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By using ULSD in trucks and buses maximized for ULSD use, fleets will be 90 percent cleaner than current models.

In 2000, EPA moved forward on schedule with its rule to make heavy-duty trucks and buses run cleaner, and the Highway Diesel Rule (the "2007 Highway Rule"), was finalized in January 2001. Beginning with the 2007 model year, the harmful pollution from heavy-duty highway vehicles will be reduced by more than 90 percent. Read more about ULSD.

Sulfur in diesel fuel must be lowered to enable modern pollution-control technology to be effective on these trucks and buses. EPA will require a 97 percent reduction in the sulfur content of highway diesel fuel from its current level of 500 parts per million (low sulfur diesel, or LSD) to 15 parts per million (ultra-low sulfurdiesel, or ULSD). Refiners began producingthe cleaner-burning diesel fuel, ULSD, for use in highway vehiclesbeginning June 1, 2006.

ULSD enables advanced pollution control technology for cars, trucks, and buses so that engine manufacturers can meet the 2007 emission standards. Engine manufacturers have the flexibility to meet the new standards through a phase-in approach between 2007 and 2010. The program also includes various flexible approaches, including additional time for some refiners and special provisions for small refiners.

Once this action is fully implemented:

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