EPA-450/3-75-072
August 1975
APPLICATION
OF THE HIWAY MODEL
FOR INDIRECT
SOURCE ANALYSIS -
USER'S MANUAL
~
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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EPA-450/3-75-072
APPLICATION
OF THE HIWAY MODEL
FOR INDIRECT
SOURCE ANALYSIS -
USER'S MANUAL
by
Kenneth Axetell, Jr.
808 S. Fairfax Street
Alexandria, Virginia 22314
Purchase Order No. 5-02-3670A
EPA Project Officer: Edwin L. Meyer, Jr.
Prepared for
U. S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, N. C. 27711
August 1975
-------
This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations - as supplies permit - from the
Air Pollution Technical Information Center, Environmental Protection
Agency, Research Triangle Park, North Carolina 27711; or, for a
fee, from the National Technical Information Service, 5285 Port Royal
Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by
Kenneth Axetell, Jr., Alexandria, Virginia 22314, in fulfillment of
Purchase Order No. 5-02-3670A. The contents of this report are repro-
duced herein as received from Kenneth Axetell, Jr. The opinions,
findings, and conclusions expressed are those of the author and not
necessarily those of the Environmental Protection Agency. Mention
of company or product names is not to be considered as an endorsement
by the Environmental Protection Agency.
Publication No. EPA-450/3-75-072
11
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APPLICATION OF THE HIWAY MODEL
FOR INDIRECT SOURCE ANALYSIS
USER'S MANUAL
PREPARED FOR THE
U.S. ENVIRONMENTAL PROTECTION AGENCY
UNDER ORDER NO. 5-02-3670A
BY
KENNETH AXETELL, JR.
JULY 23, 1975
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TABLE OF CONTENTS
1. INTRODUCTION 1
2. PROCEDURE FOR ANALYSIS USING HIWAY MODEL 3
3. SIMULATION OF PARKING LOT EMISSIONS AS LINE SOURCES 5
RATIONALE FOR SIMULATION AS LINE SOURCES 5
METHODOLOGY FOR ALLOCATING PARKING LOT EMISSIONS 7
4. COMPILATION OF EMISSION DATA 18
SOURCE CONFIGURATION 18
RECEPTOR LOCATION 27
METEOROLOGICAL DATA 29
Wind Direction 29
Wind Speed 31
Mixing Height 32
Stability Class 33
EMISSION DATA 36
Emission Rates for Parking Area Traffic Lanes 36
Emission Rates for Access Streets 37
Emission Rates for Queues 40
SELECTION OF ALTERNATIVES FOR MODELING 41
5, INPUT DATA FORMAT FOR THE HIWAY MODEL 44
6. OUTPUT DATA AND ITS PRESENTATION 49
7. ESTIMATION OF-MAXIMUM 8-HOUR CO CONCENTRATIONS 54
REFERENCES 57
APPENDIX 58
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LIST OF FIGURES
Figure Page
1. Flow diagram for indirect source analysis using 4
HIWAY model
2. Example distribution of vehicles from one entrance 9
to parking spacing
3. Convention/exhibition hall 13
4. Distribution of vehicles from entrance B to 15
parking spaces
5. Example base map with coordinate system superimposed 20
6. Simulation of curving streets with straight line 22
segments
7. Location of receptor relative to line source end 26
points
8. Composite emission factors for carbon monoxide for 39
calendar year 1975
9. Assembly of HIWAY card deck 47
10. Example of HIWAY output 50
A 41. Proposed shopping center and surrounding area 59
LIST OF TABLES
Table Page
1. Allocation of parking lot emissions to traffic links 11
2. Example allocation of parking lot emissions to 17
traffic links
3. Input data requirements for HIWAY 19
4. National Weather Service upper-air observing stations 34
5. Estimation of Pasquill stability classes 35
6. Input data format 45
11
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LIST OF TABLES (Continued)
Table Page
7. Calculation of total CO concentrations at receptor 51
sites
A 1. Traffic demand by hour on peak traffic days 60
A 2. Average speeds on access streets 61
A 3. Data on intersection designs 62
A 4. Wind directions during hours with wind speed of 64
1.0 m/sec or less
A 5. Number of annual occurrences of wind speed - 1 m/sec 65
by hour of day and concurrent stability class
A 6. Maximum 1- and 8-hour CO concentrations at an existing 66
suburban shopping center
A 7. Emission factors for access streets 69
A 8. Allocation of parking lot emissions to traffic links 71
A 9. Emission rates by lane for access streets 72
A 10. Queue lengths and emission rates 74
A 11. Configuration of line sources 75
A 12. Receptor site locations 77
A 13. Subtotals of model-predicted contributions from 32 line 79
sources under different alternatives
A 14. Predicted maximum 1- and 8-hour CO concentrations at 81
proposed site
111
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1. INTRODUCTION
This document describes a detailed methodology for employing EPA's
HIWAY model for microscale analysis of proposed indirect sources. The
recommended methodology may be used to obtain a more accurate estimate
of maximum carbon monoxide (CO) concentrations in cases where the
screening procedure in the Guidelines for the Review of Indirect Sources
indicates that the National Ambient Air Quality Standards (NAAQS) would
possibly be exceeded, or it may be used initially in complex analyses
that are not readily handled by the screening procedure. It is appli-
cable for all types of indirect sources, but was developed particularly
for those indirect sources with emissions from both access streets and
parking areas.
The methodology relies on emission estimates for specific types of
indirect sources calculated by the procedures presented in Appendices A
through G of the Guidelines, and draws upon other procedures included in
the Guidelines and its appendices (e.g., selection of receptors and
estimation of background concentrations).
Use of the HIWAY model in the analysis does require access to EPA's
UNAMAP system or installation of the HIWAY program on the user's com-
puter. However, once the program is on line, very little knowledge of
computer operations is necessary to use the HIWAY model for indirect
source analysis. Simple instructions on the preparation of input data
and interpretation of output are provided in this document. The User's
2
Guide for HIWAY is a reference for additional information on the model.
For indirect sources with pollutant contributions from access
streets, entrance/exit queues and parking areas, computer analysis
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greatly reduces the calculation effort for the several different alter-
natives that may need to be considered. For example, peak traffic on
the access street may occur at a different time of day than peak traffic
movement in the parking areas, or the most adverse meteorological
conditions may never occur during periods of the day with peak traffic.
In either of these cases, more than one time period must be analyzed.
Also, with the additive effect of pollutant contributions from several
sources, different wind directions should be investigated to determine
the direction resulting in maximum concentrations at each receptor site.
In addition to its efficient handling of multiple line sources and
of different alternatives, the HIWAY model has several analytical advan-
tages over the screening procedure:
- complicated source configurations can be simulated;
- meteorological and traffic data specifically applicable to
the site can be input;
use of the same dispersion equation for all sources is
assured.
The HIWAY model accepts only line source emissions, so a procedure
for allocating parking lot emissions to the major traffic lanes within
the parking lot has been developed. It is explained and demonstrated in
Chapter 3. Chapter 2 outlines the individual steps in the indirect
source analysis; Chapter 4 explains how to compile the required input
data; Chapter 5 describes formatting procedures for the HIWAY model;
Chapter 6 describes the output of the HIWAY model; and Chapter 7 dis-
cusses approaches for estimating 8-hour CO concentrations.
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2.0 PROCEDURE FOR ANALYSIS USING THE HIWAY MODEL
The steps involved in using the HIWAY model for indirect source
analysis are shown in the flow diagram of Figure 1. This flow diagram
may be used as a checklist while performing the analysis.
Specific information on how to perform each step is explained in
subsequent chapters. Page numbers are shown in Figure 1 to assist in
locating the appropriate instructions for each step.
As shown in Figure 1, the types of input data that must be gener-
ated are source-receptor distance measurements, CO emission rates, and
meteorological data. Most of the steps are associated with development
of these input data, but the final steps relate to handling and inter-
pretation of the HIWAY model output.
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CONFIGURATION
OP SOURCES
AND RECEPTORS
EMISSION DATA
METEOROLOGICAL
DATA
Obtain drawings or
map to scale showing
proposed site, access
streets & receptors
Make copy for use
as base map
p. 18
p. 18
p. 18
Obtain projected
traffic volumes in
parking area by hour
and by ent./exit
Obtain projected
traffic volumes and
speeds on access
streets by hour
p. 37
Obtain representa-
tive wind speed and
direction data
Select time periods
for analysis:
- 1 & 8 hour daily
periods
- season
- critical year
May need to analyze:
- peak traffic at
source
- peak traffic on
access streets
- worst met.
period
- no-build
condition
p. 41
Identify major traffic
aisles in parking lot
p. 8
Determine emission
factors & average
running times in lot
p. 6
Determine locations &
lengths of major
queues
p. 23
Determine emission
factors
p. 38
29
Specify for each
time period:
- wind speed
- mixing height
- stability clas
pp. 31-35
Mark all line sources
on map; record grid
coords, of end points
Select receptor sites
p. 21
p. 27
Distribute emissions
to lanes in parking
lot
p. 10
Calculate total
emissions for parking
lot
p. 6
Calculate emission
rates for queues
p. 40
Calculate emission
rate for each
street lane
p. 37
Select wind directions
for max. concentration
at receptors
pp. 29-30
Figure 1. Flow diagram for indirect source analysis using HIWAY model
Determine grid coords.
of receptors, includ-
ing height
Obtain or estimate
other dimensions
pp. 23-24
p. 28
Code input data,
keypunch, and run
HIWAY program
pp. 43-47
Tabulate and total
concentrations from
all sources at each
receptor
pp. 48,50
Modify concentrations
for 8-hour averages
Determine persistence
factor for 8 hours
p. 53
p. 49
Summarize CO concen-
trations for all
conditions analyzed
52
Compare with NAAQS,
draw conclusions
p. 52
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3.0 SIMULATION OF PARKING LOT EMISSIONS AS LINE SOURCES
3.1 Rationale for Simulation as Line Sources
The detailed procedures for estimating emissions in parking lots
described in Appendices B through G of the Guidelines indicate that only
a small percentage of the total automotive running times in the lots are
associated with parking and unparking the vehicles at the parking spaces.
Most of the running time and emissions are associated with movement
along the entrance/exit lanes to the parking areas, movement on the main
traffic aisles within the parking areas, and stop-and-start travel in
queues on these aisles (each with one or more traffic lanes). There-
fore, a procedure which assigns parking lot emissions to a series of
line sources representing these major traffic aisles generally should
more accurately simulate the distribution of emissions than an assump-
tion of uniform emission density throughout the parking lot. This is
particularly true when a structure such as a shopping center or stadium
occupies a large portion of the area within the parking lot.
In order to utilize the HIWAY model for parking lot analysis and to
more accurately simulate the actual distribution of emissions within
parking lots, a methodology has been developed to distribute the esti-
mated emissions among several line sources representing the major
traffic aisles. It should be emphasized that this methodology is
strictly for distribution of emissions, and that the emissions are still
to be calculated by the procedures described in Appendices B through G
of the Guidelines.
The steps in estimating emissions from the parking areas vary with
each specific type of indirect source, but all are based on the same
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principle—that total carbon monoxide emissions from motor vehicles,
exclusive of emissions from major queues, can be calculated by multiply-
ing the number of vehicles moving in the lot during any period by the
average running time per vehicle, times an appropriate emission factor
for CO emitted per vehicle-minute of operation:
, (EF) (V) (RT)
y 216,000
Q = emissions from mobile sources, gm/sec
* .•
EF = emission factor, gm/min-veh
V = traffic demand, veh/hr
RT = typical vehicle running time, sec
-= conversion factor from 3?' °"^ to gm/sec
216,000
The average running time is estimated as the sum of a base running time
required for driving between the access street and the parking spaces
under congestion-free conditions and an incremental running time result-
ing from traffic congestion.
Running times in major queues (RT ) at entrances/exits and inter-
sections within the parking lot should not be included in the estimated
running time described above. Instead, the major queues are to be
considered as separate line sources, with emission rates calculated by
the procedure described in Section 4.4.3 of this document. The parts of
the traffic aisles on which the queues occur are still identified as
line sources receiving an apportionment of parking lot emissions (Q)
because there are also cruising vehicles using these parts of the aisles.
The emission rates for the additional line sources simulating queues
only account for the excess emissions (or running times) occurrina
*See Figure 8, page 39 for appropriate emission factor values.
6
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over the queue lengths as a result of acceleration/deceleration and
idling..
In most cases the parking lots being analyzed have not yet been
built, so the process of apportioning emissions to traffic aisles within
the parking lot is just an extension of the estimating procedure used to
predict average running times in the lots. Both processes require that
assumptions of preferred parking areas and travel paths within the
parking lot be made. Also, detailed plans of the parking lot, including
locations of traffic lanes and entrances/exits, are necessary in both
cases. Comparatively, more latitude may be exercised in predicting
vehicle movement within parking lots for purposes of emission distri-
bution, since any rational traffic assignment should result in an im-
provement over the assumption of vehicles being uniformly distributed
throughout the lots.
Thus, the traffic assignments can be made from a knowledge of the
entry points and destinations of vehicles within the parking area by
subjectively determining preferred travel routes. The methodology for
apportioning emissions is outlined in detail in Section 3.2.
3.2 Methodology for Allocating Parking Lot Emissions to Traffic Lanes
1. Obtain estimates of the number of vehicles entering and exiting
at each entrance/exit to the parking area during the time period of
concern.
2. Identify the desired ultimate destination points within the
development and the number or percent of trips bound for each identified
destination point (based on building entrances, tenant mix, ticket booth
locations, walking distances from parking area, etc.).
7
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3. Using a drawing or map to scale of the development and its
parking area, mark the major movement routes of vehicles to parking
spaces nearest the destination points. Some of the traffic aisles may
be used on routes from more than one entrance. Do not show the indi-
vidual parking aisles unless traffic other than that parking along the
aisle would normally use it in traveling through the parking lot.
4. Mark nodes on the drawing at points where the traffic movement
splits or where there should be a significant change in traffic volume
as some of the cars park. Number the resulting traffic links between
each pair of nodes.
5. Starting at one entrance, estimate the distribution of vehicles
at each node (intersection) by assigning percentages of the traffic
reaching the node to each link (aisle) leading away from that node. The
traffic volume leaving the node will not equal 100 percent if some
vehicles park in the vicinity of that node. Continue splitting the
traffic coming from the entrance onto subsequent links until it is all
distributed to parking areas. Repeat this procedure for the other
entrances. (There is no need to consider links carrying less than two
percent of the total traffic in the parking lot, as this would increase
the number of line sources in the HIWAY model without greatly increasing
the accuracy of emission distribution.) This step is shown schemati-
cally in Figure 2.
6. If aisles are two-way and motorists would normally use the same
aisles to exit as they did to enter, no separate distribution for
exiting vehicles need be performed. However, if the aisles are designed
for one-way traffic or if entrances and exits are located at different
points on the periphery of the parking lot, the procedure described
8
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( !
n
2850 veh/hr in (60% of total) c
240 veh/hr out (60% of total) 1 -^
entrance A |
link 1 I
50% 1
30% ^_,
parking 1
'
70%
60%
par
40%l
•king 40%
4 parking
40%
-H
r-\
30%
link 7 y
70%
50% 5,°%
parking
H
rH
I •
•H
i-H
C
•H
•
door 1
30%
door 2
'', 30%
\
[ door 3
/ 40%
parking
Figure 2. Example distribution of vehicles from one entrance to
parking spaces
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in step 5 should also be conducted for traffic exiting during the corre-
sponding time period. The starting points with exiting traffic are the
parking lot exits; otherwise, the procedure is completely analogous to
that described above.
7. Measure the length of each link carrying two or more percent of
the traffic and record these values in the tabular format shown in Table
1-
8. Determine a weighting factor for each link by multiplying its
length by the fraction of total traffic traveling in the aisle. Total
the weighting factors, then determine the constant (c) for calculating
line source emission rates for the HIWAY model by dividing the estimated
parking lot emissions by the total of the weighting factors:
c = —:—*— , where
^-1 i i
Q = parking lot emissions, gm/sec
P. = fraction of running vehicles using traffic
link i
L. = length of link i, any consistent units
If separate analyses are performed for entering and exiting traffic,
then subtotals for emissions due to entering vehicles (Q. ) and exiting
vehicles (Q ) must be used to calculate separate weighting factors for
the two analyses.
9. Calculate the line source strength of each link (in gm/sec-m):
q. = cP./z , where
z = factor to convert units of length to meters
These calculations should be recorded in the same table as used in steps
7 and 8.
10
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Table 1. ALLOCATION OF PARKING LOT EMISSIONS TO TRAFFIC LINKS
Traffic
link
Length
Fraction of entering or exiting
vehicles using this link
Weighting
factor
Line source strength,
gm/sec-m
11
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10. Divide the total line source strength for each link into
emission rates per lane. The relative emission rates for traffic in
each direction on two-way aisles are estimated to be the same as the
ratio of entering to exiting vehicles at the entrance/exit serving
this traffic aisle. If separate distributions are performed for entering
and exiting traffic (see step 6 above), the traffic volumes in each
direction on the aisle can be calculated. Unless specific information
to the contrary is available, the emissions from travel in each direc-
tion should be divided uniformly among the lanes in that direction.
11. Indicate the locations of major queues in the parking area
that were segregated to be input as separate line sources. The line
source strength and upstream length of each queue should be calculated
per the instructions in Section 4.4.3 and 4.1, respectively.
EXAMPLE
Problem. The convention/exposition hall design shown in Figure 3
has two parking lot entrances/exits. During the peak hour, traffic
through the main entrance is estimated to be 2,850 in and 240 out.
Traffic through the other gate would be 1,900 in and 160 out. All
internal traffic aisles have two lanes and are designed for two-way
traffic.
The developer estimates that approximately 60 percent of the
persons entering the hall will enter through doors 1 and 2 (30 percent
each) while 40 percent will enter through door 3. Average vehicle
running times (in O£ put) during the peak hour are estimated to be 175
seconds, and parking lot emissions (Q) are calculated to be 79.3 gm/sec.
Distribute the emissions to line sources within the parking lot and
estimate line source strengths for input to HIWAY.
12
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residential area
commercial
main
ent.
apartments
commercial
x \ • \ \,
''t&rrace ^'v x ,
Figure 3. Convention/exposition hall
13
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Solution.
a. Traffic volumes and destination points are given. From this
information and the map showing locations of traffic lanes and parking
spaces, major movement routes can be identified and traffic links can
be identified and marked. This is shown separately for each of the
entrances in Figures 2 and 4.
b. The distribution of vehicles at each intersection is determined
subjectively. The vehicles from Entrance A (Figure 2) account for 60
percent of the total and are nearest doors 1 and 2, which likewise
account for about 60 percent of the attraction points. Since there is
adequate parking approximately equidistant from the two doors, the
traffic would probably split in half at the first intersection. Traffic
on link 2 would park as near to door 1 as possible, with those vehicles
unable to find a parking space (50 percent) continuing on to link 3. A
similar process would occur with vehicles on links 4 and 5, except that
some might continue on this traffic lane attempting to find a parking
space near door 3. However, they would be competing for these spaces
with vehicles from Entrance B.
In summary, the estimates of traffic splits and vehicles parking
are based on available parking spaces and proximity to the convention
hall entrances. The values for vehicle distribution presented in this
example are for illustrative purposes and should not be applied directly
in other analyses.
c. Distribution of vehicles from Entrance B (Figure 4) is based
primarily on attraction to door 3, although some vehicles (16 percent in
this example) would undoubtedly continue along the main traffic lane to
park nearer to door 2."
14
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door 1
20%
20%
•4
link 8
40%"
parking
Oi
40%-* - L
V
link 7
80% 20%
parking parking
40%
10% •**"""
parking
vD
/
30%
I'door 2
\r 30%
P/
door 3
40%
j//s ////// j/j/se/ xx
50%
entrance B
link 12
1900 veh/hr in (40% of total)
160 veh/hr out (40% of total)
Figure 4. Distribution of vehicles from entrance B to parking spaces
15
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d. The length of each link is scaled from the map and recorded in
Table 2.
e. The fraction of total incoming vehicles using each link is then
calculated as shown in Table 2, and a weighting factor determined for
each link.
f. The constant for calculating line source strengths is deter-
mined to be .0643 by dividing parking lot emissions (79.3) by the sum of
the weighting factors (1,234).
g. The line source strengths for each link are then calculated
using the equation q. = cP./z. The conversion factor (z) from feet to
meters is 0.305. Resulting values are recorded in Table 2.
h. The ratio of entering to exiting vehicles is the same at both
entrances/exits, 11.83 to 1. The emission rates for each lane are
calculated from this ratio, with the emission estimates for links 5, 6
and 9 also requiring data on the percentage of traffic from each en-
trance. The emission data for input to HIWAY are summarized in Table 2.
16
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Table 2. EXAMPLE ALLOCATION OF PARKING LOT EMISSIONS TO TRAFFIC LINKS
Traffic
link
1
2
3
• 4
5
6
7
8
9
10
11
12
Length
feet
500
720
350
400
400
450
380
380
450
350
280
650
Fraction of entering or exiting
vehicles using this link (p)
(.6) = .60
(.6) (.5) = .30
(.6) (.5) (.5) = .15
(.6) (.5) = .30
(.6) (.5) (.7) +
(.4) (.4) (.4) (.2) = .22
(.6) (.5) (.7) (.4) +
(.4) (.4) (.4) = .15
(.6) (.5) (.7) (.4) (.3) +
(.4) (.4) (.4) = .09
(.6) (.5) (.7) (.2) +
(.4) (.4) (.4) (.4) = .07
(.6) (.5) (.7) (.2) (.4) +
(.4) (.4) (.4) (.2) = .03
(.4) = .40
(.4) (.4) = .16
(.4) (.5) = .20
Weighting
factor
300
216
52
120
88
68
34
27
14
140
45
130
1,234
Line source
strength, g/ra-s
0.1264
0.0632
0.0315
0. 0632
0.0464
0.0315
0.0190
0.0147
0.0063
0.0843
0.0337
0.0421
Emission rate
S or E lane
0.1166
0.0583
0.0291
0.0049
0.0059
0.0139
0.0015
0.0011
0.0028
0.0778
0.0311
0.0388
by lane, gm/sec-m
N or W lane
0.0098
0.0049.
0.0024
0.0583
0.0405 s
0.0176
0.0175
0.0136
0.0035
0.0065
0.0026
0.0033
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4.0 COMPILATION OF INPUT DATA
The data that must be compiled in order to run the HIWAY model are
shown in Table 3. These data may be classified into four general cate-
gories: source configuration (measurements of the site and surrounding
area), receptor location, meteorological data, and emission data. The
steps to be followed in obtaining or generating all of these data are
explained in this chapter. The final section of this chapter describes
the selection of specific combinations of emission data and meteoro-
logical data for input to the model to simulate CO concentrations during
different time periods.
4.1 Source Configuration
The distance between sources and receptors must be accurately
defined in the analysis. This is normally accomplished by obtaining an
engineering drawing or site plan of the proposed development plus a
large enough surrounding area to include all potential receptor sites.
A copy of the drawing or plan should be made so that notations and
additional markings can be written on it. A base map should then be
prepared from this copy by placing a coordinate system on the map and
marking each access street and parking lot traffic link as a straight
line (along the centerline of the street or lane) with well-defined end
points.
Any convenient units can be used for the coordinate system; prob-
ably those of the base map would be easiest to apply. If the arbitrary
origin of the coordinate system is placed to the south and west of all
line source end points and receptor locations, the (x,y) coordinates
18
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Table 3. INPUT DATA REQUIREMENTS FOR HIWAY
Source Configuration
Coordinates (x,y) of line source end points
Source height
Total width of highway
Width of center strip
Number of traffic lanes
Cut section or at-grade highway
Width of cut section
Factor to convert site measurements to kilometers
Receptor Location
Coordinates (x,y) of receptor
Receptor height
Meteorological Data
- Wind direction
- Wind speed
Mixing height
Stability class
Emission Data
Line source emission rate for each traffic lane
19
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2500
Figure 5. Example base map with coordinate system superimposed
20
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will all be positive. However, the model will accept negative coordi-
nates. An example base map with a coordinate grid superimposed is shown
in Figure 5.
The locations of the line sources are input to the HIWAY model by
the grid coordinates of the two end points of each link. Distances
between line sources and receptors are calculated in the model from
their respective coordinates. Because of the importance of the source-
receptor configuration to the accuracy of the analysis, it is recom-
mended that coordinates used in the model be checked by calculating
distances between key points trigonometrically and comparing these
values with measurements between the corresponding points scaled directly
from the base map. For crucial dimensions, such as the distance of a
public sidewalk from the edge of an access street or parking lot entrance,
field measurements of these small distances (if facilities are already
in existence, this is preferable to scaling from the base map) should be
used in conjunction with coordinates for the line source to calculate
the exact grid coordinates of the receptor. (Receptor location is also
discussed in Section 4.4.) Calculation of receptor coordinates relative
to line source end points is demonstrated in the example at the end of
this section.
Non-linear streets or lanes must be represented in the HIWAY model
by straight-line segments. Generally, this may be done more accurately
by keeping the line on the base map over some part of the street rather
than by connecting points on the centerline of the curving street. The
correct procedure is shown in Figure 6. Attention to this procedure is
important only when receptors are to be specified in the model near the
non-linear street's edge.
21
-------
Incorrect
Correct
Incorrect
Correct
Figure 6. Simulation of Curving Streets with Straight Line Segments
22
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If emission rates change substantially along a street due to
different traffic volumes or speeds, the street should be split into
separate line sources at the points where the emission rates change.
For an access street on which emission rates remain fairly constant over
the length of the street, end points of the line source should be
extended sufficiently so that any portion of the length that would
impact on a downwind receptor (with a wind direction specified in the
analysis) is included.
No distinction is made in the model among any of the three types of
line sources that are included—access streets, major traffic aisles in
parking areas, and major queues on either the access streets or the
parking areas.
The sources representing queues have a finite length. This length
is calculated from equations presented in the Guidelines:
At signalized intersections
V(l-G/Cy)D
CPH
where L = queue length, meters
V = traffic demand, veh/hr
G/Cy = green time to signal cycle ration, dimensionless
D = spacing between successive vehicle tailpipes in
the queue, assumed to be 8 m/veh
CPH =' number of signal cycles per hour
At rioh-signalized intersections
r v2 ,
L
where C = capacity, veh/hr, and other symbols are as
defined above
23
-------
One end point for the queue is the intersection. The other end point
can be calculated after the length of the queue is determined. If the
queue length is less than 25 meters (about three vehicles), it should
not be included in the model as a separate line source.
Several other dimensions and data values must be provided to fully
define the source configuration. The additional dimensions are: (1)
height of the line source above ground level, (2) total width of the
street, (3) width of the median strip (if present), and (4) width of cut
section at its top (if the street is in a cut section). All of these
dimensions must be input in units of meters rather than the units used
for the coordinate system. Three other pieces of information must be
specified: (1) the number of lanes in the street, (2) whether the
street is in a cut section, and (3) the scale factor for converting the
coordinate system units to kilometers. Scale factors for the most
common units are shown below:
Map units Scale factor
feet 0.0003048
miles 1.6093
meter 0.001
kilometers 1.
The HIWAY model is only applicable to relatively flat terrain. For
at-grade streets, the height of the line source may be estimated as 0.0
rather than tailpipe height (0.5 meter) without any loss of accuracy
because an initial vertical dispersion of 1.5 meters is included in the
model.
The width of the street or highway should include the width of any
center median present, but not the highway shoulders. If the width is
not specified in the material submitted and cannot be accurately measured
24
-------
from the drawing, an estimate of 12 feet (3.66 meters) per lane may be
made for modern main streets and highways. If the right-of-way width
is obviously limited by existing development, an estimate of 10 feet
(3.05 meters) per lane may be more appropriate.
EXAMPLE
Problem. A receptor site located on the centerline of a sidewalk
is 6 feet from the edge of the curb of a major access street to a shop-
ping center, as shown in Figure 7. The street, including curbs, is 52
feet wide. The coordinates (in feet) specified for its end points are
(165, 300) and (366, 416). If the receptor is 80 feet (measured along
the street) from the intersection denoted by the coordinates (165, 300),
what are the coordinates of the receptor site?
Solution.
a. Distance (d) of the receptor from the centerline of the street
is:
d = 52_ + 6
2
32 feet
b. The angle (a) formed by the street and the x-axis is calculated
as follows:
416 - 300
a = arctan 366 - 165
arctan 0.557
= 30.0°
c. The coordinates of the receptor can then be calculated trigo-
nometrically:
x = 165 + 80 cos a + 32 sin a
i\
250
y = 300 + 80 sin a - 32 cos a
R
312
25
-------
416
165
Figure 7. Location of receptor relative to line source end points
26
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4.2 Receptor Location
Critical receptor sites are usually the nearest "reasonable" loca-
tions to streets tor traffic lanes with the highest line source strength
and locations immediately downwind of a group of line sources. For an
indirect source with emissions from both access streets and a parking
area, these locations are usually near an intersection of access streets
or near an entrance/exit to the parking area. By using the HIWAY model,
all potential points of maximum CO concentration can be evaluated simul-
taneously. Up to 50 receptor sites can be specified in the HIWAY run.
The Guidelines recommend that receptor site selection be through
joint review of maps and plans of the area by the reviewing agency and
the applicant. Several examples of locations that would generally be
regarded as reasonable and unreasonable receptor sites are presented in
the Guidelines and are repeated herein:
Examples of Reasonable Receptor Sites
1. All sidewalks where the general public has access on a more or
less continuous basis for 1- or 8-hour periods.
2. A vacant lot in which a neighboring facility is planned and in
whose vicinity the general public (including employees if the neigh-
boring facility is not being built for the prime purpose of traffic
control) would have access continuously for 1- and 8-hour periods.
3. Portions of a parking lot to which pedestrians have access
continuously for 1- and 8-hour periods.
4. The vicinity of a parking lot's entrances and exits, providing
there is an area nearby, such as a public sidewalk, residences, or
structures (e.g., an auto service center at a shopping center), where
27
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the general public is likely to have continuous access for 1 or 8 hours.
5. The property lines of all residences, hospitals, rest homes,
schools, playgrounds, and the entrances and air intakes to all other
buildings.
Examples of Unreasonable Receptor Sites
1. Median strips on roadways.
2. Locations within the right-of-way on limited access highways.
3. Within intersections or on crosswalks at intersections.
4. Tunnel approaches.
5. Within tollbooths.
6. Portions of parking lots where the general public is not
likely to have access for 1- or 8-hour periods.
Some other receptor sites may be of special interest, even though
they are not anticipated to be points of maximum CO concentration in the
area, because sensitive members of the population are likely to be
exposed there. These special receptors might include schools, play-
grounds, day care centers, hospitals, sanitariums, nursing homes, and
parks.
The x and y coordinates of all receptor sites must be specified in
the same units as the line source end points. It is important that the
receptors' grid coordinates be determined from the same base map used to
fix the location of the line sources so that possible errors in defining
the source-receptor relationship are minimized.
The heights of all receptor sites must be specified in meters.
Normally, receptor height would be about two meters above ground level,
at nose height.
28
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4.3 Meteorological Data
Meteorological input data for the analysis should be specified to:
(1) result in the maximum Co concentrations that may occur at receptor
sites and (2) be consistent with observed meteorological conditions that
are representative of the site for the time periods of concern. Four
different meteorological inputs are required for the HIWAY model:
- wind direction
wind speed
- mixing height
stability class
To provide assurance that the specified data are consistent with
actual meteorological conditions, a full year's records from a nearby
meteorological station should be obtained and reviewed. Joint frequency
distribution for wind direction, wind speed, and stability class (e.g.,
the STAR program output available from the National Climatic Center)
will indicate whether certain critical combinations of these three
variables occur with sufficient frequency to be considered in the anal-
ysis. However, these frequency distributions are not normally generated
for a specific hour of the day, so the raw data still must be scanned to
determine whether the critical combinations of wind direction, wind
speed, and stability class ever occur during the hour(s) with highest
emission rates. If not, it is also important to determine the hours in
which these adverse meteorological conditions do occur.
4.3.1 Wind Direction
The wind directions to be investigated should be selected based on
the locations of receptors relative to sources, with the receptors
29
-------
falling downwind of major line sources. Obviously, this may require the
analysis of several wind directions if receptors have been specified in
different directions from the proposed development site. Since there is
no simple procedure for isolating the wind direction or receptor site
that will result in the highest CO concentrations, each wind direction
must be modeled separately. A major advantage of the HIWAY model com-
pared to the screening procedure is its ability to analyze several
receptors and alternative sets of meteorological input data efficiently.
The base map showing locations of sources and receptors provides an
excellent aid in establishing the wind directions for use in the model.
Several general guidelines are applicable to the selection of wind
directions for the model:
1. For receptors near a large number of short line source segments,
as in a parking lot or adjacent to intersection approaches, a wind
direction that places the maximum number of these sources directly
upwind should be used.
2. For receptors near (within about 10 meters) access street line
sources which extend for a long distance (more than 100 meters) beyond
the receptor location, a wind direction parallel or nearly parallel to
the line source should be considered in estimating maximum 1-hour con-
centrations. Parallel winds are not appropriate for estimating 8-hour
concentrations because winds would not persist parallel to the street
for such an extended period.
3. For receptors more distant from sources, the wind direction
should place the receptor directly upwind of the nearest access street
intersection or parking lot entrance/exit.
30
-------
4. The wind direction most frequently associated with D or E
stability classes and low wind speeds should be considered.
4.3.2 Wind Speed
This is the most sensitive input in the estimation of CO concen-
trations because the diffusion equation in the model calculates ambient
concentrations as being inversely proportional to wind speeds. For
example, a change in wind speed from 2.0 to 1.0 m/sec in the model
doubles the predicted CO concentration.
With this inverse relationship, predicted concentrations approach
infinity as the average wind speed approaches zero. Therefore, the
model is not appropriate for wind speeds less than 0.5 m/sec and usually
overpredicts for wind speeds less than 1.0 m/sec. A 1.0 m/sec minimum
should be observed in indirect source analyses.
The number of annual occurrences of a 1.0 m/sec wind speed in
conjunction with a D or E stability class and the selected wind di-
rection during the time period of concern should be determined from raw
meteorological data, if available, or National Weather Service monthly
climatological summaries before the 1.0 value is used in the model. If
this combination of adverse meteorological conditions has not occurred
during the year, the minimum wind speed recorded for the time period
with the assumed stability class and wind direction should be input
instead. Alternately, a different wind direction or stability class for
which a 1.0 m/sec wind speed has been recorded may be considered.
The wind speed data should be representative of the winds at the
height of the plume from the line source. For at-grade highways and
nearby receptors, the most appropriate height is two meters above
31
-------
ground level. Surface wind measurements taken at the more common height
of 10 meters may be used directly, but measurements from greater heights
should be adjusted to corresponding speeds at 10 meters height. Wind
profiles (variations in wind speed with height) which can be used to
estimate the ratio of the wind speeds at the two heights are shown in
the Workbook of Atmospheric Dispersion Estimates, Figures 1-1 and 1-2.
4.3.3 Mixing Height
In contrast to wind speed, mixing height is not a critical input
for indirect source analysis. The distances between sources and recep-
tors, generally less than 100 meters, are so small that the ceiling on
vertical dispersion imposed by the mixing height has no effect on pre-
dicted concentrations at the receptors.
Sufficiently accurate values for use in the model can be obtained
from the EPA publication Mixing Heights, Wind Speeds, and Potential for
4
Urban Air Pollution throughout the Contiguous United States, Figures 1
through 10. This compilation of mixing height data provides a selection
of values specific for the time of day, season, and national location
being analyzed. Mean annual early morning (mimimum for the day) mixing
heights shown in this publication are 300 to 700 meters for most parts
of the country. Afternoon (maximum for the day) mixing heights range
from 1,000 to 2,600 meters.
Morning and afternoon mixing height values for specific dates
(e.g., to compare model results with CO sampling data) can be readily
calculated from vertical temperature profiles and surface temperature
readings available from the National Climatic Center, Asheville,
North Carolina, for any of the 62 national locations at which upper-air
32
-------
measurements are routinely made. The 62 cities are listed in Table 4
and the method for calculating mixing height from the vertical temper-
4
ature profile is explained in the publication cited above. This more
detailed estimation of mixing height is not warranted for predicting
future CO concentrations in the indirect source analysis.
4.3.4 Stability Class
Pasquill stability classes A (very unstable) through F (moderately
stable) are used in the HIWAY model to indicate the rate of atmospheric
mixing. For the source-receptor configurations in indirect source
analysis, higher CO concentrations are generally predicted with increas-
ing atmospheric stability. In order to determine the most stable poten-
tial stability class for a particular analysis, the time of day and
urban/rural location of the development site must be known.
. In a relatively flat and open area, stability is primarily a func-
tion of wind speed and incoming solar radiation (during the day) or
cloud cover (during the night). The relationship is shown in Table 5.
Note that neither E nor F stability normally occurs during the daytime.
Therefore, D stability should be used to estimate the highest CO con-
centrations for all daytime hours.
Day is defined as the period from one hour after sunrise until one
hour before sunset. National Weather Service stations record the local
times of sunrise and sunset each day, or the official times for any date
and U.S. city can be obtained from the Naval Observatory, Washington,
D.C.
Guidelines for estimating stability classes for open land or rural
areas are presented in Table 5. In urban areas, the atmosphere is
likely to be less stable as a result of the mechanical turbulence
33
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Table 4. NATIONAL WEATHER SERVICE UPPER-AIR OBSERVING STATIONS
Location
NWS
Abbr.
Location
NWS
Abbr.
Albany, New York ALB
Albuquerque, New Mexico ABQ
Amarillo, Texas AMA
Athens, Georgia AHN
Bismarck, North Dakota BIS
Boise, Idaho BOI
Brownsville, Texas BRO
Buffalo, New York BUF
Burwood, Louisiana BRJ
Cape Hatteras, N. C. HAT
Caribou, Maine CAR
Charleston, S. C. CHS
Columbia, Missouri CBI
Dayton, Ohio DAY
Denver, Colorado DEN
Dodge City, Kansas DDC
El Paso, Texas ELP
Ely, Nevada ELY
Flint, Michigan FNT
Glasgow, Montana GGW
Grand Junction, Colo. GJT
Great Falls, Montana GTF
Green Bay, Wisconsin GRB
Greensboro, N. C. GSO
Huntington, W. Va. HTS
International Falls, Minn. INL
Jackson, Mississippi JAN
Jacksonville, Florida JAX
Lake Charles, Louisiana LCH
Lander, Wyoming LND
Las Vegas, Nevada LAS
Little Rock, Arkansas LIT
Medford, Oregon MFR
Miami, Florida MIA
Midland, Texas MAF
Montgomery, Alabama MGM
Nantucket, Massachusetts ACK
Nashville, Tennessee BNA
New York, New York JFK
North Platte, Nebraska LBF
Oakland, California OAK
Oklahoma City, Okl. OKC
Peoria, Illinois PIA
Pittsburgh, Penn. PIT
Portland, Maine PWM
Rapid City, S. D. RAP
St. Cloud, Minnesota STC
Salem, Oregon SLE
Salt Lake City, Utah SLC
San Antonio, Texas SAT
San Diego, California SAN
Santa Monica, Calif. SMO
Sault Ste. Marie, Mich. SSM
Seattle, Washington SEA
Shreveport, Louisiana SHV
Spokane, Washington GEG
Tampa, Florida TPA
Topeka, Kansas TOP
Tucson, Arizona TUS
Washington, D. C. DIA
Winnemucca, Nevada WMC
Winslow, Arizona • INW
Source: Mixing Heights, Wind Speeds, and Potential for Urban Air Pollution
throughout the United States. U.S. Environmental Protection
Agency. Research Triangle Park, North Carolina. 1972. Table A-l.
34
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Table 5. ESTIMATION OF PASQUILL STABILITY CLASSES
Surface wind
speed (at 10 m) ,
m/sec
< 2
2-3
3-5
5-6
> 6
Day
Incoming
solar
Strong Moderate
A
A-B
B
C
C
A-B
B
B-C
C-D
D
radiation
Slight
B
C
C
D
D
Night
Thinly
overcast
or >4/8
low cloud
E
D
D
D
<3/8
cloud
F
E
D
D
The neutral class, D, should be assumed for overcast conditions
during day or night.
Source: Workbook of Atmospheric Dispersion Estimates. U.S. Depart-
ment of Health, Education, and Welfare, Public Health Service.
Cincinnati, Ohio. 1970. Table 3-1.
35
-------
created by vehicles, aerodynamic effects of buildings, and heat island
effects in highly paved areas. This increased atmospheric mixing would
preclude E and F stability classes from occurring, except in special
situations, in urban areas. Therefore, D stability should be used to
estimate the highest CO concentrations for urban locations, even for
nighttime periods. For open suburban sites, E stability may be used to
stimulate night stability.
4.4 Emission Data
The only emission data required by the HIWAY model are the line
source emission rates (q) in gm/sec-m for each lane of traffic in the
study area. Point or area source CO emissions cannot be input. There is
no upper limit to the number of line sources that can be considered in a
single run. One lane or any even number of lanes from 2 to 24 can be
specified for each line source. The emission rates for multiple-lane
sources should be listed in order from left to right as the line source
is viewed from end point 1 to end point 2.
4.4.1 Emission Rates for Parking Area Traffic Lanes
The emission rates for traffic lanes in parking lots are calculated
by first estimating the total emissions per hour in the parking area and
then apportioning this total to the individual traffic lanes by the pro-
cedure described in Chapter 3. This procedure produces emission rates
in gm/sec-m for direct input to the HIWAY model.
The emissions attributable to major queues at entrances/exits and
intersections within the parking lot are not included in the emission
rates calculated for these traffic lanes. The queue emissions, like
those from queues occurring along access streets, are considered as
36
-------
separate line sources. Calculation of emission rates from queues is
explained in Section 4.4.3 below.
4.4.2. Emission Rates for Access Streets
Emission rates for access streets are calculated by a procedure
described in detail in Appendix A of the Guidelines, "Methods for
Estimating Emissions from Highways." The equation used in that pro-
cedure is presented here, but it is recommended that the detailed
description be followed in the calculations.
This equation estimates the uniform emission intensity for each
lane of freely flowing traffic on the street or highway. The excess
emissions that occur as a result of queues at intersections are esti-
mated by additional calculations described in the next section and are
handled as separate line sources. It should be noted that the emission
rate calculated for the free flowing segments of the access street also
extends over the length of the queue; the additional line source repre-
senting the queue only simulates the extra emissions due to acceler-
ation/deceleration and idling.
The equation for estimating emission rates by lane is:
q. . = (1.036 x 10~5) (EF) . . (V../S..)
13 ID 13 13
where q.. = line source emission rate in lane j for road segment
i, resulting from free flowing traffic, gm/sec-m
V. . = traffic volume demand, veh/hr
S. . = average vehicle operating speed, mph
(EF).. = speed corrected emission factor, gm/min-veh
(1.036 x 10 ) = conversion factor from gm/min-mi to gm/sec-m
Volume demands for some time period(s) on all access streets
should be provided by the applicant. If average daily traffic (ADT)
37
-------
volume is provided, the volume demand for the 1-hour periods of concern
can be estimated as a fraction of ADT by using data on local diurnal
traffic patterns. Traffic volumes during particular seasons may be
estimated by applying seasonal adjustment factors. Traffic volumes are
usually given separately for travel in each direction on a street, but
not by lane. Therefore, the total one-way volume must be apportioned to
the lanes in that direction.
The average operating speed on a highway link is a function of the
volume-to-capacity ratio of the link and its design speed. Estimated
speeds during specific hours may also be provided by the applicant. If
not, operating speeds may be estimated from Figures A2 through A5 in
Appendix A of the Guidelines.
The CO emission factors, a function of operating speed, are pre-
sented for the year 1975 in Figure 8. These values in units of gm/min-
veh were derived from data in EPA publication AP-42, Supplement Number
5. For years other than 1975, the appropriate emission factor may be
estimated as follows:
(EF) . = (EF)__ (ef/55)
yr 75
where (EF) = emission factor for year of concern
yr
(EF) = emission factor obtained from Figure 8
ef = emission factor in gin/mi for the year of concern:
Calendar year ef for CO
1972
1973
1974
1975
1976
1977
1978
1979
1980
70.6
65.6
61.6
55.0
48.2
41.5
35.0
29.1
23.2
38
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10 15
20 25 30 35 40 45
VEHICLE SPEED, mph
50
55 60
65
Figure 8. Composite emission factors for carbon monoxide for calendar year 1975
-------
Several assumptions were made in the derivation of data in Figure 8:
- a national average mix of vehicles by model year
88 percent of VMT by light-duty vehicles, 12 percent of
VMT by light-duty trucks
20 percent of vehicles operating from a cold start
o o
ambient temperature in range of 68 F to 86 F
a low altitude location outside California
If any of these assumptions are not applicable, correction factors
should be obtained from the Guidelines (Tables 1 and 2) or from AP-42,
Supplement Number 5.
4.4.3 Emission Rates for Queues
The emission rate for a queue on either an access street or in a
parking area is calculated from equations presented in Appendix A of the
Guidelines. Two different types of queue formation are considered—at
signalized intersections and at non-signalized intersections. The
average emission rate over the finite length (as determined by the
method described in Section 4.1, page 23) of a queue at signalized and
non-signalized intersections may be estimated as follows:
At Signalized Intersections
q. . = (EF) . . + 0.5 (EF) ' . . (1 - G/Cy)
60 D
where q^ _. = excess line source emission intensity to be applied
over the finite queue length L..
section approach i, gm/sec-m
over the finite queue length L.. in lane j at inter-
(EF).. = average emission factor for accelerating and decel-
erating vehicles over the estimated queue length,
gm/min-veh
(EF)'.. = emission factor for idling vehicles in the queue,
„ gm/min-veh
40
-------
G/Cy = green time to signal cycle ratio at approach i,
dimensionless
D = spacing between successive vehicle tailpipes in the
queue, assumed to be 8 m/veh
The emission factors used for (EF).. and (EF)'.. are not presented in
Appendix A, but can be derived from Supplement 5 to AP-42 and the U.S.
EPA Modal Emission Analysis Model. Summary tables of source intensity
(q) in Appendix A of the Guidelines indicate that EF.. and (EF)'..
are a function of both signal cycle length and traffic volume. Values
for q.. should be obtained from Tables A8 to A12 of Appendix A.
At Non-signalized Intersections
q.. = (EF)../60D
ID ID
where (EF).. = average emission factor for vehicle speeds about
0 mph, gm/min-veh, and other symbols are as defined
above
The emission factor (EF).. is the same as described in Section 4.4.2, so
ID
the value of 20 gm/min-veh for 1975 (from Figure 8) and the calculation
procedure for estimating the factor for years other than 1975 are
applicable.
4-5 Selection of Alternatives for Modeling
The objective of the indirect source microanalysis is to determine
the highest 1- and 8-hour CO concentrations likely to occur at a reason-
able receptor site in the vicinity of a proposed development. In making
this determination, several different alternatives that possibly require
separate modeling analyses should be evaluated:
different wind directions must be input to produce maximum
CO concentrations at different receptors;
1-hour and 8-hour periods have different source emission
rates and meteorological conditions;
41
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peak traffic periods and most adverse meteorological condi-
tions may occur at different times of day.
peak traffic volumes on access streets may not coincide with
peak traffic movement periods in the parking area;
CO concentrations at receptor sites without the impact of
the proposed development (no-build alternative) may be of
concern.
Each of the above situations should be considered in preparing a
list of alternatives to be modeled for a specific indirect source anal-
ysis. Some of the potential alternatives may drop out without perform-
ing a modeling analysis. For example, if emission rates are 15 percent
higher during the peak traffic period than during the hour with worst
meteorology and wind speed is twice as high in the peak traffic period,
then it should be clear that the hour with worst meteorology would
produce the higher predicted CO concentrations, because the concentra-
tion is inversely proportional to wind speed.
In some cases, there are no means of readily determining which
alternative will produce the highest predicted concentration without
running the alternatives in the HIWAY model. The only input data that
are variables after the source-receptor configuration of the site has
been established are line source emission rates and meteorological data.
These data are input on only a few punch cards, so it may be advanta-
geous to make two or more runs with changes in a few data cards rather
than to include all alternatives in one run. Another benefit of this
procedure is that it provides an opportunity for an interim review of
results.
Analyses of 8-hour periods should be accomplished with relatively
high priority, since the 8-hour NAAQS of 10 mg/m (9 ppm) for CO is
42
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exceeded more often than the 1-hour NAAQS of 40 mg/m (35 ppm). If the
first run shows that the 8-hour standard is threatened but not the 1-hour
standard, further analysis of alternatives could focus exclusively on
8-hour periods. Methods of estimating maximum 8-hour CO concentrations
with the HIWAY model are discussed in Chapter 7.
43
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5.0 INPUT DATA FORMAT FOR THE HIWAY MODEL
This chapter describes how the data generated per the instructions
in the .previous chapter are transformed into an input data card deck for
the HIWAY program. The discussion concentrates on batch (card deck)
rather than interactive (computer terminal keyboard) operation because
the amount of data generally necessary for the indirect source analysis
would be too time-consuming to input with the interactive mode.
A minimum of seven data cards are required for each line source in
the analysis. Table 6 shows the sequence and format for these seven
types of input data cards.
Note that all data, except the heading (card type 1) are in floating
point format with 10-space field widths. It is crucial that a decimal
point be placed in each field. Otherwise, the data will be misread and
results will be incorrect. It is recommended that the data be left-
oriented in the fields, as shown in the columns titled "Forms," to
facilitate keypunching and verification.
For indirect source analysis, many line sources (e.g., 10 to 50)
will probably be input as a single data set representing one time
period. Also, more than one of these data sets of several sources may
be included in a computer run of the model. Before the seven types of
data cards for another line source are placed in the deck, a card with
the value 9999. in columns 1 through 5 should be used to separate this
input data from the previous line source's data. The same card should
be used between data sets for different alternatives. The card with
9999. should not be used after the final set of line source input data.
Data on card types 5, 6 and 7 are the same for all line sources in
a data set representing one time period. Therefore, these cards can be
44
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Table 6. INPUT DATA FORMAT
Card/ input name
Type 1 (1 card)
Heading
Type 2 (1 card)
REP1
SEP1
REP2
SEP 2
H
WIDTH
CNTR
XNL
Type 3 (up to
3 cards)
QLS
Type 4 (1 card, -may
be blank
Columns
1-80
1-10
11-20
21-30
31-40
41-50
51-60
61-70
71-80
1-80
for at-grade)
CUT
WIDTC
1-10
11-20
Format
20A4
F10.0
F10.0
F10.0
F10.0
E10.0
F10.0
F10.0
F10.0
F10.0
F10.0
F10.0
Form
AAAA
XXXX.XXX
XXXX.XXX
XXXX.XXX
XXXX.XXX
XX. X
XX.
XX.
X.
.xxxxxxxx
X.
XX.
Description
Alphanumeric descrip-
tion of line source
segment & other inform-
ation (e.g., time pd.)
East coordinate, pt. 1
North coord. , point 1
East coord. , point 2
North coord., point 2
(end points of the
line source are at
centerline of road)
Height of source
Total width of road
incl. center strip
(not input for cut
section)
Width of center
strip (not input for
cut section)
Number of traffic
lanes
Emission rate for
each lane (in order
from left to right
viewed from pt. 1)
0. if at-grade
1. if cut section
Width of top of cut
section
Units
-
Map units
Map units
Map units
Map units
Meters
Meters
Meters
_
Gm/sec-m
-
Meters
Value
limits
-
-
-
-
0. or +
_
< width
1. or even
integer 2 .
to 24.
-
0. or 1.
_
45a
-------
Table 6. INPUT DATA FORMAT (continued)
Card/input name
Type 5 (1 card)
THETA
U
HL
XKST
Type 6 (1 card)
GS
Type 7 ( up to
50 cards)
XXRR
XXSR
Z
Columns
1-10
11-20
21-30
31-40
1-10
1-10
11-20
21-30
Format
F10.0
F10.0
F10.0
F10.0
F10.0
F10.0
F10.0
F10.0
Form
XXX.
XX. X
XXXX.
X.
X . XXXXXXX
XXXX . XXX
XXXX. XXX
XX.
Description
Wind direction, degrees
from north
Wind speed
Height of mixing layer
Pasquill stability
class:
A = 1. D = 4.
B = 2. E = 5.
C = 3. F = 6.
Scale factor for map
units:
kilometers =1.0
meters = 0.001
feet = 0.0003048
miles = 1.6093
East coordinate of
receptor*
North coordinate of
receptor
Height of receptor
Units
Degrees
M/sec
Meters
Map units
Map units
Meters
Value
limits
0.-360.
1.0 or
greater
>100
1. to 6.
-
-
0. or +
*A value of 9999. is entered in this field following the last receptor card
if another set of data is to follow.
45b
-------
duplicated to produce the appropriate number of copies for compilation
of the data deck.
The data cards for a run are placed behind the HIWAY program deck
as shown in Figure 9. Job control cards for the specific computer
system are located at the front of the deck, between the HIWAY program
and input data decks, and at the end of the input data. The program can
be run on computers that read FORTRAN IV.
The computer CPU time required to run the program is a function of
many factors, including the number of sources and receptors. On an
IBM 370 computer, about 17 seconds are required to compile the program
plus about 0.2 seconds running time for every source-receptor combina-
tion. For example, an analysis with 20 sources and 12 receptor sites
would take about 65 seconds CPU time (17 + 20 x 12 x 0.2) on this computer.
Depending on the number of sources and receptors, either a 3- or 5-
.minute upper limit should be specified for an IBM 370 in case of an
error in the input data.
To simulate a different alternative, only the emission rates (card
type 3) and/or meteorological conditions (card type 5) will change.
Type 3 and type 5 cards containing data for the second alternative can
be manually inserted in the deck, replacing the corresponding cards from
the first run. The revised deck is then ready to be run again, although
the printout from the first run should be reviewed for errors or unexpected
results before the deck is resubmitted.
If the interactive operation of HIWAY through the UNAMAP system is
used for an uncomplicated analysis, the same input data must be avail-
able. After the computer is accessed, the HIWAY program is initiated by
typing the command "hiway." All communication by the user is in lower
46
-------
job control card /
data set for f
. U.MK a
third line source (/eRoA»w»y,u*»iK» *""" NE *
spacer card
data set for A
second line source^
spacer card £-
card types 7
card type 6
card type 5
card type 4
472.3. 1102.
*.0
/ o.ooo&o^a
/ 04.5. r*
card type 3
card type 2
card type 1
.0015
.0095 .CO/ 7 .OOI1 .0019
/'
11*1. O.0
/ FIPTH ST., LJfJfc »
N« S PM
OATA
job control cardiiy ^
HIWAY
program
job x
control
cards
Figure 9. Assembly of HIWAY card deck
47
-------
case letters. Input data are entered as the computer calls for them.
Result?-, are output after the data for each line source have been enter-
ed. After the results are printed, options are available to run the
model for new receptor locations or a new road segment (line source), or
to end the program.
48
-------
6.0 OUTPUT DATA AND ITS PRESENTATION
The model-calculated CO concentrations, in uq/m and ppm, at all
specified receptor locations resulting from the traffic lanes of a
single line source are output in the format shown in Figure 10. Notice
that the name assigned to the line source on input card 1 is printed as
the heading for the output for that data set, and that all other input
data are summarized above the tabular presentation of CO concentrations.
The combined impact on any receptor site of all line sources in the
vicinity of the proposed development is determined by adding the concen-
trations contributed by each line source. The same meteorological input
data must be used with every source in a data set representing the
combined effect of all sources. A convenient tabular format for calcu-
lating total predicted CO concentrations at each receptor is shown in
Table 7.
The impact of the nearby traffic considered in the model is usually
predominant at the specified receptor locations. However, the total CO
concentration at any receptor would also have some contribution from
other, more distant traffic, commonly referred to as the urban back-
ground component. As indicated in Table 7, a value representing the CO
background should be added to the model-predicted concentrations at each
receptor site before these estimated total concentrations are compared
with the National Ambient Air Quality Standards (NAAQS).
Several approaches for estimating background concentrations,
depending on what data are available, are described in Section 4.3 of
the Guidelines and in Appendix H of the Guidelines. The approaches are
summarized below, but it is recommended that the full descriptions from
the original references be reviewed before calculating background con-
centrations .
49
-------
HI WAY VERSION:
EN DP 01 NTS OF
THE LINE SOURCE
.220 ANC ,<»15
IPO
EMISSION
EMISSION
HEIGHT TS .COP METERS
RATE ( GRAKS /S ECOVD* METF R)
OF
1 LANECS)
.300-02
WT3TH OF AT-GRADE
WIDTH
WIND
HIGHWAY TS
5.0 M
OF CENTER
DIRECTION
.0
DEGREES
WIND SPEED I
STABILITY
HEIGHT OF
THE SCALE
STRIP IS
S 10.
i.o METCpr/src
CLASS TS 4
LIMITING Lib" IS Z CD 0.0 METERS
OF THE COORDINATE AXES IS l.OCDC USER UNTTS/KH.
RECEPTOR
X
.2C50
.3350
.7850
.tZOQ
.4650
.5B50
.8850
.3375
.2000
.2000
.9000
LOCATION
Y
-.OC75
-.0075
-.CC75
-.0075
-.CC75
-.0075
-.G075
-.0125
-.0125
.2200
-.0125
HEIGHT
Z( M)
Z. GOOD
2. OC 00
2. CD 00
2. CO CD
2. 00 00
2.CCOO
2. CD 00
2. CO 00
2. CDOC
2. OCOO
2. 00,00
CONCENTRATION
UGM/MET[IR**3
0.
27.
87 7
J *J •
59.
0.
0.
0.
612.
0.
0.
r.
PPM *
.000
• 02«»
.725
.052
.noo
.pro
.CPO
.532
• OPO
.ono
.ono
* PPM CONCENTRATIONS CORPfCT FCR CARSON MONOXIDE ONLY.
Figure 10. Example HIWAY output
50
-------
Table 7. CALCULATION OF TOTAL CO CONCENTRATIONS AT RECEPTOR SITES
Hour of Day
Season
Wind Direction
Wind Speed, m/sec
Mixing Height, m
Stability Class
Receptor No.
Receptor
Coordinates
Line Source
Subtotal , ppm
Estimated Back-
ground , ppm
Total Concen-
tration , ppm
CO Concentration, ppm
51
-------
Approaches for Estimating Background Concentrations
1. Note the second highest 1- and 8-hour concentrations observed
at a continuous monitoring station near the site of the proposed source
over the past year during the time period of concern. These values
should be adjusted to account for the effect that the Federal Motor
Vehicle Emission Control Program will have by the first year of the
proposed source's operation.
2. Use results of a calibrated mesoscale diffusion model such as
APRAC-1A to estimate the highest representative 1- and 8-hour concen-
trations likely to occur during the time period of concern.
3. If ambient sampling data for a limited period (assumed to be 14
days) at the proposed site plus a full year's data by hour for another
site in the urban area (located at least 100 meters from major traffic
lanes) are available, the background (x ) may be calculated as follows:
Max. observed l-hr/8-hr cone.
at proposed site during oper-
ating hours
Max. observed l-hr/8-hr cone.
at historical site during
source operating hours in
_past year
Max. observed l-hr/8-hr cone.
at historical site during
source operating hours during
_the limited sampling period _
4. If ambient sampling data for a limited period at the proposed
site plus maximum observed concentrations at another site in the urban
area are available, the background may be calculated as follows:
52
-------
fMax. observed l-hr/8-hr cone.
at proposed site during oper-
[ ating hours
Max. observed l-hr/8-hr cone."
at historical site during
past year
Max. observed l-hr/8-hr cone.
at .historical site during
the limited sampling period
5. If only ambient sampling data for a limited period at the pro-
posed site are available, the background may be calculated as follows:
Max. observed l-hr/8-hr cone.
at proposed site during oper-
ating hours
Max. X/Q in site's locale
for any season from Figures
42 - 45 of AP-101
"X/Q" in site's locale from Figures
42 - 45 of AP-101 during time of
year in which sampling is performed
6. If the source is to be located in a rural area, a natural back-
ground of 1 ppm may be assumed.
For each time period and set of meteorological conditions simulated,
a different CO concentration is predicted at any given receptor site. The
maximum concentration, including background, predicted at a receptor site
under any alternative is compared with the 1-hour NAAQS of 40 mg/m
(35 ppm) or 8-hour NAAQS of 10 mg/m (9 ppm) as the final step in the
indirect source analysis. If one or more of the predicted concentrations
exceed the NAAQS, the proposed source's application may not be approved
until its traffic handling facilities have been redesigned so that NAAQS
can be met.
53
-------
7.0 ESTIMATION OF MAXIMUM 8-HOUR CO CONCENTRATIONS
In most instances, peak 8-hour CO concentrations are more likely to
exceed the NAAQS than are peak 1-hour concentrations. However, there is
presently no completely satisfactory procedure for estimating peak 8-
hour concentrations, since the HIWAY model is designed to accept input
data for 1-hour averaging periods.
The procedure described in Section 4.2 of the Guidelines for
estimating peak 8-hour concentrations is to manually modify predicted 1-
hour concentrations by applying a persistence factor. The persistence
*
factor, which is always less than 1.0, accounts for variations in meteor-
ology (primarily in wind direction) occurring over an 8-hour period as
opposed to a 1-hour period.
The other modification necessary to predict peak 8-hour concen-
trations by the persistence factor procedure is to input emission rates
consistent with the mean hourly traffic volume during the 8-hour period
of concern rather than peak 1-hour emission rates. The mean traffic
volume for the 8-hour period is always less than peak 1-hour volume.
A method for calculating an appropriate meteorological persistence
factor from concurrent wind data, CO sampling data, and traffic data at
a site "similar" to the proposed one is also presented in Section 4.2 of
the Guidelines.
The persistence factor is calculated as follows:
a. Select an existing indirect source similar to the proposed
one.
b. Concurrently monitor hourly traffic volume, wind speed, wind
direction, and CO concentrations.
54
-------
c. Note the highest 1-hour CO concentrations (with wind speed
<2m/sec) and traffic volume during that hour for each day.
d. Note the highest 8-hour average CO concentration and average
hourly traffic volume during that period for each day.
e. Calculate a persistence factor, p, for each day:
(Max. 8-hr av. CO) Vl
P =
(Max. 1-hr. CO with u<2m/sec) V
8
f. Select the highest observed daily persistence factor for
estimating maximum 8-hr CO concentrations.
The steps involved in estimating peak 8-hour concentrations are
summarized below:
1. Determine the mean hourly traffic volumes and emission rates
on each traffic lane for the 8-hour period of interest.
2. Determine the meteorological input data for the peak 1-hour
emission period during the 8 hours according to the instructions out-
lined in Section 4.3 of this document.
3. , Run the HIWAY model with the emission and meteorological input
data obtained in steps 1 and 2.
4. Multiply predicted concentrations at each receptor site by the
calculated persistence factor to account for lack of persistence in the
adverse meteorological conditions.
5. Add a background concentration for the 8-hour period, calcu-
lated by one of the approaches described in Chapter 6, to the predicted
concentrations to determine the estimated peak 8-hour concentrations for
comparison with the NAAQS of 9 ppm.
In addition to the procedure based on a persistence factor relating
1-hour and 8-hour concentrations, several other procedures for estimating
55
-------
peak 8-hour concentrations at proposed developments are discussed in
Appendix H of the Guidelines. All of the procedures are empirical in
that they require analysis and application of wind data and/or air
quality data from the proposed development site or a similar location.
Two of these alternate procedures are:
1. Using predicted maximum hourly traffic volumes for an 8-hour
period and observed adverse meteorological data on an hourly basis for
that same time period, run the HIWAY model eight times to simulate the
successive 1-hour concentrations. Peak 8-hour concentrations can then
be obtained by averaging these eight values.
2. Using wind speed and direction observations for the peak 8-hour
emission period/ construct conditional hourly wind direction change
Q
frequency distributions for those periods with low wind speeds. These
wind direction change frequency distributions can then be input to a
simulation of the proposed site in which receptors are strategically
placed, and the simulation repeated with several sets of wind direction
change data. To estimate peak 8-hour concentrations for comparison with
NAAQS, the highest ratio between estimated 1-hour and 8-hour concentra-
tions at each receptor should be used.
It should be emphasized that these procedures do require collection
of wind speed and direction data at a location that is determined to be
representative of the proposed site. Any of these three procedures for
estimating peak 8-hour concentrations can be used if the necessary data
are available and if applied appropriately.
56
-------
REFERENCES
U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards; "Guidelines for the Review of the Impact of Indirect Sources
on Ambient Air Quality"; EPA-450/4-74-010; (January 1975); Research
Triangle Park, N. C. 27711.
2
Zimmerman, J. R. and R. S. Thompson; "User's Guide for HIWAY: A Highway
Air Pollution Model"; Environmental Monitoring Series EPA-650/4-008;
(February 1975); National Environmental Research Center, U.S. Environ-
mental Protection Agency, Research Triangle Park, N. C. 27711.
American Association of State Highway Officials; "A Policy on Geometric
Design of Highways in Urban Areas"; (1957); Washington, D. C.
4
U.S. Environmental Protection Agency, Office of Air Programs; "Mixing
Heights, Wind Speeds and Potential for Urban Air Pollution Throughout
the Contiguous United States"; Office of Air Programs Publication Number
AP-101; (January 1972); Office of Technical Information and Publications,
Research Triangle Park, N. C. 27711.
Turner, D. B.; "Workbook of Atmospheric Dispersion Estimates"; PHS Publi-
cation No. 999-AP-26; (1969); U.S. Environmental Protection Agency,
Research Triangle Park, N. C. 27711.
6
U.S. Environmental Protection Agency; "Compilation of Air Pollutant
Emission Factors"; Publication Number AP-42; Supplement No. 5 to the
Second Edition; (April 1975) ; Office of Technical Information and
Publications, Research Triangle Park, N. C. 27711.
7
Kunselman, P., H. T. McAdams, C. J. Domke and M. Williams; Automobile
Exhaust Emission Modal Analysis Model; (January 1974); U.S. Environmen-
tal Protection Agency, Ann Arbor, Michigan.
8
Meyer, E. L., Jr., and J. E. Quon; "A Method for Simulating Wind Con-
ditions During Atmospheric Stagnation Periods"; J. Appl. Met. 11;
(August 1972).
57
-------
APPENDIX. EXAMPLE ANALYSIS
Problem. A regional shopping center of 780,000 square feet leasable
floor space and 3800 parking spaces is to be built in a Southeastern
metropolitan area. Completion is expected by January 1978. A plan of
the proposed shopping center and surrounding area is shown in Figure
A 1.
Traffic volumes on access streets and at entrances/exits to' the
parking lot for a peak shopping period have been projected by the
developer with input from the Highway Department. Estimated traffic
demand by hour for each access street and entrance/exit is shown in
Table A 1. Average speeds by hour on the access streets are shown in
Table A 2. During the peak seasonal shopping period, it is estimated
that ambient temperature would be approximately 50 F and that about 30
percent of the vehicles in the parking lot (20 percent on the access
streets) would be operating from a cold start. Traffic in the parking
area and on 68th and Mill Streets will be about 88 percent light-duty
vehicles, 12 percent light-duty trucks. On other streets and highways,
the split will be about 80 percent LDV, 12 percent LDT, and 8 percent
heavy-duty truck (assume negligible diesel-powered trucks). Extensive
queuing is anticipated at two signalized intersections—Florida Boulevard
at Irving Boulevard and at Mill Street. Queuing will probably also
occur at the non-signalized intersection at 68th Street and Irving
Boulevard. The approximate signal times for the signalized intersections
and approach capacities for the non-signalized intersection are summarized
in Table A 3.
58
-------
Scale 1" = 250 feet
•H
U
o
U
N
INTERSTATE 85
- 3000
v- 2500
8
Irving Blvd. 1
B
. F
11
10
-2000
Mill St.
R5 R4
12
L
CN
I
CQ
(8
•O
•rl
M
O
R2
-1500
Irving Blvd. 2:
Irving Blvd. 3
R6
I
3000
3500
I
4000
Figure A 1. Proposed shopping center and surrounding area
59
CQ
n)
T)
•H
0
rH
fe
•RI
I
4500
_1000
-------
Table A 1. TRAFFIC DEMAND BY HOUR ON PEAK TRAFFIC DAYS
-------
Table A 1 (continued). TRAFFIC DEMAND BY HOUR ON PEAK TRAFFIC DAYS
Hour
Beginning
7 a.m.
8
9
10
11
12 noon
1 p.m.
2
3
4
5
6
7
8
9
10
Mill,
E
40
60
60
50
30
80
90
70
80
140
200
180
160
100
90
80
Mill,
W.
160
200
130
70
60
110
90
70
80
60
80
180
200
60
50
30
1-85,
E
3410
2600
2520
2250
2280
2770
2590
2600
3180
4350
4600
2160
1880
1470
1750
1210
1-85,
W
3850
4220
3160
2100
2350
2920
2480
2740
2660
3390
2700
1690
1950
1520
1300
980
Traffic
Ramp A,
E
130
100
90
80
90
120
110
100
150
210
280
120
80
50
60
40
demand ,
Ramp B,
E
60
90
40
30
30
30
50
40
30
100
80
100
70
110
80
20
vehicles/hour
Ramp C,
80
120
100
50
40
40
80
100
160
240
250
90
90
50
40
30
East
ent.
0
20
450
260
450
710
510
320
260
390
580
770
840
450
320
130
East
exit
0
0
190
130
260
640
710
390
190
320
450
510
580
770
770
510
South
ent.
0
0
130
70
130 .
.210
150
90
70
110
170
220
240
130
90
40
South
exit
0
0
60
40
70
190
210
110
60
90
.130
..150
170
'220
220
150
S.W. S.W.
ent. exit
0 0
10 0
240 100
140 70
240 140
370 340
270 370
170 200
140 100
200 170
310 240
410 270
440 310
240 410
170 410
70 270
E = eastbound
W = westbound
N = northbound
S = southbound
-------
Table A 2. AVERAGE SPEEDS ON ACCESS STREETS
Street
Irving Boulevard,
all sections
68th Street
Mill Street
Ramps A, B, and C
1-85, eastbound
1-85, westbound
Florida Boulevard,
sections 1 and 2
Florida Boulevard,
section 3
Lanes
4
2
2
1
3
3
4
4
Time period
All hours
All hours
All hours
All hours
All hours except
those listed
7-8 a.m.
3-4 p.m.
4-5 p.m.
5-6 p.m.
All hours except
those listed
7-8 a.m.
8-9 a.m.
9-10 a.m.
4-5 p.m.
All hours except
those listed
7-8 a.m.
8-9 a.m.
12-1 p.m.
4-5 p.m.
5-6 p.m.
All hours except
those listed
8-9 a.m.
5-6 p.m.
Average speed, mph
25
20
20
35
50
42
43
34
27
50
39
36
43
42
30
27
26
28
24
24
30
27
27
61
-------
Table A 3. DATA ON INTERSECTION DESIGNS
Intersection
Florida and
Irving Boulevards
;' < ! ' f
Florida Boulevard
and Mill Street
Irving Boulevard
and 68th Street
Approach
northbound
southbound
eastbound
westbound
:., ,:.,.•
northbound
southbound
eastbound
westbound
northbound
southbound
eastbound
westbound
.._.
Green time
to signal
cycle ratio
0.67
0.67
: 0.33
0.33
0.67
0.67
0.33
0.15
Cycles
per hr
* 40
40
Capacity,
veh/hr
600*
900
1400
1400
Estimated at half of lane capacities assuming traffic in each direction
has right of way half the time.
62
-------
Based on tenant location, the developer predicts that the building
entrances will attract the following percentages of the center's customers:
Building entrance Percent of customers entering
A 20
B 16
C 12
D 11
E 14
F 6
G 20
H 1
Meteorological data recorded at a nearby airport representative of
the shopping center location indicated that the average wind speed was
2.0 m/sec or less in 380 of the hours between 9 a.m. and 11 p.m. during
the past year. In the same time periods, wind speed was 1.0 m/sec or
less in 131 hours. Wind directions and stability classes corresponding
to the hours with wind speed - 1.0 m/sec are shown in Tables A 4 and
A 5, respectively.
Ambient CO sampling has been conducted for a two week period on the
proposed site (near the coordinates 3600, 1800). The maximum observed
CO concentration during that time was 2.5 ppm, from 6 to 7 p.m. on
Friday. The maximum 8-hour concentration during source operating hours
was 1.8 ppm, from 3 to 11 p.m. on Friday. CO sampling data are also
available for another suburban shopping center site in the same city.
The maximum 1- and 8-hour values recorded at that similar site on several
days throughout the past year are summarized in Table A 6.
63
-------
Table A 4. WIND DIRECTIONS DURING HOURS WITH
WIND SPEED OF 1.0 M/SEC OR LESS
Wind direction,
degrees from north
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
Number of annual
occurrences, hours
2
4
0
0
0
. ,. 3
' 1
• 1
0
1
2
4
3
3
0
0
3
7
9
7
14
5
4
4
4
3
3
4
7
12
8
5
2
4
1
1
Total 131
64
-------
Table A 5. NUMBER OF ANNUAL OCCURRENCES
OF WIND SPEED - 1 M/SEC BY HOUR OF
DAY AND CONCURRENT STABILITY CLASS
Hour
Beginning
9 a.m.
10
11
12 noon
1 p.m.
2
3
4
5
6
7
8
9
10
Total
Stability
ABC
2
1
1 1
2
2 1
2
1 1
2 3
3
3
8 17 0
Class
D E F
4
5
4
2
4
3
3
4
9
10
12 1
10 3
13 2
14 3
97 9 0
Total
6
6
6
4
7
5
5
9
12
13
13
13
15
17
131
Daytime stability classes estimated from Table 5, p. 35. Nighttime
stability estimated to be D if sky cover - *t, and E if < ^ because of
suburban location.
65
-------
.Table A 6. MAXIMUM 1- AND 8-HOUR CO CONCENTRATIONS
AT AN EXISTING SUBURBAN SHOPPING CENTER
Date
Jan.
Jan.
Feb.
Feb.
Feb.
Apr.
Jun.
Jun.
Jun.
Sep.
Sep.
Sep.
Oct.
Nov.
Nov.
Nov.
Dec.
Dec.
Dec.
Dec.
Dec.
Dec.
19
23
1
23
26
19
7
8
12
14
20
30
5
6
22
23
6
7
14
17
20
21
Max. 1-hour
CO, ppm*
18.0
15.5
12.1
14.6
15.8
20.1
10.9
14.5
15.1
16.0
15.5
12.8
16.5
16.5
11.7 .
19.0
16.5
16.1
21.3
26.6
23.2
27.7
Time period
1600-1700
1900-2000
1600-1700
1100-1200
1700-1800
1700-1800
2000-2100
1200-1300
1600-1700
1600-1700
1700-1800
1700-1800
1100-1200
1700-1800
1800-1900
1600-1700
1900-2000
1200-1300
1400-1500
1600-1700
1700-1800
1700-1800
Max. 8-hour
CO, ppm
8.8
7.0
7.3
6.5
9.3
12.0
6.5
8.5
9.1
9,0
8.1
7.7
8.5
9.9
6.8
11.1
7.2
9.4
10.7
12.8
13.0
12.9
Time period
1300-2100
1500-2300
1300-2100
1000-1800
1400-2200
1500-2300
1500-2300
1100-1900
1500-2300
1000-1800
1500-2300
1400-2200
1100-1900
1500-2300
1400-2200
1200-2000
1300-2100
1200-2000
1300-2100
1500-2300
1400-2200
1400-2200
Wind speeds during these hours were - 2 m/sec.
66
-------
Determine whether the traffic associated with the proposed shopping
center will cause either.CO standard to be exceeded and, if so, where
the expected violations will occur.
Solution. The steps in this solution follow those outlined in Figure 1.
Many of the initial steps shown in Figure 1 have already been completed
as part of the problem description.
1. Select time periods and alternatives for analysis. By reviewing
the traffic volume and speed data, it can be determined that the highest
emission rates in the vicinity of the shopping center will probably
occur between 5 and 6 p.m., as a result of heavy commuter traffic on
access streets. The meteorological data in Table A 5 indicate that the
most adverse conditions for dispersion (E stability) are likely to occur
from 8 to 11 p.m. Therefore, both the 5 to 6 p.m. and 8 to 9 p.m.
periods should be analyzed as possible peak 1-hour periods.
Depending on which of those two hours shows the highest CO concen-
trations, either the 12 noon to 8 p.m. or 3 p.m. to 11 p.m. 8-hour
period will be used to calculate the maximum 8-hour concentration. The
noon to 8 p.m. period has the highest traffic volumes and the 3 to 11
p.m. period has the most hours of E stability.
The peak traffic season for which the traffic data are applicable
is December, which coincides with the time of year with highest proba-
bility for low wind speeds and stable atmospheric conditions. There-
fore, no other seasonal conditions need to be analyzed. The year to be
simulated in the analysis should be 1978, the first year that the
shopping center will be open.
67
-------
2. Determine emission factors. The emission factor for movement
in the parking lot can be calculated by adjusting the value obtained
from Figure 8 for year, ambient temperature, and percent of vehicles
operating from a cold start. An average speed of 10 mph is assumed in
the parking lot.
(EF)_0 = (EF)__ (ef/55) (factor for 50° F, 30% cold start)
/O / D
= (19.0) (35/55) (1.6)
= 19.3 gm/min-veh
The correction factor of 1.6 is obtained from Table 1 of the Guidelines.
Additional calculations are required to determine emission factors
for access streets because of the different speeds for each link and the
heavy-duty vehicles present. These factors are summarized in Table A 7.
The HDV emission rate, 56.4 gm/min at 18 mph, must be calculated from
6
Supplement No. 5 of AP-42.
3. Calculate total emissions for parking lot. Emissions are
estimated from the equation:
fe .(EF) (V) (RT)
y 216,000
The emission factor, EF, was determined in step 2 above. Traffic
volume, V, is the sum of all vehicles either entering or leaving the
parking lot during the time period. According to the data in Table A 1,
the values for V in veh/hr are:
5 to 6 p.m. - 1880
8 to 9 p.m. - 2220
12 to 8 p.m. - 1856
3 to 11 p.m. - 1782
Base running time for movement into and out of a parking space has been
68
-------
Table A 7. EMISSION FACTORS FOR ACCESS STREETS
Emission factor, with
Average speed, mph Street section 8% HDV, gm/min-veh
50 (1-85 E and W, 8-9 p.m. 17.2
1-85 W, 5-6 p.m. and
12-8 p.m.)
44
35
30
28
27
25
24
20
(1-85 E, 12-8 p.m.)
(Ramps A, B, and C)
(Florida Boulevard 1, 2,
and 3, 8-9 p.m.)
(Florida Boulevard 1 and 2,
12-8 p.m.)
(Florida Boulevard 3 and
1-85 E, 5-6 p.m.)
(Irving Boulevard)
(Florida Boulevard 1 and 2,
5-6 p.m.)
(68th Street, Mill Street)
17.4
18.2
18.9
19.3
19.5
19.9
20.0
15.0
(0% HDV)
The above factors are based on 50° F temperature and 20 percent of
vehicles operating from a cold start in 1978.
69
-------
estimated at 130 seconds. There should be no extra running time due to
congestion during the 5 to 6 p.m. period because the parking lot is only
about 25 percent (960/3800) full at the beginning of the hour. Accumu-
lation in the parking lot is also less than the 80 percent full level at
which running times start increasing appreciably at 8 p.m. Therefore,
the base running time can be used for all time periods of interest, and
emissions are estimated as follows:
5 to 6 p.m. - 21.8 gm/sec
8 to 9 p.m. - 25.8
12 to 8 p.m. - 21.6
3 to 11 p.m. - 20.7
4. Distribute emissions to lanes in parking lot. Using the pro-
cedure presented in Section 3, the parking lot emissions can be allo-
cated to the 12 major traffic links identified in Figure A 1. The
calculations for this distribution and the resulting line source emission
rates for the 5 to 6 p.m. period are summarized in Table A 8. For other
time periods, emission rates by link are proportioned to total parking
lot emission rate for the period compared to the 5 to 6 p.m. period.
5. Calculate emission rates for access streets. Emissions rates
can be determined directly by use of the equation presented in Section
4.4.2, page 37. In order to obtain the emission rates per lane, the
calculated value must be divided by the number of lanes carrying traffic
in the given direction on the street. The emission rates are shown in
Table A 9.
6. Calculate lengths and emission rates for queues. Using the
two equations on page 23 and data from Table A 3, queue lengths during
70
-------
Table A 8. ALLOCATION OF PARKING LOT EMISSIONS TO TRAFFIC LINKS
Traffic
link
1
2
3
4
5
6
7
8 "
9
10
11
12
Length ,
feet
250
110
520
520
110
720
880
280
520
280
190
350
Fraction of entering or exiting
vehicles using this link
(.55) .55
(.55) (.6) .33
(.55) (.3) .16
(.55) (.6) (.6)+ (.16) (.4) (.8) (.7)+ .29
(.29) (.6) (.5) (.8) (.7)+(.29) (.3) (.6) (.2)
(.55) (.6) (.6) (.2) +(.55) (.3) (.3) +(.16) (.4) (.8) (.7) (.1)+
(.29) (.6) (.5)(.8)(.7)(.2) .10
(.55) (.6) (.6) (.4) +(.55) (.3) (.3) (.8) +(.29) (.3) (.6)+
(.16) (.4) (.8) (.7) (.3)+ (.29) (.6) (.5) (.8) (.7) (.3) .20
(.55) (.6) (.6) (.4) (.3)+(.55) (.3) (.3) (.8) (.3)+ .16
(.29) (.3)+ (.16) (.3) (.4)+ (.55) (.6) (.4) (.4) (.9) (.3)
(.29) .29
(.55) (.6) (.4) (.4) (.9)+(.29) (.6)+(.16) (.3) .27
(.16) .16
(.55) (.6) (.4) (.4)+(.29)(.6) (.5)+(.16) (.4) .20
(.55) (.6) (.4)+(.29) (.6) (.5) (.8)+(.16) (.4) (.8) .25
Weighting
factor
137
36
83
151
11
144
141
81
140
45
38
88
1095
Line source
strength, g/s-m
.0359
.0215
.0104
.0189
.0065
.0131
.0104
.0189
,0176
.0104
.0131
.0163
Emission rate by
lane, gm/sec-m
5-6 p.m. ,
south or
east lane
.0078
.0094
.0059
.0106
.0033
.0061
.0055
.0106
.0091
.0059
.0069
.0082
5-6 p.m. ,
north or
west lane
.0101
.0121
.0045
.0083
.0032
.0070
.0049
. 0083
.0085
.0045
.0062
.0081
-------
Table A 9. EMISSION RATES BY LANE FOR ACCESS STREETS
Street
Irving 1
Irving 2
Irving 3
68th Street
Florida 1
Florida 2
Florda 3
Mill Street
1-85
Ramp A
Ramp B
Ramp C
Direction
eastbound
westbound
eastbound
westbound
eastbound
westbound
northbound
southbound
northbound
southbound
northbound
southbound
northbound
southbound
eastbound
westbound
eastbound
westbound
eastbound
eastbound
SE-bound
NW-bound
Emission
5-6 p.m.
.0054
.0019
.0049
.0020
.0035
.0014
.0011
.0016
.0079
.0101
.0087
.0101
.0048
.0063
.0016
.0006
.0115
.0032
.0015
.0004
.0013
.0013
rate for
8-9 p.m.
.oois
.0031
.0014
.0024
.0014
.0017
.0004
.0005
.0028
.0037
.0029
.0042
.0023
.0026
.0008
.0005
.0017
.0018
.0003
.0006
.0003
.0003
each lane,
12-8 p.m.
.0032
.0019
.0030
.0018
.0021
.0013
.0010
.0011
.0055
.0058
.0056
.0059
.0032
.0036
.0010
.0008
.0041
.0030
.0008
.0003
.0007
.0007
gm/sec-m
3-11 p.m.
.0030
.0021
.0028
.0019
.0010
.0014
.0008
.0009
.0043
.0054
.0046
.0055
.0028
.0033
.0010
.0007
.0035
.0024
.0007
. 0004
.0006
.0006
72
-------
peak traffic hours can be estimated. For signalized intersections,
traffic volume (V) should be per lane. For the significant queues
(greater than 25 meters in length), emission rates over the queue length
are then estimated with the equations in Section 4.4.3. These calcula-
tions are summarized in Table A 10.
7. List all line sources, record the grid coordinates of their
end points, and obtain other dimensions. As indicated in the previous
steps of this analysis, there will be 12 access street links, 12 major
traffic aisle links in the parking lot, and eight queues. End point
coordinates are scaled from Figure A 1 and other dimensions should be
obtained from the developer and/or a site visit. These data are pre-
sented in Table A 11.
8. Select receptor sites. Receptor sites should be specified at
locations near the highest line source emission rates, in directions
that are normally downwind of these sources during the periods with
adverse meteorology, and at points where the general public is likely to
have access for 1- or 8-hour periods. With these criteria, receptors on-
the east side of Florida Boulevard are likely to have the highest CO
concentrations in the vicinity of the shopping center. Due to the
right-of-way areas on both sides of 1-85, no potential receptor sites
can be found near this highway even though it has high emission rates.
For this shopping center, the traffic aisles in the lot are shown
to have approximately the same emission rates as the access streets.
Therefore, receptor sites should be specified at reasonable locations in
or adjacent to the lot. One receptor should be established near the
main (east) gate of the shopping center because of the potential queues
73
-------
Table A 10. QUEUE LENGTHS AND EMISSION RATES
Intersection
Florida and
Irving Boulevards
Florida Boulevard
and Mill Street
Irving Boulevard
and 68th Street
Approach
northbound
southbound
eastbound
westbound
northbound
southbound
eastbound
westbound
northbound
southbound
eastbound
westbound
Queue length , meters
5-6 p.m.
60
77
80
23
67
82
30
14
1
1
109
2
8-9 p.m.
29
43
24
28
29
40
52
10
0
3
30
2
Emission rate, gm/sec-m
5-6 p.m.
.0084
.0085
.0149
.0136
.0085
.0085
.0136
• —
__
—
.0425
8-9 p.m.
.0068
.0078
.0136
.0136
. 0068
.0078-:
.0142-
—
__
—
.0425
—
74
-------
Table A 11. CONFIGURATION OF LINE SOURCES
Line source
Access streets
Irving 1
Irving 2
Irving 3 .
68th Street
Florida 1
Florida 2
Florida 3
Mill Street
1-85
Ramp A
Ramp B
Ramp C
Parking lot aisles
1
2
3
4
5
6
7
8
9
10
11
12
Queues
F lor ida/I r ving-
northbound
southbound
eastbound
westbound
Florida/Mill-
northbound
southbound
eastbound
Irving/68th-
eastbound
End point coordinates, ft.
Xl Yl Xz Yz
2500
3358
4444
3358
4444
4444
4444
4444
2500
4018
4505
4500
4174
4067
4174
4067
4067
3358
3358
3358
3358
3877
3877
4067
4462
4426
4413
4475
4462
4426
4399
3343
1119
1119
1119
700
700
1119
1782
1782
2650
2557
2217
2548
1776
1776
1776
1776
2302
2302
1425
1119
1425
1119
1425
1425
1092
1147
1105
1133
1751
1801
1763
1105
3358
4444
5000 -
3358
4444
4444
4439
5000
5000
4340
5125
4668
4444
4174
4174
4067
4174
4067
3358
3358
3877
3877
4067
4067
4462
4426,
4151,
4550
4462
4426,
4300
*
2985
1119
1119
1119
1119
1119
1782
3200
1782
2650
2443
2565
2338
1776
1776
2302
2302
2302
2302
2302
1425
1425
1425
1425
1776
*
895,
1400
1105
1133
*
1531,
2070
1763
1105
Width of
road., m
16.5
16.5
15.9
7.2
18.9
18.9
27.4
7.1
45.7
4.2
4.2
8.4
15.3
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
4.0
4.0
4.1
4.1
4.0
4.0
3.7
4.1
Width of
median, m
0
0
0
0
3.0
3.0
3.0
0
17.7
0
0
0
0.7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Number of
lanes
4
4
4
2
4
4
6
2
6
1
1
2
4
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
For 5 to 6 p.m.
other hours.
period; queue length and end point are different for
75
-------
at this exit. The highest queue emission rate is at the eastbound
Irving Avenue approach to the intersection with 68th Street. Therefore,
a receptor should also be specified at the nearest reasonable location
to this intersection approach.
The probable critical receptor sites at this proposed development
are shown in Figure A 1. Their grid coordinates, summarized in Table
A 12, have been calculated based on the street dimensions presented in
Table A 11 and reasonable distances away from the curbs.
9. Specify wind speed, mixing height, and stability class for
each time period. Based on the data in Tables A 4 and A 5, wind speeds
of 1.0 m/sec or less occur in conjunction with most wind directions and
during all hours that the shopping center will be in operation. There-
fore, this wind speed should be used in the analysis for all alterna-
tives. As discussed above, D stability class is the most adverse
condition likely during the 5 to 6 p.m. period and E stability is the
4
most adverse for the 8 to 9 p.m. period. Reference to AP-101, Figure
7, indicates that the mean winter afternoon mixing height for the
metropolitan area in which the shopping center is located is 1000
meters. Mixing height for the 8 to 9 p.m. period is estimated to be
midway between the morning (minimum) mixing height of 400 meters and the
afternoon mixing height. Thus, the approximate 8 to 9 p.m. mixing
height is 700 meters.
io. Select wind directions. Wind directions which put the line
sources and queues upwind of the receptors plus wind directions nearly
parallel to the major line sources should be considered. These
76
-------
Table A 12. RECEPTOR SITE LOCATIONS
Receptor site
Coordinates, ft.
x y
Height, m
R 1
R 2
R 3
R 4
R 5
R 6
4483
4498
4505
4350
4200
3275
1080
1723
2122
1748
1748
1086
2
2
2
2
2
2
77
-------
conditions can both be met for the five receptor sites by analysis of
three different wind directions—200 , 290 , and 330 .
11. Code input data and run HIWAY model. In order to model the
alternatives described above, 12 different data sets must be run: four
different emission rates times three wind directions. Three different
computer runs of the program will be made, one for each wind direction.
12. Tabulate and total the model-predicted concentrations at each
receptor. The contribution from each of the 32 sources in each of the
12 alternatives can be recorded in a tabular format such as presented in
Table 7, page 51. The subtotals (minus background) at the six receptor
sites under each alternative are summarized in Table A 13.
13. Determine persistence factor for 8 hours. Using the equation
presented in the Guidelines, the persistence factor can be calculated as
follows:
_ (Max. 8-hr average concentration) f 1
(Max. 1-hr concentration with wind \V
speed < Z m/sec) 8
where V = traffic volume demand during hour in which highest
CO concentration was observed
V = average hourly traffic volume demand during 8-hour
period in which highest CO concentrations were
observed
Due to lack of concurrent traffic and CO data at the similar site, it is
assumed that average traffic demand during the 8 hours is the same as
during the hour with highest CO concentration, or V /V = 1.0. With
J. o
this assumption, the highest observed persistence factor during the year
of data shown in Table A 6 is 0.603. The model-predicted concentrations
using average 8-hour traffic volumes are multiplied by this empirical
factor to estimate maximum 8-hour CO concentrations.
78
-------
Table A 13. SUBTOTALS OF MODEL-PREDICTED CONTRIBUTIONS FROM 32
LINE SOURCES UNDER DIFFERENT ALTERNATIVES
Alternative
5-6 p.m. ,
5-6 p.m. ,
5-6 p.m. ,
8-9 p.m. ,
8-9 p.m. ,
8-9 p.m. ,
12-8 p.m. ,
12-8 p.m. ,
12-8 p.m. ,
3-11 p.m.
3-11 p.m.
3-11 p.m.
winds
winds
winds
winds
winds
winds
winds
winds
winds
, winds
, winds
, winds
200°
o
290
o
330
200°
o
290
330°
200°
rt
290°
330°
200°
O
290°
330°
Unadjusted
1
30.
28.
27.
14.
21.
20.
22.
18.
18.
18.
24.
22.
0
2
7
6
1
4
3
0
6
8
2
3.
CO concentration
2 3
27.8
36.2
22.4
18.1
31.2
17.3
16.6
34.2
14.9
22.2
28.6
20.4
24
14
13
22
10
6
18
10
8
22
10
9
.8
.8
.9
.1
.0
.3
.8
.4
.0
.9
.4
.9
at receptor
4 5
4.4
29.7
22.3
5.3
34.9
23.6
2.8
29.2
20.8
4.9
29.4
20.1
3.
10.
17.
3.
17.
17.
2.
10.
16.
3.
14.
14.
site
1
6
6
9
6
7
8
4
1
4
2
2
, ppm
6
neg.
56.1
24.1
neg.
23.4
22.5
neg.
31.2
23.0
neg.
31.3
22.7
79
-------
14. Estimate background concentrations. Background values for the
proposed site can be obtained from the limited sampling data at the site
plus additional data from a non source oriented CO sampling station,
using approach number 3, page 52. The estimated maximum background
values are:
(2.5) (4.4) „ n
. - = 3.8ppm
8-hour xb = '2.1' = 2'1 Ppm
15. Summarize predicted CO concentrations and compare to NAAQS.
After the adjusted 8-hour concentrations have been calculated using the
persistence factor and appropriate background concentrations have been
added, the resulting values can be compared to the NAAQS. The data
shown in Table A 14 indicate that the 1-hour air quality standard of
35.0 ppm would be exceeded under certain conditions at three of the
receptor sites, generally as a result of emissions from nearby queuing
traffic lines. However, violation of the 8-hour standard would be more
widespread, with concentrations above 9.0 ppm occurring at all six
receptor sites, during both 8-hour time periods evaluated, and with
prevailing winds from any of three directions.
80
-------
Table A 14. PREDICTED MAXIMUM 1- AND 8-HOUR CO
CONCENTRATIONS AT PROPOSED SITE
Alternative
1-hour
5-6 p.m. ,
5-6 p.m. ,
5-6 p.m. ,
8-9 p.m. ,
8-9 p.m. ,
8-9 p.m. ,
8 -hour
12-8 p.m.,
12-8 p.m.,
12-8 p.m. ,
3-11 p.m.
3-11 p.m.
3-11 p.m.
winds
winds
winds
winds
winds
winds
winds
winds
winds
, winds
, winds
, winds
200°
290°
330°
200°
Q
290
o
330
200°
290°
330°
200°
290°
330°
CO
1
33
32
31
18
24
24
15
13
13
13
16
15
.8
.0
.5
.4
.9
.2
.5
.1
.3
.4
.7
.5
concentration at
2 3
31.
40.
26.
21.
35.
21.
12.
22.
11.
15.
19.
14.
6
0
2
9
0
1
1
7
1
5
3
4
28.6
18.6
17.7
25.9
13.8
10.1
13.5
8.4
6.9
15.9
8.4
8.1
receptor
4
8.
33.
26.
9.
38.
27.
3.
19.
14.
5.
19.
14.
2
5
1
1
7
4
8
7
6
1
8
2
site,
5
6.9
14.4
.21.4
7.7
21.4
21.5
3.8
8.4
11.8
4.2
10.7
10.7
ppm
6
3.8
59.9
27.9
3.8
27.2
26.3
2.1
20.9
16.0
2.1
21.0
15.8
81
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 450/3-75-072
2.
3. RECIPIENT'S ACCESSION- NO.
4. TITLE AND SUBTITLE
5. REPORT DATE
Application of the HIWAY
Analysis: User's Manual
Model for Indirect Source
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Kenneth Axetell, Jr.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Kenneth Axetel1 , Jr.
Engineering Consultant
808 South Fairfax
Alexandria, Virginia 22314
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
5-02-3670A
12. SPONSORING AGENCY NAME AND ADDRESS
U. S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Research Triangle Park, N. C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A procedure for characterizing emissions of carbon monoxide occurring within
parking lots as line sources of pollution is described. A line source dispersion
model (HIWAY) is then used to illustrate an approach for estimating the maximum
impact of emissions from vehicles in parking lots on nearby 1- and 8- hour ambient
concentrations of carbon monoxide.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Air Pollution
Airborne Wastes
Atmospheric Contamination Control
Vehicular Traffic
Atmospheric Models
Carbon Monoxide
HIWAY Model
Parking Lots
Indirect Sources
13/02
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
85
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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