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US EPA Heavy-Duty Highway Engines page
EPA information on truck and bus emissions. Includes heavy-duty engine emission regulations, fact sheets, Urban Bus Retrofit/Rebuild notices.
US EPA Cleaner Trucks, Buses, and Diesel Fuel page
EPA information on the 2007 diesel emission and diesel fuel regulation.
US EPA HD Highway Engines Consent Decree page
Information on the Consent Decree, reached in 1998 between the EPA and US HD engine manufacturers on the issue of off-cycle NOx emissions.
“Asleep at the Wheel”

Committee on Commerce, US House of Representatives, March 2000

A report outlining the history of events leading to the EPA - engine manufacturers Consent Decree and charging the EPA with failure to enforce emission standards for heavy-duty diesel trucks.
US EPA Nonroad CI Engine Emissions page

US EPA

Information on nonroad diesel engine emission regulations.
Reducing Nonroad Diesel Emissions

US EPA

Information on Tier 4 emission legislation from nonroad diesel engines.
California Urban Transit Bus Regulations

California Air Resources Board

Information and regulatory documents on California emission regulations for urban buses.