"Over the last decade in particular, the diesel industry has invested billions of dollars in development of cleaner diesel fuels, advanced engines, and emissions control technology. The greatest benefits from these new technologies come as they are introduced into the population. Today we estimate that more than one-third of all the heavy-duty commercial trucks on the road in the U.S. are 2007 or later model year and have the most sophisticated emissions control technology."Beyond meeting low particulate and NOx emissions standards, manufacturers of medium and heavy duty trucks and engines for the U.S. are now on course to meet the first-ever greenhouse gas reductions and fuel economy standards ever enacted. These new standards that begin in model year 2014 will reduce CO2 emissions by 10 to 23 percent depending on type of truck", Schaeffer said. Diesel Emissions Reduction Act Important In Modernizing Older Diesel Engines"Beyond the new technology advancements in reducing particulate emission, the opportunities for modernizing and upgrading existing diesel engines and equipment will also be important in reducing black carbon," Schaeffer said. "We continue to work with national environmental and health organizations to increase funding for the highly-successful voluntary and incentive-based Diesel Emissions Reduction Act, which is helping to modernize and upgrade older diesel engines in school and transit buses, commercial trucks, construction and agricultural equipment, and marine vessels." California Air Quality Improvements Aided By Diesel Advancements The California Air Resources Board (ARB) has identified the top-10 contributors to PM 2.5. Diesel engines and equipment rank as the 8 th and 9 th highest contributors, Schaeffer said, behind: 1) wildfires, 2) residential fuel combustion, 3) managed burning & disposal, 4) paved road dust, 5) unpaved road dust, 6) fugitive windblown dust, 7) farming operations. According to the ARB, diesel particulate emissions from on-road heavy-duty trucks have declined from 7.5 percent in 1990 to 3.8 percent in 2008, with future projections in 2020 for the category to account for only 1.6 percent of all emissions.