Control of Emissions of Air Pollution From 2004 and Later Model Year Heavy-Duty Highway Engines and Vehicles; Revision of Light-Duty Truck Definition

We are proposing to take several actions relating to emission standards and test procedures for heavy-duty engines and vehicles intended for operation on roads and highways. The proposed provisions are for the 2004 and later model years. First, we are proposing new more stringent emissions standards and related provisions for all heavy-duty Otto-cycle (e.g., gasoline-fueled) engines and vehicles. Vehicles in this category include large full size pick-up trucks, full size cargo and passenger vans, and the largest sport utility vehicles. For heavy-duty Otto-cycle engines and vehicles, today's proposal would reduce the standards for oxides of nitrogen and hydrocarbons by approximately 75 percent from current standards. Second, we propose to reaffirm that the NMHC+NO<INF>X</INF> standard promulgated in October, 1997 for diesel heavy-duty engines is both necessary and feasible. This standard represents about a 50 percent reduction in emissions of nitrogen oxides, as well as reductions in hydrocarbons, from diesel trucks and buses. Third, we are proposing to require on-board diagnostics systems for all heavy-duty vehicles and engines at or below 14,000 lbs gross vehicle weight rating (GVWR), and to revise the on- board diagnostics requirements for diesel light-duty vehicles and trucks. These systems will identify the failure of components of the emissions control system. Fourth, we are proposing the addition of new test procedures and associated standards for heavy-duty diesel engines and vehicles. Fifth, we are proposing to include heavy models of gasoline and diesel-fueled sport-utility vehicles and similar heavy- duty vehicles used primarily for personal transportation in the Tier 2 program that EPA proposed earlier this year. Today's proposal would result in lower emissions of oxides of nitrogen and hydrocarbons, as well as lower particulate matter due to reductions in secondary particulate formation (secondary particulate matter is not emitted directly from the engine, but is formed when emissions of oxides of nitrogen react with ammonia in the atmosphere to produce ammonium nitrate particulates), and would assist states and regions facing ozone air quality problems that are causing a range of adverse health effects, particularly respiratory impairment and related illnesses.