Business Green: The US government yesterday proposed the first fuel-efficiency standards for heavy vehicles, claiming the new rules would provide $41bn (£25.6bn) in economic benefits when they come into effect between 2014 and 2018. The Environmental Protection Agency (EPA) and the National Highway Traffic Safety Association proposed the long-awaited standards on three classes of vehicle: combination tractors, heavy pickup trucks, and vocational vehicles. Under the new rules, combination …