SEPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/2-78-038a
OAQPS No. 1.2-104a
August 1978
Air
Series
Supplementary
Guidelines for Lead
Implementation
Plans — Revised
Section 4.3 (Projecting
Automotive Lead
Emissions)
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EPA-450/2-78-038a
OAQPS No. 1.2-104a
Supplementary Guidelines for Lead
Implementation Plans Revised Section 4.3
(Projecting Automotive Lead Emissions)
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
July 1979
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INTRODUCTION
The following material is a complete revision to Section 4.3,
Projecting Automotive Lead Emissions, in the "Supplementary Guidelines
for Lead Implementation Plans," U.S.EPA, EPA-450/2-78-038, Research
Triangle Park, North Carolina, August 1978.
This revision changes the basic equation for projecting automotive
lead emissions presented in the original edition of the Supplementary
Guidelines. In addition, new data on automotive fuel economy and lead
content of gasoline are presented.
The procedure herein should be used to project automotive lead
emissions instead of the procedure given in the original Supplementary
Guidelines. The new procedure will generally result in higher
projections of automotive lead emissions.
Those agencies developing State Implementation Plans for
lead should also note the revision being made affects the EPA guide-
line, "Development of an Example Control Strategy for Lead"
(EPA-450/2-79-002). Specifically affected are equations 2.3 (p. 14),
2.4 and 2.5 (p. 15) and the related discussion, which are based on
the previous procedure. The new procedure should be used in lieu of
that given on pp. 14 and 15 and related pages of the example control
strategy for lead.
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4.3 PROJECTING AUTOMOTIVE LEAD EMISSIONS
Lead emissions from mobile sources are calculated based on emissions
at different speeds, the lead content of gasoline, vehicle fuel economy
and the model year mix of vehicles on the road. The lead content of
gasoline and the model year vehicle mix are a function of the calendar
year of interest. Vehicle fuel economy is averaged for all vehicles of
the same model year.
4.3.1 Lead Emissions from Automobiles
4.3.1.1 Individual Roadways—For any given year subsequent to 1974, the
total population of automobiles on the road consists of vehicles using
either leaded or "nonleaded" (i.e., 0.05 gram/gal.) gasoline. It is
assumed that 95 percent of the model year automobiles from 1975 and
beyond require the use of nonleaded gasoline. The emission rate from
automotive sources from an individual roadway (line source) is
calculated by the following equation:
?['
Vs - ^ | PbNM
(1)
where:
e = emission rate for calendar year n and speed s (g/road mile-day);
ag = percentage of lead burned that is exhausted; available from
Figure 4.3-1 (nondimensional; expressed as a decimal); for
roadway portions subject to full-throttle acceleration (0-60 mph)
assume a =10.0;
T = average daily traffic (vehicles/day);
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Ct = traffic flow correction factor; C =1.2297 for free-flow
traffic; Ct=0.866 for city (stop-and-go) traffic (nondimen-
sional);
PbMI = lead content of "nonleaded" gasoline in calendar year n from
111— $ n
Table 4.3-3 (g/gal);
Pb. = average lead content of leaded gasoline in calendar
L ,n
year n from Table 4.3-3 (g/gal);
mNL i = fracti°n of annual travel by model year i vehicles using
nonleaded gasoline (nondimensional, expressed as a decimal);
m, . = fraction of annual travel by model year i vehicles using
L » '
leaded gasoline (nondimensional, expressed as a decimal);
C . = speed-dependent fuel economy correction factor for model year i;
calculation is described below in equation (2) (nondimensional);
E . = city/highway combined fuel economy for model year i from
c, i
Table 4.3-5 (vehicle-road mile/gal).
To calculate the emission rate in units of grams/meter-second,
o
e can be corrected by dividing by 1.39 x 10 .
n ,s
C$ ^, the nondimensional speed dependent fuel economy correction
factor for model year i, is calculated by the following equation:
4
Cs i = Z, A.SJ (2)
S>1 j=0 J
where:
A = correction factor from Table 4.3-1.
S = vehicle speed (miles/hour) [Note: S°=l].
To simplify the computation, the values of C . for the years 1967 to
s, i
1985 are reproduced in Table 4.3-2.
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4.3.1.2 Area Source Automotive Emissions—Equation (1) may be used to
calculate automotive emissions as an area source rather than as specific
line sources; however, certain computational modifications will need to
be made. The term "T" should be replaced by the term "V," the vehicle
miles travelled in the area on a daily, monthly or greater time basis.
When VMT data are used, the emission rate, e , will be expressed in
n ,s
grams per day, month, etc. Also, when the VMT data indicate a balance
of free-flow and city-type driving, the traffic flow correction factor,
C. , can be assumed equal to unity (C. = 1) since fuel economies are
representative of combined city/highway driving. Where the VMT data
indicate primarily free-flow or city-type driving, correction factors
of 1.2297 or 0.866, respectively, should be used as is the case with
line source estimates.
The computation of area emissions precludes the use of Figure 4.3-1
for determining the percentage of burned lead exhausted, a . Figure 4.3-1
is based primarily on tests of lead emissions from vehicles operating
at steady speeds over short test periods. An emission factor of 0.70
(i.e., 70 percent of the lead burned is exhausted) should be assumed
when calculating automotive emissions as an area source rather than as
specific line sources. The 0.70 factor is based on tests which measured
exhaust emissions under city-type driving conditions.
Finally, the determination of the speed dependent fuel economy
correction factor, C ., should be based on the average vehicle speed
5,1
for the area of concern. The average area vehicle speed should be a
weighted average based on average speeds and VMT data for the various
roadway classifications, such as limited access (greater than 50 mph),
suburban roads (35 mph) and urban streets (25 mph or less).
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4.3.2 Lead Emissions from Other Gasoline Powered Vehicles
Motorcycles and diesel-powered vehicles are assumed to emit
quantities of lead that are insignificant compared to other gasoline-
powered vehicles.
There are no known measurements of lead emissions from either light-
er heavy-duty trucks. Therefore, for purposes of calculating emissions,
the percentage of lead burned that is exhausted from these vehicles
at various speeds is assumed to be the same as that for automobiles
(Figure 4.3-1).
Light-duty gasoline-powered trucks are assumed to have the same
gasoline economy as automobiles; new light-duty trucks (model year
1979 and beyond) are assumed to require the use of non-leaded gasoline
to meet emissions standards for CO and hydrocarbons through the use
of catalysts. Therefore, the emission rate for light-duty gasoline-
powered trucks is calculated using the same procedures and parameters
as for automobiles (except, of course, that the starting point for
calculating emissions from nonleaded vehicles is 1979 rather than 1975).
Heavy-duty gasoline-powered trucks are assumed to burn leaded
gasoline for all future years. Also, their fuel economy for any calendar
year is assumed to be equal to 5.7 miles/gal. Therefore, the emission rate
for heavy-duty gasoline-powered trucks is calculated by using the following
modification of equation (1):
en,s = asTPbL.n
5.7
-------
where:
en s = emission rate for calendar year n (gram/road mile-day);
a = percentage of lead burned that is exhausted (non-dimensional;
expressed as a decimal);
T = average daily traffic (trucks/day);
Pb. = average lead content of leaded gasoline in calendar
L ,n
year n from Table 4.3-3.
4.3.3 Example Calculation of Automobile Lead Emissions
Problem: For a city street with a speed of 16 miles per hour and
average daily traffic of 28,000 vehicles, calculate the lead emission
rate for the year 1983.
Solution: Use Equation (1):
11983 1983
PbNL,83 ^ f_mNLJ \ + Pb, 00 ^ / m,
f '*S
a!6T PbNL,83 ^
^r L -1975
Cl .
1 O ) 1 C 9 1
From Figure 4.3-1, for a cruise speed of 16 mph, approximately 12.25
percent of the lead being burned is emitted. Therefore, a,c = 0.123.
Ib
The average daily traffic, T, is given as 28,000 vehicles/day. Since
the roadway is a city street, the traffic flow correction factor C =0.866.
From Table 4.3-3, the lead content of leaded gasoline in 1983
is 1.5 grams/gal., and the lead content of nonleaded gasoline is 0.05
gram/gal.
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1983 1983
The summations, ^ I NL.i ) and .^ ( '"L,J
1=1975 Vfl6,1Ec.1
m
for vehicles burning nonleaded and leaded gasoline, respectively, must
now be calculated. First, the fraction of annual travel, m., for each
model year is determined by setting the fraction for 1 year old
vehicles (Table 4.3-4) at the calendar year, n, for which lead emissions
are being estimated. For this example, n=1983, therefore, m,gg~=0.106
(vehicle age=l). [NOTE: The term, m., accounts collectively for all
vehicles — leaded and nonleaded--in a given model year (i.e., m^n^L n- +
m, .)• The calculation of this term is presented in Table 4.3-4, and its
L 5 I
use is illustrated in Table 4.3-6.]
Next, it is necessary to calculate C,g ., the speed-dependent
fuel economy correction factor for model years 1967 through 1983,
using Equation (2):
4
Ci6,i = 2 V16)j
j=0
= AQ + A^ie) + A2(16)2 + A3(16)3 + A4(16)4
The A, coefficients appear in Table 4.3-1 for each model year.
J
Table 4.3-6 presents the results of that calculation for this
example. Table 4.3-6 also presents the appropriate values for m.
from Table 4.3-4, and E . from Table 4.3-5.
c, i
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Finally, by applying the assumption that 95 percent of the model
year vehicles from 1975 and beyond use nonleaded gasoline (i.e.,
mNL i=0-95 mn-)> the summations for nonleaded and leaded gasoline can
be completed as shown in Table 4.3-6. As that table indicates:
1983
= 0.0552/vehicle-road miles/gal
1=1975 *• Cl6,1Ec,i
and,
19L
mL,i ^ = 0.0127/vehicle-road miles/gal.
i=1967 ' '=
Substituting the above results into Equation (1), we obtain:
= 0.123 x 28 x 10 vehicles/day
"""" 0.866
= 86.74 g/road-mile-day
In units of g/m-sec, this becomes:
0.05g/gal x 0.0552 + 1.5g/gal x
veh-road mile/gal veh-road mi
0.0137
le/galj
' ifi = 86.74 o= 6.24 x 10 g/m-sec.
('lb 1.39 x 10°
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Figure 4.3-1
PERCENTAGE OF BURNED LEAD EXHAUSTED
vs.
VEHICLE CRUISE SPEED
• • 10 ''': •'::•;-:,to..: u . ;::
VEHICLE CRUISE SPEED (MILES PER HOUR)
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TABLE 4.3-1
FUEL ECONOMY CORRECTION FACTORS BY MODEL YEAR
(NORMALIZED TO 32.7 MILES/HOUR)
Model Year AQ __ A] A,, A
Pre-controlled 2.4697E-2 7.55258E-2 -2.42452E-3 4.01469E-5 -2.68893E-7
1968 1.75941E-2 6.90954E-2 -2.01359E-3 3.19426E-5 -2.12343E-7
1969 3.43032E-3 7.24956E-2 -2.18976E-3 3.54015E-5 -2.36485E-7
1970 6.00124E-3 6.90443E-2 -1.98463E-3 3.13931E-5 -2.09286E-7t
1971 9.76255E-3 6.84494E-2 -1.96781E-3 3.13719E-5 -2.11167E-7
1972 8.57745E-2 7.0882E-2 -2.15219E-3 3.57324E-5 -2.44316E-7
1973-74 6.29988E-2 5.96559E-2 -1.59874E-3 2.59441E-5 -1.84877E-7
1975-85 4.01016E-2 7.50056E-2 -2.44301E-3 4.12554E-5 -2.82512E-7
Fuel Economy Correction Factor = AQ + A-jS + A2$2 + A3$3 + A»S4
where S = vehicle speed in miles per hour
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TABLE 4.3-2
o
MODEL
YEAR:
SPEED (MPH)
5
10
15
20
25
30
35
40
45
50
55
60
1967
.347
.575
.734
.844
.920
.975
1.016
1.048
1.069
1.077
1.063
1.015
1968
.317
.537
.698
.816
.903
.963
1.020
1.060
1.089
1.104
1.098
1.062
C . VALUES
s > i
1969
.315
.542
.706
.823
.908
.972
1.021
1.060
1.088
1,101
1.093
1.052
1970
.305
.527
.690
.811
.900
.969
1.023
1.066
1.097
1.113
1.108
1.073
1971
.307
.527
.689
.809
.899
.968
1.023
1.066
1.098
1.114
1.109
1.072
1972
.391
.613
.773
.889
.976
1.042
1.098
1.139
1.172
1.189
1.183
1.143
1973/4
.324
.524
.676
.795
.888
.965
1.027
1.078
1.116
1.136
1.133
1.095
1975-85
.359
.584
.740
.843
.923
.977
1.018
1.049
1.069
1.074
1.054
0.995
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TABLE 4.3-3
LEAD CONTENT OF GASOLINE
Leaded Gasoline*
Nonleaded Gasoline
(g/gal)
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
* 1974 - 1978: Lead content based upon historical sales data for leaded
and nonleaded gasoline and data indicating the actual pooled average
lead content.
1979 - 1990: Lead content based upon sales projections for leaded and
nonleaded gasoline and requirements for pooled average lead content.
Year
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
(g/gal)
1.75
1.9
2.0
1.9
1.9
2.1
1.6
1.2
1.3
1.5
1.8
2.2
2.8
3.0
3.0
3.0
3.0
11
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Table 4.3-4
TRAVEL WEIGHTING FACTOR CALCULATION*
Light-Duty Vehicles
(a)
Vehicle Fraction Total
Age Registration
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0.075
0.107
0.107
0.106
0.100
0.092
0.085
0.077
0.066
0.052
0.039
0.027
0.018
0.014
0.009
0.006
0.005
0.005
0.005
0.004
(b)
Annual Mileage
Accumulation Rate (a)(b)
15900
15000
14000
13100
12200
11300
10300
9400
8500
7600
6700
6600
6200
5900
5500
5100
5000
4700
4400
4400
SUM:
1192.5
1605.0
1498.0
1388.6
1220.0
1039.6
875.5
723.8
561.0
395.2
261.3
178.2
111.6
82.6
49.5
30.6
25.0
23.5
22.0
17.6
11301.0
[(a)(b)/(SUM]
Fraction of Annual LDV
Travel by Model Year.m.
0.106
0.142
0.133
0.123
0.108
0.092
0.077
0.064
0.050
0.035
0.023
0.016
0.010
0.007
0.004
0.003
0.002
0.002
0.002
0.002
*Mobile Source Emission Factors, March 1978 [EPA-400/9-78-005]
12
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Table 4.3-5
CITY/HIGHWAY COMBINED FUEL ECONOMY
(miles/gallon)
Fuel Economy
Model Year E. ,
' " 671
1967 16.2
1968 15.6
1969 15.5
1970 15.4
1971 15.2
1972 15.2
1973 14,9
1974 15,2
1975 14.5*
1976 17.0*
1977 17.5*
1978 18.0**
1979 19.0**
1980 20.0**
1981 22.0**
1982 24.0**
1983 26.0**
1984 27.0**
1985 27.5**
* From U.S. DOT Report, "Automotive Fuel Economy Program"
(44 FR, 5748, January 29, 1979)
** From U.S. DOT Report, "Automotive Fuel Economy Program"
(44 FR, 5762, January 29, 1979)
13
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TABLE 4.3-6
EXAMPLE CALCULATIONS
MODEL YEAR
1983
1982
1981
1980
1979
1978
1977
1976
1975
1974
1973
1972
1971
1970
1969
1968
pre-1968
* V,i = °
AGE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17+
.95m.
.106
.142
.133
.123
.108
.092
.077
.064
.050
.035
.023
.016
.010
.007
.004
.003
.008
C16,i
.765
.765
.765
.765
.765
.765
.765
.765
.765
.702
.702
.799
.716
.718
.732
.725
.759
Ec,i
26.0
24.0
22.0
20.0
19.0
18.0
17.5
17.0
14.9
15.2
14.9
15.2
15.2
15.4
15.5
15.6
16.2
mNL,i
C16,iEc,i
.0050
.0073
.0075
.0076
.0070
.0064
.0055
.0047
.0042
-
-
-
-
-
-
-
_
.0552
mL,i
C16,iEc,i
.0003
.0004
.0004
.0004
.0004
.0003
.0003
.0002
.0002
.0034
.0022
.0013
.0009
.0006
.0004
.0003
.0007
.0127
14
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA-450/2-78-038a
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Supplementary Guidelines for Lead Implementation
Plans, Revised Section 4.3 -- Projecting Automatic
Lead Emissions
5. REPORT DATE
July 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHQR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Paniel J. deRoeck
OAQPS No. 1.2-104a
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, N,C, 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Revision - Final
1"4, SPONSORING AGEN.CY CODE
15. SUPPLEMENTARY NOTES
. ABSTRACT
This guidance is a complete revision to Section 4,3 (Projecting Automotive
Lead Emissions), in the "Supplementary Guidelines for Lead Implementation Plans,"
U.S. EPA, EPA-450/2-78-038, Research Triangle Park, North Carolina, August 1978.
This revision changes the basic equation for projecting automotive lead emissions.
It al§o clarifies, thi procedure for determining area source automotive emissions
and provides updated information on automotive fuel economy and lead content of
gasoline.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERSyOPEN ENDED TERMS
COS AT I Field/ Group
Air pollution
Atmosphere contamination control
Lead
State implementation plai
National ambient air
quality standard
13-B
8. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
16
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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