"background": "Transport maintenance depots in sub-Saharan Africa face systemic inefficiencies, leading to suboptimal asset availability and high operational costs. There is a recognised lack of rigorous, field-based evidence on the impact of systematic interventions within these complex engineering systems. ", "purpose and objectives": "This case study aimed to methodologically evaluate a randomised field trial designed to measure and optimise yield—defined as the proportion of vehicles fully operational—within a representative depot network. The primary objective was to quantify the causal effect of a revised maintenance scheduling protocol on overall fleet yield. ", "methodology": "A pragmatic randomised controlled trial was implemented across 24 depots. Depots were randomly assigned to either a treatment group, implementing a new predictive maintenance scheduling system, or a control group continuing standard practice. Yield was measured monthly over an operational period. The treatment effect was estimated using a linear mixed model: Y{it = \0 + \1 Ti + \ Xit + ui +, where Yit is yield, Ti is the treatment indicator, Xit are time-varying covariates, and uᵢ are depot random effects. ", "findings": "The intervention produced a statistically significant positive effect. Depots using the new protocol achieved a mean yield increase of 8. 7 percentage points (95% CI: 5. 2, 12. 1) compared to control depots. The effect was robust to different model specifications and showed increasing benefit over the trial's duration. ", "conclusion": "The randomised field trial confirmed that structured, data-informed scheduling can substantially improve operational yield in real-world maintenance engineering contexts. The methodology proved feasible and generated high-quality causal evidence. ", "recommendations": "Depot managers should adopt predictive scheduling systems underpinned by continuous data collection. Policymakers should support further field trials to test scalable interventions across different engineering asset classes. ", "key words": "randomised controlled trial, maintenance
Mwakalinga et al. (Tue,) studied this question.