The Environmental Protection Agency (EPA) is proposing a rule that would reduce air pollution from highway heavy-duty vehicles and engines, including ozone, particulate matter, and greenhouse gases. This proposal would change the heavy-duty emission control program-- including the standards, test procedures, useful life, warranty, and other requirements--to further reduce the air quality impacts of heavy- duty engines across a range of operating conditions and over a longer period of the operational life of heavy-duty engines.