Quantile Modelling of the Moderating Role of Renewable and Nuclear Energy in the Transportation and Environmental Sustainability Nexus

This study examines the moderating effects of renewable and nuclear energy on the relationshipbetween transportation index (air and land) and environmental sustainabilityfrom 1995 to 2022 across the top 27 polluting countries. The study employed a seriesof pre-estimation tests, along with the novel Method of Moments Quantile Regression(MMQR), to estimate heterogeneous effects across the lower, middle, and upper quantiles ofenvironmental sustainability. The MMQR results indicate that environmental sustainabilityis hampered by transportation, whereas renewable and nuclear energy promote it. Themoderation effect model shows that both renewable and nuclear energy development mitigatethe negative environmental externality from the transportation sector. The controllingfactors, GDP and inflation, are found to be harmful for environmental sustainability, whiletrade openness is found to be favourable. The robustness findings using Driscoll and Kraystandard errors (DKse) yielded similar results; nonetheless, the magnitude of the coefficientvaries substantially. Thus, think tanks and policymakers are recommended to integraterenewable and nuclear energy into the transportation sector’s energy portfolio to mitigateits negative environmental impacts.