How does aviation industry measure safety performance? current practice and limitations

In this paper we present a review of existing aviation safety metrics and we lay the foundation for our four-years research project entitled “Measuring Safety in Aviation – Developing Metrics for Safety Management Systems”. We reviewed state-of-the-art literature, relevant standards and regulations, and industry practice. We identified that the long-established view on safety as absence of losses has limited the measurement of safety performance to indicators of adverse events (e.g., accident and incident rates). However, taking into account the sparsity of incidents and accidents compared to the amount of aviation operations, and the recent shift from compliance to performance based approach to safety management, the exclusive use of outcomes metrics does not suffice to further improve safety and establish a proactive monitoring of safety performance. Although the academia and aviation industry have recognized the need to use activity indicators for evaluating how safety management processes perform, and various process metrics have been developed, those have not yet become part of safety performance assessment. This is partly attributed to the lack of empirical evidence about the relation between safety proxies and safety outcomes, and the diversity of safety models used to depict safety management processes (i.e. root-cause, epidemiological or systemic models). This, in turn, has resulted to the development of many safety process metrics, which, however, have not been thoroughly tested against the quality criteria referred in literature, such as validity, reliability and practicality.