Research pick: The long and winding road to net-zero - "Can air transportation reach to zero carbon emissions: comparative econometric analysis between transportation modes in the USA"

Research in the International Journal of Shipping and Transport Logistics has analysed four decades of freight transportation data across the USA and shows how different modes of transport contribute to carbon dioxide emissions. The work reveals a complex picture wherein transportation is indeed a major source of greenhouse gases, alongside electricity generation, but air, rail, road, water, and pipeline make different contributions to the problem.

The researchers used an Autoregressive Distributed Lag model to consider both short-term and long-term relationships between transportation activity and emissions. This allowed them to smooth out the information even when the underlying data are uneven. Such a level of detail is uncommon in climate and transport studies, which often focus on a narrower time frame or fewer transport categories.

Surprisingly, a negative relationship between both air and pipeline transport and carbon emissions over the period 1980 to 2022 showed that even as these two forms of freight activity increased, emissions actually declined slightly: by 0.03% for every 1% rise in air transport activity, and by 0.06% for pipeline transport. Such figures seem small, but they could be statistically meaningful when scaled across the vast transport systems of the USA and over several decades. The findings suggest that adoption of cleaner technologies, especially in aviation, is having an effect. Innovation in the road and rail sectors could reap similar rewards, the research suggests.

The various interdependencies suggest that emissions, energy consumption, and transport activity are all so closely intertwined that coordinated policy responses is now essential rather than isolated reforms if we are to achieve net-zero.

The researchers suggest that by breaking down the environmental impact of individual transport modes, it is possible to develop more targeted climate strategies. For example, expanding pipeline infrastructure or accelerating the rollout of sustainable aviation technology may deliver greater emissions reductions than blanket policies applied across all transport sectors.

Ergen, H., Aslan, A. and Ayvaz, E.E. (2025) ‘Can air transportation reach to zero carbon emissions: comparative econometric analysis between transportation modes in the USA’, Int. J. Shipping and Transport Logistics, Vol. 21, No. 1, pp.71–99.