A pilot program is slated to begin in 2005 with the fully enforceable program beginning in 2007 when the new requirements take effect. The proposal stems from a June 2003 settlement agreement between the agency and the Engine Manufacturers Association that seeks to ensure that the benefits of more stringent emission standards are realized under real-world driving conditions.

For the proposal, see www.epa.gov/otaq/hd-hwy.htm. To learn about the agency's clean diesel program, visit www.epa.gov/cleandiesel.