\45\ A draft of MOVES2004 was released for public comment on
Dec. 31, 2004.
    \46\ Koupal, J., and L. Landman, E. Nam, J. Warila, C. Scarbro,
E. Glover, R. Giannelli. MOVES2004 Energy and Emissions Report--
Draft Report. U.S. Environmental Protection Agency, No. EPA420-P-05-
003, March 2005, pp 57-63. Web site: http://www.epa.gov/otaq/models/ngm/420p05003.pdf
.

Start Fuel Use Relative to that at 75 [deg]F =
    1 + 0.01971 x (Ambient Temperature - 75) + 0.000219 x (Ambient
Temperature - 75)\2\

As will be seen below, we do not need an absolute estimate of start
fuel use, simply an estimate of start fuel use relative to some
specified ambient condition, such as 75 [deg]F, which is the nominal
temperature of the FTP test.
    MOVES does not yet include the effect of soak time on start fuel
use. Therefore, we obtained a relationship between start fuel use and
ambient temperature which was developed by the California Air Resources
Board for use in their emission inventory model, EMFAC2000.\47\ EPA
utilizes the results of this study in our current emission model,
MOBILE6.2, to estimate the effect of soak time on regulated emissions
during start-up. The equation for fuel use versus soak time (in
minutes) relative to the fuel use after a 12 hour soak is as follows:
---------------------------------------------------------------------------

    \47\ California Air Resources Board. Public Meeting to Consider
Approval of Revisions to the State's On-Road Motor Vehicle Emissions
Inventory--Technical Support Document. California Environmental
Protection Agency, March 2000. See Section 6.7 (Start Correction
Factors). Web site: http://www.arb.ca.gov/msei/on-road/doctable_test.htm
.

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

For soaks of 90 minutes or less:

Start Fuel Use = 0.00433672 x Soak Time - 0.000002393 x (Soak Time)\2\

For soaks greater than 90 minutes:

Start Fuel Use = 0.25889542+0.0014848 x Soak Time - 0.0000006364 x
(Soak Time)\2\

As is assumed in EMFAC2000 and MOBILE6.2, we assumed that these
relationships are independent of ambient temperature.

    In order obtain the combined effect of ambient temperature and soak
time, we multiplied the two above equations together, as follows:

For soaks of 90 minutes or less:

Start Fuel Use = [lfloor]0.00433672 x Soak Time - 0.000002393 x (Soak
Time)\2\[rfloor]x[1+0.01971 x (Ambient Temperature - 75)+0.000219 x
(Ambient Temperature - 75)\2\]

For soaks greater than 90 minutes:

Start Fuel Use = [lfloor]0.25889542+0.0014848 x Soak Time -
0.0000006364 x (Soak Time)\2\[rfloor]x[1+0.01971 x Ambient Temperature
- 75)+0.000219 x (Ambient Temperature - 75)\2\]
    The hot and cold starts contained in the standard and cold
temperature FTP tests occur after 10 minute and 12 hour soaks,
respectively. The above equations relating the effect of soak time on
start fuel use indicate that the start fuel use after a 10 minute soak
is only 4 percent of that after a 12 hour soak. The above equation
relating the effect of temperature on start fuel use indicates that
start fuel use at 20 [deg]F is 2.75 times that at 75 [deg]F. Combining
these effects, the start fuel use after a 10 minute soak at 20 [deg]F
is about 11 percent that of a 12 hour soak at 75 [deg]F. Thus, the
start fuel use after the hot starts of both standard and cold
temperature FTP tests are relatively small compared to that of a cold
start at 75 [deg]F.
    In contrast to the cold start after a 12 hour soak, the hot starts
for Bag 3 of the standard and cold temperature FTP tests and the US06,
SC03 and HFET tests occur after only a 10 minute soak. The above
equation indicates that the fuel use for a hot start is only 4 percent
of that for a cold start.
    In order to estimate start fuel use throughout the U.S. under
average ambient conditions, we need estimates of the soak times for
typical vehicle operation, as well as the ambient temperature at start
up. The amount of time a vehicle has sat prior to start up varies
dramatically depending on the time of day at which it is started. For
example, for vehicles started up at 6 a.m., nearly all have sat idle
overnight. However, for vehicles started at noon, most have been driven
in the past 4-5 hours. Ambient temperature varies significantly during
the day. Thus, it is more accurate to evaluate start fuel use by hour
of the day rather than simply at the daily average temperature. Ambient
temperatures also vary dramatically across the U.S., as does the
distribution of vehicle miles traveled (VMT). Therefore, we combined
estimates of vehicle starts and prior soak times by hour of the day
with estimates of ambient temperature and VMT by county in order to
reflect the effects of both soak time and ambient temperature on start
fuel use.
    We obtained estimates of each of these input parameters from EPA's
MOBLE6.2 and MOVES emission models. The draft MOVES2004 model includes
estimates of ambient temperature by hour of the day for each month of
the year for each county in the U.S. These estimates were obtained from
the National Weather Service and represent 30-year averages. The draft
MOVES2004 model includes estimates of vehicle miles traveled (VMT) by
vehicle type for every county in the U.S. during 2002. We used these
estimates to determine the percentage of VMT by cars and light trucks
in each county. MOBILE6.2 includes estimates of the frequency
distributions of vehicle soak times by time of day, as well as the
frequency distribution of vehicle starts by hour of the day. Draft
MOVES2004 also includes estimates of VMT by month of the year for the
nation as a whole.
    We first estimated the effect of soak time on start fuel use by
hour of the day. These estimates ranged from a low of 0.25 of an
overnight soak at 2 p.m. to a high of 0.68 of an overnight soak at 6
a.m. This makes sense, as most vehicles being started at 6 a.m. in the
morning have sat overnight, while most vehicles being started in the
middle of the afternoon have been used in the past few hours. These
estimates are independent of temperature, because the temperature
during any particular hour is assumed to be constant.
    In order to estimate start fuel use across the nation throughout
the year, we calculated the start fuel use for each hour of the day by
month for each county in the U.S. and then weighted each estimate by
the relative number of starts occurring in each hour of the day and by
the relative amount VMT in each month and county. Finally we summed the
weighted start fuel use estimates across all hours of the days, months
and counties and found the average.
    The average start fuel use resulting from this process was 0.4665
of an overnight soak at 75 [deg]F. We can simulate this average start
fuel use with a variety of combinations of hot and cold starts at 20
[deg]F and 75 [deg]F. For example, the level of start fuel use is equal
to a 0.4665 weighting of the cold start fuel use in Bag 1 of the FTP at
75 [deg]F and no weighting of the start fuel use at 20 [deg]F.

Or, this level of start fuel use is also equal to a lower weighting of
the cold start fuel use in Bag 1 of the FTP at 20 [deg]F and no
weighting of the start fuel use at 75 [deg]F. In order to select a
single combination which best incorporated the measured start fuel use
at both 20 [deg]F and 75 [deg]F, we evaluated start fuel use only as a
function of soak time and time of day, assuming temperature was
constant throughout the day. We found that the typical start fuel use
was 0.330 times that of a cold start (12 hour soak). We then determined
that a weighting of 0.24 for a cold start at 20 [deg]F and 0.76 for a
cold start at 75 [deg]F, combined with an overall weighting of 0.330
for cold starts produced the same level of start fuel use as 0.4665
times a cold start at 75 [deg]F, or the average level of start
emissions estimated to occur in-use.
    In terms of the use of the FTP test results, Bag 3 contains the
start fuel use after a 10-minute soak, and Bag 1 contains the start
fuel use after a 12 hour soak. Other aspects of Bag 1 and Bag 3 are the
same (i.e., the vehicle is driven exactly the same, only the soak time
prior to start up differs). As indicated above, however, the start fuel
use after a 10 minute soak can be assumed to be negligible compared to
that after the 12 hour soak.\48\ This means that the difference between
fuel use in Bag 1 and Bag 3 is the start fuel use following a 12 hour
soak. Thus, the average start fuel use in the U.S. is 0.24 times 0.330
times the difference between fuel use in Bag 1 and Bag 3 of the cold
temperature FTP plus 0.76 times 0.330 times the difference between fuel
use in Bag 1 and Bag 3 of the standard FTP at 75 [deg]F.
---------------------------------------------------------------------------

    \48\ The Draft MOVES2004 model also assumes that start fuel use
after a hot start is negligible.
---------------------------------------------------------------------------

    Hybrids are tested over what is commonly referred to as a 4-bag FTP
test, with Bag 4 consisting of a Bag 2 repeated after Bag 3. In this
case, the cold start fuel use would be determined exactly as described
above. However, these four bags can also be combined into two bags,
with Bag 1 consisting of a typical Bag 1 and Bag 2 and Bag 2 consisting
of a typical Bag 3 and Bag 4. In this case, cold start fuel use would
be determined from the difference in fuel use between Bags 1 and 2 of
the 2-bag FTP test.
    This estimate of start fuel use is in terms of total fuel use per
start. In order to combine this with running fuel use in terms of
gallons per mile, start fuel use must be divided by the average trip
length. We based our estimate of the average trip length in the U.S. on
the National Household Travel Survey (NHTS). The NHTS was performed in
2001 and statistically surveyed approximately 26,000 households in the
U.S. This survey represents the sixth in a series of surveys dating
back to 1969. (The name of the survey has changed a few times and the
precise survey methods have varied to some degree.) NHTS found that the
average trip taken using a personal vehicle in the U.S. was 9.8 miles
long. This estimate excludes very long trips, such as those taken on
vacations, as well as commercial trips, such as those by taxi cabs.
Based on the survey questionnaire, we believe that the survey also
excludes brief stops (e.g., those at gas stations or convenience
stores), as well as extremely short trips (e.g., moving a vehicle out
of a driveway to allow another vehicle to exit, moving from one
shopping center to another just across the street). Using trip
information from instrumented vehicles in Baltimore and Spokane
(described in more detail below), about 27 percent of all trips fall
into one of these two categories. Thus, we believe that a more precise
estimate of trip length, and one that is more consistent with our
estimate of the fraction of cold starts described above, is 7.7 miles
(9.8 miles divided by 1.27).
    This trip length of 7.7 miles includes all driving, both city and
highway oriented. NHTS does not attempt to split driving into city and
highway categories. Therefore, additional information was needed to
perform this split. As will be described in more detail below, we
estimate that 43 percent of all U.S. driving falls under our definition
of city driving, while 57 percent falls into the highway driving
category. The highway fuel economy label assumes no cold starts (i.e.,
it is based solely on the HFET, which is a hot start test), except
insofar that the effect of a cold start is included in the 22 percent
adjustment factor. Since even long trips have a beginning and often
begin with a cold start, we assumed that the average highway trip had a
length of 60 miles. This is somewhat arbitrary. However, once trip
length is over 20 miles, start fuel use has very little impact on fuel
economy. Still, the inclusion of some start fuel use in the highway
fuel economy estimate makes this estimate more realistic. Assuming an
average trip length of 60 miles for highway driving, the average length
of a city trip must be 3.5 miles for the overall average to be 7.7
miles. Using these two estimates of average trip length allows us to
convert fuel use per engine start into fuel use per mile.
    The total volume of fuel used in either Bag 1 or Bag 3 of the FTP
can be determined by dividing the number of miles of driving during
these portions of the test (3.59 miles for either bag) by the fuel
economy measured during that bag. Thus, the equation for fuel use per
start at either 20 [deg]F or 75 [deg]F is as follows:
    For vehicles tested over either a 3-Bag FTP or 4-Bag FTP:
    [GRAPHIC] [TIFF OMITTED] TP01FE06.021

For vehicles tested over either a 2-Bag FTP:
[GRAPHIC] [TIFF OMITTED] TP01FE06.022

where x is either 20 [deg]F or 75 [deg]F.

    The equation for start fuel use in terms of gallons per mile is:
    For city driving:

[GRAPHIC] [TIFF OMITTED] TP01FE06.023

    For highway driving:
    [GRAPHIC] [TIFF OMITTED] TP01FE06.024

2. Running Fuel Use
    Running fuel use depends primarily on how the vehicle is driven and
the use of fuel to power accessories. Of the latter, air conditioning
is the most significant and the primary accessory addressed in the
emission and fuel economy dynamometer tests. Once the vehicle is warmed
up, ambient temperature has only a modest effect on fuel use.
    The five dynamometer tests include four distinct driving cycles, or
patterns of driving. In addition, the FTP and US06 cycles (the latter
as proposed to be modified) each include two distinct driving patterns.
Two basic characteristics of these driving patterns are depicted in
Table II-2: average speed and a basic measure of the average power
required by the engine.

  Table II-2.--Driving Characteristics of the Current Dynamometer Tests
------------------------------------------------------------------------
                                                           Average power
                  Cycle                    Average speed         A
------------------------------------------------------------------------
FTP (Bags 2 and 3)......................            19.6            40.9
    FTP: Bag 3..........................            25.6            53.6
    FTP: Bag 2..........................            16.1            33.8
HFET....................................            48.2            34.9
US06....................................            48.0           104.3
    US06: City Bag......................            21.5           152.9
    US06: Highway Bag...................            61.0            78.2
SC03 (run with air conditioning on).....            21.4            49.2
Cold Temperature FTP (same driving cycle            19.6           40.9
 as FTP)................................
------------------------------------------------------------------------
A Power defined as velocity times the change in velocity per second
  during cruise or accelerations. Power is set equal to zero during
  decelerations and not considered in the determination of average
  power.

    The FTP and the cold temperature FTP both involve the same driving
cycle, just at different ambient temperatures. Thus, their average
speeds and power are identical, both for the total cycle and for each
bag of emissions measured. The FTP and SC03 involve distinct, but
similar driving cycles. Both are low speed cycles having similar
average speeds and power levels. As the SC03 test is only run with the
air conditioning on and all the other tests are run with air
conditioning off, it is not possible to isolate the effect of the
driving cycle differences between the FTP and SC03 tests directly.
Thus, this leaves five distinct driving patterns which can be used to
represent typical U.S. driving: Bag 2 of the FTP, Bag 3 of the FTP,
HFET, City Bag of US06 and Highway Bag of US06.
    As shown in Table II-2, both Bags 2 and 3 of the FTP are low speed
cycles, but their average power requirements differ by a factor of 1.7.
As will be seen below, it is useful to consider each bag separately in
simulating typical city and highway driving.
    The current US06 test currently consists of 600 seconds of driving
and the emissions are collected in one bag (i.e., one single collection
of pollutants emitted during the test). Thus, the fuel economy result
is over the entire cycle. The US06 driving cycle consists of 5 hills,
or 5 driving segments which begin and end with the vehicle at idle. All
but the second and third hills consist of relatively low speed driving,
while the second hill reaches 71 mph and the third hill reaches 80 mph.
Therefore, in terms of predicting fuel economy, it is useful to
separate the low speed driving from the high speed driving. For
practical reasons, when separating the city into ``city'' and
``highway'' portions, we grouped the second hill with the four low
speed hills in the city bag and the highway bag consists of the
relatively long third hill. Overall, seconds 0-131 and 496-600 of the
cycle would comprise the city bag and seconds 132-495 would comprise
the highway bag. The description of the hills within US06 and their
designation is summarized in Table II-3 below.

                                             Table II-3.--Split of US06 Cycle Into City and Highway Portions
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Maximum speed
               Hill                               Portion of driving cycle (cumulative seconds)                        (mph)             Designation
--------------------------------------------------------------------------------------------------------------------------------------------------------
1................................  0-43                                                                                44.2  City.
2................................  44-134                                                                                70.7  City.
3................................  134-499                                                                                80.3  Highway.
4................................  500-563                                                                                29.8  City.
5................................  564-600                                                                                51.6  City.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    As described in the Introduction, driving at an average speed below
45 mph is defined as city driving, while that above 45 mph is defined
as highway driving. We obtained a description of average U.S. driving
from the Draft MOVES2004 motor vehicle emissions model. This
description included a distribution of vehicle speeds and levels of
vehicle specific power. Using the definition of city and highway
driving, we separated the MOVES description of driving into city and
highway categories. We then performed a linear regression to estimate
what two combinations of the five driving cycles or bags best fit
average U.S. city and highway driving patterns, respectively. The
results are two sets of cycle combinations in terms of time spent
driving. These are shown in Table II-3. We then used the average speeds
of the various cycles and bags to convert these to combinations to a
mileage basis. The combinations of cycles found to best represent
onroad driving in terms of both time spent driving and mileage driven
are shown in Table II-4.

                    Table II-4.--Weighting Factors for the Five Dynamometer Cycles (Percent)
----------------------------------------------------------------------------------------------------------------
                                                                    City driving             Highway driving
                                                             ---------------------------------------------------
                            Cycle                                 Time       Mileage        Time       Mileage
                                                               (percent)    (percent)    (percent)    (percent)
----------------------------------------------------------------------------------------------------------------
Bag 3 FTP...................................................           32           41            0            0
Bag 2 FTP...................................................           60           48            0            0
HFET........................................................            0            0           25           21
US06 City...................................................            8           11            0            0
US06 Hwy....................................................            0            0           75           79
----------------------------------------------------------------------------------------------------------------

    From the results shown in Table II-4, over 90 percent of the time
spent in city driving, and nearly 90 percent of the mileage, is best
explained by Bags 2 and 3 of the FTP cycle. Roughly 80 percent of both
driving time and mileage of highway driving is best explained by the
highway portion of the US06 cycle. These findings confirm that the FTP
(the current basis for the city fuel economy label) is still generally
representative of most low speed driving in the U.S. However, the
relatively low speed and mild accelerations of the HFET (the current
basis for the highway fuel economy label) is not representative of
higher speed driving in the U.S.
    These results also confirm the separation of the two types of
driving contained in the US06 cycle. Only the city portion of US06
appears in the description of city driving and only the highway portion
of US06 appears in the description of highway driving. At the same
time, the relative weights for Bags 2 and 3 in the description of city
driving are similar to that implicit in the FTP, which is 52 percent
and 48 percent, respectively.
    As mentioned above, the fuel use over the three dynamometer cycles,
when combined using these weighting factors, best matches the fuel use
which would occur during typical city and highway driving. The
weighting is performed in terms of fuel use, or fuel consumption per
mile. For example, fuel use during city driving is 0.48 times the
multiplicative inverse of the fuel economy measured over Bag 2 of the
FTP cycle plus 0.41 times the multiplicative inverse of the fuel
economy measured over Bag 3 of the FTP cycle plus 0.11 times the
multiplicative inverse of the fuel economy measured over the city bag
of the US06 cycle.
[GRAPHIC] [TIFF OMITTED] TP01FE06.025

[GRAPHIC] [TIFF OMITTED] TP01FE06.026

    These estimates of running fuel use accounts for a wider variety of
city and highway driving patterns than the FTP and HFET cycles alone.
However, these combinations of fuel use still do not include any fuel
use related to air conditioning or cold temperature. Fuel use related
to air conditioning is estimated using the SC03 test. As shown in Table
II-2, the driving pattern contained in the SC03 test is similar to that
of the FTP, but not identical.
    Using the MOVES2004 methodology for modeling fuel use, we estimated
the combination of Bags 2 and 3 of the FTP which would match the fuel
use over the SC03 cycle with the air conditioning turned off. This
combination is 0.39 times the fuel consumption over Bag 2 and 0.61
times the fuel consumption over Bag 3. Thus, we propose to estimate the
incremental fuel use due to the operation of the air conditioner as the
difference in fuel use measured over the SC03 versus this combination
of fuel use over Bags 2 and 3 of the standard FTP.
    This difference in fuel use between the two tests provides a direct
estimate of the impact of air conditioning use for the conditions
present during the SC03 test. The SC03 test is performed at 95 [deg]F
and 40 percent relative humidity. The test only lasts 10 minutes and
the vehicle is pre-heated with radiant lamps for 10 minutes prior to
the test. Thus, the air conditioning compressor is generally engaged
throughout the entire test. As shown in Table II.-2., the speed of the
vehicle during the SC03 test is also relatively low, at an average
speed of 21.5 mph. Of course, onroad, vehicles operate at different
speeds and ambient temperatures and the compressor may not be engaged
100 percent of the time, particularly during longer trips. All three of
these factors can affect the impact of air conditioning on fuel
economy. We therefore adjust the estimate of the impact of air
conditioning on fuel use from the SC03

test in three ways to account for these three factors.
    The largest factor is portion of driving time during which the
compressor is actually engaged to cool inlet air to the vehicle. The
Draft MOVES2004 model contains an algorithm which estimates the
percentage of time which the compressor is engaged as a function of
ambient temperature and humidity. This algorithm was developed from the
direct measurement of air conditioning operation of 20 vehicles in
Phoenix, Arizona during the summer and fall of 1992.\49\ The algorithm
considers both the frequency that the system is turned on by the driver
and the frequency that the compressor is engaged once the system is
turned on. We combined this algorithm with long term average
meteorological conditions for each county in the U.S. to estimate the
percentage of driving time during which the compressor was engaged
under those conditions. We considered both diurnal and seasonal
temperature variations, as well as variations in the amount of driving
performed throughout the day and across seasons. We estimate that
drivers have the air conditioning turned on 23.9 percent of the time on
average across the U.S., and the compressor is engaged 15.2 percent of
the time.
---------------------------------------------------------------------------

    \49\ Koupal, J. W. Air Conditioning Activity Effects in MOBILE6
(M6.ACE.001). U.S. Environmental Protection Agency, No. EPA420-R-01-
054, November 2001. Website: http://www.epa.gov/otaq/models/mobile6/r01054.pdf
.

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

    We then adjusted this latter percentage to account for reduced
compressor loads at temperatures less than 95 [deg]F and higher loads
above 95 [deg]F.\50\ Again this was done for each county in the U.S.,
accounting for diurnal and seasonal temperature and driving
differences. From this, we estimate that the average load of the air
conditioning compressor in-use is about 87 percent of that at 95 [deg]F
(i.e., during the SC03 test). Thus, the average load of the compressor
in-use is the same as 13.3 percent (15.2 percent x 0.87) of the load
experienced during the SC03 test.
---------------------------------------------------------------------------

    \50\ Nam, Edward K., ``Understanding and Modeling NOX
Emissions From Air Conditioned Automobiles,'' 2000, SAE
2000-01-0858.
---------------------------------------------------------------------------

    Finally, the impact of air conditioning on fuel economy varies with
vehicle driving pattern. Most air conditioning compressors are belt-
driven by the engine. The efficiency of both the engine and compressor
varies with engine speed and load. This variation is difficult to
model, as the speed and load of engines in various vehicles varies
dramatically based on the vehicle's drivetrain design, even over the
same driving cycle. Therefore, we assume that the efficiency of the
engine and air conditioning compressor implied in the SC03 test applies
to other types of driving, as well. However, a more basic effect
related to driving pattern is that the faster a vehicle is moving, the
shorter the amount of time that the vehicle needs to be cooled while it
travels a specific distance. Other factors being equal, this reduces
the amount of energy needed to cool the vehicle per mile of travel.
Therefore, for a specific set of ambient conditions, we assume that the
impact of air conditioning on fuel use is constant with driving time
(i.e., fuel use in terms of gallons per hour is constant). This means
that the excess fuel use due to operating the air conditioner varies
inversely proportional to vehicle speed. In other words, at low vehicle
speeds, like that of the SC03 test, excess fuel use is relatively high
on a per mile basis. At high vehicle speeds, like that of highway
driving, the excess fuel use due to operating the air conditioner is
relatively low on a per mile basis. We confirmed this assumption by
testing five vehicles over a variety of test cycles at EPA's Ann Arbor
laboratory with both the air conditioning turned on and off. The
results of this test program and an analysis of the data are described
in the Draft Technical Support Document.
    The air conditioning compressor is also often engaged when the
defroster is turned on to keep the windshield from fogging up. The air
conditioning dehumidifies the air and excesses the effectiveness of the
defroster. Today's proposal does not include a specific weighting for
demisting activity. We lack a direct estimate of the frequency that the
defroster is turned on or the compressor is engaged during demisting.
Due to the fact that the defroster tends to be operated at lower
ambient temperatures than the air conditioner, the load on the engine
is generally much lower than that during summertime air conditioning.
Thus, the impact of demisting on fuel economy is likely much smaller
than that of summertime air conditioning.
    Given the above, the impact of air conditioning on running fuel use
is estimated as 13.3 percent of the difference between fuel use per
mile over the SC03 and a combination of Bags 2 and Bag 3 of the FTP
times 21.5 mph and divided by the average speed of either city or
highway driving. Based on the descriptions of city and highway driving
from Draft MOVES2004, the average speeds are 19.9 mph and 57.1 mph,
respectively. Thus, the excess fuel use due to air conditioning
operation is:
[GRAPHIC] [TIFF OMITTED] TP01FE06.027

[GRAPHIC] [TIFF OMITTED] TP01FE06.028

    Finally, we have to add the impact of colder ambient temperatures
on running fuel use. We can obtain a direct estimate of the impact of
colder ambient temperatures on running fuel use by comparing the fuel
use over the standard and cold temperature FTP tests. By focusing on
Bag 2 of each FTP test, we exclude the impact of cold temperature on
start up fuel use, which was already addressed in Section II.B.1 above.
For hybrid vehicles, which are tested over the bag 2 driving cycle
twice (the first time as Bag 2 and the second time as Bag 4), we
propose to harmonically average the fuel economies from Bags 2 and 4.
    We considered including Bag 3 in the determination of the effect of
cold temperature on running fuel use. Bag 3 includes some higher speed
driving, so its inclusion broadens the overall driving pattern included
in the estimate. This would particularly improve the representativeness
of the estimate for highway driving. However, Bag 3 begins with a hot
start, unlike Bag 2 which simply follows directly after Bag 1 with no
engine shut-off and restart in between. At 75 [deg]F, a hot start
requires a negligible volume of additional fuel use. However, at 20
[deg]F, even a hot start can require some excess fuel use. Thus,
including the difference between Bag 3 fuel use at 20 and 75 [deg]F in
the estimate of the impact of cold temperature on running fuel use
could also include some excess fuel use related to engine warm up, as
well. Available data indicate that the relative impact of operation at
20 [deg]F versus 75 [deg]F is nearly identical for the two bags (10
percent for Bag 2 and 11 percent for Bag 3). However, the fuel economy
over Bag 3 is lower than over Bag 2, so the absolute difference in fuel
use between 20 [deg]F and 75 [deg]F is actually lower in Bag 3 than Bag
2. We request comment on whether the impact of cold temperature on
running fuel use should only involve Bag 2 or should involve both Bags
2 and 3.
    Neither MOBILE6.2 nor MOVES2004 include correlations of the effect
of ambient temperature on running fuel use. However, as just described,
the impact of colder ambient temperatures on running fuel use is small
(i.e., 10 percent over a drop in temperature of 55 [deg]F). We believe
that the additional fuel use is primarily due to the loss of heat to
the cooler ambient air, higher friction in the slightly cooler moving
parts, as well as slight changes in the properties of the cooler intake
air and air fuel mixture during combustion. All of these changes are
expected to be gradual and fairly linear. Therefore, we assume that the
excess fuel use increases linearly as temperatures decrease below 75
[deg]F. Above 75 [deg]F, we assumed that there was no further reduction
in running fuel use. (This latter assumption was confirmed as part of
the five vehicle test program described above.) We also assume that the
excess fuel use is independent of driving pattern. In other words, the
excess fuel use is the same for city and highway driving on an absolute
basis. We request comment on assuming that the excess running fuel use
due to colder temperatures is independent of driving pattern on a
relative basis (i.e., in percentage terms).
    Using the same meteorological and VMT inputs described above
related to start fuel use, we estimate the average temperature in the
U.S. at which driving occurs is 58.7 [deg]F. This temperature is 70
percent of the way from 75 [deg]F to 20 [deg]F. Thus, any excess fuel
use associated with operation at 20 [deg]F should be weighted by 100
percent minus 70 percent, or 30 percent.
    Given the fact that over 80 percent of city driving is represented
by Bags 2 and 3 of the FTP, we decided to use the fuel economy measured
during Bags 2 and 3 of the cold FTP directly to represent the fuel
economy of city driving at 20 [deg]F. We repeated the regression of the
VSP distribution of city driving from Draft MOVES2004 against the VSP
distributions of just Bags 2 and 3. The best fit produced a 50/50
weighting of the two bags. Thus, we propose to represent the fuel
economy of city driving at 20 [deg]F by a 50/50 harmonic average of the
fuel economy over Bags 2 and 3 of the cold FTP. Mathe- matically, then,
for city driving:
[GRAPHIC] [TIFF OMITTED] TP01FE06.029

    Highway driving occurs at higher speeds than those typical of the
cold FTP. We conducted a detailed review of past test programs which
evaluated the impact of colder temperatures on fuel economy at highway
driving speeds. This review is described in the Draft Technical Support
Document. There, we concluded that the effect of cold temperature on
fuel economy at city driving speeds could overestimate the effect at
higher speeds. Thus, we decided not to use the fuel economy measured
over the cold FTP directly to represent the impact of cold temperature
on highway fuel economy. Instead, we believe that it is more prudent at
this time to simply assume that running fuel use at 20 [deg]F at
highway speeds is 4 percent greater than that at 75 [deg]F. Thus,
mathematically, for highway driving:

[GRAPHIC] [TIFF OMITTED] TP01FE06.030

    Combining the estimates of running fuel use at 75 [deg]F without
the air conditioning system running with the estimate of excess fuel
use of running the air conditioning system and the estimate of excess
fuel use due to colder ambient temperatures produces the following
formulae for running fuel use:
For city driving:
[GRAPHIC] [TIFF OMITTED] TP01FE06.031

For highway driving:
[GRAPHIC] [TIFF OMITTED] TP01FE06.032

3. Adjustment Factor for Non-Dynamometer Effects
    Fuel economy estimated using the five current dynamometer tests can
account for many factors, including vehicle design, driving pattern,
trip length, cold temperature and air conditioning. However, there are
still a large number of factors which affect vehicle fuel economy that
cannot be addressed by dynamometers tests. These include roadway
roughness, road grade (hills), fuel quality, large vehicle loads (e.g.,
trailers, cargo, multiple passengers), wind, precipitation, to name
just a few. Even when a factor is addressed by a dynamometer test, such
as driving pattern or air conditioning, the effect can only be
approximated, as all realistic driving patterns cannot possibly be
included in a test having a reasonable length of time. Nor can all the
possible ambient conditions affecting air conditioner operation be
tested. Thus, any estimate of in-use fuel economy derived from the five
dynamometer tests is necessarily approximate, both with respect to
factors addressed directly by the tests and those which are not.
    The impacts of a number of these factors on onroad fuel economy
relative to that measured on a dynamometer is possible to estimate,
while others are difficult to estimate. One factor which can be
estimated is fuel quality. EPA's certification test fuel contains no
oxygenates, while commercial gasoline contains significant volumes of
ethanol and methyl tertiary butyl ether (MTBE). Both ethanol and MTBE
contain less energy per gallon, so vehicles operating on fuel
containing these oxygenates tend to achieve lower fuel economy,
generally in proportion to the reduction in the energy content of the
finished gasoline. For example, the driver of a vehicle operating on
gasoline containing ten percent ethanol by volume would experience a
3.5 percent decrease in fuel economy compared to gasoline not
containing any ethanol or other oxygenate. We expect the nation's
gasoline supply to contain roughly 5.4 billion gallons of ethanol by
2008. This is equivalent to 37 percent of the nation's gasoline supply
containing 10 percent ethanol by volume. Thus, by 2008, we expect
commercial gasoline on average to contain about 1.2 percent less energy
per gallon than EPA test fuel. Thus, this difference in energy content
means that onroad fuel economy will be about 1.2 percent less than that
estimated using the 5-cycle formulae described in the previous section.
This effect could increase beyond 2008 as more ethanol is used in the
nation's gasoline supply.
    Another factor which can be estimated is tire pressure. In February
2001, NHTSA conducted a survey of the tire pressure of in-use vehicles.
Tire pressures were measured on over 11,500 vehicles at 24 locations
throughout the U.S. The results of the study and our analysis of the
data are described in the Draft Technical Support Document. We found
that the tires of the average car were under-inflated by 1.1 pounds per
square inch (psi), while those on light trucks were under-inflated by
1.9 psi. Using estimates of the effect of tire pressure on fuel economy
presented by NHTSA, we estimate that the fleet-wide effect of under-
inflation is 0.5 percent.
    Another factor which can be estimated, though more approximately,
is wind. Wind affects vehicular fuel economy in two ways. First,
aerodynamic drag is proportional to the square of vehicle speed (i.e.,
the higher the vehicle speed, the faster aerodynamic drag increases for
a given increase in speed). Thus, increasing wind speed by 1 mph
increases aerodynamic drag, and thus, reduces fuel economy, more than
the effect of decreasing wind speed by 1 mph. Second, both the
effective area of a vehicle and its drag coefficient increases as the
true wind direction moves to either side from head-on. Basically,
vehicles are designed to move forward through the air, not sideways.
Thus, any side wind increases drag and decreases fuel economy. Based on
a distribution of wind speeds (yielding an average wind speed in the
U.S. of 9.4 mph), we estimate that these two effects reduce onroad fuel
economy on average by 5-6 percent.
    Several other factors are still relevant to a 5-cycle fuel economy
estimate, namely altitude, road grade, road surface, road curvature,
brake drag, wheel alignment, tire switching, and vehicle load. EPA
estimated the impact of these factors to be 8 percent at the time of
the 1984 label adjustment rule.

We have reduced the impact of road surface from 4 percent to 1-3
percent due to increased urbanization and road paving which has
occurred since that time. Thus, we estimate these other factors to
reduce onroad fuel economy by 5-7 percent. Combining this estimate with
those of fuel quality, tire pressure and wind produces an overall
downward effect of 11-15 percent.
    As described further in Section II.E below, we also compared the 5-
cycle fuel economy values to fleet-wide estimates of fuel economy made
by FHWA for 2002 and 2003, after we made several adjustments to improve
the comparability of the two estimates. The 5-cycle fuel economy values
best match the FHWA-based estimates when we include a factor of 0.88-
0.91 in the 5-cycle fuel economy formulae (i.e., a reduction of 9-12
percent due to factors not addressed by the 5-cycle formulae). We
propose to average these two ranges (i.e., the 9-12 percent range based
on FHWA, and the 11-15 percent range based on the analysis of non-
dynamometer effects discussed above) and account for these factors by
including a factor of 0.89 in the 5-cycle city and highway formulae
(i.e., a reduction of 11 percent in both city and highway fuel
economy).

D. Derivation of the MPG-Based Approach

    The mpg-based approach to fuel economy label adjustments utilizes
the results of applying the 5-cycle formulae to all vehicles for which
we were able to gather fuel economy data for all five dynamometer
cycles. We requested that all manufacturers submit to us all their
available fuel economy data for vehicles which had been tested over at
least one of the US06, SC03 or cold FTP tests. We combined this data
with our own fuel economy data to develop a database of 423 recent
model year vehicles which had been tested over all five cycles. We
applied the above 5-cycle formulae to these vehicles. We then developed
a relationship between the 5-cycle city and highway fuel economies and
the city and highway fuel economies using the current adjustment
factors, respectively.
    We evaluated two options for developing this relationship. One
option plotted 5-cycle fuel economy versus fuel economy using the
current adjustment factor. The other option plotted the inverse of 5-
cycle fuel economy (i.e., fuel consumption) versus the inverse of fuel
economy using the current adjustment factor. As indicated from the
description of the 5-cycle fuel economy formulae, most of the modeling
of fuel economy is performed in terms of fuel consumption (i.e.,
gallons of fuel burned per mile versus miles traveled per gallon of
fuel burned). While both types of plots produce relationships with a
high degree of correlation, the plots in terms of fuel consumption are
linear, while those in terms of fuel economy are non-linear. Given that
the linear relationship is simpler and the degrees of correlation are
essentially the same, we are proposing to base the mpg-based
adjustments on the correlations in terms of fuel consumption. However,
the label values themselves would remain in terms of fuel economy, as
required by EPCA. We request comment on the use of the correlations
performed in terms of fuel consumption versus those performed in terms
of fuel economy. Both approaches are described in detail in the Draft
Technical Support Document.
    Figures II-5 and II-6 show the relationship between the inverse of
5-cycle city (or highway) fuel economy (i.e., fuel consumption) versus
the inverse of FTP (or HFET) fuel economy. Figure II-5 shows city fuel
consumption, while Figure II-6 shows highway fuel consumption.
[GRAPHIC] [TIFF OMITTED] TP01FE06.033

[GRAPHIC] [TIFF OMITTED] TP01FE06.034

    The results of regressing 5-cycle fuel consumption versus fuel
consumption over the FTP or HFET are shown in the above figures. In
terms of fuel economy:
[GRAPHIC] [TIFF OMITTED] TP01FE06.035

[GRAPHIC] [TIFF OMITTED] TP01FE06.036

    The standard deviation of the difference between the mpg-based
equations and the 5-cycle fuel economies are 2 percent for city and 5
percent for highway. These differences are roughly equivalent to 0.5
mpg for city fuel economy and 1-2 mpg for highway fuel economy. Thus,
while the mpg-based equations represent much of the difference in fuel
economy represented by the 5-cycle formulae, differences between the
fuel efficiency of individual vehicles on the order of 0.5-2 mpg are
muted by the mpg-based approach.
    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 annually
using all of the available 5-cycle fuel economy estimates for the
previous three model years. EPA would publish the mpg-based equations
for the upcoming model year's labels by March 1 of the previous year
(i.e., by March 1, 2007 for the 2008 model year).

E. Effect of the New Formulae on Fuel Economy Label Values

    The impact of today's proposal on city and highway fuel economy
label values was assessed using the same database of 423 late model
year vehicles used to develop the mpg-based adjustments above. Table
II-5 presents the results of this comparison for all 423 vehicles, as
well as various sub-sets of vehicles.

                                     Table II-5.--Effect of 5-Cycle Formulae on City and Highway Fuel Economy Labels
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                            City                         Highway                     Combined *
                                                               -----------------------------------------------------------------------------------------
                                                                 Current   5-cycle   Percent   Current   5-cycle   Percent   Current   5-cycle   Percent
                                                                  (mpg)     (mpg)    change     (mpg)     (mpg)    change     (mpg)     (mpg)    change
--------------------------------------------------------------------------------------------------------------------------------------------------------
Hybrids.......................................................        42        32       -23        41        37        -9        41        34       -16
Diesels.......................................................        26        23       -13        35        31       -11        30        27        -9
---------------------------------------------------------------
                                                                  Conventional vehicles
--------------------------------------------------------------------------------------------------------------------------------------------------------
12 Highest FE.................................................        30        26       -15        36        33        -8        33        30       -10

12 Lowest FE..................................................        11        10       -11        15        14        -8        12        12        -6
Average.......................................................        19        16       -13        25        22        -9        21        19       -8
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Combined fuel economy for Current MPG is based on weighting of 55%/45% city/highway, respectively.
Combined fuel economy for 5-Cycle MPG is based on weighting of 43%/57% city/highway, respectively.

    As can be seen from Table II-5, use of the 5-cycle formulae would
reduce both current city and highway fuel economy label values. For
conventional vehicles, city and highway fuel economy values would be
reduced an average of 13 percent and 9 percent, respectively. The
reduction in city fuel economy label values for higher than average
fuel economy vehicles would be slightly higher, while that for lower
than average fuel economy vehicles would be slightly lower. The
reduction in highway fuel economy label values varies only slightly.
    The impact on hybrid vehicles would be greater, averaging a 23
percent reduction for city fuel economy and 9 percent for highway fuel
economy. This greater impact occurs primarily because a number of the
fuel efficient aspects of hybrid vehicles produce their maximum benefit
under conditions akin to the FTP and HFET tests, and are somewhat less
beneficial during aggressive driving, colder ambient temperatures and
when the air conditioner is turned on. However, these vehicles would
still remain among the top fuel economy vehicles.
    There is one diesel vehicle in our 5-cycle fuel economy database.
The impact of the 5-cycle formulae on this one diesel is very similar
to that for the average conventional, gasoline-fueled vehicle.
    The impact of the mpg-based formulae would be very similar on
average to those shown in Table II-5 above for conventional vehicles.
This is not surprising, since the mpg-based formulae are based
essentially on the average results of the 5-cycle formulae. However,
the mpg-based formulae would increase the city fuel economy of hybrid
vehicles slightly, as indicated in Table II-6. This occurs because
there are only 9 hybrid vehicles in the database, compared to 413
gasoline-fueled, conventional vehicles. The mpg-based regression of
city fuel economy, therefore, represents essentially the impact of the
5-cycle formulae on conventional vehicles, which is less than that for
hybrids. The mpg-based regression of highway fuel economy is
essentially the same for conventional and hybrid vehicles.

                Table II-6.--Effect of MPG-Based Formulae on Conventional and Hybrid Fuel Economy
----------------------------------------------------------------------------------------------------------------
                                                     City                                 Highway
                                   -----------------------------------------------------------------------------
                                      Current     MPG-based     Percent      Current     MPG-based     Percent
                                       (mpg)        (mpg)        change       (mpg)        (mpg)        change
----------------------------------------------------------------------------------------------------------------
Conventional......................           19           16          -13           25           22           -9
Hybrids...........................           42           34          -18           41           37          -10
----------------------------------------------------------------------------------------------------------------

F. Comparison to Other Onroad Fuel Economy Estimates

    In the 1984 label adjustment rule, EPA was able to compare
fleetwide estimates of a variety of city and highway fuel economy label
options to a number of independent estimates of onroad fleet fuel
economy. In the late 1970's and early 1980's, EPA and several auto
manufacturers had collected onroad fuel economy estimates from tens of
thousands of drivers which could be compared to the EPA city and
highway fuel economy labels. The fleetwide combined EPA fuel economy
estimate could also be compared to onroad fuel economy based on
estimates of total VMT and total fuel consumption from the Federal
Highway Administration (FHWA). EPA primarily used the driver-based fuel
economy estimates to develop the current 10 percent and 22 percent
adjustments to fuel economy over the FTP and HFET, respectively.
    Repeating this type of comparison is more complicated today than it
was in 1984. First, 5-cycle fuel economy estimates are not available
for the current car and light truck fleet. Emission standards based on
the US06 and SC03 tests just began to be phased in with the 2001 model
year. Also, these tests are only performed on a limited number of
vehicle configurations. Second, studies of driver-based fuel economy
similar to those available in 1984 have not been performed of late. At
the same time, as mentioned in the Introduction above, a number of
consumer organizations have begun conducting their own fuel economy
tests. Several governmental organizations have been monitoring onroad
fuel economy, focused particularly on new hybrid technology. While the
findings of these various organizations were compared to the current
EPA label fuel economy values in the Introduction, here they will be
compared to the 5-cycle and mpg-based fuel economy estimates.
    We begin with a comparison of the 5-cycle fuel economy values with
the fleetwide fuel economy estimates developed by FHWA. Because we do
not have fuel economy data for all vehicles over all 5 dynamometer
cycles, and therefore cannot develop a 5-cycle fuel economy estimate
for the current onroad fleet directly, this comparison requires a
three-step process.
    The first step in this process compares fleetwide fuel economy
estimates based on EPA's current fuel economy labels to the FHWA
estimate of onroad fuel economy. The second step in this process is to
compare combined city-highway fuel economy using the 5-cycle formulae
to that using the current EPA city and highway label procedures. This
comparison is performed for vehicles for which we have 5-cycle fuel
economy data. We will assume that this relationship also applies to
those

vehicles for which we do not have 5-cycle data. The third step
evaluates changes in FTP and HFET test procedures which accompanied the
implementation of the US06 and SC03 testing requirements. The most
important change was the removal of a 10 percent increase in tractive
road load horsepower which was intended to represent the use of air
conditioning in the summer. This effectively increased fuel economy
label values with no accompanying change in onroad fuel economy. The
vehicles assessed by FHWA were nearly all tested with the 10 percent
adjustment in road load, while those in the 5-cycle certification
database were not. Therefore, this difference needs to be accounted for
when connecting the results of the two previous comparisons.
    Overall, the difference between 5-cycle fuel economy and FHWA
onroad fuel economy is the combination of the percentage differences
from the three comparisons:
    (1) Current EPA label fuel economy (with 10 percent road
adjustment) to FHWA onroad fuel economy,
    (2) 5-cycle fuel economy to current EPA label fuel economy (without
10 percent road load adjustment), and
    (3) the effect of the removal of the 10 percent road load
adjustment.
    FHWA publishes fleet-wide estimates of onroad fuel economy for cars
and light trucks in their annual Highway Statistics publication.\51\ We
will focus on the combined estimates for cars and light trucks here,
since various states use different criteria to distinguish between the
two vehicle classes. At the same time, the criteria used to distinguish
between cars plus light trucks and other vehicles are very consistent.
The FHWA definition of light trucks (actually 4-tire, 2-wheel trucks)
includes some vehicles which EPA classifies as heavy-duty vehicles. We
have adjusted the FHWA estimates upward to provide a more direct
comparison. After this adjustment, the FHWA-based estimate of fleet-
wide onroad fuel economy for cars and light trucks is 20.3 mpg for 2002
and 20.5 mpg for 2003.
---------------------------------------------------------------------------

    \51\ U.S. Department of Transportation, Federal Highway
Administration. Highway Statistics 2003. See Table VM-1. Web site:
http://www.fhwa.dot.gov/policy/ohim/hs03/htm/vm1.htm.

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

    We used the EPA MOBILE6.2 in-use emission model to calculate fleet-
wide average EPA combined fuel economy label values for these two
years. For both years, average label fuel economy was 21.1 mpg. Thus,
for 2002 and 2003, the FHWA-based onroad fuel economy was 4 percent and
3 percent lower than the current combined EPA label value,
respectively. Thus, the result of the first step in this process is an
indication that the current labeling formulae, based on FTP and HFET
testing with the 10 percent road load adjustment, could be over-
estimating onroad fuel economy by 3-4 percent.
    Moving to the second step, in Table II-5 above, we presented city
and highway fuel economy label values using both current and 5-cycle
formulae for 423 2003-2005 model year vehicles. The FHWA estimates
apply to all driving, both city and highway. Therefore, we are
primarily interested in combined city-highway fuel economy values.
Also, we are using FHWA estimates for the 2002 and 2003 calendar years,
as these are the most recent available. The number of hybrid vehicles
on the road was negligible during this timeframe. Therefore, we will
only use the 5-cycle fuel economy estimates for the 414 non-hybrid
vehicles in our database. There is no need to perform this comparison
separately for the mpg-based formulae, since the average fuel economy
from the 5-cycle and mpg-based formulae are identical for non-hybrid
vehicles.
    The combined fuel economy using the current label formulae is a 55/
45 harmonic weighting of the current city and highway fuel economy
labels. The average combined fuel economy using the current EPA label
values for these 414 vehicles is 20.9 mpg. However, it is important to
note that the FTP and HFET testing upon which these values are based
were performed without the 10 percent increase in road load horsepower
to account for air conditioning and other accessories. For the proposed
5-cycle formulae, combined fuel economy is a 43/57 harmonic weighting
of the 5-cycle city and highway fuel economies. This city/highway split
for the 5-cycle fuel economies is based on:
    (1) The assumption that driving generally less than 45 mph is city
driving and that above 45 mph is highway driving, and
    (2) the description of onroad driving patterns contained in MOVES.
    We seek comment on any other data that may indicate what
constitutes city and highway driving. The mathematical formula for
converting the 5-cycle city and highway fuel economy values into an
estimate of average onroad fuel economy is as follows:
[GRAPHIC] [TIFF OMITTED] TP01FE06.037

    The average combined 5-cycle fuel economy using this formula for
the 414 conventional vehicles is 19.2 mpg, which is 8 percent lower
than that based on the current label values. This is the result of the
second step in the process.
    Moving to the third step, prior to the implementation of the
Supplemental FTP standards and the running of the US06 and SC03 tests,
EPA approximated the occasional load on the engine of the air
conditioner and other accessories by increasing the tractive road load
horsepower setting on the dynamometer by 10 percent of each vehicle's
normal road load. This increase was equivalent to increasing the
rolling resistance of the tires and aerodynamic drag of moving the
vehicle through the air by 10 percent. When the explicit testing of
emissions with the air conditioning system turned on during the SC03
test, EPA removed this 10 percent adjustment on the FTP and HFET tests.
This was appropriate for emissions testing, given the direct
measurement of emissions with the air conditioning on during the SC03
test. However, since the fuel economy over the SC03 test is not
included in the calculation of the fuel economy label values, the
removal of the 10 percent adjustment during FTP and HFET testing
effectively increased the city and highway label values with no
accompanying change in onroad fuel economy.
    Using a detailed model of a vehicle's energy use on the road
(please see the Draft Technical Support Document for details), we
estimate that removing the 10 percent adjustment in road load increased
fuel economy over the FTP and HFET by 2 percent and 5 percent,
respectively. Decreasing the FTP and

HFET fuel economy values for the 414 conventional vehicles in our 5-
cycle certification database by these amounts decreased combined EPA
fuel economy on average by 3 percent. The average combined fuel economy
using the current label formulae decreased from 20.9 mpg to 20.2 mpg.
Thus, instead of decreasing the current combined label value by 8
percent, when considered in terms of test procedures effective for the
2002-2003 onroad fleet, the 5-cycle formulae only decrease label fuel
economy by an average of 5 percent. This 5 percent decrease represents
the combined effects of steps 2 and 3 in our process.
    Overall, then, from step 1, the current label values over-estimate
onroad fuel economy per FHWA (with some adjustments by EPA) by 3-4
percent, while the 5-cycle formulae decrease current label values (of
the 2002-2003 fleet) by 5 percent. Thus, the proposed 5-cycle formulae
should move the combined fuel economy label values to within 1-2
percent of a comparable estimate of fleetwide fuel economy using FHWA
techniques.
    Next, several governmental and non-governmental organizations
perform their own fuel economy assessments. Of these, the American
Automobile Association (AAA) and Consumer's Union (CU) have tested the
greatest number of vehicles. Oak Ridge National Laboratory (ORNL) has
recently begun a program where drivers can submit their own fuel
economy measurements via the Internet. Argonne National Laboratory
(ANL) has also been operating an extensive hybrid demonstration project
for a few years as part of DOE's Freedom Car project.
    Each of these estimates of onroad fuel economy have their relative
strengths and weaknesses. The strengths of the non-governmental
organization testing include the fact that the vehicles are tested on
actual roads, usually in traffic and under real environmental
conditions. The primary weaknesses of this testing include:
    (1) The fact that the driving patterns involved are not typically
published, so they may or may not be representative of average U.S.
driving,
    (2) Vehicles are tested throughout the year, so some vehicles are
tested in hot weather and others in cold weather and some under
moderate conditions, and
    (3) In some cases, the actual test procedures used to measure the
volume of fuel consumed during the test are not described, leaving some
doubt as to their accuracy. Still, because of the public interest in
these estimates, we believed that they should be considered here.
    Consumer Report recently published their fuel economy estimates for
303 2000-2005 model year vehicles. Consumer Report makes three fuel
economy measurements: one for city driving, one for highway driving and
one for a 150-mile trip. They also publish a combined fuel economy
value which is a harmonic average of the three fuel economy
measurements.
    We were able to match 151 of these vehicles with those in our 5-
cycle fuel economy database. For these 151 vehicles, we compared
Consumer Report's city, highway and combined fuel economy measurements
to the analogous current EPA label, 5-cycle and mpg-based fuel economy
estimates. The results show that the Consumer Report city fuel economy
values are well below both the current label or 5-cycle label values,
though the difference for the 5-cycle values are half those of the
current label values. The reverse is true for highway fuel economy. The
current EPA combined label values average 10 percent higher than the
Consumer Report values. However, the average of the combined 5-cycle
values is only 1 percent higher than the average combined Consumer
Report fuel economy.
    More specifically, the vehicles tested by Consumer Report include 6
hybrid vehicles. We have 5-cycle fuel economy estimates for five of
these vehicles. A comparison of the Consumer Report, current EPA label
and 5-cycle label fuel economy values shows that the current combined
EPA label fuel economy values average 27 percent higher than the
combined fuel economy measured by Consumer Report. The difference
between EPA and Consumer Report combined fuel economy decreases
dramatically with the 5-cycle approach. On average, the EPA 5-cycle
combined fuel economy is only 5 percent higher than that measured by
Consumer Report. This is slightly higher than the zero percent
difference found for non-hybrids. Thus, the vehicle-specific 5-cycle
approach appears to reflect some of the factors measured with Consumer
Report testing which are missed by the current fuel economy tests (FTP
and HFET). As expected, the differences increase with the mpg-based
approach, since the mpg-based adjustments are based essentially on non-
hybrid vehicle results. Additional discussion and analysis of the
Consumer Reports data can be found in the Draft Technical Support
Document.
    As discussed above, AAA also develops its own fuel economy
estimates. In their 2004 report, AAA presented their test results and
the EPA label values for 163 models. As AAA only develops a single fuel
economy estimate for each vehicles (i.e., no separate city or highway
estimates), we compared their estimates to a combined mpg-based fuel
economy value. As discussed above, the mpg-based city fuel economy was
weighted 43 percent and the highway value was weighted 57 percent. We
did not compare the 5-cycle fuel economy values to the AAA estimates
due to the relatively low number of models which were in both the AAA
and EPA certification fuel economy database.
    The average mpg-based combined fuel economy for the 163 vehicles
was 2 percent higher than the average AAA fuel economy. The combined
mpg-based fuel economy was higher than the AAA estimate for 91 models
and lower for 71 models. The two estimates matched for one model. These
comparisons are quite similar to those between the current label fuel
economy values and the AAA values. However, the mpg-based fuel economy
more closely matches those of AAA for the two hybrids in the AAA
database. For the Insight and Prius, the current combined EPA fuel
economy values exceed those of AAA by 6-8 percent. The combined mpg-
based fuel economy values straddle the AAA estimates, one being one
percent higher and the other being two percent lower.
    The ORNL Your MPG data discussed in Section I are similar in nature
to the much larger databases analyzed for the 1984 label adjustment
rule. Drivers measure their own fuel economy and provide a perceived
split of their driving into city and highway categories. The strength
of this type of data is the fact that the vehicle is being operated by
the owner or regular driver in typical use. The weaknesses are the
unknown representativeness of the sample, the unknown nature of the
technique used by the owner/driver to measure fuel economy and the
short time period over which fuel economy is generally assessed (e.g.,
a couple of tanks full). In the particular case of the ORNL database,
its current size is still small (2544 estimates of fuel economy for
1794 vehicles) compared to those available in 1984, though it is
growing daily.
    We compared the fuel economy estimates submitted to the ORNL
website with the mpg-based fuel economy values. We did not attempt to
estimate 5-cycle fuel economy values for these vehicles, as we lacked
5-cycle fuel economy data for most of the vehicles. However, on average
for non-hybrid vehicles, the mpg-based values match the 5-cycle values.
We combined the mpg-based city and highway values using each driver's
estimate of the

percentage which was city and highway. If a driver did not provide an
estimate of the breakdown of their driving pattern, we assumed that
their driving was 43 percent city and 57 percent highway. We also
conducted separate comparisons for conventional gasoline vehicles,
hybrids and diesels. The results are shown in Table II-9 below.

                           Table II-9.--Your MPG Versus Current EPA Label Fuel Economy
----------------------------------------------------------------------------------------------------------------
                                               Fuel economy (mpg)
-----------------------------------------------------------------------------------------------------------------
                                                                                MPG-based EPA
                                                 Number of                      combined label:  Difference from
                Vehicle type                     estimates         Your MPG      vehicle city/    MPG-based (%)
                                                                                hwy weighting
----------------------------------------------------------------------------------------------------------------
Conventional Gasoline.......................             2315             23.7             23.4              1.3
Hybrid Gasoline.............................              239             46.1             47.1             -2.2
Diesel......................................               88             41.0             38.8              5.7
----------------------------------------------------------------------------------------------------------------

    As can be seen, diesels appear to perform the best with respect to
their mpg-based fuel economy values, outperforming the proposed mpg-
based combined label by 5.7 percent. Conventional gasoline vehicles
also appear to slightly outperform the mpg-based label values by 1.3
percent. Hybrids are the only category to fall short, but do so by a
small margin of 2.2 percent.
    The Department of Energy has overseen the real world operation of a
number of electric hybrid vehicles for a period of years. The Advanced
Vehicle Testing Activity (AVTA), conducted jointly by the Idaho
National Laboratory (INL) and the National Renewable Energy Laboratory
(NREL), has been benchmarking hybrid electric vehicle performance as
part of the FreedomCAR & Vehicle Technologies Program. The strength of
the FreedomCAR program testing of hybrid vehicles lies in the fact that
the vehicles are operated on the road over long term periods similar to
what consumer-purchased vehicles experience, albeit often in commercial
applications. Over a million miles of operation have been assessed and
careful fuel consumption and mileage records are kept. The weaknesses
are that some of the vehicles are in commercial use (e.g., company pool
vehicles) for accelerated mileage accumulation and that the vehicles
are operated exclusively in the Southwest, mainly Phoenix, Arizona and
surrounding areas. Nevertheless, the vehicles are operated just as any
other vehicle would be in that application and the vehicles are subject
to all of the environmental and roadway factors which affect the fuel
economy of typical vehicles, such as winds, rough roads, hills, traffic
congestion, etc. Because of the limited geographic area of the program,
the vehicles are more likely to experience hot temperatures and air
conditioning use than cold temperatures.
    The vehicles' operators report mileage and fuel usage to FreedomCAR
which posts the monthly and cumulative fuel economy of each electric
hybrid fleet on a monthly schedule.\52\ Therefore, seasonal changes in
fuel economy can be observed. The results of the fleets are shown in
Table II-10.
---------------------------------------------------------------------------

    \52\ http://energy.inel.gov/x-web/other/framed.shtml?http://http://avt
.inel.gov.

                                 Table II-10.--FreedomCAR Hybrid Fleet Cumulative Versus EPA Combined Label Fuel Economy
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Fuel economy (mpg)                   Difference (%)
                                                                                ---------------------------------------------------------------------
                                                            Accumulated     Fleet                EPA combined label \A\
                         Vehicle                              mileage       size             ------------------------------                       MPG-
                                                                                Onroad                         MGP-     Current   5-cycle    based
                                                                                Current   5-cycle    based
--------------------------------------------------------------------------------------------------------------------------------------------------------
2001 Honda Insight......................................         417,000         6      45.2      61.0      51.5      52.6        35        14        16
2002 Toyota Prius.......................................         458,000         6      41.0      48.6  ........  ........        19  ........  ........
2003 Honda Civic........................................         378,000         4      37.6      46.3      38.0      40.0        23         1         6
2004 Toyota Prius.......................................         102,000         2      44.4      54.6      45.9      46.0        23         3         4
2004 Chevrolet Silverado 2wd............................          21,000         1      18.5      18.8  ........  ........         2  ........  ........
2004 Chevrolet Silverado 4wd............................          28,000         1      17.7      16.9      14.9      15.3        -5       -16       -14
2005 Ford Escape 2wd....................................          28,000         1      28.1      33.6  ........  ........        20  ........  ........
2005 Ford Escape 4wd....................................          29,000         1      25.5      29.9      24.1      25.9        17        -5        -2
2005 Honda Accord.......................................          62,000         2      27.6      32.3      26.3      29.1        17        -5         5
2005 Lexus RX400h.......................................          20,000         2      26.3      28.1      24.8      24.8         7        -6        -6
Average.................................................         154,000       2.6      31.2      37.0      32.2      33.4        16        -2        2
--------------------------------------------------------------------------------------------------------------------------------------------------------
\A\ Current combined is a \55/45\ weighting of city/highway fuel economy. 5-cycle combined is a \43/57\ weighting of city/highway fuel economy, as
  explained further in this section.

    As can be seen, EPA's current label formulae over-estimate the
onroad fuel economy achieved by all but one of the hybrid vehicle
fleets. It should be noted that the values for current combined fuel
economy are those from EPA's certification database and are not the
official label values. The official label values are even higher due to
differences between the worse case vehicles tested over the
Supplemental FTP cycles and the average vehicle sold. The largest
shortfall was 35 percent for the Honda Insights. The Chevrolet
Silverado was the only model which

exceeded the current label value of the test vehicle in our
certification database. This is likely related to the fact that its
hybrid design includes limited fuel economy targeted features. Except
for the Chevrolet Silverado, the onroad fuel economy for each fleet
never exceeded either the city or highway fuel economy label. This
indicates that regardless of whether the vehicles were driven
predominantly in city or highway driving modes, other real world
factors reduced onroad fuel economy beyond that captured in the FTP and
HFET and the current 10 percent and 22 percent adjustment factors.
    Table II-10 also presents combined fuel economy values using the
proposed 5-cycle and mpg-based formulae for those vehicles for which we
have 5-cycle fuel economy data. The proposed combined 5-cycle label
values exceed onroad fuel economy for three out of seven models, while
the proposed mpg-based values do so for five out of seven models. The
average of the differences is very small in both cases. On average, the
combined 5-cycle value is 2 percent lower than those measured onroad.
However, as mentioned above, the specific vehicles in our 5-cycle
database tend to be worse case. For example, the current official label
values exceed those shown in Table II-10 by 3 percent. If we increased
the combined 5-cycle values commensurately, they would exceed the
onroad values by 1 percent. Thus, while both of the proposed approaches
do a much more reasonable job at predicting the onroad fuel economy
achieved in the DOE FreedomCar program than the current label formulae,
the proposed 5-cycle formulae appear to be particularly accurate when
compared to the FreedomCar experience.
    When analyzing monthly reported fuel economy, large seasonal
fluctuations in fuel economy were observed on most of the hybrid
fleets. The seasonal fluctuations are especially noticeable on the
fleets that had been in service for over one year. The fuel economy
during the hot and often humid summer weather months when heavy air
conditioning usage could be expected was as much as 15 mpg lower than
observed fuel economy during mild Phoenix area winter months. Fuel
economy over the SC03 air conditioning test for the three hybrids with
the highest rated fuel economy shown in Table II-10 (Prius, Insight and
Civic) tends to be 15-20 mpg lower than that over the FTP. No cold
weather operation similar to northern states or the Cold FTP (20
[deg]F) was reported which would likely have resulted in further
shortfalls.
    The FreedomCAR program is continuing to accumulate mileage on all
of the 2004 and 2005 models listed above. While the time in service and
accumulated mileage is relatively low compared with the original fleets
that have completed service, the initial results support similar
substantial shortfall likely due to the same real world factors not
currently captured during the FTP or HFET.

III. What Major Alternatives Were Considered?

    As explained in Section I, the current city and highway test
results for fuel economy are adjusted downward by 10 and 22 percent,
respectively, to derive the current fuel economy label values. One
possible approach that we evaluated would be to simply revise these
adjustment factors, presumably to further ``discount'' the test
results, to achieve results that more closely mirror real-world fuel
economy. However, this is a fundamentally flawed approach that does not
solve the problems with the current fuel economy estimates.
    There is little doubt that revising the current adjustment factors
could result in city and highway fuel economy values that better
approximate real-world values on average across the U.S. vehicle fleet.
This approach might be more accurate for certain vehicle models.
However, the fundamental problem with this approach is that it ignores
the variation in how different vehicle models respond to factors that
impact fuel economy. As we discussed in Section I, there is a wide
variation in how different vehicles respond to factors such as the use
of air conditioning, cold temperature operation, and higher speeds and
accelerations. For example, in our database of about 420 vehicles,
operation on the city test cycle at 20 degrees F resulted in fuel
economy that was anywhere from 0 to 40 percent worse than fuel economy
achieved on the same test cycle at 75 degrees F. Because there are now
additional tests in place (for emissions compliance) that have the
ability to measure a vehicle's fuel economy over this wider range of
driving operation, we have an opportunity to design the new fuel
economy label methodology in a way that relies on these test results,
and is thus inherently more vehicle-specific. In this way, our fuel
economy test methods would yield results that are not only more
accurate across the fleet, but also more reflective of the fuel economy
consumers can expect to achieve from a given vehicle in the real-world.

IV. Revisions to the Fuel Economy Label Format and Content

    In addition to our proposal to revise the methods for calculating
the ``city'' and ``highway'' mpg estimates, we are proposing revisions
to the way these estimates and the other information on the label are
presented to the consumer.
    Our goal is to improve the label format and content so that
consumers more readily understand and use it. To gain a better
understanding of how consumers are using the current fuel economy
label, we conducted a series of focus groups in five cities around the
country in March 2005. The input received from the participants
confirmed some of our perceptions about weaknesses of the current
label, and also brought up some constructive suggestions for
improvements that we could address. The contractor that conducted the
focus groups issued a report to EPA of their findings, which is
included in the docket for this proposed rulemaking.\53\
---------------------------------------------------------------------------

    \53\ PRR, Inc. ``EPA Fuel Economy Label Focus Groups--Report of
Findings,'' prepared for EPA by PRR Inc., March 2005.
---------------------------------------------------------------------------

    In the focus groups, we clearly heard that people are very familiar
with the big, bold City and Highway estimates on the label. We tested
whether consumers preferred to see the estimates continue to be
expressed as City and Highway mpg values or replacing the City and
Highway designations with a fuel economy range. Consumers agreed that
the City and Highway distinction is useful information and wanted it to
remain intact. Consumers had a very strong negative reaction to a
range, and indicated it was not something they could easily compare to
other cars. Thus, we are proposing to retain the City and Highway mpg
estimates. As discussed in Section I, our new test methods are designed
to reflect the average fuel economy, so the City and Highway mpg
estimates on the label will reflect the fuel economy expected to be
achieved by half of drivers. We seek comment on whether the average is
the appropriate value for the large, bold, City and Highway estimates.
In other words, we invite comment on whether it would be more
appropriate to capture a greater proportion of consumers' experience by
using a lower fuel economy estimate, for example, an estimate that
would capture 75 percent, or even a greater percentage, of drivers'
experience.
    Further, the consumer focus groups indicated that people are not
noticing or reading the current ``fine print'' range of fuel economy
expressed on today's label. Yet, we believe it is important to

continue to report an expected fuel economy range in smaller print, in
addition to the City and Highway mpg estimates, so that consumers can
better understand how much their fuel economy in actual driving can
vary from the estimate. To accompany the City and Highway mileage
estimates, we propose to express the range of expected fuel economy as
a 10th percentile to a 90th percentile fuel economy. In that way, the
range represents 80 percent of driving experience--10 percent of
drivers may get fuel economy below the lower end of the range, and 10
percent may get fuel economy greater than the higher end. We seek
comment on other approaches to expressing the expected fuel economy
range on the label. For example, we ask for comments on whether this
range should be wider to capture even more of drivers' experience, such
as a 5th percentile to a 95th percentile, which would capture 90
percent of all drivers' fuel economy experience.\54\
---------------------------------------------------------------------------

    \54\ Based on the assumption of a normal distribution and
available data that allows us to estimate the standard deviation,
the 10th and 90th percentiles are equal to the mean 17
percent, and the 5th and 95th percentiles are equal to the mean
21 percent.
---------------------------------------------------------------------------

    Finally, we are interested in commenters' feedback on what
additional information could be made available either in the annual
Fuel Economy Guide or the http://www.fueleconomy.gov Web site, administered

jointly by EPA and DOE. We recognize that some of the ideas we are
presenting here may become too much information to include on the label
itself. We would like to make additional information available to those
consumers who are most interested in more detail, and the Fuel Economy
Guide, or http://www.fueleconomy.gov Web site, may be good places to include

such information. Some have suggested the idea of a fuel economy
calculator on the Web site, that would enable consumers to calculate an
estimated fuel economy that is more tailored to their specific driving
conditions. A similar tool already exists on the Web site in the form
of a calculator to estimate individualized annual fuel costs, based on
specific cost and mileage data input by the user. A fuel economy
calculator could be designed that would allow the user to input their
specific driving conditions, such as the amount of time spent with air
conditioning on, what climate they live in, how much driving is done
under higher speed/aggressive driving conditions, etc. These inputs
could go into an algorithm that would estimate the fuel economy for a
specific vehicle under the conditions input by the user. For instance,
drivers in areas of climactic extremes may want to know the fuel
economy impact of driving exclusively in those conditions. EPA requests
comments on the merits of adding such a calculator to the
fueleconomy.gov Web site, and welcomes further input on how such a tool
might best be designed.
    Based on input from the focus groups, as well as our own
observations from implementing the fuel economy labeling program for
the past 20 years, we are proposing to revise the fuel economy label as
discussed below. For a point of reference, a sample of the current Fuel
Economy Label is provided below, followed by four proposed label
formats on which we are requesting comment. Sample A takes a more
traditional approach by preserving some of the ``look and feel'' of the
current label. Samples B and C are graphical updates and offer
different ways of presenting the same information. Sample D has the
same look as Sample B, but presents a different option for illustrating
the comparable class information. One benefit of adopting a less
traditional look is to signal to consumers that the new label design
coincides with our new way of calculating the fuel economy estimates.
    We are planning to conduct a series of focus groups after
evaluating the public comments received on these label designs, to
assure that the final design will be understood and useful for
consumers. More details about this proposal are in section VIII.B
below.

BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TP01FE06.038

[GRAPHIC] [TIFF OMITTED] TP01FE06.039

[GRAPHIC] [TIFF OMITTED] TP01FE06.040

[GRAPHIC] [TIFF OMITTED] TP01FE06.041

[GRAPHIC] [TIFF OMITTED] TP01FE06.042

BILLING CODE 6560-50-C

A. Estimated Annual Fuel Cost

    The EPCA statute requires the label to include the estimated annual
fuel cost. EPA's current regulations specify that this information just
include the dollar amount, but gives manufacturers the option to also
include the per-gallon fuel costs and annual miles driven (i.e., to
explain how annual fuel costs were derived). However, most
manufacturers do not take that option, so most labels include only the
cost number. It was clear from the focus group research that consumers
care a lot about this information but currently do not find it
adequate. They desired more information about how this cost was
determined, including the assumed per-gallon fuel costs and miles-per-
year driven. Therefore, we are proposing to require this information on
the label in addition to the estimated annual fuel cost. The per-gallon
fuel costs and annual miles driven will be that which EPA provides to
manufacturers each year via guidance letters.\55\ Providing per-gallon
fuel costs each year through guidance ensures that the information
stays as current as possible while still providing a common basis to
allow comparisons of annual fuel cost information across all vehicles.
The fuel economy basis on which the estimated annual fuel costs are
determined would be the adjusted combined fuel economy (as determined
by the proposed weighting of 43 and 57 percent for city and highway,
respectively, as discussed in Section II). The label information is
proposed to read: ``Estimated Annual Fuel Costs = $XXXX (based on
XX,XXX miles at $X.XX per gallon).'' We also seek comment on whether
the label text should include the combined fuel economy number as part
of the derivation for Estimated Annual Fuel Cost.
---------------------------------------------------------------------------

    \55\ The estimated annual fuel costs are derived from
information provided by DOE's Energy Information Administration.
Separate costs are determined for regular and premium gasoline,
diesel, CNG, LPG, ethanol (E85), electricity and hydrogen. See EPA's
Guidance Letter CCD-05-11 in the Docket for this rulemaking for an
example of how EPA transmits this information to manufacturers.
---------------------------------------------------------------------------

B. Fuel Economy of Comparable Vehicles

    The EPCA statute requires the label to include the fuel economy of
comparable vehicles. This requirement was intended to help car shoppers
compare the fuel economy of similar vehicles. EPA's current regulations
require that the label include the following statement: ``For
comparison shopping, all [vehicles/trucks] classified as [insert
category as determined in Sec.  600.315] have been issued mileage
ratings ranging from -- to -- mpg city and -- to -- mpg highway.''
Based on the focus group research, it appears that car buyers do not
notice this statement since it appears in small print and has lengthy
text. Some perceived it as ``fine print,'' and thus less important.
There are two ways to address these concerns. The first would shorten
the statement to lessen its ``fine print'' look. The sample labels A
through C above contain a revised statement as follows: ``For
comparison shopping, the range of fuel economy for all [INSERT
COMPARABLE CLASS] is -- to -- MPG city and -- to -- MPG highway.''
    After completion of the focus groups, we considered another option
for presenting the fuel economy of comparable vehicles that might aid
consumers by replacing the ``fine print'' text with a graphic
representation. This approach would use combined fuel economy as the
comparison basis (versus separate city and highway comparisons), to
simplify the fuel economy values presented. Combined fuel economy has
not previously appeared on the label, but is used as an input to
calculate the estimated annual fuel costs. The graphic presentation is
similar in concept to DOE's ``EnergyGuide'' label, which has been
effectively used for years to illustrate where an electrical appliance
falls on an energy-usage comparison scale. Therefore, we believe this
visual may be familiar to consumers. A sample label with the graphical
presentation of comparable fuel economy appears in the Sample D label
above. The graphic would replace the text regarding comparable class
fuel economy. We request comment on the merits of this graphical
concept for depicting the fuel economy of comparable class vehicles,
and whether it would enhance consumers' understanding.
    In addition, we welcome comment on whether it would be useful to
include additional information, either on the label or a Web site, that
would give consumers a better understanding of how a given vehicle's
fuel economy compares with the range of fuel economy of other vehicle
classes. This may be particularly useful for those consumers shopping
for cars across vehicles classes (e.g., SUVs vs. large sedans).
However, including this much information on the label may be
problematic due to space limitations. The annual Fuel Economy Guide
already includes graphical information on the fuel economy range for
all comparable classes, so that consumers can identify where a given
vehicle fits within these ranges. We welcome input on whether
additional information on comparable class fuel economy would be
useful, and if so, how best to present that information in a user-
friendly way for consumers.
    Another change that will help improve the usefulness of this
information to consumers is to revise the comparable vehicle class
categories themselves, since they have not been updated in twenty
years. A discussion of proposed changes to the comparable vehicle
classifications is in Section V below.

C. ``Your mileage will vary * * *'' Range of Expected Fuel Economy
Information

    The current label has a statement explaining why actual fuel
economy will vary from the EPA estimates, and gives an expected range
of fuel economy for that vehicle, determined by 15 percent
of the city and highway estimates. While not statutorily required to be
on the label, as discussed in Section I above, EPA included it in the
1984 fuel economy rule since many drivers would not precisely achieve
the estimated fuel economy. EPA agrees that it is important to
emphasize on the label that the city and highway numbers are estimates
and do not necessarily reflect the actual fuel economy a driver can
expect at any given time. Providing the range of expected city and
highway fuel economy on the label gives the consumer a better
understanding of what fuel economy they can expect across a wider
spectrum of real-world driving conditions. The current label format
does this in a single statement that gives a few reasons why mileage
will vary, as well as the range of expected city and highway fuel
economy. Unfortunately, this information is often disregarded by car
buyers. Similar to the comparable class information, focus group
participants viewed this information as ``fine print,'' and as a sort
of disclaimer. Once they had taken the time to consider it, the focus
groups understood why actual in-use fuel economy may vary from the
estimates, and concluded that this type of information was useful.
    To improve consumer comprehension, the proposed statement has been
reworded and reformatted to be more noticeable. The proposed text for
presenting the range of expected fuel economy is ``Your actual mileage
can vary significantly depending on how you drive and maintain your
vehicle and other factors.'' We propose to place the range of expected
fuel economy underneath (or on the side of, depending on the label) the
actual city and highway estimates to provide

consumers with a clearer understanding of the fuel economy they can
expect to achieve on the road. We request comments on the effectiveness
of this format in conveying this message, as well as on the specific
wording of this statement.

D. Other Format Changes

    Based on the focus group research, the current label would benefit
from some graphic updating. In the sample labels, we have included a
more modern-looking fuel pump. Many focus group participants did not
understand that EPA was the source of the fuel economy estimates (many
thought that the auto manufacturers or dealers were responsible). Once
they did, they thought the association with the government added
credibility to the ratings. We believe that more prominent government
logos (EPA and DOE), will make it clearer to consumers that these
Agencies are responsible for the fuel economy estimates. The web link
to the EPA-DOE Fuel Economy Guide Web site, http://www.fueleconomy.gov, has

also been added so that interested consumers may obtain additional
information related to fuel economy.

V. Other Related Proposals

A. Comparable Class Categories

    The EPCA statute requires that the label contain ``the range of
fuel economy of comparable automobiles of all manufacturers,'' but does
not specify what constitutes ``comparable automobiles.'' \56\
Therefore, EPA has discretion to interpret how to best define these
categories. The comparable class categories in place today are the same
as those established in 1976.\57\ Cars were split according to size
based on their interior volume (with one exception), and trucks were
split according to their utility and GVWR into the following groups:
---------------------------------------------------------------------------

    \56\ See 49 U.S.C. 32908.
    \57\ See 41 FR 49752, November 19, 1976.
---------------------------------------------------------------------------

    Cars: Two-seater; mini-compact; compact sedan; medium sedan; large
sedan; station wagon.
    Trucks: Small pickup truck; standard pickup truck; van; special
purpose vehicle.
    Clearly, the U.S. vehicle fleet looks significantly different that
it did nearly 30 years ago. Since the time these classes were created,
there have been many vehicle design changes that are not reflected in
the above class designations. For example, the sport utility vehicle
(SUV)--one of the most popular vehicle types today--does not even have
its own class designation. The same is true for minivans. Another trend
in vehicle design is vehicles that defy classification in design and
utility. Known commonly as ``crossover'' vehicles, they do not fit
neatly into any of EPA's existing classifications. All of the above
shortcomings have limited the usefulness of the comparable vehicle fuel
economy information on the label. Having more clearly-defined classes
that reflect the current market will improve the usefulness of this
information on the label. There are several challenges with assigning
comparable class categories: we need to accommodate a dynamic market of
changing vehicle designs; the categories should be as objective as
possible and not rely upon subjective qualities that are difficult to
define (such as ``luxury'' or ``sporty''); and there should be enough
classes to allow consumers to differentiate, but not so many as to
cause confusion.
    The following discussion explains the specific issues associated
with the existing comparable classes, and how we propose to address
them. It should be noted that the comparable vehicle categories are
used only for fuel economy labeling, and in no way determine if a
vehicle is a ``passenger vehicle'' or ``nonpassenger vehicle'' for the
purpose of CAFE compliance. That determination is made by DOT-NHTSA.
1. Create New Classes for SUVs and Minivans
    The ``Special Purpose Vehicle'' class was created to contain
vehicles that had off-road capability and other features that weren't
covered by the pickup truck or van category. Since it was first
created, the ``special purpose vehicle'' class has come to include two
widely-popular, high-selling, but very different, vehicle types--SUVs
and minivans. EPA and DOE have recognized the evolution of these two
classes informally by including them in the annual Fuel Economy Guide
as subdivisions of the ``special purpose'' vehicle class. The
determination of these classes was left to individual manufacturer's
discretion.\58\ However, these subdivisions are not used on the fuel
economy label because EPA's current regulations have clear instructions
that manufacturers must use the comparable classes as defined by those
regulations. This means a consumer looking at the label on an SUV will
see the range of fuel economy for all ``special purpose vehicles.'' We
believe it is appropriate to update the comparable class regulations by
creating separate classes for SUVs and minivans. We are also proposing
to revise the ``special purpose vehicle'' class to capture vehicles
that do not fit into any other category.
---------------------------------------------------------------------------

    \58\ EPA Guidance Letter VPCD-99-08, June 23, 1999, provides
guidance to manufacturers on using SUV and minivan designations.
---------------------------------------------------------------------------

    Minivan: Minivans have not neatly fit into EPA's ``Van'' class due
to the way vans are defined in the regulations: ``* * * any light truck
having an integral enclosure fully enclosing the driver compartment and
load carrying device, and having no body sections protruding more than
30 inches ahead of the leading edge of the windshield.'' \59\ Minivans
generally do not meet the last criterion, thus they have been placed in
the ``Special Purpose Vehicle'' class. In general, minivans are smaller
than full-size vans, and have rear seats that are designed to be easily
removable or stowable. Taking those distinguishing characteristics into
account, we are proposing that minivans be defined as vehicles which
are designed primarily to carry no more than eight passengers having an
integral enclosure fully enclosing the driver, passenger, and load-
carrying compartments, with a total interior volume at or below 180
cubic feet and rear seats readily removed or folded to floor level to
facilitate cargo carrying.
---------------------------------------------------------------------------

    \59\ See 40 CFR 600.002-93.
---------------------------------------------------------------------------

    SUV: Sport Utility Vehicles likewise do not fit into the ``van''
class because of the 30 inch protuberance criterion. The class of
vehicles which may be closest in design to the SUV is a station wagon,
defined in the regulations as ``* * * a passenger automobile with an
extended roof line to increase cargo or passenger capacity, cargo
compartment open to the passenger compartment, a tailgate, and one or
more rear seats readily removed or folded to facilitate cargo
carrying.'' The most significant difference is that SUVs are
``nonpassenger automobiles.'' \60\ The proposed definition of SUVs is a
nonpassenger automobile with an extended roof line to increase cargo or
passenger capacity, cargo compartment open to the passenger
compartment, and

one or more rear seats readily removed or folded to facilitate cargo
carrying.
---------------------------------------------------------------------------

    \60\ ``Nonpassenger automobile'' is a term used in EPCA and by
EPA's current comparable class definitions. It includes vehicles
which do not fall under the EPCA definition of passenger automobiles
and that are ``capable of off-highway operation that the Secretary
decides by regulation (A) has a significant feature (except 4-wheel
drive) designed for off-highway operation; and (B) is a 4-wheel
drive automobile or is rated at more than 6,000 pounds gross vehicle
weight.'' The DOT regulations that further define the distinguishing
features of these vehicles are found at 49 CFR 523.5(a). It should
be noted that the methods of classification of ``nonpassenger
automobiles'' or ``light trucks'' for the purpose of creating
comparable vehicle classes for fuel economy labeling are not related
to those used to administer the federal emission compliance
requirements.
---------------------------------------------------------------------------

2. Redefine ``Small Pickup Truck'' Class
    Pickups are currently divided into ``small'' and ``standard''
categories, with ``small'' pickups distinguished from ``standard pickup
truck'' by GVWR (greater than 4500 lbs is ``standard''). For the past
several years, no vehicles certified have been classified as ``small
pickup trucks.'' To provide better comparable classes for pickup
trucks, we are proposing to increase the weight limit distinguishing
small and standard standard pickups to 6000 pounds GVWR. Pickups less
than 6000 pounds GVWR would be considered ``small'' and those at or
above would be considered ``standard.''
3. ``Crossover'' Vehicles
    These are vehicles that may not fit neatly into one classification.
Examples are SUVs or station wagons that may have characteristics of
both classes. Our policy in that regard has been to work with the
manufacturer to determine which of the prescribed comparable classes
the vehicle is most appropriate. We are concerned that by defining
specific parameters for crossover classes, we will be building
obsolescence into our regulation. Our preference is to retain our
current policy in which manufacturers propose to EPA which of the
existing comparable classes their ``crossover'' vehicles best fit, with
the caveat that if they advertise within-class fuel economy it must be
with the selected class. We request comments on whether we should
continue this policy for crossover vehicles or whether we should create
a new class.
    EPA requests general comments on the proposed modifications to
comparable classes, and also welcomes comments on other possible ways
to classify vehicles for comparison purposes. Comments should address
how the classifications will be useful for the consumer who is
comparison shopping.

B. Electronic Distribution of Dealer-Supplied Fuel Economy Booklet

    A statutory provision in EPCA requires car dealers to provide to
consumers a copy of the annual fuel economy booklet (Fuel Economy
Guide).\61\ Historically, DOE has printed and sent copies of the Guide
to dealers at government expense, although this is not an EPCA
requirement. At the time that these EPA regulations were written, the
internet was non-existent, and personal computers were not readily
available. Today's proposal modifies the ways in which the Fuel Economy
Guide can be distributed by giving dealers the option to provide it
electronically. There are a number of ways that this can happen.
Dealers can present the Guide on an on-site computer that customers can
view, or they can provide them with a diskette or CD containing the
Guide, or they can print paper copies directly from the government Web
site that has the Guide (http://www.fueleconomy.gov). These methods are

superior to the current hard-copy method for a number of reasons.
First, it spares the government the large expense of printing many
thousands of copies and mailing them to dealers. Second, it allows
consumers to have more up-to-date information. The deadline for
manufacturers to provide fuel economy data for inclusion in the annual
printed Guide is generally October of the calendar year prior to the
model year (e.g. the deadline for the 2005 Guide was October, 2004). In
reality, some manufacturers are not able to meet this deadline, due to
late introduction of models or other timing issues, so those vehicles
will not appear in the printed Guide, which is printed only once per
year. However, the electronic version on the Guide posted on the
internet is updated regularly to include new models. Thus consumers can
get more accurate information from the internet than from the printed
Guide. This method has been used on a trial basis for the 2004 and 2005
model years with much success, and EPA is today proposing to codify the
electronic dissemination of the Guide. This change would be effective
with the 2008 model year. EPA has consulted with DOE on this topic and
DOE concurs it would be an effective means of providing information to
car buyers.
---------------------------------------------------------------------------

    \61\ See 49 U.S.C. 32908(c)(3).
---------------------------------------------------------------------------

C. Testing Provisions

1. Testing Requirements for Vehicles Currently Exempt From Certain
Emission Tests
    Certain vehicles are currently exempt from some of the emission
tests that we are including in the 5-cycle method. In order to use the
5-cycle method for these vehicles, additional fuel economy testing
provisions are necessary.
    a. Alternative-Fueled Vehicles. There are two types of alternative-
fueled vehicles: (1) Flexible-fuel vehicles (FFVs; also known as dual-
fueled or bi-fueled vehicles) that can operate on gasoline or diesel
and/or some alternative fuel (i.e., ethanol, methanol, etc.), and (2)
dedicated alternative fueled vehicles that operate only on some
alternative fuel.
    FFVs are subject to the SFTP and Cold CO emission standards and
test requirements, but only when operating on gasoline. Therefore, we
propose that the fuel economy label values of FFVs when operating on
gasoline be determined using the same mpg-based or 5-cycle approaches
applicable to dedicated gasoline or diesel fueled vehicles and, thus,
additional testing for US06, SC03 and Cold FTP while operating on
alternative fuel would not be required. In addition, although the fuel
economy values when operating on an alternative fuel are not required
to be reported on the label, they are included in the annual Fuel
Economy Guide. Accordingly, we propose that the city and highway fuel
economy label values must reflect the same adjustment factors relative
to FTP and HFET fuel economy, respectively, developed using the
applicable mpg-based or 5-cycle approach for gasoline. In other words,
if the city FTP fuel economy is 24 mpg for operation on gasoline and
the calculated label value using the mpg-based or 5-cycle approach is
20 mpg, then the city label value for operation on alternative fuel
would be the FTP fuel economy measured when the vehicle is operated on
alternative fuel multiplied by the ratio of 20 over 24.
    Dedicated alternative-fueled vehicles are exempt from the SFTP and
Cold CO emission standards according to 40 CFR 86.1810(i)(4) and 40 CFR
86.1811-04(g). As a result, these vehicles will not have the SFTP and
Cold CO fuel economy data needed to determine 5-cycle fuel economy
values. We propose that manufacturers of dedicated alternative-fueled
vehicles be able to use the mpg-based approach in 2011 and beyond, as
well during 2008-2010 in order to avoid conducting additional tests for
fuel economy reasons only. Since the mpg-based approach uses fuel
economy values measured in terms of miles per gallon of gasoline or
diesel fuel, the fuel economy of dedicated alternative fuel vehicles
must be expressed in terms of its gasoline equivalent prior to using
the mpg-based formula. Currently, all dedicated alternative-fueled
vehicle fuel economy values are expressed in terms of gasoline
equivalent. In this case, the fuel economy values for a dedicated
alternative vehicle expressed in gasoline equivalents can be directly
determined using the mpg-based approach. However, if the fuel economy
values for a dedicated alternative vehicle is expressed in alternative
fuel equivalents, then, the fuel economy in terms of miles per gallon
of the alternative fuel would be adjusted by

the ratio of the mpg-based value to the FTP or HFET value, as
applicable, just as described above for FFVs.
    We are also proposing that manufacturers of dedicated alternative-
fueled vehicles may optionally use the 5-cycle approach at their
discretion. In this case, all the fuel economy values used in the
formulae would be expressed in terms of operation on the alternative
fuel. If this option is used, the manufacturer would be required to
conduct all applicable 5-cycle test procedures and use both the 5-cycle
city and highway calculation methods to determine fuel economy label
values.
    b. Diesel Vehicles. Diesel fuel vehicles are not currently subject
to Cold CO emission standards and, thus, do not have a 20 degree
Fahrenheit (F) FTP fuel economy result to use in the 5-cycle based
approach. Therefore, beginning with the 2008 model year for
certification diesel vehicles, we are proposing that a 20 degree F FTP
be performed for the purpose of collecting fuel economy data.
Accordingly, for a 20 degree FTP only, the manufacturer must use a
1-D (winter-grade) diesel fuel as specified in ASTM D975-04c
``Standard Specification for Diesel Fuel Oils'' \62\ and that complies
with 40 CFR Part 80,\63\ where the level of kerosene added shall not
exceed 20 percent. Alternatively, manufacturers may use, with EPA
approval, a manufacturer-specified diesel fuel in lieu of conventional
diesel fuel under alternate test procedure provisions in 40 CFR Sec.
86.113-94, where the level of kerosene added shall not exceed 20
percent. We request comment on these proposed winter-grade diesel fuel
specifications.
---------------------------------------------------------------------------

    \62\ ASTM International Specification D975-04C ``Standard
Specification for Diesel Oil Fuels'' (November 1, 2005) describes
the seven grades of diesel fuel oils suitable for various types of
diesel engines. This specification is under the jurisdiction of ASTM
Committee D02 on Petroleum Products and Lubricants and is the direct
responsibility of subcommittee D02.E0 on Burner, Diesel, Non-
Aviation Gas Turbine, and Marine Fuels.
    \63\ 40 CFR Part 80--Control of Air Pollution from New Motor
Vehicles: Heavy-Duty Engines and Vehicle Standards and Highway
Diesel Fuel Sulfur Control Requirements: Final Rule and Regulation
of Fuels and Fuel Additives: Fuel Quality Regulations for Highway
Diesel Fuel Sold in 1993 and Later Calendar Years.
---------------------------------------------------------------------------

    We expect that the impact of extending the cold FTP test
requirement to light-duty diesel vehicles will be very small, given
that there are so few diesel vehicles currently certified. In model
year 2006, for example, only five diesel light-duty vehicles were
certified for sale in the U.S. Further discussion of how we evaluated
this requirement in our estimated cost impacts is contained in Section
VI.
2. Modifications to Existing Test Procedures
    To ensure that the 5-cycle method is reflective of real-world
operating conditions, there are a few minor procedural changes that
need to be made to certain existing emission tests procedures. First,
we are proposing minor procedural changes in the US06 tests, as
described below. Second, we are seeking comment on the issue of
requiring manufacturers to run the heater and/or defroster during the
cold FTP test. Third, we are proposing to codify the existing practice,
which has been done through special test procedure provisions, of
requiring four-bag FTP measurements for gasoline-electric hybrid
vehicles.
    a. Revisions to US06 Bag Measurements. The US06 drive cycle
contains elements of both city and highway driving, yet the exhaust
sample is collected in only one sample, or ``bag.'' 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 cycle into the
highway fuel economy estimate, we are proposing a revised test protocol
that would require collecting the exhaust sample into two bags. 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.
    In assessing the split of US06 into two bags, we undertook a test
program to determine that it was technically feasible to do so, and
that it would not have a significant impact on emission results for
compliance purposes. To do this, we evaluated the effects of conducting
a US06 split-phase emissions test versus the current US06 single-phase
emission test on ten vehicles at EPA's National Vehicle and Fuel
Emissions Laboratory (NVFEL) in Ann Arbor. Based on this evaluation,
the US06 split-phase sampling methodology was shown to be feasible for
fuel economy purposes and required only initial software reprogramming
for the revised sampling periods and minimal hardware changes to enable
the emissions analyzers to perform US06 split-phase emission testing.
In addition, creating a US06 split-phase sampling period did not result
in any significant difference in criteria pollutant emissions results.
The full report on this US06 split phase evaluation program is
available in the docket.\64\ Our proposed changes to the US06 test
procedure to incorporate the split-phase sampling are found in the
proposed regulations at 40 CFR 86.159-08. We have also accounted for
any additional costs to manufacturers in making the necessary changes
to their testing equipment and data collection software in our cost
analysis discussed in Section VI. We estimate these costs to be
minimal.
---------------------------------------------------------------------------

    \64\ Mitcham, A. & Fernandez, A., ``Feasibility of Revising the
US06 Test Cycle into a Split Phase Sampling Test Procedure'' U.S.
EPA, Office of Transportation & Air Quality, 2005.
---------------------------------------------------------------------------

    b. Heater/Defroster Usage During the Cold FTP. The current Cold FTP
conducted at 20 degrees F includes the option to use the heater and/or
defroster.\65\ While we understand that some manufacturers today are
using the heater and/or the defroster during the Cold FTP, it is not
mandatory and therefore subject to inconsistent usage across
manufacturers and vehicle lines. We expect that, in the real-world, it
would be highly unusual for drivers not to use the heater/defroster
when the temperature is cold, including at 20 degrees F experienced
during the Cold FTP. In order to more closely reflect real world
operation, and to ensure a level playing field across manufacturers and
vehicle lines when performing this test, we are seeking comment on
requiring that manufacturers operate the heater and/or defroster during
the Cold FTP.
---------------------------------------------------------------------------

    \65\ See 40 CFR 86.230-94(f).
---------------------------------------------------------------------------

    To better understand the potential impact of heater and/or
defroster usage on fuel economy at cold temperatures, we attempted to
determine the fuel economy impacts of heater and defroster usage at 20
degrees F. In order to quantify the impact of heater and/or defroster
usage on fuel economy, we conducted testing through the Southwest
Research Institute (SwRI). This program measured the impacts of heater
and defroster operation on fuel economy for three vehicles during a 20
degree Cold FTP. We compared the fuel economy results with heater/
defroster operational with the results of the heater/defroster non-
operational on each vehicle. The Cold FTP fuel economy with the heater/
defroster on was significantly lower than that with the heater/
defroster off, ranging from -6.0 percent (~1 mile per gallon lower on a
non-hybrid vehicle) to -17.9 percent (~8 miles per gallon lower on a
hybrid vehicle). We did not observe a significant impact on CO or other
measured emissions as a result of the use of the heater/defroster on
the Cold FTP. The results of this test program indicated that different
vehicles were impacted more than others, suggesting that it would be
important to capture the impact on fuel economy of heater

and defroster use during cold conditions. The full report of this test
program is contained in the docket.\66\
---------------------------------------------------------------------------

    \66\ Fernandez, A. & Mitcham, A., ``Fuel Economy Impacts of
Interior Heater/Defroster Usage on Conventional and Hybrid Gasoline
powered Vehicles'', U.S. EPA, Office of Transportation & Air
Quality, 2005.
---------------------------------------------------------------------------

    Since heater and defroster operation can have an additional impact
on fuel economy beyond cold temperature operation, and since these
accessories are used in the real-world at cold temperatures including
20 degrees F, we are seeking comment on how this condition should be
captured in the fuel economy label estimates. Specifically, we are
seeking comment on requiring the use of heater/defroster during the
Cold FTP, rather than to continue to allow it as an option only.
    There are many approaches for how the heater and defroster usage
could be incorporated into the Cold FTP test procedures, including
specifying appropriate fan speed settings, timing of turning on the
heater/defroster during the test, and accounting for various vehicle
climate control designs. One concept that we have considered is as
follows. This concept would involve starting the test with the airflow
directed to the windshield for optimal defrosting, the airflow source
set to outside air (not recirculation), and the air temperature set to
high. Approximately two minutes into the test, the fan speed could be
turned to maximum and left there for the duration of the test. This
would mimic typical driver behavior in that we expect many drivers
typically would not turn the fan to maximum until the engine is
producing some level of heat, which most vehicles will do within a
couple minutes of driving. Automatic climate control systems could be
set to achieve an inside air temperature of 72 degrees F, and the fan
speed, if independently selectable, would be operated as described
above. Vehicles with multiple zones (either driver and passenger, or
front and rear) could be required to operate the controls for all zones
as described above. We anticipate that some climate control systems
might not be compatible with these instructions, and to address these
we could allow a manufacturer to request the use of special test
procedures, subject to EPA approval. We seek comment on this possible
concept for how heater/defroster usage could be specified in the cold
FTP procedure, as well as comments on alternative approaches.
    c. Gasoline-Electric Hybrid Vehicle Testing Provisions. 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 for conventional vehicles, 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). The virtual hot start stabilized phase (Bag 4) is
accounted for in the emission and fuel economy results mathematically
by including Bag 2 twice in the calculation.
    Because gasoline-electric hybrid vehicles have two energy sources
that can be combined in many ways, EPA and manufacturers recognized
that the assumption regarding the equivalence of the stabilized phases
of the hot and cold start tests may not be valid for hybrid vehicles.
Consequently, we have been requiring vehicles with gasoline-electric
hybrid systems to perform the complete set of four phases of the FTP,
under existing provisions in the regulations that allow special test
procedures. However, rather than continue to do this under the special
test procedures, we believe it is appropriate to codify this practice
in the testing regulations. Additionally, the 5-cycle formula for
gasoline-electric hybrid vehicles requires the four phases of the FTP
as inputs for these vehicles. Therefore, we are proposing to require
that gasoline-electric hybrid vehicles conduct all four phases of the
FTP for both emissions and fuel economy testing. We propose that four
bags be required for all tests using the FTP, including the cold
temperature FTP, for those vehicles defined as hybrid electric
vehicles. We request comment on this proposal, and on whether use of
the phrase ``hybrid electric vehicle'' is sufficient to describe and
identify vehicles for which the four-bag FTP would be required.

D. Voluntary Fuel Economy Labeling for Vehicles Exceeding 8500 Pounds
GVWR

    The EPCA statute explicitly excludes automobiles weighing over 8500
pounds GVWR from fuel economy labeling requirements.\67\ However, over
the past several years there has been a growing market for these
heavier vehicles, which fall into a number of utility classes, such as
SUVs, pickups, and vans (including heavier versions of such models as
Hummer, Ford Excursion, Chevy Silverado and Dodge Ram). We believe that
consumers would be interested in using fuel economy estimates for these
vehicles when comparison shopping. The rising fuel prices of recent
times certainly have increased consumer awareness of the costs
associated with owning a vehicle.
---------------------------------------------------------------------------

    \67\ See 49 U.S.C. 32908(a)(1).
---------------------------------------------------------------------------

    We encourage auto manufacturers of vehicles weighing over 8,500
pounds to voluntarily provide fuel economy information for these
vehicles, and we request comments on the value of such a voluntary
program and how it could be implemented.

E. Consideration of Fuel Consumption vs. Fuel Economy as a Metric

    EPCA defines fuel economy as ``* * * the average number of miles
traveled by an automobile for each gallon of gasoline (or equivalent
amount of other fuel) used, as determined by the Administrator under
section 32904(c) of this title.'' Thus, EPA's fuel economy information
program has always expressed fuel efficiency in miles per gallon. It is
a metric that Americans have come to know and understand.
    Notwithstanding this requirement, a few auto manufacturers have
suggested that it may be more meaningful to express fuel efficiency in
terms of consumption (e.g., gallons per 100 miles) rather than in terms
of economy (miles per gallon). A fuel consumption metric is currently