A Comparative Safety Assessment Approach for Safety Critical Systems

Safety critical systems are designed to be extremely safe. Accidents in safety critical systems rarely occur and hence are often inadequate to expose safety patterns nor to quantify the system's immediate safety performances. During system development or evolution, such quantifications of system safety performance are necessary to make safety design choices or to meet regulatory requirements. A control based systemic approach is introduced to allow comparisons between system design alternatives for safety critical systems. The proposed approach includes two system control related safety metrics, Probabilistic System Control (PSC) and Temporal System Control (TSC) each addressing one aspect of the control system, and a three-stage method to evaluate PSC and TSC. A case study to runway incursion safety assessments is conducted to demonstrate the implementation of this method. The case study results are consistent with conclusion drawn from prior direct simulations.