The reliability of municipal infrastructure assets in Tanzania is crucial for sustainable urban development. A Bayesian hierarchical model was applied to municipal infrastructure data, accounting for spatial variability and heterogeneity across regions. The analysis revealed significant differences in system reliability between urban and rural areas, with an estimated mean reliability of 85% (95% credible interval: 70-92%). The developed model provides a robust framework for assessing municipal infrastructure systems' performance. Policy makers should prioritise maintenance in regions with lower system reliability to improve overall urban resilience. Bayesian Hierarchical Model, Municipal Infrastructure, System Reliability, 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.