{ "background": "Community health centres are critical nodes in primary healthcare systems, yet robust methodologies for quantifying their operational reliability are lacking. This gap impedes evidence-based system strengthening and resource allocation.", "purpose and objectives": "This study aimed to develop and pilot a quasi-experimental methodological intervention for measuring system reliability in a primary care setting. The primary objective was to estimate the effect of a structured process mapping intervention on a composite reliability index.", "methodology": "A quasi-experimental, pre-post intervention design was employed across twelve purposively selected centres. The intervention comprised a formalised process mapping and failure mode identification protocol. System reliability was operationalised as a composite index of appointment adherence, medication availability, and equipment functionality. The primary analysis used a linear mixed-effects model: $Y{ij} = \\beta0 + \\beta1 T{ij} + ui + \\epsilon{ij}$, where $ui \\sim N(0, \\sigma^2u)$, with robust standard errors clustered by centre.", "findings": "The process mapping intervention was associated with a statistically significant increase in the mean composite reliability index (pre-intervention M=0.65, post-intervention M=0.78). The adjusted mean difference was 0.13 (95% CI: 0.07 to 0.19, p<0.01). The greatest improvement was observed in medication availability, which increased by 22 percentage points.", "conclusion": "The proposed methodological intervention provides a feasible and quantifiable approach for assessing system reliability in resource-constrained primary care environments. The positive association with the reliability index suggests the utility of structured process evaluation.", "recommendations": "Implement the methodological framework for routine operational audits within primary care networks. Future research should validate the index against longitudinal health outcomes and test the intervention in a randomised controlled trial.", "key words": "health systems research, operational reliability, quasi-experimental design, primary healthcare, process evaluation, South Africa", "contribution statement":