Air and Radiation EPA420-P-04-015

April 2004

NR-015a

Weekday and Weekend Day

Temporal Allocation of

Activity in the Draft

NONROAD2004 Model
EPA420-P-04-015

Revised April 2004

Weekday and Weekend Day Temporal Allocation of

Activity in the Draft NONROAD2004 Model

NR-015a

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.
Weekday and Weekend Day Temporal Allocation of Activity

In The Draft NONROAD2004 Model

Report No. NR-015a

Revised April 2004

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 latest version of this model is draft NONROAD2004. 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-004b).

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 draft NONROAD2004 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.
1 Environmental Protection Agency, Office of Air and Radiation. Nonroad Engine and Vehicle

Emission Study, 21A-2001, November 1991.

2 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.

2

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

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 NONROAD2004, the fractions for residential lawn and garden

equipment, commercial lawn and garden equipment, and recreational marine equipment are

based on available survey data. For the remaining equipment types for which survey data are not

available, fractions are based on EPA’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

NONROAD2004 and OFFROAD have similar weekday and weekend day activity fractions for

common equipment types.

3. Methodology

The draft version of the NONROAD2004 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

NONROAD2004

The default weekly activity allocation fractions contained in the draft version of NONROAD

are shown in Table 1.
3

Table 1

Default Weekday and Weekend Day Activity Allocation Fractions 

Used in Draft NONROAD2004*

Equipment Category Weekday Weekend Day

Recreational 0.1111111 0.2222222

Construction 0.1666667 0.0833334

Industrial 0.1666667 0.0833334

Residential Lawn and Garden 0.1111111 0.2222222

Commercial Lawn and Garden 0.1600000 0.1000000

Agricultural 0.1666667 0.0833334

Light Commercial 0.1666667 0.0833334

Logging 0.1666667 0.0833334

Airport Service 0.1428571 0.1428571

Railway Maintenance 0.1800000 0.0500000

Recreational Marine 0.0600000 0.3500000

Transportation A/C Refrigeration 0.1428571 0.1428571

Underground Mining 0.1666667 0.0833334

Oil Field Equipment 0.1428571 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
3 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.

4 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.

5 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.

4

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

provided of the percent of weekly activity for each day of the week for both residential and
6 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.

5

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 inhouse 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.