EPA's Mobile Sources
http://www.epa.gov/otaq/standards/basicinfo.htm
EPA Fact Sheet - Diesel Exhaust in the US
http://www.epa.gov/cleandiesel/documents/420f03022.pdf
Non-road Diesel Engine, Vehicle and Equipment Information
http://www.epa.gov/otaq/nonroad-diesel.htm
Clean diesel fuel program information
http://www.epa.gov/otaq/fuels/dieselfuels