Accident investigation reports from the Dutch Labour Inspectorate are used by the Dutch National Institute for Public Health & Environment (RIVM) to analyse major hazard chemical accidents in a structured way. The purpose of the analyses is to improve understanding of accident causes and of ways to improve detection of major accident precursors. A bow-tie framework was developed in a collaborative process of engineers, psychologists and inspectors over many years. The nature of the model is that it combines technical, human and management components while preserving the temporal sequence of events of each accident scenario. Six lines of defence define the causal pathway from initiating events to accident and impact on man and environment. Different safety barriers in these lines of defence represent the different ways in which the lines of defence can fail or be successful. Sets of underlying human, management and organisational factors are provided at barrier level to better understand why barriers fail. More than 300 Dutch accidents that occurred at Seveso sites since 2003, have been analysed. The resulting publically available data set shows the variety of ways in which accidents can develop as well as some general patterns that are emerging.
This paper describes recent changes applied to the model, suggestions on how the model could be useful, and the potential for analysing near misses and successful recoveries.