High back booster seats: in the field and in the laboratory.

High back booster (HBB) seat use was studied in the field and in the laboratory. This paper presents details of a case series of 19 children using HBBs in real world crashes. More than half were using HBBs when a forward facing restraint would have been more suitable (i.e. inappropriately), and incorrect use was identified in 3 cases. All serious injury occurred in children inappropriately or incorrectly using HBBs. Laboratory simulations modelled on real world cases demonstrate a greater injury potential in misused HBBs than in correctly used HBBs due to excessive upper body excursion.