The Obama administration will issue new national requirements for the emissions and mileage of cars and light trucks in an effort to end a long-running conflict among the states, the federal government and auto manufacturers, industry officials said Monday. President Obama will announce as early as Tuesday that he will combine California’s tough new auto-emissions rules with the existing corporate average fuel economy standard to create a single new national standard, the officials said. As a result, cars and light trucks sold in the United States will be roughly 30 percent cleaner and more fuel-efficient by 2016. The White House...