Multispecies remote sensing measurements of vehicle emissions on Sherman Way in Van Nuys,California

As part of the 2010 Van Nuys tunnel study, researchers from the University of Denver measured on-road fuel-specific light-duty vehicle emissions from nearly 13,000 vehicles on Sherman Way (0.4 miles west of the tunnel) in Van Nuys, California, with its multispecies Fuel Efficiency Automobile Test (FEAT) remote sensor a week ahead of the tunnel measurements. The remote sensing mean gram per kilogram carbon monoxide (CO), hydrocarbon (HC), and oxide of nitrogen (NO_x) measurements are 8.9% lower, 41% higher, and 24% higher than the tunnel measurements, respectively. The remote sensing CO/NO_x and HC/NO_x mass ratios are 28% lower and 20% higher than the comparable tunnel ratios. Comparisons with the historical tunnel measurements show large reductions in CO, HC, and NO_x over the past 23 yr, but little change in the HC/NO_x mass ratio since 1995. The fleet CO and HC emissions are increasingly dominated by a few gross emitters, with more than a third of the total emissions being contributed by less than 1% of the fleet. An example of this is a 1995 vehicle measured three times with an average HC emission of 419 g/kg fuel (two-stroke snowmobiles average 475 g/kg fuel), responsible for 4% of the total HC emissions. The 2008 economic downturn dramatically reduced the number of new vehicles entering the fleet, leading to an age increase (>1 model year) of the Sherman Way fleet that has increased the fleet's ammonia (NH₃) emissions. The mean NH₃ levels appear little changed from previous measurements collected in the Van Nuys tunnel in 1993. Comparisons between weekday and weekend data show few fleet differences, although the fraction of light-duty diesel vehicles decreased from the weekday (1.7%) to Saturday (1.2%) and Sunday (0.6%).

Implications: On-road remote sensing emission measurements of light-duty vehicles on Sherman Way in Van Nuys, California, show large historical emission reductions for CO and HC emissions despite an older fleet arising from the 2008 economic downturn. Fleet CO and HC emissions are increasingly dominated by a few gross emitters, with a single 1995 vehicle measured being responsible for 4% of the entire fleet's HC emissions. Finding and repairing and/or scrapping as little as 2% of the fleet would reduce on-road tailpipe emissions by as much as 50%. Ammonia emissions have locally increased with the increasing fleet age.     

An Analysis of Michigan and California CO Remote Sensing Measurements

Abstract

Remote sensing measurements of CO emissions from on-road vehicles were made in California in 1991 and in Michigan in 1992. It was determined that both fleets had a small linear increase in the high emitter frequency (vehicles emitting more than 4% CO) as a function of vehicle age for 1986 and newer model vehicles. Although high emitting vehicles were only a small minority of the fleet, they had a dominant impact on the mean CO and total CO emitted by the fleet. In Michigan, the highest emitting 5% of passenger cars generated 45% of the CO from cars. In California, the highest emitting 5% of passenger cars generated 38% of the CO from cars. There was a high correlation between the mean CO emitted by each model year of vehicle and the frequency of high emitting vehicles within the model year for both the Michigan and California fleets. The frequency of high emitters within any model year had no obvious relation to that model year’s certification standards. The high emitter frequencies for vehicles less than nine years old were very similar for the California and Michigan fleets. An increase in the high emitter frequency in the ten-year-old and older Michigan passenger car fleet (relative to the California passenger car fleet), suggests, but does not conclusively demonstrate, that the rate of high emitters in Michigan and California is reduced by the inspection and maintenance (I/M) programs.     

A Multipurpose Flare Stack for Control of Chemical Process Wastes

Abstract

To test the effectiveness of California’s vehicle inspection/ maintenance (I/M) program, exclusive of vehicle-owner intervention, a fleet of more than 1,100 vehicles that previously had failed California’s Smog Check test were sent to randomly selected Smog Check stations in the Los Angeles area for covert inspections and repairs. The two-speed idle test was used for repairs. For those vehicles that were repaired at the first inspection, their FTP emission reductions were 25%, 14%, and 11% for hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO_x), respectively, although emissions testing for NO_x was not performed at the Smog Check stations. Idle HC and CO emissions increased for 35% and 43% of the vehicles, respectively, after repairs. This data set shows that most vehicles that fail the Smog Check inspection are only marginal emitters, with 61% and 44% of the total potential for HC and CO emission reductions, respectively, coming from only 10% of the vehicles that currently fail the inspection. When the vehicles were rank-ordered by idle emissions from dirtiest to cleanest, emission reduction costs for the highest-emitting 10% of the fleet averaged $l,100/ton and $250/ton for HC and CO, respectively, attributing all the costs to each pollutant exclusively. For the remaining vehicles, costs increased dramatically.     

Emission Factors for High-Emitting Vehicles Based on On-Road Measurements of Individual Vehicle Exhaust with a Mobile Measurement Platform

ABSTRACT

Fuel-based emission factors for 143 light-duty gasoline vehicles (LDGVs) and 93 heavy-duty diesel trucks (HDDTs) were measured in Wilmington, CA using a zero-emission mobile measurement platform (MMP). The frequency distributions of emission factors of carbon monoxide (CO), nitrogen oxides (NO_x), and particle mass with aerodynamic diameter below 2.5 μm (PM_2.5) varied widely, whereas the average of the individual vehicle emission factors were comparable to those reported in previous tunnel and remote sensing studies as well as the predictions by Emission Factors (EMFAC) 2007 mobile source emission model for Los Angeles County. Variation in emissions due to different driving modes (idle, low- and high-speed acceleration, low- and high-speed cruise) was found to be relatively small in comparison to intervehicle variability and did not appear to interfere with the identification of high emitters, defined as the vehicles whose emissions were more than 5 times the fleet-average values. Using this definition, approximately 5% of the LDGVs and HDDTs measured were high emitters. Among the 143 LDGVs, the average emission factors of NO_x, black carbon (BC), PM_2.5, and ultrafine particle (UFP) would be reduced by 34%, 39%, 44%, and 31%, respectively, by removing the highest 5% of emitting vehicles, whereas CO emission factor would be reduced by 50%. The emission distributions of the 93 HDDTs measured were even more skewed: approximately half of the NO_x and CO fleet-average emission factors and more than 60% of PM_2.5, UFP, and BC fleet-average emission factors would be reduced by eliminating the highest-emitting 5% HDDTs. Furthermore, high emissions of BC, PM_2.5, and NO_x tended to cluster among the same vehicles.

IMPLICATIONS This study presents the characterization of on-road vehicle emissions in Wilmington, CA, by sampling individual vehicle plumes. Approximately 5% of the vehicles were high emitters, whose emissions were more than 5 times the fleet-average values. These high emitters were responsible for 30% and more than 50% of the average emission factors of LDGVs and HDDVs, respectively. It is likely that as the overall fleet becomes cleaner due to more stringent regulations, a small fraction of the fleet may contribute a growing and disproportionate share of the overall emissions. Therefore, long-term changes in on-road emissions need to be monitored.     

Development of a High-Speed Ultraviolet Spectrometer for Remote Sensing of Mobile Source Nitric Oxide Emissions

ABSTRACT

The University of Denver (DU) has developed a new remote sensor for the measurement of mobile source nitric oxide (NO). This system is integrated with an existing infrared remote sensor and is capable of measuring carbon monoxide and hydrocarbons in addition to NO, at a rate of more than 1000 vehicles/hr. The detection limit on a low-emitting vehicle under typical measurement conditions is 24 parts per million NO (3σ). Measurements from this instrument correlated well in a side-by-side comparison with the previous NO remote sensor developed at DU, and we have used this study to confirm a suspected interference by aromatic hydrocarbons in the older instrument. The results of an extended field experiment using the new instrument, conducted in fall 1997, are also presented. The NO emissions of the fleet measured in this study (averaging 15.0 g NO/gal) exhibit a skewed distribution typical of mobile sources. This paper also describes the relationship between NO emissions and model year and NO emissions and vehicle acceleration, as measured by the new remote sensor.     

On-Road,In-Use Gaseous Emission Measurements by Remote Sensing of School Buses Equipped with Diesel Oxidation Catalysts and Diesel Particulate Filters

Abstract

A remote sensing device was used to obtain on-road and in-use gaseous emission measurements from three fleets of schools buses at two locations in Washington State. This paper reports each fleet’s carbon monoxide (CO), hydrocarbon (HC), nitric oxide (NO), and nitrogen dioxide (NO₂) mean data. The fleets represent current emission retrofit technologies, such as diesel particulate filters and diesel oxidation catalysts, and a control fleet. This study shows that CO and HC emissions decrease with the use of either retrofit technology when compared with control buses of the same initial emission standards. The CO and HC emission reductions are consistent with published U.S. Environmental Protection Agency verified values. The total oxides of nitrogen (NO_x), NO, and the NO₂/NO_x ratio all increase with each retrofit technology when compared with control buses. As was expected, the diesel particulate filters emitted significantly higher levels of NO₂ than the control fleet because of the intentional conversion of NO to NO₂ by these systems. Most prior research suggests that NO_x emissions are unaffected by the retrofits; however, these previous studies have not included measurements from retrofit devices on-road and after nearly 5 yr of use. Two 2006 model-year buses were also measured. These vehicles did not have retrofit devices but were built to more stringent new engine standards. Reductions in HCs and NO_x were observed for these 2006 vehicles in comparison to other non-retrofit earlier model-year vehicles.     

On-road remote sensing measurements and fuel-based motor vehicle emission inventory in Hangzhou,China

Motor vehicles are one of the largest sources of air pollutants worldwide. Despite their importance, motor vehicle emissions are inadequately understood and quantified, esp. in developing countries. In this study, the real-world emissions of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxide (NO) were measured using an on-road remote sensing system at five sites in Hangzhou, China in 2004 and 2005. Average emission factors of CO, HC and NO_x for petrol vehicles of different model year, technology class and vehicle type were calculated in grams of pollutant per unit of fuel use (g l⁻¹) from approximately 32,260 petrol vehicles. Because the availability of data used in traditional on-road mobile source estimation methodologies is limited in China, fuel-based approach was implemented to estimate motor vehicle emissions using fuel sales as a measure of vehicle activity, and exhaust emissions factors from remote sensing measurements. The fuel-based exhaust emission inventories were also compared with the results from the recent international vehicle emission (IVE) model. Results show that petrol vehicle fleet in Hangzhou has significantly high CO emissions, relatively high HC and low NO_x, with the average emission factors of 193.07±15.63, 9.51±2.40 and 5.53±0.48 g l⁻¹, respectively. For year 2005 petrol vehicles exhaust emissions contributed with 182,013±16,936, 9107±2255 and 5050±480 metric ton yr⁻¹ of CO, HC and NO_x, respectively. The inventories are 45.5% higher, 6.6% higher and 53.7% lower for CO, HC and NO_x, respectively, than the estimates using IVE travel-based model. In addition, a number of insights about the emission distributions and formation mechanisms have been obtained from an in-depth analysis of these results.     

Analysis of Remote Sensing Errors of Omission and Commission Under FTP Conditions

Abstract

Second-by-second modal emissions data from a 73-vehicle fleet of 1990 and 1991 light duty cars and trucks driven on the Federal Test Procedure (FTP) driving cycle were examined to determine remote sensing errors of commission in identifying high emissions vehicles. Results are combined with a similar analysis of errors of omission based on modal FTP data from high emissions vehicles. Extremely low errors of commission combined with modest errors of omission indicate that remote sensing should be very effective in isolating high CO and HC emitting vehicles in a fleet of late model vehicles on the road.     

Emission Characteristics of Mexico City Vehicles

The University of Denver remote sensor for automobile exhaust was set up for nine days at five locations in the Mexico City area. A total of 31,838 valid readings for CO and HC emissions were obtained. The emissions distribution was unlike any other we have observed in North America or Europe, in that the emissions for both CO and HC were vastly greater than seen elsewhere. The readings are discussed in terms of the fraction of CO and HC which would be measured by a tailpipe probe, and in terms of grams emitted per gallon of gasoline. The median CO emission was 3.8 percent, with half of the CO emissions coming from the 24 percent of the fleet with over 6.6 percent CO in the exhaust. The median HC emission was 1,100 parts per million measured as propane equivalent, while half the emissions come from twelve percent of the fleet with more than 4,000 ppm propane equivalent in the exhaust.     

Ammonia emissions from a representative in-use fleet of light and medium-duty vehicles in the California South Coast Air Basin

We used Fourier Transform Infrared Spectroscopy (FTIR) to measure tailpipe ammonia emissions from a representative fleet of 41 light and medium-duty vehicles recruited in the California South Coast Air Basin. A total of 121 chassis dynamometer emissions tests were conducted on these vehicles and the test results were examined to determine the effects of several key variables on ammonia emissions. Variables included vehicle type, driving cycle, emissions technology, ammonia precursor emissions (i.e. CO and NOx) and odometer readings/model year as a proxy for catalyst age. The mean ammonia emissions factor was 46 mg km^?1 (σ = 48 mg km^?1) for the vehicle fleet. Average emission factors for specific vehicle groups are also reported in this study. Results of this study suggest vehicles with the highest ammonia emission rates possess the following characteristics: medium-duty vehicles, older emissions technologies, mid-range odometer readings, and higher CO emissions. In addition, vehicles subjected to aggressive driving conditions are likely to be higher ammonia emitters. Since the vehicles we studied were representative of recent model year vehicles and technologies in urban airsheds, the results of our study will be useful for developing ammonia emissions inventories in Los Angeles and other urban areas where California-certified vehicles are driven. However, efforts should also be made to continue emissions testing on in-use vehicles to ensure greater confidence in the ammonia emission factors reported here.     

Prospects of inspection and maintenance of two-wheelers in India.

Two-wheeler vehicles in Delhi, India--roughly 70% of the total vehicle fleet--are responsible for a significant portion of the city's vehicle emissions and petroleum consumption. An inspection and maintenance (I/M) program that ensures vehicle emission control systems are well maintained can complement other emission reduction strategies. This paper presents the initial findings of extensive data collected on vehicle characteristics and emissions for two-wheeler vehicles operating in Delhi in a series of I/M camps conducted by the Society of Indian Automobile Manufacturers and various partners in late 1999. The analysis shows idle HC and CO emissions [measured in terms of parts per million (ppm) and volume % (vol %), respectively] in a slow declining trend with subsequent model years, reflecting tighter emission standards and more advanced emission technologies. The I/M benefits--3 vol % and 39% reduction in idle and mass CO, respectively; 40 vol % and 22% reduction in idle and mass HC, respectively; and a 10-20% increase in fuel efficiency--were higher than those reported in the literature. Although these benefits are substantial, any implementation strategy needs to consider cost-effectiveness. In the present study, only 10% of vehicles--contributing 22% of the total vehicle emissions--failed the idle CO standard. Fleet emissions data variability necessitates a large sample size to develop a baseline for the vehicle fleet, but a smaller, scientifically designed sample and better data collection quality could periodically track the benefits at future camps.     

Emission factors for high-emitting vehicles based on on-road measurements of individual vehicle exhaust with a mobile measurement platform

Fuel-based emission factors for 143 light-duty gasoline vehicles (LDGVs) and 93 heavy-duty diesel trucks (HDDTs) were measured in Wilmington, CA using a zero-emission mobile measurement platform (MMP). The frequency distributions of emission factors of carbon monoxide (CO), nitrogen oxides (NO(x)), and particle mass with aerodynamic diameter below 2.5 microm (PM2.5) varied widely, whereas the average of the individual vehicle emission factors were comparable to those reported in previous tunnel and remote sensing studies as well as the predictions by Emission Factors (EMFAC) 2007 mobile source emission model for Los Angeles County. Variation in emissions due to different driving modes (idle, low- and high-speed acceleration, low- and high-speed cruise) was found to be relatively small in comparison to intervehicle variability and did not appear to interfere with the identification of high emitters, defined as the vehicles whose emissions were more than 5 times the fleet-average values. Using this definition, approximately 5% of the LDGVs and HDDTs measured were high emitters. Among the 143 LDGVs, the average emission factors of NO(x), black carbon (BC), PM2.5, and ultrafine particle (UFP) would be reduced by 34%, 39%, 44%, and 31%, respectively, by removing the highest 5% of emitting vehicles, whereas CO emission factor would be reduced by 50%. The emission distributions of the 93 HDDTs measured were even more skewed: approximately half of the NO(x) and CO fleet-average emission factors and more than 60% of PM2.5, UFP, and BC fleet-average emission factors would be reduced by eliminating the highest-emitting 5% HDDTs. Furthermore, high emissions of BC, PM2.5, and NO(x) tended to cluster among the same vehicles.     

Three decades of on-road mobile source emissions reductions in South Los Angeles

In May 2018, the University of Denver repeated on-road optical remote sensing measurements at two locations in Lynwood, CA. Lynwood area vehicle tailpipe emissions were first surveyed in 1989 and 1991 because the area suffered from a large number of carbon monoxide (CO) air quality violations. These new measurements allow for the estimation of fuel-specific CO and total hydrocarbon (HC) emissions reductions, changes in the longevity of emission-control components, and the prevalence of high emitters in the current fleet. Since 1989 CO emissions decreased approximately factors of 10 (120 ± 8 to 12.3 ± 0.2 gCO/kg of fuel) and 20 (210 ± 8 to 10.4 ± 0.4 gCO/kg of fuel) at our I-710/Imperial Highway and Long Beach Blvd. sites, respectively. These reductions are also reflected in the local ambient air measurements. Tailpipe HC emissions have decreased by a factor of 25 (50 ± 4 to 2.1 ± 0.3 gHC/kg of fuel) since 1991 at the Long Beach Blvd. location. The decreases are so dramatic that the vast majority of vehicles now have HC measurements that are indistinguishable from zero. The decreases have increased the skewedness of the emissions distribution with the 99th percentile now responsible for more than 37% (CO) and 28% (HC) of the totals. Ammonia emissions collected in 2018 at both Lynwood locations peak with 20-year-old vehicles (1998 models), indicating long lifetimes for catalytic converters.

In 1989 and 1991, the on-road Lynwood fleets had significantly higher emissions than fleets observed in other locations within the South Coast Air Basin. The 2018 fleets now have means and emissions by model year that are consistent with those observed at other sites in Los Angeles and the U.S. This indicates that modern vehicle combustion management and after-treatment systems are achieving their goals regardless of community income levels.

Implications: Recent on-road vehicle emission measurements at two locations in the Lynwood, CA area, first visited in 1989, found significant fuel specific CO and HC emission reductions. CO emissions have decreased by a factor of 10 and 20 at each location and HC emissions have declined by a factor of 25. This has increased the skewedness in both species emissions distribution. The 2018 fleets have means and emissions by model year that are now consistent with those observed at other U.S. sites indicating that modern vehicle emissions control advancements are achieving their goals regardless of community income levels.     

Estimating Full IM240 Emissions from Partial Test Results: Evidence from Arizona

ABSTRACT

The expense and inconvenience of enhanced-vehicle-emissions testing using the full 240-second dynamometer test has led states to search for ways to shorten the test process. In fact, all states that currently use the IM240 allow some type of fast-pass, usually as early in the test as second 31, and Arizona has allowed vehicles to fast-fail after second 93. While these shorter tests save states millions of dollars in inspection lanes and driver costs, there is a loss of information since test results are no longer comparable across vehicles. This paper presents a methodology for estimating full 240-second results from partial-test results for three pollutants: HC, CO, and NO_x. If states can convert all tests to consistent IM240 readings, they will be able to better characterize fleet emissions and to evaluate the impact of inspection and maintenance and other programs on emissions over time. Using a random sample of vehicles in Arizona which received full 240-second tests, we use regression analysis to estimate the relationship between emissions at second 240 and emissions at earlier seconds in the test. We examine the influence of other variables such as age, model-year group, and the pollution level itself on this relationship. We also use the estimated coefficients in several applications. First, we try to shed light on the frequent assertion that the results of the dynamometer test provide guidance for vehicle repair of failing vehicles. Using a probit analysis, we find that the probability that a failing vehicle will pass the test on the first retest is greater the longer the test has progressed. Second, we test the accuracy of our estimates for forecasting fleet emissions from partial-test emissions results in Arizona. We find forecasted fleet average emissions to be very close to the actual fleet averages for light-duty vehicles, but not quite as good for trucks, particularly when NO_x emissions are forecast.     

The Formation of Mg3Ca(S04)4 during the Sulfation Reaction of Dolomite

Abstract

Inspection and maintenance programs for motor vehicles in the United States increasingly use loaded mode mass emissions testing (IM240). A method was developed to predict mass emission rates and mass emission changes, particularly from repair benefits, using a low-cost, portable four-gas non-dispersive infrared (NDIR) vehicle exhaust gas analyzer. A single vehicle was tested several times with the analyzer while on the dynamometer and undergoing successive repairs. Excellent correlations for CO and HC were observed. Five vehicles were measured using an on-road driving loop before and after emissions-related repairs, while another three vehicles were tested with no repairs performed. The on-road concentration data used to guide the repair process were converted to grams per gallon; when divided by estimated miles per gallon, this gave grams per mile emissions for comparison to IM240. Correlation coefficients (r²) of 0.87 for CO and 0.76 for HC were achieved for the 13 tests. The linear correlations between IM240 and emissions measured by this method would allow repair facilities to perform a relatively inexpensive test for diagnostic purposes and to estimate repair effectiveness without the need for a dynamometer.     

Investigating the real-world emission characteristics of light-duty gasoline vehicles and their relationship to local socioeconomic conditions in three communities in Los Angeles,California

This paper discusses results from a vehicular emissions research study of over 350 vehicles conducted in three communities in Los Angeles, CA, in 2010 using vehicle chase measurements. The study explores the real-world emission behavior of light-duty gasoline vehicles, characterizes real-world super-emitters in the different regions, and investigates the relationship of on-road vehicle emissions with the socioeconomic status (SES) of the region. The study found that in comparison to a 2007 earlier study in a neighboring community, vehicle emissions for all measured pollutants had experienced a significant reduction over the years, with oxides of nitrogen (NO_X) and black carbon (BC) emissions showing the largest reductions. Mean emission factors of the sampled vehicles in low-SES communities were roughly 2–3 times higher for NO_X, BC, carbon monoxide, and ultrafine particles, and 4–11 times greater for fine particulate matter (PM_2.5) than for vehicles in the high-SES neighborhood. Further analysis indicated that the emission factors of vehicles within a technology group were also higher in low-SES communities compared to similar vehicles in the high-SES community, suggesting that vehicle age alone did not explain the higher vehicular emission in low-SES communities.

Evaluation of the emission factor distribution found that emissions from 12% of the sampled vehicles were greater than five times the mean from all of the sampled fleet, and these vehicles were consequently categorized as “real-world super-emitters.” Low-SES communities had approximately twice as many super-emitters for most of the pollutants as compared to the high-SES community. Vehicle emissions calculated using model-year-specific average fuel consumption assumptions suggested that approximately 5% of the sampled vehicles accounted for nearly half of the total CO, PM_2.5, and UFP emissions, and 15% of the vehicles were responsible for more than half of the total NO_X and BC emissions from the vehicles sampled during the study.

Implications: This study evaluated the real-world emission behavior and super-emitter distribution of light-duty gasoline vehicles in California, and investigated the relationship of on-road vehicle emissions with local socioeconomic conditions. The study observed a significant reduction in vehicle emissions for all measured pollutants when compared to an earlier study in Wilmington, CA, and found a higher prevalence of high-emitting vehicles in low-socioeconomic-status communities. As overall fleet emissions decrease from stringent vehicle emission regulations, a small fraction of the fleet may contribute to a disproportionate share of the overall on-road vehicle emissions. Therefore, this work will have important implications for improving air quality and public health, especially in low-SES communities.     

Evaluation of a Low-Cost Transient Mass Measurement System in Vehicle Inspection and Maintenance Testing: Results of a Gordon-Darby Study

Abstract

A study was performed at a Gordon-Darby centralized inspection and maintenance (I/M) test lane in Phoenix, AZ, in December 1999 for the purpose of evaluating the accuracy of production Vehicle Mass Analysis System (VMAS) equipment relative to standard IM240 equipment. Simultaneous transient mass measurements were made on random vehicles using VMAS and IM240 systems on two test lanes during regular I/M testing. Cumulative mass emissions for 846 valid tests were correlated using least-squares regression analysis. Correlation indices were >0.99 for both carbon monoxide (CO) and nitric oxide (NO) and 0.93 for hydrocarbon (HC), and the standard errors of regression were 1.38 g/mi, 0.123 g/mi, and 0.245 g/mi for CO, NO, and HC, respectively. These strong correlation results are reflected by high excess emission identification rates of 99.4% for CO, 99.3% for NO, and 94.5% for HC when applying final IM240 cut points with a <2% error of commission for all pollutants.     

Remote Sensing Data and a Potential Model of Vehicle Exhaust Emissions

In June 1991, General Motors Research and Development Center (GMR&D) participated in a remote sensing study conducted by the California Air Resources Board and the U. S. Environmental Protection Agency. During this study, the GMR&D remote sensor was used to measure the carbon monoxide (CO) and hydrocarbon (HC) emissions from approximately 15,000 vehicles. The vehicle type (passenger car, light-duty truck, or medium/heavy-duty truck), manufacturer, and model year were identified for each vehicle by acquiring registration data from the state of California. Analyses were performed separately for each vehicle type and for passenger cars by separate model years. The data indicate that the passenger cars with the highest 10% of CO emissions generated approximately 58% of the total CO from all cars. Similarly, the 10% highest HC-emitting cars generated 65% of the total HC from cars. It was found that for each model year of vehicle, the distribution of emission concentrations followed a logarithmic relationship. The logarithmic functions that describe these relationships can be used to estimate the fraction of vehicles that emitted at or above any given concentration of CO or HC. However, these logarithmic functions only describe measured distributions for vehicles emitting more than 1% CO and 0.015% HC.     

Estimations of Real-World N2O Emissions from Road Vehicles by Means of Measurements in a Traffic Tunnel

Abstract

Ambient air measurements of N₂O, NO_x, CO, and HC based on grab sampling were conducted in a major traffic tunnel in Sweden, that carries up to 4,000 vehicles per hour, in order to estimate real-world emissions of N₂O for road traffic. Two different methods—relative and mass balance—were used to calculate a N₂O emission factor for the mixed vehicle fleet, which gave an average emission factor, at average speeds of 30-70 km/h, of approximately 25 mg N₂O/ km, with a range of 7-56 mg/km.     

Effect of methyl tertiary butyl ether concentrations on exhaust emissions from gasoline used in the metropolitan area of Mexico City

In this work, the primary objective was to assess the impact of oxygenated fuel on the exhaust emissions from an important fraction of vehicles in the Metropolitan Area of Mexico City (MAMC). The results aim to provide information on the actual effect of MTBE on a fleet that represents more than 60% of the in-use vehicles in the MAMC. Ten vehicles were tested with a low-octane base gasoline, and 10 more with a regular-grade unleaded base gasoline. Three MTBE concentrations, 5, 10, and 15 vol %, were tested following the U.S. Federal Test Procedure (FTP). CO, total HC, and NOx from the exhaust gases were quantitatively evaluated and also characterized for FTP speciated organic emissions. From this data, the O3-forming potential of the fuels was calculated. Results show that for the fleet using low-octane gasoline, the addition of 10% MTBE substantially reduced CO emissions, but total HC concentration in the exhaust showed a modest decrease. For the regular gasoline, the 10% MTBE blend seemed to be the best choice, but there was not a significant decrease in emissions. The specific reactivity of each fuel, expressed in grams of O3 per gram of nonmethane organic gases, increased with MTBE concentration in both cases. This result is important to consider, especially for a region like Mexico City, which has high atmospheric O3 concentrations.