Infasecure explains why the H Harnesses are no longer recommended for car seats.

A joint study on the efficency of child accessory harnesses (H harness) carried out by members of the Prince of Wales Medical Research Institute and the New South Wales Centre for Road Safety found that, “Based on pelvic restraint, head excursion and abdominal injury potential, results from this study suggest that in frontal impact at least, accessory child safety harness systems provide no better protection than lap–shoulder belt systems.

When the accessory child safety harness systems are misused the level of protection provided is seriously degraded. Given the high frequencies of child safety harness system misuse seen in field observation studies, and the fact that even when correctly used these system provide no improvement over a lap–shoulder belt, it seems likely that the risks of injury outweigh any perceived benefit of a child safety harness system over a lap–shoulder system.”

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Infasecure also conducted their own comparative testing program, and observed the same results as were published in the report – there was no increase in protection when an accessory child harness was used, compared to a standard lap-sash seatbelt, and in instances when the accessory child harness was not fitted correctly, the result was far, far worse.

This testing resulted in InfaSecure discontinuing the sale of child accessory harness, and modifying booster seats to be incompatible with other brands of accessory harnesses.


Infasecure explains, “the way the dummy slides underneath the lap portion of the seatbelt is known as ‘submarining’ and can be deadly. Submarining of this nature can cause horrific internal injuries, and has tragically lead to the deaths of a number of children.

While submarining can occur without the use of child accessory harness, the design of a child accessory harness is such that it makes submarining more prevalent when fitted or used incorrectly (which is reported to be as high as 100% of the time).

This certainly explains why I couldn’t find them recently when I went to grab one! Glad I didn’t hunt around too much.

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Main image via infasecure

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  • Anything that makes it harder to get your babies out is not a good idea… especially in an accident.


  • Interesting – learned something new today!


  • These were an option 30 years ago when cars only had lap belts in the middle of the rear seat and the child was too big for a babyseat and the eldest child had to sit in the middle. At time they were better than nothing. The lap belt went through the loops at the bottom of the H belt, the top of the H belt was anchored to the anchor attached shelf above the back of the car seat.
    Later and current cars have 3 lap sash belts so the H belts shouldn’t even exist any more.


  • I can’t remember I ever have seen one of these around.


  • Great that these are no longer going to be used.


  • Good to know they won’t be in use.


  • I would have just assumed the harness was safer. Thanks for this important safety read!


  • Glad these will no longer be used.


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