Real-World Vehicle Emissions: A Summary of the Seventeenth Coordinating Research Council On Road...

Real-World Vehicle Emissions: A Summary of the 14thCoordinating Research Council On-Road Vehicle EmissionsWorkshop

Steven H. CadleGeneral Motors R&D Center, Warren, MI

Timothy C. BelianCoordinating Research Council, Alpharetta, GA

Kevin N. BlackFederal Highway Administration, Washington, DC

Fred MinassianSouth Coast Air Quality Management District, Diamond Bar, CA

Mani NatarajanMarathon Ashland Petroleum, Findlay, OH

Eugene J. TierneyU.S. Environmental Protection Agency, Ann Arbor, MI

Douglas R. LawsonNational Renewable Energy Laboratory, Golden, CO

ABSTRACTThe Coordinating Research Council held its 14th VehicleEmissions Workshop in March 2004, where results of themost recent on-road vehicle emissions research were pre-sented. We summarize ongoing work from researcherswho are engaged in improving our understanding of thecontribution of mobile sources to ambient air quality and

emission inventories. Participants in the workshop dis-cussed efforts to improve mobile source emission models,light- and heavy-duty vehicle emissions measurements,on- and off-road emissions measurements, effects of fuelsand lubricating oils on emissions, as well as topics forfuture research.

INTRODUCTIONThe 14th Coordinating Research Council (CRC) On-RoadVehicle Emissions Workshop was held March 29–31, 2004,in San Diego, CA. These workshops, which began in 1990,provide a forum for presenting the most recent results onunderstanding the role and contribution of mobile sourcesto air quality. One hundred seventy representatives fromBelgium, Canada, Finland, Italy, Hong Kong, Japan, Portu-gal, Sweden, and the United States, representing industry,government, academia, and consulting groups, took part inthe meeting. The objectives of the Workshop were topresent the most recent results from research on:

• Portable emissions and activity measurement sys-tems;

IMPLICATIONSMobile source emissions are an important contributor tourban emission inventories throughout the world. Newmethods to evaluate the role of mobile source impacts onair quality are needed to provide improved inputs to mobilesource emission models that are being updated and/orreplaced by the U.S. Environmental Protection Agency andthe California Air Resources Board. This summary providesa synopsis of current research projects designed to under-stand the significance of mobile source emissions, and itidentifies areas of future research. In some cases, prelimi-nary conclusions were presented that might be modifiedonce the work is completed.

TECHNICAL PAPER ISSN 1047-3289 J. Air & Waste Manage. Assoc. 55:130–146

Copyright 2005 Air & Waste Management Association

130 Journal of the Air & Waste Management Association Volume 55 February 2005

• U.S. Environmental Protection Agency’s (EPA) Mo-tor Vehicle Emissions Simulator (MOVES) model;

• Mobile source modeling: MOBILE 6, NMIM, andmodal models;

• On-road gasoline and diesel vehicle emissions;• Fuel effects on vehicle emissions;• Emission inventories;• Measurement methods; and• Unregulated emissions.There were 54 presentations in nine sessions and 31

displays in poster sessions during the Workshop. Overall,Timothy Belian and Brent Bailey and the CRC staff pro-vided workshop coordination, with Steven Cadle of Gen-eral Motors (GM) and Mani Natarajan of Marathon Ash-land Petroleum serving as Workshop co-chairmen. BarryWallerstein, Executive Officer of the South Coast AirQuality Management District (SCAQMD), was the key-note speaker at the Workshop. Session chairmen wereFred Minassian of the SCAQMD, Eugene Tierney of EPA,Mark Carlock of California Air Resources Board (CARB),Rob Graze of Caterpillar, Mani Natarajan, Kevin Black ofthe Federal Highway Administration (FHWA), TimothyBelian, Hannah Murray from Toyota, and Douglas Law-son of the National Renewable Energy Laboratory (NREL).

The complete Workshop proceedings are availablefrom the Coordinating Research Council, 3650 MansellRoad, Suite 140, Alpharetta, Georgia 30022; phone: 678-795-0506; fax: 678-795-0509; e-mail address: [email protected]. This paper summarizes oral and poster presen-tations given in each session at the Workshop. Summariesof the CRC workshops have been published in the Journalof the Air & Waste Management Association; the three mostrecent summaries are found in Vol. 52, pp. 220–236; Vol.53, pp.152–167; and Vol. 54, pp. 8–23.

In addition to the technical papers and posters pre-sented at the Workshop, several vendors provided on-sitedemonstrations of mobile laboratory and emission mea-surement equipment.

PORTABLE EMISSIONS AND ACTIVITYMEASUREMENT SYSTEMSRobert Anderson from Rupprecht & Patashnick reportedon the first phase of a project to develop the Simple,Portable On-board Test (SPOT) system, an on-board vehi-cle exhaust conditioning and sampling system for mea-suring exhaust particles and mobile source air toxics. Keyfeatures of the system combine a number of componentsto perform primary and secondary dilution schemes, aswell as a virtual impactor to collect particulate matterPM2.5. Carefully maintained temperature and humiditycontrols were also employed for proper measurement ofPM to be equivalent with the EPA’s new heavy-duty (HD)2007 emission standards. Results correlated very well with

a standard tapered element oscillating microbalance(TEOM) and filter sampling methods.

Peter Witze of Sandia National Laboratories discussedon-board, time-resolved measurements of PM emissionsusing a laser-induced incandescence (LII) instrument. TheLII measures elemental carbon (EC) volume fraction inexhaust, not total PM mass. The instrument and ancillaryequipment were placed in the trunk and fold-down backseat area of a 2002 Volkswagen Jetta with a 1.9-liter TDIdiesel engine. An on-board diagnostics (OBD-II) scan toolinterface was used to access the vehicle and engine speeds.These measurements were then time-matched with theLII data to obtain a synchronized data set correlatingtime-resolved EC PM emissions with vehicle operatingconditions that included accelerations from a stop, hillclimbing, freeway driving, and a winding descent.

David Booker from Booker Systems Ltd. discussed theuse of the quartz crystal microbalance (QCM) to measureconcentrations of aerosols. By measuring the frequencyshift of the crystal when exposed to a stream of particles,the mass and/or concentration can be determined. Hereported on recent advances associated with using a QCMfor in-use particle measurements in vehicle exhaust. Thetopics and the field measurement data included real-timeaerosol concentration measurements, intelligent dilutionsystems, and parameters such as humidity, temperature,and pressure influencing accuracy and repeatability.

Mridul Gautam of West Virginia University (WVU)discussed the development of an on-board, in-use emis-sions measurement system called the Mobile EmissionsMeasurement System (MEMS) that allows determinationof in-use, brake-specific emissions from HD diesel-pow-ered vehicles. He outlined the in-use emission resultsfrom on-highway and off-road engines and discussed thein-use test procedures, system accuracy, and precision.Gautam introduced the concept of a Compliance Factor,which would be derived by on-board, fuel-based emissionmeasurements from the MEMS. The Compliance Factor,the ratio of a pollutant species to carbon dioxide (CO2) inthe exhaust, as compared with the same ratio under cer-tification conditions, would determine the on-road emis-sions impact of the vehicle under consideration.

Karl Oestergaard from Horiba Instruments describeddata collected during an effort to compare on-board emis-sion measurement systems (Horiba OBS-1000 and theMEMS built by WVU) with test cell equipment duringdynamometer runs (Federal Test Procedure [FTP]) and anon-road route. Emissions data for oxides of nitrogen(NOx) and CO2 collected by the OBS in general agreed towithin 6–11% of data collected with the laboratory equip-ment. Tests where simulated light-duty (LD) vehicle Low-Emission Vehicle/Ultra Low-Emission Vehicle (LEV/ULEV) levels of exhaust gas were injected into an

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on-board system were also discussed. The experimentshowed errors of 5–8% for the pollutants measured. Oes-tergaard also reported on a “relay race around the world”using an on-board system as the “baton,” where morethan 30,000 kilometers were driven and 1.5 million datapoints were collected. Data from the relay race will beavailable in the future.

In an attempt to reduce the size of vehicle particlesampling systems, partial exhaust dilution systems havebeen developed. David Booker discussed the developmentof the Micro Proportional Sampler (MPS) to provide apartial flow dilution system that offers greater speed ofoperation, which increases the accuracy of the system formeasurements during transient engine operation. Thepresentation also discussed the main design principles ofthe system that enables the high-operational controlspeeds of the dilution flow, the predicted and measureduncertainties, and the application of this technology forreal-world gaseous and particulate emission measure-ments.

Matthew Spears of EPA summarized some of EPA’spolicies and activities regarding on-vehicle emissionsmeasurement. He outlined EPA’s anticipated rulemakingschedule for on-vehicle emissions-related regulatory ac-tions. He also described 32 individual 8-mile on-vehicleemissions tests that were conducted over a combined timeperiod of three hours at the Infineon Raceway in Sonoma,CA. The vehicles were contestants at Michelin Tire Com-pany’s 2003 “Challenge Bibendum.” Spears’ presentationdescribed how to efficiently conduct on-vehicle emissionstesting. The emissions test results indicated that the low-est emitting vehicles were new, original equipment man-ufacturer’s hybrid, and alternative fuel vehicles, whilesome of the highest emitting vehicles were from retrofitalternative fuel vehicles.

Andrew Reading from Sensors, Inc. discussed the Por-table Activity Monitoring System or PAMS, a robust, mod-ular data acquisition system designed for on-vehicle mon-itoring. PAMS uses a combination of Activity InterfaceModules (AIMs) to measure the vehicle activity (e.g., po-sition, speed, oil temperature, RPM). These AIMs commu-nicate via a Controller Area Network (CAN) bus. A rangeof AIM modules has been designed to provide data to acommon data logger utilizing a CAN interface. In thisway, multiple analyzer modules can be connected in adaisy chain without the installation being dependent ona bank of connections and wires.

Michal Vojtisek-Lom from Clean Air Technologiesdescribed real-world measurements of PM on low-emis-sion diesel engines. Measurements were carried out withan instrument that samples raw, undiluted exhaust andutilizes laser light scattering as the detection method toprovide measurements at one-second intervals. The

instrument is integrated into a briefcase-sized, portable,on-board monitoring system, which also measures gas-eous pollutant concentrations, computationally deter-mines exhaust flow and mass PM emissions, and has beenused extensively on vehicles and construction equip-ment. On transient cycles driven on the road or on adynamometer, test-to-test repeatability of 5–10% can beobtained, including on engines equipped with trapshaving very low PM emissions (�0.01 grams per brakehorsepower-hour [g/bhp-hr]).

Mary Julian of Clean Air Technologies described theuse of a portable Fourier-transform IR analyzer for opera-tion on board a moving vehicle. The instrument is in-tended for real-world measurement of emissions on HDvehicles, locomotives, vessels, and off-road equipment. Ashydrocarbon (HC) composition and toxicity among vari-ous alternative fuels varies, it is believed that speciated HCmeasurements will allow for better comparison of emis-sions from alternative fuels. If feasible, ammonia mea-surements will allow for evaluation of ammonia slip onselective catalytic reduction and lean-burn catalysts. Theproject is in its early stages of development.

MOVES MODELMegan Beardsley of EPA provided an update on MOVES,which is intended to replace EPA’s MOBILE6 and NON-ROAD emission models. MOVES2004, known as the Fleetand Activity Model and scheduled for completion in2004, establishes two essential components—highwayvehicle activity and fleet characteristics. MOVES2004 willcalculate fuel consumption and CO2 emissions, allowingfor top-down validation of fleet and activity estimates. Itwill also calculate methane (CH4) and nitrous oxide (N2O)emissions. MOVES2004 will estimate well-to-pump emis-sions, and it will include a built-in feature to model “whatif” scenarios, including variations in the mix of futurevehicle fuels and technologies. Future versions of themodel will add emissions from aircraft, locomotive,and marine engines (MOVES2005), highway vehicles(MOVES2006), and nonroad engines (MOVES2007).

EPA’s MOVES2004 model will incorporate a broadrange of fleet and activity data that characterize vehiclesand driving behavior. These data were compiled fromvarious sources and are stored in a database MOVES pro-cesses to compute energy use and emissions. The inputdata include estimates of vehicle populations, vehiclesales and scrappage rates, distributions of vehicle age,fuel, and weight. It also includes estimates of travelgrowth and distributions of vehicle activity by vehicletype, county, road type, time of day, day of week, andmonth of year. Vehicle driving behavior is characterizedby average speed distributions and driving cycles.

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John Koupal of EPA reported that the MOVES modelwill characterize energy and emission rates using 17“bins” defined by Vehicle Specific Power (VSP) and in-stantaneous vehicle speed. This approach allows the esti-mation of emissions over any driving pattern and can beapplied at multiple scales. A proof-of-concept validationshowed good agreement in aggregate fuel consumption aswell as HC, CO, and NOx emissions for both LD and HDvehicles. MOVES2004 will employ the bin approach forenergy consumption only but will be expanded in futureversions. Key issues to consider for criteria pollutants arewhether higher VSP bins are needed, and how to bestcharacterize high emitters.

Ed Nam from EPA described the Physical EmissionsRate Estimator (PERE), a model that simulates emissionsfrom advanced technology vehicles as part of the MOVESmodel. He presented results from the energy consump-tion modeling of conventional gasoline, gasoline hybrid,diesel, and hydrogen fuel cell hybrid passenger vehicles.The model accepts driving cycles as input, and outputs(Pump-to-Wheel) fuel and energy consumption, as well asbattery state of charge. The advanced vehicle models havebeen validated against the certified fuel economy of var-ious production vehicles. These estimates will be com-bined with an upstream model (Greenhouse Gases, Reg-ulated Emissions, and Energy Use in Transportation[GREET]) to perform a full (Well-to-Wheel) life cycle anal-ysis.

Ed Nam noted that empirically determined emissionrates in MOVES are supplemented by PERE, a model basedon fuel consumption. PERE calculates fuel rate from ve-hicle tractive power, transmission, engine friction andefficiency. Parameters for diesel vehicles have been deter-mined from in-use data for city transit buses and fortractor-trailers with weights ranging from 58,000–62,000pounds. The buses followed typical routes in the city ofAnn Arbor, MI. The trucks were driven on-road betweenRiverside and other California cities. Total fuel consump-tion and CO2 calculated with the model are within 10%of measured values. Based on this model, other diesel fuelconsumption rates will be passed into MOVES, where dataare inadequate.

Christian Lindhjem from ENVIRON reviewed thedraft design of EPA’s MOVES2004 model. Emissions datawere shown to correlate primarily with VSP for LD andHD vehicles, although VSP is not the only variable thatfully explains exhaust emissions. He recommended thatEPA’s approach of binning VSP be revisited to considerusing statistical regression to allow the analysis to includemore detailed activity distributions. The activity data thatare currently collected are limited to average speed forlong road segments and would not permit the MOVESmodeling method to be fully implemented. The current

design using VSP as the primary variable describes CO2

emissions well, but N2O and CH4 are much less impor-tant. Portable emission monitoring systems (PEMS) are apromising new technology to collect emission and activ-ity data, but, as is the case for modal laboratory data, EPAneeds to develop proper data handling procedures.

John Koupal described EPA’s efforts to calculate baseenergy-consumption rates for running operation inMOVES2004, in which they compiled second-by-secondlaboratory data from existing test programs. They classi-fied the data by fuel type, engine technology, model-year,engine displacement and vehicle weight, with a 5-waycombination of these characteristics defined as a “sourcebin.” Within source bins, EPA sub-classified data into 17operating modes defined in terms of VSP, speed, andacceleration. They calculated cell means and associateduncertainty for 2,778-source bin � operating mode com-binations (“cells”). Based on two statistical evaluationcriteria, results for �80% of these cells will be used inMOVES. Means for the remaining cells will be estimatedby modeling.

Bruce Cantrell of EPA reported that his agency hasassembled emission and activity data from non-EPA andEPA emission programs into their Mobile Source Obser-vation Database. This database will be incorporated intoEPA’s new mobile emissions model MOVES. Cantrell de-scribed EPA’s overall process to plan for the data, convertit to a common format, review it, amend it, and publish itfor use. The documentation of the process, the QualityAssurance Program Plan, is an EPA requirement.

MOBILE SOURCE MODELING: MOBILE6, NMIM,AND MODAL MODELSTill Stoeckenius from ENVIRON performed a top-downevaluation of recent temporally and spatially disaggre-gated MOBILE6-based emission inventories by comparinginventory volatile organic compound ([VOC])/NOx andCO/NOx ratios with corresponding ratios from ambientmonitoring data at locations strongly influenced by emis-sions from on-road mobile sources. Results showed gen-erally good agreement between ambient and inventoryVOC/NOx ratios on weekday mornings except in Detroit,where results are affected by a lack of NOx data; and Lynn,MA, where the results suggest a potential problem witheither the area or point source emissions. Ambient CO/NOx ratios exceeded inventory ratios, but at least some ofthis difference may be attributable to the influence ofbackground CO.

Harvey Michaels of EPA summarized the objectives inbuilding EPA’s National Mobile Inventory Model (NMIM)as consolidation, automation, efficiency, and consistencyin producing national, county-level mobile-source inven-tories. NMIM comprises graphical and command line user

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interfaces, a county database, and the MOBILE6 andNONROAD models. NMIM’s county database consoli-dates the information needed to develop inventories ofcriteria pollutants, hazardous air pollutants (HAPs), anddioxins/furans. The analysis years potentially availableare limited only by MOBILE6 and NONROAD. Consis-tency is achieved by using the same input data (i.e., fuelproperties, temperatures, inspection and maintenance[I/M] programs) for both models and all pollutants.NMIM can run on a single desktop or use multiple net-worked computers to speed processing; the only require-ment is a shared folder.

H. Christopher Frey of North Carolina State Univer-sity reviewed an ongoing project focusing on the devel-opment of vehicle-specific energy use and emissionsmodels based upon portable on-board emissions measure-ments. A key focus of work to date has been on assessmentof the sensitivity of emissions predictions to road gradeand comparison and evaluation of three methods for es-timating road grade: (1) roadway design drawings; (2)global positioning system (GPS) data; and (3) light detec-tion and ranging (LIDAR) data. LIDAR data were demon-strated to provide a reliable basis for estimating roadgrade, comparable to the design drawing data, whereasGPS data were less reliable. He discussed a computer-basedsoftware tool for processing and analyzing on-board dataand described preliminary approaches for development ofvehicle-specific energy and emissions models.

Ted Younglove from the Statistical Consulting Col-laboratory at the University of California, Riverside, rec-ommended supplementing in-use driving data with a pre-determined driving procedure to enhance mobileemissions model development. This is due to the fact thatdrivers in real-world situations do not always drive theirvehicles under conditions that are represented by stan-dard modal modeling driving cycles, such as hard accel-erations and decelerations. By including a short drivingprocedure that could be performed immediately after in-stallation or before removal of PAMS/PEMS units in test-ing conditions, data could be collected that properly rep-resent high-load events that are not currently captured byreal-world driving of many motorists.

Hesham Rakha from Virginia Tech described the ad-equacy of predicting vehicle fuel consumption and emis-sions along roadway segments using a limited number ofeasily measurable input variables. Specifically, his pro-posed model estimates vehicle emissions using averagespeed, number of vehicle stops per unit distance, andaverage stopped delay as input. The model uses thesevariables to construct synthetic drive cycles for the road-way segment and then predicts average fuel consumptionand emission rates by analyzing the decelerating, idling,accelerating, and cruising portions of the cycle. The

model was demonstrated to successfully predict trends invehicle fuel consumption and HC emission rates and, to alesser degree, trends in CO and NOx emissions.

Rakha also summarized how on-road emission mea-surement (OEM) data can be utilized to develop emissionmodels for heavy-duty vehicles that are suitable for esti-mating instantaneous mobile source emissions. His re-search utilized the OEM-2100™, manufactured by CleanAir Technologies International, Inc., to collect vehicleengine and emission data. The paper demonstrated thatthe models that were developed estimate vehicle emis-sions of CO, NOx, and PM to within 15% of field-mea-sured emissions on average.

The standard vehicle dynamics model for predictingtypical driver acceleration behavior applies a constantreduction factor to the maximum acceleration rate. Hes-ham Rakha reported that the typical acceleration reduc-tion factor is observed to fit a normal distribution with amean of 0.6 and a standard deviation of 0.08. Males andyounger drivers tend to be more aggressive; however, theresults do not reveal any statistical differences associatedwith driver gender and/or age. In addition, his work dem-onstrates that while the deceleration rate typically in-creases as the vehicle approaches its desired final speed,the use of a constant deceleration rate over the entiredeceleration maneuver is adequate for environmentalmodeling purposes.

Carol Wong of the Environmental Protection Depart-ment in Wan Chai, Hong Kong, described her agency’sefforts to obtain a robust estimation of emission inven-tory for motor vehicles by using CARB’s mobile emissionmodel EMFAC2002. She has modified some of the param-eters within EMFAC2002 to suit Hong Kong’s situation.These include using different fuel correction factors andintroducing two diesel vehicle regimes for PM emissionsin the model. Local data such as technology group frac-tions, vehicle population distributions, fuel properties,Reid vapor pressure, relative humidity, temperature, ac-crual rates, and vehicle kilometers traveled are included tothe extent possible. For zero mile emission factors anddeterioration rates, MOBILE5/6 or EMFAC2002 data thatare suitable for Hong Kong were selected.

Seungju Yoon from Georgia Tech developed twoheavy-duty vehicle (HDV) vehicle miles traveled (VMT)translation methods with a new visual HDV classificationscheme (X-scheme), which were developed with grossvehicle weight ratings and the number of axles. Method 1was the apportionment of HDV2b to HDV7 with theirnationwide VMT fractions. Method 2 was the use of theX-scheme and translation factors obtained from the R.L.Polk HDV registration data. Predicted changes in emis-sions rates for each method relative to the use of the EPAconversion guidance were as follows: method 1 showed

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34% and 32% increases of NOx and PM2.5, while method2 showed 36% and 34% increases, respectively.

Tao Huai from the College of Engineering, Center forEnvironmental Research and Technology (CE-CERT) atthe University of California, Riverside, summarized thedevelopment of ammonia (NH3) emission modules forCE-CERT’s Comprehensive Modal Emissions Model(CMEM). The module is based on previous NH3 measure-ments conducted at CE-CERT using a tunable diode laser.This represents one of the first attempts to incorporatevehicle NH3 emissions into a more comprehensive emis-sions model. This new emissions component will en-hance the emission capabilities of the CMEM to meet thedemand for greater levels of spatial and temporal resolu-tion necessary for evaluating the effects of vehicle fleetand traffic changes on NH3 emissions.

Tao Huai also presented results on measurements ofoperational activity for nonroad diesel constructionequipment. Eighteen pieces of nonroad equipment wereinstrumented in this study with data collected includingintake manifold air pressure, exhaust temperature, and,on a subset of vehicles, engine rpm and throttle position.The equipment included backhoes, compactors, dozers,motor graders, loaders, and scrapers used in applicationssuch as landfill operation, street maintenance, and gen-eral roadwork. The activity patterns of the nonroad equip-ment varied considerably depending on the type of equip-ment and the application. The equipment operated lessthan 30 min to more than 8 hr per day, with an averagefive starts per day and �25% idle time. Duty cycles basedon exhaust temperature/throttle position profiles werealso developed.

Randall Guensler from Georgia Tech analyzed morethan 350,000 trips collected by instrumented vehiclesaccumulating more than 3000 mi/yr in representativeAtlanta, GA, households. A variety of cross-tab analysesexamined soak time distributions as a function of time ofday, day of week, vehicle class, model year, householdsize, household income, and driver age. In general, oldervehicles, households with high vehicle ownership,smaller households, and low-income households werepositively correlated with longer soak times.

Guensler also stated that recent license plate observa-tion studies in Atlanta indicate that the on-road freewayvehicle fleet during the commute period is much newerthan forecast by MOBILE6. To further examine this, morethan 350,000 trips collected (09/03 through 02/04) byinstrumented vehicles in representative Atlanta, GA,households were analyzed. Younger vehicles made moretrips and traveled greater distances than older vehicles. Inthe morning commute period, vehicles made longer trips,but more miles were generally accumulated in theafternoon. The older vehicles in the instrumented fleet

did not appear to be used significantly differently (interms of trip duration) across days of the week or timeof day.

ON-ROAD DIESEL EMISSIONSNigel Clark from WVU reported on the E-55 Phase 1.5study, in which regulated emissions from 12 heavy heavy-duty diesel trucks (HHDDT) were quantified using a chas-sis dynamometer and full-scale dilution tunnel. For thetransient mode of the HHDDT test schedule, the emis-sions of NOx from trucks with model years before 1999were variable, but after 1999 the levels were all �15 g/mi.Although trends varied from truck to truck, NOx and PMemissions generally increased with test weight. Threetrucks were selected for engine control unit “reflash.” Onthe cruise mode, NOx values for the three changed from24.2–16.8 g/mi, 26.6–19 g/mi, and 28.1–24.4 g/mi as aresult of re-flash.

Eduardo Behrentz from the University of California,Los Angeles (UCLA) described a method for quantitativelymeasuring the contribution a bus’s own exhaust makes tothe within-cabin pollutant exposure of children commut-ing on school buses. Analysis of tracer gas concentrationsalso provided a powerful tool for identifying potentiallyhigh exposure conditions. The percentage of pollutantconcentration inside the bus cabin originating from theexhaust was a function of bus type and age, and a strongfunction of window position. They estimated up to 0.3%of the air inside the cabin was from the bus’s own exhaustfor older buses and 25% of the black carbon (BC) concen-tration variance was explained by the buses’ self-pollu-tion.

Rob Ireson, a consultant, reported on diesel PM con-centrations inside a school bus attributable to its ownexhaust (DPMSB). A fuel-soluble iridium tracer provided aquantitative marker for exhaust particles. The DPMSB:iridium mass ratio was measured in dynamometer emis-sions tests, and in-bus iridium concentrations were mea-sured during on-road tests. The resulting sensitivity ofin-bus DPMSB measurements was 0.001 �g/m3— approx-imately 100 times better than nonspecific, carbon-basedmethods. The average in-bus DPMSB concentration was0.22 �g/m3. This is less than 2% of values reported inother studies, but those other studies are not definitivedue to their dependence on ambiguous marker species(e.g., BC) and non-PM tracers.

Arthur Winer of UCLA summarized his research tocharacterize the range of exposures experienced by chil-dren during school bus commutes, especially under po-tentially high exposure conditions. Short-term peak pol-lutant concentrations inside buses occurred withwindows partially opened in close proximity to otherdiesel vehicles whereas highest mean concentrations

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occurred with windows closed, in part due to self-pollu-tion. Bus commutes were more important than bus stopsor loading/unloading zones in terms of exposure becausechildren spend much more time commuting and concen-trations are higher in bus cabins. Compressed natural gasfuel and particle traps reduced pollutant concentrationsinside buses.

Guido Lenaers of VITO, the Flemish Institute forTechnological Research in Belgium, assessed the perfor-mance of two retrofit PM traps on a EURO 2 bus using theVOEMLow on-board measurement system. The regulatedemissions during a variety of traffic conditions—city, ru-ral and motorway—were measured in three configura-tions: the bus with standard exhaust, the bus with cata-lytic PM trap, and the bus with PM trap with fuel-borncatalyst. Both PM traps had PM reduction efficienciesranging from 96–99% combined with high reduction ef-ficiencies for HC and CO (80–98%). For these emissions,the EURO-II engine combined with either PM trap per-forms better than the EURO-IV requirements. Moreover,no significant increase of fuel consumption was found.

Olavi Koskinen from the Ministry of Transport inFinland compared European HD vehicle engines of differ-ent generations from the viewpoint of the optimal drivingtechnique. In general, the development of the HD en-gines has led to reduced NOx emissions but increased fuelconsumption. With older engines, the optimal drivingtechnique (gearshift strategy) is compatible both for thefuel economy and NOx emissions. This does not affect thenewest engines, where the optimal gearshift strategy forfuel consumption is the worst driving technique for NOx

emissions. This contradiction concerns the engines in theEURO-III class but will be removed from the engines inthe future EURO classes.

Hector Maldonado of CARB described results fromthe E-55 project, designed to improve the California emis-sions inventory both mass emissions and chemical spe-ciation) for on-road HD trucks, with an emphasis on HDdiesel trucks. Results to date (42 of 75 vehicles to betested) confirm that NOx emissions were relatively un-changed (or increasing) between the mid-1980s and 2002,peaking during the “off-cycle NOx” model years 1994–1998, and then being reduced for the 2003� model years(2 g/bhp-hr NOx standard), at least over highway opera-tion. PM emissions showed a trend consistent with reduc-tions in the certification standards, but late model(1998�) high PM emitters dominate average emissionsfor engines certified to the 0.1 g/bhp-hr PM standard.

Heejung Jung of the University of Minnesota (UMN)discussed the development of methods to understand thekinetics of diesel particle oxidation in the engine and inafter-treatment systems. Particles are oxidized underreaction-limited conditions that allow measurement of

intrinsic rates without being corrupted by heat and masstransfer. The influence of metal fuel additives on particlesize distribution, especially on nanoparticle emissionsand kinetics of diesel particle oxidation, was investigated.Transmission electron microscopy images and energy dis-persive spectrometry analysis of diesel particles usingmetal additives showed that there are two kinds of parti-cles: the first was composed mainly of agglomerates ofcarbonaceous spherules; the second kind was a few, con-siderably smaller metal oxide nanoparticles.

Matthew Barth of CE-CERT summarized a projectdesigned to evaluate fuel economy and emissions benefitsof HD diesel trucks being driven in platoons, where trucksfollow each other at short spacings under carefully con-trolled conditions using electronic towbar automationtechnology. Under automated conditions, the truck spac-ing was varied from 10 m down to 4 m. Because of theaerodynamic draft effect, fuel economy and emissionbenefits were observed. For the lead vehicle, moderatebenefits were observed, with 1–15% and up to 7% in fueleconomy and NOx emissions, respectively. For the follow-ing vehicle, fuel benefits and NOx emission reductionswere 5–16% and 5%, respectively.

Patrick Merritt of the Southwest Research Institute(SwRI) provided an update on the first phase of a programto develop a reproducible standard diesel exhaust mix-ture. An in-depth literature survey was conducted to as-sess engine-out emissions only. A Microsoft Access data-base was created to store these data. While this databaserepresents a large and varied data set, it is still not ade-quate to fully define emissions as a function of speed,load, fuel, and engine technology. The primary reasonsare that there is insufficient coverage of LD engines, andthe bulk of the data was reported as composite valuesrather than as discrete power/load points.

Sandip Shah from CE-CERT described a project toevaluate organic carbon (OC) and EC PM emissions fromdiesel backup generators (BUGs) with after-treatment de-vices. Baseline and controlled exhaust emissions fromBUGs ranging from 300–350 kW were tested on the ISO8178 5-mode test cycle using CE-CERT’s mobile emissionslaboratory. He concluded that the diesel oxidation cata-lyst (DOC) produces overall PM reductions of 6–45%, andthat it is effective on OC-dominated sources but not ef-fective with EC-dominated sources. Diesel particle filters(DPF) reduced both EC and OC emissions, but increasedNO2 due to catalytic regeneration. Fuel-borne catalystswith the DOC reduced EC, OC, and PM emissions inamounts similar to stand-along DOCs.

Hector Maldonado described a CARB project to mapengine-out NOx emissions from HD diesel trucks. WhileHD engines are certified on engine dynamometers, theseengines are driven in vehicles whose operating conditions

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differ considerably from those tested on an engine dyna-mometer. Because of the impracticality and cost ofremoving engines from vehicles, the ability to test anengine in a vehicle is a necessity. Using chassis dynamom-eter techniques, CARB personnel have obtained excellentresults testing engines in-frame. These testing techniquesmay provide a valuable tool for in-use surveillance, Not-To-Exceed (NTE) testing, and verification of emissionscompliance from diesel-powered vehicles.

Brian Beckmann from SUNY at Buffalo discussed lowcost, nonintrusive measurement of NOx emissions fromidling trucks. Engine rpm is determined with the humanear using the “acoustic grouping” method. Exhaust flow iscalculated from engine rpm, ambient temperature, andengine displacement obtained from truck maintenancerecords. Exhaust gas is sampled via a probe lifted into thetailpipe by a special pole. A bank of five-gas analyzersrunning in a support vehicle measured exhaust gas con-centrations. Preliminary measurements of eight tractor-trailers at a fleet yard in Houston, TX, show relatively high(100–300 g/hr) NOx emissions during real-world ex-tended idling.

Michal Vojtisek-Lom summarized the effect of ex-tended idling on diesel engine PM emissions. Data fromover-the-road trucks suggest that extended idling leads toincreased PM both during idling and subsequent opera-tion under load. Extended idling also appears to reducethe effectiveness of exhaust gas after-treatment devices. Acombination of the above factors, plus slow dilution ofthe exhaust plume while idling, may lead to substantialambient PM concentrations at border crossings and sim-ilar places where HD trucks are idled and accelerated. Hereported that these observations correlate with highasthma levels reported in Buffalo, NY, near Peace BridgeU.S.-Canadian border crossing.

FUEL EFFECTS ON VEHICLE EMISSIONSTeresa Alleman from NREL presented emissions data fromsix Class 6 trucks operating in southern California usinggas-to-liquid (GTL) fuel and catalyzed diesel particle fil-ters. Three vehicles were fueled with CARB diesel fuel andno emission control devices, and three vehicles were fu-eled with GTL fuel and retrofit with Johnson Matthey’sCCRT™ filter. Exhaust emissions were collected using achassis dynamometer over the City-Suburban Heavy-Ve-hicle Route and New York City Bus cycles. Average HC,CO, NOx, and PM reductions over both test cycles for theGTL fuel without the filter were 5%, 65%, 11%, and 27%,respectively. The GTL fuel and the CCRT filter reducedHC, CO, and PM emissions by greater than 95%.

H. Christopher Frey spoke about an ongoing projectto quantify the episodic nature of real-world emissions ofbiodiesel and diesel-fueled trucks in the North Carolina

Department of Transportation (NCDOT) fleet. Based uponan analysis of chassis dynamometer data reported in theliterature, the substitution of B20 soy-based biodiesel forpetroleum diesel leads to statistically significant reduc-tions in emissions of CO, PM, and HC but a slight increasein NOx. However, there is a lack of in-use data to assessthe real-world comparison of biodiesel versus diesel andto identify opportunities for improved operation and re-duced emissions. He described a pilot data collection ef-fort using a PEMS system with an NCDOT truck.

Mridul Gautam described a study to reduce emissionsfrom a natural gas-fueled HD vehicle with a custom-de-signed exhaust after-treatment system comprising a cata-lyzed PM trap and an oxidation catalyst. A natural gasengine, meeting the California ULEV levels, was certifiedwith a catalyst for regulated emissions. Unlike a typicaldiesel engine exhaust after-treatment system, Gautam ex-ploited the higher temperatures of the natural gas engineexhaust and located the oxidation catalyst downstream ofthe PM trap. Preliminary results from chassis dynamom-eter tests showed that emissions of lube oil-based ele-ments, nanoparticle size distribution and concentrations,and total PM were reduced to background levels.

Pierre Bonnel of the European Commission Joint Re-search Council presented an overview of the on-goingregulatory developments in Europe concerning HD vehi-cles. He described a program being prepared in Europe todevelop a standard testing protocol for the use of PEMSsystems as an in-use conformity checking procedure forHD vehicles. He discussed the work that will be conductedto assess the capability of validated PEMS systems beforeprogressing to road trials and the development of stan-dard protocols. The respective roles of the participants(institutions, heavy-duty industry, and instrument man-ufacturers), as well as the testing phase of the project,were described.

Matthew Thornton of NREL reviewed the Depart-ment of Energy’s (DOE) Advanced Petroleum-Based Fuels-Diesel Emission Control (APBF-DEC) light-duty passengercar project. This is one of several projects focusing on thesulfur tolerance of NOx adsorber/diesel particle filter(NAC/DPF) systems. The platform for this project is anAudi A4 Avant with a 1.9 l CIDI engine. Data comparingthe chassis dynamometer NOx emissions from a freshNAC/DPF system with the on-road emissions from thesame system were presented. The FTP results for this freshNAC/DPF system showed NOx emission below tier 2 bin 5levels of 0.04 g/mi. The on-road NOx emissions of 0.12g/mi were higher but still demonstrated the high effi-ciency of the NOx adsorber system, even under aggressivereal-world driving conditions.

Shawn Whitacre from NREL reviewed the lubricantseffects on catalyst performance, also being studied under

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APBF-DEC. Particular attention is being given to lubri-cant-derived sulfur because of the potential to impactNOx adsorber catalyst life. Total sulfur emissions can bepredicted based on the sulfur content of the fuel andlubricant. However, sulfur derived from the lubricant baseoil tends to yield higher sulfur dioxide (SO2) emissionswhen compared with sulfur derived from the lubricantadditive package. As a result, constraints on total lubri-cant sulfur that are arbitrary to the source of the sulfurmay be inadequate to control emissions and/or catalystdeterioration. He suggested that the source of the sulfursignificantly impacts the rate of sulfur dioxide emissions.

Michal Vojtisek-Lom spoke about emissions from pri-vate passenger vehicles running on raw recycled cookinggrease from restaurants. Emissions were measured withthe OEM-2100 and Semtech-D portable, on-board moni-toring systems. A 1981 Vanagon running on grease exhib-ited significantly lower PM, HC, and CO emissions thanwhen running on diesel fuel; NOx emissions were un-changed. A 2002 VW Golf and a 2003 VW Jetta runningon cooking grease had both substantially lower NOx (20–30%); the effects on PM, HC, and CO were not consistent.Preliminary results thus show that, unlike biodiesel, rawrecycled cooking oil has a potential as an alternative fuelcapable of reducing diesel NOx emissions.

EMISSION INVENTORYLaurel Driver of EPA described EPA’s October 2002 releaseof the new version of its motor vehicle emission factormodel, MOBILE6.2. The model has been used to developcounty-level nationwide emission criteria inventories forbase years 1978, 1987, 1990, 1996, and 1999 through2002, as well as motor vehicle HAPs for 1990, 1996, 1999,and 2002. Her paper discussed the results of those runs,which show that, while ammonia emissions increase withVMT, most hazardous air pollutant and criteria emissionsdecrease with time and increasing VMT. She also dis-cussed the regulatory programs that influence thesetrends.

Eric Fujita of Desert Research Institute discussedDOE’s Gasoline/Diesel PM Split Study conducted to quan-tify the relative contributions from gasoline and dieselengine to ambient PM concentrations in Los Angeles. Thestudy was conducted using the chemical mass balancemodel methods. It involved testing 59 LD vehicles (in-cluding diesel) and 34 HD vehicles on transportable LDand HD chassis dynamometers, in a format consistentwith the Northern Front Range Air Quality Study. Dieselvehicles are the dominant source of EC. For “normal”emitters, most PM emissions are from the cold start andhigh accelerations. He reported that emission rates ofseveral high molecular weight polynuclear aromatic

hydrocarbons (PAHs) are proportionally higher for gaso-line vehicles than for diesel vehicles.

Kimberly Prather of the University of California atSan Diego presented research on fast, real-time measure-ments of particle composition and how this can contrib-ute to our understanding of the processes affecting parti-cle emissions from gasoline and diesel vehicles. Herpresentation described using a relatively new technique,aerosol time-of-flight mass spectrometry, for obtainingtemporal resolution on size-resolved composition of par-ticles emitted from HD and LD vehicles during dyna-mometer testing. Single particle mass spectral signaturesshow that although not all particle signatures are unique,there are distinct mass spectral signatures emitted fromdiesel versus gasoline vehicles. These signatures will ulti-mately be used for ambient source apportionment ofPM2.5 and ultrafine particles.

Greg Yarwood of ENVIRON described his evaluationof whether CARB’s EMFAC model updates have improvedagreement between ozone models and ambient data forLos Angeles. There was generally good agreement forVOC/NOx ratios with both EMFAC2001 and EMFAC7Gfor both 1997 and 1987. Modeled ozone levels werehigher with EMFAC2001/2002 than with EMFAC7G. Sen-sitivity tests showed a strong NOx inhibition effectthroughout the Los Angeles basin, for both 1-hr and 8-hrozone, with both the CB4 and SAPRC99 chemical mech-anisms, with EMFAC versions 7G, 2001 and 2002. Mod-eled VOC composition was evaluated against ambientdata and several issues were identified that require furtherinvestigation.

Randall Guensler of Georgia Tech (GT) described hisvehicle activity study using 487 instrumented vehicles inthe Commute Atlanta research effort to understand thetravel patterns of the typical Atlanta household driver.Each vehicle was equipped with a GT Trip Data Collectorto monitor second-by-second travel activity for every ve-hicle trip. As of March 2003, vehicle activity data frommore than 350,000 trips were collected and processed. Hispresentation provided a project update and offered someof the preliminary emissions-producing vehicle activityfindings including the types of household and vehicle tripsummary statistics, speed/acceleration profiles, and en-gine start and soak distributions that can be analyzed.

Steve Stewart from the British Columbia AirCare pro-gram presented a method for developing fuel consump-tion and CO2 emissions from a Fast-Pass IM240 inspec-tion. For groups of vehicles, there is very little averageerror. The mean difference in fuel consumption betweenpassing and failing inspections for 1992–2000 passengervehicles was 6.7% and 9.9% for trucks. Approximately2.9% were specifically attributable to emission repairs.The repairs that improved fuel consumption most were

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made to vehicles failing HC and CO, but passing NOx. Therepairs with most negative effect were made to vehiclesthat failed HC and NOx, but passed CO. In cases whereCO emissions were reduced significantly, the CO2 emis-sions usually increased even though fuel consumptionwas reduced.

Ralph McGill of Oak Ridge National Laboratory(ORNL) presented a progress report on his collaborativeeffort with the University of Tennessee characterizing theambient air quality in a truck travel center. The objectiveis to evaluate the air quality benefits of installing a systemsuch as the IdleAire electrification system to mitigate theidling of trucks parked at a truck travel center. NOx,PM2.5, and CO are being monitored over a period ofmonths, while aldehydes and heavy metals are beingmonitored in a series of week-long, intensive campaigns.Preliminary results to date include baseline emissionsconcentrations for NOx, PM, and the aldehydes, and base-line meteorological data. The impact of the idle reduc-tions system will be studied in the future.

MEASUREMENT METHODSRob Caldow of TSI, Inc., discussed the Engine ExhaustParticle SizerTM (EEPSTM) spectrometer designed specifi-cally to measure engine exhaust emission transientevents. The spectrometer measures size distributions ofparticles in the 5.6–560 nm size range at a rate of 10 sizedistributions per second. The distributions are reported as16 channels per decade based on a real-time data inver-sion from 22 individual low-noise electrometers. Themeasurement is based on the same electrical measure-ment as the industry standard scanning mobility particlesizer (SMPS) instrument. Comparison with SMPS mea-surements under steady-state conditions shows goodagreement. Data for load-varying transient measurementsalso show good correlation with condensation particlecounter (CPC) and electrical aerosol detector (EAD) mea-surements.

Sandip Shah of CE-CERT presented a new fast scan-ning SMPS system capable of elucidating particle size dis-tribution in near real-time. A radial differential mobilityanalyzer combined with a mixing-CPC allows for theminimization of delay times that are typically associatedwith traditional SMPS systems and, thus, allows for fasterscans without sacrificing resolution. The instrument iscapable of performing scans in 2.5 sec for classifying andcounting particles in the range of 4–110 nm. Severalimprovements are planned for the instrument, afterwhich it will be used to measure transient size distribu-tions for vehicles operated on the road using CE-CERT’smobile emissions laboratory.

Bruce Cantrell with the EPA evaluated the perfor-mance of a QCM and a TEOM to measure diesel exhaust

PM mass. Exhaust PM from a Detroit Diesel Series 60engine fueled with ultra-low sulfur fuel was measuredwith and without exhaust after-treatment using JohnsonMatthey CRT and Engelhard DPX exhaust particle filtertraps. The TEOM and QCM measured PM mass within20% of the CVS PALL TX-40 reference filter. For trap-outPM, the integrated mass from both instruments measuredlower PM levels than the reference filter. With a Zefluorfilter used as the reference filter, the TEOM registered fourtimes the PM mass, but the QCM was within 40% of thereference. Different measurement methods may be mea-suring different components of the sampled exhaust PM.

Imad Khalek with SwRI described a solid particle mea-surement system (SPMS) that measures real-time solid andtotal (solid plus volatile) particle mass, size, and numberin the size range from less than 10 nm to 500 nm in dieselengine exhaust. The presence of solid nanoparticles in thesub-20 nm size range and potentially in the undetectablesub-8 nm size range is observed. The data indicate accu-mulation mode particle number-weighted size distribu-tions (50 nm to 300 nm) may contain a significant num-ber of volatile particles, particularly at light load engineoperation. Thus, the accumulation mode is not alwaysindicative of a strong presence of soot or solid particles.

Peter Witze acquired unattended, around-the-clockLII measurements over the HD FTP. The LII system ran inthis mode for 7.5 weeks, logging 1078 individual dieselengine tests during continuous operation of the dilutiontunnel facility. Among the tests logged were 363 FTPsteady-state mode tests and 250 FTP transient tests forwhich gravimetric measurements of total PM were ob-tained. Of these tests, volatile extraction was performedon 142 and 147 of the tests, respectively. The dry gravi-metric measurements for the steady-state tests were usedto calibrate the LII measurements, resulting in excellentagreement between the LII and dry gravimetric measure-ments for the transient tests.

Rob Graze of Caterpillar noted that concern overpotential 2007 engine development and certificationchallenges and proposed off-highway transient cycle re-quirements prompted development of a transient partialflow dilution system for PM sampling at Caterpillar andSierra Instruments. Proportional sampling requirementswere addressed by a proprietary dilution air controlscheme. Optimization of dilution system wall area, sys-tem sampling rates, flow measurement accuracy, andpneumatic capacitance were required to achieve designobjectives. The system passed all ISO16183 requirements,as well as the EPA 1065 paired–t and F test statisticalcriteria. Future efforts will focus on achieving a formalEPA equivalency statement and developing the system asa diluter for gaseous emissions sampling and measure-ment.

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John Storey reported on ORNL’s remote sensing sys-tem, which combines a new LIDAR approach with an UVsystem that uses differential optical absorption for nitricoxide (NO) measurement with the emphasis on arraydetection for speed and low cost for measuring PM fromon-road trucks. He presented measurements of the plumefrom a diesel vehicle on a chassis dynamometer andacoustic sensing of truck engine conditions. The systemcalculates vehicle speed as well as rpm, number of cylin-ders, and turbocharger rpm for the engine as it passes.This information will be used to determine exhaust flowand, when combined with concentration data, can pro-vide mass flux of emissions.

Peter Witze described the following high-energy,pulsed-laser diagnostics applicable to both extractive sam-pling and in situ (undiluted), time-resolved measure-ments of PM emissions: (1) LII measures soot volumefraction (EC only) and the diameter of the primary parti-cles that make up soot aggregates; (2) Elastic laser scatter-ing (ELS) measures particle size and morphology, includ-ing the mean equivalent-sphere diameter, radius ofgyration and fractal dimension of aggregates; (3) Laser-induced desorption with ELS (LIDELS) measures the solidvolume fraction of PM; and (4) Laser-induced breakdownspectroscopy (LIBS) identifies elemental species and mea-sures their concentrations, and is well-suited to investi-gate the metallic ash in diesel PM.

Angela Monateri of the University of Denver (DU)described the advances in the use of remote sensing de-vices to detect high-emitting vehicles. Using an IR cam-era, the differences between hot, malfunctioning grossemitters and cold-start vehicles can be identified. Hotvehicles have a very bright underbody reflection, hot ex-haust system metal, and bright uniform IR emissions fromthe tires. Cold vehicles have either weak or no underbodyreflection and nonemitting or nonuniformly emittingtires. When combined with remote sensing exhaust mea-surements, emissions can be compared with the IR imageto determine whether or not a grossly emitting vehicle isin a cold-start mode.

Michael Gebel from the CARB presented work identify-ing the cause for 1,3-butadiene loss in exhaust matricesusing an atmospheric oxidation model with the initial con-ditions present in gasoline and diesel exhaust matrices. TheCARB study explored the stability of other individual toxicspecies, such as benzene, toluene, ethylbenzene and xylenes(BTEX) in exhaust. The decay of 1,3-butadiene in gasolineexhaust is caused by its reaction with NO2. The model isused to show that for a hypothetical diesel sample contain-ing 1,3-butadiene, the decay rate is much faster than forgasoline exhaust due to higher NOx levels. CARB also foundthat BTEX is stable in gasoline exhaust matrices for holdingtimes exceeding one day.

UNREGULATED EMISSIONSDaniel Carder of WVU described a study characterizingin-use emissions from on-highway class 8 diesel vehiclesoperating within the NTE zone. Emissions were measuredwith the MEMS while vehicles were driven on threeroutes: 75%, 18%, and 10% of the time in the NTE zonewas spent in cruise, acceleration, and deceleration modes,respectively. Brake-specific NOx and CO2 emissions werehighest in the cruise mode, slightly less during accelera-tion, and lowest during deceleration. The need for real-time, on-road PM measurement was noted.

David Kittelson from the UMN utilized his group’smobile emission laboratory (MEL) as a platform for real-world animal exposure experiments with an emphasis onmeasuring nuclei mode nanoparticles. The goal of obtain-ing high, relatively stable concentrations delivered to theanimal chambers was met by sampling the naturally di-luted exhaust from the MEL, which is powered by a mod-ern diesel engine. On-road aerosol sampling from mixeddiesel traffic was less successful. Most of the particle num-ber was found below 10 nm. The nuclei mode was nearlyall volatile and increased with decreasing temperature.Care should be taken to measure concentrations in expo-sure chambers because losses appeared to reduce numberconcentrations up to a factor of six.

Sandip Shah described progress in quantifying theemission rates of selected PAH and aliphatic compoundsduring on-road operation of HD diesel trucks. Emissionstests were conducted using CE-CERT’s mobile emissionslaboratory operated on the CARB 4-mode driving cycle.On a per mile basis, the average emission rates of PAHsand aliphatics from five trucks were 38 and 27 timeshigher, respectively, on the creep mode than the cruisemode. For all modes, slower vehicle operation led tohigher emission rates on a per mile basis. Additionally, itwas noted that a large fraction of the species measuredwas captured on the PUF-XAD cartridge place behind thefilter. This is due to the semivolatile nature of many of thecompounds together with sampling at the 2007 regula-tory sampling temperature of 47 °C.

Nigel Clark presented research on the transient sizedistribution of PM for a 1995 Mack tractor truck followingthe Heavy-Duty Urban Dynamometer Driving Schedule(UDDS) cycle on a chassis dynamometer. A Cambustiondifferential mobility spectrometer (DMS 500), which iscapable of measuring particle number in 41 particle sizebins ranging from 3.2 nm-1000 nm at a max frequency of10Hz, was used. There was a strong correlation betweenvehicle speed and number count. A high PM numberconcentration with a peak at 100 nm was observed duringacceleration, while, at light load, smaller particles averag-ing 5–10 nm were also measured. The total particle num-ber per cubic centimeter was �107.

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Eduardo Behrentz summarized results of a pilot studyto determine N2O emission rates from in-use, LD gasolinevehicles in California and to characterize the variablesthat affect those rates. Emissions were measured from 37passenger cars, SUVs, and LD trucks using the UDDS cycleand the Unified Driving Cycle (UDC). Tests included awinter and a summer fuel. The average N2O emission ratewas 20 � 4 mg/km. The average value for N2O/NOx emis-sion ratios was 0.095 � 0.035. The study results supportCARB’s approach of using N2O/NOx ratios and NOx emis-sion rates to estimate the LD mobile source N2O emissionsinventory.

Peter McClintock of Applied Analysis described anon-road remote sensing study conducted in 2003 to assessthe utility of using remote sensing in the Lower FraserValley region of British Columbia. RSD4000 units wereused at 21 sites to collect 200,000 vehicle emissions mea-surements. The results were compared with AirCare I/Mvehicle inspection data. The correlations between meanmodel year remote sensing measurements and AirCareIM240 data were 0.96, 0.98, and 0.99 for CO, HC, andNOx, respectively. ASM correlation was weaker for HC.Remote sensing measurements identified differences inthe mean on-road emission levels of vehicles with differ-ent OBD-II malfunction indicator light (MIL) status. AnR2 of 0.87 was obtained between mean RSD4000 smokemeasurements and AirCare diesel opacity tests.

Xiaona Zhu from CE-CERT presented mobile sourceair toxic trends for the Los Angeles Basin. Included in theinventory were benzene, 1,3-butadiene, formaldehyde,acetaldehyde, and acrolein. CE-CERT and literature datawere combined to obtain average emission rates and airtoxics/total organic gases ratios as a function of vehiclecategory and control technology, and to estimate anemission inventory from 1970 through 2020. Emissionestimates for all of the toxics compounds showed reduc-tions of 97% from 1970–2020. The contributions of LDgasoline vehicles to total toxic emissions will decreasefrom 94% in 1970 to 59% in 2020. The ambient concen-trations of all toxic compounds are projected to be re-duced at least 96% from 1970 to 2020 in Los Angeles.

Tom Wenzel from Lawrence Berkeley National Labo-ratory analyzed I/M test results from vehicles receivingtests before their normal scheduled date in Arizona, Cal-ifornia, and Colorado. Large numbers of vehicles failedthe test within a few months of passing their previoustest. Test fraud was ruled out as a possible cause of thefailures, and inadequate vehicle preconditioning wasmostly ruled out. Other possible causes include gascap “failures,” inadequate repairs, unrelated emissionsproblems, and intermittent emissions problems with“flipper” (variable emissions) vehicles. It was estimatedthat, at most, 90% of all fail-pass cars could be flippers,

with a 20–30% chance of failing an I/M test. The possi-bility of flippers should be analyzed as part of I/M evalu-ations to ensure that program benefits are not overstated.

Daniel Burgard from DU reported on the modifica-tion of the Fuel Efficiency Automobile Test remote sens-ing instrument to include UV detection of sulfur dioxide(SO2). The minimum detection limit was 25 ppm SO2 inexhaust. The system was tested on a LEV using low sulfurfuel and a vehicle using fuel doped with 2000 ppm sulfurby weight. It was concluded that a vehicle using 2000ppm fuel sulfur can be identified 58% of the time withoutmisidentifying a low emitter. Measurements on vehiclesusing fuels up to 3000 ppm sulfur gave average SO2 ex-haust concentrations approximately half the calculatedvalues. It was concluded that sulfur was being stored onthe emission control catalyst under the driving condi-tions used.

GASOLINE VEHICLE EMISSIONSDonald Stedman of DU discussed on-road vehicle emis-sions deterioration. Slopes from a snapshot of emissionsas a function of model year mimic deterioration, have thesame units, but are not correct. To correctly determinedeterioration, observations are required over multiplemeasurement years of the same model year (but not re-stricted to the same vehicles). He suggested that the EPAMOBILE6 deterioration parameters made this mistake.Stedman reported that emissions of 1996 model year andnewer US vehicles are markedly lower than 1995 andolder vehicles. DU’s historical remote sensing data indi-cate that the combination of Swedish technology andmaintenance surpass the U.S. and the United Kingdom interms of lower on-road emissions.

John Collins of CE-CERT used an on-board measure-ment system to measure exhaust mass emission rates ofcriteria pollutants from a fleet of extremely clean, in-usevehicles. The vehicles included 13 ULEV and three partialzero-emission vehicle (PZEV) vehicles. The emissions weremeasured while driving on a dynamometer over standardcycles and while driving with traffic on freeways, arterialroads, and residential roads in southern California. Themeasurement data show that the in-use vehicles are meet-ing expectations based on their emission certification lev-els. The data also show that the current emission inven-tory models need to be updated to correctly reflect thebreakdown between start and running emissions and theeffect of vehicle soak times on start emissions.

Nicole Davis from CE-CERT described the study ofExtremely Low Emitting Vehicle (ELEV) program, whichhas measured �18 ELEV vehicles in real-world driving.These data have been used to update emission factors andcreate a new module in CE-CERT’s CMEM model. Theprogram has demonstrated that low mileage ELEV

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vehicles consistently perform on the road with very lowemissions. However, emission spikes and start emissionsas a function of soak time are not well understood ormodeled. Additionally, the measurements from the ELEVvehicles are different than the current policy model pre-dictions. Air quality modeling results indicate that in-creasing the number of ELEV vehicles would help theSouth Coast (Los Angeles) Air Basin meet attainment.

Doug Lawson of NREL presented second-by-secondPM and gas-phase emissions data from LD vehicles sam-pled during DOE’s Gasoline/Diesel PM Split Study. Hereported that although the vehicles in this data set haveunique, second-by-second emissions patterns, “normal”or well-maintained vehicles have low emissions the ma-jority of the time over the UDC. For normal emitters, themajority of emissions came from the cold start and fromsome high-speed and/or high-acceleration events. Cold-start conditions produced at least 30% and up to morethan 50% of the total CO and HC emissions from normalemitters during the UDC. High emitters produced highand irregular amounts of gas-phase and PM emissionsduring the majority of the UDC driving cycle conditions.

Robert Slott, a consultant, reported that high emitteridentification is important for reducing vehicle emissions,evaluating I/M programs, and modeling vehicle emis-sions. He summarized results from other studies wherevehicles identified by remote sensing were immediatelytested on a dynamometer and where the next I/M test wascompared with prior remote sensing readings. Also, sec-ond-by-second dynamometer data (SBSDD) were con-verted into remote sensing data. SBSDD were used from13 vehicles on two driving cycles with VSP from 3–23kW/t for estimating how well remote sensing could detecthigh emitters under dramatically different driving condi-tions. The vehicles included low emitters, high emitters,and vehicles that became high emitters under mild orsevere acceleration.

Richard Barrett from the Colorado Department ofPublic Health and Environment presented data showingthe effects of the Denver area’s high volatility/high etha-nol content fuels on vehicle emissions at elevated tem-peratures. IM240 data show increased CO and HC emis-sions and failure rates, across all vehicle model years, athigh temperatures. On-road remote sensing data, col-lected in Colorado, show a similar relationship. Analysisof Colorado I/M data for multiple years, where fuel com-position varied considerably, show strong correlation ofthis increase in emissions with both fuel ethanol contentand volatility. A comparison shown for I/M data fromMissouri and relative RSD data from California, where thefuels had no ethanol and lower volatility, showed nosimilar increase of emissions with ambient temperature.

WORKSHOP SYNOPSISThere is considerable interest in improving the character-ization of exhaust PM emissions. Regulatory requirementsare based on particle mass determined from filter samples.The mass collected by filters is sensitive to collectiontemperature, humidity, flow rate, and interference by spe-cies that adsorb on the filter. Hence the measured mass isoperationally defined. This is especially true for low PMemitters such as trap-equipped diesels and most gasolinevehicles. This makes the development of equivalentmethods difficult. The QCM and the TEOM remain theleading contenders for real-time mass measurement ofPM, but a study showed that their agreement with filtermass remains poor, especially at low mass emission rates.

Other researchers have focused on measuring onlythe solid portion of the exhaust PM. This information isuseful for characterizing the nature of the PM and, hence,its possible formation mechanism, and for calculating PMtrap efficiencies. The solid particle measurement system(SPMS, not to be confused with the SMPS) discussed at theconference is an example of this technology. LII is an-other approach that measures EC, the major constituentof the solid particles. The LII instrumentation has provento be very robust in a test laboratory situation, and theresults correlate very well with the filter measurements ofdry PM (i.e., organics have been removed). It was notedthat other laser methods being developed could comple-ment LII by measuring the solid volume PM fraction(LIDELS) and the concentration of elemental species(LIBS) such as those present in metallic ash. Photoacousticinstruments have also been shown to provide real-timeBC data.

An additional aspect of exhaust PM laboratory mea-surement is that a full flow dilution tunnel is required.There have been many efforts to develop transient partialflow dilution systems to use in place of dilution tunnels.A presentation at the workshop discussed a new systemthat is expected to seek formal EPA equivalency.

Particle size distribution is another important aspectof PM characterization. The SMPS has been the mostcommonly used instrument for this purpose, but its par-ticle size scan time prevents its use during transient en-gine operation. Three instruments were discussed at theworkshop that have fast scan times, thereby permittingthe collection of continuous particle size distributiondata. Two of these are commercially available instru-ments, the Engine Exhaust Particle Sizer™ (EEPS™) andthe differential mobility spectrometer (DMS500). Resultsto date indicate good agreement between these instru-ments and other measures of PM number and size. Thethird instrument is a fast scanning SMPS using a newdesign. It currently has a scan time of 2.5 sec, but isundergoing additional improvements.

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PEMS are instrument packages that collect continu-ous exhaust emission rate data along with data on vehicleoperating conditions and vehicle location. They are de-signed for rapid installation in vehicles for in-use exhaustmeasurements. There are commercial PEMS units offeredby Horiba, Sensors, Inc., and Clean Air Technologies, andresearch units such as WVU’s MEMS that measure theregulated gaseous emissions. In general, these units havebeen shown to be in good agreement with conventionalmeasurement methods when tested under controlled lab-oratory conditions. While optical methods of measuringPM have been used in PEMS units, it has been a researchobjective to have continuous PM mass measurements.The QCM and TEOM technologies mentioned above re-main the leading contenders to fulfill this role.

Proper sampling of vehicle exhaust is a challenge foron-board PM PEMS measurement. Two approaches underdevelopment were described. One uses secondary dilutioncombined with careful temperature and humidity con-trol. The second uses a Micro Proportional Sampler that isable to operate at 10 Hz. At the time of the workshop,successful PEMS PM mass measurement had not beenreported. It should be noted, however, that the LII hasbeen demonstrated on-board vehicles to obtain continu-ous EC emission rates. Addition of toxic compound mea-surement to PEMS is also a research goal. The aforemen-tioned sampling systems will be useful in this regard aswell. FTIR has been used on a research basis for some timeto measure some of the air toxics on board vehicles. Acommercial FTIR PEMS unit is under development.

PEMS systems are now starting to be deployed in fieldstudies. For example EPA used them to measure emissionsduring the 2003 Challenge Bibendum and WVU is usingthem to explore emissions in the NTE operating zone ofclass 8 diesel trucks. CE-CERT has been using them tostudy in-use emissions from extremely low emission ve-hicles.

Europe is also interested in PEMS. It was reported thata program is being prepared to develop a standard testingprotocol for the use of PEMS for conformity testing ofheavy-duty vehicles. That work should be valuable toefforts in the U.S. as well.

Another approach to obtaining on-road PM emissionrates is the use of remote sensing. Several organizationspresented papers at past meetings on PM remote sensingdevelopment. This year there was one paper on a newLIDAR approach. The system remains in the researchstage. The unique feature of this system is an acousticsensing of the engine rpm that is used to obtain estimatedexhaust flow. The RSD4000 commercial remote sensorhas an optical smoke measurement that was reported tocorrelate well with diesel opacity tests in one study. We

are not aware, however, of any remote sensor that hasbeen successfully correlated with PM mass measurements.

In-use diesel exhaust emission rates have been anactive area of research since the existing database is verypoor and there is a lot of interest in NOx and PM emissioninventories. The CRC E-55/E-59 project has been emissiontesting HD diesels on a chassis dynamometer. Results todate indicate that PM emissions have been reduced overthe last 20 years, but there was little progress for NOx

through 2002. The newest trucks, however, have reducedNOx emissions. This program has also investigated theimpact of load on emissions and the impact of vehiclerepairs on high-emitting vehicles. Another study exploredhow driving technique impacts emissions of HD Euro-pean trucks. For the newer vehicles driving to optimizefuel economy tends to maximize NOx emissions. Studiescontinue to show that there will be dramatic improve-ments in diesel PM emissions starting in 2007 when par-ticle traps are utilized. In addition, CARB reported thatthey have successfully mapped engine-out NOx emissionon a chassis dynamometer, thereby providing a tool thatcan be used in verification of emission compliance ofdiesel vehicles.

There is continued interest in diesel idle emissionssince some diesel trucks spend significant time at idle, andthis can be important for certain microenvironments.Two studies were reported at the conference, both ofwhich noted that real-world idle emissions are relativelyhigh. It was noted that extended idle increases PM emis-sions during the idle and subsequent operation. The Uni-versity of Tennessee, Knoxville and ORNL are conductingan air quality study at a truck travel center to determinethe impact of reduced idle emissions.

Penetration of exhaust into school bus interiors wasaddressed in three presentations. One study used an SF6

tracer to show that �25% of the variance in BC in schoolbus interiors was due to the bus’s own exhaust. A secondstudy used an iridium fuel-borne tracer to conclude thatpenetration of a bus’s own exhaust is much lower thanestimated in previous studies. A third study concludedthat bus commutes are more important than loading/unloading events, although it was noted that highestconcentrations occurred when windows were partiallyopen in the vicinity of other buses.

The impact of fuels on emissions remains an impor-tant research area. A study comparing GTL fuels withcommercial diesel fuel showed significant emission ben-efits for all regulated pollutants. A second study is exam-ining the in-use impact of B20 (20% soy-based biodiesel)on emissions. Currently the comparison to commercialdiesel is hampered by a lack of data for on-road dieselemissions. The APBF program continues to examine theimpact of fuel and lubricant sulfur on advanced

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after-treatment systems. A fresh NOx absorber/particletrap system gave encouraging results on the road, butlong-term durability data have not been collected. Lubri-cant studies have shown that more exhaust SO2 is gener-ated from the sulfur in the base oil than the sulfur con-tained in the oil additive package. Hence, looking at totallubricant sulfur content may be misleading in terms of itspotential impact on emissions control devices.

While there was a definite emphasis at the workshopon diesel emissions, gasoline vehicle emissions studieswere also covered. Several studies used remote sensing toexplore various aspects of the in-use fleet emissions. Thevalue of remote sensing in identifying high emissionlight-duty vehicles was reviewed, and it was noted that ithas proven to be very effective. One question about re-mote sensing data has been how traffic conditions affectthe results. Fleet average remote sensing data were foundto be independent of traffic conditions when adjusted forthe VSP and model year. Remote sensing has also beenused to track average light-duty vehicle emissions andemissions deterioration as a function of model year bylooking at year-to-year changes at the same location. Newvehicles in the U.S. are becoming progressively cleanerand staying cleaner than older vehicles. A study in BritishColumbia showed that model year average remote sens-ing data correlate very well with model year averageIM240 data. The remote sensing results also showedhigher average emissions for vehicles with a MIL illumi-nation. Both remote sensing data and IM240 data col-lected in Denver show increased emissions at high ambi-ent temperatures. Denver uses fuels with ethanol. Areasthat do not use ethanol-blended gasoline do not show thesame temperature effect. The results are suggestive butneed more thorough investigation. PEMS systems havebeen used to examine in-use emissions of ULEV and PZEVvehicles. Their in-use emissions were found to be consis-tent with their certification levels. It was noted that theeffect of soak time on vehicle start emissions and on-roademission spikes are not well understood or modeled.

A pilot laboratory study of N2O emissions from light-duty gasoline vehicles was conducted. Several variableswere explored. Nitrous oxide to NOx ratios were fairlyrobust, suggesting that this is a viable approach for mod-eling N2O emissions. UV SO2 measurement capability wasadded to a remote sensor. It was demonstrated that thesensor could distinguish between vehicles using high andlow sulfur fuel. Hence, it may be useful in the future toexamine misfueling issues. CE-CERT has assembled a mo-bile source air toxics inventory for the LA basin for 1970through 2020. Over this time frame, air toxics are ex-pected to decrease by 97%. The light-duty vehicle contri-bution to ambient air toxics levels will drop from 94% to59%. CE-CERT is using their on-road heavy-duty mobile

emissions laboratory to quantify emission rates of se-lected PAH and aliphatic compounds as a function ofdriving mode. It was noted that a large fraction of thespecies was in the gas phase under the sampling condi-tions used. The University of Minnesota mobile emissionslaboratory was used to feed diluted exhaust from thetractor pulling the laboratory to animal exposure cham-bers located on-board. It was found that nanoparticles,which were mostly smaller than 10 nm, have very highloss rates in the chambers.

While previous workshops discussed a variety of is-sues related to I/M programs, there was only one presen-tation on that issue. That presentation noted that theremay be a significant number of vehicles that have variableemissions and that their impact on IM program benefitsmust be considered since they could lead to overestima-tion of effectiveness.

MOBILE6.2 has been used to update the NationalEmissions Inventory for both regulated pollutants andHAPs. Despite continued growth in VMT, most pollutantsshow large decreases between 1978 and 2002. Ammonia isan exception. Questions remain as to how well currentmodels calculate mobile source PM. The DOE Gasoline/Diesel PM Split Study has shown that most of the carbo-naceous aerosol in the LA Basin is due to mobile sources.Gasoline and diesel vehicle source profiles have been gen-erated but the apportionment was not completed at thetime of the Workshop. An alternate apportionmentmethod relies of source profiles for individual particlesgenerated by aerosol time-of-flight single particle mea-surements. This method looks promising for the separa-tion of gasoline and diesel exhaust PM, especially forultrafine particles. While CO2 emissions are not calcu-lated by MOBILE6, they will be the subject of the firstversion of the MOVES model. In-use fuel economy (i.e.,CO2 emissions) traditionally has not been a focus of thisworkshop. However, one paper did report that fast-passIM240 data can be used to generate CO2 emissions datafor pre- and post-vehicle repair. Although vehicle activitydata needs do not get as much research attention as emis-sions, they remain a critical model input. A very large dataset is being generated in Atlanta using on-board, second-by-second data collection. To date, the data have beenused to examine soak time patterns and to investigateon-road activity as a function of vehicle age.

MOVES is the next generation mobile source modelunder development by the EPA. It is being developed instages, with the first version to be released in 2004. Thisversion is focused on energy consumption and green-house gas emissions from on-road vehicles and will in-clude the ability to obtain well-to-pump calculations viathe GREET model. Emissions in the MOVES model areclassified by engine technology, engine displacement,

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vehicle model year, vehicle weight and fuel type. For eachof these source bins, the emissions are separated into 17operating modes based on vehicle-specific power. A largedatabase has been assembled to provide input for thesebins. It is planned to continuously update the database asmore data become available. There are little data for ad-vanced technology vehicles and some classes of heavy-duty diesel vehicles. In these cases, emissions are calcu-lated by the separate PERE model. PERE model outputshave been validated against production vehicles withgood success. With this binning approach, the MOVESmodel is expected to be able to calculate emissions fromany driving cycle, thereby enabling it to handle emissioninventories ranging from the microscale to the mac-roscale. There is still debate regarding this binning ap-proach, however, since VSP is not the only variable effect-ing exhaust emissions and algorithms might be developedthat would be more robust. In regards to binning, it wasnoted by another group that in-use data tend to be weakfor high emission events, such as cold starts, hard accel-erations, and high-speed conditions, which can cause sig-nificant emissions. It is recommended that driving proce-dures be developed that supplement in-use data withcollection of data during those conditions. Another groupemphasized the importance of understanding road grade,and recommended the use of airborne LIDAR to measureroad grade.

While MOVES is expected to replace MOBILE6.2, itwill be several years before MOVES is released for use instate implementation plans (SIPs). In addition to its use inthe U.S., modified versions of MOBILE are used elsewhere,such as Canada and Mexico. It was also reported thatHong Kong is using MOBILE emission factors and deteri-oration rates in a modified version of EMFAC2002, theCalifornia-specific mobile source emission factor model.Hence, it is important that limitations in MOBILE con-tinue to be investigated. The one study that examined thisissue found that ambient and inventory VOC/NOx ratiosare in generally good agreement, but ambient CO/NOx

ratios exceed the inventory ratios. EPA has recently re-leased its National Mobile Inventory Model. This modelcombines utilizes MOBILE6 and NONROAD togetherwith a county database and a convenient graphical userinterface to create county-level mobile-source invento-ries.

While most of the modeling focus was on MOVESand MOBILE it was noted that CE-CERT continues todevelop their modal emission model, CMEM. They haverecently added ammonia emissions predictions to themodel and have improved the handling of very lowemissions vehicles. In addition, Virginia Tech has beendeveloping a model for use in evaluating the environmen-tal impacts of transportation projects. It addresses hot

stabilized, light-duty vehicle emissions utilizing as mainvariables average travel speed, number of stops and aver-age stop time. To date, the model works best for fuelconsumption and HC emission rates. They are lookingfurther into the impact of vehicle speed and accelerationon emissions. In a companion effort, they are investigat-ing the use of PEMS heavy-duty data for developing aheavy-duty model. The results using data from one vehi-cle were promising.

FUTURE RESEARCH PRIORITIESWith the commercialization of PEMS units for gaseousregulated pollutants, there is a strong possibility thatthere will be a very large increase in real-world vehicleemissions data in the near future. Methods for the anal-ysis and quality assurance of this data are needed. Move-ment of PEMS outside the current research environmentinto more routine use must be done with care to ensurehigh data quality. With several manufacturers providingPEMS, it is time to conduct a methods comparison study.Research needs to continue on the development of PEMS-based PM measurement capability and, as a second prior-ity, other HAPs.

The relative contributions of nonroad gasoline anddiesel, and on-road gasoline and diesel vehicle exhaustPM emissions remains uncertain. Improving the inven-tory for the various classes of vehicles in these categoriesremains a priority. Addition of PM capability to the PEMSwill be very helpful in this regard. Results from CRC’sE-55/59 study, DOE’s Gasoline/Diesel PM Split Study, andEPA’s Kansas City light-duty gasoline study are expectedto improve the on-road data considerably. Nonroad emis-sion inventories clearly need more attention.

As discussed above, PM mass emission rates are oper-ationally defined due to the semivolatile nature of somecomponents of the PM. An improved understanding ofhow tailpipe measurements relate to atmospheric concen-trations needs to be developed. This will likely requiremodeling of particle processes as a function of the com-position of the semivolatile species, ambient conditions,background aerosol concentrations, dilution, and resi-dence time.

The release of MOVES2004 will start a model evalua-tion effort that will include, for the first time, the consid-eration of well-to-pump issues. With new releases ofMOVES planned for 2005, 2006, and 2007, this validationeffort will clearly be ongoing. As noted earlier, MOBILE6and EMFAC2000 limitations need to be understood fur-ther since these models will remain in use, and some ofthe algorithms and emission rates they use may be carriedover into MOVES modeling.

The designation of many areas of the country asbeing out of compliance with the new ambient ozone

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standard will put new pressure on understanding the ben-efits of I/M programs and the impact of OBD systems onvehicles. It may be possible to design optimized I/M pro-grams with greater benefit-to-cost ratios.

Diesel fuel and lubricant changes will be imple-mented by 2007, in support of the heavy-duty dieselemissions regulations. 2007 HDDs are expected to beequipped with particle traps. There will be a need tocharacterize emissions from these new vehicle/fuel sys-tems. In addition, as with any new technology, deterio-ration will need to be examined. There is growing interestin renewable fuels as well. The impact of greater use ofethanol and biodiesel needs to be carefully considered.

Given the continued regulatory challenges facing themobile source community, we look forward to the 15thCRC On-Road Vehicle Emissions Workshop, which willbe held in San Diego, CA, April 4–6, 2005.

DISCLAIMERThe statements and conclusions in this paper represent in-formation presented at the Workshop by the individualpresenters and are not necessarily those of the CoordinatingResearch Council, Inc., the SCAQMD, the U.S. Departmentof Energy, or the U.S. Environmental Protection Agency.The mention of trade names or commercial products doesnot constitute endorsement or recommendation of use.

ACKNOWLEDGMENTSThe authors appreciate the efforts of Brent Bailey, ShirleyBradicich, Lois Mott, and Jan Tucker, the CRC staff

members who made this Workshop a success. In additionto the CRC, the CARB, the SCAQMD, the U.S. Departmentof Energy’s Office of FreedomCAR & Vehicle Technolo-gies, and the U.S. Environmental Protection Agency pro-vided financial support for the Workshop. The authorsalso thank the session chairmen for their help in organiz-ing and coordinating the Workshop.

About the AuthorsSteven H. Cadle is a principal research scientist with GeneralMotors R&D Center in Warren, MI. Timothy C. Belian is Exec-utive Director of the Coordinating Research Council in Al-pharetta, GA. Kevin N. Black is a highway engineer at theFederal Highway Administration, Washington, DC. FredMinassian is a technology implementation manager at theSCAQMD in Diamond Bar, CA. Mani Natarajan is a seniorengineering consultant at Marathon Ashland Petroleum LLC,in Findlay, OH. Eugene J. Tierney is director of the Air Qualityand Modeling Center with the U.S. Environmental ProtectionAgency, Ann Arbor, MI. Douglas R. Lawson (correspondingauthor) is a principal scientist at the National Renewable En-ergy Laboratory in Golden CO. Address correspondence to:Douglas R. Lawson, National Renewable Energy Laboratory,1617 Cole Boulevard, Golden, CO 80401; phone: �1-303-275-4429; e-mail: [email protected].

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