Office of Transportation

and Air Quality

EPA420-B-04-002

January 2004

Guidance for Quantifying and

Using Long Duration Switch

Yard Locomotive Idling

Emission Reductions in State

Implementation Plans

 Printed on Recycled Paper
EPA420-B-04-002

January 2004

Guidance for Quantifying and Using

Long Duration Switch Yard Locomotive

 Idling Emission Reductions in

State Implementation Plans

Transportation and Regional Programs Division

Office of Transportation and Air Quality

and

Air Quality Strategies and Standards Division

Office of Air Quality Planning and Standards

U.S. Environmental Protection Agency
TABLE OF CONTENTS

Page

Section A: Background Information

1. What is the purpose of this guidance? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2. How does this guidance relate to existing Clean Air Act requirements? . . . . . . . . . . . 1

3. What are switch yard locomotive idling emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . 2

4. What is an idle reduction technology? ..................................... 2

5. What are the benefits from using technologies to reduce SYL idling emissions? . . . . 2

Section B: Basic Criteria Requirements for Long Duration Switch Yard Locomotive Idling

Emissions Reductions

6. What are the basic criteria requirements for using emission reductions in SIPs? . . . . 3

7. What should you consider when implementing an idle reduction control measure? . . 4

Section C: Specific Considerations for Using Long Duration Switch Yard Locomotive Idling

Emission Reductions

8. Are SYL idling emissions part of the state's emission inventory? . . . . . . . . . . . . . . . . 6

9. How can the estimated emission reductions be used for SIP purposes? . . . . . . . . . . . 6

Section D: Quantifying Long Duration Switch Yard Locomotive Idling Emission Reductions

10. How do you quantify emission reductions from the use of an idle reduction

technology? ......................................................... 7

11. How do you quantify emission reductions for other criteria air pollutants or

precursors? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Section E: Monitoring and Penalties

12. What monitoring and record keeping should occur to document long

duration SYL idling emission reductions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

13. What kind of validation and reconciliation should occur for emission

reductions in SIPs approved under the Voluntary Measures Policy? . . . . . . . . . . . . 12

14. What types of penalties can be assessed for not complying with CAA

requirements? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Section F: The SIP Process for Using Long Duration SYL Idling Emission Reductions

15. What must a state submit to EPA to meet the requirements for

incorporating a source specific control measure in a SIP? . . . . . . . . . . . . . . . . . . . . 13

Section G: Contact Information

16. Who should you contact for additional information? . . . . . . . . . . . . . . . . . . . . . . . . 13

Appendix A: Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Appendix B: NOx and PM Emission Factors for Long Duration Switch Yard Locomotives . . 16

Appendix C: Quantification Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Appendix D: Example Quantification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
LIST OF ABBREVIATIONS

AC Air Conditioning

APU Auxiliary Power Unit

CAA Clean Air Act

g/bhp-hr Grams per brake horsepower hour

g/kW-hr Grams per kilowatt hour

g/hr Gram per hour

hp Horsepower

hr Hour

lbs Pounds

NOx Nitrogen Oxides

PM Particulate Matter (2.5 and 10)

RPM Revolutions per minute

RFP Reasonable Further Progress

ROP Rate of Progress

SIP State Implementation Plan

SYL Switch Yard Locomotive
1

Guidance for Quantifying and Crediting Locomotive Idling Emission Reductions

(Note: As used in this document, the terms "we", "us" and "our" refer to EPA.  The terms "you"

and "your" refer to a state air pollution control agency.)

Section A:  Background Information

1. What is the purpose of this guidance?

The purpose of this document is to provide you with guidance on quantifying emission

reductions from technologies which reduce long duration switch yard locomotive (SYL) idling

emissions.  You may wish to use the emission reductions resulting from implementing an idling

reduction technology for meeting emission reduction requirements such as an RFP/ROP,

attainment or maintenance SIP.  Guidance on using these emission reductions for New Source

Review offset purposes is addressed in a separate document.

2. How does this guidance relate to existing Clean Air Act requirements?

This document provides guidance to state air pollution control agencies and the general

public on how control measures to reduce truck idling emissions may be used to meet SIP

requirements.  SIP requirements can be found in Sections 110(a)(2) and 172(c) of the CAA.  This

document does not substitute for those provisions, nor is it a regulation itself.  Unless otherwise

indicated, it does not impose binding, enforceable requirements on any party. Further, it does not

assure that EPA may approve all instances of its application, and thus the guidance may not apply

to a particular situation based upon the circumstances.  The EPA and state decision makers retain

the discretion to adopt approaches on a case-by-case basis that differ from this guidance where

appropriate.  Any decisions by EPA regarding a particular SIP demonstration will only be made

based on the statute and applicable regulations, and will only be made following notice and

opportunity for public review and comment.  Therefore, interested parties are free to raise

questions and objections about the appropriateness of the application of this guidance to a

particular situation; EPA will, and states should, consider whether or not the recommendations in

this guidance are appropriate in that situation.  This guidance is a living document and may be

revised periodically without public notice.  The EPA welcomes public comments on this

document at any time and will consider those comments in any future revisions of this guidance

document.

Readers of this document are cautioned not to regard statements recommending the use of

certain procedures as either precluding other procedures or information or providing guarantees

that using these procedures will result in actions that are fully approvable.  As noted above, EPA

cannot assure that actions based upon this guidance will be fully approvable in all instances, and

all final actions may only be taken following notice and opportunity for public comment.
1

  Based on data collected, almost all diesel PM is submicron in size.  Therefore, we

believe it is reasonable to use the same idling emission factor for both PM2.5 and PM10.  

2

3. What are switch yard locomotive idling emissions?

SYL engines are designed or used solely for the purpose of propelling railroad cars a

short distance within a confined area.  They usually idle their engines when not in use, and they

idle for a variety of reasons, such as maintaining engine operating temperature during cold

weather to avoid engine freezing (most locomotive engines do not have anti-freeze).  Other

reasons for idling include immediate engine availability, preventing start-up engine damage,

maintaining air brake pressure, and in some cases, company policy or habit.

4. What is an idle reduction technology?

An idle reduction technology consists of the use of an alternative energy source in lieu of

using the main SYL engine or a device designed to reduce long duration idling.  Some of these

technologies are mobile and attach onto the SYL (mobile auxiliary power units (APUs)), and

provide heat or electrical power.

Another technology involves electrifying SYL parking spaces (stationary locomotive

parking electrification) and modifying the SYL.  In general, this involves installing electric

powered heating systems on SYL which connect to the electrical grid and provide energy to

operate on-board equipment.  

This guidance addresses emission reductions generated from both mobile and stationary

technologies.  EPA maintains a list of commercially available idle reduction technologies on its

web site at the following address:  http://www.epa.gov/otaq/retrofit/idlingtech.htm.  This list is

for informational purposes only, is not an endorsement or verification of any specific idle

reduction technology, and is not intended as a complete list of all available idle reduction

technologies.  

5. What are the benefits from using technologies to reduce SYL idling emissions?

The primary purpose of this guidance is to quantify emission reductions in criteria air

pollutants and their precursors.  This guidance specifically addresses emission reductions of NOx

and PM2.5 and PM10.

1

  In addition, there are other important benefits associated with reductions in

long duration SYL idling emissions including:

C Reductions in the emissions of toxic air pollutants such as formaldehyde, and trace

metals such as nickel.

C Reductions in emissions of carbon dioxide.

C Reductions in fuel consumption, decreased maintenance costs, and longer engine life

which results in cost savings to the locomotive owner.
3

C Reductions in noise levels.

C Decreased dependency on oil imports.

Local communities near switch yards, some of which are comprised of low income and

minority populations, may benefit from the reduced pollution and noise levels as will SYL

operators and switch yard staff.

Section B: Basic Criteria Requirements for Long Duration Switch Yard Locomotive Idling

Emissions Reductions

6. What are the basic criteria requirements for using emission reductions in SIPs?

In order to be approved as a measure which provides additional emission reductions in a

SIP, a control measure reducing long duration SYL idling emissions cannot interfere with other

requirements of the CAA, and would need to be consistent with SIP attainment, maintenance, or

RFP/ROP requirements.  Specifically, the control measure must provide emission reductions that

meet the criteria requirements described below.  These requirements are found in the CAA

section 110 provisions concerning SIPs.   

(A)  Quantifiable - The emission reductions from a control measure to reduce long duration SYL

idling emissions are quantifiable if they can be reliably and replicably measured.  Emission

reductions must be calculated for the time period for which the reductions will be used.  Section

D of this document provides you with a method for quantifying emission reductions.  You can

also submit your own quantification protocol which we will review and make a decision as to the

appropriateness of its use on a case-by-case basis.

(B)  Surplus - Emission reductions are generally surplus and can be used as long as they are not

otherwise relied on to meet other applicable air quality attainment and maintenance requirements.

In the event that the measure to reduce long duration SYL idling emissions are relied on by you

to meet such air quality related program requirements, they are no longer surplus and are not

appropriate to be used for additional credit.  In addition, to be considered surplus the emissions

from long duration SYL idling must be a part of the SIP's emissions inventory.  

(C) Federally Enforceable - Depending on how the emission reductions are to be used, control

measures to reduce long duration SYL idling emissions must be enforceable through either:  (1) a

SIP or SIP revision; or (2) a permit issued under a SIP approved permitting program  Where the

emission reductions are part of a rule, regulation, or permit they are considered federally

enforceable if they meet all of the following requirements:

C They are independently verifiable.

C Violations are defined, as appropriate.

C You and EPA have the ability to enforce the measure if violations occur.

C Those liable for violations can be identified.
2

  For a description of this policy consult the following web site:

http://www.epa.gov/otaq/transp/traqvolm.htm.

4

C Citizens have access to all the emissions-related information obtained from the

responsible party.

C Citizens can file suits against the responsible party for violations.

C Violations are practicably enforceable in accordance with EPA guidance on

practicable enforceability.

C A complete schedule to implement and enforce the measure has been adopted by the

implementing agency or agencies.

If a SIP revision is approved under EPA's Voluntary Measures Policy, the state is

responsible for assuring that the reductions credited in the SIP occur.  The state would need to

make an enforceable SIP commitment to monitor, assess and report on the emission reductions

resulting from the voluntary measure and to remedy any shortfalls from forecasted emission

reductions in a timely manner.  Further, the total of all voluntary measures (including the idle

emission reduction measures) may not exceed 3% of the total reductions needed to meet any

requirements for RFP/ROP, attainment or maintenance as described under the policy.  In the

circumstance where the actual emission reductions achieved are more than the amount estimated

in the SIP, you may take credit for the additional emission reductions provided it does not exceed

the 3% cap on voluntary measures and meets the other provisions of the Voluntary Measures

Policy.  If you wish to have a SIP revision approved under the Voluntary Measures Policy consult

that policy for further information.2

(D)  Permanent - The emission reduction must be permanent throughout the term that the

emission reduction is used.

(E)  Adequately Supported - The state must demonstrate that it has adequate funding, personnel,

and other resources to implement the control measure on schedule.   

7. What should you consider when implementing an idle reduction control measure?

(A) Use a commercially available idle reduction technology to provide SYL needs (such as

engine and oil heat), and/or reduce idling during the operator's long duration rest or wait period,

in lieu of idling the main locomotive engine;

(B) Use an idle reduction technology that is equipped with a non-resettable meter, data logger, or

computerized data acquisition system capable of measuring total hours it operated;

(C) Comply with all necessary monitoring, recordkeeping, reporting, validation, and

reconciliation requirements as described in Section E of this guidance.

(D) In the case of mobile idle reduction technologies:
3

  If any SYL leaves due to routinely scheduled maintenance and will return to the same

rail yard (or another rail yard within the same nonattainment or maintenance area), the

responsible party should not have to notify you.  In this case, the data meter or logger should

account for the reduced operating time of the idle reduction technology.

4

  The historic idling activity should be used to estimate the idling emission reductions to

be achieved from the use of an idle reduction technology.  This estimate should be compared

with the actual emission reductions achieved after the monitoring period, as discussed in Section

E.

5 If dealing with large numbers of SYLs, you can use fleet idling averages to determine

the historic long duration idling activity as demonstrated by existing event recorder data on a

representative sample of SYLs that operate in the nonattainment or maintenance area.

5

(1)  Ensure the SYL engine is located in a nonattainment or maintenance area for the

pollutant or precursor for which emission reductions are generated;

(2) If any SYL leaves the nonattainment or maintenance area, the responsible party should

notify you of this occurrence so the emission reductions are adjusted appropriately to

reflect this change;3 and

(3)  Prior to quantifying emission reductions, determine the historic idling activity for

each SYL that will be generating emission reductions.4

  This information should include

sufficient documentation, such as data from an event recorder to determine the following

information:

(a) The historic number of hours the SYL idled per day for an average summer

weekday for the past year (if pursuing NOx emission reductions in an ozone

nonattainment/maintenance area); or

(b) The historic number of hours the SYL idled per day for an average annual

weekday for the past year (if pursuing PM or NOx emission reductions in a PM

nonattainment or maintenance area).5

(3)  Prior to generating emission reductions, you should collect the following information

for the mobile idle reduction technology only:  the manufacturer and manufacture date of

the idle reduction technology, its engine model, and average daily horsepower load for the

time period for which you will be generating emission reductions.

(E) In the case of stationary idle reduction technologies:

(1)  Ensure the technology is located in a nonattainment or maintenance area for the

pollutant or precursor for which emission reductions are generated; and
6

  If dealing with large numbers of SYLs, you can use fleet idling averages to determine

the historic idling activity.  

6

(2)  Prior to quantifying emission reductions, determine the historic idling activity for

each SYL location that will be generating emission reductions.  This information should

include sufficient documentation, such as survey or direct observation methods to

determine the following information:

(a)  Number of SYLs operating at the location throughout the year;

(b)  Of the number in (a) above, the percentage of those SYLs which idle for a

long duration (defined as 15 consecutive minutes or more at idle); and

(c)(1)  Of the SYLs in (b) above, the historic number of hours the SYLs idled per

day for an average summer weekday for the past year (if pursuing NOx emission

reductions in an ozone nonattainment/maintenance area); or

(c)(2)  Of the SYLs in (b) above, the historic number of hours the SYLs idled per

day for an average annual weekday for the past year (if pursuing PM or NOx

emission reductions in a PM nonattainment or maintenance area).6

Section C:  Specific Considerations for Using Long Duration Switch Yard Locomotive

Idling Emission Reductions

8. Are SYL idling emissions part of the state's emission inventory?

You must demonstrate that the emissions from the SYLs (from which the emission

reductions will take place) are accurately included in the SIP emissions inventory.  In addition,

the crediting of the emission reductions must also be consistent with the assumptions in the

emission inventory upon which the attainment or maintenance demonstration is based.  If they

are not already in the SIP inventory, no credit can be given for idling emission reductions unless

the SIP inventory baseline is reassessed to include such emissions at its current level.

9. How can the estimated emission reductions be used for SIP purposes?

For your SIP RFP/ROP, attainment or maintenance strategy, you should use the emission

reductions which are, or expected to be, generated from the idling reduction technology by

applying the following criteria:

(A) Based on the historic idling hours as determined in question 7(D)(3) and 7(E)(2)

above, the estimated and actual emission reductions per day from the idle reduction

project should be a percentage of the historic idling hours per day.  In the circumstance

where the estimated or actual hours idled exceeds the historic idling hours, you should
7

  For both mobile and stationary idle reduction technologies, determining the historic

idling hours forms the basis for estimating the potential emission reductions.  Differences

between the historic idling hours and estimated or actual idling hours may occur due to, for

example, warmer or colder temperatures than the historic time period.

8 If dealing with large numbers of SYLs, you can use fleet idling averages to determine

the historic long duration idling activity as demonstrated by existing event recorder data on a

representative sample of SYLs that operate in the nonattainment or maintenance area.

7

provide an explanation as to the reason for the difference if you decide to seek credit for

the additional amount (that is, the actual amount).  We will evaluate the reason for the

difference and make a decision as to the quantity of the emission reduction available on a

case-by-case basis.7

(B) Where required, emission reductions must account for seasonality.  For example, if

your SIP only credits those reductions which take place during the summer ozone season,

then only reductions in idling emissions which take place during that season may be

credited.    

(C)  The total emission reductions from all controls on long duration SYL idling for each

criteria pollutant or precursor is not to exceed the amount in the state's air emissions

inventory for SYL emissions in the year or years the emission reductions are relied upon.

Section D: Quantifying Long Duration Switch Yard Locomotive Idling Emission

Reductions

The following steps describe how to estimate the emission reductions from a proposed

idle reduction project.  In addition, these same steps can be used to determine the actual emission

reductions achieved from the project.  Step 1 establishes the historic idling activity from which

you will estimate an emission reduction.  Steps 2 and 3 describe how to estimate the SYL

emissions that are reduced when using an idle control technology.  Step 4 describes how to

estimate the emissions associated with the idle reduction technology (this step is usually not

necessary if using a stationary idle reduction technology).  Steps 5 and 6 describe how to estimate

the net reduction in emissions for the entire project.  Finally, Steps 7 and 8 describe how to

determine how much of the net reduction is creditable in a SIP.  Appendix C provides a summary

of Steps 1-6.  Appendix D provides a quantification example for a mobile technology.

10. How do you quantify emission reductions from the use of an idle reduction technology?

Step 1:  Determine the historic idling activity of the SYLs involved in the project.

For each SYL using a mobile idle reduction technology, determine the historic idling

hours as described in question 7(D)(3).   Likewise, for each SYL space which will have a

stationary idle reduction technology installed, determine the historic idling hours as described in

question 7(E)(2).8
8

Step 2:  Select the emission factor for the criteria air pollutant or precursor.

In Appendix B, we provide emission factors for NOx and PM.  These emission factors

represent average emissions from a long duration idling SYL. For NOx emissions, the emission

factor is 800 g/hr (2 stroke engine) or 620 g/hr (4 stroke engine).  For PM emissions, the

emission factor is 26 g/hr (2 stroke engine) or 32 g/hr (4 stroke engine).  Consult Appendix B for

a full explanation of the basis for the emission factors.  In the future, we may update the emission

factors or include other criteria air pollutants or precursors.  

Step 3:  Multiply the emission factor in Step 2 by the number of hours per day the idle reduction

technology is estimated to be used.

Estimate the average number of hours per day of idling emissions to be eliminated by the

use of the idle reduction technology.  The estimated hours should be a percentage of the historic

idling activity as determined in Step 1.  In the case of mobile technologies, estimate the number

of hours that the technology will reduce long duration idling for each SYL while in the

nonattainment/maintenance area.  For stationary technologies, estimate the number of hours that

the technology will reduce long duration idling for each parking space.  When determining the

actual emission reductions from an existing project, using a mobile or stationary technology, use

the actual hours the technology was used.

When estimating the number of reduced hours of idling per day you need to consider the

particular pollutant or precursor and how the idling may vary by season or annually (for example,

average summer weekday or average annual weekday) as described in question 7(D)(3) and

7(E)(2).

Thus, to determine the emissions (g/day) from an individual SYL prior to the use of an

idle reduction technology use the following equation:

Emission Per Day =  EFBASE

* ALIRT

Where,

EFBASE = SYL baseline emission factor (NOx or PM in g/hr) (See Appendix B)

ALIRT = Estimated hours of use of idle reduction technology (hr/day)

Step 4(a):  Determine emission factor for the mobile idle reduction technology.

In the case of stationary locomotive parking electrification project, for the purpose of this

guidance, it may be presumed that all emissions from power plants (including any increase in

demand resulting from a stationary project) will be accounted for in projections of, or limits on,

overall power plant emissions in the SIP's emission inventory.  Therefore, related stationary
9

  To the extent that there may be a concern that the power plant emission increases

resulting from a stationary project are not otherwise reflected in the state's overall consideration

of power plant emissions, then the power plant increases in the nonattainment/maintenance area

from a stationary project, where quantifiable, should be considered when quantifying the amount

of emission reductions.

9

project emissions at power plants should not be considered when quantifying the emission

reductions associated with a stationary project.9

If a stationary project does not rely on energy from the electrical grid, but instead is using

an alternative source of electricity (for example, a portable generator), then you should provide

data that demonstrates the emissions associated with that energy source.  The data should comply

with EPA regulations regarding the measurement of emissions from that energy source.  If no

regulations exist, provide all emissions data available to you for the energy source.  We will

review this information and determine its appropriateness for use on a case-by-case basis.

You will now determine the emission factor associated with the mobile idle reduction

technology used.  If the mobile idle reduction technology is an EPA certified diesel fueled nonroad engine, as is the case with many APUs, use the emission factor provided for that engine

family by the manufacturer as part of its certification application under 40 CFR Part 89.  This

factor is in g/kW-hr or g/bhp-hr and is publicly available (in Step 4(b) you will convert this factor

to g/hr so the terms are consistent with Step 3).  You should know the engine manufacturer's

name, year of manufacture, and 12-character EPA engine family number.  This information is

available on the engine label.  You can obtain the emission data by contacting EPA's Office of

Transportation and Air Quality (Certification and Compliance Division) or consulting the

certification data at http://www.epa.gov/otaq/certdata.htm (search under "Non-Road

Compression Ignition Engine" and "Engine Family General Information" using the engine's

manufacture date).

Step 4(b):  When using a mobile idle reduction technology, multiply emission factor from 4(a) by

the average daily horsepower load of the mobile idle reduction technology.  Skip this step for a

stationary idle reduction technology.

Since the mobile idle reduction technology emission factor is usually in g/bhp-hr, you

should convert this emission factor to g/hr by multiplying by the average daily horsepower load.

This step involves determining the average daily horsepower load which refers to the power use

of the technology.  This power use will differ during different times of the year depending on

power needs (AC or heat).  For mobile auxiliary power units, the average daily horsepower load

ranges from 5-10 hp.  You should contact the idle reduction technology manufacturer (not the

engine manufacturer) to determine the average daily horsepower load within this range for the

time period considered.  If the technology emission factor is in kW, you should convert this to

horsepower by multiplying the kW by 1.34.  Multiplying the emission factor by the daily

horsepower load gives a gram per hour emission factor for the engine.
10

Step 4(c):  When using a mobile idle reduction technology, multiply the g/hr factor by the

number of operating hours (per day) it is estimated to be used.  Skip this step for a stationary

idle reduction technology.

Thus, to determine the emissions (g/hr) for the idle reduction technology you should

follow the following equation:

Idle Reduction Technology Emission =  EFIRT* HP * ALIRT

Where,

EFIRT = Idle reduction technology emission factor (NOx or PM in g/bhp-hr)

HP    = Average daily HP load

ALIRT = Estimated hours of use of idle reduction technology (hr/day)

Step 5:  Determine the net emission reduction for the mobile technology.  Skip this step for a

stationary idle reduction technology.

To determine the net emission reduction, subtract the emissions associated with the idle

reduction technology as determined in Step 4 from the SYL emissions as determined in Step 3.

The equation is as follows:

NER = (EFBASE* ALIRT) - (EFIRT* HP * ALIRT)

Where,

NER = Net emission reductions in grams per day

EFBASE = Baseline emission factor (NOx or PM in g/hr)

ALIRT = Estimated hours of use of the idle reduction technology (hr/day)

EFIRT = Idle reduction technology emission factor (NOx or PM in g/bhp-hr)

HP    = Average daily HP load

ALIRT = Estimated hours of use of the idle reduction technology (hr/day)

Net average daily emission reductions can be converted from grams to pounds by

dividing by 454.  If necessary for estimating annual reductions of NOx or PM, average daily
11

emissions reduced can be converted to annual emissions reduced by multiplying by the number

of days in the year it is assumed the technology will be used.

Step 6:  Sum all emission reductions for the project.

For a stationary project, the sum would include the emission reductions from the use of

all the electrified parking spaces.  For mobile technologies, the sum would include the emission

reductions from all the participating SYLs.  

Step 7:  Make sure net average daily emissions reduced from the idling reduction project do not

exceed the historic idling activity of the SYLs involved in the project as determined in Step 1.

The daily emission reductions per day from the idle reduction project should be a

percentage of the historic idling hours per day.  In the circumstance where the actual hours idled

exceeds the historic idling hours, you should provide an explanation as to the reason for the

difference if you seek credit for the additional reduction.  We will evaluate the reason for the

difference and make a decision as to the quantity of the emission reduction available on a caseby-case basis.  Where verified, the additional emission reduction may be credited.

Step 8:  Make sure the net average daily emission reductions from all idling reduction projects

do not exceed the total long duration idle emissions accounted for in the SIP's regional inventory

analysis.

The net average daily emission reductions for all existing and new long duration SYL

idling reduction projects in a nonattainment or maintenance area should be summed to determine

the total reductions from all programs for a given year.  The total reductions claimed for all

programs is not to exceed the emission estimate for SYLs for any criteria air pollutant or

precursor used in the applicable SIP inventory for the calendar year in question.  See Section C

for detailed discussion.

11. How do you quantify emission reductions for other criteria air pollutants or precursors?

To quantify emission reductions for other criteria air pollutants or precursors (such as

hydrocarbon emissions), you can follow the same steps outlined in this section, substituting an

EPA approved idling emission factor for that pollutant or precursor.  Once we have identified an

idling emissions factor for use, similar to those listed or referenced in this document, it may

subsequently be used in the same manner without additional review by us. If no idling emission

factor has been identified, you can submit data supporting an idling emission factor and we will

review this data on a case-by-case basis and make a decision as to the appropriateness of its use.
12

Section E: Monitoring and Penalties

12. What monitoring and record keeping should occur to document long duration SYL idling

emission reductions?

(A) For each SYL or stationary location generating emission reductions, the responsible

party (for example, railroad company) should monitor and record the following

information for each time period for which an emission reduction is generated (or other

information capable of demonstrating the emission reductions to our satisfaction):

(1)  For mobile and stationary technologies, the number of hours the idle

reduction technology operated while the main SYL engine did not idle, recorded

by a non-resettable meter, data logger, or computerized data acquisition system

capable of recording total hours operated on each SYL.

(2)  For mobile technologies only, demonstrate that the SYLs are located in a

nonattainment or maintenance area for the pollutant or precursor for which

emission reductions determined in (1) above occurred in the nonattainment or

maintenance area.

(B) All information to be monitored and recorded in accordance with this guidance for

existing SIP requirements should be maintained by the responsible party for a period of

no less than five years.

13. What kind of validation and reconciliation should occur for emission reductions in SIPs

approved under the Voluntary Measures Policy?

The SIP submission for a voluntary measure should contain a description of the

evaluation procedures and time frame(s) in which the evaluation of SIP reductions will take

place.  Once the voluntary control measure is in place emission reductions should be evaluated

by you as required to validate the actual emission reductions.  You should submit the results of

your evaluation to EPA in accordance with the schedule contained in the SIP.  If the review

indicates that the actual emission reductions are not consistent with the estimated emission

reductions, then the amount of credit should be adjusted appropriately and applicable remedial

measures should be taken under the Voluntary Measures Policy.  See the EPA's Voluntary

Measures Policy for further information regarding validation and reconciliation requirements for

such measures.  

14. What types of penalties can be assessed for not complying with CAA requirements?

Use of this guidance does not relieve the responsible party of any obligation to comply

with all otherwise applicable CAA requirements, including those pertaining to the crediting of

emission reductions for your SIP, such as emission reductions for your attainment or
13

maintenance strategy.  Violations of CAA requirements are subject to administrative, civil,

and/or criminal enforcement under Section 113 of the CAA, as well as to citizen suits under

Section 304 of the CAA.  The full range of penalty and injunctive relief options would be

available to the federal or state government (or citizens) bringing the enforcement action.  

Section F: The SIP Process for Using Long Duration SYL Idling Emission Reductions

15. What must a state submit to EPA to meet the requirements for incorporating a source

specific control measure in a SIP?

The state must submit to EPA a written document which:

(A)  Identifies and describes the idle reduction project and its implementation schedule to

reduce long duration SYL idling emissions within a specific time period;

(B)  Contains a quantification methodology to estimate the emission reductions from the

idle reduction project.  You can follow the quantification methodology provided in

Section D of this document or you can submit your own.  If you submit your own

quantification methodology for quantifying the emission reductions, you must provide all

relevant technical support documentation, including the information and quantification

uncertainties used to calculate emission reductions.  You must rely on the most recent

information available at the time the SIP is developed;

(C)  Contains federally enforceable requirements for the responsible party (for example,

railroad company) to monitor and record the appropriate information;

(D)  Under the Voluntary Measures Policy only, enforceably commits to evaluate and

report the resulting emission reductions of the measure as applicable;

(E)  Enforceably commits to remedy any SIP emission shortfall in a timely manner if the

measure does not achieve estimated emission reductions; and

(F)  Meets all other requirements for SIP revisions under sections 110 and 172 of the

CAA.

Section G: Contact Information

16. Who should you contact for additional information?

State agencies, the regulated community and members of the public with questions

concerning a case-specific application of this guidance should contact the EPA Regional Office

with responsibility for air quality planning in the area where the switch yard is located.  A contact
14

list of your EPA Regional Office is available at the following web address:

http://www.epa.gov/epahome/locate2.htm

For general questions regarding the quantification of SYL idling emissions reductions,

please contact Paul Bubbosh of EPA's Office of Transportation and Air Quality at (202) 343-

9322 or David Solomon of EPA's Office of Air Quality Planning and Standards at (919) 541-

5375.
15

Appendix A

DEFINITIONS

For the purposes of this guidance only, the following definitions apply:

(A)  ACTUAL IDLING EMISSION REDUCTIONS means the emission reductions

achieved from an idle reduction project.

(B) ESTIMATED IDLING EMISSION REDUCTIONS means the projected emission

reductions from an idle reduction project which is based on a percentage of the historic

idling activity.

(C)  GLOBAL POSITIONING SYSTEM means a satellite-based radio navigation

receiver capable of providing the time, the date, and position of the switch yard

locomotive.

(D)  HISTORIC IDLING ACTIVITY means the demonstrated past long duration idling

of a switch yard locomotive, or past long duration idling from switch yard locomotives at

a particular location, in the nonattainment or maintenance area.

(E)  IDLE REDUCTION TECHNOLOGY means a commercially available technology or

device that provides cab comfort or engine needs, or otherwise reduces the need for longduration switch yard locomotive idling.

(F) LOCOMOTIVE SWITCHER means a locomotive designed or used solely for

the primary purpose of propelling railroad cars a short distance.

(G)  LONG DURATION IDLING means the operation of a switch yard locomotive's

propulsion engine for a period greater than 15 consecutive minutes at a time at which the

main drive engine is not engaged in gear.
10  Fritz, S.G., J.C. Hedrick, V.O. Markworth, M.B. Treuhaft, and J.F. Wakenell.  Diesel

Fuel Specification and Locomotive Improvement Program: Tenth Research Phase Final Report.

AAR Report No. R-771. Engine and Vehicle Research Division, Southwest Research Institute.

San Antonio, TX.  December, 1989; Fritz, S.G., V.O. Markworth and R.L. Mason. Locomotive

Exhaust Emission Field Tests: Phase 1, EMD SD40-2 and GE C40-8 Locomotives. Final Report,

AAR Report No. R-877, Association of American Railroads, Research and Test Department,

Washington, DC; SwRI Project No. 03-4171, Southwest Research Institute, San Antonio, TX.  

October, 1994; Fritz, S.G. Emission Measurements for Locomotives: Final Report.  SwRI 5374-

024. Southwest Research Institute, San Antonio, TX.  August, 1995; Hare, C.T., and K.J.

Springer. Exhaust Emissions from Uncontrolled Vehicles and Related Equipment Using Internal

Combustion Engines: Final Report, Part I, Locomotive Diesel Engines and Marine

Counterparts. Contract No. EHS 70-108.  Southwest Research Institute, Antonio, TX. October

1972.

16

Appendix B

NOx and PM Emission Factors for Long Duration Switch Yard Locomotives

Two Stroke Locomotive Engines

NOx g/hr PM g/hr

800 26

Four Stroke Locomotive Engines

NOx g/hr PM g/hr

620 32

Emission factors listed above are derived from various sources.10  In some cases, multiple

trials or replicate measurements were reported for the idle mode for individual locomotives.

Before deriving the final means, all replicates for individual locomotives were averaged to give a

single mean for each locomotive, to give each locomotive equal weight in the resulting emission

rate.  

Throughout, measurements obtained for locomotives on "special settings" were not

included. Special settings included retarded timing and continuous throttle.

Measurements of particulate matter from Hare & Springer (1972) were not included in

the calculation of the PM emission rate. The apparatus used for particulate measurement in that

study was experimental, and the resulting measurements are not considered reliable.
17

Appendix C

Quantification Summary

The purpose of this quantification summary is to provide a concise formula to calculate

the net emission reduction for long duration switch yard locomotive (SYL) idling.  This summary

is intended to be consistent with the more detailed step-by-step process in Section D.

NER = (EFBASE* (ALIRT / CFG/LBS )) - (EFIRT* HP * (ALIRT / CFG/LBS))

Where,

NER = Net emission reduction

EFBASE = SYL baseline emission factor (NOx or PM in g/hr)

ALIRT = Estimated hours of use of the idle reduction technology (hr/day)

CFG/LBS = Conversion factor for grams to pounds which is 454

EFIRT = Idle reduction technology emission factor (NOx or PM in g/bhp-hr)

HP = Average daily horsepower load (ranges from 5-10 hp depending on the

technology; consult the technology manufacturer)

ALIRT = Estimated hours of use of the idle reduction technology (hr/day)

There are three essential parts to this formula.  First, you determine the emissions from

the SYL by selecting the emission factor for the pollutant or precursor for reduction, multiply this

factor by the number of hours you estimate the technology will reduce long duration idling

emissions.  This number is divided by the conversion factor to derive a grams per hour number.

The second part is to determine the emissions associated with the idle reduction technology (this

step typically does not apply to stationary idle reduction technologies).  This requires determining

the emissions associated with the technology, multiplying this by the horsepower to derive a

grams per hour number, multiplying this number by the number of hours the technology will

operate, and then dividing this number by the conversion factor.  The final part is simply

subtracting the emissions from the second part (idle reduction technology emissions) by the first

part (switch yard locomotive's baseline emissions) to arrive at the net emission reduction.
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Appendix D

Example Quantification

This example is for the purpose of illustrating the quantification steps only, and it does

not address the additional considerations to credit the reductions generated.  In this example we

will quantify the NOx long duration idling emission reductions from a two stroke locomotive

engine using a mobile idle reduction technology.  In the nonattainment area, 10 SYLs will use

this technology 8 hours per day.

For the idle reduction technology, we will use an auxiliary power unit (APU).  The APU

allows an idling SYL to be shut down by heating and circulating the coolant and oil, charging the

batteries and powering the cab heaters  It is important to note that not all idling can be

eliminated.  In certain circumstances, such as when the wait from active use to active use is not

long, the operator may decide to keep the SYL engine idling.  

Per the steps outlined in this guidance document, the NOx emission reduction associated

with the use of the APU is calculated as follows:

Step 1:  Determine the historic idling activity of the SYL involved in the project.

You should follow the discussion provided in question 7(D)(3) in this guidance to derive

the historic number of hours the SYL idled for an average summer weekday in the nonattainment

or maintenance area.  In this example, we determined a SYL's long duration idling occurred an

average of 10 hours per day.  

Step 2:  Select the emission factor for the criteria air pollutant or precursor.

We are evaluating NOx emission reductions for a two stroke SYL so the emission factor

is 800 grams per hour.

Step 3:  Multiply the emission factor in Step 2 by the number of hours per day the idle reduction

technology is estimated to be used.

We estimated that the APU will reduce 8 of the 10 hours of long duration idling.

Therefore, the average daily emissions reduced is 800 grams/hr * 8 hours/day = 6,400 grams/day.

Step 4(a):  Determine emission factor for the mobile idle reduction technology.
11  For purposes of this example we have selected a specific engine model to better

illustrate the APU's emissions.  The use of this engine model does not confer any endorsement of

this company or its products.

12  In some circumstances, the NOx emission factor is reported as a combined NOx + HC

emission factor.  You will need to contact the engine manufacturer to determine the NOx only

value.

19

In this example, the APU uses a 2003 Lister Petter engine (EPA engine family

2L5XL1.86LWS )

11 which was certified under 40 CFR Part 89.   By examining the certification

data for this engine family, we find the certified NOx emission level is 6.69 g/kW-hr.12

Step 4(b):  When using a mobile idle reduction technology, multiply emission factor from 4(a) by

the average daily horsepower load of the mobile idle reduction technology.

Since the emission factor is in kW, we begin by converting this to hp (6.69 g/kW-hr *

1.34  = 8.9 g/bhp-hr).  According to an APU manufacturer, the average daily hp load for this

engine during typical summer weekdays is 8 hp.   So the grams per hour emission rate of the

auxiliary power unit is 8.9 g/bhp-hr * 8 hp = 71 g/hr.

Step 4(c):  When using a mobile idle reduction technology, multiply the g/hr factor by the

number of operating hours (per day) it is estimated to be used.

As a result, the total average daily emissions of the APUs are 71 grams/hr * 8 hours/day =

568 grams/day.

Step 5:  Determine the net emission reduction.

The estimated net emissions reductions from this program are 6,400 grams/day - 568

grams/day = 5832 grams/day or 12.8 lbs/day.

Step 6:  Sum all emission reductions for the project.

In this example, we estimate that all SYLs will operate in a similar manner.  In practice,

each SYL could have its own idling emission reductions.  We add the total amount of idling for

all 10 participating SYLs in the project, which is 10 * 5832 = 58,320 grams/day or 128 lbs/day.

Step 7:  Make sure the net average daily emission reductions from the idling reduction project

do not exceed the historic idling activity of the SYLs involved in the project as determined in Step

1.

This step involves taking your estimate of idling activity (or the actual emission reduced)

and reconciling this estimate (or actual number) with your historic idling hours from Step 1
20

(following question 7(D)(3)).  If the estimate (or actual number) exceeds the historic idling

hours, you will need to explain this increase if you seek credit for the estimated (or actual)

amount.  In this example, the estimate does not exceed the historic idling activity.

Step 8:  Make sure the net average daily emission reductions from all idling reduction projects

do not exceed the total long duration idle emissions accounted for in the regional inventory used

in the SIP.

In this example, you will need to assess the total SYL NOx emissions projected in the

inventory for the year or years the emission reductions are to be relied upon, and ensure that the

estimated emission reductions do not exceed this amount.  If the emission reductions do not

exceed this amount, full credit for the project can be taken assuming all other requirements are

met.