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RS20247: EPA's Tier 2 Proposal for Stricter Vehicle Emission
Standards: David M. Bearden June 24, 1999 The Clean Air Act Amendments of 1990 established "Tier 1" standards to limit tailpipe emissions from new motor vehicles, and the Environmental Protection Agency (EPA) is required to determine if more stringent requirements are needed to attain or maintain National Ambient Air Quality Standards. EPA also must assess the availability and cost-effectiveness of technologies necessary to control emissions. In a report submitted to Congress in August 1998, EPA concluded that tougher standards are necessary and that essential technologies are available and cost-effective.1 As a result, EPA proposed stricter "Tier 2" standards on May 13, 1999.2 The agency will receive public comment until August 2, 1999, prior to issuing a final rule. The proposed standards would be phased in beginning in model year (MY) 2004 and require new passenger vehicles and light trucks up to 6,000 pounds to achieve full compliance by MY2007 and new light trucks between 6,001 and 8,500 pounds to meet the same standards by MY2009. Because sulfur in gasoline impairs the operation of emission controls, the proposal also would limit gasoline sulfur levels to an average of 30 parts per million (ppm) nationwide beginning on January 1, 2004, roughly 90% less than the current national average of 340 ppm.3 EPA's proposal would require manufacturers to certify their vehicles according to stricter standards for carbon monoxide (CO), formaldehyde (HCHO), nitrogen oxides (NOx), non-methane organic gases (NMOG), and particulate matter (PM). However, manufacturers would demonstrate compliance only by averaging the NOx emissions of their vehicle fleets. The proposed standards would require the most reductions in emissions of NMOG and NOx to help control the formation of ground-level ozone pollution. Relative to the Tier 1 standards, the fleet average standard for NOx would require vehicle manufacturers to reduce overall emissions by 88% to 95%. The proposed standards also would require at least an 80% reduction in PM emissions but would require less stringent reductions in CO emissions. The standard for HCHO would reduce emissions of carcinogenic pollutants. The table on page 2 compares the current Tier 1 standards, which became effective in MY1994, to the proposed Tier 2 standards that would begin in MY2004. This fact sheet will be updated as developments occur. Footnotes 1EPA. Office of Air and Radiation. Tier 2 Report to Congress. July 31, 1998.55 p. 2 EPA. Federal Register. May 13,. 1999. p.26004-26142. 3 For further discussion of EPA's gasoline sulfur proposal, refer to CRS Report RS20163.
Comparison of Tier 1 and Proposed Tier 2 Tailpipe Emission Standards for Motor Vehicles
a The intermediate useful life standards set a benchmark for the amount of pollutants that a vehicle is expected to emit after being driven for 50,000 miles. The Tier 1 full useful life standards reflect the amount of pollutants that a vehicle is expected to emit after 100,000 miles of vehicle use. EPA's Tier 2 proposal would increase the full useful life standards to 120,000 miles. Tier 1 vehicles are subject to the testing procedure for NMHC, but Tier 2 vehicles would be subject to the testing procedure foe NMOG. Both pollutants are closely related hydrocarbon compounds that can combine with NOx in the presence of sunlight to form ozone. EPA is proposing to use the NMOG testing procedure under Tier 2 because it more accurately measures hydrocarbon levels.c During the phase-in period for LDVs and LDTs between MY2004 and MY2006, vehicles not certified according to the Tier 2 basic standards would be subject to the interim standards. The phase-in of the Tier 2 basic standards for HLDTs would begin later in MY2008. However, vehicle manufacturers would still be required to certify an increasing percentage of their HLDTs according to the interim standards between MY2004 and MY2007. Each manufacturer would be required to demonstrate full compliance with the Tier 2 basic standards for LDVs and LDTs in MY2007 and for HLDTs in MY2009 Each manufacturer would have the flexibility to select any set, or "bin", of emission standards when certifying different models of vehicles, as long as it meets the fleet average requirement for NOx emissions.
Prepared by the Congressional Research Service based on data from the Environmental Protection Agency. |
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