Evaluating Vehicle Emissions Inspection and Maintenance Programs (2001) / Chapter Skim
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1 Motor Vehicle Emissions and Regulation
1 Motor Vehicle Emissions and Regulation
Pages 17-45
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From page 17... ...
programs, setting tighter new vehicle tailpipe and evaporative emissions standards, and promoting alternative and reformulated fuels. This report focuses on vehicle-emissions I/M programs, which are designed to identify vehicles that have higher than allowable emissions and to try to ensure that they are repaired or removed from the fleet.
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From page 18... ...
3. Identify criteria for the evaluation of I/M programs, including equipment needs, program costs, repair effectiveness, program effectiveness for vehicle categories, and effects of human behavior (such as vehicle tampering and I/M avoidance due to cost, inconvenience, program perceptions, and nonresponse to on-board diagnostic (OBD)
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From page 19... ...
, these emissions inventory estimates are lower than those estimated from on-road vehicle studies and The terms VOCs and HC are used in this report to denote organic compounds that are emitted as vapors under typical atmospheric conditions. Unless quoting an emissions inventory source or a regulation that uses another term, the report uses the term HC exclusively.
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From page 20... ...
The heavier HDVs, however (those with gross vehicle weights Heater than 26,000 pounds) , are fueled almost exclusively with diesel fuel.
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In WAS, or-road end non-road mobile sources were est~matedto contribute over 75°/0 of CO emissions nationwide (about 70,000 thousand short tons) , about 50°/0 of the NOx (about ~ 3,000 thousand short tons)
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From page 22... ...
contribute 50% oftotal HC, 89°/O of NOx, and94% of CO emissions in the South Coast Air Basin (which encompasses Los Angeles and Orange
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Gasoline-powereU vehicles dominate VOC and CO emissions, and vehicles that operate on diesel fuel represent a significant fraction of NOX and direct PM emissions. As noteipreviously, however, mobilesource emissions have been underestimated and are subject to considerable uncertainty.
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Because these vehicles are significant sources of PM and NOX emissions and they have not been subjected to extensive I/M programs, significant emissions reduction opportunities may exist. Currently, 1 ~ states have testing programs for assessing smoke emissions from heavy-duty diesel vehicles.
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Vehicle Exhaust Emissions Standards Over the past 3 decades, efforts to reduce emissions from mobile sources have focused on reducing exhaust and non-tailpipe emissions from on-road
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These standards were slightly modified and delayed, however, and were not fully implemented until the Clean Air Act Amendments of ~ 990 (CAAA90) , which produced the Tier ~ emissions standards beginning with the ~ 994 model year.
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From page 27... ...
CThe proposed Tier 2 standards are a corporate average standard with a focus on NOX emissions. This allows NMHC and CO emissions standards to "float," in that fleet emissions rates depend on the mix of vehicles used to meet the NOX standard.
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1973 NOX control added 1975 Lower standards forcing catalytic converters and lead-free fuel 1976 High-altitude emissions requirements 1981 Lower standards forcing three-way catalysts (closed-loop systems) 1994 Lower "Tier 1 " standards (EPA 1991 ~ 2000 Control of emissions from aggressive driving and A/C operation (supplementalfederaltest procedure)
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In 1998, EPA concluded that more stringent vehicle standards, known as Tier 2 standards, were needed to meet the National Ambient Air Quality Standard (NAAQS) for ozone and that the technology to meet these vehicle emissions standards was available and cost-effective.
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DISTRIBUTION OF VEHICLE EMISSIONS Numerous studies conducted over the past 2 decades have produced a fairly comprehensive characterization of mobile-source emissions and the sThe EMFAC model is used to estimate vehicle emissions and the effectiveness of control strategies such as I/M, reformulated fuels, and emissions standards. It is similar to EPA's MOBILE model, which is discussed in detail in Chapter 5 and in the NRC (2000)
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From page 31... ...
The ~ 992 Air Quality Improvement Research Program, for example, classified a high emitter as having CO emissions greater than 15 g/mi and/or HC emissions greater than 1.1 g/mi (Knepper et al.
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From page 32... ...
reported to CARB that 47% of the CO emissions generated in FTP measurements were produced by only ~ 2% of vehicles tested. Since that time, remote sensing, I/M data, and roadside pullover studies have supported those initial observations (Stedman ~ 989; Lawson et al.
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2000) using remote sensing of automobile emissions indicate that the skewness of vehicle emissions might have increased in recent years.
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34 Evaluating Vehicle Emissions I/M Programs ~ 4 ~ a' .~ age c .
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For example, in the California I/M pilot study cited above, the data in Figure 1-9 have been used to demonstrate that about 75% of the excess aggregated CO, HC, and NOX emissions were produced by only 10% ofthe fleet. Excess emissions are defined here as the difference between a vehicle's current emissions rate and two times its certification standard.
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Noblet, University of California, Berkeley. the gasoline lost becomes a significant contributor to the HC emissions inventory.
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Vehicle I/M programs were identified as an option for improving air quality in the ~ 970 Clean Air Act, and the first T/M program was implemented in New Jersey in ~ 974. In that program, exhaust emissions at idle conditions were tested for light-duty, gasoline-powered vehicles manufactured dunog or after 1968.
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From page 38... ...
It should be noted that EPA never described how these data would be used, and the agency has not enforced these requirements. Implementation ofthe model I/M program was projected to achieve reductions of 28% in HC, 3 ~ % in CO, and 9% in NOX for enhanced I/M regions, compared with emissions in the absence of an I/M program, by the year 2000 i°Nonattainment areas are areas violating federal air-quality standards for the criteriapollutants: sulfur dioxide, particulate matter, nitrogen dioxide, carbon monoxide, ozone, and lead.
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From page 39... ...
This proposed rule would provide states additional flexibility to tailor their I/M programs to better meet current and fixture needs. Among these is the need to maximize program efi iciency i2The MOBILE model is used to estimate vehicle emissions and the effectiveness of control strategies such as I/M, reformulated fuels, and emissions standards.
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Chapter 3 discusses a selection of state-sponsored and independent evaluations. As data on program effectiveness have become available, comparisons have been made between the emissions reductions initially projected for I/M programs and the emissions reductions suggested by the program evaluation data.
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42 x q Fin ¢ En _ ~ .o ~ ~ ~ Ct ~ on m ~ C`: .
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recently reported that mobile-source emissions are the most significant contributor to human exposure to air toxic s. Increased understanding ofthe effects of air tonics end PM, as well as the implementation of stricter standards for ozone and PM, might place new demands on future vehicle I/M programs.
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From page 44... ...
This includes a categorization of emissions by vehicle type, exhaust standards, evaporative standards, emissions distributions, a brief overview of existing T/M programs, and an assessment of future I/M issues. Motor vehicles represent a significant fraction of overall emissions, especially in urban areas, and a relatively small fraction of on-road vehicles are responsible for a large fraction ofthe emissions.
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From page 45... ...
Increased durability and the lack of need for periodic maintenance should reduce the testing burden throughincreased use of clean screening of vehicles. Technological innovations in OBD systems might speed up the inspection process and perhaps eventually make the remote monitoring or reporting of vehicle emissions characteristics a reality.
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