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Review of the 21st Century Truck Partnership
Appendix D Vehicle Emission Regulations
BACKGROUND
Air pollution from the combustion of coal became a serious problem in the 18th century with the Industrial Revolution in Europe. Concerns about air pollution in the United States arose in Los Angeles in the early 1940s. By 1952, the city’s smog had been identified as arising from the exhaust products of the internal combustion engine. (The irritant, ozone, one of the constituents of smog, is formed through complex chemical reactions between precursor emissions of volatile organic compounds (VOCs) and oxides of nitrogen (NOx) in the presence of sunlight.) Subsequently, air pollution from all potential sources, both vehicular and stationary, was recognized as a national concern.
The Clean Air Act of 1963 was the beginning of federal influence over mobile-source emissions. Subsequent amendments established the U.S. Environmental Protection Agency (EPA), gave EPA broad responsibility for regulating motor vehicle pollution, and directed the agency to set health-based National Ambient Air Quality Standards (EPA, 1994). EPA established maximum concentrations for six “criteria pollutants” as indicators of air quality, above which adverse effects on human health may occur. The six criteria pollutants are ozone, carbon monoxide (CO), nitrogen dioxide, sulfur dioxide, particulate matter (PM) and lead (EPA, 2007b). To curtail exceedance of the maximum concentrations of the criteria pollutants, EPA currently regulates emissions from a variety of mobile and stationary sources. The currently regulated emissions from motor vehicles, which are predominately passenger cars, light-duty trucks, and heavy-duty trucks, include the following: total hydrocarbons (HCs) and nonmethane hydrocarbons (NMHCs) or nonmethane organic gases (NMOGs), that includes oxygenated and nonoxygenated HC emissions, CO, NOx, and PM. Lead in gasoline is also regulated to near-zero levels, which also facilitates long life for the catalytic converter in gasoline-fueled vehicles.
EVOLUTION OF EMISSION STANDARDS
The control of emissions from motor vehicles began with model year 1963 when California implemented the requirement for positive crankcase ventilation that recycles the discharged blowby that had previously been vented to the atmosphere by the road draft tube.
Attention subsequently was focused on the control of exhaust emissions of motor vehicles. The first exhaust emission standards were introduced in California effective with 1966 model year passenger vehicles and in the United States as a whole with model year 1968 vehicles. The progressively more stringent federal emission standards for light-duty vehicles are shown in Figure D-1.
Since the early 1960s when exhaust emissions were unregulated, the subsequent exhaust emission regulations by model year 2004 have resulted in the reduction of exhaust emissions from light-duty vehicles by the following amounts:
Hydrocarbons
99 percent reduction
Carbon Monoxide
96 percent reduction
Oxides of Nitrogen
99 percent reduction
Emission standards for light-duty trucks with a gross vehicle weight rating (GVWR) under 8,500 lb have been somewhat higher than passenger car standards because of differences in weight. However, in the near future, light-duty truck standards will be the same as passenger car standards, as shown in Table D-1.
Control of emissions from the engines of heavy-duty trucks with GVWRs over 8,500 lb began in 1969 in California and in the United States as a whole in 1974 (Johnson, 1988). The progressively more stringent emission standards for heavy-duty diesel engines are shown in Figure D-2 (DOE, 2006).
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Appendix D
Vehicle Emission Regulations
BACKGROUND
Air pollution from the combustion of coal became a serious problem in the 18th century with the Industrial Revolution in Europe. Concerns about air pollution in the United States arose in Los Angeles in the early 1940s. By 1952, the city’s smog had been identified as arising from the exhaust products of the internal combustion engine. (The irritant, ozone, one of the constituents of smog, is formed through complex chemical reactions between precursor emissions of volatile organic compounds (VOCs) and oxides of nitrogen (NOx) in the presence of sunlight.) Subsequently, air pollution from all potential sources, both vehicular and stationary, was recognized as a national concern.
The Clean Air Act of 1963 was the beginning of federal influence over mobile-source emissions. Subsequent amendments established the U.S. Environmental Protection Agency (EPA), gave EPA broad responsibility for regulating motor vehicle pollution, and directed the agency to set health-based National Ambient Air Quality Standards (EPA, 1994). EPA established maximum concentrations for six “criteria pollutants” as indicators of air quality, above which adverse effects on human health may occur. The six criteria pollutants are ozone, carbon monoxide (CO), nitrogen dioxide, sulfur dioxide, particulate matter (PM) and lead (EPA, 2007b). To curtail exceedance of the maximum concentrations of the criteria pollutants, EPA currently regulates emissions from a variety of mobile and stationary sources. The currently regulated emissions from motor vehicles, which are predominately passenger cars, light-duty trucks, and heavy-duty trucks, include the following: total hydrocarbons (HCs) and nonmethane hydrocarbons (NMHCs) or nonmethane organic gases (NMOGs), that includes oxygenated and nonoxygenated HC emissions, CO, NOx, and PM. Lead in gasoline is also regulated to near-zero levels, which also facilitates long life for the catalytic converter in gasoline-fueled vehicles.
EVOLUTION OF EMISSION STANDARDS
The control of emissions from motor vehicles began with model year 1963 when California implemented the requirement for positive crankcase ventilation that recycles the discharged blowby that had previously been vented to the atmosphere by the road draft tube.
Attention subsequently was focused on the control of exhaust emissions of motor vehicles. The first exhaust emission standards were introduced in California effective with 1966 model year passenger vehicles and in the United States as a whole with model year 1968 vehicles. The progressively more stringent federal emission standards for light-duty vehicles are shown in Figure D-1.
Since the early 1960s when exhaust emissions were unregulated, the subsequent exhaust emission regulations by model year 2004 have resulted in the reduction of exhaust emissions from light-duty vehicles by the following amounts:
Hydrocarbons
99 percent reduction
Carbon Monoxide
96 percent reduction
Oxides of Nitrogen
99 percent reduction
Emission standards for light-duty trucks with a gross vehicle weight rating (GVWR) under 8,500 lb have been somewhat higher than passenger car standards because of differences in weight. However, in the near future, light-duty truck standards will be the same as passenger car standards, as shown in Table D-1.
Control of emissions from the engines of heavy-duty trucks with GVWRs over 8,500 lb began in 1969 in California and in the United States as a whole in 1974 (Johnson, 1988). The progressively more stringent emission standards for heavy-duty diesel engines are shown in Figure D-2 (DOE, 2006).
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FIGURE D-1 Historical trend in emission standards for light-duty vehicles. Individual emission standards for HC, CO, and, NOx are combined for illustration only. SOURCE: Data from Ehlmann and Wolff (2005).
FIGURE D-2 Historical trend in emission standards for heavy-duty diesel engines.
CURRENT AND FUTURE EXHAUST EMISSION STANDARDS
The emission standards currently in effect in the United States are promulgated by the U.S. Environmental Protection Agency (EPA) for the 49 states and by the California Air Resources Board (CARB) for the state of California. California is the only state that has been granted authority, within the original Clean Air Act, to establish separate, stricter standards for vehicle emissions, independent of the federal government. All other states are required to comply with the federal vehicle emission standards or adopt the stricter California standards. Numerous states have adopted the latest CARB emission standards.
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Passenger Car and Light-Duty Truck
Federal Emission Standards
The Tier 2 federal passenger car emission standards, phased in beginning with the 2004 model year, are listed in Table D-1. For the first time since the enactment of emission standards in the United States, the same standards are to be applied to both passenger cars and light-duty trucks. EPA created a “bin” system, with eight emission standard bins, that allows manufacturers to average emissions across their fleets each year. The passenger car (PC), LDT1, LDT2, LDT3, and LDT4 fleet average NOx requirement is 0.07 (g/mi) at 120,000 miles for model year 2009 and beyond. The standards listed are the emission limits at “full useful life” of 120,000 miles.
California Emission Standards
California’s Low Emission Vehicle II (LEV II) standards were introduced for 2004 and subsequent model years. These standards for all passenger cars and light-duty trucks under 8,500 lb are listed in Table D-2. California categorizes the standards as LEV, Ultra Low Emission Vehicle (ULEV), and Super Ultra Low Emission Vehicle (SULEV) standards. The manufacturer selects the appropriate category for each vehicle line so that the fleet average NMOG meets the CARB mandated fleet average, which deceases with each model year through 2010.
Heavy-Duty Engine Emission Standards
The federal emissions standards for highway trucks were harmonized with California standards beginning in the model year 2004. The emission standards that apply to model year
TABLE D-1 Federal Tier 2 Light-Duty Vehicle Emission Standards: Emission Limits at Full Useful Life of 120,000 Miles
Bin
Vehicle Class
Mandatory for Model Year 2009 and Beyond
NMOG (g/mi)
CO (g/mi)
NOx (g/mi)
PM (g/mi)
Mileage Requirement
8
PC/LDT1/2
0.125
4.2
0.2
0.02
120,000
LDT3/4/MDPV
0.156
4.2
0.2
0.02
120,000
7
All
0.09
4.2
0.15
0.02
120,000
6
All
0.09
4.2
0.1
0.01
120,000
5
All
0.09
4.2
0.07
0.01
120,000
4
All
0.07
2.1
0.04
0.01
120,000
3
All
0.055
2.1
0.03
0.01
120,000
2
All
0.01
2.1
0.02
0.01
120,000
1
All
0
0
0
0
120,000
NOTE: ALVW, adjusted load vehicle weight, average of curb (empty) weight and the GVWR; GVWR, gross vehicle weight rating, maximum fully loaded vehicle weight; LVW, loaded vehicle weight, nominal empty vehicle weight + 300 lb; LDT1, light-duty truck 1, up to 6,000 lb GVWR and 3,750 lb LVW; LDT2, light-duty truck 2, up to 6,000 lb GVWR and between 3,751 and 5,750 lb LVW; LDT3, light-duty truck 3, between 6,001 and 8,500 lb GVWR and between 3,751 and 5,750 lb ALVW; LDT4, light-duty truck 4, between 6,001 and 8,500 lb GVWR and over 5,750 lb ALVW; MDPV, medium-duty passenger vehicle, trucks between 8,501 and 10,000 lb GVWR; PC, passenger car.
TABLE D-2 Current California LEV II Light-Duty Vehicle Emission Standards
GVWR (lb)
Emission Category
NMOG (g/mi)
CO (g/mi)
NOx (g/mi)
PM (g/mi)
Mileage (Durability) Requirement
All PCs and
LEV
0.09
4.2
0.07
0.01
120,000a
LDTs 8,500 lb
ULEV
0.055
2.1
0.07
0.01
120,000a
and less
SULEV
0.01
1.0
0.02
0.01
120,000a
MDV
LEV
0.195
6.4
0.2
0.12
120,000a
8,501-10,000 lb
ULEV
0.143
6.4
0.2
0.06
120,000a
Test at ALVW
SULEV
0.1
3.2
0.1
0.06
120,000a
MDV
LEV
0.23
7.3
0.4
0.12
120,000a
10,000-14,000 lbs
ULEV
0.167
7.3
0.4
0.06
120,000a
Test at ALVW
SULEV
0.117
3.7
0.2
0.06
120,000a
NOTE: ALVW, adjusted load vehicle weight, average of curb (empty) weight and GVWR; GVWR, gross vehicle weight rating, maximum fully loaded vehicle weight; LDT, light-duty truck; MDV, medium-duty vehicle; PC, passenger car. Other acronyms in the table are defined in Appendix E.
aOptional 150,000 mileage durability requirement for partial zero emission vehicle.
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TABLE D-3 Heavy-Duty Emission Standards: Model Year 2007 and Beyond
Non-Methane Hydrocarbons (NMHC) (g/bhp-hr)
Carbon Monoxide (CO) (g/bhp-h)
Nitrogen Oxides (NOx) (g/bhp-h)
Particulate Matter (PM) (g/bhp-h)
0.14a
15.5
0.20a
0.01
TABLE D-4 Service Classes Used by EPA
Service Class
Required Useful Lives of Engines
Light heavy-duty diesel engine (LHDDE): Under federal regulations, between 8,500 and 19,500 lb gross vehicle weight rating (GVWR); in California, between 14,000 and 19,500 lb GVWRa
8 yr or 110,000 mi
Medium heavy-duty diesel engine (MHDDE): 19,500 lb to 33,000 lb GVWR
8 yr or 185,000 mi
Heavy heavy-duty diesel engine (HHDDE) (including those for diesel buses): heavier than 33,000 lb GVWR
10 yr or 435,000 mi or 23,000 hr
aUnder federal light-duty Tier 2 regulations, vehicles of GVWR up to 10,000 lb used for personal transportation are reclassified as medium-duty passenger vehicles (MDPV—primarily SUVs and passenger vans) and are subject to light-duty vehicle legislation.
TABLE D-5 Additional Emission Requirements
Test
Limits
Supplemental Emission Test (SET)
Federal Test Procedure (FTP) Standards
Not-to-exceed (NTE) Limits
1.5 × FTP Standards
2007 and later heavy-duty highway engines are listed in Table D-3. Federal regulations do not require that complete heavy-duty diesel vehicles be chassis-certified; instead requiring the certification of their engines. Consequently, the emissions standards are expressed in grams per brake horsepower hours (g/bhp-hr) and require emission testing over the transient Federal Test Procedure (FTP) engine dynamometer cycle. Table D-4 lists the useful lives of the engines in various service classes; the required useful life of Class 8 engines as required by the emission standards is 435,000 miles, or 10 years, or 22,000 hours.
Additional emission testing requirements, first introduced in 1998, are shown in Table D-5 and include the Supplemental Emission Test (SET) and Not-to-Exceed (NTE) limits.
The SET is a 13-mode steady-state test that was introduced to help ensure that heavy-duty engine emissions are controlled during steady-state type driving, such as a line-haul truck operating on a freeway.
The NTE limits have been introduced as an additional instrument to ensure that heavy-duty engine emissions are controlled over the full range of speed and load combinations commonly experienced in use. The NTE requirement establishes an area (the “NTE zone”) under the torque curve of an engine where emissions must not exceed a specified value for any of the regulated pollutants.
For Further Information
The preceding review of current and future emission standards is intended to provide an overview of the key aspects of current and future emission standards that either are applicable to the 21CTP or provide background information to aid in evaluating the Partnership. For a complete understanding of past and present emission standards highlighted in this section, the reader is directed to the actual regulations promulgated by the U.S. Environmental Protection Agency and the California Air Resources Board.
EMISSION STANDARDS NOT ADDRESSED BY THE 21CTP
Evaporative Emissions
Evaporative emissions, produced from the evaporation of fuel, have been a large contributor to urban smog, because the heavier molecules of unburned fuel stay closer to ground level. Fuel evaporates from a vehicle in the following ways: by gas tank venting, from running losses, and from refueling losses. Evaporative emission standards were first promulgated for 1971 model year vehicles when charcoal canisters were introduced to trap gasoline vapors. These
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TABLE D-6 Timetable for Implementation of On-Board Diagnostic (OBD) II Systems for Heavy-Duty Vehicles (more than 14,000 lb GVWR)
Regulatory Body
Model Year
Comments
California Air Resources Board (CARB)
2007
Basic Engine Manufacturer Diagnostic (EMD) system
CARB
2010 Proposed
Comprehensive OBD II system
U.S. Environmental Protection Agency
2010 Proposed
Notice of Proposed Rule
standards become more stringent in recent years. The most stringent evaporative emission standards have recently been introduced for gasoline-fueled vehicles. California currently has an optional zero evaporative emission standard, which is one of the requirements for certifying a vehicle with SULEV exhaust emissions as a partial zero emission vehicle.
In recognition of the high temperatures that diesel fuel can reach in modern common rail fuel systems, evaporative emission standards for diesel fuel vehicles have also been adopted. Because technology to control diesel evaporative emissions are not considered to be a significant issue, these emissions are not included in the scope of 21CTP and will not be discussed in this report.
On-Board Diagnostic II (OBD II) System
The On-Board Diagnostic II (OBD II) system was phased in on light-duty vehicles beginning with the 1994 model year vehicles. The purpose of the on-board diagnostic system on vehicles is to ensure the emission control system and other engine-related components are operating properly. When the OBD II system detects a problem, a corresponding “Diagnostic Trouble Code” (DTC) is stored in the computer’s memory and a special light on the instrument cluster called a Malfunction Indicator Lamp (MIL) is illuminated.
The OBD II system is intended to ensure proper emission system operation for every vehicle throughout its lifetime, and notifies the driver of a problem before the vehicle’s emissions have increased significantly.
Heavy-duty engine OBD II, also referred to as the engine manufacturer diagnostic system, is similar to the light duty OBD II system, except that the monitors are not required to be tied to the emission standards (Dieselnet, 2005; EPA, 2006).
The timetable for implementation of OBD II for heavy-duty vehicles as shown in Table D-6.
Although OBD II is a key element in maintaining the stringent emission levels that are the focus of the 21CTP, the development and application of OBD II are not included in the scope of this partnership and are not discussed further in this report.
Defeat Devices
Manufacturers must ensure that vehicle emission control systems operate in use as they do on the prescribed test cycles. If, without properly informing EPA, an emission control system operates differently when in use, the emission control system is considered “defeated” and a “defeat device” is present. EPA may seek judicial penalties for each vehicle sold containing a defeat device (EPA, 2007a).
REFERENCES
Dieselnet. 2005. California adopts OBD requirements for heavy-duty engines. July 22. Available at http://www.dieselnet.com/news/2005/07carb.php. Accessed May 29, 2007.
DOE (U.S. Department of Energy). 2006. 21st Century Truck Partnership Roadmap and Technical White Papers. Doc. No. 21CTP-003. Washington, D.C. December.
Ehlmann, James, and George Wolff. 2005. Automobile Emissions—The Road Toward Zero. Air and Waste Management Association. January.
EPA (U.S. Environmental Protection Agency). 1994. Fact Sheet OMS-12, August.
EPA. 2006. Regulatory Announcement: Proposed Rule on OBD for Heavy Duty Engines. EPA 420-F-06-058. Washington, D.C.: Office of Transportation and Air Quality. April.
EPA. 2007a. Clean Air Act Enforcement. Available at http://www.epa.gov/compliance/civil/caa. Accessed September 7, 2007.
EPA. 2007b. Green Book [Non-attainment Areas under the Clean Air Act of 1972 as Amended]. Available at http://www.epa.gov/air/oaqps/greenbk/index.html. Accessed June 14, 2007.
Johnson, J. H. 1988. Automotive Emissions. P. 45 in Air Pollution, the Automobile, and Public Health. Washington, D.C.: National Academy Press.
