United States Air and Radiation EPA420-F-99-017
Environmental Protection May 1999
Agency
Office of Mobile Sources
vvEPA Emission
Facts
The History of Reducing
Tailpipe Emissions
1970-1975: The First Standards
In 1970, Congress passes the Clean Air Act, which called for the first
tailpipe emissions standards. The pollutants controlled are carbon mon-
oxide (CO), volatile organic compounds (VOC), and oxides of nitrogen
(NOx). The new standards go into effect in 1975 with a NOx standard for
cars and light-duty trucks of 3.1 grams per mile (gpm).
1977-1988: Tightening Standards for the First Time
In 1977, Congress amends the Clean Air Act and tightens emission
standards again in two steps. First, between 1977 and 1979, the NOx
standard becomes 2.0 gpm for cars. Then in 1981, the NOx standard for
cars is reduced to 1.0 gpm. Effective in 1979, pursuant to the Clean Air
Act requirements, EPA tightens standards for light-duty trucks to 2.3
gpm. Effective in 1988, EPA then sets the first tailpipe standards for
heavier trucks at 1.7 gpm and revises the standard for lighter trucks to 1.2
gpm.
1990-1994: Tier 1
In 1990, Congress again amends the Clean Air Act, further tightening
emission standards. The NOx standard is set at 0.6 gpm for cars, effective
in 1994. The new standard called "Tier 1"is a 40 percent reduction
from the 1981 standard. For trucks, the new standard ranges from 0.6 to
1.53 gpm, depending on the weight of the vehicle.
> Printed on Recycled Paper
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The Clean Air Act Amendments of 1990 also require EPA to assess the
air quality need, cost effectiveness, and feasibility of tighter emission
standards for the 2004 model year and beyond.
1998: Voluntary For
In 1998, the Clinton Administration with the auto industry and the
Northeast states strike an innovative, voluntary agreement to put cleaner
cars on the road before they could be mandated under the Clean Air Act.
The new cars are called National Low Emission Vehicles (NLEV). The
first NLEV cars under the agreement reach consumers in New England
in 1999 and will reach the rest of the country in 2001. NLEV cars oper-
ate with a NOx standard of 0.3 gpm, a 50 percent reduction from Tier 1
standards. The NLEV agreement also calls for a 0.5 gpm NOx standard
for lighter trucks only, a 17 percent reduction from Tier 1 requirements
for these vehicles.
In 1998, as required by the Clean Air Act Amendments of 1990, EPA
issues the Tier 2 Report to Congress. The report contains strong evidence
of the need, cost-effectiveness and feasibility for tighter tailpipe emission
standards in the future beginning in 2004. Three main factors support
EPA's decision:
1) currently vehicles make up 30 percent of smog-forming emissions
nationally, and because the number of miles driven is increasing (up
127 percent since 1970) they will continue to be a significant
contributor to pollution;
2) larger vehicles like SUVs, that currently do not meet the same
standards as cars, pollute 3-5 times as much and make up 50 per-
cent of the vehicles sold today; and
3) the technology to meet tighter standards is available and cost-
effective.
In 1998, EPA also determines that sulfur reductions in gasoline are
needed to enable the full performance of low emission-control devices.
1999: Tier 2
In 1999, EPA proposes Tier 2 tailpipe emissions standards beginning in
2004the first time both cars and light-duty trucks are subject to the
same national pollution control system. The new standard is 0.07 gpm
for NOx, a 77-86 percent reduction for cars and a 92-95 percent reduc-
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tion for trucks beyond the NLEV agreement. EPA also proposes a reduc-
tion in average sulfur levels to 30 parts per million (ppm) (maximum of
80 ppm) to achieve the full performance of vehicle emission control
technologies.
As part of these new standards, EPA has included several measures to
ensure maximum flexibility and cost-effectiveness. These flexibilities
include:
allowing averaging to meet both the car emission and gasoline
sulfur standards;
allowing extra time for larger vehicles between 6000 and 8500
pounds and smaller refiners to meet their respective standards; and
allowing for a market-based credit trading-and-banking system for
both industries to reward those who lead the way in reducing pollu-
tion.
Cars
Year
NOx
Standard
NOx
Reduced
(from
previous
standard)
1975
3.1
1977
2.0
35%
1981
1.0
50%
1994
0.6
40%
1999
0.3
50%
2004-2009
0.07
77%
Smaller SUVs, Light Trucks
that Ibs)
Year
NOx
Standard
(gpm)
NOx
Reduced
(from
previous
standard)
1975
3.1
1979
2.3
26%
1988
1.2
48%
1994
0.6
50%
1999
0.5
17%
2004-2009
0.07
86%
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LargerSUVs,Varis,
and Ibs)
Year
NOx
Standard
NOx
Reduced
(from
previous
standard)
1988
1.7
1994
1.53
10%
2004-2007
0.2
87%
2008-2009
0.07
65% or
95% from
1994
standard
For
Additional documents on emission standards for cars and light trucks are
available electronically from the EPA Internet server at:
http ://www. epa.gov/oms/ld-hwy.htm
Information on the Tier 2 standards is available on the Tier 2 home page
at:
http://www.epa.gov/oms/tr2home.htm
Document information is also available by writing to:
Tier 2 Team
U.S. Environmental Protection Agency
Office of Mobile Sources
2000 Traverwood Drive
Ann Arbor, MI 48105
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