{ "background": "Process-control systems are critical for mitigating operational risks in structural engineering projects, yet there is a paucity of field-based evidence comparing the efficacy of different methodological approaches in low-resource construction environments.", "purpose and objectives": "This study aimed to empirically compare the risk reduction performance of two distinct process-control system methodologies—a prescriptive checklist-based system and a performance-based dynamic monitoring system—within live construction projects.", "methodology": "A randomised field trial was conducted across multiple infrastructure sites. Contractors were randomly assigned to implement one of the two systems. Risk reduction was measured as the proportional decrease in weekly recorded hazard counts from a baseline period. The primary analysis used a mixed-effects model: $\\Delta Risk{it} = \\beta0 + \\beta1 Methodologyi + \\gamma X{it} + ui + \\epsilon{it}$, where $ui$ represents site random effects. Robust standard errors were clustered at the site level.", "findings": "The performance-based system yielded a significantly greater mean reduction in identified hazards (38.2%, 95% CI [34.5, 41.9]) compared to the prescriptive system (22.7%, 95% CI [19.1, 26.3]). The treatment effect remained statistically significant (p < 0.01) after controlling for project scale and crew experience.", "conclusion": "The performance-based, dynamic monitoring methodology demonstrated superior effectiveness for on-site risk reduction under the trial conditions, suggesting that adaptive, data-driven control processes outperform static checklist approaches in this context.", "recommendations": "Adoption of performance-based process-control systems should be prioritised. Further research should investigate the integration of such systems with digital monitoring technologies and their long-term cost-benefit implications.", "key words": "process control, risk reduction, randomised trial, construction safety, field experiment, engineering management", "contribution statement": "This study provides the first comparative, randomised field evidence on process-control methodologies