Reuters: U.S. regulators on Friday proposed a 24 percent improvement in fuel efficiency for heavy trucks by 2027 as part of the Obama administration's plan to reduce greenhouse gas emissions. The Environmental Protection Agency said the new standards for truck tractors would reduce carbon emissions by a total of 1.1 billion tons (1 billion metric tons) and begin with model year 2021. The regulators also proposed efficiency standards for trailers. If adopted by the federal government next year, the regulations...