Long-Run Dynamics Between Transport Infrastructure, Energy Consumption, and Economic Growth in Nigeria: A Cointegration Analysis

The long-run macroeconomic relationships between transport infrastructure, energy consumption, and economic growth constitute a complex trivariate system whose dynamics have important implications for sustainable infrastructure investment strategy in Nigeria. This study examines the long-run dynamics and causal directions between these three variables using cointegration analysis and vector error correction modelling on annual time-series data from 1980 to 2024. Data on transport infrastructure are proxied by road network paved ratio, railway freight tonne-kilometres, and port throughput indices sourced from the Federal Ministry of Works, the Nigerian Railway Corporation, and the Nigerian Ports Authority. Energy consumption is measured as total primary energy consumption in million barrels of oil equivalent. GDP at constant 2015 prices is the growth indicator. The study employs Johansen cointegration tests, Granger causality within a vector error correction framework, and impulse response functions. Findings confirm two cointegrating vectors among the three variables, establishing long-run equilibrium relationships. Granger causality tests reveal bidirectional causality between transport infrastructure and economic growth and unidirectional causality running from energy consumption to transport infrastructure. The long-run elasticity of GDP with respect to transport infrastructure capital is estimated at 0.42, exceeding prior cross-country estimates for sub-Saharan Africa. The study contributes original time-series evidence filling a gap in the Nigerian macroeconomic transport infrastructure literature and challenges the energy-led growth hypothesis by demonstrating that transport infrastructure mediates energy-growth relationships. Policy implications for energy transition planning in the transport sector are discussed. Keywords: transport infrastructure, cointegration, economic growth, energy consumption, Nigeria.