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 relationship between transportation index (air and land) and environmental sustainability from 1995 to 2022 across the top 27 polluting countries. The study employed a series of pre-estimation tests, along with the novel Method of Moments Quantile Regression (MMQR), to estimate heterogeneous effects across the lower, middle, and upper quantiles of environmental sustainability. The MMQR results indicate that environmental sustainability is hampered by transportation, whereas renewable and nuclear energy promote it. The moderation effect model shows that both renewable and nuclear energy development mitigate the negative environmental externality from the transportation sector. The controlling factors, GDP and inflation, are found to be harmful for environmental sustainability, while trade openness is found to be favourable. The robustness findings using Driscoll and Kray standard errors (DKse) yielded similar results; nonetheless, the magnitude of the coefficient varies substantially. Thus, think tanks and policymakers are recommended to integrate renewable and nuclear energy into the transportation sector’s energy portfolio to mitigate its negative environmental impacts.