Office of Transportation EPA420-F-05-059
Uoited States and Air Quality December 2005
Environmental Protection
Agency
Frequently Asked
Questions
Guidance Document on Quantifying
Emission Reductions from Retrofit
Projects for SIPs and Conformity
Q: What is the status of EPA's "Guidance for Quantifying and Using
Emission Reductions from Mobile Source Retrofit Projects in State
Implementation Plans and Transportation and General Confor-
mity"?
A: EPA has released a draft version of this retrofit guidance document,
which has been posted on the web at www.epa.gov/otaq/transp/conform/
policy.htm. EPA plans to finalize this guidance by mid-January 2006.
Q: What is the purpose of the retrofit guidance?
A: The retrofit guidance document provides information on how to
quantify and use emission reductions from retrofit vehicles and engines
in State Implementation Plans (SIPs) and conformity analyses. This
information is provided for state and local air quality and transportation
agencies who will develop those SIPs and conformity analyses, as well
as fleet owners and others interested in understanding the application of
retrofit projects to SIP and conformity requirements.
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Q: What kinds of retrofit projects does this guidance apply to?
A: This guidance applies to retrofit projects for highway and nonroad
diesel vehicles and engines that reduce emissions of nitrogen oxides
(NOx), hydrocarbons (HC), particulate matter (PM10 and PM2.5), and
carbon monoxide (CO). Retrofit projects can include EPA or California
Air Resources Board (CARB) verified emission control technologies
and fuels, or EPA-certified engines as engine repowers or replacements.
Retrofit projects can be fleet-specific or fleet-wide.
Q: What are fleet-specific and fleet-wide retrofit projects?
A: A fleet-specific project has a specific number of vehicles/engines to
be retrofitted about which detailed and precise information on vehicle/
engine types, model years, and activity information is known. A package
delivery company implementing a retrofit program would be an example
of a "fleet-specific" project. In this case, detailed information on the
vehicles retrofitted and their activity would be readily available.
A fleet-wide project refers to a retrofit effort based on more general man-
dates or goals which result in retrofits being applied to a wide range of
vehicles or engines for which precise information about vehicle/engine
types, model years, and activity is not known. Fleet-wide retrofits may
arise from a state regulation or voluntary program. A state or local ordi-
nance that requires a percentage of trucks in certain classes to be retrofit
with a particular technology would be an example of a "fleet-wide" proj-
ect. In this case, the detailed information on the actual vehicles retrofit-
ted and their activity would not be readily available.
This distinction between fleet-specific and fleet-wide projects is par-
ticularly important when quantifying the emission reductions from the
project.
Q: How do you quantify the emission reductions from retrofit proj-
ects?
A: States other than California should use the latest version of EPA's
National Mobile Inventory Model (NMIM2005) to quantify the emission
reductions. EPA is not providing guidance at this time for the quantifica-
tion of emission reductions from retrofit projects in California.
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Q: What is NMIM2005?
A: NMIM2005 is a computer program that runs the MOBILE6.2 and
NONROAD2005 emissions models using a graphical user interface and
a database of county-level input information for inputs. NMIM2005
creates input files based on information in the database, runs MO-
BILE6.2 and NONROAD2005, and process the results to create high-
way and nonroad emission inventories for the county or counties the
user specifies. NMEVI2005 was created to simplify the process of de-
veloping county-by-county emission inventories for multi-county areas,
states or the entire nation.
NMIM2005 includes retrofit modules that allow users to specify the de-
tails of a retrofit project. Based on these details, NMEVI2005 adjusts the
output from MOBILE6.2 and NONROAD2005, as determined using the
local conditions for an area in the database, to reflect the emission reduc-
tions from the retrofit project.
Q: Does the Guidance provide details of how to run NMIM2005?
A: No, details of how to run NMEVI2005 are provided in the NMEVI2005
User Guide. The guidance discusses some of the issues that users face
when developing input data for NMEVI2005. For example, NMIM2005
requires an estimate of the vehicle miles traveled (VMT) or hours of
activity for vehicles or engines that have been retrofit. The guidance
specifies that, for SIP and conformity purposes, only VMT or hours of
activity that occur within the nonattainment or maintenance area are
creditable.
Q: What are the basic requirements for using retrofit emission re-
ductions in SIPs?
A: The guidance describes in detail the five basic requirements for
control measures that provide additional emission reductions in a SIP.
These emission reductions must be:
1. Quantifiable
2. Surplus
3. Federally enforceable
4. Permanent
5. Adequately supported
The guidance also describes the documentation, calculations, and en-
forceable requirements and commitments that must be included in the
SIP for the control measure.
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Q: Can emission reductions from highway retrofit projects be in-
cluded in transportation conformity determinations?
A: Yes, the guidance document provides details on specific require-
ments for including emission reductions from highway retrofit programs
in a transportation conformity determination. The process for doing this
varies depending on whether or not the retrofit project requires a spe-
cific regulatory action to be implemented.
Q: Can emission reductions from nonroad retrofit projects be in-
cluded in transportation conformity determinations?
A: The guidance describes in detail two options that may be used to
reflect reductions from nonroad retrofit projects in transportation con-
formity determinations. These two options are:
1. Apply nonroad retrofit emission reductions (as a "safety
margin") to the on-road motor vehicle emissions budgets
through a SIP revision; or
2. Establish a trading mechanism in the SIP to allow emissions
to be traded from one emissions sector to another.
Q: Can emission reductions from retrofit projects be included in
general conformity determinations?
A: Subject to the general conformity requirements and limitations de-
scribed in the guidance, emissions reductions from retrofit programs can
be used to mitigate or offset emission increases at federal or federally
permitted facilities that are subject to the general conformity regulation.
Q: How can I find out more?
A: The retrofit guidance document provides much more detail on these
and other related topics. A draft version of the retrofit guidance is avail-
able on the web at www.epa.gov/otaq/transp/conform/policy.htm . EPA
plans to finalize this guidance by mid-January 2006. The draft retrofit
guidance also includes contact information for additional questions.
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