EPA-600/4-77-016
April 1977
Environmental Monitoring Series
       DIURNAL VARIATIONS  IN TRAFFIC FLOW  AND
                CARBON MONOXIDE  CONCENTRATIONS
                                   Environmental Sciences Research Laboratory
                                        Office of Research and Development
                                       U.S. Environmental Protection Agency
                                   esearch Triangle Park, North Carolina  27711

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                RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate funher development and  application of en-
vironmental technology.  Elimination of traditional grouping  was  consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

      1.  Environmental  Health Effects Research
      2.  Environmental  Protection Technology
      3.  Ecological Research
      4.  Environmental  Monitoring
      5.  Socioeconomic Environmental Studies
      6.  Scientific and Technical Assessment Reports (STAR)
      7.  Interagency Energy-Environment Research and Development
      8.  "Special" Reports
      9.  Miscellaneous Reports

This report  has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and  instrumentation for the identification and quantification of environmental
pollutants at the lowest conceivably significant concentrations. It also includes
studies to determine the ambient concentrations of pollutants in the  environment
and/or the variance of pollutants as a function of time or meteorological factnrc
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia  22161.

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                                           EPA-600/4-77-016
                                           April  1977
    DIURNAL VARIATIONS IN TRAFFIC FLOW
    AND CARBON MONOXIDE CONCENTRATIONS
            Gerard A. DeMarrais
    Meteorology and Assessment Division
Environmental Sciences Research Laboratory
    Research Triangle Park, N.C.  27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
    OFFICE OF RESEARCH AND DEVELOPMENT
   U.S. ENVIRONMENTAL PROTECTION AGENCY
   RESEARCH TRIANGLE PARK, N.C.  27711

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                               DISCLAIMER
      This report has been reviewed by the Office of Research and Develop-
ment, U.S. Environmental Protection Agency, and approved for publication.
Mention of trade names or commercial products does not constitute endorse-
ment or recommendation for use.
      Mr. DeMarrais is a meteorologist in the Meteorology and Assessment
Division, Environmental  Sciences Research Laboratory, Environmental
Research Center, Research Triangle Park, N.C.  27711.  He is on assign-
ment from the National Oceanic and Atmospheric Administration, U.S.
Department of Commerce.
                                   11

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                                 ABSTRACT
   Traffic count and carbon monoxide (CO) data for January and July from
three states are compared in order to reveal any diurnal variations in the
two measurements.  The diurnal patterns for the 18 traffic count stations
indicate that there are average patterns of traffic flow that are represen-
tative of all stations for periods of one month.  Comparisons of data for
the 36 CO monitoring stations show correlations which vary from large posi-
tive to large negative.  However, eliminating a few monitoring stations
which show relatively poor correlations yields groups within each state
that have consistent patterns.  The diurnal variations in CO concentrations
are not well correlated with traffic patterns.  Part of the poor correla-
tion appears to be due to the diurnal variations in vertical mixing and
wind speeds and part to the exposures and locations of the sampling
instruments.
                                     iii

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                                CONTENTS
Abstract	iii
Figures	    vi
Tables	viii
     1.  Introduction 	     1
     2.  Conclusion	     2
     3.  Methodology	     3
              Traffic count data	     3
              Carbon monoxide concentrations	     3
              Traffic densities versus concentrations 	     4
              Analyses of data	     4
     4.  Results	     5
              Traffic counts	     5
              CO concentrations 	     6
              Intermonth correlation of CO concentrations 	     9
              Comparison of traffic and CO'concentrations 	     9
     5.  Summary	    11
References	    13

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                                   FIGURES


Number                                                                  Pa9e

  1   Diurnal  variation  in  percentage  of 24-hour traffic flow for
       each hour at 18  stations  during  January	15-16

  2  Diurnal  variation  in  percentage  of 24-hour traffic flow for
       each hour at 18  stations  during  July	17-18

  3  Diurnal  variation  in  average traffic,  18 stations (vertical
       lines show ranges of +_ 1  standard deviation	     19

  4  Diurnal  variation  in  CO concentrations,  Colorado stations,
       January (numbers in parentheses  are  average hourly concent-
       rations in ppm)	     20

  5  Diurnal  variations in CO concentrations, Colorado stations,
       July (numbers in parentheses are average hourly concen-
       tration? in ppm)	     21

  6  Diurnal  variations in CO concentrations, Maryland stations,
       January (numbers in parentheses  are  average hourly concent-
       in ppm)	     22

  7  Diurnal  variations in CO concentrations, Maryland stations,
       July (numbers in parentheses are average hourly concent-
       rations in ppm)	„     23

  8  Diurnal  variations in CO concentrations, New Jersey stations,
       January (numbers in parentheses  are  average hourly concent-
       rations in ppm)	„  24-25

  9  Diurnal  variations in CO concentrations, New Jersey stations,
       July (numbers in parentheses are average hourly concent-
       rations in ppm)	26-27

 10  Diurnal  variations of CO concentrations, composite for six
       Colorado stations (vertical lines show ranges of + 1
       standard deviation)	~~	    28

 11  Diurnal  variation  of CO concentrations, composite for selected
       Maryland stations (vertical lines show ranges of +_ 1
       standard deviation)	~~	    29
                                     VI

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                                   FIGURES


Number                                                                  Page

 12  Diurnal variation of CO concentrations, composite for selected
       New Jersey stations (vertical lines show ranges of +_
       standard deviation) 	  30

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                                     TABLES

Number                                                                       Pa9e

  1   Types and Locations of Traffic Counting  Stations 	   31

  2  Description of CO Monitoring Sites	32-36

  3  Correlations of Less Than 0.90 in Diurnal  Variations in Traffic
       for January	   37

  4  Correlations of Less Than 0.90 in Diurnal  Variations in Traffic
       for July, 18 Stations3   .......  	   38

  5  Correlation Between January and July Diurnal  Variations in
       Traffic at Individual Stations8	   39

  6  Bivariate Correlations of Diurnal Variations  in CO Concentrations
       at Colorado Stations, January	   40

  7  Bivariate Correlations of Diurnal Variations  in CO Concentrations
       Colorado Stations, July	   41

  8  Bivariate Correlations of Diurnal Variations  in CO Concentrations
       Maryland Stations, January ..... 	   42

  9  Bivariate Correlations of Diurnal Variations  in CO Concentrations,
       Maryland Stations, July	   43

 10  Bivariate Correlations of Diurnal Variations  in CO Concentrations
       at 13 Selected New Jersey Stations, January	   44

 11  Bivariate Correlations of Diurnal Variations  in CO Concentrations
       at Five Selected New Jersey Stations,  January. 	   45

 12  Bivariate Correlations of Diurnal Variations  in CO Concentrations
       at 13 Selected Stations July .	   46

 13  Bivariate Correlations of Diurnal Variations  in CO Concentrations
       at 6 Selected New Jersey Stations, July	   47

 14  Correlations of January and July Diurnal Variations of  CO
       Concentrations 	   48

 15  Correlations of Diurnal Variations, January and July  	   49


                                      v i i i

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                            1.  INTRODUCTION


     The major source of man-made carbon monoxide (CO) in the atmosphere is
the automobile.  In evaluating the CO air pollution problem, attempts have
been made to correlate CO concentrations with traffic density (1-5).   The
findings of a short study (T) conducted in ar. unidentified city in the north-
eastern United States during the summer of 1959, and a year-long study
(2) in 1964-1965 in Frankfurt/Main, Germany, found that the correlations
between CO concentrations and traffic density were relatively high.   A
more recent study by the author (3) using data for 1973 from the Baltimore
area showed correlations less than 0.50 between hourly CO concentrations
and traffic counts.  Since the results of this third study were inconsistent
with those of the two earlier studies a large volume of CO concentration
and traffic count data were sought.  The objective was to determine  the
diurnal patterns of CO concentration and traffic at a number of sites
and then compare the patterns.  Meteorological phenomena are discussed
only when they obviously caused an anomaly or when they did not appear
to be the cause of a discrepancy.  A better understanding of the combined
effects of traffic and meteorology on CO concentrations is being sought
in a separate study in which wind data from the individual monitoring sites,
area mixing height data, CO concentrations from four Maryland sites,  and
local traffic counts are being analyzed.
     To minimize the possibility of differences in CO concentrations  being
attributed to differences in sampling procedures or times, new data,  which
were collected in a standard manner, were sought for this study.  Each
state air pollution control agency is now required by Federal regulations
(6) to continuously collect hourly CO data at stations within its boundary
according to a standard procedure.  Highway agencies throughout the  United
States also collect hourly traffic data at a number of permanent counting
stations.  In order to determine whether there might be differences  in
diurnal patterns of CO concentrations between states or possibly between
regions, data from the air pollution control agencies and highway depart-
ments of the States of Colorado, Maryland, and New Jersey were obtained.
The National Air Data Bank (NADB) of the U.S. Environmental Protection
Agency, (EPA), which stores air pollution data gathered from throughout
the United States, provided the carbon monoxide information for the  three
states considered in the study.

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                             2.   CONCLUSIONS


     Traffic at 18 sites,  which  ranged from resorts in Colorado to the
beltline in Baltimore, showed relatively consistent patterns in diurnal
variations.  By comparison,  the  diurnal  variation in CO concentrations
at 36 sites showed large differences and were not well-correlated with
traffic patterns.   Much of the poor agreement was due to:   1)  diurnal
variations in vertical mixing and wind speed and 2) the differences in
the locations of the air sampling intakes with regard to sources (tail-
pipes).  The poor agreement due  to intake locations will be eliminated
when agencies comply with the U.S. Environmental Protection Agency
guidelines (12) for siting CO instruments; more readily comparable CO
data will then be available for  correlating with traffic and meteorology

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                          3.  METHODOLOGY

TRAFFIC COUNT DATA

     The traffic data collection programs of Colorado,  Maryland,  and  New
Jersey differ slightly, although all three states use automatic counters  at
permanent stations.  In Colorado, data are continuously collected for
opposing lanes of traffic and the total  count is listed for  each  hour.  In
Maryland, the traffic for each direction is recorded separately
on Interstate highways, but only the total is recorded  on  other roads.
In New Jersey,  traffic is recorded for one direction at a time;  every
week or two the counters are moved from one side of the road to the other.
     Hourly traffic counts for Colorado (7) were obtained  for four urban
stations in the Denver area, an urban station in Pueblo, and two  stations
in resort areas.  Of the 39 available Maryland stations (8), the  following
were selected:  two on major highways between Baltimore and  Hashington,
two on the beltline around Baltimore, two near a small  city, one  at an
ocean resort, and one at a mountain resort.  The available New Jersey
data (9) consisted of one station on a truck route in Jersey City, one
on a highway in a resort city, and one on a road on the outskirts of  a
small city.  A brief description of each station is given  in Table 1.

CARBON MONOXIDE CONCENTRATIONS

    The CO data collection programs of the three states are  similar
because all states are required to summarize the data in an  identical
format for submission to the NADB.
    Hourly CO concentrations for Colorado were obtained for  three stations
in the downtown Denver area and three in areas that were 5 to 6 miles from
downtown Denver.  In Maryland, data were obtained for one  site in Baltimore;
four in Washington, DC, suburbs; four in Baltimore suburbs;  and one in
Cumberland in the northwest part of the state.  New Jersey stations
included:  eight in the metropolitan New York area--Bayonne, Elizabeth
(Broad St.), Elizabeth (Turnpike), Hackensack, Jersey City,  Newark,
Paterson, and Perth Amboy; three in coastal areas--Asbury, Atlantic City,
and Toms River; two in the Philadelphia-Camden conplex--Camden (N. 6th  St.)
and Camden (Copewood); one in Trenton; and six in smaller  cities  and  towns
throughout the state—Burlington, Camden (Ancora), Freehold, Paulsboro,
Penns Grove, Phillipsburg, and Somerville.  A brief description of each
station is shown in Table 2.  The intakes (third column of Table  2) for
the sample air are located from 10 to 17 feet above the ground over a
trailer or out over city streets at a majority of the stations.
    The Colorado and Maryland networks are predominantly trailer-type
operations, but most of the New Jersey data are collected  by instruments
exposed over city streets.  The intakes of the New Jersey  instruments

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are generally much closer to the traffic, and the stations except Camden 3
(Ancora) are in metropolitan or urban areas.   Another major difference in
intake exposures is that a majority of the Maryland stations have metal
boxes (approximately (I1 x I1  x 2') covering  the intakes (opening is
toward the ground).  Thus there may be large  differences in concentrations
patterns because:   1) New Jersey collects at  sampling sites which for the
most part are in confined street canyons  very close to the traffic;
2) Colorado collects air samples over trailers parked in open lots some
distance from traffic;  and 3)  Maryland uses trailers in open lots and
restricts the free air  flow, at most stations, with metal  boxes.

TRAFFIC DENSITIES  VERSUS CONCENTRATIONS

     In each of the three states,  no permanent counting station is closer
than 2 miles to a  CO monitoring station.   Because high CO  concentrations
are localized phenomenon (10), data from  individual  traffic count sites
and CO monitoring  stations are not directly comparable.  However, pre-
dominant statewide patterns of the diurnal  variations of CO concentrations
and traffic density can be compared.

ANALYSES OF DATA

     The distribution of traffic count and  CO monitoring stations provides
for an analysis of spatial  similarities and differences.  For seasonal
comparisons January and July data  are examined.   To indicate how  the
absolute values differed among the stations,  the average daily traffic
(ADT) for each counting station and the average hourly CO  concentration
in parts per million (ppm)  for each monitoring station are shown  in
graphical presentations.  Each hourly value is plotted as  a point at the
midpoint of the observation period.  All  the  data were normalized before
being graphically  presented or analyzed;  all  hourly values were converted
to percentage of the 24-hour total.

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                              4.  RESULTS

TRAFFIC COUNTS

    The diurnal variations of traffic during January for the 18 counting
stations are shown in Figure 1.  A consistent feature of the distribution is
the occurrence of a traffic peak late in the afternoon.  In addition, two-
thirds of the stations show pronounced morning peaks.  All stations have
marked increases in volume in the early morning, and a few show the increase
persisting until the afternoon peak is attained.  All stations also show a
steep, generally steady decline in traffic density between the afternoon
peak and midnight.  All three of the mountain resort stations (C7,  C39,  M35)
are single-peak stations, but both ocean resorts (M17, NJ208) show  two
marked peaks, similar to those found in the heavy traffic stations  (C22,
M31, M32) in metropolitan areas.  Only 30 to 40 percent of the total  24-
hour traffic is counted before noon at all of the stations.  The ADT  ranges
from 1,137 at a mountain resort in Colorado (C39) to 94,818 in downtown
Denver (C22).
    In July, (Figure 2), all stations except one (M25) experience greater
ADT than they do in January (see Figure 1).  The average increase in  volume
from January to July at the 13 nonresort stations in 19 percent; whereas, at
the five resort stations it is 200 percent.  The ADT during July for  all
stations ranges from 5,796 to 115,812.  Although features of the January
distribution reoccur in July, they appear in a modified form.  The  peak
hourly flow still occurs in the afternoon at all stations except Ml7  but
is not as marked as in January.  At most stations, the morning peak is
also lower.  The sharp increase in traffic in the morning and the steep
decline during the evening (6 PM to 9 PM) are almost as prominent as  they
were in January.  At all of the resort stations except NJ208, the traffic
count is high from late in the morning until 4 to 5 PM.  Overall, the
general traffic patterns at the 13 nonresort sites do not vary much
between January and July.
    To examine the interrelationships among the traffic count distributions,
the data in Figures 1 and 2 were statistically analyzed.  The bivariate
correlation analyses of the January data showed that 75 percent of  the
paired stations were correlated at the 0.90 level or greater.  Correlations
that were less than 0.90 are shown in Table 3.  The lower valued correla-
tions are associated with the New Jersey sites and the resort stations.
Even the poorest correlation (0.78 between MJ409 and C39) means that
more than 60 percent of the variance at the resort in Colorado can  be
explained by the variations at a suburban site in New Jersey.  It is
concluded, therefore, that traffic patterns are similar among these
18 diverse stations.  The bivariate analyses of the July data showed
that 80 percent of the correlations were 0.90 or greater.  Table 4  shows
the correlations that were less than 0.90.  The lower-valued correlations
generally occur where heavy urban traffic is compared with resort traffic

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and with the suburban traffic of the small  New Jersey city.   The poorest
correlation in July (0.76)  occurs between  the mountain resort in Maryland
and an interstate highway location in Denver.   In this case,  58 percent
of the variance at one place is  explained  by the variation at the other.
Again, traffic patterns appear fairly consistent among the 18 stations.
The seasonal variations at  the individual  stations  were checked by
comparing the diurnal variations of January and July.   The results are
shown in Table 5.  The poorest correlation  is 0.87  and a majority of
the correlations are 0.97 or more.  Thus, winter and  summer  patterns are
very similar for these stations.
    Because the statistical  results indicate that the  monthly average daily
traffic pattern varies little from station  to station, the data for the 18
stations were combined.  The composite traffic patterns for  January and
July, including standard deviations, are quite similar (see  Figure 3).
The standard deviations indicate that the  greatest  spatial variations occur
around the time of the morning peak traffic flow in both months and the
afternoon peak flow in January.

CO CONCENTRATIONS

     The results of the CO  analyses showed  more intrastate than interstate
consistency.  The results for each state,  therefore,  are considered sepa-
rately.
     The January diurnal variations of CO  concentrations for  the six stations
in Colorado (Figure 4) show a fairly consistent pattern.  There are two
peaks in concentrations that approximately  coincide with times  of peak
traffic flow (see Figure 3).  The average  hourly concentrations, shown
in parentheses in the figure, range from 3.1  to 7.8 ppm.  The morning
peak in concentrations is as high or higher than the  afternoon  peak at
all stations.  At half of the stations, the midday  concentrations and the
lowest nighttime concentrations  are very similar.   This phenomenon of
concentrations being the same at night and  midday was  common  (it occurred
at Maryland and New Jersey  stations) and is attributed to the diluting
capacity (vertical mixing and wind speed)  of the atmosphere.   Vertical
mixing spreads emissions through a surface-based layer which  varies in
depth from a minimum during the  nighttime  hours to  a  maximum  in late
afternoon or evening and wind speed transports and  spreads emissions down-
wind and is also at a minimum at night and  maximum  in  the afternoon or
evening.  During midday the diluting capacity is near  the maximum so the
concentrations are reduced  to low values.   There are  seasonal  and spatial
differences in these mixing height and wind speed patterns  (11) but the
timing of the maximum and minimum dilution  change only a little.  The
cross-relation analyses of  station data show that the  Wei by  station is
the least correlated with other  stations (Table 6).  Excluding  Welby,
all the correlations are 0.61 or better.   (By comparison, the poorest
correlation in January among the seven traffic counting stations in
Colorado was 0.85.)
     The July diurnal variations of CO concentrations  for the Colorado
stations, (Figure 5) show no consistent pattern.  The average hourly
concentrations, except at Colfax, are at most half  of the January levels,
ranging from 1.1 to 3.9 ppm.  Although there is a peak in concentration

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at 6 to 7 AM at five of the six stations, the afternoon concentration
peak corresponding to the peak traffic hours is seen at only three
stations.  The morning peaks in July are displaced to slightly earlier
times than those of January (Note that these CO concentrations are
plotted at standard times and in July daylight times were observed).
At five stations, marked peaks occur between 8 and 11 PM.  These time
delayed peaks in concentrations in July were common (they occurred at
Maryland and New Jersey stations) and are attributed to meteorological
causes; the principal causes of dilution, vertical mixing and wind
speed, are at their maximums (11) at the time of peak traffic flow and
do not subside until evening.  At Julian, the concentration is consider-
ably Tower in the middle of the day than it is at night, but the reverse
is true at Arvada, Broadway, Colfax, and Huron.  The correlations for
July (see Table 7) show that the distributions are much less correlated
than they were in January, with most correlations less than 0.60 and
many of these negative.  Since the traffic patterns are fairly consistent
(Table 4) one might suspect that variations in meteorology (mainly
vertical mixing and wind speed) might cause these relatively poor
correlations.  However it is difficult to believe that differences
in the meteorology in such a small area (all of the Colorado stations
are within six miles of downtown Denver) could be large enough to
account for inconsistent correlations.
     In January diurnal variations in CO concentrations for the 10
stations in Maryland (Figure 6) are very similar to the January variations
in Colorado.  There are two peaks in concentrations that approximately
coincide with the peaks in traffic flow.  The average hourly concen-
trations, which range from 0.9 to 3.7 ppm, are considerably less than
those for Colorado.  At all but one of the sampling sites, the morning
peaks are markedly higher than the afternoon peaks and the lowest
daytime concentrations are very similar to those at night.  As shown
in the figure, the distributions at Riviera Beach are obviously incon-
sistent with those from the remaining nine stations and, therefore,
are rot included in the summary statements that follow.  Results of
the regression analyses of these January data (Table 8) show that the
variations for Riviera Beach are very poorly correlated with the
variations for the other stations.  In general, the correlations among
the other nine stations are high and comparable to the January correla-
tions found in Colorado.
     The July variations in CO concentrations for the Maryland stations
(Figure 7) show a fairly consistent pattern when the results from Riviera
Beach are not considered.  The average hourly concentrations, which range
from 0.5 to 2.9 ppm, are generally slightly lower than they were in
January.  The morning peaks are displaced to earlier times (the morning
rush hour is earlier because of daylight saving time) and are smaller
than they were in January.  The afternoon peaks are displaced to much
later times, generally 8 to 10 PM; there is very little indication of
a peak in CO concentrations occurring at the time of peak traffic flow.
At seven of the nine stations, the afternoon peak concentrations are
higher than the morning peak concentrations; during January the peaks
were higher in the morning.  At a majority of the stations, the midday
concentrations are lower than the lowest concentrations that occur

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at night.  The bivan ate analyses of the July data (Table 9)  shew
similar results to those ^cr January.   Piviera Beach data are, again,
very poorly correlated.   The correlations among the other nine stations
are comparable tc those for January at the Maryland stations  but are
generally greater than the correlations shown in July in Colorado.
     The January diurnal variations in CO concentrations for  the 20
stations in New Jersey (Figure £) are  not similar to the January varia-
tions for Colorado and Maryland.   Close inspection indicates  that
increases in concentration do occur at the times of peak traffic volumes
at most stations.  These January  peaks are not as pronounced  as  those
for Colorado and Maryland, however. The average concentrations  range
from 1.0 to 8.7 ppm and span the  relatively high values  of Colorado
and low values of Maryland.  The  Maryland data for January consistently
showed that the highest concentrations occurred during the morning  peak
traffic flow; whereas, this phenomenon occurs at only six stations  in
New Jersey.  Again in  contrast to the  Maryland data, the New  Jersey
data do not show similar values in the middle of the day and  the early
morning.  The regression analyses demonstrate that about two-thirds of
the stations correlate reasonably well  (all  pairings were 0.72 or greater.
Table 10 lists the stations showing correlations of 0.72 or greater while-
Table 11 lists trhe 5 stations (in the  vertical)  and values associated
with poorer correlations (in Figure 8  the stations showing correlations
of 0.72 or greater are marked with an  asterisk and the poorer with  two
asterisks).  Note that four of the five stations showing poorer
correlations also show relatively low  average hourly concentrations.
     The variations of CO concentrations for the New Jersey stations
(Figure 9) show less consistency  in July than in January and  are thus
similar to the Colorado and Maryland data.   The values of average hourly
concentration range from 1.3 to 7.3 ppm, a slightly lower average concen-
tration than in January.  It is interesting that 10 stations  show increases
and 10 show decreases  in average  hourly concentration from January  to
July.  Features that do stand out in the July diurnal  variations are:
1) at a majority of the stations, there is an increase in early  morning
concentrations that appears associated with the morning  peak  traffic flow;
2) at seven stations,  the lowest  concentrations occur in the  middle of
the day; 3) no increase in concentration cccurs at the time of increased
traffic (4 to 5 PM standard time); and 4) at a majority of stations,
as with the stations in Colorado  and Maryland, there are late evening
(7 to 10 PM) peaks in  concentrations.   The July statistics for the
stations that showed good and poor correlations in January are shown
in Tables 12 and 13, respectively.  It is obvious that the correlations
from January to July decrease markedly.  A sixth station, Camden 3,
is added to the poorly correlated, group because it showed correlations
ranging from 0.69 to -0.72.
     Five of these New Jersey stations, Bayonne, Elizabeth 1  and 2,
Jersey City, and Newark, are in a five mile square area and three show
well correlated data with other stations while two show poorer correla-
tions.  Again it is difficult to  believe that meteorological  variations
from place to place would be great enough to cause these large differences
in the small area.

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INTERMONTH CORRELATION OF CO CONCENTRATIONS

    Because the bivariate analyses showed that the correlations between
stations decreased from January to July, a month-to-month comparison
was made at each station.  The resulting comparisons, Table 14,  show:
     1.  No correlations better than 0.70 among the Maryland stations
     2.  Correlations that range from 0.55 to 0.86 at the Colorado sites
     3.  Correlations that range from -0.26 to 0.94 in New Jersey

COMPARISONS OF TRAFFIC AND CO CONCENTRATIONS

     The composite distribution for the six CO monitoring stations in
Colorado for January and July are presented in Figure 10.  The vertical
line at the middle of the hour shows the range of one standard deviation.
The January data show a smooth two-peak distribution with the peaks
appearing to coincide or follow within 1 hour of the peak in traffic
flow (see Figure 3).  The morning peak CO concentration is 50 percent
greater than the afternoon peak concentration although the traffic data
show the afternoon peak to be half again as great as the morning peak.
The lower concentrations with the greater traffic flow (greater  emissions)
is attributed to the meteorology; in the morning, vertical mixing and
wind speed, the causes of dilutions, are at their minimums and in the
afternoon at their maximums.  The standard deviations are relatively
small during the night and early morning hours, indicating that  there
is generally little spatial variation from this CO pattern.  The daytime
standard deviations are moderate, indicating there is a fair amount of
spatial variation from the composite pattern.  The July pattern  is not
as smooth as that for January, but the CO peak associated with the heavy
morning traffic is again evident.  A slight peak occurs in the afternoon
just before the time of peak traffic flow; a dip in concentration levels
is then evident just before the primary evening peak concentration occurs
at between 8 and 9 PM (9 to 10 PM daylight time).  The standard  deviations
are relatively large, indicating considerable spatial variation  from
the average July pattern.
     The composite results for the nine selected CO monitoring stations
in Maryland (Riviera Beach data are not included in the average) for
January and July are seen in Figure 11.  These January data show a
smooth two-peak distribution similar to those for Colorado.  Each CO
peak coincides or follows within 1 hour of the peak in traffic density.
The morning CO concentration peak is 50 percent larger than the  after-
noon peak; the direct opposite is true of the comparable traffic peaks.
Unlike the Colorado results, the Maryland data show concentrations as
low during the day as they are at night.  The standard deviations indicate
that there is a large amount of spatial variation at the time of the
morning peak and a fair amount at other times.  The July pattern, like
the January pattern, has two peaks.  The morning peak, however,  occurs
earlier and is diminished in size, and the evening peak occurs later
and is greater.  Compared to the July CO pattern for Colorado, the
Maryland pattern is more systematic.  Like the Colorado results, the
peak afternoon CO concentration occurs several hours after the peak
in traffic flow.  In addition, at the time of the peak traffic,  no

-------
marked increase in CO concentration occurs.  In the middle of the
day, concentrations are very similar to the lowest nighttime values.
The standard deviations are large after 7 PM,  indicating that there is
a considerable amount of spatial  variation in  the evening.
     The composite results for the 15 selected CO monitoring stations
in New Jersey (the five stations  with poor correlations are not included)
are seen in Figure 12.  Like the  Colorado and  Maryland data for January,
the New Jersey data show a smooth two-peak distribution, although the
peaks are less pronounced.  The peaks do coincide with the peaks in
traffic flow, however.  Unlike the Maryland data, the New Jersey data
show the daytime concentrations remaining high after the morning peak
and always being about 2.5 times  as great as the lowest morning values.
The afternoon peak is higher in Mew Jersey; the morning peak was higher
in Colorado and Maryland.   The smal-1  standard  deviations indicate that
the spatial variations are relatively small, however.   The July data,
like those for Colorado and Maryland, show a less systemized variation
than the January data.  These July data show three slight peaks:   one
with the morning peak traffic; the second about the time of the afternoon
peak traffic; and the final several hours after the peak traffic flow.
The second and third peaks are similar to the  July afternoon peaks in
Colorado.  The standard deviations are larger  in July than in January,
indicating that the July pattern  shows larger  spatial  variations.
     The numerical correlations of the statewide variations of CO
concentrations with the traffic pattern averaged for the 18 counting
stations vary over a large range  (see Table 15).   In January, the
poorest correlation, 0.25, is associated with  the Maryland CO data
and the best, 0.94, with the New  Jersey data.   The indication is  that
traffic variations explain only 6 percent of the CO variation in
Maryland, 27 percent in Colorado, and 88 percent in Mew Jersey.   In
July, the correlation between traffic and Colorado Co variations
increases, but in the other two cases it decreases.   The Maryland data,
in fact, even show a negative correlation.   The interstate CO comparisons
in Table 15 show wide variations  in correlations in both January and
July.  In January, the correlation between  Maryland and New Jersey data
is only 0.42, and in July  it decreases to 0.31.   In July,  the variation
in one state can be used to explain less than  10 percent of the
variation in the other.   With the states being so close to one another,
a better correlation was anticipated.  The  interesting phenomena  in
the Colorado-Maryland and  Colorado-New Jersey  correlations is the exchange
of absolute values from January to July.  It is strange that the  variations
in CO in Colorado can be used to  explain 72 percent of the variation in
Maryland in January and only 43 percent in  July;  for New Jersey the
Colorado concentrations  explain 41  percent  in  January and  better  than
75 percent in July.
                                     10

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                              5.  SUMMARY

     The  results  of  the  study are summarized  in the following paragraphs:
     The  hourly variations of ADT at 18 permanent counting stations located
in various types of areas in three states during January and July showed
considerable spatial and temporal consistency even though the ADT counts
ranged from 1,000 to 100,000 vehicles.  For periods of a month,  there
are average patterns of diurnal variation of traffic flow that are
representative of all stations.
      The diurnal variations of CO concentrations for 36 monitoring
stations, located for the most part in urban areas or near well-traveled
roads in  the three states, showed correlations that varied from large
positive  to large negative when one-to-one comparisons were made.
      Although comparisons of data from all 36 monitoring stations
showed correlations varying over a large range, intrastate comparisons
showed smaller ranges in July and much smaller ranges in January.
Eliminating stations that showed poor correlations yielded groups within
each state that showed consistent patterns.
     The  Maryland stations generally showed lower average hourly concen-
trations  than the Colorado and New Jersey CO monitoring stations.  The
Maryland  stations have metal boxes over their intakes that may account
for the differences with the Colorado stations.  The New Jersey stations
are generally closer to the traffic than the Maryland stations—a fact
that may  account for the higher observed values.  Before attempting
to correlate traffic and meteorology with CO concentrations in various
states, it would be desirable to have the siting of instruments
standarized.  The U.S. Environmental Protection Agency has published
guidelines (12) for siting instruments and with time state and local
agencies may comply with these guidelines and provide comparable data.
     The  relatively high CO concentrations that occur late in the
day in July were an unexpected anomaly.  Because they occurred in so
many places, there is little doubt that they are real.  This time delay
in peak concentration is attributed to the diurnal variations in
vertical mixing and wind speed.  These pheonmena provide for
maximum dilution at the time of peak traffic flow and at later
times, when the speeds and mixing heights are much lower, concentrations
increase.
     The comparison of the January versus July CO variations at the
individual stations showed:   1) poor correlations in Maryland (all
less than 0.70); 2) correlations in Colorado ranging from 0.55 to
0.86;  and 3)  correlations ranging from -0.26 to 0.94 in New Jersey.
These correlations are much more erratic than the comparable traffic
correlations,  which ranged upward from 0.87 with a majority being
greater than 0.96.  It appears there is a significant seasonal change
in CO concentrations.
                                     11

-------
     In comparing the January diurnal variations of CO concentrations
and traffic volume, there was an obvious correlation of the timing of
the diurnal peaks of each.  There was not a good one-to-one correlation
between concentrations and traffic density, however, because the traffic
pattern showed an afternoon peak that was twice as great as the morning
peak.  In addition, Colorado and Maryland concentration patterns showed
peaks in the afternoon that were half as great as those in the morning.
The diurnal variations in vertical mixing and wind speed partially
account for this apparent anamoly.  These phenomena allow for minimum
dilution of emissions with peak morning traffic and maximum dilution
with peak afternoon traffic.
     In Maryland in January and July and at three stations in Colorado
in January and seven stations in Mew Jersey in July, the midday concen-
trations were consistently as low as the lowest nighttime values.
There was almost an order of magnitude difference in traffic volume at
the two different times.   Traffic density and concentration were very
poorly correlated at these stations and times.   The diurnal variation
of meteorological parameters are the cause of this discrepancy.
Emissions are diluted very little at night because vertical mixing and
wind speed are at their minimums and around midday emissions are
readily spread through much larger volumes as vertical  mixing and  wind
speed are approaching maximums.
     Even when the CO data were compiled into average diurnal  variations
for each state, the correlations between traffic and CO concentrations
were still erratic; in Colorado in January, 27  percent of the variation
in CO concentrations was  explained by the traffic and in July 33
percent; in Maryland the  correlation was 0.25 in January and -0.19
in July; in New Jersey 88 percent of the variation in CO concentrations
was explained by the traffic in January and 62  percent in July.
     The results of this  study are inconsistent with those studies
(1,2) that found high correlations between CO concentrations and traffic.
The instruments used in this study were modern, were checked for accuracy.
and were in locations comparable tc those used  in the other studies
(about 30 to 50 feet from traffic in the northeastern city [1]  and
about ? to 3 meters from  the building walls in  Frankfurt/Main [2]).
This study indicates that the diurnal variations of traffic are
spatially and seasonally  consistent but that the diurnal  variations
of CO concentrations are  inconsistent.   There are times and places,
however, at which there may be a high correlation between the variations
of the parameters.   This  appears to have been the situation in  the
northeastern city and in  Frankfurt/Main in the  earlier studies.
                                     12

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                                 REFERENCES
1.  Brief, R.S., A.R. Jones, and D. Yoder.  Lead, Carbon Monoxide  and
    Traffic.  J. Air Poll. Cont. Assoc.  10:384-388,  413, 1960.

2.  Georgii, H.W., E. Busch, and E. Weber.  EPA translation  #^77 of
    Investigation of the Temporal and Spatial  Distribution of  the
    Emission Concentration of Carbon Monoxide in Frankfurt/Main.
    Report of the Institute for Meteorology and Geophysics of  the
    University of Frankfurt/Main.  May 1967.  66 p.

3.  DeMarrais, G.A.  Diurnal Variations in Carbon Monoxide Concentrations
    Traffic Counts and Meteorology.  U.S.  Environmental  Protection
    Agency, Research Triangle Park, NC.  (In press,  1976).

4.  McCormick, R.A., and C. Xintaras.  Variation of  Carbon Monoxide-
    Concentrations as Related to Sampling  Interval,  Traffic  and
    Meteorological Factors.  J. of Appl.  Meteor. 1:237,  1962.

5.  Johnson, W.B., F.L. Ludwig, W.F. Dabberdt, and R.J.  Allen.  An
    Urban Diffusion Simulation Model for Carbon Monoxide.  J.  Air
    Poll. Cont. Assoc.  23:490, 1973.

6.  Clean Air Act of 1970.  PL 61-604, 42  USC  1857 et seq, United
    States Congress, Washington, DC.  December 1970.

7.  Fritts, 6.W.  Hourly Traffic Data, Seven Selected Stations, State
    Department of Highways, Denver, CO.,  1975.

8.  Bureau of Traffic Engineering, Traffic Trends 1973,  State  Highway
    Administration of Maryland Department  of Transportation, Baltimore,
    MD., 1974.

9.  Kandu, J.C.  Hourly Traffic Data, Three Selected  Stations, Department
    of Transportation, Trenton, NJ, 1975.

10.  Midurski, T.P., and A.M.  Castaline.   Guidelines  for Identification
     and Evaluation of Localized Violations of Carbon Monoxide Standards.
     GCA Corporation, Bedford, MA., GCA-TR-75-35-G(l),  1976.

11.  Holzworth, G.C.   Mixing Heights, Wind Speeds and Potential for
     Urban Air Pollution Throughout the Contiguous United States
     AP-101.   U.S.  Environmental  Protection Agency,  Research Triangle
     Park, North Carolina, 1972.   118 pp.


                                     13

-------
12.   Ludwig,  F.L.  and  J.H.S.  Kealoha.   Selecting Sites for Carbon
     Monoxide Monitoring.   Report  prepared  for U.S. Environmental
     Protection  Agency by  Stanford  Research  Institute, MenTo Park,
     California,  Contract  No.  68-02-1471, 1975.  150 pp.
                                    14

-------
     STATION C1
     METRO-D
     ADT 16,311
                                         STATION C8
                                         METRO-D
                                         ADT 20,683
                                         STATION C22
                                       —METRO-D
                                         ADT 94,818
                                                                                       STATION Cl
                                                                                       RESORT
                                                                                       ADT 2918
STATION C23
METRO-D
ADT 31.612
STATION C40
URBAN
ADT 36,475
     STATION C39
     RESORT
     ADT 1137
                                                                                  STATION M39
                                                                                  INT-C-H
                                                                                  ADT 39 307
STATION M25
INT-C-H
ADT 38.631
LEGEND:
           9  NOON  3
              TIME

    C  = COLORADO
                               NJ =  NEW JERSEY
       6    9  NOON  3    6    9   12
              TIME
       INT-C-H =  INTERCITY HIGHWAY
            D =  DENVER
12   3    6     9   NOON   3    6
                 TIME
   B  = BALTIMORE
ADT  = AVERAGE DAILY TRAFFIC
         M  = MARYLAND   METRO =  METROPOLITAN

       Figure 1. Diurnal variation in percentage of 24-hour traffic flow for each hour at 18 stations during January.
                                                                                                                     9   12

-------
                                                                               STATION MB
                                                                               SMALL CITY
                                                                               ADT 14.338
STATION M31
METRO B
ADT 81,945
STATION M32
METRO B
ADT 84,461
                                                                               STATION M35
                                                                               MOUNTAIN
                                                                               RESORT
                                                                               ADT 2763
STATION M23
SMALL CITY
ADT 10.983
STATION M17
OCEAN RESORT
ADT 5824
                                                                                STATION NJ409
                                                                                SMALL CITY
                                                                                ADT 6191
STATION NJ204
TRUCK ROUTE
ADT 31,575
STATION NJ208
OCEAN RESORT
ADT 18,485
  6    9  NOON
          TIME
 C =  COLORADO
                          NJ  = NEW JERSEY
           9  NOON  3
              TIME
        INT-C-H =  INTERCITY HIGHWAY
             D =  DENVER
             9   NOON  3    6
                TIME
  B  =  BALTIMORE
ADT  =  AVERAGE DAILY TRAFFIC
M =  MARYLAND   METRO  =  METROPOLITAN

Figure 1 (continued). Diurnal variation in percentage of 24-hour traffic flow for each hour at 18 stations
during January.

-------
                9   NOON   3

                   TIME
                                                9  NOON  3

                                                   TIME
                9   NOON  3
                   TIME
                                                9  NOON  3
                                                   TIME
                                                                                             9   NOON   3

                                                                                                TIME
                                                                                                               12
     STATION C23
     METRO-D
     ADT 35.235
                                     STATION C40
                                     URBAN
                                     ADT 43.179
                                                                                 STATION C7
                                                                               — RESORT
                                                                                 AOT6733
                                                                               12    12
                                                                                            9  NOON  3
                                                                                               TIME
                                                                                       STATION M39
                                                                                       INT-C-H
                                                                                       ADT 48.160
                                     STATION M25
                                     INT-C-H
                                     ADT 38,393
STATION C39
RESORT
ADT 5796
  12    3

LEGEND:
  6    9   NOON   3
          TIME

C  = COLORADO       NJ =  NEW JERSEY
M  = MARYLAND   METRO =  METROPOLITAN
                                                    9   NOON   3    6    !
                                                       TIME

                                                INT-C-H =  INTERCITY HIGHWAY
                                                     D =  DENVER
                                                                               12    12
        6    9   NOON  3     6
                TIME
  B  = BALTIMORE
ADT  = AVERAGE DAILY TRAFFIC
                                                                                                                       12
         Figure 2. Diurnal variation in percentage of 24-hour traffic flow for each hour at 18 stations during July.

-------
00
                    STATION M31
                    METRO-B
                    ADT 88.828
                                      STATION M32
                                      METRO-B
                                      ADT 98.868
                                                                369   NOON   369

                                                                            TIME
                                                                                          9   NOON   3    6

                                                                                             TIME
                    STATION M23
                    SMALL CITY
                    ADT 13.136
                                                                               STATION M35
                                                                               MOUNTAIN
                                                                               RESORT
   STATION M17
   OCEAN RESORT
   ADT 21.022
                               9  NOON  3
                                  TIME
                                                                                          9  NOON   3    6
                                                                                             TIME
                 12    3
                10
                          I
                    STATION NJ204
                    TRUCK ROUTE
                    ADT 33.857
                                                         10
                0
                 12   3

              LEGEND:
  6     9  NOON   3
         TIME

C =  COLORADO
                                      STATION NJ208
                                      OCEAN RESORT
                                      ADT 29,198
                                                     12
                                              NJ =  NEW JERSEY
12    3    6    9  NOON   369
                 TIME
          INT-C-H =  INTERCITY HIGHWAY
                                                                                                            9    12
                                            STATION NJ409
                                            SMALL CITY
                                            ADT 6822
                        M =  MARYLAND   METRO =  METROPOLITAN
                                                  D =  DENVER
12    12  3    6    9   NOON  3     6
                      TIME
        B =  BALTIMORE
      ADT =  AVERAGE DAILY TRAFFIC
9   12
                        Figure 2 (continued). Diurnal variation in percentage of 24-hour traffic flow for each hour at 18 stations
                        during July.

-------
=    12
Q
LLJ
C3
cc
114
u
cc
                                9      NOON      3

                                LOCAL STANDARD TIME
12
                               LOCAL DAYLIGHT TIME
      Figure 3. Diurnal variation in average traffic, 18 stations (vertical lines
     show ranges of + 1 standard deviation).
                                       19

-------
            10
no
CD
                                                         BROADWAY
                                                           (7.8)
                       6    9  NOON   3    6
                        LOCAL STANDARD TIME
                                                  12
                                12
     9   NOON  3     6
  LOCAL STANDARD TIME
             12
6    9   NOON  3    6
 LOCAL STANDARD TIME
6    9   NOON  3    6
  LOCAL STANDARD TIME
                                                                                           12
                                                                                                12
                                                                                               10
                                                                                           12
                                                                                                12
6    9   NOON  3    6
  LOCAL STANDARD TIME
                                                                                                     WE LBV
                                                                                                      (4.3)
6    9   NOON  3    6
 LOCAL STANDARD TIME
                  Figure 4.  Diurnal variation in CO concentrations, Colorado stations, January (numbers in parentheses are average
                  hourly concentrations in ppm).
                                                                                                                                 9    12
                                                                                                                                 9    12

-------
          6    9  NOON  3    6
           LOCAL STANDARD TIME
                                         6    9   NOON  3
                                           LOCAL STANDARD TIME
  9   NOON 3    6
LOCAL STANDARD TIME
12
          6    9  NOON  3    6
           LOCAL STANDARD TIME
                                     12
                                         12
6    9  NOON   3    6
  LOCAL STANDARD TIME
                                       6    9  NOON  3    6
                                        LOCAL STANDARD TIME
       Figure 5. Diurnal variations in CO concentrations, Colorado stations, July (numbers in parentheses are average
       hourly concentrations in ppm).
                                                                                                                   9    12

-------
                                            10
   10
              6    9  NOON   3    6
               LOCAL STANDARD TIME
                                               BALTIMORE
                                                  (1.9)
U- <
o cr
     CUMBERLAND
         (1.6)
12    12

   10
6    9   NOON  3    6
  LOCAL STANDARD TIME
                                                                                  12
                                                                                       12
                                                                                     10
6    9   NOON  3    6
  LOCAL STANDARD TIME
    12
              6    9  NOON  3    6
               LOCAL STANDARD TIME
                                         12
                                              12
6    9  NOON   3    6
  LOCAL STANDARD TIME
                                                                                  12
                                                                                      12
6    9  NOON   3    6    9
 LOCAL STANDARDTIME
   10
    12
              6    9  NOON  3    6
               LOCAL STANDARD TIME
    12
             6    9  NOON  3    6
              LOCAL STANDARD TIME
                                        12
      Figure 6.  Diurnal variations in CO concentrations, Maryland stations, January (numbers in parentheses are average
      hourly concentrations in ppm).
                                                                                                                           12
                                                                                                                           12

-------
ro
CO
                  10
               u- <
               o cc
               cc «=
               UJ O
               Q_ CJ
                     LINTHICUM
                       (1.7)
                                                             10
                             CM ,_
                             U. <^
                             O CC
                             1-1-5
                    12
                  10
                             6    9  NOON  3    6
                              LOCAL STANDARD TIME
                                  BALTIMORE (JUNE, NOT JULY)
                                     (1.3)
                           12
                                 12
•a- 2
a cc

si
CO CJ
                     CUMBERLAND
                        (1.3)
                                                             10
                                          6    9   NOON  3    6
                                            LOCAL STANDARD TIME
                                                                      12
                                                                                           BETHESDA (AUGUST, NOT JULY)
                                                                                             (0.5)
                                                                                                   6    9   NOON  3    6
                                                                                                     LOCAL STANDARD TIME
                                  GAITHERSBURG
                                      (2.9)
                    12
                             6    9  NOON  3    6
                              LOCAL STANDARD TIME
                           12
                                                              12
                                          6    9   NOON  3    6
                                            LOCAL STANDARD TIME
                                                                      12
                                                                           12
                                                                                                   6    9  NOON   3    6
                                                                                                    LOCAL STANDARD TIME
                    12
                             6    9  NOON   3    6
                               LOCAL STANDARD TIME
                                          6    9  NOON  3    6
                                            LOCAL STANDARD TIME
                                                                                                       9  NOON  3    6
                                                                                                     LOCAL STANDARD TIME
                    12
6    9   NOON  3    6
 LOCAL STANDARD TIME
                                                         12
                        Figure 7. Diurnal variations in CO concentrations, Maryland stations, July (numbers in parentheses are average
                        hourly concentrations in ppm).
                                                                                                                                             12
                                                                                                                12
                     RIVIERA (JUNE, NOT JULY)
                     BEACH
                      (1.6)

-------
    10
 u. <
 O CC
         ASBURY
          (3.8)
     12
    10
               6    9  NOON   3     6
                 LOCAL STANDARD TIME
 u- <
 o cc
        CAMDEN1
          (2.9)
     12
    10
 u. <
 o cc
 i- t: 5
               6    9  NOON   3     6
                LOCAL STANDARD TIME
      ELIZABETH 1
         (6.1)
     12
    10
6    9  NOON  3     6
  LOCAL STANDARD TIME
u. et
O CC
CC ^
LU O
Q. CJ
      HACKENSACK
          (4.9)
     12
6    9   NOON   3     6
 LOCAL STANDARD TIME
   10

II
CXI ,_
O CC
                                             111 O
                                             0- U
                                     BAYONNE
                                       (1.0)
                                                                                           10
                                                                          u. <
                                                                          o cc
                                                                          1-1-5
                                                                          uj O
                                                                          0. CJ
                                   BURLINGTON
                                      (5.6)
                                            12
                                  12
                                               10
                                            6     9   NOON  3    6
                                              LOCAL STANDARDTIME
                                                                                       12
                                                                                            12
                                    CAMDEN2
                                      (2.7)
                                                                                           10
                                           6    9  NOON  3    6
                                             LOCAL STANDARD TIME
                                                                         ex, ,_
                                                                         U- <
                                                                         0 0=,
                                                                                        O CJ
                                                                                        CC ^
                                                                                        LU O
                                                                                        D- LJ
                                    CAMDEN3
                                      (1.3)
                                            12
                                                 12
                                                10
                                            6     9   NOON  3    6
                                             LOCAL STANDARD TIME
                                                                                       '12
                                                                                            12
                                           6    9  NOON   3    6
                                             LOCAL STANDARD TIME
                                            12
                                                 12
                                               10
6    9  NOON  3     6
  LOCAL STANDARD TIME
                                O
                              Q.CJ
                                   JERSEY CITY
                                      (5.8)
                                                                                           10
                                                              9  NOON   3     6
                                                           LOCAL STANDARD TIME
                                                                          o o
                                                                          cc ^
                                                                          LU O
                                     NEWARK
                                       (4.4)
                                           12
                                                 12
6    9  NOON   3    6
  LOCAL STANDARD TIME
                                                                                       12
                                                                                            12
                                                         6    9  NOON   3     6
                                                           LOCAL STANDARD TIME
                                                                                                                                   12
                                                                                                                                   12
                                                                                                                                   12
                                                                                                                                   12
        Figure 8.  Diurnal variations in CO concentrations. New Jersey stations, January (numbers in parentheses are average
        hourly concentrations in ppm).

-------
ro
01
               10
            LL. <
            o cc
                  PATERSON
                     (6.6)
                 12
               10
                          6    9   NOON  3    6
                           LOCAL STANDARD TIME
            ~
            O OC
CJ CJ
CC. Z
LLJ O
Q- O
                  PERTH AMBOY
                     (5.9)
                 12
                          6    9  NOON  3    6
                           LOCAL STANDARD TIME
                 12
              6    9  NOON  3    6
                LOCAL STANDARD TIME
                                                         10
                                          u. <
                                          O CC
                                               PAULSBORO
                                                  (4.2)
                                                     12
                                              12
                                                         10
6    9   NOON  3    6
  LOCAL STANDARD TIME
                                               PHILLIPSBURG
                                                   (1.9)
                                                   *#
                                                     12
                                                          12
                                                       6    9  NOON  3    6
                                                         LOCAL STANDARD TIME
                                                             TRENTON
                                                               (8.7)
                                                      12
                                                          12
6    9   NOON  3    6
  LOCAL STANDARD TIME
                                                                                                  10
                                                                                                UJ O
                                                                                                Q. U
                                 PENNSGROVE
                                    (5.9)
                                                                                  12
                                                                                                  10
                                12    3    6    9   NOON  3    6
                                           LOCAL STANDARD TIME
                                                                                                                                        12
                                                                                                it •*
                                                                                                o oc,-
                                                                                                K 1-5
                            0 CJ
                            oc z
                                 SUMERVILLE
                                    (5.3)
                                                                                              12
                                                                                                   12
                                         I    9  NOON   3    6
                                          LOCAL STANDARD TIME
                                                                                                                                        12
                                                                                               12
                                 *    STATIONS SHOWING 0.72 OR GREATER
                                     CORRELATIONS

                                 **   STATIONS WITH MAJORITY OF CORRE-
                                     LATIONS LESS THAN 0.72

                                 NO* STATIONS IN-BETWEEN ABOVE TYPES

                                 (CORRELATIONS BASED ON STATION-TO-
                                 STATION COMPARISONS - SEE TEXT)
                   Figure 8 (continued). Diurnal variations in CO concentrations, New Jersey stations, January (numbers in parentheses
                   are average hourly concentrations in ppm).

-------
IV)
CTl
               10
            LL, <
            O CC
            oc 2
            UJ O
            Q. O
                     ASBURY
                      (2.0)
                 12
               10
                           6     9   NOON   3     6
                            LOCAL STANDARD TIME
            u. <
            O DC
            CC 2
            LLJ O
                   CAMDEN1
                     (3.4)
                12
                           6     9   NOON   3     6
                            LOCAL STANDARD TIME
                           6     9   NOON  3     6
                            LOCAL STANDARD TIME
               10
           u. <
           O CC
           CC ^
           LLJ O
           0- LJ
                 HACKENSACK
                     (3.3)
                12
6    9  NOON   3     6
 LOCAL STANDARD TIME
                                                            10
                                                         O CC
                                                         1-1-5
                                  .
                               in O
                                                             0
                                      BAYONNE
                                        (2.1)
12   12

    10
                                                  9   NOON   3     6
                                               LOCAL STANDARD TIME
                                                         0.0
                                     CAMDEN 2
                                       (4.0)
12    12

    10,—
                                                  9   NOON   3     6
                                              LOCAL STANDARD TIME
                                                              ELIZABETH 2
                                                                 (2.9)
                             12    12

                                 10r—
   9   NOON  3    6
 LOCAL STANDARDTIME
                                    JERSEY CITY
                                       (6.4)
                                                        12    12
   9   NOON  3    6
LOCAL STANDARD TIME
                                                                                                        10
                                                                           u. <
                                                                           O CC
                                                                           LU O
                                                                           O- O
                                                                                                         0
                                  BURLINGTON
                                     (4.0)
12    12

    101—
                                           6     9   NOON   3     6
                                             LOCAL STANDARD TIME
                                              <» _
                                              
-------
   10
  <
  cc
cc
LU
Ou
      PATERSON
         (3.9)
                                            10
                            •» r
                            LL. <
                            O CC
PAULSBORO
   (4.7)
    12
   10
              6    9  NOON   3    6
               LOCAL STANDARD TIME
 . «f
  DC
     PERTH AMBOY
         (7.3)
12    12

   10|—
                                         6    9   NOON  3    6
                                           LOCAL STANDARD TIME
                            u-«t
                            occ ,
                                 PHILLIPSBURG
                                    (1.3)
    12
   10
              6    9  NOON   3    6
               LOCAL STANDARD TIME
                                         6   9  NOON   3    6
                                          LOCAL STANDARD TIME
     12
6    9   NOON   3    6
 LOCAL STANDARD TIME
                                         12
                                              12
        6    9  NOON  3    6
          LOCAL STANDARD TIME
                                                                                      10
                                    LL. <
                                    O CC
                                                                     o"
                                                                     ocg
                                                                     LU O
                                                                     a. u
                                               PENNSGROVE
                                                  (3.5)
12    12

    10i—
                                                 6    9  NOON  3    6
                                                  LOCAL STANDARD TIME
                                          a- O
                                        SOMERVILLE
                                            (3.8)
                                                                                  12
                                                                                      12
                                                6    9  NOON  3    6
                                                  LOCAL STANDARD TIME
                                                                                                                           12
                                                                                                                          12
                                                                                       *    STATIONS SHOWING 0.72 OR GREATER
                                                                                            CORRELATIONS IN JANUARY

                                                                                       **   STATIONS SHOWING WITH POORER COR-
                                                                                            RELATIONS IN JANUARY

                                                                                       NO* STATIONS IN-BETWEEN ABOVE TYPES

                                                                                       (CORRELATIONS BASED ON STATION-TO-
                                                                                        STATION COMPARISONS  SEE TEXT)
        Figure 9 (continued).  Diurnal variations in CO concentrations, New Jersey stations, July (numbers in parentheses
        are average hourly concentrations in ppm).

-------
                            LOCAL STANDARD TIME
Figure 10.  Diurnal variations of CO concentrations, composite for six
Colorado stations (vertical lines show ranges of + 1 standard deviation).
                                28

-------
10
  12
9      NOON      3

 LOCAL STANDARD TIME
Figure 11.  Diurnal variation of CO concentrations, composite for selected
Maryland stations (vertical lines show ranges of + 1 standard deviation).
                                29

-------
o
p
<
O
o

cc
u
cc
                               LOCAL STANDARD TIME

   Figure 12.  Diurnal variation of CO concentrations, composite for selected

   New Jersey stations (vertical lines show ranges of + 1 standard deviation).
                                    30

-------
                    TABLE 1.   TYPES AND LOCATIONS OF TRAFFIC COUNTING STATIONS
 Station0
Type
Location
 C 1                Urban
 C 8                Urban
 C 22              Urban
 C 23              Urban
 C 40              Urban
 C 7                Resort

 C 39              Resort

 M 25         Intercity highway

 M 39         Intercity highway
 M 31           Urban beltway

 M 32           Urban beltway
 I'M 5           Small city highway
.M 23         Small city highway
 M 17            Ocean resort
 M 35           Mountain resort
 NJ 204       Truck route in city

 NJ 208          Ocean resort

 NJ 409       Small city roadway
                  1-25 North of downtown Denver
                  US-36 Southeast of Broomfield (near Denver)
                  1-25 Valley Highway in Denver
                  First Avenue in downtown Denver
                  1-25 Freeway in Pueblo
                  1-70 East of Glenwood Springs (140 miles
                  west of Denver)
                  US-34 East of Estes Park (60 miles NW of
                  Denver)
                  Baltimore-Washington Expressway South of
                  MD-176
                  1-95 North of MD-175
                  1-695 West of Raltimore-Harrisburg Express-
                  way
                  1-695 South of U.S. 40
                  U.S. 301 South of Waldorf
                  MD-5 East of Waldorf
                  U.S. 50 West of Ocean City
                  U.S. 219 at McHenry
                  U.S. IT, Jersey City, between Duncan and
                  Sip Avenues
                  U.S. 30 Atlantic City, 0.5 mile East of
                  Delilah Road
                  South Collins Road, Camden, between
                  Kearsarqe and Tuckahoe Road
 Numbering system is that used by the  respective  states; C=Colorado, M=Maryland,
  NJ=New Jersey
 bBetween Baltimore and Washington

-------
                                  TABLE 2.  DESCRIPTION OF CO MONITORING SITES
   Station
       Area description
    Intake
   Exposure
       Nearby traffic
Arvada
   (C)

Broadway
    (C)
Julian
   (C)

Col fax
   (C)

Huron
  (C)

Wei by
  (C)

Baltimore
   (M)
(Calvert St)

Bethesda
   (M)

Cumberland
    (M)
Open field in a residential area
6 miles northwest of downtown area

Small triangular plot in downtown
area
Small parking lot near hospital
2 miles west of downtown area

Field near hospital in center
city commercial area

Field 5 miles south of downtown
area

Open field in rural area 6 miles
north northeast of downtown

100-car parking field next to
thoroughfare
Meadow in metropolitan area
Grassy field next to thoroughfare
      (c)
17 feet above
ground on side
of building

      (c)
      (c)


      (c)


      (c)


      (d)



      (d)


      (d)
60 feet to road carrying 3,500
vehicles

21 feet to road carrying 1,700 vehicles
and 30 feet to road carrying 7,500
vehicles

36 feet to dne road and 61 feet to
another; each carries 1,000 vehicles

Many major intersections and road-
ways nearby

Adjacent streets carry .light traffic
but nearby streets carry heavy traffic

42 feet to road carrying less than
1,000 vehicles

90 feet to road carrying heavy after-
noon traffic
300 feet to road carrying about
100 vehicles

20 feet to road carrying heavy
morning traffic

-------
                                                       TABLE 2.   (continued).
OJ
CO
Station3
Gaithersburg
(M)

Hyattsville
(M)
Linthicum
(M)
Riviera Beach
(M)
Silver Spring
(M)
Suit! and
(M)
Tows on
(M)
Asbury
(MJ)
Bayonne
(NJ)
Area description
Near thoroughfare in suburb

Grassy field near the thoroughfare
in metropolitan area
Packed earth parking field at
end of road
Parking field next to little
used side road
Park area next to thoroughfare
Edge of 500-car, asphalt covered
parking field
Edge of wooas
City street
City park
Intake
Exposure
35 feet above
ground, 18 in.
from side of
building
(d)
(d)
(d)
(d)
(d)
12 feet above
ground atop
building
(e)
(f)
Nearby trafficb
75 feet from road carrying 27,000
vehicles

Below level of road and 75 feet from
road carrying 30,000 vehicles
80 feet from road carrying about 100
vehicles and 600 feet from major
thoroughfare
10 feet from road carrying 100 vehicles
and 0.25 miles from thoroughfare
50 feet from 8-land thoroughfare
carrying 90,000 vehicles
150 feet from road carrying 18,500
vehicles
Closest road, 500 feet away, carries
76,500 vehicles
Road carries moderate to light traffic
3 blocks from ocean
Trailer is 0.75 miles from road with
moderate traffic

-------
                                                      TABLE 2.   (continued).
OJ
-pi
Station3
Burlington
(NJ)
Camden 1
(NJ)
(N. 6th st.)
Area description
City street
City street
Camden 2 Open field at medical research
(NJ) center
(Copewood & Davis)
Camden 3
(NO)
(Ancora)
Elizabeth 1
(NJ)
(Broad St.)
Elizabeth 2
(NJ)
(N.J. Turnpike)
Freehold
(.NJ)
Hackensack
(NJ)
Jersey City
(NJ)
Rural state hospital 20 miles
southeast of Camden
Center city street
Turnpike interchange
Center city street
City street
Street near city center
Intake
Exposure
(e)
(e)
(f)
About 30 feet
above ground
3 feet from side
of building
(e)
(f)
(e)
(e)
(e)
Nearby trafficb
Road is a main street but carries
only moderate to light traffic
Downtown road which carries light
traffic
A block from light traffic; 3 blocks
from heavy traffic
No nearby traffic; heavily travelled
2 and 3 miles away
Road carries heavy traffic
Trailer is about 150 feet from exit-
entrance area
Street carries moderate to light
traffic
Sampler is about 50 feet from light
traffic and 400 feet from heavy traffic
Street carries very heavy traffic

-------
                                                     TABLE 2.  (continued).
to
en
Station3
Newark
(NJ)
Paterson
(NJ)
Paulsboro
(NJ)
Penns Grove
(NJ)
Perth Amboy
Phillipsburg
(NJ)
Somerville
(NJ)
Toms River
(NJ)
Trenton
(NJ)
Area description
Corner of two streets
City street
Center city street
Center city street
Center city street
Near corner of two streets
Center city street
Near corner on main street
Center city street
Intake
Exposure
(f)
(e)
(e)
(e)
(e)
(e)
(e)
(e)
(e)
Nearby traffic
Each street is a one-way street; each
carries heavy traffic
Street carries light traffic; large
amount of heavy-duty, gasoline-burning
equipment used in nearby city dump
Street carries light traffic
Street carries light, traffic
Street carries very heavy traffic
Sampler is 20 feet above sidewalk;
street 20 feet away carries light traffic
street 50 feet away carries heavy traffic
Street carries moderate traffic
Street carries heavy traffic typical
of area with a small population
Street is now a mall; traffic was
heavy

-------
                                                           TABLE 2.  (continued).
                 All  Colorado  (C)  stations  are  in Denver area; (M)=Maryland; (NJ)=New Jersey





                 Vehicle  counts are  in  counts per day; estimate of NJ traffic based on observation
                 Exposure  is  15  feet above ground atop trailer
CTl
                 Exposure  is  10  feet above ground atop trailer





                Exposure  is  3 feet from side of building (projecting out from window) about 10-12 feet above ground





                 Exposure  is  12  feet above ground atop trailer

-------
       TABLE 3.   CORRELATIONS OF LESS THAN 0.90 IN DIURNAL VARIATIONS  IN  TRAFFIC  FOR JANUARY,  18 STATIONS'


C7
C39
Ml 7
M35
NJ204
NJ208
NJ409
CMCCCCCMM
1 8 22 23 40 7 39 25 39
0.89 0.85 ------
0.88 0.87 	
_________
0.89 0.87 	
_________
0.87 0.88 - 0.84 - - -
0.82 0.83 0.80 0.84 0.84 0.82 0.78 0.83 0.81
M M M M M M NJ NJ NJ
31 32 5 23 17 35 204 208 409
0.87 0.88 ----- 0.84 0.82
0.89 0.89 - - - - - 0.78
0.79
0.86 0.31
0.83 O.u4
0.89 0.89 0.89 - 0.86 0.88 - 0.39
0.81 0.83 0.83 0.81 0.79 0.81 0.84 0.89
 All pairs not shown or marked by  '-  were 0.90 or more.
C=Colorado, M=Maryland, NJ=New Jersey

-------
CO
oo
                 TABLE 4.  CORRELATIONS OF LESS THAN 0.90 IN DIURNAL VARIATIONS  IN  TRAFFIC  FOR  JULY,  18  STATIONS3


C7
C39
HI 7
M35
NJ409
C C
1 8
0.86
0.88
0.87
0.86 0.80
0.89 0.87
C C
22 23
0.83
0.85 -
0.83 -
0.76 0.86
0.84 0.89
C C C M
40 7 39 25
0.85
0.87
0.87
0.83
0.83 0.82 0.89
M
39
0.89
_
0.82
0.86
M
31
0.81
0.83
0.85
0.77
0.87
M M
32 5
0.80 -
0.82 -
0.84 -
0.79 -
0.89 -
M M M NJ NJ NJ
23 17 35 204 208 409
0.83
0.82
_
______

         aAll pairs not shown or marked by ••-- were 0.90 or more.

         C=Colorado, M=Maryland, NJ=New Jersey

-------
TABLE 5.  CORRELATION BETWEEN JANUARY AND JULY DIURNAL VARIATIONS IN
                   TRAFFIC AT INDIVIDUAL STATIONS3
Station
Cl
C8
C22
C23
C40
C7
C39
M25
M39
Correlation
0.99
0.99
0.99
0.99
0.98
0.98
0.95
0.98
0.99
Station Correlation
M31
M32
M5
M23
M17
M35
NJ204
NJ208
NJ409
0.98
0.97
0.97
0.95
0.87
0.93
0.98
0.92
0.91
aC=Colorado, M^Maryland, NJ=New Jersey
                                39

-------
TABLE 6.   BIVARIATE CORRELATIONS OF DIURNAL VARIATIONS IN CO CONCENTRATIONS
                       AT COLORADO STATIONS,  JANUARY

Wei by
Huron
Col fax
Julian
Broadway
Arvada
0.88
0.71
0.75
0.85
0.77
Broadway
0.51
0.66
0.90
0.61

Julian
0.77
0.84
0.66


Col fax Huron
0.46 0.46
0.83



                                    40

-------
TABLE  7.   BIVARIATE  CORRELATIONS OF DIURNAL VARIATIONS IN CO CONCENTRATIONS,
j                           COLORADO STATIONS, JULY.

Wei by
Huron
Col fax
Jul ian
Broadway
Arvada
0.23
0.84
0.80
-0.07
0.67
Broadway Julian
0.58 0.75
0.51 -0.19
0.48 -0.21
0.04

Col fax Huron
-0.02 -0.03
0.92



                                     41

-------
TABLE 8.  BIVARIATE CORRELATIONS OF DIURNAL VARIATIONS IN CO CONCENTRATIONS,  MARYLAND STATIONS,
                                            JANUARY

Towson
Suitland
Silver Spring
Riviera Beach
Hyattsville
Gaithersburg
Cumberland
Bethesda
Baltimore
Linth-
icum
0.79
0.78
0.92
0.08
0.77
0.88
0.88
0.88
0.80
Balti-
more
0.84
0.62
0.81
-0.04
0.81
0.63
0.63
0.66

Cumber- Gaithers- Hyatts- Riviera Silver Suit-
Bethesda land burg ville Beach Spring land
0.71 0.59 0.70 0.84 0'.03 0.87 0.60
0.70 0.81 0.89 0.46 0.20 0.77
0.90 0.81 0.85 0.84 0.25
0.31 0.38 0.33 0.16
0.78 0.56 0.60
0.84 0.92
0.81



-------
co
            TABLE  9.   BIVARIATE  CORRELATIONS OF DIURNAL  VARIATIONS  IN  CO  CONCENTRATIONS, MARYLAND STATIONS,
                                                         JULY

Tows on
Suitland
Silver Spring
Riviera Beach
Hyattsville
Gaithersburg
Cumberland
Bethesda
Baltimore
Linth-
icum
0.64
0.89
0.45
-0.36
0.77
0.66
0.69
0.65
0.54
Balti-
more
0.76
0.77
0.91
-0.02
0.75
0.70
0.84
0.71

Bethesda
0.86
0.69
0.74
-0.24
0.85
0.75
0.72


Cumber-
land
0.77
0.84
0.83
-0.02
0.71
0.87



Gaithers-
burg
0.78
0.78
0.77
0.13
0.61




Hyatts-
ville
0.84
0.81
0.66
-0.44





Riviera Silver Suit-
Beach Spring land
-0.19 0.69 0.75
-0.32 0.69
0.09







-------
TABLE 10.  BIVARIATE CORRELATIONS OF DIURNAL VARIATIONS  IN  CO  CONCENTRATIONS AT  13 SELECTED NEW JERSEY
                                          STATIONS,  JANUARY.

Trenton
Toms River
Perth Amboy
Penns Grove
Paulsboro
Newark
Jersey City
Hackensack
Freehold
Elizabeth 1
Camden 2
Burlington
Asbury
0.88
0.90
0.90
0.93
0.91
0.95
0.93
0.93
0.93
0.95
0.89
0.92
Burl-
ington
0.94
0.90
0.94
0.94
0.82
0.86
0.85
0.88
0.95
0.96
0.91

Camden
2
0.88
0.85
0.82
0.87
0.78
0.87
0.83
0.80
0.88
0.90


Eliza-
beth 1
0.93
0.93
0.92
0.97
0.88
0.91
0.92
0.90
0.97



Free-
hold
0.85
0.87
0.84
0.92
0.91
0.85
0.89
0.89




Hack-
ensack
0.80
0.77
0.84
0.82
0.88
0.82
0.83





Jersey Pauls-
City Newark boro
0.83 0.87 0.72
0.90 0.89 0.80
0.84 0.87 0.73
0.91 0.91 0:83
0.89 0.87
0.95






Penns Perth Toms
Grove Amboy River
0.95 0.96 0.93
0.97 0.93
0.94


,







-------
TABLE 11. BIVARIATE CORRELATIONS OF

Bayonne
Camden 1
Elizabeth 2
Paterson
Phillipsburg
Asbury
0.32
0.69
0.78
0.29
0.72
Bay-
onne

0.27
0.13
-0.21
0.23
Burl-
ington
0.48
0.67
0.69
0.28
0.66
DIURNAL
Camden
1
0.27

0.87
0.45
0.83
VARIATIONS IN CO CONCENTRATIONS
STATIONS, JANUARY
Camden
2
0.37
0.59
0.65
0.20
0.57
Camden
3
0.25
0.56
0.51
0.32
0.49
Eliza-
beth 1
0.36
0.68
0.74
0.33
0.70
Eliza-
beth 2
0.13
0.87

0.62
0.93
AT FIVE SELECTED NEW JERSEY
Free-
hold
0.37
0.76
0.81
0.48
0.76
Hack-
ensack
0.32
0.83
0.87
0.37
0.82
Jersey
City
0.08
0.55
0.73
0.38
0.64
Newark
0.14
0.53
0.69
0.28
0.63

-------
          Table  12.   Bivariate Correlations of Diurnal Variations in CO Concentrations at 13 Selected  Stations,
                                                              July.
en

Trenton
Toms River
Perth Amboy
Penns Grove
Paulsboro
Newark
Jersey City
Hackensack
Freehold
Elizabeth 1
Camden 2
Burlington
Asbury
0.85
0.90
0.80
0.29
0.19
0.72
0.70
0.23
0.73
0.79
0.80
0.65
Burl-
ington
0.73
0.55
0.18
0.72
0.64
0.52
0.27
0.63
0.76
0.68
0.78

Camden
2
0.93
0.74
0.42
0.28
0.26
0.74
0.54
0.29
0.89
0.71


Eliza-
beth 1
0.67
0.78
0.67
0.60
0.60
0.90
0.83
0.26
0.69



Free-
hold
0.90
0.81
0.44
0.43
0.34
0.62
0.46
0.06




Hack-
ensack
0.22
-0.05
-0.25
0.44
0.52
0.22
-0.07





Jersey Pauls- Penns Perth
City Newark boro Grove Amboy
0.48 0.67 0.19 0.24 0.49
0.68 0.65 0.18 0.33 0.83
0.82 0.59 -0.03 0.09
0.17 0.29 0.85
0.25 0.41
0.86






Toms
River
0.83












-------
Table 13.    Bivariate Correlations of Diurnal  Variations  in  CO  Concentrations at  6 Selected New Jersey
                                                Stations,  July.

Bayonne
Camclen 1
Elizabeth 2
Paterson
Phillipsburg
Camden 3
As bury
0.29
0.36
0.12
0.36
0.75
0.52
Bay-
onne

0.77
0.66
0.52
0.20
-0.72
Burl-
ington
0.27
0.10
0.35
0.60
0.81
-0.09
Camden
1
0.77

0.70
0.65
0.15
-0.64
Camden
2
-0.12
-0.25
0.29
0.44
0.61
0.15
Camden
3
-0.72
-0.64
-0.44
-0.29
0.24
1.00
Eliza-
beth 1
0.18
0.13
0.64
0.74
0.84
0.19
Eliza-
beth 2
0.66
0.70

0.82
0.41
-0.44
Free-
ho!4
-0.06
-0.33
0.21
0.30
0.58
0.18
Hack-
ensack
0.29
0.47
0.27
0.61
0.55
-0.33
Jersey
City
-0.05
0.01
0.54
0.48
0.52
0.35
Newark
-0.04
0.10
0.62
0.66
0.65
0.23

-------
Table 14.   Correlations  of January and July  Diurnal  Variations  of
                             CO Concentrations
Station
Linthicum
Baltimore
Bethesda
Cumberland
Gai thersburg
Hyattsvi lie
Riviera Beach
Silver Spring
Sui tland
Towson
Arvada
Broadway
Correlation
0.15
0.35
0.28
0.39
0.34
0.24
0.61
0.44
0.24
0.38
0.55
0.86
Station
Julian
Col fax
Huron
Uelby
Asbury
Bayonne
Burlington
Camden 1
Camden 2
Camden 3
Elizabeth 1
Elizabeth 2
Correlation
0.58
0.80
0.57
0.70
0.79
-0.26
0.39
-0.08
0.55
0.47
0.65
0.68
Station
Freehold
Hackensack
Jersey City
Newark
Paterson
Paulsboro
Penns Grove
Perth Amboy
Phillipsburg
Somerville
Toms River
Trenton
Correlation
0.90
0.80
0.79
0.82
0.65
0.67
0.87
0.94
0.78
0.66
0.90
0.90

-------
Table 15.   Correlations  of  Diurnal Variations, January and July.
Basic

traffic
verses
statewide CO

Traffic:
Traffic:
Traffic:

Traffic:
Traffic:
Traffic:
January
Colorado
Maryland
patterns

patterns

CO
CO
New Jersey CO
July
Colorado
Maryland

CO
CO
New Jersey CO




0
0
0

0
-0
0




.52
.25
.94

.58
.19
.79
Interstate CO






correlations








January
Colorado
Colorado
Maryland

Colorado
Colorado
Maryland
CO
CO
CO

CO
CO
CO
: Maryland CO
: New
: New
July
Jersey
Jersey

CO
CO

: Maryland CO
: New
: New
Jersey
Jersey
CO'
CO
0
0
0

0
0
0
.85
.54
.42

.56
.37
.31
                                 49

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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
 i. REPORT NO.
  EPA-600/4-77-016
                                                           3. RECIPIENT'S ACCESSIOI^NO.
4. TITLE AND SUBTITLE
  DIURNAL  VARIATIONS IN TRAFFIC FLOW AND  CARBOr
  MONOXIDE CONCENTRATIONS
             5. REPORT DATE
               April  1977
             6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
                                                          8. PERFORMING ORGANIZATION REPORT NO
  Gerard  A.  DeMarrais*
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 Environmental  Sciences Research Laboratory
 Office  of Research and Development
 U.S.  Environmental Protection Agency
 Research Triangle Park, NC  27711
             10 PROGRAM ELEMENT NO.
                1AA603
             11. CONTRACT/GRANT NO.
 12. SPONSORING AGENCY NAME AND ADDRESS
  Environmental  Sciences Research Laboratory  -  RTP,  NC
  Office of Research and Development
  U.S.  Environmental Protection Agency
  Research Triangle Park, NC  27711
             13. TYPE OF REPORT AND PERIOD COVERED
                Inhouse  3/76-2/77
             14. SPONSORING AGENCY CODE
                EPA/600/09
 15. SUPPLEMENTARY NOTES
  *0n  assignment from the National Oceanic  and  Atmospheric Administration,
  U.S.  Department of Commerce.
 16. ABSTRACT
       Traffic count and carbon monoxide  (CO)  data for January and July  from three
  states are compared in order to reveal  any  diurnal  variations in the two
  measurements.   The diurnal patterns  for the  18 traffic count stations  indicate
  that there are average patterns of traffic  flow that are representative  of all
  stations for periods of one month.   Comparisons of data for the 36  CO  monitoring
  stations show correlations which vary from  large positive to large  negative.
  However, eliminating a few monitoring stations which show relatively poor
  correlations yields groups within each  state that have consistent patterns.   The
  diurnal  variations in CO concentrations are  not well correlated with traffic
  patterns.   Part of the poor correlation appears to be due to the diurnal  variations
  in vertical  mixing and wind speeds and  part  to the exposures and locations of the
  sampling instruments.
                               KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                             b.IDENTIFIERS/OPEN ENDEDTERMS
                                                                          cos AT I Field/Group
     Air pollution
     Carbon monoxide
     Traffic surveys
     Diurnal variations
     Correlation
     Meteorological data
                                 13B
                                 07B
                                 13B
                                 04B
       RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
      UNCLASSIFIED
21. NO. OF PAGES

      58
                                             20. SECURITY CLASS (This page)
                                                   UNCLASSIFIED
                           22. PRICE
EP.
       2220-1 (9-73)
                                            50

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