A federal program that has cleaned up or removed 50,000 high-polluting diesel engines from U.S. roads is scheduled to be cut by 70 percent under President Barack Obama’s latest budget. The program eliminated 230,000 tons of soot and smog-causing pollutants, slashed more than two million tons of carbon dioxide emissions, and saved 205 million gallons of fuel. But the program’s budget has faced steady cuts in recent years, falling from $50 million in fiscal year 2011, to $20 million in 2013, to a proposed $6 million in fiscal year 2014. The diesel cleanup program has succeeded in removing only a fraction of the 11 million dirty, pre-2006 diesel vehicles on the road. But environmentalists say that the program has been successful in helping clean the air in low-income communities that often are situated near ports, highways, and other areas with high diesel traffic.