The state of California has made the switch to new Ultra Low Sulfur Diesel (ULSD) fuel in preparation for new, cleaner-operating heavy-duty trucks equipped with advanced emission control systems that debut next January. Effective September 1, 2006, the fuel change will reduce the pollution emitted by California's 1.2 million diesel engines. The federal government mandated switch to ULSD for all refineries will take place on October 15, 2006. Those new vehicles will meet the tightest emission standards ever set for heavy-duty trucks and buses and require very low sulfur fuel to operate properly. The new engines will use emission control equipment such as particulate traps to control toxic particulate soot and catalysts that limit ozone-forming nitrogen oxide emissions, the most common pollutants emitted by diesels. The new fuel also will allow the California Air Resources Board to continue its diesel risk reduction plan (RRP), a set of regulations designed to cut the public health risks of diesel particulate by 85 percent in 2020. The risk reduction plan calls for slashes in diesel particulate from a number of pollution sources such as trucks and buses, farm and construction equipment as well as pumps and boilers.