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					 Collection and Analysis of
Weekend/Weekday Emissions
    Activity Data in the
   South Coast Air Basin
               Presented by
     Dana Coe Sullivan and Lyle R. Chinkin
          Sonoma Technology, Inc.
               Petaluma, CA

                 Presented at the
     Chairman's Air Pollution Seminar Series
         California Air Resources Board
                 Sacramento, CA

                 June 30, 2004
   What is the Weekend Effect?
Emissions of ozone precursors tend to be
 lower on weekends (WE) than on weekdays
 (WD).

However, in many cities, WE ozone
 concentrations now tend to be equal to or
 higher than WD concentrations.

This paradox—the weekend effect—appears
 to be growing more common and spreading
 geographically over time.
                                             2
   The Weekend Effect in Los Angeles
Los Angeles ozone air quality
improved from 1980 to 1999.
– Number of 1-hr exceedances
  decreased from about 150 to
  only 50 per year.


WE peaks = WD peaks.
– From 1980-1999, WD-WE
  difference became more
  pronounced.



    Source of figure: Austin, J.; Tran, H. “A Characterization of the Weekend-Weekday Behavior of
    Ambient Ozone Concentrations in California.” Draft staff report prepared by the Technical Support
    and Planning Division, California Air Resources Board, Sacramento, CA, 1999.
                                                                                                        3
     Purpose and Objectives
Purpose: Address a lack of WE-specific
 emissions data, which are needed to
 support air quality modeling exercises
 for WE conditions in Los Angeles.

Objective: Characterize WD-WE activity
 patterns for a variety of emissions
 sources in Los Angeles.



                                          4
Importance of On-Road Mobile Sources
         2003 SoCAB Emissions (tons per day)
 1,200
                                   Natural Sources

 1,000                             Other Mobile Sources
                     Other
                     Mobile        On-Road Motor Vehicles
                    Sources
  800     Other                    Area: Miscellaneous Processes
          Mobile
         Sources                   Area: Solvent Evaporation
  600
         On-Road                   Point: Industrial Processes
          Motor     On-Road
         Vehicles    Motor         Point: Petroleum Production And Marketing
  400               Vehicles
                                   Point: Cleaning And Surface Coatings
  200                              Point: Waste Disposal

                                   Point: Fuel Combustion
   -
                               Source: ARB, 2004
         ROG        NOx        http://www.arb.ca.gov/emisinv/emsmain/emsmain.htm

                                                                                   5
       Brief Overview – Methods
• Apply an array of methods (e.g., surveys,
  in-vehicle instruments, etc.) to directly
  measure activities for a variety of emissions
  source types.
  –   On-road mobile sources
  –   Non-road mobile sources
  –   Area sources
  –   Major point sources
• Direct the majority (80%) of effort and
  resources to on-road mobile sources.
                                                  6
        Brief Overview – Findings
• Traffic activities follow predictable weekly patterns.
   –   Vehicle-miles traveled (VMT)
   –   Frequencies of soaks or trips
   –   Speed distributions
   –   Types of roads driven
   –   Fleet distributions (heavy-duty versus light-duty)
• Some residential activities—especially recreational
  activities—tend to increase on WEs.
• Business-related activities and emissions from
  major point sources tend to decline dramatically
  on WEs.

                                                            7
        Presentation Overview
• Data Collection Methods and
  Highlights of Findings
  – Telephone and mail surveys
  – Instrumented vehicle study
  – Surface-street traffic counters
  – Caltrans weigh-in-motion (WIM) traffic volumes for
    freeways
  – Continuous emissions monitoring systems (CEMS) data
    for major point sources
  – Special studies of neighborhoods near air quality
    monitoring sites
• Recommendations
• Closing Remarks and Acknowledgments
                                                          8
Telephone and Mail Surveys




                             9
          Survey Participation
• Participants were recruited randomly
  throughout the SoCAB or from specific,
  targeted neighborhoods.
• Results for the randomly selected groups and the
  targeted neighborhoods were comparable.
• Compared to past experience, refusal rates were
  typical or low for residential and businesses
  surveys.
• All participants completed telephone
  questionnaires; some completed daily
  activity diaries by mail.

                                                     10
Daily Activity Diaries




                         11
               Survey Participation

                            No. Respondents
                                         Daily
                            Telephone   Activity
                                                   Refusal
 Group          Areas        Survey     Diaries     Rate
                Targeted
Households
               and random     870        488        41%
Small
businesses
                Targeted      137        n/a        14%
Construction
businesses
                Random        258        n/a        25%

                                                             12
       Survey Participation
Targeted neighborhoods were near key air
 quality monitoring sites in the SoCAB.




                                           13
Survey Participation – Households




                                    14
   Survey Results – Household Activities
                                                                           Mon-Thurs    Friday     Saturday   Sunday
Some activities increased
from WDs to WEs by 25% to                                                  30%
165%, including uses of                                                    25%
   –   barbecues*




                                       Estimated DOW Allocation Factor .
   –   recreational boats*                                                 20%
   –   recreational off-road RVs*
   –   paints or solvents*                                                 15%

Some activities varied little                                              10%
by DOW, including uses of
                                                                            5%
   – personal care products
   – water heating                                                          0%
                                                                                  BBQ      Rec.       Rec.   Paint/
                                                                                           Boats     Off-Rd Solvent
                           *see plot                                                                  RVs


                                                                                                                       15
    Survey Results – Household Activities
Some activities occurred at certain times of day.
                                                                                    Personal Care Products
–     Evening: WD BBQ use*
                                                                             100%
–     Afternoon: Recreational boats                                          80%
–     Morning: personal care products*                                       60%
                                                                             40%
Some activities varied day-to-day.                                           20%




                                                     Diurnal Distributions
– WD BBQ use*: 8% to 12% of total in afternoon;                               0%




                                                                                    (N=845)

                                                                                              (N=412)

                                                                                                        (N=446)

                                                                                                                  (N=404)
  90% in evening




                                                                                     Mo-Th




                                                                                                                    Sun
                                                                                                          Sat
                                                                                                Fri
– WE BBQ use*: 24% to 33% of total in afternoon;
  66% to 74% in evening                                                                       Barbecues

                                                                             100%

Some activities did not vary day-to-day.                                     80%

– personal care products*                                                    60%
                                                                             40%
– water heating
                                                                             20%
                                                                              0%




                                                                                    (N=102)




                                                                                                                  (N=100)
                                                                                              (N=60)

                                                                                                        (N=72)
                                         *see plot




                                                                                     Mo-Th




                                                                                                                   Sun
                                                                                                         Sat
                                                                                               Fri
                                                                                                                            16
Survey Results – Household Activities
  DOW Allocation Factor
                          25%              Weekdays             Saturday   Sunday
                          20%
                          15%

                          10%
                            5%

                            0%




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                                                               WD-to-Sat        WD-to-Sun
                          Business Type
                                                               % Reduced        % Reduced
       All businesses
                                                                  74%                82%
       (aggregate)
       Gas ovens                                                  61%                80%
       Construction                                               90%                99%
                                                                                               17
     Survey Results – Household Activities
Aggregate average patterns
 – On WDs, business activities peaked from 8 a.m.-4 p.m.
 – On WEs, business activities were evenly distributed 8 a.m.-12 a.m.
                                                                    100%                             100%
Business type-specific

                           Diurnal Distribution
                                                                     80%                             80%                                 8pm-
patterns                                                             60%
                                                                                                                                         midnight
                                                                                                     60%
                                                                                                                                         4pm- 8pm
 – Activity with gas                                                 40%                             40%
   ovens is sustained                                                20%
                                                                                                     20%                                 noon- 4pm
   late into the evening                                             0%
                                                                                                      0%
                                                                              All Businesses
                                                                                                                                         8am- noon
   and late-night hours                                                                                             Gas Ovens
                                                                    100%                             100%
 – Activities of                                                                                                                         4am- 8am
                                             Diurnal Distribution




                                                                    80%                               80%
   lawn/garden and
                                                                                                                                         midnight-
                                                                    60%                               60%
   construction                                                                                                                          4am
                                                                    40%                               40%
   businesses peak
                                                                    20%                               20%
   early, then drop off
                                                                                                       0%
   fast after 4 p.m.                                                 0%
                                                                                                             Weekday Saturday Sunday
                                                                           Weekday Saturday Sunday
                                                                             Lawn and Garden                All Construction Companies


                                                                                                                                                     18
               Surveys – Findings
• Some recreational activities increased 25-165% on WDs
  when compared to WEs.
   – Residential use of barbecues
   – Recreational boats and off-road vehicles (note small sample sizes)
   – Use of paints or solvents
• Diurnal patterns for some residential activities varied by
  day of week.
   – WD use of barbecues occurs primarily in the evening, but afternoon
     use becomes significant on WEs.
• Other types of residential activities varied less than 25% by
  day of week.
   – Residential uses of personal care products
   – Water heating for showers, baths, and automatic home appliances.


                                                                          19
          Surveys – Findings
• Business activities declined by 60-99% on
  WEs.
• Business activity levels typically peaked
  from 8 a.m. to 4 p.m. on WDs and leveled
  out on WEs. However, exceptions existed.
  – Work at lawn/garden and construction
    businesses peaked from 4 a.m. to 4 p.m. on
    WDs and was negligible on Sundays.
  – Work at businesses with gas ovens peaked
    later in the day on WDs and sustained through
    the evening and on WEs.
                                                    20
Instrumented Vehicle Study




                             21
   Instrumented Vehicle Study Participation
• A subset of household survey participants was
  recruited.
  – 68 households
  – 107 vehicles
• Global positioning system (GPS) receivers with
  data loggers—GeoLoggers—were installed in all
  household vehicles.
• Time-activity data were recorded at 5-second
  intervals for 10 to 15 days.
  – Vehicle position
  – Vehicle speed
• Approximately 1200 vehicle-days of data were
  collected.
                                                   22
GeoLogger




            23
GeoLogger Study Participation




                                24
GeoLogger Study – Example Data




                                 25
           GeoLogger Study – Results
                       Average Daily VMT per Vehicle
               35

               30

               25
Average VMT.




               20

               15            29        28                     29                           28
                    26                             27
                                                                       25                                 22
               10                                                                 20

                5

                0




                                                                                           Avg Mon-Fri
                    Monday




                                                                                                         Avg Sat-
                                                                                  Sunday
                                                              Friday

                                                                       Saturday
                             Tuesday




                                                   Thursday
                                       Wednesday




                                                                                                           Sun
                                                                                                                    26
              GeoLogger Study – Results
  Average Daily VMT per Vehicle by Road Type
                                             Major Hwys                  Arterials                 Other Roads
              20
                                 18
              18
                                            16           16              16            16                        16
              16   15
                                                                                                                                14
              14                                                                                     13
Average VMT




              12
              10                              8                            9
                                   8                       8                                                       8
               8     7
                                                                                         6                                        5
               6                                                                                       5
                             3          4            4               4             4                                        4
               4                                                                               3                                           3
                                                                                                            2
               2
               0
                                                          Thursday




                                                                                                                                 Avg Sat-Sun
                                  Tuesday




                                                                                                       Sunday
                                                                                        Saturday
                    Monday




                                             Wednesday




                                                                                                                  Avg Mon-Fri
                                                                          Friday




                                                                                                                                               27
                                   GeoLogger Study – Results
Driving patterns for high-mileage vehicles (“top 25”)
  differed somewhat from those of other vehicles.




                                                                                                                                                     Average VMT (All Other Vehicles).
 Average VMT (Top 25 Vehicles).




                                  70
                                  60             64                                                                                             20
                                                             58                      61                                  59
                                  50   57                                                 18        18
                                                      18          18 55 18                                                    18
                                            16                                                             46
                                  40                                                           45                                    46 15
                                  30                                                                            12                              10
                                  20
                                  10
                                  0                                                                                                             0
                                                                          Thursday
                                                   Tuesday




                                                                                                            Sunday
                                                                                                Saturday
                                        Monday




                                                              Wednesday




                                                                                                                          Avg Mon-


                                                                                                                                     Avg Sat-
                                                                                      Friday




                                                                                                                                       Sun
                                                                                                                             Fri
                                                 Top 25 Vehicles (Left Axis)                               All Others (Right Axis)
                                                                                                                                                                                         28
                          GeoLogger Study – Results
                                     WD-WE VMT VMT by Speed
                                   Average Daily by Speed DistributionBin
                                                 Weekday    Weekend

                        0.18
                        0.16
Fraction of Total VMT




                        0.14
                        0.12
                         0.1
                        0.08
                        0.06
                        0.04
                        0.02
                           0
                               5      15    25      35       45        55   65   75   >80
                                                         Speed (mph)
                                                                                            29
               GeoLogger Study – Results
                        Average Hourly VMT per Vehicle
              3.5


               3

                                                                                      Mon
              2.5
                                                                                      Tue
Average VMT




                                                                                      Wed
               2
                                                                                      Thu
                                                                                      Fri
              1.5                                                                     Mon-Fri

               1                                                                      Sat
                                                                                      Sun
              0.5


               0
                    0   2   4   6   8   10   12         14   16   18   20   22   24
                                        Hour of Day
                                         (0=midnight)
                                                                                                30
                                                    GeoLogger Study – Results
                                                        Average Daily No. of Soaks per Vehicle
                                                    6
Average Daily No. of Soaks Observed per Vehicle .




                                                    5



                                                    4



                                                    3
                                                                                5.6
                                                        4.8   4.9   5.0   5.1                       5.1

                                                    2                                   4.1
                                                                                                          3.8
                                                                                              3.6


                                                    1



                                                    0
                                                        Mon   Tue   Wed   Thu   Fri     Sat   Sun   WD    WE
                                                                                Day of Week

                                                                                                                31
    GeoLogger Study – Findings
• Accruals of VMT at high speeds were observed.

                                 Proportion of VMT
      Time Period              Accrued Above 65 mph
      Monday-Friday                    28%

     Saturday-Sunday                   42%

Monday-Friday, 7 a.m.-9 a.m.           28%

Monday-Friday, 4 p.m.-7 p.m.           28%


                                                      32
   GeoLogger Study – Findings
• Weekly patterns of VMT were observed.
                        Change
   Day of     Average   (Relative to
                                       Percent
   Week        VMT      Mon-Thurs)     Change

    Friday      29      Increase        0-4%


   Saturday     25      Decrease        0-24%


    Sunday      20      Decrease       22-33%


                                                 33
    GeoLogger Study – Findings
• Patterns in the frequencies of trips were observed.


       Day of Week         Average No. of Trips
      Monday-Thursday             4.8 to 5.1

            Friday                   5.6

          Saturday                   4.1

           Sunday                    3.5



                                                        34
Surface Street Traffic Counters

         Data Logger



                Pneumatic Hose
                   Sensors




                                  35
  Surface Street Traffic Counters
• Counters were deployed at 30 sites for 10-day periods.




                                                           36
Surface Street Traffic Counters – Example Data
                               Eastbound                                            Westbound
                               8 per. Mov. Avg. (Eastbound)                         8 per. Mov. Avg. (Westbound)
                 1000
 =15 Min. Volume X 4
   Rate (veh/hour)




                       800
                       600
                       400
                       200
                         0
                             8/2/02

                                      8/3/02

                                               8/4/02

                                                        8/5/02

                                                                 8/6/02

                                                                           8/7/02

                                                                                      8/8/02

                                                                                               8/9/02

                                                                                                        8/10/02

                                                                                                                  8/11/02

                                                                                                                            8/12/02
                                                                          Date
                                                                                                                                      37
Surface Street Traffic Counters – Results
        Traffic Volumes by Road Type




                                            38
Surface Street Traffic Counters – Results
       Traffic Volumes by Vehicle Type




                                            39
  Surface Street Traffic Counters – Findings
• Diurnal patterns of VMT were observed.

        Day of      Peak      Times of
        Week       Pattern      Peak

       Monday-               7 a.m.-8 a.m.
                    Sharp
        Friday               4 p.m.-5 p.m.


       Saturday-
                   Gradual   Noon-5 p.m.
        Sunday



                                               40
  Surface Street Traffic Counters – Findings
• Patterns in traffic volumes were observed.

                          Change
  Vehicle      Day of     (Relative to
                                         Percent
   Type        Week       Mon-Thurs)     Change
               Saturday   Decrease        25%
  Light duty
               Sunday     Decrease        33%

               Saturday   Decrease        56%
  Heavy duty
               Sunday     Decrease        83%

                                                   41
Caltrans WIM Data




          Source of Photos: Oak Ridge National Laboratory




                                                       42
Acquisition of WIM Data




                          43
Example WIM Data




                   44
                     WIM Data Analyses – Results
                     Average Diurnal Traffic Volumes: Light-Duty Vehicles
                     3500




                     3000




                     2500
                                                                                                                          Sun
Number of Vehicles




                                                                                                                          Mon

                     2000                                                                                                 Tues
                                                                                                                          Wed
                                                                                                                          Thurs
                     1500                                                                                                 Fri
                                                                                                                          Sat


                     1000




                      500




                        0
                            0:00



                                   2:00



                                          4:00



                                                 6:00



                                                        8:00



                                                               10:00



                                                                          12:00



                                                                                  14:00



                                                                                          16:00



                                                                                                  18:00



                                                                                                          20:00



                                                                                                                  22:00
                                                                       Hour
                                                                                                                                  45
          WIM Data Analyses – Results
Average Diurnal Traffic Volumes: Heavy-Duty Vehicles
                     250




                     200



                                                                                                                         Sun
Number of Vehicles




                                                                                                                         Mon
                     150
                                                                                                                         Tues
                                                                                                                         Wed
                                                                                                                         Thurs

                     100                                                                                                 Fri
                                                                                                                         Sat




                     50




                      0
                           0:00



                                  2:00



                                         4:00



                                                6:00



                                                       8:00



                                                              10:00



                                                                         12:00



                                                                                 14:00



                                                                                         16:00



                                                                                                 18:00



                                                                                                         20:00



                                                                                                                 22:00
                                                                      Hour
                                                                                                                                 46
 WIM Data Analyses – Findings
Vehicle
 Type        Day of     Diurnal      Percent
             Week       Pattern      Change

             Weekday    Bimodal        n/a

Light duty
                                     Decrease
             Weekend   Single mode
                                      11-26%

             Weekday   Single mode     n/a

Heavy duty
                                     Decrease
             Weekend   Single mode
                                      50-75%
                                                47
CEMS Data




            48
     Acquisition of CEMS Data
• CEMS data were provided by the South
  Coast Air Quality Management District.
  – SoCAB major point sources
  – May 2002 through October 2002
  – Daily total NOx
  – Confidential information withheld




                                           49
                     Daily Total NOx Emissions (lbs)




                                                                 100,000
                                                                           120,000
                                                                                     140,000




                             20,000
                                      40,000
                                               60,000
                                                        80,000




                         0
              5/1/2002

             5/15/2002

             5/29/2002

             6/12/2002

             6/26/2002

             7/10/2002

             7/24/2002



     Date
              8/7/2002

             8/21/2002

              9/4/2002

             9/18/2002
                                                                                               Example CEMS Data




             10/2/2002

            10/16/2002

            10/30/2002
50
                 CEMS Data Analyses – Results
                            Error bars represent +/- 1 standard error of the mean

                 60
                 55
NOx (1000 lbs)




                 50
                 45
                 40
                 35
                 30
                      Mon     Tue         Wed        Thu          Fri     Sat       Sun
                                                Day of the Week

                                    Original Data       With June 30 Normalized
                                                                                          51
 CEMS Data Analyses – Results
                        NOx Emissions (1000 lbs)
                 Largest 20    Other 58
Time of Week     Emissions    Emissions       Total
                  Sources      Sources
Average WD
                   40.23         9.67         49.90
(Mon-Thu)
Average Friday     37.92         9.26         47.18
Average WE
                   38.17         8.58         46.75
(Sat-Sun)
% Decrease
                  5.11%        11.25%         6.30%
WD to WE

                                                      52
 CEMS Data Analyses – Findings
• NOx emissions from major point sources declined
  6% on Friday-Sunday (relative to Monday-
  Thursday).
• Low-emitting facilities experienced larger WD-WE
  variability than high-emitting facilities.
• Emissions from high-emitting facilities declined
  Friday-Sunday.
• Emissions from low-emitting facilities declined only
  on Saturday and Sunday.



                                                         53
Special Studies in Neighborhoods




                                   54
    Neighborhood Special Studies
• WD-WE field observers’ diaries
• Ground-truth surveys of potential emissions sources




                                                        55
        Summary and Wrap-Up
•   Key Findings
•   Recommendations for Modeling
•   Recommendations for Further Research
•   Closing Remarks
•   Acknowledgments




                                           56
                Key Findings
• Activity levels for on-road mobile and business-
  related sources decline on WEs relative to WDs.
• Activity levels for recreation-related sources
  increase on WEs relative to WDs.
• NOx emissions from major point sources decline
  on WEs.
• Substantial accrual of VMT occurs at vehicle
  speeds above 65 miles per hour, especially on
  WEs.
• Travel predominantly occurs on major highways,
  especially on WEs.
                                                     57
 Recommendations for Modeling
                 Average Value,
 Variable          Monday-          Units
                   Thursday

 Light-duty                        Miles per
                       28
    VMT                           vehicle-day


 Light-duty                        Soaks per
                       5
soaks or trips                    vehicle-day

                                                58
Recommendations for Modeling
             Day of                Percent
Variable                Change
             Week                  Change
              Friday    Increase    3.5%
Light-duty   Saturday   Decrease   10-20%
   VMT
             Sunday     Decrease    30%
              Friday    Increase    10%
Light-duty
 soaks or    Saturday   Decrease    20%
   trips     Sunday     Decrease    30%
                                             59
  Recommendations for Modeling
                   Day of                   Percent
 Variable                       Change
                   Week                     Change
 Heavy-duty        Saturday     Decrease     55-70%
   VMT             Sunday       Decrease     75-80%
Activity levels   Saturday or   Increase     25-165%,
      for          Sunday                  depending on
 recreational                               the source
   sources                                   category
Activity levels   Saturday or   Decrease     60-99%,
      for          Sunday                  depending on
 commercial                                 the source
   sources                                   category

                                                          60
  Recommendations for Modeling
• Apply changes to activity patterns for light-duty
  vehicles.
   – Apply a single-mode diurnal profile to represent WE
     activity patterns.
   – Slightly increase the proportion of VMT occurring on
     Friday afternoons and evenings.
   – Adjust speed distributions to reflect high proportions of
     VMT occurring at high speeds.
• Apply diurnal profiles to recreational emissions
  sources favoring activities in the afternoons.
• Apply day-specific emissions data for NOx from
  point sources.

                                                                 61
 Recommendations for Further Research
• Continue to mine the databases generated
  through this project.
• Develop emission factors for on-road vehicles that
  correspond to high speeds above 65 mph.
• Investigate further whether the modeled number of
  starts and/or soaks per day should be reduced.
• Investigate further the extent to which emissions
  should be spatially re-allocated on WEs.
• Investigate further the differences in activity
  patterns for light-duty utility vehicles and
  passenger vehicles.

                                                       62
           Closing Remarks
• Significant WD-to-WE variability occurs
  across all components of the emission
  inventory: point, area, and mobile.
• Much of this variability can now be
  quantified for the SoCAB.




                                            63
               Acknowledgments
• Leon Dolislager of the California Air Resources
  Board (ARB) was the ARB technical contact and
  Project Officer.
• Population Research Systems of San Francisco conducted
  surveys and recruited study volunteers.
• Wiltec, Inc. of Antioch, California, deployed surface street
  traffic counters.
• Caltrans provided freeway weigh-in-motion data.
• GeoStats of Atlanta, Georgia, supplied the in-vehicle
  sensors (GeoLoggers) and performed initial data
  processing and quality assurance.
• South Coast Air Quality Management District provided
  continuous emissions monitoring systems data.

                                                                 64
         For More Information
For more information, please visit the ARB’s web
  sites for “weekend effect” and air pollution
  research.
  www.arb.ca.gov/aqd/weekendeffect/weekendeffect.htm

  www.arb.ca.gov/research/apr/past/atmospheric.htm

A copy of the final report may be downloaded from
  the following location:
  www.arb.ca.gov/research/abstracts/00-305.htm



                                                       65

				
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