EPA-420-P-98-021
 

Nonroad Engine Population Estimates 

Report No. NR-006A 

December 9, 1997
 

revised June 15, 1998
 

Christian E. Lindhjem
 

Nonroad Emissions Modeling Team
 

Assessment and Modeling Division
 

EPA, Office of Mobile Sources
 

Purpose 

The purpose of this memorandum is to document the source of the nonroad engine 

population values used in EPA’s NONROAD emission inventory model. Engine populations 

were provided as default values in EPA’s NONROAD emission inventory model categorized by 

equipment type, power level, and fuel type for individual states. This categorization allows the 

NONROAD model to determine the phase-in of new emission standards and other unique 

aspects of emissions or allocations by application, fuel type, or power level. 

Introduction 

The default base year application populations are used as a starting point to estimate 

future and past year engine populations in the NONROAD emissions model. The NONROAD 

model tracks engines rather than equipment because present and planned nonroad emissions 

regulations focus on engines instead of equipment. EPA anticipates that future nonroad emission 

regulations would also focus on engines. 

The engine populations were divided into many applications because of the variety of 

ways nonroad engines are used. A complete description of these applications is provided in 

Appendix A of this document. This variety of applications allows for application-specific 

geographic and temporal allocations, activity, emission rates, and other input factors to 

characterize nonroad engine usage and emissions. 

The engine populations were also divided into 5 fuel types: diesel (2 and 4-stroke 

combined), gasoline 2-stroke, gasoline 4-stroke, compressed natural gas (CNG) (2 and 4-stroke 

combined), and liquid petroleum gas (LPG) (2 and 4-stroke combined). The diesel, CNG, and 

LPG engine populations for 2 and 4-stroke engines were combined because these engines exhibit 

little difference in emission rates between 2 and 4-stroke engines, most likely because these 

1
 
engines use fuel injection to deliver the fuel to the combustion chamber. Gasoline 2 and 4-stroke 

engines were separated because of the availability of information indicating widely different 

emission rates, especially for hydrocarbon emissions. Each combination of application and fuel 

has been assigned a unique “Source Classification Code” (SCC). 

The engine populations by application and fuel were further divided into 19 power level 

categories to account for emission regulations and some technology differences associated with 

power level. The power level categories provided were 0-1 hp, 1-3 hp, 3-6 hp, 6-11 hp, 11-16 

hp, 16-25 hp, 25-40 hp, 40-50 hp, 50-100 hp, 100-175 hp, 175-300 hp, 300-600 hp, 600-750 hp, 

750-1000 hp, 1000-1500 hp, 1500-2000 hp, 2000-3000 hp, and 3000+ hp. While this detailed 

disaggregation by application, fuel type, and power level allows users to make fine distinctions in 

understanding the effects of control strategies, it also might lead to very small engine populations 

for some states for some application and power segments. 

Base Year Population 

The base year (1996) default in-use engine populations came from estimates made by 

Power Systems Research (PSR), an independent marketing research firm.(1) NONROAD uses 

the PSR estimates for state and national populations, but, as described in the report on 

geographic allocation, the model uses other methods to allocate populations to the county level. 

The PSR estimates were determined from engine manufacturer sales surveys, experimentally 

determined engine life, and surveys of usage of these engines. The population estimates were 

verified by equipment owner surveys over the course of several years. A review and evaluation 

of the PSR methodology was provided by Pechan, another independent contractor. (2) The 1996 

base year population estimates were released in the middle of 1997, so they represent the most 

recently available information. The Nonroad Engine and Vehicle Emission Study (NEVES) 

report (3) used 1989 in-use year estimates from PSR, so the current estimates represent an update 

to the previous estimates. 

PSR developed engine population estimates for 2 and 4-stroke diesel, gasoline, liquid 

petroleum gas (LPG), and compressed natural gas (CNG) engines. These populations were 

further divided by power level for the NONROAD model to determine appropriate fleet turnover 

rates and appropriate engine emission standard phase-in strategies. Appendix A describes how 

PSR application codes correspond to the source categorization codes (SCC) for 2-stroke gasoline 

engines. The SCCs for other fuel and engine categories are identical in their last 6 digits, but 

differ in their prefix. Diesel engines are 2270xxxxxx, 4-stroke gasoline engines are 2265xxxxxx, 

LPG engines are 2267xxxxxx, and CNG engines are 2268xxxxxx. The remaining numbers 

marked by the “x” determine the applications where these engines are used. 

Exceptions to the coding system just described are marine (recreational, commercial, and 

military), rail (locomotives and maintenance equipment), and aircraft. Commercial and military 

vessels, locomotives, and aircraft are not yet included in the NONROAD model. Airport service 

2
 
equipment is included in the coding system described previously. The recreational marine 

equipment and coding is described below in a separate section and in Appendix B. Railway 

maintenance equipment uses 228500x015 for the SCC with the “x” replaced by “2” for diesel, 

“3” for 2-stroke gasoline, “4” for 4-stroke gasoline, “6” for LPG, and “8” for CNG engines. 

Equipment Inventory Changes 

Previous equipment estimates in the Nonroad Engine and Vehicle Emission Study 

(NEVES) were also provided by PSR in 1990 for the 1989 in-use engine populations. (3) The 

NEVES work led to development of source category codes (SCCs) for given applications. 

NEVES did not include several equipment classes and power ranges of some types of equipment. 

The current PSR estimate included those additional engines and revised the 1990 PSR estimate 

of the 1989 in-use engine population with the 1997 PSR estimate of the 1996 in-use engine 

population. These two factors, a revised PSR estimate and the new equipment classes and power 

range additions, accounted for the majority of changes that affect the engine population. 

Appendix B describes both significant and minor changes between the data derived from 

the NEVES report and the NONROAD model for some SCCs. New equipment classes and 

power range additions for some equipment types were included in the NONROAD model, 

altering the engine population estimates. There were other minor changes that did not affect 

engine populations but rather changed the description of the codes. 

Another change, not described in Appendix B, is that LPG and CNG engines, which were 

not included in previous nonroad engine populations, were added to the NONROAD model. 

New SCCs were added to accommodate these new engines. This added a number of additional 

engines for some applications and not for other applications. As described below, small CNG 

and LPG engines were lumped with other small spark-ignition engines for the purpose of keeping 

consistency with the emissions regulations. 

In order to apply the new emission standards expected for small (<25 hp) and recreational 

marine spark-ignition engines, the 2 and 4-stroke gasoline, LPG, and CNG engines were 

combined into one category (while still maintaining power level distinctions). The new emission 

standards intend to produce cleaner engines in part by reducing the number of 2-stroke in favor 

of 4-stroke engines. The reasons for and associated problems with combining these engines are 

described in more detail below. 

Mobile and Stationary Nonroad Engines 

One challenge in preparing a mobile source inventory is that engines used for generators, 

pumps, compressors and other applications may be either mobile or stationary, and, thus, may be 

subject to different regulations. Therefore it was necessary to determine the fraction of engines 

3
 
used as mobile and stationary emission sources. The NONROAD model estimates emissions 

from ‘mobile’ equipment. The legal definition of a mobile nonroad engine is an engine that 

moves from one place within a 12-month period. (4) In some cases the distinction may not be 

clear because engines that might appear stationary are in fact considered as mobile. For example, 

a palette-mounted engine is easily moved from one site to the next with a forklift or other type of 

lift truck over the course of several months. To account for mobile nonroad engines, EPA used 

the only information available which was derived from a report to the California Air Resources 

Board by Booz, Allen, and Hamilton (5) and given in Table 1 to provide fractions of engines 

used as mobile nonroad engines for the few application classes in which some of the engines are 

used and regulated as stationary sources. Generator sets, pumps, compressors, and welders were 

the applications which were determined to have some stationary engines. The fraction of mobile 

engines was applied to the state equipment populations for the appropriate applications as 

provided by PSR in order to avoid counting stationary sources in the nonroad mobile sources 

inventory. EPA would like reviewers to consider whether other similar applications such as 

General Industrial (22xx003040), Hydro Power Units (22xx005050), and Irrigation Sets 

(22xx005060) might also be classified primarily stationary applications for larger engines. 

Table 1: Fraction of Generator Sets (22xx006005), Pumps (22xx006010), Compressors 

(22xx006015 and 22xx006020), and Welders (22xx006025) Considered to be 

Mobile Sources 

Power Range (Hp) Percent Mobile 

Equipment 

0 to 25 90 

25 to 40 90 

40 to 100 70 

100 to 175 20 

175 to 300 15 

300 to 500 10 

500+ 0 

Small (<25 hp) Spark-Ignition Engines and Equipment 

Two important issues regarding small (<25 hp) spark ignition (SI) engines and equipment 

require further discussion: treating commercial and residential users separately, and accounting 

for the effects of new regulations. 

4
 
Many of the small spark-ignited engines are used in lawn and garden equipment 

applications, and lawn and garden equipment is used both by commercial and residential users. 

The commercial users are grounds keepers for nonresidential buildings, large apartment 

complexes, and some single-family homes. Commercial equipment therefore has significantly 

different usage in terms of hours per year and hours per weekday versus hours per weekend day 

than residential equipment. To account for these differences in equipment usage, separate SCCs 

were defined to account for commercial and residential lawn and garden equipment. The engine 

populations derived by PSR were then divided into residential and commercial fractions from 

information derived by California and shown in Table 2. (6) For applications not shown in Table 

2, 100% commercial use was assumed for the engines because these applications include such 

categories as construction, agricultural, commercial, and many other engines applications already 

considered commercial. 

The sales fraction combined with the average life (in years under average operation 

shown in another report, NR-003) of the engines was used to calculate an in-use population 

fraction of residential and commercial equipment. The calculation uses the sales fraction 

multiplied by the average life for both residential and commercial equipment and the population 

fraction determined from the two populations as shown in the equation below. 

Commercial Population Fraction = (Commercial Sales Fraction * Commercial Average Life in Years) / 

(Commercial Sales Fraction * Commercial Average Life + Residential Sales 

Fraction * Residential Average Life) 

The results of this calculation are shown in Table 2 below. The fraction of in-use population of 

residential equipment is higher because residential equipment lasts longer (in other words, the 

average life in years is higher) reducing the attrition. The reduced attrition accounts for the 

different population fraction. 

5
 
 

 

Table 2: Residential and Commercial Percentages of Small Spark-Ignition Engine Equipment 

SCC Application Residential Commercial 

Sales Population Sales Population 

22xx004010 

22xx004011 

Lawn mowers 90.00% 96.3% 

10.00% 3.7% 

22xx004025 

22xx004026 

Trimmers/edgers/cutters 81.85 89.4 

18.15 10.6 

22xx004020 

22xx004021 

Chainsaws 75.00 93.5 

25.00 6.5 

22xx004030 

22xx004031 

Leaf blowers/vacuums 86.87 92.5 

13.13 7.5 

22xx004015 

22xx004016 

Tillers <6 hp 82.00 85.7 

18.00 14.3 

22xx004035 

22xx004036 

Snowblowers 90.00 90.0 

10.00 10.0 

22xx004071 

Commercial turf equipment 0.00 0.0 

100.00 100.0 

22xx004040 

22xx004041 

Rear engine rider 95.00 97.4 

5.00 2.6 

22xx004055 

22xx004056 

Lawn and garden tractors 95.00 97.4 

5.00 2.6 

22xx004075 

22xx004076 

Other lawn and garden 

equipment 

25.00 45.7 

75.00 54.3 

22xx004045 

22xx004046 

22xx004065 

22xx004066 

22xx004070 

22xx004071 

All others 

Front Mowers 

Chippers\Stump Grinders 

Commercial Turf 

All other equipment 

0.00 0.0 

100.00 100.0 

Lawn and garden and other small (<25 hp) spark-ignition engines fall under EPA 

regulations targeting mainly hydrocarbon emissions. (7) The regulations to be proposed define 

new engine classes (I through V) based on use and displacement, while the NONROAD model 

classifies engines by application and power level. The regulations to be proposed require 

reduced emission rates in future years, and, among other consequences, are estimated to reduce 

the number of two-stroke engines sold in favor of four-stroke engines. With the current 

NONROAD modeling methodology, it was not possible to keep the 2-stroke and 4-stroke spark6
 
ignition engines in separate SCCs in the emissions model and account for the shift of 2-stroke to 

4-stroke engines. Therefore, spark-ignition engines of less than 25 horsepower were lumped into 

one SCC category, eliminating the SCC distinction between 2 and 4-stroke gasoline, LPG, and 

CNG engines. The SCC description was changed to reflect the new engine classes described 

below. The distinction between 2 and 4-stroke gasoline, LPG, and CNG engines will be 

maintained for sales fraction and emission rates by using technology groups within the SCC. 

The small spark-ignition engine regulations to be proposed incorporate five classes of 

engines defined by use (handheld versus nonhandheld) and displacement. For the purposes of 

inventory modeling, the five classes are defined by application and power level. Table 3 below 

describes the definitions of engine class by application and power level that were used in the 

NONROAD model. The PSR populations were used to define the total population, and to assign 

the base year technology group sales fractions distinguishing 2 and 4-stroke gasoline, LPG, and 

CNG engines. 

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Table 3: Initial Year Engine Population by Small Engine Class 

SCC Description Power Range & 

Engine Cycle 

Engine Class 

22xx004020(1) 

22xx007005 

Chainsaws 0 to 1 hp 

(2 and 4-stroke) 

III 

1 to 3 hp 

(2 and 4-stroke) 

IV 

3 to 25 hp 

(2 and 4-stroke) 

V 

22xx002006 

22xx002039 

22xx004025(6) 

22xx004030(1) 

22xx004035(6) 

22xx004071 

Tampers and Rammers 

Concrete\Industrial Saws 

Trimmers\Edgers\Cutters 

Leaf blowers 

Snow blowers 

Commercial Turf 

0 to 1 hp 

(2 and 4-stroke) 

III 

1 to 3 hp 

(2 and 4-stroke) 

IV 

3 to 6 hp 

(2-stroke) 

V 

3 to 6 hp 

(4 stroke) 

I 

6 to 25 hp 

(2 and 4-stroke) 

II 

22xx004015(6) 

22xx005040 

All Others 

Tillers 

All Others 

0 to 1 hp 

(2 and 4-stroke) 

III 

1 to 3 hp 

(2 and 4-stroke) 

IV 

3 to 6 hp 

(2 and 4-stroke) 

I 

6 to 25 hp 

(2 and 4-stroke) 

II 

22xx001050 

22xx001060 

22xx002015 

22xx002024 

22xx002030 

22xx002033 

22xx002042 

22xx002072 

22xx002078 

22xx003050 

22xx004010 (1) 

22xx004040 (1) 

22xx004045 (6) 

22xx004050 (1) 

22xx007010 

22xx004055 (6) 

22xx004065 (6) 

22xx004075 (6) 

22xx005030 

22xx008005 

228500x015 

Golf Carts 

Speciality Carts 

Rollers 

Surfacing Equipment 

Trenchers 

Bore\Drill Rigs 

Cement\Motar Mixers 

Skid Steer Loaders 

Dumpers\Tenders 

Other Material Handling 

Lawnmower 

Rear Engine Riding Mower 

Front Mowers 

Shredders 

Lawn & Garden Tractors 

Chippers and Stump Grinders 

Other Lawn & Garden Equipment 

Agricultural Mowers 

Aircraft Support 

Railway Maintenance 

0 to 6 hp 

(2 and 4-stroke) 

I 

6 to 25 hp 

(2 and 4-stroke) 

II 

22xx004065(6) indicates that both 22xx004065 and 22xx004066 SCC are considered, for 

instance. 

8 
One problem with lumping 2-stroke and 4-stroke engines together is that the different 

engine types have different conversion factors for converting total hydrocarbons (THC) to other 

hydrocarbon types (TOG, NMHC, NMOG, and VOC). This problem was ameliorated somewhat 

by defining the population to be primarily 2-stroke or primarily 4-stroke fuel types. In the base 

year, engine classes of III, IV, and V were primarily 2-stroke gasoline engines, so they were 

assigned SCCs of 2260xxxxxx. Engine classes I and II are primarily 4-stroke gasoline, therefore 

they were assigned SCCs of 2265xxxxxx. This means that 2-stroke hydrocarbon conversion 

factors were used for engine classes III, IV, and V, and 4-stroke conversion factors were used for 

engine classes I and II. 

Recreational Marine Equipment 

In its rulemaking on recreational marine equipment, EPA determined that alternatives to 

PSR population estimates provided more accurate information for spark-ignition recreational 

marine engines. The new population estimates were derived from sales information provided to 

EPA during the rulemaking to produce base year 1996 national population estimates. (8) 

The LPG and CNG recreational marine engine population values were estimated to be 

zero, which was confirmed with the PSR estimates. There were some diesel recreational marine 

engines not covered by the emissions regulations for spark-ignition marine engines and therefore 

not included in the recreational marine estimate just described. 

Recreational marine spark-ignition engines fall under EPA regulations targeting mainly 

hydrocarbon emissions. (9) The regulations require reduced emission rates and, among other 

consequences, are estimated to reduce the number of two-stroke engines sold in favor of fourstroke engines. With the current NONROAD modeling methodology, it was not possible to keep 

the 2-stroke and 4-stroke spark-ignition engines in separate SCCs in the emissions model and 

account for the expected effects of the regulations. Therefore, spark-ignition engines are lumped 

into one SCC, which eliminates two and four-stroke distinctions. 

As with small gasoline engines, one problem with lumping 2-stroke and 4-stroke 

recreational marine engines into a single SCC is that the different engine types have different 

conversion factors for converting total hydrocarbons (THC) to other hydrocarbon types (TOG, 

NMHC, NMOG, and VOC). This problem is ameliorated somewhat by defining the population 

to be primarily 2-stroke or primarily 4-stroke fuel types. For outboard (SCC 2282005010) and 

personal water craft (SCC 2282005015), the primary engine type in the base year is 2-stroke; for 

inboard engines (SCC 2282010005), the primary engine type in the base year is 4-stroke. The 

NONROAD model uses these primary engine types as the basis for the conversion factors for 

these SCCs. 

As described in Appendix A, three types of recreational marine equipment are 

differentiated: inboard, outboard, and personal water craft. The NEVES report documents three 

9
 
types of recreational applications; inboard, outboard, and sterndrive. Sterndrive was not 

considered to be a unique application type, and was eliminated. Personal water craft, sometimes 

known by the brand name Jet Ski, were added to what was formerly the sterndrive category, and 

the SCC description was changed accordingly. 

The base year 1996 national engine populations for recreational marine engines were 

estimated by EPA, departing in this category from the PSR estimates. (8) These base year 

populations are 8,619,722 for outboard engines, 2,567,067 for inboard, and 1,026,387 for 

personal water craft. These populations are totals derived from sales information and are higher 

than the PSR estimates. In order to reflect the average power level accurately, the national 

engine populations just described were assigned to power ranges using the fraction of engines in 

each power range as derived from the PSR information. The final assignments are shown in 

Table 4 below. 

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Table 4: 1996 National Population Estimates for Spark-Ignition Recreational Marine Engines 

SCC Description Power Range 2-Stroke 

Population 

4-Stroke 

Population 

2282005010 Outboard 

Engines 

1 to 3 hp 193,730 3,862 

3 to 6 2,343,410 6,501 

6 to 11 1,515,688 56,799 

11 to 16 472,490 14,093 

16 to 25 1,189,604 677 

25 to 40 786,243 4,493 

40 to 50 374,852 2,767 

50 to 100 761,251 0 

100 to 175 730,785 0 

175 to 300 162,479 0 

2282010005 Inboard 

Engines 

25 to 40 hp 0 2,016 

40 to 50 hp 0 0 

50 to 100 hp 0 17,225 

100 to 175 hp 0 1,775,317 

175 to 300 hp 0 772,509 

2282005015 Personal Water 

craft 

16 to 25 hp 1,340 4,806 

25 to 40 hp 34,225 0 

40 to 50 hp 83,392 0 

50 to 100 hp 734,208 0 

100 to 175 hp 168,416 0 

Sailboat auxiliary propulsion engines are also included in the outboard and inboard 

engine categories. The national estimates include these engines, so NONROAD does not use this 

category to avoid double counting. PSR estimates that these engines only account for slightly 

11
 
more than 30,000 engines nationwide and thus represent a small percentage of recreational 

marine engines. 

The population of diesel recreation marine engines provided in the default engine 

populations was derived from the PSR estimates and uses SCCs of 22820200xx. The ‘xx’ here 

denotes inboard as ‘05’, outboard as ‘10’, and sailboat auxiliary as ‘25.’ The categories of ‘15’ 

and ‘20’ were not used because sterndrive is no longer a category, and the sailboat auxiliary 

diesel engines were of a low horsepower design resembling outboard engines rather than inboard 

engines. There is little distinction between inboard and outboard for activity, allocations, or any 

other parameter, so assigning these sailboat auxiliary engines to outboard rather than inboard is a 

moot issue. 

References 

(1)	 Power Systems Research, “US Parts Link Edition 6.2,” St. Paul, MN. 

(2)	 E.H. Pechan, “Evaluation of Power Systems Research (PSR) Nonroad Population Data 

Base,” prepared for Office of Mobile Sources, U.S. Environmental Protection Agency, 

September 1997, EPA Contract No. 68-D3-0035, Work Assignment No. III-107, Pechan 

Report No. 97.09.003/1807. 

(3)	 EPA, “Nonroad Engine and Vehicle Emission Study,” EPA-21A-2001, November, 1991. 

(4)	 EPA, “Determination of Significance for Nonroad Sources and Emission Standards for 

New Nonroad Compression-Ignition Engines At or Above 37 kW; Final Rule,” 59 FR 

31306, June, 17, 1994. 

(5)	 Booz, Allen and Hamilton Inc., “Off-Road Mobile Equipment Emission Inventory,” 

January, 1992. 

(6)	 California Air Resources Board, “Technical Support Document for California Exhaust 

Emission Standards and Test Procedures for 1994 and Subsequent Model-Year Utility 

and Lawn and Garden Equipment Engines,” Attachment C to CARB Mailout # 92-06, El 

Monte, CA. January 1992. 

(7)	 EPA, “Statement of Principles for Nonroad Phase 2 Small Spark-Ignited Engines; 

Proposed Rule,” 62 FR 14740, March, 27, 1997. 

(8)	 EPA, “Regulatory Impact Analysis: Control of Air Pollution Emission Standards for 

New Spark-Ignition Marine Engines,” October, 1996. 

(9)	 EPA, “Air Pollution Control; Gasoline Spark-Ignition Marine Engines; New Nonroad 

Compression-Ignition and Spark-Ignition Engines, Exemptions; Rule”, 61 FR 52088, 

October 4, 1996. 

12
 
Appendix A 

The conversion from PSR applications to SCC categories. 

SCC SCC Description PSR 

Code 

PSR Description 

22xx001010 Mobile Sources Off-Highway Vehicle Gasoline, Recreational Vehicles Motorcycles: Off-Road Included in 

22xx001030 

22xx001020 Mobile Sources Off-Highway Vehicle Gasoline, Recreational Vehicles Snowmobiles 71 Snowmobile 

22xx001030 Mobile Sources Off-Highway Vehicle Gasoline, Recreational Vehicles All Terrain Vehicles 91 All-Terrain 

Vehicles 

22xx001040 Mobile Sources Off-Highway Vehicle Gasoline, Recreational Vehicles Minibikes 93 Mini-Bikes 

22xx001050 Mobile Sources Off-Highway Vehicle Gasoline, Recreational Vehicles Golf Carts 94 Golf Carts 

22xx001060 Mobile Sources Off-Highway Vehicle Gasoline, Recreational Vehicles Speciality Vehicle Carts 62 Specialty 

Veh./Carts 

22xx002003 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Asphalt Pavers 41 Pavers 

22xx002006 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Tampers/Rammers 95 Tampers/Rammer 

22xx002009 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Plate Compactors 61 Plate Compactors 

22xx002012 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Concrete Pavers Unused 

22xx002015 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Rollers 39 Rollers 

22xx002018 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Scrapers 29 Scrapers 

22xx002021 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Paving Equipment 35 Paving Equipment 

22xx002024 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Surfacing Equipment 23 Surfacing 

Equipment 

22xx002027 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Signal Boards 73 Light Plants 

22xx002030 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Trenchers 42 Trenchers 

22xx002033 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Bore/Drill Rigs 37 Bore/Drill Rigs 

22xx002036 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Excavators 28 Excavators 

22xx002039 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Concrete/Industrial Saws 77 Concrete/lnd 

Saws 

22xx002042 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Cement & Mortar Mixers 57 Cem/Mtr Mixers 

22xx002045 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Cranes 27 Cranes 

22xx002048 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Graders 30 Graders 

22xx002051 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Off-highway Trucks 40 Off-Highway 

Truck 

22xx002054 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Crushing/Proc. Equipment 34 Crush/Proc 

Equipment 

22xx002057 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Rough Terrain Forklifts 84 Rough Terrain 

Forklifts 

22xx002060 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Rubber Tire Loaders 33 R/T Loader 

22xx002063 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Rubber Tire Dozers 32 R/T Dozer 

22xx002066 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Tractors/Loaders/Backhoes 43 Tractor\Loader\Ba 

ckhoe 

22xx002069 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Crawler Dozer 31 Crawler Dozers 

22xx002072 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Skid Steer Loaders 38 S/S Loader 

22xx002075 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Off-Highway Tractors 68 Off-Hwy Tractors 

22xx002078 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Dumpers/Tenders 60 Dumpers/Tenders 

22xx002081 Mobile Sources Off-Highway Vehicle Gasoline, Construction Equipment Other Construction Equipment 36 Other 

Construction 

22xx003010 Mobile Sources Off-Highway Vehicle Gasoline, Industrial Equipment Aerial Lifts 64 Aerial Lifts 

22xx003020 Mobile Sources Off-Highway Vehicle Gasoline, Industrial Equipment Forklifts 18 Forklifts 

22xx003030 Mobile Sources Off-Highway Vehicle Gasoline, Industrial Equipment Sweepers/Scrubbers 21 Scrubbers/ 

Sweepers 

13
 
22xx003040 Mobile Sources Off-Highway Vehicle Gasoline, Industrial Equipment Other General Industrial Equipment 74 Other General 

Industrial 

22xx003050 Mobile Sources Off-Highway Vehicle Gasoline, Industrial Equipment Other Material Handling 

Equipment 

19 Other Material 

Handling 

22xx003060 Mobile Sources Off-Highway Vehicle Gasoline, Industrial Equipment AC\Refrigeration 14 Refrigeration/AC 

22xx003070 Mobile Sources Off-Highway Vehicle Gasoline, Terminal Tractors 16 Terminal Tractors 

22xx004010 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Lawn mowers (Residential) 65 Lawn Mowers* 

22xx004011 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Lawn mowers (Commercial) 65 Lawn Mowers* 

22xx004015 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Rotary Tillers < 6 HP 59 Tillers* 

22xx004016 as above except (Commercial) 59 Tillers* 

22xx004020 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Chain Saws < 6 HP 70 Chainsaws* 

22xx004021 as above except (Commercial) 70 Chainsaws* 

22xx004025 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Trimmers/Edgers/Brush 

Cutters 

53 Trimmer/Edger/ 

Cutter* 

22xx004026 as above except (Commercial) 53 Trimmer/Edger/ 

Cutter* 

22xx004030 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Leafblowers/Vacuums 66 Leaf Blower/Vac* 

22xx004031 as above except (Commercial) 66 Leaf Blower/Vac* 

22xx004035 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Snowblowers 56 Snowblower* 

22xx004036 as above except (Commercial) 56 Snowblower* 

22xx004040 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Rear Engine Riding Mowers 82 Rear Engine 

Rider* 

22xx004041 as above except (Commercial) 82 Rear Engine 

Rider* 

22xx004045 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Front Mowers 88 Front Mowers* 

22xx004046 as above except (Commercial) 88 Front Mowers* 

22xx004050 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Shredders < 6 HP 96 Shredders* 

22xx004051 as above except (Commercial) 96 Shredders* 

22xx004055 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Lawn & Garden Tractors 63 Lawn & Garden 

Tractor* 

22xx004056 as above except (Commercial) 63 LawniGarden 

Tractor* 

22xx004060 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Wood Splitters 75 Wood Splitter* 

22xx004061 as above except (Commercial) 75 Wood Splitter* 

22xx004065 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Chippers/Stump Grinders 26 Chippers/ 

Grinders* 

22xx004066 as above except (Commercial) 26 Chippers/ 

Grinders* 

22xx004070 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Commercial Turf Equipment Unused 

22xx004071 as above except (Commercial) 67 Commercial Turf* 

22xx004075 Mobile Sources Off-Highway Vehicle Gasoline, Lawn & Garden Equipment Other Lawn & Garden 

Equipment 

76 Other Lawn 

Garden* 

22xx004076 as above except (Commercial) 76 Other Lawn 

Garden* 

22xx005010 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment 2-Wheel Tractors 98 2-Wheel Tractors 

22xx005015 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Agricultural Tractors 45 Agricultural 

Tractor 

22xx005020 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Combines 47 Combines 

22xx005025 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Balers 49 Balers 

22xx005030 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Agricultural Mowers 55 Agricultural 

Mowers 

22xx005035 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Sprayers 69 Sprayers 

22xx005040 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Tillers > 6 HP 59 Tillers 

22xx005045 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Swathers 48 Swathers 

22xx005050 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Hydro Power Units 85 Hydro Power Unit 

14
 
22xx005055 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Other Agricultural Equipment 46 Other Ag 

Equipment 

22xx005060 Mobile Sources Off-Highway Vehicle Gasoline, Farm Equipment Irrigation Sets 44 Irrigation Sets 

22xx006005 Mobile Sources Off-Highway Vehicle Gasoline, Light Commercial Generator Sets 9 Generator Sets 

22xx006010 Mobile Sources Off-Highway Vehicle Gasoline, Light Commercial Pumps 11 Pumps 

22xx006015 Mobile Sources Off-Highway Vehicle Gasoline, Light Commercial Air Compressors 10 Air Compressors 

22xx006020 Mobile Sources Off-Highway Vehicle Gasoline, Light Commercial Gas Compressors 89 Gas Compressors 

22xx006025 Mobile Sources Off-Highway Vehicle Gasoline, Light Commercial Welders 17 Welders 

22xx006030 Mobile Sources Off-Highway Vehicle Gasoline, Light Commercial Pressure Washers 58 Pressure Washer 

22xx007005 Mobile Sources Off-Highway Vehicle Gasoline, Logging Equipment Chain Saws > 6 HP 70 Chainsaws 

22xx007010 Mobile Sources Off-Highway Vehicle Gasoline, Logging Equipment Shredders > 6 HP 96 Shredders 

22xx007015 Mobile Sources Off-Highway Vehicle Gasoline, Logging Equipment Skidders 24 Forest Equipment 

22xx007020 Mobile Sources Off-Highway Vehicle Gasoline, Logging Equipment Fellers/Bunchers Unused 

22xx008005 Mobile Sources Off-Highway Vehicle Gasoline, Airport Service Equipment Airport Support Equipment 81 Aircraft Support 

22xx008010 Mobile Sources Off-Highway Vehicle Gasoline, Airport Service Equipment Terminal Tractors Unused 

22xx009010 Mobile Sources Off-Highway Vehicle Gasoline, Other Underground Mining Equipment 13 Underground 

Mine Equipment 

22xx010010 Mobile Sources Off-Highway Vehicle Gasoline, Other Oil Field Equipment 12 0il Field 

Equipment 

22820xx020 

22820xx025 

Mobile Sources Marine Vessels, Recreational Pleasure Craft, Gasoline Sailboat Aux. Outboard 79 Sailboat Aux. 

Unused** 

228500x015 Mobile Sources Railroad Gasoline Railway Maintenance 80 Railway 

Maintenance 

22820xx005 Mobile Sources Marine Vessels, Recreational Pleasure Craft, Gasoline Inboards 50 Powerboats** 

22820xx010 Mobile Sources Marine Vessels, Recreational Pleasure Craft, Gasoline Outboards 99 Outboard 

Motors** 

2282005015 Mobile Sources Marine Vessels, Recreational Pleasure Craft, Gasoline Personal Water Craft 92 New SCC 

Description** 

* See Small Spark-Ignition Engines for a more complete description of these categories 

** New National Non-PSR Data Source (See Recreational Marine Equipment and Appendix 

B for further descriptions of these categories) 

15
 
Appendix B 

Engine Population Inventory Changes in NONROAD from NEVES 

SCC SCC Description Comment 

22xx003060* Mobile Sources Off-Highway Vehicle, Industrial Equipment 

AC\Refrigeration 

New Category 

22xx005060 Mobile Sources Off-Highway Vehicle, Farm Equipment 

Irrigation Sets 

New Category 

22xx009010 Mobile Sources Off-Highway Vehicle, Other Underground 

Mining Equipment 

New Category 

22xx010010 Mobile Sources Off-Highway Vehicle, Other Oil Field 

Equipment 

New Category 

2285002015 Mobile Sources Railroad Diesel Railway Maintenance New Category 

2285003015 Mobile Sources Railroad 2-Stroke Gasoline Railway 

Maintenance 

New Category 

2285004015 Mobile Sources Railroad 4-Stroke Gasoline Railway 

Maintenance 

New Category 

2285006015 Mobile Sources Railroad LPG Railway Maintenance New Category 

2285008015 Mobile Sources Railroad CNG Railway Maintenance New Category 

22xx006005 Mobile Sources Off-Highway Vehicle Gasoline, Light 

Commercial Generator Sets 

Engines Greater than 50 hp are included 

22xx006010 Mobile Sources Off-Highway Vehicle Gasoline, Light 

Commercial Pumps 

Engines Greater than 50 hp are included 

22xx006015 Mobile Sources Off-Highway Vehicle Gasoline, Light 

Commercial Air Compressors 

Engines Greater than 50 hp are included 

22xx006020 Mobile Sources Off-Highway Vehicle Gasoline, Light 

Commercial Gas Compressors 

Engines Greater than 50 hp are included 

22xx006025 Mobile Sources Off-Highway Vehicle Gasoline, Light 

Commercial Welders 

Engines Greater than 50 hp are included 

22xx002012 Mobile Sources Off-Highway Vehicle Construction Equipment 

Concrete Pavers 

Unused; population included in 

22xx002003 

22xx002003 Mobile Sources Off-Highway Vehicle Construction Equipment, 

Pavers 

New Description (Asphalt + Concrete) 

Pavers 

22xx007020 Mobile Sources Off-Highway Vehicle Logging Equipment 

Fellers/Bunchers 

Unused; population included in 

22xx007015 

22xx008010 Mobile Sources Off-Highway Vehicle Gasoline, 2-Stroke Airport 

Service Equipment Terminal Tractors 

Changed SCC to 22xx003070 because this 

is not Airport Service Equipment 

22xx007015 Mobile Sources Off-Highway Vehicle Logging Equipment 

Forest Equipment 

New Description (Skidders + 

Fellers\Bunchers) 

22xx004010 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Lawn mowers (Residential) 

New Description 

22xx004011 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Lawn mowers (Commercial) 

New SCC 

22xx004015 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Rotary Tillers < 6 HP (Residential) 

New Power Level, Description 

22xx004016 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Rotary Tillers < 6 HP (Commercial) 

New SCC 

22xx004020 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Chain Saws < 6 HP (Residential) 

New Power Level, Description 

16
 
22xx004021 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Chain Saws < 6 HP (Commercial) 

New SCC 

22xx004025 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Trimmers/Edgers/Brush Cutters (Residential) 

New Description 

22xx004026 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Trimmers/Edgers/Brush Cutters (Commercial) 

New SCC 

22xx004030 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Leafblowers/Vacuums (Residential) 

New Description 

22xx004031 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Leafblowers/Vacuums (Commercial) 

New SCC 

22xx004035 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Snowblowers (Residential) 

New Description 

22xx004036 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Snowblowers (Commercial) 

New SCC 

22xx004040 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Rear Engine Riding Mowers (Residential) 

New Description 

22xx004041 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Rear Engine Riding Mowers (Commercial) 

New SCC 

22xx004045 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Front Mowers (Residential) 

New Description 

22xx004046 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Front Mowers (Commercial) 

New SCC 

22xx004050 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Shredders < 6 HP (Residential) 

New Power Level, Description 

22xx004051 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Shredders < 6 HP (Commercial) 

New SCC 

22xx004055 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Lawn & Garden Tractors (Residential) 

New Description 

22xx004056 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Lawn & Garden Tractors (Commercial) 

New SCC 

22xx004060 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Wood Splitters (Residential) 

New Description 

22xx004061 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Wood Splitters (Commercial) 

New SCC 

22xx004065 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Chippers/Stump Grinders (Residential) 

New Description 

22xx004066 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Chippers/Stump Grinders (Commercial) 

New SCC 

22xx004070 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Commercial Turf Equipment (Residential) 

Unused; no ‘residential’ commercial turf 

equipment 

22xx004071 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Commercial Turf Equipment (Commercial) 

New SCC 

22xx004075 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Other Lawn & Garden Equipment (Residential) 

New Description 

22xx004076 Mobile Sources Off-Highway Vehicle, Lawn & Garden 

Equipment Other Lawn & Garden Equipment (Commercial) 

New SCC 

22xx002069 Mobile Sources Off-Highway Vehicle, Construction Equipment 

Crawler Dozer 

New Description (Changed from Tractor to 

Dozer) 

22xx004015 Mobile Sources Off-Highway Vehicle, 2-Stroke Lawn & 

Garden Equipment Rotary Tillers < 6 HP 

New Power Level 

22xx007005 Mobile Sources Off-Highway Vehicle, 2-Stroke Logging 

Equipment Chain Saws > 6 HP 

New Power Level 

22xx007010 Mobile Sources Off-Highway Vehicle, 2-Stroke Logging 

Equipment Shredders > 6 HP 

New Power Level 

2282005015 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 2-stroke Personal Water Craft 

New Description (Changed from Sterndrive 

to Personal Water Craft) Primarily 2-stroke 

2282005010 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 2-Stroke Outboards 

Includes 2 and 4-stroke engines 

17
 
2282010005 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 4-Stroke Inboards 

Includes 2 and 4-stroke engines 

2282010015 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 4-Stroke Sterndrive 

Unused 

2282010010 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 4-Stroke Outboard 

Unused (included in 2282005010 as a 

technical type) 

2282005020 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 2-Stroke Sailboat Aux. Inboard 

Unused (included in 4-stroke Inboard) 

2282005025 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 2-Stroke Sailboat Aux. Outboard 

Unused (included in 4-stroke Outboard) 

2282010020 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 4-Stroke Sailboat Aux. Inboard 

Unused (included in 4-stroke Inboard) 

2282010025 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 4-Stroke Sailboat Aux. Outboard 

Unused (included in 4-stroke Outboard) 

2282005005 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Gasoline 2-Stroke Inboards 

Unused (included in 228201005 as a 

technical type) 

2282020015 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Diesel Sterndrive 

Unused (included in 2282020005) 

2282020020 Mobile Sources Marine Vessels, Recreational Pleasure Craft, 

Diesel Sailboat Aux. Inboard 

Unused (included in 2282020025) 

* The “xx” denotes that all fuel types (diesel (“70"), 2-stroke gasoline (“60"), 4-stroke gasoline 

(“65"), LPG (“67"), and CNG (“68") engines) are included with the new or altered application 

categories. 

18