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Transportation Air Quality Facts and Figures January 2006

Emissions Standards

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Federal Emissions Standards

The Clean Air Act of 1963 and subsequent amendments set federal emissions-control standards for all new cars and light trucks sold in the United States. The most recent Clean Air Act Amendments (CAAA) in 1990 established more stringent "Tier 1" emissions standards, which became effective in 1994. The CAAA also required studying more stringent "Tier 2" emission standards. In 1999, EPA determined that these were needed and cost-effective. Starting in 2004, all classes of passenger vehicles, including sport-utility vehicles, and light trucks, had to comply with new average tailpipe standards of .07 grams per mile for nitrogen oxides.

VOC

VOC. Click image for source data.

NOx

NOX. Click image for source data.

CO

CO. Click image for source data.

PM10

PM10. Click image for source data.

Source: U.S. Department of Energy, Office of Energy Efficiency and Renewal Energy. Transportation Energy Data Book: Edition 24, ORNL-6973. December 2004.
Web site: http://cta.ornl.gov/data/chapter12.shtml 28 June 2005.

Tier 2 Emissions Standards

Light-Duty Vehicle Emissions Under Tier 2 and Low-Sulfur Gasoline Rule

Light-Duty Vehicle Vehicle Emissions Under Tier 2 and Low-Sulphur Gasoline Rule. Click image for source data.

Assumes VMT growth rate of 1.7% per year from 2007 to 2030.

Source: U.S. Environmental Protection Agency. Cleaner Vehicles and Cleaner Gasoline Tier 2/Gasoline Sulfur Rule, 22, December 1999. Web site: http://www.epa.gov/otaq/regs/ld-hwy/tier-2/index.htm 29 June 2005.

EPA's engine and gasoline standards, commonly known as Tier 2, took effect in 2004. The standards were designed to reduce emissions from new passenger cars and light trucks, including pickup trucks, minivans, and sport-utility vehicles (SUVs). In 2004, the Nation's refiners and importers of gasoline began to manufacture gasoline with sulfur levels capped at 300 parts per million (ppm), approximately a 15-percent reduction from the previous industry average of 347 ppm. By 2006, refiners will meet a 30-ppm average sulfur level with a cap of 80 ppm. These fuels will enable vehicles to use emissions controls that will reduce tailpipe emissions of NOx by 77 percent for passenger cars and by as much as 95 percent for pickup trucks, vans, and SUVs. When fully implemented, this program is expected to reduce mobile source emissions equivalent to taking 164 million cars off the road.

Sources: National Archives and Records Administration, Code of Federal Regulations. Title 40 Volume 11 Part 80. 1 July 1999. Web site: http://www.gpo.gov/fdsys/pkg/FR-2000-02-10/pdf/00-19.pdf 28 June 2005.
National Archives and Records Administration, Code of Federal Regulations, Title 40 Volume 2 Part 86. 1 July 1999. Web site: http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&sid=514af1194ec2c86760a86ae275f6db1b&rgn=div5&view=text&node=40:19.0.1.1.1&idno=40 28 June 2005.
U.S. Environmental Protection Agency, Transportation and Air Quality. Tier 2 Vehicle & Gasoline Sulfur Program - Clean Vehicles + Clean Fuel = Cleaner Air. Publication No. EPA420-F-04-002. January 2004.
Web site: http://www.epa.gov/otaq/regs/ld-hwy/tier-2/420f04002.pdf 28 February 2005.

Heavy-Duty Diesel Emissions Standards

Due to the growth in freight movement, regulation of vehicles used to transport freight, as in the Clean Diesel Truck and Bus Rule, is becoming increasingly important.

In December 2000, EPA issued the final rule for a two-part strategy to reduce diesel emissions from heavy-duty trucks and buses. This included new diesel-engine standards in model year 2004 for all diesel vehicles over 8,500 pounds. Additional diesel standards and test procedures will begin in 2007. These standards are based on the use of high-efficiency advanced emissions controls.

Because emissions-control devices are damaged by sulfur, EPA also initiated a program requiring cleaner diesel fuels. Refiners are required to start producing diesel fuel for highway vehicles with a sulfur content of no more than 15 ppm, beginning in 2006. This is down from the current level of 500 ppm, a 97 percent reduction. In order to ensure a smooth transition, these rules will be phased in between 2006 to 2010.

Source: U.S. Environmental Protection Agency. Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements. December 2000.

Heavy-Duty Vehicle Emissions Under Heavy-Duty Engine/Fuel Rule

Heavy-Duty Vehicle Emissions Under Heavy-Duty Engine/Fuel Rate. Click image for source data.

Source: U.S. Environmental Protection Agency. Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements, Regulatory Impact Analysis. Tables II.B-19, II.B-20, II.B-21. December 2000.
Web site: http://www.epa.gov/otaq/regs/hd-hwy/2000frm/420r00026.pdf February 28, 2005.
Note: Assumes a variable growth rate for VMT by Heavy-Duty Diesel Engines that averages 2.5 percent per year.

Non-Road Emissions Standards

In May 2004, EPA issued the Non-Road Diesel Rule, which will cut emissions from construction, agricultural, and industrial diesel-powered equipment by more than 90 percent. The new rule will also remove 99 percent of the sulfur in diesel fuel by 2010, resulting in dramatic reductions in soot from all diesel engines. The Non-Road Diesel Rule complements the Clean Diesel Truck and Bus Rule.

The Non-Road Diesel Rule will result in the widespread introduction of emissions control systems, which is comparable to the advent of catalytic converters for cars in the 1970s. The new standards, to be phased in over the next several years, will result in reductions of pollution equivalent to having some two million fewer trucks on the road.

Non-Road Diesel Emissions Reductions

Non-Road Diesle Emissions Reductions. Click image for source data.

Source: U.S. Environmental Protection Agency. Nonroad Diesel Rule Summary. May 2004. Web site: http://www.epa.gov/otaq/nonroad-diesel.htm 14 June 2004, and Clean Air Nonroad Diesel Rule-Facts and Figures. Publication No. EPA420-F-04-037, May 2004.

Updated: 04/07/2014
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