[Federal Register: February 1, 2006 (Volume 71, Number 21)]
[Proposed Rules]
[Page 5425-5513]
[DOCID:fr01fe06-23]

-----------------------------------------------------------------------

Part II

Environmental Protection Agency

-----------------------------------------------------------------------

40 CFR Parts 86 and 600

Fuel Economy Labeling of Motor Vehicles: Revisions To Improve
Calculation of Fuel Economy Estimates; Proposed Rule

-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 86 and 600

[EPA-HQ-OAR-2005-0169; FRL-8021-8]
RIN 2060-AN14

Fuel Economy Labeling of Motor Vehicles: Revisions To Improve
Calculation of Fuel Economy Estimates

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of proposed rulemaking.

-----------------------------------------------------------------------

SUMMARY: The Environmental Protection Agency (EPA) is proposing changes
to the test methods used to calculate the fuel economy estimates that
are posted on window stickers of all new cars and light trucks sold in
the United States. A fundamental issue with today's fuel economy
estimates is that the underlying test procedures do not fully represent
real-world driving conditions. Although no single test or set of tests
can ever account for the wide variety of conditions experienced by
every driver, the new fuel economy estimates would more accurately
reflect a number of important factors that drivers are likely to
experience on the road. These changes will take effect starting with
2008 model year vehicles. Under the new methods, the City MPG estimates
for most vehicles would drop 10 percent to 20 percent from today's
labels, depending on the vehicle. The Highway MPG estimates would
generally drop 5 percent to 15 percent for most vehicles. Although
today's proposed fuel economy test methods would provide more accurate
estimates for many consumers, there will always continue to be drivers
who get higher or lower fuel economy than the window sticker numbers.
Currently the same test procedures are used for both the window sticker
estimates and the fuel economy values used to determine a
manufacturer's corporate average fuel economy (CAFE). However, this
proposal would not alter the test procedures, driving cycles,
measurement techniques, or the calculation methods used to determine
CAFE.

DATES: Comments: Comments must be received on or before April 3, 2006.
Under the Paperwork Reduction Act, comments on the information
collection provisions must be received by OMB on or before March 3,
2006. See Section VII.A of the SUPPLEMENTARY INFORMATION section for
more information about written comments.
    Hearings: We will hold a public hearing in Romulus, Michigan, on
March 3, 2006. See Section VII.C of the SUPPLEMENTARY INFORMATION
section for more information about public hearings.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2005-0169, by one of the following methods:
     http://www.regulations.gov: Follow the on-line instructions for

submitting comments.
     Fax:<PHONE_NUMBER>.
     Mail: Environmental Protection Agency, EPA Docket Center
(EPA/DC), Air and Radiation Docket, Mail Code 6102T, 1200 Pennsylvania
Avenue, NW., Washington, DC 20460, Attention Docket ID No. EPA-HQ-OAR-
2005-0169. In addition, please mail a copy of your comments on the
information collection provisions to the Office of Information and
Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk
Officer for EPA, 725 17th St., NW., Washington, DC 20503.''
     Hand Delivery: Docket Center, (EPA/DC) EPA West, Room
B102, 1301 Constitution Ave., NW., Washington, DC, Attention Docket ID
No. OAR-2005-0169. Such deliveries are only accepted during the
Docket's normal hours of operation, and special arrangements should be
made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2005-0169. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information provided,

unless the comment includes information claimed to be Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute. Do not submit information that you consider to
be CBI or otherwise protected through http://www.regulations.gov or e-mail.

The http://www.regulations.gov Web site is an ``anonymous access'' system,

which means EPA will not know your identity or contact information
unless you provide it in the body of your comment. If you send an e-
mail comment directly to EPA without going through http://www.regulations.gov

your e-mail address will be automatically captured and included as part
of the comment that is placed in the public docket and made available
on the Internet. If you submit an electronic comment, EPA recommends
that you include your name and other contact information in the body of
your comment and with any disk or CD-ROM you submit. If EPA cannot read
your comment due to technical difficulties and cannot contact you for
clarification, EPA may not be able to consider your comment. Electronic
files should avoid the use of special characters, any form of
encryption, and be free of any defects or viruses. For additional
information about EPA's public docket visit the EPA Docket Center
homepage at http://www.epa.gov/epahome/dockets.htm. For additional

instructions on submitting comments, go to Section VII of the
SUPPLEMENTARY INFORMATION section of this document.
    Public Hearing: The public hearing will be at the Crowne Plaza
Hotel, Detroit--Metro Airport, 8000 Merriman Road, Romulus, Michigan.
    Docket: All documents in the docket are listed in the
http://www.regulations.gov index. Although listed in the index, some

information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the EPA Docket Center, EPA/

DC, EPA West, Room B102, 1301 Constitution Ave., NW., Washington, DC.
This Docket Facility is open from 8:30 a.m. to 4:30 p.m., Monday
through Friday, excluding legal holidays. The EPA Docket Center
telephone number is<PHONE_NUMBER>. 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.

FOR FURTHER INFORMATION CONTACT: Rob French, U.S. EPA, Voice-mail (734)
214-4636; E-mail<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Regulated Entities

    This proposed action would affect companies that manufacture or
sell new light-duty motor vehicles. Regulated categories and entities
include:

----------------------------------------------------------------------------------------------------------------
                                                                                Examples of potentially
            Category                             NAICS codes \A\                        regulated entities
----------------------------------------------------------------------------------------------------------------
Industry........................  336111, 336112...............................  Motor vehicle manufacturers.
Industry........................  811112, 811198, 541514.......................  Commercial Importers of
                                                                                Vehicles and Vehicle
                                                                                Components.
----------------------------------------------------------------------------------------------------------------
\A\ North American Industry Classification System (NAICS).

    This list is not intended to be exhaustive, but rather provides a
guide regarding entities likely to be regulated by this action. To
determine whether particular activities may be regulated by this
action, you should carefully examine the proposed regulations. You may
direct questions regarding the applicability of this action to the
person listed in FOR FURTHER INFORMATION CONTACT.

Table of Contents

I. Introduction
    A. History of Federal Fuel Economy Requirements
    B. Why is Today's Action Warranted?
    C. What New Requirements Are We Proposing?
    D. Today's Proposal Does Not Impact or Change CAFE Test
Procedures
    E. When Will the New Fuel Economy Estimates Take Effect?
    F. How Will EPA Communicate to the Public the Transition Between
the Old Label Values and New?
    G. Statutory Provisions and Legal Authority
II. Description of the Proposed Fuel Economy Label Methodology
    A. Proposed Fuel Economy Label Formulae
    B. Application of the Formulae To Develop Fuel Economy Labels
for Specific Vehicles
    C. Derivation of the Proposed 5-Cycle Fuel Economy Formulae
    D. Derivation of the MPG-Based Approach
    E. Effect of the New Formulae on Fuel Economy Label Values
    F. Comparison to Other Onroad Fuel Economy Estimates
III. What Major Alternatives Were Considered?
IV. Revisions to the Fuel Economy Label Format and Content
    A. Estimated Annual Fuel Cost
    B. Fuel Economy of Comparable Vehicles
    C. ``Your mileage will vary * * *'' Range of Expected Fuel
Economy Information
    D. Other Format Changes
V. Other Related Proposals
    A. Comparable Class Categories
    B. Electronic Distribution of Dealer-Supplied Fuel Economy
Booklet
    C. Testing Provisions
    D. Voluntary Fuel Economy Labeling for Vehicles Exceeding 8500
Pounds GVWR
    E. Consideration of Fuel Consumption vs. Fuel Economy as a
Metric
    F. Environmental Information on Fuel Economy Labels
VI. Projected Impacts of the Proposed Requirements
    A. Information and Reporting Burden
    B. Fees
    C. Aggregate Costs
VII. Public Participation
    A. How and To Whom Do I Submit Comments?
    B. How Should I Submit CBI to the Agency?
    C. Will There Be a Public Hearing?
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
    I. National Technology Transfer Advancement Act
IX. Statutory Provisions and Legal Authority

I. Introduction

    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. The fuel economy estimates essentially serve
two purposes: to provide consumers with a basis on which to compare the
fuel economy of different vehicles, and to provide consumers with a
reasonable estimate of the range of fuel economy they can expect to
achieve. While the estimates historically have been a valuable tool for
comparison shopping purposes, attention has been focused recently on
how closely the EPA estimates approximate consumers' real-world fuel
economy experience.
    Today, we are proposing changes to EPA's fuel economy test methods
to bring the estimates closer to the fuel economy consumers are
achieving in the real-world. We believe these estimates will provide
car buyers with useful information when comparing the fuel economy of
different vehicles. 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, 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 real-world
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 today's 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.
    It is essential that our fuel economy estimates continue to be
derived from controlled, repeatable, laboratory tests. However, the
inputs to our estimates are based on data from actual real-world
driving behavior and conditions. Because the test is controlled and
repeatable, an EPA fuel economy test result can be used for comparison
of different vehicle models and types. 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. Variations in temperature,
road grade, driving patterns, and other variables do not impact the
result of the test. While such external conditions impact fuel economy
on a trip-to-trip basis, they do not change the laboratory test result.
Therefore, a repeatable test provides a level playing field for all
vehicles, which is essential for comparing the fuel economy of one
vehicle to another. 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. No other fuel
economy test program provides the level of repeatability as the EPA
program.
    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, this approach introduces a wide number of variables--
different drivers, driving patterns, weather conditions, temperatures,
etc.--that make repeatability impossible. Our proposed fuel economy
test methods are more representative of real-world

conditions than the current fuel economy tests--yet we would retain our
practice of relying on controlled, repeatable, laboratory tests.
    The methods used today for calculating the city and highway mpg
estimates were established in the 1970's, and were adjusted in the mid-
1980's. Since these adjustments were made, America's driving behavior
has changed. In the past 20 years, speed limits have increased and
vehicles have been designed for higher power--as a result, Americans
are driving faster and more aggressively than ever before. Vehicle
technology has changed markedly, and many more vehicles are equipped
with energy-consuming accessories like air conditioning. These and
other factors are not accounted for in the current test procedures used
to determine the city and highway mpg estimates. Our analyses indicate
that if these factors were better accounted for, the city and highway
fuel economy label estimates would be generally lower and closer to the
average real-world experience of consumers.
    A fundamental issue with today's fuel economy estimates is that the
underlying test procedures do not fully represent real-world driving
conditions. Some of the key limitations are that the highway test has a
top speed of only 60 miles per hour, both the city and highway tests
are run at mild climatic conditions (75 deg. F), both tests have mild
acceleration rates, and neither test is run with the use of
accessories, such as air conditioning. However, since the time of the
last fuel economy labeling revisions in the mid-1980's, EPA has
established several additional test procedures, used for emissions
compliance purposes, which capture a much broader range of real-world
driving conditions. Specifically, these emissions test cycles capture
the effects of higher speeds, more aggressive driving (i.e., higher
acceleration rates), the use of air conditioning at higher ambient
temperatures, and colder temperature operation. Our analysis indicates
that these factors can have a significant impact on fuel economy, and
that the impacts can vary widely across different vehicles.
    Today, we are proposing that three additional emission tests,
already used by manufacturers, could be utilized to derive more
accurate fuel economy estimates. These three test procedures encompass
a much broader range of real-world driving, as they incorporate the
effects of higher speeds, more rapid accelerations, air conditioning
use, and cold temperatures. Our proposed approach would utilize these
additional emission tests, together with the current two fuel economy
tests, so that our fuel economy test methods reflect a much broader
range of driving conditions.
    In the Energy Policy Act of 2005, Congress required EPA to update
or revise adjustment factors to better reflect a variety of real-world
factors that affect fuel economy. Section 774 of the Act directs EPA to
``* * * update or revise the adjustment factors in [certain sections of
the fuel economy labeling regulations] to take into consideration
higher speed limits, faster acceleration rates, variations in
temperature, use of air conditioning, shorter city test cycle lengths,
current reference fuels, and the use of other fuel depleting
features.'' \1\ Today's proposal does take into account these
conditions and would address this statutory requirement.
---------------------------------------------------------------------------

    \1\ Pub. L. 109-58, 119 Stat. 835 (2005).
---------------------------------------------------------------------------

    Over the past few years, there have been several independent
studies comparing EPA's fuel economy estimates to the real-world
experience of consumers. These studies confirm that there is
considerable variation in real-world fuel economy, and provide further
evidence that EPA's mileage ratings often overestimate real-world fuel
economy. Although these studies differ in a number of variables,
including their test methods, driving conditions, and fuel economy
measurement techniques, they indicate that EPA's approach to estimating
fuel economy needs to be improved to better represent some key real-
world fuel economy impacts.
    Currently the same test procedures are used for both the window
sticker estimates and the fuel economy values used to determine a
manufacturer's corporate average fuel economy (CAFE), although the
label estimates are adjusted downward. This proposal would not alter
the test procedures, driving cycles, measurement techniques, or the
calculation methods used to determine CAFE. The Energy Policy and
Conservation Act of 1975 requires that CAFE values be determined from
the EPA test procedures in place as of 1975 (or procedures that give
comparable results), meaning that whatever action we take to improve
the window sticker estimates must leave in place the existing tests
used for CAFE determination. The proposed test methods for determining
the new fuel economy label estimates would be incorporated in sections
of the regulations that are entirely separate from the CAFE
regulations.
    This section begins with a history of EPA's involvement in fuel
economy programs. Then we discuss why we are taking action, including
discussions of the limitations of the current tests, various data
sources of real-world fuel economy, the additional real-world driving
conditions captured by other emissions tests procedures, and the impact
of these factors on fuel economy. We then provide an overview of our
proposed new fuel economy test methods (which are discussed in detail
in Section II), and conclude with a discussion of the relevant Federal
statutes and how they bear on this proposal.

A. History of Federal Fuel Economy Requirements

    The Energy Policy and Conservation Act of 1975 (EPCA) established
two primary fuel economy requirements: (1) Fuel economy information,
designed for public use, in the form of fuel economy labels posted on
window stickers of all new motor vehicles, and the publication of an
annual booklet of fuel economy information to be made available free to
the public by car dealers; and (2) calculation of a manufacturer's
average fuel economy and compliance with a standard (later, this
compliance program became known as the Corporate Average Fuel Economy
(CAFE) program). The responsibilities for these requirements were split
between EPA, the Department of Transportation (DOT) and the Department
of Energy (DOE). EPA is responsible for establishing the test methods
and procedures both for determining the fuel economy estimates to be
posted on the window stickers and in the annual booklet, and for the
calculation of a manufacturer's corporate average fuel economy. DOT is
responsible for administering the CAFE compliance program, including
establishing standards for non-passenger automobiles and determining if
manufacturers were complying with the applicable CAFE standards, and
assessing any penalties as needed. DOE is responsible for publishing
and distributing the annual fuel economy information booklet.
    EPA published regulations implementing portions of the EPCA statute
in 1976.\2\ The provisions in this regulation, effective with the 1977
model year, established procedures to calculate fuel economy values for
labeling and CAFE purposes that used the Federal Test Procedure (FTP or
``city'' test) and the Highway Fuel Economy Test (HFET or ``highway''
test) data as the basis for the calculations. At that time, the
fundamental process for determining fuel economy was the same for
labeling as for CAFE, except that the

CAFE calculations combined the city and highway fuel economy into a
single number.
---------------------------------------------------------------------------

    \2\ See 41 FR 38685, which is promulgated at 40 CFR Part 600.
---------------------------------------------------------------------------

    After a few years of public exposure to the fuel economy estimates
on the window stickers of new vehicles, it soon became apparent that
drivers were disappointed that they were not often achieving these
estimates on the road and that they expected them to be as accurate as
possible. In 1978, Congress recognized the concern about differences
between EPA estimated fuel economy values and actual consumer
experience and mandated a study under section 404 of the National
Energy Conservation Policy Act of 1978.\3\ In February, 1980, a set of
hearings were conducted by the U.S. House of Representatives
Subcommittee on Environment, Energy, and National Resources. One of the
recommendations in the subsequent report by the Subcommittee was that
``EPA devise a new MPG system for labeling new cars and for the Gas
Mileage Guide that provides fuel economy values, or a range of values,
that most drivers can reasonably expect to experience.'' \4\
---------------------------------------------------------------------------

    \3\ Pub. L. 95-619, Title IV, 404 (November 9, 1978).
    \4\ See House Committee on Government Operations, ``Automobile
Fuel Economy: EPA's Performance,'' Report 96-948, May 13, 1980.
---------------------------------------------------------------------------

    EPA commenced a rulemaking process in 1980 to revise its fuel
economy labeling procedures, and analyzed a vast amount of in-use fuel
economy data.\5\ In 1984, EPA published new fuel economy labeling
procedures that were applicable to 1985 and later model year
vehicles.\6\ The decision was made to retain the FTP and highway test
procedures, primarily because those procedures were also used for other
purposes--emissions certification and CAFE determination. Based on the
in-use fuel economy data, however, it was evident that the final fuel
economy values put on the labels needed to be adjusted downward in
order to more accurately reflect consumers' average fuel economy
experience. The final rule, therefore, included downward adjustment
factors for both the city and highway label fuel economy estimates. The
city values (based on the raw FTP test data) were adjusted downward by
10 percent and the highway values (likewise based on the raw highway
test data) were adjusted downward by 22 percent.
---------------------------------------------------------------------------

    \5\ See ``Passenger Car Fuel Economy: EPA and Road,'' U.S.
Environmental Protection Agency, Report no. EPA 460/3-80-010,
September, 1980, and ``Technical Support Report for Rulemaking
Action: Light Duty Vehicle Fuel Economy Labeling,'' U.S.
Environmental Protection Agency, Report no. EPA/AA/CTAB/FE-81-6,
October, 1980.
    \6\ See 49 FR 13845, April 6, 1984, and 49 FR 48149, December
10, 1984.
---------------------------------------------------------------------------

    EPA projected at the time that these adjustments would put the
average city and highway MPG values in the middle of the range of fuel
economy values experienced by consumers.\7\ During the rulemaking
process, the Office of Management and Budget (OMB) expressed concern
that fuel economy estimates based on the average experience would
result in a significant number of drivers failing to achieve that fuel
economy. They requested that EPA provide a range of values on the label
that would encompass the expected fuel economy of about 75 percent of
the driving population.\8\ To address this concern, in the final rule,
EPA required the label to contain the range of city and highway fuel
economy that most drivers should expect. Based on our understanding of
the frequency distribution of in-use fuel economy data at the time, the
range was set at plus or minus 15 percent of the stated city and
highway estimates, and appears on fuel economy labels today as small
print text. Further in this section, we discuss, in the context of
today's proposal, similar issues regarding how best to communicate to
the public the level of the city and highway mpg estimates, as well as
the range of drivers' fuel economy experience.
---------------------------------------------------------------------------

    \7\ See 49 FR 13832, April 16, 1984.
    \8\ See 49 FR 13835, April 16, 1984.
---------------------------------------------------------------------------

B. Why Is Today's Action Warranted?

    The fundamental problem with the current fuel economy estimates is
that the test procedures on which they are based do not reflect a broad
enough range of in-use driving conditions. The current test procedures
omit several critical factors that are prevalent in the real-world and
that can have a significant impact on fuel economy. Key among these are
higher speeds, faster accelerations, the use of air conditioning, and
colder temperatures. The impact of these factors on fuel economy can
vary widely from vehicle to vehicle. However, for emissions compliance,
we have already developed additional test procedures to account for
these factors, and these test procedures are already being regularly
used by the auto companies. Today, we are proposing to use these tests,
in conjunction with the existing fuel economy tests, as an input into
the calculation of fuel economy estimates. In doing so, the fuel
economy test methods would reflect a much broader range of real-world
conditions than they do today.
    There is broad-based support among automobile manufacturers and
other stakeholders proposing changes to current fuel economy estimates.
Congress recognized the need for action by including a provision in the
Energy Policy Act of 2005 requiring EPA to revise its fuel economy
estimates. EPA has worked closely with auto manufacturers, states, and
other organizations in developing this proposed rule.
    Bluewater Network petitioned EPA to revise the fuel economy
labeling test procedures.\9\ EPA published a Federal Register notice
requesting comments on the petition, and received over 33,000
comments.\10\ Nearly all of these comments support the revision of
EPA's fuel economy estimates to better reflect real world driving.
Today's proposal is responsive to this petition.
---------------------------------------------------------------------------

    \9\ The Bluewater Network petition was submitted to EPA on June
7, 2002.
    \10\ See 69 FR 16188, March 29, 2004.
---------------------------------------------------------------------------

1. Fuel Economy Labels Could Be Improved To Better Reflect Real-World
Driving
    First, it is important to stress that the EPA city and highway mpg
ratings are estimates--they are not intended to give consumers an exact
indication of the fuel economy they will achieve. The complete range of
consumer fuel economy experience can not be represented perfectly by
any one estimate. Fuel economy varies based on a wide range of factors,
which we have discussed above. There will always be consumers that
achieve real-world fuel economy both better and worse than a given
estimate.
    In the past few years, there have been a number of studies,
conducted by a variety of sources, suggesting that there is often a
shortfall between the EPA estimates and real-world fuel economy.
Several organizations have provided consumers with their own fuel
economy estimates, which in some cases vary from EPA's estimates. For
example, Consumer Reports utilizes on-road driving to measure fuel
economy under a variety of conditions. They derive city, highway, and
overall fuel economy estimates, and their methods clearly demonstrate
the large degree of variation across vehicles. While their city fuel
economy estimates fall on average below the EPA label values, their
highway estimates are, on average, higher than the EPA label values.
Consumer Reports' overall fuel economy estimates range from 27 percent
below to 20 percent above the EPA overall rating. The Automobile
Association of America (AAA) likewise publishes the

fuel economy results they achieve in their annual auto guide for new
cars and trucks. In their 2004 auto guide, about half of their
estimates were below the EPA combined city/highway value, and about one
half were above the EPA city/highway combined value. Their estimates
ranged from 40 percent lower than EPA's to 22 percent higher, again
reflecting a great deal of vehicle-to-vehicle variation. Other sources
of fuel economy data include Edmunds.com, the Department of Energy's
(DOE) ``Your MPG'' database on the fueleconomy.gov Web site, and DOE's
FreedomCar program.
    Each of these studies differs in its test methods, driving cycles,
sampling of vehicles, and methods of measuring fuel economy. There are
strengths and weaknesses of each study, which we discuss further in
Section II and in the Draft Technical Support Document. Collectively,
these studies indicate there are many cases where real-world fuel
economy falls below the EPA estimates. The studies also indicate that
real-world fuel economy varies significantly depending on the
conditions under which it is evaluated. Nevertheless, taken as a whole,
these studies reflect a wide range of real-world driving conditions,
and show that fuel economy can be much lower than EPA's estimates if
more real-world conditions are considered.
    The fundamental problem with the current fuel economy estimates is
that the test procedures on which they are based are missing a number
of critical factors that exist in real-world driving and have a
significant impact on fuel economy. The following section discusses the
limitations of our existing fuel economy test procedures.
2. Today's Fuel Economy Tests Do Not Represent the Full Range of
Driving Conditions
    The current city and highway fuel economy tests do not represent
the full range of real-world driving conditions. The 1985 adjustment
factors were designed to ensure that the fuel economy estimates across
the vehicle fleet reflected the average impacts of a number of
conditions not represented on the tests. However, as we noted earlier,
many changes have occurred since then that make it once again a
reasonable time to reevaluate the fuel economy test methods. Given the
significant degree of variation that is apparent across vehicles, we
believe it is important to reconsider the approach of ``one-size-fits-
all'' adjustment factors and instead move to an approach that more
directly reflects the impacts of fuel economy on individual vehicle
models.
    The city fuel economy estimate is based on the Federal Test
Procedure (FTP), which was designed to measure a vehicle's tailpipe
emissions under urban driving conditions. The driving cycle used for
the FTP is called the LA-4, which was developed in the mid-1960's to
represent home-to-work commuting in Los Angeles. The FTP is also one of
the tests used to determine emissions compliance today. The FTP
includes a series of accelerations, decelerations, and idling (such as
at stop lights). It also includes starting the vehicle after it has
been parked for an extended period of time (called a ``cold start''),
as well as a start on a warmed-up engine (called a ``hot start''). The
total distance covered by the FTP is about 11 miles and the average
speed is about 21 mph, with a maximum speed of about 56 mph.
    The highway fuel economy estimate is based on the Highway Fuel
Economy Test (HFET), which was developed by EPA in 1974 and was
designed to represent a mix of interstate highway and rural driving. It
consists of relatively constant higher-speed driving, with no engine
starts or idling time. The HFET covers a distance of about 10 miles, at
an average speed of 49 mph and a top speed of about 60 mph.
    There are several key limitations in the FTP and HFET tests that
cause them to not adequately reflect real-world driving today. First,
most consumers understandably think ``highway'' fuel economy means the
fuel economy you can expect under freeway driving conditions. In fact,
the highway test has a top speed of only 60 mph, since the test was
developed more than 20 years ago to represent more rural driving
conditions at a time when the national speed limit was 55 miles per
hour. The national speed limit since has been eliminated, states have
established speed limits of 65 to 70 miles per hour, and much driving
is at even higher speeds. Recent real-world driving studies indicate
that about 28 percent of driving (vehicle miles traveled, or VMT) is at
speeds of greater than 60 mph. (This analysis is detailed in the Draft
Technical Support Document). These studies also show that 33 percent of
real-world driving VMT falls outside the FTP/HFET speed and
acceleration activity region. Thus, a substantial amount of high speed
driving is not captured at all in today's FTP or HFET tests. This is a
critical weakness in our current fuel economy test procedures. Since
higher speed driving has a negative impact on fuel economy,
incorporating these higher speed driving conditions into the fuel
economy tests would lower the fuel economy estimates.
    Second, the maximum acceleration rates of both the FTP and HFET
tests are a relatively mild 3.3 miles-per-hour per second, considerably
lower than the maximum acceleration rates seen in real-world driving.
Recent real-world driving studies indicate that maximum acceleration
rates are as high as 11 to 12 mph/sec and significant activity occurs
beyond 3.3 mph/sec. Even at the time these tests were first developed,
the real-world accelerations were higher than 3.3 mph/sec, but the test
cycle's acceleration rates needed to be constrained to the mechanical
limitation of the dynamometer test equipment. These constraints no
longer exist with today's dynamometers, so we now have the ability to
incorporate higher maximum acceleration rates that more closely reflect
those of actual driving. In fact, we have incorporated higher
acceleration rates into a test recently developed for emissions
compliance, which we discuss in the next section. As with high speed
driving, higher acceleration rates have a negative impact on fuel
economy; thus, if these higher accelerations were factored into our
fuel economy methods, the estimates would be lower.
    The maximum deceleration rate of the FTP and HFET tests is
important to consider as well, because it relates to the regenerative
breaking effect of hybrid electric vehicles. The FTP and HFET tests
include a mild maximum deceleration rate of -3.3 mph/sec; yet in recent
real-world driving rates as high as -11 to -17 mph/sec were recorded.
Under higher deceleration rates, the effects of regenerative breaking
for hybrid electric vehicles are diminished, thereby lowering fuel
economy. In this regard, today's FTP and HFET tests result in better
fuel economy, which is seldom achieved under actual driving conditions.
    Third, both tests are run at mild ambient conditions (approximately
75 degrees Fahrenheit), while real-world driving occurs at a wide range
of ambient temperatures. Fuel economy is lower at temperatures colder
or warmer than the 75 degree F test temperature. Only about 20 percent
of VMT occurs between 70 and 80 degrees F--approximately 15 percent of
VMT occurs at temperatures above 80 degrees F, and 65 percent occurs
below 70 degrees F. Moreover, neither the FTP nor HFET tests are run
with accessories operating, such as air conditioners, heaters, or
defrosters. These accessories, most notably air conditioning, can have
a significant impact on a vehicle's fuel economy.

    Finally, there are many factors that affect fuel economy that
cannot be replicated on dynamometer test cycles in a laboratory. These
include road grade, wind, vehicle maintenance (e.g., tire pressure),
snow/ice, precipitation, fuel effects, and others. It is not possible
to develop a test cycle that captures the full range of factors
impacting fuel economy. However, it is clear that the FTP and HFET
tests alone are missing some critical elements of real-world driving.
All of these factors have a negative impact on fuel economy. This
largely explains why our current estimates often do not reflect
consumers' real-world fuel economy experience. However, since the 1985
adjustment factors were established, EPA has adopted several new test
cycles for emission compliance purposes, which collectively represent a
much broader range of in-use driving conditions than those captured by
the FTP and HFET tests. These additional emission tests, discussed
below, can be brought into the fuel economy estimate calculations.
3. Additional Emissions Tests Reflect a Broader Range of Real-World
Driving Conditions
    Since 1984 when we last updated the fuel economy estimate
methodology, EPA has established several new test cycles for emissions
certification. EPA was concerned that the FTP omitted many critical
driving modes and conditions that existed in actual use, and that
emissions could be substantially higher during these driving modes
compared to the FTP. Manufacturers were frequently designing their
vehicles' emission control systems to meet the specified FTP test
conditions, and actual emission levels could be quite different under
the broader range of real-world ``off-cycle'' conditions.
    The need for these actions was recognized by Congress, in the
passage of Sections 206(h) and 202(j) of the Clean Air Act Amendments
of 1990 (CAAA).\11\ Section 206(h) required EPA to study and revise as
necessary the test procedures used to measure emissions, taking into
consideration the actual current driving conditions under which motor
vehicles are used, including conditions relating to fuel, temperature,
acceleration, and altitude. Section 202(j) of the CAAA required EPA to
establish emission standards for carbon monoxide under cold (20 deg. F)
temperature conditions.
---------------------------------------------------------------------------

    \11\ See 42 U.S.C. 7525(h), 42 U.S.C. 7521(j).
---------------------------------------------------------------------------

    In 1992, EPA published rules implementing the 202(j) cold
temperature testing requirement, acknowledging that the ambient
temperature conditions of the FTP test (run between 68 and 86 [deg]F)
do not represent the full range of ambient temperature conditions that
exist across the United States and that cold temperature had different
emissions effects on different vehicle designs.\12\ EPA's cold
temperature emission regulations required manufacturers to conduct FTP
testing at 20 [deg]F. By promulgating this new test procedure and
associated emission standard, EPA sought to encourage manufacturers to
employ better emission control strategies that would improve ambient
air quality across a wider range of in-use conditions.
---------------------------------------------------------------------------

    \12\ See 57 FR 31888, July 17, 1992.
---------------------------------------------------------------------------

    In fulfillment of the 206(h) CAAA requirement, EPA published a
report in 1993 which concluded that the FTP cycle did not represent the
full range of urban driving conditions that could impact the in-use
driving emission levels.\13\ Consequently, EPA promulgated a rule in
1996 that established two new test procedures, with associated emission
standards, that addressed certain shortcomings with the current
FTP.\14\ Known as the ``Supplemental FTP,'' or ``SFTP,'' these
procedures, similar to the cold temperature FTP, encouraged the use of
the better emission controls across a wider range of in-use driving
conditions in order to improve ambient air quality.
---------------------------------------------------------------------------

    \13\ U.S. Environmental Protection Agency. Federal Test
Procedure Review Project: Preliminary Technical Report. U.S.
Environmental Protection Agency, No. EPA420-R-93-007, May 1993.
Website: http://www.epa.gov/otaq/sftp.htm.

    \14\ See 61 FR 54854 published on October 22, 1996.
---------------------------------------------------------------------------

    One of the new test cycles, the US06, was designed to address high
speed, aggressive driving behavior (with more severe acceleration rates
and speeds) as well as rapid and frequent speed fluctuations. The US06
test contains both lower-speed city driving and higher-speed highway
driving modes.\15\ Its top speed is 80 mph, and average speed is 48
mph. The top acceleration rate exceeds eight mph per second. The other
new SFTP test, the SC03, was designed to address air-conditioner
operation under a full simulation of high temperature (95 [deg]F), high
sun-load, and high humidity. The SC03 drive cycle was designed to
represent driving immediately following a vehicle startup, and rapid
and frequent speed fluctuations.\16\ Its top speed is about 55 mph and
average speed is 22 mph. The top acceleration rate is about five mph
per second.
---------------------------------------------------------------------------

    \15\ See 40 CFR Part 86 Appendix I (g).
    \16\ Ref. 40 CFR Part 86 Appendix I (h).
---------------------------------------------------------------------------

    The basis for the SFTP rulemaking was a study of real-world driving
in four cities, Baltimore, Spokane, Atlanta and Los Angeles, where
driving activity was measured on instrumented vehicles as well as by
chase cars.17 18 At that time, it was found that 18 percent
of the driving (in Baltimore) occurred outside of the speed/
acceleration distribution of the FTP drive schedule. More recent real-
world driving activity data indicates that driving has become even more
aggressive than it was in 1992. Recent real-world activity data
collected in California and Kansas City found that about 28 percent of
driving (vehicle miles traveled) is at speeds greater than 60 mph.
Further, about 33 percent of recent real-world driving falls outside of
the FTP/HFET speed and acceleration activity
region.19 20 21 22 This is based on extensive chase car
studies in California and instrumented vehicle studies in Kansas City.
Our assessment of these recent real-world driving activity studies is
described in detail in the Draft Technical Support Document.
---------------------------------------------------------------------------

    \17\ Final Technical Report on Aggressive Driving Behavior for
the Revised Federal Test Procedure Notice of Proposed Rulemaking,
1995. Website: http://www.epa.gov/otaq/sftp.htm.

    \18\ U.S. Environmental Protection Agency. Federal Test
Procedure Review Project: Preliminary Technical Report. U.S.
Environmental Protection Agency, No. EPA420-R-93-007, May 1993.
Website: http://www.epa.gov/otaq/sftp.htm.

    \19\ Sierra Research, Inc., ``Task Order No. 2 SCF Improvement--
Field Data Collection,'' Sierra Report No. SR02-07-04, July, 2002.
    \20\ U.S. EPA Draft Technical Support Document ``Fuel Economy
Labeling of Motor Vehicles: Revisions to Improve Calculation of Fuel
Economy Estimates,'' December, 2005.
    \21\ Brzezinski, D., E. Nam, J. Koupal, G. Hoffman. Changes in
Real World Driving Behavior: Analysis of Recent Driving Activity
Data. Proceedings of the 15th Coordinating Research Council On Road
Vehicle Emissions Workshop, 2005.
    \22\ Eastern Research Group. Late Model Vehicle Emissions and
Fuel Economy Characterization Study: Addendum to the Kansas City
Exhaust Characterization Study-Draft Report. ERG No.
0<IP_ADDRESS>, September 26, 2005.
---------------------------------------------------------------------------

    Clearly, the FTP and HFET tests alone do not fully capture the
broad range of real-world driving conditions. In order for EPA's fuel
economy tests to be more representative of key aspects of real-world
driving, it is critical that we consider the test conditions
represented by these additional emission tests.
4. Fuel Economy on Driving Modes Represented by Additional Emissions
Tests is Lower for Many Vehicles
    As discussed above, there are several key conditions missing from
the current fuel economy test procedures that are prevalent in real-
world driving. These conditions--higher speeds, faster

accelerations, air conditioning operation, and cold temperatures--have
already been incorporated into our test procedures for emissions
compliance, as a result of our finding in the 1990's that they have a
significant impact on emissions. Our analysis below demonstrates that
these additional driving conditions can also have a significant impact
on fuel economy--and that these impacts vary widely from vehicle to
vehicle. Thus, we believe that these factors need to be included in our
fuel economy test methods.
    We analyzed fuel economy data collected by manufacturers for
emissions certification purposes in the 2003, 2004 and 2005 model
years. This analysis included data from all five tests used for
emissions compliance today, including the FTP, HFET, US06, SC03, and
Cold Temperature FTP. The fuel economy measured on the standard fuel
economy tests (FTP and HFET) was compared to the fuel economy on the
other emissions certification tests (US06, SC03, and Cold FTP) in order
to assess the impact of these factors on fuel economy. The analysis
includes data from more than 400 vehicles. Comparisons were made to the
unadjusted city and highway fuel economy test results, and the findings
are summarized below. Because so many other factors bear on real-world
consumer experience, it is important to point out that these
comparisons are not intended to indicate the exact impact of a given
factor on real-world fuel economy. However, comparing these different
test results is informative because we establish the relative magnitude
of the impacts and of the variation across vehicles. The entire report
of this analysis is in the docket for this rulemaking.\23\
---------------------------------------------------------------------------

    \23\ U.S. Environmental Protection Agency, Office of
Transportation and Air Quality, ``Vehicle Fuel Economy Labeling and
The Effect of Cold Temperature, Air-Conditioning Usage and
Aggressive Driving on Fuel Economy,'' Draft Staff Report, August
2005.
---------------------------------------------------------------------------

    a. Cold Temperature Operation. To assess the impact of cold
temperature operation on fuel economy, we compared the fuel economy
measured over the Cold FTP test directly to that over the standard FTP
test. The driving cycles in these two tests are identical (i.e., the
LA4 cycle). Both tests include both cold and hot starts at their
respective ambient temperatures, and both tests are generally run with
accessories turned off. The difference in fuel economy should therefore
be entirely due to the difference in ambient temperature: 20 [deg]F
versus 75 [deg]F.
    On average, fuel economy over the Cold FTP was about 12 percent
lower than over the standard FTP. There was wide vehicle-to-vehicle
variation, with the loss in fuel economy due to the cold conditions as
much as 40 percent. Figure I.B-1 below shows the range of cold
temperature impacts. Hybrid vehicles tended to show the greatest
sensitivity to cold temperature. Of the six vehicles showing a cold
temperature impact of greater than 30 percent, five are hybrids.
Overall, conventional gasoline vehicles averaged a cold temperature
effect of about -11 percent, while the impact on hybrid vehicles
averaged about -32 percent.
[GRAPHIC] [TIFF OMITTED] TP01FE06.000

    b. Air Conditioning. To assess the impact of air conditioning on
fuel economy, we compared the fuel economy measured over the SC03 test
to a comparable portion of the FTP. The SC03 test is run with the air-
conditioning turned onto its maximum setting in a test cell set at 95
[deg]F with strong sun load and moderate humidity. On average, air
conditioner operation at 95 [deg]F reduced fuel economy by about 21
percent. The impact of air conditioning ranged from -41 percent to -25
percent for more than a third of the vehicles. Similar to the cold
temperature impacts, there was a great deal of vehicle-to-vehicle
variation in the impact of air conditioning on fuel economy. Figure
I.B-2 shows the distribution of the percentage differences (negative
numbers indicate lower fuel economy over SC03). As can be seen in the
figure, the vast majority of vehicles show an impact of -27.5

percent to -7.5 percent. Hybrid vehicles tended to show greater
sensitivity to air conditioning operation than conventional vehicles.
The effect of air conditioning operation reduced hybrid fuel economy by
31 percent, 50 percent greater than the 20 percent impact on
conventional vehicle fuel economy.
[GRAPHIC] [TIFF OMITTED] TP01FE06.001

    c. Aggressive and High-Speed Driving. The US06 test was designed to
address aggressive driving behavior, such as high acceleration rates
and high speeds. The US06 test contains both lower-speed but aggressive
urban driving and higher-speed highway driving modes. Because of the
different driving modes contained on the US06 test, for the purpose of
assessing the impacts of high speed and aggressive driving we developed
a combination of the city and highway tests which is roughly comparable
to that contained in the US06 cycle.
    On average, the fuel economy over the US06 cycle was almost 30
percent lower than over the composite FTP and HFET fuel economy. The
observed impacts ranged from -44 percent to -25 percent for more than
80 percent of the vehicles. Figure I.B-3 shows the distribution of per
vehicle impacts due to the aggressive driving of the US06 cycle. Hybrid
vehicles showed a slightly greater impact of aggressive driving on fuel
economy than conventional gasoline vehicles (33 percent versus 29
percent, respectively).

[GRAPHIC] [TIFF OMITTED] TP01FE06.002

    d. Conclusions. Many of the vehicles whose fuel economies were most
affected by these driving conditions were hybrids and other high mile-
per-gallon vehicles. In general, 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 show up as a relatively larger
percentage fuel consumption increase. Two, because of the non-linearity
of fuel economy with respect to fuel consumption, an increase in fuel
consumption 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.
    Hybrids, most of which achieve relatively high mpg and therefore
share the issues discussed above, also face some additional challenges.
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.
    This analysis clearly shows that the driving conditions represented
by US06, SC03 and Cold FTP tests can have substantial, measurable
negative impact on fuel economy. There also is a large amount of
vehicle-to-vehicle variation--that is, different vehicles are impacted
differently by these factors. These findings call into question the
appropriateness of the continued use of the current ``one-size-fits-
all'' 10 and 22 percent adjustment factors applied, respectively, to
FTP and HFET fuel economy test results. The FTP and HFET tests clearly
do not adequately reflect the broad range of conditions that exist in
today's real-world driving. The 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. Thus,
these additional emission test cycles need to be brought into the fuel
economy test methods, so that the estimates themselves will be more
representative of the fuel economy consumers can expect to achieve in
the real-world.

C. What New Requirements Are We Proposing?

    We are proposing to revise and improve the methods used to
determine the city and highway fuel economy estimates by incorporating
fuel economy results over a broader range of driving conditions. An
overview of this proposal is provided below. Section II provides a
detailed explanation of the proposed new test methods, as well as the
data and analysis upon which it is based.
    In addition, we are proposing minor changes to revise the format
and content of the fuel economy label to make the information more
useful to consumers. We also are proposing minor changes related to the
fuel economy information program, including revising the comparable
vehicle classes and adding a new provision for the electronic
distribution of the annual Fuel Economy Guide. An overview of each of
these proposals follows.
1. Revised Test Methods for Calculating City and Highway Fuel Economy
Estimates
    Today's proposal would revise the test methods by which the city
and highway fuel economy estimates are calculated. We are proposing to
replace the current method of adjusting the city (FTP) test result
downward by 10 percent and the highway (HFET) test result downward by
22 percent. Instead, we are proposing a new approach that incorporates
additional test methods that address factors that impact fuel economy,
but are missing from today's tests--specifically, higher speeds, more
aggressive driving (e.g., higher acceleration rates), the use of air
conditioning, and the effect of cold temperature. The proposed test
methods

would bring into the fuel economy estimates the test results from the
five emissions tests in place today: FTP, HFET, US06, SC03, and Cold
FTP. Thus, we refer to this as the ``5-cycle'' method. Under our
proposal, rather than basing the city mpg estimate solely on the
adjusted FTP test result, and the highway mpg estimate solely on the
adjusted HFET test result, each estimate would be based on a
``composite'' calculation of all five tests, weighting each
appropriately to arrive at new city and highway mpg estimates. The new
city and highway estimates would each be calculated according to
separate city and highway ``5-cycle'' formulae that are based on fuel
economy results over these five tests. The conditions represented by
each test would be ``weighted'' according to how much they occur over
average real-world city or highway driving. For example, we have
derived weightings to represent driving cycle effects, trip length, air
conditioner compressor-on usage, and operation over various
temperatures. This methodology is described in detail in Section II.
    We also are proposing a downward adjustment to account for effects
that are not reflected in our existing five test cycles. 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. Thus, we
need to account for these factors in our new test methods, as they will
lower a driver's fuel economy beyond those factors we are accounting
for from our existing test cycles. We are proposing an 11 percent
downward adjustment to account for these non-dynamometer effects. Our
basis for this downward adjustment factor is detailed in Section II.C.3
and the Draft Technical Support Document.
    The 5-cycle approach, including this 11 percent downward adjustment
factor to account for non-dynamometer effects, will result in city and
highway estimates that reflect average fuel economy. We are proposing
to continue to set the city and highway mpg estimates at the average,
or mean, level. However, we understand that many drivers expect to
achieve or exceed the fuel economy indicated by these mpg estimates. By
continuing to set the estimates at the average level, by definition,
half of drivers will get worse fuel economy than the label values. We
seek comment on whether the city and highway estimates should be set a
level that is lower than average--for example, to ensure that 75
percent, or even more, of drivers achieve or exceed the label values.
    Because the 5-cycle method is inherently vehicle-specific, the
difference between today's values and the new fuel economy estimates
could vary widely from vehicle to vehicle. Today's proposed approach
would result in city fuel economy estimates that are between 10 to 20
percent lower than today's labels for the majority of conventional
vehicles. For vehicles that achieve generally better fuel economy, such
as gasoline-electric hybrid vehicles, new city estimates would be about
20 to 30 percent lower than today's labels. The new highway fuel
economy estimates would be 5 to 15 percent lower for the majority of
vehicles, including hybrids.
    Today's proposal would greatly improve the EPA fuel economy
estimates, so that they come closer to the fuel economy that consumers
achieve in the real-world. However, as discussed previously in this
notice, these are still estimates. Even with the improved fuel economy
test methods proposed today, some consumers will continue to get fuel
economy that is higher or lower than the new estimates.
    Under this new 5-cycle approach, some auto manufacturers have
expressed concern about the potential for increased test burden. The
three additional emission tests that we propose to include in the fuel
economy calculation are run today on a much more limited number of
vehicle groups than are the FTP and HFET tests. Typically, for every 3-
4 FTP and HFET tests conducted, only one US06 or SC03 test is run, and
cold FTP testing is even more limited. If we were to require full 5-
cycle testing across all vehicle types, the testing demands for the
auto industry could increase dramatically, and could trigger the need
for a major expansion of their testing facilities.
    Thus, we are proposing to implement the new fuel economy test
methods in a way that gives the auto industry sufficient lead time to
plan for their increased testing needs. This enables us to implement an
improved fuel economy label methodology as soon as possible--in the
2008 model year. We also are implementing an approach that mitigates
the testing burden where warranted. We have done this in two key ways.
    First, for the first three model years (2008 through 2010), we
would provide manufacturers with the option of using a scale of
adjustments based on an analysis of data developed from the 5-cycle
method. This approach, called the mpg-based approach, incorporates the
effects of higher speed/aggressive driving, air conditioning use, and
colder temperatures, but less directly than the 5-cycle vehicle-
specific method. The mpg-based adjustments were derived by applying the
5-cycle formulae to a data set of recent fuel economy test data, and
developing a regression line through the data. (See Section II for a
full description of this approach). These adjustments differ based on
the mpg a vehicle obtains over the FTP (City) or HFET (Highway) tests.
In other words, every vehicle with the same mpg on the FTP test would
receive the same adjustment for its city fuel economy label. Likewise,
every vehicle with the same mpg on the HFET test would receive the same
adjustment for its highway fuel economy label. This method of
adjustment would not require any testing beyond the FTP/HFET tests
already performed today, thus, it can be implemented sooner than the 5-
cycle approach as an interim improvement to our fuel economy test
methods. However, during this timeframe, manufacturers may choose to
run full 5-cycle testing for any of their vehicle models. This approach
would provide consumers with more accurate estimates, while allowing
the industry the necessary lead time to prepare for the necessary
testing under the 5-cycle approach.
    Second, when we move to the 5-cycle vehicle-specific approach in
model years 2011 and beyond, we are proposing criteria that would
select specific vehicle groups for full 5-cycle testing, rather than
requiring complete 5-cycle data generation for every vehicle. We
believe this approach would result in fuel economy estimates that are
generally as accurate as they would be under full 5-cycle testing. In
other words, we are only requiring full 5-cycle testing where we can
predict with reasonable certainty that the fuel economy results under
the 5-cycle method would yield a significantly different result than
the mpg-based adjustments.
    We propose to establish a tolerance band around the mpg-based city
and highway adjustment lines. Manufacturers would be required to
calculate a 5-cycle fuel economy estimate for each vehicle group for
which 5-cycle data exists for emissions purposes. If the 5-cycle fuel
economy estimate for this vehicle group falls below the respective
tolerance band around the mpg adjustment line, then the manufacturer
would be eligible to use the mpg-based adjustments for each

vehicle configuration represented by that set of 5-cycle data. That is,
the 5-cycle vehicle group may include within it several vehicle
groupings, or specific vehicle model types, for which additional FTP/
HFET data is available. The manufacturer would be able to use the MPG
line to determine the fuel economy label adjustments for each of these
model types with associated FTP/HFET test data. Fuller 5-cycle testing
would be required for all vehicles represented by a vehicle group for
which the 5-cycle fuel economy is below the tolerance bands. Section II
further describes the level of these tolerance bands and how this
concept would be implemented. A full discussion of our proposed
methodology and results is contained in Section II.
2. Revised Label Format
    To make the label more easily understood by consumers, we are also
proposing changes to the fuel economy label format specified in the
regulations. The proposed changes include updating the look of the
label, simplifying its contents, and improving its graphics, among
others. The purpose of these changes is to present the fuel economy
information in a manner that is easier for the consumer to understand
and use. The proposed changes are discussed in detail in Section IV.
3. Revised Comparable Vehicle Classes
    The comparable vehicle classes are currently defined in EPA's fuel
economy regulations. They are needed to fulfill the EPCA statutory
requirement to provide fuel economy information about comparable
vehicles on the label.\24\ These classes were last revised in 1984.
Since that time, there have been some significant changes to vehicle
designs which warrant changes to the defined classes. Briefly, we are
proposing to add SUV and Minivan classes, and to consolidate some
classes which have become less prevalent in the market. This is
discussed in more detail in Section V.
---------------------------------------------------------------------------

    \24\ See 49 U.S.C. 32908(b)(1)(C).
---------------------------------------------------------------------------

4. Minor Changes in Certain Test Procedures
    We are proposing minor procedural changes in certain test
procedures. First, the US06 drive cycle contains elements of both city
and highway types of driving, yet the exhaust sample is collected in
only one ``bag,'' yielding one overall fuel economy result. In order to
more accurately reflect the city portion of the drive cycle into the
city fuel economy estimate, and the highway portion of the US06 into
the highway fuel economy estimate, we are proposing a revised test
protocol that would require collecting the exhaust sample into two
bags, thus providing separate results from the city and highway
portions. This has the benefit of more accurately capturing how a
vehicle's fuel economy would be impacted over the various types of
driving reflected in the cycle, but with very minimal cost impact.
    Second, today diesel vehicles are not required to run the cold FTP
test since they are currently exempt from the cold carbon monoxide
standard. We are proposing that diesel vehicles be required to run this
test for 5-cycle fuel economy purposes.
    Finally, the current cold FTP test gives manufacturers the option,
but does not require them to, run the heater or defroster while
performing this test at 20 degrees F. We expect that in most cases in
the real world, consumers would indeed be running these accessories in
colder temperatures, which will impact their fuel economy. We also
understand that some, but not all, manufacturers today do run these
accessories during the test. Therefore, to ensure this test most
accurately reflects real-world conditions, and to ensure these
conditions are run uniformly across manufacturers, we are seeking
comment on requiring manufacturers to run the heater and defroster
while performing the cold FTP test.
5. Other Fuel Economy-Related Topics
    In addition to the proposed fuel economy label calculations and
label formats, we are proposing a few other changes related to the fuel
economy labels and annual fuel economy booklet. These topics are
discussed in Section V.

D. Today's Proposal Does Not Impact or Change CAFE Test Procedures

    Today's proposal does not alter the FTE and HFET driving cycles,
the measurement techniques or the calculation methods used to determine
CAFE. EPCA requires that CAFE 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.\25\ Today's proposal will not adjust the CAFE calculations; the
new method for calculating fuel economy label estimates will fall under
regulations that are separate from the CAFE regulations (currently, the
regulations for calculating CAFE are in 40 CFR 600.501-85 through 513-
91).
---------------------------------------------------------------------------

    \25\ See 49 U.S.C. 32904(c).
---------------------------------------------------------------------------

E. When Will the New Fuel Economy Estimates Take Effect?

    We want the public to benefit from the improved information
provided by the new fuel economy estimates as soon as possible.
Therefore, we propose that these new regulations take effect with the
2008 model year, which will be available for sale at dealers in the
fall of 2007. We believe this is the earliest possible date for
implementation, since some manufacturers typically begin certifying
model year 2008 vehicles as early as late 2006. We also encourage
manufacturers to voluntarily utilize these new methods sooner, and are
therefore proposing that manufacturers may voluntarily comply with the
new regulations as soon as the final regulations are published.

F. How Will EPA Communicate to the Public the Transition Between the
Old Label Values and New?

    To ensure that the public understands the relationship between the
old estimates and the new, EPA plans to conduct extensive public
outreach concurrent with the implementation of a final rule. We will
provide information about the new estimates and how to use them via
web-based information, fact sheets, and other communication methods.
This information will be designed to explain all aspects of any new
calculation methods, including their impact on label estimates from
previous model years.

G. Statutory Provisions and Legal Authority

1. EPCA
    The statutory authority for today's proposal is provided by the
Energy Policy and Conservation Act (EPCA). Most of the labeling
provisions applicable to vehicle labeling and information are found at
49 U.S.C. 32908. This section restricts EPA's requirements for fuel
economy labeling to automobiles rated at no more than 8,500 pounds
gross vehicle weight. It requires manufacturers of automobiles to
attach a fuel economy label to a prominent place on each automobile
manufactured in a model year and also requires the dealers to maintain
the label on the automobile.\26\
    EPCA requires EPA to promulgate regulations to measure and
calculate fuel economy.\27\ To the extent practicable, EPCA requires
that fuel

economy tests be carried out with emissions tests performed under
section 206 of the Clean Air Act (42 U.S.C. 7525).\28\
    EPA's resulting fuel economy regulations are found in 40 CFR Part
600. EPA has broad discretion in determining how to measure and
calculate fuel economy for purposes of labeling under 49 U.S.C.
32908(b).\29\ The fact that EPA's current fuel economy labeling
regulations includes the reporting of separate ``city'' and ``highway''
fuel economy is a result of a series of EPA regulations as discussed in
Section I.A. above. Thus, in developing today's proposal (discussed in
Section III below), we considered, but ultimately are not proposing,
other methodologies for reporting fuel economy.
---------------------------------------------------------------------------

    \26\ See 49 U.S.C. 32908(b)(1).
    \27\ See 49 U.S.C. 32904(c).
    \28\ Id.
    \29\ EPCA places testing restrictions on corporate average fuel
economy (CAFE), discussed below. Today's proposal does not impact
those restrictions.
---------------------------------------------------------------------------

    EPCA imposed some specific requirements for the information to be
included on the fuel economy label.\30\ Today's proposal retains these
items:
---------------------------------------------------------------------------

    \30\ See 49 U.S.C. 32908(b)(2)(A) through (F).
---------------------------------------------------------------------------

    a. The fuel economy of the automobile.
    b. The estimated annual fuel cost of operating the automobile.
    c. The range of fuel economy of comparable automobiles of all
manufacturers.
    d. A statement that a booklet is available from the dealer to
assist in making a comparison of fuel economy of other automobiles
manufactured by all manufacturers in that model year.
    e. The amount of the automobile fuel efficiency tax imposed on the
sale of the automobile under section 4064 of the Internal Revenue Code
of 1986 (26 U.S.C. 4064).
    f. Other information required or authorized by the Administrator
that is related to the information required [within items a. through
d.]
    EPCA also 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 EPA.\31\ Thus, today's
proposal retains the requirement to report fuel economy as miles-per-
gallon.
---------------------------------------------------------------------------

    \31\ See 49 U.S.C. 32901(a)(10).
---------------------------------------------------------------------------

    EPCA requires EPA to prepare a fuel economy booklet containing
information that is ``simple and readily understandable.'' \32\ It
further instructs DOE to publish and distribute the booklet. EPA is
required to ``prescribe regulations requiring dealers to make the
booklet available to prospective buyers.'' \33\ This booklet is more
commonly known as the annual ``Fuel Economy Guide.''
---------------------------------------------------------------------------

    \32\ See 49 U.S.C. 32908(c).
    \33\ Id.
---------------------------------------------------------------------------

    EPCA also contains statutory provisions for average fuel economy
(known widely as ``Corporate Average Fuel Economy,'' or CAFE).\34\
Under these provisions, EPA is required to prescribe testing and
calculation procedures to measure fuel economy for each model and
calculate average fuel economy for a manufacturer, using the same
procedures that were used for 1975 model year passenger automobiles
(weighted 55 percent urban cycle and 45 percent highway cycle), or
procedures that give comparable results.\35\ This requirement does not
apply to the fuel economy information manufacturers apply to the fuel
economy label required in 49 U.S.C. 32908(b).\36\
---------------------------------------------------------------------------

    \34\ See 49 U.S.C. 32902-32904.
    \35\ See 49 U.S.C. 32904(c).
    \36\ Id.
---------------------------------------------------------------------------

    EPA is also required to consult with the Federal Trade Commission
(FTC), DOT and DOE in carrying out the fuel economy information
requirements in EPCA.\37\
---------------------------------------------------------------------------

    \37\ See 49 U.S.C. 32908(f).
---------------------------------------------------------------------------

2. Energy Policy Act of 2005
    Section 774 of the Energy Policy Act of 2005 (EPAct) directs EPA to
``update or revise the adjustment factors in sections 600.209-85 and
600.209-95, of the Code of Federal Regulations, CFR Part 600 (1995)
Fuel Economy Regulations for 1977 and Later Model Year Automobiles to
take into consideration higher speed limits, faster acceleration rates,
variations in temperature, use of air conditioning, shorter city test
cycle lengths, current reference fuels, and the use of other fuel
depleting features.'' \38\
---------------------------------------------------------------------------

    \38\ See Pub. L. 109-58, 119 Stat. 835 (2005).
---------------------------------------------------------------------------

    In today's proposal, the 5-cycle approach changes the adjustment
factors by establishing a new method to calculate fuel economy
estimates that uses fuel economy results from additional test
procedures combined with a changed adjustment factor. The mpg-based
approach uses the same test methods as the current fuel economy program
(i.e., the FTP and HFET tests), but changes the adjustment factors
applied to those test results. These options satisfy the EPAct
provisions as follows.
    First, the 5-cycle method proposed today directly includes the
effects of higher speed limits, faster acceleration rates, variations
in temperature, and use of air conditioning by including fuel economy
measured during tests that incorporate these features. The mpg-based
approach also takes these factors into consideration, but less
directly, as it incorporates the effects of these factors by basing the
adjustment factor on an analysis of data developed from the 5-cycle
method. Under our proposal, we use the mpg-based approach as an interim
option to establish an appropriate period of lead time for
manufacturers. We also allow its continued use only where the average
effects reflected under the mpg-based adjustments (of higher speed/
acceleration, air conditioning, and cold temperature) on a specific
vehicle configuration would be representative of those measured under
actual 5-cycle testing.
    Second, we interpret the statute's reference to ``shorter city test
cycle lengths'' to mean shorter than the current FTP cycle used to
determine city fuel economy. We have addressed that concern in the
proposal by weighting in updated factors for ``cold starts'' and ``hot
starts'' (where the engine is not warmed up or has been parked for a
brief amount of time and then restarted) into the equation for
determining city fuel economy. This simulates shorter city test cycle
lengths where a vehicle's engine is more frequently shut down and
restarted than in the current FTP test. Also, the US06 and SC03 test
cycles are physically shorter in length than the FTP (the FTP is about
11 miles in length, whereas the US06 is about 8 miles, and the SC03 is
about 3.6 miles.)
    Third, we interpret the statutory reference to ``current reference
fuels'' to mean the laboratory fuels used to perform the fuel economy
tests, and that the underlying concern of Congress was that the high-
quality lab fuels would give higher fuel economy than the typical fuel
used by consumers. The quality of the laboratory test fuel is specified
in EPA regulations for emission compliance.\39\ The test gasoline fuel
is roughly equivalent to premium, high-octane fuel available at the
pump. It is necessary that all vehicles use the same grade of fuel to
provide a level playing field for manufacturers to compare the emission
compliance results to the federal emission standards, since certain
fuel specifications can have an impact on tailpipe emissions. The
impact of the higher-octane test fuel on fuel economy is less
significant but there are other real-world fuel differences that can
have a noticeable impact, as discussed in Section II. For instance,
ethanol has a lower energy content than gasoline, and

when blended with gasoline, with all other things being equal, will
slightly lower fuel efficiency. Other seasonal variations in fuel
composition (e.g., oxygenates in winter fuel) may also cause a slight
reduction in fuel economy. EPA is proposing an adjustment factor to
account for fuel differences and other fuel-depleting features as
described further in Section II.
---------------------------------------------------------------------------

    \39\ See 40 CFR 86.113-94.
---------------------------------------------------------------------------

3. Relationship of Today's Proposal With Other Statutes and Regulations
    a. Automobile Disclosure Act. A provision in EPCA (at 49 U.S.C.
32908(b)(2)) allows the fuel economy information to be included on the
window sticker label of vehicle manufacturing and price information
required by the Automobile Disclosure Act at 15 U.S.C. 1232 (the so-
called ``Monroni'' label.). To that end, the Federal Trade Commission
issued a ``Fuel Guide'' concerning the fuel economy advertising for new
automobiles, published in the Federal Register at 16 CFR Part 259. This
guide refers back to EPA's fuel economy regulations and specifically to
how manufacturers are permitted to advertise the city and highway fuel
economy of their vehicles.
    b. Internal Revenue Code. This code contains the provisions
governing the administration of the Gas Guzzler Tax.\40\ It contains
the table of applicable taxes and defines which vehicles are subject to
the taxes. The IRS code specifies that the fuel economy to be used to
assess the amount of tax will be the combined city and highway fuel
economy as determined by using the procedures in place in 1975, or
procedures that give comparable results (similar to EPCA's requirements
for determining CAFE). Today's proposal does not impact these
procedures.
---------------------------------------------------------------------------

    \40\ See 26 U.S.C. 4064.
---------------------------------------------------------------------------

    c. Clean Air Act. Reference is made in EPCA to the Clean Air Act
statute. Specifically, EPCA states that fuel economy shall to the
extent practicable include the emissions tests required under Section
206 of the Clean Air Act.\41\ Today's proposal incorporates three
additional types of emissions tests required under the Clean Air Act
for fuel economy testing, as discussed in detail in Section II. We also
propose to make several changes to existing emissions tests. These
changes are being proposed under the statutory authority of Section 206
of the Clean Air Act, which permits the Administrator to define, and to
revise from time to time, the test procedures used to determine
compliance with applicable emission standards.
---------------------------------------------------------------------------

    \41\ See 49 U.S.C. 32904(c).
---------------------------------------------------------------------------

    d. Additional Provisions in the Energy Policy Act of 2005 and
Transportation Equity Act of 2005. This action is expected to have no
impact on the alternative motor vehicle federal income tax credits the
Internal Revenue Service (IRS) is establishing under Section 1341 of
the Energy Policy Act of 2005. IRS is in the process of preparing the
final guidance for these new federal income tax credits for consumers
who purchase new hybrid, diesel, dedicated alternative fuel, or fuel
cell vehicles beginning on January 1, 2006. The Energy Policy Act of
2005 requires EPA to coordinate with and support IRS' implementation of
these new tax credits, and EPA is providing input on a number of
technical issues. EPA anticipates that the fuel economy values used to
help determine tax credit eligibility for light-duty vehicles will be
``unadjusted'' laboratory city fuel economy test values. Accordingly,
the changes being proposed today are anticipated to have no impact on
the tax credit program.
    Similarly, this action is expected to have no impact on the ``HOV
Facilities'' regulations EPA is establishing under section 1121 of the
Transportation Equity Act of 2005. EPA is in the process of developing
proposed regulations to identify low emission and energy-efficient
vehicles for the purpose of assisting states administering high-
occupancy lane transportation plans. EPA anticipates that the fuel
economy values used to identify these vehicles will be the
``unadjusted'' FTP-based fuel economy test values. Accordingly, the
changes proposed today are anticipated to have no impact on the HOV
facilities program.

II. Description of the Proposed Fuel Economy Label Methodology

    The current fuel economy label values utilize measured fuel economy
over city and highway driving cycles and adjust these values downward
by 10 and 22 percent, respectively, to account for a variety of factors
not addressed in EPA's vehicle test procedures. These factors include
differences between the way vehicles are driven on the road and over
the test cycles, air conditioning use, widely varying ambient
temperature and humidity, varying trip lengths, wind, precipitation,
rough road conditions, hills, etc. The purpose of the new formulae for
city and highway fuel economy labels is to widen the base for the
labels to include actual vehicle testing over a wider range of driving
patterns and ambient conditions than is currently covered by the FTP
and HFET tests.
    For example, vehicles are often driven more aggressively and at
higher speeds than is represented in the FTP and HFET tests. The
incorporation of measured fuel economy over the US06 test cycle into
the fuel economy label values would make the label values more
realistic. Drivers often use air conditioning in warm, humid
conditions, while the air conditioner is turned off during the FTP and
HFET tests. The incorporation of measured fuel economy over the SC03
test cycle into the fuel economy label values would reflect the added
fuel needed to operate the air conditioning system. Vehicles also often
are driven at temperatures below 75 degrees Fahrenheit (F), at which
the FTP and HFET tests are performed. The incorporation of measured
fuel economy over the cold temperature FTP test into the fuel economy
label values would reflect the additional fuel needed to start up a
cold engine at colder temperatures.
    The proposed vehicle-specific, 5-cycle approach to fuel economy
label estimation would incorporate estimates of the fuel efficiency of
each vehicle during high speed, aggressive driving, air conditioning
operation and cold temperatures into each vehicle's fuel economy label.
It would combine measured fuel economy over the two current fuel
economy tests, the FTP and HFET, as well as that over the US06, SC03
and cold FTP tests into estimates of city and highway fuel economy for
labeling purposes. The test results from each cycle (and in some cases,
portions of cycles or emission ``bags'')\42\ would be weighted to
represent the contribution of each cycle's attributes to onroad driving
and fuel consumption. The vehicle-specific, 5-cycle approach would
eliminate the need to account for the effect of aggressive driving, air
conditioning use and colder temperatures on fuel economy through
generic factors (as done today) which may not reflect that particular
vehicle's sensitivity to these factors. A generic adjustment would
still be necessary to

account for factors not addressed by any of the five dynamometer tests.
The magnitude of such an adjustment is comparable to today's 10 and 22
percent generic adjustments. Overall, under the vehicle specific 5-
cycle approach, each vehicle's label fuel economy would better reflect
the capabilities of that vehicle on the road.
---------------------------------------------------------------------------

    \42\ 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. Because the
stabilized phase of the hot start test is assumed to be identical to
the stabilized phase of the cold start test, only the cold start
stabilized phase is typically run. These ``phases'' are often called
``bags,'' terminology that results from the sample bags in which the
exhaust samples are collected. The phases are run in the following
order: Cold start transient (Bag 1), cold start stabilized (Bag 2),
and hot start transient (Bag 3).
---------------------------------------------------------------------------

    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 are proposing
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).\43\ We are also proposing that manufacturers be
allowed to use the interim approach to fuel economy label estimation,
the mpg-based approach, indefinitely when the available 5-cycle fuel
economy data indicate that a vehicle's specific 5-cycle fuel economy is
very close to that estimated by the mpg-based curve.
---------------------------------------------------------------------------

    \43\ EPA's current policy for analytically derived fuel economy
estimates for the FTP and HFET tests is contained in the EPA
memorandum entitled, ``Updated Analytically Derived Fuel Economy
(ADFE) Policy for 2005 Model Year,'' March 11, 2004, CCD-04-06 (LDV/
LDT).
---------------------------------------------------------------------------

    Even with these policies, we expect that some manufacturers would
have to perform some additional US06, SC03, or cold FTP tests to
address differences in vehicle designs which are not covered by the
analytical derivation methodology. Other manufacturers may decide to
perform additional tests simply to improve accuracy over the analytical
derivation methodology. Depending on how manufacturers choose to apply
this method, this additional testing could involve the construction of
additional test facilities. (Test burden issues are discussed further
in Section VI of this preamble.) Therefore, in order to allow
sufficient lead-time for the construction of these facilities, we are
proposing to allow manufacturers the option of using an alternative,
interim set of adjustments through the 2010 model year until the 5-
cycle approach becomes mandatory with the 2011 model year. However, a
manufacturer can still use the 5-cycle formula prior to the 2011 model
year for specific vehicle models, if it so desires.
    The interim set of adjustments is termed the ``mpg-based''
adjustment. (See Figure II-1 in the following section for a graphical
depiction of these adjustments.) The mpg-based approach is a sliding
scale of adjustments which varies according to a vehicle's measured
fuel economy over the FTP and HFET tests. The mpg-based adjustment
factors were developed from applying the 5-cycle formulae to 423 recent
model year vehicles and determining the average difference between the
5-cycle and current city and highway fuel economies. Thus, because the
data used to develop the average adjustment factors were derived from
5-cycle fuel economies, the mpg-based adjustment factors include the
effect of high speeds, aggressive driving, air conditioning, and colder
temperatures. However, they do so based on the impact of these factors
on the average vehicle, not the individual vehicle, which is the case
with the 5-cycle formulae. For example, for vehicles with FTP fuel
economy of 20-30 mpg, the mpg-based approach would adjust the FTP fuel
economy downward by 22-24 percent, versus today's 10 percent downward
adjustment. Thus, city fuel economy label values under the mpg-based
approach tend to be about 13-15 percent lower than today's label
values. For vehicles with HFET fuel economy of 25-35 mpg, the mpg-based
approach would adjust the HFET fuel economy downward by 29 percent,
versus today's 22 percent downward adjustment. Thus, highway fuel
economy label values under the mpg-based approach would tend to be
about 9 percent lower than today's label values.
    As mentioned above, the mpg-based equations described above were
developed from the 5-cycle fuel economy estimates for 423 2003-2005
model year vehicles. We propose 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. These revised mpg-based
equations would be issued through the publication of an EPA guidance
document. EPA would publish the mpg-based equations by January 1 of the
calendar year prior to the model year to which the equations first
apply (e.g., for model year 2010 fuel economy calculations the
equations would be made available before January 1, 2009). In order to
keep the mpg-based equations up-to-date and based on recent technology
vehicles, EPA would update these equations periodically, but no more
than on an annual basis. However, rather than publish the equations
applicable to 2008 model year vehicles via guidance, the proposed
regulations contain the equations that would be applicable to 2008
model year vehicles, as well as the components of the equations to be
utilized for future model year vehicles. We request comment on this
updating of the mpg-based equations.
    In addition to proposing the mpg-based adjustment factors for the
2008-2010 model years, as mentioned above, we propose to allow use of
this method of label estimation to be used for 2011 and later model
years for those vehicles which meet certain criteria (discussed in
detail below) that indicate that the full 5-cycle testing would not
likely result in significantly different fuel economy label values.
Each year, a number of vehicles are tested over all five dynamometer
test cycles for emission certification purposes (i.e., emission data
vehicles). The fuel economy data for the five dynamometer test cycles
for each emission data vehicle can be inserted into the 5-cycle
formulae and the 5-cycle city and highway fuel economy values
determined. Emission data vehicles also undergo testing over the FTP
and HFET. Thus, the mpg-based city and highway fuel economy values for
each emission data vehicle can also be determined using the available
FTP and HFET fuel economy values. The 5-cycle city and highway fuel
economy values can be compared to the mpg-based city and highway fuel
economy values, respectively, for each emission data vehicle.
    The mpg-based line represents the effects of high speed, high
acceleration, air conditioning, and colder temperatures of the average
new vehicle. Therefore, 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 testing) indicates that the
particular vehicle design reflects at least these average effects. To
accomplish this, we defined the lower bound of a tolerance band around
the mpg-based line as the criteria for whether the mpg-based line could
be used or whether 5-cycle testing would be required. We chose four and
five percent as the tolerance bands for the 5-cycle city and 5-cycle
highway fuel economy values, respectively. Mathematically, the
tolerance line is defined by Y x mpg-based fuel economy, where Y is
0.96 for city fuel economy and 0.95 for highway fuel economy. In other
words, if the 5-cycle city fuel economy value is greater than 0.96
times the mpg-based city fuel economy, all the vehicle configurations

represented by the emission data vehicle (i.e., all vehicles within the
vehicle test group) would be eligible to use the mpg-based approach.
Similarly, when the 5-cycle highway fuel economy is less than the mpg-
based highway fuel economy minus five percent, all vehicle
configurations represented by the emission data vehicle would be
required to use the vehicle-specific 5-cycle approach. This could be
done using ADFE estimates, when appropriate. This approach is
appropriate because those vehicles above the upper tolerance band that
used the mpg-based line would simply be reducing their fuel economy
down to the average level, even though the 5-cycle data indicated
better than average performance was likely for that vehicle group.
Because of the better-than-average performance, we expect that most
manufacturers will want to do complete 5-cycle testing for vehicles
likely to be above the upper tolerance band. However, we request
comment on whether there may be some inherent variability regarding all
outliers above and below the tolerance band that would make it
desirable to require 5-cycle testing in all of these cases.
    If the 5-cycle city fuel economy fell below the mpg-based city fuel
economy by more than four percent, but the 5-cycle highway fuel economy
did not fall below the mpg-based highway fuel economy by more than five
percent, all the vehicle configurations represented by the emission
data vehicle would be required to use the vehicle-specific 5-cycle
approach for both city and highway fuel economy, since fuel economy
values for all five cycles are important in estimating 5-cycle city
fuel economy. However, if the 5-cycle highway fuel economy was less
than the mpg-based highway fuel economy by more than five percent, but
the 5-cycle city fuel economy was not more than four percent lower than
the mpg-based city fuel economy, all the vehicle configurations
represented by the emission data vehicle would use mpg-based approach
to estimate the city fuel economy label. For highway label estimation,
all the vehicle configurations represented by the emission data vehicle
would use an approximate 5-cycle formula for highway fuel economy which
includes vehicle-specific fuel economy measurements for the FTP, HFET
and US06 tests, but the values for the SC03 and cold FTP tests could be
estimated based on relationships developed from other vehicles. This is
appropriate because the impact of the cold FTP test on highway fuel
economy is not vehicle-specific, but modeled. Also the impact of the
SC03 test on highway fuel economy is very small, particularly compared
to that for the US06 test.
    The proposed criteria for long term use of the mpg-based approach
(5-cycle city fuel economy above -4.0 percent and 5-cycle highway fuel
economy above -5.0 percent) are based on the balance of three factors.
One, we designed them to be sufficiently large so that simple test-to-
test variability would not cause an emission data vehicle to fail the
criteria. This was a greater concern for the highway fuel economy
comparison, due to the dominance of the US06 fuel economy (which
inherently has greater test-to-test variability than the other tests)
in the 5-cycle formula. Two, we desired to minimize the potential error
in the fuel economy label. Label fuel economy values are rounded to the
nearest one mpg. Thus, we desired to keep the difference between the 5-
cycle and mpg-based fuel economy values within roughly one mpg, if
possible. Three, we desired to avoid additional fuel economy testing
that had little 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 fuel
economy formula, the effect of test-to-test variability should be much
lower than 4.0 percent. Based on the 5-cycle test results of 423 recent
model year vehicles, we estimate that 90 percent of all emission data
vehicles would meet the 4.0 percent. 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
fuel economy 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
fuel economy formula. We estimate that 75 percent of all emission data
vehicles would meet the 5.0 percent. Thus, again, we believe that this
criterion adequately satisfies the three factors mentioned above.
    Overall, allowing the continued use of the mpg-based approach would
reduce the number of additional SC03 and cold FTP tests by about 90
percent and reduce the number of additional US06 tests by about 75
percent indefinitely. We request comment on the continued use of the
mpg-based approach beyond the 2010 model year and on the 4.0 and 5.0
percent criteria for its use.
    Section II.A presents the proposed interim mpg-based formulae and
the proposed vehicle-specific 5-cycle formulae for city and highway
fuel economy label values. Section II.B describes how these formulae
would be applied to develop labels for specific grouping of vehicles.
Section II.C describes how the 5-cycle formulae were derived. Section
II.D describes how the mpg-based formulae were derived. Section II.E
describes how the current city and highway fuel economy values would
change under the proposed formulae.

A. Proposed Fuel Economy Label Formulae

    Currently, manufacturers test their vehicles over two dynamometer
tests in order to develop their fuel economy label values: the FTP or
city test and the HFET or highway test. Fuel economies measured over
these two tests are multiplied by 0.90 and 0.78, respectively. These
``adjusted'' fuel economies are then sales-weighted using procedures
outlined in Subpart D of Part 600 of Title 40 of the Code of Federal
Regulations (CFR) to develop fuel economy label values by model type.
    Under today's proposal, we would replace the 0.90 and 0.78 factors
with new factors which are not simply constants. For model years 2008-
2010, a manufacturer would have the option of using two distinct
methodologies to calculate the city and highway fuel economy values for
any specific test vehicle. One approach is called the mpg-based
approach or formula, since the city and highway label values are based
on the fuel economy (or MPG) measured over the FTP and HFET,
respectively. The other approach is called the vehicle-specific 5-cycle
approach, since the city and highway label values are based on the test
results of five test cycles, the FTP, HFET, US06, SC03 and cold FTP.
Beginning with the 2011 model year, we propose that manufacturers would
use the vehicle-specific 5-cycle method, but that the mpg-based
approach could still be used by qualifying vehicles. Below we present
the specific equations under the two approaches which would be used to
convert fuel economies measured over the dynamometer cycles into city
and highway fuel economy values prior to sales weighting. We are not
proposing any changes to the methods for combining city and highway
fuel economy values for specific vehicles into label values for a model
type.

    The formulae for the 5-cycle approach are, as indicated by its
name, based on the fuel economy measurements over the five test cycles
(FTP, HFET, US06, SC03 and cold FTP). Both approaches also include an
additional downward adjustment to represent effects impossible to
incorporate in laboratory dynamometer testing. However, the formulae
for the mpg-based approach are also based on fuel economy measurements
over the five test cycles. The difference is the set of 5-cycle fuel
economy measurements that are used. Under the vehicle-specific 5-cycle
approach, the fuel economy measurements over the 5 dynamometer test
cycles would all be performed on (or estimated for) a specific vehicle
in the current model year. Under the mpg-based approach, historic fuel
economy data over the 5 test cycles would have been analyzed to produce
a fleet-wide average relationship between (1) FTP fuel economy and 5-
cycle city fuel economy, and (2) HFET fuel economy and 5-cycle highway
fuel economy. Under the mpg-based approach, a specific vehicle's city
and highway fuel economy labels are based on this fleet-wide average
relationship, as opposed to that vehicle's own results over the 5 test
cycles. In other words, every vehicle with the same measured FTP fuel
economy would receive the same city fuel economy label value. Likewise,
every vehicle with the same measured HFET fuel economy would receive
the same highway fuel economy label value. Figure II-1 shows the 5-
cycle city fuel economy for 423 recent model year vehicles and the mpg-
based city fuel curve which has been developed from these data. The
horizontal axis is the measured FTP fuel economy.
[GRAPHIC] [TIFF OMITTED] TP01FE06.003

Application of the 5-cycle approach to these vehicles would have
produced the city fuel economy values indicated by the diamonds in the
plot. (The nine hybrid vehicles are indicated by large squares.)
Application of the mpg-based formula to these vehicles would have
produced city fuel economy values by reading a number off of the curved
line in the plot.
    Figure II-2 shows the 5-cycle highway fuel economy for the same 423
recent model year vehicles and the mpg-based highway fuel economies
which have been developed from these data. The horizontal axis is the
measured HFET fuel economy.

[GRAPHIC] [TIFF OMITTED] TP01FE06.004

    Both Figure II-1 and II-2 include several data points which are
represented by large squares. These are vehicles which incorporate
hybrid technology. Hybrids appear to fall well below the mpg-based
curve for city fuel economy, but not for highway fuel economy. This
issue will be discussed in more detail below.
    Given that both approaches utilize the 5-cycle fuel economy
formulae in some fashion, it is useful to begin this section with a
description of how the fuel economy measured over the 5 test cycles are
combined to represent onroad city and highway fuel economy. Then we
will describe how the fleet-average formulae for the mpg-based approach
were derived from these 5-cycle fuel economy estimates.
    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. In this section
and in the Draft Technical Support Document, we fully describe the
basis for developing these formulae. We seek comment on all aspects of
the formulae and the underlying data upon which they are based. We also
encourage interested parties to submit any additional data that would
be relevant in our final analysis. Further, we want to ensure the 5-
cycle approach continues in future years to reflect updated conditions
impacting real-world fuel economy. Therefore, we encourage the public
to submit any such data in the future so that EPA may assess such new
information and evaluate the need for changes to this approach over
time.
    Since our goal is to develop a consistent, objective approach that
applies to all vehicles, we have assumed that all types of vehicles are
driven and maintained similarly, and we have proposed to weight the
five driving cycles and apply non-dynomometer adjustments in the same
way for all types of vehicles. However, if data showed that a specific
type of vehicle is driven or maintained very differently, and this
impacted fuel economy significantly (e.g., an unusually low incidence
of aggressive driving, A/C usage, etc.), then one might consider
different weights or adjustment factors on this basis. We seek comment
on any data that would inform whether unique weighting factors or non-
dynomometer adjustments should be considered for specific vehicle
technologies (e.g., hybrids or diesels). For example, hybrids may be
purchased preferentially by people whose driving patterns take
advantage of their performance characteristics, and hybrid owners may
be more conscious of driving techniques (such as mild braking) that
improve fuel economy. Even if this were the case today, this difference
would not necessarily persist as hybrids become more prevalent in the
fleet. Moreover, it is not clear how such vehicle technology-specific
factors can or should be reflected in EPA's fuel economy test methods
or calculations. We seek comment on the contribution of such factors to
the on-road fuel economy experience of consumers, and on the relevance
of these factors to the fuel economy label. We also seek comment on the
extent to which such unique factors might reduce the perceived
objectivity of the fuel economy estimates if they presume differences
in driving behavior.
    1. MPG-Based Approach (Available in 2008-2010 Model Years)
    Under the mpg-based approach, the city fuel economy value would be
calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP01FE06.005

where

FTP FE = the fuel economy in miles per gallon of fuel during the FTP
test conducted at an ambient temperature of 75 [deg]F.
    This value is normally a sales-weighted average of the vehicle
models included in the ``fuel economy grouping'' (e.g., model type) as
defined in 40 CFR 600.002-93.
    Likewise, the highway fuel economy value would be calculated as
follows:
[GRAPHIC] [TIFF OMITTED] TP01FE06.006

where

HFET FE = fuel economy in mile per gallon over the HFET test.
    This value is normally a sales-weighted average of the vehicle
models included in the ``fuel economy grouping'' (e.g., model type) as
defined in 40 CFR 600.002-93.
    The rationale for the various constants in Equations (1) and (2) is
described in Section II.B.
2. Vehicle-Specific 5-Cycle Approach (Applicable to 2011 and Later
Model Years and Optional in Prior Model Years)
    Under the vehicle-specific 5-cycle approach, the city fuel economy
value would be calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP01FE06.007

, where[GRAPHIC] [TIFF OMITTED] TP01FE06.008

where,
[GRAPHIC] [TIFF OMITTED] TP01FE06.009

or,
[GRAPHIC] [TIFF OMITTED] TP01FE06.010

where
Bag y FEx = the fuel economy in miles per gallon of fuel
during the specified bag of the FTP test conducted at an ambient
temperature of 75 [deg] or 20[deg]
    F. The rationale for the various constants in the equations is
described below in Section II.B. Likewise,
[GRAPHIC] [TIFF OMITTED] TP01FE06.011

where

US06 FE = fuel economy in mile per gallon over the US06 test,
HFET FE = fuel economy in mile per gallon over the HFET test,
SC03 FE = fuel economy in mile per gallon over the SC03 test.

    Vehicles tested over a 4-bag FTP would substitute the fuel economy
over Bag 4 for Bag 2 in the above equation.
    Under the vehicle-specific 5-cycle formula, the highway fuel
economy value would be calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP01FE06.012

, where[GRAPHIC] [TIFF OMITTED] TP01FE06.013

[GRAPHIC] [TIFF OMITTED] TP01FE06.014

where the various symbols have the same definitions as described under
the formula for the vehicle-specific 5-cycle city fuel economy value.

B. Application of the Formulae To Develop Fuel Economy Labels for
Specific Vehicles

    We are not proposing any major changes to the way that vehicle
configurations are grouped for fuel economy labeling purposes. For
model years 2008-2010, when the mpg-based formulae are applicable,
there would be no change in the procedure by which specific vehicle
labels are developed.\44\ Since the mpg-based formulae are based solely
on the current fuel economy test cycles, no additional tests would need
to be conducted. Only the effective adjustment factors would be
modified.
---------------------------------------------------------------------------

    \44\ See 40 CFR 600 and relevant EPA guidance.
---------------------------------------------------------------------------

    Starting with the 2011 model year, vehicle manufacturers would
first utilize their available 5-cycle fuel economy testing of emission
data vehicles to determine which test groups could utilize the mpg-
based approach and which would have to use the vehicle-specific 5-cycle
approach. The test groups for which their emission data vehicles passed
the 4.0 percent and 5.0 percent criteria described above would face no
additional testing requirements. Just as in 2008-2010, the mpg-based
formulae would be applied to fuel economy values measured over the FTP
and HFET already being performed and city and highway label values
determined.
    Figure II-3 shows how the 4.0 percent criterion would work for city
fuel economy.
[GRAPHIC] [TIFF OMITTED] TP01FE06.015

    The upper line in the figure is the mpg-based formula for city fuel
economy. The lower line represents a difference of 4.0 percent from
city fuel economy based on the mpg-based formula. The points shown in
Figure II-3 represent city fuel economy of emission data vehicles
estimated by the 5-cycle fuel economy formula. The model types
represented by emission data vehicles whose 5-cycle city fuel economy
values fall above the lower line would be allowed to use the mpg-based
approach for that model year. The model types represented by emission
data vehicles whose 5-cycle city fuel economy values fall below the
lower bounding line would be required to use the 5-cycle approach for
that model year. Implicit in this proposal is that manufacturers would
be allowed to use the mpg-based approach for a particular test group if
the 5-cycle fuel economy for an emission data vehicle exceeded the mpg-
based curve by more than the 4.0 or 5.0 percent criteria on the high
side, since this would result in a lower fuel economy label value.
    The test groups for which their emission data vehicles did not pass
the 4.0 percent and 5.0 percent criteria described above could face
some additional testing requirements. All the vehicle sub-
configurations contained in these test groups would require fuel
economy values over all five cycles for

use in the 5-cycle city and highway fuel economy formulae. The city and
highway label values produced by the 5-cycle fuel economy formulae
would then be averaged and sales-weighted just as they are today.
However, the fuel economy values over the five test cycles could be
generated in either of two ways in most instances. One way would be to
test the vehicle over the US06, SC03 and cold FTP tests (the FTP and
HFET tests already being performed under current requirements). The
other way would be estimate fuel economy values over the US06, SC03 and
cold FTP tests analytically (i.e., ADFEs) from testing of a similar
vehicle over these three cycles. Specifically, we propose to allow
manufacturers to estimate the effect of differences in inertial 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).
A procedure to estimate the effect of these three vehicle parameters on
FTP and HFET fuel economy has already been developed. We plan to work
with manufacturers to develop analogous formulae for the US06, SC03 and
cold FTP tests. We would implement these estimation procedures using
agency guidance, as is currently done for FTP and HFET fuel economy.
    It is possible for the 5-cycle fuel economy values to meet the
above criteria for either city or highway fuel economy, but not the
other. If the 5-cycle fuel economy values for a specific emission data
vehicle are more than four percent below the mpg-based estimate for
city fuel economy, but no more than five percent below the mpg-based
estimate for highway fuel economy, all the vehicle configurations
represented by that emission data vehicle would be required to use the
5-cycle formulae in complying with the fuel economy label requirements
for both city and highway fuel economy. All five cycles play a
significant role in the 5-cycle city fuel economy formula. Once the
five tests have been performed for the city estimate, there is little
reason not to use the same information to derive the highway fuel
economy estimate.
    We propose a different approach for the opposite situation. If the
5-cycle fuel economy values for a specific emission data vehicle are no
more than four percent below the mpg-based estimate for city fuel
economy, but more than five percent below the mpg-based estimate for
highway fuel economy, all the vehicle configurations represented by
that emission data vehicle would be allowed to use the mpg-based
formulae in deriving the city fuel economy label value. The highway
fuel economy value, however, would be based on an alternative,
simplified 5-cycle formula as opposed to the full 5-cycle highway fuel
economy formula. This alternative 5-cycle highway formula would be
based on fuel economy values over the FTP, HFET and US06 tests. The
impact of the SC03 and cold FTP tests is relatively small in the 5-
cycle highway fuel economy formula, as explained in the Draft Technical
Support Document.
    This approach requires that we develop a simplified 5-cycle highway
fuel economy formula which is consistent with the full 5-cycle formula.
We developed this simplified formula using estimates of the average
impact of the SC03 and cold FTP test results on 5-cycle highway fuel
economy. In both cases, we estimated this average impact by regressing
the impact of these test cycles on the 5-cycle highway fuel economy for
the 423 vehicles in our certification database against fuel economy
values which would be available from FTP, HFET and US06 testing. This
analysis (described in detail in the Draft Technical Support Document)
results in the following alternative calculation for highway fuel
economy.
[GRAPHIC] [TIFF OMITTED] TP01FE06.016

[GRAPHIC] [TIFF OMITTED] TP01FE06.017

[GRAPHIC] [TIFF OMITTED] TP01FE06.018

[GRAPHIC] [TIFF OMITTED] TP01FE06.019

    We expect that the continued use of the mpg-based approach and the
development of analytical estimation procedures for US06, SC03 and cold
FTP fuel economy would allow manufacturers to avoid the vast majority
of additional tests that would have been required if every vehicle
currently tested over the FTP and HFET tests had to be tested over the
US06, SC03 and cold FTP tests. The option to use the mpg-based approach
after 2010 should alone eliminate 90 percent of the potential need for
additional SC03 and cold FTP testing and 75 percent of the potential
need for US06 testing. At the same time, we expect that there would be
some need for additional testing when the available estimation
procedures mentioned above do not apply. For example, the current
estimation procedures for FTP and HFET fuel economy address changes in
axle ratio, tractive road load horsepower and inertia test weight.
Differences involving changes in transmission design, engine
displacement, turbo-charging, etc., require actual testing. We expect
that a similar situation would exist with the estimation of US06, SC03
and cold FTP fuel economy.
    We request comment on the appropriateness of the continued use of

the mpg-based approach beyond the 2010 model year. We also request
comment on the appropriateness of the 4.0 and 5.0 percent tolerance
bands for city and highway fuel economy, respectively. We also seek
comment on alternative approaches that may employ concepts similar to
the tolerance band, or other ways of extrapolating fuel economy test
results to a broader group of vehicle configurations. We specifically
request comment on an approach which would employ tighter criteria
(e.g., a tolerance of 3 percent) that would allow the use of the mpg-
based approach beyond 2010 model year, but which would include other
aspects which would avoid full 5-cycle testing of all the model types
which failed to pass the criteria. For example, failing the initial
criteria might require the manufacturer to generate fuel economy data
over the US06, the least expensive of the three additional cycles. City
and highway fuel economy values could then be calculated using three
cycles (the FTP, HFET, and US06), and tested with additional criteria
(e.g., comparison to a tolerance band around the appropriately
generated mpg-based line) to assess whether the mpg-based approach
could be used or whether full 5-cycle testing would be required.

C. Derivation of the Proposed 5-cycle Fuel Economy Formulae

1. Five-Cycle Fuel Economy Estimates
    The purpose of the 5-cycle fuel economy formulae is to best
represent city and highway fuel economy in the U.S. using the test
results from the 5 test cycles. To the fullest extent possible, we
desire to account for the effect of seasonal and geographical
variations on automotive fuel economy, as well as the different driving
habits of individual drivers. As described in Section I., we chose to
base the fuel economy label values on 5 vehicle emission and fuel
economy tests which are already being performed. This maximizes the use
of fuel economy information that is already currently being collected,
while at the same time minimizes the costs associated with the
proposal, as described in more detail below in Section VI. The five
current emission and fuel economy tests and their key aspects are
described below in Table II-1. Actual second by second descriptions of
these driving cycles can be found in Section 86 of Title 40 of the Code
of Federal Regulations.

                                      Table II-1.--Key Features of the Five Current Emission and Fuel Economy Tests
--------------------------------------------------------------------------------------------------------------------------------------------------------
              Test                                        Driving                         Ambient  temperature        Engine start          Accessories
--------------------------------------------------------------------------------------------------------------------------------------------------------
FTP.............................  Low speed.............................................  75 [deg]F...........  Cold and hot............  None.
HFET............................  Mid-speed.............................................  75 [deg]F...........  Hot.....................  None.
US06............................  Aggressive; low and high speed........................  75 [deg]F...........  Hot.....................  None.
SC03............................  Low speed.............................................  95 [deg]F...........  Hot.....................  A/C on.
Cold FTP........................  Low speed.............................................  20 [deg]F...........  Cold and hot............  None.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We have highlighted in bold the distinctive features of the five
current vehicle tests. The FTP, HFET and US06 are all performed at an
ambient temperature of 75 [deg]F. Each test consists of a distinctive
driving pattern. In addition, the FTP test consists of three distinct
measurements, called bags. Bags 1 and 3 consist of the exact same
driving pattern, but Bag 2 consists of a different pattern. Given that
separate emission measurements are already made for each bag, we
considered each bag of the FTP to be its own driving cycle. In
addition, as discussed in Section V, the US06 cycle includes both low
and high speed driving. We are proposing that separate emission
measurements be made for these two types of driving, again providing
separate estimates of fuel use for these two driving patterns.
Therefore, we have available fuel economy estimates for five distinct
driving patterns:
    (1) Bags 1 and 3 of the FTP,
    (2) Bag 2 of the FTP,
    (3) HFET,
    (4) the city portion of US06 and
    (5) the highway portion of US06.

We propose to combine the results of these five tests to represent
typical city and highway driving patterns. (The separation of the US06
test into two distinct sections is discussed further below.)
    The FTP and the cold FTP are the only tests which include a cold
start (i.e., an engine start after an overnight soak); the fuel needed
to warm up the engine at 75 [deg]F is taken from the FTP results. The
SC03 test is the only test to be performed with the air conditioning
system operational. Therefore, its results are used to augment the fuel
economy from the five driving pattern tests for the fuel needed to
operate air conditioning. The cold FTP is the only test performed at a
temperature below 75 [deg]F. Therefore, its results are used to
represent the additional fuel needed to warm up an engine after a cold
start, as well as any fuel needed to operate a warmed up engine, at
colder temperatures.
    As implied above, we estimate the fuel needed to start and warm up
the engine separately from fuel used to operate the engine after start-
up, or running fuel use. This is consistent with the approach taken in
EPA emission models, such as MOBILE6.2 and MOVES. In terms of a
mathematical formulae,
    Total fuel use = start fuel use + running fuel use

and,
[GRAPHIC] [TIFF OMITTED] TP01FE06.020

    We describe the estimation of start fuel use in Section II.B.1 and
the estimation of running fuel use in Section II.B.2. In Section
II.B.3, we discuss other aspects of driving which are not addressed by
the dynamometer tests and which are addressed by applying an overall,
or off-test adjustment factor to the city and highway fuel economy
formulae. The reader is referred to Chapter II of the Draft Technical
Support Document for a more detailed discussion of each of the inputs
to the fuel economy formulae.

1. Start Fuel Use
    For a specific vehicle, the fuel needed to warm up the engine
depends primarily on two factors:
    (1) The ambient temperature at which the vehicle has been sitting,
and
    (2) the length of time which the vehicle has been sitting since it
was last used (commonly referred to as soak time).

Emissions during engine start up have been studied for some time. Most
recently, estimates of start fuel use as a function of ambient
temperature were made for use in EPA's new emission inventory model,
MOVES (MOtor Vehicle Emission inventory System).\45\ The relationship
between start fuel use relative to that at 75 [deg]F at other ambient
temperatures is as follows: \46\
---------------------------------------------------------------------------