A global push to reduce vehicle emissions and create cleaner air for future generations has been underway for half a century now.
However, while many governments around the world have introduced lower emission and higher fuel-efficiency standards for passenger cars, another large contributor to global emissions has mostly traveled under the radar.
Those are heavy trucks or semi trucks.
Recently completed studies from the International Energy Agency, cited by The Financial Times (subscription required), show that policy surrounding heavy truck emissions and efficiency is lacking.
Across the globe, 40 countries have put energy-efficient regulations in place for passenger cars. Only four countries have similar rules for semi trucks.
Heavy-truck transport is often tied to economic growth in developing countries, as shown by India's increasing demand for oil to fuel its transport industry.
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The trucking industry in China, the United States, and the European Union together account for one-fifth of global oil demand: 17 million barrels of oil per day.
The IEA notes one-third of transport-related carbon emissions globally come from heavy trucks, meaning the potential to reduce emissions—semi trucks in much of the world use dirtier diesel fuel—is high.
“The volumes of oil consumed and carbon emissions given out by these vehicles is huge," said Fatih Birol, executive director of the Paris-based IEA, "but policy attention has been very little."
If no action is taken and countries continue to fuel their heavy road transport industry in the same ways, oil demand from road-freight transport is expected to rise another 40 percent by 2050, representing an additional 5 million barrels of oil a day.
The effects on air quality could be significant with nearly 900 million tons of additional carbon dioxide emissions spewed into the air through that year.
However, the tide is starting to turn.
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The transportation industry is moving toward new, more efficient technologies, but their effects won't be seen overnight.
Analysts agree that by far the best way to produce speedier change is a push by governments to introduce new policies.
Still, the narrow margins and slim profits in highly competitive trucking industries may impede acceptance of expensive emission-control gear, even if fuel savings outweigh its cost over the lifetime of a vehicle.
Private companies may take the lead in launching lower- or zero-emission heavy trucks.
Toyota previously showed its interpretation of future heavy truck transport with its Project Portal semi truck.
The truck runs exclusively on hydrogen fuel cells and doesn't compromise power to move the heavy truck.
Toyota 'Project Portal' proof-of-concept hydrogen fuel-cell powered semi tractor, for Port of LA
Tesla has promised it will launch an all-electric semi tractor, and a private startup company has unveiled its Nikola one hydrogen fuel-cell rig.
It may be easier to fuel heavy trucks with hydrogen at a limited number of fueling stations on highways than it would be to set up a nationwide or global fueling network for hydrogen passenger cars.
But, without real action and change, emissions from the world's trucking industry will remain a significant drag on positive environmental action through reductions of carbon emissions.
[EDITOR'S NOTE: Green Car Reports thanks our tipster, who prefers to remain an International Man of Mystery.]