C-1 

# Appendix C:

Emission Inventory Analysis and ResultsC-2

APPENDIX C: Emission Inventory Development - Analys is and Results

A. Emissions Inventory Data Sources

A variety of data sources were used to establish th e tractor and trailer population impacted by the proposed rule. These include the f ollowing: ARB Motor Vehicle Emissions Inventory (ARB Inventory), U.S. Bureau of Census 2002 Vehicle Inventory and Use Survey (VIUS) 1 , Americas Commercial Transportation Research Compa ny (ACT Research), U.S. Bureau of Census Current Indus trial Reports (CIR), and Commercial Carrier Journal. The following sections describe these data sources and the methodology used to estimate the tractor and tr ailer population impacted by the proposed regulation and the greenhouse gas emission benefits.

1. ARB Heavy-Duty Vehicle Inventory

On-road mobile source emissions in California are c urrently calculated using the EMFAC2007 (ARB, 2006) model that was released in De cember of 2006. Since the last EMFAC release, ARB staff members have conducte d a re-evaluation of the heavy duty diesel truck emissions inventory to support th e Proposed Regulation to Reduce

Emissions from In-Use On-Road Diesel Vehicles. In developing this new analysis, staff has integrated new data and assumptions into an exp anded methodology that builds upon current modeling in EMFAC2007. The updated in ventory categorizes heavy-duty vehicles into separate inventory groups by body typ e and operational characteristics while keeping the existing weight class based vehic le categories (medium-heavy and heavy-heavy duty vehicle classes). Within the exis ting weight class groups, the updated inventory categorizes vehicles into Califor nia registered and out-of-state registered vehicles. California registered trucks are further split into intrastate and interstate trucks while the out-of-state registered trucks are split into trucks based in neighboring states and trucks based in non-neighbor ing states. The intrastate trucks are further sub-grouped by body type into single un it trucks and tractors. Also within the intrastate trucks separate inventories are develope d for agricultural trucks, port trucks, solid waste collection vehicles, and public and uti lity fleets. A detailed discussion of the inventory development and data sources used is foun d in Appendix G, of the “ Staff Report: Initial Statement Of Reasons For Proposed Rulemaking Proposed Regulation

For In-Use On-Road Diesel Vehicles ” (ARB, 2008a).

The new baseline inventory for selected calendar ye ars is shown in Table C-1 and C-3. Staff used this updated inventory as the basis for developing inventory for this proposal. Since only a subset of the total heavy-duty vehicle inventory is affected by the proposed regulation, the base inventory must be adjusted to determine the fraction of vehicles affected by this proposal. Furthermore, since the proposed regulation applies only to

Class 7 and 8 tractors 2 , the medium-heavy duty diesel vehicle inventory sh own in Table

1 http://www.census.gov/svsd/www/vius/products.html

2 Class 7 tractors are tractors with gross vehicle w eight rating between 26,001 and 33,000 pounds while Class 8 tractors’ are tractors with gr oss vehicle weigh rating of 33,001 pounds and greater.C-3

C-2, must be adjusted to include only Class 7 tract ors. Table C-3 also shows the baseline population and the fraction of VMT accrued inside California by out-of-state, California interstate, and California intrastate he avy-duty vehicles (ARB, 2008a).

Table C-1 – Baseline Class 8 Tractors (ARB, 2008a)

Class 8 Tractors(Gross Vehicle Weight Rating > 33,0 00 pounds)

Non-neighboring

Out-of-state

Tractors Neighboring

Out-of-state

Tractors CA

Interstate

Tractors CA

Intrastate

Tractors

CY Population

2010 469,323 43,049 62,239 66,037

2015 543,681 51,132 73,924 78,519

2020 626,853 58,008 83,866 89,294

CY Vehicle Miles Traveled (10 6 miles per Year)

2010 3,935 1,274 2,673 3,360

2015 4,661 1,509 3,166 3,980

2020 5,316 1,721 3,611 4,540

Table C-2 – Medium-Heavy Duty Diesel Vehicles (ARB, 2008a).

Medium-Heavy Duty Diesel Vehicles (Gross Vehicle Weight Rating between 14,001 and 33, 000 pounds)

Out-of-State CA Interstate CA intrastate

CY Population
2010 7,631 1,752 209,116
2015 8,282 1,901 227,426
2020 8,898 2,042 244,223

CY Vehicle Miles Traveled (10 6 miles per Year)
2010 14 24 4,146
2015 15 27 4,517
2020 16 28 4,846C-4 Table C-3 – Population and CA Share of VMT (ARB, 20 08a)

CY Category Population CA Share of VMT

Heavy-Heavy Duty Vehicles

2008 Out-of-State Tractors 492,340 12.1%

2008 CA Interstate Tractors 60,263 57.0%

2008 CA Intrastate Tractors 63,684 100%

Medium-Heavy Duty Vehicles

2008 Medium-Heavy Intrastate 198,525 100%

2008 Medium-Heavy Interstate 8,896 18.7%

2. 2002 Vehicle Inventory and Use Survey

The VIUS is a stratified statistical data of the na tion’s trucking fleet collected every 5 years by the Bureau of Census as part of the econom ic census (Census, 2002). It provides data, at the state and national level, on the physical and operational characteristics of registered private and commercia l trucks. Since the state of registration of the truck is provided, a statistica l profile of the truck fleet by state can be developed and analyzed to determine the characteris tics of the state’s trucking fleet. The last survey was conducted in 2002.

3. Bureau of Census, Current Industrial Reports (CI R):

The U.S. Bureau of Census CIR program provides peri odic reports on production and shipment of selected products. The CIR provides da ta on factory shipments of complete truck trailers between 1988 and 2000 (Cens us, 2000). Staff used these data to determine the fraction of box-type trailers sold each year.

4. ACT Research, LLC.

ACT Research collects commercial vehicle data from manufacturers

, analyses it, and disseminates the results to its subscribers. Among other things, it collects and analyzes

data related to North American Class 8 trucks and t railers. Among other things, it collects and analyses data related to North America n Class 8 trucks and tractors and trailers. ACT provided staff with information on t he fraction of 53-foot or longer box-type

trailers sold nationwide.

5. Commercial Carrier Magazine (CCJ)

CCJ magazine, published monthly by Randall Reilly P ublishing Company, LLC, provides news and business information for professi onals responsible for running trucking companies and maintaining equipment. The CCJ publishes once a year, information on the nation’s top freight carriers, i ncluding the number of tractors andC-5

trailers owned by each company. Carrier performanc e data from the August 2007 and August 2008 issues of CCJ were used to assess the a verage ratio of trailers to tractors. Staff used these data to approximate the trailer to tractor ratio which was used to determine the total number of trailers affected by this rule.

B. Fraction of Long Haul Tractors

The VIUS data (Census, 2000) were used to determine the fraction of long haul tractors by base state of registration for California intras tate, California interstate, and neighboring out-of-state tractors. Since ARB inven tory does not provide a separate inventory for Class 7 trucks, staff also used the V IUS data to determine the fraction of medium-heavy duty vehicles that are long haul Class 7 tractors.

Specifically, the VIUS data provided staff with inf ormation on (1) the primary range of operation (to determine the percentage of vehicles with a primary range of operation greater than 100 miles), and (2) jurisdiction in wh ich the vehicle was most driven (to determine whether fleets operate interstate or excl usively intrastate). As shown in Table C-4, this information was used by staff to co nclude that 23 percent of California’s intrastate tractors and 71 percent of California’s interstate tractors range of operation to be greater than 100 miles. For out-of-state regist ered tractors, 69 percent of tractors registered in neighboring states are affected, whil e 100 percent of non-neighboring states that operate in California are affected. In addition, analysis of VIUS data provided that approximately 5 percent of the total medium-heavy duty diesel vehicles are Class 7 tractors with primary range of operatio n greater than 100 miles (Census, 2002).

The VIUS database was also used to determine the VM T fraction accrued by tractors with primary range of operation greater than 100 mi les, shown in Table C-4. This VMT fraction was applied to the baseline vehicle miles traveled provided by ARB inventory (discussed in A.1 above) to determine the total VMT accrued by the long haul tractors.

Table C-4 - Percentage of Class 7 and 8 Tractors wi th Primary Range of Operation

Greater than 100 Miles and their VMT fraction

Fleet Percentage of Tractors

with Primary Range of Operation > 100 Miles Percentage of VMT by Tractors with Primary Range of Operation > 100 Miles

CA Intrastate 23% 34%

CA Interstate 71% 80%

Neighboring

Out-of-State 69% 84%

Non-neighboring
Out-of-State 100% 100%C-6

C. Fraction of Long Haul Tractors that Pull 53-Foot or Longer Box-Type

Trailers

Staff analyzed trailer production data from the 199 7 to 2000 CIR reports (Census, 2000), which showed that the percentage of box-type trailers sold each year from 1988 to 2000 varied from 70 to 77 percent with an overal l average of 73 percent. As shown in Table C-5, staff assumed that this average was a ppropriate for California intrastate, interstate, and neighboring out-of-state fleets ope rating in California. It was also assumed that since essentially all non-neighboring out-of-state tractors pull loads for greater distances, it would be appropriate to assum e that more than 73 percent are boxtype. Staff assumed that 90 percent of these tract ors pull box-type trailers. The fractions shown in Table C-5 include all box-type t railers of all lengths. To determine the fraction that are 53-foot or longer, staff cons ulted two trailer manufacturers and ACT

Research. The two trailer manufacturers indicated that 90 percent or more of the boxtype trailers to be 53-foot or longer. According t o ACT Research, 85 to 90 percent of refrigerated van and dry van trailers are 53-foot o r longer (Vieth, 2008). Based on this information, staff assumes that 85 percent of the b ox-type trailers pulled by California intrastate, interstate, and neighboring out-of-stat e tractors, and 90 percent of those pulled by non-neighboring out-of-state tractors are 53-foot or longer.

Table C-5 - Percentage of 53-Foot Box Type Trailers

Fleet Percent Box-Type

Trailers Percent that are

53-foot or Longer

CA Intrastate 73 85

CA Interstate 73 85

Neighboring

Out-of-State 73 85

Non-neighboring

Out-of-State 90 90

Based on the above assumptions (Tables C-4 to C-5) and the baseline population and VMT provided by ARB inventory (ARB, 2008a), the tra ctor population impacted by the proposed regulation and the corresponding VMT are c alculated and shown in Table C-6 for calendar years 2010 and 2020.C-7

Table C-6: 2010 and 2020 Impacted Tractor Populati on and the Corresponding

Annual VMT

Impacted Tractor Population Annual VMT

(10 6 miles) Fleet

2010 2020 2010 2020

CA Intrastate 9,547 12,910 705 952

CA Interstate 27,462 37,005 1,320 1,783

Neighboring Out-of-State 18,525 24,962 663 896

Non-neighboring Out-of-State 380,152 507,751 3,187 4,306

Total 435,686 582,628 5,875 7,937

D. Impacted Box-Type Trailer Population

Available data were used to estimate the number of tractors that would be impacted by the proposed rule, as discussed above. For trailer s, no database exists that provides a complete inventory on the total number of box-type trailers that would be impacted by the proposed rule. The ratio of trailers-to-tracto rs in many fleets is often not one-to-one (in which case the same numbers provided in Table C -6 for tractors could have been used to estimate trailer inventory). The ratio var ies considerably from fleet to fleet. Many fleets typically own more trailers than tracto rs in order to maximize efficiency and reduce downtime for the tractor while waiting for t he trailer to be loaded and unloaded. The ratio varies from zero for some owner-operators that own only tractors and pull trailers owned by other businesses, to “infinity” f or some shippers that own only trailers and use the services of carriers to pull their trai lers. Since data describing the tractortrailer composition of all fleets that operate in C alifornia were not available, staff determined an approximate trailer-to-tractor ratio using data from annual CCJ publications (Vise, 2007; Vise, 2008). The publish ed data included the number of trailers and tractors owned by the top 250 carriers in the country in calendar years 2006 and 2007. Analysis of the two annual datasets prov ided an estimated ratio of 2.5-to-1 trailers to tractors for both years.

The number of box-type trailers impacted by the pro posed rule was then estimated by multiplying the trailer-to-tractor ratio of 2.5 by the number of tractors impacted by the proposed rule shown in Table C-6. Table C-7 shows the resulting 53-foot box-type trailer population impacted by staff’s proposal for calendar years 2010 and 2020.C-8 Table C-7: 2010 and 2020 Impacted 53-Foot Box-Type Trailers

Fleet 2010 2020

CA Intrastate 23,868 32,275

CA Interstate 68,655 92,513

Neighboring Out-of-State 46,313 62,405

Non-neighboring Out-of-State 950,380 1,269,378

Total 1,089,215 1,456,570

E. Estimated GHG Benefits

The GHGs associated with diesel exhaust are CO 2 , methane, and nitrous oxide, with

CO 2 being the major component of the three. Since CO 2 is emitted in direct proportion to the fuel combusted, any reduction in CO 2 emissions requires reduction in the fuel burned to propel the vehicle. The proposed regulat ion would reduce GHG emissions by reducing the fuel consumption of HDVs achieved thro ugh improvements in aerodynamic drag and tire rolling resistance. The GHG reductio ns would contribute towards attaining AB 32 goals for the year 2020.

The following equation was used to calculate the GH G reductions from the proposed regulation.

CO 2 e Reduced = Fuel Savings*EF/1000 (Equation C-1)

Where: CO 2 e Reduced = average annual reduction in GHGs in met ric tons CO 2 e Fuel Savings = Annual fuel savings in gallons per year EF = GHG emission factor from diesel fuel combusti on (10.4 kilograms CO 2 e

per gallon of diesel fuel (ARB, 2008c)) 1000 = Conversion factor from kilograms (kg) to met ric tons (1000 kg = 1 MT)

Annual Fuel Savings : The annual fuel savings is determined from the p ercent fuel efficiency improvement, annual VMT, and the baselin e fuel economy, as follows:

Fuel Savings (gallons/year) = Annual VMT*%FS/FE

Where: Annual VMT is the vehicle miles traveled per year %FS is the fuel consumption improvement due to impr ovements in aerodynamic drag and rolling resistance. FE is the fuel economy in miles per gallon.

Percent Fuel Efficiency Improvements : The percent fuel efficiency improvements used to quantify the GHG benefits are shown in Tabl e C-8. These were determinedC-9

based on the minimum aerodynamic and tire rolling r esistance performance requirements specified in the proposed regulation. For example, the proposed regulation would require a minimum fuel efficiency improvement of 3 percent from lowrolling resistance tires on the combined tractor an d the trailer, a minimum of 4 percent from trailer side skirts, and a minimum of 1 percen t from front or rear gap fairings on dry-van trailers. Thus, for this example, an in-us e pre-2011 model year tractor pulling a dry-van trailer would achieve an overall fuel effic iency improvement of 8 percent, as

shown in Table C-8.

The fuel efficiency improvements of currently certi fied aerodynamic devices are determined from track tests conducted at speeds of 60 to 62 miles per hour and utilizing the “SAE J1321 Type II” test procedures. These aer odynamic devices also reduce drag at lower speeds, though to a lesser extent, since a erodynamic drag varies with the square of the vehicle speed.

Annual VMT

: The annual VMT applicable to tractors pulling 53 -foot or longer box-type trailers was determined using the baseline VMT (ARB , 2008a) and the factors shown in Tables C-3 to C-5. However, the resulting total VM T cannot be directly applied to the fuel efficiency improvements shown in Table C-8, si nce the VMT is accrued at various speeds, while the fuel efficiency improvements are determined at speeds of approximately 60 miles per hour. Thus, the speed-V MT distribution of the impacted tractors and fuel efficiency improvements at differ ent speeds are needed in order to accurately quantify the GHG emission benefits. Howe ver, such data were not available

and therefore staff estimated the GHG benefits usin g only the VMT accrued at highway speeds, without taking into account benefits that o ccur at lower speeds. Accordingly, for non-neighboring out-of-state tractors, staff as sumed 85 percent of the VMT to be at highway speeds, since these tractors travel long di stances, spending the majority of their VMT at highway speeds. For neighboring out-o f-state, California interstate, and California intrastate tractors, staff assumed 75 pe rcent of the VMT to be at highway speeds, benefiting fully for 75 percent of the VMT from the aerodynamic devices and low rolling resistance tires.C-10

Table C-8: Fuel Efficiency Improvements – Based on Proposed Requirements

Tractor Improvements Trailer Improvements 3 Fuel Savings

1 2011+ model year SmartWay certified sleeper cab tractor (3.5%) Dry-van trailer – SmartWay certified or

retrofitted with side skirts and front gap fairings (6.5%) 10.0%

2 2011+ model year SmartWay certified sleeper cab tractor (3.5%) Refrigerated-van trailer – SmartWay certified or

retrofitted with side skirt (5.5%) 9.0%

3 2011+ model year day cab tractors and all pre-2011 model year in-use tractors - Tire Improvements (1.5%) Dry-van trailer – SmartWay certified or

retrofitted with side skirts and front gap fairings (6.5%) 8.0%

4 2011+ model year day cab tractors and all pre-2011 model year in-use tractors - Tire Improvements (1.5%) Refrigerated-van trailer – SmartWay certified or

retrofitted with a side skirt (5.5%) 7.0%

Fuel Economy of On-Road Heavy-Duty Diesel Vehicles in California ARB staff has recently reviewed multiple data sourc es to characterize the variations in the fuel economy values of heavy-duty tractors in C alifornia, including data from the United States Department of Energy (U.S. DOE, 2007) , Coordinating Research Council E55/59 study by West Virginia University (CRC, 2007 ), the International Fuel Tax Agreement for trucks operating in California, and C onsent Decree, in-use study by West Virginia University. The detailed methodology and results are discussed in Appendix G,

of the “ Staff Report: Initial Statement Of Reasons For Pro posed Rulemaking Proposed Regulation For In-Use On-Road Diesel Vehicles ” (ARB, 2008a). Results of the analysis, presented in Tables C-9, were used to est imate fuel savings and GHG emission benefits for this proposal.

3 The trailer aerodynamic technologies specified in the table are meant for illustration purposes. Fleets can meet the requirements using other aerody namic technologies that meet or exceed the minimum performance requirements.C-11 Table C-9 - Fuel Economy Values by Model Year

Model Year Fuel Economy

(miles per gallon) Model Year Fuel Economy (miles per gallon)

Pre-1988 5.20 2003-2006 5.75

1988-1990 5.39 2007 5.61

1991-1993 5.58 2008 5.59

1994-1995 5.76 2009 5.58

1996 5.95 2010 5.78

1997-1998 5.95 2011 5.78

1999-2002 5.48 2012 5.80

For the purposes of quantifying the emission reduct ions, staff also assumed that all fleets would adopt the large fleet trailer complian ce plan which provides a compliance option for in-use pre-2011 trailers based on a phas e-in schedule specified in Appendix F of this report. Staff also assumed that in the abs ence of the proposed regulation, 20 percent of the tractors sold each year from 2010 to 2020 would be SmartWay certified and 25 percent of the in-use pre-2011 model year tr actors would use fuel efficient tires.

The GHG emission benefits were calculated for the y ears 2010 to 2020 based on VMT

accrued within California and nationwide. Table C- 10 summarizes the 2010, 2015, and

2020 statewide and nationwide GHG emission benefits of the proposed regulation. Staff estimates that from 2010 to 2020, as new fuel efficient tractors and trailers are

introduced and in-use ones retrofitted with fuel ef ficient technologies, GHG emissions will be reduced by a cumulative total of approximat ely 8 MMT CO 2 e statewide and approximately 52 MMT CO 2 e nationwide. The 2020 benefits are approximately 1 MMT
CO 2 e statewide and 7 MMT CO 2 e nationwide. Figure C-1 shows the statewide basel ine and controlled GHG emissions for calendar years 201 0 to 2020. As seen in Figure C-1, GHG emissions from long-haul tractors continue to i ncrease even with implementation of the proposed regulation because the trucking ind ustry will grow substantially between now and 2020 (ARB, 2008a).C-12

Table C-10: 2010, 2015, and 2020 GHG Emission Bene fits - Statewide and Nationwide (MMT CO 2 e)

California Nationwide

Calendar Year Baseline Reductions Baseline Reductio ns

2010 8.5 0.2 55.6 0.9

2015 10.1 0.8 65.7 5.5

2020 11.4 1.0 74.6 6.7

7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0

2009 2011 2013 2015 2017 2019 2021

Calendar YearGHG Tailpipe Emissions(MMTCO2e) Baseline

With Regulation

Figure C-1. Statewide GHG Emissions With and Witho ut the Regulation (Longhaul tractor pulling 53-foot box-type trailers)

Estimated Oxides of Nitrogen (NOx) Emission Benefit s In addition to GHG benefits, reducing aerodynamic d rag and rolling resistance also reduces NOx emissions (Bachman, 2005; Bachman, 2006 ). Thus, the proposed regulation is expected to provide NOx emission redu ction benefits that would contribute towards attainment of ambient air quality standards for ozone. Staff used theC-13

methodology specified in the U.S. EPA SmartWay Stat e Implementation Plan (SIP) and Transportation Conformity guidance document (U.S. E PA, 2007) to quantify the NOx emission benefits from the proposed regulation.

Because the effects of the SmartWay technologies on NOx emissions of trucks with particulate matter and NOx aftertreatment controls is not yet determined, the U.S. EPA recommends that, for SIP and conformity determinati ons, the NOx reductions not be applied to trucks of model years newer than 2006. Furthermore, the NOx emission reductions associated with SmartWay retrofit applic ations vary by speed, requiring the VMT to be distributed by speed. Since speed distri bution data for the fleet that is impacted by the proposed regulation were not availa ble, staff made the following assumptions on VMT-speed distribution of long-haul tractors. That is, for nonneighboring out-of-state tractors, staff assumed 85 percent of the VMT to be at highway speeds and a corresponding NOx reduction of 9.5 per cent. For the remaining 15 percent of the VMT staff assumed an average speed o f 35 miles per hour and a NOx reduction of 4.6 percent. For California intrastat e, California interstate, and neighboring out-of-state tractors, staff assumed 75 percent of the VMT to be at highway speeds and a corresponding NOx reduction of 9.5 percent. For the remaining 25 percent of the VMT, staff assumed an average speed of 35 miles per hour and a corresponding NOx reduction of 4.6 percent. Based on these assumptio ns and U.S. EPA guidelines, California specific NOx reductions were estimated t o be 4.3 and 1.4 tons per day in 2014 and 2020 respectively. These reductions assum e a “business as usual” scenario, where they do not take into account the impact of o ther proposed regulations that would impact NOx emissions.C-14

F. References

ARB, 2006. California Air Resources Board. EMFAC2 007. Available at: http://www.arb.ca.gov/msei/onroad/latest_version.ht m Last Accessed: October
22,2008.

ARB, 2008a. California Air Resources Board. Staff Report: Initial Statement Of Reasons For Proposed Rulemaking. Proposed Regulati on For In-Use On-Road Diesel Vehicles. Appendix G – Emissions Inventory Methodology and Results

. Sacramento: October 2008.

ARB, 2008c. California Air Resources Board. Climate Change Proposed Scoping Plan. Appendices Volume II: Analysis and Documentation. (Appendix II, p.I-6).

Sacramento: October 2008

. http://www.arb.ca.gov/cc/scopingplan/document/scopi ngplandocument.htm

Bachman, 2005. Bachman, Leon J., Anthony Erb, Cher yl Bynum. Effect of Single Wide Tires and Trailer Aerodynamics on Fuel Economy and NOx Emissions of Class 8

Line-Haul Tractor-Trailers. Society of Automotive Engineer 2005-01-3551 http://www.epa.gov/smartway/transport/documents/tec h/effects-on-fuel-economy.pdf

Bachman, 2006. Bachman , L J., A. Erb, C. Bynum, B. Shoffner, H. De La Fuente, C.

Ensfield. Fuel Economy Improvements and NOx Reduction by Redu ction of Parasitic Losses: Effect of Engine Design. Society of Automotive Engineer, 2006-

01-3474. http://www.epa.gov/smartway/transport/documents/tec h/fuel-economyimprovements.pdf

Census, 2000. Bureau of Census. Current Industrial Reports, M336L - Truck Trailers. http://www.census.gov/cir/www/336/m336l.html

Census, 2002. United States Bureau of Census. 2002 Vehicle Inventory and Use Survey Microdata. http://www.census.gov/svsd/www/vius/products.html

CRC, 2007. Coordinating Research Council, Inc. Heavy-Duty Vehicle Chassis Dynamometer Testing for Emissions Inventory, Air Qu ality Modeling, Source Apportionment and Air Toxics Emissions Inventory. August 2007. Available at: http://www.crcao.com/reports/recentstudies2007/E-55 -59/E55_59_Final_Report_23AUG2007.pdf

U.S. DOE, 2008. Department of Energy, Oak Ridge Na tional Laboratory. Transportation Energy Data Book: Edition 27. ORNL 6891. http://www-cta.ornl.gov/data/tedb27/Edition27_Cover .pdf

U.S. EPA, 2007. U.S. Environmental Protection Agen cy. SmartWay SIP and Transportation Conformity Guidance: Accounting for NOx Reductions from TrailerC-15

Aerodynamic Kits and Low Rolling Resistance Tires. EPA420-B-07-004.

June 2007. www.epa.gov/otaq/stateresources/transconf/policy/42 0b07004.pdf

Vieth, 2008. Vieth, Ken. Telephone Communication with Mr. Ken Vieth, Senior Partner and General Manager of Americas Commercial Transpor tation Research co., LLC (ACT Research). July 2, 2008

Vise, 2007. Vise, Avery. The CCJ Top 250: Mediocre at Best

. Commercial Carrier

Journal . August 2007. pp. 61-110. http://www.rrpub.com/etrucker/ccj/ccj0807_250.pdf

Vise, 2008. Vise, Avery. The CCJ Top 250: Slower But Solid. Commercial Carri er Journal . August 2008. pp. 52-103. http://www.rrpub.com/ccj/pdfs/top250_07.pdf