Scenario-based Human Factors modelling of safety-security escalation in critical socio-technical systems.

Abstract

Cyber incidents in safety-critical systems rarely produce accidents through technical failure alone. Instead, they alter operational conditions by increasing cognitive demands, degrading information quality, and reshaping human–system interactions. These changes influence operator performance, creating escalation pathways through which cybersecurity disruptions propagate into safety-critical outcomes. Conventional safety and cybersecurity risk assessments often treat human performance as stable or secondary, limiting their ability to anticipate socio-technical failure mechanisms. This paper presents a human factors-driven, scenario-based modelling approach for analysing safety-security interactions in complex socio-technical systems. The method represents operator tasks, cognitive workload, interface behaviour, automation responses, and organisational influences within scenarios contrasting stable and cyber-degraded operations. By modelling how Performance Shaping Factors (PSFs) shift during disruption, the approach makes human performance visible as the mediating layer between cyber events and safety consequences. Implementation within the CAIRIS socio-technical modelling environment demonstrates how degraded operational states, human performance pressures, hazards, and escalation pathways can be captured in structured engineering artefacts. Illustrative rail signalling and defence supervisory control examples show how the approach reveals latent vulnerabilities in interfaces, procedures, and automation reliance often overlooked in traditional assessments. The work contributes a practical socio-technical modelling method that complements system-theoretic analyses by explicitly representing performance variability during cyber-disrupted operations and linking these dynamics to safety risk.