Median Life, Annual Activity, and Load 

Factor Values for Nonroad Engine 

Emissions Modeling 
Median Life, Annual Activity, and Load 


Factor Values for Nonroad Engine 


Emissions Modeling
 

NR-005d
 

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. 

EPA-420-R-10-016 

NR-005d 

July 2010 
Median Life, Annual Activity, and Load Factor Values 

for Nonroad Engine Emissions Modeling 

Report No. NR-005d 

July 2010 

Assessment and Standards Division 

EPA, Office of Transportation and Air Quality 

Purpose 

EPA’s NONROAD model computes emission inventories for nonroad engines. This 

report documents the default input values of median life, annual activity, and load factor for 

various types of nonroad engines. The model uses annual activity and load factor values to 

calculate yearly emissions for each engine type. In addition, the model uses activity and load 

factor, in combination with median life, to calculate the fleet age distributions for each engine 

type, as it projects future (or past) engine populations. Relative to the previous April 2004 

version of this report, this version includes median life, activity, and load factor estimates for 

high performance sterndrive and inboard (SD/I) recreational marine engines. Also, beginning 

with NONROAD2005, the hydro power unit SCCs have been changed from 22xx005050 to 

22xx006035, reflecting a reclassification from the farm to the commercial category. 

Introduction 

This report documents the default annual activity, load factor, and median life values. 

The model uses the following equation to calculate exhaust emissions from nonroad engines. 

The derivation of default values for equipment population, average rated power, and emission 

factors are discussed in reports NR-006e, NR-009d, and NR-010f. 

Emissions = (Pop) × (Power) × (LF) × (A) × (EF) 

where Pop = Engine Population 

Power = Average Power (hp) 

LF = Load Factor (fraction of available power) 

A = Activity (hrs/yr) 

EF = Emission Factor (g/hp-hr) 

This report also documents the default values for the median life of engines. In the 

population input files (*.pop) this parameter is expressed in “hours of life at full load.” In 

1 
developing the age distribution for a given equipment type, the model begins by converting the 

hours-at-full-load to years at average load, on the basis of average activity and load factor, as 

defined above and as shown in the equation below. 

Median Life (hrs) Median Lifetime ( years) = 

Activity (hrs/yr) × Load Factor 

The use of median life in calculating the scrappage and resulting age distribution of each 

equipment type is explained in report NR-007c, “Calculation of Age Distributions in the 

Nonroad Model: Growth and Scrappage.” 

Values Used in NONROAD for Median Life, Annual Activity, and Load Factor 

This report describes the default estimates for median life, activity, and load factor used 

as default data in the input files provided with NONROAD2008a. 

Median Life 

Engine life varies with engine type and power level. In general, larger engines (i.e., 

higher rated power and bigger displacement) last longer than smaller ones, and diesel engines 

last longer than gasoline engines. 

The NONROAD model uses median (expected) life estimates based primarily on those 

used in the OFFROAD model, developed by the California Air Resources Board (ARB). (1) 

These estimates are listed by horsepower class and engine type in Table 1, with horsepower 

classes defined in Table 2. In certain cases, the ARB horsepower ranges were adjusted to match 

the ranges used in the NONROAD model. The 120 hp dividing point used by ARB was the 100 

hp point in NONROAD; the 250 hp point was used as the 300 hp point in NONROAD; and 

ARB’s 500 hp point was used as the 600 hp dividing point in NONROAD. Additional 

modifications that EPA made to the ARB median life values for diesel engines, small gasoline 

engines, and recreational equipment are described below. 

2 
 

 

Table 1. Expected Engine Life in Hours at Full Load (1, 2) 

Engine 

Type 

HP 1 HP 2 HP 3 HP 4 HP 5 HP 6 HP 7 HP 8 HP 9 HP 10 

Diesel 2500 2500 2500 4667 4667 4667 7000 7000 7000 --

2-stroke 

Gasoline 

150 200 750 -- -- -- -- -- -- --

4-stroke 

Gasoline 

200 400 750 1500 3000 3000 3000 3000 3000 3000 

CNG/ 

LPG 

200 400 750 1500 3000 3000 3000 3000 3000 3000 

Table 2. Horsepower Classes for Median Life (1, 2) 

HP Class Diesel 2-stroke 4-stroke 

HP 1 16 3 6 

HP 2 17-25 3-16 6-16 

HP 3 26-50 16-25 16-25 

HP 4 51-100 26-50 26-50 

HP 5 101-175 51-100 51-100 

HP 6 176-300 101-175 101-175 

HP 7 301-600 176-250 176-300 

HP 8 601-750 301-600 301-600 

HP 9 751+ 601-750 601-750 

HP 10 -- 751+ 751+ 

In early versions of NONROAD, the median life estimates of most equipment (CI and SI) 

were based on the values in the 1997 documentation for the ARB OFFROAD model, prepared 

by Energy and Environmental Analysis (EEA). (1) These are presented in EPA's technical 

report NR-005a (revised 6/15/1998) and in Table 3 below. For CI these numbers were either 

1,250, 2,500, 4,000, or 6,000 hours at full load, depending on rated horsepower. 

3 
Table 3. CI Median Life Comparison 

Hp Range OFFROAD Median 

Life 

NONROAD 

Median Life 

Regulatory 

Useful Life* 

0 - 16 1,250 2,500 3,000 

16 - 25 2,500 2,500 3,000 

25 - 50 2,500 2,500 5,000 

50 - 300 4,000 4,667 8,000 

300+ 6,000 7,000 8,000 

* The Regulatory Useful Life is considered to represent in-use loads, rather than full load. 

NONROAD model diesel load factors range from 0.21 to 0.59.
 

In researching the issues related to estimation of equipment sales, population, diesel fuel 

consumption, load factors, and median life, EPA asked EEA for more complete documentation 

of the values that had been provided to ARB. At EPA's request, EEA supplemented the 

documentation of their previous work. The resulting report is attached as Appendix B. (2) 

After reviewing the new EEA report, EPA determined that modifications to the median 

life estimates were appropriate. Information that EEA gathered from highway diesel engine 

manufacturers suggested an expected life for heavy-duty diesel highway engines of 7,000 hours 

at full load. In preparing initial estimates for use in OFFROAD, EEA had reduced this estimate 

by 15% to compensate for the "rough-duty" use of off-road engines relative to highway engines. 

 This yielded the 6,000 hour estimate mentioned above for engines over 300 hp. In reviewing 

this work, EPA determined that it did not make sense to reduce the 7,000 hour estimate for offroad applications, since when engines are used in off-road applications they are typically derated 

to compensate for the rougher operating conditions. Thus the horsepower rating of the offroad 

engine may be lower than its highway counterpart, but its expected life would not be lower. 

EEA estimated medium duty diesel engine life to be two-thirds that of the heavy-duty 

engines and applied that to diesel engines in the range of 50 - 300 hp. EPA applied this same 

factor to the 7,000 hour value yielding a median life estimate of 4,667 hours at full load for 50 - 

300 hp engines. For engines in the 16 - 50 hp range EEA based its estimate of 2500 hours at full 

load on information from light-duty highway diesels. No adjustments were made by EEA or 

EPA for off-road use, since these engines are typically not used in rough duty applications. For 

engines under 16 hp EEA had somewhat arbitrarily cut the life estimate of the 16 - 50 hp engines 

in half, yielding the 1,250 hour estimate mentioned above. Since this low estimate was not 

supported by any data, and since after accounting for load factors it can yield expected life 

values less than the regulatory useful life set by EPA for these engines, EPA decided to use the 

4 
2,500 hour estimate in NONROAD for all diesel engines from 0 - 50 hp, rather than have a 

separate lower life category under 16 hp. 

Liquid petroleum gas (LPG) and compressed natural gas (CNG) engines are primarily 

four-stroke spark-ignition engines and hence have many similarities with four-stroke gasoline 

engines. Because LPG and CNG engines are similar in design to gasoline engines, their median 

life is likely to be similar to the median life of gasoline engines. For this reason and the lack of 

relevant data to the contrary, LPG and CNG engines are assumed to have the same median life as 

gasoline engines in the NONROAD model. 

The values described represent the most comprehensive review available of the engine 

life associated with engine type and power level. They represent median values of engine life, 

not distinguishing the engine by make or model. Individual engine models may have longer or 

shorter median lives. Surveys of engine life by application or engine type are encouraged to 

improve the estimates shown here. 

Small Spark-Ignition Engines (rated at <25 hp) 

The median life (the point where 50% of engines have been scrapped) for several 

applications of nonroad engines have been estimated previously in terms of years of use. (3,4) 

For use in the NONROAD model, these estimates were converted from units of years to units of 

hours using the equation previously shown. Median life in years from Table 4 was multiplied by 

hours per year and load factor (described later in the report and given in Table 5) to create the 

Median Life (Hours at Full Load) entry in Table 4, which is used as input to the NONROAD 

model. 

The final values for the median life used in NONROAD for these selected applications 

are shown in Table 4. Lower or higher power level engines use the default values from ARB per 

Tables 1 and 2 above. 

5 
Table 4. Median Life for the Bulk of Several Small Spark-Ignition Engine Applications 

Application Use Power 

(min.) 

Power 

(max.) 

Median Life 

(Hours at Full Load) 

Median Life 

(Years) (3, 5) 

Lawn Mowers Residential 1 6 47.9 5.8 

Commercial 1 6 268 2 

Trimmer/Edger/Cutter Residential 0 3 35.3 4.3 

Commercial 0 3 286.8 2.3 

Chainsaws Residential 0 6 39.2 4.3 

Commercial 0 6 191 0.9 

Leaf Blower/Vacuum Residential 0 6 40.4 4.3 

Commercial 0 6 609.7 2.3 

Tillers Residential 0 11 39.4 5.8 

Commercial 0 11 830.7 4.4 

Snowblowers Residential 0 6 12.3 4.4 

Commercial 0 6 209.4 4.4 

Commercial Turf Commercial 3 25 988.9 2.9 

Rear Engine Rider Residential 3 16 79.3 5.8 

Commercial 6 16 627 2.9 

Lawn and Garden 

Tractor 

Residential 3 25 114.8 5.8 

Commercial 6 25 920 2.9 

Recreational Marine Stern-Drive/Inboard Engines (SD/I) 

For purposes of median life, NONROAD once treated gasoline-powered stern-drive and 

inboard engines the same as spark-ignition engines over 50 hp. Per Table 1 this meant they were 

assigned a median life of 3,000 hours at full load. Upon review, it became apparent that when 

annualized, this result was implausible; this median life, divided by the product of activity and 

load factor, gave an annualized estimate of 300 years (3,000 hours/(48 hr/year 0.21) = 300 

years). To address this issue, NONROAD assumes a median life of 20 years (197 hrs at full 

load) for all gasoline SD/I engines, except high performance SD/I engines. 

Previous versions of NONROAD did not include high-performance SD/I marine engines. 

 High-performance marine engines are a niche product and were not included in the data set used 

6 
to develop the engine populations for the model. Manufacturers have more recently commented 

that approximately 1,500 high-performance engines are produced in the U.S. per year. These 

engines are designed to sacrifice service life for power, but with rebuilds, generally are used for 

7-8 years (8 years is used in NONROAD2008a). Using this estimate together with an activity of 

30 hours per year and a load factor of 0.21, the median life is calculated to be 50 hours at full 

load. (6) 

Recreational Equipment 

The median life values used for snowmobiles, all-terrain vehicles (ATVs), and offroad 

motorcycles are given in Table 5. The regulatory support document for the final rulemaking for 

large spark-ignition and recreational engines provides a detailed description of the most recent 

median life estimates. (7) 

Table 5. Median Life for Snowmobiles, All-Terrain Vehicles, and Offroad Motorcycles 

Application 

Median Life 

(Hours at Full Load or Miles) 

Median Life 

(Years) 

Snowmobiles 252 hours 13 

All-Terrain Vehicles 20,410 miles 13 

Offroad Motorcycles 19,200 miles 12 

Equipment Activity 

Activity represents annual equipment usage expressed in hours of operation (hours/year). 

 Except as noted below, we use equipment activity estimates from a 1998 database developed by 

Power Systems Research, Inc. (PSR), an independent research firm, as default input values in 

NONROAD. The PSR data represents the most comprehensive review of application-specific 

activity available to EPA. PSR conducts several yearly surveys of equipment owners and 

determines a mean usage rate for engines by application and fuel type. (8) The PSR 

methodology is described and evaluated in a report produced by E.H. Pechan & Associates. (4) 

It should be noted that the activity estimates in the NONROAD model do not currently 

take into account the effect of equipment age on activity. EPA has encountered some general 

information indicating that equipment activity declines as the equipment gets older. For 

example, older pieces of agricultural or construction equipment might be kept as spares to be 

used if newer equipment breaks down or if another piece of equipment is needed to complete a 

task once in awhile. Unfortunately, EPA has been unable to obtain precise quantifiable data to 

model this relationship for any type of nonroad equipment. 

7 
We are unaware of activity estimates specific to LPG and CNG engines. These engines 

are similar to gasoline engines in that they employ spark-ignition. Because LPG and CNG 

engines are presumably used in applications where gasoline engines are used, we assume that 

their usage rates are similar to those for gasoline engines. 

The activities in NONROAD2008a for each equipment type are provided in Appendix A. 

Load Factor 

Rated power is the maximum power level that an engine is designed to produce at its 

rated speed. Engines typically operate at a variety of speeds and loads, and operation at rated 

power for extended periods is rare. To take into account the effect of operation at idle and 

partial load conditions, as well as transient operation, a load factor is developed to indicate the 

average proportion of rated power used. For example, at a 0.3 (or 30 percent) load factor, an 

engine rated at 100 hp would be producing an average of 30 hp over the course of normal 

operation. Load factor can vary widely for nonroad engines, depending on their usage patterns. 

Due to the inclusion of engine idle time in both the load factor and activity inputs of the model, 

and the dependence of median life on both of these inputs, it is important that any replacement 

model input data provided by a user would be consistent with this approach. 

PSR also estimates the load factor from surveys of equipment users. PSR calculates the 

fraction of load from the estimate of hours of usage per year, the fuel consumption per year, and 

the fuel consumption rate at rated power for each engine in the field. A median fraction of 

available power is determined for specific applications. The load factor is determined from 

actual and maximum fuel consumption rates for various pieces of equipment. For reference, the 

PSR methodology is explained in detail in the Pechan report. (4) 

For the NONROAD2008a model, PSR load factors were used with the exceptions 

described below. As was the case for activity levels, LPG and CNG engines are assigned the 

load factors for gasoline engines. The load factors in the NONROAD2008a model for each 

equipment type are also provided in Appendix A. 

Small (<25 hp) Spark-Ignition Engines 

The activity for small spark-ignition engines, mainly lawn and garden equipment, were 

derived from data supplied to EPA during the comment period for the regulation of these 

applications. The supporting documentation for those regulations include estimates of activity 

for a few important applications. (3) These alternate values are shown in Table 6 and represent a 

departure from the PSR values. For applications not shown in Table 6, PSR values were used 

because the PSR survey includes such categories as construction, agricultural, commercial, and 

many other engine applications that were not included in the data submitted for the rulemaking. 

8 
The load factors for lawn mowers, tillers, snowblowers, rear engine riders, and lawn and 

garden tractors in Table 6 were also derived from the same data supplied to EPA during the 

comment period for the regulation of small SI engines. 

Table 6. Usage and Load Factors for Several Small Spark-Ignition Engine Applications 

Application Use Annual Hours Load Factor 

(fraction of power) 

Lawn Mowers Residential 25 0.33 

Commercial 406 0.33 

Trimmer/Edger/Cutter Residential 9 0.91 

Commercial 137 0.91 

Chainsaws Residential 13 0.70 

Commercial 303 0.70 

Leaf Blower\Vacuum Residential 10 0.94 

Commercial 282 0.94 

Tillers Residential 17 0.40 

Commercial 472 0.40 

Snowblowers Residential 8 0.35 

Commercial 136 0.35 

Commercial Turf Commercial 682 0.60 

Rear Engine Rider Residential 36 0.38 

Commercial 569 0.38 

Lawn and Garden Tractor Residential 45 0.44 

Commercial 721 0.44 

For the three most populous handheld applications (i.e., chainsaws, 

trimmers/edgers/brush cutters, and blowers/vacuums), the draft model versions prior to 

NONROAD2005 assumed a load factor of 0.50. The estimate of 0.50 was supplied by 

manufacturers to the California Air Resource Board in 1990 and is based on manufacturers’ 

9 
belief that it accurately reflects the typical usage pattern of most portable two-stroke power 

equipment. In support of a more recent effort to analyze the test cycle currently used for 

certification of Phase 1 handheld engines, manufacturers monitored the in-use operation of a 

number of chainsaws, trimmers/edgers/brush cutters, and blowers/vacuums to determine the 

appropriate weighting of wide open throttle (WOT) and idle operation for certification testing 

purposes. Based on this information, the load factors for chainsaws, trimmers/edgers/brush 

cutters, and blowers/vacuums are 0.70, 0.91, and 0.94, respectively. (5) 

For commercial turf equipment, the load factor is 0.60, based on 1998 PSR data. 

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, large apartment complexes, and 

some single-family homes. Commercial equipment therefore has significantly different usage in 

terms of hours per year and weekday and weekend day than residential equipment. To account 

for these differences in equipment usage, separate SCCs are used to distinguish commercial from 

residential lawn and garden equipment. 

Recreational Marine Engines 

As described in the technical report on nonroad engine populations (NR-006e), 

recreational marine engines are divided into three applications: inboard, outboard, and personal 

watercraft. Due to the similarity of engines, the inboard category includes the inboard/outboard 

sterndrive engines formerly considered as a separate SCC category. The inboard engines are 

associated with the PSR category "powerboats." 

The June 1998 draft of the NONROAD model used fuel consumption data to estimate 

activity for outboard engines (9). The April 1999 draft version and subsequent drafts of the 

model have used activity data collected during the recreational marine rulemaking process, 

provided by the National Marine Manufacturers Association and individual marine vessel 

manufacturers. (10) NONROAD2008a continues to use these estimates, which are shown in 

Table 7. 

Table 7. Recreational Marine Activity and Load Factors 

Recreational Marine 

Engine/Equipment Type 

Activity 

(hours/year) 

Load Factor 

(fraction of power) 

Four-stroke Inboards; 0-600 hp 47.6 0.21 

Four-stroke Inboards; >600 hp 30 0.21 

Two-stroke Outboards 34.8 0.21 

Personal Watercraft 77.3 0.21 

10 
Based on other comments, we revised the load factor to reflect the average load for the 

marine engine certification test cycle (20.7%). In-use data for load factor are not available, and 

the PSR estimates of load factor (32% for outboard, 38% for inboard, and 42% for personal 

watercraft) are not currently documented. 

For high-performance SD/I marine engines, one manufacturer stated that they performed 

a survey on the annual use of these engines for warranty purposes. The result was an average 

annual use of 30 hours per year, which is used in NONROAD2008a. (6) 

Recreational Equipment 

In the course of the rulemaking process for recreational equipment and large sparkignition engines, the activity and load factor estimates for recreational equipment (i.e., 

snowmobiles, all-terrain vehicles, and off-road motorcycles) were updated in draft 

NONROAD2002. (11,12) In estimating operating hours for recreational vehicles, a number of 

sources are available for each vehicle type. 

For snowmobiles, activity information is available from: (a) studies on the economic 

impact of snowmobile operation in seven states (12-18), (b) consumer-satisfaction survey results 

from the snowmobile industry, and (c) snowmobile enthusiasts’ self-reported usage estimates 

compiled and provided by the Bluewater Network (an environmental organization). These 

sources presented usage information in terms of average or typical miles ridden per year. To 

convert the mileage estimates to operating hours, we estimated the average speed for typical 

snowmobile operation. 

The information available on average speed was collected on instrumented machines 

during development of an emissions test cycle for snowmobiles, performed by Southwest 

Research Institute under sponsorship of the International Snowmobile Manufacturers 

Association. (11) The cycle development work encompassed operation over varied conditions, 

including moderate and aggressive trail riding, lake riding, off-trail freestyle riding, and 

operation with single and double riders. Sled speeds ranged from 14 to 32 mph, although the 

bulk of the data falls between 20 and 30 mph. Because of the large variation in speed estimates, 

it is difficult to determine what average speed is the most representative. We know that the 

correct speed is somewhere within this range and that the mode of the estimates fell at the 

midpoint of the range. Therefore, we are using an average speed of 23 mph for snowmobile 

operation. We believe that this value is reasonable and it is supported by the snowmobile 

manufacturers per discussion. 

Having estimated average speed, it is possible to convert the estimated average yearly 

mileage into yearly operating hours. The range of average yearly mileage estimates available to 

us is 540 to 1,800 miles. Manufacturers have indicated that for winters with average or above 

average snowfall, the average yearly mileage is approximately 1,500 miles and that for poorer 

winters, with less than average snowfall, the average yearly mileage is approximately 1,200 

11 
 

miles. These estimates fall well within the range of estimates given above. In fact, several of the 

state economic studies indicated that their estimates for mileage were low due to poor snowfall 

during the winter in which they performed their studies. Therefore, we estimate the average 

yearly travel distance for snowmobiles at 1,300 miles. Given an average speed of 23 mph and an 

average mileage of 1,300 miles, we estimate the average yearly activity at 57 hours per year. 

For snowmobiles, the load factor of 0.34 is derived from data collected during the cycle 

development project described above. (11) 

Based on analyses of data conducted in support of the Final Rule for control of emissions 

from recreational engines, we have revised the activity estimate for all-terrain vehicles (ATVs). 

(21) For reference, the prior estimate, which is superseded by the estimate described in this 

report and referenced Rule documents, is presented and described in the docket memorandum 

Emission Modeling for Recreational Vehicles (EPA420-F-00-051, Docket A-98-01).1 

Data sources used to derive the revised estimate include: (a) a phone survey sponsored by 

Honda in which owners of TRX model utility ATVs were requested to report odometer and 

hour-meter readings, (b) a database of warranty claim information provided by another 

manufacturer, which included odometer and hour-meter readings, (c) a national survey of ATV 

population and usage sponsored by the Consumer Product Safety Commission (19), and (d) a 

“market panel” survey of ATV usage sponsored by major manufacturers. The manufacturers’ 

survey was performed during the same time period as the CPSC study, employed similar 

interview methods and obtained very similar results. 

Based on these sources, ATV activity has been re-estimated at 1,608 miles/year. 

For off-road motorcycles, usage in miles per year was estimated by multiplying gallons 

per year by miles per gallon. The gallons per year value of 57 is based on the average of four 

state fuel consumption studies. The fuel economy value of 28 miles per gallon was derived from 

FTP results from EPA testing and in-use results from CE-CERT. Combining the value of 28 

miles per gallon with the fuel consumption value of 57 gallons per year results in an average 

usage of 1,600 miles per year. (7) 

For ATVs and off-road motorcycles, load factors are no longer necessary, since the 

emission factors are expressed as grams per mile. As a result, for these equipment types, load 

factors and average rated horsepower inputs are simply set to 1.0 in the input file. This 

modification effectively converts the emissions calculation from a power-output basis to a 

distance-traveled basis, similar to that used for cars and trucks. The operating hours, mileage, 

and load factors used for recreational vehicles are listed in Table 8. 

1

 This memorandum supplements the Advance Notice of Proposed Rulemaking: Control of Emissions from 

Nonroad Large Spark Ignition Engines, Recreational Engines (Marine and Land-based), and Highway Motorcycles 

(November 20, 2000). See http://www.epa.gov/otaq/regs/nonroad/proposedregs.htm#20011005. 

12 
Table 8. Activity and Load Factors for Recreational Vehicles 

Application Type Load Factor Hours per Year Mileage per 

Year 

ATVs 2 & 4-stroke 1.0* ---- 1,608 

Off-Road 

Motorcycles 

2 & 4-stroke 1.0* ---- 1,600 

Snowmobiles 2-stroke 0.34 57 ----

* Average rated horsepower is also set at 1.0, effectively removing power output (rated power * load factor) from 

the equation; emissions are thus calculated on the basis of EF*Act*Population, where units equal 

g/mile*miles/year = g/year, which the model converts to tons/year. 

Compression-Ignition (CI) Equipment 

For CI equipment, we are using activity estimates from the 1998 PSR database. 

The PSR CI load factors used in versions of NONROAD prior to 2005, which are based 

on information obtained from surveys of equipment owners, have been replaced by load factors 

obtained from actual engine testing over several transient cycles. The transient cycle 

development and engine tests were conducted by Southwest Research Institute under contract to 

EPA (with some of the cycle development work also co-sponsored by the Engine Manufacturers 

Association). (20,21,22). Seven transient cycles were developed: agricultural tractor, backhoe 

loader, crawler dozer, rubber-tire loader, skid-steer loader, arc welder, and excavator. For the 

rubber-tire loader, skid-steer loader, and arc welder cycles, both “typical transient” and “high 

transient” versions of the cycles were developed; for this work, the typical versions were used. 

The load factors for the seven transient cycles are given in Table 9. The seven load 

factors were further binned into three categories, “High,” “Low,” and “steady-state ” 

(represented by an average of the seven cycles). We consider this approach simpler and more 

defensible, given the limited number of cycles designed to represent in-use operation for specific 

equipment types and uncertainty in extrapolating the test data to broader equipment populations. 

 This approach is also consistent with that used to develop the transient adjustment factors in the 

model. The high load factor bin includes the following cycles: agricultural tractor (LF=0.78), 

crawler dozer (LF=0.58), rubber-tire loader (LF=0.48), and excavator (LF=0.53). The low load 

factor bin includes the remaining cycles: backhoe/loader (LF=0.21), skid-steer loader (LF=0.23), 

and arc welder (LF=0.19). The “high” load factor cycles were averaged to obtain a composite 

High LF (0.59). Similarly, the “low” load factor cycles were averaged to obtain a composite 

Low LF (0.21). The load factors for all seven cycles were averaged to obtain a composite 7-

cycle average “steady-state” LF (0.43). See Table 9. 

13 
 

Table 9. Compression-Ignition Load Factors 

Cycle Cycle Load Factors Assignmen 

t 

Average 

Agricultural 

Tractor 

0.78 

High 0.59 Crawler Dozer 0.58 

Rubber-tired 

Loader 

0.48 

Excavator 0.53 

Backhoe 

Loader 

0.21 

Low 0.21 

Skid-steer 

Loader 

0.23 

Arc Welder 0.19 

7-cycle average --- Steady-state 0.43 

Each diesel nonroad equipment type was assigned one of these three composite load 

factors (Hi LF, Lo LF, or 7-cycle average). To apply these load factors, we matched nonroad 

applications with the test cycle that most closely represents the nonroad activity for the 

application. Table 10 lists the diesel nonroad applications used in the NONROAD model and 

the load factor assignment considered representative of that application. If steady-state operation 

is typical of an application, the 7-cycle average load factor was assigned. For diesel recreational 

marine equipment, the PSR-based load factor of 0.35 is used instead. (8) 

The resulting load factors for each equipment type are provided in Appendix A. 

14 
 

Table 10. CI Load Factor Assignments by Equipment Type 

SCC Equipment Type Representative 

Cycle 

Load Factor 

Assignment 

2270001000 Recreational Vehicles All Backhoe Lo LF 

2270001020 Recreational Vehicles Snowmobiles None Avg 7-cycle 

2270001030 Recreational Vehicles All Terrain Vehicles None Avg 7-cycle 

2270001040 Recreational Vehicles Minibikes None Avg 7-cycle 

2270001050 Recreational Vehicles Golf Carts None Avg 7-cycle 

2270001060 Recreational Vehicles Speciality Vehicle Carts Backhoe Lo LF 

2270002003 Construction Equipment Pavers Crawler Hi LF 

2270002006 Construction Equipment Tampers/Rammers None Avg 7-cycle 

2270002009 Construction Equipment Plate Compactors None Avg 7-cycle 

2270002015 Construction Equipment Rollers Crawler Hi LF 

2270002018 Construction Equipment Scrapers Crawler Hi LF 

2270002021 Construction Equipment Paving Equipment Crawler Hi LF 

2270002024 Construction Equipment Surfacing Equipment Crawler Hi LF 

2270002027 Construction Equipment Signal Boards None Avg 7-cycle 

2270002030 Construction Equipment Trenchers Crawler Hi LF 

2270002033 Construction Equipment Bore/Drill Rigs None Avg 7-cycle 

2270002036 Construction Equipment Excavators Excavator Hi LF 

2270002039 Construction Equipment Concrete/Industrial Saws Crawler Hi LF 

2270002042 Construction Equipment Cement & Mortar Mixers None Avg 7-cycle 

2270002045 Construction Equipment Cranes None Avg 7-cycle 

2270002048 Construction Equipment Graders Crawler Hi LF 

2270002051 Construction Equipment Off-highway Trucks Crawler Hi LF 

2270002054 Construction Equipment Crushing/Proc. Equipment None Avg 7-cycle 

2270002057 Construction Equipment Rough Terrain Forklifts RTLoader Hi LF 

2270002060 Construction Equipment Rubber Tire Loaders RTLoader Hi LF 

2270002063 Construction Equipment Rubber Tire Dozers Crawler Hi LF 

2270002066 Construction Equipment Tractors/Loaders/Backhoes Backhoe Lo LF 

2270002069 Construction Equipment Crawler Dozer Crawler Hi LF 

2270002072 Construction Equipment Skid Steer Loaders SSLoader Lo LF 

2270002075 Construction Equipment Off-Highway Tractors Crawler Hi LF 

2270002078 Construction Equipment Dumpers/Tenders Backhoe Lo LF 

2270002081 Construction Equipment Other Construction Equipment Crawler Hi LF 

2270003010 Industrial Equipment Aerial Lifts Backhoe Lo LF 

2270003020 Industrial Equipment Forklifts RTLoader Hi LF 

2270003030 Industrial Equipment Sweepers/Scrubbers None Avg 7-cycle 

2270003040 Industrial Equipment Other General Industrial Equipment None Avg 7-cycle 

2270003050 Industrial Equipment Other Material Handling Equipment Backhoe Lo LF 

2270003060 Industrial Equipment AC\Refrigeration None Avg 7-cycle 

2270003070 Terminal Tractors Crawler Hi LF 

2270004000 Lawn & Garden Equipment ALL None Avg 7-cycle 

2270004010 Lawn & Garden Equipment Lawn mowers (Residential) None Avg 7-cycle 

2270004011 Lawn & Garden Equipment Lawn mowers (Commercial) None Avg 7-cycle 

2270004015 Lawn & Garden Equipment Rotary Tillers < 6 HP None Avg 7-cycle 

2270004016 Lawn & Garden Equipment Rotary Tillers < 6 HP (Commercial) None Avg 7-cycle 

2270004020 Lawn & Garden Equipment Chain Saws < 6 HP None Avg 7-cycle 

2270004021 Lawn & Garden Equipment Chain Saws < 6 HP (Commercial) None Avg 7-cycle 

15 
 

Table 10. CI Load Factor Assignments by Equipment Type 

SCC Equipment Type Representative 

Cycle 

Load Factor 

Assignment 

2270004025 Lawn & Garden Equipment Trimmers/Edgers/Brush Cutters None Avg 7-cycle 

2270004026 Lawn & Garden Equipment Trimmers/Edgers/Brush Cutters 

(C i l) 

None Avg 7-cycle 

2270004030 Lawn & Garden Equipment Leafblowers/Vacuums None Avg 7-cycle 

2270004031 Lawn & Garden Equipment Leafblowers/Vacuums (Commercial) None Avg 7-cycle 

2270004035 Lawn & Garden Equipment Snowblowers None Avg 7-cycle 

2270004036 Lawn & Garden Equipment Snowblowers (Commercial) None Avg 7-cycle 

2270004040 Lawn & Garden Equipment Rear Engine Riding Mowers None Avg 7-cycle 

2270004041 Lawn & Garden Equipment Rear Engine Riding Mowers 

(C i l) 

None Avg 7-cycle 

2270004045 Lawn & Garden Equipment Front Mowers None Avg 7-cycle 

2270004046 Lawn & Garden Equipment Front Mowers (Commercial) None Avg 7-cycle 

2270004050 Lawn & Garden Equipment Shredders < 6 HP None Avg 7-cycle 

2270004051 Lawn & Garden Equipment Shredders < 6 HP (Commercial) None Avg 7-cycle 

2270004055 Lawn & Garden Equipment Lawn & Garden Tractors None Avg 7-cycle 

2270004056 Lawn & Garden Equipment Lawn & Garden Tractors 

(C i l) 

None Avg 7-cycle 

2270004060 Lawn & Garden Equipment Wood Splitters None Avg 7-cycle 

2270004061 Lawn & Garden Equipment Wood Splitters (Commercial) None Avg 7-cycle 

2270004065 Lawn & Garden Equipment Chippers/Stump Grinders None Avg 7-cycle 

2270004066 Lawn & Garden Equipment Chippers/Stump Grinders 

(C i l) 

None Avg 7-cycle 

2270004071 Lawn & Garden Equipment Commercial Turf Equipment 

(C i l) 

None Avg 7-cycle 

2270004075 Lawn & Garden Equipment Other Lawn & Garden Equipment None Avg 7-cycle 

2270004076 Lawn & Garden Equipment Other Lawn & Garden Equipment 

(C i l) 

None Avg 7-cycle 

2270005010 Farm Equipment 2-Wheel Tractors AgTractor Hi LF 

2270005015 Farm Equipment Agricultural Tractors AgTractor Hi LF 

2270005020 Farm Equipment Combines AgTractor Hi LF 

2270005025 Farm Equipment Balers AgTractor Hi LF 

2270005030 Farm Equipment Agricultural Mowers AgTractor Hi LF 

2270005035 Farm Equipment Sprayers AgTractor Hi LF 

2270005040 Farm Equipment Tillers > 6 HP AgTractor Hi LF 

2270005045 Farm Equipment Swathers AgTractor Hi LF 

2270005050 Farm Equipment Hydro Power Units None Avg 7-cycle 

2270005055 Farm Equipment Other Agricultural Equipment AgTractor Hi LF 

2270005060 Farm Equipment Irrigation Sets None Avg 7-cycle 

2270006000 Light Commercial ALL None Avg 7-cycle 

2270006005 Light Commercial Generator Sets None Avg 7-cycle 

2270006010 Light Commercial Pumps None Avg 7-cycle 

2270006015 Light Commercial Air Compressors None Avg 7-cycle 

2270006020 Light Commercial Gas Compressors None Avg 7-cycle 

2270006025 Light Commercial Welders ArcWelder Lo LF 

2270006030 Light Commercial Pressure Washers None Avg 7-cycle 

2270007005 Logging Equipment Chain Saws > 6 HP RTLoader Hi LF 

2270007010 Logging Equipment Shredders > 6 HP RTLoader Hi LF 

2270007015 Logging Equipment Forest Equipment RTLoader Hi LF 

2270008005 Airport Service Equipment Airport Support Equipment RTLoader Hi LF 

2270009010 Other Underground Mining Equipment Backhoe Lo LF 

2270010010 Other Oil Field Equipment None Avg 7-cycle 

2282020005 Recreational Pleasure Craft, Inboards PSR-based N/A 

16 
Table 10. CI Load Factor Assignments by Equipment Type 

SCC Equipment Type Representative 

Cycle 

Load Factor 

Assignment 

2282020010 Recreational Pleasure Craft, Outboards PSR-based N/A 

2282020015 Recreational Pleasure Craft, Personal Water Craft PSR-based N/A 

2282020025 Recreational Pleasure Craft, Sailboat Aux. Outboard PSR-based N/A 

2285002015 Railway Maintenance Backhoe Lo LF 

17 
References 

(1) California Air Resources Board. (CARB). "Documentation of Input Factors for the New 

Off-Road Mobile Source Emissions Inventory Model," Energy and Environmental 

Analysis, Inc., February, 1997. Table 3-1. 

(2) Energy and Environmental Analysis, Inc. "Documentation of Diesel Engine Life Values 

Used in the ARB Off-Highway Model." Unpublished Report, prepared for U. S. 

Environmental Protection Agency, Office of Transportation and Air Quality, September 

2001. 

(3) U. S. Environmental Protection Agency. “Phase 2 Emission Standards for New 

Nonhandheld Engines at or below 19 Kilowatts (kW).” Office of Mobile Sources, 

Regulatory Impact Analysis, EPA420-R-99-003, March 1999. 

(4) E.H. Pechan & Associates. "Evaluation of Power Systems Research (PSR) Nonroad 

Population Data Base," prepared for U.S. Environmental Protection Agency, Office of 

Mobile Sources. EPA Contract No. 68-D3-0035, Work Assignment No. III-107, Pechan 

Report No. 97.09.003/1807. September, 1997. 

(5) U. S. EPA. "Phase 2 Final Rule: Emission Standards for New Nonroad Handheld 

Spark-Ignition Engines At or Below 19 Kilowatts." Office of Transportation and Air 

Quality. Final Regulatory Impact Analysis, EPA420-R-00-004. March 2000. 

(6) U.S. EPA. “Control of Emissions from Marine SI and Small SI Engines, Vessels, and 

Equipment.” Office of Transportation and Air Quality. Final Regulatory Impact Analysis, 

EPA420-R-08-014. September 2008. 

(7)	 United States Environmental Protection Agency. "Final Regulatory Support Document: 

Control of Emissions from Unregulated Nonroad Engines." EPA420-R-02-022, 

September 2002. 

(8) Power Systems Research, Inc. "Reference Guide, U.S. PartsLink.” Edition 6.2, St. Paul, 

MN. 

(9) United States Environmental Protection Agency. “Median Life, Annual Activity, and 

Load Factor Values for Nonroad Engine Emissions Modeling,” Office of Mobile 

Sources, Assessment & Modeling Division. NONROAD Technical Report NR-005A. 

June 15, 1998. 

18 
 

(10) United States Environmental Protection Agency. “Regulatory Impact Analysis: Control 

of Air Pollution Emission Standards for New Nonroad Spark-Ignition Marine Engines." 

Office of Air and Radiation. ANR-443. June 1996. 

(11) United States Environmental Protection Agency. “Emission Modeling for Recreational 

Vehicles,” Memorandum to Public Docket A-98-01. EPA420-F-00-051, November 13, 

2000. 2 

(12)	 Mc Elvany, Norman D. 1995. Snowmobiling in Vermont: An Economic Study and 

Snowmobile User Survey. Johnson State College, Johnson, VT. Prepared for Vermont 

Association of Snow Travelers (VAST). 

(13)	 Robertson, Robert A. Assessment of Snowmobiling in New Hampshire "1996:" 

Summary and Recommendations. Tourism Planning and Development Program, 

Department of Resource Economics and Development, University of New Hampshire, 

Durham. Prepared for the New Hampshire Snowmobile Association. August, 1996. 

(14)	 Sylvester, James T. Snowmobile Gasoline Usage in Montana. Bureau of Business and 

Economic Research, University of Montana, Missoula. Prepared for Montana 

Department of Fish, Wildlife and Parks, and Montana Snowmobile Association. 

September 28, 1996. 

(15)	 Reiling, Stephen; Kotchen, Matthew; Kezis, Alan. An Economic Evaluation of 

Snowmobiling in Maine. Department of Resource Economics and Policy, University of 

Maine, Orono. Maine Agricultural and Forest Experiment Station No. 2069. Prepared for 

the Maine Snowmobile Association. January, 1997. 

(16)	 Nelson, Charles M., Lynch, Joel A., Stynes, Daniel J. An Assessment of Snowmobiling 

in Michigan by Snowmobilers with Michigan Trail Permits. Department of Park, 

Recreation and Tourism Resources, Michigan State University, East Lansing. Prepared 

for Michigan Department of Natural Resources, Forest Management Division. February 

10, 1998. 

(17)	 Merwin Rural Services Institute. Snowmobiling in New York: An Analysis of Economic 

Impact and Overview of the Industry in the Empire State. State University of New York, 

Potsdam. Prepared for New York State Snowmobile Association, Inc. April, 1998. 

2

 This memorandum supplements the Advance Notice of Proposed Rulemaking: Control of Emissions from 

Nonroad Large Spark Ignition Engines, Recreational Engines (Marine and Land-based), and Highway Motorcycles 

(November 20, 2000). See http://www.otaq.gov/otaq/recveh.htm. 

19 
(18)	 Loomis, David K; Lundrigan, Heather. 1999 Assessment of Snowmobiling in 

Massachusetts. Human Dimensions Research Unit, Department of Natural Resources 

Conservation University of Massachusetts, Amherst. Prepared for Snowmobiling 

Association of Massachusetts. March 30, 2000. 

(19)	 United States Consumer Product Safety Commission. “Report on 1997 ATV Exposure 

Survey.” Directorate for Economic Analysis, Bethesda, Maryland. April 1998. 

(20) Fritz, S.G. and M.E. Starr, “Emission Factors for Compression Ignition Nonroad Engines 

Operated on Number 2 Highway and Nonroad Diesel Fuel,” Southwest Research 

Institute. SwRI 08-7601-822, March 1998. 

(21)	 Starr, Michael E., “Nonroad Engine Emissions Testing,” Southwest Research Institute. 

September 1999. 

(22)	 Starr, Michael E., “Excavator Cycle Development,” Southwest Research Institute. SwRI 

2206-801, September 1999. 

20 
Appendix A 

Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2260001010 2-Stroke Motorcycles: Off-Road 1.00 1600* 

2260001020 2-Stroke Snowmobiles 0.34 57 

2260001030 2-Stroke All Terrain Vehicles 1.00 1608* 

2260001050 2-Stroke Golf Carts 0.46 1080 

2260001060 2-Stroke Specialty Vehicle Carts 0.58 65 

2260002003 2-Stroke Asphalt Pavers 0.66 392 

2260002006 2-Stroke Tampers/Rammers 0.55 160 

2260002009 2-Stroke Plate Compactors 0.55 166 

2260002012 2-Stroke Concrete Pavers 0.55 0 

2260002015 2-Stroke Rollers 0.62 621 

2260002018 2-Stroke Scrapers 0.70 540 

2260002021 2-Stroke Paving Equipment 0.59 175 

2260002024 2-Stroke Surfacing Equipment 0.49 488 

2260002027 2-Stroke Signal Boards 0.72 318 

2260002030 2-Stroke Trenchers 0.66 402 

2260002033 2-Stroke Bore/Drill Rigs 0.79 107 

2260002036 2-Stroke Excavators 0.53 378 

2260002039 2-Stroke Concrete/Industrial Saws 0.78 610 

2260002042 2-Stroke Cement & Mortar Mixers 0.59 84 

2260002045 2-Stroke Cranes 0.47 415 

2260002048 2-Stroke Graders 0.64 504 

2260002051 2-Stroke Off-highway Trucks 0.80 450 

2260002054 2-Stroke Crushing/Proc. Equipment 0.85 241 

2260002057 2-Stroke Rough Terrain Forklifts 0.63 413 

2260002060 2-Stroke Rubber Tire Loaders 0.71 512 

2260002063 2-Stroke Rubber Tire Dozers 0.75 900 

2260002066 2-Stroke Tractors/Loaders/Backhoes 0.48 870 

2260002069 2-Stroke Crawler Dozer 0.80 700 

2260002072 2-Stroke Skid Steer Loaders 0.58 310 

2260002075 2-Stroke Off-Highway Tractors 0.70 155 

2260002078 2-Stroke Dumpers/Tenders 0.41 127 

2260002081 2-Stroke Other Construction Equipment 0.48 371 

2260003010 2-Stroke Aerial Lifts 0.46 361 

2260003020 2-Stroke Forklifts 0.30 1800 

2260003030 2-Stroke Sweepers/Scrubbers 0.71 516 

2260003040 2-Stroke Other General Industrial Equipment 0.54 713 

2260003050 2-Stroke Other Material Handling Equipment 0.53 386 

2260003060 2-Stroke Refrigeration 0.46 605 

2260003070 2-Stroke Terminal Tractors 0.78 827 

2260004010 2-Stroke Lawn mowers (Residential) 0.33 25 

2260004011 2-Stroke Lawn mowers (Commercial) 0.33 406 

2260004015 2-Stroke Rotary Tillers < 6 HP (Residential) 0.40 17 

2260004016 2-Stroke Rotary Tillers < 6 HP (Commercial) 0.40 472 

2260004020 2-Stroke Chain Saws < 6 HP (Residential) 0.70 13 

2260004021 2-Stroke Chain Saws < 6 HP (Commercial) 0.70 303 

2260004025 2-Stroke Trimmers/Edgers/Brush Cutters 0.91 9 

2260004026 2-Stroke Trimmers/Edgers/Brush Cutters 0.91 137 

2260004030 2-Stroke Leafblowers/Vacuums (Residential) 0.94 10 

2260004031 2-Stroke Leafblowers/Vacuums (Commercial) 0.94 282 

A1 
Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2260004035 2-Stroke Snowblowers (Residential) 0.35 8 

2260004036 2-Stroke Snowblowers (Commercial) 0.35 136 

2260004040 2-Stroke Rear Engine Riding Mowers (Res.) 0.38 36 

2260004041 2-Stroke Rear Engine Riding Mowers (Comm.) 0.38 569 

2260004045 2-Stroke Front Mowers (Residential) 0.65 86 

2260004046 2-Stroke Front Mowers (Commercial) 0.65 86 

2260004050 2-Stroke Shredders < 6 HP (Residential) 0.80 50 

2260004051 2-Stroke Shredders < 6 HP (Commercial) 0.80 50 

2260004055 2-Stroke Lawn & Garden Tractors (Residential) 0.44 45 

2260004056 2-Stroke Lawn & Garden Tractors (Commercial) 0.44 721 

2260004060 2-Stroke Wood Splitters (Residential) 0.69 76 

2260004061 2-Stroke Wood Splitters (Commercial) 0.69 76 

2260004065 2-Stroke Chippers/Stump Grinders (Res.) 0.78 488 

2260004066 2-Stroke Chippers/Stump Grinders (Comm.) 0.78 488 

2260004070 2-Stroke Commercial Turf Equipment (Res.) 0.60 682 

2260004071 2-Stroke Commercial Turf Equipment (Comm) 0.60 682 

2260004075 2-Stroke Other Lawn & Garden Equipment 0.58 61 

2260004076 2-Stroke Other Lawn & Garden Equipment 0.58 61 

2260005010 2-Stroke 2-Wheel Tractors 0.62 286 

2260005015 2-Stroke Agricultural Tractors 0.62 550 

2260005020 2-Stroke Combines 0.74 125 

2260005025 2-Stroke Balers 0.62 68 

2260005030 2-Stroke Agricultural Mowers 0.48 175 

2260005035 2-Stroke Sprayers 0.65 80 

2260005040 2-Stroke Tillers > 6 HP 0.71 43 

2260005045 2-Stroke Swathers 0.52 95 

2260005055 2-Stroke Other Agricultural Equipment 0.55 124 

2260005060 2-Stroke Irrigation Sets 0.60 716 

2260006005 2-Stroke Light Commercial Generator Set 0.68 115 

2260006010 2-Stroke Light Commercial Pumps 0.69 221 

2260006015 2-Stroke Light Commercial Air Compressors 0.56 484 

2260006020 2-Stroke Light Commercial Gas Compressors 0.85 6000 

2260006025 2-Stroke Light Commercial Welders 0.68 408 

2260006030 2-Stroke Light Commercial Pressure Wash 0.85 115 

2260006035 2-Stroke Hydro Power Units 0.56 450 

2260007005 2-Stroke Logging Equipment Chain Saws > 6 HP 0.70 303 

2260007010 2-Stroke Logging Equipment Shredders > 6 HP 0.80 50 

2260007015 2-Stroke Logging Equipment Skidders 0.70 350 

2260007020 2-Stroke Logging Equipment Fellers/Bunchers 0.70 0 

2260008005 2-Stroke Airport Support Equipment 0.56 681 

2260009010 2-Stroke Other Underground Mining Equipment 0.80 260 

2260010010 2-Stroke Other Oil Field Equipment 0.90 1104 

2265001010 4-Stroke Motorcycles: Off-Road 1.00 1600 

2265001020 4-Stroke Snowmobiles 0.34 57 

2265001030 4-Stroke All Terrain Vehicles 1.00 1608 

2265001050 4-Stroke Golf Carts 0.46 1080 

2265001060 4-Stroke Specialty Vehicle Carts 0.58 65 

2265002003 4-Stroke Asphalt Pavers 0.66 392 

2265002006 4-Stroke Tampers/Rammers 0.55 160 

2265002009 4-Stroke Plate Compactors 0.55 166 

2265002012 4-Stroke Concrete Pavers 0.55 0 

2265002015 4-Stroke Rollers 0.62 621 

A2 
Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2265002018 4-Stroke Scrapers 0.70 540 

2265002021 4-Stroke Paving Equipment 0.59 175 

2265002024 4-Stroke Surfacing Equipment 0.49 488 

2265002027 4-Stroke Signal Boards 0.72 318 

2265002030 4-Stroke Trenchers 0.66 402 

2265002033 4-Stroke Bore/Drill Rigs 0.79 107 

2265002036 4-Stroke Excavators 0.53 378 

2265002039 4-Stroke Concrete/Industrial Saws 0.78 610 

2265002042 4-Stroke Cement & Mortar Mixers 0.59 84 

2265002045 4-Stroke Cranes 0.47 415 

2265002048 4-Stroke Graders 0.64 504 

2265002051 4-Stroke Off-highway Trucks 0.80 450 

2265002054 4-Stroke Crushing/Proc. Equipment 0.85 241 

2265002057 4-Stroke Rough Terrain Forklifts 0.63 413 

2265002060 4-Stroke Rubber Tire Loaders 0.71 512 

2265002063 4-Stroke Rubber Tire Dozers 0.75 900 

2265002066 4-Stroke Tractors/Loaders/Backhoes 0.48 870 

2265002069 4-Stroke Crawler Tractors 0.80 700 

2265002072 4-Stroke Skid Steer Loaders 0.58 310 

2265002075 4-Stroke Off-Highway Tractors 0.70 155 

2265002078 4-Stroke Dumpers/Tenders 0.41 127 

2265002081 4-Stroke Other Construction Equipment 0.48 371 

2265003010 4-Stroke Aerial Lifts 0.46 361 

2265003020 4-Stroke Forklifts 0.30 1800 

2265003030 4-Stroke Sweepers/Scrubbers 0.71 516 

2265003040 4-Stroke Other General Industrial Equipment 0.54 713 

2265003050 4-Stroke Other Material Handling Equipment 0.53 386 

2265003060 4-Stroke Industial AC\Refrigeration 0.46 605 

2265003070 4-Stroke Terminal Tractors 0.78 827 

2265004010 4-Stroke Lawn mowers (Residential) 0.33 25 

2265004011 4-Stroke Lawn mowers (Commercial) 0.33 406 

2265004015 4-Stroke Rotary Tillers < 6 HP (Residential) 0.40 17 

2265004016 4-Stroke Rotary Tillers < 6 HP (Commercial) 0.40 472 

2265004020 4-Stroke Chain Saws < 6 HP (Residential) 0.70 13 

2265004021 4-Stroke Chain Saws < 6 HP (Commercial) 0.70 303 

2265004025 4-Stroke Trimmers/Edgers/Brush Cutters 0.91 9 

2265004026 4-Stroke Trimmers/Edgers/Brush Cutters 0.91 137 

2265004030 4-Stroke Leafblowers/Vacuums (Residential) 0.94 10 

2265004031 4-Stroke Leafblowers/Vacuums (Commercial) 0.94 282 

2265004035 4-Stroke Snowblowers (Residential) 0.35 8 

2265004036 4-Stroke Snowblowers (Commercial) 0.35 136 

2265004040 4-Stroke Rear Engine Riding Mowers (Res.) 0.38 36 

2265004041 4-Stroke Rear Engine Riding Mowers (Comm) 0.38 569 

2265004045 4-Stroke Front Mowers (Residential) 0.65 86 

2265004046 4-Stroke Front Mowers (Commercial) 0.65 86 

2265004050 4-Stroke Shredders < 6 HP (Residential) 0.80 50 

2265004051 4-Stroke Shredders < 6 HP (Commercial) 0.80 50 

2265004055 4-Stroke Lawn & Garden Tractors (Residential) 0.44 45 

2265004056 4-Stroke Lawn & Garden Tractors (Commercial) 0.44 721 

2265004060 4-Stroke Wood Splitters (Residential) 0.69 76 

2265004061 4-Stroke Wood Splitters (Commercial) 0.69 76 

2265004065 4-Stroke Chippers/Stump Grinders (Res.) 0.78 488 

A3 
Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2265004066 4-Stroke Chippers/Stump Grinders (Comm.) 0.78 488 

2265004070 4-Stroke Commercial Turf Equipment (Res.) 0.60 682 

2265004071 4-Stroke Commercial Turf Equipment (Comm) 0.60 682 

2265004075 4-Stroke Other Lawn & Garden Equipment 0.58 61 

2265004076 4-Stroke Other Lawn & Garden Equipment 0.58 61 

2265005010 4-Stroke 2-Wheel Tractors 0.62 286 

2265005015 4-Stroke Agricultural Tractors 0.62 550 

2265005020 4-Stroke Combines 0.74 125 

2265005025 4-Stroke Balers 0.62 68 

2265005030 4-Stroke Agricultural Mowers 0.48 175 

2265005035 4-Stroke Sprayers 0.65 80 

2265005040 4-Stroke Tillers > 5 HP 0.71 43 

2265005045 4-Stroke Swathers 0.52 95 

2265005055 4-Stroke Other Agricultural Equipment 0.55 124 

2265005060 4-Stroke Irrigation Sets 0.60 716 

2265006005 4-Stroke Light Commercial Generator Sets 0.68 115 

2265006010 4-Stroke Light Commercial Pumps 0.69 221 

2265006015 4-Stroke Light Commercial Air Compressors 0.56 484 

2265006020 4-Stroke Light Commercial Gas Compressors 0.85 6000 

2265006025 4-Stroke Light Commercial Welders 0.68 408 

2265006030 4-Stroke Light Commercial Pressure Washers 0.85 115 

2265006035 4-Stroke Hydro Power Units 0.56 450 

2265007005 4-Stroke Logging Equipment Chain Saws > 6 HP 0.70 303 

2265007010 4-Stroke Logging Equipment Shredders > 6 HP 0.80 50 

2265007015 4-Stroke Logging Equipment Skidders 0.70 350 

2265007020 4-Stroke Logging Equipment Fellers/Bunchers 0.70 0 

2265008005 4-Stroke Airport Support Equipment 0.56 681 

2265009010 4-Stroke Other Underground Mining Equipment 0.80 260 

2265010010 4-Stroke Other Oil Field Equipment 0.90 1104 

2270001020 Diesel Snowmobiles (unused) 0.34 40 

2270001030 Diesel All Terrain Vehicles/MC (unused) 0.42 0 

2270001050 Diesel Golf Carts (unused) 0.49 1150 

2270001060 Diesel Specialty Vehicle Carts 0.21 435 

2270002003 Diesel Pavers 0.59 821 

2270002006 Diesel Tampers/Rammers (unused) 0.43 460 

2270002009 Diesel Plate Compactors 0.43 484 

2270002012 Diesel Concrete Pavers (unused) 0.59 0 

2270002015 Diesel Rollers 0.59 760 

2270002018 Diesel Scrapers 0.59 914 

2270002021 Diesel Paving Equipment 0.59 622 

2270002024 Diesel Surfacing Equipment 0.59 561 

2270002027 Diesel Signal Boards 0.43 535 

2270002030 Diesel Trenchers 0.59 593 

2270002033 Diesel Bore/Drill Rigs 0.43 466 

2270002036 Diesel Excavators 0.59 1092 

2270002039 Diesel Concrete/Industrial Saws 0.59 580 

2270002042 Diesel Cement & Mortar Mixers 0.43 275 

2270002045 Diesel Cranes 0.43 990 

2270002048 Diesel Graders 0.59 962 

2270002051 Diesel Off-highway Trucks 0.59 1641 

2270002054 Diesel Crushing/Proc. Equipment 0.43 955 

2270002057 Diesel Rough Terrain Forklifts 0.59 662 

A4 
Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2270002060 Diesel Rubber Tire Loaders 0.59 761 

2270002063 Diesel Rubber Tire Dozers 0.59 899 

2270002066 Diesel Tractors/Loaders/Backhoes 0.21 1135 

2270002069 Diesel Crawler Tractors 0.59 936 

2270002072 Diesel Skid Steer Loaders 0.21 818 

2270002075 Diesel Off-Highway Tractors 0.59 855 

2270002078 Diesel Dumpers/Tenders 0.21 566 

2270002081 Diesel Other Construction Equipment 0.59 606 

2270003010 Diesel Aerial Lifts 0.21 384 

2270003020 Diesel Forklifts 0.59 1700 

2270003030 Diesel Sweepers/Scrubbers 0.43 1220 

2270003040 Diesel Other General Industrial Equipment 0.43 878 

2270003050 Diesel Other Material Handling Equipment 0.21 421 

2270003060 Diesel AC\Refrigeration 0.43 1341 

2270003070 Diesel Terminal Tractors 0.59 1257 

2270004010 Diesel Lawn mowers (Residential) 0.43 320 

2270004011 Diesel Lawn mowers (Commerical) 0.43 320 

2270004015 Diesel Rotary Tillers < 6 HP (Residential) 0.43 172 

2270004016 Diesel Rotary Tillers < 6 HP (Commercial) 0.43 172 

2270004020 Diesel Chain Saws < 6 HP (Residential) 0.43 70 

2270004021 Diesel Chain Saws < 6 HP (Commercial) 0.43 70 

2270004025 Diesel Trimmers/Edgers/Brush Cutters (Res.) 0.43 60 

2270004026 Diesel Trimmers/Edgers/Brush Cutters (Comm.) 0.43 60 

2270004030 Diesel Leafblowers/Vacuums (Residential) 0.43 120 

2270004031 Diesel Leafblowers/Vacuums (Commercial) 0.43 120 

2270004035 Diesel Snowblowers (Residential) 0.43 400 

2270004036 Diesel Snowblowers (Commercial) 0.43 400 

2270004040 Diesel Rear Engine Riding Mowers (Res.) 0.43 480 

2270004041 Diesel Rear Engine Riding Mowers (Comm.) 0.43 480 

2270004045 Diesel Front Mowers (Residential) 0.43 480 

2270004046 Diesel Front Mowers (Commercial) 0.43 480 

2270004050 Diesel Shredders < 6 HP (Residential) 0.43 120 

2270004051 Diesel Shredders < 6 HP (Commercial) 0.43 120 

2270004055 Diesel Lawn & Garden Tractors (Residential) 0.43 544 

2270004056 Diesel Lawn & Garden Tractors (Commercial) 0.43 544 

2270004060 Diesel Wood Splitters (Residential) 0.43 265 

2270004061 Diesel Wood Splitters (Commercial) 0.43 265 

2270004065 Diesel Chippers/Stump Grinders (Residential) 0.43 465 

2270004066 Diesel Chippers/Stump Grinders (Commercial) 0.43 465 

2270004070 Diesel Commercial Turf Equipment (Res.) 0.43 1068 

2270004071 Diesel Commercial Turf Equipment (Comm.) 0.43 1068 

2270004075 Diesel Other Lawn & Garden Equipment (Res.) 0.43 433 

2270004076 Diesel Other Lawn & Garden Equipment (Comm.) 0.43 433 

2270005010 Diesel 2-Wheel Tractors 0.59 544 

2270005015 Diesel Agricultural Tractors 0.59 475 

2270005020 Diesel Combines 0.59 150 

2270005025 Diesel Balers 0.59 95 

2270005030 Diesel Agricultural Mowers 0.59 363 

2270005035 Diesel Sprayers 0.59 90 

2270005040 Diesel Tillers > 6 HP 0.59 172 

2270005045 Diesel Swathers 0.59 110 

2270005055 Diesel Other Agricultural Equipment 0.59 381 

A5 
Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2270005060 Diesel Irrigation Sets 0.43 749 

2270006005 Diesel Light Commercial Generator Sets 0.43 338 

2270006010 Diesel Light Commercial Pumps 0.43 403 

2270006015 Diesel Light Commercial Air Compressors 0.43 815 

2270006020 Diesel Light Commercial Gas Compressors 0.43 8500 

2270006025 Diesel Light Commercial Welders 0.21 643 

2270006030 Diesel Light Commercial Pressure Washer 0.43 145 

2270006035 Diesel Hydro Power Units 0.43 790 

2270007005 Diesel Logging Equipment Chain Saws > 6 HP 0.59 70 

2270007010 Diesel Logging Equipment Shredders > 6 HP 0.59 120 

2270007015 Diesel Logging Equip Fell/Bunch/Skidders 0.59 1276 

2270007020 Diesel Logging Equip Fell/Bunch (unused) 0.59 0 

2270008005 Diesel Airport Support Equipment 0.59 732 

2270009010 Diesel Other Underground Mining Equipment 0.21 1533 

2270010010 Diesel Other Oil Field Equipment 0.43 1231 

2267001020 LPG Snowmobiles 0.34 40 

2267001050 LPG Golf Carts 0.46 1080 

2267001060 LPG Specialty Vehicle Carts 0.58 65 

2267002003 LPG Asphalt Pavers 0.66 392 

2267002006 LPG Tampers/Rammers 0.55 160 

2267002009 LPG Plate Compactors 0.55 166 

2267002012 LPG Concrete Pavers 0.55 0 

2267002015 LPG Rollers 0.62 621 

2267002018 LPG Scrapers 0.70 540 

2267002021 LPG Paving Equipment 0.59 175 

2267002024 LPG Surfacing Equipment 0.49 488 

2267002027 LPG Signal Boards 0.72 318 

2267002030 LPG Trenchers 0.66 402 

2267002033 LPG Bore/Drill Rigs 0.79 107 

2267002036 LPG Excavators 0.59 378 

2267002039 LPG Concrete/Industrial Saws 0.78 610 

2267002042 LPG Cement & Mortar Mixers 0.59 84 

2267002045 LPG Cranes 0.47 415 

2267002048 LPG Graders 0.64 504 

2267002051 LPG Off-highway Trucks 0.80 450 

2267002054 LPG Crushing/Proc. Equipment 0.85 241 

2267002057 LPG Rough Terrain Forklifts 0.63 413 

2267002060 LPG Rubber Tire Loaders 0.71 512 

2267002063 LPG Rubber Tire Dozers 0.75 900 

2267002066 LPG Tractors/Loaders/Backhoes 0.48 870 

2267002069 LPG Crawler Tractors 0.80 700 

2267002072 LPG Skid Steer Loaders 0.58 310 

2267002075 LPG Off-Highway Tractors 0.70 155 

2267002078 LPG Dumpers/Tenders 0.41 127 

2267002081 LPG Other Construction Equipment 0.48 371 

2267003010 LPG Aerial Lifts 0.46 361 

2267003020 LPG Forklifts 0.30 1800 

2267003030 LPG Sweepers/Scrubbers 0.71 516 

2267003040 LPG Other General Industrial Equipment 0.54 713 

2267003050 LPG Other Material Handling Equipment 0.53 386 

2267003060 LPG AC\Refrigeration 0.46 605 

2267003070 LPG Terminal Tractors 0.78 827 

A6 
Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2267004010 LPG Lawn mowers (Residential) 0.33 25 

2267004011 LPG Lawn mowers (Commercial) 0.33 406 

2267004015 LPG Rotary Tillers < 6 HP (Residential) 0.40 17 

2267004016 LPG Rotary Tillers < 6 HP (Commercial) 0.40 472 

2267004020 LPG Chain Saws < 6 HP (Residential) 0.70 13 

2267004021 LPG Chain Saws < 6 HP (Commercial) 0.70 303 

2267004025 LPG Trimmers/Edgers/Brush Cutters (Res.) 0.91 9 

2267004026 LPG Trimmers/Edgers/Brush Cutters (Comm.) 0.91 137 

2267004030 LPG Leafblowers/Vacuums (Residential) 0.94 10 

2267004031 LPG Leafblowers/Vacuums (Commercial) 0.94 282 

2267004035 LPG Snowblowers (Residential) 0.35 8 

2267004036 LPG Snowblowers (Commercial) 0.35 136 

2267004040 LPG Rear Engine Riding Mowers (Residential) 0.38 36 

2267004041 LPG Rear Engine Riding Mowers (Commercial) 0.38 569 

2267004045 LPG Front Mowers (Residential) 0.65 86 

2267004046 LPG Front Mowers (Commercial) 0.65 86 

2267004050 LPG Shredders < 6 HP (Residential) 0.80 50 

2267004051 LPG Shredders < 6 HP (Commercial) 0.80 50 

2267004055 LPG Lawn & Garden Tractors (Residential) 0.44 45 

2267004056 LPG Lawn & Garden Tractors (Commercial) 0.44 721 

2267004060 LPG Wood Splitters (Residential) 0.69 76 

2267004061 LPG Wood Splitters (Commercial) 0.69 76 

2267004065 LPG Chippers/Stump Grinders (Residential) 0.78 488 

2267004066 LPG Chippers/Stump Grinders (Commercial) 0.78 488 

2267004070 LPG Commercial Turf Equipment (Residential) 0.60 682 

2267004071 LPG Commercial Turf Equipment (Commercial) 0.60 682 

2267004075 LPG Other Lawn & Garden Equipment (Res.) 0.58 61 

2267004076 LPG Other Lawn & Garden Equipment (Comm.) 0.58 61 

2267005010 LPG 2-Wheel Tractors 0.62 286 

2267005015 LPG Agricultural Tractors 0.62 550 

2267005020 LPG Combines 0.74 125 

2267005025 LPG Balers 0.62 68 

2267005030 LPG Agricultural Mowers 0.48 175 

2267005035 LPG Sprayers 0.65 80 

2267005040 LPG Tillers > 6 HP 0.71 43 

2267005045 LPG Swathers 0.52 95 

2267005055 LPG Other Agricultural Equipment 0.55 124 

2267005060 LPG Irrigation Sets 0.60 716 

2267006005 LPG Light Commercial Generator Sets 0.68 115 

2267006010 LPG Light Commercial Pumps 0.69 221 

2267006015 LPG Light Commercial Air Compressors 0.56 484 

2267006020 LPG Light Commercial Gas Compressors 0.85 6000 

2267006025 LPG Light Commercial Welders 0.68 408 

2267006030 LPG Light Commercial Pressure Washers 0.85 115 

2267006035 LPG Hydro Power Units 0.56 450 

2267007005 LPG Logging Equipment Chain Saws > 6 HP 0.70 303 

2267007010 LPG Logging Equipment Shredders > 6 HP 0.80 50 

2267007015 LPG Logging Equipment Skidders 0.70 350 

2267007020 LPG Logging Equipment Fellers/Bunchers 0.70 0 

2267008005 LPG Airport Support Equipment 0.56 681 

2267009010 LPG Other Underground Mining Equipment 0.80 260 

2267010010 LPG Other Oil Field Equipment 0.90 1104 

A7 
Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2268001020 CNG Snowmobiles 0.34 40 

2268001050 CNG Golf Carts 0.46 1080 

2268001060 CNG Specialty Vehicle Carts 0.58 65 

2268002003 CNG Asphalt Pavers 0.66 392 

2268002006 CNG Tampers/Rammers 0.55 160 

2268002009 CNG Plate Compactors 0.55 166 

2268002012 CNG Concrete Pavers 0.55 0 

2268002015 CNG Rollers 0.62 621 

2268002018 CNG Scrapers 0.70 540 

2268002021 CNG Paving Equipment 0.59 175 

2268002024 CNG Surfacing Equipment 0.49 488 

2268002027 CNG Signal Boards 0.72 318 

2268002030 CNG Trenchers 0.66 402 

2268002033 CNG Bore/Drill Rigs 0.79 107 

2268002036 CNG Excavators 0.53 378 

2268002039 CNG Concrete/Industrial Saws 0.78 610 

2268002042 CNG Cement & Mortar Mixers 0.59 84 

2268002045 CNG Cranes 0.47 415 

2268002048 CNG Graders 0.64 504 

2268002051 CNG Off-highway Trucks 0.80 450 

2268002054 CNG Crushing/Proc. Equipment 0.85 241 

2268002057 CNG Rough Terrain Forklifts 0.63 413 

2268002060 CNG Rubber Tire Loaders 0.71 512 

2268002063 CNG Rubber Tire Dozers 0.75 900 

2268002066 CNG Tractors/Loaders/Backhoes 0.48 870 

2268002069 CNG Crawler Tractors 0.80 700 

2268002072 CNG Skid Steer Loaders 0.58 310 

2268002075 CNG Off-Highway Tractors 0.70 155 

2268002078 CNG Dumpers/Tenders 0.41 127 

2268002081 CNG Other Construction Equipment 0.48 371 

2268003010 CNG Aerial Lifts 0.46 361 

2268003020 CNG Forklifts 0.30 1800 

2268003030 CNG Sweepers/Scrubbers 0.71 516 

2268003040 CNG Other General Industrial Equipment 0.54 713 

2268003050 CNG Other Material Handling Equipment 0.53 386 

2268003060 CNG AC\Refrigeration 0.46 605 

2268003070 CNG Terminal Tractors 0.78 827 

2268004010 CNG Lawn mowers (Residential) 0.33 25 

2268004011 CNG Lawn mowers (Commercial) 0.33 406 

2268004015 CNG Rotary Tillers < 6 HP (Residential) 0.40 17 

2268004016 CNG Rotary Tillers < 6 HP (Commercial) 0.40 472 

2268004020 CNG Chain Saws < 6 HP (Residential) 0.70 13 

2268004021 CNG Chain Saws < 6 HP (Commercial) 0.70 303 

2268004025 CNG Trimmers/Edgers/Brush Cutters (Res.) 0.91 9 

2268004026 CNG Trimmers/Edgers/Brush Cutters (Comm.) 0.91 137 

2268004030 CNG Leafblowers/Vacuums (Residential) 0.94 10 

2268004031 CNG Leafblowers/Vacuums (Commercial) 0.94 282 

2268004035 CNG Snowblowers (Residential) 0.35 8 

2268004036 CNG Snowblowers (Commercial) 0.35 136 

2268004040 CNG Rear Engine Riding Mowers (Residential) 0.38 36 

2268004041 CNG Rear Engine Riding Mowers (Commercial) 0.38 569 

2268004045 CNG Front Mowers (Residential) 0.65 86 

A8 
Load Factor and Activity Estimates in NONROAD2008a 

SCC Equipment Description Load Factor 

(fraction of power) 

Activity 

(hours/year) 

2268004046 CNG Front Mowers (Commercial) 0.65 86 

2268004050 CNG Shredders < 6 HP (Residential) 0.80 50 

2268004051 CNG Shredders < 6 HP (Commercial) 0.80 50 

2268004055 CNG Lawn & Garden Tractors (Residential) 0.44 45 

2268004056 CNG Lawn & Garden Tractors (Commercial) 0.44 721 

2268004060 CNG Wood Splitters (Residential) 0.69 76 

2268004061 CNG Wood Splitters (Commercial) 0.69 76 

2268004065 CNG Chippers/Stump Grinders (Residential) 0.78 488 

2268004066 CNG Chippers/Stump Grinders (Commercial) 0.78 488 

2268004070 CNG Commercial Turf Equipment (Residential) 0.60 682 

2268004071 CNG Commercial Turf Equipment (Commercial) 0.60 682 

2268004075 CNG Other Lawn & Garden Equipment (Res.) 0.58 61 

2268004076 CNG Other Lawn & Garden Equipment (Comm.) 0.58 61 

2268005010 CNG 2-Wheel Tractors 0.62 286 

2268005015 CNG Agricultural Tractors 0.62 550 

2268005020 CNG Combines 0.74 125 

2268005025 CNG Balers 0.62 68 

2268005030 CNG Agricultural Mowers 0.48 175 

2268005035 CNG Sprayers 0.65 80 

2268005040 CNG Tillers > 6 HP 0.71 43 

2268005045 CNG Swathers 0.52 95 

2268005055 CNG Other Agricultural Equipment 0.55 124 

2268005060 CNG Irrigation Sets 0.60 716 

2268006005 CNG Light Commercial Generator Sets 0.68 115 

2268006010 CNG Light Commercial Pumps 0.69 221 

2268006015 CNG Light Commercial Air Compressors 0.56 484 

2268006020 CNG Light Commercial Gas Compressors 0.85 6000 

2268006025 CNG Light Commercial Welders 0.68 408 

2268006030 CNG Light Commercial Pressure Washers 0.85 115 

2268006035 CNG Hydro Power Units 0.56 450 

2268007005 CNG Logging Equipment Chain Saws > 6 HP 0.70 303 

2268007010 CNG Logging Equipment Shredders > 6 HP 0.80 50 

2268007015 CNG Logging Equipment Skidders 0.70 350 

2268007020 CNG Logging Equipment Fellers/Bunchers 0.70 0 

2268008005 CNG Airport Support Equipment 0.56 681 

2268009010 CNG Other Underground Mining Equipment 0.80 260 

2268010010 CNG Other Oil Field Equipment 0.90 1104 

2282005010 2-Stroke Outboards 0.21 34.8 

2282005015 2-Stroke Personal Watercraft 0.21 77.3 

2282010005 4-Stroke Inboards; 0-600 hp 0.21 47.6 

2282010005 4-Stroke Inboards; >600 hp 0.21 30 

2282020005 Diesel Inboards 0.35 200 

2282020010 Diesel Outboards 0.35 150 

2282020025 Diesel Sailboat Aux. Outboard (unused) 0.35 68 

2285002015 Diesel Railway Maintenance 0.21 943 

2285003015 2-Stroke Gasoline Railway Maintenance 0.62 184 

2285004015 4-Stroke Gasoline Railway Maintenance 0.62 184 

2285006015 LPG Railway Maintenance 0.62 184 

2285008015 CNG Railway Maintenance 0.62 184 

* Activities for off-road motorcycles and all terrain vehicles are in units of miles per year. 

A9 

Appendix B 

Documentation of the Median Life Values in the California OFFROAD Model 

B1 
DOCUMENTATION OF DIESEL ENGINE LIFE 

VALUES USED IN THE ARB 

OFF-HIGHWAY MODEL 

Prepared for: 

OFFICE OF MOBILE SOURCES 

ENVIRONMENTAL PROTECTION AGENCY 

Ann Arbor, MI 

EPA Purchase Order: 1A-0462-NASX 

Prepared by: 

ENERGY AND ENVIRONMENTAL ANALYSIS, INC. 

1655 North Fort Myer Drive 

Suite 600 

Arlington, VA 22209 

September 2001 

B2 
TABLE OF CONTENTS 

Page 

1. BACKGROUND .......................................................................................................... 1 

2. PSR DATA DESCRIPTION ........................................................................................ 2 

3. EEA ANALYSIS OF THE PSR DATA....................................................................... 3 

4. USEFUL LIFE VALUES IN THE MODEL................................................................ 8 

5. SUMMARY.................................................................................................................. 13
 

APPENDIX A: LIST OF CONTACTS....................................................................... 14 

LIST OF TABLES 

Page 

Table 1 PSR Data on Engine Life at Rated Load........................................................... 6 

Table 2 1991 Engine Models by Horsepower Category ................................................ 9 

LIST OF FIGURES 

Page 

Figure 1 51-750 HP Diesel Engine Life Spans ............................................................... 7 

B3 
1. BACKGROUND 

In the 1992-1993 time frame, EEA developed a model for the California Air Resources Board 

(ARB). The model estimates emission inventory from off-highway mobile sources of all types. 

The model’s emissions calculations require tracking of the population of each equipment 

type/engine combination by vintage. The vintage distribution of any particular type of offhighway equipment and engine type is determined from a scrappage model that requires engine 

useful life as an input. The same engine type can be utilized across a number of equipment types 

that place different loads on the engine. The scrappage model is constructed in a manner that 

allows useful life for a given equipment type to vary based on the simple formulation that engine 

life in application “i” is given by: 

(Engine Life) full load (Engine Life)i = 

(Load Factor)i 

Hence, engine life in a particular application is inversely proportional to the average load factor, 

and engine life at full load is specified within the model. 

Engines were categorized by fuel type, horsepower range and engine cycle (two- versus fourstroke). At this subcategory level, the population of engines was assumed to be homogeneous, 

based on the fact that engines competing in the marketplace for the same market segment offer 

competitive durability. The development of specific engine life estimates for each engine 

subcategory is described in this memorandum. 

It should be noted that the ARB Off-Highway Model is the first of its kind, and was developed in 

a period when virtually all information had to be obtained from original sources and very few 

were available publicly. Given the wide range of engines and equipment available in the offhighway market, a number of simplifying assumptions had to be made. Some of the data and 

inputs in the model are potentially outdated, based on new research and testing conducted in the 

last decade years following its development. 

Second, it should be noted that the single most important source of data for equipment type, 

population and useful life was Power Systems Research (PSR), that has a proprietary database 

on off-highway equipment sales, population and scrappage. While the Power Systems Research 

data was the single largest and most unified source of data, EEA conducted a detailed assessment 

of PSR populations and sales data provided by comparing these data with data from other 

sources. In many instances, we found PSR data could not be justified, and EEA changed the 

data based on inputs from industry associations and engine manufacturers. In particular, the PSR 

engine life data appeared to be most incorrect for smaller engines. 

B4 
This memo first describes the PSR data and specifically identifies areas where our comparison 

indicated that PSR was likely in potential error. Second, EEA describes the methodology by 

which we derived other data that were judged more appropriate for the model. 

2. PSR DATA DESCRIPTION 

Data purchased from PSR included detailed breakouts of California off-highway populations by 

engine type, fuel type and horsepower range. PSR also provide a separate data file on the mean 

engine life by engine model in hours at rated load. 

The PSR methodology for estimating population is based on sales and scrappage. PSR obtains 

sales data from a number of proprietary sources including manufacturers and dealers. 

Nationwide sales are allocated to regions based on survey data and dealer based information. 

Scrappage is estimated as a function of vintage and engine mean life. Central to the estimates is 

a non-dimensional survival curve that provides survival rates in percent on the Y-axis against 

fraction of engine life used. The curve is S-shape, and starts at one at zero engine life used. At 

engine life equal to one, the survival rate is fifty percent, and at engine life equal to two, survival 

rate is zero. Hence, the engine life value is the point where half of all engine are scrapped. 

Engine life in a particular application is engine life at rated load divided by the load factor on a 

typical duty cycle for the application. PSR has developed load factors for each application 

although we have no explicit understanding of how the load factors were developed. Engine life 

at rated load is determined by a proprietary formula that related life to bore/stroke, design type 

and specific output. The formula itself is proprietary and undocumented. Nevertheless, we 

obtained a detailed database on life by engine model to allow us to assess the formula. 

Population is derived from sales with the formula: 

Population = ∑ iSalesi × Survival Ratei 

summed over i = 0 to twice the engine life in the application. Engine life in years for an 

application is given by: 

Engine Life at Rated HP (hours)
 

Load Factor ×Use (hours / year)
 

For equipment types that have no time trend in sales, we can estimate population using: 

Population ≅ Average Sales × Engine Life ( years) 

B5 
We utilized the above formula in several instances to estimate populations from available sales 

data. In many cases, sales of off –highway equipment have shown no growth trend over a long 

period, so that the above formula can provide a reasonable estimate of population. 

3. EEA ANALYSIS OF THE PSR DATA 

A very detailed comparison of PSR population estimates by equipment category was undertaken. 

 Briefing charts presented to the ARB documenting all the comparisons have been provided to 

EPA, and only the key data and major conclusions are presented here. 

In lawn and garden equipment, PSR population data from most non-commercial equipment such 

as chain saws and lawn mowers were a factor of ten higher than estimates from the industry or 

estimates based on (sales x useful life). For commercial equipment, PSR’s estimates were more 

reasonable and comparable to other estimates. However, most lawn and garden equipment are 

powered by gasoline engines. For recreational equipment such as motorcycles, snowmobiles and 

ATVs, PSR estimates were very low relative to other estimates. This category also has no diesel 

powered equipment. 

For industrial equipment, PSR totals across all fuel types and horsepower categories were 

comparable to estimates from industry associations. However, the gasoline (and LPG)-to-diesel 

split was very different. Diesel engine equipment populations were significantly over-estimated 

by PSR (by a factor of three to four), while gasoline engine equipment populations were 

underestimated significantly. Similar trends were also found for transport refrigeration units, 

and diesel airport ground support equipment. These equipment typically are powered by diesel 

engines in the 25 to 100 HP range. 

No validation of PSR data could be done for light commercial equipment such as generator sets, 

pumps and compressors. One study by Booz-Allen Hamilton suggested PSR estimates for 

diesels were incorrect by more than an order of magnitude, although the Booz-Allen numbers for 

diesels are not well documented. Equipment in this category utilize diesel engines under 50 HP. 

PSR population data for agricultural tractors (typically in the 50 to 150 HP range) were also 

significantly higher than estimates from the Agricultural Census and sales based estimates. The 

differences were in the range of 50 to 150 percent. 

Finally PSR estimates of populations for construction equipment were much closer to those 

derived from sales or industry data on populations. These equipment typically use diesel engines 

over 200 HP. PSR estimates were higher than those from industry, but the margin of difference 

was not large, ranging from 10 to 30 percent. 

B6 
As a result of this comparison, we concluded that PSR’s diesel engine life estimates appeared to 

be optimistic, and the level of optimism increased with decreasing HP. It appeared that for small 

diesel engines (less than 50 HP), the PSR life estimates were potentially in serious error. As a 

result of the population analysis, we requested and obtained the detailed PSR life data by engine 

model. Due to its proprietary nature, only aggregate statistics are provided in this report. 

Table 1 provides the PSR useful life data after filtering the data for zeroes and blanks. (There 

were only a very small number of such cases, including one obvious typographical error). As 

shown in Table 1, the average engine life by HP range declines with increasing horsepower, 

although the decline is not large relative the distribution of values within engine HP range. For 

example, all engines in the 25 to 750 HP range have an average life of 10,700 1300 hours. 

Based on our knowledge of engines and their applications, the declining trend as well as the 

absolute values appeared incorrect, especially for the smaller engines. 

Since the variation of useful life with HP ranges were larger than the changes to the averages 

across HP ranges, we use investigated the data more thoroughly. The detailed data showed that 

engine life appeared to be a stronger function of its aspiration (turbocharged or naturally 

aspirated) than its displacement or power output. Within naturally aspirated engines, there was a 

trend to increasing average useful life with size and horsepower, ranging from 12,000 hours for 

small engines to 18,000 hours for the largest engines. (A few engines had even higher useful life 

numbers, but it was not clear why). However, a given engine model’s useful life was found to be 

inversely proportional to its horsepower output. For example, most of the larger engines are 

offered in naturally aspirated, turbocharged and aftercooled models at a variety of HP ratings. 

The PSR model simply scales the life in exact inverse proportion to the HP rating. 

Figure 1 shows the distribution of useful life ratings from engines in the 50 to 750 HP range. 

Most naturally aspirated engine are in the upper end of the life range, turbocharged engines in 

the middle of the range and turbocharged/aftercooled engines in the lower end of the useful life 

range, in concert with their increasing specific output. Two stroke engine, with specific output 

almost twice the specific output of four-stroke engines, had the lowest useful life values. The 

decline in average useful life with increasing HP in Table 1 is due to the fact that a larger 

proportion of high HP engines are turbocharged, or turbocharged and aftercooled, but is not 

related to the larger engine size. 

B7 
TABLE 1 

PSR DATA ON ENGINE LIFE AT RATED LOAD 

(hours) 

HP Range Sample Size Average* Maximum Minimum Standard 

Deviation 

2.1 – 15 104 13,704 29,713 5,579 1,705 

15.1 – 25 88 12,364 16,062 4,178 2,404 

25.1 – 50 118 11,315 23,625 5,406 3,463 

50.1 – 120 241 10,331 22,627 4,469 3,463 

120.1 – 175 106 11,994 31,171 3,910 4,135 

175.1 – 250 17 11,038 20,847 3,029 3,907 

250.1 – 500 189 10,076 19,452 4,464 2,695 

500.1 – 750 36 9,490 18,968 3,927 2,986 

750+ 27 8,264 18,654 5,070 2,818 

* Average across all engine models without sales weighting. 

B8 
B9 
EEA’s knowledge of engines suggested that the PSR approach was incorrect. For example, 

Detroit Diesel’s two-stroke engines do not have the reputation for wearing out twice as fast as 

other competitive four-stroke engines in truck applications. In addition, we are generally 

unaware of any major decrease in life for turbocharged and aftercooled engines in the onhighway segment relative to turbocharged or naturally aspirated engines. Hence, EEA decided 

to specify the useful life data independently of PSR data. 

4. USEFUL LIFE VALUES IN THE MODEL 

EEA took a three-step approach to determining the correct useful life, as follows. First, we 

identified popular (high sales) engines within each horsepower category. Second, we contacted 

a subset of the engine manufacturers of these popular engines to obtain their views on engine 

life. Third, we developed engine life based on a combination of manufacturer comments and 

available data from on-highway engines. 

The identification of popular engine models by horsepower range was based on data developed 

under earlier studies for ARB by EEA. Table 2 shows the data for diesel engines above 50 HP. 

(The horsepower ranges in the table do not exactly correspond to those in the model, since ARB 

requested some changes in the ranges towards the end of the project). 

In general, the four major on-highway diesel engine manufacturers (Cummins, Caterpillar, 

Detroit Diesel and IH, now Navistar) offer versions of their on-highway products for the offhighway market. In addition, John Deere is the only the other major domestic engine 

manufacturer that sells engines directed almost completely to the off-highway market. Kubota, 

Deutz and Perkins are the major import engine brands in the market for engines over 50 HP. 

In the 50–120 HP market, sales are dominated by four-cylinder versions of six-cylinder onhighway medium heavy-duty engines such as the Cummins B and C series, the Caterpillar 

1.1L/cylinder series and the 3200 series, and Detroit Diesel’s 53 Series engines. In the next 

higher range of 120 to 175 HP, on-highway medium-heavy duty engines and some naturally 

aspirated versions of heavy-heavy duty engines dominate sales. Above 175 HP, a majority of 

engines are derivatives of heavy-heavy duty on-highway engines, except at the highest 

horsepower end, over 500 HP. At these high HP levels, some specialized engines such as 

Caterpillar’s 3500 series, DDC’s 149 series and Cummins KT series are available and are not 

generally sold in the on-highway market. Sales of engines in the very high HP categories are 

quite small. 

In the lower horsepower ranges below 50 HP, two types of engines dominate sales. In industrial 

tractors and small airport ground support equipment, derated versions of passenger car diesel 

engines (from manufacturers like Perkins, VW, Isuzu and Toyota) are utilized. Such engines are 

typically rated from 30 to 50 HP. 

B10 
TABLE 2 

1991 ENGINE MODELS BY HORSEPOWER CATEGORY 

Manufacturer 50 to120 HP 120 to 250 HP 250 to 500 HP Over 500 HP 

Caterpillar 3114T 

3204NA 

3304NA 

3116T 

3208NA 

3306NA 

3306T/TA 

3406T/TA 

3408T/TA 

3412T/TA 

3408TA 

All 3500 series 

Cummins 4A2.3 

6A3.4 

4B3.9 

6B5.9T/TA 

6C8.3T/TA 

L-10T/TA 

NTC-855T/TA 

KT-19 

VT-28 

KV-38 

Detroit Diesel 3-53N/T 

4-53N 

8.2L N 

3-53T 

4-53T 

6-71N 

6-71T/TA 

8-71T/TA 

6-92N/T/TA 

8-92T/TA 

12-92T/TA 

All 149 series 

Deere 3-179N/T 

4-239N/T 

4-276N/T 

6-359T/TA 

6-414T/TA 

6-466T/TA 

6-619T/TA 

8-955T/TA 

IH D-239N/T 

D-360N 

D-360T 

D-466N/T/TA 

Komatsu 4D-94N/T 

4D-95N/T 

4D-105N 

4D-130N/T 

6D-95N/T 

6D-105N/T 

6D-125T/TA 

6D-140N/T 

6D-155N/T 

6D-170T/TA 

8V-170T/TA 

12V170T/TA 

Deutz FL912N/T 

FL913N/T 

FL913T/TA 

FL413N/T 

FL413T/TA 

FL513T/TA 

Perkins 3-153N/T 

4-236N/T 

6-354N/T 

8-540N/T 

6-734T/TA 

8-1062T/TA 

N is for naturally aspirated, T for turbocharged and A for aftercooled. 

B11 
 

Small two- or three-cylinder engines from manufacturers such as Kubota, Yanmar, Onan, and 

Teledyne-Wisconsin are utilized in the 15–40 HP range and are a mix of air cooled and watercooled engines. Engines under 15 HP are also offered by these same manufacturers and are 

mostly single-cylinder air-cooled diesels. Most of these engines find application is light 

commercial equipment. 

Useful life estimates for engines over 50 HP were based on information from heavy-duty diesel 

engine manufacturers. EEA spoke with representatives from Caterpillar, Cummins, Navistar and 

Detroit-Diesel.3 All were questions about the: 

_ correctness of the PSR algorithm of scaling life by load factor, and by specific output; 

_ typical useful life in on-highway applications; 

_ comparability to useful life in off-highway applications. 

Information obtained was subjective and experienced based, but no hard data was provided by 

manufacturers. 

On PSR’s useful life algorithms, manufacturers agreed that load factor was inversely related to 

engine life but cautioned that this relationship could not hold over the entire range of load factors 

from zero to one. They believed it would overestimate life at very light load factors and 

underestimate life as load factor approached one. They did not agree, however, with PSR’s 

method of derating life at full load inversely with specific output across all aspiration types. 

While suggesting that there is variation in life with increasing output, manufacturers also stated 

that many components are upgraded in turbocharged engines relative to their naturally aspirated 

counterparts, and that warranty protection is the same for all engine types. They also pointed to 

the evidence that inspite of increasing specific output in the late-1980s and early 1990s, they had 

not observed any significant change in useful life. 

For heavy-heavy duty on-road engines, most manufacturers agreed that engine life (defined as 

the point when the engine is removed from the truck for a rebuild) for an over-the-road 

application, i.e., mostly highway miles, was in the 700,000 to 750,000 miles range. Note that 

this referred to engines from the last decade, as we understand that current engines last up to a 

million miles. Manufacturers suggested that miles could be converted to hours by assuming that 

most mileage was accumulated at highway speeds of, say, 60 mph as an average. Manufacturers 

also generally agreed that EPA’s original durability finding that medium-heavy duty engines 

have two-thirds the life of heavy-heavy duty engines was a reasonable estimate. 

3

* contact names are listed in Appendix A. 

B12 
 

 

In order to develop useful life at rated HP, a load factor corresponding to 60 MPH operation is 

required. Simulation models such as “TCAPE” show that an 80,000 lb. GVW truck cruising on 

a level road at 60 mph requires 210 to 220 HP. A typical engine rated HP for the application is 

350 HP to 375 HP, suggesting a load factor of 0.6. It is also known that trucks are geared to 

operate at close to the best bsfc point at cruising speed. The best bsfc point usually occurs at 70 

percent of peak torque and close to the peak torque RPM which is about 70 percent of rated 

RPM. Peak torque is usually about 20 percent higher than trque at rated RPM. Since: 

Rated HP = (Torque)R x (RPM)R 

where subscript R is for rated values, we can calculate 

Peak Torque 

RPM @ Peak Torque 

Cruise Point 

= 

0 

1.2 x (Torque)R 

0.7 x (RPM)R 

0.7 x Peak Torque x RPM @ Peak Torque 

= 0.7 x 1.2 x (Torque)R x 0.7 x (RPM)R 

0.6 x (Torque)R x (RPM)R 

Hence, the cruise point calculation also implies a load factor of about 0.6. 

From this, we can derive a life at rated power in hours: 

700,000miles Life = × Load Factor

60 mph 

= 7000 hours 

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Manufacturers had only subjective opinions for the life in off-road use, and suggested some 

adjustment factor for “rough-duty” conditions. These suggestions were to reduce the onhighway life by 10 to 20 percent, and we selected 15 percent as an approximate average. 

Adjusting the on-highway life of 7000 hours by 15 percent provided a useful life rating for offhighway engines of 6000 hours. Using the fact that medium duty engines offered two-thirds the 

life of heavy-heavy duty engines, we estimated their life at 4000 hours. 

Useful life for smaller engines (under 50 HP) was based on less information. EEA contacted 

representatives from Kubota, Yanmar, Perkins and VW to obtain information on diesel engine 

useful life but they had no specific information on hours. One manufacturer suggested using 

information on forklift truck scrappage, but we found that the Industrial Truck Association only 

has an average life for all fork-lifts (gasoline and diesel), and the data was not directly useful. 

Several members commented that the engines were physically similar in design to light-duty 

automotive diesels, which was the basis for our estimate of life. Because of the very low load 

factor (around 0.1) in typical automotive use, a mileage based estimate leads to very long useful 

life (>10,000 hours). Rather, we utilized the fact that small light duty (passenger car) diesel have 

durability comparable to gasoline engines of similar displacement. Data from automanufacturers show that a typical wide open throttle durability requirement for gasoline fourcylinder engines is about 2500 hours. This value was used for diesel engines in the 15 to 50 HP 

range. No adjustments were made for off-highway use, since these engines are typically not 

used in rough duty applications. 

Diesels in the under 15 HP category are typically small single cylinder air-cooled engines. 

Again, no specific life figures were obtained from manufacturers. However, they believed that 

durability was lower than the value of the larger water cooled multi-cylinder units in the 15-50 

HP category. EEA selected 1250 hours as a plausible value, but recognize that this is not 

supported by any data. It also reflects the fact that it is about ten percent of PSR’s estimate. 

Given that PSR estimates of small diesel populations are over ten times the estimates of other 

organizations, the value appears to be a reasonable estimate. 

5. SUMMARY 

Based on detailed comparison of populations, it appeared that PSR overestimates diesel 

equipment populations, with the level of overestimate increasing from the 20 percent range for 

the largest diesels to over 1000 percent for the smallest diesels. 

A detailed examination of their data on engine useful life at rated load showed counterintuitive 

estimates, with the smallest diesel engine having substantially higher useful life relative to the 

largest diesels. These estimate were traced to assumptions about the relationship of engine life 

to specific output (HP/liter) that EEA believes are incorrect. 

EEA developed its own estimates by comparison with on-road engines useful life, where engine 

types in each HP range were matched with on-road counterparts. Data for engines under 50 HP, 

however, was unavailable and based largely on subjective comments from the manufacturers. 

The ratio of EEA useful life estimates to PSR estimates for each HP category is quite similar to 

the ratio of equipment population estimates from other sources to PSR’s equipment population 

estimates, suggesting that EEA useful life estimates are reasonable. 

B14 
APPENDIX A 

LIST OF CONTACTS 

Caterpillar Don Dowdall 

Cummins Mike Brand 

Navistar (IH) Ed Sienecke 

Detroit Diesel John Fisher 

Kubota Kevin Kokrda 

Yanmar Norman Weir and Kozuhiro Nomura 

Perkins P.A. Harrison (England) 

VW Wolfgang Groth 

B15