Light-Duty Automotive Technology,
Carbon Dioxide Emissions, and Fuel
Economy Trends:
1975 Through 2009
Appendix A
Database Details and Calculation Methods
Compliance and Innovative Strategies Division
and
Transportation and Climate Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
NOTICE
This technical report does not necessarily represent final EPA decisions or
positions. It is intended to present technical analysis of issues using data
that are currently available. The purpose in the release of such reports is to
facilitate the exchange of technical information and to inform the public of
technical developments.
SER&
United States
Environmental Protection
Agency
EPA420-R-09-014
November 2009
-------
Harmonically Averaging Fuel Economy Values
Dimensionally, fuel economy is miles divided by gallons. Then, presented with more
than one fuel economy value, an approach to averaging the values is to compute the result by
determining the total miles traveled and dividing that by the total gallons used.
Example: A motorist's fuel economy log for May shows that 704 miles were accumulated
around town in which the fuel economy was 16 mpg, and one 216 mile highway trip was taken
on which the fuel economy was 24 mpg. What is the average fuel economy for May?
The total miles are 704 + 216 = 920. The total gallons thus are 704 / 16 = 44 plus
216/24 = 9 or a total of 53 gallons. The average mpg is 920 / 53 = 17.4 mpg. Notice that the
arithmetic average of the two fuel economy values (16 + 24) / 2 = 20 mpg gives an individual
result that is higher than the total miles/total gallons result.
Even if the around-town miles traveled and the highway trip miles traveled were the same
(460 miles), the average fuel economy would not be 20; it would be 19.2 mpg. This is because
in the total miles/total gallons approach, fuel consumption is arithmetically averaged, butfiiel
economy is harmonically averaged, so for the second example (equal trip distances), the
calculation would be:
Average MPG = 2 / (1/16 + 1/24) = 19.2 MPG,
which is the same as arithmetically averaging the two fuel consumption values.
A specific example of this type of averaging approach is shown in the calculation of the
overall average fuel economy using the EPA "city" (MPGc) and EPA "highway" (MPGn) fuel
economy values.
Average MPG = Total Miles
Total Gallons
Total Miles
City Gallons + Highway Gallons
Total Miles
City Miles/City MPG + Highway Miles/Highway MPG
EPA-420-R-09-014 A-l November 2009
-------
Now, if city miles are 55 percent of total miles and highway miles are the remaining 45
percent, after dividing by total miles,
Average MPG = 1
(.55/MPGc) + (.45/MPG H)
and this average mpg would represent a composite mpg value based on the 55% city/45%
highway driving in this example. This 55% city/45% highway weighting is the metric in this
report for laboratory composite fuel economy values.
The same approach can be used when the average mpg of a group of vehicles with
different mpg values is to be calculated. Suppose a fleet of 100,000 vehicles is made up of two
classes, one of 70,000 vehicles whose fuel economy is 10 mpg and the other of 30,000 vehicles
whose fuel economy is 14 mpg. Each vehicle in the fleet is assumed to travel the same number
of miles (M),
Total Miles = 100,000 M
Total Gallons = 70,000 M / 10 + 30,000 M / 14
and the average fuel economy is:
Average Fuel Economy = 1
.7/10+ .3/14
10.9 mpg
where .7 and .3 are the relative shares of each vehicle class in the fleet. Notice that, again, the
arithmetic average of the class fuel economy values (10 + 14)/2 = 12 mpg is higher.
In general, some form of a weighted harmonic mean must be used when averaging
different fuel economy values in order to maintain mathematical integrity.
While fuel economy values (in miles per gallon) must be harmonically averaged to
maintain mathematical integrity, fuel consumption values (in gallons per mile) and carbon
dioxide emissions values (in grams per mile) can be arithmetically averaged.
EPA-420-R-09-014 A-2 November 2009
-------
Estimated and Final Production Data
Table A-l compares average laboratory 55/45 fuel economy for model years 1998
through 2008 at three points in time:
(1) an initial estimate determined early in the model year using projected production;
(2) for some years, a revised estimate determined by using trade publication sales
data that were obtained after the end of each model year, but before the final
CAFE data were submitted by automakers to the Federal Government; and
(3) final fuel economy values determined from CAFE compliance data provided
by the manufacturers to the Federal Government after the end of the model year.
The final car plus truck fuel economy values have varied from 0.4 mpg lower to 0.6 mpg
higher compared to the original estimates based exclusively on projected production. The final
car plus truck value for MY2008 in this report is 0.3 mpg higher than the initial estimate for
2008 in last year's report, which suggests that sustained, higher gasoline prices have led to small
changes in consumer demand relative to what manufacturers expected prior to the start of 2008.
Table A-l
Comparison of Laboratory 55/45 MPG
Model Initial Revised Final
Year Estimate Estimate Value
Cars 1998 28.6 28.6 28.5
1999 28.1 28.2 28.1
2000 28.1 28.3 28.2
2001 28.3 28.3 28.4
2002 28.5 28.5 28.6
2003 29.0 28.9 28.9
2004 28.7 28.9 28.9
2005 28.9 29.2 29.5
2006 28.8 29.2 29.2
2007 29.4 30.3 30.3
2008 30.3 30.5 30.5
Trucks 1998 20.6 20.6 20.9
1999 20.3 20.4 20.5
2000 20.5 20.5 20.8
2001 20.3 20.4 20.6
2002 20.4 20.3 20.6
2003 20.8 20.9 20.9
2004 20.9 20.9 20.8
2005 21.3 21.2 21.4
2006 21.5 21.9 21.8
2007 22.1 22.1 22.1
2008 22.5 22.7 22.7
Both 1998 24.4 24.4 24.5
1999 23.8 24.0 24.1
2000 24.0 23.9 24.3
2001 23.9 24.0 24.2
2002 24.0 23.9 24.1
2003 24.4 24.2 24.3
2004 24.4 24.4 24.0
2005 24.6 24.6 24.8
2006 24.6 25.3 25.2
2007 25.3 25.7 25.8
2008 26.0 26.3 26.3
EPA-420-R-09-014 A-3 November 2009
-------
Use of 3-Year Moving Averages
Use of the three-year moving averages, which effectively smoothes the trends, results in
an improvement in discriminating real trends from what might be relatively small year-to-year
variations in the data. For this report, as shown in Table A-2, these three-year moving averages
are tabulated at the midpoint. For example, the midpoint for model years 2007, 2008, and 2009
is MY2008.
Table A-2
Light-Duty Vehicle Laboratory Fuel Economy and Truck Sales Fraction
Actual Data Three-Year Moving Average
55/45 Fuel Economy Truck 55/45 Fuel Economy Truck
Year Cars Trucks Both Production Cars Trucks Both Production
Fraction Fraction
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
15.8
17.5
18.3
19.9
20.3
23.5
25.1
26.0
25.9
26.3
27.0
27.9
28.1
28.6
28.1
27.8
28.0
27.6
28.2
28.0
28.3
28.3
28.4
28.5
28.2
28.2
28.4
28.6
28.9
28.9
29.5
29.2
30.3
30.5
30.9
13.
14.
15.
15.
14.
18.
20.
20.
20.
20.
20.
21.
21.
21.
20.
20.
21.
20.
21.
20.
20.
20.
20.
20.
20.
20.
20.
20.
20.
20.
21.
21.
22.
22.
22.
,7
,4
, 6
,2
,7
, 6
,1
,5
,9
,5
,6
,4
, 6
,2
,9
,7
,3
,8
,0
,8
,5
,8
,6
,9
,5
,8
, 6
, 6
,9
,8
,4
,8
,1
,7
,9
15,
16,
17,
18,
18,
22,
24,
24,
24,
24,
25,
25,
25,
25,
25,
25,
25,
24,
25,
24,
24,
24,
24,
24,
24,
24,
24,
24,
24,
24,
24,
25,
25,
26,
26,
.3
.7
.7
.6
.7
.5
.1
.7
.6
.6
.0
.7
.9
.9
.4
.2
.4
.9
.1
.6
.7
.8
.5
.5
.1
.3
.2
.1
.3
.0
.8
.2
.8
.3
.4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.194
.212
.200
.227
.222
.165
.173
.197
.223
.239
.254
.283
.278
.298
.307
.302
.322
.334
.360
.404
.380
.400
.424
.449
.449
.449
.461
.485
.496
.520
.495
.471
.471
.472
.487
17.1
18.5
19.4
21.1
22.8
24.8
25.7
26.1
26.4
27.0
27.6
28.2
28.3
28.2
28.0
27.8
27.9
28.0
28.2
28.2
28.3
28.4
28.4
28.3
28.3
28.4
28.7
28.8
29.1
29.2
29.7
30.0
30. 6
14.5
15.1
15.2
16.0
17.5
19.7
20.5
20.6
20.6
20.8
21.2
21.4
21.2
20.9
21.0
20.9
21.0
20.8
20.7
20.7
20.7
20.8
20.7
20.7
20.6
20.6
20.7
20.8
21.0
21.3
21.7
22.2
22.6
16.
17.
18.
19.
21.
23.
24.
24.
24.
25.
25.
25.
25.
25.
25.
25.
25.
24.
24.
24.
24.
24.
24.
24.
24.
24.
24.
24.
24.
24.
25.
25.
26.
,5
, 6
,3
,8
,5
,7
,5
,6
,7
,1
,5
,8
,8
,5
,3
,2
,1
,8
,8
,7
,7
,6
,4
,3
,2
,2
,2
,1
,4
,7
,2
,7
,2
0.202
0.213
0.216
0.205
0.187
0.178
0.197
0.219
0.239
0.258
0.272
0.286
0.294
0.302
0.310
0.319
0.339
0.366
0.381
0.395
0.401
0.424
0.441
0.449
0.453
0.465
0.481
0.500
0.504
0.495
0.480
0.471
0.477
EPA-420-R-09-014
A-4
November 2009
-------
Table A-2 (Continued)
Light-Duty Vehicle Adjusted Fuel Economy
Cars
Model
Year
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
Each Year's Data
CITY HWY COMP
3 Year Moving Avg.
CITY HWY COMP
12,
13,
14,
15,
15,
18,
19,
20,
19,
20,
20,
21,
21,
21,
20,
20,
20,
20,
20,
20,
20,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
20,
20,
20,
.3
.7
.4
.5
.9
.3
.6
.1
.9
.2
.7
.2
.2
.4
.9
.5
.5
.0
.3
.0
.0
.8
.8
.7
.4
.3
.4
.4
.5
.3
.6
.4
.1
.3
.5
15
16
17
19
19
22
24
25
25
26
26
27
27
28
27
27
27
27
27
27
28
28
28
28
27
27
27
27
27
27
27
27
28
28
28
.2
.6
.4
.1
.2
.6
.2
.5
.5
.0
.8
.6
.7
.2
.9
.5
.6
.5
.9
.7
.1
.0
.0
.0
.5
.3
.3
.2
.5
.4
.6
.5
.3
.5
.8
13,
14,
15,
16,
17,
20,
21,
22,
22,
22,
23,
23,
23,
24,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
22,
23,
23,
23,
23,
23,
23,
24,
24,
24,
.5
.9
.6
.9
.2
.0
.4
.2
.1
.4
.0
.7
.8
.1
.7
.3
.4
.1
.5
.3
.4
.3
.4
.4
.0
.9
.0
.1
.2
.1
.5
.3
.1
.3
.5
13,
14,
15,
16,
17,
19,
19,
20,
20,
20,
21,
21,
21,
20,
20,
20,
20,
20,
20,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
20,
.4
.5
.3
.5
.8
.3
.8
.1
.3
.7
.0
.3
.2
.9
.6
.3
.2
.1
.1
.9
.9
.8
.6
.5
.3
.4
.4
.4
.4
.4
.7
.9
.3
16,
17,
18,
20,
21,
24,
25,
25,
26,
26,
27,
27,
27,
27,
27,
27,
27,
27,
27,
27,
28,
28,
27,
27,
27,
27,
27,
27,
27,
27,
27,
28,
28,
.3
.6
.5
.2
.8
.1
.1
.7
.1
.8
.4
.8
.9
.8
.7
.5
.6
.7
.9
.9
.0
.0
.8
.6
.4
.3
.3
.4
.5
.5
.8
.1
.6
14,
15,
16,
18,
19,
21,
21,
22,
22,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
23,
24,
.6
.8
.6
.0
.4
.2
.9
.2
.5
.0
.5
.9
.9
.7
.5
.3
.3
.3
.4
.3
.4
.4
.2
.1
.0
.0
.1
.2
.3
.3
.6
.9
.3
EPA-420-R-09-014
A-5
November 2009
-------
Table A-2 (Continued)
Light-Duty Vehicle Adjusted Fuel Economy
Trucks
Model
Year
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
Each
CITY
10,
11.
12,
12,
12,
14,
16,
16,
16,
16,
16,
16,
16,
16,
15,
15,
15,
15,
15,
15,
15,
15,
14,
14,
14,
14,
14,
14,
14,
14,
14,
14,
15,
15,
15,
.9
.5
.6
.4
.1
.8
.0
.3
.5
.1
.2
.8
.8
.2
.9
.6
.9
.5
.5
.3
.0
.1
.8
.9
.6
.7
.6
.4
.6
.3
.6
.9
.1
.5
.6
Year ' s
HWY
12
13
14
13
13
17
18
19
19
19
19
20
20
20
19
19
20
19
20
19
19
19
19
19
19
19
19
19
19
19
19
20
20
21
21
.7
.2
.1
.7
.1
.1
.6
.0
.6
.3
.4
.2
.5
.2
.8
.8
.3
.9
.1
.7
.5
.9
.5
.8
.2
.4
.1
.1
.3
.2
.8
.1
.4
.0
.4
Data
COMP
11,
12,
13,
12,
12,
15,
17,
17,
17,
17,
17,
18,
18,
17,
17,
17,
17,
17,
17,
17,
17,
17,
17,
17,
16,
16,
16,
16,
16,
16,
17,
17,
17,
18,
18,
.6
.2
.3
.9
.5
.8
.1
.4
.8
.4
.5
.2
.3
.9
.6
.4
.8
.4
.5
.2
.0
.2
.0
.1
.7
.9
.7
.7
.9
.7
.2
.5
.7
.2
.4
3 Year Moving Avg.
CITY HWY COMP
11,
12,
12,
13,
14,
15,
16,
16,
16,
16,
16,
16,
16,
15,
15,
15,
15,
15,
15,
15,
15,
14,
14,
14,
14,
14,
14,
14,
14,
14,
14,
15,
15,
.7
.2
.4
.0
.1
.7
.3
.3
.3
.4
.6
.6
.3
.9
.8
.7
.6
.4
.2
.1
.0
.9
.8
.7
.6
.6
.5
.4
.5
.6
.9
.1
.4
13,
13,
13,
14,
15,
18,
19,
19,
19,
19,
20,
20,
20,
19,
20,
20,
20,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
19,
20,
20,
20,
.3
.7
.6
.4
.9
.2
.1
.3
.4
.6
.0
.3
.2
.9
.0
.0
.1
.9
.7
.7
.6
.7
.5
.5
.2
.2
.1
.2
.4
.7
.1
.5
.9
12.3
12.8
12.9
13. 6
14.9
16.7
17.4
17.5
17. 6
17.7
18.0
18.1
17.9
17.6
17. 6
17.5
17.5
17.3
17.2
17.1
17.0
17.1
16.9
16.9
16.8
16.8
16.8
16.8
16.9
17.1
17.5
17.8
18.1
EPA-420-R-09-014
A-6
November 2009
-------
Table A-2 (Continued)
Light-Duty Vehicle Adjusted Fuel Economy
Cars and Trucks
Model
Year
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
Each Year's Data
CITY HWY COMP
3 Year Moving Avg.
CITY HWY COMP
12.
13.
14.
14.
14.
17.
18.
19.
19.
19.
19.
19.
19.
19.
19.
18.
18.
18.
18.
17.
17.
17.
17.
17.
16.
16.
16.
16.
16.
16.
16.
17.
17.
17.
17.
,0
,2
,0
,7
,9
,6
,8
,2
,0
,1
,3
,8
,8
,6
,1
,7
,8
,2
,2
,8
,7
,6
,4
,2
,9
,9
,8
,6
,7
,3
,8
,0
,3
,7
,8
14.
15.
16.
17.
17.
21.
23.
23.
23.
24.
24.
25.
25.
25.
24.
24.
24.
24.
24.
23.
24.
24.
23.
23.
23.
23.
22.
22.
22.
22.
23.
23.
23.
24.
24.
6
7
6
5
4
5
0
9
9
0
4
0
3
2
8
6
7
4
4
8
1
0
6
6
0
0
8
5
7
4
1
4
9
4
6
13.
14.
15.
15.
15.
19.
20.
21.
21.
21.
21.
21.
22.
21.
21.
21.
21.
20.
20.
20.
20.
20.
20.
20.
19.
19.
19.
19.
19.
19.
19.
20.
20.
21.
21.
,1
,2
,1
,8
,9
,2
,5
,1
,0
,0
,3
,8
,0
,9
,4
,2
,2
,8
,9
,4
,5
,4
,1
,1
,7
,8
, 6
,4
,6
,3
,9
,1
, 6
,0
,1
13.
13.
14.
15.
16.
18.
19.
19.
19.
19.
19.
19.
19.
19.
18.
18.
18.
18.
17.
17.
17.
17.
17.
17.
16.
16.
16.
16.
16.
16.
17.
17.
17.
,0
,9
,5
, 6
,9
,5
,0
,1
,1
,4
, 6
,7
,5
,1
,9
,6
,4
,1
,9
,7
,6
,4
,1
,0
,9
,8
,7
,6
, 6
,7
,0
,3
, 6
13.
13.
14.
15.
16.
18.
19.
19.
19.
19.
19.
19.
19.
19.
18.
18.
18.
18.
17.
17.
17.
17.
17.
17.
16.
16.
16.
16.
16.
16.
17.
17.
17.
,0
,9
,5
, 6
,9
,5
,0
,1
,1
,4
, 6
,7
,5
,1
,9
,6
,4
,1
,9
,7
,6
,4
,1
,0
,9
,8
,7
,6
, 6
,7
,0
,3
, 6
15
16
17
18
20
22
23
23
24
24
24
25
25
24
24
24
24
24
24
24
23
23
23
23
23
22
22
22
22
23
23
23
24
.6
.6
.2
.6
.3
.8
.6
.9
.1
.5
.9
.2
.1
.9
.7
.6
.5
.2
.1
.0
.9
.7
.4
.2
.0
.8
.7
.6
.7
.0
.5
.9
.3
14.
15.
15.
16.
18.
20.
20.
21.
21.
21.
21.
21.
21.
21.
21.
21.
21.
20.
20.
20.
20.
20.
20.
19.
19.
19.
19.
19.
19.
19.
20.
20.
20.
,1
,0
,6
,8
,3
,2
,8
,0
,1
,4
,7
,9
,7
,5
,3
,1
,0
,7
, 6
,4
,3
,2
,0
,8
,7
, 6
,5
,4
, 6
,8
,2
, 6
,9
EPA-420-R-09-014
A-7
November 2009
-------
Vehicle Classification Exceptions
The truck size classification scheme used in this report is based primarily on published
wheelbase data. For cars, vehicle classification as to vehicle type, size class, and manufacturer/
marketing group generally follows fuel economy label, Fuel Economy Guide, and fuel economy
standards protocols; exceptions are listed in Table A-3. The classification of a vehicle for this
report is based on the authors' engineering judgment and is not a replacement for definitions used
in implementing automotive standards legislation.
Table A-3
Group/Manufacturer/Vehicles
Chrysler Colt 4WD Wagon*
Chrysler Colt Vista*
Chrysler Pacifica*
Chrysler PT Cruiser
Chrysler PT Cruiser Convertible
Chrysler Summit Wagon*
Chrysler Dodge Ram Charger*
Chrysler Dodge Magnum*
Chrysler Eagle 4WD Wagon*
Ford: Ford Pinto Van*
Ford: Volvo V70 XC
GM: HHR
GM: Isuzu Oasis*
GM: Pontiac Vibe
Nissan: Infiniti EX35
Toyota: Lexus RX300*
Toyota: Matrix
VW: Audi Allroad*
Other: Subaru Outback AWD Wagon
Other: Subaru Forester
Other: Subaru Baja*
Other: Suzuki X-90*
Other: Mitsubishi Expo*
Other: Mitsubishi Space Wagon*
Other: Mercedes R-Series
Are Classified As:
Small Wagon
Small Van
Large Wagon
Small Wagon
Subcompact
Small Van
Large Sedan
Midsize Wagon
Car
Car
Midsize Wagon
Small Wagon
Midsize Van
Small Wagon
Midsize SUV
Midsize SUV
Small Wagon
Midsize Wagon
Midsize Wagon
Small SUV
Small Pickup
Small SUV
Small Van
Small Van
Large Wagon
* Not manufactured for MY2009.
EPA-420-R-09-014
A-8
November 2009
-------
Methodology for Adjusted Fuel Economy Values
for Model Years 1986-2009
On December 27, 2006, EPA published regulations that changed the methodology for
calculating the city and highway fuel economy label estimates for new passenger cars and light
trucks (71 Federal Register 77872). This revised methodology provides fuel economy estimates
to consumers that better reflect real world fuel economy. The methodology incorporates test
data that directly account for several important factors that affect fuel economy in the real world,
such as high speeds, aggressive accelerations and decelerations, the use of air conditioning, and
operation in cold temperatures, and indirectly account for a number of other factors that are not
reflected in EPA laboratory test data such as changing fuel composition, road conditions, etc.
These vehicle fuel economy label changes were implemented beginning with the 2008
model year. For model years 2008-2010, manufacturers have two options for calculating city
and highway fuel economy labels: 1) use vehicle-specific "5-cycle" (Federal Test Procedure for
urban stop-and-go driving, Highway Fuel Economy Test for rural driving, US06 test for high
speeds and aggressive driving, SCO3 test for air conditioning operation, and cold FTP test for
cold temperature operation) fuel economy test data in "composite" equations that calculate
vehicle-specific city and highway fuel economy values using weighting factors for data from
each of the 5 EPA test cycles, or 2) use an industry-average "mpg-based" method, which yields
mpg-based adjustments based on a regression of recent 5-cycle fuel economy data for the
industry as a whole. Beginning in 2011, manufacturers must use the 5-cycle method. For more
details on the derivation of these options, the specific equations that allow an automaker to
calculate new label values using either the vehicle-specific 5-cycle test data or the industry-
average mpg-based approach, and the impact of these changes on average fuel economy label
values, see the Preamble to the new regulations (71 Federal Register 77881-77893).
Beginning with the 2007 Trends report, EPA has made significant changes in how
adjusted (ADJ) fuel economy values for model years 1986 through 2009 are calculated to reflect
the revised EPA fuel economy label methodology. These changes affect every table and figure
in this report that involve adjusted fuel economy data. Accordingly, adjusted fuel economy
values for 1986 and later model years should not be compared with the corresponding values
from pre-2007 reports in this series. Specifically, the adjusted fuel economy values for 1986-
2009 in this report differ from those in pre-2007 reports as explained below.
• For model years 2005-2009, EPA calculates adjusted fuel economy values for most of
the individual models in the fuel economy trends database using the following city
and highway "mpg-based" equations from the EPA fuel economy labeling
rulemaking:
1
New ADJ CITY =
0.003259+ 1.1805
LAB CITY
1
New ADJ HWY =
0.001376+ 1.3466
LAB HWY
EPA-420-R-09-014 A-9 November 2009
-------
The above equations are not used if a manufacturer chooses the option of providing
vehicle-specific 5-cycle test data for an individual model. In that case, the adjusted
fuel economy values are calculated using equations with weighting factors for the
data from the 5-cycle tests. For MY2009, manufacturers chose this option for a small
number of individual models.
Calculating fleetwide adjusted city and highway fuel economy values for a given
model year requires a harmonic, production-weighted average of all of the adjusted
city and highway fuel economy values for individual models.
The above equations yield a greater downward adjustment for higher fuel economy
vehicles than for lower fuel economy vehicles. For example, compared to the older
fuel economy label methodology, a 15 mpg city value will be reduced by an
additional 10%, while a 50 mpg city value will be reduced by an additional 18%.
Likewise, a 20 mpg highway value will be reduced by an additional 7%, while a 50
mpg highway value will be reduced by an additional 11%. EPA projected an overall
average fleetwide adjustment of 11% lower for city fuel economy and 8% lower for
highway fuel economy, beyond that in the older label adjustment methodology that
has been used in pre-2007 reports in this series. These factors can be used to convert
older adjusted fuel economy values to the newer adjusted fuel economy values for the
current fleet as a whole, but would not be appropriate factors to use for individual
models or for a future fleet with different mpg characteristics.
This report seldom uses separate city and highway fuel economy values, but typically
uses the composite city/highway fuel economy value. Pre-2007 reports used a 55%
city/45% highway weighting for adjusted composite fuel economy values, the same
weighting used for laboratory composite values and for the CAFE compliance
program. The analysis of real world driving activity underlying the newer fuel
economy label methodology assumed a "speed cutpoint" of 45 miles per hour to
differentiate between city and highway driving (71 Federal Register 77904). Based
on this speed cutpoint, the correct weighting for correlating the new city and highway
fuel economy values with real world driving, on a miles driven basis, is 43%
city/57% highway. Accordingly, the 43% city/57% highway weighting is now used
for all adjusted composite city/highway fuel economy values in this report beginning
with the 2005 model year (note that the historic 55% city/45% highway weighting is
still used for both CAFE compliance and fuel economy labels).
The appropriate fleetwide factors to convert laboratory or older adjusted fuel
economy values to the newer adjusted fuel economy values are dependent on the city
fuel economy-to-highway fuel economy ratios in the fleet. On average, for the
current fleet, combining the 11% lower adjustment for city fuel economy, the 8%
lower adjustment for highway fuel economy, and the shift to the 43% city/57%
highway weighting, the newer adjustment for city/highway composite fuel economy
values is 6% lower than that used in the older label adjustment methodology. This
6% lower value is the average impact for a fleet with the mpg and city fuel economy-
to-highway fuel economy characteristics of the current fleet, and would not be the
appropriate value for individual models, partial fleet segments, or for future fleets
with different mpg and city fuel economy-to-highway fuel economy distributions.
EPA-420-R-09-014 A-10 November 2009
-------
• For model years 1986 through 2004, EPA calculates adjusted fuel economy values
based on the assumption that the impacts of the factors that have led to lower real
world fuel economy have occurred in a gradual (i.e., linear) manner over the 20 years
from 1986 through 2005. On April 6, 1984, EPA published regulations that
established the older fuel economy label adjustment factors of 0.9 for city fuel
economy and 0.78 for highway fuel economy that took effect for model year 1985
vehicles (49 Federal Register 13832). EPA believes that these adjustment factors
were appropriate through the 1985 model year. EPA has not attempted to perform a
year-by-year analysis to determine the extent to which the many relevant factors
(including highway speed limits, more aggressive driving, vehicle horsepower-to-
weight ratio, suburbanization, congestion, use of air conditioning, gasoline
composition, et al) that have affected real world fuel economy since 1985 have
changed over time. Rather, EPA has made the simplifying, but we think reasonable,
assumption that the collective impact of these changes has been a linearly increasing
impact over the 20 years from 1986 through 2005. Using the equations shown above
for individual models, EPA has assumed 1/20 of the fully phased-in downward
adjustment for city and highway values would be reflected in the 1986 data, 2/20 of
this adjustment would be reflected in the 1987 data, etc., up to 19/20 of this
adjustment in 2004 and the full adjustment in 2005 and later years. Likewise, EPA
has assumed the 55/45 city/highway weighting changes to a 43/57 city/highway
weighting in a linear fashion over the 1986 to 2005 time period as well. As discussed
above, the average fleetwide composite city/highway fuel economy values for 2005-
2009 are 6% lower than the composite city/highway fuel economy value calculated
with the older adjustment factors.
To generate precise adjusted city, highway, or composite fuel economy values for
individual models or for future fleetwide averages with different mpg or city fuel economy-to-
highway fuel economy ratios than the current fleet, it is essential to use the above equations to
calculate adjusted city and highway fuel economy values for individual models, then use the
43% city/57% highway weighting to generate an adjusted composite fuel economy value for
individual models, and then calculate the harmonically production-weighted average of the
individual models to yield the average composite fuel economy for the fleet as a whole.
Alternatively, for a first-order estimate of generic fleetwide factors that one could use to convert
values from the historic fuel economy trends database to the newer adjusted fuel economy levels,
see the factors in Table A-4, which are based on the mpg and city fuel economy-to-highway fuel
economy characteristics of the current fleet. For example, the industry-wide adjusted composite
city/highway fuel economy value for model year 1986 in this year's report, which will be
reported as ADJ COMP, is about .997 (1.0 minus 0.003, where 0.003 equals 0.3%, and the latter
is equal to 6% divided by 20) times the adjusted composite city/highway fuel economy value, or
ADJ 55/45, from pre-2007 reports in this series. Likewise, the same industry-wide ADJ COMP
value for 1986 can be approximated by multiplying the laboratory composite 55/45 value for
1986 by 0.851. The industry-wide ADJ COMP fuel economy values for model years 2005-2009
in this year's report are all equal to 0.80 times the laboratory composite 55/45 values.
EPA-420-R-09-014 A-ll November 2009
-------
It is important to note that the above discussion, as well as all the data in this report, is
focused on new model year vehicle fleets, i.e., the data for a MY2000 vehicle is most directly
relevant for that vehicle operated on the road in calendar year 2000. Because most (though not
all) of the real world factors reflected in this methodology are relatively independent of vehicle
design, the best approximation of the adjusted fuel economy of a used MY2000 vehicle in
calendar year 2008 would be to use the 2008 factors in Table A-4.
Table A-5 provides a comparison of adjusted composite fuel economy values, for cars
and trucks combined, using both the older fuel economy label methodology that has been used in
pre-2007 reports in this series as well as the newer fuel economy label methodology described
above and used in 2007 and later reports.
No changes have been made in the way EPA calculates adjusted fuel economy values for
1975-1985. For these model years, EPA still uses the 0.9 city/0.78 highway fuel economy
adjustments established in 1984, along with the 55% city/45% highway weighting factor. EPA
believes that this methodology was appropriate for the late 1970s and early 1980s and is not
making any changes to adjusted fuel economy values for 1975 through 1985.
No changes have been made in the laboratory (LAB) fuel economy values in this report.
The laboratory city value remains the fuel economy value over the EPA Federal Test Procedure,
the laboratory highway value remains the fuel economy value over the EPA Highway Fuel
Economy Test, and the laboratory 55/45 is a weighted value of these two tests, with a 55%
weighting of the Federal Test Procedure and a 45% weighting of the Highway Fuel Economy
Test. The laboratory 55/45 values are used for CAFE compliance, in conjunction with
alternative fuel vehicle credits and test procedure adjustments. Because the underlying
methodology for generating and reporting the laboratory fuel economy values have not changed
since this series began in the mid-1970s, these values provide an excellent basis with which to
compare long-term fuel economy trends from the perspective of vehicle design, apart from the
factors that affect real world fuel economy that are reflected in the adjusted fuel economy values.
Finally, this same methodology for including real world factors in the adjusted fuel
economy values is also reflected in the adjusted carbon dioxide (CO2) emissions data as well.
As discussed in Section IV, EPA back-calculated all CO2 emissions values in this report from
corresponding fuel economy values in the historical Trends database. Accordingly, the adjusted
CO2 emissions values explicitly account for the above methodology for 1986 and later model
years.
EPA-420-R-09-014 A-12 November 2009
-------
Table A-4
Approximate Factors for Converting Industry-Wide Fuel Economy Values from Pre-2007
Reports to the Newer Adjusted Fuel Economy Values in This Report
Factors to Convert Old ADJ to New ADJ
Factors to Convert LAB to New ADJ
1975-1985
1986
1987
1998
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
CITY
1.00
.995
.989
.984
.978
.973
.967
.962
.956
.951
.945
.940
.934
.929
.923
.918
.912
.907
.901
.896
.890
.890
.890
.890
.890
HWY
1.00
.996
.992
55/45
1.00
.997
.994
.991
CITY
.900
.895
.890
.885
.984
.980
.976
.972
.968
.964
.960
.956
.952
.948
.944
.940
.936
.932
.928
.924
.920
.920
.920
.920
.920
.985
.982
.979
.976
.973
.970
.967
.964
.961
.958
.955
.952
.949
.946
.943
.940
.940
.940
.940
.940
.875
.870
.865
.860
.855
.850
.845
.840
.835
.830
.825
.820
.815
.810
.805
.800
.800
.800
.800
.800
HWY
.780
.777
.774
.771
.768
.765
.762
.759
.756
.753
.750
.747
.744
.741
.738
.735
.732
.729
.726
.723
.720
.720
.720
.720
.720
55/45
.854
.851
.849
.846
.843
.841
.838
.835
.832
.830
.827
.824
.822
.819
.816
.814
.811
.805
.803
.800
.800
.800
.800
.800
Important Notes for Table A-4:
1. Multiplying the factors above times the appropriate values from pre-2007 reports
approximates the newer adjusted (ADJ) fuel economy values in this report. Also, these factors
can be used "in reverse" to convert new adjusted fuel economy values in this report to
corresponding old adjusted fuel economy values or to corresponding laboratory fuel economy
values, e.g., dividing an adjusted, combined city/highway MY2009 fuel economy value in this
report by .940 would yield a corresponding adjusted fuel economy value based on the
methodology used in pre-2007 reports.
2. These factors are first-order approximations relevant only for industry-wide fuel economy
values for the 1986 through 2009 timeframe.
3. Precise estimates for individual models require the use of the mpg-based equations for ADJ
CITY and ADJ HWY provided above as well as a linear phase-in, over the 1986 to 2005 time
period, for both the mpg-based equations and the change from a 55/45 city/highway weighting to
a 43/57 city/highway weighting.
4. These approximations would yield the largest error for individual models or fleets with high
mpg and/or high city fuel economy-to-highway fuel economy ratios.
EPA-420-R-09-014
A-13
November 2009
-------
Table A-5
Comparison of "Old" and "New" Adjusted Composite Fuel Economy Values,
for Cars and Trucks Combined, for 2003 - 2009
Cars and Trucks Combined
Model "Old" "New"
Year Adjusted Adjusted
Composite Composite
2003 20.7 19.6
2004 20.5 19.3
2005 21.2 19.9
2006 21.5 20.1
2007 22.0 20.6
2008 22.4 21.0
2009 22.6 21.1
Important Notes for Table A-5:
1. "Old" adjusted composite fuel economy values are based on the EPA fuel economy label
methodology used in previous reports in this series, i.e., 10% downward city adjustment, 22%
downward highway adjustment, and a 55% city/45% highway weighting factor.
2. "New" adjusted composite fuel economy values are based on the new EPA fuel economy
label methodology, applicable to MY2009 vehicles and used for the first time in the 2007 report
and described in the previous section.
3. The "new" adjusted composite fuel economy values for cars and trucks combined are
approximately 6% lower than the "old" adjusted composite fuel economy values for cars and
trucks combined. For cars only, the "new" adjusted composite fuel economy values would be
more than 6% lower than the "old" values, while for trucks only, the "new" adjusted composite
fuel economy values would be less than 6% lower than the "old" values.
EPA-420-R-09-014 A-14 November 2009
-------
Comparison of EPA and NHTSA Data, 1975-2009
Table A-6 compares CAFE performance data reported by the National Highway Traffic
Safety Administration ("Summary of Fuel Economy Performance" report dated March 30, 2009
and available at www.nhtsa.gov) with the adjusted and unadjusted (laboratory) composite fuel
economy data in this report. The NHTSA values in Table A-6 are generally higher than the EPA
laboratory values due to differences in alternative fuel credits, test procedure adjustment factors
for cars, and vehicle classification. In recent years for which both Agencies report final data, the
NHTSA values are typically 0.6-0.8 mpg higher than the EPA values. For MY2009, the
preliminary NHTSA value is 1.8 mpg higher than the preliminary EPA value. These preliminary
projections are based on different data sets. The EPA value is based on automaker submissions
in the spring and summer of 2008 to support vehicle fuel economy labels. The NHTSA value is
based on automaker estimates provided in pre-model year CAFE reports later in 2008. Given the
volatility in gasoline prices in 2008, it is not surprising that these estimates could vary. Final
MY2009 results will be reported in next year's report.
Table A-6
EPA Adjusted, Laboratory, and NHTSA CAFE Fuel Economy Values by Model Year
Cars Trucks Both Cars and Trucks
Model
Year
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
EPA
Adj.
13.5
14.9
15.
16.
17.
20.
21.
22.
22.
22.
23.
23.
23.
24.
23.
23.
23.
23.
23.
23.
23.
23.
23.
23.
23.
22.
23.
23.
23.
23.
23.
23.
24.
24.
24.
, 6
,9
,2
,0
,4
,2
,1
,4
,0
,7
,8
,1
,7
,3
,4
,1
,5
,3
,4
,3
,4
,4
,0
,9
,0
,1
,2
,1
,5
,3
,1
,3
,5
EPA
LAB
15.8
17.5
18.3
19.9
20.3
23.5
25.1
26.0
25.9
26.3
27.0
27.9
28.1
28.6
28.1
27.8
28.0
27.6
28.2
28.0
28.3
28.3
28.4
28.5
28.2
28.2
28.4
28. 6
28.9
28.9
29.5
29.2
30.3
30.5
30.9
NHTSA
CAFE
n/a
n/a
n/a
19.9
20.3
24.3
25.9
26.6
26.4
26.9
27.6
28.2
28.5
28.8
28.4
28.0
28.4
27.9
28.4
28.3
28.6
28.5
28.7
28.8
28.3
28.5
28.8
29.0
29.5
29.5
30.3
30.1
31.2
31.2
32.6
Diff .
.0
.0
.8
.8
. 6
.5
.6
. 6
.3
.4
.2
.3
.2
.4
.3
.2
.3
.3
.2
.3
.3
.1
.3
.4
.4
. 6
.6
.8
.9
.9
.7
1.7
EPA
Adj.
11.6
12.2
13,
12,
12,
15,
17,
17,
17,
17,
17,
18,
18,
17,
17,
17,
17,
17,
17,
17,
17,
17,
17,
17,
16,
16,
16,
16,
16,
16,
17,
17,
17,
18,
18,
.3
.9
.5
.8
.1
.4
.8
.4
.5
.2
.3
.9
.6
.4
.8
.4
.5
.2
.0
.2
.0
.1
.7
.9
.7
.7
.9
.7
.2
.5
.7
.2
.4
EPA
LAB
13.7
14.4
15.6
15.2
14.7
18.6
20.1
20.5
20.9
20.5
20.6
21.4
21.6
21.2
20.9
20.7
21.3
20.8
21.0
20.8
20.5
20.8
20.6
20.9
20.5
20.8
20.6
20.6
20.9
20.8
21.4
21.8
22.1
22.7
22.9
NHTSA
CAFE
n/a
n/a
n/a
n/a
18.
18.
20.
20.
20.
20.
20.
21.
21.
21.
21.
20.
21.
20.
21.
20.
20.
20.
20.
21.
20.
21.
20.
21.
21.
21.
22.
22.
23.
23.
24.
2
5
1
5
7
6
7
5
7
3
0
8
3
8
0
8
5
8
6
0
9
3
9
4
8
5
1
5
1
6
2
Diff.
3.5
-.1
-.2
.1
.1
.1
.1
.1
.1
.1
.1
.4
.5
.3
.8
.9
.7
.7
.7
1.0
.9
1.3
EPA
Adj.
13.1
14.2
15.1
15.8
15.9
19.2
20.5
21.1
21.0
21.0
21.3
21.8
22.0
21.9
21.4
21.2
21.2
20.8
20.9
20.4
20.5
20.4
20.1
20.1
19.7
19.8
19.6
19.4
19. 6
19.3
19.9
20.1
20. 6
21.0
21.1
EPA
LAB
15.3
16.7
17.
18.
18.
22.
24.
24.
24.
24.
25.
25.
25.
25.
25.
25.
25.
24.
25.
24.
24.
24.
24.
24.
24.
24.
24.
24.
24.
24.
24.
25.
25.
26.
26.
,7
,6
,7
,5
,1
,7
,6
,6
,0
,7
,9
,9
,4
,2
,4
,9
,1
, 6
,7
,8
,5
,5
,1
,3
,2
,1
,3
,0
,8
,2
,8
,3
,4
NHTSA
CAFE
n/a
n/a
Diff
n/a
19,
20,
23,
24,
25,
24,
25,
25,
25,
26,
26,
25,
25,
25,
25,
25,
24,
24,
24,
24,
24,
24,
24,
24,
24,
25,
24,
25,
25,
26,
27,
28,
.9
.1
.1
.6
.1
.8
.0
.4
.9
.2
.0
.6
.4
.6
.1
.2
.7
.9
.9
.6
.7
.5
.8
.5
.7
.1
.6
.4
.8
.6
.0
.2
1.3
1.4
. 6
.5
.4
.2
.4
.4
.2
.3
.1
.2
.2
.2
.2
.1
.1
.2
.1
.1
.2
.4
.5
.3
. 6
.8
.6
.6
. 6
.8
.7
1.8
EPA-420-R-09-014
A-15
November 2009
-------
Comparison of EPA and NHTSA Data for MY2008 by Marketing Group
The primary differences between EPA unadjusted laboratory fuel economy data and
NHTSA CAFE values are flexible fuel vehicle (FFV) credits that are available to manufacturers
that produce vehicles capable of operation on an alternative fuel (generally a blend of 85 percent
ethanol and 15 percent gasoline), and test procedure adjustment (TPA) credits that apply to
manufacturers of passenger cars.
Table A-7 shows a detailed MY2008 comparison, for the ten highest-volume
manufacturers, of the EPA laboratory fuel economy values from this report and projected
NHTSA CAFE values based on the mid-model year fuel economy report data provided to
NHTSA by automakers. This table attempts to show how EPA laboratory values, FFV credits,
and TPA credits "add up" to CAFE values. It is important to emphasize that while the values in
Table A-7 approximately add up for most manufacturers, in most cases they do not add up
precisely. The primary explanation for this is that, for MY2008, the EPA laboratory values are
based on final CAFE reports, while the NHTSA CAFE estimates are based on mid-model year
reports, and MY2008 was an unusual year due to record gasoline prices. Slight differences in car
and truck classification can also affect the individual car and truck comparisons, though not the
combined car and truck values.
The manufacturer column in Table A-7 differs from the marketing group columns
elsewhere in this report in two ways, in order to be consistent with the way NHTSA reports
CAFE data for MY2008. One, Hyundai and Kia are listed separately. Two, Ford includes
Mazda, Rover, and Jaguar (Table 32 gives different EPA laboratory fuel economy values for the
Ford marketing group excluding Mazda, Rover, and Jaguar, consistent with the Trends database
approach where changes in current marketing groups are retroactively applied so as to allow
long-term trends to be identified independent of marketing group composition).
The FFV credit values in Table A-7 for the truck column were obtained directly from
EPA's fuel economy compliance program (trucks are not eligible for TPA credits). The FFV and
TPA credits for the car columns were generated by weighting the values for domestic cars and
import cars by the NHTSA sales for each car category (see cite below). The FFV and TPA
credit values for the combined car and truck columns were generated using the car and truck
sales from the EPA Trends database. For MY2008, three manufacturers earned FFV credits for
cars and four manufacturers did so for trucks. All ten manufacturers were eligible for the TPA
credits for cars.
All of the NHTSA CAFE estimates in Table A-7 were taken or generated from the March
30, 2009 NHTSA report "Summary of Fuel Economy Performance" available at www.nhtsa.gov.
The car values were generated from the NHTSA fuel economy and production estimates for the
separate domestic car and import car CAFE categories. The truck values were taken directly
from the NHTSA report. The combined car and truck values were generated from the NHTSA
fuel economy and production estimates for the separate domestic car, import car, and light truck
CAFE categories. While there are no CAFE standards for combined cars and trucks, this column
is shown for illustrative purposes.
EPA-420-R-09-014 A-16 November 2009
-------
Table A-7
Comparison of MY2008 EPA Laboratory and Mid-Model Year NHTSA CAFE Estimates
by Highest Sales Manufacturers
Manufacturer
< Passenger Car >
EPA FFV TPA NHTSA
LAB Credit Credit CAFE*
< Light Truck > <— Cars and Trucks —>
EPA FFV TPA NHTSA EPA FFV TPA NHTSA
LAB Credit Credit CAFE* LAB Credit Credit CAFE*
General Motors
Toyota
Chrysler
Honda
Nissan
Ford
Hyundai
Kia
BMW
Volkswagen
6.5
* Mid-model year estimates based on manufacturer reports to NHTSA summarized in "Summary of
Fuel Economy Performance" dated March 30, 2009 and available at www.nhtsa.gov
EPA-420-R-09-014
A-17
November 2009
------- |