The interface conditions or variables between motor vehicles and child restraint systems (CRS) may adversely affect the performance of CRS and consequently the severity of injuries of children. The amount of interior space may determine the likelihood of head impact. The accessibility in a 2-door vs. a 4-door car may increase misuse. The larger size of a child within the same CRS may be a reason for body contact with subsequent injuries etc. Furthermore crash or CRS-specific conditions like the occurrence of pre-impact braking, seating location of the child, upright or reclined position of the CRS may influence the outcome in a crash.

On the basis of in-depth studies of real-life crashes done by the Accident Research Unit of the Medical University Hannover / Germany and the assessment of accident reports obtained by Britax Römer, Ulm / Germany the effects of variable interface conditions and use modes are investigated.