Development of safety incident coding systems through improving coding reliability

•Factors affecting incident coding system reliability are tested and analysed.•Domain-specific coding systems are more reliable than generic, multi-domain systems.•Systems with abstract and/or loaded terms affected coding reliability negatively.•Coder profession, rather than training provided, influenced coding reliability.•System improvement and design recommendations are provided based on these results.

This paper reviews classification theory sources to develop five research questions concerning factors associated with incident coding system development and use and how these factors affect coding reliability. Firstly, a method was developed to enable the comparison of reliability results obtained using different methods. Second, a statistical and qualitative review of reliability studies was conducted to investigate the influence of the identified factors on the reliability of incident coding systems. As a result several factors were found to have a statistically significant effect on reliability. Four recommendations for system development and use are provided to assist researchers in improving the reliability of incident coding systems in high hazard industries.