The transport maintenance depot systems in Ghana are critical for ensuring efficient vehicle operations, but there is limited empirical research on their effectiveness and cost-effectiveness. A randomized field trial was conducted across multiple depots in Ghana, with data collected over a six-month period. Depot efficiency and costs were measured using statistical models. Depot A showed an average reduction of 15% in vehicle downtime compared to the control group (p < 0.05), indicating improved maintenance system effectiveness. The randomized field trial demonstrated significant cost savings for Depots B and C, with a confidence interval of ±3%, suggesting robust performance metrics. Based on findings, depots should invest in advanced diagnostic tools to further enhance efficiency and reduce downtime. The maintenance outcome was modelled as $Y_{it}=\beta_0+\beta_1X_{it}+u_i+\varepsilon_{it}$, with robustness checked using heteroskedasticity-consistent errors.