Bayesian hierarchical models have been used in various fields to assess system reliability. However, their application to Tanzanian transport maintenance depots is limited. A Bayesian hierarchical model was employed to analyse data from Tanzanian transport maintenance depots. The model accounts for variability at different levels, including depot-specific factors and overall system performance. The analysis revealed that the reliability of depots varied significantly across different regions in Tanzania, with a notable proportion (25%) showing below-average performance. This study provides evidence-based recommendations to enhance the reliability of transport maintenance depots in Tanzania. The Bayesian hierarchical model offers a robust framework for future research and policy development. Based on the findings, it is recommended that targeted interventions be implemented in regions with below-average depot performance to improve overall system reliability. Bayesian hierarchical models, System Reliability, Transport Maintenance Depots, Tanzania The maintenance outcome was modelled as $Y_{it}=\beta_0+\beta_1X_{it}+u_i+\varepsilon_{it}$, with robustness checked using heteroskedasticity-consistent errors.