President Obama has announced the first ever emissions standards for trucks and other heavy-duty vehicles. They'll be shooting for a 9 to 23 percent reduction in fuel consumption by 2018, depending on the type of vehicle. Big rigs will need to achieve approximately a 20 percent reduction, for example; garbage trucks will need more like 10 percent.

It might not feel this way when you go on a long road trip, but trucks are only a small percentage of the vehicles on the road. They drive way more than family cars, though, and spend more time idling. Plus, they're super gas guzzlers; average fuel efficiency is only 6 miles per gallon. (The new standards should raise it to 8 MPG.) So controlling the efficiency of heavy vehicles could make a big difference in greenhouse-gas emissions and fuel use. The new standards could reduce oil consumption by 530 million barrels and cut greenhouse-gas pollution by 270 million metric tons.

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