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Reliability analysis of air traffic control

A reliability analysis was made for the process air traffic control at the Area Control Centre (ACC) at the Air Traffic Control Centre (ATCC), Malmoe, Sweden. The method is called disturbance-effect-barrier analysis (DEB-analysis). It is a proactive method for risk assessment, based on a process view on accidents. According to this view accidents are seldom the results of isolated operator errors. Instead accidents evolve due to latent system failures (weaknesses) and insufficient safety barriers, making the system intolerant against human errors, and provoking these errors due to poor design of the operator-system interface. The DEB-analysis consists of a meticulous action sequence mapping, generation of hypotheses on disturbances, validation of these through observation and interviewing, analysis of effects on the system of the disturbances, and identification of latent system weaknesses and insufficient safety barriers as possible causes for negative system influence. This analysis points to some latent system failures, amongst others, lack of clarity and implementation of some of the written procedures, ill-defined roles for watch supervisors, and the burden on cognitive workload in handling the Air Traffic Control Automated System (ATCAS). The analysis suggests strengthening of some administrative safety barriers, for instance, counter reading from ATC (Air Traffic Control) to aircraft of flight level, and some technical barriers in the form of a medium term conflict alert, a clearancetransponder-check, and a system aid for the surveillance of conflicts. The system is considered basically ”non forgiving” to its operators, with weak barriers between an operator error and system failure, i.e. loss of separation between aircrafts. Quantifying the analysis by means of a good coverage local reporting system of incidents is discussed, and also how the analysis could be used during a development phase of new systems.