The Wrong Question to the Right People. A Critical View of Severity Classification Methods in ATM Experimental Projects

Abstract

The knowledge of operational experts plays a fundamental role in performing safety assessments in safety critical organizations. The complexity and socio-technical nature of such systems produce hazardous situations which require a thorough understanding of concrete operational scenarios and cannot be anticipated by simply analyzing single failures of specific functions. This paper addresses some limitations regarding state-of-the-art safety assessment techniques, with special reference to the use of severity classes associated to specific outcomes (e.g. accident, incident, no safety effect, etc.). Such classes tend to assume a linear link between single hazards considered in isolation and specified consequences for safety, thus neglecting the intrinsic complexity of the systems under analysis and reducing the opportunities for an effective involvement of operational experts. An alternative approach is proposed to overcome these limitations, by allowing operational people to prioritize the severity of hazards observed in concrete operational scenarios and by involving them in the definition of the possible means of mitigation.