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EPA-AA-CPSB-81-03

ATTACHMENT n14-

The Effect of Vehicle Mileage Accumulation on Tested Fuel Economy
by
Kevin R. Tuckey

February 1981

Notice

This is a technical support report for regulatory action and it does not
necessarily represent the final EPA decision on regulatory issues. They
are intended to present a technical analysis of issues and recommendations
resulting from the assumptions and constraints of that analysis. Agency
policy constraints or data received subsequent to the date of release of
this report may alter the recommendations reached. Readers are cautioned

to seek the latest analysis from EPA before using the information contained
herein.

Technical Support Section
Certification Policy and Support Branch
Office of Mobile Source Air Pollution Control
U.S. Environmental Protection Agency


crD Feo inte vasw

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seesFoRD 2 is 20.0 RATIO: 1.0808
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B. Data Base Used

CAFE recaliculations were performed for the 1979
through 1982 model years.1 The 1981 model year was the last
model year for which we had a complete CAFE data base at the
time of the analysis. The 1982 model year was partially incom-
plete, missing final CAFE data for AMC and Chrysler. In order
to reduce the complexity of the analysis, only the top ten
sales manufacturers' CAFE's were examined. They account for
approximately 95 percent of U. S. sales. These manufacturers
are American Motors, Chrysler, Ford, General Motors, Honda,
Nissan, Toyo Kogyo, Toyota, Volkswagen, and Fuji. Separate
CAFE standards apply to the categories of passenger auto-
mobiles, 2-wheel-drive trucks, and 4-wheel-drive trucks.
Therefore, those categories were examined for each of the ten
manufacturers.

For the mileage accumulation trend analysis, data
were available for the 1976 through the 1983 model years. This
data ‘base consisted of all passing valid tests used to support
certification, fuel economy labeling, and CAFE's. The vehicles
generating the data were emission-data vehicles, fuel economy
data vehicles, and running change vehicles. This amounted to
about 33,000 data points.

Iv. Results
A. Mileage Accumulation Trends

Figures 1 and 2 illustrate average test vehicle
mileages for the 1976 through the 1983 model years. As can be
seen from the overall trend line, the average mileage of vehi-
cles when tested has generally increased over these years.
Although the average test mileage for these years was only
approximately 4,500 miles (only a 500-mile increase over the
1975 baseline), nearly 20 percent of the test mileages were in
the 5,000- to 10,000-mile range. The impact of these higher
mileage vehicles is not necessarily indicated by their pro-
portion in the total population. Their impact on CAFE is

1. CAFE standards went into effect in the 1978 model year;
however, EPA records for that year are not readily accessible
and may not be analytically compatible with subsequent model
years.


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COUNTS(4K): CITY.EMISS + $2 KW.EMISS © 92 CITY.FE © 280 HW.PE D2
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1 PCRT USED 448000 samrize
1 . 14.8 RATIO: 1.0000
s2aa7 cet 0 PRCT USED ase708 a3ma-76
, ° 14.8 RATIO: 1.081
wwe 2 1 PNCT USED 448000 eameize
ww? ° PNCT NTUS  4eac00 aaMe 128
2 is 18.4 RATIO: — 1.0000
92038 HW:2 8 PNCT USED 48p708 vame-Te819C
2 te 18.4 RATIO: totter
eizie ct .
yesies cot 1
1 .
s2eg0 ct ° PNCT NTUS 472300
' ° 17.9 RATIO: 1.0838
a12200 MWe? s Puct useo 438800
yazesy wiz ° PNCT NTU 438800
2 a 23.8 aaTiO: 1.0000
e2ear awe Ss50.0 PNeT NTUS 472300 94p2-487)
2 S858.0 23.9 RATIO: 0
7esz0s co: ares wer _usi a3ea02 Fao
, aie : 18.8 RATIO: — 1.0000
a2708 ct ° PNCT usED 472306 sae2-aa71
' 2.0 18.8 o: 1.01
798208) Hw:2 a PNCT USEO 438802 senrso
2 3 24.6) RATT 1.00
270 :2 ° uct NTus 47230: p2-aa7t
798238 2 7 PMcT UsEO 472304 224871
2 2 24.6 Ratt 1.0628
ezeez co: rz PNCT NTUS 478700 e2-saras
1 fe 18.2 Ratt 1.0000
ezee7 oc 7321.0 PNCT NTUS 478700 a-sa18s
yearns cord yeael2 PNCT USED 478700 oan2-se188
1 2408.1 va.2 Ratio: 0
e283 Wwe? 3882.0 PNCT NTUS 478700 eenz-setes
2 3883.0 24.1 RATIO: — 1.0000
°: wwe 7322.0 PNCT NTUS 475700
798101 Ww? 748810 PNCT useD 478700
2 739818 26.1 RATIO: 0
eize6 cst 8 PNCT NTUS 642600 sears
yea33e cot 3 PCRT USED 642600 sauree
' 1 a.8 Matra: — 1.0000
e205 cet 410.0 PNCT USED 466800 euacariier
1 6a10.0 16.6 RATIO: 1.1028
91267 Awe 6 4 ems) ewer Nrus 2600 sauroe
793337 nw? 320.2 Em: 1 PNCT USED 442600 geuree
2 4 20.8 FeaK: 20.8 RaTI0: 1.0000
e2008 Kw:2 6378.0 21.3 FE:2 PRCT USED 486900 rerereser yg
92086 KW: lo 22.2 Fe:2 pwct useo 466! ayaceTiier
2 Ts 2117 weak: 20.8 Ratio:
1262 ct 3877.2 18.8 EM:) PNET NTUS 440800 Prorat
yeasze oc: sors.3) 0 1a.3 em: 1 pcAT useD 0800 oeuras
1 398.3 14.6 FEGK: 14.6 RATIO: 1.0000
92007 6460.0 14.9 FE:2 PNCT NTUS saueca7tier
az088 6S00.0 18.2 FE:2 PNCT NTUS PPOrer santa
yeeery crt 8563.8 14.8 Fez PNCT USED 46. payece7iier
1 6$07.9 18.0 PEAK: 14.6 RATIO:
91263 Hw: 3913.6 20.1 em:1 PHCT NTUS 440800 sauras
793825 KWw:2 4030.) 19.8 em: 1 PNET USED s4oso0 sauras,
2 3871.8 200 FREAK: 20.0 RATIO: 1.0000
32098 Kw:2 B470.0 20.8 -PE:2 PCT NTUS 46601
$2100 kw:2 8510.0 20.8 «-Fe:2 PNET NTUS 486901
798872 Mw? $581.0 20.0 -FE:2 PNCT USED
2 €820.3 20.5 FEAK: 20.0 RATIO
arses ct 3777.0 13.4 em) PNET USED seucit7
e3002 3aso.t 12.8 eM: 1 POAT NTUS seucii7
3a1a.8 12.9 FeaK: 17.9 RATIO
a2198 ct 9723.0 13.4 Fe:2 PNCT USED 488600
' 8723.0 013.6 PeeK: 12.9 RATIO: 1.0208
e127 wwe 3788.8 20.4 M:1 PACT NTUS 463200 a
yeatia Wwe? 3900.8 20.) EM: 1 PNET USED 463200 seucui7
2 3aae.6 © 20.2 FeaK: 20.2 RATIO: 1.0000
92200 Kw:2 9735.0 20.8 -Fe:2 PNCT USED 4eesco 2040-s038e


ATTACHMENT IL
Regression Results

Correction Factors gt
Std. Various Test Points

Regression Data R-Coef- Error Equation’ 4000 6200 10000
Linear city 0.421 0.027 969 + -820 x 1072 (m) 1.0018 1.0198 1.0510
Highway 0.407 0.030.969 + «862 x 1073 (m) 1.0035 1.0224 1.0552
All 0.413 0.029 969 + -842 x 10-7 (m) 1.0027. 1.0212 1.0532
Logarythmic City 0.427 0.027 -596 + -488 x 107} (In m) 1.0007 1.0221 1.0455
Righway 0.422 0.030 +566 + 526 x 10_) (in m) 1.0023 1.0253 1.0505
AlL 0.424 0.028 = 581 + .507 x 10” (In m) 1.0015 1.0237 1.0480
2nd Order City 0.429 0.027.940 + -182 x 107f(m) + -.795 x 10 2(m)> 1.0001 1.0223 :1-0425
Highway 0-439 0.029 +899 + .331 x 10_,() + -.195 x 10_g(m), 1-0002 1.0293 1.0350
AlL 0.432 0.028 © 920 + «256 x 10" (m) + --13R x 10° (m) 1.0003 1.0257. 1.0380
3rd Order city 0.439 0.027 «764 + -109 x 107m) + --157 x 1072(m), + -770 x 10_12(m)3 0-9981 11-0198 1.0540
Highway 0.440 0.029 «B53. + «571 x 10_, (m) + -.587 x 10_>(m)> + -202 x 107) (m) 1.0004 11-0295 1.0390
ALL 0.435 0.028 = «808 + «832 x 10 “(m) + --108 x 10 /(m)” + -485 x 10” (m) 0-9990 1.0243 1.0450,

1. m = System miles accumulated prior to test point. For system kilometers, divide the kilometers by 1-609344 to
get miles or adjust the multiplicative constants in the equations.

2. To find the percent increase, substract one from the factor and multiply by 100. For example, linear correction
factor at 10,000 miles = 1.0532 or 5.32 percent increase.

-8I-


710-

B. CAFE Impacts

The results of the CAFE recalculations for the 1979
through 1982 model years are shown in Tables 1 through 3. Each
table represents a CAFE category and lists the mpg offset from
high test vehicle mileage for each manufacturer and model year.
For the latest available complete model year (1982) the pas-
senger automobile overall sales-weighted CAFE offset is 0.18
mpg. For two-wheel drive light-duty trucks the 1982 offset is
0.44 mpg, and for four-wheel drive light-duty trucks, the 1982
offset is 0.19 mpg.

Table 1

Passenger Automobiles

[CAFE original ~ CAFE adjusted!

(mpg)
Manufacturer 1979 1980 1981 1982
AMC 0.01 0.01 0.27 0.01
Chrysler 0.06 0.07 0.27 0.25
Ford 0.18 0.11 0.09 0.20
Fuji 0.06 0.14 0.04 0.03
GM 0.21 0.26 0.50 0.23
Honda 0.05 0.01 0.01 0.14
Nissan 0.02 0.02 0.01 0.01
Toyo Kogyo 0.00 0.00 0.01 0.02
Toyota 0.00 0.07 0.00 0.02
vw 0.07 0.02 0.01 0.01
Sales Weighted Average: 0.17 0.18 0.29 0.18

Table 1 shows the passenger automobile CAFE offsets
for each manufacturer. The overall averages for the 1979
through 1982 model years appear to be fairly constant except
for the 1981 model year average. Looking more closely at the
sources of the 1981 increase, Table 1 shows that three manu-
facturers, AMC, Chrysler, and GM, accounted for virtually all
of the 1981 offset. GM, in particular, had nearly double the
offset of either AMC or Chrysler, and since the overall aver-
ages are sales-weighted, the high GM offset had a strong
influence on the average value. However, in the 1982 model
year, AMC and GM significantly reduced their offsets to values
closely in line with the 1979 and 1980 model years. In


5600

5400

5200

5000

4800

4600

4400

4200

4000

3800

-7-

Figure 2

rF ee Overall
G—1O Honda
a-aA WwW
rF ©O--—© Nissan/Toyo Kogyo/Toyota/Fuji
L
T
a
L ywe-- Aw A LUA eo)
Z N s >
“7TM N
a y ‘ ye Oo ~
~
N vA
L Ww
n n 1 n 1 i i” iz
T q T T v T T T
76 77 78 79 80 81 82 83

Model Years


5600

$400

5200

$000

4800

4600

4400

4200

4000

3800

o--o
a-a
o---o
$u-+

Figure 1

Overall
AMC

Chrysler

Ford
GM

76

77 78 79 80

Model Years

81

82

83


ATTACHMENT IIT 718

The following pages contain the data points used in this analysis. Each
grouping of data contains the individual test result(s) for a given
subconfiguration at a test point (separately for city and highway tests).
The last line in each group, denoted by an indented manufacturer's name,
contains the following:

A. The harmonically averaged fuel economy value.

B. The standard four thousand mile test points harmonically
averaged fuel economy values (FE 4K).

C. The ratio of (A) divided by (B).

The headings are defined as follows:
MFR - Manufacturer of the vehicle.
ACYR - Active model year the test point is used for.
K - Code number, unique for each subconfiguration. This number has
been assigned by the computer to sort the groups but cannot be
used to identify what parameters were unique to the subconfiguration.
TNUM - Test number, assigned by EPA.
TPRO ~ Test procedure: C:1 - City test cycle; H:2 - Highway test cycle.
ODO - Odometer, in miles, at the test point.

RWMG - Rounded miles per gallon at the test point.

TTYP - Test type: EM:1 - Emission data vehicle;
FE:2 ~ Fuel economy data vehicle.

CTD - Certification test disposition;
pert! - Passed emission standards, used for emission certification.
pyer! ~- Passed emission standards, not used for emission certification.
FED - Fuel economy disposition;
useD" - Used for fuel economy calculations.
ntvs? - Not used for fuel economy calculations.
T. PCRT, PNCT--EPA uses only one test, coded PCRT, to issue on umission
Certificate of Conformity, the other tests that pass the emission standards
but are not used are coded PNCT.
2. USED, NTUS--EPA is restricted in its selection of fuel economy data for

use in fuel economy calculations. Data that is used in these calculations
are coded USED, data that were not selected are coded NTUS.


Figure 3
5600 + —~+ EDV's
O---O R/Cts
~--+ — FEDV's iN
s4o0 L _
/ \
/ \
\
/
5200 + / wea
/ \
7 \
sooo + / \
/ \
/ \
/
4800 + 4
a
ro
/
4600 + / P
/ o7
/ a o
/ uN ae
4400 4 / v4 Sow
Z
& “
/
L 7
4200 y
7
4000 +
3800 +
1 1 | 4 1 |. 1 |
T T v ~ T ms T T
76 77 78 79 80 81 82 83

Model Years


wen acyr x TNUM -TPRO ono RWG UTTYP CTD Feo iwre vasM vio

vean: (7.0 Ratio; (0000
fe:2 pMcT useD — seasos our-8.awee-se3
Peax: 17.0 RATIO‘ 1.0088 -25-
pwct usta 27s0ocor7aa
Tale RATIOS 1.0000
owct useo 842700 corors
PERT NTUS  Saz700 covers
tere nario! 0.8787
pect usso 627800 cari7ze
PuET NTUS  G27800 ceriqae

22.8 RATIO: — 1.0000

PMcT useD 42700 corors
PNCT NTUS 642700 corots
22.8 RATIO: 0.9618

PNCT USED Seo802 conzea
: 10.8 RATIO: — 1.0000

PRT useD  seoso3 cowzes
1 10.8 RATIO: 0.0883

PCY uso seoso2 conzes
24.7 RATIO: — 1.0000

cm a0 4082 wwe puct useo  seose3 conzea
sees Gm 80 4082 2 24.7 RATIO: 1.0081
om avez cut Puct TUS  Seez04 osvezs
sees GM 80 ave2 1 21.) RATIO: — 1.0000
om a 4102 vesee cet ° 2 pnct useo 308 os7eze
sees GM 80 a182 1 ° :2t.1 RATIO: 0.9908
cm 80 a162 ser) Hwee ° muey nvus 3048 087426
tee aM bo avez 2 te a RATIO: 1.0000
om 8 a1e2 19843 nwiz ° Pucr useo saeaoe on7ezs
tert GM 80 4162 2 ° 31.8 RATIO: 0,0843
cm 80 ai7e gerse crt ° PNCT NTUS 582200
Cort 471 reaate Cet 2 PCAT USED 200
. 18.9 RATIO: — 1.0000
seose cst ° PNCT TUS 882202 osecey
1 ° 16.8) RATIO: 22
wwe? © 24.6 EM:1 PNET NTUS 582200
nw [8 2617 AMS) PNCT USED 582200
2 8 24.8 PeaK: 24.6 RATIO: 1.0000
wie ° EM: 1 PNCT NTUS 882202
2 ° Feax: 26.5 Ratio: 1.0307
s7osa ct 3980.8 9 18.1 eM:1 PNET NTUS  S38301
s73zas cr) soso.o 4.) Fe: Pucr useo $3830!
' 2 0el) Pea: ta.d RATIO: 00
eu 9 17-2 Ws r Pear useo | saeae seers
' 5001702 Fea: test Ratio’ o-9s03
97089 Mw:2 3978.0 <8 EM: 1 PNET NTUS  SaBz0r seorts
97390 Wwe? s101.0 . PNCT USED 530301 eset
2 4039.8 s 124.8 RATIO: 1.0000
A678 Mw: ° ny PNCT useo  s24202 osenis
2 ° 24.8 RATIO: 0.0718
et ° 6 ems) per useo 0
eur 2 2 EM:s PORT NTUS 663600
1 © 18a reek: 18.4 RATIO: — 1.0000
cm 80 4223 saseocct so78.0 18.8 ems) PERT TUS 612801
cM 80 4223 aees1 oc ct saaz0 188 PNCT USEO 812801
sees GM 80 4223 1 $288.0 0 18.6 18.4 RATIO: 1.0109
4223 rio MWe 3792.0 PNCT USED 863800 Bsoisa
0223 a01e7) Hw:2 3972. PNCT NTUS  BEa8ee aso1sa
eee 4223 2 3482.0 24.8 RATIO: — 1.0000
om 80 223 osa5s ws? 3090.0 PNCT seo  61z601 aesi7e
cm 80 4223 eoes2 Hw:2 prrrery PNCT NTUS 612601 Beate
tees am 80 4223 2 s20s.0 24.8 RATIO: 1.0083
om 80 «zu sasas crt azi7.0 PNCT NTUS $2202 pasez
sees GM BO 4230 azine 18.1 Ratio: 1.0000
Gm 80 4236 esaoe cet 5313.0 PwcT useD $3202 Base2
tts eM 80 4236 1 5313.0 16.1 RATIO: 1.0188
cM 80 oases Kw 4278.0 PMcT useD  §s3202
sees Gm ae 2 4228.0 22.8 RATIO: — 1,0000
om 80 e4o0 Kw? ° PNcT NTUS  sBa202 pase2
sees GM 80 2 ° 22.8 RATIO:" 0.9825
cm 80 earze cost ° PCRT useO s82301 eceiss
Sees GM 80 4237 1 ° 17,1 Ratio: 1.0000
om 80 4237 eerma cost ° PCRT USED 83208
sees GM 80 ‘ ° 17.1 RATIO: 0,048
cM 80 earzs hw:2 ° PNCT USED 53301
sees M 80 2 ° 23.8 RATIO: 1.0000
cm 80 9173 KW: 3.0 PNcT NTUS 85320! 2
cm 80 11100 HW: ° ouct useo  ssaz0e pacer
tres cM 80 2 ° 23.8 RATIO:
Flay 80 esers cost 0 20.4 PNCT NTUS  $42700 osror7a
Fat se cut 8 20.3 PCAT USED 542700 0470173
sersrTAT 80 ' (6 20.3 20.3 RATIO: 1.0000
rar 12072, cst 0 20.3 PERT usED 678001 oassore
se erTaT , @ 20.3 120.3 RATIO: 0.9876
Fiat 80 wwe © 28.4 EM) PNET NTUS — $42700 oa7or7a
FIAT 0 wwe 7 24.4 EM:1 PNET USED 542700 0470173
seeFTAT 80 2 [320.9 Feax: 24.8 Ratio: — 1.0000
iar aaar 12973 Hw: -© 28.8 Pe:2 PNCT USED 678001 ose



EPA Report No.:
EPA=AA-CPSB-83-04

Technical Report

The Effects of Test Vehicle
Mileage on Corporate Average
Fuel Economy Calculations

November, 1983

NOTICE

This is a technical support report for regulatory action and

it does not necessarily represent the final EPA decision on
regulatory issues. They are intended to present a technical
analysis of issues and recommendations resulting from the
assumptions and constraints of that analysis. Agency policy
constraints or data received subsequent to the date of release
of this report may alter the recommendations reached. Readers
are cautioned to seek the latest analysis from EPA before using
the information contained herein. .

U. S. Environmental Protection Agency
Office of Air, Noise, and Radiation
Office of Mobile Sources
Certification Division
Certification Policy and Support Branch
2565 Plymouth Road
Ann Arbor, Michigan , 48105


qi2-

Table 3

Light-Duty Trucks, 4-Wheel Drive

(CAFEoriginal ~ CAFEadjusted!

(mpg)
Manufacturer 1979 1980 1981 1982
AMC 0.00 0.00 0.09 0.02
Chrysler ee 0.08 0.13 0.16**
Ford ** 0.22 0.24 0.30**
GM . * 0.34 0.34 0.18
Nissan *e 0.00 0.03 0.00
Toyota ** 0.00 0.00 0.00
Sales Weighted Average: ialal 0.18 -16 0.19

** - See 2-wheel drive trucks for combined 2-wheel drive and
4-wheel drive results.

Tables 2 and 3 show the 1979 through 1982 CAFE
offsets for the two light-duty truck classes. These classes
are more difficult to analyze because some manufacturers in
some model years elected to combine the two-wheel drive (2WD)
and four-wheel drive (4WD) vehicles into one CAFE class.
(These occurrences are indicated in Tables 2 and 3.)

The overall 2WD averages widely fluctuate over the
1979 through 1982 model year span. This fluctuation appears to
be caused primarily by GM's offset fluctuation over that
period. In particular, the overall 1982 2WD average of 0.44
mpg was due to GM's offset of 0.81 mpg which is more than twice
any other manufacturer's offset. As with the passenger car
class, Volkswagen and the Japanese manufacturers exhibited
virtually no offset due to test vehicle mileage accumulation,
whereas the domestic manufacturers were usually in the 0.15 mpg
to 0.35 mpg range.

The 4WD class (Table 3) showed much the same pattern
as the 2WD class concerning domestic manufacturers versus the
Japanese manufacturers, although there were only two Japanese
Manufacturers in this class. However, AMC showed virtually no
offset for its 4WD trucks. Overall, the offsets for this class
tended to be lower than in the 2WD class, and GM did not exhibit
the same fluctuations as they did in the 2WD class. (In fact,
GM showed a significant offset drop in 1982 for this class.)


-1l-

contrast, for 1982, Ford exhibited an increase in tneir offset
after showing decreases for the 1979 through 1981 model years.
Given these fluctuations in offsets over these years, there
does not seem to be a clear trend of increasing or decreasing
offsets for any domestic manufacturer.

As reflected in the mileage accumulation trends
(Figures 1 and 2), the domestic manufacturers have consistently
exhibited higher passenger automobile CAFE offsets than the
foreign manufacturers. The exception to this is VW, which is
actually a domestic manufacturer but shows consistently very
small offsets as do the Japanese manufacturers. All of the
Japanese manufacturers had negligible offsets for all model
years for passenger cars, except for Honda which showed a
significant increase for 1982. This increase is also reflected
in Honda's mileage accumulation trend (Figure 2).

Table 2

Light-Duty Trucks, 2-Wheel Drive

[CAFEoriginal - CAFEadjusted]

(mpg)
Manufacturer 1979 1980 1981 1982
No No
AMC 0.30 Vehicles Vehicles 0.00
Chrysler 0.01** 0.13 0.08 0.16**
Ford 0.23** 0.34 0.34 0.30**
GM 0.19** 0.36 0.14 0.81
Nissan -  0.00** 0.00 0.07 0.01
Toyo Kogyo 0.00** 0.00 0.00 0.00
Toyota 0.00** 0.00 0.01 0.01
vw 0.00** 0.00 0.00 0.00
Sales Weighted Average: 0.16** 0.29 0.19 0.44

** - Combined with 4-wheel drive trucks as a manufacturer
option.


dependent on the sales fraction they represent in a manu-
facturer's product line. Thus, these mileage data only serve
the purpose of illustrating the trends toward higher test
vehicle mileages since 1975, but do not accurately reflect CAFE
impacts.

On a manufacturer-specific basis, Figures 1 and 2
also illustrate individual manufacturer trends and compare
general manufacturer positions. Domestic manufacturers,
particularly General Motors and Ford, test their vehicles at
significantly higher mileages than the foreign manufacturers.
General Motors, Ford, and Chrysler also have tended to increase
their average test mileages over those model years. American
Motors tended to look more like the foreign manufacturers until
1982 when they exhibited a drastic increase in average test
Mileage. In general, with the exception of Honda, foreign
Manufacturers do not appear to have made an overall effort to
test at higher mileages. Their averages have remained at near
the 4,000-mile baseline through the years. It appears that
Honda has greatly increased test mileage in 1982 and 1983.

Average test mileages of each of the previously
described vehicle types are plotted by model year in Figure 3.
It can be seen that on an overall average, FEDV's test mileages
increased rapidly until the 1980 model year, then dropped off.
It is not clear why this peak occurred, but from Figure 1 it
appears to be heavily influenced by General Motors. (However,
the General Motors peak is also unexplained.) Running change
vehicles have exhibited a steady rise in test mileages, also
exhibiting a slight peak in the 1979 model year. As expected,
the EDV test mileages remained steady at around 4,000 miles,
until the 1983 model year. For the 1983 model year, new rules
took effect that allow manufacturers to test EDV's at any mile-
age. Although this was originally intended to save manufac-
turers money by running them at less than 4,000 miles, average
EDV mileage data indicate an increase in mileage, presumably
to obtain a fuel economy advantage. This increase in overall
average EDV test mileage was nearly entirely due to the in-
creases of American Motors, Chrysler, and Honda for 1983.
(General Motors had a small increase of 200 miles over 1982.

To summarize the test mileage trends, the over-
all trend from the 1975 baseline of 4,000 miles had to
increase test mileage. The domestic manufacturers have
tended to accumulate significantly more miles than the for-
eign manufacturers. Manufacturers appear to be using the new
flexibility to test EDV's at higher mileages beginning in
the 1983 model year, as evidenced by the increase in average
EDV test mileages between the 1982 and 1983 model years.


Foro 78
FORD 78
FORD 78

Ford
FORO
FORO

sos FORD

roro
Foro
FORD 78

Foro 79
Foro’ 78

Fono 79
ror 79
sessFoRD 78
Foro 79
Foro 79

ceserDRD 78,

foro 79

Foro 73
FORD 79
‘oro 79
Foro 79
FORD 79
sereFoRD 78
Foro 78
FORD 79
seesroRD 79
roro 79
Foro 79
ceteroRD 78
rorD 79
Foro 79
cessFORD 78
ForD 78
Foro 79

seseroRD 79

Foro 79
FORD 79
Foro 79

ss-FORO 79
Foro 79
FORD 79

stesFORO 78

cm 79
om 79

see ome

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10: 1.0000
8274808
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527408
THO: 10631

s1820
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2 PHcT ust 02
PNCT useD 496902
14.4 RATIO: O.
pwct wrus 487
PNCT USED 417800
20.6 RATIG: 1.0000
PucT useD  4as902
pect useo 902
20.8 RATIO: 1.0221
PNcT NTUS 428200
CRT USED 625200
14.7 RATIO: 1.0000
PNCT NTUS 428206
PERT USED 428208
14.7 RATIO: 0.9788
PNCT NTUS 428200
PNCT USED 428200
21.0 RATIO: 1.0000
PNCT NTUS 426206
PCT USED 428208
21.0 RATIO: 0.9841
Fe:2 pect NTUS 428202
PNCT NTUS 428202
18.3 RATIO: 1.0000
Pe:2 PNCT useD 428202
FREAK: 15.3 RATIO: 0,9780
PucT NTUS 625202
PNCT NTUS 428202
22.6 RATIO: 1.0000
PwcT useo 428202
PNeT USED 425202
22.6 RATIO: 0.9960
Pwct useD 434800
PCRT NTUS 434500
12.2 RATIO: —1,0000
PNcT useD «93900
PNCT USED 493900
13.2 RATIO: 0.9777
PNCT NTUS 434800
PNCT useD 434800
18.0 RATIO: 1.0000
puct usen 493900
PNCT USED 483900
19.0 RATIO: 1.0687
PNCT USED 438300
119.8 RATIO: 1.0000
PNcT useo — §19300
PNCT USED 619300
13.§ RATIO: 1.0332
PNCT NTUS 458300
MCT USED 488300
PNcT USED  assz00
20.1 RATIO: 1.0000
PNCT USED $19200
PNCT USED $19300
20.1 RATIO: 1.0089
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-22-


III. Data Analysis
A. General Methodology

The basic approach used to quantify the CAFE credit
attributable only to test vehicle mileage was to adjust test
results generated at over 4,250 miles to the 4,000-mile level
and evaluate new CAFE's. These were then subtracted from the
original CAFE's to obtain the mileage credit for each manu-
facturer and each CAFE class.

The equation used to factor test results to the 4,000-
mile level was developed as part of a proposed fuel economy
rulemaking (FR 26698, June 9, 1983), in which EPA proposed the
equation to adjust test values generated from vehicles at over
6,200 miles, for labeling purposes only. This same equation
was implemented in the October 13, 1981 rulemaking, applying it
to emission-data vehicles at over 6,200 miles (FR 50498, October
13, 1981). The equation is as follows:

FE4,000m = FEp [0.969 + 0.842 X 1075 (m)j-1
Where: FE4,Q00m = Fuel economy data adjusted to
4,000-mile test point

FEyp = Tested fuel economy value

The equation was derived by examining mileage effects
on fuel economy within the fuel economy and certification data
base for the 1977 through the 1981 model years. A detailed
report on this derivation is attached and is titled, "The
Effect of Vehicle Mileage Accumulation on Tested Fuel Economy."

For each CAFE category, individual test results that
went into the original CAFE calculation were factored (adjusted
to the estimated level at 4,000 miles) if the vehicle that
generated the results had accumulated more than 4,250 miles.
The CAFE was then recalculated with the adjusted test results
using the same sales distribution as the original CAFE calcu-
lation. The fuel economy “mileage credit" is the original CAFE
value minus the adjusted CAFE value, for each model year,
Manufacturer, and CAFE category.

Summary statistics were also derived for average test
vehicle mileages in order to illustrate trends in mileage accu-
mulation. These are illustrated in Figures 1 through 3.


-15-

Background

EPA currently accepts fuel economy test data generated by vehicles with up
to 10,000 miles accumulation on the drivetrain system. These data and data
generated near the standard 4,000-mile test point are all used in the
calculation of fuel economy values for the fuel economy labels and the
Corporate Average Fuel Economy (CAFE). The vehicles tested above the
standard 4,000-mile test point tend to produce higher measured fuel economy
values than they would at the 4,000-mile test point. This increase is
perhaps due to the effect of vehicle break-in which reduces drivetrain
friction. The higher measured fuel economy value tends to bias upward the
fuel economy calculations for labeling and CAFE when compared to calcula~
tions using only data generated close to the standard test point. EPA is
proposing to adjust test values back to the projected 4,000-mile level when
the mileage accumulation at the test point significantly influences the
measured fuel economy value. This document presents the derivation of the
proposed adjustments.

Data

We have examined several previous studies of mileage effects on tested fuel
economy values. All of these previous studies were based on either certi-
fication emission durability vehicles, tested to 50,000 miles, or data from
in-use fleets of vehicles. The durability data includes only two test
points, at 5,000 and 10,000 miles, within the allowable range of testing
for fuel economy calculation data. The in-use data included the effects of
different drivers, vehicle maintenance, weather, etc. These variables can
effect measured fuel economy values as much or more than the increase in
vehicle mileage, thus preventing an analysis of the data for mileage
effects alone. Therefore, we judged the existing studies of mileage
effects on fuel economy as inadequate for our purposes.

To perform our own study of the effect of mileage accumulation on measured
fuel economy values, we used the actual data being submitted to EPA for
fuel economy calculation, i.e., the emission certification and fuel economy
data vehicles. We examined all data with valid and passing emission tests
that could have been used for fuel economy calculations, even if that
particular test had not been selected or needed for the fuel economy
calculation.

These data were then grouped by subconfiguration (a unique combination

of engine displacement, fuel system, transmission, engine calibration, axle
ratio, test weight, and road-load horsepower). Those groups were sorted to
find groups that contained at least one city/highway test pair at (or
within 250 miles of) the standard 4,000-mile test point, and another
city/highway test pair at a test point more than 4,000 miles. There were
over 800 tests that met these criteria. Multiple tests were averaged to
include all available data, thus minimizing lab-to-lab and test-to-test
differences in these data. These averaged data were normalized to a ratio


ATTACHMENT I

Sources. of the Data Points Used in the Analysis

Distribution by Manufacturer and Model Year

-17-

Model Year

Mfr.
Manufacturer 1977 1978 1979 1980 1981 Total
AMC -- 4 -- - 12 16
Chrysler -- 8 8 26 32 74
Ford 4 36 46 64 40 190
GM 8 54 78 32 36 208
Fiat -- -- 8 4 -- 12
Model Year Total 12 102 140 126 120 500


-3-

2. Certification running change vehicles:

These are treated the same as emission-data
vehicles, but are used to demonstrate compliance for design
changes made after original certification. There has generally
been no mileage limitations on these vehicles, except that they
be stabilized. However, historically, running change test
vehicles averaged 4,000 miles. Unlike emission-data vehicles,
data from running change vehicles are not factored for mileage
accumulation over 6,200 miles.

3. Fuel economy data vehicles:

These are vehicles used specifically for
generating fuel economy data. These vehicles may, for example,
have originally been emission-data vehicles, running change
vehicles, or development vehicles. These too must be stabi-
lized, but there is an upper limit of 10,000 miles accumulation.
EPA allows up to 10,000 miles on FEDV's so that manufacturers
can make increased use of the vehicles by repeated reconfig-
uration and retesting. In providing this greater test mileage
flexibility, EPA did not intend nor expect that the fuel
economy data would become biased so as to decrease the repre-
sentativeness of label values or the stringency of the fuel
economy standards.

D. To the extent that manufacturers now use test
vehicles for fuel economy testing that have accumulated greater
than 4,000 miles, their CAFE's will be higher than they would
have been if the 4,000 miles had been adhered to since 1975.
This increase is not due to design improvements that are re-
flected in actual in-use reductions in fuel consumption.
Therefore, manufacturers may be getting false credit in their
CAFE's due to a technical loophole.

E. Average FEDV mileages have increased since 1975. For
all manufacturers, the average FEDV mileage was 4,900 for the
1983 model year (non-sales weighted), and peaked at 5,500 miles
in the 1980 model year. Although this does not appear to be a
significant increase over the 4,000-mile 1975 baseline, there
was a wide variance in the test mileages for each model year
(standard deviations of 950 miles to 1,600 miles). A signi-
ficant amount of tests were conducted at mileages much greater
than the average. Since CAFE is a sales-weightea average, the
CAFE benefit from high-mileage test vehicles depends upon the
sales representation of the test vehicle as well as the mile-
age. This report quantifies that benefit.


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~2-

I. Purpose

The purpose of this analysis is to estimate the annual
CAFE credit manufacturers obtain by testing vehicles at greater
than 4,000 miles accumulation.

II. Background

A. A vehicle's fuel economy performance usually improves
with mileage accumulation due to the gradual reduction in fric-
tion between various drivetrain parts. This improvement is
most rapid during the initial "break-in" period of the vehicle
(the first few thousand miles) and gradually levels off at
higher mileages (twenty thousand to thirty thousand miles)
before eventually declining in fuel economy at very high mile-
ages due to losses in engine efficiency.

B. In 1975, Congress passed the Energy Policy and
Conservation Act (EPCA) which mandated a 100 percent improve-
ment in vehicle fuel economy by 1985. The baseline used for
this improvement standard was the EPA fuel economy data base
using the 1975 test procedures. This data base consisted of
emission test vehicles that were required to be at 4,000 miles,
+ 250 miles. Thus, any general increase in average CAFE test
vehicle mileages over 4,000 miles will result in CAFE benefits
due only to test vehicle mileage effects.

Cc. Data from several different types of test vehicles go
into the CAFE calculation. These vehicle types along with
their mileage restrictions are as follows:

1. Certification emission-data vehicles:

These are test vehicles used to demonstrate
compliance with emission standards to obtain initial certi-
fication. Prior to the issuance of certification cost
reduction regulations on October 13, 1981, emission-data
vehicles were required to have 4,000 miles (+ 250 miles)
accumulated at the time of testing. The new regulations now
allow emission-data vehicles to have accumulated any mileage,
as long as it is greater than a minimum mileage for vehicle
stabilization, established by the manufacturer. However, if an
emission-data vehicle accumulates more than 6,200 miles, the
fuel economy results must be factored back to the 4,000-mile
baseline.


-13-

In summary, for the four model years where we have
been able to recalculate CAFE's, the CAFE offsets vary greatly
between manufacturers. However, domestic manufacturers tend to
account for virtually all of the overall offsets. Except ina
few cases, the CAFE offsets show no definite model year trends.
However, our average vehicle test mileage data for the 1976
through 1983 model years indicates a general trend of increasing
test vehicle mileage accumulation.


-16-

This equation gives a maximum correction factor of 5.3 percent at 10,000
miles. For example, a vehicle tested at 10,000 miles with test results of
25.0 mpg city and 35.0 mpg highway would be adjusted to the 4,000-mile test
point fuel economy with values of 23.7 and 33.2 mpg. The benefit of the
increased mileage on these test results were thus estimated to be about 1.3
mpg in the city and 1.8 mpg in the highway value.

Attachments