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US EPA signs final Tier 2 emission standards and gasoline requirements for light-duty vehicles

21 December 1999

On 21 December 1999, the US EPA signed the final Tier 2 emission regulations that were proposed in May, 1999. The rule sets new, much more stringent exhaust emission standards for light-duty vehicles to be phased-in beginning in 2004 and establishes new maximum sulfur level in gasoline. Full text of the regulation will be published shortly in the Federal Register.

The Tier 2 standards apply for new passenger cars and light-duty trucks. The program focuses on reducing emissions of ozone-forming gases, including nitrogen oxides (NOx) and non-methane organic gases (NMOG), and particulate matter (PM) from these vehicles. The same set of federal standards, expressed in grams of pollutants emitted per mile (g/mi), applies to all passenger cars, light trucks, and medium-duty passenger vehicles, regardless of the vehicle or engine size. Under this approach, which reflects the EPA's concern with increasing market share and emissions from minivans and sport utility vehicles (SUV), larger vehicles will have to employ cleaner engine and emission control technologies than those needed for vehicles with small engines. The same requirements will apply to all vehicles regardless of the fuel, i.e., gasoline and diesel fueled vehicles will be certified to the same emission standard.

The regulation applies to the following vehicle categories: (1) passenger cars, (2) “light light-duty trucks” (LLDT), at less than 6000 lbs gross vehicle weight rating (GVWR), (3) “heavy light-duty trucks” (HLDT), at more than 6000 lbs GVWR, and (4) “medium-duty passenger vehicles” (MDPV), a new class of vehicles introduced by this rule that includes SUVs and passenger vans rated at between 8,500 and 10,000 GVWR.

The Tier 2 standards will reduce new vehicle NOx levels to an average of 0.07 g/mi. For new passenger cars and light LDTs, these standards will phase in beginning in 2004, with the standards to be fully phased in by 2007. For heavy LDTs and MDPVs, the Tier 2 standards will be phased in beginning in 2008, with full compliance in 2009. During the phase-in period from 2004-2007, all passenger cars and light LDTs not certified to the primary Tier 2 standards will have to meet an interim average standard of 0.30 g/mi NOx, equivalent to the current NLEV standards for LDVs and more stringent than NLEV for LDT2s (e.g., minivans). During the period 2004-2008, heavy LDTs and MDPVs not certified to the final Tier 2 standards will phase in to an interim program with an average standard of 0.20 g/mi NOx, with those not covered by the phase-in meeting a per-vehicle standard (i.e., an emissions “cap”) of 0.60 g/mi NOx (for HLDTs) and 0.09 g/mi NOx (for MDPVs). The Tier 2 standards shall be met over a full useful vehicle life of 120,000 miles.

For comparison, the existing Tier 1 standards establish NOx limits of 1.0 g/mi for diesel cars and 0.4 g/mi for gasoline cars over 50,000 miles of vehicle life. Higher limits apply to heavier vehicles, as well as to 100,000 miles vehicle useful life period.

In the anticipation of a possible substantial future growth in the sales of light-duty diesel vehicles in the USA, the EPA also set stringent Tier 2 particulate matter standards. Manufacturers will have a choice of certifying their vehicles to any of 10 “certification bins”, which, for PM, will vary from 0 (“zero emission vehicle”), through 0.01, to a maximum of 0.02 g/mi. Three temporary bins, scheduled to expire at the end of 2006 model year (2008 for HLDTs), allow for certification to up to a 0.08 g/mi standard, which is identical to the Tier 1 PM limit for diesel cars.

The Tier 2 regulation will also reduce average gasoline sulfur levels in the USA. These reductions could begin to phase in as early as 2000, with full compliance for most refiners occurring by 2006. The program requires that most refiners and importers meet a corporate average gasoline sulfur standard of 120 ppm and a cap of 300 ppm beginning in 2004. By 2006, the average standard will be reduced to 30 ppm with 80 ppm sulfur cap. Temporary, less stringent standards will apply to a few small refiners through 2007. In addition, temporary, less stringent standards will apply to a limited geographic area in the western USA for the 2004-2006 period.

Lower sulfur levels will enable improved emission control technology necessary to meet the more stringent standards over the extended useful life of the vehicles. In addition, as soon as the lower sulfur gasoline is available, all gasoline vehicles already on the road will have reduced emissions from less degradation of their catalytic converters.

The adopted regulation has not addressed the issue of sulfur levels in diesel fuel. A concern was voiced during the discussion of the EPA proposal that, unless ultra low sulfur diesel fuels are legislated, the Tier 2 standard is not feasible for diesel vehicles. The EPA said it would address this issue in a separate rule, with a Notice of Proposed Rulemaking (NPRM) expected in early spring of 2000.

According to EPA estimates, complying with the Tier 2 standards will cause a cost increase of less than $100 per passenger car, an average cost increase of less than $200 for light trucks, an average cost increase of about $350 for medium-duty passenger vehicles, and an average increase of less than 2 cents per gallon of gasoline (or about $120 over the life of an average vehicle).

Source: US EPA