I. ABSTRACTThe performance advantage of seat belt pretensioners is well documented. But what is the effect for child restraints? We tested four categories of CRS with and without seat belt pretensioners on adult seat belts, using the ECE44.03 dynamic test. We compared outcomes in terms of head excursion, head and chest deceleration and HIC (“Head Injury Criterion”) and used a common type of pyrotechnic pretensioner. For infant restraints, pretensioned conditions lead to a reduction in head excursion and HIC. Two forward facing toddler seats showed lower HIC, and one a large reduction in excursion. Pretensioning led to reductions in HIC for forward facing impact shield boosters and for belt positioning boosters. Three CRS were also tested in a pre-impact braking mode, with and without pretensioner. Here the differences were less pronounced.On the whole, pretensioners did improve the outcome for CRS, in particular for designs which did less well in the “normal” mode. The tests revealed no major ill effects for these models of CRS when used in adult seat belts with pretensioners.