101 Generation of Human Reliability Data for the Air Traffic Industry (PSAM-0030)

Air Traffic Management (ATM) deals with the safe and efficient passage of aircraft across national and international airspace. In Europe, ATM, as with other industries, must now comply with formalized risk assessment procedures, for example those embodied in EUROCONTROL Safety Regulatory Requirements (ESARR) 4 [1]. In order to demonstrate that systems are acceptably safe, a Safety Assessment Methodology (SAM) has been proposed by EUROCONTROL [2] and is being applied by many countries in Europe. Safety cases for existing or new systems, or significant system changes, can utilize fault and event tree (or equivalent) approaches to model and quantify risk as is done in other industries such as nuclear power, chemical, process, and petrochemical. However, there has been little emphasis to date on Human Reliability Assessment (HRA) in the world of ATM, although it is recognized that the high degree of safety evident in this industry is mainly due to the human element (in particular the air traffic controller). The context of this paper therefore concerns the feasibility of HRA in air traffic risk assessments. As a first step towards HRA in ATM, this paper focuses on the degree to which quantitative human error data can be generated to substantiate or calibrate an ATM HRA approach.

Two separate exercises are reported. The first concerns collection of human error data from a real-time simulation involving air traffic controllers and pilots. This study focused on communication errors between controllers and pilots. The second relates to a formal expert judgment study using direct numerical estimation (also called Absolute Probability Judgment) and Paired Comparisons protocols to elicit and structure the controller and pilot expertise.

The results showed that stable HEPs can be provided from real time simulations, at least with respect to communications activities, and to a lesser extent from expert judgment approaches. These results suggest that the approach of HRA can be adapted to ATM safety case methodologies and frameworks. An example of a recent developing air traffic safety case which has utilized the HRA approach is briefly discussed.

The conclusion is that HRA is feasible, but that more data do need to be collected, since ATM dynamics and safety scenario timings, as well as its operational culture and performance shaping factors, are different to other industries where HRA application is ‘the norm’.