Belt systems are an appropriate means for realizing effective occupant protection. There are technical possibilities known, e.g. belt force limiters and preloading devices, which permit extreme safety requirements to be fulfilled by means of purposive coordination of the belt system to the structural deformation behaviour. The results presented here provide an example. It is at present difficult to evaluate the effectiveness of an occupant restraint system. One reason among others is the lack of an uniform complex Evaluation Index. In this paper, a suggestion is made concerning this problem: Introduction of the Evaluation Index EI.