Article pubs.acs.org/est
Development of Hot Exhaust Emission Factors for Iranian-Made Euro‑2 Certified Light-Duty Vehicles Ehsan Banitalebi† and Vahid Hosseini*,† †
Mechanical Engineering Department, Sharif University of Technology, Azadi Avenue, Tehran 11365-11155, Iran S Supporting Information *
ABSTRACT: Emission factors (EFs) are fundamental, necessary data for air pollution research and scenario implementation. With the vision of generating national EFs of the Iranian transportation system, a portable emission measurement system (PEMS) was used to develop the basic EFs for a statistically significant sample of Iranian gasolinefueled privately owned light duty vehicles (LDVs) operated in Tehran. A smaller sample size of the same fleet was examined by chassis dynamometer (CD) bag emission measurement tests to quantify the systematic differences between the PEMS and CD methods. The selected fleet was tested over four different routes of uphill highways, flat highways, uphill urban streets, and flat urban streets. Real driving emissions (RDEs) and fuel consumption (FC) rates were calculated by weighted averaging of the results from each route. The activity of the fleet over each route type was assumed as a weighting factor. The activity data were obtained from a Tehran traffic model. The RDEs of the selected fleet were considerably higher than the certified emission levels of all vehicles. Differences between Tehran real driving cycles and the New European Driving Cycle (NEDC) was attributed to the lower loading of NEDC. A table of EFs based on RDEs was developed for the sample fleet.
1. INTRODUCTION The city of Tehran is facing serious air quality problems. In the past two years, 160 and 116 days were marked as unhealthy in Tehran. Emission inventories play an important role in air pollution management and control.1 They are necessary tools for identifying each source and its contributions during a given time period. Individual emission factors (EFs) of each pollutant from various sources are essential in order to develop a reliable emission inventory. EFs are fundamental, necessary data for air pollution research and scenario implementation.2−5 Prior studies have shown that exhaust emission from motor vehicles is one of the important sources of carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC) emitted in urban areas.6−8 Because of the difference in fleet composition, driving behavior, fuel quality, and maintenance programs, available international emission data are not accurately applicable in Iran. Lack of reliable and accurate EFs for mobile sources have caused difficulties in creating accurate and reliable emission inventories, development of air pollution dispersion models of all scales, and development of air pollution forecasting. This problem is not limited to Iran. In several other countries and regions around the world, scientists are in need of EFs for mobile sources. Therefore, developing EFs for Iran’s transportation fleet is not only necessary for an Iranian national emission inventory, but also quite useful for countries with similar fleet composition, driving behavior, fuel quality, and maintenance programs. © 2015 American Chemical Society
The only available Tehran emission inventory was developed by the Japan International Co-operation Agency (JICA) in 1997. The study showed that passenger cars were responsible for 58% of the CO, 50% of the HC, 14% of the SOx, and 55% of the NOx emitted in the greater Tehran area.9 Since then, despite major changes in fleet composition, vehicle technologies, vehicle population, and fuel quality, the inventory has not been updated. As such, a large experimental campaign was conducted to measure the real driving emissions (RDEs) of nationally manufactured LDVs fueled by gasoline. Chassis dynamometer (CD) tests and portable emission measurement system (PEMS) tests are two main methods for developing exhaust EFs from vehicles. Because of the repeatable nature of CD tests, it is used extensively in the type-approval testing,2 assessing the performance characteristics of different emission control technologies,10,11 and studying the effect of alternative fuels on vehicle emissions.12,13 However, the relation of the results to real-world driving emissions is debatable.2 Several studies have used the PEMS method to estimate EFs and fuel consumption (FC).14−17 The PEMS method is less repeatable in comparison with CD tests. Studies are available for the repeatability and accuracy of PEMS tests.18,19 In recent years, portable emissions testing has been Received: May 16, 2015 Accepted: November 23, 2015 Published: November 23, 2015 279
DOI: 10.1021/acs.est.5b05611 Environ. Sci. Technol. 2016, 50, 279−284
Article
Environmental Science & Technology
Figure 1. Comparison of PEMS and CD real-time instantaneous emission rate measurements in an NEDC driving cycle for a sample vehicle; the measurement was done in parallel with both devices.
done after time synchronization of various data and removal of outliers from various data sets. CD tests were performed in a standard laboratory which is also used for regulatory purposes. The laboratory was equipped with a 250 kW Froude Consine dynamometer. The laboratory is able to measure emissions up to ECE R85/05 standard. A standard loading system, dilution system, emission bags, and a set of HORIBA emission analyzers were included in the tests. 2.2. Sample Fleet Characteristics. A total of 33 Iranianmanufactured vehicles were selected for the purpose of this study. The study was focused on light-duty, gasoline-fueled, privately owned and operated domestic cars with mileages between 0 and 200 000 km. Since 2003, all Iranian vehicle manufacturers which produce under the license of international brands are obliged to obtain Euro-2 level emission certifications. So, all selected cars are certified at the Euro-2 emission standard level. The fueling system on all the engines is multi-point fuel injection. The exhaust after-treatment system consists of a 3-way catalytic converter with one oxygen sensor upstream of the catalyst. None of the catalysts in any of the vehicles have been replaced, even for the high-mileage vehicles. As the selected fleet and number of vehicles in each model category are not a true representation of the actual fleet, weighted averages are implemented in the final emission inventory calculation. 2.3. Test Procedure. EFs are not constant values, as they can be affected by various operational and ambient conditions including road type, traffic conditions, and use of auxiliaries.24,25 On the basis of design of experiment (DOE) tests, road gradient, road type and air conditioning system were considered as effective parameters on emissions and FC. Therefore, each vehicle was tested in eight (23) conditions. Accordingly, four routes were selected with different levels for slope (flat, uphill) and road type (urban, highway). Each test subject was repeated three times, considering the no soak time before the start of the test. Each selected vehicle was examined before the test for obvious defects and malfunctioning engine. Defected vehicles were removed from the sample, and the results were excluded from the final calculations. As traffic conditions change with time, all of the tests were performed in the narrow time period and similar for each test subject, such that the effect of traffic speed is minimized on the results. Also the order of tests in various routes for all vehicles were similar.
considered as a suitable method of RDE measurement, and the certainty of emissions is well controlled in real use. For instance, the European Commission has announced in its “CARS 2020 Action Plan”20 the intention to include an additional PEMS test for RDEs of light duty vehicles (LDVs) from the start of implementation of the Euro-6c standard. Portable testing is planned to be gradually implemented from 2014 onward, initially by the inclusion of test procedures in the Euro-6 regulations, with the introduction of “Conformity Factors” proposed for the Euro-6c stage starting in 2017.21−23 In this study, the PEMS technique is used to develop the basic EFs for a statistically significant sample of domestic gasoline-fueled privately owned LDVs. A smaller sample size of the same fleet undergoes CD tests to quantify the systematic differences between the PEMS and CD methods and to estimate a correction factor for the data collected by PEMS. The experiments were designed to identify the effective parameters and to reduce the number of tests in the PEMS method. Also instantaneous kinematic parameters of tested vehicles are collected to identify the appropriate driving cycle for future CD tests.
2. METHODOLOGY 2.1. Instruments and Experimental Apparatus. A portable exhaust gas analyzer was used for onboard measurement of O2, CO2, CO, NOx, and HC. A sample probe was connected to the exhaust of the vehicle. The gas analyzer was located on the back seat of the vehicle, while the sample line was routed to the analyzer. The analyzer was powered by a separate battery, avoiding extra load on the engine. The onboard emission data were logged using a laptop. A GPS sensor was connected to the same laptop, logging the vehicle speed and position and the elevation of the street. Engine operating parameters such as manifold absolute pressure (MAP), intake air temperature (IAT), and engine speed as well as vehicle speed were logged using an OBD II or OBD I hardware interface between the engine control unit (ECU) and a laptop. A matching method was used to correlate the data after experiments. For each experiment, the weather conditions, detailed vehicle specifications, and three sets of data from the gas analyzer, GPS, and ECU interface were recorded. Data analyses were performed off-line after the experiments. Massbased EFs were calculated assuming equal intake and exhaust flow rates (no leak), with MAP, IAT and ideal gas law. This was 280
DOI: 10.1021/acs.est.5b05611 Environ. Sci. Technol. 2016, 50, 279−284
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Environmental Science & Technology
4. OVERALL EMISSION FACTORS CALCULATION The overall EFs and FC of each vehicle were calculated by weighted averaging of the results of each route. The activity of the fleet for each route type was assumed as a weighting factor.
Just like PEMS tests, all tested vehicles were examined by CD and had warm engines at similar coolant temperatures above 90 °C at the start of the test. Simultaneous emission data were collected using PEMS emission analyzers in parallel with a CD laboratory emission bench. New European Driving Cycle (NEDC) was used in all of the CD tests.
4
EFoverall =
3. DATA VALIDATION To verify the calculated instantaneous EFs and FC, a CD modal test was performed on a sample vehicle equipped with portable instruments, and exhaust emission analyses were performed by both PEMS and CD laboratory instruments. Figure 1 shows the calculated emission rates and emission rates reported from the emission analyzers of the CD laboratory. The comparison shows that, while the PEMS instruments measure CO and CO2 concentrations comparable to those of the laboratory emission analyzers, HC and NOx measurements are not as precise. Similar results were seen in recent works.26,27 The reason is the slow response time of the PEMS instrument to fast changes of emissions during a standard cycle. This could have a more pronounced significance when the PEMS instrument is used under real-world driving conditions in which transit conditions and sudden changes in operating characteristics are stronger. The portable exhaust gas analyzer in the PEMS package measures all gaseous emissions using a nondispersive infrared (NDIR) technique, while the CD laboratory used in this study uses different precise methods, such as chemiluminescence (CLD) for NOx and a flame ionization detector (FID) for HC measurement. In order to quantify the relative difference between the PEMS and CD emission measurements, 20 CD bag measurements were conducted in parallel with the portable instrument on an NEDC driving cycle. The total EFs and FC obtained by both methods were compared for each test. The relative differences in total emissions measured by the two methods were examined, and a linear correction factor, as shown by eq 1, was obtained, which was applied to all PEMS results. The reason for using a linear correction factor was that due to limited resources, only bag measurement results were available. A similar approach was used for correcting EFs in literature where emission measurements were conducted using NDIR.28 EF measured by CD analyzer correction factor = EF measured by PEMS analyzer (1)
CO
HC
NOx
FC
1.05 0.04
1.26 0.24
4.48 2.67
1.49 0.18
1.02 0.05
(2)
Table 2. Percentage of Kilometers Traveled by Personal Cars for Different Routes during Morning Rush Hour (7:30−8:30 AM) route type
flat highway
uphill highway
flat urban
uphill urban
VKT (%)
65.2
9.9
18.3
6.6
Combining eq 2 with the weighting factors of Table 2, yields eq 3, which was used to calculate the overall EFs and FC. EFoverall = 65.2 × EFFH + 9.9 × EFUH + 18.3 × EFFU + 6.6 × EFUU 100 (3)
where FH is flat highway, UH is uphill highway, FU is flat urban, and UU is uphill urban.
5. RESULTS AND DISCUSSION Figure 2 shows the overall EFs of each test subject obtained over all routes and corrected with correction factors of Table 1 for PEMS measurements. Also, CD results are included in the figure. CD results were obtained using NEDC, and PEMS results were of real driving. Different vehicle mileage classes are distinguished with various symbols. PEMS and CD results are also distinguished in Figure 2. The Euro-2 certification limit is shown by the solid line. Although there is no clear relation between vehicle mileage and its emission level, vehicles with lower mileage had a slightly greater chance to drop under the Euro-2 certification limit. Despite the fact that all selected models were Euro-2 certified, up to three times higher CO emission and about six times higher HC + NOx emission was observed in PEMS and CD results. As the cold start emissions have not been accounted for, even higher emissions are expected compared to those of the Euro-2 certification limits. A comparison of CD and PEMS results in Figure 2 shows the significant effect of real-word driving on emission rates. The same vehicles were tested with both CD and PEMS methods.
Table 1. Correction Factors Applied to PEMS Measurements Obtained from Parallel Emission Measurement with CD and PEMS Emission Analyzers on a Standard CD Test and NEDC Cycle CO2
4
∑i = 1 VKTi
As shown in eq 2, i determines each route type including flat highway, uphill highway, uphill urban, and flat urban routes. VKTi and EFi specify the mileage traveled and EF related to ith route type, respectively. In this study, link-based activity data have been obtained from the EMME/2 travel demand model (TDM). Outputs from the TDM provide estimated travel times and traffic flows for all of the 17 441 individual links in Tehran. The total number of kilometers traveled on different types of roads for each type of vehicle is one of the outputs of this model.29 The percentage of kilometers traveled for personal cars on different types of roads during morning rush hour (7:30−8:30 AM) were used as weight factors of eq 2 in order to calculate the overall EF. Table 2 presents these weighting factors.
Table 1 summarizes the correction factor for each gas, averaged over 20 test vehicles. The correction factor
average correction factor standard deviation
∑i = 1 (VKTi × EF) i
compensate for the slow response time of the PEMS emission measurement device. The small magnitudes of standard deviations, except for HC, could translate to meaningful correction factors. However, the ratios of PEMS emission rates to RDEs are nearly constant. Therefore, correction factors confidently could be used to transform the PEMS measurement to RDEs. 281
DOI: 10.1021/acs.est.5b05611 Environ. Sci. Technol. 2016, 50, 279−284
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were determined as being characteristic driving conditions in Tehran, which are not found in NEDC. To illustrate the importance of driving cycle, the average hot exhaust EFs and FC of the selected fleet over four types of roads are shown in Table 4. Because of the large differences between EFs and FC of each route, a small change in weighting factors of eq 2 may affect the overall EFs and FC. A variety of emissions and FC in different routes could be explained with some physical reasons: • Road gradient exert additional load on engine, which increase FC, CO2, and NOx emission. • Engine idling, reduced NOx emission. It could be seen in urban routes with long periods of traffic jam. • Rapid increase of engine load forces the injection system to deliver additional fuel. Direct consequences are incomplete combustion and hence growth of CO and HC concentrations in engine outlet. This case could be seen when the vehicle faces congested traffic situations or uphill routes. • Highly transient conditions cause deviation of lambda from 1. Hence, catalyst efficiency decreases and pollutant concentrations will increase. Table 5 summarizes the overall FC and EFs which are calculated based upon eq 3. The results of the current study are compared with the Euro-2 certification limits, NAEI and COPERT (Tier 2) EFs. Measured RDEs with PEMS are much higher than those of Euro-2 certification limits. Compared to other RDEs, EFs for the current study are also higher. Considering that reported values are only for hot exhaust emissions and cold start emission rates are not measured, this could translate to even higher emission rates. Further investigations are needed to understand the possible cause. There are major country-specific factors that could contribute to such high values.
Figure 2. A comparison of EFs obtained from PEMS and CD with Euro-2 certification limits, values indicate only hot exhaust emission, CD results are from the NEDC cycle, and the PEMS results are from RDE.
The violation of Euro-2 certification limits was much higher in vehicles tested with PEMS method. The driving cycles of all PEMS tests are shown in Figure 3. A typical driving cycle for each route was illustrated with a red line. For urban routes with low driving speeds, some fast transient operations were observed while for highway driving the transient behavior was lower. Transient conditions in real-world driving are much more common than in the NEDC driving cycle, which has the same pattern of acceleration and deceleration and also large periods of cruising. To clarify the differences between NEDC and realworld driving, kinematic parameters of NEDC and four types of routes including flat highway, uphill highway, flat urban, and uphill urban are compared in Table 3. NEDC driving cycles consist of higher average speeds, longer cruising time, and considerably lower average positive accelerations compared to those of PEMS driving cycles, particularly congested urban routes under uphill conditions. Intense acceleration and braking
Figure 3. All of the portable test driving cycles of (a) flat highway, (b) uphill highway, (c) flat urban, and (d) uphill urban routes, wherein the red line shows typical driving cycles. 282
DOI: 10.1021/acs.est.5b05611 Environ. Sci. Technol. 2016, 50, 279−284
Article
Environmental Science & Technology Table 3. Kinematic Parameters of NEDC and Four Types of Routes Used in Portable Tests flat highway
uphill highway
flat urban
uphill urban
NEDC−urban phase
NEDC−highway phase
54 25 0.4 0.6 −0.6
68 32 0.0 0.6 −0.5
23 18 1.7 0.7 −0.6
12 21 10.9 0.7 −0.6
18 25 4.0 0.3 −0.4
62 49 0.3 0.3 −0.4
average speed (km/h) % of time cruising stops per kilometer average positive acceleration (m/s2) average negative acceleration (m/s2)
Table 4. Hot Exhaust Emissions and FC Averaged over the Selected Fleet for Different Routes Measured by PEMS Instruments flat highway CO2 (g/km)
141
CO (g/km)
4.28
HC (g/km)
0.20
NOx (g/km)
0.63
FC (Lit/100 km)
6.1
flat urban
uphill highway
+8.5 −5.6 +2.29 −1.15 +0.10 −0.05 +0.08 −0.07 +0.39 −0.26
240
+6.2 −4.8 +8.36 −3.38 +0.17 −0.06 +0.19 −0.17 +0.52 −0.37
13.59 0.30 1.54 10.9
200 5.40 0.31 0.84 8.7
uphill urban
+11.2 −8.6 +1.79 −0.92 +0.10 −0.05 +0.07 −0.06 +0.46 −0.38
416
+16.2 −18.1 +5.91 −3.53 +0.31 −0.16 +0.22 −0.17 +0.90 −0.80
9.12 0.40 1.46 17.9
Table 5. Overall EFs and FC of Personal Gasoline-Fueled Cars at 7:30 to 8:30 AM (peak of traffic); Euro-2 and COPERT (Tier 2) Hot Exhaust EFs are Included EFs (g/km) current study Euro-2 certification limit COPERT (Tier 2a) NAEI, urban NAEI, rural NAEI, motorway a
CO2
CO
HC
NOx
HC + NOx
180 ± 15.0
5.7 ± 0.84 2.2 2.04 1.26 1.139 1.596
0.24 ± 0.014
0.82 ± 0.138
1.06 ± 0.152 0.5
215 187 201
FC (L/100 km) 7.9 ± 0.72
0.255 0.206 0.201 0.219
For 1.4−2.0 L engine displacement volume.
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ASSOCIATED CONTENT
FC PEMS CD RDE
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.5b05611. Gas analyzer details; sample fleet details; test routes (PDF)
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fuel consumption portable emission measurement system chassis dynamometer real driving emission
REFERENCES
(1) Emission Inventory. http://www.epa.gov/airquality/aqmportal/ management/emissions_inventory/. (2) Franco, V.; Kousoulidou, M.; Muntean, M.; Ntziachristos, L.; Hausberger, S.; Dilara, P. Road vehicle emission factors development: A review. Atmos. Environ. 2013, 70, 84−97. (3) Reis, S.; Simpson, D.; Friedrich, R.; Jonson, J.; Unger, S.; Obermeier, A. Road traffic emissions−predictions of future contributions to regional ozone levels in Europe. Atmos. Environ. 2000, 34 (27), 4701−4710. (4) Xia, L.; Shao, Y. Modelling of traffic flow and air pollution emission with application to Hong Kong Island. Environmental Modelling & Software 2005, 20 (9), 1175−1188. (5) Vojtisek-Lom, M. Time-Resolved Emissions Characteristics of Modern Passenger Vehicle Diesel Engines Powered by Heated Vegetable Oil; SAE Technical Paper: 2007−24−0129. (6) Guo, H.; Zhang, Q.; Shi, Y.; Wang, D. On-road remote sensing measurements and fuel-based motor vehicle emission inventory in Hangzhou, China. Atmos. Environ. 2007, 41 (14), 3095−3107. (7) Zhang, Q.; Streets, D. G.; Carmichael, G. R.; He, K.; Huo, H.; Kannari, A.; Klimont, Z.; Park, I.; Reddy, S.; Fu, J. Asian emissions in 2006 for the NASA INTEX-B mission. Atmos. Chem. Phys. 2009, 9 (14), 5131−5153.
AUTHOR INFORMATION
Corresponding Author
*Phone: 98912-4025772; fax: 9821-66166209; e-mail:
[email protected] (V.H.). Author Contributions
V.H. and E.B. contributed equally. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The contribution of The Organization of Transportation and Traffic of Tehran Municipality in providing project funding (project no. 40/1027043) is greatly acknowledged and appreciated. The support of the Tehran Air Quality Control Co. (AQCC) by providing PEMS instruments to the project is acknowledged.
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ABBREVIATIONS EF emission factor 283
DOI: 10.1021/acs.est.5b05611 Environ. Sci. Technol. 2016, 50, 279−284
Article
Environmental Science & Technology
FID measurements. J. Air Waste Manage. Assoc. 1996, 46 (2), 148− 158. (27) Andersson, J.; May, J.; Favre, C.; Bosteels, D.; de Vries, S.; Heaney, M.; Keenan, M.; Mansell, J. On-Road and Chassis Dynamometer Evaluations of Emissions from Two Euro 6 Diesel Vehicles. SAE International Journal of Fuels and Lubricants 2014, 7, 919−934. (28) Frey, H.; Unal, A.; Chen, J.; Li, S.; Xuan, C. Methodology for Developing Modal Emission Rates for EPA’s Multi-Scale Motor Vehicle & Equipment Emission System; EPA420-R-02−027; 2002. (29) Oppenheim, N. Urban Travel Demand Modeling: From Individual Choices to General Equilibrium; John Wiley and Sons: New York, 1995.
(8) Rao, V.; Tooly, L.; Drukenbrod, J. 2008 National Emissions Inventory: Review, Analysis and Highlights; EPA-454/R-13−005; 2013. (9) JAICA The Study on an integrated Master Plan for Air Pollution Control in The Greater Area in The Islamic Republic of Iran; 1997. (10) Bergmann, M.; Kirchner, U.; Vogt, R.; Benter, T. On-road and laboratory investigation of low-level PM emissions of a modern diesel particulate filter equipped diesel passenger car. Atmos. Environ. 2009, 43 (11), 1908−1916. (11) Biswas, S.; Verma, V.; Schauer, J. J.; Sioutas, C. Chemical speciation of PM emissions from heavy-duty diesel vehicles equipped with diesel particulate filter (DPF) and selective catalytic reduction (SCR) retrofits. Atmos. Environ. 2009, 43 (11), 1917−1925. (12) Fontaras, G.; Martini, G.; Manfredi, U.; Marotta, A.; Krasenbrink, A.; Maffioletti, F.; Terenghi, R.; Colombo, M. Assessment of on-road emissions of four Euro V diesel and CNG waste collection trucks for supporting air-quality improvement initiatives in the city of Milan. Sci. Total Environ. 2012, 426, 65−72. (13) Kousoulidou, M.; Ntziachristos, L.; Fontaras, G.; Martini, G.; Dilara, P.; Samaras, Z. Impact of biodiesel application at various blending ratios on passenger cars of different fueling technologies. Fuel 2012, 98, 88−94. (14) Gao, Y.; Checkel, M. D. Emission Factors Analysis for Multiple Vehicles Using an on-Board, In-Use Emissions Measurement System; SAE Technical Paper: 2007−01−1327. (15) Gao, Y.; Checkel, M. D. Experimental Measurement of On-Road CO2 Emission and Fuel Consumption Functions; SAE Technical Paper: 2007−01−1610. (16) Frey, H. C.; Unal, A.; Rouphail, N. M.; Colyar, J. D. On-road measurement of vehicle tailpipe emissions using a portable instrument. J. Air Waste Manage. Assoc. 2003, 53 (8), 992−1002. (17) Frey, H. C.; Zhang, K.; Rouphail, N. M. Vehicle-specific emissions modeling based upon on-road measurements. Environ. Sci. Technol. 2010, 44 (9), 3594−3600. (18) Rubino, L.; Bonnel, P.; Carriero, M.; Krasenbrink, A. Portable Emission Measurement System (PEMS) for Heavy Duty Diesel Vehicle PM Measurement: The European PM PEMS Program; SAE Technical Paper: 2009−24−0149. (19) Liu, H.; Barth, M.; Scora, G.; Davis, N.; Lents, J. Using portable emission measurement systems for transportation emissions studies: Comparison with laboratory methods. Transp. Res. Rec. 2010, 2158, 54−60. (20) Communication from the Commission to the European Parliament, The Council, the European Economic and Social Committee and the Committee of the Regions. Cars 2020: Action Plan for a Competitive and Sustainable Automotive Industry in Europe; COM(2012) 636 final; 2012. (21) EC Working Group for the Development of a Real-Driving Emissions Test Procedure for Light-Duty Vehicles (RDE-LDV): Scope Mandate; 2011. (22) Weiss, M.; Bonnel, P.; Kühlwein, J.; Provenza, A.; Lambrecht, U.; Alessandrini, S.; Carriero, M.; Colombo, R.; Forni, F.; Lanappe, G. Will Euro 6 reduce the NO x emissions of new diesel cars?−Insights from on-road tests with Portable Emissions Measurement Systems (PEMS). Atmos. Environ. 2012, 62, 657−665. (23) Weiss, M.; Bonnel, P.; Hummel, R.; Steininger, N. A Complementary Emissions Test for Light-Duty Vehicles: Assessing the Technical Feasibility of Candidate Procedures; EUR 25572 EN; JRC: 2013. (24) Joumard, R.; Andre, J.-M.; Rapone, M.; Zallinger, M.; Kljun, N.; Andre, M.; Samaras, Z.; Roujol, S.; Laurikko, J.; Weilenmann, M. Emission factor modelling and database for light vehicles. Artemis deliverable 2007, 3, 237. (25) Frey, H. C.; Rouphail, N. M.; Unal, A.; Colyar, J. D. Measurement of on-road tailpipe CO, NO, and hydrocarbon emissions using a portable instrument. In Proceedings, Annual Meeting of the Air & Waste Management Association, 2001; Citeseer: 2001. (26) Stephens, R. D.; Mulawa, P. A.; Giles, M. T.; Kennedy, K. G.; Grobiicki, P. J.; Cadle, S. H.; Knapp, K. T. An experimental evaluation of remote sensing-based hydrocarbon measurements: A comparison to 284
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