A Quasi-Experimental Evaluation of Reliability in Nigerian Transport Maintenance Depot Systems

{ "background": "Maintenance depot systems are critical for transport infrastructure reliability, yet their operational performance in developing economies is under-studied. Existing assessments often lack rigorous, quantitative frameworks for evaluating systemic reliability, leading to reactive rather than proactive management.", "purpose and objectives": "This study aimed to develop and apply a quasi-experimental methodology to quantitatively evaluate the reliability of transport maintenance depot systems. The primary objective was to measure the causal effect of depot system configuration on reliability metrics.", "methodology": "A quasi-experimental, pre-test/post-test design with non-equivalent control groups was implemented across multiple depots. System reliability was modelled using a Weibull failure process. The core statistical model was $R(t) = \\exp^{-(t/\\eta)^\\beta}$, where $\\eta$ is the scale parameter and $\\beta$ the shape parameter. Data were collected via direct observation and maintenance logs, with inference based on robust standard errors to account for heteroskedasticity.", "findings": "Depots implementing a standardised preventive maintenance protocol showed a statistically significant 34% improvement in mean time between unscheduled repairs (95% CI: 22% to 46%). The shape parameter $\\beta$ shifted from 0.8 (indicating infant mortality) to 1.1 (indicating random failures), suggesting a fundamental change in the failure regime.", "conclusion": "The quasi-experimental design successfully isolated the impact of systematic interventions on depot reliability. The results demonstrate that structured preventive maintenance protocols can substantially enhance the reliability of depot systems in this context.", "recommendations": "Transport authorities should adopt standardised, data-driven preventive maintenance schedules. Future depot designs should integrate reliability-centred maintenance principles from the planning phase.", "key words": "maintenance engineering, system reliability, quasi-experimental design, transport infrastructure, preventive maintenance", "contribution statement": "This paper provides a novel methodological framework for the causal evaluation of engineering system reliability in real-world operational settings, moving beyond descriptive