In August, the EPA and NHTSA jointly announced the first fuel economy standards that affect both medium and heavy duty trucks. Those standards didn't include specific MPG targets, like the standards for passenger vehicles do. Instead, the truck standards are intended to reduce both fuel efficiency and greenhouse gas production, with truck operators given a wide leeway in determining the best way to achieve those savings.
For large over-the-road trucks, the savings target is a 20 percent reduction by 2018. Medium duty vehicles, including dump trucks and local delivery vehicles, have a target reduction of 10 reduction by 2018. For most medium duty trucks, this should save about one gallon for every 100 miles traveled. In other words, for the average new truck they're being asked to take their efficiency from a bit under 10 mpg and turn it up to 11. Looking at the medium duty requirements last year, a panel of experts projected that rather than costing money for the operators, the changes required would actually be more than paid for in decreased fuel use. (This is why.)
The Pacific Legal Foundation, which filed the lawsuit, did so on the basis that the EPA didn't follow protocol in issuing the new rules, and that the federal government wanted to "dictate the design" of trucks and tractors. PLF's language suggests that the changes would cost "thousands of dollars" for every truck. One of those listed in the suit objected that the new regulation could force his existing fleet of vehicles off the road, even though the regulations only affect new vehicles.
Some vehicles now being introduced, such as the Peterbuilt medium-duty hybrid pictured above, exceed the new regulations and reach 30 to 50 percent reduction.