{ "background": "The reliability of transport maintenance depot systems is critical for infrastructure sustainability and economic development. In many developing nations, systematic evaluations of these systems are scarce, leading to inefficient asset management and increased lifecycle costs.", "purpose and objectives": "This study aimed to develop and apply a novel panel-data methodology to evaluate the operational reliability of a national network of transport maintenance depots. The objective was to quantify system reliability trends and identify key determinants of performance.", "methodology": "A methodological framework was constructed using unbalanced panel data from a national depot inventory. System reliability was modelled as a function of technical, operational, and resource variables. The core estimation used a fixed-effects model: $R{it} = \\alphai + \\beta1 X{1,it} + ... + \\betak X{k,it} + \\epsilon{it}$, where $R{it}$ is the reliability index for depot $i$ in period $t$. Inference was based on cluster-robust standard errors.", "findings": "The analysis revealed a statistically significant decline in aggregate system reliability over the study period, with a mean annual decrease of 2.3% (95% CI: 1.7% to 2.9%). Depot age and spare parts inventory turnover were the most robust predictors of reliability outcomes.", "conclusion": "The applied panel-data methodology provides a robust, evidence-based tool for diagnosing systemic weaknesses in maintenance infrastructure. The results indicate a concerning trend of deteriorating reliability within the studied network.", "recommendations": "Infrastructure policy should prioritise targeted recapitalisation of ageing depot assets and reform supply chain mechanisms for critical spares. The adopted methodological framework should be institutionalised for ongoing performance monitoring.", "key words": "infrastructure reliability, maintenance engineering, panel data analysis, fixed-effects model, asset management, developing countries", "contribution statement": "This paper provides the first application of a panel-data econometric framework to model the reliability of transport maintenance depot systems at a