he fell asleep, he was totally lying down in the back which I hadn't really anticipated and made me feel quite anxious. The next year, we rented a different car and it came with a HBB which was actually taller than the one he'd previously had and he was able to fit into it, and so it supported him when he fell asleep. If you are going on longer journeys where even older children might sleep, or if you have an older child with disabilities that affect their posture and muscle tone, or possibly just even if your child tends to slouch, then the body support of a HBB may be beneficial.

Also if your car is older, and doesn't have very good side impact protection for rear passengers, a good modern HBB with good rating for side impact protection might be beneficial. But if you have a modern car with curtain airbags and the child is the right height to benefit from those airbags, then they will probably protect them better than the HBB, especially if you have an older HBB or one where the side impact protection is not rated very well.

You can get to a point where the child's shoulder is higher than the shoulder belt guide, in which case the belt is routing up and over their shoulder which is poor fit and at this point the HBB should be abandoned (or converted to backless perhaps).

In general I think unless you have a very old car or a child with physical or behavioural difficulties, there does come a tipping point after which it doesn't really make sense to use the HBB any more. Lap belt position is the most important thing, so if you can get a good lap belt position without it then it might be worth weighing up the pros and cons.

Thanks @CatsOnTheChair that's really interesting.

@BertieBotts fantastic - I love to see that detail and reasoning. Our cars are reasonably modern, DS has no disabilities and it's incredibly rare for him to fall asleep in the car. Sounds like I will have to play it by ear. It's weird to think that after all the effort and expense I've invested into making sure he always has the safest car seat over the years, we are months away from no car seat at all. I'm not ready 🙈

To be honest, if you've put that much into car seats, then you're more likely to get benefits out of continuing to use it, because you have likely researched and got one with really good side impact protection, and you are likely to be using it properly, at the correct setting etc. But you are in a minority - the majority of HBBs on the market, especially 7/8 years ago, though I suspect you switched later than this, did not have great side impact protection and a lot of people misuse HBBs by having the headrest at the wrong height or the lap belt routed incorrectly around the belt guides, both of which would increase risk compared with an almost-or-correctly fitted seatbelt alone.

But seatbelts work very well and modern cars have some incredible safety features even for passengers in the back, so don't be worried about making the switch. Have a read of your vehicle manual, if you have one. I recently looked at ours and discovered that there are seatbelt pretensioners in the back.

If you do decide to ditch it before it is completely physically outgrown, it might be worth keeping it in a cupboard somewhere in case you do go on any long holiday type drives where sleeping might happen. Because yes - in general I don't expect DC to be sleeping in the car past about age 3 maybe 4 - but when you drive 10+ hours in one day or through the night or into the evening it does happen.

Oh yes he was ERF and only had the HBB about 4 years I think - it was a well rated, fairly pricey one (but has done good service for 4 years so no complaints).

DH and I are both terrible long distance drivers 😂 so we never do trips more than 3hrs; still if it's been a long day (at say the beach) and we are driving home later in the evening there is a chance he would fall asleep. Either way I will be keeping hold of it incase his little sister can use it in a few years.