An analysis of the content of questions and responses in incident investigations: Self reports in the investigation of signals passed at danger (SPADs)

Information from a range of sources is used in the investigation of industrial incidents. In the rail industry, a large amount of evidence is collected in the investigation of signals passed at danger (SPADs) and this includes various forms of self reported information. This study aimed to compare the different types of self reports which are collected during the investigation of SPADs, along with an analysis of questions used to collect information. This was carried out with the overall intention of determining whether there were opportunities to build upon the investigation process, which is well established within the industry, and identify findings which are applicable more widely in incident investigation. Reports relating to six SPAD incidents were analysed in depth, with each incident providing four self report types: recordings of a conversation between the driver and signaller, a written statement from the driver, an initial interview transcript, and an investigative interview transcript. The analysis was grounded in established psychological theory of questioning and reporting. A classification and comparison of the content of the four types of report has been produced, along with a classification of the types of questions used in interviews during the investigations. The findings will provide useful baseline information for the rail organisations (such as for the evaluation of the effectiveness of programmes to improve the investigation process). More generally, in the field of accident investigation, the findings provide insights into the selection of appropriate question types and the factors to consider when interpreting associated responses.