Development of a FTA versus Parts Count Method Model: Comparative FTA

This study adopts a special Fault Tree Analysis (FTA) method called Comparative FTA to compare the reliability of an electronic braking system with its mechanical counterpart. To this end two Top Events, ‘Ineffective parking braking’ and ‘Wheels jamming during emergency braking’, were analysed. One of the limitations of classic FTA is that the setting up of the tree diagram requires the long-term involvement—one to two months according to Fiat Auto—of specialists of the system being studied. For this reason, therefore, when dealing with relatively complex systems, classic FTA is only used when safety is involved. This paper introduces a simplified FTA model based on the same principle as the Parts Count Method, which limits its attention to the new branches, thereby avoiding the study of all the branches of the tree, in order to make FTA management easier and to encourage its use. The probability that a Top Event takes place is therefore evaluated by studying the different causes which diversify the solutions considered. This approach is a lean practice to minimize the resources and the time of the analysis. It has guaranteed very satisfactory results and, therefore, Fiat Auto has introduced the practice in their Corporate Instructions.