1

Seasonal and Monthly Activity Allocation Fractions 

For Nonroad Engine Emissions Modeling

Report No. NR-004

December 9, 1997

Greg Janssen

and

Rich Wilcox

Nonroad Engine Emission Modeling Team

Assessment and Modeling Division

EPA, Office of Mobile Sources

Introduction

The Nonroad Engine Emission Modeling Team (NEEMT) is developing a national

nonroad air emissions inventory model called NONROAD. The model uses estimates of annual

activity for each equipment type, e.g., generally expressed in terms of hours of operations 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., week or

weekend day) basis by allocating annual activity to these smaller time periods. This

memorandum documents the seasonal and monthly activity allocation fractions used by the

model. Daily activity allocation fractions are addressed in a separate technical memorandum. 

The NEEMT currently considers these fractions to be final inputs for the beta version of

NONROAD.

The remainder of this memorandum is organized into two parts. The first part contains a

basic description of the overall approach and sources of information that are used to develop the

requisite temporal allocation fractions. The second part explains how this information is used

and describes the final default values for each state. 

Background

The NONROAD model allocates annual activity for the various equipment categories to

each month of the year based on the general climate and geographic location of the state and the

time of year in which the equipment is used. Seasonal inventories are computed by combining

the monthly activity fractions that comprise each of the four seasons as shown in Table 1.
Environmental Protection Agency, Office of Air and Radiation. Nonroad Engine and Vehicle Emission Study, 1

21A-2001, November 1991.

Energy and Environmental Analysis. Documentation of Input Factors For the New Off-Road Mobile Source 2

Emissions Inventory Model - Draft. Prepared for the California Air Resources Board, August 1995. OFFROAD

was formerly know as MVOFF

The derivation of allocation factors for the fall and spring using the NEVES summer and winter values is 3

explained in the next section.

2

Table 1

Season and Month Correspondence

Season Month

Summer June, July, and August

Fall September, October, and November

Winter December, January, and February

Spring March, April, and May

The monthly activity allocation fractions used in NONROAD were derived from the

seasonal activity factors contained in the November 1991 Nonroad Engine and Vehicle Emission

Study (NEVES) and monthly activity factors contained in a technical report for the California 1

Air Resources Board (CARB) nonroad emissions model - OFFROAD. The NEEMT decided to 2

develop the activity allocation fractions based on these two documents as final default values for

the beta version of NONROAD. To the best of the NEEMT’s current knowledge, these two

sources of information represent the most comprehensive work that has been done to date

concerning the distribution of activity by season and month for a broad range of nonroad

equipment categories on a statewide (CARB) and nationwide (EPA) basis. EPA recognizes that

states and other users of NONROAD may have more detailed information on their local activity

levels by season and month. Such users of NONROAD may substitute activity allocation

fractions derived for a state, county, or air quality management district based on surveys or other

studies for any of the equipment categories.

The data from NEVES can be found in Appendix L, Tables L-02, L-03, and L-04 of that

document, which contain percentages of activity for summer and winter use only (Attachment

1). More specifically, Table L-02 contains summer and winter activity allocations for 3

agricultural, construction, industrial, lawn and garden (excluding chainsaws),

snowblower/snowmobile, commercial marine, airport service, logging (including chainsaws),

and light commercial equipment. These percentages were derived from a paper written by Hare
Hare, C.T., and K.J. Springer. Exhaust Emissions from Uncontrolled Vehicles and Related Equipment Using 4

Combustion Engines, Part 5, No. APRD-1494. San Antonio, TX:Southwest Research Institute, October 1973.

California Air Resources Board. Technical Support Documents for California Exhaust Emission Standards and 5

Test Procedures for 1994 and Subsequent Model Year Utility and Lawn and Garden Equipment Engines. 

Attachment C to CARB Mailout #90-64. El Monte, CA:State of California, December 1991.

Irwin Broh & Associates, Inc. NMMA Boat Usage Survey. Prepared for the National Marine Manufacturers 6

Association, Des Plaines, IL, August 1991.

Burke Marketing Research. 1990 Survey of Motorcycle Ownership and Usage: Final Results Waves 1-12, 7

Volume II. Conducted for the Motorcycle Industry Council, Inc. May 1991.

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and Springer, 1987 state implementation plan (SIP) inventories, and the CARB Technical 4 

Support Document for proposed regulations applicable to lawn and garden equipment. Separate 5

summer and winter activity allocations for these general equipment categories are provided for

three climatological and geographical regions (cold/northern, medium/central, and

warm/southern). These regions are defined by the average January temperature and latitude

criteria shown in Table 2. 

Table 2

Seasonal Activity Allocation Fraction Regions Defined by Hare and Springer

Region Temperature (EF) Latitude

Average January

Cold/Northern < 35E 43E and north

Medium/Central 35E - 44E 37E to 43E

Warm/Southern > 45E 37E and south

Table L-03 contains summer and winter activity allocations for recreational marine

equipment from a boat usage survey done for the National Marine Manufacturers Association

(NMMA). The factors in this table are arranged into eight geographical regions: Northeast, 6

Southeast, Mid-Atlantic Coast, Great Lakes, Southwest, Rocky Mountains, Northwest, and West

Coast. 

Table L-04 contains summer and winter activity allocations for recreational equipment

from a survey done for the Motorcycle Industry Council (MIC). Table L-04 lists twelve regions. 7

However, the list of regions was subsequently found to be in error, based on a list received from

the MIC that defines the geographical regions used for its survey. The corrected information was

used in the development of the allocation scheme for the NONROAD model. 

The MIC organized the seasonal activity usage results into four regions (East, Midwest,

South, West), which the MIC further divided into eight subregions: New England and Middle
In NEVES, Middle Atlantic was changed to be Mid-Atlantic Coast. However, in the documentation of the 8

geographic definitions received from the MIC, it is labeled at Middle Atlantic. 

For commercial marine, as well as aircraft and locomotives, baseline emissions in tons per day were directly 9

entered into the OFFROAD model and a growth factor was used to project emissions into the future. Therefore,

seasonal activity allocation fractions were not needed. No explanation is given for why no seasonal activity

allocation fractions are listed for recreational marine equipment. 

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Atlantic (East); East Central and West Central (Midwest); Southeast and Southwest (South); and 8

Rocky Mountains and Pacific (West). In Table L-04, the allocations for the main regions are

averages of the two subregions that form each of the main regions.

The CARB model has activity allocations for the State of California, which are expressed

in monthly form (Attachment 2). The allocation fractions are described in the OFFROAD

model’s technical support document. The CARB factors differ from those contained in NEVES

for agriculture, construction, industrial, lawn and garden, snowblowers/snowmobile, and

recreational equipment. The CARB technical document did not contain allocations for certain

categories (i.e., commercial and recreational marine ), and it differed from NEVES in that it 9

contained separate factors for tillers, chainsaws less than or equal to five horsepower and

transportation refrigeration units. CARB and NEVES had equivalent allocations for the

remaining categories where usage was judged to be essentially uniform over the year. As

described in the next section, the CARB allocation factors are used directly in NONROAD to

model emissions in the State of California.

Methodology/Results

NEVES-Based Regional Activity Allocations

Because each of the seasonal allocation tables in NEVES contains different numbers and

types of geographical regions, composite regions were created for use in NONROAD by

geographically matching the less defined regions from Tables L-02 and L-03 to those in Table L04. This correspondence is shown in Table 3. The resulting ten composite regions represent an

attempt to reconcile and link the regions defined in each of the three tables so that they are

geographically coherent and compatible.
Regional and Seasonal Designations, Table L-01, NEVES Appendices, p. L-2 10

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Table 3

Mapping of Seasonal Activity Allocation Regions From NEVES to NONROAD

NEVES

General NEVES NEVES NONROAD

Equipment Recreational Marine Recreational Equipment Composite 

Table L-02 Table L-03 Table L-04 Regions

Cold/Northern Northeast, Great Lakes, Midwest, New England, Northeast/New England,

Northwest, Rocky Mountains Rocky Mountains, East Great Lakes/Midwest,

Central Rocky Mountains,

Northwest

Medium/Central Mid-Atlantic Coast, West Mid-Atlantic Coast, West Middle Atlantic, West

Coast Central, Pacific, Coast, Central West

Warm/Southern Southeast, Southwest South, Southeast, Southwest Southeast, Southwest,

South Central

There were two exceptions in regard to the general method of defining the regions

discussed above. The first involved a decision to leave out the East Central region found in

Table L-04 for recreation equipment from the composite regions because the region that it

defined could be included in and reasonably characterized by the Great Lakes/Midwest region. 

 The second exception pertained to the allocation factors used for the general equipment

categories included in the Rocky Mountains category for NONROAD. In Table L-02, the

general equipment categories used in this geographic area would have been classified as

Medium/Central by the criteria previously shown in Table 2. This classification may seem

reasonable since the Rocky Mountains region is generally located in the central part of the U.S. 

However, the climatic conditions found in most of the Rocky Mountains more closely resemble

the northern part of the U.S. than the central section of the country. Therefore, NONROAD uses

the Cold/Northern seasonal activity allocation factors from Table L-02 for the general equipment

categories included in the Rocky Mountains category. This rationale is also supported by Table

L-01 in NEVES, which classified the nonattainment area of Denver as being within a cold

region.10

Since the seasonal allocation factors for all of the categories except recreational

equipment were arranged in more general regions than the ten composite regions described

above, these values were used multiple times based on the matching strategy in Table 3. For

example, the cold/northern fractions from Table L-02 are used in the Northeast/New England,

Midwest/Great Lakes, Rocky Mountains, and Northwest regions.
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Because the allocation tables in NEVES include only summer and winter factors, it was

also necessary to develop allocations for the remaining two seasons. These allocations were

determined by taking the sum of the summer and winter allocation percentages for each

equipment category and geographical region represented in the NEVES tables, and subtracting

this value from one hundred. The resulting value was then divided by two to obtain the fall and

spring allocation percentages. 

The monthly allocation fractions required by NONROAD can be computed from the

NEVES-based seasonable allocation percentages by first dividing the seasonal percentages for

each equipment category and region described above by 100 to convert from percentile to

fractional form. Second, each seasonal allocation fraction was then divided by three to produce

the allocation fraction for each month of the respective season (Table 1). The resulting monthly

allocation fractions by equipment category for all regions except the West Coast, which is

described below, are shown in Table 4. 

This approach assumes that the four seasons are contained in specific three month

periods, within which usage in each category is constant. For example, this results in

NONROAD apportioning the use of snow-related equipment to December, January, and

February because these are defined as the winter months. However, it is common knowledge

that significant snow can occur in late fall and early spring in certain areas. While the NEVESbased method does not optimally reflect such conditions, in the absence of more specific regional

or local data, the method provides a reasonable and logical approximation of the seasonal

impacts on nonroad equipment usage for a national emission inventory model. 

CARB-Based Regional Activity Allocations

An exception to the NEVES-based approach described above resulted from using the

available fractions from the CARB OFFROAD technical support document for the State of

California, which is represented in NONROAD by the West Coast region. Commercial and

recreational marine were not included in the CARB model, so NONROAD uses allocations

derived from NEVES. The resulting monthly allocation fractions by equipment category for the

West Coast and for each of the other regions are shown in Table 4, starting on the next page. 
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Table 4

Monthly Seasonal Activity Allocation Fractions

(Based on Tables L-02, L-03, and L-04 in Appendix L in NEVES)

Northeast/New England

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.073 0.073 0.073 0.167 0.167 0.167 0.073 0.Construction 0.033 0.033 0.078 0.078 0.078 0.143 0.143 0.143 0.078 0.Industrial 0.067 0.067 0.083 0.083 0.083 0.100 0.100 0.100 0.083 0.Lawn and Garden excl. chainsaws 0.020 0.020 0.073 0.073 0.073 0.167 0.167 0.167 0.073 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.003 0.003 0.052 0.052 0.052 0.230 0.230 0.230 0.052 0.Recreational Equipment 0.047 0.047 0.070 0.070 0.070 0.146 0.146 0.146 0.070 0.
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Table 4 Continued

Great Lakes/Midwest

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.073 0.073 0.073 0.167 0.167 0.167 0.073 0.Construction 0.033 0.033 0.078 0.078 0.078 0.143 0.143 0.143 0.078 0.Industrial 0.067 0.067 0.083 0.083 0.083 0.100 0.100 0.100 0.083 0.Lawn and Garden excl. chainsaws 0.020 0.020 0.073 0.073 0.073 0.167 0.167 0.167 0.073 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.000 0.000 0.050 0.050 0.050 0.233 0.233 0.233 0.050 0.Recreational Equipment 0.027 0.027 0.077 0.077 0.077 0.153 0.153 0.153 0.077 0.

Rocky Mountains

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.073 0.073 0.073 0.167 0.167 0.167 0.073 0.Construction 0.033 0.033 0.078 0.078 0.078 0.143 0.143 0.143 0.078 0.Industrial 0.067 0.067 0.083 0.083 0.083 0.100 0.100 0.100 0.083 0.Lawn and Garden excl. chainsaws 0.020 0.020 0.073 0.073 0.073 0.167 0.167 0.167 0.073 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.000 0.000 0.052 0.052 0.052 0.230 0.230 0.230 0.052 0.Recreational Equipment 0.027 0.027 0.080 0.080 0.080 0.147 0.147 0.147 0.080 0.
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Table 4 Continued

Mid-Atlantic

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.090 0.090 0.090 0.133 0.133 0.133 0.090 0.Construction 0.050 0.050 0.078 0.078 0.078 0.127 0.127 0.127 0.078 0.Industrial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Lawn and Garden excl. chainsaws 0.020 0.020 0.090 0.090 0.090 0.133 0.133 0.133 0.090 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.007 0.007 0.068 0.068 0.068 0.190 0.190 0.190 0.068 0.Recreational Equipment 0.040 0.040 0.078 0.078 0.078 0.137 0.137 0.137 0.078 0.

Southeast

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.100 0.100 0.100 0.113 0.113 0.113 0.100 0.Construction 0.067 0.067 0.078 0.078 0.078 0.110 0.110 0.110 0.078 0.Industrial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Lawn and Garden excl. chainsaws 0.020 0.020 0.100 0.100 0.100 0.113 0.113 0.113 0.100 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.023 0.023 0.075 0.075 0.075 0.160 0.160 0.160 0.075 0.Recreational Equipment 0.057 0.057 0.080 0.080 0.080 0.117 0.117 0.117 0.080 0.
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Table 4 Continued

Northwest

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.073 0.073 0.073 0.167 0.167 0.167 0.073 0.Construction 0.033 0.033 0.078 0.078 0.078 0.143 0.143 0.143 0.078 0.Industrial 0.067 0.067 0.083 0.083 0.083 0.100 0.100 0.100 0.083 0.Lawn and Garden excl. chainsaws 0.020 0.020 0.073 0.073 0.073 0.167 0.167 0.167 0.073 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.016 0.016 0.063 0.063 0.063 0.190 0.190 0.190 0.063 0.Recreational Equipment* 0.043 0.043 0.073 0.073 0.073 0.143 0.143 0.143 0.073 0.

West Coast

Note: West Coast table uses CARB OFFROAD Seasonal Activity Allocation Fractions except for marine.

Equipment Category January February March April May June July August September OcAgricultural 0.054 0.054 0.086 0.086 0.108 0.108 0.108 0.108 0.108 0.Construction 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Industrial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Lawn and Garden excl. chainsaws 0.057 0.067 0.086 0.086 0.095 0.095 0.095 0.095 0.095 0.Snowblowers/Snowmobiles 0.200 0.200 0.180 0.060 0.020 0.000 0.000 0.000 0.000 0.Commercial Marine* 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.

Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine* 0.023 0.023 0.075 0.075 0.075 0.160 0.160 0.160 0.075 0.Recreational Equipment 0.060 0.060 0.070 0.080 0.090 0.100 0.100 0.100 0.090 0.

*CARB MVOFF doesn't have marine seasonal allocation fractions, so NEVES data are used for these.
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Table 4 Continued

Central West

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.090 0.090 0.090 0.133 0.133 0.133 0.090 0.Construction 0.050 0.050 0.078 0.078 0.078 0.127 0.127 0.127 0.078 0.Industrial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Lawn and Garden excl. chainsaws 0.020 0.020 0.090 0.090 0.090 0.133 0.133 0.133 0.090 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.023 0.023 0.075 0.075 0.075 0.160 0.160 0.160 0.075 0.Recreational Equipment 0.027 0.027 0.080 0.080 0.080 0.147 0.147 0.147 0.080 0.

Southwest

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.100 0.100 0.100 0.113 0.113 0.113 0.100 0.Construction 0.067 0.067 0.078 0.078 0.078 0.110 0.110 0.110 0.078 0.Industrial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Lawn and Garden excl. chainsaws 0.020 0.020 0.100 0.100 0.100 0.113 0.113 0.113 0.100 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.023 0.023 0.075 0.075 0.075 0.160 0.160 0.160 0.075 0.Recreational Equipment 0.040 0.040 0.085 0.085 0.085 0.123 0.123 0.123 0.085 0.
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Table 4 Continued

South Central

Equipment Category January February March April May June July August September OcAgricultural 0.020 0.020 0.100 0.100 0.100 0.113 0.113 0.113 0.100 0.Construction 0.067 0.067 0.078 0.078 0.078 0.110 0.110 0.110 0.078 0.Industrial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Lawn and Garden (excl. chainsaws) 0.020 0.020 0.100 0.100 0.100 0.113 0.113 0.113 0.100 0.Snowblowers/Snowmobiles 0.333 0.333 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.Commercial Marine 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Airport Service 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Logging (incl. chainsaws) 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Light Commercial 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.Recreational Marine 0.023 0.023 0.075 0.075 0.075 0.160 0.160 0.160 0.075 0.Recreational Equipment 0.050 0.050 0.082 0.082 0.082 0.120 0.120 0.120 0.082 0.
13

As a general practice, EPA welcomes and encourages the use of locally-derived activity

allocation data in place of national or regional default data. It is the NEEMT’s judgement that

state or local agencies, such as CARB, are usually in a better position than EPA to collect, assess,

and/or develop local nonroad activity-oriented data that more realistically mirror local conditions. 

In the specific case of California, NONROAD’s use of the CARB fractions will help to ensure

that EPA’s NONROAD model produces compatible results with those from California’s

OFFROAD model when NONROAD is run for California. If possible, EPA will incorporate

data from other local sources in future model revisions when such information becomes

available.

Assignment of Region Activity Allocations to States

The final task involves assigning states to each of the regions. These assignments are

shown in Table 5. As mentioned above, California is the only state apportioned to the West

Coast region. Many of the other states have logical assignments. However, some states do not

clearly belong in a particular region because they span more than one of the defined regions

and/or have several climatic tendencies that resemble more than one region. New York could be

included in the Great Lakes/Midwest, Northeast/New England, or Middle Atlantic regions. 

Pennsylvania could be included in the Great Lakes/Midwest or Middle Atlantic regions. 

Wyoming could be included in the Central West, Rocky Mountain, or Northwest regions. In

these cases, the NEEMT’s best judgement was used based on general knowledge of the state’s

climate, general geographical position, and information from the NEVES report. Alaska, which

has two CO nonattainment areas (Fairbanks and Anchorage), presented another problem. It

should have its own unique seasonal allocation fraction data. However, lacking this data, it

seemed logical to classify it as a Midwest/Great Lakes state, since the climatic conditions in

Alaska bear the closest resemblance to the states assigned to that region.
14

Table 5

Mapping of States to Regions Used For Defining Monthly Activity Allocation Fractions

State Region 

1. Alabama Southeast

2. Alaska Great Lakes/Midwest*

3. Arizona Southwest

4. Arkansas South Central

5. California West Coast

6. Colorado Rocky Mountains

7. Connecticut Mid-Atlantic

8. Delaware Mid-Atlantic

9. Florida Southeast

10. Georgia Southeast

11. Hawaii West Coast

12. Idaho Northwest

13. Illinois Great Lakes/Midwest

14. Indiana Great Lakes/Midwest

15. Iowa Great Lakes/Midwest

16. Kansas Central West

17. Kentucky South Central

18. Louisiana Southeast

19. Maine Northeast/New England

20. Maryland Mid-Atlantic

21. Massachusetts Northeast/New England

22. Michigan Great Lakes/Midwest

23. Minnesota Great Lakes/Midwest

24. Missouri Great Lakes/Midwest

25. Mississippi Southeast

26. Montana Northwest

State Region
15

27. Nebraska Central West

28. Nevada Central West

29. New Hampshire Northeast/New England

30. New Jersey Mid-Atlantic

31. New Mexico Southwest

32. New York Northeast/New England

33. North Carolina Mid-Atlantic

34. North Dakota Great Lakes/Midwest

35. Ohio Great Lakes/Midwest

36. Oklahoma South Central

37. Oregon Northwest

38. Pennsylvania Mid-Atlantic

39. Rhode Island Mid-Atlantic

40. South Carolina Southeast

41. South Dakota Great Lakes/Midwest

42. Tennessee South Central

43. Texas Southwest

44. Utah Central West

45. Vermont Northeast/New England

46. Virginia Mid-Atlantic

47. Washington Northwest

48. Washington, D.C. Mid-Atlantic

49. West Virginia Mid-Atlantic

50. Wisconsin Great Lakes/Midwest

51. Wyoming Rocky Mountains

*Although Alaska should have unique seasonal adjustment fractions, for the purpose of default data, Alaska has been

equated with the Midwest/Great Lakes profile because of a lack of data at this time. 
Attachment 1

NEVES Seasonal Activity Allocation Fractions

Table L-02. Summer and Winter Percentages of Yearly Activity

Equipment Category

Cold/Northern Medium/Central Warm/Southern

Summer Winter Summer Winter Summer Winter

(%) (%) (%) (%) (%) (%)

Agricultural 50 6 40 6 34 6

Construction 43 10 38 15 33 20

Industrial 30 20 25 25 25 25

Lawn and Garden (excl. chain saws) 50 6 40 6 34 6

Snowblowers/Snowmobiles 0 100 0 100 0 100

Commercial Marine 25 25 25 25 25 25

Airport Service 25 25 25 25 25 25

Logging (including chain saws) 25 25 25 25 25 25

Light Commercial 25 25 25 25 25 25

Table L-03. Summer and Winter Percentages of Yearly Activity for 

Recreational Marine Equipment

Region % During Summer % During Winter

Northeast 68 1

Southeast 48 7

Mid-Atlantic Coast 57 2

Great Lakes 70 0

Southwest 48 7

Rocky Mountains 69 0

Northwest 57 5

West Coast 48 7
17

Table L-04. Summer and Winter Percentages of Yearly

Activity for Recreational Equipment*

Region % During Summer % During Winter

East 42 12

Midwest 46 8

South 36 15

West 44 11

New England 44 14

Mid-Atlantic Coast 41 12

East Central 48 9

West Central 44 8

Southeast 35 17

Southwest 37 12

Rocky Mountains 44 8

Pacific 43 13

National Average 42 12

* Excluding snowmobiles
18

ATTACHMENT 2

CARB OFF-ROAD EQUIPMENT USE BY MONTH OF YEAR

Equipment Category

Fraction of Annual Use

Jan Feb Mar Apr May June July Aug Sep Oct 

Recreational Vehicles 0.061 0.061 0.071 0.081 0.091 0.101 0.101 0.101 0.091 0.091 Construction Equipment 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 Industrial Equipment 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 Lawn and Garden Equipment 0.057 0.067 0.086 0.086 0.095 0.095 0.095 0.095 0.095 0.086 Farm Equipment 0.054 0.054 0.086 0.086 0.108 0.108 0.108 0.108 0.108 0.0.75 Light Commercial Equipment 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 Logging Equipment 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 Aircraft GSE 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 Transportation Refrigeration Units 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 0.083 Snowmobiles & Snowblowers 0.200 0.200 0.180 0.060 0.020 0.000 0.000 0.000 0.000 0.000 Chainsaws (#5 HP) 0.090 0.090 0.090 0.050 0.050 0.040 0.080 0.090 0.090 0.110 Tillers 0.030 0.030 0.040 0.150 0.150 0.150 0.110 0.110 0.110 0.040