Response to Comments: 

Fuel Economy Labeling of Motor Vehicles 

Office of Transportation and Air Quality 

EPA420-R-06-016 

December 2006 
Response to Comments: 

Fuel Economy Labeling of Motor Vehicles 

Assessment and Standards Division 

and 

Certification and Innovative Strategies Division 

Office of Transportation and Air Quality 

U.S. Environmental Protection Agency 

EPA420-R-06-016 

December 2006 
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Table of Contents

LIST OF COMMENTING ORGANIZATIONS AND ABBREVIATIONS .........................................................iv

COMMENTS SUBMITTED DURING THE COMMENT PERIOD ........................................................................................iv

COMMENTS SUBMITTED AFTER THE CLOSE OF THECOMMENT PERIOD ....................................................................vi

PUBLIC HEARING TESTIMONY........................................................................................................................ vii

INTRODUCTION.......................................................................................................................................................1

CHAPTER 1: GENERAL ISSUES........................................................................................................................2

1.1 GENERALCOMMENTS SUPPORTINGPROPOSAL...........................................................................................2

1.2 GENERALCOMMENTS OPPOSING PROPOSAL...............................................................................................3

1.3 ESTIMATES ARE BASED ON CONTROLLED,REPEATABLE TESTS .................................................................4

1.4 THERE IS NO PERFECT TEST........................................................................................................................5

1.5 CAFE PROGRAM.........................................................................................................................................5

1.6 SHOULD LABEL ESTIMATE COVER 50TH OR 75TH PERCENTILE?....................................................................7

1.7 PUBLIC AVAILABILITY OF FUEL ECONOMY TEST DATA..............................................................................8

1.8 OVERALL PURPOSE OF FUEL ECONOMY ESTIMATES ...................................................................................8

1.9 SMALL VOLUME MANUFACTURERS ............................................................................................................9

1.10 TYPOGRAPHICAL ERRORS AND REGULATORY REFERENCES......................................................................10

1.11 MISCELLANEOUS REGULATORY COMMENTS.............................................................................................12

1.12 DAYTIME RUNNING LIGHTS ......................................................................................................................13

CHAPTER 2: LABEL FORMAT AND CONTENT ..........................................................................................14

2.1 GENERAL LABEL PREFERENCES................................................................................................................14

2.2 LABELFORMAT EFFECTIVE DATE.............................................................................................................17

2.3 LABELCONTENT ISSUES ...........................................................................................................................19

2.3.1 Fuel Economy of Comparable Vehicles...............................................................................................19

2.3.2 Estimated Annual Fuel Cost................................................................................................................23

2.3.3 Combined Fuel Economy Calculation.................................................................................................25

2.3.4 Range of Expected Fuel Economy .......................................................................................................26

2.3.5 “Your Mileage Will Vary” Statement..................................................................................................27

2.3.6 Graphical Updates and Government Logos ........................................................................................28

2.3.7 Environmental Information on Fuel Economy Labels.........................................................................29

2.3.8 Vehicle Descriptor Information...........................................................................................................31

2.3.9 Website Reference................................................................................................................................32

2.3.10 Transition Language.......................................................................................................................33

2.3.11 City and Highway Numbers............................................................................................................34

2.4 LABELSIZE AND ORIENTATION ISSUES.....................................................................................................34

2.5 IMPLEMENTATION OUTREACH...................................................................................................................35

2.6 COMPARABLE CLASS DESIGNATIONS ........................................................................................................36

2.7 LABELING REQUIREMENTS FOR DUAL FUELED VEHICLES ........................................................................38

CHAPTER 3: IMPLEMENTATION ISSUES ....................................................................................................40

3.1 IN-USE VALIDATION OF 5-CYCLE COEFFICIENTS ......................................................................................40

3.2 PERIODIC REVIEW AND UPDATING OF THE MPG-BASED CURVES ..............................................................44

3.3 USE OFBAG DATA FACTORS IN THE 5-CYCLE EQUATIONS .......................................................................45

3.4 FLEXIBILITY TO APPLY THE MPG-BASED ADJUSTMENTS AT THE MODEL TYPE LEVEL .............................46

3.5 CRITERIA FOR ADDITIONAL 20°F / SFTP TESTING....................................................................................47

3.6 ANALYTICALLY DERIVED FUEL ECONOMY...............................................................................................49

3.7 CONSUMER EDUCATION ISSUES ................................................................................................................50

3.8 GOVERNMENT-INDUSTRYWORKING GROUPS...........................................................................................51

3.9 WHEN CITY FUEL ECONOMY IS GREATER THAN HIGHWAY FUEL ECONOMY ...........................................51

3.10 TECHNOLOGY-SPECIFIC, MODEL-SPECIFIC, OR MANUFACTURER-SPECIFIC ADJUSTMENT FACTORS ........52
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3.11 USE OF FUEL ECONOMY ESTIMATES IN ADVERTISING ..............................................................................55

CHAPTER 4: OTHER RELATED PROPOSALS .............................................................................................56

4.1 VOLUNTARY FUEL ECONOMY LABELING FOR VEHICLES EXCEEDING 8500 POUNDS GROSS VEHICLE

WEIGHT RATING......................................................................................................................................................56

4.2 ELECTRONIC DISTRIBUTION OF DEALER-SUPPLIED FUEL ECONOMY BOOKLET........................................59

4.3 CONSIDERATION OF FUEL CONSUMPTION VS. FUEL ECONOMY AS A METRIC............................................60

4.4 WEB-BASED DRIVER-SPECIFIC FUEL ECONOMY CALCULATOR.................................................................62

CHAPTER 5: CITY AND HIGHWAY FUEL ECONOMY ESTIMATES AND METHODOLOGY ..........64

5.1 THE PROPOSED FORMULAE ARE COMPLEX ...............................................................................................64

5.2 VALIDATION OF THE 5-CYCLE FORMULAE FOR INDIVIDUAL VEHICLES .....................................................65

5.3 SOME FORMULAE COEFFICIENTS ARE COUNTER-INTUITIVE......................................................................73

5.4 START FUEL USE MAY NOT BE ACCURATE ON PER VEHICLE BASIS.........................................................78

5.5 RELATIVE ACCURACY OF THE MPG-BASED EQUATIONS VERSUS THE 5-CYCLE FORMULAE FOR

INDIVIDUAL VEHICLES ............................................................................................................................................79

5.6 MPG-BASED OR “GENERIC” ADJUSTMENTS TO FTP AND HFET ................................................................82

5.7 THE THREE NEW TEST CYCLES ARE EXTREME .........................................................................................83

5.8 WEIGHTING OF NEW CYCLES....................................................................................................................86

5.9 INTERPOLATION OF FUEL ECONOMY USING FIVE CYCLES ........................................................................87

5.10 MISUSE OF EMISSION FACTOR MODELS ....................................................................................................99

5.11 DERIVATION OFVEHICLE-SPECIFIC 5-CYCLE METHOD ..........................................................................102

5.11.1 Start Fuel Use ...............................................................................................................................102

5.11.1.1 Start Fuel..................................................................................................................................................102

5.11.1.2 Trip Length.............................................................................................................................................. 104

5.11.1.3 Formula for Start Fuel Use....................................................................................................................... 109

5.11.2 Running Fuel Use..........................................................................................................................110

5.11.2.2 Representative Mix of Dynamometer Driving Cycles............................................................................. 110

5.11.3 Effect of Air Conditioning on Fuel Economy................................................................................116

5.11.3.1 Approximating Excess Fuel Use Due to Air Conditioning...................................................................... 116

5.11.3.2 Available In-Use Data and Analysis ........................................................................................................118

5.11.3.3 Driver Behavior.......................................................................................................................................120

5.11.3.4 Accounting for Energy Reduction Technologies..................................................................................... 121

5.11.3.5 Temperature Impact on Compressor Power.............................................................................................124

5.11.3.6 Estimates of National A/C and Defroster Use..........................................................................................125

5.11.4 Effect of Cold Temperatures on Fuel Economy ............................................................................126

5.11.5 Adjustment Factor for Non-Dynamometer Effects........................................................................129

5.11.6 mpg Approach Equation Tolerances.............................................................................................131

5.12 ONROAD FUEL ECONOMY ESTIMATES BY OTHER ORGANIZATIONS ........................................................135

CHAPTER 6: TESTING PROVISIONS...........................................................................................................143

6.1 GENERAL TEST PROCEDURE ISSUES ........................................................................................................143

6.2 TEST REQUIREMENTS FOR VEHICLES CURRENTLY EXEMPT FROM CERTAIN EMISSIONS TESTS ..............145

6.2.1 Diesel Vehicles...................................................................................................................................145

6.2.2 Alternative-Fueled Vehicles...............................................................................................................147

6.3 MODIFICATIONS TO EXISTING TEST PROCEDURES ..................................................................................147

6.3.1 Revisions to US06 Bag Measurements...............................................................................................147

6.3.2 Heater/Defroster Use During the Cold FTP......................................................................................150

6.3.3 4-Phase, 4-Bag FTP for Gasoline-Electric Hybrid Vehicles.............................................................152

6.4 TEST FUELS .............................................................................................................................................156

6.5 HYBRID-ELECTRIC VEHICLEBATTERY STATE OFCHARGE .....................................................................157

CHAPTER 7: COST ANALYSIS.......................................................................................................................159

7.1 TESTING BURDEN....................................................................................................................................159

7.1.1 Testing Burden for Small Manufacturers...........................................................................................159

7.1.2 2008 – 2010 Model Year Testing Costs: Testing Issues....................................................................160

7.1.3 2011 and Later Model Year Testing Costs: Inclusion of MDPVs......................................................161
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7.2 FACILITIES COSTS ............................................................................................................................................162

7.2.1 Facility Upgrades for Cold FTP Testing ................................................................................................162

7.3 STARTUP BURDEN............................................................................................................................................163

7.3.1 Dual Information Systems for CAFE/Gas Guzzler and Label Calculations.........................................163

7.3.2 Additional Startup Costs.........................................................................................................................164
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List of Commenting Organizations and Abbreviations

The abbreviations and annotations in this list are used throughout this document to refer

to various organizations that submitted written and/or oral comments on the proposed

rulemaking. We also received comments from more than 2,800 members of the public.

Comments Submitted During the Comment Period

Organization Abbreviation Docket Document Number

Alliance of Automobile Manufacturers AAM EPA-HQ-OAR-2005-0169-0110

EPA-HQ-OAR-2005-0169-0110.1

American Automobile Association AAA EPA-HQ-OAR-2005-0169-0105

EPA-HQ-OAR-2005-0169-0105.1

American Council for an Energy-Efficient

Economy

ACEEE EPA-HQ-OAR-2005-0169-0119

EPA-HQ-OAR-2005-0169-0119.1

EPA-HQ-OAR-2005-0169-0119.2

American Honda Motor Co., Inc. Honda EPA-HQ-OAR-2005-0169-0115

EPA-HQ-OAR-2005-0169-0115.1

Association of International Automobile

Manufacturers

AIAM EPA-HQ-OAR-2005-0169-0110

EPA-HQ-OAR-2005-0169-0110.1

Bluewater Network Bluewater EPA-HQ-OAR-2005-0169-0100

Consumers Union CU EPA-HQ-OAR-2005-0169-0137

DaimlerChrysler DCX EPA-HQ-OAR-2005-0169-0121

EPA-HQ-OAR-2005-0169-0121.1

Delphi LLC Delphi EPA-HQ-OAR-2005-0169-0116

EPA-HQ-OAR-2005-0169-0116.1

Environmental Defense ED EPA-HQ-OAR-2005-0169-0124

EPA-HQ-OAR-2005-0169-0124.1

EPA-HQ-OAR-2005-0169-0138

Ferrari S.p.A. Ferrari EPA-HQ-OAR-2005-0169-0112.1

Fuji Heavy Industries USA, Inc. (Subaru of

America)

Subaru EPA-HQ-OAR-2005-0169-0114

EPA-HQ-OAR-2005-0169-0114.1

EPA-HQ-OAR-2005-0169-0114.2

General Motors Corporation GM EPA-HQ-OAR-2005-0169-0106

EPA-HQ-OAR-2005-0169-0106.1

Mitsubishi Motors Mitsubishi EPA-HQ-OAR-2005-0169-0125

EPA-HQ-OAR-2005-0169-0125.1

Montana Coalition for Health, Environmental &

Economic Rights

Montana

CHEER

EPA-HQ-OAR-2005-0169-0072
v

Organization Abbreviation Docket Document Number

National Automobile Dealers Association NADA EPA-HQ-OAR-2005-0169-0131

EPA-HQ-OAR-2005-0169-0131.1

EPA-HQ-OAR-2005-0169-0131.2

EPA-HQ-OAR-2005-0169-0131.3

EPA-HQ-OAR-2005-0169-0131.4

National Renewable Energy Laboratory NREL EPA-HQ-OAR-2005-0169-0108

EPA-HQ-OAR-2005-0169-0108.1

Natural Resources Canada, Transportation

Energy Use Division

NRC-TEUD EPA-HQ-OAR-2005-0169-0109

EPA-HQ-OAR-2005-0169-0109.1

Natural Resources Defense Council NRDC EPA-HQ-OAR-2005-0169-0117

EPA-HQ-OAR-2005-0169-0117.1

EPA-HQ-OAR-2005-0169-0135

EPA-HQ-OAR-2005-0169-0128

EPA-HQ-OAR-2005-0169-0128.1

New York State Department of Environmental

Conservation

NYDEC EPA-HQ-OAR-2005-0169-0078

EPA-HQ-OAR-2005-0169-0078.1

Nissan Motor Company Limited Nissan EPA-HQ-OAR-2005-0169-0113

EPA-HQ-OAR-2005-0169-0113.1

PPG Industries PPG EPA-HQ-OAR-2005-0169-0130

Public Citizen PC EPA-HQ-OAR-2005-0169-0123.1

EPA-HQ-OAR-2005-0169-0128

EPA-HQ-OAR-2005-0169-0128.1

Toyota Motor Corporation Toyota EPA-HQ-OAR-2005-0169-0118

EPA-HQ-OAR-2005-0169-0118.1

EPA-HQ-OAR-2005-0169-0136

Union of Concerned Scientists UCS EPA-HQ-OAR-2005-0169-0127

EPA-HQ-OAR-2005-0169-0127.1

EPA-HQ-OAR-2005-0169-0128

EPA-HQ-OAR-2005-0169-0128.1

Volkswagen of America, Inc. VW EPA-HQ-OAR-2005-0169-0120
vi

Comments Submitted after the Close of the Comment Period

Organization Abbreviation Docket Document Number

American Honda Motor Co., Inc. Honda EPA-HQ-OAR-2005-0169-0143

Ford Motor Company Ford EPA-HQ-OAR-2005-0169-0141

Alliance of Automobile Manufacturers AAM EPA-HQ-OAR-2005-0169-0142

EPA-HQ-OAR-2005-0169-0142.1

EPA-HQ-OAR-2005-0169-0142.2

Selle DorTse LLC EPA-HQ-OAR-2005-0169-0140

Bluewater Network – compendium of emails

from J. Wilson et al.

Bluewater EPA-HQ-OAR-2005-0169-0139
vii

Public Hearing Testimony

Mantill Williams, Director of Public Affairs

American Automobile Association (AAA)

Ed Tonkin, Chairman of the Regulatory Affairs Committee

Andy Koblenz, Vice President and General Counsel

National Automobile Dealers Association (NADA)

Giedrius Ambrozaitis,

Alliance of Automobile Manufacturers

David Raney, Senior Manager of Environmental and Energy Affairs

John German

American Honda Motor Company

Dr. John DeCicco

Environmental Defense

Dr. Russell Long, Founder

Bluewater Network

Vice President, Friends of the Earth U.S.
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Introduction

On February 1, 2006, we published a Notice of Proposed Rulemaking (NPRM)

that proposed changes to the testing and calculation procedures for fuel economy

estimates that are posted on the window stickers of all new cars and light trucks sold in

the United States. In addition to proposing a new calculation methodology that would

bring the estimates closer to the real-world experience of consumers, we proposed

revisions to the design and content of the label, as well as to some of the information

that appears on it.

We held a public hearing on the NPRM in Romulus, Michigan on March 3, 2006.

At that hearing, oral comments on the NPRM were received and recorded. A written

comment period remained open until April 3, 2006. A complete list of organizations that

provided comments on the NPRM is shown in the following table, along with

abbreviations for these organizations that are used throughout this document. In

addition to the organizations shown in the following table, we received comments from

many individual stakeholders. All comments and hearing testimony have been placed

in the docket for this rulemaking. Publicly available docket materials are available either

electronically through www.regulations.gov or in hard copy at the Air and Radiation

Docket, EPA/DC, EPA West, Room B102, 1301 Constitution Ave., NW, Washington,

DC. See Docket ID No. EPA-HQ-OAR-2005-0169. The Public Reading Room is open

from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The

telephone number for the Public Reading Room is (202) 566-1744, and the telephone

number for the Air and Radiation Docket is (202) 566-1742.

This Response to Comments contains a detailed summary of all comments we

received on the NPRM as well as our analysis of each comment and our response. In

many cases this document also summarizes what we proposed in the NPRM, but we

can not repeat the same level of detail that was presented in the NPRM. For that

reason we refer readers to the NPRM for detailed descriptions of what we proposed.

The reader should also refer to the final rulemaking notice in the Federal Register and

to the Final Technical Support Document.
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Chapter 1: General Issues

1.1 General Comments Supporting Proposal

What commenters said:

We received general support from many stakeholders, including automotive

dealers, states, automotive manufacturers, environmental organizations, consumer

groups, and individual consumers. Supporting comments often noted the growing

dissatisfaction with the frequent gap between the EPA label values and real-world

experience. All agreed that consumers deserve the most useful, accurate, and up-todate information in order to make educated purchasing decisions. Auto companies

tended to support the general improvements and the conclusion that the new

procedures will result in more accurate fuel economy information, but they expressed

some reservations regarding specific details of the program. We address the specific

comments from the auto industry later in this document. Comments of this general

nature came from Toyota, DaimlerChrysler, GM, Mitsubishi, Nissan, NADA, NYDEC,

AAA, PC, AAM/AIAM, PPG, NRDC, UCS, many citizens, and multiple anonymous

commenters.

Bluewater Network stated that the evidence demonstrates “conclusively that

there are staggering inconsistencies between the mileage motorists are actually

achieving, and the values on the labels.” They commend EPA “for advancing a strong

proposal to attempt to rectify this problem.” Despite their support, they note several

areas which they believe must be strengthened.

AAA commissioned a study by the Automobile Club of Southern California’s

Automotive Research Center. This study tested a number of the most popular vehicles

on the US06 test. They also collected in-use fuel economy data from more than 40 of

these vehicles. They argue that their results both confirm the shortcomings of the

existing fuel economy labeling tests and indicate that EPA “...is on the right track with

its proposal...”

Several comments implicitly support our proposal by virtue of commenting

negatively on the current label’s reflection of reality. For example, one commenter

suggested that “EPA allows automobile manufacturers to mislead and defraud

unsuspecting consumers by placing faulty mileage estimates on automobile stickers.”

Another stated that “EPA has been hoodwinking american [sic] consumers for years...”

Our response:

We agree with and appreciate the general comments of support. The NPRM

outlined in detail the deficiencies of the current methods and the resulting gap between

the current fuel economy estimates and what consumers are achieving in real-world

driving. We continue to believe that the case for action is strong, and that the proposal

advanced a technically sound approach for dramatically improving the accuracy of the
3

EPA fuel economy estimates. After consideration of all the comments, we are finalizing

a new program that in many respects matches the basic framework of the proposed

program. However, we are also addressing numerous public comments in the final

program, as discussed throughout this document.

1.2 General Comments Opposing Proposal

What commenters said:

Only one comment specifically suggested taking no action at all. His concern is

that the new methods will discourage consumers from considering hybrid vehicles. He

suggests no action or simply reducing the current labels by a flat 15 percent for all

vehicles. Environmental Defense urged EPA to proceed with caution, citing conflicting

sources of information regarding the magnitude of the discrepancy between the EPA

label values and real-world values.

Our response:

As noted above under Section 1.1, we continue to believe that the case for taking

action is strong, and consequently we are finalizing a program essentially identical to

the proposed approach. We do not agree with comments that suggest a flat one-sizefits-all adjustment factor. Our analysis in the NPRM clearly showed a large amount of

vehicle-to-vehicle variation over the US06, SC03, and Cold FTP tests. These findings

call into question the appropriateness of the continued use of “one-size-fits-all”

adjustment factors. These additional emission test cycles incorporate several critical

factors that are present in real-world driving, and that can have a significant impact on

fuel economy. Use of these test cycles will result in fuel economy estimates that are

essentially tailored to each vehicle’s response to the impacts of each test cycle (higher

speeds, more aggressive driving, air conditioning, and cold temperatures).

We do not believe that the new approach will discourage consumers from

purchasing or considering hybrid vehicles. While it is true that many vehicles that get

high fuel economy, including hybrids, will see a greater reduction in the label values

than lower mpg vehicles, we do not believe that this will discourage consumers from

considering those high-mpg vehicles. High mpg vehicles will be more sensitive to

changes in driving conditions for two reasons. One, because they use relatively little

fuel in the first place, any increase in fuel consumption will be relatively larger in

percentage. Two, because of the non-linearity of fuel economy (distance per unit of fuel

volume, e.g. miles per gallon) with respect to fuel consumption (unit of fuel volume per

distance, e.g. gallons per 100 miles), a fixed increase in fuel consumption (e.g., due to

air conditioning) will lower the fuel economy of a high mpg vehicle much more than it will

lower the fuel economy of a low mpg vehicle. For example, the fuel consumption

increase associated with a 35 mpg rating that actually achieves 30 mpg in the real-world

is the same as a 15 mpg rating that actually achieves 14 mpg. In addition, we have no

interest in perpetuating label values that bear little relationship to reality. Even with the
4

adjusted label values, hybrid vehicles will remain among the most fuel-efficient vehicles

available in the marketplace. Hybrids may well be the most significant powertrain

technology innovation driven to market commercialization primarily because of its fuel

economy potential. In addition, the nature of hybrid technology (the addition of a battery

as a second source of on-board power, sophisticated control systems, sometimes a

smaller engine) suggests that fuel economy will likely be more sensitive to certain

conditions such as high acceleration and deceleration rates, cold ambient temperatures,

etc. Finally, by industry standards, hybrids are a relatively young technology, and there

is every reason to believe that as the technology matures, hybrid vehicle fuel economy

will become much more robust over a broader range of driver behavior and climate

conditions.

1.3 Estimates Are Based on Controlled, Repeatable Tests

What we proposed:

The methodology we proposed was based on the use of controlled, repeatable

tests conducted in emission and fuel economy testing facilities that conform to EPA’s

stringent regulations on test procedures.

What commenters said:

Several supporting comments further expressed agreement with EPA’s

assessment in the NPRM that it is essential that the fuel economy estimates be based

on controlled, repeatable laboratory tests that provide manufacturers with a level playing

field. Some of these commenters also agreed that the auto manufacturers should

remain the primary parties responsible for performing the fuel economy testing and

calculation of the mpg estimates.

Our response:

It is essential that our fuel economy estimates continue to be derived from

controlled, repeatable, laboratory tests. We noted in the NPRM that these laboratory

tests provide a level playing field for all vehicles, which is essential for comparing the

fuel economy of one vehicle to another. EPA and manufacturers test over 1,250 vehicle

models annually and every test is run under identical conditions and under a precise

driver’s trace, which assures that the result will be the same for an individual vehicle

model no matter when and where the laboratory test is performed. Finally, EPA must

preserve the ability to confirm the values achieved by the manufacturers’ testing, and

this can only be achieved with a highly repeatable test or set of tests.

However, the EPA fuel economy test methods need to reflect real world

conditions as well as being a repeatable test. While some organizations have issued

their own fuel economy numbers based on on-road driving, their approach introduces a

wide number of variables – different drivers, driving patterns, weather conditions,
5

temperatures, etc. – that make repeatability, and therefore vehicle-to-vehicle

comparisons, impossible. The new fuel economy test methods are more representative

of real-world conditions than the current fuel economy tests, yet we retain in this final

rule our practice of relying on controlled, repeatable, laboratory tests.

1.4 There is No Perfect Test

What we proposed:

We emphasized in the NPRM that it is impossible to design a “perfect” fuel

economy test that will provide accurate real-world fuel economy estimates for every

consumer.

What commenters said:

Some comments expressed agreement with the principle that there is no perfect

test that can accurately predict the fuel economy for every driver under all

circumstances, and that there will inevitably be times when a driver’s actual fuel

economy will be higher or lower due to differences in vehicle use, driving styles, and

conditions. For example, AAA noted that because people’s driving habits vary

significantly, there is no single test that will yield 100% accuracy.

Our response:

We agree with the comments, and will continue to stress this fundamental point.

It is important to emphasize that fuel economy varies from driver to driver for a wide

variety of reasons, such as different driving styles, climates, traffic patterns, use of

accessories, loads, weather, number of passengers, and vehicle maintenance. Even

different drivers of the same vehicle will experience different fuel economy as these and

other factors vary. Therefore, it is impossible to design a “perfect” fuel economy test

that will provide accurate fuel economy estimates for every consumer. With any

estimate, there will always be consumers that get better or worse actual fuel economy.

The EPA estimates are meant to be a general guideline for consumers, particularly to

compare the relative fuel economy of one vehicle to another. Nevertheless, we do

believe that the new fuel economy test methods will do a better job of giving consumers

a more accurate estimate of the fuel economy they can achieve in the real-world.

1.5 CAFE Program

What we proposed:

We noted in the NPRM that the proposal would not impact the test procedures,

driving cycles, measurement techniques, or the calculation methods used to determine

fuel economy values for CAFE compliance calculations.
6

What commenters said:

A number of commenters addressed the connection between the CAFE program

and the fuel economy label estimates. NADA stressed that it is important that EPA’s

action not have an impact on CAFE. A number of others expressed disagreement with

this opinion, however. The NYDEC recommended that the CAFE test methods be

updated to match the proposed revised methodology. Their fear, in particular, is that

“EPA’s efforts to inform the public about fuel economy will be thwarted by the use of

different standards for the vehicle labels than those used for [CAFE]...” In agreement,

M. R. King put it this way: “If the window fuel economy sticker is not accurate, why

should the CAFE calculation continue to be inaccurate?” If the CAFE test methods

remain fixed, NYDEC requests that the CAFE value assigned to the vehicle be put on

the label.

Bluewater Network notes that they have observed “a great deal of confusion”

over the several different sets of fuel economy values published by EPA and NHTSA

(CAFE values, EPA “adjusted” values, and EPA “unadjusted” values). For this reason,

they suggest that EPA end any public dissemination of the unadjusted EPA values,

including in the EPA Trends Report. They find “no compelling justification or public

good” that results from these values, and absent a legal mandate to make these values

public, they urge us to not make them publicly available.

Our response:

Our final rule does not alter the FTP and HFET driving cycles, the measurement

techniques or the calculation methods used to determine CAFE. EPCA requires that

CAFE for passenger automobiles be determined from the EPA test procedures in place

as of 1975 (or procedures that give comparable results), which are the city and highway

tests of today, with a few small adjustments for minor procedural changes that have

occurred since 1975. The new method for calculating fuel economy label estimates fall

under regulations that are separate from the CAFE regulations.

EPCA requires that CAFE for passenger automobiles be determined from the

EPA test procedures in place as of 1975 (or procedures that give comparable results),

which are the city and highway tests of today, with a few small adjustments for minor

procedural changes that have occurred since 1975.1 Today's final rule will not impact

the CAFE calculations.2

EPA notes the comment by Bluewater Network regarding the release of

unadjusted fuel economy values and will focus future EPA Fuel Economy Trends

reports on information that is useful to consumers.

1

See 49 U.S.C. 32904(c).

2

See 49 U.S.C. 32904(c).
7

1.6 Should Label Estimate Cover 50th or 75th Percentile?

What we proposed:

We proposed to continue to set the city and highway mpg estimates at the

average, or mean, level, consistent with analytical approaches of the past. However,

we expressed our understanding that many drivers expect to achieve or exceed the fuel

economy indicated by these average mpg estimates. By continuing to set the estimates

at the average level, by definition, the average driver will achieve of exceed the fuel

economy label values fifty percent of the time. We invited comment on whether the city

and highway estimates should be set a level that is lower than average – for example,

to ensure that the average driver will achieve or exceed the label value 75 percent of

the time.

What commenters said:

AAM/AIAM supported EPA’s position in the NPRM, which retains the existing

practice of setting the city and highway fuel economy label estimates at the average, or

mean, level. AAM/AIAM note that an alternative, such as that suggested above, would

amount to applying an arbitrary discount to the mean value produced from 5-cycle

testing, in addition to the proposed 11% downward adjustment for non-dynamometer

effects, and would add no value to the label as a useful tool for comparative purposes.

The also believe that consumers understand that fuel economy label values represent

the average fuel economy experienced by drivers. Rather than arbitrarily setting a level

that is lower than average to ensure more driver coverage, AAM/AIAM suggest that a

more prudent approach would be to validate the accuracy of the current 5-cycle

approach through analysis of real-world fuel economy data. NYDEC and PC concurred

with the view of AAM/AIAM, noting that the average is more consistent with how

consumers understand the label values, and that using an alternative would result in

label values that are inaccurate by a greater degree for a higher percentage of

consumers. NADA commented that the goal should be to present label numbers that

are a “hypothetical average.” Natural Resources Canada suggests reducing the

weighting given to high speed and aggressive driving, or shifting the estimates to a

percentile whereby more than 50 percent of drivers would not achieve the label value.

Our response:

We received no comments opposing the proposed approach or supporting an

alternative approach to the one that was proposed. We agree with the commenters and

continue to believe that the labels should express consumer’s average fuel economy

experience, thus we are finalizing the city and highway estimates as average values as

proposed.
8

1.7 Public Availability of Fuel Economy Test Data

What we proposed:

We did not propose anything specific with respect to making fuel economy test

data publicly available. However, we have historically made fuel economy data

available in several ways. Fuel economy information for all cars and light trucks has

always been published in the statutorily required Fuel Economy Guide available at

automobile dealerships. We have also historically published the Fuel Economy Trends

report, which presents an annually analysis of fuel economy data. And we have always

made public the raw fuel economy test data, and have posted data going back to 1978

on our web site.

What commenters said:

ACEEE commented that EPA should continue to make fuel economy information

available with a high degree of transparency.

Our response:

We plan to continue to make fuel economy data available to the public in the

most useful ways possible.

1.8 Overall Purpose of Fuel Economy Estimates

What we proposed:

The EPA fuel economy estimates have appeared on the window stickers of all

new cars and light trucks since the late 1970’s and are well-recognized by consumers.

In the NPRM we noted that these estimates essentially serve two purposes: (1) to

provide consumers with a basis on which to compare the fuel economy of different

vehicles, and (2) to provide consumers with a reasonable estimate of the fuel economy

they can expect to achieve. While the EPA fuel economy estimates have generally

been a useful tool for comparing the relative fuel economy of different vehicles, it is also

important that they reflect the fuel economy that consumers can reasonably expect to

achieve in the real world. Consumers need to be provided with accurate, easily

understandable, and relevant information regarding the fuel economy of new vehicles.

What commenters said:

Natural Resources Canada took some issue with our use of the label estimates

to represent driving that by definition results in poor fuel economy. In particular, they

focus on the representation of aggressive and fast driving through the inclusion of the

US06 driving cycle. A more appropriate use of the label, from their perspective, is to act

as a benchmark that drivers can reasonably expect to achieve through fuel-efficient
9

driving techniques. They agree that making adjustments to the label estimates to

account for items that the driver has limited control over (e.g., climate and fuel factors)

is appropriate, “...but making adjustments to the label value to correct for poor driving

behavior may not fairly represent the fuel economy that a driver could (and in our view

should) attain.” In their view a significant part of narrowing the gap between the label

estimates and actual in-use fuel economy should be the education of consumers to

promote better driving behavior. Our approach, they suggest, diminishes the label’s

ability to promote good driving behavior.

UCS comments that the primary goal of the fuel economy ratings should be to

“provide consumers with a reliable basis for comparing the fuel economy and costs of

individual vehicles.” A secondary goal, they state, is to ensure that policymakers and

the public have a reliable means for measuring the average fuel economy performance

of the fleet as a whole.

Our response:

We continue to believe that the fuel economy labels serve two key purposes: (1)

to provide consumers with a basis on which to compare the fuel economy of different

vehicles, and (2) to provide consumers with a reasonable estimate of the fuel economy

they can expect to achieve. Natural Resources Canada’s point is really about a

philosophical choice between two ways of representing fuel economy. We have always

determined that the labels should represent typical U.S. driving habits and conditions,

without making judgments as to whether driving behavior is poor and inefficient or

conservative and efficient. We do not believe that we are necessarily correcting for

“poor driving behavior,” rather, we see it as representing real-world driving behavior.

Representing fuel economy levels that could be achieved with good driving techniques

under good conditions would not solve the current problem (in fact, it would enhance it)

of a large disconnect between label values and real-world fuel economy. We have to

represent the typical driver and typical conditions, and at the same time ensure that

vehicle owners receive useful information regarding what they can do to improve fuel

economy.

1.9 Small Volume Manufacturers

What we proposed:

We did not propose any specific provisions for small volume manufacturers, as

our analysis indicated that none were necessary. We proposed features designed to

provide adequate lead time and to minimize test burden that equally apply to both large

and small volume manufacturers.
10

What commenters said:

Ferrari, while in general support of our proposal, expressed concern about

additional testing burden needed to run all five test cycles on each model. They

suggest to adopt a manufacturer-specific correlation factor in lieu of performing the

US06, SC03 and Cold FTP tests, or to use the "worst case" fuel economy data to

represent untested configurations.

Our response:

Our proposal does not require manufacturers to run all five test cycles on each

model. First, until 2011, all manufacturers will be able to employ the mpg line method,

which only continues to rely on the same FTP and HFET tests as today. Second, for

2011 and later models, full five-cycle model type testing will only be required when the

criteria set forth in the final rule are exceeded. Based on these criteria, we project that

only four percent of test groups will need to perform Cold FTP and SFTP tests and only

13 percent will need to perform US06 tests. However, EPA's regulations allowing data

substitution (worst case fuel economy data substituted for untested configurations) and

for analytically derived data (where the fuel economy from an untested configuration

can be mathematically determined by using the data from a similar tested vehicle that is

more fuel efficient.) These provisions should address Ferrari's concerns about test

burden.

1.10 Typographical Errors and Regulatory References

What commenters said:

Some commenters found what they believe to be errors or inconsistencies in the

regulatory text. Mitsubishi alerted us to the following issues:

o In 600.010-08(b)(1) the text should read “The manufacturer shall generate city

and HFET fuel economy data...” rather than “The manufacturer shall generate

city and FTP fuel economy data...”

o The equation for Running FC in 600.114-08(a) should be the following, where the

denominator of the second term in the second parenthetical term is Bag320FE,

not Bag220FE as it was in the NPRM:

























    













  











  



SC FE Bag FE Bag FE

Bag FE Bag FE US City FE Bag FE Bag FE

Running FC

75 75

75 75 20 20

2

0.39

3

0.61

03

1

19.9

21.5

0.133

3

0.5

2

0.5

0.30

06

0.11

3

0.41

2

0.48 0.70
11

o In 600.115-08(b) the equation for Derived 5-Cycle Highway Fuel Economy

should read “HFET FE” where the NPRM read “FTP FE”:

 

 















 

HFET FE

Highway Slope Highway Intercept

Derived cycleHighway Fuel Economy

1

5

o Section 600.116-08(a)(1) references 600.114-08(b) for the 5-cycle city fuel

economy equation. Mitsubishi believe that the referenced section actually

related to the 5-cycle highway fuel economy equation, and that the appropriate

reference is 600.114-08(a).

o Section 600.116-08(a)(3)(B)(1) references 600.114-08(c), a section that does not

exist. Mitsubishi believes that the appropriate reference is 600.114-08(b).

NREL commented that the air conditioning equation as expressed in the Draft

TSD on pages 67 and 75 is incorrect, and that the correct form of the equation appears

on pages 101 and 113. They believe that the correct form of the equation is the

following:











   

75 2 75

0.39

3

0.61

03

1

/

SC FE Bag FE Bag FE

A CFC

NREL commented that the coefficient for Ambient Temperature in the equation

on page 71 should be 0.084, not 0.84.

Mitsubishi encountered ambiguity in some of the regulatory references in

600.116-08. They note that there are two references to 600.010-08 as a method for

calculating 5-cycle city fuel economy and 5-cycle highway fuel economy. However,

their confusion stems from the fact that 600.010-08 does not define the 5-cycle

equations, but merely the calculations for each specific cycle in the equations. They

suggest that it may be more appropriate to reference 600.114-08, where the 5-cycle

equations are defined. Mitsubishi recommends that EPA explain these references more

clearly, or change the references to the appropriate section.

The comments from AAM/AIAM included a long list of incorrect, obsolete, or nonexistent regulatory references which should be changed. They also offer a number of

suggests for correction or clarification of regulatory language.

Our response:

We appreciate the level of detail with which these commenters reviewed the

proposed regulatory text. Many of their comments and suggestions are valid, and we

have incorporated their suggestions as appropriate. Readers of the final regulations will

find that these and other errors and typographical mistakes have been corrected.
12

1.11 Miscellaneous Regulatory Comments

What commenters said:

AAM/AIAM recommended that a number of definitions be added to the definitions

list in 40 CFR 600.002-08. They proposed adding definitions of US06-City and US06-

Highway to Part 600 rather than modifying Part 86, as was done in the proposal. Their

proposed definitions are as follows:

o Two-bag FTP means the FTP for HEVs as described in section 86.1811-04(n).

o US06-City means the combined periods of the US06 Test that occur before and

after the US06-Highway period.

o US06-Highway means the period of the US06 Test that begins at the end of the

deceleration which is scheduled to occur at 128 seconds of the driving schedule

and terminates at the end of the deceleration which is scheduled to occur at 493

seconds of the driving schedule.

o Five-cycle means the FTP, HFET, US06, SC03 and cold temperature FTP tests

as described in Subpart B and C of this Part.

o Alcohol means a mixture containing at least 85 percent by volume denaturized

ethanol, or because of requirements relating to cold start, safety, or vehicle

functions, a mixture containing at least 70 percent by volume denaturized

ethanol.

o Alcohol dual fuel automobile means an automobile:

o Which is designed to operate on alcohol and on gasoline; and

o Which provides equal or greater energy efficiency as calculated in

accordance with section 600.510(g)(1) while operating on alcohol as it

does while operating on gasoline; and

o (iii)Which, in the case of passenger automobiles, meets or exceeds the

minimum driving range established by the Department of Transportation in

49 CFR part 538.

o Certification vehicle means a vehicle that is selected under section 86.1828-01 of

this chapter and used to determine compliance under section 86.1848-01 of this

chapter for issuance of an original certificate of conformity.

Our response:

We agree with AAM/AIAM that the majority of these definitions add clarity to the

regulations, and with one exception we have incorporated them into the final regulatory
13

text. We are not finalizing a definition for “Two-bag FTP” because it is not a term that is

used in the final regulations.

1.12 Daytime Running Lights

What we proposed:

We did not propose anything specific with respect to daytime running lights.

What commenters said:

An anonymous commenter suggested that EPA “repeal” the manufacturer

guidance letter CD-94-02, which allows manufacturers to disable daytime running lights

(DRLs) while determining fuel economy. Their reasons for this were several: (1) DRLs

can impact fuel economy; (2) an impact of up to 0.25 mpg equates to millions of barrels

simply to support DRLs; (3) increased refueling events exposes consumers to toxic

chemicals and fire injury potential; (4) safety advantages of DRLs are unproven; and (5)

manufacturers have made it increasingly difficult to disable DRLs.

Our response:

We believe that DRLs have generally evolved to minimize power usage,

especially relative to those that were in use when the guidance memo was issued.

Nevertheless, allowing them to be disabled is inconsistent with the intent of the new fuel

economy estimates to better reflect the conditions that vehicles experience in actual

real-world use. Thus, we intend to reevaluate the provisions of the guidance memo in

the future, in consultation with NHTSA.
14

Chapter 2: Label Format and Content

2.1 General Label Preferences

What we proposed:

We proposed to revise the design and informational content of the fuel economy

window sticker to convey fuel economy information more clearly to consumers. The

proposal included four label options under consideration.3 While Alternatives 1 and 2

preserve some of the “look and feel” of the current label, Alternatives 3 and 4 depart

from the traditional label design, presenting the same information graphically.

Alternative 4 is similar to Alternative 3, but illustrates the comparable class information

graphically. The four alternatives are shown below:

3 Note that the NPRM contained four alternatives, printed in the Appendix to the proposed regulations

on pages 5510-5513, labeled Alternative 1, 2, 3, and 4. These same labels were posted on EPA’s

website, but in a slightly different order and with different nomenclature (Label A, B, C, and D). In the

following discussion we refer to the labels printed in the NPRM and use that nomenclature.
15

What commenters said:

Nearly all of the commenters (almost 3000 in total) preferred Alternative 4,

attributing their choice to the graphic expressing the vehicle’s fuel economy relative to

other vehicles in its class. Alternative 4 contained the only within-class comparison

graphic, which many likened to the Energy Star graphic comparing energy use of

appliances. One commenter stated that Alternative 4 “best clarifies the relative fuel

economy against competitors in the same vehicle class.” Another noted that Alternative

4 “looks sufficiently different from the current sticker to make it easy for consumers to

notice the change.” [NYDEC, AAA, F. Schmitt, Bluewater Network, B. Kotlier, multiple

anonymous]

However, many automobile manufacturers expressed that the “portrait”

orientation of Alternatives 2 and 4 (the current label format is “landscape”) would pose

significant implementation issues. [AAM/AIAM, GM] Subaru supported the industry

position, adding that the shadow figure of a full-size gray gas pump (a “watermark”)

would conflict with the Subaru logo watermark currently displayed on their labels.

NADA noted that each of the proposed label formats offered pluses and minuses

for dealership sales personnel who frequently address consumers’ concerns at the

point-of-sale. They stated that an “informal, non-statistical” survey of some dealers

suggested “overwhelming support” for Alternative 1 and a consensus against

Alternatives 3 and 4. This preference was attributed to Alternative 1’s similarity to the

current label, which they saw as an advantage to the public, noting that it offers a

“cleaner, simpler, and more straight-forward approach” than the current label or the

other proposed alternatives. Alternatives 3 and 4 were viewed by the surveyed dealers

as “...too radical a departure from the time-honored label currently in use.” They added

that the final label should be as simple as possible.

Natural Resources Canada supported the layouts of Alternatives 3 and 4 and

mentioned that Alternative 3 may be more familiar to consumers because it retains a

landscape orientation and does not diverge dramatically from the current format. They

preferred the contemporary design of Alternative 4, because although it may require the

consumer to look carefully at first, it clearly highlights the fact that information has been

updated and improvements have been made.

Two anonymous commenters expressed a preference for Alternative 1. While

one failed to explain why, the other suggested that the similarity to the current label

would make it easier for consumers to locate it on the window sticker. This commenter

also stated that Alternative 1 showed the annual fuel cost estimate more prominently

than the other labels. [Anonymous#1, Anonymous#3]

ACEEE advised EPA that consumers may not fully benefit from the label largely

because labels are not optimized for consumers. Consequently ACEEE recommended

that EPA hire “one or more outside specialists in visual communication or quantitative
16

information to design from scratch a label for EPA’s consideration that will maximize

comprehension, motivation, and message effectiveness.”

Bluewater Network commented that they strongly support the approach taken in

Alternative 4 “because it provides a great deal of valuable consumer information very

clearly.”

Our response:

Clearly, no one label design can address every comment, but with the exception

of NADA, the groups generally agreed that a new appearance is desirable. We

acknowledge NADA’s concern that the new label should not be a "radical departure"

from the current design and recognize that dealers are highly involved in answering

public questions about the label. Although the new label will present the facts

differently, it will retain most of the content. Much of the new information will be selfexplanatory, such as the web link to www.fueleconomy.gov, or the added basis for the

estimated annual fuel costs (price per gallon and miles per year.) However, the public

did not share NADA's "overwhelming [dealer] support" for a more "time-honored,"

conservative label design; while the pictorial representation of the comparable fuel

economy is the most transformed feature that dealers may need to explain, commenters

indicated that the new graphic is a highly desirable improvement over the textual

version. The label design we are adopting does retain some familiar design aspects,

specifically the location of the city and highway estimates on either side of the fuel pump

graphic. We believe that we can address NADA's concerns about consumer

comprehension by jointly-sponsoring an outreach campaign with car dealers that could

include explanatory materials, such as a brochure that dealers could distribute to

customers. We also plan to conduct outreach and education targeted at the general

public to raise consumer awareness of the new label and its contents.

We acknowledge the ACEEE suggestion that EPA utilize outside experts to help

design the label. The old fuel economy label, portions of which were developed in the

1970's, was designed by EPA engineers and not by graphic designers. Based on a

limited amount of market research for the new label, we discovered that prospective

buyers did not understand much of the information on the label other than the large city

and highway numbers, and that we lacked the expertise to develop a label format that

would be more user-friendly. Therefore, we contracted a professional graphic design

firm before the proposal, to help us both create and market-test new designs, resulting

in the four proposed alternatives. We also enlisted their assistance after the proposal

in order to market-test alternatives based on comments received. This contractor then

incorporated suggestions from public comments and the focus groups into the final label

design recommendations for EPA’s consideration. Comments and suggestions from

the focus groups are located in the Focus Group Report and the Docket.4 The final label

design is shown below:

4

Each of these can be found in the public docket, which is available at www.regulations.gov.

Search under EPA Docket ID No. EPA-HQ-OAR-2005-0169.
17

2.2 Label Format Effective Date

What we proposed:

The NPRM proposed changes to the methodology for calculating label values

and changes to the design and content of the label, beginning with 2008 models.

What commenters said:

AAM/AIAM noted that when new fuel economy labels become effective (the 2008

model year), the auto companies will be simultaneously be implementing the new safety

rating label requirements finalized by the National Highway Traffic Safety Administration

(NHTSA) on September 12, 2006.5

AAM/AIAM also argued that lead time for changing the format is inadequate

because the few months between EPA’s finalization of the rule and the potential start of

2008 model year production in January of 2007 is not enough time to work with

suppliers on creating new labels. Consequently, they requested that any changes to

the look, font, orientation, content, or language be made voluntary for the 2008 model

year. They specifically noted that they are not proposing to delay the presentation of

5

See 71 FR 53572 (Sept. 12, 2006).
18

the new label values, only that changes to the appearance be voluntary for the 2008

model year. They further recommended that EPA allow manufacturers to maintain the

old label format, provided that text is added in the variable text field (under the fuel

pump, above the Estimated Annual Cost) that states “New 2008 Method.”

Subaru commented that manufacturers frequently purchase pre-printed

Monroney pricing labels in bulk, thus making it likely that some will already have label

stock for the 2008 model year vehicles long before EPA’s rule is finalized.

The industry’s view was that if a final rule were published by September 2006,

modifications to the look, font, orientation, content, or language on the label could be

implemented on vehicles manufactured on or after September 1, 2007. They indicated

that if the fuel economy label effective dates are aligned with the statutorily-mandated

timing of the safety label requirements, they require only one round of significant

modification to their overall pricing labels. General Motors reiterated this position in their

comments, citing their staggered model production throughout the calendar year and

the difficulty in applying labels to early 2008 vehicles with the first build event scheduled

for January of 2007.

NADA suggested that the final rule clarify that manufacturers are free to provide

dealers with replacement labels for installation on undelivered vehicles initially labeled

under the old rules. Providing this flexibility, they argue, will reduce consumer

confusion.

Our response:

We believe that the new fuel economy estimates should ideally be accompanied

by a new fuel economy label design that clearly announces this fact to the public.

Recognizing that a typical dealer's lot may contain vehicles from multiple model years

(e.g. 2007 and 2008) for the first or second calendar years of implementation,

consumers would be able to readily distinguish the new estimates by the new look of

the label, and thus more likely to understand that the fuel economy of 2007 models will

be different from that of 2008 models. We also realize that the timing of this final rule

will cause some significant practical difficulties for those manufacturers introducing 2008

models early in the calendar year 2007. Manufacturers remarked that the new NHTSA

safety ratings are statutorily required on vehicles manufactured on or after September 1,

2007, and that harmonizing the new fuel economy label effective with that same date

would ease some of their implementation burden. In general, the traditional "start" of

the new model year has been October of the previous calendar year (e.g., model year

2008 would begin in October of calendar year 2007). However, as manufacturers have

indicated, staggered production schedules throughout the calendar year have become

widespread across the industry. We now understand that some manufacturers have

very early model year 2008 (e.g., January/ February, 2007) launches planned for

several vehicle models. We are therefore finalizing a requirement that aligns mandatory

use of the new label format with the NHTSA label date. This will give manufacturers

needed lead time to phase in the new labels without multiple changes to the vehicle
19

pricing (Monroney) sticker. All 2008 models manufactured on or after September 1,

2007 will have the new label format. We agree with NADA's comment that

manufacturers should be allowed to use the new label design as soon as possible, and

we strongly encourage manufacturers to apply them on a voluntary basis to 2008

models for sale before that date. Those 2008 models using the current fuel economy

label design will be required to include, at a minimum, the following information on the

label:

1. The city and highway estimates, based on the new calculation methods

contained in this final rule.

2. A statement in bold print that says "These estimates reflect new EPA

methods beginning with 2008 models.”.

2.3 Label Content Issues

2.3.1 Fuel Economy of Comparable Vehicles

What we proposed:

The EPCA statute requires that the label include the fuel economy of comparable

vehicles: This provision was intended to help car shoppers compare the fuel economy

of similar vehicles. EPA's current regulations require that the label include the following

statement: “For comparison shopping, all [vehicles/trucks] classified as [insert category

as determined in §600.315] have been issued mileage ratings ranging from ___ to ___

mpg city and ___ to ___ mpg highway.” Based on pre-proposal focus group research, it

appeared that car buyers disregarded this statement since we learned in small print and

contained lengthy text. Many perceived it as “fine print,” and thus less important. We

showed the pre-proposal focus groups label samples with less text for comparable fuel

economy, and they generally preferred these versions. A few participants suggested

that a pictorial representation may be even more clear. In our proposal, three of the four

sample labels contained a revised statement to lessen the “fine print” look, and the

fourth was a graphical representation similar in concept to DOE’s EnergyGuide label on

which we requested comment. This graphic based the fuel economy comparison on

combined city/highway fuel economy instead of separate city and highway comparisons,

as demonstrated in the old label and the proposed alternatives 1 through 3.

What commenters said:

We received many comments on this issue with suggestions and alternatives

provided below.

AAM/AIAM noted that EPA’s current class definitions are quite broad, and as a

result “the range in fuel economy in any one class is generally very large, and the class

leaders are typically lower volume specialty vehicles.” They remarked that a Toyota

Prius and a Rolls-Royce Phantom are both classified as mid-size vehicles, yet they are
20

clearly not in the same market segment. Citing this wide variation, AAM/AIAM

suggested retaining the current label language on the fuel economy of comparable

vehicles. They requested that if EPA were to receive comments on this issue specifying

a substantial preference for a graphical approach, they “would like to work with the

agency...on the correct look, feel, and format of a graphic that ensures our competitive

concerns are addressed.”

NADA commented that an informal and non-statistical survey of dealers on their

Regulatory Affairs Committee found that the graphical presentation of comparable class

fuel economy “...failed to offer advantages...” over the text used in EPA’s proposed

Alternative 1 label. However, they held that the label should continue to contain this

information in some form.

Toyota submitted a label concept that included the following recommendation for

a graphic combining both the annual estimated fuel cost and the fuel economy range of

comparable vehicles.

Public Citizen suggested that customers will less likely dismiss a pictorial

representation because it may more effectively convey information. They also

remarked that non-English speakers may understand the graphic more easily. In

addition to graphically comparing the combined fuel economy, they recommended that

this approach be used for both city and highway fuel economy estimates. For

implementation, they suggested that EPA conduct focus groups to determine the best

format for a graphical comparison of comparable class fuel economy.

Bluewater Network noted that “the bar graph is also consistent with the

EnergyGuide Label, and highly comprehensible to consumers.”

UCS argued that with the recent proliferation of vehicle designs and the “fading

class distinctions” exemplified by crossover vehicles, consumers have increased

shopping across classes and should be presented with information comparing vehicles

on the dealer lot to the full range of vehicles on the market. They proposed the two

following alternative comparable class graphics for the label including comparisons to

the whole fleet and to the specific class.
21

Placed on the Alternative 4 label and similar to that of the EnergyGuide program,

commenters generally understood the graphical element and preferred it over the

current text. Many commenters preferred Alternative 4 because the visual was more

powerful and comprehensible. [A. Benenson, AAA, R. Appel]. Natural Resources

Canada stated that a graphical representation should be on the final label design. An

anonymous commenter suggested that since this graphic presented useful information

and was the label’s only reference to combined fuel economy, it should be displayed in

a font size “nearly as large as the City and Highway numbers.” This commenter also

noted that while the within-class range is useful, it would be even more useful to see the

average combined fuel economy for that class of vehicles.

One commenter remarked that the graphical depiction of comparable class fuel

economy is “statistically lacking” because it does not convey information about how

many vehicles are in the relevant vehicle class and how their fuel economy values are

distributed between the minimum and maximum. Since one of the endpoints of the

range (e.g., the maximum fuel economy in the class) could be an outlier and the bulk of

the vehicles in the class might be clustered nearer the minimum value, this commenter

suggested making the graphic a small histogram and provided an example of this

concept. As illustrated in the following graphic, a car could be at the midpoint between

22 and 40 mpg, suggesting that it achieves average or median fuel economy in the

class. The histogram, however, would more accurately indicate that a midpoint value

would actually indicate a higher combined fuel economy than most vehicles in the class.

[D. Fitz-Randolph]
22

Our response:

While public commenters preferred a graphic representation of comparable fuel

economy, manufacturers were concerned about competitive fairness. We examined

this element further with post-proposal focus groups, which highly supported the

graphic. Although many noted that including the combined fuel economy was

important, since most drivers do not drive exclusively in the city or highway style, others

remarked that while the information would be useful to some, it would be of no use to

them because they did not shop within a specific class of vehicle. We thought the UCS

comment to show the fuel economy range of all vehicles had merit, and we tested the

following versions of this graphic with the focus groups:

Version 1: Within-Class Range of Vehicles Version 2: Added Range of All Vehicles

The focus groups slightly preferred Version 1 because of its simplicity, many

participants noting that they already knew which class of vehicles they would be

considering. Others preferring Version 2 mentioned that it could influence some people

to reconsider vehicles with higher fuel economy. Although some participants thought the

added fuel economy range in Version 2 was useful, many thought it was too much

information or were confused by what it represents.6

We are requiring a graphic for comparable fuel economy and the scale showing

the range of fuel economy for vehicles in the comparable class because it was well6

The comparable classes that EPA designates are related to how the comparable fuel economy is

presented on the label. Section 2.6 contains a separate discussion of comparable classes.
23

received by the public commenters and focus groups. People responded favorably to

its likeness to the widely-used EnergyGuide graphic. We recognize manufacturers’

concern that showing comparable fuel economy information may be misleading in some

cases, since the class ranges are often broad and sometimes defined by lower sales

volume vehicles. However, this issue is derived more from how to create class

distinctions, rather than how to present the information. Some focus group participants

noted that if a certain class of vehicles had a particularly wide fuel economy range, a car

shopper could solicit the informational sources provided on the label (Fuel Economy

Guide or web site) to determine if the more fuel efficient models in that class would

meet their vehicle needs. We agree with this observation and are retaining a simpler

graphic similar to that in Alternative 4, because the label information is more clear and

concise.

2.3.2 Estimated Annual Fuel Cost

What we proposed:

The EPCA statute requires that estimated annual fuel cost be reported on the

label. Currently, the EPA requires only the dollar amount in the cost estimate, but

allows manufacturers to voluntarily include the per-gallon fuel cost and annual miles

driven, items that derive annual fuel cost. However, since manufacturers typically do

not include this optional information, most labels contain only the annual cost. We

proposed to require also the per-gallon fuel cost and annual miles driven on the label in

the following statement: “Estimated Annual Fuel Costs = $XXXX (based on XX,XXX

miles at $X.XX per gallon).” We also sought comments on whether the text should

include the combined fuel economy number as part of the derived Estimated Annual

Fuel Cost.

What commenters said:

While opinions on the presentation of estimated annual fuel cost differed, no one

opposed including per-gallon fuel cost and annual mileage, the bases for the estimate.

Some commenters suggested showing a range of estimated fuel costs based on either

a five-year projection of fuel costs or an analysis of fuel volatility. [Bluewater Network,

A. Benenson, anonymous] Bluewater Network suggested a font size for this element at

least as large as the mpg values and also urged EPA to present a fuel cost range from

100% city driving to 100% highway driving, because it is useful to those who drive

exclusively in the city or on the highway. A. Benenson stated that EPA should revise

the per-gallon fuel cost at least annually, and MT-CHEER noted that the label should

use the most realistic fuel economy number, whether it is the combined, city, or highway

figure to estimate the annual cost. AAA and NADA generally supported these notions,

and an anonymous commenter stated that annual fuel cost is “one of the most important

pieces of information for the consumer.” Another anonymous commenter noted that the

label lacked a fuel consumption metric, and suggested displaying the estimated annual

fuel cost more prominently, since it is a useful proxy for fuel consumption.
24

Public Citizen and UCS commented that because the combined fuel economy

number is important in determining the estimated annual fuel cost, it should be included

in the explanation, since it makes the calculation less transparent to consumers. They

suggested, however, that EPA conduct a focus group study to examine consumer

response.

AAM/AIAM and Subaru supported including both miles per year and dollars per

gallon of fuel on the label, because this information may be valuable to fuel-economyconscious consumers. They recommended that EPA continue to update the fuel cost

annually and not more often because frequent changes may be problematic, confusing,

and costly. Toyota submitted the following label concept which combines both the

annual estimated fuel cost and the fuel consumption range of comparable vehicles.

Our response:

Focus group participants and public commenters expressed interest in fuel cost

information, remarking that the added bases for this calculation (cost-per-gallon and

miles-per-year) substantially improved the label. We agree that we should enlarge the

fuel cost font. We tested various sizes with focus groups; most focus group participants

preferred seeing the fuel cost information more prominently on the label. However, the

fuel cost value will not be as large as the city and highway estimates in the final label,

because we believe that it is confusing to display three large numbers of the same size.

There is now a smaller fourth number for the combined fuel economy shown on the

comparable class fuel economy graphic that competes for space on the label. The final

font size for fuel cost and combined fuel economy is the same, and the city and highway

numbers are slightly larger.

We appreciated Bluewater’s suggestion that adding a range of fuel cost based on

100% city driving or 100% highway driving may be useful to those who drive

predominantly in urban or rural areas. We tested the following graphics with the focus

groups:
25

Option 1: Proposed fuel cost info O Option 2: With added city and highway

fuel cost

The focus groups had mixed reactions to these options, but slightly preferred Option 1

because it was simpler and provided all of the vital information. Others thought that the

combined estimate would be more accurate, since they did not drive exclusively in

either city or highway conditions. Alternatively, those that preferred seeing the added

city/highway fuel costs did so because they did drive under one condition more often

than another; others simply preferred having more information.

We are finalizing Option 1 based on positive response from both public

commenters and focus groups. While the option to include separate city and highway

annual fuel costs may provide additional useful information for some consumers, others

may disregard it altogether because of its complexity. Furthermore, there is enough

information provided on the simpler graphic that a person could determine their own

customized fuel cost estimate by modifying one or more parameters (e.g. mpg, dollarsper-gallon, or miles-per-year).

2.3.3 Combined Fuel Economy Calculation

What we proposed:

We proposed that the combined fuel economy used in the comparable class

graphic to calculate the estimated annual fuel costs be the weighted average of 43%

city mpg and 57% highway mpg, instead of the current 55% city mpg and 45% highway

mpg. This change is consistent with the ratio used to determine combined 5-cycle fuel

economy for the fleet. This 43/57 ratio is based on national driving patterns indicating

average mileage driven (not time spent) in "city" versus "highway" conditions.

What commenters said:

Bluewater Network noted that the proposed 43/57 city/highway split for

determining combined fuel economy was not accounting for the amount of time spent in

city or highway conditions. They suggested that EPA use a 50/50 city/highway split

because it more closely aligns with how many customers consider their driving patterns

(in terms of time spent versus miles driven).
26

Alliance/AIAM agreed that while the proposed 43/57 split may be statistically

valid on a miles-driven basis, it does not account for time spent during the trip. They

believed that people relate their driving habits most closely to the current 55/45 split,

and that the current division may be preferable, but also recommended that EPA collect

more data including the effects of modern-day congestion.

Our response:

The two public comments submitted on this topic suggested that most people

intuitively consider how much time they spend driving in either city or highway-type

conditions, rather than the percent of miles driven, and moreover, that most people think

of their driving as 50% city and 50% highway, or something close to that. We are

inclined to agree with this, since the label is designed for the general public's use. We

also note that the combined fuel economy used for corporate average fuel economy

(CAFE) and the Gas Guzzler tax remains 55% city/45% highway, according to EPCA

and IRS statutory requirements. Thus, in order to maintain continuity, we are

maintaining the weights for combined fuel economy at the current 55% city and 45%

highway weights.

2.3.4 Range of Expected Fuel Economy

What we proposed:

Although not statutorily required, the current label provides a single statement

explaining why actual fuel economy will vary from the EPA estimates and an expected

range of fuel economy for that vehicle, determined by +/- 15 percent of the city and

highway estimates. Providing the range of expected city and highway fuel economy on

the label helps consumers predict their fuel economy across a wider spectrum of driving

conditions. The current label presents a few reasons why mileage will vary and

includes the range of expected city and highway fuel economy. Earlier focus group

research showed that consumers were not easily associating the ranges given with city

and highway numbers with the vehicle. Some thought that this information was

associated with the city number, since it was located directly below it. We proposed to

split this statement into two separate elements: 1) the general statement that fuel

economy will vary, and 2) the numerical range of expected city and highway fuel

economy. In order to help consumers determine their realistic fuel economy, we

proposed to place the range of expected fuel economy closer to (underneath or on the

side of, depending on the label) the actual city and highway estimates. We also

proposed to increase the range to +/- 17 percent, representing a 10th to 90th percentile

of expected in-use fuel economy.

What commenters said:

AAM/AIAM noted that this information is not statutorily required by EPCA and

stated their belief that it adds little value. They recommended removing this information
27

from the label, “thus making the look of the label less cluttered and making the

remaining information more bold, concise, and noticeable.” They also suggested that

the expected fuel economy range be provided in EPA’s Fuel Economy Guide and on the

fuel economy web site, www.fueleconomy.gov.

Our response:

We agree with the industry comment that since the current label’s presentation of

expected fuel economy is difficult to comprehend, it is not useful to car buyers in that

form. However, we maintain that it is important to inform consumers that fuel economy

will vary and to provide a reasonable range given this variability. Focus group

participants more favorably received the shortened disclaimer language and its new

location. The groups recognized that fuel economy would vary based on the driver and

driving conditions. Some stated that since the estimated values can easily be mistaken

for reality, it is necessary to include the expected range as a disclaimer. Others

commented that this information may be particularly useful for younger, first-time car

buyers, who may not be aware of how fuel economy can vary. We acknowledge these

comments and are finalizing this requirement as proposed.

2.3.5 “Your Mileage Will Vary” Statement

What we proposed:

We proposed to separate the range of expected fuel economy and the statement

that actual fuel economy will vary from the EPA estimates, in order to emphasize to

consumers that the mpg values are estimates only and that drivers may experience

different fuel economy depending on many factors. Since many focus group

participants did not notice the current label’s text, which includes reasons why mileage

will vary, we proposed to reword and reformat it to convey the message more

effectively. The proposed text was “Your actual mileage can vary significantly

depending on how you drive and maintain your vehicle and other factors.”

What commenters said:

NADA commented that this “disclaimer/qualifier” is an “all-important” item and

should continue to be on the label.

Bluewater Network suggested replacing the proposed language with the

following, in order to educate consumers about maintenance and driving habits that

affect fuel economy: “For best mileage performance, please keep tires fully inflated,

conduct regular tune-ups, use cruise control, avoid rapid acceleration and high speeds,

and reduce air conditioning, defrosting, or heating when possible.” They also

recommended that EPA delete the “actual fuel mileage may vary” or relegate it to a

footnote.
28

Toyota suggested adding detail to the “Your mileage will vary” statement by

listing items a driver typically can and cannot control. Their proposed language was the

following:

Our response:

Most commenters recognized the importance of the disclaimer statement but

took issue with how much detail should be provided in this statement. We tested

alternative wordings with the focus groups to see if additional explanation, as suggested

by Bluewater Network and Toyota, would be necessary and the general consensus was

that fewer words were better. Nearly all of the groups independently suggested the

same revision to the disclaimer statement, which was a combination of a simple

statement and a web link. Since all groups were able to list multiple reasons why fuel

economy varies, including weather, driving habits, and maintenance, we considered that

it may not be necessary to provide detailed reasons on the label. Many advised that

including too much detail would be "preaching to the choir," and suggested a web link

for young first-time buyers who may not know these details, since younger drivers may

be more inclined to use the internet. We are finalizing a shorter disclaimer statement:

"Your actual mileage will vary depending on how you drive and maintain your vehicle."

However, we are not adding the web site to the statement, because the final label

includes this link in the bottom border, directly beneath this text.

2.3.6 Graphical Updates and Government Logos

What we proposed:

We proposed to update the appearance of the label. In the sample labels, we

included a more contemporary fuel pump design. Since many focus group participants

were unaware that the EPA issues the fuel economy estimates, rather than auto

manufacturers or dealers, we proposed label designs with more prominent EPA and

DOE logos to clarify that the mpg values originate from government testing. We also

proposed adding a link to the EPA-DOE Fuel Economy Guide website

(www.fueleconomy.gov) to provide additional information for interested consumers.
29

What commenters said:

Public Citizen supported making the government logos more prominent to

indicate that EPA and DOE are responsible for the fuel economy labels and testing.

AAM/AIAM agreed with enhancing the EPA and DOE logos and label heading.

Subaru initially objected to the gray gas pump watermark in the background of

two of the proposed labels because it would cover the Subaru brand logo artwork that

currently appears on their Monroney label, but agreed with the more prominent display

of the government logos. In a subsequent comment, Subaru informed EPA that it was

implementing a new design and was no longer concerned with the fuel pump graphic.

Our response:

We are requiring the enhanced EPA and DOE logos on the label and the "EPA"

designation in the label title because commenters and focus group participants clearly

indicated that the government seals add credibility to the label.

2.3.7 Environmental Information on Fuel Economy Labels

What we proposed:

Historically, EPA used the Green Vehicle Guide web site

(www.epa.gov/greenvehicles) to rate vehicle fuel economy and emissions information

on a 0 to 10 scale. Some suggested adding similar information to the label to convey

more completely a vehicle’s environmental performance and to provide a graphical

vehicle to vehicle comparison. Prior to the proposal, we showed examples of fuel

economy labels that included environmental ratings (for Air Pollution and Greenhouse

Gas) to focus group participants and asked for their impressions. Although there was

confusion arising from the newness of the information, they generally agreed that the

ratings could be useful in the future. We requested comment in the NPRM on a

possible voluntary environmental labeling program.

What commenters said:

AAM/AIAM stated that they “...support making available to the consumer, data

on vehicle emissions and fuel economy but do not support ratings or rankings of

vehicles that must ultimately be based on subjective methodologies.” They continued,

“...we believe that fuel economy and exhaust emissions data should be reported

separately to the consumers.” They argued that the label should report exhaust

emissions data to the consumer on the vehicle’s certification standard and not a

subjective “1 to 10” or other type of scale, because skeptics can raise numerous

questions on how the factors are weighted. They suggested that EPA make factual

information available to the public to ensure that each individual can make informed
30

decisions, although they also noted from the focus groups that additional information

dilutes the meaning of the overall information. They recommended that we exclude this

information on the label, but publish it on the web site for those interested.

While NADA commented that “no environmental descriptor is necessary,” Public

Citizen suggested that EPA require this information and that it would “greatly enhance

consumers’ ability to purchase a vehicle that meets their environmental demands.”

UCS commented that EPA should execute its authority under U.S.C. Section

32908(b)(1)(F) to require environmental information on fuel economy labels. UCS

preferred numerical and graphical representations of the vehicle’s greenhouse gas and

smog scores like those set forth in the NPRM, noting that these scores should compare

vehicles with all new vehicles, instead of those within a certain class. UCS also

suggested that EPA include an official “seal of approval” on the label for the most

environmentally benign vehicles.

ACEEE agreed that the label should include greenhouse gas and smog ratings,

since space is available. They cited their 2005 report, “Environmental Performance

Labels for Vehicles: Findings of Research with Consumers and Stakeholders,” as a

potential source for different forms of presenting this information. They further suggest

that the time is ripe for adding this information to the label because of the label redesign

process that our proposal put in motion.

Environmental Defense did not support a voluntary environmental label with

EPA's greenhouse gas rating from 0-10, which they criticized as "too coarse". They

commented that we should instead educate consumers on the relation of fuel economy

and the environment and emphasize that individuals can reduce impact on the

environment by choosing a vehicle with high fuel economy.

An anonymous commenter suggested that EPA include “CO/mile” (but

undoubtedly meaning CO2 emissions per mile) to raise awareness about the vehicle’s

impact on global warming.

Our response:

While some environmental groups wanted to add other environmental

information to the label, automobile manufacturers and NADA were reluctant, since they

were concerned with the subjective nature of the 0 - 10 scale. Focus group participants

repeatedly indicated that a simpler label conveyed the fuel economy message better.

At this point in time, we believe it is premature to add environmental or GHG score

information to the label. Since there was no clear consensus from the public comments

and several commenters raised concerns about the scales for these scores, we believe

the issue needs further evaluation.

However, to fully consider the suggestions from environmental groups, we tested

the following brief statement linking fuel economy and the environment with the focus
31

groups: "Buying a vehicle with better fuel economy helps protect the environment and

reduces dependence on oil." Reaction to this statement was strongly divided; some

declared that the statement was "preachy," obvious, and unnecessary, while others

stated that it was important and reflected EPA's mission. Because public comments

and focus group reactions were strongly divided, and because we would like the label to

be as simple and uncluttered as possible, we are not requiring other environmental

information on the label at this time. We agree with automakers that the EPA Green

Vehicle Guide and Fuel Economy web sites are better places to publish information on

environmental impacts from vehicle ownership, since there is more space for

elaboration. Thus, we are not currently addressing a voluntary environmental labeling

effort, but may choose to do so in the future.

2.3.8 Vehicle Descriptor Information

What we proposed:

Consistent with the current regulations, we proposed that fuel economy labels

within the "Monroney" price sticker not contain vehicle descriptor information, but those

affixed separately must include it.

What commenters said:

AAM/AIAM agreed with the deletion of fuel metering, catalyst usage, and

California systems from the vehicle description requirements in 40 CFR 600.307-08(c).

They additionally suggested that we delete “(iv) Number of engine cylinders or rotors”

as a separate line item subsection and include it instead in the category of “additional

engine information, if necessary." Thus, they suggested changing paragraph (v) from

its proposed reading (“Additional engine description, if necessary to distinguish

otherwise identical model types, as approved by the Administrator; and”) to the

following: “Additional engine description (for example, number of cylinders or rotors or

number of valves), if necessary to distinguish otherwise identical model types, in

accordance with good engineering judgment; and...."

NADA suggested that EPA reconsider whether to require all of the vehiclespecific description information in the proposed section 600.307-08(c) and noted that

EPA has considerable statutory authority in this regard.

Several commenters recommended that the label continue to contain the vehicle

descriptor information on the label, because they thought the proposed labels omitted

information such as the vehicle model, engine and transmission type, etc.

Our response:

Our goal for vehicle descriptor information is to provide consumers enough detail

to distinguish between visually identical models on a dealer's lot that may have different
32

fuel economy because of differences in engine design, (such as number of cylinders,

rotors, etc.). We agree with the manufacturers’ suggestion and are revising the

regulation accordingly. We also recognize that EPA has considerable statutory

authority regarding vehicle descriptor information, and would like to finalize the

minimum text required for consumers to match the vehicle and its fuel economy. This

information would appear only on those fuel economy labels that are physically

separate from the price stickers, an infrequent occurrence, based on an informal survey

of car makers.

We are also finalizing details for the location, font size and other design

information. To assist manufacturers, we are including an example label that contains

the vehicle description information.

2.3.9 Website Reference

What we proposed:

We proposed to require that the label include a web link to the jointly sponsored

EPA-DOE website, fueleconomy.gov, which contains information on vehicle fuel

economy matters and includes downloadable versions of the Fuel Economy Guides,

1985 to present.

What commenters said:

NADA commented that the label should refer prospective purchasers to the

www.fueleconomy.gov website and the DOE/EPA Fuel Economy Guide for more

information, noting that those purchasers who consider fuel economy an important

factor in their choice will likely use these tools to compare options before arriving at the

dealer. Public Citizen likewise supported placing the website reference on the new

label. UCS commented that “the prominent inclusion of [the website address] on the

label is essential.”

Our response:

We agree with the commenters that the web link is an important addition to the

label. The pre-proposal and post-proposal focus groups confirmed that the web link

was useful and important information, and thus we are finalizing it on the label.
33

2.3.10 Transition Language

What we proposed:

We requested comments on the need for a temporary transitional statement on

the label to indicate that that the fuel economy estimates were based on new methods.

We also requested comments on how long it should appear on the label.

What commenters said:

Several commented that for a period of time after the new labels are introduced,

the label should include a statement explaining that fuel economy estimates are based

on new methods. For example, A. Benenson suggested the following:

“Starting with 2008 model year vehicles, EPA has improved the way it estimates

vehicle mileage. Because of this change, the mpg estimates on this label more

accurately reflect the mileage drivers will actually obtain.”

The Alliance/AIAM agreed that a brief statement would be a positive addition to

the label and suggested "New 2008 Methods."

Our response:

We agree that a transitional statement is needed, although A. Benenson’s

statement may be too wordy and the auto makers’ statement too brief. We tested the

following text with the post-proposal focus groups: "These estimates reflect new EPA

methods beginning with 2008 models." The groups understood the sentence but felt

that it left the reader to ask, "What are the new methods?" They then concluded that

they might find the answer at the web site provided or in the Fuel Economy Guide.

Since this is the goal of the website reference, we are finalizing the statement tested

with the focus groups. It will be centered near the top of the label.

When asked how long the transitional statement should appear on the label,

focus group response varied widely. Some suggested the expected duration of a

consumer’s vehicle purchase cycle and others recommended one year, indicating that

this information would become "stale" after a while. We are requiring this transitional

statement on all fuel economy labels for the 2008 and 2009 model years, because

dealer lots may contain vehicles with both label designs. When 2010 models are

offered, however, all models on dealer lots will have the new label design, and the text

will not be necessary anymore.
34

2.3.11 City and Highway Numbers

What we proposed:

We proposed to retain the large "city" and "highway" numbers as the most

prominent information on the label. The numbers on the four alternate labels were all

the same size, and were slightly larger than the old label.

What commenters said:

An anonymous commenter, citing a memory that after the 1972 oil embargo the

city estimate had a larger font than the highway estimate, desired to see this again,

believing that the city estimate is a more accurate estimate of overall fuel economy.

Our response:

The commenter is correct that in the early stages of fuel economy labeling, an

EPA regulation eliminated the highway estimate from the label, because many

consumers complained that the highway number was unrealistically high When EPA

revised the label in 1984, it reinstated the highway estimate with a 22% downward

adjustment to reflect real world driving more accurately. The new calculations we are

finalizing today reflect changes in driving behavior and technology since 1984, and

better predict today’s on-road city and highway fuel economy. Although no single

estimate can ever capture a person's complete real world experience, we believe that

consumers will be more likely to achieve the new estimates. While we are continuing to

provide consumers with the range of city and highway fuel economy they can expect to

achieve on the road, we are also introducing a combined fuel economy estimate on the

label. Finally, when we showed pre-proposal focus groups a label having a single range

instead of separate city and highway estimates, they strongly preferred to see both

numbers, because this format was familiar, and the new presentation confusing.

Therefore, we are requiring both the city and highway estimates.

2.4 Label Size and Orientation Issues

What we proposed:

Of the four proposed labels, two were positioned vertically (“portrait”), and two

horizontally (landscape). The vertical format was 4.5 inches wide and 7 inches tall,

while the horizontal format (currently used) was 7 inches wide and 4.5 inches tall.

What commenters said:

Several manufacturers commented that the portrait format would require a

complete redesign of the "Monroney" price sticker label. AAM/AIAM noted that

changing the orientation would require “significant and costly modifications” to
35

manufacturers’ fuel economy labeling and vehicle pricing systems, and recommended

that we retain the current landscape format. GM stated that they recently redesigned

their Monroney pricing sticker to include the newly required NHTSA safety ratings, with

a horizontal fuel economy label, and that changes would be costly. Subaru suggested

letting the manufacturers choose between portrait or landscape versions.

The general public preferred the appearance of Alternative 4, positioned

vertically, but specifically favored its graphic of comparable fuel economy.

Our response:

We agree that the new estimates should be represented by a more contemporary

label. We acknowledge industry cost concerns about redesigning pre-existing price

stickers and recognize the challenges posed by simultaneously incorporating two new

labels onto the price sticker - the NHTSA crash rating label and the fuel economy label.

Although public commenters preferred the vertical orientation, the primary reasons

provided were more relevant to the design elements (particularly the gray “watermark”

fuel pump design with information it its “window” and the bar graphic showing

comparable fuel economy) rather than the label orientation itself. Therefore, in order to

address both the consumers’ needs and the automakers’ concerns, we are finalizing a

horizontal label orientation and requiring those elements of the vertical format that were

appealing to the public, such as the new fuel pump graphic, the bar graph of

comparable fuel economy, clearly indicated fuel cost information, expected fuel

economy ranges located close to the city and highway numbers, a disclaimer statement

that is set apart, a web link, and a transitional statement announcing the new estimates.

We do not agree with Subaru that we should let manufacturers choose their

orientation, because customers we believe it is important for consumers to recognize a

constant label design.

2.5 Implementation Outreach

What we proposed:

In the preamble to the proposal, we discussed the need for an extensive

outreach campaign to ensure that the public understands that the estimates and label

design are new.

What commenters said:

AAM/AIAM urged EPA to plan several media announcements in early 2007 to

inform consumers about the changes to the estimates and the label design.

Toyota recommended that EPA aggressively promote the new fuel economy

label to assure that customers comprehend the changes in fuel economy numbers,
36

during the label transition process. Toyota specifically suggested that EPA increase

public awareness of the transition through the Fuel Economy Guide, the fuel economy

website, and other methods, such as a pamphlet explaining the label transition.

Our response:

We concur and will work with the automotive industry and other interested parties

to inform the public on changes to the fuel economy label and estimates.

2.6 Comparable Class Designations

What we proposed:

We proposed to add SUVs and Minivans to the pre-existing list of comparable

classes, and to expand the "Small Pickup Truck" class weight limit of 4500 lbs to 6000

lbs.

We did not propose a class definition for "crossover" vehicle types, but requested

comments on how to classify vehicle designs that do not clearly fall into a single

category, based on the EPA definitions. We proposed to retain our current policy of

allowing manufacturers to recommend,, subject to EPA approval, which class they

believe best fits a "crossover" vehicle.

What commenters said:

AAM/AIAM supported adding minivans and SUVs to the list of comparable

classes, suggesting that the proposed definition of minivan be modified to read:

"minivan means a light truck which...," instead of "minivan means an automobile

which...," to align with the definition of light truck given in 40 CFR Section 600.315-

08(a)(2)(iv). They also recommended that we clarify the distinction between minivans

and SUVs by adding a rear sliding door to the minivan definition. They agreed with the

proposed increase in weight delineation for the small pickup truck class from 4500

pounds GVWR to 6000 pounds GVWR. For "crossover" vehicles, they agreed that EPA

should continue to determine the most suitable class on a case-by-case basis. They

commented that although they did not recommend changing any of the other

comparable class designations, they were concerned about the graphic presentation of

the range of fuel economy for comparable vehicles, as discussed previously in Section

2.3.1.

UCS commented that the addition of SUVs and minivans to the vehicle class list

was "good in principle," but that since the definitions of the two are similar, it is likely

that many vehicles will fit both definitions.

UCS commented that class distinctions have been blurring in recent years, and

that any prescribed definition could quickly become obsolete. They further noted that
37

EPA should present information on the label to accommodate consumers, who are

increasingly shopping across a number of classes, such as minivan, SUV, large car,

etc. They proposed a comparable class fuel economy graphic that gave the range of

fuel economy for all vehicles and the range of the given class.

Our response:

We agree with auto manufacturers and UCS that we should clarify minivan and

SUV definitions, and are adopting the suggestions from AAM/AIAM.

We also agree that we should retain our current policy to determine a class for

"crossover" vehicles on a case-by-case basis. So-called “crossover” vehicles are those

that meet the definition of more than one vehicle class, and thus are difficult to

categorize. EPA currently uses discretion to assign these vehicles to a class on a caseby-case basis. For example, we attempt to determine which class assignment makes

sense from a consumer perspective (e.g., is it more likely to be considered by

consumers looking for a minivan or for an SUV) and what marketing segment is being

targeted by the manufacturer. We did not propose to change how we are addressing

the recent proliferation of “crossover” vehicles, but we requested comments on whether

we should create a separate “crossover” class. Some public comments supported the

creation of this class, but did not suggest how to define it. Auto companies were

opposed to it, citing the difficulties in creating a meaningful class definition. Lacking

such a definition that would clearly distinguish between a “crossover” vehicle and other

vehicle classes, we are not creating a separate class for crossover vehicles. It should

also be noted that the EPA-defined vehicle classes are used only to provide consumer

information about fuel economy and serve no other regulatory purpose (i.e., they are

not used to determine CAFE compliance, and they are not used for the purpose of

determining compliance with EPA emission standards.)

In portraying the range of fuel economy for comparable vehicles on the label,

several commenters noted that the comparable class structure does not adequately

provide consumers with meaningful fuel economy comparisons, and that class

distinctions have been blurring in recent years. Commenters noted that many

consumers shop across classes. These commenters did not suggest any specific

revisions to the class structure to address these concerns; rather, their suggestions

relate to the presentation of the comparable class information on the label, which is

addressed in Section III. Additionally, manufacturers expressed concern that the wide

fuel economy ranges of some classes are not necessarily representative of vehicles that

consumers would normally compare (the example they cite is the midsize class, which

contains the Toyota Prius and the Rolls Royce Phantom). Auto manufactures further

noted that the highest sales vehicles are typically near the midpoint of the range, and

that vehicles at either end of the range (low and high fuel economy) are typically

vehicles with low sales volume or “niche” vehicles. They suggest that consumers

usually shop within subsets of the defined vehicle classes, and not across the entire

class. To address these concerns, manufacturers recommended against using a

graphical representation of the comparable class fuel economy, and that EPA should
38

continue to use the text that is used today. However, they did not suggest any specific

changes to the class structure to address these concerns.

We believe that with the changes we are finalizing today, the comparable class

structure generally represents the distinctions between vehicle types offered in the fleet

today. Absent suggestions during the public comment period for new comparable

vehicle classifications, we are finalizing the comparable class structure largely as

proposed, with minor changes as discussed above. We welcome interested parties to

continue working with EPA in the future on how to ensure that the comparable classes

are kept current with the dynamic vehicle fleet. If it becomes necessary in the future to

further modify the comparable class structure, EPA would do so through a rulemaking.

2.7 Labeling Requirements for Dual Fueled Vehicles

What we proposed:

Currently, manufacturers may voluntarily include the alternative fuel’s estimated

fuel economy and annual cost on the label, but are not required to do so. The EPCA

statute currently requires that the label should:

“(A) indicate the fuel economy of the automobile when operated on gasoline or

diesel fuel;

(B) clearly identify the automobile as a dual fueled automobile;

(C) clearly identify the fuels on which the automobile may be operated; and

(D) contain a statement informing the consumer that the additional information

required by subsection (c)(2) of this section is published and distributed by

the Secretary of Energy." Ref. 49 U.S.C. 32908 (c)(3).”

The current labeling requirements for dual fueled vehicles are consistent with

these EPCA requirements. We neither proposed changes to these requirements, nor

sought comment on the topic.

What commenters said:

EPA received a late public comment from several environmental and consumer

groups urging EPA to require manufacturers to include for E85 vehicles the fuel

economy and estimated annual fuel costs of both gasoline and ethanol. With increased

marketing and availability of these vehicles, the late comment suggested that the label

be required to not only display separate gasoline and ethanol fuel economy and annual

cost estimates, but also to provide EPA smog and greenhouse gas scores and the ratio

of ethanol to gasoline (which is not always 85:1) on the label. The additions would

inform customers that, when operating an E85 vehicle with E85 fuel, their fuel economy

will be decreased, not a condition that most consumers expect from vehicles touted as

“environmentally friendly”. They also noted that these additions would educate
39

customers that although E85 fuel economy may be lower than that of gasoline, the

alcohol-based fuel reduces greenhouse gas emissions.

Our response:

We believe that a mandatory requirement for manufacturers to display E85 fuel

economy information on the label in addition to gasoline deserves a more carefully

considered approach. Before requiring the inclusion of E85 fuel economy for FFVs, we

must consider many issues pertaining to the design and placement of this information,

such as: 1) how to clearly present E85 mpg relative to gasoline; 2) how to educate

consumers that E85 helps reduce greenhouse gases; 3) how to best convey estimated

annual fuel costs of E85 (given the varying cost of E85 prices nationwide), and 4) how

to graphically depict comparable class fuel economy for E85 in addition to gasoline.

Since we did not request comments on this topic, we are not finalizing

requirements today that differ from the current regulations. However, we agree that it is

important to provide consumers with complete fuel economy information on alternatively

fueled vehicles, particularly in light of the rising sale of flex-fueled vehicles and a

developing E85 fuel infrastructure. We agree that it is important for consumers to

understand that fuel economy on E85 is typically 20-30 percent lower than on gasoline,

because E-85 has a lower energy density.7 Consumers can view the gasoline and E85

estimates of all FFVs in the Fuel Economy Guide and on the www.fueleconomy.gov

web site.

We strongly encourage manufacturers to voluntarily include the E85 (or other

alternative fuel) mpg and estimated annual fuel costs on the label. The final label

design includes a placeholder for such information. In the near future, we plan to work

with interested stakeholders to determine how best to present E85 fuel economy

information on the label.

7

Based on fuel economies of gasoline and E85 reported in the Model Year 2006 Fuel Economy

Guide, p. 18.
40

Chapter 3: Implementation Issues

3.1 In-Use Validation of 5-Cycle Coefficients

What we proposed:

In the proposal, we expressed an interest in ensuring that the new methods

continue to reflect real-world fuel economy into the future, and we encouraged

stakeholders to submit data that would inform future analysis and potential changes to

the methodology. While we did not propose a specific program for validation of the 5-

cycle formulae, the NPRM clearly expressed that we would be receptive to new and

additional data. We noted that the 5-cycle formulae are derived from extensive data on

real-world driving conditions, such as driving activity, temperatures, air conditioner

operation, trip length, and other factors. We requested comment on the formulae and

on the underlying data on which they are based. We encouraged stakeholders to

submit data that might inform the 5-cycle analyses, and we expressed our desire to

ensure that the 5-cycle approach continues in future years to reflect updated conditions

impacting real-world fuel economy. Therefore, in the NPRM we encouraged

stakeholders to submit data so that EPA may evaluate the need for changes to this

approach over time.

What commenters said:

AAM/AIAM expressed support for the 2008 mpg-based approach, calling it “...a

good compromise between urgency and use of available data...” However, they believe

that “EPA has an obligation to validate the proposed five-cycle equations against

available in-use data to ensure the continual integrity of the labeling program.” They

raise a number of concerns with the 5-cycle approach that they believe warrant

additional validation. For example, they believe that the equations may be appropriate

for predicting aggregate fleet-wide fuel economy, but that they may break down when

applied to individual vehicles. They also cite technical reasons for questioning the

accuracy, particularly with respect to the inherent variability of the US06 cycle and how

that might carry through to the label values given the high weighting of the US06 in the

highway equation. They further note that the cycles used in the 5-cycle approach were

designed as worst-case emission test cycles, and that the 5-cycle approach

assumptions that these “extreme” cycles can be used to accurately predict fuel

economy performance over a wide range of operation may be incorrect, especially for

new technologies such as hybrid vehicles and cylinder deactivation. (These specific

criticisms are addressed in Section 5 of this Response to Comments Document.)

AAM/AIMA makes it clear that they are not asking for new driving cycles, but rather for

adjustments to equations and coefficients if warranted by investigation of in-use data.

They believe that EPA must take a leadership role in this effort, and further urge EPA to

“...place a milestone date in the rule (approximately August of 2009) before which the

agency would review all available data and determine if the available data raise

questions or concerns about the effectiveness of the labeling program.” If this question
41

is answered in the affirmative, AAM/AIAM requests that EPA initiate a supplementary

rulemaking to propose and finalize changes.

Honda likewise expressed support for the mpg-based methodology, noting that “it

addresses an immediate need for responding to customer concerns...” They expressed

a preference that the equations be validated, but mitigating this concern is the fact that

any errors in the methodology would be applied equally to all vehicles.

DaimlerChrysler and other automobile companies commented that the new

regulation must allow for future review and adjustments based on assessments of realworld fuel economy data. They asked that EPA affirm a commitment to adjusting the

formulae if data suggests that that the resulting fuel economy values do not reflect realworld experience. They noted the importance of this with respect to assuring that new

technologies receive accurate label values.

Toyota echoed these comments, stating that “Toyota believes that the formulas

promulgated in the NPRM need to be validated...,” expressing their support for an inuse fuel economy data collection program. Honda similarly encouraged EPA to support

a testing program of in-use vehicles to validate the 5-cycle equations. Nissan

commented that they could support surveys of in-use vehicles for fuel economy

purposes, but that EPA-mandated testing of in-use vehicles by manufacturers would be

overly burdensome.

Toyota expressed an opinion that periodic updating of the fuel economy

coefficients for the 5-cycle equations should be done every 3-4 years. Specifically, they

suggest that the equations should be updated when an innovative technology to

improve fuel economy has been introduced.

Bluewater Network stressed that allowing 20 years to transpire between

adjustments to the fuel economy procedure is unacceptable. They asked that EPA put

in place a system to “(1) monitor accuracy of test results across all manufacturers and

models and (2) to make adjustments as necessary to reflect changed technology,

driving conditions, driving habits, speeds, temperatures, etc.” They suggest three ways

to monitor accuracy: requiring manufacturers to submit onboard computer data,

instituting a consumer data collection program, and monitoring fuel economy testing

done by other institutions.

Public Citizen argues for a thorough study of real-world driving behavior and fuel

economy test procedures that ultimately reflect the findings of such a study. They

argue, for example, that the US06 and SC03 tests may no longer be accurate because

they were developed from driving surveys conducted in 1992, and driving has changed

since then (e.g., driving has become more aggressive). They state that “it is critical that

EPA’s testing procedures reflect current real-world driving conditions.” They argue that

a study is needed both in the short term to feed into new label estimates, and

periodically thereafter, to ensure that the label estimates continue to reflect real-world

driving conditions.
42

NRDC likewise commented that “...this nation’s overall fuel economy program

efforts...would critically benefit from a statistically robust collection of in-use fueleconomy data,” urging the auto companies and EPA to commit to a public/private

partnership to ensure that such a program is implemented quickly. They suggest that

the current situation is largely due to the lack of an ongoing mechanism to collect and

evaluate fuel economy data. They also ask that EPA commit to modifying the

methodology if in-use data demonstrates that a change is needed. They argue that an

ongoing program of data collection is necessary to “...ensure consumers are receiving

accurate information in the future, to prevent “gaming” of the system by manufacturers,

and to adequately support the nation’s overall fuel economy program.” NRDC is also

concerned about some criticisms that have been raised regarding the statistical validity

and accuracy of the proposed 5-cycle methodology, particularly with respect to hybrid

vehicles, and they suggest that the proposal would benefit greatly from the collection of

more data from hybrid vehicles. Section 3 of the Technical Support Document (TSD)

contains an analysis of the accuracy and validity of the 5-cycle methodology for hybrid

vehicles.

UCS states that the proposed 5-cycle methodology is “a promising interim

solution,” but that EPA needs to take the next step and begin a comprehensive study of

real-world driving patterns and fuel economy. They further state that EPA should

develop new test cycles based on the results of the in-use data collection. They argue

that by testing vehicles under the same conditions in which they are likely to be used,

the need for vehicle-specific adjustment factors can be eliminated. Further, they

suggest that new test cycles will fairly reflect the potential fuel savings of various

existing and emerging technologies, which may not be true of the proposed 5-cycle

methodology. They specify that a study of in-use driving patterns and fuel economy

would involve collecting data on fuel consumption, speed on a second-by-second basis,

trip start and end times, air conditioner and defroster usage, ambient and engine

temperatures, additional use of accessories, and other factors relevant to fuel economy.

UCS commented that in addition to updating the mpg-based equations

periodically, which will ensure that the mpg-based adjustments reflect evolution in the

relationship between 5-cycle and FTP/HFET results, EPA should update the weightings

of the various cycles within the 5-cycle equations as data becomes available.

NADA commented that EPA should implement the first phase of the program, but

“...reserve the potential implementation of the second phase until appropriate validation

testing suggests it makes sense to do so.”

AAA expressed no opposition to further research, and in fact said that it should

not be precluded, but concluded that the increasingly-important emphasis on gas prices

and fuel-efficiency mandates that EPA “...get this program up and running quickly.”

Bluewater Network similarly stated that there should be no further delay in issuing a

final rule.
43

PPG recommended that EPA consider Federal laboratories such as the National

Renewable Energy Laboratory (NREL) as a qualified source of data, and factor any

appropriate data from such agencies into the new mileage ratings.

Finally, several commenters suggested that EPA conduct an evaluation of the 5-

cycle method prior to model year 2011, when the 5-cycle method becomes required.

Our response:

In the proposal, we expressed an interest in ensuring that the new methods

continue to reflect real-world fuel economy into the future, and we encouraged

stakeholders to submit data that would inform future analysis and potential changes to

the methodology. We remain open to reviewing any valid test data that would show that

any of the 5-cycle assumptions were inappropriate for a specific vehicle and considering

modifications to the 5-cycle formulae to account for these differences. We believe it is

critical to ensure that the fuel economy methods are periodically evaluated. We are

committed to evaluating the 5-cycle method every several years (e.g., five years) to

ensure that it appropriately accounts for advancements in vehicle technology, changes

in driving patterns, and any new data collected on in-use fuel economy. We welcome

stakeholders to submit any such future data for use in our periodic evaluation of the fuel

economy test methods.

We are also committed to offering technical guidance to any stakeholder

interested in undertaking an in-use testing and data-collection program. By seeking our

technical input up front, stakeholders can better ensure that the data is collected in a

way that is ultimately best-suited to evaluate potential changes to the methodology. It is

important to note that collection of in-use fuel economy data alone is interesting, but can

only be used to indicate whether the 5-cycle estimates are too high or too low; it does

not inform how the 5-cycle methodology could be improved. The 5-cycle approach is

based on emission test results over the five test cycles and on the weighting of a

number of factors based on their average impact across all U.S. driving. Data on in-use

fuel economy alone, without complementary driving behavior and activity data, does not

provide any insight on what changes may be appropriate to the 5-cycle weighting

factors.

If appropriate data is submitted before the end of 2008, we would plan to review

it in a timely manner. If such data suggests that changes to the 5-cycle approach are

necessary, we would plan to issue a separate rulemaking to address changes to the

methodology, providing adequate lead time to the industry to comply.
44

3.2 Periodic Review and Updating of the mpg-Based Curves

What we proposed:

We proposed to update the mpg-based curves periodically, using all of the

available five-cycle fuel economy estimates for the previous three or more model years.

The proposal stated that we would publish the equations for the mpg-based approach

by January 1 of the calendar year prior to the model year to which the equations would

first apply (e.g., for model year 2010 fuel economy calculations, the equations would be

made available before January 1, 2009). We also indicated in the proposal that

updating would take place periodically, but no more than on an annual basis.

What commenters said:

While expressing general support for periodic and timely updates, AAM/AIAM

describes concerns with lead time and with the frequency of such updates. AAM/AIAM

commented that making the equations available on January 1 of the model year prior to

the model year for which they first apply provides insufficient lead time for

manufacturers. They note that the start of production for some vehicles can be as early

as January 2 of the calendar year prior, thus giving manufacturers a new labeling

equation after product designs are locked down, leaving manufacturers unable to

respond to the new equations. Consequently, they advocate making the new equations

available no later than January 1 of the model year two years prior to the model year to

which the equations would first apply. AAM/AIAM agrees that EPA should have the

flexibility to update the mpg-based equations periodically (especially if validation data

identifies a specific need), but they believe that doing so on an annual basis would be

costly and time-prohibitive. They recommend that EPA update the mpg-based

equations “only when such an update is warranted based on statistical significance,

rather than at specified intervals.”

Our response:

We plan to update the mpg-based curves periodically using all of the available 5-

cycle fuel economy estimates for the previous three or more model years. We

proposed that these revised mpg-based equations would be issued through the

publication of an EPA guidance document which would be released by January 1 of the

calendar year prior to the model year to which the equations first apply. We suggested

in the proposal that this meant, for example, that mpg equations for the 2012 model

year would be published prior to January 1 of 2011. However, we now recognize that

the model year for many manufacturers can begin almost a full year before the start of

the identically-named calendar year (i.e., the 2012 model year can begin on January 2,

2011). Manufacturers commented that issuing guidance applicable to a given model

year potentially mere days or weeks from the start of that model year for some vehicle

lines did not provide adequate lead time. We agree with manufacturers that more lead

time is needed than what we proposed. However, we do not believe a full year before

the earliest model year introduction date is necessary. We believe a period of 6 months
45

prior to the first possible model year provides sufficient lead time, and also gives EPA

ample time to issue new mpg-lines based on more current data. We are thus finalizing

regulations that require EPA to issue guidance regarding revisions to the equations by

no later than July 1 of the calendar year prior to the earliest start of the model year that

starts in the following calendar year. In other words, for new equations to be applicable

to the 2010 model year (which can begin as early as January 2, 2009), EPA must issue

guidance prior to July 1, 2008.

3.3 Use of Bag Data Factors in the 5-Cycle Equations

What we proposed:

In the Draft Technical Support Document, we derived the mpg-based equations

from a fuel economy database that consisted of both bag-specific fuel economy

measurements and estimated bag measurement data. Those vehicles with bag fuel

economy data were used to develop relationships between bag and whole cycle fuel

economy, and from these relationships the bag data was then estimated for those

vehicles lacking complete bag fuel economy data. We also estimated the relationship

between US06-City and US06-Highway fuel economy and overall US06 fuel economy

based on test data from 80 vehicles.

What commenters said:

AAM/AIAM proposed that manufacturers be allowed to use these same factors

for the initial 5-cycle regression equation when using the 5-cycle approach. They

suggested that this would “aid in the adoption of the five-cycle equation” and “promote

process simplicity going forward.” They noted that both EPA and manufacturer data

systems are not currently capable of incorporating bag data, and that use of these

factors would provide some lead time for getting these systems updated and modified.

They suggested that manufacturers not be precluded from submitting bag data, but that

if they do such data should be posted to the EPA website that provides supplementary

information to the Test Car List. They propose new regulatory language that would

implement these factors.

Our response:

We do not believe that it is necessary to allow the use of these bag data factors

for early use of the 5-cycle equation. The 5-cycle method is optional in the first several

years of the new program (model years 2008-2010). EPA will be prepared to receive

bag data in these instances. Manufacturers will have the necessary bag data to

incorporate into the 5-cycle test, regardless of whether the data systems are completely

ready to accept such data. We do not believe it is appropriate or reasonable to allow

manufacturers to estimate bag data using these factors, as it would lessen the accuracy

of the 5-cycle result for a given vehicle. Moreover, manufacturers would possess the

bag data results. Therefore, we are requiring that manufacturers use actual bag fuel
46

economy data in their 5-cycle fuel economy calculations, and that they submit that

information to EPA.

3.4 Flexibility to Apply the mpg-Based Adjustments at the Model Type Level

What we proposed:

Section 600.115-08 of the proposed regulations would apply the mpg-based

adjustments at each test result level supporting the fuel economy label instead of at the

model type level. These values then feed into section 600.207, which determines the

fuel economy values for each vehicle configuration, which ultimately feed into section

600.210 to calculate the label value.

What commenters said:

AAM/AIAM noted that current regulations apply an adjustment factor at the model

type level (sections 600.209a and 600.207b), not at the test result level, and that

manufacturer and EPA data systems are not configured to apply an adjustment factor at

the test result level. According to AAM/AIAM, many manufacturers do not have

separate data systems for fuel economy labeling and CAFE, and unless EPA allows

flexibility to apply the adjustments at the model type level, this change would impact

manufacturer’s CAFE databases. They propose specific language for section 600.210

that would accomplish the desired result.

Our response:

We agree with AAM/AIAM that allowing flexibility in applying an adjustment factor

at the model type level instead of the test result level will be less costly to implement

and we are modifying the regulatory text to reflect this. The city and highway test

results obtained from certification and fuel economy test vehicles shall first undergo the

vehicle configuration and model type calculations for FTP and HFET-based fuel

economy (sections 600.206-08 and 600.208-08), and then the resulting FTP-based and

HFET-based model type fuel economy values shall undergo the derived 5-cycle

calculations. This change is consistent with the placement of the current fuel economy

label downward adjustments (-10% city and -22% highway), which are performed after

the model type fuel economy is determined.

As a result, Section 86.600.115-08 has been removed, and the remaining

sections in Subpart B renumbered accordingly, and the appropriate derived 5-cycle

calculations and associated text has been added to section 86. 600.210-08. The final

label values will not be impacted in any significant way, except for possible minor

rounding differences.
47

3.5 Criteria for Additional 20°F / SFTP Testing

What we proposed:

Each year, manufacturers must demonstrate compliance with federal emission

standards by performing tests over all five test procedures. The vehicles on which

these tests are performed are known as “emission data vehicles”, which are selected to

represent the “worst-case” emitting vehicle in a group of vehicles, known as a “test

group”, which share common engine and emission control designs.8 EPA issues

certificates of emission conformity for each test group of vehicles in each model year.

Thus, for each test group, there exists a set of official certification test data from all five

test cycles - FTP, HFET, US06, SC03 and Cold FTP. The fuel economy measured from

these official certification tests can be inserted into the 5-cycle city and highway

formulae to determine city and highway fuel economy values. Since FTP and HFET

testing is included in the official certification data, the mpg-based city and highway fuel

economy values can also be determined. Thus, for each emission data vehicle, the 5-

cycle city and highway fuel economy values then can be compared to the mpg-based

city and highway fuel economy values. We believe that it is reasonable to allow

continued use of the mpg-based line when the available 5-cycle fuel economy data

(from emissions certification) indicates that the mpg-based fuel economy determined

from the official FTP and HFET tests performed for the test group are similar enough to

the 5-cycle fuel economy determined from the official FTP, HFET, US06, SC03 and

Cold FTP tests for that same test group. In that case, the manufacturer can use the

mpg-based method for all model types covered under the EPA certificate of conformity

that is represented by the 5-cycle data submitted to represent those vehicles. The

manufacturer will not need to conduct 5-cycle testing for fuel economy labeling for these

model types.

What commenters said:

AAM/AIAM expressed concerns that EPA’s proposed rule does not sufficiently

address certain common and uncommon certification vehicle test processes that would

present challenges in determining whether or not the criteria for additional testing are

applicable. They provide the following examples:

8

The “emission data vehicle” is the test vehicle chosen to represent a “test group” for emission

certification purposes. A “test group” is made up of vehicles that share common combustion cycle,

engine type, fuel type, fuel metering system, catalyst construction and precious metal content, engine

displacement, number and arrangement of cylinders, and emission standards. The emission data vehicle

is required to be the vehicle within the test group that is expected to be worst-case for exhaust emissions.

In general the criteria that cause the emission data vehicle to be worst-case for emissions will also cause

it to be worst-case for fuel economy (e.g., it will be the heaviest vehicle in the test group, with an

automatic transmission, four-wheel drive, etc.). In general, the FTP, HFET, US06 and SC03 are

performed on the emission data vehicle to demonstrate that the test group complies with the federal

emission standards. The Cold FTP is performed on the worst-case vehicle within a durability group, which

represents a larger group of vehicles, including those covered in the test group.
48

 When a model type is certified under multiple test groups (e.g., a model type

certified under both Federal and California test groups);

 When the five cycles are not conducted on the same vehicle sub-configuration

(e.g., SC03 tested at ALVW and US06 tested at LVW);

 When the EDV conducts multiple tests for any of the five cycles (e.g.,

manufacture-conducted testing and agency confirmatory testing);

 When the test group is dual-certified (at heavier and lighter test weights).

AAM/AIAM provides proposed language to be added to section 600.116-08 which they

believe would add consistency and fairness to the process. They propose that the

regulations specify that:

 In general, manufacturers should evaluate data generated in the same vehicle

sub-configuration to determine if the criteria for additional testing are met.

 EPA will provide guidance by the end of 2008 on how manufacturers should

evaluate if the criteria are met when multiple test data exist, when multiple sets of

5-cycle data exist, and when model types are certified under multiple test groups.

 Once a model type is approved as not requiring additional 20F/SFTP testing,

then the manufacturer may proceed with the labeling of products of evaluation of

meeting the criteria will not be revisited.

 A requirement to conduct additional 20°F/SFTP testing for 2011 and later model

year products is only to be based on the test group's 2011 and later model year

five-cycle test data. For example, if a 2010 MY product is carried over to the

2011 MY, and the 2010 MY product used the mpg Approach to calculate the

label, then the 2011 MY product should be allowed to use carryover label values.

 If the criterion to conduct additional 20°F/SFTP testing is not met based on

manufacturer-conducted testing, but data from subsequent agency-confirmatory

testing result in the criteria being met, then manufacturers shall be allowed to use

the mpg-based equations for calculating label values for all model types in the

same test group as the certification vehicle except for the model type

represented by the certification vehicle's configuration. That model type would

then be required to use the five-cycle equations to calculate the label values and

would be allowed to use appropriate agency-confirmatory test data to calculate

the label values. On principle, AAM/AIAM believes that evaluations to determine

if the criteria for additional testing are met should be based on five-cycle test

results conducted on the same test vehicle at the same test facility. AAM/AIAM

is concerned that if agency-confirmatory test data suddenly resulted in a

requirement for additional testing, manufacturers could not reasonably complete

all additional five-cycle tests required for affected models in that test group and

produce fuel economy labels before production.

Our response:

We agree that whenever possible manufacturers should evaluate data generated

by the same vehicle configuration or sub-configuration. Although we acknowledge the

manufacturer’s point that this may not always be possible, we believe that in most cases
49

the official EPA test data should suffice, without adjustment or substitution. The

manufacturers noted several situations where the results for the five test procedures

might not meet the ideal in terms of comparability (e.g., tests done on different subconfigurations with differing test weights). It may be appropriate in some of these

situations to allow the manufacturers to make adjustments to fuel economy test results

in order to achieve results that are comparable across the five tests. For example, if

four tests are conducted with a test weight of 4500 lbs and one is tested at 4750 lbs, we

expect that an appropriate method could be identified that would enable the

manufacturer to adjust the test result at the heavier test weight to represent a lower test

weight. To address this situation, a provision has been added to the regulations

allowing the Administrator to approve adjustments or substitutions to the official

certification test data. We intend to issue guidance that will address a range of

reasonable adjustments and substitutions of fuel economy data, and that will maintain a

level playing field across the industry.

3.6 Analytically Derived Fuel Economy

What we proposed:

Currently, the US06, SC03 and cold FTP tests are only performed on a sub-set

of new vehicle configurations. In contrast, for fuel economy purposes, FTP and HFET

tests are performed on many more vehicle configurations. In order to minimize the

number of additional US06, SC03 and cold FTP tests resulting from this proposal, we

proposed that manufacturers be allowed to estimate the fuel economy over these three

tests for vehicle configurations that are not normally tested for emission compliance

purposes using the fuel economy measurements that are normally available. This is

currently done on a more limited basis for both the FTP and HFET, and is referred to as

analytically derived fuel economy (ADFE).

What commenters said:

AAM/AIAM support the use of ADFE, but expressed concern that no definitive

timetable was established to ensure that a method will be approved by the EPA before

5-cycle testing is required for some labels beginning in the 2011 MY. They suggest that

the regulations should state clearly that EPA will provide guidance by the end of the

2008 calendar year on how to estimate five-cycle fuel economy for configurations not

normally tested over all five cycles. They also request that the regulations provide

sufficient flexibility to allow EPA to consider other proposals for determining analyticallyderived estimates that may be offered by manufacturers. As an example, they note a

possible method using the ratio of “five-cycle city fuel economy” to “FTP fuel economy”

of the certification vehicle, applying that quotient to the FTP fuel economy of the FEDV

in the same test group to estimate five-cycle city fuel economy of the FEDV. A similar

approach could also be used to estimate highway fuel economy. They also note that

EPA may want to consider other more sophisticated methods to estimate individual

US06, SC03 and 20°F fuel economy results analogous to currently approved methods

to estimate FTP and HFET fuel economy.
50

Our response:

When a vehicle is required to generate data from all five test cycles, there are

multiple ways for the manufacturer to accomplish this. One way would be to perform

the three additional tests – the US06, SC03, and cold FTP tests (the FTP and HFET

would be performed under current and future requirements). The other way is to

estimate fuel economy values over the US06, SC03 and cold FTP tests analytically (i.e.,

analytically derived fuel economy, or ADFE) from testing of a similar vehicle over these

three cycles. Under this method, manufacturers will be allowed to estimate the effect of

differences in inertia test weight, road load horsepower, and N/V ratio (the ratio of

engine revolutions to vehicle speed when the vehicle is in its highest gear) on fuel

economy, and use these estimates to calculate predicted fuel economy over the three

new fuel economy test cycles. A procedure to estimate the effect of these three vehicle

parameters on FTP and HFET fuel economy has already been developed.9 We plan to

work with manufacturers to appropriately analytically derive fuel economy for the US06,

SC03 and cold FTP tests. We will implement these estimation procedures using

agency guidance, as is currently done for FTP and HFET fuel economy.

3.7 Consumer Education Issues

What we proposed:

While we did not propose anything specific with respect to consumer education,

our effort in redesigning the label is to improve how we communicate fuel economy

information to consumers.

What commenters said:

AIAM/AAMA and Subaru suggested that EPA plan several media

announcements in early 2007 to inform consumers that new changes have been made

to the method for estimating the fuel economy values that will appear on the window

stickers of 2008 MY vehicles, including any early introduction vehicles that may be

available soon.

Toyota supports and recommends an EPA initiative to improve consumer

education on fuel economy improvements that can be achieved through better vehicle

maintenance and driving techniques which promote fuel conservation. NADA opined

that it will continue to be necessary to remind vehicle buyers that variations in climate,

traffic, driving styles, accessory use, loads, tire pressure, weather, vehicle age, vehicle

modifications, maintenance, and other factors, the fuel economy actually achieved inuse may be higher or lower than the EPA label values.

9 U.S. EPA Memorandum “Updated Analytically Derived Fuel Economy (ADFE) Policy for 2005 MY

and Later,” CCD-04-06 (LDVLDT), March 11, 2004. Available in the public docket for review.
51

Our response:

We are always looking for new and better ways to communicate fuel economy

information to consumers, and our redesigned label and the www.fueleconomy.gov

website accomplish much in this regard. We are planning to conduct additional public

outreach when the rule is released, and we are working with stakeholders on how to

best communicate the change in fuel economy label values to consumers. Part of this

outreach will include educating consumers that they can have a great deal of impact on

the fuel economy they achieve.

3.8 Government-Industry Working Groups

What we proposed:

We did not propose anything specific with respect to a government-industry

working group.

What commenters said:

General Motors recommended that EPA convene a working group to address a

number of specific details that they believe require further discussion and analysis

before full implementation can be achieved. GM volunteered to lead and help

coordinate such an effort.

Our response:

As always, we will work with industry representatives and other stakeholders as

needed to achieve the smoothest possible implementation of the new program. We

appreciate GM’s offer to assist in this effort.

3.9 When City Fuel Economy is Greater Than Highway Fuel Economy

What we proposed:

Consistent with the language of current regulations, we proposed that if the city

value exceeds the highway value for a model type, the city value will be set equal to the

highway value. In cases where special vehicle design features may result in city values

that exceed highway values, we proposed that the manufacturer may request EPA

approval to waive this requirement. Our proposal would require that such a request be

accompanied by on-road fuel economy data which demonstrates that the fuel economy

during city-type driving is higher than fuel economy during highway-type driving.
52

What commenters said:

AAM/AIAM stated that they fail to see the necessity for the proposed provisions

which would require on-road fuel economy data to demonstrate that city fuel economy

exceeds highway fuel economy. They argue that if a vehicle is designed to optimize city

fuel economy and that is reflected in the testing results, there should be no reason why

additional on-road testing is necessary. They comment that “...imposing an additional,

unspecified on-road testing requirement would amount to a significant burden on

manufacturers that would add cost, complexity, and time burdens which could impede

the development of vehicles with attributes desirable to millions of commuters who live

and drive in congested urban areas.” They consequently recommend that paragraphs

(c) and (d)(2) of the proposed regulations in section 600.210-08 be deleted.

Our response:

We agree with the comment from manufacturers, and the final rule thus deletes

the paragraphs in 600.210-08. Hybrid vehicles in particular are more likely to achieve

better city fuel economy than highway fuel economy, and in the context of this

technology we no longer believe that the existing requirements are needed or

reasonable.

3.10 Technology-Specific, Model-Specific, or Manufacturer-Specific Adjustment

Factors

What we proposed:

We proposed a methodology that would apply similarly to all vehicles, without

any adjustment factors based on specific technologies, models, or manufacturers. We

did not specifically propose a methodology for making adjustments to fuel economy

results based on vehicle technology, vehicle models, or on the manufacturer.

What commenters said:

Because they observed that “a small number of vehicles appear to have realworld gas mileage that falls significantly below the proposed new mileage values,”

Bluewater Network suggests that EPA consider finalizing regulations that allow separate

adjustments for individual vehicle models which have test data that differs markedly

from real-world values. One approach they suggest would be allowing EPA to make

these adjustments based on real-world results reported by consumers and “reputable

sources conducting independent testing” although they acknowledge the potential

difficulty with determining a protocol for deciding if a vehicle’s real-world performance is

far enough from the label value to warrant an adjustment. A second approach they

suggest is to allow manufacturers to collect and submit onboard computer data that

could be used to make adjustments for individual vehicle models. However, they
53

recognize the potential for “gaming” of the system using such data, and urge EPA to

use caution if such an approach is considered.

Bluewater Network commented that they believe plug-in hybrids will be

commercially available in the future and EPA should consider how this emerging

technology should be addressed with respect to fuel economy labeling and testing.

Honda suggested that EPA allow manufacturers to collect real-world fuel

economy data which could then feed back directly into fuel economy estimates. Under

their concept, the manufacturer would gather in-use fuel economy data from actual

customer vehicles during the first 6 to 12 months of production, and then label future

production using the average of the in-use data.

Volkswagen expressed concerns that the proposed procedures may unfairly

penalize diesel vehicles. They believe that a high percentage of their diesel vehicle

customers come closer to achieving today’s current labels than is suggested by the

proposed methodology, and that additional factors that reduce the label estimate may

represent an unnecessary penalty for diesel technology. They acknowledge that little

data exists to support or refute this concern and that they intend to collect some and

present it to EPA.

AAM/AIAM commented that EPA’s proposed changes to the fuel economy label

accounts for many variables that can affect fuel economy, but that expanding the

program to account for technology differences would introduce significant complexity

and not be consistent with the intent of the Fuel Economy Guide as a convenient

consumer tool. They point out that validation of the technology adjustment factors

would be necessary to ensure their integrity, and that such validation could only be

accomplished after extensive field experience was demonstrated. They point to EPA’s

1984 final rule on labeling, in which EPA explicitly rejected the technology-specific

approach to adjustment factors.10 A rationale for rejecting technology-specific factors at

that time, and one that AAM/AIAM suggests is even more relevant today, is that “...such

factors could become outdated so fast as to provide no better (and in some cases,

worse) estimates of expected in-use fuel economy.” AAM/AIAM points out that

“...hybrid technology is progressing so rapidly and there are so many different types of

hybrid systems that hybrid-specific factors would be difficult to determine and would

quickly become outdated.” They recommend that EPA should not consider adopting

technology-specific weighting factors at this time. Toyota also expressed opposition to

technology-specific solutions.

UCS recommends that EPA not consider calculation procedures or adjustments

that are specific to certain technologies, or to vehicles deemed to be used by certain

groups of drivers, unless definitive data can demonstrate no other way to reliably

provide fuel economy estimates. Any specific procedures could undermine the

impartiality of the fuel economy testing, and should be avoidable by developing new

10 See 49 FR 13834 (April 6, 1984).
54

cycles that accurately reflect the range of in-use driving conditions experienced by most

drivers. UCS solidified their argument by noting that “The best chance for EPA’s fuel

economy ratings to remain the gold standard of objectivity is to ensure that all vehicles

are tested under an appropriately wide set of identical conditions.”

Our response:

We are not finalizing a methodology by which in-use data can feed back into

adjusting the fuel economy estimates. At this time, we do not believe that it is possible

to determine a method for this that is fair, equitable, and that retains a level playing field

across manufacturers. Allowing this would open up the serious potential for unfair

practices – manufacturers could selectively choose the specific vehicles for which inuse data is collected, thereby giving them an opportunity to boost fuel economy results

where they believe the in-use data to be an advantage, but simultaneously ignore those

vehicles that might actually be performing below the label values in real-world use.

Additionally, adjusting the results of individual vehicles or technologies undermines the

credibility of the fuel economy estimates because vehicles would no longer be tested in

an identical and repeatable way. Rather, we would encourage manufacturers that

collect in-use data to share it with EPA such that the data could contribute to our

periodic evaluation of the 5-cycle method.

Our analyses in the Technical Support Document do not indicate an issue with

respect to diesel vehicles. However, we always remain open to hearing from

manufacturers with specific concerns, and we encourage manufacturers with such

concerns to collect and evaluate appropriate data and bring it to our attention.

Commercial hybrids available today ultimately obtain all propulsion energy from

liquid fuel stored in the fuel tank, while a plug-in hybrid uses a combination of liquid fuel

and supplemental energy from the electric grid stored in the battery (i.e., overnight

charge). Properly accounting for this supplemental electric energy is the central issue in

assessing the performance of plug-in hybrids. Therefore, plug-in hybrids will require a

more comprehensive assessment in order to determine the proper test procedures for

fuel economy and emissions. Since plug-in hybrid technology is rapidly advancing, we

will work with key stakeholders in the next few years to assess the appropriateness of

the 5-cycle methodology in capturing the fuel economy impact of the plug-in technology.

We agree strongly with those commenters urging against technology-specific

adjustment factors. We are especially concerned that such an approach would create

an uneven playing field across vehicles. We are aware that technologies are rapidly

developing, and we intend to ensure, as part of our ongoing evaluation of the fuel

economy test methods, that new and developing technologies are represented

appropriately.
55

3.11 Use of Fuel Economy Estimates in Advertising

What we proposed:

We did not propose anything specific with respect to the use of fuel economy

estimates in advertising.

What commenters said:

An anonymous commenter “is appalled” that auto manufactures are allowed to

advertise using solely their highway fuel economy estimates, while the city values are

relegated to the fine print.

Our response:

Use of the fuel economy estimates in advertising is governed by the Federal

Trade Commission (FTC). In the mid-1970’s the Federal Trade Commission (FTC)

“took note of the dramatic increase in the number of fuel economy claims then being

made and of the proliferation of test procedures then being used as the basis for such

claims.” 11 They responded by promulgating regulations in 16 CFR Part 259 entitled

“Guide Concerning Fuel Economy Advertising for New Vehicles” (“Fuel Guide”). The

Fuel Guide, adopted in 1975 and subsequently revised twice, provides guidance to

automobile manufacturers to prevent deceptive advertising and to facilitate the use of

fuel economy information in advertising. The Fuel Guide advises vehicle manufacturers

and dealers how to disclose the established fuel economy of a vehicle, as determined

by the Environmental Protection Agency's rules pursuant to the Automobile Information

Disclosure Act (15 U.S.C. 2996), in advertisements that make representations regarding

the fuel economy of a new vehicle. The disclosure is tied to the claim made in the

advertisement. If both city and highway fuel economy claims are made, both city and

highway EPA figures should be disclosed. A claim regarding either city or highway fuel

economy should be accompanied by the corresponding EPA figure. A general fuel

economy claim would trigger disclosure of the EPA city figure, although the advertiser

would be free to state the highway figure as well. The authority for the Fuel Guide is

tied to the Federal Trade Commission Act (15 U.S.C. 41-58) which, briefly stated,

makes it illegal for one to engage in “unfair methods of competition in or affecting

commerce and unfair or deceptive acts or practices in or affecting commerce.”

11 See 40 FR 42003 (Sept. 10, 1975).
56

Chapter 4: Other Related Proposals

4.1 Voluntary Fuel Economy Labeling for Vehicles Exceeding 8500 Pounds

Gross Vehicle Weight Rating

What we proposed:

In the NPRM, we sought comment on a voluntary labeling program for vehicles

above 8,500 pounds gross vehicle weight rating (GVWR), and how such a program

might be implemented. Over the past several years there has been a growing market

for these heavier vehicles, which fall into a number of utility classes, such as SUVs,

pickups, and vans (including heavier versions of such models as Hummer, Ford

Excursion, Chevy Silverado and Dodge Ram). We believe that consumers would be

interested in using fuel economy estimates for these vehicles when comparison

shopping. The rising fuel prices of recent times certainly have increased consumer

awareness of the costs associated with owning a vehicle. When our proposal was

published we did not have the authority under the relevant statutes to require labeling of

these vehicles.

What commenters said:

NYDEC expressed support for calling for manufacturers to place fuel economy

window stickers on vehicles over 8,500 pounds GVWR, citing the fact that a large

number of these vehicles are frequently used as passenger vehicles for personal

transportation. Public Citizen argued that “EPA has clear authority to test and label

vehicles above 8,500 lbs. and should do so,” providing a lengthy legal argument

supporting their contention. UCS agreed, summarizing the Public Citizen legal analysis

in their comments. UCS stated that EPA should develop a mandatory fuel economy

labeling program for these vehicles, noting that these vehicles typically consume more

fuel than other consumer-oriented vehicles and without a label consumers have no idea

what to expect from them. UCS also recommended that EPA work with DOE to gather

“Your mpg” data from real world users of these vehicles and include this information on

the www.fueleconomy.gov website. Bluewater Network commented that, while it was

unclear to them whether EPCA allows EPA to require labeling of these vehicles, it does

not appear that EPA is precluded from requiring that fuel economy information for these

vehicles be provided in other forums. Bluewater suggested that EPA require

manufacturers to publish fuel economy values for these vehicles in vehicle user

manuals and other sales materials. They also suggested that EPA make the same

information available in EPA’s Green Vehicle Guide, on EPA’s website, and in other

relevant publications, to the extent that EPCA allows.

AAM/AIAM argued that EPA’s request for voluntary labeling is understandable,

but it may not provide information that is of significant value. They noted that tests

currently performed for these vehicles can vary dramatically from the tests performed

for light duty regulated vehicles. For example, current regulations require that many of

these vehicles be tested using significantly different procedures from light duty test
57

procedures that generate the fuel economy label values (e.g., some are enginecertified). They also noted that highway tests are not required for all fuel types, even in

California where most of these vehicles are chassis-certified. As a result, AAM/AIAM

suggested that labeling of these heavier vehicles will not produce information that is

comparable to the labels on light duty vehicles, and may in fact create more confusion

and misunderstanding than additional value in the marketplace.

Ford submitted a comment after the close of the comment period that responded

in detail to the legal analysis presented by Public Citizen. Ford’s analysis was

subsequently supported by comments from the Alliance of Automobile Manufacturers.

Ford detailed why they believe that Public Citizen’s assertion that EPA has the authority

to require fuel economy labeling for vehicles over 8,500 lbs GVWR is faulty. Ford

concludes that Public Citizen’s “expansive” reading EPCA is inconsistent with the

statutory language and principles of statutory construction. Further, they note that at a

minimum, “it must be acknowledged that [EPCA] does not explicitly authorize EPA to

issue rules expanding the scope of labeling, in contrast to the authority granted to

NHTSA...with respect to the CAFE program,” and that “At most, EPA should allow

NHTSA to determine the scope of the CAFE program under its authority, and follow suit

in its administration of the labeling program.” Finally, they conclude that “EPA should

not seek to require fuel economy labeling on any vehicles not required to comply with

CAFE standards, because doing so would ignore Congress’ clearly-stated intent to

avoid having the labeling program drive additional testing requirements, thereby

overburdening manufacturers.”

NADA did not object to EPA’s suggestions that manufacturers voluntarily post

fuel economy information on vehicles over 8,500 pounds GVWR.

Our response:

We are finalizing in this rule a fuel economy labeling program for Medium-Duty

Passenger Vehicles (MDPVs), a subset of vehicles between 8,500 and 10,000 lbs

GVWR. MDPVs were first defined in the regulation that put in place the “Tier 2”

emission standards.12 This recently-defined class of vehicles includes SUVs and

passenger vans between 8,500 and 10,000 lbs GVWR, but excludes large pick-up

trucks. The specific regulatory definition was designed to capture in the light-duty

vehicle emissions program those vehicles that are designed predominantly for

passenger use.13

12 See 65 FR 6698 (Feb. 10, 2000).

13 This is the regulatory definition of Medium-Duty Passenger Vehicle, found in 40 CFR 86.1803-01:

Medium-duty passenger vehicle (MDPV) means any heavy-duty vehicle (as defined in this subpart)

with a gross vehicle weight rating (GVWR) of less than 10,000 pounds that is designed primarily for the

transportation of persons. The MDPV definition does not include any vehicle which:

(1) Is an “incomplete truck” as defined in this subpart; or

(2) Has a seating capacity of more than 12 persons; or

(3) Is designed for more than 9 persons in seating rearward of the driver's seat; or

(4) Is equipped with an open cargo area (for example, a pick-up truck box or bed) of 72.0 inches
58

Under the Energy Policy and Conservation Act (EPCA), EPA is required to

establish regulations that require a manufacturer to attach a label to each “automobile”

manufactured in a model year.14 “Automobile” is defined as a vehicle not more than

6,000 lbs GVWR, and those vehicles between 6,000 and 10,000 lbs GVWR that DOT

determines are appropriate for inclusion in the CAFE program.15 “Automobile” for the

purposes of labeling also includes vehicles at no more than 8,500 lbs GVWR whether or

not DOT has included those vehicles in the CAFE program.16 EPA has no authority to

require labels on vehicles that are not automobiles, therefore EPA has no authority to

require labeling of either vehicles above 10,000 lbs GVWR, or vehicles between 8,500

and 10,000 lbs GVWR that are not included by DOT in the CAFE program.

Since the time of EPA’s proposal, DOT has included some vehicles above 8,500

lbs GVWR and below 10,000 lbs in its CAFE program, beginning in model year 2011.17

Since these vehicles now meet the definition of automobile, EPA is authorized to

include these vehicles in labeling program.

MDPVs are currently subject to emission standards that apply on the existing

Federal Test Procedure, and many also undergo emission testing on the current

Highway Fuel Economy Test due to requirements in California. Beginning with the 2011

model year, manufacturers will be routinely testing MDPVs over the FTP and the HFET

tests in order to comply with the CAFE program. However, MDPVs are not today

subject to all of the additional emission tests we are utilizing for the 5-cycle method.18

Specifically, MDPVs are not subject to the 1996 Supplemental Federal Test Procedure

(SFTP) regulations.19 The SFTP regulations include the US06 and SC03 test

procedures, both of which are necessary elements of the 5-cycle fuel economy

methodology. These two test cycles represent high speed and aggressive driving

(US06), and impacts of air conditioner operation (SC03). We do not believe it is

appropriate to require SFTP testing for MDPVs for fuel economy purposes alone, but

we are not prepared at this time to establish SFTP standards for MDPVs. In the Tier 2

regulations, we acknowledged that MDPVs were not covered by SFTP requirements,

and we specifically noted that SFTP emission standards would be addressed in a future

regulation.20 We believe that the appropriate time to consider 5-cycle fuel economy

testing for MDPVs is during or after development of appropriate SFTP emission

standards for MDPVs. We plan to address SFTP emission standards for MDPVs in the

in interior length or more. A covered box not readily accessible from the passenger compartment will be

considered an open cargo area for purposes of this definition.

14 See 49 U.S.C. 32908(b).

15 See 49 U.S.C. 32901(a)(3).

16 See 49 U.S.C. 32908(a).

17 See 71 F.R. 17565, (April 6, 2006).

18 MDPVs are currently required under the Tier 2 program to meet a carbon monoxide standard on

the cold FTP test; compliance with this standard is being phased in over the 2008 and 2009 model years.

19 See 61 FR 54852 (Oct. 22, 1996).

20 See 65 FR 6789 (Feb. 10, 2000)
59

near future. At that time, we will also assess the appropriateness of 5-cycle fuel

economy testing for MDPVs. However, we are finalizing a program that requires

MDPVs to use the mpg-based adjustments to calculate fuel economy estimates. The

mpg-based approach does not require testing beyond what will be required to meet the

CAFE program in model year 2011. Manufacturers will simply take their FTP and HFET

test results (conducted for the CAFE program) and apply them to the mpg-based

equation to determine their fuel economy label values.

4.2 Electronic Distribution of Dealer-Supplied Fuel Economy Booklet

What we proposed:

A statutory provision in EPCA authorizes EPA to prescribe regulations that

require car dealers to provide to consumers a copy of the annual Fuel Economy

Guide.21 Historically, DOE has printed and sent copies of the Guide to dealers, at

government expense, although this is not an EPCA requirement. In recent model years,

dealers have been allowed, on a trial basis, to provide the Guide electronically. Dealers

can have an on-site computer for customers, or they can provide the Guide on a CD or

diskette, or they can print a paper copy for the customer. This has been working well,

and DOE agrees with our proposal to codify these options effective with the 2008 model

year.

What commenters said:

NADA stated at the public hearing and in their written comments that EPA’s

existing approach appeared to be working very well, and that they support EPA’s

proposal. Public Citizen opposed allowing dealers the option of electronically providing

the Fuel Economy Guide to customers. Their primary opposition is (1) that some

people are disinclined to use computers, and (2) that EPA presented no evidence that

the trial program was in fact successful. In an oral testimony given at the public

hearing, NADA supported EPA’s proposal, stating that the approach “seemed to be

working very well.”

Our response:

We are finalizing our proposal to allow the electronic distribution of the Fuel

Economy Guide by dealerships. We proposed adding language to the regulations that

allows dealers to fulfill their requirement to provide customers with copies of the Fuel

Economy Guide booklet by using an on-site computer. This method has been used on

a trial basis in recent years. The National Automobile Dealer Association (NADA)

commented that this proposal should be finalized, because it is a more efficient,

effective way of providing customers with this information. EPA's regulations do not

relieve dealerships of the responsibility to make the Guide “available to prospective

21 See 49 U.S.C. 32908(c)(3).
60

buyers.”22 We agree with Public Citizen that there are people who may be disinclined

to use a computer. However, we would expect dealers who opt to provide the guide

electronically would also provide assistance as needed to those car shoppers in

accessing and viewing the Guide. The electronic version of the Guide is an easy-to-use

PDF file, which can be viewed a page at a time, exactly the same way a paper copy is

viewed.

4.3 Consideration of Fuel Consumption vs. Fuel Economy as a Metric

What we proposed:

EPCA defines fuel economy as “...the average number of miles traveled by an

automobile for each gallon of gasoline (or equivalent amount of other fuel) used, as

determined by the Administrator under section 32904 (c) of this title.”23 Thus, EPA's

fuel economy information program has always expressed fuel efficiency in miles per

gallon. It is a metric that Americans have come to know and understand.

Notwithstanding this requirement, a few auto manufacturers have suggested that it may

be more meaningful to express fuel efficiency in terms of consumption (e.g., gallons per

100 miles) rather than in terms of economy (miles per gallon). A fuel-consumption

metric is currently used in Canada and in Europe. Fuel consumption numbers speak

directly to the amount of fuel used, to which a consumer can relate in terms of cost

when filling up. Because a few stakeholders have expressed interest in a fuelconsumption metric, we requested comments on the gallons-per-mile fuel consumption

metric, and how it could be best used and presented publicly, such as whether it should

be included in the Fuel Economy Guide.

What commenters said:

Public Citizen noted that, while there is some merit to a fuel consumption metric,

consumers are comfortable today with the miles-per-gallon metric. Any change, they

argue, should be carefully deliberated and should involve a massive public outreach

campaign to educate consumers. They also suggest that the estimated annual fuel cost

provides information derived from a consumption basis.

Toyota believes that fuel consumption is a more meaningful measurement than

miles-per-gallon for expressing fuel efficiency, although they recognize EPA’s statutory

limitations. They note that the miles-per-gallon metric is fundamentally non-linear in

relation to issues of consumer interest, such as cost of fuel or gallons of fuel used, and

they suggest that anecdotal evidence shows that the non-linear aspects of miles-pergallon can itself lead to consumer confusion. They conclude that “...this is a matter on

which the EPA is obligated to educate the public as fuel consumption, not fuel economy,

is a direct reflection of the environmental impact of vehicles in use.”

22 See 49 U.S.C. 32908 (c)(3).

23 See 49 U.S.C. 32901(a)(10).
61

NADA noted no opposition to including fuel consumption information on the

www.fueleconomy.gov website or in the annual DOE/EPA Fuel Economy Guide.

An anonymous commenter expressed disappointment that none of the EPA’s

proposed label designs prominently lists fuel consumption as opposed to fuel economy.

They note that only the consumption metric truly allows for simple comparisons of fuel

savings between different vehicles.

Our response:

The final rule will continue the past practice of expressing the City and Highway

estimates in fuel economy units of miles per gallon, rather than as fuel consumption

units. We are statutorily required to report miles per gallon on the label by EPCA, which

defines fuel economy as “...the average number of miles traveled by an automobile for

each gallon of gasoline (or equivalent amount of other fuel) used, as determined by the

Administrator under section 32904 (c) of this title.”24 We have always expressed fuel

efficiency in miles per gallon, and it is a metric that Americans have come to know and

understand.

Our experience is that consumers are very familiar with the miles-per-gallon

estimates given on the label. Given that we are obligated statutorily to report fuel

economy in terms of miles per gallon, we cannot change the metric on the fuel economy

label, and we believe it would be far too confusing to report a fuel consumption metric in

addition to the miles per gallon estimates. We are concerned that consumers would not

understand a different fuel-efficiency metric and, without a long-term, comprehensive

public awareness campaign, it would be very confusing to the public. We also

understand that some manufacturers plan to pursue some public outreach and

education in regards to using the fuel consumption metric.

However, the labels do provide an easy way to compare the relative fuel

consumption – and therefore, fuel and dollar savings – of different vehicles. The

estimated annual fuel cost information on the label is based on a fuel consumption

metric: it is simply the dollar equivalent of the number of gallons consumed over 15,000

miles. Thus we believe the inclusion of the estimated annual fuel cost on the label is

already a valuable metric for consumers, which relates directly to fuel consumption.

Moreover, we believe it would take a long-term educational process for consumers to

begin to relate to the fuel consumption metric of gallons per mile.

24 See 49 U.S.C. 32901(a)(10).
62

4.4 Web-based Driver-Specific Fuel Economy Calculator

What we proposed:

We requested feedback from stakeholders regarding what additional information

could be made available either in the annual Fuel Economy Guide or the

www.fueleconomy.gov web site. We acknowledged that overall space on the label is

limited, but that we would like to be able to make more information available to

consumers who are interested in a greater depth of detail. The web site and the Fuel

Economy Guide are logical places to include additional detail that does not lend itself to

presentation on the label. We requested specific comment on including a fuel economy

calculator on the web site that would enable consumers to calculate an estimated fuel

economy that is tailored to their specific driving conditions and behavior. Such a fuel

economy calculator could be designed that would allow the user to input their specific

driving conditions, such as the amount of time spent with air conditioning on, what

climate they live in, how much driving is done under higher speed/aggressive driving

conditions, etc. These inputs could go into an algorithm that would estimate the fuel

economy for a specific vehicle under the conditions input by the user.

What commenters said:

Public Citizen is supportive of the addition of a fuel economy calculator to allow

consumers to obtain a fuel economy estimate tailored to their specific driving conditions

and styles. However, they emphasize that EPA must be careful to ensure that such a

calculator produces accurate estimates. They suggest that such a calculator, if or when

it is finalized, be referenced on the fuel economy label. Although UCS agrees that such

a tool could provide users with valuable insight into the effects of many factors on fuel

economy, they recommend that EPA wait to establish such a calculator until additional

data is gathered after the final rule is issued.

Subaru expressed general support for such a calculator, noting that it “could

prove to be an educational tool to consumers.” Natural Resources Canada also

expressed support, recommending that such a calculator be designed to suggest an

optimum target fuel economy and areas where a driver could, through changes in

behavior or technique, improve fuel economy. AAM/AIAM agreed that a more detailed

calculator on the EPA fuel economy website could prove to be useful to consumers.

They suggested that the calculator include driving types, temperatures, and accessory

loads.

Our response:

Based on the analyses that now underlie the new fuel economy estimates, we

believe at this time that we could construct a web-based calculator as described in the

proposal. We agree with those who commented that such a calculator could be a useful

and educational tool for consumers. For example, a user could input their vehicle

information, their passenger load, their air conditioner use, and other factors, and
63

receive as outputs a variety of information regarding the impact of various factors on

their fuel economy and fuel economy estimates that are specific to their situation. We

agree with commenters that it is important to ensure the accuracy of such a tool, since

the algorithms required to complete these calculations are non-trivial. We plan to

consider further how to best design and implement a calculator tool, and we may seek

additional input from interested stakeholders.
64

Chapter 5: City and Highway Fuel Economy Estimates and

Methodology

5.1 The Proposed Formulae are Complex

What we proposed:

We proposed new methods for calculating fuel economy that are in fact more

complex than the previous methods. However, the proposed methods will also better

predict the fuel economy that customers will achieve in real-world use.

What commenters said:

Natural Resources Canada, which fields consumer complaints and questions

about fuel economy, expressed concern that the proposed formulae will be too complex

to communicate to consumers. They suggest that “A new system for estimating vehicle

fuel economy would be simpler and more meaningful to consumers if it did not factor in

extreme driver behavior and if the final equations were streamlined to remove any of the

non-significant coefficients or factors.”

Our response:

We do not believe that most consumers will be interested in or concerned about

the actual mathematical equations used to combine the fuel economy measurements

made over the various dynamometer test cycles in city and highway fuel economy

labels. The focus groups indicated to us a general aversion on the part of consumers to

complex and detailed information, except in a very few cases (and in those cases, the

information is available via the website that will be included on the new label). We

believe that it will be sufficient for most consumers to understand that EPA included

actual fuel economy measurements while the vehicle was driven at high speeds and

rates of acceleration, at colder temperatures and with the air conditioning turned on.

One of the most difficult tasks we currently face is explaining to consumers how we

historically estimated onroad fuel economy by testing vehicles at a maximum speed of

60 mph only at 75°F with the air conditioning off.

We also believe that consumers are sufficiently intelligent to understand that

engineering equations can sometimes appear complex, even if the principles involved

can be explained rather simply. The alternative is to simplify the equation and lose

accuracy for the subjective advantage of being able to show a simple equation in the

regulations or an article explaining our new label procedure. We do not believe that this

is a necessary or appropriate trade-off.
65

5.2 Validation of the 5-cycle Formulae for Individual Vehicles

What we proposed:

We did not propose a specific method for validating the accuracy of the 5-cycle

formulae on an individual vehicle basis.

What commenters said:

Honda commented that: “the individual (understood to mean 5-cycle) label

adjustments are based primarily upon analyses of driving behavior alone. ... By

ignoring the effect of changes in driving behavior and conditions on the in-use fuel

consumption of individual vehicles, the Proposal implicitly assumes that all vehicles

have the same relationship between fuel consumption and real world driving conditions.

However, the proposal makes no attempt to validate this assumption, either analytically

or with in-use fuel economy data.”

UCS states that “Because the 5-cycle methodology begins to test for a number of

important factors, it is appropriate for use as an interim solution while new test cycles

are being developed.” They argue that because the 5-cycle approach is based on

models (MOBILE and MOVES) that are designed to consider the entire vehicle fleet, the

methodology may improve the average fuel economy ratings for the fleet without

leading to corresponding improvements in the accuracy of individual vehicle ratings.

They suggest the possibility that the 5-cycle approach is delivering the correct results by

virtue of errors canceling one another out. For example, the relative importance of cold

starts could be exaggerated, but be balanced out by an underestimation of air

conditioner impacts. Consequently, they recommend that EPA strengthen the

methodology through validation with in-use data.

Our response:

In addressing the comments by Honda and UCS, it is useful to first summarize

certain key aspects of EPA’s general approach to developing the fuel economy label, as

well as describing the basis for the 5-cycle formulae and how it compares to the current

labeling formula and the mpg adjustment approach.

The fuel economy label on any vehicle model has two basic functions - to provide

information on the city and highway fuel economy that can be expected from that

individual model, and to allow for a comparison between different models. Meeting

these goals has to take into account that there is a very wide variety of different in-use

driving conditions - speed, acceleration rates, deceleration rates, fluctuations in speed

and accelerations/decelerations, vehicle operating conditions such as AC use that

increase the load on the engine, ambient conditions like temperature and wind speed,

road conditions like grading, vehicle conditions like tire pressure and wear, and so on.

All of these factors can affect the fuel economy of a vehicle. In addition, this wide

variety of driving patterns reflects the wide variety among drivers and how and where
66

they drive their vehicles. Since a single fuel economy label needs to provide useful

information to a wide variety of persons nationwide, EPA’s general approach has been

to provide label values that predict in-use fuel economy for the vehicle assuming that it

will be driven in a way that is generally representative of average nationwide patterns.

This recognizes that a single label value cannot be developed that identifies for each

person the fuel economy they would experience based on that individual’s unique

driving patterns. The use of a common benchmark of representative in-use driving

patterns, however, provides information that is still quite useful for each person in

gauging the likely fuel economy they can expect for themselves, as well as providing a

consistent basis for comparison of expected fuel economy between different vehicles.

.

Fuel economy label values are derived using fuel economy data obtained by

testing a vehicle over a limited number of prescribed driving conditions in the laboratory,

and then making projections of the vehicle’s fuel economy when it is operated in-use

under a wide variety of conditions including those not tested in the laboratory. The

current label formula combines data on fuel economy from testing over the driving

conditions found on the FTP and the HFET, and then adjusts these results by a set

percentage. The FTP represents a subset of city driving conditions – relatively low

speed, mild acceleration and deceleration rates, about 75F ambient temperature,

accessories like the AC are off, and the engine is first started up after a long time sitting

at the same 75F temperature. The FTP fuel economy value is then adjusted by a set

percentage to then predict city fuel economy over the wide variety of conditions found in

in-use city driving, including the many types of driving conditions that are not included in

the FTP – higher speeds, more aggressive acceleration and deceleration, AC use, and

the myriad other variations in in-use driving conditions.

Under the current label formula, if two vehicles have the same fuel economy

result on the FTP they have the same label value for city fuel economy. If their FTP fuel

economy data differs – for example, one is a set percentage lower than the other - then

they will have different labeled values for city fuel economy which will continue to show

the same relative difference as the vehicles showed on the FTP. This is based on two

assumptions. The first is that a vehicle with a certain fuel economy during specified

laboratory driving conditions will continue to have the same fuel economy during in-use

driving conditions that are basically the same as those under the test. The common

adjustment factor reflects a second assumption - that every vehicle will react the same

way to the wide variety of in-use driving conditions that are not included in the tests, and

for which we therefore do not have vehicle specific data. In effect, the current label

formula predicts that if a vehicle were driven under conditions that are representative of

the wide variation in in-use driving conditions, it’s in-use city fuel economy would always

be a set percentage below the value it shows when tested on the FTP driving

conditions.

The impetus behind this rulemaking was the large amount of in-use data from a

number of sources indicating that the current formula does not do a satisfactory job of

meeting the two informational goals described above. In developing an updated

approach to address these concerns, a significant amount of information on in-use
67

driving conditions is now available to better characterize the variety of in-use driving

conditions. There are also several additional laboratory tests available that allow for

collection of fuel economy test data from individual vehicles over a wider variety of

driving conditions.

In developing the 5-cycle formulae, EPA uses much of the same basic framework

described above: (1) the formula is designed to predict fuel economy over

representative in-use driving conditions, using a common benchmark for labeling

different vehicles, (2) the formula assumes that if a vehicles achieves a certain fuel

economy during testing under a certain kind of driving, then the vehicle will continue to

achieve that fuel economy value under similar in-use driving conditions, and (3) where

we do not have data to allow projection of individual vehicle fuel economy test data to

similar in-use driving conditions, then a common, generic adjustment factor is used to

account for all conditions not generally represented by the laboratory tests.

For example, there are five tests that are now available to provide fuel economy

values for an individual vehicle. As a group, they reflect a much wider variety of driving

conditions. They cover several distinct kinds of driving patterns (based on factors such

as average speed and power - Bag 3 FTP, Bag 2 FTP, HFET, USO6 City, US06 Hwy),

different temperature conditions (75F, 20F, 95F), different accessory loads (AC use on,

AC use off) and different amounts of time sitting between engine start (soak time - 10

min., 12 hour). There is also a large amount of information on in-use driving conditions

to use in deriving a characterization of representative in-use driving conditions.

For example, fuel economy during in-use driving is made up of two parts – the

fuel used during warm-up of the engine when that engine is started (start fuel use), and

the fuel used after the engine is warmed up (running fuel use). For each of these, EPA

developed a comprehensive picture of average conditions. For example, for running

fuel use EPA developed a description of average U.S. driving from the Draft

MOVES2004 motor vehicle emissions model. EPA determined that about 41% of inuse city driving is under driving conditions that are similar to the driving conditions of

Bag 3 of the FTP, 48% of in-use driving is similar to the driving conditions of Bag 2 of

the FTP, and 11% is similar to the more aggressive driving conditions in the USO6City.

EPA also evaluated temperature conditions during which in-use driving occurs, and

determined that the average temperature in which driving occurs is approximately

58.7F, and on average the air conditioner compressor is engaged and putting load on

the engine approximately 15.2 percent of the time. EPA then developed a formula that

properly weights the varied kinds of test driving conditions by their relative contribution

to this benchmark of average in-use driving. In some cases this required additional

analysis. For example, the tests are driven at 75F and 20F, but not at 58.7F. Using

engineering analysis and test data on how fuel economy changes as temperature

changes, EPA developed a relationship for the change in fuel use related to starting the

engine as temperature increases from 20F to 75F. This relationship, along with an

individual vehicle’s test data at 20F and 75F, is used to predict the fuel economy at

58.7F.
68

The 5-cycle formulae therefore reflects EPA’s use of a common benchmark for

labeling - average in-use driving conditions nationwide – and the assumption that a

vehicle’s fuel economy during a certain kind of driving in the lab reflects the vehicle’s

fuel economy during similar in-use driving conditions. For example the running use

formula assigns a rating to Bag 3 of the FTP that is consistent with the fact that the

driving on Bag 3 is similar to 41% of the average city driving. The formula is based on

the assumption that the fuel economy a vehicle achieves during Bag 3 of the FTP is a

good predictor of the fuel economy it will receive during the 41% of average in-use city

driving that is similar to the driving during Bag 3. The formula also incorporates the fuel

economy test data at 20F and 75F to numerically provide the proper discount to reflect

that average city driving is at 58.7F. For conditions that are represented by the test

driving, EPA assumes that in-use driving will show the same variation in fuel economy

that the test driving does – different vehicles that have different fuel economy during the

test driving will show the same variation in fuel economy when driving in-use over

similar conditions. This is reflected in the weightings used in the 5-cyle formulae.

The 5-cycle formula also uses a generic adjustment factor to account for the

variety of conditions that occur during in-use driving that are not fairly represented by

the driving conditions under which individual vehicles are tested, such as variations in

wind speed, road conditions, tire pressure, and the like. For these conditions EPA

does not have test data for individual vehicles and assumes that all vehicles will show

the same effect notwithstanding differences in design between different vehicles. This

is reflected in the generic adjustment factor.

There are therefore two basic differences between the current label formula and

the 5-cycle formula. The range of in-use conditions over which EPA is able to use test

data to identify differences in fuel economy between different vehicles is a broader

range of driving conditions for the 5 cycle than the current label, and the range of in-use

conditions over which EPA assumes all vehicles react the same way is a narrower set

of conditions over the 5-cycle than the current label.

Honda commented that: “the individual [5-cycle] label adjustments are based

primarily upon analyses of driving behavior alone. ... By ignoring the effect of changes

in driving behavior and conditions on the in-use fuel consumption of individual vehicles,

the Proposal implicitly assumes that all vehicles have the same relationship between

fuel consumption and real world driving conditions. However, the proposal makes no

attempt to valid ate this assumption, either analytically or with in-use fuel economy

data.”

This is not an accurate description of the 5-cycle formula. It is based upon

analysis of in-use driving behavior, but not primarily on that alone. An analysis of

driving behavior is a central element, but just one element. The analysis of in-use

driving patterns is critical because it allows EPA to accurately characterize average

driving conditions across the US, and use this as a benchmark. It also allows EPA to

accurately identify which parts of this average in-use driving are represented by the

various kinds of driving conditions in the laboratory tests, and properly weigh the test
69

driving so it accurately reflects the contribution that that kind of driving makes to the

benchmark of average in-use driving. Having done that, the 5-cycle then applies the

vehicle specific fuel economy data generated in the test driving, weighing it properly to

reflect the contribution of that driving to overall, representative in-use driving. Thus the

analysis of average in-use driving behavior is a central element of the formula, but it is

not used alone or in isolation, but instead is combined with individual vehicle specific

fuel economy data generated during testing.

The 5-cycle formula does not “ignore[e] the effect of changes in driving behavior

and conditions on the in-use fuel consumption of individual vehicles.” It does the

opposite. The 5-cycle formula uses a broader range of driving conditions under which

individual vehicles are tested, which then identifies whether and how much a change in

driving conditions changes fuel consumption for the individual vehicle. The formula then

assigns that change in fuel economy to similar in-use driving conditions. It does this

over a broader range of driving conditions than the current label formula, because the

driving tests cover a broader range of driving conditions. The generic adjustment used

in the 5-cycle formula does ignore differences between individual vehicles, and

assumes that all vehicles will react the same way to the changes in in-use driving

conditions covered by the generic adjustment factor. This applies to the conditions not

fairly represented by the test driving conducted on individual vehicles. However this

assumption covers a much narrower range of driving conditions for the 5-cycle formula

than for the current label.

The 5-cycle formula does not “implicitly assum[e] that all vehicles have the same

relationship between fuel consumption and real world driving conditions.” As described

above, for the broad range of driving conditions covered by the test driving conditions, it

identifies an individual vehicle’s fuel consumption. This identifies differences between

vehicles over these driving conditions. These differences in fuel economy are then

properly weighted to reflect their occurrence during in-use driving. It is only for the

generic adjustment that the 5-cycle formula assumes all vehicles have the same

relationship between fuel consumption and real world driving conditions. However for

the 5-cycle formula this is a narrower range of in-use driving conditions than the current

label formula.

Honda objects that EPA did not validate this implicit “assumption”, either

analytically or with in-use fuel economy data for individual vehicles, before making the

5-cycle formulae mandatory. As noted above, EPA does not make the assumptions

Honda suggests, except for the generic adjustment factor. The technical basis for the

generic adjustment factor is explained in Section III.A.5 of the Final TSD. Honda does

not appear to object to the technical basis for the generic adjustment, however. Its call

for validation is aimed at the parts of the 5-cycle formula that use vehicle specific test

data, and not the generic adjustment which is not vehicle specific. For the vehicle

specific parts of the formulae, as discussed above, EPA did not make the assumptions

that Honda states, and in fact made distinctly different assumptions.
70

Honda does not appear to object to several of the basic elements of EPA’s

approach. For example, Honda does not appear to object to the assumption that the

fuel economy an individual vehicle demonstrates when tested under certain driving

conditions also fairly represents the fuel economy the vehicle will show during similar inuse driving conditions. While in-use fuel economy data for individual vehicles arguably

would be relevant to validate this assumption, it is clearly a reasonable engineering

judgment to make and in any case there is no apparent dispute on this issue.

Honda does not appear to raise significant objections to the concept of using

average in-use driving conditions as the benchmark for fuel economy labeling. That is,

the fuel economy label should be based on a projection of the fuel economy of the

vehicle over a driving pattern that fairly represents average US driving conditions.25

While Honda states there is a need to validate the 5-cycle formula for in-use fuel

economy for individual vehicles, such in-use fuel economy validation would not be

relevant to characterizing this average US driving pattern. The average driving pattern

is not intended to be vehicle specific; it is an average that is then used as the

benchmark for labeling. The weightings of the formula are likewise not vehicle specific,

but are intended to reflect the correlation between the kind of driving during testing and

the amount of such driving in the average US driving. In use fuel economy data would

not inform you about the validity of this average driving pattern, because it is a driving

pattern, not a fuel economy value. It is true that information on in-use driving of

individual vehicles would provide additional data about in-use driving patterns,

irrespective of the in-use fuel economy. However absent a broad range of in-use data

over a variety of models, manufacturers, and driving conditions, it would not be a useful

way to identify whether the average driving pattern needs to be revised. Again, that is

because this benchmark and the related weightings in the formula are not vehicle

specific but are intended to be an average covering a wide range of in-use conditions.

The vehicle specific part of the 5-cycle formula is the fuel economy data derived

for an individual vehicle over the kinds of driving covered by the various tests. In-use

fuel economy validation from individual vehicles is not needed to validate the laboratory

results themselves, and as discussed above it is not needed to validate the assumption

that the individual test data for the vehicle represents the fuel economy it will achieve

when driving under conditions in-use that are similar to those during testing.

Arguably Honda is referring to EPA’s invitation for comment on whether certain

vehicle technologies are generally driven in a way that is distinctly different from the

average, e.g. unusually low incidence of aggressive driving, A/C usage, etc. See 71 FR

5442 (col2-3). For example, Honda suggests using the 5-cycle formula only until a

manufacturer collects enough fuel economy data on an individual model from in-use

drivers of that model, and then substituting this manufacturer derived fuel economy

value for the 5-cycle value. As discussed in the preamble of the proposal, in this

situation in-use data would be used to show that a different average benchmark (with

25 Honda does object to various details of the benchmark average driving pattern developed by EPA,

and those objections are responded to elsewhere.
71

correlated changes to the weightings in the 5-cycle formula) should appropriately be

used for a specific kind of technology. That is a different issue, however, than the need

for in-use validation before using the 5-cycle formula for it’s stated purpose – to predict

in-use fuel economy over a broad national average of driving conditions, based on fuel

economy test data for an individual vehicle gathered over a broad but necessarily

limited variety of driving conditions. The fact that in-use fuel economy data might be

necessary and useful in deciding whether to provide an exception to the benchmark

average driving pattern for certain vehicles or a certain kind of technology does not

indicate that such in-use data is needed or useful in validating the average in-use

driving pattern itself. As noted above, it generally is not.

As will be discussed further below, the proposed 5-cycle formulae are based in

part on some assumptions about how vehicles respond to conditions that are not tested

directly by the five dynamometer tests. E.g., the effect on fuel economy of ambient

temperatures between the 20F and 75F is subject to an engineering analysis and

certain test data to establish the relationship between fuel economy at the average US

driving temperature, 58.7F, and fuel economy measured at 20F and 75F. Likewise,

EPA makes certain assumptions about the AC compressor load during driving patterns

not included in the test driving. However, these assumptions are much less extensive

than those involved in either the current label formula or the proposed mpg adjustment

formula. All the assumptions regarding how fuel economy varies under conditions “in

between” the various tests were supported by the results of dynamometer testing or

engineering analysis. Honda has provided no data to indicate that any particular

assumption was inappropriate for any specific vehicle. EPA remains open to reviewing

any valid test data which would show that any of its assumptions were inappropriate for

a specific vehicle and considering modifications to the 5-cycle formulae to account for

these differences. But the need to perform these analyses is not a basis for delaying

use of the 5-cycle formulae. EPA's analyses are supported in the record, as noted, and

EPA believes the 5-cycle formula presents significantly less risk of error in labeling than

the much more extensive assumptions that made and not supported in the current label

formula.

For the reasons noted above, EPA does not believe that it needs in-use

validation data from individual vehicles prior to making the 5-cycle formula mandatory.

In large part this is based on the extensive technical analyses underlying the 5-cycle

formula, the validity of the representative in-use driving pattern used as a benchmark,

and the increased ability to use individual vehicle test data to represent the vehicle’s inuse fuel economy. In addition, this is based on the view that the 5 cycle formulae

would still be a better choice for fuel economy labeling that the mpg adjusted formula or

the current label formula.

It is inconsistent to reject the 5-cycle formula because it has not been validated

through data on in-use fuel economy for individual vehicles, but to accept the mpg

adjusted formula or the current label formula. The mpg adjusted formula is basically a

streamlined way to predict the 5-cycle formula result for an individual vehicle. For the

large majority of vehicles, the mpg adjustment formula does a good job of accurately
72

predicting the 5-cycle formula value for that vehicle. If the 5-cycle formula is

inappropriate because of various problems and the lack of in-use validation, then the

mpg adjustment is inappropriate for the same reasons because the mpg adjustment

formula is just a shorthand way to develop the 5-cycle formula result. There are

vehicles where the mpg adjustment formula does not do a very good job of accurately

predicting their 5-cycle formula results. For this subset of vehicles, the mpg adjustment

basically assigns them the average 5-cycle fuel economy derived from the large

majority of vehicles where the mpg adjustment does a good job of predicting the 5-cycle

value. For these cars, any basic defect of the 5-cycle formula would also apply to the

mpg adjusted value. If there is not a valid technical basis to use the 5-cycle formula

then logically there is not a valid technical basis to use the mpg adjustment formula.

EPA believes, however, that there is a valid basis to use the 5 cycle-formula, hence a

valid basis to use the mpg adjustment formulae as well, especially for the large majority

of vehicles where there is a close correlation between the 5 cycle result the and the

mpg adjustment result.

It also would be inconsistent to delay the 5-cycle formulae pending further in-use

validation, while continuing to use the current label formula. The current label has not

been validated for individual in-use vehicles, and in general in-use data shows that the

current label formula generally overestimates fuel economy and masks differences in

fuel economy between individual vehicles. This is because it generates vehicle specific

fuel economy data over a narrow range of laboratory driving conditions, and it uses a

generic factor, that does not discriminate between individual vehicles, to cover all other

driving conditions. The 5-cycle formula generates vehicle specific fuel economy data

over a wider range of test driving conditions, and relies on a generic adjustment factor

to cover a narrower range of the remaining driving conditions. The comparison of 5-

cycle results to the current label, as reflected in the mpg adjustment formula, indicates

that the 5 cycle formula does a better job than the current label formula of predicting inuse fuel economy and identifying fuel economy differences between different vehicles.

The real solution to the issue raised by Honda and explicitly suggested by UCS –

greater accuracy in predicting individual vehicle fuel economy - is not to delay use of the

5-cycle formula but to expand the extent of individual vehicle fuel economy testing in the

laboratory (i.e., more driving patterns, intermediate colder and hotter temperatures,

intermediate soak times, etc.), assuming the increase in accuracy was worth the

increased testing. Honda and the other vehicle manufacturers have argued strongly

against this approach. Absent such an increase in fuel economy testing of individual

vehicles, for the reasons discussed above EPA believes there is not a valid technical

basis to delay the use of the 5-cycle formulae pending validation by in-use fuel economy

testing of individual vehicles, with reliance on either the mpg adjustment or the current

label formula in the meantime.
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5.3 Some Formulae Coefficients are Counter-Intuitive

What we proposed:

We proposed weightings of the various cycles or bags that were based on

extensive analyses of in-use driving data and vehicle test data.

What commenters said:

Honda commented that the overall contributions of several of the cycles or bags

in the 5-cycle formulae do not make engineering sense, as some of the contributions

are negative. In terms of fuel consumption (as opposed to fuel economy), Honda

consolidated the various terms of the 5-cycle formulae in order to identify the overall

weight given to each cycle or bag. The results are shown in Table 5-1.

Table 5-1: Proposed Coefficients for the 5-Cycle Fuel Economy

City Highway

FTP – Bag 1 25.7% 1.5%

FTP – Bag 2 28.0% -2.0%

FTP – Bag 3 -5.8% -4.6%

HFET 21.3%

US06 – City Bag 7.7%

US06 – Highway Bag 79.9%

SC03 14.4% 5.0%

Cold FTP – Bag 1 8.1% 0.5%

Cold FTP – Bag 2 15.0%

Cold FTP – Bag 3 6.9% -0.5%

Honda presents five concerns related to the figures in this table.

1) The negative coefficients for Bag 3 of the FTP in both formulae, and the

negative coefficient for Bag 2 of the FTP in the highway formula. These

negative coefficients mean that if a manufacturer increases a vehicle’s fuel

economy during this type of driving, the vehicle’s 5-cycle fuel economy will

actually decrease, not increase.

2) The weighting for SC03 in the city formula is 14.4% but the driving

conditions represented by this cycle only represent 3% of all driving.

3) The total weighting for cold FTP in the city formula is over 30%, but the

driving conditions represented by this cycle only represent 2% of all

driving.

4) In total, the extreme cycles represent over half of the weighting of the city

formula, while only representing 5% of all driving.
74

5) For the highway driving, the extreme cycles account for over 85% of the

highway label value.

Our response:

We conducted our own analysis to determine the overall weightings of the

various bags and cycle in the two 5-cycle formulae and confirmed the reasonableness

of the figures shown in Table 5-1. Thus, we agree with Honda that, from a purely

mathematical perspective, the figures in Table 5-1 indicate how the fuel consumptions

measured over the various bags and cycles contribute to the overall estimate of fuel

consumption during either city or highway driving and thus, to the 5-cycle city and

highway fuel economy label values.

Regarding Honda’s concern about negative bag coefficients, we believe that this

concern is purely theoretical, and does not represent a real problem with the 5-cycle

formulae. For example, we recalculated the overall coefficients for the various bags and

cycles using a very large average trip length (i.e., 10,000 miles) which effectively

removes any contribution from the cold start towards city or highway fuel economy. The

results are shown in Table 5-2.

Table 5-2: Proposed Coefficients for the 5-Cycle Fuel Economy with

Infinite Trip Length

City Highway

FTP – Bag 1 0% 0%

FTP – Bag 2 27% -2%

FTP – Bag 3 17% -3%

HFET 17%

US06 – City Bag 10%

US06 – Highway Bag 81%

SC03 16% 7%

Cold FTP – Bag 1 0% 0%

Cold FTP – Bag 2 16%

Cold FTP – Bag 3 14% 0%

As can be seen, the negative coefficient for Bag 3 of the FTP in the city formula

changes to a relatively large positive 17% with the removal of cold start fuel use. Thus,

the -5.8% coefficient in the proposed 5-cycle city formula is clearly due to the presence

of cold starts in city driving (i.e., short trips). The method for estimating cold start fuel

consumption is via the difference between fuel consumption over Bags 1 and 3 of either

the FTP or cold FTP. The driving pattern during both bags is exactly the same. The

only difference is that Bag 1 begins with a cold start and Bag 3 begins with a hot start.

Thus, the difference in fuel consumption over the two bags is clearly due to the

presence of the cold start in Bag 1. This difference has been used in emission

modeling, such as that performed in the EPA MOBILE models for thirty years and is well

established.
75

Honda did not suggest excluding the impact of cold starts from the 5-cycle

formulae. Nor do we believe that they meant to imply that the impact of cold starts

should not be included. Still, this indicates that their concern about the negative

coefficient is theoretical, and not practical. For example, there are a number of ways to

improve fuel economy over Bag 3 of the FTP, such as reducing vehicle weight or

aerodynamic drag, or modifying gear ratios, etc. However, in the vast majority of these

cases, fuel economy over Bag 1 will improve as well, since it involves exactly the same

type of driving. As seen in Table 5-2, the coefficient for Bag 1 vastly exceeds that of

Bag 3. Thus, even if the change in Bag 1 fuel consumption was somewhat smaller than

that of Bag 3, 5-cycle city fuel economy would improve. In addition, since Bag 2 of the

FTP and the SC03 test consist of very similar, low speed driving, the vehicular changes

described above would likely improve fuel consumption over these other bags and

cycles as well, further improving 5-cycle city fuel economy.

Honda did not provide any examples of technologies or techniques which could

improve fuel consumption over Bag 3, but which would not improve fuel consumption

over any of the other bags and cycles. Thus, we do not believe that the existence of a

negative effective coefficient for an individual cycle or bag is necessarily a problem in

the 5-cycle formulae.

The negative coefficients for Bags 2 and 3 in the 5-cycle highway formulae are

primarily due to the inclusion of the effect of air conditioning in the formulae. The effect

of air conditioning is estimated via the difference in fuel consumption over the SC03 test

and a mix of Bags 2 and 3 of the FTP. Again, it seems extremely unlikely that a

manufacturer could improve fuel consumption over Bags 2 and 3 of the FTP without

also improving fuel consumption over SC03, since the driving patterns are quite similar.

Thus, again, we believe that Honda’s concern in this case is more theoretical than

practical.

Regarding the effective coefficient of 14% for SC03, Honda states that the driving

conditions represented by this test only occur 3% of the time on the road. Honda did

not explain or provide data to support the basis for this percentage. However, it is likely

that the 3% represents the percentage of onroad driving which occurs at 95 degrees

Fahrenheit or higher. If so, this characterization is very biased, because it assumes that

if driving occurs at a temperature below 95 degrees Fahrenheit, it is adequately

represented by the other bags or cycles. This is clearly not the case. Drivers use their

air conditioning systems at temperatures below 95 degrees Fahrenheit. None of the

other bags or cycles involves operation of the air conditioning system. Thus, to

completely exclude driving at lower ambient temperatures when the air conditioning is

operational when assessing the applicability of the SC03 test to onroad driving is

technically unjustifiable.

The contributions of fuel consumption over SC03 in the 5-cycle formulae

explicitly consider the variation in use of air conditioning over the range of ambient

conditions, the cycling of the compressor at various ambient conditions and the effect of
76

air conditioning on fuel consumption as a function of vehicle speed. Honda neither

challenged any of these analyses, nor provided suggestions for their improvement.

Overall, these analyses (which are described in the TSD) indicate that the air

conditioning compressor is engaged about 15% of the time on the road. Since the

SC03 cycle essentially consists of city driving, it is not surprising that the weighting of

the SC03 test in the 5-cycle city formula is very close to this figure. In addition, the

SCO3 results are combined with other results to approximate the effect of the air

conditioner compressor on fuel economy irrespective of ambient temperature, and this

impact is then weighted to reflect that the compressor is on during approximately 15%

of VMT. Thus, the actual percent of VMT represented by the SCO3 driving cycle is not

directly relevant, as the test data is used to isolate the impact of the compressor load

irrespective of driving cycle.

Starting with the cold CO test, we agree with Honda that only 2% of national VMT

occurs below 20°F. However, to cite this statistic as the only indication of the relevance

of the cold FTP test is misleading. This implies that the standard FTP at 75°F is a better

representation of the remaining 98% of driving, particularly cold starts. As indicated in

Figure 1 of Honda’s comments, this is not the case. The FTP at 75°F is not a better

indicator of fuel economy at temperatures just slightly above 20°F than the cold CO test.

A temperature of 50°F is roughly halfway between the nominal temperatures of the two

FTP tests. Figure 1 indicates that roughly 30-35% of national VMT occurs at

temperatures which fall closer to the 20°F test than to the 75°F test. Thus, when

examined in greater depth, the 20°F cold FTP is not as “extreme” as it appears at first

blush, especially given the fact that the weighting factor for the various bags of the cold

FTP in the 5-cycle formulae are between 0.24 and 0.30.

This is even more true for the SC03 and US06 tests. Honda points out that the

SC03 test is performed at 95°F, when again only 2% of national VMT occurs at this

temperature or greater. However, the SC03 test is an air conditioning test, not simply

an FTP at 95°F. Our analysis indicates that the air conditioning system is turned on

23.9% of the time in-use (Section III.A.3. of the Final TSD). As discussed there, the

National Energy Research Laboratory estimates even higher use, 29%. An FTP

performed at 75°F with the air conditioning off is not a better indicator of the incremental

fuel use associated with air conditioning than the SC03 test, even if the temperature is

below 95°F. Thus, the percentage of driving occurring with the air conditioning on is

much more relevant to the benefit of the SC03 test than the percentage of driving

occurring at or above the temperature of the SC03 test.

Drivers rarely use their air conditioning below 70 F. Thus, the amount of driving below

70 F is irrelevant to the representativeness of the SC03 test. When the air conditioning

system is turned off, it has no effect on fuel economy and our analysis accounts for the

fact that it has no effect on fuel economy. The issue is how to best estimate the impact

of air conditioning on fuel consumption. The 5-cycle formulae isolates the impact of air

conditioning at 95°F by comparing the fuel consumption over the SC03 test to that over

a combination of Bags 2 and 3 of the FTP designed to match the driving cycle of the

SC03 test. The 5-cycle formulae then weights this incremental fuel consumption by 1)
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the percentage of driving occurring with the air conditioning turned on, 2) the

percentage of time that the air conditioning compressor is on relative to that occurring

during the SC03 test, 3) the relative load of the compressor on the engine at the

temperature at which the driving is occurring, and 4) the speed of city and highway

driving relative to that of the SC03 test. Each adjustment accounts for differences

between the specific conditions occurring during the SC03 test and those existing on

the road. The alternative is to assume that the impact of air conditioning is proportional

to fuel use over the FTP, a test where the air conditioning is not operating. Honda

presents no data to indicate that this alternative is a better estimate of the impact of air

conditioning. Available data of fuel consumption over the SC03 and FTP tests indicates

that the impact of air conditioning is not proportional to fuel use over the FTP (see

Figure III-11 of the Draft TSD). Thus, Honda’s statement that only 2% of in-use driving

occurs above 95°F does not address the major issue, that of air conditioning and its

effect on onroad fuel economy.

In response to Honda’s comment that the vehicle in the SC03 test has been

sitting for 10 minutes in the sun prior to the test, we do not believe that this is extreme.

Prior to driving, vehicles can be parked under a roof, but often they are parked in the

open. Our in-use data on vehicle starts indicates that only 1% of all starts in-use occur

after a vehicle soak of 10 minutes or less. Thus, when vehicles are parked outside in

sunny conditions, their inside temperature is likely much higher than that in the SC03,

even when the ambient temperature is below 95°F. While the test is relatively short, 10

minutes or 3.5 miles, this is exactly our estimate of the average trip length during “city”

driving. Thus, with respect to both its vehicle soak time and its length, the SC03 cycle is

not “extreme”.

Honda’s comments about the “extreme” cycles representing half to 85% of the

contributions to the 5-cycle formulae extend the same thinking to the US06 cycle. Few

if any specific vehicles are driven exactly like any of the bags or cycles. Thus, they are

all extreme in this sense. As examined in Section III of the TSD, the US06 cycle is also

extreme in the sense that only a small percentage of onroad driving tends to fall outside

of its speed-acceleration envelope. But like the contributions of the SC03 and cold FTP

tests, the issue with the US06 contribution is which bag or cycle best represents onroad

driving, not whether one or the other bag or cycle exactly matches it. Honda neither

presented any new onroad driving activity data, nor suggested any way to improve the

analyses which determined the relative contributions of the various bags or cycles to

describe onroad driving. As described in Appendix A of the TSD, recent California

chase car data indicates that 20% of city driving time and 41% of highway driving time

fell outside of the speed-acceleration envelope of the FTP and HFET cycles. This does

not imply that the US06 cycle can only represent these percentages of city and highway

driving. It just means that these percentages of driving in California are not represented

by even one second of driving on either the FTP or HFET cycles. The weighting of

driving at the edges of the FTP/HFET speed-acceleration “envelope” may be much

lower than those found on the road. The VSP-based cycle analysis of city driving

indicated that the US06 contribution was much lower than the 20% figure based on the

FTP/HFET speed-acceleration envelope. In contrast, the VSP-based cycle analysis of
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highway driving indicated that the US06 contribution was much higher than the 41%

figure based on the FTP/HFET speed-acceleration envelope. Both types of analysis

show that the contributions of the various bags and cycles, including those referred to

as extreme by Honda, appear to be appropriate at this time.

5.4 Start Fuel Use May Not Be Accurate on Per Vehicle Basis

What we proposed:

In the proposal we assessed the sensitivity of the 5-cycle equations to several

factors and alternative assumptions. We evaluated the effect of soak time and ambient

temperature on start fuel use using test results from 50 degree F testing required by

California. Based on this data, we concluded that it was unlikely that uncertainty in the

effect of ambient temperature on start fuel use would significantly affect city 5-cycle fuel

economy. We also concluded that it would have no effect on 5-cycle highway fuel

economy, due to the extremely low contribution of start fuel use in highway driving.

Hybrids would likely show the greatest variability in this area, due to the greater number

of technological factors that could be affected, but even for these vehicles we found that

the 5-cycle fuel economy for the vehicle reflecting the greatest difference in temperature

sensitivity was only changed 1%.

What commenters said:

UCS commented that the comparison of start fuel use at 50 degrees and 20

degrees Fahrenheit presented in the Draft Technical Support Document should not be

interpreted too broadly. They suggest that the model may correctly predict the average

start fuel use for the nine vehicles, it is not clear that each individual vehicle’s start fuel

use is accurately reflected. They point to the data for hybrid vehicles, which indicates

that the appropriate weighting for the 20 degree start fuel use may vary by a factor of

two between different vehicle models. They suggest that it will be important to validate

the approach for individual vehicles, rather than on the basis of a group average.

Our response:

UCS’ comment about the possibility that the correct weighting factors for 20°F

and 75°F operation might differ between individual vehicles was addressed with the

previous comment by Honda. As discussed there, the current label procedure, as well

as the mpg-based equations, not only assumes the same rate of change of start fuel

use with temperature, but the same overall degree of change between 20°F and 75°F.

Both the degree of change occurring between 20°F and 75°F and the rate at which this

change occurs are important. The 5-cycle formulae utilize actual vehicle test data to

obtain the degree of change between 20°F and 75°F, while assuming that the rate of

change between 20°F and 75°F matches that of the vehicles which have been actually

tested at intermediate temperatures, as well as at 20°F and 75°F. The other two

approaches assume both factors (degree of change between 20F and 75F, and rate of
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change between those temperatures), and assume all vehicles react to changes in

temperature in the same way in both regards. The 5-cycle approach is clearly superior

in this regard.

5.5 Relative Accuracy of the mpg-Based Equations Versus the 5-cycle

Formulae for Individual Vehicles

What we proposed:

We proposed the use of the mpg-based equations for model years 2008 through

2010, then implementation of the vehicle-specific 5-cycle method starting with the 2011

model year.

What commenters said:

Honda commented: “We believe EPA has done a credible analysis based upon

air quality modeling methodologies to create an equation that incorporates new, more

aggressive driving conditions to predict aggregate fuel economy for the fleet in actual

use. Reducing the equation as EPA has done into the mpg-based equation works

because this is not attempting to make the results vehicle specific. However, little inuse data exists to validate the coefficients in the 5-mode equation for use in predicting

vehicle specific results. Thus, Honda supports the 2008 mpg-based approach but we

do have some concerns with applying the formula to individual vehicles in 2011.”

Our response:

These two statements reflect a basic misunderstanding about the relationship

between the three approaches to developing fuel economy label values discussed in the

NPRM: 1) the current label formulae, 2) the mpg-based equations, and 3) the 5-cycle

formulae. All three approaches produce vehicle specific fuel economy label values.

The foundation of all three approaches is a set of measured fuel economy values based

on the testing of the vehicle being labeled. Thus, all three approaches are “vehicle

specific.” All three approaches also include “fleet average” adjustments to the “vehicle

specific” fuel economy measurements. The difference between the three approaches is

in the degree of vehicle specificity, not a fundamental difference where two of the

approaches are appropriately fleet average and the third (5-cycle) is vehicle specific.

Honda appears to be looking only at the portion of the various fuel economy label

formulae beyond the current FTP and HFET testing. Viewed in this way, the current

label formulae apply generic city and highway percentage adjustments to all measured

FTP and HFET fuel economy values. While slightly more elegant in its mathematics,

the mpg-based equations do essentially the same thing, as the effective percentage
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adjustment applied to the FTP and HFET fuel economy values varies only slightly

except for roughly three hybrid vehicles with extremely high city fuel economy.26

The 5-cycle formulae, in contrast, introduce measured fuel economy values from

other test cycles. Because of this, Honda appears to perceive these fuel economy

values as “vehicle-specific adjustments” to the FTP and HFET fuel economy values.

However, these additional three tests are no more vehicle-specific in concept than those

measured over the FTP and HFET tests. Thus, the distinction being drawn by Honda is

more related to history (how are the current “vehicle specific” fuel economy labels

changing) than based on fundamental engineering or technical considerations. Going

back further historically, the original fuel economy label values were based solely on the

FTP. The use of the HFET for highway label values was introduced at a later date.

This modification was in fact a vehicle specific adjustment to the original, FTP-based

label values. (Fuel economy measured over the HFET is obviously vehicle specific.)

Viewed much more simply, the current label procedures utilize vehicle specific

data on the fuel economy of vehicles driven under relatively mild city and highway

driving conditions at 75°F. The driving cycles for these tests were developed from fleetaverage driving surveys which consisted of much less data than was used to develop

the driving cycles contained in the US06 and SC03 tests. The FTP and HFET tests

have never been justified on a vehicle specific basis in the way that Honda seems to be

implying needs to be done for the three additional tests.

However, no effort was made in the past to determine if the FTP and HFET were

the “best” indicators of city and highway fuel economy, respectively. The FTP and

HFET were simply two reasonable driving cycles with average speeds in the range

desired and were believed to provide reasonable estimates of onroad fuel economy.

Obviously, in 1984, it was shown that these cycles significantly over-estimated onroad

fuel economy and required adjustment. This was done in a fleet-average manner.

However, neither EPA nor any other organization concluded that there were no vehicle

specific factors which contributed to the shortfall indicated by the data. In fact, as

described above, the impact of high speed, aggressive driving, air conditioning and cold

temperature on fuel economy, while being correlated to a vehicle’s fuel economy over

the FTP or HFET, has a vehicle specific component which can often be traced to its

specific design (e.g., power to weight ratio, body style, etc.).

Also, while the FTP fuel economy can appear to be a single fuel economy value,

it is really the result of weighting of three fuel economy values, one for each test “bag.”

The weightings of these bags, particularly Bags 1 and 3, were based on the same type

26 It is important to note that this does not indicate that the mpg adjustment approach and the current

label approach use similar methodologies or similar types of assumptions, as they do not. The mpg

approach is basically a way to estimate an individual vehicle’s 5-cycle result, thus it is a surrogate for the

5-cycle approach, and not a different approach relying on different assumptions or data. It turns out that

for the large majority of cars the 5-cyce results do tend to cluster in ways that are similar to using a

common adjustment factor
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of “fleet-average” data (i.e., the in-use distribution of vehicle soak times prior to engine

start-up) that were used in developing the weighting factors in the 5-cycle formulae.

The 43% weighting of Bag 1 and 57% weighting of Bag 3 have never been validated on

a vehicle-specific basis, as Honda is saying is required for the 5-cycle formulae. The

driving cycles which comprise the FTP and HFET tests were based on much less

onroad vehicle driving activity data than those used to develop the weighting factors for

the 5-cycle formulae. Even the weighting factors for Bag 1/3 and Bag 2 of the FTP used

in the current label formulae have never been “validated” on a vehicle specific basis.

Thus, Honda’s perception that the current fuel economy label formulae do not need to

be validated, but the 5-cycle formulae require such validation, is clearly arbitrary and not

based on any real technical distinction.

The same is true for the assumed trip lengths for city and highway driving. The

city fuel economy label is based on the FTP’s length of 7.5 miles (with respect to cold

starts), while the highway fuel economy label is based on an infinite trip length (i.e., zero

cold starts). Likewise, the FTP and HFET are both performed at a nominal 75°F.

These factors have also never been validated on a vehicle-specific basis.

In fact, all of these factors implicit in today’s fuel economy labels and the

proposed 5-cycle labels would differ slightly for individual vehicles. The volume of fuel

needed to start and warm up the engine as a function of soak time and ambient

temperature varies between vehicles. If all vehicles were thoroughly tested across the

wide range of situations encountered in-use and the results condensed so that a cold

start at 75°F was averaged with a hot start at 75°F, the fraction of cold starts would

differ. This can be easily shown using the data on start fuel use presented in the TSD.

The issue is not that the appropriate weighting factor would be exactly the same for

each individual vehicle design, but that the weighting factors do not vary too widely. If

this were the case, the solution, again, would be to measure fuel economy under more

conditions. The solution would not be to return to generic, fleet-average adjustments.

It should also be noted that Honda did not provide any data supporting the ability

of the FTP and HFET to accurately reflect any additional fuel consumption related to

other driving patterns, air conditioning and defroster use, and cold temperature,

including the effect of heating the passenger compartment. Nor did they provide any

data to indicate that the US06, SC03 or cold FTP tests reflected fuel economy impacts

not indicative of those occurring in-use. In fact, even a simplistic analysis of engine and

vehicle design and their effect on fuel economy would demonstrate that specific

vehicles are going to respond differently to the factors not covered by the FTP and

HFET tests. Honda itself argues that vehicles respond differently to such factors. Thus,

their own arguments, when appropriately applied to the currently label procedures and

the proposed mpg-based equations, highlight the limitations in these two approaches

relative to the proposed 5-cycle formulae.

The 5-cycle formulae assume that the US06, SC03 and cold FTP tests, in

addition to the FTP and HFET, contain vehicle specific information with respect to

onroad fuel economy. Honda makes a number of specific arguments which attempt to
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challenge this position which we address below. However, overall, Honda provides no

vehicle activity or fuel economy data which demonstrate that the US06, SC03, and cold

FTP tests do not provide information which is relevant to estimating a vehicle’s onroad

fuel economy. It is clear that vehicles are often driven faster and more aggressively

than the FTP and HFET and at temperatures below 75°F, and drivers often use their air

conditioning. The NPRM also provide substantial fuel economy data that the impact of

these factors have a differential effect on specific vehicle’s fuel economy. Thus, broadly

speaking, Honda did not provide any justification for not utilizing this information while

still trusting the information provided by the FTP and HFET tests. Therefore, we find

this distinction being made by Honda incorrect and reject their suggestion that the

coefficients in the 5-cycle formulae need a level of justification not required by the

current label procedure and mpg-based equations.

5.6 mpg-based or “Generic” Adjustments to FTP and HFET

What we proposed:

The mpg-based method that we proposed bears some similarity to the current

method, in that the method makes adjustments to FTP and HFET test results.

However, the mpg-based adjustments we proposed are not flat percentage amounts,

but differ based on the fuel economy achieved on the FTP and HFET tests.

What commenters said:

Honda strongly supports the application of mpg-based adjustments to the FTP

and HFET fuel economy measurements. In support of this, they state that “if there is

some error in the methodology, it is applied equally to all products.”

Our response:

We appreciate Honda’s support for the first phase of our proposed changes to

the fuel economy label calculation procedures. However, we disagree that the error in

the mpg-based equations, if they exist, are equivalent for all vehicle models. A very

simple example demonstrates this. While relatively few vehicles are sold without air

conditioning today, this was more frequent in the past. Manufacturers would often sell

the same vehicle model with and without air conditioning. These two vehicle

configurations would achieve essentially identical fuel economy over the FTP and HFET

tests, since the air conditioning was never operative and the weight of the air

conditioning system itself is quite small compared to that of the vehicle and might not

even move the vehicle up to a higher inertia weight class. However, their onroad fuel

economy would clearly differ, due to the one vehicle’s air conditioning use. Both the

current label procedure and the mpg-based adjustments would indicate that both

vehicles would achieve the same onroad fuel economy. This would be obviously

incorrect. The onroad shortfall for the vehicle equipped with air conditioning would be

greater than that for the vehicle without air conditioning. Thus, applying a generic
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adjustment to FTP and HFET fuel economy does not automatically minimize the

difference between onroad and label fuel economy.

In fact, this comment by Honda directly conflicts with a later comment. Later in

their comments Honda states that: “By ignoring the effect of changes in driving behavior

and conditions on the in-use fuel consumption of individual vehicles, the Proposal

implicitly assumes that all vehicles have the same relationship between fuel

consumption and real world driving conditions.” The proposed 5-cycle formulae does

this to some degree, in that some of its weighting factors are based in part on

interpolations of how fuel economy changes between values measured over two tests,

such as the cold FTP and FTP, or SC03 and the FTP. However, the generic

adjustments recommended by Honda assume that the fuel economy of all vehicles

respond in the same way to any conditions not included in the FTP and HFET tests.

Ample data was presented in the Draft Technical Support Document which proved this

not to be the case for colder temperatures, air conditioning use and high speed and

aggressive driving.

Honda appears to be willing to accept the vehicle specific fuel consumption

information which is generated by the FTP and HFET tests, but not any other tests.

This is again odd, since the driving cycles of both tests have never been representative

of any driving studies, even the studies upon which they were based. For example, all

accelerations and decelerations which were found to occur in-use which exceeded 3.3

mph per second were reduced to this value, due to problems with operating a vehicle

under these conditions on the older twin-roll dynamometers. These equipment driven

limitations in the FTP and HFET cycles have continued to this date. Yet Honda makes

no mention of this problem.

This comment by Honda overlaps significantly with a number of their other

comments. Because of this, we will present additional analyses below which also bear

on the comment being addressed here. However, we believe that even this cursory

evaluation shows that Honda did not present any information to justify accepting the

vehicle specific nature of the FTP and HFET tests, while rejecting all additional vehicle

specific information. Nor did they supply any data to support their assertions in this

area.

5.7 The Three New Test Cycles are Extreme

What we proposed:

We proposed that three test procedures currently used for emissions compliance

purposes be incorporated into the fuel economy estimate calculations. These test

procedures are the US06, SC03, and Cold FTP. These procedures allow the fuel

economy methodology to account for vehicle-specific responses to conditions that are

not represented by the current tests, such as high speed driving, rapid accelerations

and decelerations, the use of air conditioning, and cold temperatures.
84

What commenters said:

Honda states that the conditions addressed by the three tests are “worst-case”,

or in other words, rarely occur in-use. Honda states, for example, that only 2% of

national vehicle miles traveled (VMT) occurs when the temperature is 20°F or less.

Our response:

Starting with the cold CO test, we agree with Honda that only 2% of national VMT

occurs below 20°F. However, to cite this statistic as the only indication of the relevance

of the cold FTP test is misleading. This implies that the standard FTP at 75°F is a better

representation of the remaining 98% of driving, particularly cold starts. As indicated in

Figure 1 of Honda’s comments, this is not the case. The FTP at 75°F is not a better

indicator of fuel economy at temperatures just slightly above 20°F than the cold CO test.

A temperature of 50°F is roughly halfway between the nominal temperatures of the two

FTP tests. Figure 1 indicates that roughly 30-35% of national VMT occurs at

temperatures which fall closer to the 20°F test than to the 75°F test. Thus, when

examined in greater depth, the 20°F cold FTP is not as “extreme” as it appears at first

blush, especially given the fact that the weighting factor for the various bags of the cold

FTP in the 5-cycle formulae are between 0.24 and 0.30.

This is even more true for the SC03 and US06 tests. Honda points out that the

SC03 test is performed at 95°F, when again only 2% of national VMT occurs at this

temperature or greater. However, the SC03 test is an air conditioning test, not simply

an FTP at 95°F. Our analysis indicates that the air conditioning system is turned on

23.9% of the time in-use (Section III.A.3. of the Final TSD). As discussed there, the

National Energy Research Laboratory estimates even higher use, 29%. An FTP

performed at 75°F with the air conditioning off is not a better indicator of the incremental

fuel use associated with air conditioning than the SC03 test, even if the temperature is

below 95°F. Thus, the percentage of driving occurring with the air conditioning on is

much more relevant to the benefit of the SC03 test than the percentage of driving

occurring at or above the temperature of the SC03 test.

Drivers rarely use their air conditioning below 70 F. Thus, the amount of driving

below 70 F is irrelevant to the representativeness of the SC03 test. When the air

conditioning system is turned off, it has no effect on fuel economy and our analysis

accounts for the fact that it has no effect on fuel economy. The issue is how to best

estimate the impact of air conditioning on fuel consumption. The 5-cycle formulae

isolates the impact of air conditioning at 95°F by comparing the fuel consumption over

the SC03 test to that over a combination of Bags 2 and 3 of the FTP designed to match

the driving cycle of the SC03 test. The 5-cycle formulae then weights this incremental

fuel consumption by 1) the percentage of driving occurring with the air conditioning

turned on, 2) the percentage of time that the air conditioning compressor is on relative

to that occurring during the SC03 test, 3) the relative load of the compressor on the

engine at the temperature at which the driving is occurring, and 4) the speed of city and
85

highway driving relative to that of the SC03 test. Each adjustment accounts for

differences between the specific conditions occurring during the SC03 test and those

existing on the road. The alternative is to assume that the impact of air conditioning is

proportional to fuel use over the FTP, a test where the air conditioning is not operating.

Honda presents no data to indicate that this alternative is a better estimate of the impact

of air conditioning. Available data of fuel consumption over the SC03 and FTP tests

indicates that the impact of air conditioning is not proportional to fuel use over the FTP

(see Figure III-11 of the Draft TSD). Thus, Honda’s statement that only 2% of in-use

driving occurs above 95°F does not address the major issue, that of air conditioning and

its effect on onroad fuel economy.

In response to Honda’s comment that the vehicle in the SC03 test has been

sitting for 10 minutes in the sun prior to the test, we do not believe that this is extreme.

Prior to driving, vehicles can be parked under a roof, but often they are parked in the

open. Our in-use data on vehicle starts indicates that only 1% of all starts in-use occur

after a vehicle soak of 10 minutes or less. Thus, when vehicles are parked outside in

sunny conditions, their inside temperature is likely much higher than that in the SC03,

even when the ambient temperature is below 95°F. While the test is relatively short, 10

minutes or 3.5 miles, this is exactly our estimate of the average trip length during “city”

driving. Thus, with respect to both its vehicle soak time and its length, the SC03 cycle is

not “extreme”.

Finally, Honda characterizes the US06 test as representing the 99.5 percentile of

onroad speed and acceleration conditions. Honda did not provide data to support this

statement. The US06 cycle was constructed primarily from segments of the REP05

cycle, which represented 28% of onroad driving in 3 U.S. cities in early 1990’s.27 (One

hill of the US06 cycle came from a high speed, high load cycle developed by CARB that

was analogous to the REP05 cycle.) Thus, the US06 cycle represents less than 28% of

the urban driving monitored in these three cities at that time. However, conditions have

changed dramatically since the early 1990’s in at least two important ways. One,

freeway speed limits have increased from 55 mph to 70 mph or even higher. Two, the

power to weight ratio of vehicles has increased dramatically over the past 15 years. For

example, between 1975 and 1990, the horsepower to weight ratio of new cars ranged

from 0.0320-0.0402 hp/lb. In contrast, between 1990 and 2005, the horsepower to

weight ratio of new cars ranged from 0.0402-0.0525 hp/lb, an increase of 20-30%.28

Thus, it is inappropriate to judge any driving cycle, but especially one focused on high

speeds, using onroad driving activity data developed 15 years ago.

One indication of how representative the US06 cycle is for today’s highway

driving is the comparison of its vehicle-specific power (VSP) frequency distribution to

27 U.S. Environmental Protection Agency. Regulatory Impact Analysis (Final Rule) – Federal Test

Procedure Revisions. U.S. EPA, August 15, 1996.

Website: http://www.epa.gov/otaq/regs/ld-hwy/ftp-rev/sftp-ria.pdf

28 “Light-Duty Automotive Technology and Fuel Economy Trends: 1975 Through 2005", Appendix E,

U.S. EPA, EPA420-R-05-001, July 2005.
86

estimates of onroad highway driving. Of particular interest are those VSP bins with the

highest power levels and highest fuel consumption rates. Table 5-3 presents the VSP

frequency distribution for the five highest power bins for highway driving as represented

in the 5-cycle highway fuel economy formula (79% US06 highway bag plus 21% HFET),

as well as the VSP frequencies from three independent estimates of current highway

driving onroad. All three sources of onroad driving, the EPA Draft MOVES2004 model,

EPA testing conducted in Kansas City, and California ARB sponsored chase car studies

conducted in California, are described in the TSD.

Table 5-3: Comparison of Driving Activity in High Speed, High Power

Modes

Frequency of Driving in VSP Bins During Highway Driving

VSP

Bin

5-Cycle (79% US06

Highway)

MOVES Kansas City (nonhybrids)California

Chase Car *

26 1.7% 4.7% 1.0% 0%*

36 10.9% 10.1% 15.7% 12.5%

37 12.8% 9.8% 6.5% 12.3%

38 8.1% 8.0% 4.5% 10.6%

39 12.3% 10.7% 11.2% 13.8%

Total 45.8% 43.3% 38.9% 49.2%

* Estimated from speed-acceleration frequency distributions. Value of 0% for bin 26 is likely an

artifact of the processing of driving activity between 40 mph and 50 mph into city and highway

driving, which is assumed to have a speed cut-point of 45 mph.

As can be seen, the frequency of driving in any particular high power VSP bin

can vary by a few percent. Overall, the total amount of driving in the five highest power

VSP bins in the 5-cycle highway formula varies from the onroad estimates by -3.4% to +

6.9%. Thus, with a 79% contribution to highway driving, the US06 highway bag cannot

be described as extreme with respect to several estimates of current onroad highway

driving. In contrast, while not shown in the table, only 8.1% of the HFET cycle falls into

these five high power VSP bins. Thus, the HFET cycle by itself is clearly not a good

indicator of current highway driving. However, if one had to choose between the HFET

cycle and US06 highway bag as being an “extreme” description of highway driving, from

the point of view of fuel consumption, one would have to conclude that the HFET was

the more extreme cycle of the two, being extremely mild in its required engine power

levels.

5.8 Weighting of New Cycles

What we proposed:

We proposed weightings of the 5-cycle test data that were based on extensive

analyses of real-world and laboratory test data.
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What commenters said:

Honda states that: “The proposed 5-cycle coefficients assign most of the weight

of a given type of in-use operation to the extreme cycles.”

Our response:

Except for the representation of most of highway driving by the highway bag of

the US06 test, Honda’s statement is clearly incorrect. The effective weighting factor for

air conditioning use is only 0.144 in city driving and 0.050 in highway driving. These

factors are clearly well below 50% of vehicle operation. The factors for the various bags

of the cold FTP are between 0.24 and 0.30, again well below 50%. As discussed

above, we also disagree with Honda’s claim that these cycles are “extreme.”

5.9 Interpolation of Fuel Economy Using Five Cycles

What we proposed:

Where made possible by available data, the 5-cycle method uses interpolation to

determine the fuel economy at intermediate conditions not represented directly by test

data. We found this to be more accurate and preferable to using extrapolation

techniques.

What commenters said:

Honda states that “these extreme cycles cannot represent the broadband and

midpoints of driving and fuel economy performance. Thus, the 5-mode proposal

implicitly assumes that interpolation of fuel consumption can properly represent all

conditions on all vehicles. This assumption is valid only if there is a smooth relationship

between fuel consumption and driving conditions without non-linear steps and if all

vehicles have the same fuel consumption response to changes in driving condition.

Again, these assumptions have not been validated.” Further on, Honda states that:

“The proposed 5-cycle coefficients assign most of the weight of a given type of in-use

operation to the extreme cycles. [This previous statement is addressed immediately

above.] This is not necessarily representative of the entire range of the real world

driving conditions and the characteristics of the middle ground between the various

conditions represented in the 5-cycle equation.” Honda also states that the

discontinuities present in a number of newer fuel efficient technologies may cause the

proposed 5-cycle formulae to under value their efficiency (i.e., penalize them relative to

their benefit in the real world).

Our response:

In this comment, Honda is basically arguing that the US06, SC03 and cold FTP

tests are so extreme that any interpolations based on them is fraught with error. In fact,
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as discussed above, Honda is basically arguing that extrapolating fuel economy effects

from only the FTP and HFET fuel economy values is better than interpolating fuel

economy effects using all five cycles.

It is common knowledge that interpolation is generally more accurate than

extrapolation due to the availability of additional data. Extrapolation is based on pure

speculation of the effect of the parameter being extrapolated. Interpolation at minimum

bounds the effect, since the effect under intermediate conditions will fall between the

two conditions tested. Thus, Honda is taking a very extreme position with this

comment. They are arguing that the three new tests are so extreme (i.e., their

conditions rarely occur in-use) that knowledge of fuel economy under these conditions

provides little value.

In addition, Honda states that the effect of driving patterns, air conditioning and

colder temperatures on the fuel economy of modern vehicles is extremely non-linear

and even discontinuous in nature. Therefore, they imply that knowledge and use of fuel

economy data over the three new test cycles will actually misrepresent fuel economy

over conditions intermediate between these tests and the FTP and HFET tests.

We have already shown above that the three new tests are not as extreme as

Honda asserts. In addition, the concept of interpolation is much less applicable to the

US06 and HFET tests, than for the SC03, cold FTP and FTP tests. For example, the

US06 driving cycle itself contains a wide range of driving, ranging from idle to over 80

mph, high rates of acceleration and deceleration, as well as relatively steady state

cruising. On average, the US06 highway and HFET driving patterns are quite different.

However, over 50% of the time spent driving in the two cycles occurs in VSP bins where

both cycles have significant operation (i.e., bins 0, 33, 35, and 36). Thus, it is not the

case where fuel consumption is being averaged at idle and wide open throttle. Both

cycles represent a range of highway driving. The HFET represents relatively low speed

highway driving coupled with very low rates of acceleration and deceleration. The US06

highway bag represents higher speed driving coupled with some more severe

accelerations and decelerations. Weighted together in the 5-cycle highway formula,

their combined driving pattern matches the best available description of onroad driving

patterns contained in the EPA’s Draft MOVES2004 model, fairly well. Thus, the 5-cycle

formula for highway fuel economy does not interpolate between the HFET and US06

driving patterns as much as it combines them. The concept of interpolation is much

more applicable to the use of the SC03 and cold FTP data in the proposed 5-cycle

formulae.

First, Honda did not provide any data to support the fact that fuel economy

effects developed from the US06, SC03 and cold FTP tests were not indicative of

changes in fuel economy which would occur at more intermediate conditions. Honda

claims that discontinuities in fuel economy effects occur with modern vehicles, but again

provides no data to support this contention. Therefore, we have to consider Honda’s

concerns as hypothetical at this point. Still, we consider the possibility for such a

hypothetical situation to exist below.
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In contrast, in many cases where EPA interpolated between the conditions

represented by two of the five dynamometer tests (e.g., ambient temperature, air

conditioning), test data at intermediate levels of the parameter of interest (e.g., cold start

fuel use at 50°F) were used directly to develop the linear or curvilinear shape of the

curve depicting the effect of the parameter on fuel consumption. These data at the

intermediate temperatures indicated that vehicles generally responded to lower

temperatures in a similar manner (i.e., start fuel use increased), though there was some

variability between individual vehicle’s response. Some of this difference may have

been due to the normal variability in fuel economy measurement. However, some of the

difference in vehicles’ response to colder temperatures is likely due to differences in

design. It is helpful to look at an example.

In developing the weighting factor for start fuel use, we used the results of FTP

testing 580 vehicles at a variety of ambient temperatures (Section III.A.1 of the TSD).

We further evaluated this database and found 295 vehicles which were tested at the

same three ambient temperatures, 15-35 F, 42-60 F, and 68-80 F. To this database,

we added the 13 Honda and Toyota vehicles described in Section III.A.1 of the TSD,

which were tested over the FTP at 20°F, 50°F, and 75°F. We determined the start fuel

use for the cold start of the FTP at each of these temperatures for each vehicle. The

average start fuel use for the three temperature ranges was:

15-35 F 0.0735 gallons

42-60 F 0.0457 gallons

68-80 F 0.0246 gallons

The issue here is how to best estimate the start fuel use at the intermediate

temperature range. Is it better to apply a fleet-wide adjustment to the start fuel use at

68-80 F, or to interpolate between the start fuel use estimates for both the high and low

temperature ranges?

The first approach is that used by the current fuel economy label procedure. This

is basically to determine the average impact of temperature on start fuel use and apply

this to every vehicle. This can be done in either of two ways: additive and multiplicative.

We will evaluate both ways here. The additive approach indicates that the start fuel use

at the intermediate range is 0.0211 gallons higher than that at 68-80 F. The

multiplicative approach indicates that the start fuel use at the intermediate range is

1.856 times higher than that at 68-80 F.

The second approach is that used in the 5-cycle formula. This approach

estimates the start fuel use for the intermediate temperature range on the start fuel use

in the lowest and highest temperature ranges. This approach indicates that the start

fuel use at the intermediate range is 43.1% of the way from the start fuel at 68-80 F to

that at 15-35 F.
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On average, all three approaches work. Any errors made in predicting the start

fuel use for individual vehicles always balance out. The issue is which approach

provides the best estimate for each vehicle individually. We assess this by calculating

the coefficient of variation of the error between the estimated start fuel use at the

intermediate temperature and that actually measured. The additive version of the fleetwide approach produced a coefficient of variation of 34%, while the multiplicative

version of this approach produced a coefficient of variation of 37%. The interpolation

approach produced a coefficient of variation of 24%, well below that of either fleet-wide

approach. The interpolation approach, which is that imbedded in the 5-cycle formulae,

clearly produces the smallest error in predicting start fuel use at intermediate

temperatures.

We repeated this analysis for the 13 Toyota and Honda late model vehicles. The

results were the same. The additive and multiplicative extrapolation approaches

produced coefficients of variation of 20% and 19%, respectively. Interpolation produced

a coefficient of variation of 9%. It is interesting to note that, while this group of vehicles

was small, it consisted of a wide variety of vehicle types and included four hybrids.

Honda appears most concerned about the application of the 5-cycle formulae to

advanced technology vehicles. Yet when applied to exactly such a group, the

interpolation approach embedded in the 5-cycle formulae performed well and much

better than the approach taken in the current label formulae and the mpg-based

equations.

Thus, it is clear, at least for the effect of ambient temperature on cold start fuel

use, that interpolation is far superior to extrapolation. Given that start fuel use is by far

the dominant effect of the cold FTP on 5-cycle fuel economy, this example essentially

addresses the main issue related to the use of the cold FTP in the 5-cycle formulae. If

Honda concern was valid, the “extremely” low temperatures of the lowest temperature

range would have produced misleading predictions of start fuel use for the intermediate

temperature range. That this did not occur indicates that Honda’s concern is invalid, at

least for this the effect of ambient temperature on start fuel use.

We believe that it is useful to illustrate in a more conceptual manner the

circumstances which must come together in order for Honda’s concerns to become

reality. All three label procedures, current, mpg-based and 5-cycle, incorporate the

effect of a variety of operational and environmental conditions on fuel economy.

However, they do so in different ways. We will focus our discussion on the current and

5-cycle procedures. The mpg-based procedure basically represents the average effect

of the 5-cycle procedure adjusted for a vehicle’s fuel economy over the FTP and HFET.

Thus, conceptually, it differs only slightly from the current procedure with respect to the

issue being addressed here.

Figure 5-1 illustrates the change in relative start fuel consumption with a drop in

ambient temperature from 75°F to 20°F for three vehicles; one with a relatively low

response to temperature, one with an average response and one with a high response.
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For simplicity, we assumed that start fuel use varies linearly with temperature in each

case. We will address the issue of non-linearity below.

Figure 5-1. Effect of Ambient Temperature on Cold Start Fuel Use

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1.5

2

2.5

3

20 30 40 50 60 70 80

Temperature (F)

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F

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Low

Average

High

The current label procedures are based on dynamometer testing at 75°F. Thus,

only start fuel use at 75°F is known for a specific vehicle. As mentioned above, the 10%

adjustment factor for city driving implicitly assumes that all vehicles’ cold start fuel use

changes with temperature to the same degree. No other projection can be made, since

no other information is available. We know from available test data at both 20°F and

50°F that this is not the case. The start fuel use of individual vehicles responds

differently to temperature. Thus, the current label procedure is clearly in error when it

assumes that this response is identical for all vehicles.

The 5-cycle formulae base their estimates of start fuel use on testing at both

20°F and 75°F. Therefore, it does not need to assume this effect. This effect is based

directly on the fuel economy measured over both the FTP and cold FTP tests. Honda

does not appear to be acknowledging this direct use of test data in the 5-cycle formulae.

The weighting factors for start fuel use in the 5-cycle formulae are based on an

assumed shape of the curve of start fuel use in between 20°F and 75°F. Figure 5-1

shows this effect to be linear. However, in reality it can be linear, curvilinear, or even

discontinuous, as pointed out by Honda. Figure 5-2 shows the change in relative start

fuel use versus temperature for three vehicles which all show the same total effect of

moving from 75°F to 20°F. One vehicle’s response is linear, another’s is curvilinear

(increasing slowly at first and then accelerating as the temperature approached 20°F),
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while the third vehicle’s is linear with a discontinuity at 50°F. The last vehicle’s

discontinuity might be due to the shut-off of some fuel saving technology, like engine

shut off when the vehicle is stopped.

Figure 5-2. Possible Shape of Start Fuel Use Versus Temperature

1

1.2

1.4

1.6

1.8

2

20 30 40 50 60 70 80

Temperature (F)

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F

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Linear

Curvilinear

Discontinuous

In-use, vehicles are operated over a range of ambient temperatures. From a

driving perspective, the average ambient temperature is just under 60 F (see Section

III.A.4 of the TSD). Driving is more frequent at this temperature that it is at higher or

lower temperatures. Average start fuel use in-use is then the start fuel use at any

specific temperature weighted by the frequency of starts at that temperature. If vehicles

were tested over small intervals of ambient temperature, for example every 5 F, the

differences in the three vehicles’ start fuel use responses shown in Figure 2 would be

fully reflected in the predicted average fuel consumption. However, since vehicles are

only tested at 20°F and 75°F, the weighting of these two test results needed to produce

the average start fuel use with respect to ambient temperature would differ to some

degree.

For example, the weighting of start fuel use at 20°F for the vehicle with the

curvilinear response would be lower than that for the vehicle with the linear response.

This would be the case, because the vehicle with the curvilinear response would have

lower fuel consumption at every temperature in between 20°F and 75°F and would

necessarily have a lower start fuel use than the vehicle with the linear response. (We

are ignoring what happens below 20°F and above 75°F in this example, which is

relevant in the real world.)
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There is no way to reflect this difference in the current label procedures. The two

vehicles’ start fuel use at 75°F is reflected in their FTP tests and incorporated into the

label values. However, the increase in start fuel use at lower ambient temperatures is

based on the fleet-average vehicle and comprises a portion of the 10% and 22%

generic adjustment factors. Thus, as discussed above with respect to the vehicles

depicted in Figure 1, the current label procedure assumes that all vehicles have the

same relationship between start fuel use versus temperature.

The 5-cycle procedure includes the ability to reflect differences in vehicles’ start

fuel use at both 20°F and 75°F. However, it, like the current label procedures, cannot

reflect differences in the shape of the curve in between these two temperatures. Thus,

the 5-cycle procedure is better than the current procedure in one respect, but still not

ideal. Additional testing at intermediate temperatures would be required to further

improve the accuracy of the label value. However, Honda and other manufacturers

clearly recommend against this, and currently EPA believes it is unnecessary.

The mpg-based procedure converts the individual vehicle responses estimated

by the 5-cycle formulae to their fleet-wide averages as a function of FTP or HFET fuel

economy. If the effect of ambient temperature on start fuel use in relative terms

changes with vehicles’ FTP fuel economy, then the mpg-based procedure will reflect

this. However, if the differences in vehicles’ response to temperature are due to other

factors, then the mpg-based procedure reduces basically to the current label procedure

with a different adjustment factor. In fact, the mpg-based equations create a city fuel

economy label by reducing FTP fuel economy by 20-28%; the adjustment to HFET fuel

economy is 29-30%. Thus, the mpg-based equations reflect a portion of the difference

in individual vehicle responses to various factors which affect city fuel economy.

However, regarding factors which affect highway fuel economy, the mpg-based

equation is nearly identical to the current label procedure with a higher downward

adjustment.

It is impossible to theoretically predict how the average start fuel use for the

vehicle with the discontinuous response to ambient temperature would compare to that

for the other vehicles. Its average start fuel use, and thus, its weighting of start fuel use

at 20°F, could be higher or lower depending on where the discontinuity occurs (e.g., 30

F or 60 F) and the degree that fuel consumption changes at the discontinuity. None of

the three label procedures is capable of accurately accounting for such discontinuous

effects of ambient and operation conditions on fuel economy. Aside from testing

vehicles over a much wider and comprehensive set of ambient and operating

conditions, the only issue is how to use the available test results to best estimate

onroad fuel consumption. Again, we can use the example of the effect of ambient

temperature on start fuel use to evaluate which of the three procedures best uses the

available information to predict onroad fuel economy.

As shown in Figures 5-1 and 5-2, vehicles can vary in their total response to a

change in temperature from 20°F to 75°F, as well as in the rate of change in this

response as temperature moves from one end to the other. The 5-cycle formulae
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clearly can account for the total difference in this response between the dynamometer

tests which are conducted. Thus, the only potential inaccuracy in the formulae is due to

differences in the shape of the curves between the two endpoints. With the current

label procedure, neither the degree of the change in fuel consumption between 20°F

and 75°F, nor the shape of the curve is known. Thus, all vehicles are assumed to have

the same relative change in fuel consumption at every ambient temperature other than

75°F. The only way that the 5-cycle formulae could produce a worse estimate of onroad

fuel economy would be if vehicles’ response to ambient temperature between, for

example, 40 F and 75°F was inconsistent with their response at 20°F. Even in this

situation, the degree of error would need to be relatively large to be worse than the

current label procedure, since the latter completely misses all differences in vehicles’

response to any relevant factor.

While this is theoretically possible, it requires that the change in start fuel use at

20°F differ so substantially from that at intermediate temperatures that vehicles with

higher increases in fuel consumption at 20°F have lower increases at, for example, 45

F, and vice versa. In other words, the types of curves shown in Figures 5-1 and 5-2

have to criss-cross. It is highly unlikely that differing degrees of curvature in a vehicle’s

response could produce this result. The most likely situation would involve a severe

discontinuity in a vehicle’s response. Figure 5-3 shows this situation.

Figure 5-3. Potential Source of Error in the 5-Cycle Weighting Factors

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20 30 40 50 60 70 80

Temperature (F)

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Curvilinear

Discontinuous

As shown in Figure 5-3, the vehicle with the curvilinear response has a lower

increase in start fuel use at 20°F relative to 75°F than the vehicle with the discontinuous
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response. However, over most the temperature range shown, the vehicle with the

discontinuous response has the lower increase in start fuel use. Thus, the onroad fuel

consumption of the vehicle with the discontinuous response is likely to be the lower of

the two vehicles. However, a weighting of the start fuel use at 20°F and 75°F would

indicate the opposite. In order for the use of the 20°F measurement to cause this

problem, the discontinuity indicated in Figure 3 must be both large and occur close to

20°F.

This is the situation about which Honda appears to be concerned. While

theoretically possible, we have no fuel economy data which indicate such a severe

discontinuity exists with any currently marketed vehicle or any future technology.

Honda submitted no data to support the existence of such severe discontinuities.

Honda also submitted no data indicating that such discontinuities would occur in a way

that the vehicle would be in high fuel consumption mode frequently over the SC03,

US06 or cold FTP tests, but less frequently in-use compared to the weighting of these

tests in the 5-cycle formulae. As presented above, the existing data clearly support the

superiority of the interpolation approach followed in the 5-cycle formulae.

Practically, such a large discontinuity only occurs when a piece of equipment or a

technology turns off or on. Examples would be engine shut off at vehicle idle or mild

driving and cylinder deactivation at low engine loads. Such technologies are currently

applied in only a very limited number of models. A practical example related to colder

temperatures could involve use of the heater and its effect on the engine shut-off

strategy for hybrids. Most hybrids save fuel by shutting the engine off when the vehicle

is idling. However, many current hybrid systems disable this engine shut-off when the

heater is turned on, as the heat comes from the engine. Thus, the savings related to

engine shut-off disappear in the range of ambient temperatures when people tend to

turn on their vehicle heater. If people tend to turn on their heater just above 20°F, then

the situation indicated in Figure 3 could occur. However, people tend to turn on their

heater well above this temperature. The weighting factor for the cold FTP with respect

to start fuel use is 24%, while that for running fuel use is 30%. In the case of the heater

affecting engine shut-off, as long as the heater was turned on 24-30% of the time inuse, even if this caused a large discontinuity in fuel use, the 5-cycle formulae would

provide a reasonable estimate of onroad fuel consumption. Roughly 35% of all driving

occurs below 50°F, while about 21% occurs below 40 F. Nearly all people will have

their heater turned on at 40 F. Many, if not most drivers will turn on their heater at 50°F.

Thus, in this case, the weighting factor for the fuel consumption over the cold FTP

appears quite appropriate with respect to the impact of heater use on engine shut-off

and fuel consumption.

In contrast, we have ample evidence that vehicles vary in their fuel economy

response to ambient temperature. The 5-cycle formulae allow these differences to be

incorporated into the label values. The current formulae do not. The mpg-based

equations only allow them to be incorporated to the extent that the differences are a

function of FTP or HFET fuel economy. Other differences in the response to

temperature are lost with the mpg-based equations. The only advantage of the current
96

or mpg-based equations would be to avoid the hypothetical situations where the

incorporation of the three new tests over-estimates significantly the impact of these

conditions on onroad fuel economy value.

It is interesting to note that the mpg-based equations have the same potential for

error as the 5-cycle formulae should the hypothetical technologies which reflect severe

discontinuities become the predominant technology in the new vehicle fleet. In this

situation, 5-cycle fuel economy values of most of the vehicle fleet would reflect the

problem asserted by Honda. The mpg-based regression of these 5-cycle fuel economy

values would fully reflect the effect of the 5-cycle weighting of the three new tests.

In addition to interpolating start fuel use between 20°F and 75°F, Honda also

cites concerns about interpolating between: 1) the low highway speeds and power

levels of the HFET and the high highway speeds and power levels of theUS06 highway

bag and 2) the 75°F non-air conditioning operation of the FTP and the 95°F air

conditioning operation of the SC03 test. As we have already discussed, the 5-cycle

formulae does not interpolate between fuel economy over the HFET and the highway

bag of US06, as much as it combines them. Some in-use highway operation occurs like

that of the HFET and some occurs like that of the US06 highway bag. Both cycles

include a range of vehicle speeds and power levels. Together, there are no large gaps

in vehicle operation in terms of VSP, unlike that in between the cold and standard FTP.

Thus, Honda’s concern about interpolating in between the HFET and US06 fuel

economy values is unfounded.

Regarding air conditioning use, there are at least a couple of ways in which the

weighting factors in the 5-cycle formulae were developed utilizing interpolation. We

estimated the percentage of time that the compressor is engaged at temperatures and

humidities both above and below those existing during the SC03 test. We also

estimated the change in load which the compressor places on the engine at

temperatures other than 95°F. Individual vehicles might respond differently to these

“off-cycle” conditions. Had we used fuel economy data over these intermediate

conditions for various vehicles, we might have developed somewhat different weighting

factors for the effect of air conditioning use in the 5-cycle formulae. However, as stated

a number of times already, the alternative is to simply apply the same factor to all

vehicles’ fuel economy based on its fuel economy over the FTP and HFET. This is

highly uncertain and clearly wrong in several instances. One, vehicles without air

conditioning would receive the same adjustment as those with air conditioning. Second,

larger vehicles with optional rear passenger air conditioning would receive the same

adjustment with or without the option. Under the 5-cycle approach, the vehicle with the

larger or second compressor would achieve a lower fuel economy over SC03 and a

lower 5-cycle fuel economy.

In Section 5 of their comments, Honda also cites data referenced in the Draft

TSD that indicates that the engagement of the air conditioning compressor over SC03

varied between vehicles. Honda states that these data show that the assumption about

air conditioning compressor engagement based on fleet wide averages do not apply to
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individual vehicles. We reevaluated the data cited by Honda and it appears that Honda

misunderstands how the weighting factors of the proposed 5-cycle formula work in

practice for a specific set of vehicles. This same is true for the current label procedure.

Honda cites data from six vehicles on the percentage of time that the air

conditioning compressor is disengaged during the SC03 test. Honda states that these

percentages range from 3% to 37%. The implication is that a single value cannot

represent both 3% and 37% and therefore, the weighting factor in the proposed 5-cycle

formulae must be wrong. First, the 5-cycle formulae do not assume any compressor on

time for a specific vehicle operated over SC03. This percentage is implicit in the SC03

test itself. The vehicle is operated over the SC03 test, the air conditioning compressor

is engaged to cool the cabin as would be the case onroad under the ambient conditions

of the test and this compressor engagement increases fuel consumption in the same

way. The fundamental impact of running the air conditioning system is determined by

the test, not by some assumed formulae.

The 5-cycle formulae do assume that the impact of air conditioning under more

moderate conditions is a specific fraction of the impact over a short trip at 95°F. If a

vehicle shows a relatively high impact of air conditioning over SC03, then the proposal

assumes that this vehicle will also show a relatively high impact at more moderate

conditions. The same assumption is made regarding a vehicle showing a relatively low

impact of air conditioning over SC03. The data cited by Honda actually confirms the

reasonableness of this assumption.

Table 5-4 shows the percentage of time that the air conditioning compressor is engaged

during the SC03 test.29 We show the percentage of time that the compressor is

engaged, rather than disengaged, since air conditioning increases fuel use when the

compressor is engaged, not when it is disengaged. Three test conditions are shown.

The first is the official test temperature of 95°F with the required solar load. The second

set of runs was performed at 75°F, again with solar load. The third set of runs was

performed at 75°F without any solar load, but with the heater turned all the way up to

simulate the effect of solar load on compressor engagement.

Table 5-4. Air Conditioning Compressor Engagement over SC03 (% of

time)

95°F 75°F With Solar Load 75°F With Heater On

Escort 63 40 44

Mustang 93 53 71

Town Car 97 66 95

Bronco 97 76 95

Windstar 97 68 98

Corolla 97 68 100

29 SAE Nam paper on A/C load
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As indicated by Honda, the percentage of time which the compressor was

engaged varied between the vehicles. However, the primary issue with respect to the

weighting factors for air conditioning use in the proposed 5-cycle formulae is the

correlation between compressor engagement over the SC03 test and that at other,

usually less severe conditions. We performed a regression between the percentage of

time which the compressor was engaged over SC03 and that at 75°F with solar load.

The adjusted r-square was 0.760. The p-value for the factor relating the two

compressor usages was 0.022, indicating a very strong statistically significance. The

same type of regression was performed between compressor engagement over SC03

and that at 75°F with the heater turned on and the results showed an even stronger

correlation (adjusted r-square of 0.827 and a p-value of 0.008. These strong

correlations indicate that the degree of compressor usage over SC03 is a very good

indicator of compressor usage at lower temperatures. Since this is the precise

assumption made in developing the weighting factor for the impact of air conditioning on

fuel economy in the 5-cycle formulae, these data are a strong confirmation of the

proposal and do not refute the formulae, as asserted by Honda.

While these data confirm the proposed 5-cycle formulae, they do refute the

assumption inherent in the current label formulae. The current label procedure utilizes

no vehicle-specific information regarding compressor engagement or the impact of air

conditioning on onroad fuel economy. The impact of air conditioning on onroad fuel

economy is assumed to be the same for all vehicles and is implicitly included in the

generic 10% and 22% adjustment factors applied to the FTP and HFET fuel economy

measurements. The test program producing the above data did not report fuel

economy, so we cannot evaluate the impact of air conditioning use on a vehicle specific

basis for these vehicles. However, we know from the certification database presented

in the NPRM that there is some variability in vehicles’ fuel economy response to air

conditioning. The data in Table 5-4 confirm this difference by indicating that the

compressors of some vehicles run all the time over SC03, while others run much less.

Thus, the implicit assumption in the current label procedures that the impact of air

conditioning is a constant percentage for all vehicles is challenged by the data from this

test program.

In summary, Honda suggests that we ignore significant amounts of valid fuel

economy obtained with the three new tests in order to avoid a purely hypothetical

situation where the use of these data might produce a less realistic estimate of onroad

fuel economy than the current procedure or the mpg-based equations. In doing so,

Honda ignores the fact that the current label procedure (and the proposed mpg-based

procedure) involves more extensive assumptions about the response of various

vehicles’ fuel economy to ambient and operational conditions than the proposed 5-cycle

formulae. A generic adjustment to FTP and HFET fuel economy produces a fuel

economy label which is just as vehicle specific as the 5-cycle formulae. Assuming that

all ambient and operational conditions which differ from the FTP and HFET have the

same effect on each vehicle’s fuel economy does not automatically minimize error. In

fact, as will be shown below for start fuel use at colder temperatures, a generic

adjustment produces a much larger error than using fuel economy values measured
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over the FTP and cold FTP tests. This should be no surprise. Additional testing

provides additional information which allows more accurate fuel economy estimates to

be developed. In fact, if cost was not an issue, even more testing covering an even

wider set of driving patterns and ambient conditions would be beneficial.

Put a slightly different way, Honda has pointed out a number of uncertainties

associated with the proposed 5-cycle formulae which we agree are present. What they

fail to acknowledge is that the same type of evaluation of the current label procedure

and the proposed mpg-based equations would reach the same conclusion, only more

so. Thus, we conclude that Honda’s comment that the proposed 5-cycle formulae

assume that all vehicles have the same relationship between fuel consumption and real

world driving conditions is false. In contrast, it is actually true for the current label

procedure which we propose to replace with the 5-cycle fuel economy formulae.

5.10 Misuse of Emission Factor Models

What we proposed:

We proposed weighting factors in the 5-cycle formulae that were developed

using fleet-average driving activity and fuel consumption data. The basis for some of

these weighting factors was data that are currently used in our MOBILE and MOVES

emission factor models.

What commenters said:

Honda goes through the development of the 5-cycle formulae as described in

detail in the Draft TSD and identifies 15-20 areas where EPA used fleet-average activity

or fuel consumption data to develop the weighting factors in the formulae. One example

is the change in a vehicle’s fuel consumption as the ambient temperature decreases

from 75°F to 20°F. Honda believes that EPA should validate that the weighting factors

developed in each of these areas applies to individual vehicles, as well as to the fleetaverage vehicle. Honda’s concerns are increased by the belief that modern computer

controls allow significant non-linearity to be introduced into vehicle operation. While

historically, the fuel consumption of conventional vehicles might have increased

gradually as ambient temperature decreased, the fuel consumption of modern vehicles

might change suddenly at some specific temperature. A weighting of fuel consumption

at 20°F and 75°F based on fleet average data reflecting the gradual change might not

be appropriate for a specific vehicle exhibiting the sudden dramatic change. Most

importantly, Honda believes that without such validation, the 5-cycle formulae as

proposed might produce a worse estimate of onroad fuel economy than the current

label procedures.
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Our response:

We do not take issue with Honda’s comment that the weighting factors in the 5-

cycle formulae were developed using fleet-average driving activity and fuel consumption

data. Nor do we claim to have validated these factors on an individual vehicle basis. In

fact, we presented some data in the Draft TSD which indicates that a set of 5-cycle

formulae “tuned” to an individual vehicle would likely differ to some degree (e.g., the

comparison of appropriate weighting factors for start fuel use at 20°F for hybrids versus

conventional vehicles in Section III.A of the TSD). However, we disagree with Honda

that these two facts make the proposed 5-cycle formulae somehow inappropriate or

unjustified. In order to demonstrate this, we address each of Honda’s concerns below.

Regarding Honda’s concern that fleet-averages were used to develop the

weighting factors, this approach is the same as that used to develop the current fuel

economy labels. For example, the city fuel economy value is 90% of the fuel economy

value measured over the FTP. The 90% factor was based on the difference between

onroad fuel economy estimated for a large number of in-use vehicles (i.e., the fleet) and

the average of these vehicles’ FTP fuel economy values. This factor should have been

larger for some vehicles and smaller for others. However, the only way to know this for

certain for individual vehicles is to measure the onroad fuel economy of each vehicle

and compare it to its FTP fuel economy. However, once the onroad fuel economy is

available, there is no need for an adjustment factor, one could just use the onroad fuel

economy value and skip measuring fuel economy over the FTP. Of course, the major

problem with this approach is that onroad fuel economy values would only be available

after a considerable number of vehicles of the particular model have been sold and

operated for some time. It is also difficult to obtain a fully representative sample. Thus,

the 90% factor represents an acceptable adjustment factor on average.

The FTP itself includes at least two aspects which were based on fleet average

estimates. First, the driving cycle was based on the average speeds of individual

vehicles which were driven over a particular road route in Los Angeles circa 1970.

Different vehicles of various power-to-weight ratios and other design criteria were likely

driven over this road route differently. Also, vehicles are obviously driven on many

other types of road routes during “city” driving. The relationship between each vehicle’s

average onroad fuel economy and its fuel economy over LA road route #4 will vary.

Yet, all vehicles’ city fuel economy label values are based on their fuel economy over

this single road route. The same is true for the highway fuel economy label.

The other aspect of the FTP which is based on fleet average estimates is the

57% weighting of fuel consumption following a hot start (i.e., 10 minute soak) and the

43% weighting of fuel consumption following a cold start (i.e., 12 hour soak). Vehicles

are started in-use after a wide range of soak times. Even if every vehicle model was

found to have the same distribution of pre-start soak times in-use, the relative weight of

hot start fuel use and cold start fuel use which produced each vehicle’s average start

fuel use in-use would likely vary. The current FTP weighting factors of 43% and 57%
101

represent factors which were determined to be reasonable on average in the early

1970’s.

Neither of these two aspects of the FTP have these been validated on an

individual vehicle basis in the way Honda asserts must be done in order for the 5-cycle

formulae to be valid. Numerous studies have shown a statistical correlation between

FTP fuel economy and “city” fuel economy and between HFET fuel economy and

“highway” fuel economy. However, as will be discussed below regarding fuel economy

data obtained from Strategic Visions, there is a high degree of correlation between the

fuel economy values measured over all five of the driving cycles. Thus, the fact that

past studies showed a good correlation between FTP fuel economy and onroad city fuel

economy means very little. A similar analysis would have indicated a good correlation

between SC03 FTP fuel economy and onroad city fuel economy, even though air

conditioning is used much less than half of the time in-use. The same would be true for

a correlation between US06 fuel economy and onroad highway fuel economy. As the

Honda analysis indicates, even fuel economy over HFET is a good predictor of city fuel

economy. No study has been performed which shows or “validates” that the FTP and

HFET are the appropriate tests on an individual vehicle basis.

The driving patterns contained in the FTP and HFET, as well as the cold/hot start

weighting factors are examples of the use of fleet-average data and relationships

explicitly included in the current label procedure. However, essentially every

relationship which we used to develop the 5-cycle formulae, and which Honda criticizes,

is implicitly included in the current label procedure, as well. (Because the mpg-based

equations apply the differences between the 5-cycle label values and FTP or HFET fuel

economy values, the mpg-based equations involve these same relationships, as well.)

For example Honda criticizes EPA’s development of the weighting factor for the

highway bag of US06 in the 5-cycle highway fuel economy formula. However, the

current highway label procedure assumes that the effect of driving patterns which differ

from the HFET is the same for all vehicles. This factor is not explicitly identified. It is

simply a portion of the overall 22% downward adjustment applied to HFET fuel

economy. However, it is assumed to be identical for all vehicles. Honda’s own

comments state that they believe that the fuel economy of individual vehicles will

respond to different driving patterns differently. The assumption that all vehicles

respond identically has never been validated on an individual basis. If such an attempt

were made, it would likely fail. The differential relationship between fuel economy over

the HFET and US06 highway bag is also evidence of this difference.

As stated above, unless vehicles are tested over all possible modes of operation

and ambient conditions occurring in-use, some judgment must be applied to, in a sense,

estimate fuel economy over the untested conditions. We believe that it is much better to

perform this estimation via interpolation between actual fuel economy measurements,

as opposed to extrapolating from a single fuel economy measurement, such as the FTP

or HFET. The proposed 5-cycle formulae involve the actual measurement of fuel

economy over ten individual sets of operation and conditions. The current label

procedure involves three measurements. The fuel economy effect of the assessed
102

range of operation and ambient conditions included in these ten distinct measurements

is determined for each vehicle directly from the testing of that vehicle. These

measurements involve no assumptions. The current label procedures, as well as the

proposed mpg-based equations, do not involve the direct measure of fuel economy at

the extra seven sets of operation and conditions. These approaches must “assume”

these fuel economy effects. All approaches have to estimate fuel economy for

operation and conditions not tested. However, with the proposed 5-cycle formulae,

these assumptions are usually bracketed by real test data. With the current and mpgbased procedures, there are not extra data points which provide such bracketing.

Estimation of fuel economy during all operation and conditions not included in the FTP

or HFET are assumed based on fleet-wide relationships of the type criticized by Honda.

Thus, we must reject Honda’s repeated assertions that the 5-cycle formulae are

inherently deficient because these relationships have not been “validated” for individual

vehicles. Honda has simply failed to understand the greater role of these same

relationships in the current and mpg-based procedures.

Honda has also inconsistently applied its own criticism of the use of fleet-wide

fuel economy relationships by assuming that fleet-wide adjustments to FTP and HFET

fuel economy, as is done with the current and mpg-based procedures, is inherently

accurate, while criticizing the use of such relationships under more restricted conditions

in the development of the weighting factors for the 5-cycle formulae.

5.11 Derivation of Vehicle-Specific 5-Cycle Method

5.11.1 Start Fuel Use

5.11.1.1 Start Fuel

What we proposed:

We proposed that start fuel consumption for a vehicle be determined by

calculating the difference between its FTP Bag 1 (cold start) fuel consumption and its

FTP Bag 3 (hot start) fuel consumption.

What commenters said:

UCS commented that the proposed methodology is reasonable in principle, but it

is valid only if the vehicle is fully warmed up by the end of Bag 1 of the FTP. If the

vehicle is not fully warmed up until Bag 2, then the start fuel use would be the difference

in fuel use between Bags 1 and 2 combined and that of Bags 3 and 4 combined, with a

4-bag FTP. By only considering the difference between Bags 1 and 3, they argue, the

proposed methodology may omit some start fuel use that occurs in Bag 2, thus

underestimating the start fuel consumption and overestimating the running fuel

consumption during Bag 2. As a potential indicator that this might be the case, UCS

points to the data in Table III.A-22 in the Draft TSD, where in many cases the Bag 4 fuel
103

economy is higher than the Bag 2 fuel economy, especially at 20 degrees F. They

further note that no data points to hybrids as being unique in this regard, and thus it is

possible, they postulate, that conventional vehicles may also not be warmed up by the

end of Bag 1. They suggest that a modest test program on a dynamometer could

determine whether vehicles are warmed up after Bag 1, Bag 2, or not until later, and 75

and 20 degrees F.

They further argue that different vehicles must be tested in similar and consistent

ways in order to ensure fairness. Start fuel for hybrids, tested on the 4-bag FTP and

where the vehicle is “allowed” to warm up through Bags 1 and 2, might produce results

inconsistent with a conventional vehicle tested on a 3-bag FTP, where the vehicle is

assumed to warm up by the end of Bag 1.

Our response:

As described in the Draft TSD, testing at 75°F has assumed that vehicles are

fully warmed up after Bag 1 for over 20 years. As also discussed in the Draft TSD, it is

less clear that this is true at 20°F. If the vehicle is not fully warmed up after Bag 1 at

either temperature, its cold start fuel use will be under-estimated, as pointed out by

UCS. However, the vehicle’s warmed up fuel use, which is taken in part from Bag 2, will

be over-estimated. Thus, the net impact on estimated fuel use would be less than that

indicated just by the under-estimation of start fuel use.

Throughout this rule, we have made it a premise to avoid adding to the current

tests which are performed. There have been exceptions to this premise, such as

requiring diesels to be tested at 20°F. However, this change is the extension of a

testing requirement already applicable to nearly all vehicles to a few vehicles which had

been granted an exception. We have also proposed some changes to the test

procedures, such as splitting the US06 test in to two bags and requiring the heater to be

turned on during the cold FTP test. However, these changes would not extend the test

and would have little long term impact on test costs.

In contrast, requiring all vehicles to be tested over a 4-bag FTP would increase

the cost of every FTP both in terms of dynamometer and personnel time. This would

particularly be true for cold FTP testing. The increase in accuracy of the fuel economy

label due to this change is unknown, but likely to be small. Table III.A-21 in the Draft

TSD presents the result of a DOE test program performed at several temperatures. It

found fuel economy over Bag 1 to be 26% lower at 20°F than at 75°F, while this

difference was only 8% for both Bags 2 and 3. Roughly 2% out of these differences

was likely due to difference in summer and winter fuel. Thus, even if all of the

remaining difference in Bag 2 and 3 fuel economy was due to further warm up, this 6%

difference would only represent one-fourth of that found in Bag 1. Some of this

remaining 6% difference is likely due to factors normally associated with colder

temperatures, such as increased friction in the drivetrain. Thus, the three-bag FTP

could be capturing more than 80% of the cold start fuel use and part of the remainder

would be captured through an increase in running fuel use.
104

We believe that this is adequate for the purpose of fuel economy labeling. It is

certainly better than the current procedure where we assume that every vehicle has the

same percentage increase in start fuel use at colder temperatures relative to its start

fuel use at 75°F. To the decrease that a small amount of start fuel use is missed by the

current cold FTP test procedure, this is captured in a generic way through the nondynamometer factor.

5.11.1.2 Trip Length

5.11.1.2.1 City/Highway VMT Split of 43/57 Percent

What we proposed:

The combined fuel economy using the current label formulae is a 55/45 harmonic

weighting of the current city and highway fuel economy labels. For the proposed 5-

cycle formulae and related analyses, we used a 43/57 harmonic weighting of the 5-cycle

city and highway fuel economies to represent combined overall fuel economy. This

city/highway split for the 5-cycle fuel economies was based on:

1) The assumption that driving generally less than 45 mph is city driving and that

above 45 mph is highway driving, and

2) The description of onroad driving patterns contained in MOVES.

Note that there are two separable issues here: one relating to the 5-cycle

equations and related background analyses that have little direct impact on the label,

and the other relating to those items on the label that are directly influenced by the

city/highway split and highly visible to consumers (e.g., the average annual fuel cost

and combined fuel economy). It may in fact be reasonable to use different weightings in

these two different cases. This section addresses the weightings used in the 5-cycle

analyses; Section 2.0 addresses the use of the combined fuel economy on the label

itself.

What commenters said:

AAM/AIAM notes that the proposed change in the EPA city/highway split, from

55/45 to 43/57, suggests that today’s drivers are more frequently traveling at speeds

greater than 45 miles per hour, or at least more frequently than twenty years ago when

the adjustment factors were first developed. They point out that the proposed change

assumes that drivers commuting on the road would get there more quickly today than

they would have were they to drive the same route twenty years ago. AAM/AIAM finds

that this is statistically valid on a miles-driven basis, but they believe that their analysis

reveals that EPA’s proposed change does not take into account modern-day

congestion. As a result, they point out that the methodology produces counter-intuitive

predictions, such as most drivers are driving at highway speeds 57% of the time as EPA

reports in their NPRM. They believe that the current 55/45 split aligns more closely with
105

the way many customers think of their driving patterns – a 50/50 split – than the

proposed split, which hints at a precision that departs from many drivers. Being

unconvinced that a change is needed, AAM/AIAM recommends that EPA pursue further

data collection and validation, which include the effects of modern-day congestion.

Our response:

The split of U.S. driving into city and highway fractions was based on an analysis

of estimates of U.S. driving as a whole contained in the Draft MOVES2004 emissions

model. This split is inherently subjective, as it can involve both the immediate driving

pattern of the vehicle, as well as the overall driving pattern of the trip. Various drivers

are highly likely to use different definitions and would estimate different driving splits

even if they were to drive exactly the same route at the same time of day. The

city/highway split of 43/57 was developed using the approximate boundary of 45 mph,

applied to a segment of driving, and not on a second-by-second basis. This worked

well for the various driving cycles used in MOVES2004 to represent onroad driving

activity. However, in real life, many trips would contain driving segments in both the city

and highway categories which would be difficult to separate in a quantitative way.

As described in Section III.E of the TSD pertaining to the comparisons of fuel

economy label values to onroad fuel economy estimates, it is most accurate to compare

combined fuel economy in both cases. This avoids the need to split driving in to city or

highway categories. The most important factor in this case is that the city and highway

driving be re-combined in the same as it was originally split. As outlined in Section III.F

of the TSD, we evaluated alternative definitions of city and highway driving which in turn

changed the split of VMT between the two categories. None of these alternatives

appeared to carry any advantages, particularly in terms of being able to be simulated by

the various dynamometer cycles. We have no new data or insight which would change

this conclusion.

Regarding the impact of congestion on the split between city and highway

driving, we believe that AAM/AIAM is confusing the impact of congestion on driving time

and mileage. Congestion increases the length of a trip in terms of time, but does not

necessarily change its mileage. Thus, congestion by itself would not be expected to

increase the city fraction of VMT. The 43/57 split is based on VMT, not time. It is

possible that congestion would shift some driving which was formerly at highway

speeds to that which is now considered to be city driving. This would tend to increase

city fraction of all driving.

The other trend which has been occurring for the last 30 years is urban and

suburban sprawl. This tends to increase trip length, as confirmed by the National

Personal Travel Survey results. Urban beltways and other new freeways have allowed

relatively efficient additional travel to occur with city driving at either ends. At the same

time, some of these freeways become congested at rush hour and convert to city

driving. This congestion likely increases city driving less than might be thought, again

due to the difference between time and mileage. It takes a long time to move a mile on
106

a congested freeway. Even those people who spend most of their time in what seems

like a parking lot likely achieve most of their mileage at a much higher speed.

The final factor affecting the comparison of the current 55/45 and the proposed

43/57 city/highway split is the fact that they were based on different definitions of city

and highway driving, as outlined in Section III.A.2 of the TSD. The 55/45 split was

consistent with the urban/rural split of VMT as estimated by FHWA in the late 1970’s

and early 1980’s. As indicated by the characterization of driving patterns in

MOVES2004 and supported by common sense, more highway driving occurs on

freeways in urban areas than low speed driving occurs in rural areas. Thus, breaking

down city and highway driving by vehicle speed is likely to yield a lower fraction of city

driving than a breakdown based on urban driving. This is likely the biggest factor

yielding the change in the city/highway split.

5.11.1.2.2 Highway Trip Length

What we proposed:

We proposed a highway trip length of 60 miles.

What commenters said:

Mitsubishi expressed concern over the use of the denominator of “60” in the

following equation, found in proposed 600.114-08(b). They commented that EPA did

not clearly explain why the number is used, and how it was derived, arguing that it

appeared to be arbitrarily chosen. UCS likewise expressed some concerns with EPA’s

assumptions regarding trip length in the 5-cycle equations and how they may impact the

calculated fuel economy, especially given EPA’s language that the trip length of 60

miles was “somewhat arbitrary.” They agree with EPA’s assessment that once highway

trip length is over 30-40 miles the denominator in the equation makes little difference,

but they argue that it has not been clearly established that the average in-use highway

trip is indeed greater than 30 miles.

 

 



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

     

60

75 24 20 0.76 0.

0.330 StartFuel StartFuel StartFC gallons per mile

More importantly, UCS argues, is the fact that highway trip length has an indirect

impact on city fuel economy because EPA has fixed the city/highway mileage ratio and

the average trip length, thus making city trip length a de facto function of highway trip

length. They recommend that EPA focus on determining more accurately the length of

the average city trip, then allowing the highway trip length to be determined as a

function of the city trip length, if necessary.
107

Our response:

EPA’s derivation of the trip lengths for all driving, city driving and highway driving

is explained in great detail in Section III.A.1 of the TSD. Many vehicle trips in real life

involve a mix of city and highway driving. There is no single method for assigning these

trips to either type of driving. Thus, it is impossible to determine a precise estimate of

trip lengths for either city or highway driving. One can estimate the length of the

average vehicle trip from studies of vehicle operation. In the TSD, we estimate this

length to currently be 7.68 miles. The estimates of city and highway VMT coupled with

the trip lengths for city and highway driving must be consistent with this overall trip

length of 7.68 miles.

The city/highway split of VMT in the U.S. of 43/57 comes from our analysis of the

characterization of driving contained in the MOVES2004 model and our definition of city

and highway driving. This estimate is independent of any assumptions regarding trip

length. Given an estimate of either city or highway trip length, the other trip length is

determined by the other information. Table 5-5 shows how the two trip lengths interact.

Table 5-5. Relationship Between City and Highway Trip Length (miles)*

City Highway City Highway

3.0 -48.7 5 12.8

3.5 60 ** 6 9.7

4.0 24.3 7 8.3

4.5 16.2 7.7 7.7

* Figures based on more precise city/highway VMT split of 42.5/57.5.

** Rounded, per proposed 5-cycle formulae.

As can be seen, relatively small changes in city trip length produce large

changes in highway trip length. Highway trip length becomes infinite for a city trip

length of 3.27 miles, so city trips cannot be shorter than this length. Also, highway and

city trip length become equivalent for a city trip length of 7.7 miles. Since it is counterintuitive that city trip would be longer than highway trips, city trips cannot be longer than

this length.

Regardless of the specific city and highway trip lengths, the excess fuel use

associated with engine starts will be accounted for in either the city or highway fuel

economy estimate. The only issue is where to concentrate the start fuel use. The

current procedure concentrates all measured start fuel use in city driving. The HFET is

a hot start test. Assigning a finite 60 mile trip length to highway driving decreased 5-

cycle highway fuel economy by 0.5%. Because of the interaction between city and

highway trip length, this increased city fuel economy by 0.4%. Decreasing the highway

trip length from 60 to 20 miles would decrease 5-cycle highway fuel economy by 0.9%,

while increasing city fuel economy by 1%. This change would tend to bring the city and

highway fuel economy label values closer together (by roughly 2%). A change of this

magnitude would only affect the actual label values of a very small fraction of vehicles

given that labels are rounded to whole mpg figures.
108

Changing the highway trip length to a lower value than 60 miles would be no less

arbitrary than the original 60 mile estimate. Many drivers commute 60 miles to work, so

this distance fits many drivers’ situation. It is also long enough that any “city” driving at

the beginning and end of the trip is likely to be relatively short. Drivers also often

assess their fuel economy on even longer trips. Thus, an estimate made using a 60 mile

trip length is still very applicable to an all day highway trip, for example. At the same,

many drivers commute 20 miles to work and might appreciate a shorter trip length than

60 miles. One number will not be preferred by all drivers or interested parties. At this

time, we believe that a wider difference between city and highway fuel economy

highlights the difference in driving patterns and provides useful information to the

consumer. Thus, we do not choose to change the trip length for highway driving to a

lower figure.

As described above, there is an inter-relationship between the trip length for city,

highway and all driving. As described in Section III.A.1 of the Draft Technical Support

Document, the average trip length for city driving was estimated to be 3.5 miles. This

estimate was based on two estimates of trip length. One source was a set of

instrumented vehicle studies conducted in the early 1990’s in support of EPA’s

Supplemental FTP rulemakings. The other source was the National Household Travel

Survey (NHTS), which shows a national average trip length of 9.8 miles.

The results of the instrumented vehicle studies are shown in Table 5-6 below.

This is the same information that was presented in Table III.A-7 of the Technical

Support Document for the NPRM. The estimate of average trip length used in

MOBILE6.2 is based on the average trip lengths found in Baltimore and Spokane, which

is believed to be the most unbiased methodology of those used in the various cities.

Table 5-6. Estimates of In-Use Average Trip Length

Location Average Trip Length (miles)

Instrumented Vehicle Studies Chase Car Studies

Baltimore – Exeter 4.0 Not Available

Baltimore – Rossville 5.9 Not Available

Baltimore – Combined 4.9 7.5

Spokane 3.6 5.8

Atlanta 6.0 Not Available

Los Angeles Not Available 7.8

MOBILE6.2 4.49 Not Applicable

As pointed out in the Draft TSD, there is a fundamental inconsistency between

the MOBILE6.2 trip length of 4.49 miles and the NHTS trip length of 9.8 miles. The

MOBILE6.2 estimate should be considered to apply to urban driving, while the NHTS

estimate represents a nationwide average. Still, given that urban driving represents
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over half of all U.S. driving, the MOBILE6.2 trip length results in more urban trips than

the NHTS estimate implies to occur nationwide.

In the NPRM, we removed this inconsistency by reducing the NHTS trip length to

7.7 miles based on a presumption that a survey of this nature misses trips which are of

a very short duration, or counts a sequence of trips that are interrupted by very short

engine off times as single trips.

Since the time of the NPRM, EPA obtained more recent data on the operation of

vehicles in Atlanta from Georgia Tech. Georgia Tech has been instrumenting vehicles

in the Atlanta area for some time and gathering operational data. As with the previous

instrumented vehicle studies, this type of study captures all vehicle trips no matter how

short. The major difference between this more recent work and the previous studies is

the amount of data being collected. To date, Georgia Tech has collected data on over

620,000 vehicle trips. In contrast, the previous instrumented vehicle studies involved

about a week’s worth of operation for less than a hundred vehicles per city. Thus, the

recent data represents almost two orders of magnitude more data than was evaluated in

the instrumented vehicle studies described in Table 5-6 above.

The average number of trips per day found for these 620,000 trips was 4.62.

Unfortunately, the analysis of the number of miles traveled per trip is still underway and

will not be available until later this year. Nationally, vehicles travel about 34 miles per

day. Urban vehicles might drive somewhat less than rural vehicles. However, given

that Atlanta is a sprawling metropolis, its driving is probably close to the national

average in terms of miles traveled per day. Assuming this, the average trip length in

Atlanta is about 7.4 miles. This is 24% greater than the average trip length of 6.0 miles

found in the early 1990’s. The series of NHTS have also found a general increase in

trip length nationally of about 1.0 mile between 1990 and 2001.

5.11.1.3 Formula for Start Fuel Use

What we proposed:

We proposed the following formula for start fuel use, using 3.59 and 3.91 as the

distances for the first and second bags of the FTP, respectively.



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







 

x x x x

x

Bag FE Bag FE Bag FE Bag FE

Start Fuel for vehiclestested overa bag FTP

4

3.91

3

3.59

7.5

2

3.91

1

3.59

7.5

4
110

What commenters said:

Mitsubishi noted that 40 CFR 86.144-90 describes the distance of the first

bag/phase of the FTP as 3.598 miles, and the distance of the second bag/phase as

3.902 miles. They point out that the proposed equation in 600.114-08(a) uses figures

slightly inconsistent with these values. Mitsubishi recommends that EPA use the

published distances in 86.144-90, rather than the proposed values.

Our response:

The regulations in 40 CFR 86.144-90 do in fact describe the distances as

Mitsubishi notes, but this is only in the context of an example calculation. For the actual

calculations from a given test, the manufacturer is required to use the measured driving

distance of the appropriate phase as calculated from the measured roll or shaft

revolutions. This may or may not be equal to the distances shown in the example

calculations in 40 CFR 86.144-90. In order to be consistent with other terms in the 5-

cycle formulae, we will use the figures from 40 CFR 86.144-90, but we will round off

these figures to one decimal place (i.e., 3.6 and 3.9 miles).

5.11.2 Running Fuel Use

5.11.2.2 Representative Mix of Dynamometer Driving Cycles

What we proposed:

The Draft MOVES2004 emissions model describes on-road driving differently

than previous EPA emission inventory models. While starting with whole driving cycles,

it goes further by breaking down vehicle operation on a second by second basis into 17

categories or bins. One bin (Bin 0) contains significant decelerations. Another bin (Bin

1) contains idling operation. The other 15 bins contain brief or modest decelerations,

cruising operation and accelerations. The 15 bins are broken down into three sets of

bins by vehicle speed: Bins 11-16 contain operation at 1-25 mph, Bins 21-26 contain

operation at 25-50 mph, Bins 33-36 contain operation at 51 mph or faster. These three

sets of bins are further sub-divided according to the power required of the engine

divided by vehicle mass. This ratio is termed vehicle specific power, or VSP, and has

the units of kilowatt per megagram (kW/Mg).

The VSP distributions for the four complete dynamometer cycles plus individual

bags of the FTP and US06 cycles are shown in Table III.A-15. As was the case for the

Draft MOVES2004 inventory cycles, these VSP distributions represent a 50-50 mix of

cars and light trucks.
111

Table 5-7. VSP Distributions for Dynamometer Cycles (% of time)

BinID LA4 HFET US06

US06

City

US06

Hwy SC03 Bag 3 Bag 2

0 12.0% 3.5% 16.8% 32.6% 7.1% 10.5% 13.3% 11.2%

1 18.6% 0.7% 7.5% 14.3% 2.5% 19.7% 18.8% 18.5%

11 6.4% 0.0% 0.7% 1.3% 0.3% 3.7% 2.8% 8.5%

12 10.6% 0.1% 0.8% 1.7% 0.3% 9.2% 4.4% 14.3%

13 8.0% 0.3% 0.3% 0.9% 0.0% 5.0% 3.0% 10.9%

14 5.0% 0.1% 0.5% 1.3% 0.0% 2.4% 2.4% 6.5%

15 2.3% 0.5% 0.2% 0.4% 0.0% 2.0% 2.9% 1.9%

16 0.7% 0.1% 1.0% 2.2% 0.3% 2.1% 1.7% 0.2%

17 0.1% 0.0% 0.8% 2.2% 0.0% 0.0% 0.4% 0.0%

18 0.0% 0.0% 0.5% 1.3% 0.0% 0.0% 0.0% 0.0%

19 0.0% 0.0% 1.7% 3.5% 0.5% 0.0% 0.0% 0.0%

21 4.4% 4.1% 1.4% 3.3% 0.3% 7.7% 4.6% 4.3%

22 10.9% 3.6% 0.7% 1.5% 0.1% 9.6% 7.3% 13.0%

23 9.5% 12.4% 0.8% 1.7% 0.1% 10.3% 12.4% 7.9%

24 2.9% 17.3% 0.1% 0.2% 0.0% 6.6% 4.5% 2.0%

25 1.5% 7.5% 0.4% 1.1% 0.0% 3.9% 2.7% 0.8%

26 0.7% 2.5% 0.2% 0.4% 0.0% 4.0% 2.0% 0.0%

27 0.2% 0.4% 0.7% 1.5% 0.1% 0.0% 0.6% 0.0%

28 0.3% 0.3% 1.2% 2.4% 0.4% 0.0% 0.9% 0.0%

29 0.2% 0.0% 4.5% 9.1% 1.6% 0.0% 0.6% 0.0%

33 1.6% 6.1% 7.8% 4.6% 9.9% 1.8% 4.3% 0.0%

35 2.6% 32.3% 14.1% 3.7% 20.7% 0.6% 7.1% 0.0%

36 1.1% 6.0% 8.6% 0.4% 13.8% 0.5% 2.9% 0.0%

37 0.1% 2.0% 10.3% 0.9% 16.2% 0.4% 0.3% 0.0%

38 0.2% 0.1% 6.6% 0.9% 10.2% 0.0% 0.5% 0.0%

39 0.0% 0.0% 12.0% 6.5% 15.5% 0.2% 0.0% 0.0%

What commenters said:

Honda criticizes the development of the 5-cycle weighting factors for high speed

and aggressive driving because the highest VSP bins (bin numbers 19, 29, and 39 with

21 kw/Mg power or greater) start at a relatively modest level. About 18% of the US06

cycle falls into the highest power bins. Onroad driving follows a bell shaped curve.

Operation is concentrated at the low end of each range of power levels, while US06

operation in this bin reaches as high as 50 kw/Mg. Honda argues that this causes an

artificially high weighting for the US06 cycle. Honda also states that EPA misspoke

when it stated that the US06 driving cycle was a concentrated version of the REP05

cycle. US06 contains some operation from California’s unified cycle, as well.

Natural Resources Canada take some issue with the fact that the US06 cycle

contains speeds that are above those legally permitted in Canada or the U.S., and they
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question the high weighting factor of the US06 cycle in the highway fuel economy

estimate and whether it is too high for a fair representation of the fuel economy

performance of a vehicle. They don’t argue with the methodology or the data sources

used to arrive at the factor, which they note are robust and among the best available,

but they are unable “...to justify [the maximum speed of the US06 cycle] to both industry

and consumers as being suitable for use in a fuel economy test.” They suggest one of

two ways to resolve their concerns: (1) Ignore the fuel consumption associated

seconds 290 through 350 of the US06 cycle (i.e., a portion of the cycle with vehicle

speeds at roughly 80 mph) when calculating fuel economy; or (2) test a sample of

vehicles with and without the speed excursion between 290 and 350 seconds of the

cycle and evaluate the incremental fuel economy increase due to the 80 mph driving

segment.

Our response:

As background to this discussion, it might be helpful to review the discussion of

the concept of VSP and how it was used to derive the cycle weights in the 5-cycle

formulae in Section III.A.2. of the Draft Technical Support Document.

First, Honda points out that 18% of operation during the US06 test falls into the

three highest power bins. Three out of 26 bins is 12%. Given that US06 focuses on a

specific type of driving (high speed, aggressive), it is not surprising that the distribution

of driving across the VSP bins would not be equal. For example, as shown in Table

III.A.-15 of the Draft Technical Support Document, 32% of the operation during HFET

occurs in one VSP bin, bin 35.

Second, Honda states that the lower limit of the three highest power VSP bins,

21 mW/Mg, is modest. Yet the highest power level achieved over the HFET by a typical

car or light truck (19 mW/Mg) does not even reach this level for one second. Only 3-

3.5% of vehicle operation over the HFET is above 12 mW/Mg, the lower limit for VSP

bins 16, 26 and 36. From their comments, Honda clearly prefers to base highway fuel

economy solely on HFET testing plus a generic adjustment factor based on HFET fuel

economy. Honda does not address the issue of accurately predicting fuel consumption

at higher power levels using a test with such low power levels. Again, Honda is

applying criteria selectively to the proposed 5-cycle formulae and failing to apply it to the

current or mpg-based procedures.

Honda does not provide any data to support its claim that vehicle operation is

concentrated at the lower end of each range of power levels. Honda’s statement

appears to assume that vehicle operation can be described by a single statistical

distribution (i.e., driving activity is concentrated near the mean and diminishes in

frequency as operation varies more from the mean). However, driving is not likely to

occur randomly. Speed limits, particularly those affecting highway driving, are

concentrated in a narrow range (i.e., 55-80 mph). Thus, driving activity might not

diminish further from the mean. Two estimates of highway driving, that contained in

Draft MOVES2004 and that based on California chase car data, indicate roughly equal
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amounts of driving in bins 36, 37, 38, and 39. Thus, it is doubtful that operation in these

bins is concentrated at the low end of the range of VSP included in each bin. Operation

in bin 39 could be an exception, since it is open-ended. Even with this bin, though, the

power level at which the frequency of operation tends to tail off is unclear, as is the rate

at which it tails off.

Nonetheless, Honda’s overall point likely has some validity. EPA’s 15 car study

using a portable emission measurement unit (PEMS), which was described in the Draft

Technical Support Document, compared fuel consumption measured during

dynamometer tests to those measured onroad. In that study, the highest power VSP

bin was 36 (i.e., bin 36 included all operation contained in VSP bins 36-39 as defined in

the Draft Technical Support Document). We found that fuel consumption in bin 36 were

6% higher over US06 than onroad. This was due to a higher average power level in bin

36 over US06 than onroad. This was one of the reasons we expanded the number of

high power bins beyond that used in the Draft MOVES2004 model. In particular, bins

16, 26 and 36 were each broken down into four VSP bins, limiting the amount of driving

contained in the final, open-ended bin.

As shown in Table 5-3 above, the 5-cycle formula for highway fuel economy

includes 12% of operation in bin 39, versus 37.5% for bins 36-39. It is unlikely that the

difference between VSP bin 39 fuel consumption over US06 and onroad would be as

high as 6%, given the more limited range of operation included in bin 39 compared to

the bin 36 definition used in EPA’s 15-car PEMS study. However, even if this were the

case, a 6% over-estimation of fuel consumption for 12% of vehicle operation only

results in a 0.7% overestimation of 5-cycle highway fuel consumption. This ignores the

effect of the cold starts, air conditioning operation and operation at colder temperatures,

which all work to lower this percentage. This is a very small potential source of error.

The benefit of including US06 in the fuel economy label procedure is the direct

measurement of fuel consumption in VSP bins 36-39 which are not addressed by the

HFET and which represent 40% of highway driving in-use. The net benefit of the tradeoff is very clear.

We performed an analysis of available second by second fuel economy data

collected for 80 vehicles to directly address this issue further. As discussed in Section

III.B. of the Draft TSD, 61 cars and 19 light trucks were tested over both the FTP and

US06 tests and had their fuel consumption measured on a second by second basis.

We grouped each second of each vehicle’s operation over the warmed up portions of

the FTP (Bags 2 and 3) and US06 tests into the 26 VSP bins and calculated the

average fuel consumption for each vehicle in each VSP bin. We then weighted these

VSP fuel consumption values by the frequency of vehicle operation over the HFET cycle

and the US06 highway bag (as shown in Table 5.3 above) in order to estimate each

vehicle’s average fuel consumption over these test cycles. We repeated this weighting

procedure for the MOVES estimate of onroad highway driving (see Table 5-3 above for

the weighting factors for the high power VSP bins and Table III.A-12 of the Draft TSD

for all of the weighting factors). On average, the fuel consumption for the 80 vehicles
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over the HFET, US06 highway and MOVES highway driving patterns were 3.049, 3.609

and 3.443 gallons per 100 miles, respectively.

The current label approach estimates onroad highway fuel consumption based

on only fuel consumption over the HFET test. For these 80 vehicles, average fuel

consumption over the MOVES highway driving pattern was 12.6% higher than that over

the HFET. Per the current label approach, then, onroad highway fuel economy would

be estimated by multiplying HFET fuel consumption by a factor of 1.126. We applied

this factor to each vehicle’s HFET fuel consumption and compared the result to our

estimate of onroad highway fuel consumption per MOVES. On average, the HFET plus

generic factor over-estimated onroad highway fuel consumption by 0.6%. However,

more importantly, the standard deviation of the percentage differences was 3.2%. We

could have completely eliminated the average difference by a slight change in the

adjustment factor (i.e., 1.12 versus 1.126). However, the standard deviation would be

unaffected. It is the standard deviation which indicates the ability of the approach to

reflect differences in the fuel economy performance of individual vehicles.

We repeated this using the 5-cycle weighting of 79% US06 highway and 21%

HFET fuel consumption. On average, the 5-cycle formula over-estimated onroad

highway fuel consumption by 1.7% and the standard deviation of the percentage

differences was 0.5%. The fact that the 5-cycle approach produced a greater difference

on average is not important here, since the factor accounting for non-dynamometer

effects (i.e., 0.89 in the NPRM) adjusts the final 5-cycle fuel economy values to match

more robust estimates of onroad fuel economy, such as those made by FHWA. The

key finding is that the combination of US06 highway and HFET fuel consumption is a

much better predictor of each vehicle’s fuel consumption over the MOVES description of

highway driving than the HFET alone. This clearly refutes Honda’s concern that the

US06 test is too extreme to be a useful predictor of onroad fuel economy.

We agree with Honda that a portion of the US06 cycle came from what was then

called the California ARB-02 cycle. As stated in EPA’s technical report supporting the

development of the US06 cycle:30

A third control approach involves a hybrid cycle that shares characteristics of

both the air-fuel control approach and the representative cycle approach. The

new cycle, US06, is 600 seconds in duration and is comprised of segments of

CARB's ARB02 cycle and EPA's REP05 cycle. Similar to the air-fuel control

method, this method targets specific high emission, non-FTP operation. And like

the representative cycle, the US06 is based on actual segments of in-use driving.

And

30 “Final Technical Report on Aggressive Driving Behavior for the Revised Federal Test Procedure Notice

of Proposed Rulemaking”, EPA, January 31, 1995
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The ARB02 cycle (figure 1-7) was developed by CARB based on data from their

Los Angeles chase car study. The purpose of the cycle is to test vehicles over

in-use operation outside the boundary of the LA4, including extreme in-use

driving events.

Comparison of the REP05 and US06 cycles on a second by second basis indicates that

hills 1 and 3 were taken from the ARB02 cycle, while the remainder of US06 was taken

from the REP05 cycle. It appears that some splicing of portions of REP05 was

performed to remove cruise events and focus on accelerations and decelerations. For

example, hill 2 of US06 consists of seconds 3-52 and 364-393 of REP05, with one

second added in between to provide time for a reasonable transition between the two

segments.

Thus, all of the US06 cycle came from monitored vehicle operation via two

representative cycles developed to represent high speed and aggressive driving not

represented by the FTP. However, in order to develop a shorter test cycle which would

be less costly to run which still required emission control over the most severe portions

of the representative cycles, some of the less extreme operation outside of the FTP was

excluded and the more extreme, though still representative, operation was retained.

With respect to the comment from Natural Resources Canada, we believe that

various philosophies can be followed in developing consumer information in general and

fuel economy label values in particular. We desire to provide consumers with as best

an estimate of the fuel economy which they will achieve on the road given the way

consumers actually drive. As can be attested by even brief trips on U.S. freeways, this

often involves speeds exceeding the speed limit. Therefore, we do not believe that it is

necessary to develop alternative label values or to assess the impact of removing

driving which exceeds most speed limits from the estimate. In fact, the state of Texas

recently increased their maximum speed limit to 80 mph in some parts of the state.

Wyoming and other states have had speed limits above 70 mph for some time. Thus,

this type of driving is not illegal everywhere.

It is useful to note that the HFET contains speeds as high as 60 mph. This cycle

was developed when speed limits were no higher than 55 mph. A speed of 60 mph no

longer seems excessive. However, at the time, it exceeded the allowable speed limit,

because this was how people were found to drive. Therefore, we see no compelling

need to change this approach at this time.
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5.11.3 Effect of Air Conditioning on Fuel Economy

5.11.3.1 Approximating Excess Fuel Use Due to Air Conditioning

What we proposed:

We proposed to estimate the incremental fuel use due to the operation of the air

conditioner as the difference in fuel use measured over the SC03 versus this

combination of fuel use over Bags 2 and 3 of the standard FTP. This difference in fuel

use between the two tests provides a direct estimate of the impact of air conditioning

use for the conditions present during the SC03 test. The SC03 test is performed at

95°F and 40 percent relative humidity. The test only lasts 10 minutes and the vehicle is

pre-heated with radiant lamps for 10 minutes prior to the test. Thus, the air conditioning

compressor is generally engaged throughout the entire test. The speed of the vehicle

during the SC03 test is relatively low, at an average speed of 21.5 mph. Of course,

real-world vehicles operate at different speeds and ambient temperatures and the

compressor may not be engaged 100 percent of the time, particularly during longer

trips. All three of these factors can affect the impact of air conditioning on fuel

economy. We therefore adjust the estimate of the impact of air conditioning on fuel use

from the SC03 test in three ways to account for these three factors.

What commenters said:

UCS commented that while EPA’s approach “appears reasonable,” they question

the potential impact of differences between the FTP and SC03 driving schedules. For

example, they cite the acceleration rates of the SC03 cycle, which, while moderate, are

beyond anything that occurs on the FTP. They also suggest that the possibility exists

that that a car is not fully warmed up by Bag 2 of the FTP, whereas the SC03 is started

with a fully warmed up engine. They recommend that EPA validate this approach by

comparing the weighted FTP results of a representative sample of vehicles with the

results of a set of modified SC03 tests conducted on the same vehicles. The “modified”

SC03 tests would follow the SC03 driving schedule, but would be conducted with the air

conditioning off and at the same environmental conditions as the FTP.

Honda also states that the effect of air conditioning is determined from the

difference in fuel consumption over the SC03 test and a blend of Bags 2 and 3 of the

FTP. Honda points out that the two driving cycles are different and do not necessarily

yield the same fuel consumption absent air conditioning for all vehicles.

Honda presents a very general comment about the efficacy of testing which EPA

performed to assess the impact of air conditioning over a number of test cycles.

Our response:

Honda is generally correct. The driving pattern in SC03 differs from that

contained in the FTP. Our 39%/61% combination of Bags 2 and 3 of the FTP
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approximates the fuel consumption over SC03 at 75°F with the air conditioning turned

off. However, the blend of Bags 2 and 3 which exactly matches SC03 without air

conditioning is likely to vary somewhat across vehicles.

Again, however, this potential error in the proposed 5-cycle formulae does not

occur in a vacuum. The alternative is the current label procedure, where air

conditioning is assumed to affect all vehicles equally on a percentage basis; or the mpgbased equations, which assume that air conditioning affects vehicles in proportion to

their fuel consumption over the FTP (which is actually quite similar to the current label

procedure in this regard). Thus, it is not a matter of the 5-cycle formulae not being

entirely accurate. It is a matter of which approach produces the best estimate.

We evaluated the potential for error in the various label approaches using data

collected in support of the proposed rule.31 In this test program, six vehicles were

tested over a variety of cycles and temperatures with and without the air conditioning

system turned on. In particular, vehicles were tested over a hot start FTP at 75°F

without air conditioning, over a hot start FTP at 95°F with air conditioning, and over the

SC03 cycle at 95°F with air conditioning. The testing at 95°F was not in an

environmental chamber with solar load, etc. It was conducted in a standard

dynamometer in a test cell heated to 95°F. Thus, the SC03 fuel economy values are

not indicative of those which would occur over an official SC03 test. However, the

consistency of testing methods for all the cycles actually helps isolate the impact of test

cycle and is satisfactory for the purpose of this comparison.

The most direct measure of the impact of air conditioning is the difference in fuel

consumption over a hot start FTP at 95°F with air conditioning and a hot start FTP at

75°F without air conditioning. This comparison avoids the concerns raised by Honda,

since the driving cycles were exactly the same in both sets of measurements. Average

fuel consumption over a hot start FTP at 95°F with the air conditioning on was 0.01267

gallons per mile higher than with the air conditioning turned off. Average fuel

consumption over the hot start FTP at 75°F was 0.03867 gallons per mile. Thus, air

conditioning use over a hot start FTP at 95°F increased fuel consumption by 32.7%.

We repeated this comparison using the 5-cycle approach. Air conditioning fuel

use was determined by subtracting a 39/61% blend of fuel consumption over Bags 2

and 3 of the FTP from SC03 fuel consumption. Average fuel consumption due to air

conditioning use was 0.01160 gallons per mile. Thus, air conditioning increased fuel

consumption by 30.0%. Thus, the approach taken in the 5-cycle formulae

underestimated fuel use due to air conditioning by 8%.

Of greater importance is the ability of the various fuel economy label approaches

to predict the impact of air conditioning on a specific vehicle basis. The current label

approach assumes that air conditioning has the same percentage effect on each

31 Mitcham, A., Fernandez, A., & Bochenek, D. “Impacts of Ambient Temperature and Air

Conditioning Usage on Fuel Economy” U.S. EPA, Office of Transportation & Air Quality, 2005.
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vehicle. Thus, air conditioning use under this approach is assumed to be 32.7% of fuel

consumption over the hot start FTP. The 5-cycle approach is exactly that described

above. The mpg based approach uses the results of the 5-cycle formulae, but

correlates the fuel use due to air conditioning against the hot start FTP. Doing so and

performing a least squares regression produces an air conditioning fuel use of:

0.8581 + 0.0781 * hot start FTP fuel consumption.

As we have done above, we then determined the error in predicting each

vehicle’s air conditioning fuel use and calculated the coefficient of variation of the error.

The current label procedure produces the greatest error. The coefficient of

variation was 48.9% for the six vehicles. The mpg-based procedure reduced this error

by a factor of two, to 21.2%. However, the 5-cycle procedure reduced this latter error

again by a factor of two, to 10.6%. Thus, it is very clear that the error introduced by

using a blend of fuel consumption over Bags 2 and 3 as the basis for assessing air

conditioning fuel use is minor compared to basing this fuel use on fleet-wide estimates.

Thus, we find Honda’s assertion incorrect. UCS’ concern appears to be unwarranted.

With respect to Honda’s criticism of our test program, Honda is correct that this

testing did not simulate the flow of air through the engine compartment in a manner

representative of onroad operation. However, the point of this testing was to simply

confirm a very general principle that the air conditioning fuel use was primarily a

function of time and not mileage. Honda did not present any data to indicate that a

more representative simulation of air flow through the engine compartment would have

changed this conclusion. Thus, we see no need to change this conclusion and its

impact on the proposed 5-cycle formulae.

5.11.3.2 Available In-Use Data and Analysis

What we proposed:

The Draft MOVES2004 algorithm of compressor on fraction versus heat index

was developed from the direct measurement of air conditioning operation of over 1000

trips by 20 vehicles in Phoenix, Arizona during the summer and fall of 1992. The

algorithm considers both the frequency that the system is turned on by the driver and

the frequency that the compressor is engaged once the system is turned on.

What commenters said:

Natural Resources Canada acknowledged that there is no better set of data than

that gathered in Phoenix, Arizona in 1992 to describe the average performance

characteristics of mobile air conditioning systems. However, they question whether the

data and the resulting conclusions are valid given the advances in compressor and

climate control system design in the last 14 years. To address this, they recommend
119

that EPA repeat the Phoenix test program with newer vehicles in different U.S. cities to

capture the effect of new technologies and climatic conditions on air conditioning use.

Alternatively, they suggest that a sensitivity test could be performed using the existing

5-cycle test data, by varying the 13.3 percent air conditioning weighting factor between

estimates of its possible extreme values and noting the impact on overall fuel economy.

This would highlight the potential need (or lack thereof) for a new study.

NREL commented that the graph on page 69 of the Draft TSD reflects some

unusual trends. In particular, they find it odd that at 100F, 85% of the vehicles have the

air conditioning on, when personal experience suggests the percentage should be much

higher. They also note the “dip” at about 85F.

Our response:

It would be beneficial to repeat the 1992 study of air conditioning use in Phoenix

with late model year vehicles and in other locales. At the same time, the uncertainty

introduced by reliance on this single study appears to be quite small on average. In

Section III.A.3 of the Draft Technical Support Document, we described work by NREL

which estimated air conditioning use using a method which is completely independent of

that relied on by EPA. In the Draft Technical Support Document, we estimated that

NREL’s estimate for air conditioning use (switch turned on) for the U.S. as a whole was

24%. As described above, they have updated their analysis since that study we

referenced. Their latest estimate is 29%. Based on the Phoenix study, we estimate

that air conditioning is in use 23% of the time. While we believe our estimate is more

sound, as it is based on actual measurements of air conditioning use, the NREL

estimate can be used to estimate the potential error in this figure. Increasing our

estimate of compressor on time of 13.3% by the ratio of 29/23 yields a new compressor

on time of 16.8%. This decreases 5-cycle city and highway fuel economy by 0.8% and

0.4%, respectively. These are very small changes and would not even result in a

change in the label figure in most cases, due to round off to the nearest mpg. Thus,

uncertainty in the percentage of time that the air conditioning system is turned on does

not appear to be a significant issue at this time.

Some newer climate control systems automatically turn on the air conditioning

whenever cooling is desired and trim temperature using heat from the engine coolant

system. Air conditioning use could be higher with such systems, as the driver might not

even know that the air conditioning system was on. At the present time, such systems

are more common in Europe than the U.S. Should they become more common in the

U.S., their effect on air conditioning use could become an issue for the 5-cycle formulae.

Regarding NREL’s comments about anomalies in the Phoenix data, they are

correct. However, there are usually anomalies with real data. One would expect that

essentially 100% of drivers would utilize their air conditioning at 100 F. However, if the

drivers sampled happened to like driving with the windows down, or had just come out

of a building which was over-cooled, they might have preferred the warm outdoor air to
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the air conditioning. Since the drivers were not asked why they used or did not use air

conditioning for each trip, we will never know the answer.

Fortunately, whether 85% or 100% of drivers used air conditioning at 100 F had

little impact on the overall projection of air conditioning use, given the high levels of use

at slightly lower temperatures. As shown above, increasing air condition use by a

relative 25% had little impact on 5-cycle fuel economy values. Therefore, the anomalies

in the Phoenix data are not a major concern.

5.11.3.3 Driver Behavior

What we proposed:

We proposed that the SC03 test procedure be used, without modification, as an

element of the 5-cycle test and calculation procedures.

What commenters said:

PPG supports changes that consider air conditioner use in the fuel economy

label calculation, and they commented that EPA’s current and proposed air conditioner

fuel consumption test methodologies do not replicate actual consumer experiences. As

an example, they note that vehicles in actual use are typically exposed to a solar load

for substantially longer than the test requires. They further suggest that the proposed

test protocol requiring that the air conditioner be operated at maximum cooling with high

fan speed for the duration of the test is not representative. They suggest that this could

drive temperatures lower than the consumer’s comfort level, and that a more

representative test would be to turn down the fan speed when a set comfort level was

achieved. They suggest that the test would be more accurate if it replicated more

realistic solar heating conditions by testing after extended heat soaks and by more

accurately accounting for how consumers adjust their air conditioner settings.

Our response:

PPG’s suggestion would amount to a revision to the SC03 emissions test

procedure, which we did not propose to do. We do not necessarily agree or disagree

with PPG’s comments regarding solar load exposure and consumer behavior with

respect to the fan speed settings, but we did not propose to amend the SC03

procedure, especially in ways that could potentially impact emission results or the cost

of conducting the test. In particular, an extended heat soak could dramatically impact

the costs for manufacturers. We did not intend for our proposal to reopen the SC03 test

procedure and change it in any way; the emission standards for the SC03 were

designed with the specific test procedure as it was designed, and changing the SC03

procedure would have far-reaching impacts. In addition, the impact of air conditioner

usage on fuel economy is based on a difference in tests results, one test run with the air

conditioner on and one run with the air conditioner off, with the result used as the
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estimate of the fuel economy impact of the air conditioner at the temperature of the

SC03 test (95°F). The impact of temperature on air conditioning use is then used to

determine the percentage of time that the air conditioning system is turned on in-use

and the percentage of time that the compressor is actually engaged. The impact of

temperature on compressor load is then factored in based on other information on the

effect of temperature on load.

5.11.3.4 Accounting for Energy Reduction Technologies

What we proposed:

We did not propose any specific provisions to encourage or discourage energy

reduction technologies.

What commenters said:

Delphi commented that because the compressor is “on” throughout the entire

SC03 test, the test will not reflect any efforts by a vehicle manufacturer to improve the

energy efficiency of their air conditioner systems at lower heat loads. Because average

conditions in the U.S. are milder than those experienced during the SC03 test, they

point out that “...accounting for the differential in A/C systems performance across

these conditions is critical.” Delphi claims that the most energy-efficient systems today

may consume only 50 percent of the energy of the least efficient systems, and that

“...this difference is not likely to be seen in the SC03 test” (emphasis is Delphi’s). They

believe that more accurate estimates of compressor usage are available and that there

is a better way to establish the average energy used by today’s A/C systems and future

systems.

Delphi suggests that EPA update the “compressor on time” percentages, and

refers to field data from 1987 model year vehicles with fixed-displacement cycling

compressors and from 1997 model year vehicles with variable-displacement

compressors. They also note that since the early 1990’s, when the Phoenix data was

collected, automatic climate control systems have become more prevalent, thus

increasing compressor on-time. They present the following summary of their data,

without additional detail:

Field Test % Compressor OnTime (including

defrost)

1987 Fixed Displacement, Manual and Semi-Automatic

Systems

32%

1997 Variable Displacement, Manual Systems 45%

1997 Variable Displacement, Automatic Systems 70%
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Additionally, Delphi proposes a series of correction factors that would be

employed within the fuel economy calculation equations. These factors are intended to

reflect the effect of air conditioning technology that may not show up in the SC03 test.

They suggest factors that would adjust the fuel economy results for systems with

variable-displacement systems, electronically controlled compressors, accurate control

of evaporator temperatures, etc. They argue that these factors, while leading to more

accurate fuel use estimates, will also provide manufacturers with the incentive to adopt

some of these technologies.

NREL likewise noted some technologies that can reduce the fuel used by air

conditioning systems but that would not be accounted for in the new fuel economy

estimates. These technologies include those that reduce the thermal load in the cabin

(e.g., solar reflective glass, insulation, ventilation), more efficient equipment (e.g.,

variable-displacement compressors), improved thermal comfort technologies (e.g.,

ventilated or climate control seats), and advanced control strategies (e.g., increased use

of recirculation air). To resolve these issues, they recommend the following:

o Increase the soak period of the SC03 test or reduce the compressor-on

percentage in the adjustment calculation for vehicles with load reduction

technologies;

o Use a realistic temperature setpoint in the cabin for the test or adjust the

compressor-on percentage for vehicles with load reduction technologies;

o Reduce the compressor-on percentage for vehicles with a control system that

increases the use of recirculation air.

PPG also recommended that EPA consider modifying the proposal to consider

the impact of technologies that lead to more efficient air conditioner systems, although

their comments were focused on the potential impact of solar reflective window glazings

on air conditioner fuel use.

Our response:

The current label procedure only addresses the impact of air conditioning use on

fuel economy through the 10% and 22% generic adjustment factors which are applied to

the FTP and HFET test results. Since these factors are the same for vehicles with and

without air conditioning, the current procedure actually reduces the fuel economy label

values due to air conditioning use for vehicles not even equipped with air conditioning.

This is the status quo.

The proposed mpg-based equations actually continue this approach. While the

fuel economy projections used to develop the mpg-based equations are based on the

impact of air conditioning on individual vehicle’s fuel economy, the average adjustment

is applied to vehicles with and without air conditioning.

The proposed 5-cycle formulae incorporate the impact of air conditioning on fuel

economy through the SC03 test, with compressor usage and load adjusted for

conditions outside those included in the SC03 test. The SC03 test, by virtue of its short
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duration and short time of heat load prior to the test, reflects the impact of some aspects

of vehicles’ climate control systems realistically, while not doing so with respects to

other aspects. The adjustments in compressor usage for non-SC03 conditions were

developed from data obtained from vehicles on the road in 1992. The adjustments in

compressor load for non-SC03 conditions were based on air conditioning systems with

fixed displacement compressors which cycle on and off frequently under less than

maximum cooling conditions.

The comments summarized above point out a number of limitations with the

proposed 5-cycle formulae in terms of granting credit to certain technologies whose

benefits are either not reflected in the SC03 test or are only partially reflected. Delphi

indicates that some efficient air conditioning systems in use currently could be as much

as 50% more efficient than the systems modeled in the 5-cycle formulae. At the same

time, Delphi points out that some climate control systems may actually run the

compressor more than that indicated in the Phoenix study. This could increase the fuel

economy impact of these systems relative to those modeled in the 5-cycle formulae.

Using the 5-cycle certification database for 615 vehicles, reducing the impact of

air conditioning on fuel use (by reducing the effective compressor on percentage from

the 13.3% estimated in the 5-cycle formulae to 6.7%) improved city and highway fuel

economy by 1.6% and 0.7%, respectively. While significant, such an improvement

would not change the actual label fuel economy for most vehicles due to the rounding of

the label to one mpg. At the same, we desire to give credit to all technologies which

affect onroad fuel economy to the fullest degree possible without significantly increasing

the current test burden.

Both the current and proposed label procedure base the label values entirely on

fuel economy measurements from dynamometer tests coupled with adjustments or

weighting factors applicable to all vehicles. As described elsewhere in this document,

we considered developing separate 5-cycle weighting factors for hybrid vehicles, but

rejected that approach, in part due to the variation in what constitutes “hybrid”

technology. The same concern applies here. The effect of each of the fuel-saving

technologies mentioned in the comments would likely differ across vehicle lines and

comprise more of a continuum in technology than discrete steps. Considerable effort

would be needed to develop procedures to appropriately address such technologies.

These efforts would necessarily delay the final rule implementing 5-cycle formulae

without such adjustments for different air conditioning system technologies. Given the

relatively small impact of these technologies on the label values, and the much larger

impact of the 5-cycle approach as a whole, we do not believe it appropriate to delay the

5-cycle approach until procedures can be developed which account for differences in air

conditioning systems. Nonetheless, we encourage those familiar with such systems to

provide further information regarding their operation in-use and their impact on onroad

fuel economy. We remain open to working with all affected parties in developing

procedures which could allow the in-use efficiencies of such systems to be appropriately

incorporated into the 5-cycle formulae.
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5.11.3.5 Temperature Impact on Compressor Power

What we proposed:

Using data from the Phoenix program, we identified a relationship between

compressor cycling and ambient temperature. Following this we used a simplified

thermodynamic model to develop a correlation to reduce compressor torque as a

function of ambient temperature.

What commenters said:

NREL commented that the impact of ambient temperature on compressor power

may be double counted in our analysis. They note that on page 70 of the Draft TSD we

identify the relationship between compressor cycling and ambient temperature.

Following this we use a simplified thermodynamic model to develop a correlation to

reduce compressor torque as a function of ambient temperature. NREL suggests that

an actual air conditioning system “...will cycle the compressor to control the high side

pressure and evaporator temperature while the simplified model adjusted the

compressor power,” and that using both may be inappropriately adjusting compressor

power twice.

Additionally, NREL notes that, contrary to statements in the Draft TSD on page

71, there is available data from the SAE Alternate Refrigerant Cooperative Research

Program regarding vehicle air conditioning system design and how engine speed and

load affect its efficiency.

Honda mentions that EPA adjusted air conditioner load for ambient temperatures

below 95°F, but did not do so for humidity or solar load or vehicle soak time in the sun

prior to operation.

Our response:

We do not believe that we are performing any double counting when accounting

for both the time which the compressor is not engaged and the reduced load on the

engine at lower temperatures while the compressor is engaged. The study which

estimated (in a simplified fashion) the compressor torque (and power) as a function of

ambient temperature did so in a way which should be independent of cycling. The

compressor model in the reference was designed to be combined with a cycling clutch

model, which is briefly introduced in the paper, but not thoroughly developed. The

activity cycling factors used in the AC factors in the present analysis were based on

actual measurements of compressor use in Phoenix and should be independent.

With respect to Honda’s comment, we stated in the Draft Technical Support

Document that we did not adjust air conditioning compressor load for differences in
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humidity because we thought the effects were small. Honda provided no data to refute

this. Thus, we are not adding any further adjustment at this time.

Regarding solar load and vehicle soak time in the sun prior to operation, it is not

clear that this would affect compressor load. These factors will affect the amount of

time that the compressor is engaged. This is already accounted for through the use of

measured onroad compressor usage rates from the Phoenix study coupled with an

assumption that the compressor is engaged 100% of the time over the SC03 cycle. The

last assumption is due substantially to the solar load included in the SC03 test and the

fact that the vehicle was under significant solar load for 10 minutes prior to start of the

test.

Temperatures under the hood of a moving vehicle could be affected by solar load

and, thus, affect compressor efficiency. EPA has no data which would allow the

quantitative estimation of this effect. Honda also did not supply any data. We expect

that the effect of varying solar load would be less than the effect of ambient

temperature. Accounting for the variation in ambient temperature when the air

conditioning is operating only reduced the effective compressor on time by 15%. Thus,

ignoring the variation in solar load should be much smaller. Given that the overall

impact of air conditioning is only 2% on city fuel economy and less on highway fuel

economy, we expect this to have a negligible impact on 5-cycle fuel economy.

5.11.3.6 Estimates of National A/C and Defroster Use

What we proposed:

We used a study from NREL to determine estimates of national average air

conditioning and air conditioning plus defroster use.

What commenters said:

NREL commented that our estimates of national average air conditioning and air

conditioning plus defroster use (22.9% and 33.5%, respectively), which we derived from

an NREL study, should actually be 28.1% for air conditioning and 32.6% for air

conditioning plus defroster use after weighting by vehicle registrations. NREL also

assumed a mix of 60% cars and 40% trucks, while our analysis used a mix of 65% and

35% cars and trucks, respectively.

NREL confirms our assumption that in their analysis, the relative fuel economy

impact of air conditioning and defroster includes the impact of ambient temperature on

load and on the operating frequency of the compressor.

NREL suggested that the 61F air temperature during defroster use (Draft TSD,

page 73) seems high, noting their analysis assumed that the A/C would be used for

dehumidification when the ambient temperature was between 35 and 55 F.
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Our response:

We contacted NREL personnel to determine the source of the discrepancy

regarding their estimate of national average air conditioning usage. We determined that

they had since updated the analysis which they performed in 2002 and that the more

recent analysis indicated higher air conditioning usage. Thus, NREL currently projects

that drivers have the air conditioning system turned on 28.1% of the time, while our

estimate is 23.8%, based on the Phoenix study. This difference is not surprising given

the completely different methods used to derive these estimates. They are still quite

similar in magnitude, though obviously not as close as indicated in the Draft Technical

Support Document. We will continue to use our estimate in the developing the

weighting factor in the 5-cycle formulae, due to the fact that it is based on actual vehicle

testing, though this is admittedly limited in nature. NREL’s estimate is based on a

prediction of a driver’s comfort level and has not been confirmed by any vehicle testing.

Regarding the use of a 61F air temperature assumed for defroster operation, it is

not clear whether NREL thought this was our assumption, or, as was actually the case,

our description of their assumption. This temperature is stated in their paper (actually

as 16 C). We agree with NREL that this air temperature seems high given that they

assumed that demister use would only occur when the ambient temperature was

between 35 and 55 F. We attributed this to higher underhood temperatures, but could

be wrong in this regard. It could have been a typographical error in the report or simply

an error in their analysis. In either case, a lower temperature for demister use would

decrease the compressor load slightly, which would decrease our estimate that

demister use on average is equivalent to 1.3% of the excess fuel use per mile

measured during SC03.

More importantly, correcting NREL’s estimate of air conditioning use from 22.9%

to 28.1% and total air conditioning plus demister use from 33.5% to 32.6% reduces

demister use from 10.6% to 4.5%. This reduction is more than a factor of two and

dwarfs the effect of a lower air temperature in demister load modeling and small

changes to the assumed mix of cars and light trucks. Thus, the impact of demister use

is likely less than 1% of the excess fuel use per mile measured during SC03. This

strongly supports our decision in the Draft Technical Support Document to not include

the impact of demister use in the 5-cycle formulae.

5.11.4 Effect of Cold Temperatures on Fuel Economy

What we proposed:

We proposed to model the effect of cold temperature on city fuel economy with a

50/50 weighting of fuel consumption over bags 2 and 3 of the cold FTP.
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What commenters said:

Honda comments that EPA did not show that Bag 2 was representative of city

driving at colder temperatures. They also stated that EPA did not perform any analysis

to confirm its assumption that the effect of colder temperatures on running fuel use

changed gradually and linearly.

Honda also points out that the excess fuel use at colder temperatures also

includes a difference in driving pattern which may be confounding the results. EPA did

not evaluate the impact of this difference in driving pattern for individual vehicles.

Honda further states that EPA did not validate its assumption that running fuel

use during highway driving at 20°F was 4% higher than that at 75°F on an individual

vehicle basis.

Our response:

There was a typographical error in some of the 5-cycle city fuel economy

formulae indicating that city driving at colder temperatures was assumed to be equal to

Bag 2 fuel consumption of the cold FTP. These equations should have indicated that a

50/50 weighting of fuel consumption over Bags 2 and 3 of the cold FTP. The text

deriving this portion of the formula correctly indicated the latter understanding. This

50/50 weighting was the result of the same type of VSP modeling used to develop the

cycle weighting factors at 75°F. It is also nearly identical to the relative weighting of the

FTP itself. Thus, we see no issue with the representation of driving at colder

temperature which would require modification to the 50/50 weighting.

Our response:

This assumption that the effect of colder temperatures on running fuel use

changed gradually and linearly is used to develop the weighting factor for running fuel

use at 20°F. Assuming a linear relationship between running fuel use and ambient

temperature produced an average driving temperature of 58.7 F, which is 30% of the

way from 75°F to 20°F.

We evaluated the potential impact of our assumption that running fuel use at

highway speeds increases linearly with temperature between 75°F and 20°F. We

analyzed the trend in hot LA4 fuel consumption for the 13 Toyota and Honda vehicles

described in Section III.F.1 of the Draft Technical Support Document. Three of the four

hybrids in this database were tested over a four-bag FTP. Thus, for these three

vehicles, we used Bags 3 and 4 to represent a fully warmed up FTP, or hot LA4. This

data shows that running fuel use at 50°F was 4.6% higher than at 75°F, while that at

20°F was 19.5% higher. Thus, for city driving, the relationship between temperature

and running fuel use was non-linear, with the effect increasing gradually at first and then

increasing as the temperature decreased further from 75°F. We fit a second order
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equation to this data. The result was that running fuel use at temperature “T” relative to

that at 75°F was:

1 - 0.00035 * (T – 75°F) + 0.00006 * (T – 75°F)

2

Applying this relative running fuel use to each hour, month and county in the U.S., as

described in the Draft Technical Support Document for start fuel use and air

conditioning use, we found that relative running fuel use was on average across the

U.S. 3.6% higher than that at 75°F. This increase of 3.6% is a relative 18% of the

19.5% effect of operating at 20°F for these 13 vehicles. Thus, it is possible that the

30% factor based on an assumed linear relationship over-estimates the impact of colder

temperatures. Therefore, we will change the weighting factor in the 5-cycle formula for

running fuel use at 20°F to 0.18 from 0.30. This increases 5-cycle city fuel economy by

0.8% for the 423 vehicles in our certification database, while 5-cycle highway fuel

economy increases by 0.5%. Combined 5-cycle fuel economy increases by 0.7%.

Because this change affects the relationship between combined fuel economy based on

the FTP and HFET and that based on the 5-cycle formulae, it will tend to increase the

factor which accounts for non-dynamometer effects.

Honda is correct in understanding that running fuel use during city driving at 75°F

is based on a different composite driving cycle than that at 20°F. The reason for this is

the fact that the US06 test is not performed at 20°F. Honda is also correct in pointing

out that this difference of driving pattern is included in the description of excess running

fuel use due to colder temperatures during city driving at the end of Section III.A.4 of the

Draft Technical Support Document. However, approaching the inclusion of the effect of

colder temperatures on running fuel use during city driving as a simple addition of an

“excess” fuel use is not the best understanding of what was done. We presented this

effect as an excess in order to be consistent with other aspects of the 5-cycle equation,

like start fuel use and fuel use associated with air conditioning. It is more

straightforward to understand the treatment of colder temperatures in this case as an

averaging of running fuel use at warm temperatures (i.e., 75°F) and that at cold

temperatures (i.e., 20°F). Running fuel use at 75°F is estimated using the best fuel

economy data available, which includes the city bag of US06. Running fuel use at 20°F

is estimated using the best available data, which only consists of Bags 2 and 3 of the

cold FTP. If fuel economy over US06 was not available, then running fuel use at 75°F

would also be based solely on Bags 2 and 3 of the standard FTP. It does not improve

the accuracy of the estimate of running fuel use at 75°F to exclude the US06 city bag

data. We could have developed a factor based on the FTP and cold FTP data which

estimated the impact of cold temperature on city driving. This alternative approach was

discussed in the Draft Technical Support Document and rejected in favor of the

proposed approach. This alternative would have presumed that the change in running

fuel use over the FTP at colder temperatures also applied to US06 city driving. While

this assumption would not have been unreasonable, the proposed approach avoided

this assumption. In its place, we simply have a simplified city driving cycle at colder

temperatures. Given Honda’s preference to base fuel economy labels on procedures

which emphasize the FTP, this approach would presumably be preferential. Honda did
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not suggest an alternative approach within the 5-cycle construct. Thus, we see no need

to change this aspect of the 5-cycle city fuel economy formula at this time.

Honda’s comment that EPA did not validate its assumption that running fuel use

during highway driving at 20°F was 4% higher than at 75°F on an individual basis

seems to be a simple repetition of previous comments that EPA did not validate some

aspect of the proposed 5-cycle formulae. The impact of the 4% assumption is

essentially a 1.2% reduction in highway fuel economy for each and every vehicle. If this

factor were not included in the 5-cycle highway formula, combined 5-cycle fuel economy

would have been 0.6% higher. The comparison of combined 5-cycle fuel economy with

onroad fuel economy estimates made by FHWA, as well as the sum of estimated nondynamometer effects would have shown a 0.6% greater shortfall. Thus, the factor for

non-dynamometer effects would increase by 0.6%. This would obviously reduce both

the city and highway fuel economy of each and every vehicle by 0.6%. We have a datadriven method for accounting for colder temperatures on running fuel use during city

driving. We believe it is preferable to estimate this effect for highway driving rather than

account for it in the non-dynamometer factor which is applied to both city and highway

fuel economy. We could attempt to develop separate non-dynamometer adjustment

factors for city and highway fuel economy. However, the methodology to do so would

involve a number of assumptions and uncertainties which would defeat much of the

purpose for the separate factors.

In addition, the 4% assumption is very analogous to the approach taken in the

current label procedures and the mpg-based equations. It does not rely on the US06,

SC03, or cold FTP test results. To criticize this assumption seems to be inconsistent

with the rest of Honda’s comments.

5.11.5 Adjustment Factor for Non-Dynamometer Effects

What we proposed:

We proposed a downward adjustment to account for effects that are not reflected

in the proposed 5-cycle approach. There are many factors that impact fuel economy,

but are difficult to account for in the test cell on the dynamometer. These include

roadway roughness, road grade (hills), wind, tire pressure, heavier loads, hills,

snow/ice, effects of ethanol in gasoline, larger vehicle loads (e.g., trailers, cargo,

multiple passengers), and others. Current data indicates that these impacts can lower

fuel economy from 9 to 13 percent. We proposed an 11 percent downward adjustment

to account for these non-dynamometer effects.

What commenters said:

ACEEE commented that EPA appears to have assumed – by using a single

adjustment factor for both city and highway driving – that the non-dynamometer factors

as a group affect city and highway driving equally. They contend that this may not be a
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valid assumption, especially given the large contribution of wind resistance to the

proposed 11 percent adjustment, and the fact that the impact of wind resistance on fuel

economy changes dramatically with vehicle speed.

Bluewater Network believes that the fuel economy results for both the mpgbased approach and the 5-cycle approach are overstated for hybrids. Consequently,

they suggested that EPA add an additional non-dynamometer factor specifically for

hybrid vehicle city fuel economy, citing a large real-world shortfall that they claim is not

accounted for in the 5-cycle approach or the proposed non-dynamometer factor.

Honda argued EPA’s estimates of the effects of ethanol in the fuel and low tire

pressure seemed reasonable, but estimates for other factors were “problematic.” They

suggest that average wind speed data and the fuel economy impacts of wind speed

seem far too high. They further argue that EPA made errors in comparing the average

5-cycle fuel economy values with fleetwide estimates of in-use fuel economy made by

FHWA, and that the result of these errors leads to an overestimate of the impact of nondynamometer effects. They conclude that the overall non-dynamometer effect should

be 6 percent, not 11 percent as proposed.

Our response:

The comment by ACEEE reflects the common understanding that higher vehicle

speeds produce greater aerodynamic drag and that this leads to an increased impact of

wind on fuel economy. As discussed in the Draft Technical Support Document, this is

true for a headwind, but not for wind coming from the side of the vehicle. For a given

wind speed, the slower the vehicle is traveling, the greater the net angle that the vehicle

is traveling through the air. Changes in this net angle of movement can have an

enormous effect on total aerodynamic drag, as indicated by the analysis described in

the Draft Technical Support Document. Thus, the effect of wind is not greater for

highway driving than city driving.

More importantly, we do not have solid estimates of onroad fuel economy for city

and highway driving separately. The uncertainties in splitting total onroad fuel economy

into city and highway components are sufficiently large to counter any likely

improvement in the accuracy of having separate non-dynamometer factors. Thus, we

continue to believe that a single factor for non-dynamometer effects is appropriate.

It is possible that the proposed mpg-based equations overstate hybrid city fuel economy

relative to that for conventional vehicles, at least as indicated by a comparison of mpgbased fuel economy to 5-cycle fuel economy. This is described in Section III.B of the

Draft Technical Support Document and depicted in Figure III-17. Elsewhere, we

address the comment that we develop separate mpg-based equations for hybrid

vehicles and still conclude that a single equation for all vehicles is the most appropriate

approach at this time. The required use of the 5-cycle formulae starting with the 2011

model year should make any deficiency in this regard a short term one.
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Regarding Honda’s comment, there were three steps in our determination of the

11% downward adjustment to account for factors not represented by the various

dynamometer tests. First, we determined that the current label values over-estimate

onroad fuel economy per FHWA (with some adjustments by EPA) by 3-4%. Second,

we determined that the average combined 5-cycle fuel economy for the 414

conventional vehicles in our certification database was 3% higher than current label

values on average. Third, we determined that changes to EPA test procedures

occurring since the vast majority of the vehicles in the 2002 and 2003 in-use fleets were

certified had increased average composite city-highway fuel economy by 3%. In total,

then, the difference between the average composite 5-cycle fuel economy and FHWA

estimates of onroad fuel economy was 9-11% on a comparable basis. We chose the

upper end of this range for inclusion in the mpg-based and 5-cycle formulae.

Honda presented a number of reasons why changes to EPA test procedures

occurring over the 2000-2004 model years did not increase composite fuel economy by

3%. Honda pointed out that two other changes occurred in addition to the one cited in

the Draft Technical Support Document which basically compensated for the effect of

removing the elimination of 10% road load adjustment to simulate air conditioning.

Honda references several communications between EPA, NHTSA and industry on this

issue.

Upon reevaluating this issue, EPA agrees with Honda’s assessment that the net

effect of test procedure changes occurring in this timeframe was roughly zero. Thus,

when estimating the difference between the average composite 5-cycle fuel economy

and FHWA estimates of onroad fuel economy, no adjustment should be made because

of changes in test procedures occurring with the implementation of the Supplemental

FTP standards in the 2000-2004 timeframe.

However, other factors affecting the estimate of the non-dynamometer factor also

need to be updated. Specifically, more recent FHWA estimates of onroad fuel economy

are available. Also, the effect of requiring the heater and/or defroster to be turned on

during the cold FTP also needs to be incorporated into the analysis. Thus, a revised

estimate of the non-dynamometer factor will be made in the Final TSD.

5.11.6 mpg Approach Equation Tolerances

What we proposed:

Section 600.116-08 of the proposed regulations would require additional

20°F/SFTP testing when the certification vehicle’s city and highway five-cycle fuel

economy are less than 0.96-times and 0.95-times the certification vehicle's city and

highway mpg-based fuel economy, respectively. Because it is possible for the 5-cycle

fuel economy values to meet either one of the city or highway criteria, but not the other,

we proposed a methodology that accommodates the variety of possible outcomes. If

the 5-cycle fuel economy values for a specific emission data vehicle are more than four
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percent below the mpg-based estimate for city fuel economy, all the vehicle

configurations represented by that emission data vehicle would be required to use the

5-cycle approach for determining both city and highway fuel economy. This is because

all five cycles play a significant role in the 5-cycle city fuel economy formula. In the

case where the 5-cycle highway fuel economy values are more than five percent below

the mpg-based estimate for highway fuel economy, but the 5-cycle city values are not

more than four percent below the mpg-based city fuel economy estimate, we proposed

that all vehicle configurations represented by that emission data vehicle would be

allowed to use the mpg-based formulae to derive the city fuel economy label value. We

proposed that the highway fuel economy value, however, would in this case be based

on an alternative, simplified 5-cycle formula, which would be based only on test results

from the FTP, HFET, and US06 tests. This is because the impacts of the Cold FTP and

the SC03 tests on the 5-cycle highway formula are relatively small and can be included

in the formula as simple estimations based on existing data.

What commenters said:

AAM/AIAM evaluated the 423-vehicle database used to generate the mpg-based

equations and concluded that the proposed 0.95-times mpg-based highway fuel

economy criterion would likely impose additional testing for over ten percent of vehicles.

They suggest that this test burden would exceed the benchmark established in the

CAP2000 rulemaking for requiring additional testing through a manufacturer

confirmatory process. Their analysis of the data set also showed that the standard

deviation of the five-cycle city data (about the mpg-based city curve) is 0.61 mpg, and

the standard deviation of the 5-cycle highway data (about the mpg-based highway

curve) is 1.14 mpg. They conclude from this that the variability of 5-cycle highway

results was about 87% greater than that of 5-cycle city results, which they believe is

reflective of the great variability seen in US06 data. They believe that a criterion of 0.93-

times the mpg-based highway fuel economy would reflect this increased level of

variability and consequently they request that EPA reconsider this factor.

Nissan noted that the proposed criterion for the City tolerance band is consistent

with their experience, but they feel that the Highway tolerance band is “overly restrictive

and does not accurately reflect the greater variability of the Highway result (principally

from the greater variability of the US06 component).” They propose a factor of 0.93 x

Highway mpg.

Toyota expressed support for the mpg-based formula with the applied

“bandwidths,” believing that it will help reduce the need for additional testing. They also

expressed agreement with the proposed alternative highway fuel economy formula

based on the FTP, HFET, and US06 tests, stating that it will also achieve 5-cycle goals

and require less additional testing. However, Toyota also suggested an additional step,

involving a “3-cycle” fuel economy analysis, before a vehicle line would be committed to

the 5-cycle approach. This interim step would allow a manufacturer whose emission

data vehicle falls outside the mpg-based tolerance limits to re-evaluate fuel economy

with the Toyota 3-cycle formula. If the emission data vehicle’s 3-cycle city or highway
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values fall within +/-1 mpg of the 5-cycle results, then the other vehicles within that test

group would only have to run an additional US06, which would then be used in the

Toyota 3-cycle equation to determine the label value. If the 3-cycle values fell outside a

+/-1 mpg tolerance, then the full 5-cycle approach would be required.

UCS commented that the tolerance bands are too wide, and may fail to show

significant differences between different models. They suggested comparing two

vehicles, one which gets a highway rating of 30.4 mpg from both the 5-cycle test and

the mpg-based adjustment, and the other which gets 28.1 mpg on the 5-cycle test but

29.5 mpg using the mpg-based adjustment. The label for each vehicle would be

rounded to 30 mpg, although, UCS points out, the first vehicle gets 8 percent better fuel

economy. They recommend that EPA tighten the tolerance band requirements to

reduce the number of vehicles that are able to escape 5-cycle testing. They also

suggest that EPA make data publicly available indicating which vehicles are contained

in each test group to add transparency and opportunities to comment on their

appropriateness. UCS also questioned the assumption that all the vehicle types within

a test group can be adequately represented by the emission data vehicle and will return

similar fuel economy test results. They believe that this assertion needs to be validated.

Toyota proposes that the tolerance levels for evaluating fuel economy estimates

should be numerically expressed as +/-1 mpg, rather than a percentage-based

tolerance level. They suggest that this is necessary in order to maintain consistency

among the range of fuel economy data between high mpg and low mpg vehicles.

Our response:

The criteria for use of the mpg-based approach in model year 2011 and later (5-

cycle city fuel economy above four percent and 5-cycle highway fuel economy above

five percent) are based on the balance of three factors. First, we designed them to be

sufficiently large so that typical test-to-test variability would not cause a test group to fail

the criteria. This may be a greater concern for the highway fuel economy comparison,

due to the dominance of the US06 fuel economy (which inherently has greater test-totest variability than the other tests) in the 5-cycle formula. Second, we want to minimize

the potential error in the fuel economy label. Label fuel economy values are rounded to

the nearest whole mpg. Thus, we felt it important to keep the difference between the 5-

cycle and mpg-based fuel economy values within roughly one mpg, if possible. In other

words, if the difference between the two methods is less than 1 mpg, then the two

methods would produce the same label value. If the difference is more than 1 mpg then

we would expect the 5-cycle method to result in a different label value, and thus it is

more important to trigger the requirement for additional testing. Third, we want to avoid

requiring additional fuel economy testing that will have little to no impact on the label

values.

The four percent tolerance band for city fuel economy is equivalent to roughly

0.6-0.7 mpg on average. Due to the contribution of a number of independent fuel

economy measurements in the 5-cycle city formula, the effect of test to test variability
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should be much lower than four percent. Based on the 5-cycle test results of 615 recent

model year vehicles, we estimate that about 96 percent of test groups would fall above

the four percent tolerance line. Thus, we believe that this criterion adequately satisfies

the three factors mentioned above.

The five percent tolerance band for highway fuel economy is equivalent to

roughly 1.1 mpg on average. Thus, it is slightly higher than the typical error associated

with rounding. However, due to the dominant contribution of the US06 fuel economy in

the 5-cycle highway formula, and the fact that this test tends to have relatively high

variability, we are concerned that test-to-test variability could be on the order of 3.0

percent in the 5-cycle highway formula. We estimate that about 87 percent of test

groups would fall above the five percent tolerance line. Thus, again, we believe that this

criterion adequately satisfies the three factors mentioned above.

Overall, allowing the continued use of the mpg-based approach in this way will

reduce the number of additional SC03 and cold FTP tests by about 96 percent and

reduce the number of additional US06 tests by about 87 percent. Moreover, this

significant reduction in test burden is achieved with no significant impact on the fuel

economy estimate.

We believe that Toyota’s proposal adds unnecessary complexity with little likely

gain. As we have noted, a large majority of vehicles are expected to pass both the city

and highway criteria and thus be able to use the mpg-based adjustments. Our final rule

offers a “3-cycle” option in the event that only the highway criteria is failed, with the end

result that the burden of additional testing over five test procedures will be quite small.

Each year, manufacturers must demonstrate compliance with federal emission

standards by performing tests over all five test procedures. The vehicles on which

these tests are performed are known as “emission data vehicles”, which are selected to

represent the “worst-case” emitting vehicle in a group of vehicles, known as a “test

group”, which share common engine and emission control designs. We expect that

these vehicles will also be the worst-case configuration for fuel economy, given that the

parameters which contribute to higher emissions (e.g., transmission class, vehicle

weight, presence of accessories) also generally contribute to lower fuel economy. We

believe that it is reasonable to allow continued use of the mpg-based line when the

available 5-cycle fuel economy data (from emissions certification) indicates that the

mpg-based fuel economy determined from the official FTP and HFET tests performed

for the test group are similar enough to the 5-cycle fuel economy determined from the

official FTP, HFET, US06, SC03 and Cold FTP tests for that same test group. In that

case, the manufacturer can use the mpg-based method for all model types covered

under the EPA certificate of conformity that is represented by the 5-cycle data submitted

to represent those vehicles. The manufacturer will not need to conduct 5-cycle testing

for fuel economy labeling for these model types.
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5.12 Onroad Fuel Economy Estimates by Other Organizations

What we proposed:

In the proposal, we compared onroad fuel economy estimates developed by

several organizations to the current, mpg-based and 5-cycle fuel economy label values.

What commenters said:

Honda provided a number of comments on EPA’s presentations of the onroad

fuel economy estimates by outside organizations. Generally, Honda agreed with EPA’s

characterization of the relative strengths and weaknesses of the various estimates.

Overall, Honda believes that none of the studies cited in the proposal comes close to

being a robust source of onroad fuel economy data.

More specifically, Honda criticized the Consumer Report estimates due to their

basis on unknown and apparently unrepresentative driving cycles and adjustments for

differences in ambient temperature. Honda was especially critical of the temperature

adjustment applied by Consumer Report to hybrid fuel economy. Honda also criticized

EPA for comparing EPA label values to the Consumer Report estimates for the vehicle

fleet as a whole and not on an individual vehicle basis.

Honda also criticized the unknown nature of the basis for the AAA estimates.

Honda also criticized AAA’s conclusion that the US06 test better characterized onroad

fuel economy than the current label values.

With respect to the Oak Ridge National Laboratory “Yourmpg” database, Honda

pointed out that their hybrids did not perform any worse than conventional vehicles.

Honda criticized EPA’s use of onroad fuel economy estimates from the

Department of Energy’s FreedomCar program, most of the vehicles in this program are

in commercial service. Honda cites the need for extensive maintenance of FreedomCar

vehicles as evidence of extreme service.

Honda also criticized EPA’s analyses of its fuel economy data collected recently

in Kansas City, concerned that the presence of the PEMS equipment affected the fuel

economy measurements. Honda also presented a number of concerns with the quality

of the speed data. Honda also believed that comparisons should be performed in terms

of fuel consumption instead of fuel economy, that relative performance between vehicle

models is more important than absolute fuel economy comparisons.

Finally, Honda presented an analysis of onroad fuel economy estimates obtained

from Strategic Vision. Honda also made a supplemental comment after the end of the

comment period presenting additional analysis of the Strategic vision data.
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In their comments at the hearing, AAA provided additional onroad and

dynamometer fuel economy estimates. AAA borrowed 41 vehicles from their owners in

Southern California, obtained their owners’ estimate of onroad fuel economy, and then

tested the vehicles using their own fuel economy test procedures, as well as over the

FTP, HFET and US06 cycles. They compared the owners’ fuel economy and their fuel

economy estimates to the current label values and to US06 fuel economy levels. AAA

found that the US06 fuel economy was a better estimate of onroad fuel economy than

the current label value.

Our response:

Regarding Honda’s criticism of various aspects of the various organizations’ test

procedures, we presented many of these elements in the NPRM and/or the Draft TSD.

If sufficient estimates were available from test programs not having the weaknesses

mentioned, it might be reasonable to avoid presentation of some or most of the

estimates. However, because estimates lacking weaknesses are currently unavailable,

we presented all of the estimates along with a complete description of their relative

strengths and weaknesses. Since Honda believes that the Strategic Vision data are the

best available, they presumably would prefer that these estimates be emphasized.

However, as discussed below, we have discovered additional concerns with this

database, as well. Thus, we believe that it is still most appropriate to present all of the

organizations’ estimates with appropriate caveats.

In response to Honda’s specific criticisms of the Consumer Report estimates, we

believe their criticism of generic temperature adjustments is exaggerated. As Honda

noted, the Consumer Report estimates do not include any cold starts or air conditioning

operation, the two conditions most affected by ambient temperature. Ambient

temperature only weakly affects the fuel economy of warmed-up conventional vehicles,

as discussed in the TSD. Hybrids could be more sensitive to temperature effects from

changes in battery charging and discharging efficiency. Thus, Honda’s criticism of

Consumer Report’s hybrid estimates could be correct in this area. However, this

difference in the impact of ambient temperature on hybrid and conventional warmed up

fuel economy argues for the 5-cycle approach, which Honda criticizes throughout their

comments. Both the current and mpg-based label approaches can only apply the same

adjustment factors to all vehicles, hybrid or conventional. If the effect of temperature

differs for these two types of vehicles, or between individual vehicles, these label setting

approaches cannot reflect these differences.

Regarding Honda’s criticism of our analysis of the Consumer Report estimates,

we added a comparison in the final TSD of the relative ability of all three label

approaches to predict onroad fuel economy as estimated by Consumer Report.

Honda’s criticism of AAA’s test procedures is very similar to their criticism of the

Consumer Report procedures. Our response is the same as described above. Honda’s

criticism of AAA’s analysis of their new onroad and US06 data is similar to their criticism

of our analysis of the Consumer Report data. Honda believed that an analysis of the
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ability of the various label approaches to match the onroad fuel economy estimates on

an individual model basis is more important than an analysis of the match-up on

average across all models. We will perform a more thorough analysis of this data in the

Final TSD. While we will examine average fuel economy differences, we will also

examine the ability of various label approaches to reflect the onroad fuel economy of

individual vehicles.

Honda presented two criticisms of the FreedomCar data. First, the vehicles are

primarily in commercial service. Second, no conventional vehicles are in the test

program. Honda was concerned that many vehicles in commercial service are operated

continuously, 6 days a week. They cited maintenance records that include catalyst and

transmission replacement, indicating extremely aggressive driving.

Although commercial operation can differ from personal use, it provides an

opportunity to obtain many hours of vehicle operation over a short period of time. The

hybrid models cited by Honda have not been offered long enough for most vehicles in

personal use to achieve greater than 100,000 miles. Thus, it is unclear whether the

maintenance received by the FreedomCar vehicles is unusual or not, particularly for

vehicles in a test program which likely receive more frequent and careful inspections

than the average vehicle. From Honda’s description, it would appear that there are

factors affecting the FreedomCar Program’s vehicles which increase fuel economy, as

well as decrease fuel economy relative to the average vehicle. Continual operation

means few cold starts. Phoenix certainly experiences little truly cold weather. Both of

these factors reduce hybrid fuel economy more than conventional vehicles.

Commercial operation might be more aggressive, but this is at best a subjective

observation. Air conditioning use will be higher in Phoenix than on average across the

U.S. However, 24-hour a day commercial operation means much more operation at

night than the average vehicle, when temperatures and solar loading are lower. Thus,

again, commercial operation in Phoenix might not be as extreme as it might look at first

glance.

The inclusion of conventional vehicles in the program would have allowed a

comparison of onroad fuel economy relative to label values for both conventional

vehicles and hybrids and would have provided more information. However, this was not

the focus of the DOE study. Overall, we do not believe that Honda has demonstrated

that the FreedomCar data is unrepresentative to the degree that it should not be

included in the discussion of available onroad fuel economy estimates relative to label

values.

Honda’s criticism of EPA’s Kansas City data includes all of the weaknesses

mentioned by EPA in the Draft TSD (e.g., few or no cold starts, little air conditioning

operation, limited monitored operation per vehicle, etc.). In addition, Honda noted that

the separate analysis of hybrid and conventional vehicle performance was

inappropriate, due to the low r-squared value for the hybrid vehicles (-0.17). This value

of r-squared is low because this study only included a few hybrids, all of which fell into a

relatively narrow range of label fuel economy (48-56 mpg, with one vehicle at 64 mpg).
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The low r-squared value indicates the relatively wide range of onroad fuel economy

values achieved with vehicles with a narrow range of label fuel economy values.

Honda also criticized EPA for performing a regression of onroad fuel economy

versus label fuel economy, believing that a regression of fuel consumption (inverse of

fuel economy) would be technically preferable. We performed a regression of onroad

fuel consumption per mile versus the inverse of the current fuel economy value for

hybrid vehicles, as Honda suggested. First, we found that the intercept was not

statistically significant (p-value of 0.684). Thus, we performed a new regression with an

intercept of zero. We found an r-squared value of 0.18, which is not much different than

that for the regression of fuel economy. The slope of the regression was 1.135,

indicating that the hybrids consumed 13.5% more fuel than predicted by the inverse of

their label values. More importantly, this slope had a p-value of 10-31, indicating that it

was extremely unlikely to be zero. The 95% confidence interval for the slope ranged

from 1.09 to 1.18.

We repeated the analysis of fuel consumption per mile for conventional vehicles

and found very different results. First, both the slope and the intercept were statistically

significant at the 90% confidence level. (The slope was statistically significant at the

95% confidence interval, but the intercept was not.) The value of the intercept was

0.008 and the slope was 0.85. Thus, vehicles with relatively low label values (i.e., 20

mpg) performed well on the road, but conventional vehicles with higher label values

(i.e., 35 mpg) showed a significant shortfall.

We then combined the conventional and hybrid data and performed a single

regression, including an offset term for hybrids. (We did not evaluate the potential for a

different slope for hybrids.) The offset term for hybrids was not statistically significant,

indicating that hybrids were not found to perform differently than conventional vehicles

during the Kansas City testing. At the same time, this testing did not include cold starts,

which is the largest factor negatively affecting hybrid fuel economy relative to

conventional vehicles.

Honda stated that EPA summarized the ORNL “Yourmpg” data well. Honda

presented two criticisms of EPA’s analysis of this database. EPA found that hybrids

had a greater discrepancy between label and onroad fuel economy than conventional

vehicles. Honda believed that higher fuel economy vehicles, hybrid or conventional,

would have a greater onroad shortfall. Two, EPA grouped all hybrids together in

making this general observation. Honda found that this database indicates that not all

hybrids show the same higher degree of onroad fuel economy shortfall. In particular,

the onroad fuel economy shortfall for the Honda Civic and Insight models were not

greater than those for conventional vehicles.

In response to Honda’s first comment on this database, we compared the onroad

fuel economy shortfall for conventional vehicles with relatively high fuel economy (i.e.,

those which had a current combined label value of at least 33 mpg) to those for all

conventional vehicles and hybrids. As discussed in more detail in Section II.A.1 of the
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Final TSD, we performed this comparison on the expanded Yourmpg database as it

existed on August 28, 2006. At this time, it consisted of roughly twice as many entries

as it did when NPRM was published, (8180 versus 4092 fuel economy entries). Using

the expanded database, we found that the onroad fuel economy shortfall for

conventional vehicles, conventional vehicles with current label values of 33 mpg or

greater, and hybrids were 1.4%, 2.3%, and 8.2%, respectively. Thus, conventional

vehicles with relatively high label values appear to have a higher fuel economy shortfall.

However, the increase is very small. Hybrids, on the other hand, showed a much

greater shortfall. Therefore, we disagree with Honda that the greater shortfall observed

for hybrids is due to their high label values.

With respect to the shortfall observed for individual hybrids, Table 5-8 shows the

shortfall observed using the current database.

Table 5-8. Hybrid Fuel Economy in the Yourmpg Database

Vehicle Model No. of Entries Onroad Fuel

Economy

Current Label

Value *

Shortfall

Insight 30 66.0 65.0 2%

Civic 113 46.1 48.9 -6%

Prius 226 47.9 53.8 -11%

Silverado 2 15.2 17.5 -13%

Escape/Mariner 58 29.8 31.9 -6%

Accord 22 30.8 32.3 -4%

Lexus 45 25.1 29.4 -15%

As can be seen, there is a range of shortfalls observed for the individual hybrid

models. However, there is also a wide range in the number of entries, so some care

needs to be taken in comparing across models. The Insight does show a smaller

shortfall than the other hybrids (actually a negative shortfall). However, there are only

30 fuel economy entries for Insights by 10 unique owners. All the other hybrids show a

greater shortfall than the high fuel economy, conventional vehicles. The shortfall for the

Accord hybrid exceeds that for the high fuel economy, conventional vehicles by only

2%, but with even less entries than the Insight. Finally, the Civic hybrid is on the lower

end of the shortfall spectrum with many more entries. However, these 113 are by only

12 owners. The likelihood of significant differences in geographic location, driving

styles, etc. for those making entries for each hybrid model is large. Thus, it is unclear

whether these differences in shortfall are real or not. Even with all hybrids combined,

there is concern that differences in driving style and location could affect the outcome.

AAA found that the US06 fuel economy indicated onroad fuel economy more

accurately than the current label values. As previously mentioned, Honda disagreed

with this finding and provided some additional regression analyses of the AAA data. We

do not believe that the AAA analysis evaluates all the available alternatives for

estimating onroad fuel economy. For example, it only examines two options: the current

label values and the US06 fuel economy, from a sample size of only 17 vehicles. Still, it

indicates the value of considering fuel economy occurring during aggressive and high
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speed driving in estimating onroad fuel economy. We believe that including both the

city and highway portions of the US06 test in the 5-cycle formulae accomplish this task.

We have added the new AAA data to our analysis of onroad fuel economy estimates in

the Final TSD along with AAA fuel economy estimates developed prior to the NPRM.

Honda presented a number of correlations between the Strategic Vision data and

label values based on the current, mpg-based and 5-cycle approaches. Specifically,

Honda was able to match 95 vehicle models which were surveyed by Strategic Vision

and were also present in EPA’s 5-cycle certification database. First, Honda performed

a regression of onroad city and highway fuel consumption from the Strategic Vision

survey against the label values using the three approaches. All three approaches

yielded good and similar correlation coefficients for both city and highway fuel economy.

The 5-cycle label values performed best for city fuel economy and the current label

values performed best for highway fuel economy. However, in all cases, the results

were very similar. As discussed more below, the approximate nature of survey

respondents’ estimates of onroad fuel economy may prevent a more precise evaluation

of the various label approaches.

Second, in their supplemental comments, Honda performed a regression of the

inverse of the average fuel economy for each of the 95 models from the Strategic Vision

survey versus the fuel consumption over each of the nine dynamometer cycles or bags.

Honda used a backward, stepwise regression technique to identify the cycles or bags

which were correlated with city or highway fuel economy at a 90% confidence level.

The results are summarized in Table 5-9 below.

Table 5-9. Dynamometer Cycles Which Correlate with Strategic Vision Fuel

Economy

City Fuel Economy Highway Fuel Economy

Significant

correlation

Non-significant

correlation

Significant

correlation

Non-significant

correlation

Bag 1, FTP Bag 2, FTP Bag 1, FTP Bag 2, FTP

Bag 1, Cold FTP Bag 3, FTP Bag 1, Cold FTP US06

HFET US06 HFET Bag 2, Cold FTP

SC03 Bag 2, Cold FTP SC03

Bag 3, Cold FTP Bag 3, FTP

Bag 3, Cold FTP

As shown in the table, Honda found that Bag 1 from both the FTP and cold FTP

tests, as well as the HFET and SC03 tests correlated with city fuel economy from the

Strategic Vision survey values. The remaining five cycles and bags did not show

statistically significant correlations once the other four bags and cycles were in the

model. For highway fuel economy, the same four cycles and bags showed a

statistically significant correlation, plus Bag 3 from both the FTP and cold FTP tests.

Some of these findings appear to be reasonable, while others are surprising. It is

reasonable that bags that include a cold start should be good predictors of city fuel
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economy. The same is true for SC03 and the impact of air conditioning on city fuel

economy. However, it is very surprising that the HFET test (basically 45-60 mph cruiselike driving) would be the best predictor of fuel consumption during relatively low speed,

start-stop, city driving. Honda expressed the same surprise.

Regarding the regression results for highway driving, it is surprising that the two

cold start bags would be important predictors of driving with presumably few cold starts.

The inclusion of the two Bag 3’s, the HFET and the SC03 tests is more reasonable.

The exclusion of US06 is surprising, given the results of the MOVES driving pattern

analysis presented in Chapter III.A.2 of the Draft TSD and the prevalence of onroad

highway speeds above 60 mph.

The fact that this type of regression analysis produces both expected and

unexpected findings is itself not surprising. In fact, such a regression analysis probably

should not have been performed, as it violates an important premise of regression

analysis. This premise is that the independent variables not be collinear. In this case,

fuel consumption values for all of the various dynamometer cycles and bags are

strongly correlated amongst themselves. Table 5-10 shows the correlation coefficients

(r-squared values) between the fuel economy values over a number of the combinations

of the various cycles and bags for the 95 vehicles that Honda used in their regressions.

Table 5-10. Correlation Between Fuel Consumption Values Over

Dynamometer Cycles

Cycles R-Squared

Value

Cycles R-Squared Value

Bag 2 FTP vs. Bag 3

FTP

0.974 Bag 3 FTP vs.

HFET

0.971

Bag 2 FTP vs. HFET 0.912 Bag 3 FTP vs.

US06

0.958

Bag 2 FTP vs. US06 0.893 Bag 3 FTP vs.

SC03

0.945

Bag 2 FTP vs. SC03 0.943 Bag 2 Cold FTP vs.

Bag 2 Cold FTP

0.966

Bag 2 FTP vs. Bag 2

Cold FTP

0.973 Bag 3 FTP vs. Bag

3 Cold FTP

0.983

Bag 2 FTP vs. Bag 3

cold FTP

0.953

As can be seen in Table 5-10, all of the correlation coefficients are 0.89 or

higher, indicating a very strong degree of collinearity between the various fuel

consumption values. This is not surprising, since large vehicles will have relatively high

fuel consumption rates over all the cycles and small vehicles will have relatively low fuel

consumption rates over all the cycles. These high correlation coefficients indicate that

one simply cannot regress onroad fuel economy estimates against fuel consumption

values from dynamometer cycles. There is insufficient independence between the fuel

consumption values over the various dynamometer cycles.
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A much more sophisticated regression analysis will be necessary to evaluate

how various dynamometer fuel economy values predict onroad fuel economy. First, it

will be necessary to utilize high quality onroad fuel economy measurements, as

opposed to survey responses. As described in Section II.A.3 of the Final TSD, there

appears to be a significant bias in the Strategic Vision survey responses towards fuel

economy values which are a multiple of 5. This indicates that a number of the survey

responders (estimated to be about 13%) were rounding off their estimates to the

nearest 5 mpg. This is insufficient detail for the type of regression performed by Honda.

Second, it will probably be necessary to incorporate descriptions of the vehicle activity

which led to specific onroad fuel economy measurements. The latter would allow the

direct evaluation of cycles or bags which are aimed at specific operating conditions, like

cold starts at various ambient temperatures and air conditioning. This would also avoid

the problems with collinearity present when all the cycles and bags are included in the

regression at the same time.
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Chapter 6: Testing Provisions

6.1 General Test Procedure Issues

What we proposed:

We proposed the following changes to fuel economy test procedures: 1)

collecting the US06 exhaust sample into two bags as opposed to the current one-bag

sample; 2) requiring heater/defroster operation during the Cold Federal Test Procedure

(FTP) testing (currently optional); 3) requiring Cold FTP testing for diesel vehicles; and

4) codifying requirements for four phase FTP testing of gasoline-electric hybrid vehicles

rather than allowing this practice under special test procedures contained in 40 CFR

§86.1840-01. As stated in the proposal, these changes were to take effect beginning

with the 2008 model year.

What commenters said:

AAM/AIAM expressed general concerns with any changes that:

 “Are required for 2008 model year testing without sufficient lead-time;”

 “Could harm data accuracy and repeatability;”

 “Could impact stringency or misrepresent real-world conditions;” or

 “Could add significant cost and complexity without a value-added benefit.”

Our response:

The general concerns expressed by AAM/AIAM apply to the entire set of test

procedure changes set forth in the proposal. As such, our responses to specific

comments on each individual test procedure change will indirectly address the general

concerns and provide more detail. However, as background for the responses to

specific comments, the following paragraphs summarize the specific test procedure

changes, identify the associated general concerns, and provide a general response.

Upon analysis of AAM/AIAM’s comments, we acknowledge the importance of

allowing enough lead time to change 2008 model year testing. We are addressing this

concern for all specific test procedure changes, except the Hybrid four-phase, four-bag

FTP, by extending the applicable effective date until the 2011 model year. We are also

finalizing alternative procedures for the 2008 through 2010 model year interim period for

manufacturers choosing to use the 5-cycle approach. Therefore, the final rule

addresses lead time concerns by providing additional lead time and alternative test

procedures for the interim period, as proposed by AAM/AIAM.

AAM/AIAM commented that dividing the US06 exhaust sample into city and

highway samples will affect data accuracy and test repeatability, although they did not

provide data to support this claim. We performed a ten vehicle study examining the

correlation and variability of the one-bag and two-bag US06 exhaust sampling
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approaches that demonstrated nearly identical fuel economy results and equivalent

variability and measurement accuracy of criteria pollutants for the one-bag and two-bag

US06.32 While we continue to believe the two-bag US06 measurement proposed is a

valid approach that will not lead to significant differences in emission results, we also

believe that the alternative approaches suggested by the auto industry could yield

technically valid results. We have therefore revised the proposal and are finalizing the

requirements for the two-bag US06 measurement as outlined in Preamble Section IV.

AAM/AIAM commented that operating the heater/defroster device during the

Cold FTP test may impact stringency or misrepresent real-world conditions. We

proposed test protocols for climate control settings including specifying appropriate fan

speed settings, timing of turning on the heater/defroster during the test, and accounting

for various vehicle climate control designs (e.g., systems with automatic temperature

adjustment). AAM/AIAM opposed some of the specific test protocols, arguing that a

driver would not likely maintain the fan at maximum speed during an entire driving trip.

AAM/AIAM stated that many electronic systems automatically control fan speed as the

vehicle warms up, and further noted that some vehicles can not operate the defroster

while the blower is off, which we proposed as a possible test protocol.

We agree with the comments from AAM/AIAM that the protocol could be modified

to better simulate how a driver would typically operate the heater/defroster system in the

real world, and we acknowledge the design challenges identified.

We disagree with the AAM/AIAM comment that operating the heater/defroster

system will impact stringency. As demonstrated in EPA’s docketed study (Docket No.

EPA-HQ-OAR-2005-0169-0067, SwRI, “Fuel Economy Impacts of Interior

Heater/Defroster Usage on Conventional and Hybrid Gasoline-Powered Vehicles” U.S.

EPA, Office of Transportation and Air Quality, 2005.), the worst case scenario of

activating the heater/defroster immediately upon start of test had an insignificant

emission impact. In addition, we are waiting until 2 minutes into the test to turn on the

heater/defroster, since, in reality, it is unlikely that passengers would blow cold air at

maximum speed when first starting the vehicle. This further reduces any potential

emissions impact, since nearly all catalyst systems should have achieved light off

temperature at that point.

To address the AAM/AIAM comment that running the heater/defroster system as

proposed may misrepresent real-world conditions, we are finalizing test protocol that

allows fan speed to be reduced 505 seconds after the start of the test during the idle

period between hill 5 and hill 6 of the FTP, which corresponds to the end of bag 1 and

the start of bag 2. We are allowing manufacturers having unique climate control

systems to use alternate heater/defroster test protocols, under the special test

procedures contained in 40 CFR §86.1840-01, with prior agency approval.

32 Mitcham, A. & Fernandez, A., “Revising the US06 Test Procedure into a Two Sample Period Test”

U.S. EPA, Office of Transportation and Air Quality, 2005. Docket No. EPA-HQ-OAR-2005-0169-0058.
145

Finally, AAM/AIAM commented that the proposed test procedure changes

impose significant additional costs without a value-added benefit. We proposed these

changes to ensure that the fuel economy test procedures more closely represent realworld conditions, and we disagree with this comment for the following reasons. First,

the proposed changes apply to existing test procedures and do not require new test

procedures or alter any of the drive schedules. Second, some modifications specifically

for the two-bag US06 exhaust collection, have an initial fixed cost for minor site

modifications, if necessary, including dynamometer analyzer software revisions,

additional analyzer sampling hardware (i.e., exhaust sample bags, exhaust tubing, etc.),

and post-revision validation testing. In response, we have modified the final rule to

allow for alternative methods of determining the city/highway ratio using a one-bag

US06. Third, we have revised certain test procedure changes in the final rule for the

Cold FTP diesel test; as a result, some anticipated hardware changes are no longer

necessary. We changed these procedures to enable manufacturers to use the 5-cycle

approach without the additional test burden of generating 5-cycle data inputs.

Therefore, we believe that the test procedure changes provide sufficient added benefit

without additional significant cost.

6.2 Test Requirements for Vehicles Currently Exempt from Certain Emissions

Tests

6.2.1 Diesel Vehicles

What we proposed:

Diesel vehicles are not currently subject to Cold CO emission standards and,

thus, do not have a 20 degree F FTP fuel economy result to use in the 5-cycle equation.

Therefore, beginning with the 2008 model year, we proposed that diesel vehicles must

perform a Cold FTP for the purpose of collecting fuel economy data. We proposed the

use of a winter grade diesel fuel for such a test.

What commenters said:

AAM/AIAM raised numerous concerns with subjecting diesels to the Cold FTP

test in the 2008 to 2010 timeframe, arguing that EPA does not recognize the significant

laboratory changes that will be needed. They cite the potential for major laboratory

retrofitting, which in some cases might not even be possible with the existing lab

configuration. They also remarked that that there are no test protocols developed for

new diesel technologies on the horizon. They also noted that the proposed regulations

would require Cold FTP testing on all diesel certification vehicles, unlike the gasoline

requirements which require testing on a durability group basis. For these reasons,

AAM/AIAM recommends that EPA wait until the 2011 model year to require diesels to

perform the Cold FTP, giving them more time to address test facility concerns.

Although they did not oppose the test fuel proposal beyond lead time issues, they
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proposed to instead calculate fuel economy based on CO and CO2 measurements,

excluding HC.

Volkswagen, DaimlerChrysler, and Nissan reiterated the concerns expressed by

AAM/AIAM. Volkswagen noted that their preliminary testing indicates the possible

presence of some issues with diesels that are not yet fully understood, thus arguing for

additional lead time. Nissan stated specific technical issues that they could not likely

overcome before the 2010 model year. DaimlerChrysler supported the notion that fuel

economy values should reflect cold testing, but reiterated AAM/AIAM’s lead time

concerns, suggesting that Cold FTP testing for diesels be optional in the 2008 – 2010

model years.

Our response:

We agree that significant laboratory changes are necessary for Cold FTP diesel

testing, since diesel vehicles are not currently subject to FTP testing at 20 degree F.

Therefore, we are revising the proposed provisions for Cold FTP diesel testing as

detailed in the paragraphs below.

First, we are not requiring the measurement of particulate matter (PM) during the

Cold FTP diesel test, since PM is not part of the fuel economy calculation, and thus has

no impact on fuel economy. This eliminates the need for a PM diesel tunnel, an

extensive change that would have been required under the proposal.

Second, we are delaying the requirement for Cold FTP diesel testing to allow

manufacturers additional lead time to address facility concerns. For manufacturers that

choose to use the 5-cycle approach during the 2008 – 2010 model years, we are

requiring diesel Cold FTP testing, but fuel economy may be reported based on CO and

CO2 measurements only. We are not requiring the measurement of hydrocarbons (HC)

during the Cold FTP diesel test during the 2008-2010 model years, because according

to current HC data, excluding HC from the fuel economy calculation has a negligible

impact (i.e., less than 0.1%) on diesel fuel economy reporting. This also provides

additional lead time for manufacturers to make laboratory upgrades such as a heated

flame ionization detector (FID), heated sample lines and additional, external drying

capacity for diesel HC measurement.

Third, in the 2011 model year, we are requiring manufacturers to conduct and

report results from the Cold FTP diesel testing, including HC measurements. Because

diesel emission control technology is evolving rapidly, we believe that HC contribution

will warrant future measurement and inclusion in the fuel economy calculation. This

should provide sufficient lead time for any laboratory changes for cold temperature

capability and specific HC measurement equipment.

Finally, any Cold FTP diesel testing performed for optional 5-cycle testing during

model years 2008-2010 and/or for 2011 beyond must use the winter grade fuel

specification discussed in the proposal and finalized in this rulemaking.
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6.2.2 Alternative-Fueled Vehicles

What we proposed:

Flexible-fuel vehicles (FFVs) are subject to the Supplemental Federal Test

Procedure (SFTP; which includes the US06 and SC03 tests) and Cold Carbon

Monoxide (CO) emission standards and test requirements, but only when operating on

gasoline. Thus, we proposed that the fuel economy label values of FFVs when

operating on gasoline be determined using the same mpg-based or 5-cycle approaches

applicable to gasoline vehicles and thus additional testing for US06, SC03 and Cold

FTP while operating on the alternative fuel would not be required. We also proposed a

methodology for how manufacturers of FFVs are to determine and report fuel economy

label values, when a FFV is operated on the alternative fuel.

What commenters said:

We did not receive any comments on this proposal.

Our response:

Since we did not receive comments on this proposal, we are finalizing it as

proposed.

6.3 Modifications to Existing Test Procedures

6.3.1 Revisions to US06 Bag Measurements

What we proposed:

The US06 driving schedule contains elements of both city and highway driving,

yet the exhaust sample is collected in only one sample, or “bag.” For an emissions test,

the one-bag sample is appropriate, since emissions are summed over the entire test to

determine compliance. However, the ideal methodology for fuel economy would be to

reflect the city portion in the city miles per gallon (mpg) estimate and the highway

portion in the highway mpg estimate. Consequently, we proposed a test protocol that

would collect the US06 exhaust sample into two-bags. We conducted a test program

that demonstrated that two-bag collection is technically feasible, requiring only some

software reprogramming and minimal hardware reconfiguration. We also demonstrated

that a split-phase sampling period does not significantly alter the criteria pollutant

emission results.
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What commenters said:

AAM/AIAM generally disagreed with EPA’s assessment that the costs of

collecting US06 exhaust emissions would be minimal, characterizing the test procedure

change as “substantial,” yet they did not provide data to support this comment. Toyota,

Nissan, Mitsubishi, and DaimlerChrysler agreed.

AAM/AIAM expressed concern with the accuracy and variability of the test when split

into two phases. They recommended that EPA not adopt the two-bag US06, but

instead allow the use of ratio factors (i.e., ratio of the US06 city portion/whole US06 test

and the US06 Highway portion/whole US06 test) or alternative methods to estimate the

city and highway fuel consumption from a traditional single-bag US06. This approach,

they argue, would result in substantially similar results at truly minimal cost. Toyota,

Nissan, Mitsubishi, and DaimlerChrysler independently expressed a preference for ratio

factors. They proposed the following:

o For conventional gasoline vehicles: Use ratio factors of 0.68 for the city fuel

economy and 1.16 for the highway fuel economy, which were used to derive the

mpg-based formulae.

o For hybrid vehicles: Use 0.68 and 1.16 ratio factors for 2008 through 2010 model

years, and gather data to evaluate whether continued use of these factors is

appropriate for hybrids.

o For diesels: Confirm the 0.68 and 1.16 ratio factors after compiling 2007 and

2008 test data.

o For all vehicles: Allow manufacturers to propose alternative ratio methods for

EPA approval (e.g., fuel injector fuel economy data, model CO2 data).

Toyota suggested that hybrid manufacturers submit data, and if it resembles that of

conventional gasoline vehicles, then those factors can be used. If hybrids are seen to

be substantially different, Toyota suggests that EPA allow each manufacturer to use

their own factors based on data and good engineering judgment.

AAM/AIAM commented that separating the two-phase bag software from the

one-phase PM sample collection system for diesels requires significant software

changes, cost, and lead-time. They also noted that diesel testing will be complicated by

the need to align integrated real-time collection of total hydrocarbon (THC) data for fuel

economy calculations with bag collection of methane (CH4) for emissions compliance.

Nissan and DaimlerChrysler reiterated these diesel issues.

DaimlerChrysler also noted that this provision as proposed in 40 CFR Part 86

would impact all US06 testing, including certification and IUVP testing, and would result

in additional unnecessary expense. They suggested that the two-phase US06

provision, if adopted, should be written into Part 60 to ensure that the context is limited

to fuel economy testing.
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Our response:

We disagree with the comments from AAM/AIAM, Toyota, Nissan, Mitsubishi,

and DaimlerChrysler that the test procedure changes and the costs of collecting US06

exhaust emissions in two-bags are “substantial.” The changes necessary to enable

two-bag US06 testing involve an initial, one-time, fixed cost software revision and, in

some cases, an additional sample bag, sample line and analyzer plumbing for collection

of US06 emissions in a second bag.

We also disagree with the comment from AAM/AIAM that splitting the US06

exhaust into two bags decreases accuracy and increases variability. As mentioned

above, EPA performed a ten vehicle study to examine the correlation and variability of

the one-bag and two-bag US06 exhaust sampling approach (Docket No. EPA-HQ-OAR2005-0169-0058, Mitcham, A. & Fernandez, A., “Revising the US06 Test Procedure into

a Two Sample Period Test” U.S. EPA, Office of Transportation and Air Quality, 2005.)

which demonstrated low variability, nearly identical fuel economy results, and equivalent

variability and measurement accuracy of criteria pollutants for the one-bag and two-bag

US06. AAM/AIAM neither addressed the results of this study nor submitted additional

data to refute the results of this study.

Regarding the suggestion from AAM/AIAM, Toyota, Nissan, Mitsubishi, and

DaimlerChrysler to use alternate ratio factors, the ratio factors in the proposal were

used for our 5-cycle assumptions based on the data available at the time. These ratio

factors are clearly inappropriate for hybrid vehicles and other advanced technology

vehicles (i.e., vehicles with cylinder deactivation, engine idle shut off operation, etc.).

Although we disagree with the comments that the cost and procedure changes

are “substantial,” we recognize that these changes take time to implement. We also

agree with the industry concern about accurately timing the real-time PM collection for

emissions compliance with the bag collection of hydrocarbons for fuel economy

information in the US06 test for diesels. Because manufactures may need additional

lead time for gasoline vehicles and because two-bag diesel fuel economy testing is

more complicated, we are revising the provisions for the applicable model years for the

two-bag US06 from the proposal. We are not requiring the two-bag US06 for model

years 2008 through 2010. However, for manufacturers choosing to use the 5-cycle

approach for model years 2008 through 2010, the two-bag US06 must be conducted or

data otherwise supplied in two-bag US06 format (as described further below).

Therefore, for model year 2011 and beyond, we are requiring a city/highway US06

calculation for use in the 5-cycle approach.

In addition, as suggested by the Alliance and AIAM, we are allowing the use of

additional methods for measuring and/or determining a two-bag US06 fuel economy in

lieu of conducting an actual two-bag US06 test. Some suggested methods include: 1)

conducting a one-bag US06 and using emissions analyzer modal data to determine the

appropriate ratio of city and highway operation; or 2) conducting a one-bag US06 and

using On-Board Diagnostic (OBD) fuel rate (e.g., grams of fuel per second) data to
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determine the appropriate ratio of city and highway operation over the one-bag US06.

Additionally, the manufacturers may use other methods based on good engineering

judgment, with EPA review and approval, as long as these methods achieve equivalent

or more technically valid results, based on manufacturer submitted data. These

additional options for deriving or measuring the city/highway US06 fuel economy are

allowed for manufacturers optionally using the 5-cycle approach in model years 2008

through 2010, and for all manufacturers in model year 2011 and beyond, when the 5-

cycle approach is required.

In the case when manufacturers conduct one-bag US06 tests and use modal

emissions and onboard diagnostic (OBD) fuel rate data, the ratio of city and highway

operation over the one-bag US06 is applied to the CO, CO2 and HC results in order to

determine the city and highway US06 fuel economy values, constituting a “virtual” twobag US06. However, this option only applies for determining the city and highway US06

fuel economy and, thus, is not applicable for determining US06 emissions. This option

should also address the concerns of one-phase PM sample collection systems,

integrated real-time total hydrocarbon data collection for fuel economy calculations, and

the timing of CH4 bag measurements for diesels since a one-bag US06 can still be

used.

We disagree with the comments from Daimler-Chrysler that writing this provision

as proposed in 40 CFR Part 86 would impact all US06 testing, including certification and

IUVP testing, resulting in additional and unnecessary expense. We proposed using

existing test procedures for emissions testing in order to minimize test burden and any

unnecessary expenses. Writing the requirements for a two-bag US06 test into Part 600

for fuel economy purposes would require manufacturers to conduct a one-bag US06 for

emissions purposes and an additional, two-bag US06 for fuel economy purposes,

adding additional, unnecessary testing and expenses, and duplicating effort. We are

writing the final regulation such that 40 CFR part 86 will contain both 1-bag or 2-bag

US06 as an option. Part 600 will require that manufacturers determine the US06

City/Highway ratios based on one of several methods, with 2-bag US06 results as one

of these options.

6.3.2 Heater/Defroster Use During the Cold FTP

What we proposed:

The current Cold FTP test conducted at 20 degrees F provides the option to use

the header and/or defroster. Some manufacturers routinely use this option to heat the

vehicle cabin, others do not. In order to more closely reflect real-world operation, and to

ensure a level playing field across manufacturers and vehicle lines when performing this

test, we requested comment on whether we should require operation of the

heater/defroster during this test. We suggested a test protocol for doing so, but we also

noted that there are many possible approaches. We proposed to set the heat level to

high and direct the airflow to the windshield for defrost. After two minutes the fan speed
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would be turned to high and left there for the duration of the test. Automatic climate

control systems would be set to defrost mode and to a temperature of 72 degrees F.

What commenters said:

AAM/AIAM proposed that EPA defer consideration of this concept until we have

a better understanding of real-world operation and of the potential impact on the

stringency of existing and upcoming emission standards (e.g., Mobile Source Air

Toxics).33 They argued that a driver would not likely maintain a maximum fan speed for

43 minutes (the effective length of the test given the emission weighting equation), and

that this worst-case scenario surpasses EPA’s intent to reflect real-world conditions.

AAM/AIAM also noted that many electronic systems automatically reduce fan speed as

the vehicle warms up, and that some vehicles can not operate the defroster without the

blower, as we proposed in the first two minutes of the test. They suggested that we

allow manufacturers choosing the 5-cycle approach in the 2008 – 2010 model years to

use the heater/defroster for testing of fuel economy data vehicles “per manufacturer

procedure using good engineering judgment and with consideration of expected typical

real-world operating patterns.”

DaimlerChrysler, Mitsubishi, and Nissan independently reiterated these

comments and recommended that EPA reevaluate how well the concept represents

real-world behavior. Mitsubishi noted that their test data indicates a far smaller impact

on fuel economy due to defroster/heater operation than EPA estimates in the proposal,

but did not provide data to support this claim. Toyota also called for more data and a

better understanding of the fuel economy and emission impacts of heater/defroster

operation, and suggested along with DaimlerChrysler that changes to the cold test

method should be reevaluated in the context of the proposed Mobile Source Air Toxics

regulations.

Bluewater Network, UCS, NYDEC, Montana-CHEER, and Public Citizen support

using the heater/defroster during the Cold FTP test. Some suggested that the protocol

could be improved with additional data and study of real-world driving conditions. UCS

suggested that EPA develop a standardized methodology based on realistic usage

patterns. Public Citizen highlighted that without a heater/defroster requirement,

manufacturers who choose to use more realistic test conditions may be penalized

relative to those who do not.

Our response:

The purpose of requiring heater or defroster use during the Cold FTP is to more

closely reflect real-world operation, and to ensure a level playing field across

manufacturers and vehicle lines when performing this test. Based on the comments we

received, we are finalizing the requirement for mandatory heater/defroster operation

during the Cold FTP. We are revising the approach outlined in the NPRM to reflect

33 See regulation in 40 CFR §86.1811-10(g) (March 29, 2006).
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more closely real-world operation, and by accommodating various climate control

systems and addressing issues of lead time with respect to applicable model years for

mandatory heater/defroster operation during the Cold FTP.

First, we agree with the AAM/AIAM comment that a driver will not likely maintain

a maximum fan speed for 43 minutes since in reality the vehicle interior would reach a

comfortable temperature for occupants and the fan speed would manually or

automatically be reduced to a lower setting. Therefore, for manual climate control

systems, the final regulations will require that the fan speed setting be reduced to the

lowest possible to maintain air flow at approximately 505 seconds after the start of the

test during the idle period between “hill” 5 and “hill” 6 of the FTP (the point that

corresponds to the end of bag 1 and the start of bag 2), and the temperature setting will

remain at the hottest setting. These settings will be held for the remainder of the test,

including the final bag following the 10 minute soak period. For automatic climate

control systems, the selector will be set to heater or defroster mode and to a

temperature of 72 degrees F for the duration of the test. We are finalizing all other

aspects of heater/defroster operation as outlined in the proposal.

For vehicles with multiple zone climate control systems, the same fan and

temperature settings should be maintained throughout the zones for both manual and

automatic interior climate control systems. This and other unique designs may require

special, alternative protocols/procedures during the Cold FTP. Therefore, with prior

agency approval, manufacturers may request and use alternative heater/defroster test

protocols/procedures if they have a unique climate control system.

Finally, we are revising the applicable model year for implementation of

mandatory heater/defroster operation during the Cold FTP from model year 2008 to

model year 2011. This will allow manufacturers time to fully assess any impacts related

to the Mobile Source Air Toxic (MSAT) cold volatile organic compound (VOC) proposed

standards, which would also be determined based on the Cold FTP test. However, if

manufacturers choose to perform 5-cycle testing between the 2008 through 2010 model

year, they must follow the heater/defroster protocols/procedures set forth in this

regulation.

6.3.3 4-Phase, 4-Bag FTP for Gasoline-Electric Hybrid Vehicles

What we proposed:

The FTP consists of two parts, referred to in the regulations as the “cold start”

test and the “hot start” test. Each of these parts is divided into two periods, or “phases”:

a “transient” phase and a “stabilized” phase. For conventional vehicles, the stabilized

phase of the hot start test has been assumed to be identical to the stabilized phase of

the cold start test, allowing the test to be shortened by not running the hot start

stabilized phase. However, because gasoline-electric hybrid vehicles have two energy

sources that can be combined in many ways, EPA and manufacturers recognized that
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the assumption regarding the equivalence of the stabilized phases of the hot and cold

start tests may be invalid for hybrid vehicles. Consequently, we have historically

required vehicles with gasoline-electric hybrid systems to perform the complete set of

four phases of the FTP under existing provisions referenced in the regulations (40 CFR

§86.1840-01) for special test procedures. Rather than continue this practice, we

proposed to develop explicit regulatory language to require full-four phase testing of

hybrid-electric vehicles. We proposed to require that hybrid vehicles conduct all four

phases of the FTP for both emissions and fuel economy testing, including the Cold FTP.

What commenters said:

AAM/AIAM cited 40 CFR 86.1811-04(n), which aligns with California, as already

requiring two full Urban Dynamometer Driving Schedules (UDDSs) for hybrid vehicles

and allowing the emissions to be collected in two-bags (one per UDDS). AAM/AIAM

supported extending the two-UDDS requirement to hybrid vehicles conducting the Cold

FTP. While they agreed that we should require all four phases of the FTP, they

disagreed with our proposal requiring that emissions be collected in four bags. They

suggested that we allow manufacturers the option to use four sample bags, because

requiring this methodology would force lead-time issues and costly facility modifications.

They also noted that the four-phase two-bag approach improves accuracy and

alignment with California. They proposed the following:

o Retaining section 86.1811-04(n) as-is;

o Consider a new section 86.1811-11(n) that would delay these requirements for

the Cold FTP test;

o Define both two-Bag FTP and four-Bag FTP in Part 600.002

o Add 5-cycle fuel economy equations that clarify the application for both two-bag

and four-bag testing;

o Weight the bag fuel consumption elements of the 5-cycle equations by theoretical

distance traveled to ensure consistent label adjustments between two- and fourbag data.

Nissan noted that in order to implement a 4-bag FTP, they would need new

hardware, software, and test equipment, thus making the 2008 model year difficult to

achieve. They also expressed concern that a 4-bag requirement might not be

consistent with California, and that auto companies may need to support two test

equipment regimes.

Our response:

There are two distinct but related protocols for FTP testing of hybrid-electric

vehicles: 1) the driving schedule, which requires performance of the FTP over four

phases (i.e., two consecutive Urban Dynamometer Driving Schedule or UDDS cycles)

versus the three phase FTP for conventional vehicles (i.e., one UDDS and repeat of

only the first 505 seconds (Hot 505) of the UDDS with the emissions from last 864

seconds of the UDDS assumed to be same as in the first UDDS), and 2) the
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measurement of emissions during the four phase FTP by either collecting emissions in

2-bags, combining emissions from the first two and last two phases, or collecting

emission in 4-bags by measuring emissions during each of the four phases. We

proposed provisions for both protocols and we will address them beginning with the

four-phase FTP and then the 4-bag versus 2-bag FTP.

The AAM/AIAM commented that 40 CFR 86.1811-04(n), which aligns with

California, already requires two full UDDSs for hybrid vehicles. Regulatory language

contained in 40 CFR §86.1811-04(n) refers to and incorporates by reference the

California procedure entitled “California Exhaust Emission Standards and Test

Procedures for 2003 and Subsequent Model Zero-Emission Vehicles, and 2001 and

Subsequent Model Hybrid Electric Vehicles, in the Passenger Car, Light-Duty Truck and

Medium-Duty Vehicle Classes” (August 5, 1999). In the California procedure, section

6.2 describes the dynamometer procedures for hybrid electric vehicle emission testing

and states: “...The dynamometer run consists of two tests, a “cold” start test...and a

“hot” start test...” by conducting two consecutive UDDS cycles. Before this statement,

the introductory paragraph for this section also states that “Alternative procedures may

be used if shown to yield equivalent results.” In addition, EPA proposed that hybrid

electric vehicles undergo a full four-phase FTP under the special test provisions in 40

CFR §86.1840-01.

In the proposal, we intended to develop explicit regulatory language that would

require manufactures to use a full four-phase FTP test for hybrid-electric vehicles

instead of continuing to reference the special test procedure provisions in 40 CFR

§86.1840-01. However, upon further review, we agree with AAM/AIAM that 40 CFR

§86.1811-04(n), which references the CARB procedure requiring the full four-phase

FTP for hybrid-electric vehicles, adequately covers the requirement for a full four-phase

FTP. Therefore, we will retain §86.1811-04(n) as written, which addresses the

comments from AAM/AIAM and Nissan and no longer need to develop further explicit

regulatory language requiring a full four-phase FTP for hybrid-electric vehicles.

EPA currently collects the emissions in four bags corresponding to the following

four phases: cold transient emissions collected in bag 1 (505 seconds), cold stabilized

emissions collected in bag 2 (864 seconds), hot transient emissions collected in bag 3

(505 seconds or a Hot 505), and hot stabilized emissions collected in bag 4 (864

seconds. For conventional vehicles, bag 4 is not repeated since we assume that the

emissions are the same as in the cold stabilized phase). Accordingly, our test

procedures are aligned with CARB for hybrid-electric vehicles, contrary to the

comments from Nissan, since both tests require the full four phases, or two consecutive

UDDS cycles. Therefore, the only difference between a four-phase, 2-bag FTP (where

bag 1+bag 2 = bag A and bag 3+bag 4 = bag B) and a four-phase, 4-bag FTP is the

emissions sample collection method and the analysis of the test results.

The AAM/AIAM commented that it supports extending the use of a four-phase

FTP to hybrid vehicles conducting the Cold FTP. However, after further consideration,

we are not going to extend the requirement for four-phase FTP testing of hybrid vehicles
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to the Cold FTP as originally stated in the proposal. The lower temperature (20o F) for

the Cold FTP versus the typical temperature (75o F) for the FTP could impact the hot

stabilized phase (i.e., bag 4) fuel economy for the Cold FTP in that the vehicle may not

truly be “hot” or “stabilized” during the normally substituted cold stabilized phase (i.e.,

bag 2) of a 3 bag test. This is the case for both conventional and hybrid vehicles and

therefore retaining the current Cold FTP 3 bag test procedures maintains a level playing

field between conventional and hybrid vehicles when calculating running fuel

consumption at 20o F. Further, the comments cited that requiring four bags would force

facility modifications with significant costs and lead time issues. We feel that is

particularly relevant in the case of 20o F Cold FTP test facilities which have been strictly

designed around the 3-bag FTP test procedures. Therefore, for hybrid-electric vehicles,

the Cold FTP will continue to omit the fourth phase of the FTP emission test and collect

the emissions for the remaining three phases (i.e., 3-bag FTP), as currently required.

AAM/AIAM disagreed with our proposal requiring that emissions be collected in

four bags, stating that the four-bag approach would require costly facility modifications

and lead-time issues. Accordingly, AAM/AIAM suggested that a 4-bag FTP be optional,

indicating that a 2-bag FTP increases accuracy and alignment with CARB. We

recognize that some manufacturers and CARB may require new hardware, software,

and test equipment to implement a 4-bag test. Since our test procedures are aligned

with CARB requiring full four phase FTP testing for hybrid-electric vehicles, this is an

issue of how to divide and analyze the emissions results. Therefore, we agree with the

AAM/AIAM suggestion to optionally allow a 4-bag FTP. As a result, we will accept both

four-phase, 2-bag FTP results and four-phase, 4-bag FTP results. Accordingly, we will

develop an optional 2-bag 5-cycle fuel economy formula/equation that will use

appropriate 5-cycle, bag fuel consumption weightings based on theoretical distance

traveled to ensure consistent label adjustments for two-bag and four-bag FTP testing,

as suggested by AAM/AIAM.

We disagree with the AAM/AIAM recommendation to consider a new section in

40 CFR §86.1811-11(n) that would delay the requirement for the four-phase, 4-bag Cold

FTP test and define both the two-bag FTP and four-bag FTP in 40 CFR §600.002. First,

the 3-bag FTP is currently required and used for Cold FTP testing of hybrid-electric

vehicles, and thus it is unnecessary to create a new section in 40 CFR §86.1811-11(n)

to delay the four-phase, 4-bag Cold FTP. Second, the FTP definition in Subpart A –

“Fuel Economy Regulations for 1977 and Later Automobiles – General Provisions” 40

CFR §600.002-85(a)(7) references “procedures described in part 86,” including 40 CFR

§86.1811-04(n), which references the California procedure and describes the fourphase, 2-bag FTP. Therefore, we also do not believe it is necessary to further define

the 2-bag and 4-bag FTP in 40 CFR §600.002, since they are completely described in

the referenced part 86 provisions.
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6.4 Test Fuels

What we proposed:

With the exception of specifying a fuel to be used for Cold FTP testing of diesel

vehicles, we did not propose changes to the fuels used for current emission or fuel

economy tests. However, in the proposed rule’s discussion of the Energy Policy Act of

2005, we interpreted the statute’s reference to “current reference fuels” to mean the

laboratory fuels used to perform the fuel economy tests. We understood the underlying

concern of Congress to be the possibility that the high-quality lab fuels would give

higher fuel economy results that the typical fuel used by consumers. The test fuel

specifications are detailed in the emission compliance regulations. The test fuel is

roughly equivalent to premium, high-octane fuel available at the pump.

What commenters said:

The NYDEC disagreed with the use of premium, high-octane fuel, and suggested

that actual in-use fuels provide fuel economy estimates closer to what consumers would

actually experience in real world conditions.

Our response:

We disagree with the comments from NYDEC regarding the use of in-use fuels.

The test fuel used for emissions certification and fuel economy testing is required to

have specific and repeatable characteristics to ensure consistency in test results. While

certification fuel is roughly equivalent to premium, high octane fuel available to

consumers, EPA has previously established requirements for emissions and fuel

economy testing that ensure that the octane level of certification fuels does not

influence emissions or fuel economy test results.

Under the provisions of 40 CFR §86.090-27, EPA requires manufacturers to

show prior to certification that knock sensor equipped vehicles, which could take

advantage of elevated octane levels, could operate on 91 research octane number

(RON) (equivalent to commercially available 87 octane fuel) without affecting emissions

or fuel economy. Manufacturers are required to perform testing on both 95 RON

(equivalent to commercially available 93 octane fuel) and 91 RON, compare the data for

91 versus 95 RON, and are not allowed to have more than a 3% difference between the

emissions and fuel economy results. These procedures were streamlined in 1997, as

detailed in the manufacturer guidance document “VPCD-97-01” available on the EPA

website (http://epa.gov/otaq/cert/dearmfr/vpcd9701.pdf) and still apply today.

Therefore, this provides some measure of confidence that premium, high-octane fuels

do not impact fuel economy results. Additionally, under our Compliance Assurance

Program 2000 (CAP 2000), the manufacturers are required to conduct In-Use

Verification Program (IUVP) FTP, highway, and US06 testing on in-use vehicles at

10,000 and 50,000 miles as-received with the in-use fuel in the fuel tank (40 CFR

§86.1845-04). Therefore, in the future, any indications of advantages resulting from
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testing on high octane, premium fuels may be detected in the IUVP fuel economy data

results.

6.5 Hybrid-Electric Vehicle Battery State of Charge

What we proposed:

EPA did not propose anything specific regarding the measurement of battery

state of charge (SOC) and fuel economy. However, the manufacturers raised a related

issue.

What commenters said:

AAM/AIAM expressed concern with the criteria used at EPA’s laboratory for

confirmatory testing of hybrid-electric vehicles, because it imposes a maximum absolute

state of charge (SOC) deviation equivalent to 1% of the battery’s rated capacity. This is

inconsistent with the criteria outlined in the Code of Federal Regulations (CFR) and in

California regulations, which include a maximum absolute SOC deviation criterion

equivalent to 1% of fuel energy consumed. They also stated that the regulations do not

provide flexibility to correct fuel economy when the SOC criterion is exceeded, thus

leading to possibly unnecessary additional testing. They recommended that EPA

immediately align laboratory practice with the SOC criterion in the CFR, and that the

regulations include flexibility to either void tests under certain criteria or validate data by

applying SOC corrections approved by EPA to the fuel economy data. They noted that

a modified version of the draft SAE J2572 procedure might be useful for determining

SOC corrections.

Toyota commented that it did not support EPA’s proposal to apply SOC criteria to

each bag. Instead, they suggested that EPA provide an option to correct fuel economy

results based on battery charge/discharge when the balance exceeds 1 percent.

Our response:

EPA did not propose any regulatory changes to the measurement of battery state

of charge (SOC). The comments regarding EPA laboratory practices are tangential to

this rulemaking effort.

Thus far, all hybrid-electric vehicles tested at EPA’s National Vehicle and Fuel

Emissions Laboratory (NVFEL) have passed compliance using the battery SOC limits of

+/- 1% 34 and the current practice of measuring the battery SOC over the entire

34 Society of Automotive Engineers (SAE) Standard J1711 – “Recommended Practice for Measuring

the Exhaust Emissions and Fuel Economy of Hybrid-Electric Vehicles,” March 1, 1999 and SAE

J2711 – “Recommended Practice for Measuring Fuel Economy and Emissions of Hybrid-Electric and

Conventional Heavy-Duty Vehicles,” September 1, 2002.
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procedure for battery SOC neutrality/equilibrium. In addition, if the SOC

neutrality/equilibrium exceeds the initial SOC by +1%, the maximum allowed SOC

deviation criterion, the manufacturers are afforded the opportunity for a re-test, at their

discretion.

Regarding comments from the AAM/AIAM and Toyota regarding flexibility to

correct fuel economy results based on battery charge/discharge when the balance

exceeds 1 percent. We would be willing to evaluate such a proposal to allow data

validation by applying battery SOC corrections to fuel economy results, in addition to the

existing provision for a discretionary re-test. We believe the following considerations

would be important: 1) statistical criteria (e.g., 95% confidence intervals, statistical fand t-test, etc.) must be defined and applied to the correction factors, 2) contiguous

data points for plotting the change in charge for the rechargeable energy storage

system (RESS) versus fuel consumption. EPA would reserve the right to request and

review the underlying data points and other information used to develop the RESS

change in charge versus fuel consumption plot. Further, EPA has been and plans to

continue participating in the development of SAE practices, specifically SAE J257235 as

mentioned by the commenters, and any other committees related to hybrid-electric

vehicle practices.

35 SAE Standard J2572 - “Recommended Practice for Measuring Fuel Consumption and Range of

Fuel Cell and Hybrid Fuel Cell Vehicles Powered by Compressed Gaseous Hydrogen,” August 1,

2006.
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Chapter 7: Cost Analysis

7.1 Testing Burden

7.1.1 Testing Burden for Small Manufacturers

What we proposed:

Testing Burden includes an estimate of the number of new tests required by the

rule, and a cost per test in terms of labor and operations and maintenance costs. The

added costs of new facilities to conduct the tests are considered separately as capital

costs, and one-time startup costs are considered separately as startup capital costs.

The proposal did not include any specific provisions that were designed to lessen

the compliance burden for small manufacturers. We did propose and finalize many

features designed to provide adequate lead time and to minimize testing burdens that

apply to both large-volume and small-volume manufacturers.

What commenters said:

Mitsubishi commented that EPA should recognize that there may be a

disproportionate testing burden for some manufacturers. Ferrari asked that EPA

recognize the unique position of small-volume manufacturers, noting that they are

especially concerned regarding the potential number of new tests they will be required

to perform.

Our response:

EPA has a number of provisions in its existing certification regulations that

reduce the burden of Clean Air Act compliance for small-volume manufacturers. For

example, special durability demonstration and in-use vehicle program testing

requirements apply under 40 CFR, Subpart S. Similarly, small manufacturers are

eligible to apply for reduced certification fees. It is true, however, that in general existing

emissions and fuel economy requirements are governed by environmental and

compliance considerations that do not vary as a function of manufacturer size, including

city and highway emissions and fuel economy testing for certification. This approach is

carried through in this rule. However, we are finalizing a number of provisions designed

to reduce test burdens that apply to large-volume and small-volume manufacturers.

During the Model Year 2008 to 2010 transition period, manufacturers have an

alternative to additional testing: they may opt to use the mpg-based fuel economy

calculation. Second, in MY 2011 and beyond, only those vehicles falling below the mpgbased tolerance bands must undergo full 5-cycle testing. Third, where applicable we

allow fuel economy data to be determined based on analytically derived fuel economy

(ADFE) calculations.
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7.1.2 2008 – 2010 Model Year Testing Costs: Testing Issues

What we proposed:

The proposal set forth specific test procedure changes as follows: 1) collection

of the US06 exhaust sample into two bags as opposed to the current one-bag sample;

2) required heater/defroster operation during the Cold FTP testing as opposed to

current optional operation; 3) requiring Cold FTP testing for diesel vehicles, which is

currently not required; and 4) codifying requirements for four-phase, four-bag FTP

testing of gasoline-electric hybrid vehicles rather than allowing this practice under

special test procedures contained in 40 CFR §86.1840-01. As stated in the proposal, all

of these changes were to take effect beginning with the 2008 model year, which, for a

particular test group, could be as early as January 2, 2007.

What commenters said:

AAM/AIAM and several manufacturers disagreed with the assessment in the

NPRM that test volume and test facility costs for the 2008 through 2010 time period will

be zero. They suggest that this assumption did not take into account the cost

associated with performing the proposed Cold FTP on diesel vehicles or performing the

two-bag US06 tests on all applicable vehicles. They believe that major test cell

modifications or new facilities will be required to perform Cold FTP tests on diesel

powered vehicles, noting that from their perspective the requirement to perform Cold

FTP tests is particularly onerous as this test data is not required for the calculation of

fuel economy label values until the 2011 model year. Concerns were also expressed

about the difficulty of compliance with the heater/defroster provisions during the

transition period, and with the four-bag FTP testing requirement both as a matter of

adequate lead time and as potentially requiring costly facility modifications, especially if

EPA requirements were inconsistent with California’s. Lead time concerns were also

expressed by NADA.

Our response:

These issues are addressed in detail in Section 6 of the Response to Comments.

The cost implications of these issues and their resolutions are highlighted here.

The final regulations clarify that the cold FTP diesel testing requirement only

begins with model year 2011 (except for those vehicles for which manufacturers choose

to voluntarily use the 5-cycle method). Consequently, the final rule continues to

anticipate no test burden or facility costs during the transition period attributable to this

cost item.

As discussed in detail in Section 6, EPA has offered alternative methods for

calculating two-bag US06 data. These alternatives are available during the transition

period for those manufacturers choosing to use the 5-cycle approach, and we feel this

largely addresses the concerns regarding lead time. EPA’s evaluation indicates that the
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hardware changes to perform two-bag collection would be minimal and that the threemodel year lead time is adequate to implement them. Information system

reprogramming as well as validation tests were already included as startup costs in the

proposal, and these have been retained.

We are finalizing a provision to require the mandatory use of heater/defroster, but

have extended the effective date until MY 2011 (except for those vehicles for which

manufacturers choose to apply the 5-cycle method). We believe this addresses any

cost concerns regarding this provision.

As discussed in detail in Section 6, for the model year 2008 four-phase FTP

testing for hybrids, we will allow consistency with California. We believe these

modifications of the proposal adequately address the lead-time and facility modification

cost issues, and consequently no cost has been added to the final cost analysis for this

item.

7.1.3 2011 and Later Model Year Testing Costs: Inclusion of MDPVs

What we proposed:

As discussed in Section 4 of the Response to Comments, EPA sought comment

on a voluntary labeling program for vehicles above 8500 pounds gross vehicle weight

rating (GVWR), and how such a program might be implemented.

What commenters said:

Environmental groups supported the proposal, and Public Citizen argued that

EPA has the authority to make the requirement mandatory. AAM/AIAM suggested that

labeling of these heavier vehicles will not produce information that is comparable to the

labels on light duty vehicles, and may in fact create more confusion and

misunderstanding than additional value in the marketplace.

Our response:

As discussed in Section 4, we are finalizing in this rule a fuel economy labeling

program for MDPVs beginning in model year 2011. Testing will be limited to the FTP

and HFET tests. This is congruent with regulations finalized by NHTSA’s expansion of

the CAFE program to include MDPVs beginning the same model year. The testing

required under the CAFE and fuel economy labeling programs are overlapping, but not

identical; in general, more vehicles must be tested for CAFE, and therefore we do not

expect that inclusion of MDPVs in the labeling program will require additional testing.

MDPVs are already subject to FTP emissions standards, and may also conduct

the HFET due to California requirements. NHTSA assessed the additional cost burden
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of testing MDPVs in its light-truck CAFE rule (see Final Regulatory Impact Analysis,

page VII-19).36

7.2 Facilities Costs

7.2.1 Facility Upgrades for Cold FTP Testing

What we proposed:

The proposal did not consider any facility costs for cold diesel testing as distinct

from the capitalized cost of facility capacity to conduct additional Cold FTP tests for all

vehicles covered, including diesel vehicles. The calculation used as a baseline the

number of city/highway fuel economy tests conducted according to EPA’s database for

model year 2004. No allowances were made for potential increases in the fleet size in

future years.

What commenters said:

AAM/AIAM along with Volkswagen, Nissan, and Daimler Chrysler, believe that

major test cell modifications or new facilities will be required to perform Cold FTP tests

on diesel powered vehicles, noting that from their perspective the requirement to

perform Cold FTP tests is particularly onerous as this test data is not required for the

calculation of fuel economy label values until the 2011 model year. As mentioned

above, they further note that the proposed two-bag US06 test would require significant

cost to change both sample system hardware and software. They do not have specific

estimates of the costs associated with these changes, but they note that the costs “are

likely to be substantial.”

Our response:

EPA agrees that there may be some facility upgrades needed for some

manufacturers conducting cold FTP testing on diesel vehicles for model year 2011 and

later. Based on cost estimates developed by EPA’s testing facilities in Ann Arbor,

Michigan, EPA has added a capital cost item corresponding to $55,000 for each of ten

cold testing facilities to conduct diesel hydrocarbon testing, including FIDs (flame

ionization detectors) as well as heated sample probes, sample lines and sample filters.

The number of cold FTP tests to be performed has also been increased to reflect the

possibility of growth in the diesel fleet between the MY 2004 dataset that was the

36 Final Regulatory Impact Analysis: Corporate Average Fuel Economy And CAFE Reform For MY 2008-2011

Light Trucks. U.S. Department of Transportation, National Highway Traffic and Safety Administration, Office of

Regulatory Analysis and Evaluation, National Center for Statistics and Analysis, March, 2006. Available at

http://www.nhtsa.dot.gov/staticfiles/DOT/NHTSA/Rulemaking/Rules/Associated%20Files/2006_FRIAPublic.pdf
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baseline for cost calculations and MY 2011, although this number is speculative

(increase from 5 test groups in MY 2006 to 10 in MY 2011). There are permanent

upgrades that will be required on a continuing basis for cold testing facilities conducting

diesel testing, and therefore are treated as facility capital costs rather than one-time

startup capital costs.

7.3 Startup Burden

7.3.1 Dual Information Systems for CAFE/Gas Guzzler and Label

Calculations

What we proposed:

The proposal contemplated no change in the existing system of translating test

vehicle fuel economy values (now to be calculated using the mpg-based or 5-cycle

formulas) into model type fuel economy label values. Under the existing system, fuel

economy label values for test vehicles are arrived at through several steps. These

ratings are computed as the sales-weighted harmonic mean of the “base levels” within

each model type, which in turn are calculated as the sales-weighted harmonic mean of

the configurations and subconfiguration fuel economy values within each base level.

This procedure is intended to insure that the most representative fuel economy values

are posted on new vehicles, which are sold by the manufacturer’s model designation

rather than categories that correspond to the test groups that are used for generating

fuel economy data as a part of the certification testing process. Under the proposal, this

same methodology would apply to the mpg-based fuel economy, or the full 5-cycle

values would similarly be plugged in at each level. Thus, the proposal applied the mpgbased adjustments at the test level. These values would then feed into fuel economy

values for each vehicle configuration, which ultimately feed into the label value.

What commenters said:

AAM/AIAM pointed out that the proposal would require one calculating system for

the new label values and a separate system, preserving the existing system, for

calculation of CAFE fuel economy values. This is because current regulations apply

10% and 22% downward adjustment factors for label values at the model type rather

than test level, whereas these adjustments are not applied to the CAFE calculation. If

label value adjustments are applied at the test level on up, as in the proposal, then the

model level fuel economy value can no longer be applied to CAFE by simply leaving off

the 10% and 22% adjustments. Accordingly, AAM/AIAM requested that the mpg-based

calculation be allowed at the model type level rather than the test level, so that the

existing information processing programming architecture could be preserved for both.
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Our response:

EPA agrees that there may be some convenience in applying the derived 5-cycle

equation at the model-type level for manufacturers who wish to use the same data

management system for reporting CAFE and label values. This may be particularly true

for the early part of the transition period. However, this approach is not available for the

vehicle-specific 5-cycle label calculations, and any manufacturers who use it during the

phase-in period during the 2008-2010 model years will encounter an information cost

not contemplated in the proposal – a dual calculation procedure will be needed.

Similarly, a dual calculating system will be needed for model years 2011 and after.

The cost analysis has been updated to account for this increased information

system burden. Based on a projection of EPA’s information development contract

costs, and an estimate of the portion of those costs attributable to the dual information

system possibility, we have increased the industry information startup costs

(unamortized) by $933,450.

7.3.2 Additional Startup Costs

What we proposed:

The proposal contained several provisions that had potential cost impacts having

to do with the timing of new requirements or possible future adjustments. The proposed

effective date for the methodology for calculating label values and changes to the

design and content of the label was model year 2008, which for some vehicles can start

as soon as January 2, 2007. Of the four proposed new labels required for model year

2008, two were positioned vertically (“portrait”). The proposal stated that we would

publish the equations for the mpg-based approach by January 1 of the calendar year

prior to the model year to which the equations would first apply (e.g., for model year

2010 fuel economy calculations, the equations would be made available before January

1, 2009).

What commenters said:

As discussed in detail in Section 2, commenters argued that the sticker label

requires prior arrangements with suppliers. In addition, the possibility was raised of two

separate rounds of label adjustments to also reflect new NHTSA safety label rating

requirements that apply to vehicles manufactured on or after September 1, 2007. The

industry argued for an effective date for label changes should be September 1, 2007, or

a year after the publication of the final rule. Similarly, several manufacturers noted that a

change from the current landscape label orientation would cause costly modifications,

particularly for those like GM, who have redesigned their label in the landscape

orientation to accommodate the new NHTSA label requirements. As for updating of the

mpg-based equations, AAM/AIAM describes concerns with lead time and with the

frequency of such updates: making the equations available on January 1 of the model
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year prior to the model year for which they first apply provides insufficient lead time for

manufacturers, since the start of production for some vehicles of a model year can be

as early as January 1 of the prior calendar year. Consequently, they advocate making

the new equations available no later than January 1 of the model year two years prior to

the model year to which the equations would first apply.

Our response:

EPA acknowledges the cost concerns about redesigning pre-existing price

stickers and recognizes the challenges posed by simultaneously incorporating two new

labels onto the price sticker - the NHTSA crash rating label and the fuel economy label.

We are therefore aligning the mandatory date for using the new fuel economy label with

that of NHTSA’s new crash test rating label. EPA believes that with these modifications

no significant new costs will be incurred by industry.

The final rule requires that all 2008 models manufactured on or after September

1, 2007 have the new label format. Manufacturers will be allowed to use the new label

design as soon as possible, and are encouraged to do so. The current label design

can be used until September 1, 2007 with certain additional information included. We

are also finalizing a horizontal label orientation. Thus, the cost concerns mentioned by

industry for redesigning the price sticker would not be realized.

As discussed in Section 3.2, we are finalizing regulations that require EPA to

issue guidance regarding revisions to the equations by no later than July 1 of the

calendar year prior to the earliest start of the model year that starts in the following

calendar year. In other words, for new equations to be applicable to the 2010 model

year (which can begin as early as January 2, 2009), EPA must issue guidance prior to

July 1, 2008.