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Abstract
Background: The concept of ‘safety voice’ captures the extent to which individuals speak-up about safety. The behaviour is deemed important for preventing accidents, yet interventions are needed because people often fail to speak-up (‘safety silence’), thus contributing to harmful outcomes across safety-critical domains. However, the concept remains disintegrated and grounded in limited evidence and methodologies. Thus, the utility of ‘safety voice’ for safety management remains unclear, prohibiting effective interventions. This thesis therefore aims to evaluate how the behavioural nature of safety voice may be optimally conceptualised, assessed and intervened on. Approach: Four articles presented a systematic literature review (n = 48 publications), twelve experimental studies (ntotal = 1,222) and an analysis of Cockpit Voice Recorder (CVR) transcripts across 172 aviation accidents (1962-2018; n = 14,128 conversational turns). Article 1 synthesised evidence from across theoretical domains. Article 2 presented the first experimental paradigm for safety voice (‘Walking the Plank’) to address nine methodological challenges. Article 3 observed safety silence in the laboratory to establish and conceptualise how the behaviour manifests in relationship to safety voice and interventions. Article 4 captured safety voice during real-life safety accidents, and investigated how risk, safety listening, power distance and CRM training impact on safety voice. Findings: Safety voice is a distinct concept that is highly ecological and situated, and that is important for understanding how safety voice contributes to accidents. A methodological reliance on self-reports and post-hoc methodologies was identified and addressed through the Walking the Plank paradigm. Safety silence, identifiable through assessing safety concerns, was scalable based on the degree of safety voice speech, with interventions uniquely impacting on five safety themes and hazard stages. Safety voice was found to occur frequently during real accidents, with the developed Threat Mitigation Model underscoring that safety concerns, safety voice and safety listening all contribute to preventing harm.
