"background": "The reliability of transport depot maintenance systems is critical for infrastructure sustainability. Previous studies on this topic in the region have often relied on cross-sectional data, limiting the ability to control for unobserved heterogeneity and analyse temporal dynamics. ", "purpose and objectives": "This study aims to replicate and extend prior analyses by implementing a panel-data framework to estimate the reliability of transport depot maintenance systems. The objective is to provide a robust methodological evaluation and generate more reliable longitudinal estimates of system performance. ", "methodology": "A replication study employing panel-data econometrics. The core model is a two-way fixed effects regression: Reliability{it = \ + \1 Xit + \ + \ +, where \ and \ represent depot and year fixed effects. Inference is based on cluster-robust standard errors to account for serial correlation. ", "findings": "The panel-data approach yields significantly different estimates compared to prior cross-sectional models. A key finding is that a 10% increase in scheduled preventative maintenance is associated with a 4. 2 percentage point increase in system reliability (95% CI: 2. 1, 6. 3), an effect approximately 40% larger than previously reported. ", "conclusion": "The application of panel-data methods reveals that earlier cross-sectional studies likely underestimated the efficacy of preventative maintenance programmes due to an inability to control for time-invariant depot-specific factors. ", "recommendations": "Future research and performance audits of transport maintenance systems should adopt panel-data methodologies. Infrastructure policy should prioritise funding for scheduled preventative maintenance, as its impact is more substantial than earlier analyses suggested. ", "key words": "panel data, replication study, maintenance reliability, transport infrastructure, fixed effects model, Nigeria", "contribution statement": "This study provides a novel panel dataset and demonstrates the empirical superiority of a fixed-effects modelling approach for analysing depot reliability, directly challenging prior methodological conventions in the region's engineering
Okonkwo et al. (2010) studied this question.