Office of Transportation EPA420-S-06-002 

and Air Quality March 2006 

Diesel Retrofit Technology 

An Analysis of the

Cost-Effectiveness of Reducing

Particulate Matter Emissions 

from Heavy-Duty Diesel

Engines Through Retrofits 
EPA420-S-06-002 

March 2006 

Diesel Retrofit Technology 

An Analysis of the Cost-Effectiveness of Reducing

Particulate Matter Emissions from Heavy-Duty

Diesel Engines Through Retrofits

Assessment & Standards Division and

Compliance & Innovative Strategies 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 an exchange of

technical information and to inform the public of technical developments.
Executive Summary 

The Environmental Protection Agency’s (EPA) National Clean Diesel Campaign 

(NCDC) is a comprehensive initiative to reduce pollution from diesel engines 

throughout the country, including vehicles on highways, city streets, construction 

sites, and ports. The NCDC comprises both regulatory programs to address new 

engines and voluntary programs to address the millions of diesel engines already 

in use. On the regulatory side, EPA is successfully implementing emissions 

standards for engines in the 2007 Heavy-Duty Highway Engine Rule and the Tier 

4 Nonroad Rule and developing new emission requirements for locomotives and 

marine diesel engines, including large commercial marine engines. On the 

voluntary side, EPA is addressing engines that are already in use by promoting a 

variety of innovative emission reduction strategies such as retrofitting, repairing, 

replacing and repowering engines; reducing idling; and switching to cleaner fuels. 

The voluntary programs are accomplished in partnership with state and local 

governments, environmental groups and industry. 

The emissions standards for new engines will reduce both highway and nonroad 

engine emissions by roughly 90%. However, these emission reductions occur 

over a long period of time as new engines are phased into the fleet. Retrofitting 

diesel engines currently in use will allow significant and immediate emission 

reductions from diesel engines that would not otherwise be addressed. 

The purpose of this technical analysis is to evaluate the cost effectiveness of 

retrofitting existing heavy-duty diesel engines to reduce particulate matter (PM). 

(The cost effectiveness of the regulatory measures EPA has implemented is 

addressed the rulemakings.) Analysts in EPA’s Office of Transportation and Air 

Quality (OTAQ) evaluated the costs and emissions benefits of retrofitting school 

buses, freight trucks, and bulldozers with diesel oxidation catalysts (DOCs) and 

catalyzed diesel particulate filters (CDPFs), two of the most common PM 

emissions reduction technologies for diesel engines. 

For highway vehicles (e.g. school buses and trucks), EPA considered two 

overarching methods to estimate the cost effectiveness of diesel retrofit 

technology. The first involved using only the current mobile source emission 

factors and inventories in EPA’s approved MOBILE6.2 model. The second 

involved using more recent data that OTAQ has collected to use in the future 

development of EPA’s next highway emissions model, MOVES (Motor Vehicle 

Emissions Simulator). EPA chose the second option for this technical paper in 

order to better reflect more recent information on highway vehicles. 

i
EPA obtained the more recent highway vehicle data from states, fleet owners, 

and technology and engine manufacturers covering factors such as annual 

vehicle miles traveled, vehicle useful life, engine emission rates, retrofit 

technology effectiveness, and technology costs. For example, this paper 

assumes heavy-duty diesel PM emissions are approximately 2.3 times higher 

than predicted in MOBILE6.2 based on results from recent chassis dynamometer 

testing from the California Air Resources Board, the Coordinated Research 

Council, EPA’s efforts to update the MOBILE model, and other sources. EPA will 

eventually use the more recent highway vehicle data to modify the MOBILE6 

model as part of a comprehensive effort to create the next generation mobile 

model, MOVES. It is important to note, however, that states and local 

governments are still using MOBILE6.2 to estimate highway vehicle emissions for 

State Implementation Plans (SIPs) and transportation conformity purposes. 

For nonroad engines (e.g. 250 hp bulldozers), EPA relied primarily on data from 

the NONROAD2004 model to determine the cost-effectiveness of DOCs. EPA 

also consulted additional data sources where appropriate. 

EPA calculated that the cost effectiveness for both school bus diesel oxidation 

catalyst (DOC) and catalyzed diesel particulate filter (CDPF) retrofits ranged from 

$12,000 to $50,500 per ton of PM reduced. The same type of retrofits for Class 

6&7 heavy-duty highway trucks (commonly found on highways and city streets) 

ranged from $27,600 to $69,900 per ton of PM reduced. The same type of 

retrofits of larger Class 8b trucks (commonly used to transport freight long 

distances) ranged from $11,100 to $44,100 per ton of PM reduced. Finally, DOC 

retrofits for 250 hp bulldozers ranged from $18,100 to $49,700 per ton of PM 

reduced. 

The results can be compared to similar estimates for other EPA programs 

targeted at reducing diesel particulate matter. For example, EPA estimates that 

the cost-effectiveness of the Urban Bus Retrofit and Rebuild program is 

$31,500/ton of PM reduced, the 2007 Heavy-Duty diesel emission standards is 

$14,200/ton, and the Nonroad Tier 4 emission standards is $11,200/ton. 

The findings from this study indicate that retrofits can be a cost effective way to 

reduce air pollution. 

ii
Table of Contents 

I. INTRODUCTION ................................................... 1

I.A. NATIONAL CLEAN DIESEL CAMPAIGN .......................... 1

I.B. STUDY OBJECTIVE & METHODS .............................. 1

II. RETROFIT EFFECTIVENESS FACTORS ................................ 2

II.A VEHICLE ACTIVITY .......................................... 3

II.A.1 School Bus Activity Analysis ............................. 3

II.A.2. Truck Activity Analysis ................................. 4

II.A.3 Nonroad Activity Analysis ............................... 4

II.B. VEHICLE SURVIVAL RATE ................................... 4

II.B.1. Highway Scrappage Analysis ............................ 4

II.C. EMISSION RATES .......................................... 5

II.C.1. Highway Emission Rate Analysis ......................... 5

II.C.2 Nonroad Emission Rate Analysis ......................... 6

II.D. COMPARISON TO EXISTING HIGHWAY EMISSIONS INVENTORY

MODEL .................................................. 7

II.E. EFFECTIVENESS OF RETROFIT TECHNOLOGIES ................ 7

II.E.1. Background on Retrofit Technology Verification ............. 7

II.E.2 Analysis ............................................ 8

 II.F COSTS .................................................... 9

II.F.1. Background ......................................... 9

II.F.2. Highway Cost Analysis ................................. 9

II.F.3. Nonroad Cost Analysis ................................ 11

II.F.4. Highway and Nonroad Operating Costs ................... 11

II.G. ESTIMATING LIFETIME EMISSION REDUCTIONS ............... 11

II.G.1. Background ........................................ 11

II.G.2. Highway Emission Reduction Analysis ................... 12

II.G.3. Nonroad Emission Reduction Analysis .................... 13

III. RESULTS ....................................................... 13

IV. CONCLUSIONS .................................................. 14

REFERENCES ...................................................... 32

iii
I. INTRODUCTION 

I.A. NATIONAL CLEAN DIESEL CAMPAIGN 

The Environmental Protection Agency’s (EPA’s) 

National Clean Diesel Campaign (NCDC) is a 

comprehensive initiative to reduce pollution from 

diesel engines. EPA’s Office of Transportation 

and Air Quality (OTAQ) manages the NCDC, 

which comprises both regulatory programs to 

address new engines and voluntary programs to 

address the millions of diesel engines already in 

use. 

Particulate matter (PM), one of the primary 

pollutants from diesel exhaust, is associated with 

many different types of respiratory and 

cardiovascular effects, and premature mortality. 

EPA has determined that it is a likely human 

carcinogen. Fine particles (smaller than 2.5 

micrometers), in particular, are a significant 

health risk as they can pass through the nose 

and throat and cause lung damage. People with 

existing heart or lung disease, asthma, or other 

respiratory problems are most sensitive to the 

health effects of fine particles as are children and 

the elderly. Children are more susceptible to air 

pollution than healthy adults because their 

respiratory systems are still developing and they 

have a faster breathing rate. EPA expects 

reductions in air pollution from diesel engines to 

lower the incidence of these health effects, as 

well as contribute to reductions in regional haze 

in our national parks and cities, lost work days 

and reduced worker productivity, and other 

environmental and ecological impacts. 

New regulations from EPA require stringent 

pollution controls on new highway and nonroad 

diesel engines, including engines operating in 

the freight, transit, construction, agriculture, and 

mining sectors. The new regulations will also 

slash sulfur content in diesel fuel by 97 percent. 

By combining tough exhaust standards with 

cleaner fuel requirements, these rules will cut 

emission levels from new engines by over 90 

percent. The new lower sulfur diesel fuel will 

result in reduced PM emissions as soon as the 

fuel is introduced into the market. New engines 

sold in the US after 2007 for highway use (and 

after 2010 for nonroad use) must meet the more 

stringent standards, but the effect of these 

cleaner engines will be achieved over time as 

the existing fleet is gradually replaced. The 

benefits of these new rules will not be fully 

realized until the 2030 time frame. As a result 

EPA is promoting a suite of voluntary programs 

to address the emissions from the existing fleet 

of diesel vehicles. 

The NCDC voluntary programs are designed to 

address existing diesel vehicles and equipment 

through emission reduction strategies that can 

provide immediate air quality and health benefits. 

The voluntary programs focus on vehicles and 

equipment in the school bus, construction, port, 

freight and agricultural sectors. The voluntary 

programs work with partners in state and local 

government, industry, and environmental 

organizations to promote a wide range of 

measures to reduce diesel emissions including 

retrofitting vehicles with new or improved 

emission control equipment, upgrading engines, 

replacing older engines with newer/cleaner 

engines, reduced idling, and using cleaner fuels. 

I.B. STUDY OBJECTIVE & METHODS 

Stakeholders - including states that are 

developing their plans to achieve the National 

Ambient Air Quality Standards for fine particles -

are searching for cost effective ways to reduce 

emissions from existing diesel engines in order 

to improve air quality and protect public health. 

The purpose of this study is to estimate the cost 

effectiveness of retrofit strategies. 

We chose to evaluate retrofit strategies for four 

types of vehicles: 

1) school buses 

2) combined class 6&7 trucks 

3) class 8b trucks, and 

4) 250 horsepower (hp) bulldozers 

Truck classes are based on the Gross Vehicle 

Weight Rating. Class 6 trucks are 19,501 -

26,000 lbs and Class 7 trucks are 26,001 -

33,000 lbs. Class 6&7 trucks are commonly 

found on highways and on city streets. Class 8b 

vehicles are greater than 60,000 lbs and are 

commonly used to transport freight long 

distances. 250 hp bulldozers are technically 

called Diesel Crawler Tractors or Crawler Dozers 

in our NONROAD emissions inventory model, 

and are prevalent on construction sites around 

the country. 

1
EPA chose these vehicle types for three 

reasons. First, we wanted to evaluate retrofits for 

both highway (e.g. school buses and trucks) and 

nonroad vehicles (e.g. bulldozers). Second, we 

had the best data for these types of vehicles 

due, in large part, to our experience with retrofit 

projects on-the-ground. Finally, these vehicles 

exist in large numbers across the country, so we 

believed that cost-effectiveness analysis for 

these vehicles would be relevant to a wide 

audience. 

We decided to evaluate the two most common 

diesel retrofit technologies, diesel oxidation 

catalysts (DOCs) and catalyzed diesel 

particulate filters (CDPFs), for all vehicle types, 

except for 250 hp bulldozers, for which we only 

analyzed DOC retrofits since CDPFs are not 

currently compatible with many bulldozers. 

For highway vehicles (e.g. school buses and 

Class 6-8b trucks), EPA considered two 

overarching methods to estimate the cost 

effectiveness of diesel retrofit technology. The 

first involved using only the current mobile 

source emission factors and inventories in EPA’s 

approved MOBILE 6 model (version 6.2), 

OTAQ’s emission factor model for predicting 

gram per mile emissions from cars, trucks, and 

motorcycles under various conditions. The 

second involved using more recent data that 

OTAQ has collected to use in the future 

development of EPA’s next highway emissions 

model, MOVES. EPA chose the second option 

for this technical paper in order to better reflect 

more recent information on highway vehicles. 

EPA obtained the more recent highway vehicle 

data from states, fleet owners, and technology 

and engine manufacturers which impacted 

factors such as annual vehicle miles traveled, 

vehicle useful life, engine emission rates, retrofit 

technology effectiveness, and technology costs. 

For example, this paper assumes heavy-duty 

diesel PM emissions are approximately 2.3 times 

higher than projected in MOBILE6.2 based on 

results from recent chassis dynamometer testing 

from the California Air Resources Board, the 

Coordinated Research Council, EPA’s efforts to 

update the MOBILE model, and others. EPA will 

eventually use the more recent highway vehicle 

data to modify the MOBILE6.2 model as part of a 

comprehensive effort to create the next 

generation mobile model MOVES (Motor Vehicle 

Emissions Simulator). It is important to note, 

however, that states and local governments are 

still using MOBILE 6.2 to estimate highway 

vehicle emissions for State Implementation 

Plans (SIPs) and transportation conformity 

purposes. 

For nonroad engines (e.g. 250 hp bulldozers), 

EPA relied primarily on data from the 

NONROAD2004 model to determine the costeffectiveness of DOCs. EPA also consulted 

additional data sources where appropriate. 

For both highway and nonroad vehicles, we 

analyzed annual vehicle miles traveled, vehicle 

useful life, engine emission rates, retrofit 

technology effectiveness, and technology costs 

to calculate the cost-effectiveness of retrofit 

strategies, in terms of $ per ton of PM reduced. It 

is important to note that, in many cases, heavyduty diesel retrofit strategies provide other 

emission benefits such as reductions in 

hydrocarbons and carbon monoxide. This study 

only evaluates the cost-effectiveness of reducing 

PM from diesel retrofits. 

The following section will detail our methods for 

calculating the cost-effectiveness of PM 

reductions from retrofits including factors such as 

vehicle activity, survival rates, emissions factors, 

costs of technologies, and emissions reductions 

from retrofit technologies. In Section 3 we will 

present our results and in Section 4 we will 

provide summary remarks about the relative 

cost-effectiveness of diesel retrofits. As 

mentioned previously EPA calculates these cost 

effectiveness figures based on more recent 

information for highway vehicles obtained from 

various sources. If EPA chose not to use this 

more recent information and instead relied 

exclusively on the MOBILE model for these 

calculations, the cost effectiveness could range 

from approximately $14K to $160K per ton. 

II. RETROFIT EFFECTIVENESS FACTORS 

In order to estimate the relative cost 

effectiveness of various PM retrofit strategies, it 

is necessary to estimate a number of factors, 

including: 

-vehicle activity

-vehicle survival rates

2
-emissions rates of vehicles 

-effectiveness of DOCs and CDPFs 

-costs of retrofits 

The following sections 2.A - 2.G outline our 

methodologies for estimating each of these 

factors. 

II.A VEHICLE ACTIVITY 

One of the first steps in estimating emission 

reductions from retrofit strategies is to develop 

an estimate of annual vehicle activity. This 

requires identifying nominal values for vehicle 

miles traveled for representative vehicle 

samples, in the case of highway vehicles (e.g. 

trucks and school buses), and operating hours 

and load for nonroad vehicles (e.g. bulldozers). 

This information can then be used to estimate 

annual vehicle emissions and emission 

reductions from retrofits. 

II.A.1 School Bus Activity Analysis 

The default MOBILE 6.2 Vehicle Miles Traveled 

(VMT) for school buses is 9,939 miles per year

1

. Anecdotal reports suggest that average school 

bus VMT has increased over time. This increase 

is attributed to suburban growth around many 

communities at a time when budget-strapped 

school districts cannot afford to expand their 

school bus fleets. 

As a test of this anecdotal information, we 

reviewed detailed school bus fleet data that 

school districts submitted to EPA in response to 

a request for applications for Clean School Bus 

USA grant funding over the summer of 2003. 

The Clean School Bus USA demonstration 

grants program attracted 120 applications from 

diverse programs around the country seeking to 

retrofit or replace aging school bus fleets. Of 

these, 72 applications contained data that were 

relevant to this exercise and that were in a 

format that could be analyzed. Most of the 

applications provided actual fleet VMT data from 

the 2002-2003 school year, with the others 

submitting data from 2001-2002. The data 

represent several hundred school districts, and 

more than 34,000 school buses from 31 states 

plus Puerto Rico. 

We analyzed the average school bus activity 

only for diesel school buses. 

We took the average per-bus VMT for each fleet 

directly from the application, or, if not provided, 

calculated it by dividing the annual fleet mileage 

by the number of buses in the fleet. If a fleet’s 

total mileage included diesel and non-diesel 

school buses, we weighted the annual mileage 

by the technology ratio to reflect only the diesel 

portion of the fleet. If applicants provided only 

total mileage and age for each bus in the fleet, 

we calculated an average VMT for each bus by 

dividing mileage by age, and then created a fleet 

average by averaging the VMTs from individual 

buses. 

To determine a representative VMT mix across 

the population of buses considered for this 

analysis, we calculated a fleet fraction for each 

school bus fleet by dividing the number of buses 

in that fleet by the total population. We then 

multiplied that fraction of the population by the 

fleet’s average VMT to create a weighted fleet 

fraction of the fleet’s VMT. We determined the 

average VMT for the total population by adding 

the weighted fleet fractions. 

The method described above yielded an average 

annual VMT of 13,248 miles per bus. This is an 

increase of approximately 3,309 miles per year 

from the default value currently in the 

MOBILE6.2 model and is used to represent 

average VMT for school buses independent of 

vehicle age. That is, school bus VMT is 

estimated to be the same in the first year and all 

subsequent years of the vehicles life. Although 

this represents a simplification of real-world 

practices, we believe that, given the fixed routes 

defined for many school buses, this is a 

reasonable assumption. However, there are no 

3
independent data available to test the 

assumption from this analysis. 

It is important to note that the annual school bus 

VMT used in our analysis represents a relatively 

large increase over the school bus VMT estimate 

from the Vehicle Inventory and Use Survey 

(VIUS) study (the basis for the values used in the 

development of MOBILE6.2). 

II.A.2. Truck Activity Analysis 

We used an estimate of annual VMT from 

MOBILE 6.2 for Class 6-8b trucks which declines 

with vehicle age. This estimate can be found in 

EPA report, Fleet Characterization Data for 

MOBILE6: Development and Use of Age 

Distributions, Average Annual Mileage 

Accumulation Rates and Projected Vehicle 

Counts for Use in MOBILE 6.2 (see Table 1 

Annual Mileage Accumulation).2 

II.A.3 Nonroad Activity Analysis 

Our methodology for estimating emission 

reductions from nonroad equipment is similar to 

that for highway vehicles in that we first needed 

to estimate annual and lifetime activity (use 

patterns). We estimated this activity based on 

data from the technical documentation for the 

NONROAD inventory emissions mode (see 

www.epa.gov/otaq/nonrdmdl.htm for a 

description of the NONROAD model). Nonroad 

engine activity is expressed in terms of hours of 

operation (annual and lifetime) and load factor 

(average engine operating power as a 

percentage of rated engine power). The estimate 

for annual hours of operation for a 250 hp 

bulldozer is 936 hours per year. The estimate for 

the typical load factor for a 250 hp bulldozer is 

0.59 (average cycle power/rated power).3 

II.B. VEHICLE SURVIVAL RATE 

The scrappage rate describes the fraction of 

vehicles (relative to the total number originally 

sold) that are no longer in the fleet from one year 

to the next. This factor reflects vehicle loss 

through accidents, deterioration, and export. 

From a retrofit perspective, scrappage is a 

necessary component of cost effectiveness 

analysis because it dictates how long older 

vehicles will stay on the road, and hence the 

potential benefit which will accrue from a retrofit 

at a certain point in time. 

II.B.1. Highway Scrappage Analysis 

An analysis of scrappage rates for selected 

model years of Heavy-Duty vehicles is published 

by Oak Ridge National Laboratory in the 

Transportation Energy Data Book (TEDB), based 

on registration data and a scrappage model 

developed by Greenspan and Cohen4

. The latest 

model year for which TEDB published data on 

scrappage rates is 1990, but we did not use 

these data for our analysis because they 

seemed unrealistically high - for example, they 

projected a 45 percent survival rate for 30 

year-old trucks. While limited data exist to 

confirm this judgement, a snapshot of 5-year 

survival rates can be derived from the VIUS for 

1992 and 1997 for comparison. According to 

VIUS, the average survival rate for model years 

1988-1991 between the 1992 and 1997 surveys 

was 88 percent. The comparable survival rate for 

1990 model year Heavy-Duty vehicles from the 

TEDB was 96 percent, while the rate for 1980 

model year trucks was 91 percent. Based on this 

analysis, we determined that 1980 model year 

survival rates are more in line with available 

data, and these rates are used in the analysis 

instead of the 1990 rates. The resulting median 

life estimate (the age at which 50% of vehicles 

have been scrapped) is 18.5 years. This 

contrasts with a median life estimated in the 

MOBILE6.2 emission model of approximately 12 

years. The difference between the two data 

values indicates that there is some degree of 

uncertainty regarding survival rates. Survival 

Rates are shown in Table 2. 

4
II.B.2 Nonroad Scrappage Analysis 

Like the MOBILE model, the NONROAD model 

has intrinsic scrappage rates built into the model. 

These rates are used to project the distribution of 

nonroad equipment in a population by age. We 

chose to use a simplified nonroad scrappage 

rate estimate for this analysis. We use the 

resulting median life estimate for nonroad 

equipment in the NONROAD model. This 

number is the number of hours of rated engine 

operation that the median example of nonroad 

diesel engine is expected to operate. Dividing 

that number by the load factor (discussed 

previously) converts the median life from hours 

of operation at rated power to hours of operation 

at typical operating power levels (i.e., it converts 

it to actual hours of operation). The median life 

for a 250 hp diesel engine from the NONROAD 

model is 4,667 hours at rated power. Dividing 

this number by the typical load factor found 

previously (4,667 hours rated / 0.59) returns a 

median life at typical operating conditions of 

7,910 hours. Given annual operating hours of 

936 hours, the expected lifetime for the median 

250hp nonroad bulldozer can be found as 8.5 

years. While this represents the expected 

median operating life, it should be recognized 

that significant variation about this median can 

be expected in practice with many pieces of 

nonroad equipment being used for periods well 

in excess of 8.5 years. 

II.C. EMISSION RATES 

MOBILE6.2 is the current, approved highway 

emission factor model used by States and local 

governments for State Implementation Plans 

(SIPs) and planning purposes. When the 

analysis portion of MOBILE6.2 was completed in 

1998, there were little heavy-duty chassis 

dynamometer data available, therefore the 

emission rates in MOBILE6.2 are based on 

engine dynamometer test data from engine 

certification tests. With chassis dynamometer 

testing, the engine remains in its vehicle 

(chassis) and the vehicle's tires drive rollers that 

produce a load in the dynamometer. This 

produces a more realistic test of the engine in 

this application than an engine dynamometer 

test where the engine is removed from the 

vehicle and connected directly to a 

dynamometer. The analysis for highway vehicles 

in this report uses more recent data, which EPA 

is planning to incorporate into EPA’s next 

highway emissions model, MOVES, when it is 

developed. 

II.C.1. Highway Emission Rate Analysis 

OTAQ completed a large data collection effort in 

2002 and 2003 on Heavy-Duty Highway vehicle 

emissions rates. There have been several 

Heavy-Duty chassis dynamometer test programs 

completed in recent years which we obtained 

from EPA’s Mobile Source Observation 

Database (MSOD) for this study. 

While there is a significant number of HeavyDuty diesel Class 8 chassis dynamometer tests 

in the MSOD, there is a lack of school bus 

chassis dynamometer emissions tests and 

limited tests for Heavy-Duty diesel Class 6&7 

vehicles (which are similar in size to many 

school buses). For this analysis we developed a 

ratio metric correlation for Heavy-Duty diesel 

Class 8 emissions from chassis dynamometer 

tests to engine dynamometer test data 

represented in MOBILE6.2, and applied this ratio 

to Heavy-Duty diesel Class 6-8 MOBILE6.2 

emissions to estimate emission rates for those 

vehicle classes. We made this estimate by 

applying the correlation described below to the 

current emission factors for Class 6-8 vehicles 

from the MOBILE 6.2 model to create new 

emission factors that should more closely match 

actual emission rates in use. This approach 

inherently assumes the ratio relevant to Class 8 

vehicles applies to Class 6 and 7. While we 

believe this approach is reasonable, we do not 

have independent data to validate this 

assumption. 

5
The available chassis data set consisted of 39 

vehicles tested on 20 different cycles for a total 

of 315 tests. The bulk of the data used federal 

diesel grade 2 or California diesel fuels. We 

eliminated other fuel types from the analysis. 

See Table 3 for a description of the data set by 

cycles, model years, and fuel type. Table 4

shows a brief description of the cycles. More 

detailed plots of the test cycles are available 

upon request by contacting MOBILE@epa.gov. 

We performed an analysis to determine if there 

was a trend by model year for the chassis to 

engine test results comparison. We did not find 

any obvious trend, and a weighted regression 

did not prove to be statistically significant. We 

compiled average PM emission rates for each 

model year on each of the two fuels used from 

the chassis data set. We computed the ratio for 

each model year of the chassis data set to the 

MOBILE6.2 emission rate, for each fuel type. 

When we took an average - including both fuels -

weighted by sample size, over each model year, 

which resulted in a ratio of 2.3 for chassis 

dynamometer emissions to engine dynamometer 

emissions. This ratio reflects the effects of real 

world driving, in-use deterioration, and in-use 

fuels. See Table 5 for the emission rates and 

ratios by model year for the data set described 

above versus MOBILE6.2. In order to make a 

conclusion on impacts of these in-use factors on 

actual PM inventories from highway vehicles, we 

would have to conduct a detailed analysis 

isolating the effects of cycles, fuel, and 

deterioration to estimate the effects over the 

range of model years and vehicle classes 

available in MOBILE6.2. We felt, however, that 

the use of the ratio approach (described above) 

to determine emission rates is appropriate for 

this cost effectiveness analysis. EPA will 

consider this information as it develops its future 

emissions models that are to be used in the 

future for official SIP or conformity purposes. 

It is important to note that the ratio we use in this 

analysis also does not appear in the newly 

released Retrofit benefits calculation module of 

the National Mobile Inventory Model (NMIM) 

which is based on MOBILE 6.2 emission rates. 

The benefits in the NMIM model come from a 

percentage tagged to each different technology 

used for retrofit. EPA would need to analyze a 

substantial amount of additional data to update 

the emission rates used in MOBILE 6.2. 

For school buses we made one additional 

change. The PM emission factors in MOBILE6.2 

are based on inputs from an earlier mobile 

source model called PART5. The PART5 model 

did not specifically identify emission factors for 

school buses, but it does contain an estimate for 

“buses”, a category which would include urban 

transit buses, coach buses, and school buses. 

MOBILE6.2 does have an emission factor for 

school buses but that factor is simply a carryover 

from the bus emission factor in PART5. The bus 

emission factor in PART5, and hence, the school 

bus emission factor in MOBILE6.2 is based 

primarily on data and emission standards for 

urban buses. This causes two problems for 

school buses. First, older school buses have 

emission factors that are likely to overestimate 

PM emissions by approximately 50 percent due 

to the use of the higher emission conversion 

factor for urban buses. Second, emission factors 

attributed to new school buses are too low due to 

the use of the lower urban bus emission 

standard to project future emission rates even 

though school buses do not need to meet the 

lower standard (the current PM standard for 

school buses is twice that of urban buses, 0.1 

g/bhp-hr versus 0.05 g/bhp-hr). Therefore, in this 

analysis we have chosen to model the school 

bus emission factor the same as combined Class 

6&7 trucks. Class 6&7 trucks are most similar to 

diesel school buses using the same engines 

meeting the same emission standards. 

DOC on construction equipment 

II.C.2 Nonroad Emission Rate Analysis 

The NONROAD engine model uses emission 

rates for nonroad diesel engines based on the 

emission standards, historic engine certification 

data, and projections of in-use deterioration of 

emissions over the lifetime of the equipment. 

Additionally, the nonroad model includes a factor 

to correct for observed differences in emissions 

production between in-use operating cycles and 

6
the steady-state emissions test results. The 

projected in-use emissions rates are therefore 

the product of the expected new certification 

emissions level, the ratio of transient emission 

rates to steady-state emission rates, and 

projected deterioration rates over time (i.e., as 

the equipment ages EPA projects emissions will 

increase). The result of this methodology is that 

new (beginning of life) nonroad equipment is 

estimated to have a lower emission rate than the 

same equipment would after a period of 

operation. In order to simplify the analysis in this 

paper, we have combined the adjustment for 

transient emissions and deterioration into a 

single static number of 1.5 (i.e., a 50% increase 

in emissions over the certification levels) which 

roughly approximates the combined factors for a 

bulldozer in the nonroad model. This approach 

may undercount the emissions from a typical 

piece of nonroad equipment when compared to 

the NONROAD model where the transient 

adjustment factor ranges from 1.23 to 1.97 and 

the deterioration factor varies from 0 at 0 hours 

to 0.473 at full useful life.5

 Hence, the 

NONROAD model adjustment would range from 

1.2 to 2.9 (1.0 X 1.23 to 1.473 X 1.97) over the 

range of engines and through the equipment life. 

We believe the use of a simplified single value of 

1.5 is appropriate for this analysis since our goal 

is to estimate a nominal ratio of emission 

reductions and cost. EPA has developed a 

retrofit modeling function within NMIM that fully 

incorporates the features of the NONROAD 

model and will allow states and local authorities 

to more accurately estimate the potential for 

emission reductions through retrofits. 

II.D. COMPARISON TO EXISTING HIGHWAY 

EMISSIONS INVENTORY MODEL 

As mentioned above, MOBILE6.2 is EPA’s 

official emissions factor model for highway 

Heavy-Duty engines and vehicles. A complete 

description of MOBILE 6.2 can be found on 

EPA’s web site at 

www.epa.gov/otaq/mobile.htm. 

In the previous sections (II.A - II.C), we analyzed 

a number of factors to estimate emissions from 

highway Heavy-Duty engines (Class 6&7, Class 

8b, and school buses) and newly developed 

estimates based on the most recent data, where 

appropriate. These factors are annual VMT for 

school buses, scrappage rates for Heavy-Duty 

vehicles, and a new engine-to-chassis 

conversion factor. Table 6 is a comparison of the 

estimates we developed for this paper and the 

emissions inventory values in MOBILE6.2. 

Table 6. Comparison of MOBILE6.2 Values to 

Retrofit Cost Effectiveness Study Values 

Factor 

MOBILE6.2 

value 

Retrofit 

Analysis 

value 

School Bus 

VMT 9,939 13,248 

Scrappage 12 year median 

life 

18.5 year 

median life 

Engine 

Based PM 

Emission 

Factor

a 

1991MY 1.948 

2000MY 0.163 

1991MY 0.518 

2000MY 0.158 

Engine-toChassis 

Conversion 

1 

(no factor used) 2.3 

a

 The engine based PM emission factors change for each 

model year, two example years are shown here. 

When considered as a whole, the estimated 

values of lifetime emissions that we developed 

for this analysis (detailed in Sections II.A - II.C) 

are approximately 3 times greater for newer 

school buses and 2.3 times greater for Class 6-8 

vehicles than the values used in MOBILE6.2. 

This general characteristic does not hold for 

model year 1993 and older school buses due to 

the much higher emission factors in MOBILE6.2 

for these vehicles when compared to this 

analysis. The results for 1993 and older school 

buses are approximately 20 percent lower in this 

analysis when compared to estimates from 

MOBILE6.2. Section 3.Ci explains our rational 

for using alternative emission factors for school 

buses in this analysis. 

II.E. EFFECTIVENESS OF RETROFIT 

TECHNOLOGIES 

II.E.1. Background on Retrofit Technology 

Verification 

The NCDC voluntary programs encourage air 

quality agencies and owners of fleets of diesel 

powered vehicles and equipment to implement 

7
clean diesel strategies such as installing new or 

enhanced emission control technology and using 

cleaner fuels. To help these organizations make 

informed decisions regarding which retrofit 

technologies are appropriate for their fleets and 

what emission reductions can be expected, EPA 

created the Retrofit Technology Verification 

Process. This process evaluates the emission 

reduction performance of retrofit technologies, 

including their durability, and identifies engine 

operating criteria and conditions that must exist 

for these technologies to achieve those 

reductions. 

Under this program, companies can apply for 

EPA verification of the effectiveness of their 

emission control technology. The verification 

protocol requires the same tests as defined by 

the Code of Federal Regulations (CFR) for new 

engine family certification before sale in the U.S. 

The protocol tests the stand-alone engine, and 

then the engine with the emission control 

technology. Both new and aged devices must be 

tested. The emission reduction percentage that 

EPA verifies will reflect the performance of the 

new and used devices. Once a technology is 

verified, the company receives an official EPA 

verification letter, and the technology is listed on 

EPA’s web site as a verified technology. There is 

no restriction on who may apply for verification. 

To date, EPA has verified nearly 20 technologies 

from different emission control technology 

companies. 

The measures that EPA verifies can be very 

general - for example, an emission control 

technology company may receive verification for 

a diesel oxidation catalyst (DOC) technology that 

can reduce particulate matter from any 

uncontrolled or Tier 1 nonroad diesel engine by 

20 percent - or the verification can be specific to 

an engine model made over specific model 

years. 

While retrofit technologies are the most common 

clean diesel strategy verified by EPA, there is a 

wide range of measures that can reduce diesel 

emissions. For example, the replacement of 

older engines or vehicles may be more beneficial 

in many cases than using retrofit technologies. If 

a fleet manager is concerned that exhaust 

emissions from their vehicles may overwhelm 

current retrofit technologies, or they are 

interested in having more up-to-date safety 

equipment, the fleet manager may prefer to 

replace older vehicles with newer models rather 

than retrofit their existing vehicles. 

II.E.2 Analysis 

We took the retrofit technology applications and 

emissions reduction information in this cost 

effectiveness study directly from EPA’s List of 

Verified Technologies. We are focusing only on 

emission reduction figures for DOCs and CDPFs 

verified for Class 6&7 Heavy-Duty engines. 

The estimated reduction in PM: 

1) from adding a DOC to a highway engine is 

20% 

2) from adding a DOC to a nonroad engine and 

changing to highway fuel (# 500 ppm S) is 

20% 

3) from adding a CDPF to a highway engine and 

changing to ultra low sulfur diesel (ULSD) fuel 

from regular highway diesel fuel is 90% 

One requirement of the verification process is 

that applicants must test their systems after they 

have been installed for a period of time. The 

manufacturer must begin in-use testing after they 

have sold a certain number of units of the 

verified system. EPA must approve the 

manufacturer’s sampling plan to gather units to 

be tested. The manufacturer must test units 

aged in the field to a minimum fraction of the 

designated durability testing period in two 

different phases. Manufacturers are given wide 

latitude in the type of emissions testing 

equipment they use, although test cycles are 

well defined. The manufacturer must test at least 

four units in each phase. Individual failures lead 

to additional testing or possible removal from the 

Verified Technology List. This part of the 

verification process is still in its infancy and, as 

such, EPA has not yet received any in-use test 

results from retrofit technology manufacturers. 

Once EPA receives these additional in-use test 

results, EPA will examine them and use them to 

help quantify real world retrofit benefits. 

The reduction of other criteria air pollutants by 

aftertreatment devices should also be 

recognized. A DOC or CDPF may reduce 

hydrocarbon and carbon monoxide emissions on 

the order of 20 to 90 percent. 

8
II.F COSTS 

II.F.1. Background 

Several sources of information are available on 

the current price of retrofit technologies. These 

include a December 2000 survey by the 

Manufacturers of Emission Controls 

Associations (MECA) and current price 

information for grant recipients in EPA’s Clean 

School Bus Program.6

 Those sources give 

ranges for CDPF prices of $3,000 to $7,500 

depending on size, expected product sales 

volumes, and configuration (i.e., in-line or muffler 

replacement). Similarly, these sources suggest 

DOCs will range in price from $425 to $1,750 

depending on size, sales volume and 

configuration. While we believe these ranges are 

reflective of current prices for PM retrofit 

technologies applied to Class 6&7 trucks and 

school buses, we also believe that future retrofit 

costs are likely to drop substantially as a result of 

the Heavy-Duty 2007 emission standards and 

the Nonroad Tier 4 emission standards. 

II.F.2. Highway Cost Analysis 

For this report, EPA has conducted a review of 

available information on the cost of PM retrofit 

technologies and has made a new projection for 

the future cost of PM retrofit technologies in 

2007. Beginning in 2007, all new Heavy-Duty 

diesel engines are required to meet a PM 

emissions standard of 0.01 g/bhp-hr. EPA 

projected in the 2007 rule-making that this 

emission standard would be met through the use 

of CDPFs. Our recent Highway Diesel Progress 

Review Report #2 confirms that all Heavy-Duty 

diesel engine manufacturers are planning to 

comply with these regulations through the use of 

CDPF technologies.7

 This means that, beginning 

in the 2007 model year, the market - and 

therefore production volumes - for CDPFs will 

increase from a few thousand units a year in the 

United States to almost a million units a year. At 

the same time, there is increasing demand in 

Japan and Europe spurred by retrofit programs 

and new emission standards. In the aggregate, 

CDPF production volumes are expected to 

increase by almost two orders of magnitude (i.e., 

from tens of thousands annually to more than a 

million annually). In manufacturing, substantial 

cost savings can typically be found with 

increasing production volumes, especially when 

those production volumes change by orders of 

magnitude. Therefore, we expect the cost for 

CDPFs to decrease significantly after 2007 

compared to today’s costs. For this analysis of 

the cost effectiveness of future retrofit programs, 

we feel it is appropriate to make an estimate of 

the future cost of retrofit technologies rather than 

relying on today’s costs. 

EPA has recently made an estimate of the 

production cost for CDPFs in the Nonroad Tier 4 

rule-making.8

 The analysis in that rule-making 

was based on preliminary data available to EPA 

regarding the actual manufacturing costs for 

CDPF and DOC technologies. We decided to 

use that analysis as a basis for our projection of 

the future retrofit cost for Class 6&7 trucks and 

school buses. We have made a number of 

additions and modifications to the Tier 4 analysis 

to account for differences between high volume 

engine manufacturing and retrofit applications. 

Specifically, we have added additional costs to 

account for the instrumentation and testing 

necessary to qualify candidate retrofit vehicles 

for CDPFs and for the installation of the retrofit 

technologies. We have also accounted for 

additional canning and packaging costs specific 

to retrofit technologies and for the differences 

between projected manufacturing costs in 2007 

(the period for this analysis) and the Tier 4 time 

frame (post 2010). 

In order to ensure successful application of 

passive CDPF technologies, retrofit companies 

typically instrument a sample of candidate 

vehicles from a retrofit fleet to confirm that 

operating conditions and exhaust temperatures 

are appropriate for CDPF regeneration. Absent 

such testing, CDPFs can inadvertently be 

installed on vehicles for which passive 

regeneration is not assured, potentially leading 

to CDPF failure. We estimated the cost for this 

testing at approximately $2,000 dollars per 

twenty vehicles retrofitted (i.e., the cost for the 

testing is estimated as $2,000 dollars and the 

results from the test are assumed to be, on 

average, applicable to twenty vehicles within a 

fleet). Thus, we estimated an average cost of 

$100 per CDPF vehicle retrofit to account for the 

total cost of this testing. 

The labor associated with installing a catalyst 

technology in a vehicle on a production line is 

quite small and not substantially different from 

the cost of installing an exhaust system. 

9
Installing a catalyst may entail more labor if the 

catalyst weighs more than an exhaust system or 

needs additional fasteners, or connection points. 

The labor cost for installing retrofit technologies, 

however, can be a significant fraction of the 

overall cost. Installing a retrofit catalyst may 

entail removing a portion of the existing exhaust 

system, on-site fabrication or welding of 

connections to the exhaust system, and then 

remounting of the exhaust system. The facilities 

available for retrofit installation, typically vehicle 

service facilities, are also not designed as 

efficiently as vehicle assembly lines when it 

comes to installing a single component on 

vehicles. For these reasons, we felt that it was 

necessary to account for the additional 

installation cost (primarily labor) of retrofit 

technologies in this analysis. To accomplish this, 

we used data from the grant proposals provided 

to EPA under the Clean School Bus USA 

program. A number of the grant proposals 

included a cost for installation of the retrofit 

technologies. The average installation cost from 

these grant proposals was $193. We have used 

this average as an estimate for the installation of 

both CDPFs and DOCs for Class 6&7 trucks and 

school buses. Although, it might be reasonable 

to assume this cost will decrease in the future, 

we do not have adequate information to project 

the degree to which this average cost might 

change. 

CDPF Installation 

In addition to higher labor costs related to 

installing retrofit technologies (relative to the 

volume of vehicle production) we also expect 

there to be additional hardware costs associated 

with unique fastening and mounting systems for 

retrofit technologies. This reflects the fact that 

older vehicles were not designed to 

accommodate PM control after-treatment 

technologies. We have estimated the cost for 

these additional hardware components 

(additional fasteners and perhaps unique 

exhaust tubing and fittings) at $87 per vehicle for 

DOC retrofits and $300 per vehicle for CDPF 

retrofits. It may be possible in the more distant 

future that these components will reach a degree 

of commonality that will lead to lower costs, 

however, at this time we did not have enough 

information to estimate the degree to which 

these costs may change. 

In order to apply the Nonroad Tier 4 Regulatory 

Impact Analysis estimate of CDPF and DOC 

costs for retrofit vehicles, we needed to address 

the difference in time horizons for the two future 

projections. This analysis is intended to project 

the cost for retrofit technologies in the year 2007, 

while the Nonroad Tier 4 analysis focused on 

technology cost in 2011 and beyond. Reflecting 

a start date beyond 2010, the Nonroad Tier 4 

analysis incorporated a 20 percent learning 

curve effect into its estimate of future CDPF 

costs (no learning curve effect was applied for 

DOCs). For this analysis, we have removed that 

learning curve effect in order to correlate the 

estimate to an earlier time period, specifically 

2007. The resulting cost for a CDPF (without the 

other costs noted previously) is $1,920 for a 

diesel engine of 8 liter engine displacement. The 

DOC cost (again without the additional costs 

listed previously) is $260 for Class 6&7 trucks 

and school buses. 

Table 7 summarizes the total estimate we have 

made for the cost of PM retrofit technologies in 

the 2007 time frame. The table shows a 

projected cost for DOCs of $540 per Class 6&7 

truck and school bus retrofitted and a projected 

cost for CDPFs of $2,500. These projections 

represent our best estimate of the nominal cost 

for retrofitting vehicles with diesel engines of 8 

liter displacement. In practice, we would expect 

significant variability above and below these 

price estimates due to a wide range of other 

factors that we did not account for in this 

analysis (e.g., retrofit fleet size, profit margin 

differences, etc.). Nevertheless, we believe 

these estimates adequately reflect the nominal 

cost for future PM retrofit technologies. 

10
The cost analysis described above is specific to 

engines with displacements of 8 liters applied to 

Class 6&7 trucks and school buses. In order to 

estimate the cost to retrofit larger Class 8b 

vehicles powered by engines with displacements 

typically between 11 and 16 liters, we have 

scaled this analysis by a ratio of 13:8 (i.e., we 

have increased the cost by 62 percent). This 

increase implicitly assumes that the retrofit cost 

is directly proportional to engine displacement 

and that 13 liters is a typical Class 8b engine 

displacement. Because many of the retrofit 

components are sized in direct proportion to 

engine displacement, we believe this 

approximation is robust. The resulting cost 

estimates for Class 8b retrofits are $880 per 

DOC retrofit and $4,100 per CDPF retrofit. As 

noted above, this estimate represents a nominal 

cost and a number of factors could result in costs 

that are lower or higher than those we have 

estimated. 

II.F.3. Nonroad Cost Analysis 

For our nonroad example application (250 hp 

bulldozer), we have taken a different approach to 

estimating the cost for future retrofit application. 

We have used a nominal average cost based on 

our current experience with nonroad retrofits. 

That typical cost is $800 per DOC retrofit on 

nonroad equipment. We have not made a future 

projection of reductions in this cost, because of 

the greater diversity and smaller retrofit fleet 

sizes typical of nonroad equipment. We expect 

nonroad retrofits to occur one piece of 

equipment at a time, even in relatively high 

volumes. We believe using today’s nominal cost 

as a future cost estimate is very conservative, 

but given the uncertainty in the nonroad retrofit 

market we do not attempt to predict future cost 

reductions. 

II.F.4. Highway and Nonroad Operating Costs 

We do not account for operating costs related to 

the application of PM retrofit technologies in this 

analysis. Operating costs could include the 

differential cost for using 15 ppm sulfur fuel, fuel 

economy impacts related to increased exhaust 

backpressure, or changes to maintenance 

practices related to the use of retrofit 

technologies. We have not accounted for a 15 

ppm sulfur fuel premium in this analysis because 

in 2007 (the time frame of this analysis) 15 ppm 

sulfur highway diesel fuel will be the predominant 

diesel fuel used in highway applications. At the 

same time nonroad engines must switch to fuel 

with less than 500 ppm sulfur. We have not 

accounted for a change in fuel consumption 

related to the use of PM retrofits in this analysis 

because current data from existing retrofits show 

no significant difference in fuel economy for 

vehicles with and without PM retrofit 

technologies.9

 In practice, the impact of retrofit 

technologies on fuel consumption is strongly 

related to engine load and therefore varies 

significantly depending upon the vehicle 

application. 

In the HD2007 rulemaking, we made estimates 

of the lifetime operating costs for maintenance 

related to cleaning accumulated oil ash from 

CDPFs. Those costs reflect a net present value 

calculation (in the year of sale) for a future 

maintenance cost that would occur after 150,000 

miles of trap operation. We project, however, 

that only a limited number of retrofitted vehicles 

in Classes 6&7 will accumulate 150,000 miles of 

operation after the CDPF retrofit. In most cases, 

we project that vehicles will be scrapped prior to 

the time when this maintenance would be 

necessary. Therefore, while some vehicles will 

receive this maintenance (for example, vehicles 

with higher annual VMT than projected in this 

analysis), we have not accounted for these 

maintenance costs for school buses and Class 

6&7 trucks in this analysis. For Class 8b trucks, 

which tend to accumulate many more miles, we 

have included the maintenance cost estimated in 

the HD2007 rulemaking of $208. 

II.G. ESTIMATING LIFETIME EMISSION 

REDUCTIONS 

II.G.1. Background 

In order to compare the relative cost 

effectiveness (i.e., tons of emissions reduced per 

dollars spent) of PM retrofit programs to other 

PM emission control programs, it is necessary to 

estimate the lifetime emissions reduction we 

project will occur with PM retrofits. In concept, 

estimating the emission reductions is simple and 

can be viewed as the product of the lifetime 

vehicle miles traveled (VMT), the baseline 

emission rate for the vehicle (grams/mile) and 

the emission reduction potential of the retrofit 

technology (e.g., 90% for CDPFs). In practice, 

11
the estimation is more complicated since we 

must account for vehicle scrappage, variations in 

vehicle miles traveled as the vehicle ages, and 

the relative value of emission reductions realized 

in the current year versus a future time. 

Furthermore, estimates of the lifetime emission 

reductions for retrofit technologies must address 

the age of the vehicle when the retrofit is 

installed (i.e., retrofitting a one year old vehicle 

would be expected to result in a larger emission 

reduction compared to a ten year old vehicle). 

We have accounted for these factors in our 

analysis for the nominal case, but it should be 

recognized that factors such as annual vehicle 

miles traveled can vary significantly between 

different vehicles. 

II.G.2. Highway Emission Reduction Analysis 

Earlier in this report, we provided an estimate of 

the average annual VMT for school buses 

participating in the Clean School Bus USA 

program and for vehicles with Class 6-8 HeavyDuty engines. These estimates for annual VMT 

reflect the mileage a vehicle may travel in each 

full 12 month period of its operating life. 

However, some vehicles will invariably be 

scrapped prior to reaching their total potential 

lifetime VMT. So while we estimate that a 20 

year old school bus may have an average VMT 

of 13,248 miles per year in this analysis, we 

would only expect a small percentage of school 

buses to remain in operation after 20 years. In a 

previous section, we described the methodology 

used to estimate the fraction of vehicles that 

survive to a particular age based on historic 

registration data. Those data show, for example, 

that after 10 years 83% of trucks are expected to 

be in operation and conversely that 

approximately 17% will have been scrapped. 

Using this information, we can weight the annual 

VMT (and hence emission reductions) of a ten 

year old vehicle by the likelihood that the vehicle 

is still in use and generating those emissions or 

emission reductions. We accomplish this by 

multiplying the annual VMT of a ten year old 

vehicle and the survival fraction of ten year old 

vehicles. We make a similar calculation for every 

year of a nominal vehicle’s life. 

This approach allows us to estimate the 

emissions of a group of newly built vehicles, but 

it is somewhat problematic for retrofits of older 

vehicles. This is because the subset of retrofit 

vehicles represent a surviving fraction from 

which the scrapped vehicles have already been 

removed, and for this analysis scrappage must 

be tracked for the retrofitted fleet according to 

when the retrofits were performed. For example, 

if we retrofitted a fleet of ten year old vehicles the 

scrappage rate for those vehicles in their first 

year of operation would be the age one 

scrappage rate of 0%, rather than the age ten 

scrappage rate of 17%. In order to account for 

the fact that retrofits of older vehicles begin with 

a subset of the survivors, we have created 

separate survival curves for retrofit vehicles of 

various ages from one year old to 28 years old at 

the time of the retrofit. We generated these 

survival curves by normalizing the survival 

fraction to 100% in the first year of operation, 

thus maintaining the general characteristics of 

the survival curve while reflecting the fact that 

retrofit vehicle groups are assured to have 

survived to the first year of their retrofit. Table 8

shows the survival fractions based on vehicle 

age and vehicle age at time of retrofit. 

Using the information in Table 8 and the annual 

VMT estimates for school buses and Class 6-8 

Heavy-Duty trucks, it is possible to make an 

estimate of weighted annual VMT for retrofit 

vehicles accounting for the survival fraction and 

the age of the vehicle at the time of retrofit. 

These estimates are presented in Tables 9, 10

and 11. 

Based on the estimate of the nominal annual 

VMT for retrofit vehicles and weighting this VMT 

by the surviving fraction of a subset of vehicles 

retrofitted at a certain age, we can use this 

information to estimate the annual emission 

reductions for retrofit technologies as the product 

of the weighted annual VMT (Tables 9-11), the 

emission rate per mile, and the emission 

reduction (percent reduction) realized from the 

retrofit for each year of a retrofit vehicle’s life. 

Tables 12 - 17 show the results of these 

calculations. Tables 12 - 17 are organized 

showing the base emission rates from 

MOBILE6.2 on a gram/mile basis. The adjusted 

emissions rates on a grams/mile basis are 

shown across the top of the table in summary 

form for retrofitted vehicles of model years 1990 

- 2006. The main body of the tables shows the 

annual emission reductions estimated as 

described above in each year of a retrofit 

vehicles life beginning with retrofit in 2007. 

12
Those annual estimates can then be brought 

back to a net present value at a defined discount 

rate (3 percent) to give a discounted lifetime 

emission reduction. This result is shown in the 

second row of the lower half of Tables 12-17. 

The ratio of the cost for the retrofit technology 

and the discounted lifetime emissions reductions 

represents the relative cost per ton reduction for 

the retrofit technology. These results are shown 

in the last row of the upper half of tables 12 - 17. 

Because vehicles retrofitted at different ages will 

have different lifetime emission reductions, we 

have made estimates for retrofits for various 

vehicle model years as if the vehicles were 

retrofitted in calendar year 2007. Hence a 2006 

model year vehicle retrofitted in model year 2007 

would be one year old, and a 2001 model year 

vehicle retrofitted in model year 2007 would be 

six years old. Tables 12 - 17 organize the 

vehicles of different ages by column designating 

both the model year of the retrofitted vehicle 

(e.g., 2001) and the age of the vehicle when 

retrofitted in 2007 (e.g., 6 years old). 

II.G.3. Nonroad Emission Reduction Analysis 

We have followed a similar process for the 250 

hp bulldozer, using inputs from the NONROAD 

inventory model and the simplifying assumptions 

described earlier in this paper. EPA has 

developed a retrofit modeling module within 

NMIM that will enable states and other interested 

parties to directly estimate the emission 

reduction potential of nonroad retrofits. 

III. RESULTS 

Table 18 below, summarizes the range of cost 

effectiveness ratios we estimated for the 

selected retrofit cases in this paper. As noted 

previously, these estimates represent a nominal 

projection of the future cost per ton of emission 

reduction. These cost effectiveness estimates 

have not factored in the co-benefits from 

reducing other pollutants such as HC. The cost 

effectiveness of retrofitted programs can vary 

significantly depending on a number of factors, 

including actual annual average activity (i.e., 

annual vehicle miles traveled for highway or 

annual operating hours for nonroad). 

Table 18 Summary of Cost Effectiveness for 

Various Diesel PM Retrofit Scenarios 

Vehicle Retrofit 

Technology 

Range of $/ton PM 

Emission Reduced 

School DOC $12,000 $49,100 

Bus CDPF $12,400 $50,500 

Class 

6&7 

Truck 

DOC $27,600 $67,900 

CDPF $28,400 $69,900 

Class 8b DOC $11,100 $40,600 

Truck CDPF $12,100 $44,100 

250 hp 

Bulldozer 

DOC $18,100 $49,700 

CDPF n/a n/a 

The results summarized in Table 18 can be 

compared to similar estimates for other EPA 

programs targeted at reducing diesel particulate 

matter. For example, EPA’s Urban Bus Retrofit 

and Rebuild program of $31,500/ton, EPA’s 

2007 Heavy-Duty diesel emission standards of 

$14,200/ton, for and EPA’s Nonroad Tier 4 

emission standards of $11,200/ton.10 

The results summarized in Table 18 above and 

given in more detail in Tables 12 - 17 are 

characterized by increasing cost per ton of 

emission reduction for the retrofit of older 

vehicles in comparison to newer vehicles. 

This characteristic is to be expected as older 

vehicles will have a shorter remaining lifetime 

and hence lower remaining emissions (or 

emission reductions) prior to vehicle scrappage. 

In some cases, the cost per ton of emission 

reductions decreases with older vehicles 

because of older vehicles’ relatively high 

emissions level. That is, retrofitting an emission 

control technology on an older engine that, due 

to historically more lenient emission standards 

has higher emissions, may lead to a larger 

emission reduction for the same retrofit cost. 

This benefit from retrofitting older dirtier vehicles 

is offset by the shorter remaining life of the older 

vehicles. 

13
IV. CONCLUSIONS 

Our analysis demonstrates that diesel retrofit 

strategies can be a cost effective way to reduce 

air pollution. We calculated that the 

cost-effectiveness of DOC and CDPF retrofits for 

school buses, Class 6-8b trucks, and 250 hp 

bulldozers range from roughly $11,000 to 

$70,000 per ton of PM reduced, depending on 

number of factors such as vehicle activity, 

survival rates, emissions rates, effectiveness of 

DOCs and CDPFs and their costs. These 

findings indicate that retrofits of diesel engines 

can be as cost-effective as recent EPA 

rule-makings to address diesel particulate 

matter, such as the 2007 Heavy-Duty rule and 

the Nonroad Tier 4 standards which EPA 

estimates will cost $14,200/ton of PM reduced 

and $11,200/ton of PM reduced, respectively. 

It is important to note that, while we based our 

cost effectiveness estimates on robust and 

recent data sources, there is a significant 

amount of variability in both the costs and the 

emissions reductions from retrofit technologies in 

the field. We believe our analysis adequately 

represents the cost effectiveness of DOC and 

CDPF retrofits for the average school bus, Class 

6-8b truck, and 250 hp bulldozer, but the 

cost-effectiveness of retrofits for specific engines 

and vehicle fleets may differ in certain situations. 

EPA has developed a module as part of the 

National Mobile Inventory Model that will allow 

users to predict the impact of retrofitting their 

particular fleets. The new module will be able to 

generate national, county-level, or fleet-specific 

mobile source emissions inventories and then 

use these inventories to estimate emissions 

reductions from retrofit technologies. 

Contact: 

Carl Wick 

U.S. EPA - Office of Transportation and Air 

Quality. E-mail: wick.carl@epa.gov

14
Table 1. Average Annual Mileage Accumulation (Curve Fit Data)1 

1

 Fleet Characterization Data for MOBILE6: Development and Use of Age Distributions, Average 

Annual Mileage Accumulation Rates, and Projected Vehicle Counts, Table 6 page 16, EPA420-R-01-047, 

September 2001 (www.epa.gov/otaq/models/mobile6/r01047.pdf). 

15
Table 2. Transportation Energy Data Book 1980 Model Year Heavy-Duty Survival Rate 

Age Survival 

Rate 

0 1.00 

1 1.00 

2 1.00 

3 1.00 

4 0.99 

5 0.97 

6 0.95 

7 0.92 

8 0.89 

9 0.86 

10 0.83 

11 0.79 

12 0.75 

13 0.72 

14 0.68 

15 0.64 

16 0.60 

17 0.56 

18 0.52 

19 0.48 

20 0.44 

21 0.41 

22 0.37 

23 0.34 

24 0.31 

25 0.28 

26 0.25 

27 0.22 

28 0.20 

29 0.18 

30 0.16 

16
Table 3. Heavy-Duty Diesel Class 8 Chassis Dynamometer Test Data Set 

Vehicle Number Model Year Cycle Number of Tests Fuel Type 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

1997 

1997 

1997 

1997 

1982 

1992 

1997 

1985 

1994 

1998 

1998 

1998 

1998 

1996 

1997 

1997 

1996 

1995 

1996 

1996 

1991 

1991 

1991 

1991 

1991 

2000 

1999 

1998 

OCRTC2 

OCRTC2 

NYGTC3 

NYGTC3 

5 Mile 

CSHVR 

TEST_D 

WVU-5P 

CSHVR 

HIWAY 

CSHVR 

HIWAY 

5 Mile 

TEST_D 

CSHVR 

HIWAY 

CSHVR 

CSHVR 

CSHVR 

CSHVR 

3CBD 

WHM 

3CBD 

WHM 

3CBD 

WHM 

2-5 Mile 

CSHVR 

CSHVR 

2-5 Mile 

CSHVR 

2-5 Mile 

CSHVR 

14R 

CBD 

CBD 

CBD 

14C 

14R 

CBD 

CBD-RT 

14R 

CBD 

CSHVR 

HIWAY 

CSHVR 

HIWAY 

CSHVR 

6 

6 

5 

6 

3 

4 

2 

10 

3 

1 

1 

1 

4 

13 

2 

2 

3 

3 

3 

3 

3 

3 

3 

3 

3 

3 

11 

12 

6 

3 

9 

5 

6 

1 

10 

7 

19 

1 

4 

15 

1 

2 

5 

1 

1 

2 

1 

2 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

California 

California 

California 

California 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

California 

California 

California 

California 

California 

California 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

California 

California 

California 

California 

California 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

California 

California 

California 

California 

California 

17
Vehicle Number Model Year Cycle Number of Tests Fuel Type 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

1998 

1998 

1998 

1998 

1998 

1998 

1998 

1998 

1998 

1998 

1992 

HIWAY 

2-5 Mile 

CSHVR 

HVDUTY 

CSHVR 

CSHVR 

2-5 Mile 

CSHVR 

CSHVR 

CSHVR 

CSHVR 

2-5 Mile 

CSHVR 

CSHVR 

20_mph 

30_mph 

40_mph 

5 Mile 

CSCYC 

CSHVR 

TEST_D 

WVU-5P 

YARD 

CSHVR 

HIWAY 

1 

8 

7 

1 

3 

6 

3 

4 

3 

6 

4 

3 

4 

3 

1 

2 

5 

4 

1 

15 

1 

3 

1 

2 

1 

California 

California 

California 

California 

California 

California 

California 

California 

California 

California 

California 

California 

California 

California 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

Federal Grade 2 Diesel 

California 

California 

315 

18
Table 4. Test Cycle Descriptions of Class 8 Heavy-Duty Diesel Chassis Dynamometer Tests 

Number of Model Year Number of 

Cycle Cycle Description Vehicles Range Tests 

20_MPH 20 mile per hour steady state driving 1 1998 1 

30_MPH 30 mile per hour steady state driving 1 1998 2 

40_MPH 40 mile per hour steady state driving 1 1998 5 

5 Mile Heavy-Duty vehicle drive cycle over 5 miles. 3 1982-1998 11 

2-5MIL The 5MILE Heavy-Duty drive cycle-twice. 6 1996-1998 33 

CBD Central Business District 5 1991 56 

CBD-RT Routized CBD 1 1991 1 

3CBD Triple Central Business District 3 1996-1997 9 

14C Modified CBD 1 1991 1 

14R Modified and routized CBD 3 1991 7 

CSCYC City Suburban Cycle 1 1998 1 

CSHVR Heavy-Duty vehicle drive cycle. 24 1992-2000 98 

CSHVR Heavy-Duty vehicle drive cycle. 2 1982-1998 19 

HIWAY 7 1992-2000 8 

HVDUTY 1 1998 1 

NYGTC3 Triple Length New York Garbage Truck Cycle 2 1997 11 

OCRTC2 Orange County Refuse Truck Cycle-twice 2 1997 12 

TEST_D UDD for Heavy-Duty Vehicles 3 1982-1998 16 

WHM 3 1996-1997 9 

WVU-5P 2 1982-1998 13 

YARD 1 1998 1 

315 

19
Table 5. Emission Rates, and Ratios of Chassis Dynamometer Emissions to Engine Dynamometer 

Emissions by Model Year 

New MSOD Data MOBILE6.2 Ratios 

D2 fuel CARB fuel D2 fuel CARB fuel 

Model Year N PM10(g/mi) N PM10(g/mi) PM10(g/mi) Ratio Ratio 

1980 2.09 

1981 2.09 

1982 19 3.95 2.01 1.97 

1983 2.00 

1984 2.00 

1985 17 3.12 1.99 1.57 

1986 1.98 

1987 2.06 

1988 1.75 

1989 1.73 

1990 1.18 

1991 65 3.82 0.64 5.97 

1992 7 0.97 0.63 1.54 

1993 0.63 

1994 4 0.57 0.23 2.45 

1995 6 0.81 0.23 3.53 

1996 6 0.58 46 0.75 0.23 2.57 3.31 

1997 35 1.06 2 0.245 0.23 4.69 1.08 

1998 33 0.51 70 0.37 0.23 2.27 1.63 

1999 3 0.71 0.23 3.12 

2000 2 0.46 0.23 2.03 

2001 0.23 

2002 0.23 

2003 0.23 

2004 0.23 

Totals: 175 140 Weighted Ratio = 2.3 

20
Table 7. Calendar Year 2007 Estimated Retrofit Costs for Combined Class 6&7 and School Buses, and for 

Class 8b 

Cost Component 

Diesel 

(DOC) 

Oxidation Catalyst Catalyzed 

(CDPF) 

Diesel Particulate Filter 

Substrate/Coating/Canning $260 $1,920 

Additional exhaust tubing and 

mounting hardware 

$87 $300 

Datalogging and testing for 

CDPF regeneration 

- $100 

Installation $193 $193 

Class 6-7 and School Buses 

Total (2 significant figures) 

$540 $2,500 

Ratio Class 6&7 to Class 8b 13/8 times 13/8 times 

Class 8b Retrofit Cost 

(2 significant figures) 

$880 $4,100 

Class 8b Maintenance Cost $208 

Total Class 8b Cost 

(2 significant figures) $4,300 

21
5

1015202530

Table 8. Retrofit Survival Fractions as a Function of Vehicle Age at Time of Retrofit 

Scrappage Table Survival Fraction (based on 1980 vehicles) 

Vehicle Age 

From New 

Age at Retrofit 

New 1 2 3 4 5 6 7 8 9 10 11 12 13 1

Years (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survival %) (survi

1 100% 0% 0% 0 0 0 0 0 0 0 0 0 0 0 2 100% 100% 0% 0 0 0 0 0 0 0 0 0 0 0 3 100% 100% 100% 0 0 0 0 0 0 0 0 0 0 0 4 98.5% 98.5% 98.5% 100.0% 0 0 0 0 0 0 0 0 0 0 

96.7% 96.7% 96.7% 98.2% 100.0% 0 0 0 0 0 0 0 0 0 

6 94.5% 94.5% 94.5% 96.0% 97.8% 100.0% 0 0 0 0 0 0 0 0 7 92.0% 92.0% 92.0% 93.5% 95.3% 97.5% 100.0% 0 0 0 0 0 0 0 8 89.1% 89.1% 89.1% 90.6% 92.4% 94.6% 97.1% 100.0% 0 0 0 0 0 0 9 86.0% 86.0% 86.0% 87.5% 89.3% 91.5% 94.0% 96.9% 100.0% 0 0 0 0 0 

82.7% 82.7% 82.7% 84.2% 86.0% 88.2% 90.7% 93.6% 96.7% 100.0% 0 0 0 0 

11 79.1% 79.1% 79.1% 80.6% 82.4% 84.6% 87.1% 90.0% 93.1% 96.4% 100.0% 0 0 0 12 75.4% 75.4% 75.4% 76.9% 78.7% 80.9% 83.4% 86.3% 89.4% 92.7% 96.3% 100.0% 0 0 13 71.6% 71.6% 71.6% 73.1% 74.9% 77.1% 79.6% 82.5% 85.6% 88.9% 92.5% 96.2% 100.0% 0 14 67.7% 67.7% 67.7% 69.2% 71.0% 73.2% 75.7% 78.6% 81.7% 85.0% 88.6% 92.3% 96.1% 100.0% 

63.7% 63.7% 63.7% 65.2% 67.0% 69.2% 71.7% 74.6% 77.7% 81.0% 84.6% 88.3% 92.1% 96.0% 10

16 59.7% 59.7% 59.7% 61.2% 63.0% 65.2% 67.7% 70.6% 73.7% 77.0% 80.6% 84.3% 88.1% 92.0% 917 55.7% 55.7% 55.7% 57.2% 59.0% 61.2% 63.7% 66.6% 69.7% 73.0% 76.6% 80.3% 84.1% 88.0% 918 51.8% 51.8% 51.8% 53.3% 55.1% 57.3% 59.8% 62.7% 65.8% 69.1% 72.7% 76.4% 80.2% 84.1% 819 47.9% 47.9% 47.9% 49.4% 51.2% 53.4% 55.9% 58.8% 61.9% 65.2% 68.8% 72.5% 76.3% 80.2% 8

44.2% 44.2% 44.2% 45.7% 47.5% 49.7% 52.2% 55.1% 58.2% 61.5% 65.1% 68.8% 72.6% 76.5% 8

21 40.6% 40.6% 40.6% 42.1% 43.9% 46.1% 48.6% 51.5% 54.6% 57.9% 61.5% 65.2% 69.0% 72.9% 722 37.1% 37.1% 37.1% 38.6% 40.4% 42.6% 45.1% 48.0% 51.1% 54.4% 58.0% 61.7% 65.5% 69.4% 723 33.7% 33.7% 33.7% 35.2% 37.0% 39.2% 41.7% 44.6% 47.7% 51.0% 54.6% 58.3% 62.1% 66.0% 724 30.6% 30.6% 30.6% 32.1% 33.9% 36.1% 38.6% 41.5% 44.6% 47.9% 51.5% 55.2% 59.0% 62.9% 6

27.6% 27.6% 27.6% 29.1% 30.9% 33.1% 35.6% 38.5% 41.6% 44.9% 48.5% 52.2% 56.0% 59.9% 6

26 24.8% 24.8% 24.8% 26.3% 28.1% 30.3% 32.8% 35.7% 38.8% 42.1% 45.7% 49.4% 53.2% 57.1% 627 22.2% 22.2% 22.2% 23.7% 25.5% 27.7% 30.2% 33.1% 36.2% 39.5% 43.1% 46.8% 50.6% 54.5% 528 19.8% 19.8% 19.8% 21.3% 23.1% 25.3% 27.8% 30.7% 33.8% 37.1% 40.7% 44.4% 48.2% 52.1% 529 17.6% 17.6% 17.6% 19.1% 20.9% 23.1% 25.6% 28.5% 31.6% 34.9% 38.5% 42.2% 46.0% 49.9% 5

15.5% 15.5% 15.5% 17.0% 18.8% 21.0% 23.5% 26.4% 29.5% 32.8% 36.4% 40.1% 43.9% 47.8% 5

22
Table 9. Annual VMT for Class 6&7 Trucks Weighted by the Survival Fraction from the Age at Retrofit 

Weight Class 6&7 (19,501-33,000 lbs) VMT Table 

6-7 New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old 11 year old 12 year old 13 year old 14 year old 

Vehicle Age total mileage 276,668 244,287 214,743 191,325 170,627 152,538 136,579 122,663 110,268 99,224 89,495 80,723 72,807 65,655 59,184 

1 40,681 40,681 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 36,872 36,872 36,872 0 0 0 0 0 0 0 0 0 0 0 0 0 3 33,420 33,420 33,420 33,420 0 0 0 0 0 0 0 0 0 0 0 0 4 30,291 29,837 29,837 29,837 30,291 0 0 0 0 0 0 0 0 0 0 0 5 27,455 26,549 26,549 26,549 26,961 27,455 0 0 0 0 0 0 0 0 0 0 6 24,885 23,516 23,516 23,516 23,890 24,338 24,885 0 0 0 0 0 0 0 0 0 7 22,555 20,751 20,751 20,751 21,089 21,495 21,991 22,555 0 0 0 0 0 0 0 0 8 20,443 18,215 18,215 18,215 18,521 18,889 19,339 19,850 20,443 0 0 0 0 0 0 0 9 18,529 15,935 15,935 15,935 16,213 16,546 16,954 17,417 17,955 18,529 0 0 0 0 0 0 

10 16,795 13,889 13,889 13,889 14,141 14,444 14,813 15,233 15,720 16,241 16,795 0 0 0 0 0 11 15,222 12,041 12,041 12,041 12,269 12,543 12,878 13,258 13,700 14,172 14,674 15,222 0 0 0 0 12 13,797 10,403 10,403 10,403 10,610 10,858 11,162 11,507 11,907 12,335 12,790 13,287 13,797 0 0 0 13 12,505 8,954 8,954 8,954 9,141 9,366 9,641 9,954 10,317 10,704 11,117 11,567 12,030 12,505 0 0 14 11,335 7,674 7,674 7,674 7,844 8,048 8,297 8,581 8,909 9,261 9,635 10,043 10,462 10,893 11,335 0 15 10,273 6,544 6,544 6,544 6,698 6,883 7,109 7,366 7,664 7,982 8,321 8,691 9,071 9,461 9,862 10,273 16 9,312 5,559 5,559 5,559 5,699 5,867 6,071 6,304 6,574 6,863 7,170 7,505 7,850 8,204 8,567 8,940 17 8,440 4,701 4,701 4,701 4,828 4,980 5,165 5,376 5,621 5,883 6,161 6,465 6,777 7,098 7,427 7,765 18 7,650 3,963 3,963 3,963 4,077 4,215 4,383 4,575 4,797 5,034 5,286 5,562 5,845 6,135 6,434 6,740 19 6,933 3,321 3,321 3,321 3,425 3,550 3,702 3,876 4,077 4,292 4,520 4,770 5,026 5,290 5,560 5,838 20 6,284 2,778 2,778 2,778 2,872 2,985 3,123 3,280 3,462 3,657 3,865 4,091 4,323 4,562 4,807 5,059 21 5,696 2,313 2,313 2,313 2,398 2,501 2,626 2,768 2,933 3,110 3,298 3,503 3,714 3,930 4,152 4,380 22 5,163 1,915 1,915 1,915 1,993 2,086 2,199 2,329 2,478 2,638 2,809 2,995 3,186 3,382 3,583 3,790 23 4,679 1,577 1,577 1,577 1,647 1,731 1,834 1,951 2,087 2,232 2,386 2,555 2,728 2,906 3,088 3,275 24 4,241 1,298 1,298 1,298 1,361 1,438 1,531 1,637 1,760 1,891 2,031 2,184 2,341 2,502 2,668 2,837 25 3,844 1,061 1,061 1,061 1,119 1,188 1,272 1,368 1,480 1,599 1,726 1,864 2,007 2,153 2,303 2,456 26 3,484 864 864 864 916 979 1,056 1,143 1,244 1,352 1,467 1,592 1,721 1,853 1,989 2,129 27 3,158 701 701 701 748 805 875 954 1,045 1,143 1,247 1,361 1,478 1,598 1,721 1,847 28 2,862 567 567 567 610 661 724 796 879 967 1,062 1,165 1,271 1,379 1,491 1,606 29 2,594 457 457 457 495 542 599 664 739 820 905 999 1,095 1,193 1,294 1,398 30 2,352 365 365 365 400 442 494 553 621 694 771 856 943 1,033 1,124 1,218 

23
Table 10. Annual VMT for School Buses weighted by the Survival Fraction from the Age at Retrofit 

School Bus VMT Table 

Vehicle Age School Bus New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old 11 year old 12 year old 13 year old 14 

[VMT] 176,671 168,723 160,537 155,747 151,435 147,805 144,600 142,007 139,565 137,243 135,208 133,037 130,704 128,180 1

1 13,248 13,248 0 0 0 0 0 0 0 0 0 0 0 0 0 2 13,248 13,248 13,248 0 0 0 0 0 0 0 0 0 0 0 0 3 13,248 13,248 13,248 13,248 0 0 0 0 0 0 0 0 0 0 0 4 13,248 13,049 13,049 13,049 13,248 0 0 0 0 0 0 0 0 0 0 5 13,248 12,811 12,811 12,811 13,010 13,248 0 0 0 0 0 0 0 0 0 6 13,248 12,519 12,519 12,519 12,718 12,957 13,248 0 0 0 0 0 0 0 0 7 13,248 12,188 12,188 12,188 12,387 12,625 12,917 13,248 0 0 0 0 0 0 0 8 13,248 11,804 11,804 11,804 12,003 12,241 12,533 12,864 13,248 0 0 0 0 0 0 9 13,248 11,393 11,393 11,393 11,592 11,830 12,122 12,453 12,837 13,248 0 0 0 0 0 

10 13,248 10,956 10,956 10,956 11,155 11,393 11,685 12,016 12,400 12,811 13,248 0 0 0 0 11 13,248 10,479 10,479 10,479 10,678 10,916 11,208 11,539 11,923 12,334 12,771 13,248 0 0 0 12 13,248 9,989 9,989 9,989 10,188 10,426 10,718 11,049 11,433 11,844 12,281 12,758 13,248 0 0 13 13,248 9,486 9,486 9,486 9,684 9,923 10,214 10,545 10,930 11,340 11,777 12,254 12,745 13,248 0 14 13,248 8,969 8,969 8,969 9,168 9,406 9,698 10,029 10,413 10,824 11,261 11,738 12,228 12,731 13,248 15 13,248 8,439 8,439 8,439 8,638 8,876 9,168 9,499 9,883 10,294 10,731 11,208 11,698 12,201 12,718 16 13,248 7,909 7,909 7,909 8,108 8,346 8,638 8,969 9,353 9,764 10,201 10,678 11,168 11,671 12,188 17 13,248 7,379 7,379 7,379 7,578 7,816 8,108 8,439 8,823 9,234 9,671 10,148 10,638 11,142 11,658 18 13,248 6,862 6,862 6,862 7,061 7,300 7,591 7,922 8,306 8,717 9,154 9,631 10,121 10,625 11,142 19 13,248 6,346 6,346 6,346 6,545 6,783 7,074 7,406 7,790 8,201 8,638 9,115 9,605 10,108 10,625 20 13,248 5,856 5,856 5,856 6,054 6,293 6,584 6,915 7,300 7,710 8,148 8,624 9,115 9,618 10,135 21 13,248 5,379 5,379 5,379 5,577 5,816 6,107 6,439 6,823 7,233 7,671 8,148 8,638 9,141 9,658 22 13,248 4,915 4,915 4,915 5,114 5,352 5,644 5,975 6,359 6,770 7,207 7,684 8,174 8,677 9,194 23 13,248 4,465 4,465 4,465 4,663 4,902 5,193 5,524 5,909 6,319 6,756 7,233 7,724 8,227 8,744 24 13,248 4,054 4,054 4,054 4,253 4,491 4,783 5,114 5,498 5,909 6,346 6,823 7,313 7,816 8,333 25 13,248 3,656 3,656 3,656 3,855 4,094 4,385 4,716 5,100 5,511 5,948 6,425 6,915 7,419 7,936 26 13,248 3,286 3,286 3,286 3,484 3,723 4,014 4,345 4,730 5,140 5,577 6,054 6,545 7,048 7,565 27 13,248 2,941 2,941 2,941 3,140 3,378 3,670 4,001 4,385 4,796 5,233 5,710 6,200 6,703 7,220 28 13,248 2,623 2,623 2,623 2,822 3,060 3,352 3,683 4,067 4,478 4,915 5,392 5,882 6,386 6,902 29 13,248 2,332 2,332 2,332 2,530 2,769 3,060 3,391 3,776 4,186 4,624 5,100 5,591 6,094 6,611 30 13,248 2,053 2,053 2,053 2,252 2,491 2,782 3,113 3,497 3,908 4,345 4,822 5,312 5,816 6,333 

24
Table 11. Annual VMT for Class 8b Trucks weighted by the Survival Fraction from the Age at Retrofit 

Weight Class8B (>60,000 lbs) VMT Table 

8b New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old 11 year old 12 year old 13 year old 14 

Vehicle Age total mileage 845,176 746,324 656,123 584,624 521,427 466,192 417,456 374,959 337,100 303,366 273,648 246,851 222,664 200,809 1

1 124,208 124,208 0 0 0 0 0 0 0 0 0 0 0 0 0 2 112,590 112,590 112,590 0 0 0 0 0 0 0 0 0 0 0 0 3 102,060 102,060 102,060 102,060 0 0 0 0 0 0 0 0 0 0 0 4 92,514 91,126 91,126 91,126 92,514 0 0 0 0 0 0 0 0 0 0 5 83,861 81,094 81,094 81,094 82,352 83,861 0 0 0 0 0 0 0 0 0 6 76,017 71,836 71,836 71,836 72,976 74,345 76,017 0 0 0 0 0 0 0 0 7 68,907 63,394 63,394 63,394 64,428 65,668 67,184 68,907 0 0 0 0 0 0 0 8 62,462 55,654 55,654 55,654 56,591 57,715 59,089 60,651 62,462 0 0 0 0 0 0 9 56,620 48,693 48,693 48,693 49,543 50,562 51,807 53,223 54,865 56,620 0 0 0 0 0 

10 51,324 42,445 42,445 42,445 43,215 44,139 45,268 46,551 48,039 49,630 51,324 0 0 0 0 11 46,523 36,800 36,800 36,800 37,498 38,335 39,358 40,522 41,871 43,313 44,848 46,523 0 0 0 12 42,172 31,798 31,798 31,798 32,430 33,189 34,117 35,171 36,394 37,702 39,093 40,612 42,172 0 0 13 38,228 27,371 27,371 27,371 27,945 28,633 29,474 30,429 31,538 32,723 33,985 35,361 36,775 38,228 0 14 34,652 23,459 23,459 23,459 23,979 24,603 25,365 26,232 27,236 28,311 29,454 30,702 31,984 33,301 34,652 15 31,411 20,009 20,009 20,009 20,480 21,045 21,736 22,522 23,433 24,406 25,443 26,574 27,736 28,930 30,155 16 28,473 16,998 16,998 16,998 17,425 17,938 18,564 19,276 20,102 20,985 21,924 22,949 24,003 25,085 26,195 17 25,810 14,376 14,376 14,376 14,763 15,228 15,796 16,441 17,189 17,990 18,841 19,770 20,725 21,706 22,713 18 23,396 12,119 12,119 12,119 12,470 12,891 13,406 13,991 14,669 15,395 16,167 17,009 17,875 18,764 19,676 19 21,208 10,159 10,159 10,159 10,477 10,858 11,325 11,855 12,470 13,128 13,828 14,591 15,376 16,182 17,009 20 19,224 8,497 8,497 8,497 8,785 9,131 9,554 10,035 10,592 11,188 11,823 12,515 13,226 13,957 14,706 21 17,426 7,075 7,075 7,075 7,336 7,650 8,033 8,469 8,974 9,515 10,090 10,717 11,362 12,024 12,704 22 15,796 5,860 5,860 5,860 6,097 6,382 6,729 7,124 7,582 8,072 8,593 9,162 9,746 10,346 10,962 23 14,319 4,826 4,826 4,826 5,040 5,298 5,613 5,971 6,386 6,830 7,303 7,818 8,348 8,892 9,451 24 12,979 3,972 3,972 3,972 4,166 4,400 4,685 5,010 5,386 5,789 6,217 6,684 7,164 7,658 8,164 25 11,765 3,247 3,247 3,247 3,424 3,635 3,894 4,188 4,530 4,894 5,282 5,706 6,141 6,588 7,047 26 10,665 2,645 2,645 2,645 2,805 2,997 3,231 3,498 3,807 4,138 4,490 4,874 5,269 5,674 6,090 27 9,667 2,146 2,146 2,146 2,291 2,465 2,678 2,919 3,200 3,499 3,818 4,166 4,524 4,892 5,269 28 8,763 1,735 1,735 1,735 1,867 2,024 2,217 2,436 2,690 2,962 3,251 3,567 3,891 4,224 4,566 29 7,944 1,398 1,398 1,398 1,517 1,660 1,835 2,034 2,264 2,510 2,772 3,058 3,352 3,654 3,964 30 7,201 1,116 1,116 1,116 1,224 1,354 1,512 1,692 1,901 2,124 2,362 2,621 2,888 3,161 3,442 

25
Table 12. Class 6&7 Truck DOC Cost per Ton Estimates 

Class 6&7 Estimates (2007 Calendar Year Retrofits) 

Class 6&7 DOC Cost 

Class 6&7 DOC Efficiency 

$540 

20% 

Model Year 

Mobile 6 Emission Rate 

Adjusted Rate 

DOC Cost Effectivness 

2007 

[g/mile] 

2.3 

2006 

0.158 

0.364 

$27,600 

2005 

0.158 

0.364 

$31,400 

2004 

0.158 

0.364 

$35,200 

2003 

0.158 

0.364 

$39,500 

2002 

0.158 

0.364 

$44,200 

2001 

0.158 

0.364 

$49,300 

2000 

0.158 

0.364 

$54,900 

1999 

0.158 

0.364 

$61,100 

1998 

0.158 

0.364 

$67,900 

1997 

0.261 

0.601 

$45,600 

1996 

0.264 

0.606 

$50,100 

1995 

0.265 

0.611 

$55,100 

1994 

0.267 

0.614 

$60,800 

1993 

0.516 

1.187 

$34,900 

19

0.

1.

$38

Weight Class 6&7 (19,501-33,000 lbs) Annual PM Reductions DOC (tons reduction) 

6-7 New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old 11 year old 12 year old 13 year old 14 year old 15 ye

Year Lifetime Tons ------> 0.020 0.017 0.015 0.014 0.012 0.011 0.010 0.009 0.008 0.012 0.011 0.010 0.009 0.015 0.0

2007 Annual Tons ------> 0.0030 0.0027 0.0024 0.0022 0.0020 0.0018 0.0016 0.0015 0.0013 0.0020 0.0018 0.0017 0.0015 0.0027 0.02008 Annual Tons ------> 0.0027 0.0024 0.0022 0.0020 0.0018 0.0016 0.0014 0.0013 0.0012 0.0018 0.0016 0.0015 0.0013 0.0023 0.02009 Annual Tons ------> 0.0024 0.0021 0.0019 0.0017 0.0015 0.0014 0.0013 0.0011 0.0010 0.0015 0.0014 0.0013 0.0012 0.0020 0.02010 Annual Tons ------> 0.0021 0.0019 0.0017 0.0015 0.0014 0.0012 0.0011 0.0010 0.0009 0.0013 0.0012 0.0011 0.0010 0.0018 0.02011 Annual Tons ------> 0.0019 0.0017 0.0015 0.0013 0.0012 0.0011 0.0010 0.0009 0.0008 0.0011 0.0010 0.0010 0.0009 0.0015 0.02012 Annual Tons ------> 0.0017 0.0015 0.0013 0.0012 0.0010 0.0009 0.0008 0.0007 0.0007 0.0010 0.0009 0.0008 0.0008 0.0013 0.02013 Annual Tons ------> 0.0015 0.0013 0.0011 0.0010 0.0009 0.0008 0.0007 0.0006 0.0006 0.0009 0.0008 0.0007 0.0007 0.0011 0.02014 Annual Tons ------> 0.0013 0.0011 0.0010 0.0009 0.0008 0.0007 0.0006 0.0005 0.0005 0.0007 0.0007 0.0006 0.0006 0.0010 0.02015 Annual Tons ------> 0.0011 0.0010 0.0009 0.0008 0.0007 0.0006 0.0005 0.0005 0.0004 0.0006 0.0006 0.0005 0.0005 0.0009 0.02016 Annual Tons ------> 0.0010 0.0008 0.0007 0.0006 0.0006 0.0005 0.0005 0.0004 0.0004 0.0005 0.0005 0.0005 0.0004 0.0007 0.02017 Annual Tons ------> 0.0008 0.0007 0.0006 0.0006 0.0005 0.0004 0.0004 0.0003 0.0003 0.0005 0.0004 0.0004 0.0004 0.0006 0.02018 Annual Tons ------> 0.0007 0.0006 0.0005 0.0005 0.0004 0.0004 0.0003 0.0003 0.0003 0.0004 0.0004 0.0003 0.0003 0.0006 0.02019 Annual Tons ------> 0.0006 0.0005 0.0005 0.0004 0.0004 0.0003 0.0003 0.0002 0.0002 0.0003 0.0003 0.0003 0.0003 0.0005 0.02020 Annual Tons ------> 0.0005 0.0004 0.0004 0.0003 0.0003 0.0003 0.0002 0.0002 0.0002 0.0003 0.0003 0.0002 0.0002 0.0004 0.02021 Annual Tons ------> 0.0004 0.0004 0.0003 0.0003 0.0003 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0004 0.02022 Annual Tons ------> 0.0004 0.0003 0.0003 0.0002 0.0002 0.0002 0.0002 0.0002 0.0001 0.0002 0.0002 0.0002 0.0002 0.0003 scra2023 Annual Tons ------> 0.0003 0.0003 0.0002 0.0002 0.0002 0.0002 0.0001 0.0001 0.0001 0.0002 0.0002 0.0002 0.0002 scrapped 2024 Annual Tons ------> 0.0003 0.0002 0.0002 0.0002 0.0001 0.0001 0.0001 0.0001 0.0001 0.0002 0.0001 0.0001 scrapped 2025 Annual Tons ------> 0.0002 0.0002 0.0002 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 scrapped 2026 Annual Tons ------> 0.0002 0.0002 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 scrapped 2027 Annual Tons ------> 0.0002 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 scrapped 2028 Annual Tons ------> 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 scrapped 2029 Annual Tons ------> 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0000 scrapped 2030 Annual Tons ------> 0.0001 0.0001 0.0001 0.0001 0.0000 0.0000 scrapped 2031 Annual Tons ------> 0.0001 0.0001 0.0000 0.0000 0.0000 scrapped 2032 Annual Tons ------> 0.0001 0.0000 0.0000 0.0000 scrapped 2033 Annual Tons ------> 0.0000 0.0000 0.0000 scrapped 2034 Annual Tons ------> 0.0000 0.0000 scrapped 2035 Annual Tons ------> 0.0000 scrapped 2036 - - scrapped 

26
Table 13. Class 6&7 Truck CDPF Cost per Ton Estimates 

Class 6&7 Estimates (2007 Calendar Year Retrofits) 

Class 6&7 CDPF Cost 

Class 6&7 CDPF Efficiency 

$2,500 

90% 

Model Year 

Mobile 6 Emission Rate 

Adjusted Rate 

DOC Cost Effectivness 

2007 

[g/mile] 

2.3 

2006 

0.158 

0.364 

$28,400 

2005 

0.158 

0.364 

$32,300 

2004 

0.158 

0.364 

$36,200 

2003 

0.158 

0.364 

$40,600 

2002 

0.158 

0.364 

$45,500 

2001 

0.158 

0.364 

$50,800 

2000 

0.158 

0.364 

$56,500 

1999 

0.158 

0.364 

$62,900 

1998 

0.158 

0.364 

$69,900 

1997 

0.261 

0.601 

$46,900 

1996 

0.264 

0.606 

$51,600 

1995 

0.265 

0.611 

$56,700 

1994 

0.267 

0.614 

$62,500 

1993 

0.516 

1.187 

$35,900 

Weight Class 6&7 (19,501-33,000 lbs) Annual PM Reductions CDPF (tons reduction) 

6-7 New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old 11 year old 12 year old 13 year old 14 year ol

Year Lifetime Tons ------> 0.088 0.077 0.069 0.062 0.055 0.049 0.044 0.040 0.036 0.053 0.048 0.044 0.040 0.070 

2007 Annual Tons ------> 0.0133 0.0121 0.0109 0.0099 0.0090 0.0081 0.0074 0.0067 0.0061 0.0091 0.0083 0.0076 0.0069 0.0121 2008 Annual Tons ------> 0.0121 0.0108 0.0097 0.0088 0.0079 0.0072 0.0065 0.0059 0.0053 0.0079 0.0072 0.0066 0.0060 0.0105 2009 Annual Tons ------> 0.0108 0.0096 0.0086 0.0078 0.0070 0.0063 0.0057 0.0051 0.0046 0.0069 0.0063 0.0057 0.0052 0.0091 2010 Annual Tons ------> 0.0096 0.0085 0.0076 0.0068 0.0061 0.0055 0.0049 0.0044 0.0040 0.0060 0.0054 0.0050 0.0045 0.0079 2011 Annual Tons ------> 0.0085 0.0075 0.0067 0.0060 0.0053 0.0048 0.0043 0.0039 0.0035 0.0052 0.0047 0.0043 0.0039 0.0069 2012 Annual Tons ------> 0.0075 0.0066 0.0058 0.0052 0.0046 0.0041 0.0037 0.0033 0.0030 0.0045 0.0041 0.0037 0.0034 0.0060 2013 Annual Tons ------> 0.0066 0.0057 0.0051 0.0045 0.0040 0.0036 0.0032 0.0029 0.0026 0.0038 0.0035 0.0032 0.0029 0.0052 2014 Annual Tons ------> 0.0057 0.0050 0.0044 0.0039 0.0035 0.0031 0.0028 0.0025 0.0022 0.0033 0.0030 0.0028 0.0025 0.0045 2015 Annual Tons ------> 0.0050 0.0043 0.0038 0.0034 0.0030 0.0027 0.0024 0.0021 0.0019 0.0028 0.0026 0.0024 0.0022 0.0039 2016 Annual Tons ------> 0.0043 0.0038 0.0033 0.0029 0.0026 0.0023 0.0020 0.0018 0.0016 0.0024 0.0022 0.0020 0.0019 0.0033 2017 Annual Tons ------> 0.0038 0.0032 0.0028 0.0025 0.0022 0.0019 0.0017 0.0015 0.0014 0.0021 0.0019 0.0018 0.0016 0.0029 2018 Annual Tons ------> 0.0032 0.0028 0.0024 0.0021 0.0019 0.0016 0.0015 0.0013 0.0012 0.0018 0.0016 0.0015 0.0014 0.0025 2019 Annual Tons ------> 0.0028 0.0024 0.0021 0.0018 0.0016 0.0014 0.0012 0.0011 0.0010 0.0015 0.0014 0.0013 0.0012 0.0022 2020 Annual Tons ------> 0.0024 0.0020 0.0017 0.0015 0.0013 0.0012 0.0011 0.0010 0.0009 0.0013 0.0012 0.0011 0.0010 0.0019 2021 Annual Tons ------> 0.0020 0.0017 0.0015 0.0013 0.0011 0.0010 0.0009 0.0008 0.0007 0.0011 0.0010 0.0010 0.0009 0.0016 2022 Annual Tons ------> 0.0017 0.0014 0.0012 0.0011 0.0009 0.0008 0.0008 0.0007 0.0006 0.0009 0.0009 0.0008 0.0008 0.0014 2023 Annual Tons ------> 0.0014 0.0012 0.0010 0.0009 0.0008 0.0007 0.0006 0.0006 0.0005 0.0008 0.0008 0.0007 0.0007 scrapped 2024 Annual Tons ------> 0.0012 0.0010 0.0009 0.0008 0.0007 0.0006 0.0005 0.0005 0.0004 0.0007 0.0007 0.0006 scrapped 2025 Annual Tons ------> 0.0010 0.0008 0.0007 0.0006 0.0006 0.0005 0.0004 0.0004 0.0004 0.0006 0.0006 scrapped 2026 Annual Tons ------> 0.0008 0.0007 0.0006 0.0005 0.0005 0.0004 0.0004 0.0003 0.0003 0.0005 scrapped 2027 Annual Tons ------> 0.0007 0.0006 0.0005 0.0004 0.0004 0.0003 0.0003 0.0003 0.0003 scrapped 2028 Annual Tons ------> 0.0006 0.0005 0.0004 0.0004 0.0003 0.0003 0.0003 0.0003 scrapped 2029 Annual Tons ------> 0.0005 0.0004 0.0003 0.0003 0.0003 0.0002 0.0002 scrapped 2030 Annual Tons ------> 0.0004 0.0003 0.0003 0.0002 0.0002 0.0002 scrapped 2031 Annual Tons ------> 0.0003 0.0003 0.0002 0.0002 0.0002 scrapped 2032 Annual Tons ------> 0.0003 0.0002 0.0002 0.0002 scrapped 2033 Annual Tons ------> 0.0002 0.0002 0.0001 scrapped 2034 Annual Tons ------> 0.0002 0.0001 scrapped 2035 Annual Tons ------> 0.0001 scrapped 2036 - - scrapped 

27
Table 14. School Bus DOC Cost per Ton Estimates 

School Bus Estimates (2007 Calendar Year Retrofits) 

School Bus DOC Cost $540

School Bus DOC Efficiency 20%

Model Year 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 

Mobile 6 Emission Rate [g/mile] 0.158 0.158 0.158 0.158 0.158 0.158 0.158 0.158 0.158 0.261 0.264 0.265 0.267 0.516 

Adjusted Rate 2.3 0.364 0.364 0.364 0.364 0.364 0.364 0.364 0.364 0.364 0.601 0.606 0.611 0.614 1.187 

DOC Cost Effectiveness $39,900 $42,000 $43,300 $44,500 $45,600 $46,600 $47,500 $48,300 $49,100 $30,200 $30,400 $30,700 $31,100 $16,500 

School Bus Annual PM Reductions DOC (tons reduction) 

Calendar Yr School Bus New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old 11 year old 12 year old 13 year old 14 year old 

(age) Lifetime Tons ------> 0.014 0.013 0.012 0.012 0.012 0.012 0.011 0.011 0.011 0.018 0.018 0.018 0.017 0.033 

2007 Annual Tons ------> 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0011 0.0018 0.0018 0.0018 0.0018 0.0035 2008 Annual Tons ------> 0.0011 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0017 0.0017 0.0017 0.0017 0.0033 2009 Annual Tons ------> 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0016 0.0016 0.0016 0.0016 0.0032 2010 Annual Tons ------> 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0009 0.0009 0.0016 0.0016 0.0016 0.0016 0.0031 2011 Annual Tons ------> 0.0010 0.0010 0.0010 0.0009 0.0009 0.0009 0.0009 0.0009 0.0009 0.0015 0.0015 0.0015 0.0015 0.0029 2012 Annual Tons ------> 0.0010 0.0009 0.0009 0.0009 0.0009 0.0009 0.0009 0.0009 0.0009 0.0014 0.0014 0.0014 0.0014 0.0028 2013 Annual Tons ------> 0.0009 0.0009 0.0009 0.0009 0.0009 0.0008 0.0008 0.0008 0.0008 0.0013 0.0014 0.0014 0.0014 0.0027 2014 Annual Tons ------> 0.0009 0.0009 0.0009 0.0008 0.0008 0.0008 0.0008 0.0008 0.0008 0.0013 0.0013 0.0013 0.0013 0.0025 2015 Annual Tons ------> 0.0009 0.0008 0.0008 0.0008 0.0008 0.0008 0.0007 0.0007 0.0007 0.0012 0.0012 0.0012 0.0012 0.0024 2016 Annual Tons ------> 0.0008 0.0008 0.0008 0.0008 0.0007 0.0007 0.0007 0.0007 0.0007 0.0011 0.0012 0.0012 0.0012 0.0023 2017 Annual Tons ------> 0.0008 0.0008 0.0007 0.0007 0.0007 0.0007 0.0007 0.0007 0.0007 0.0011 0.0011 0.0011 0.0011 0.0022 2018 Annual Tons ------> 0.0008 0.0007 0.0007 0.0007 0.0006 0.0006 0.0006 0.0006 0.0006 0.0010 0.0010 0.0011 0.0011 0.0021 2019 Annual Tons ------> 0.0007 0.0007 0.0006 0.0006 0.0006 0.0006 0.0006 0.0006 0.0006 0.0010 0.0010 0.0010 0.0010 0.0020 2020 Annual Tons ------> 0.0007 0.0006 0.0006 0.0006 0.0006 0.0006 0.0005 0.0005 0.0005 0.0009 0.0009 0.0009 0.0010 0.0019 2021 Annual Tons ------> 0.0006 0.0006 0.0006 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0008 0.0009 0.0009 0.0009 0.0019 2022 Annual Tons ------> 0.0006 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0008 0.0008 0.0009 0.0009 0.0018 2023 Annual Tons ------> 0.0005 0.0005 0.0005 0.0005 0.0005 0.0004 0.0004 0.0004 0.0004 0.0008 0.0008 0.0008 0.0009 scrapped 2024 Annual Tons ------> 0.0005 0.0005 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004 0.0007 0.0007 0.0008 scrapped 2025 Annual Tons ------> 0.0005 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004 0.0007 0.0007 scrapped 2026 Annual Tons ------> 0.0004 0.0004 0.0004 0.0004 0.0004 0.0003 0.0004 0.0004 0.0004 0.0006 scrapped 2027 Annual Tons ------> 0.0004 0.0004 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 scrapped 2028 Annual Tons ------> 0.0004 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 scrapped 2029 Annual Tons ------> 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 scrapped 2030 Annual Tons ------> 0.0003 0.0003 0.0003 0.0002 0.0002 0.0002 scrapped 2031 Annual Tons ------> 0.0003 0.0002 0.0002 0.0002 0.0002 scrapped 2032 Annual Tons ------> 0.0002 0.0002 0.0002 0.0002 scrapped 2033 Annual Tons ------> 0.0002 0.0002 0.0002 scrapped 2034 Annual Tons ------> 0.0002 0.0002 scrapped 2035 Annual Tons ------> 0.0002 scrapped 2036 - - scrapped 

28
Table 15. School Bus CDPF Cost per Ton Estimates 

School Bus Estimates (2007 Calendar Year Retrofits) 

School Bus CDPF Cost $2,500

School Bus CDPF Efficiency 90%

Model Year 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 

Mobile 6 Emission Rate [g/mile] 0.158 0.158 0.158 0.158 0.158 0.158 0.158 0.158 0.158 0.261 0.264 0.265 0.267 0.516 

Adjusted Rate 2.3 0.364 0.364 0.364 0.364 0.364 0.364 0.364 0.364 0.364 0.601 0.606 0.611 0.614 1.187 

DOC Cost Effectiveness $41,100 $43,200 $44,500 $45,800 $46,900 $47,900 $48,800 $49,700 $50,500 $31,100 $31,300 $31,600 $32,000 $16,900 

School Bus Annual PM Reductions CDPFs (tons reduction) 

Vehicle Age School Bus New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old11 year old12 year old13 year old14 year ol

Lifetime Tons ------> 0.061 0.058 0.056 0.055 0.053 0.052 0.051 0.050 0.049 0.080 0.080 0.079 0.078 0.148 

2007 Annual Tons ------> 0.0048 0.0048 0.0048 0.0048 0.0048 0.0048 0.0048 0.0048 0.0048 0.0079 0.0080 0.0080 0.0081 0.0156 2008 Annual Tons ------> 0.0048 0.0047 0.0047 0.0047 0.0047 0.0046 0.0046 0.0046 0.0046 0.0076 0.0077 0.0077 0.0077 0.0150 2009 Annual Tons ------> 0.0047 0.0046 0.0046 0.0046 0.0045 0.0045 0.0045 0.0044 0.0044 0.0073 0.0073 0.0074 0.0074 0.0143 2010 Annual Tons ------> 0.0046 0.0045 0.0045 0.0044 0.0044 0.0043 0.0043 0.0043 0.0042 0.0070 0.0070 0.0071 0.0071 0.0137 2011 Annual Tons ------> 0.0045 0.0044 0.0043 0.0043 0.0042 0.0042 0.0041 0.0041 0.0041 0.0067 0.0067 0.0067 0.0068 0.0131 2012 Annual Tons ------> 0.0044 0.0043 0.0042 0.0041 0.0040 0.0040 0.0039 0.0039 0.0039 0.0064 0.0064 0.0064 0.0065 0.0125 2013 Annual Tons ------> 0.0043 0.0041 0.0040 0.0039 0.0039 0.0038 0.0038 0.0037 0.0037 0.0060 0.0061 0.0061 0.0062 0.0120 2014 Annual Tons ------> 0.0041 0.0040 0.0039 0.0038 0.0037 0.0036 0.0036 0.0035 0.0035 0.0057 0.0058 0.0058 0.0059 0.0114 2015 Annual Tons ------> 0.0040 0.0038 0.0037 0.0036 0.0035 0.0034 0.0034 0.0033 0.0033 0.0054 0.0055 0.0055 0.0056 0.0109 2016 Annual Tons ------> 0.0038 0.0036 0.0035 0.0034 0.0033 0.0032 0.0032 0.0031 0.0031 0.0051 0.0052 0.0053 0.0053 0.0104 2017 Annual Tons ------> 0.0036 0.0034 0.0033 0.0032 0.0031 0.0030 0.0030 0.0030 0.0029 0.0049 0.0049 0.0050 0.0051 0.0100 2018 Annual Tons ------> 0.0034 0.0032 0.0031 0.0030 0.0029 0.0029 0.0028 0.0028 0.0028 0.0046 0.0046 0.0047 0.0048 0.0095 2019 Annual Tons ------> 0.0032 0.0030 0.0029 0.0028 0.0027 0.0027 0.0026 0.0026 0.0026 0.0043 0.0044 0.0045 0.0046 0.0091 2020 Annual Tons ------> 0.0030 0.0029 0.0027 0.0026 0.0026 0.0025 0.0025 0.0024 0.0024 0.0041 0.0042 0.0043 0.0044 0.0087 2021 Annual Tons ------> 0.0029 0.0027 0.0025 0.0024 0.0024 0.0023 0.0023 0.0023 0.0023 0.0038 0.0039 0.0041 0.0042 0.0084 2022 Annual Tons ------> 0.0027 0.0025 0.0024 0.0023 0.0022 0.0022 0.0021 0.0021 0.0021 0.0036 0.0037 0.0039 0.0040 0.0081 2023 Annual Tons ------> 0.0025 0.0023 0.0022 0.0021 0.0020 0.0020 0.0020 0.0020 0.0020 0.0034 0.0035 0.0037 0.0039 scrapped 2024 Annual Tons ------> 0.0023 0.0021 0.0020 0.0019 0.0019 0.0018 0.0018 0.0019 0.0019 0.0032 0.0034 0.0035 scrapped 2025 Annual Tons ------> 0.0021 0.0019 0.0018 0.0018 0.0017 0.0017 0.0017 0.0017 0.0018 0.0030 0.0032 scrapped 2026 Annual Tons ------> 0.0019 0.0018 0.0017 0.0016 0.0016 0.0016 0.0016 0.0016 0.0017 0.0029 scrapped 2027 Annual Tons ------> 0.0018 0.0016 0.0015 0.0015 0.0014 0.0014 0.0015 0.0015 0.0016 scrapped 2028 Annual Tons ------> 0.0016 0.0015 0.0014 0.0013 0.0013 0.0013 0.0014 0.0014 scrapped 2029 Annual Tons ------> 0.0015 0.0013 0.0013 0.0012 0.0012 0.0012 0.0013 scrapped 2030 Annual Tons ------> 0.0013 0.0012 0.0011 0.0011 0.0011 0.0011 scrapped 2031 Annual Tons ------> 0.0012 0.0011 0.0010 0.0010 0.0010 scrapped 2032 Annual Tons ------> 0.0011 0.0009 0.0009 0.0009 scrapped 2033 Annual Tons ------> 0.0009 0.0008 0.0008 scrapped 2034 Annual Tons ------> 0.0008 0.0007 scrapped 2035 Annual Tons ------> 0.0007 scrapped 2036 - - scrapped 

29
Table 16. Class 8b Truck DOC Cost per Ton Estimates 

Class 8b Estimates (2007 Calendar Year Retrofits) 

Class 8b DOC Cost $880 

Class 8b DOC Efficiency 20% 

Model Year 

Mobile 6 Emission Rate 

Adjusted Rate 

DOC Cost Effectivness 

2007 

[g/mile] 

2.3 

2006 

0.209 

0.482 

$11,100 

2005 

0.209 

0.482 

$12,600 

2004 

0.209 

0.482 

$14,200 

2003 

0.209 

0.482 

$15,900 

2002 

0.209 

0.482 

$17,800 

2001 

0.209 

0.482 

$19,900 

2000 

0.209 

0.482 

$22,100 

1999 

0.209 

0.482 

$24,600 

1998 

0.209 

0.482 

$27,300 

1997 

0.209 

0.482 

$30,300 

1996 

0.209 

0.482 

$33,600 

1995 

0.211 

0.486 

$37,000 

1994 

0.213 

0.489 

$40,600 

1993 

0.579 

1.332 

$16,600 

Weight Class 8b (>60,000 lbs) Annual PM Reductions DOC (tons reduction) 

8b New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old 11 year old 12 year old 13 year old 14 year o

Year Lifetime Tons ------> 0.079 0.070 0.062 0.055 0.049 0.044 0.040 0.036 0.032 0.029 0.026 0.024 0.022 0.053 

2007 Annual Tons ------> 0.0119 0.0108 0.0098 0.0089 0.0081 0.0073 0.0066 0.0060 0.0054 0.0049 0.0045 0.0041 0.0037 0.0092 2008 Annual Tons ------> 0.0108 0.0097 0.0087 0.0079 0.0071 0.0064 0.0058 0.0053 0.0048 0.0043 0.0039 0.0036 0.0033 0.0080 2009 Annual Tons ------> 0.0097 0.0086 0.0077 0.0070 0.0063 0.0056 0.0051 0.0046 0.0041 0.0038 0.0034 0.0031 0.0028 0.0070 2010 Annual Tons ------> 0.0086 0.0076 0.0068 0.0061 0.0055 0.0049 0.0044 0.0040 0.0036 0.0033 0.0029 0.0027 0.0024 0.0060 2011 Annual Tons ------> 0.0076 0.0067 0.0060 0.0054 0.0048 0.0043 0.0039 0.0035 0.0031 0.0028 0.0025 0.0023 0.0021 0.0052 2012 Annual Tons ------> 0.0067 0.0059 0.0053 0.0047 0.0042 0.0037 0.0033 0.0030 0.0027 0.0024 0.0022 0.0020 0.0018 0.0045 2013 Annual Tons ------> 0.0059 0.0052 0.0046 0.0041 0.0036 0.0032 0.0029 0.0026 0.0023 0.0021 0.0019 0.0017 0.0016 0.0039 2014 Annual Tons ------> 0.0052 0.0045 0.0040 0.0035 0.0031 0.0028 0.0025 0.0022 0.0020 0.0018 0.0016 0.0015 0.0014 0.0034 2015 Annual Tons ------> 0.0045 0.0039 0.0034 0.0030 0.0027 0.0024 0.0021 0.0019 0.0017 0.0015 0.0014 0.0013 0.0012 0.0029 2016 Annual Tons ------> 0.0039 0.0034 0.0030 0.0026 0.0023 0.0020 0.0018 0.0016 0.0015 0.0013 0.0012 0.0011 0.0010 0.0025 2017 Annual Tons ------> 0.0034 0.0029 0.0025 0.0022 0.0020 0.0017 0.0016 0.0014 0.0013 0.0011 0.0010 0.0010 0.0009 0.0022 2018 Annual Tons ------> 0.0029 0.0025 0.0022 0.0019 0.0017 0.0015 0.0013 0.0012 0.0011 0.0010 0.0009 0.0008 0.0008 0.0019 2019 Annual Tons ------> 0.0025 0.0021 0.0018 0.0016 0.0014 0.0013 0.0011 0.0010 0.0009 0.0008 0.0008 0.0007 0.0007 0.0017 2020 Annual Tons ------> 0.0021 0.0018 0.0016 0.0014 0.0012 0.0011 0.0010 0.0009 0.0008 0.0007 0.0007 0.0006 0.0006 0.0014 2021 Annual Tons ------> 0.0018 0.0015 0.0013 0.0012 0.0010 0.0009 0.0008 0.0007 0.0007 0.0006 0.0006 0.0005 0.0005 0.0013 2022 Annual Tons ------> 0.0015 0.0013 0.0011 0.0010 0.0009 0.0008 0.0007 0.0006 0.0006 0.0005 0.0005 0.0005 0.0004 0.0011 2023 Annual Tons ------> 0.0013 0.0011 0.0009 0.0008 0.0007 0.0006 0.0006 0.0005 0.0005 0.0004 0.0004 0.0004 0.0004 scrapped 2024 Annual Tons ------> 0.0011 0.0009 0.0008 0.0007 0.0006 0.0005 0.0005 0.0004 0.0004 0.0004 0.0004 0.0003 scrapped 2025 Annual Tons ------> 0.0009 0.0008 0.0006 0.0006 0.0005 0.0004 0.0004 0.0004 0.0003 0.0003 0.0003 scrapped 2026 Annual Tons ------> 0.0008 0.0006 0.0005 0.0005 0.0004 0.0004 0.0003 0.0003 0.0003 0.0003 scrapped 2027 Annual Tons ------> 0.0006 0.0005 0.0004 0.0004 0.0003 0.0003 0.0003 0.0003 0.0003 scrapped 2028 Annual Tons ------> 0.0005 0.0004 0.0004 0.0003 0.0003 0.0003 0.0002 0.0002 scrapped 2029 Annual Tons ------> 0.0004 0.0003 0.0003 0.0003 0.0002 0.0002 0.0002 scrapped 2030 Annual Tons ------> 0.0003 0.0003 0.0002 0.0002 0.0002 0.0002 scrapped 2031 Annual Tons ------> 0.0003 0.0002 0.0002 0.0002 0.0002 scrapped 2032 Annual Tons ------> 0.0002 0.0002 0.0002 0.0001 scrapped 2033 Annual Tons ------> 0.0002 0.0001 0.0001 scrapped 2034 Annual Tons ------> 0.0001 0.0001 scrapped 2035 Annual Tons ------> 0.0001 scrapped 2036 - - scrapped 

30
Table 17. Class 8b Truck CDPF Cost per Ton Estimates 

Class 8b Estimates (2007 Calendar Year Retrofits) 

Class 8b CDPF Cost $4,300

Class 8b CDPF Efficiency 90%

Model Year 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 

Mobile 6 Emission Rate [g/mile] 0.209 0.209 0.209 0.209 0.209 0.209 0.209 0.209 0.209 0.209 0.209 0.211 0.213 0.579 

Adjusted Rate [g/mile] 0.482 0.482 0.482 0.482 0.482 0.482 0.482 0.482 0.482 0.482 0.482 0.486 0.489 1.332 

DOC Cost Effectivness [$/ton] $12,100 $13,700 $15,400 $17,300 $19,300 $21,600 $24,000 $26,700 $29,700 $32,900 $36,500 $40,100 $44,100 $18,000 

Weight Class 8b (>60,000 lbs) Annual PM Reductions CDPF (tons reduction) 

6-7 New 1 year old 2 year old 3 year old 4 year old 5 year old 6 year old 7 year old 8 year old 9 year old 10 year old 11 year old 12 year old 13 year old 14 year o

Year Lifetime Tons ------> 0.356 0.313 0.279 0.249 0.223 0.199 0.179 0.161 0.145 0.131 0.118 0.107 0.097 0.239 

2007 Annual Tons ------> 0.0538 0.0487 0.0442 0.0400 0.0363 0.0329 0.0298 0.0270 0.0245 0.0222 0.0201 0.0184 0.0168 0.0415 2008 Annual Tons ------> 0.0487 0.0435 0.0393 0.0355 0.0321 0.0290 0.0262 0.0237 0.0214 0.0194 0.0176 0.0160 0.0146 0.0361 2009 Annual Tons ------> 0.0435 0.0387 0.0348 0.0314 0.0282 0.0254 0.0229 0.0207 0.0187 0.0169 0.0153 0.0139 0.0127 0.0313 2010 Annual Tons ------> 0.0387 0.0343 0.0308 0.0276 0.0247 0.0222 0.0200 0.0180 0.0162 0.0147 0.0132 0.0121 0.0110 0.0272 2011 Annual Tons ------> 0.0343 0.0303 0.0270 0.0241 0.0216 0.0193 0.0174 0.0156 0.0141 0.0127 0.0115 0.0104 0.0095 0.0236 2012 Annual Tons ------> 0.0303 0.0266 0.0237 0.0211 0.0188 0.0168 0.0151 0.0135 0.0121 0.0110 0.0099 0.0090 0.0083 0.0204 2013 Annual Tons ------> 0.0266 0.0232 0.0206 0.0183 0.0163 0.0145 0.0130 0.0117 0.0105 0.0094 0.0085 0.0078 0.0071 0.0177 2014 Annual Tons ------> 0.0232 0.0203 0.0179 0.0158 0.0141 0.0125 0.0112 0.0100 0.0090 0.0081 0.0073 0.0067 0.0062 0.0153 2015 Annual Tons ------> 0.0203 0.0176 0.0155 0.0137 0.0121 0.0108 0.0096 0.0086 0.0077 0.0070 0.0063 0.0058 0.0053 0.0132 2016 Annual Tons ------> 0.0176 0.0152 0.0133 0.0117 0.0104 0.0092 0.0082 0.0073 0.0066 0.0060 0.0054 0.0050 0.0046 0.0115 2017 Annual Tons ------> 0.0152 0.0131 0.0114 0.0100 0.0089 0.0078 0.0070 0.0063 0.0056 0.0051 0.0047 0.0043 0.0040 0.0099 2018 Annual Tons ------> 0.0131 0.0112 0.0098 0.0086 0.0075 0.0067 0.0060 0.0053 0.0048 0.0044 0.0040 0.0037 0.0034 0.0086 2019 Annual Tons ------> 0.0112 0.0096 0.0083 0.0073 0.0064 0.0057 0.0051 0.0045 0.0041 0.0037 0.0034 0.0032 0.0030 0.0075 2020 Annual Tons ------> 0.0096 0.0081 0.0070 0.0062 0.0054 0.0048 0.0043 0.0039 0.0035 0.0032 0.0029 0.0027 0.0026 0.0065 2021 Annual Tons ------> 0.0081 0.0069 0.0060 0.0052 0.0046 0.0040 0.0036 0.0033 0.0030 0.0027 0.0025 0.0024 0.0022 0.0057 2022 Annual Tons ------> 0.0069 0.0058 0.0050 0.0044 0.0038 0.0034 0.0030 0.0028 0.0025 0.0023 0.0022 0.0020 0.0019 0.0049 2023 Annual Tons ------> 0.0058 0.0048 0.0042 0.0037 0.0032 0.0029 0.0026 0.0023 0.0021 0.0020 0.0019 0.0018 0.0017 scrapped 2024 Annual Tons ------> 0.0048 0.0041 0.0035 0.0030 0.0027 0.0024 0.0022 0.0020 0.0018 0.0017 0.0016 0.0015 scrapped 2025 Annual Tons ------> 0.0041 0.0034 0.0029 0.0025 0.0022 0.0020 0.0018 0.0017 0.0016 0.0015 0.0014 scrapped 2026 Annual Tons ------> 0.0034 0.0028 0.0024 0.0021 0.0019 0.0017 0.0015 0.0014 0.0013 0.0013 scrapped 2027 Annual Tons ------> 0.0028 0.0023 0.0020 0.0017 0.0015 0.0014 0.0013 0.0012 0.0011 scrapped 2028 Annual Tons ------> 0.0023 0.0019 0.0016 0.0014 0.0013 0.0012 0.0011 0.0010 scrapped 2029 Annual Tons ------> 0.0019 0.0016 0.0013 0.0012 0.0011 0.0010 0.0009 scrapped 2030 Annual Tons ------> 0.0016 0.0013 0.0011 0.0010 0.0009 0.0008 scrapped 2031 Annual Tons ------> 0.0013 0.0010 0.0009 0.0008 0.0007 scrapped 2032 Annual Tons ------> 0.0010 0.0008 0.0007 0.0006 scrapped 2033 Annual Tons ------> 0.0008 0.0007 0.0006 scrapped 2034 Annual Tons ------> 0.0007 0.0005 scrapped 2035 Annual Tons ------> 0.0005 scrapped 2036 - - scrapped 

31
REFERENCES 

1. Bobit Publications, “School Bus Fleet 1997 Fact Book”, EPA420-R-01-047, September 2001 and 

Federal Transit Authority 1997 facts. 

2. Fleet Characterization Data for MOBILE 6: Development and Use of Age Distributions, Average 

Annual Mileage Accumulation Rates and Projected Vehicle Counts for Use in MOBILE6, EPA420-

P-99-011 April 1999 M6.FLT.007 available on EPA’s website at 

www.epa.gov/otaq/models/mobile6/m6tech.htm 

3. Median Life, Annual Activity, and Load Factor Values for Nonroad engine Emissions Modeling, 

NR-005c (EPA420-P-004-005, April 2004), available at www.epa.gov/otaq/nonrdmdl.htm#techrept

4. Alan Greenspan and Darrel Cohen, “Motor Vehicle Stocks, Scrappage, and Sales”, Federal 

Reserve Board, October 30, 1996 available at 

http://www.federalreserve.gov/pubs/feds/1996/199640/199640pap.pdf 

5. Exhaust and Crankcase Emission Factors for Nonroad Engine Modeling --Compression-Ignition, 

NR-009c (EPA420-P-04-009, April 2004), available at www.epa.gov/otaq/nonrdmdl.htm#techrept 

6. MECA Independent Cost Survey for Emission Control Retrofit Technologies, Manufacturers of 

Emission Control Association, December 5, 2000 available on EPA’s Retrofit Website, 

www.epa.gov/otaq/retrofit 

7. Highway Diesel Progress Review Report 2, March 2004 EPA420-R-04-004 available at 

www.epa.gov/otaq/highway-diesel/index.htm 

8. Nonroad Tier 4 Regulatory Impact Analysis (RIA), (EPA420-R-04-007, May 2004) 

http://www.epa.gov/nonroad-diesel/2004fr.htm

9. LeTavec, Chuck, et al, “Year-Long Evaluation of Trucks and Buses Equipped with Passive Diesel 

Particulate Filters,” SAE 2002-01-0433. 

10. Control of Emissions of Air Pollution From Nonroad Diesel Engines and Fuel, Table IV.D-4 page 

FR 39133, Federal Register Volume 69, No. 124 June 29, 2004. 

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