United States Air and Radiation EPA420-P-99-033
Environmental Protection March 1999
Agency NR-015
svEPA Weekday and Weekend
Day Temporal Allocation of
Activity In the
NONROAD Model
> Printed on Recycled Paper
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EPA420-P-99-033
March 1999
of
In the
NR-015
Assessment and Standards Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
NOTICE
This technical report does not necessarily represent final EPA decisions or positions.
It is intended to present technical analysis of issues using data that are currently available.
The purpose in the release of such reports is to facilitate the exchange of
technical information and to inform the public of technical developments which
may form the basis for a final EPA decision, position, or regulatory action.
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Weekday and Weekend Day Temporal Allocation of Activity
In The NONROAD Model
Report No. NR-015
March 31, 1999
Assessment and Standards Division
EPA, Office of Transportation and Air Quality
1. Introduction
The EPA is developing a national nonroad air emissions inventory model called NONROAD.
The model uses estimates of annual activity for each equipment type, generally expressed in
terms of hours of operation or gallons of fuel used per year, to calculate yearly emission
inventories. It will also calculate inventories on a seasonal (i.e., summer, fall, winter, spring),
monthly, or daily (i.e., weekday or weekend day) basis by allocating annual activity to these
smaller time periods. This memorandum documents the daily activity allocation fractions used in
the current, draft version of NONROAD. The fractions are expressed as weekday and weekend
day fractions of weekly activity and are provided for each equipment/category type. Seasonal and
monthly activity allocation fractions are addressed in a separate technical memorandum (Report
No. NR-004).
Section 2 provides a background and description of the basic sources of information used.
Section 3 defines the fractions and how they are used in the model. Section 4 provides a list of
the default fractions used in the model.
2. Background and Data Sources Used
The weekly temporal activity allocation feature of NONROAD allows the user to distribute
nonroad equipment activity between weekdays and weekend days. This feature coincides with
NONROAD's ability to allocate equipment activity to a specific month and season, thereby
allowing the user to model a typical weekday or weekend day during a given month and season
(e.g., a typical summer weekend day in June). State and local air agencies may want or need the
ability to model weekly activity in order to analyze the effects of episodic controls or voluntary
incentive programs involving specific categories or types of nonroad equipment.
At the weekly level, temporal activity allocation is largely dependent on people's recreational
and work patterns as well as the purpose for which the equipment is used. For example, most
commercial lawn and garden equipment activity occurs on weekdays when lawn care services
tend to operate. In contrast, recreational marine equipment is used primarily on weekends.
The Nonroad Engine and Vehicle Emission Study (NEVES)1 did not include a study of
weekly activity patterns. Its main purpose was to assess the annual and seasonal contribution of
Environmental Protection Agency, Office of Air and Radiation. Nonroad Engine and Vehicle
Emission Study. 21A-2001, November 1991.
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nonroad equipment emissions to the total air pollution inventory for all sources, so it did not
require that level of detail.
For the draft version of NONROAD, the fractions for residential lawn and garden equipment,
commercial lawn and garden equipment, and recreational marine equipment were based on
available survey data. For the remaining equipment types for which survey data were not
available, fractions were based on NEEMT's assessment of typical usage patterns and, for similar
equipment types, comparison with the off-highway model (OFFROAD, formerly known as
MVOFF) developed by the California Air Resources Board.2 The draft version of NONROAD
and OFFROAD have similar weekday and weekend day activity fractions for common equipment
types.
3. Methodology
The draft version of the NONROAD model has the capability to accept two fractions that
represent the amount of activity allocated to each weekday and each weekend day. These
fractions are contained in the seasonal/monthly allocation file (season.dat) following the
seasonal/monthly allocation fractions. The weekday fraction represents equipment activity during
each of the five weekdays and the weekend day fraction represents the activity during each of the
two weekend days. For example, survey data indicate that 80 percent of commercial lawn and
garden activity occurs Monday through Friday and 20 percent occurs during Saturday and
Sunday. The resulting weekday and weekend day fractions are:
Weekday Fraction = 0.80/5 = 0.16, or 16% per weekday
Weekend Day Fraction = 0.20/2 = 0.10, or 10% per weekend day
Through the use of Source Category Codes (SCCs), weekday and weekend day fractions are
assigned for each equipment category (e.g., construction equipment). All equipment types within
a category (e.g., excavators within the construction equipment category) are assigned the
weekday and weekend day fractions for that category. Users may substitute local activity data
where available.
4. Default Weekday and Weekend Day Activity Allocation Fractions Used in Draft
Version of NONROAD
The default weekly activity allocation fractions contained in the draft version of NONROAD
are shown in Table 1.
Energy and Environmental Analysis. Documentation of Input Factors for the New Off-Road Mobile
Source Emissions Inventory Model - Draft. Prepared for the California Air Resources Board, August
1995. OFFROAD was formerly known as MVOFF.
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Table 1
Default Weekday and Weekend Day Activity Allocation Fractions
Used in Draft Version of NONROAD*
Equipment Category
Recreational
Construction
Industrial
Residential Lawn and Garden
Commercial Lawn and Garden
Agricultural
Light Commercial
Logging
Airport Service
Railway Maintenance
Recreational Marine
Transportation A/C Refrigeration
Underground Mining
Oil Field Equipment
Weekday
0.1111111
0.1666667
0.1666667
0.1111111
0.1600000
0.1666667
0.1666667
0.1666667
0.1428571
0.1800000
0.0600000
0.1428571
0.1666667
0.1428571
Weekend Day
0.2222222
0.0833334
0.0833334
0.2222222
0.1000000
0.0833334
0.0833334
0.0833334
0.1428571
0.0500000
0.3500000
0.1428571
0.0833334
0.1428571
* The values are the fractions of weekly activity allocated to each weekday and each weekend day. To get the
fraction for all weekdays, multiply the weekday fraction by 5. Similarly, to get the weekend fraction, multiply the
weekend day fraction by 2. All equipment types within a category (e.g., excavators within the construction
equipment category) are assigned the weekday and weekend day fractions for that category.
As seen in Table 1, recreational equipment is assigned a pattern of twice as much use on the
weekend days compared to the weekdays, based on an assessment of typical usage patterns. The
fractions for recreational equipment are also in agreement with those used in California ARB's
OFFROAD model (hereafter, simply referred to as OFFROAD).
The construction, industrial, agricultural, light commercial, logging, and underground mining
categories are commercial in nature, and should be used more on weekdays than on weekend
days; therefore, it is estimated that these equipment categories are used twice as much on the
weekdays compared to the weekend days. For the construction, industrial, agricultural, light
commercial, and logging categories, this estimate is very similar to the weekday/weekend day
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activity fractions (0.164 weekday, 0.090 weekend day) specified in OFFROAD.3
Weekday/weekend day activity fractions for the underground mining category are not specified in
OFFROAD.
Airport service equipment, transportation A/C refrigeration equipment, and oil field
equipment were thought to be used uniformly throughout the week. For the airport service
equipment and transportation A/C refrigeration categories, this agrees with the estimates in
OFFROAD. Weekday/weekend day activity fractions for the oil field equipment category are not
specified in OFFROAD.
In contrast to the above equipment categories, survey data are available for the residential
lawn and garden, commercial lawn and garden, and recreational marine categories. The surveys
are described below, followed by a discussion of how they were used to develop weekday and
weekend day activity fractions for these three categories.
Systems Applications International, Inc. (SAI) conducted a survey of recreational marine use
in California for the California Air Resources Board.4 The survey was part of a larger effort to
develop an emissions inventory of pleasure craft in California. From June 1993 to May 1994,
over 10,000 surveys were sent to randomly selected owners of motorized pleasure craft registered
with the California Department of Motor Vehicles. Temporal (seasonal, weekly, and diurnal)
profiles were obtained with the survey data. Profiles are provided of the percent of weekly
activity for each day of the week, on both an annual basis and for the winter season. In both
cases, usage during the week is fairly flat (less than or equal to 10% each weekday), with 60-70%
of the total weekly activity occurring on the weekend. On an annual basis, the daily activity
fractions are as follows: Monday (0.0527578), Tuesday (0.0621816), Wednesday (0.0702681),
Thursday (0.0723208), Friday (0.1043395), Saturday (0.3039638), and Sunday (0.3341683).
When combined, the fraction of activity on all weekdays is 0.36 and the fraction of activity on
the weekend is 0.64.
SAI also conducted a telephone survey of weekly activity patterns for residential and
commercial lawnmowers in the Houston/Galveston and Beaumont/Port Arthur areas for the
Texas Natural Resources Conservation Commission (TNRCC).5 Again, this was part of a larger
effort to develop an emissions inventory for selected area and nonroad sources. Profiles are
OFFROAD has separate activity fractions for each day of the week. In order to compare the estimates
with NONROAD, the fractions for each weekday were summed and divided by five to obtain the
weekday fraction. The fractions for Saturday and Sunday were summed and divided by two to obtain
the comparable weekend day fraction.
Systems Applications International. Development of an Improved Inventory of Emissions from
Pleasure Craft in California. Contract Number A132-184, Prepared for the California Air Resources
Board, June 1995.
Systems Applications International. Bottom-Up Emission Inventory Development for Selected Source
Categories in the Houston-Galveston and Beaumont-Port Arthur Areas. Prepared for the Texas Natural
Resource Conservation Commission, May 1995.
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provided of the percent of weekly activity for each day of the week for both residential and
commercial lawnmowers. For residential lawnmowers, the daily activity fractions are as follows:
Monday (0.11), Tuesday (0.10), Wednesday (0.11), Thursday (0.15), Friday (0.16), Saturday
(0.24), and Sunday (0.14). When combined, the fraction of activity on all weekdays is 0.63 and
the fraction of activity on the weekend is 0.38. For commercial lawnmowers, the daily activity
fractions given in the SAI report are 0.16 for each weekday and 0.10 for each weekend day. This
translates into a combined weekday fraction of 0.80 and a combined weekend fraction of 0.20.
There are also estimates of weekday vs. weekend use for residential lawnmowers and
recreational marine equipment provided by the Texas Air Control Board.6 During the first week
in August 1993, the North Central Texas Council of Governments (NCTCOG) conducted an in-
house survey to measure the level of consumer lawn mower usage and the degree of weekend
usage in the Dallas-Fort Worth area. The results indicated a mean combined weekday activity
fraction of 0.504 and a combined weekend fraction of 0.496. Based upon NCTCOG survey data
of area lake authorities, the combined weekday and weekend fractions of summer boating
activity are 0.25 and 0.75, respectively.
For residential lawn and garden equipment, the SAI and NCTCOG survey results were
averaged to obtain a combined weekday fraction of 0.56 and a combined weekend fraction of
0.44. This translates into daily activity fractions of 0.11 for weekdays and 0.22 for weekend days.
For commercial lawn and garden equipment, the single source of survey data is the SAI
telephone survey in the Houston/Galveston and Beaumont/Port Arthur areas. The daily activity
fractions given in the SAI report (0.16 for each weekday and 0.10 for each weekend day) are used
directly in NONROAD.
For the commercial marine category, SAI's annual estimates of pleasure craft activity in
California were averaged with NCTCOG's estimates of summer recreational boating activity in
the Dallas-Fort Worth area to obtain a combined weekday fraction of 0.30 and a combined
weekend fraction of 0.70. This translates into daily activity fractions of 0.06 for weekdays and
0.35 for weekend days.
The EPA welcomes suggestions and comments about the approach and sources of
information used, as well as information about other surveys of nonroad equipment that have
been or are presently being conducted.
Memorandum from Everett Bacon and Michael Burbank, North Central Texas Council of Governments
to Bill Gill, Texas Air Control Board. Recreational Boating and Lawn and Garden Off-road Emission
Inventories for the Dallas-Fort Worth Nonattainment Area. August 13, 1993.
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