Each design alternative where the safety of a given system is concerned has a probability value for occurrence of an undesirable event (accident) in the system and a total cost. For a given probability value, there is a design that has the lowest total cost and meets this probability. In this paper, a method is presented for finding the optimal design and its total cost without explicitly enumerating all the possible design alternatives. In addition, it is shown how the optimal cost and design change as the acceptable probability level of the undesirable event changes. The problem of selecting an optimal restraint system for a car is presented as an example and is solved by the method.
