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6550-50-P

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 85, 86, and 1039

[EPA–HQ–OAR–2011–1032; FRL–9673-2]

RIN A2060–AR46

Heavy-Duty Highway Program: Revisions for Emergency Vehicles and SCR 

Maintenance

AGENCY: Environmental Protection Agency (EPA)

ACTION: Notice of proposed rulemaking.

SUMMARY: This proposal consists of three parts. First, EPA is proposing revisions to 

its heavy-duty diesel regulations that would enable emergency vehicles, such as dedicated 

ambulances and fire trucks, to perform their mission-critical life-saving work without 

risking that abnormal conditions of the emission control system could lead to decreased 

engine power, speed or torque. The revisions would allow manufacturers to request and 

EPA to approve modifications to emission control systems on emergency vehicles so they 

do not interfere with the vehicles’ missions. Second, EPA is proposing to revise the 

emission-related maintenance and scheduled maintenance intervals for all motor vehicles 

and nonroad compression-ignition engines to specify minimum maintenance intervals for 

replenishment of consumable chemical reductant in connection with the use of selective 

catalytic reduction technologies. Third, EPA is proposing to offer short-term relief for 
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nonroad engines from performance inducements related to the emission control system, 

for general purpose nonroad vehicles while operating in temporary emergency service. 

These actions are not expected to result in any significant changes in regulatory burdens 

or costs.

DATES: Comments on all aspects of this proposal must be received on or before July 27, 

2012. See the SUPPLEMENTARY INFORMATION section on “Public Participation” 

for more information about written comments.

Public Hearings: EPA will hold a public hearing on Wednesday, June 27, 2012 in Ann 

Arbor, Michigan. The hearing will start at 10 a.m. local time and will continue until 

everyone has had a chance to speak. For more information about the public hearing, see 

“How Do I Participate in the Public Hearing?” under the SUPPLEMENTARY 

INFORMATION section on “Public Participation” below at Section VIII.B.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OAR2011-1032, by one of the following methods:

 www.regulations.gov: Follow the on-line instructions for submitting comments.

 Email: a-and-r-docket@epa.gov

 Fax: (202) 566-9744

 Mail: Environmental Protection Agency, Air Docket, Mail-code 6102T, 1200 

Pennsylvania Ave., NW, Washington, DC 20460. 

 Hand Delivery: EPA Docket Center (EPA/DC), EPA West, Room 3334, 1301 

Constitution Ave., NW., Washington, DC, Attention Docket No. EPA-HQ-OAR2011-1032. Such deliveries are only accepted during the Docket’s normal hours of 
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operation, and special arrangements should be made for deliveries of boxed 

information.

Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-2011-1032. For 

additional instructions on submitting written comments, see the SUPPLEMENTARY 

INFORMATION section on “Public Participation” below at Section VIII.A.

Docket: All documents in the docket are listed in the www.regulations.gov index. 

Although listed in the index, some information is not publicly available, e.g., confidential 

business information or other information whose disclosure is restricted by statute. 

Certain other material, such as copyrighted material, will be publicly available only in 

hard copy in the docket. Publicly available docket materials are available either 

electronically in www.regulations.gov or in hard copy at the EPA Docket Center, 

EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW, Washington, DC. The 

Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, 

excluding legal holidays. The telephone number for the Public Reading Room is (202) 

566-1744, and the telephone number for the Air Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: Lauren Steele, Environmental 

Protection Agency, Office of Transportation and Air Quality, Assessment and Standards 

Division, 2000 Traverwood Drive, Ann Arbor, Michigan 48105; telephone number: 734-

214-4788; fax number: 734-214-4816; email address: steele.lauren (@epa.gov).

SUPPLEMENTARY INFORMATION:
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Does this action apply to me?

This proposed action would affect you if you produce or import new heavy-duty or 

nonroad diesel engines that are intended for use in vehicles that serve the emergency 

response industry, including all types of dedicated and purpose-built fire trucks and 

ambulances. You may also be affected by this action if you manufacture diesel engines 

that make use of a consumable chemical reductant to comply with emissions standards 

for nitrogen oxides. You may also be affected by this action if you produce or import 

diesel engines for nonroad applications. The following table gives some examples of 

entities that may be affected by this proposed action. Because these are only examples, 

you should carefully examine the proposed and existing regulations in 40 CFR parts 85, 

86 and 1039. If you have questions regarding how or whether these rules apply to you, 

you may call the person listed in the FOR FURTHER INFORMATION CONTACT

section above.

Category NAICS CodesaExamples of Potentially Regulated Entities

Industry 336111

336112

333618

336120

Engine and Truck Manufacturers

Industry 541514

811112

811198

Commercial Importers of Vehicles and Vehicle 

Components

Industry 811310 Engine Repair, Remanufacture, and Maintenance

Note:

a North American Industry Classification System (NAICS)

Table of Contents

I. Overview

A. Emergency Vehicle Provisions
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B. Diesel Exhaust Fluid Provisions

C. Nonroad Equipment Used Temporarily in Emergency Service

II. Statutory Authority and Regulatory Background

A. Statutory Authority

B. Background: 2007 and 2010 NOX and PM Standards

(1) On-Highway Standards

(2) Nonroad Standards

III. Direct Final Rule

IV. Emergency Vehicle Provisions

A. Background on Regulation of Emergency Vehicles

B. Current Provisions for Other Emergency Vehicles and Engines

C. Why is EPA Taking This Action?

(1) How Does a DPF Work?

(2) Why Are Emergency Vehicles Having Problems with DPF Regeneration?

(3) What Are the Concerns for Emergency Vehicles Using SCR?

D. What Would Occur if EPA Took No Action?

(1) The Industry Would Continue to Get Smarter

(2) The Fleet Would Continue to Migrate to the 2010 Standards

(3) Some Trucks Would Continue to Experience Problems

E. Proposed Regulatory Action

(1) Liberalized Regeneration Requests

(2) Engine Recalibration

(3) Backpressure Relief

F. What Engines and Vehicles Would be Affected?

(1) Newly Certified Engines and Vehicles

(2) Certified Engines and Vehicles In-Use

(3) Labeling Requirements

(4) Other Regulatory Provisions

V. Scheduled Maintenance and Maintenance Interval for Replacement of Diesel Exhaust 

Fluid

A. Background

B. Proposed Regulatory Action

(1) Scheduled Emission-Related Maintenance

(2) Maintenance Intervals for On-Highway Diesel Engines

(3) Maintenance Intervals for Nonroad Compression-Ignition Engines

VI. Nonroad Engines in Temporary Emergency Service

A. Use of Nonroad Engines in Emergency Situations

B. Proposed Regulatory Action
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(1) General Requirements

(2) Approval Criteria

(3) Allowable Use of Emergency AECD’s

VII. Economic, Environmental, and Health Impacts of Proposed Rule

A. Economic Impacts

(1) Economic Impacts of Emergency Vehicle Proposal

(2) Economic impacts of SCR Maintenance Proposal

(3) Economic Impacts for Nonroad Engines Used in Emergency Situations

B. Environmental Impacts

(1) Environmental Impacts of Emergency Vehicle Proposal

(2) Environmental Impacts of SCR Maintenance Proposal

(3) Environmental Impacts for Nonroad Engines Used in Emergency Situations

C. Health Effects

VIII. Public Participation

A. How Do I Submit Comments?

B. Will There Be a Public Hearing?

IX. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: 

Improving Regulation and Regulatory Review

B. Paperwork Reduction Act

C. Regulatory Flexibility Act

D. Unfunded Mandates Reform Act

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination with Indian Tribal 

Governments

G. Executive Order 13045: Protection of Children from Environmental Health and Safety 

Risks

H. Executive Order 13211: Energy Effects

I. National Technology Transfer Advancement Act

J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority

Populations and Low-Income Populations
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I. Overview

A. Emergency Vehicle Provisions

EPA is proposing amendments to its heavy-duty diesel engine programs that 

would specifically allow engine manufacturers to request to deploy specific emission 

controls or settings for new and in-use engines that are sold for use only in emergency 

vehicles. EPA is proposing these revisions to enable fire trucks and ambulances with 

heavy-duty diesel engines to perform mission-critical life- and property-saving work 

without risk of losing power, speed or torque due to abnormal conditions of the emission 

control systems.

EPA’s current diesel engine requirements have spurred application of emission 

controls systems such as diesel particulate filters (commonly called soot filters or DPF’s) 

and other after-treatment systems on most new diesel vehicles, including emergency

vehicles. Some control system designs and implementation strategies are more effective 

in other segments of the fleet than in emergency vehicles, especially given some 

emergency vehicles’ extreme duty cycles. By this action, EPA intends to help our 

nation’s emergency vehicles perform their missions; to better ensure public safety and 

welfare and the protection of lives and property.

B. Diesel Exhaust Fluid Provisions

EPA is proposing to amend its regulations for diesel engines to add provisions 

specifying emission-related maintenance and scheduled maintenance intervals for 

replenishment of consumable chemical reductant in connection with engines and vehicles 
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that use selective catalytic reduction (SCR) technologies. This would apply to the use of 

SCR with model year (MY) 2011 and later light-duty vehicles and nonroad compression 

ignition (NRCI) engines, and MY 2012 and later heavy-duty vehicles and engines.

Most manufacturers of diesel engines and vehicles subject to our current 

standards regulating oxides of nitrogen (NOX) have chosen to use a NOX reduction 

technology known as selective catalytic reduction (SCR) in order to meet these 

requirements. SCR systems use a chemical reductant that usually contains urea and is 

known as diesel exhaust fluid (DEF). The DEF is injected into the exhaust gas and 

requires periodic replenishment by refilling the DEF tank.

Given that SCR use is now common in the transportation sector and 

replenishment of DEF is necessary for SCR to be effective, it is appropriate to add DEF 

replenishment to the list of scheduled emission-related maintenance published in the 

Code of Federal Regulations (CFR), rather than rely on a case-by-case approval as is 

specified in the current regulations. This action would improve the clarity and 

transparency of EPA’s requirements for SCR systems.

C. Nonroad Equipment Used Temporarily in Emergency Service

EPA is proposing short-term relief from emission control system performance 

inducements for any nonroad compression ignition engine powered vehicles operating in 

temporary emergency service. This relief would address concerns about unusual 

circumstances where performance inducements could hinder equipment performance in 

emergency conditions, which are defined as conditions in which the functioning (or 

malfunctioning) of emission controls poses a significant risk to human life. We are 
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proposing provisions for a short-term emergency bypass of the normal emission controls, 

including inducement strategies, which could result in a loss of power of an engine; thus, 

allowing the equipment to temporarily perform emergency-related work. By this action, 

EPA would help our nation’s nonroad equipment perform temporary emergency service; 

to better ensure public safety and welfare and the protection of lives.

II. Statutory Authority and Regulatory Background

A. Statutory Authority

Section 202(a)(1) of the Clean Air Act (CAA or the Act) directs EPA to establish 

standards regulating the emission of any air pollutant from any class or classes of new 

motor vehicles or new motor vehicle engines that, in the Administrator’s judgment, 

causes or contributes to air pollution which may reasonably be anticipated to endanger 

public health or welfare. Such standards apply for the useful life of the vehicles or 

engines. Section 202(a)(3) requires that EPA set standards applicable to emissions of 

hydrocarbons, carbon monoxide, NOX and particulate matter (PM) from heavy-duty 

trucks that reflect the greatest degree of emission reduction achievable through the 

application of technology which we determine will be available for the model year to 

which the standards apply. We are to give appropriate consideration to cost, energy, and 

safety factors associated with the application of such technology. We may revise such 

technology-based standards, taking costs into account, on the basis of information 

concerning the effects of air pollution from heavy-duty vehicles or engines and other 

sources of mobile source related pollutants on the public health and welfare.
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Section 202(a)(4)(A) of the Act requires the Administrator to consider risks to 

public health, welfare or safety in determining whether an emission control device, 

system or element of design shall be used in a new motor vehicle or new motor vehicle 

engine. Under section 202(a)(4)(B), the Administrator shall consider available methods 

for reducing risk to public health, welfare or safety associated with use of such device, 

system or element of design, as well as the availability of other devices, systems or 

elements of design which may be used to conform to requirements prescribed by (this 

subchapter) without causing or contributing to such unreasonable risk.

Section 206(a) of the Act requires EPA to test, or require to be tested in such 

manner as it deems appropriate, motor vehicles or motor vehicle engines submitted by a 

manufacturer to determine whether such vehicle or engine conforms to the regulations 

promulgated under section 202. Section 206(d) provides that EPA shall by regulation 

establish methods and procedures for making tests under section 206. 

Section 213 of the Act gives EPA the authority to establish emissions standards 

for nonroad engines and vehicles (42 U.S.C. 7547). Sections 213(a)(3) and (a)(4) 

authorize the Administrator to set standards and require EPA to give appropriate 

consideration to cost, lead time, noise, energy, and safety factors associated with the 

application of technology. Section 213(a)(4) authorizes the Administrator to establish 

standards to control emissions of pollutants (other than those covered by section 

213(a)(3)) which “may reasonably be anticipated to endanger public health and welfare.” 

Section 213(d) requires the standards under section 213 to be subject to sections 206-209 

of the Act and to be enforced in the same manner as standards prescribed under section 

202 of the Act.
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B. Background: 2007 and 2010 NOX and PM Standards

(1) On-Highway Standards

On January 18, 2001, EPA published a rule promulgating more stringent 

standards for NOX and PM for heavy-duty highway engines (“the heavy-duty highway

rule”).1 The 0.20 gram per brake-horsepower-hour (g/bhp-hr) NOX standard in the 

heavy-duty highway rule first applied in MY 2007. However, because of phase-in 

flexibility provisions adopted in that rule and use of emission credits generated by

manufacturers for early compliance, manufacturers were able to continue to produce 

engines with NOX emissions greater than 0.20 g/bhp-hr. The phase-in provisions ended 

after MY 2009 so that the 0.20 g/bhp-hr NOX standard was fully phased-in for model 

year 2010. Because of these changes that occurred in MY 2010, the 0.20 g/bhp-hr NOX

emission standard is often referred to as the 2010 NOX emission standard, even though it 

applied to engines as early as MY 2007.

The heavy-duty highway rule adopted in 2001 also included a PM emissions 

standard for new heavy-duty diesel engines of 0.01 g/bhp-hr, effective for engines 

beginning with MY 2007. Due to the flexible nature of the phase-in schedule described 

above, manufacturers have had the opportunity to produce engines that met the PM 

standard while emitting higher levels of NOX. During the phase-in years, manufacturers 

of diesel engines generally produced engines that were tuned so the combustion process 

inherently emitted lower engine-out NOX while relying on PM after-treatment to meet the 

 

1 Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards and 

Highway Diesel Fuel Sulfur Control Requirements (66 FR 5001).
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PM standard. The principles of combustion chemistry dictate that conditions yielding 

lower engine-out NOX emissions generally result in higher engine-out PM emissions. 

This is what we call the NOX-PM trade-off. For many new low-NOX diesel engines 

today, engine-out PM emissions could be at or above the levels seen with the MY 2004 

standards (0.1 g/bhp-hr). To meet today’s stringent PM standards, manufacturers rely on 

diesel particulate filter after-treatment to clean the exhaust.

(2) Nonroad Standards

EPA adopted similar technology-forcing standards for nonroad diesel engines on 

June 29, 2004.2 These are known as the Tier 4 standards. This program includes 

requirements that will generally involve the use of NOX after-treatment for engines above 

75 hp and PM after-treatment (likely soot filters) for engines above 25 hp. These 

standards phase in during the 2011 to 2015 time frame.

III. Direct Final Rule

In addition to this notice of proposed rulemaking, EPA is also publishing a Direct 

Final Rule (DFR) addressing the emergency vehicle provisions described in Section IV of 

this document. We are doing this to expedite the regulatory process to allow engine and

vehicle modifications to occur as soon as possible. However, if we receive relevant 

adverse comment on distinct elements of the emergency vehicle provisions in this 

proposal by July 27, 2012, we will publish a timely withdrawal in the Federal Register

indicating which provisions we are withdrawing. Any provisions of the DFR that are not 

 

2 Control of Emissions of Air Pollution from Nonroad Diesel Engines and Fuel (69 FR 38958).
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withdrawn will become effective on [Insert date 60 days from date of publication in 

the Federal Register], notwithstanding adverse comment on any other provision. We 

will address all public comments in the final rule based on this proposed rule.

As noted above, EPA is publishing the DFR to expedite the deployment of 

solutions that will best ensure the readiness of the nation’s emergency vehicles. We 

request that commenters identify in your comments any portions of the emergency

vehicle proposed action described in Section IV below with which you agree and support 

as proposed, in addition to any comments regarding suggestions for improvement or 

provisions with which you disagree. In the case of a comment that is otherwise unclear 

whether it is adverse, EPA would interpret relevant comments calling for more flexibility

or less restrictions for emergency vehicles as supportive of the direct final rule. In this 

way, the EPA will be able to adopt those elements of the DFR that are fully supported 

and most needed today, while considering and addressing any adverse comments 

received on the proposed rule, in the course of developing the final rule.

Note that Docket Number EPA-HQ-OAR-2011-1032 is being used for both the 

DFR and this Notice of Proposed Rulemaking (NPRM).

IV. Emergency Vehicle Provisions

A. Background on Regulation of Emergency Vehicles

Typically, the engines powering our nation’s emergency vehicles belong to the 

same certified engine families as engines that are installed in similarly sized vehicles sold 
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for other public and private uses.3 Historically, engine and vehicle manufacturers have 

sought EPA certification for broad engine families and vehicle test groups that are 

defined by similar emissions and performance characteristics. Engine families typically 

only consider the type of vehicle in which the engine is intended to be installed to the 

extent that it fits into a broad vehicle weight class and, to a lesser extent, the vehicle’s 

intended duty cycle (i.e. urban or highway).

Because of the above-described manufacturing practices and the narrow CAA 

authority for any exemptions, EPA has historically regulated engines for emergency

vehicles, including ambulances as well as police vehicles and fire-fighting apparatus, in 

the same manner as other engines. 

In the public comments received on the proposed heavy-duty highway rule, EPA 

received some comments about DPF technologies and regeneration cycles on heavy-duty 

trucks, including one comment that expressed concerns that the systems may not be 

failsafe.4 However, none of the comments specifically raised technical feasibility with 

respect to emergency vehicles, and EPA’s response was based on the best information 

available at the time. After publishing the final rule requiring heavy-duty highway

engines to meet performance standards that compelled technologies such as DPF’s, EPA 

received a letter from the National Association of State Fire Marshals, requesting some 

 

3

In this proposal, emergency vehicle is defined as a fire truck or an ambulance for on-highway 

applications, and for nonroad applications, we are defining emergency equipment as specialized vehicles to 

perform aircraft rescue and firefighting functions at airports, or wildland fire apparatus. See Section IV.C 

and proposed revisions at 40 CFR 86.1803-01 and 40 CFR 1039.801.

4 Heavy-Duty Highway Final Rule, December 21, 2000 Response to Comments, Section 3.2.1, “Technical 

Feasibility of Engine/Vehicle Standards//Diesel Engine Exhaust Standards,” page 3-58 to 3-60, available at 

http://www.epa.gov/otaq/highway-diesel/regs/2007-heavy-duty-highway.htm.
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provision for public safety in implementing this new rule, considering that fire 

departments across the nation have trouble covering basic costs and may not have funds 

for more expensive trucks.5 This letter did not raise any technical feasibility issues, and 

EPA did not see a need to take action. 

More recently EPA has received letters from fire apparatus manufacturers and 

ambulance companies requesting relief from power or speed inducements related to low 

levels of DEF for SCR systems on emergency vehicles.6 Power and speed reduction 

inducements were new on vehicles equipped with SCR. These were not specifically 

mandated by EPA but designed by manufacturers to occur if DEF levels became low, to 

induce operators of the vehicles to perform the required emission-related maintenance in 

use. More discussion on this, including why the emergency response community

requested relief and what action EPA took, is found below in Section IV.C(3). 

Recently, beginning in October 2011, EPA received a series of comment letters 

from fire chiefs and other interested stakeholders, requesting regulatory action to relieve 

emergency vehicles from the burden of complying with the 2007 PM standards.7 EPA 

promptly opened a dialogue with the fire chiefs and engine manufacturers to understand 

the issues. Power and speed reductions were occurring on some vehicles with soot filters 

but without SCR systems, in part related to engine protection measures designed by

 

5 Letter dated February 1, 2001 to C. Whitman, EPA Administrator from G. Miller, President, National 

Association of State Fire Marshalls

6

See, for example, letter dated October 22, 2009, from Roger Lackore of the Fire Apparatus 

Manufacturers’ Association and Randy Hanson of the Ambulance Manufacturers Division, to Keisha 

Jennings of EPA.

7

See, for example, letter dated October 4, 2011 from Congressman Filner to EPA Administrator Jackson, 

and letter dated October 14, 2011, from Director Cimini of the Southeast Association of Fire Chiefs to EPA 

Administrator Jackson.
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manufacturers. Essentially, these soot filters are supposed to be self-cleaning by

periodically burning off accumulated soot during normal vehicle use. The cleaning 

process is called regeneration, and when this doesn’t work as designed, the filter 

gradually gets more clogged, which can lead to engine problems. EPA has determined 

that while other pathways are available for resolving some issues related to soot filters on 

emergency vehicles, there remains a public safety issue related to design of engines and 

emission control systems on emergency vehicles that should be addressed through this 

rulemaking. More discussion of this, including why relief was requested and what other 

actions can be taken in addition to EPA regulation, is found below in Sections IV.C and 

IV.D.

B. Current Provisions for Other Emergency Vehicles and Engines

On December 1, 2011, in a proposed rule issued jointly with the National 

Highway Traffic Safety Administration (NHTSA), EPA proposed to exclude light-duty 

emergency and police vehicles from all phases of greenhouse gas (GHG) emissions 

standards, in part due to concerns related to technical feasibility, and in part to harmonize 

with NHTSA’s program. Consistent with authority under the Energy Policy and 

Conservation Act, NHTSA’s corporate average fuel economy program already provides 

manufacturers with the option to exclude emergency vehicles.8The agencies are 

considering and responding to comments on this proposal, and plan to finalize this rule in 

summer 2012.

 

8

See 49 U.S.C. 32902(e).
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In addition to the above proposed exemption for on-highway engines from GHG 

standards, EPA has provided limited regulatory relief for other types of emergency-use 

engines. First, EPA’s May 6, 2008 final rule adopting Tier 3 and Tier 4 standards for 

marine diesel engines allows for emergency and rescue vessels to meet an earlier, less 

stringent tier of standards under 40 CFR parts 89, 94 and 1042.9 We adopted these 

provisions to avoid compromising engine performance during emergency operation, and 

to ensure that more stringent emission standards did not cause a situation where there 

were no certified engines available for emergency vessels. Such engines are not subject 

to the Tier 4 standards, which generally involve selective catalytic reduction and diesel 

particulate filters. The regulations also allow for meeting less stringent standard if there 

are no suitable engines that are certified to the current standards. 

EPA also adopted limited exemption provisions for emergency rescue equipment 

for small spark-ignition nonroad engines in 1999.10 Under this provision, equipment 

manufacturers needed to demonstrate that no engine models certified to current emission 

standards were available to power the emergency rescue equipment. We recently moved 

this provision to 40 CFR part 1054 and included a variety of elements to clarify and 

improve oversight of the exemption in a later final rule.11 These elements include a 

requirement that the engines meet the most stringent standards feasible (but less than the 

 

9

Final Rule: Control of Emissions of Air Pollution from Locomotives and Marine Compression-Ignition 

Engines Less Than 30 Liters per Cylinder, 73 FR 25098, May 6, 2008, and republished to correct 

typographical errors on June 30, 2008, 73 FR 37096.

10 Final Rule: Phase 2 Emission Standards for New Nonroad Spark-Ignition Nonhandheld Engines at or 

Below 19 Kilowatts, 64 FR 15208, March 30, 1999.

11 Final Rule: Control of Emissions from Nonroad Spark-Ignition Engines and Equipment, 73 FR 59034, 

October 8, 2008.
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current standards for certification) and annual reporting to EPA on the availability of 

compliant engines that meet the needs of other emergency equipment using such engines.

In these rules, EPA recognized that equipment and vessels designed and purposebuilt exclusively for use in emergency equipment have demanding performance 

specifications and in some cases extreme duty cycles. The marine diesel provisions also 

recognize that engines certified to the latest emissions standards requiring emissions 

after-treatment may create some interference with engine performance or effectiveness 

that may be needed in emergency circumstances, when installed in some emergency

equipment or vessels. 

While these provisions do offer limited relief from the latest round of emissions 

standards for these engines, there is a general requirement to use engines meeting the 

most stringent emission standards as practical. There are also additional administrative 

responsibilities related to engine labeling, periodic reporting to EPA, and recordkeeping. 

These provisions in some cases also expire if compliant engines become available that 

can practically be used to provide power for the equipment in question. Furthermore, 

these limited exemption provisions are only applicable to newly certified engines. The 

regulations do not apply these provisions to in-use engines that are certified and deployed 

in emergency equipment.

C. Why is EPA Taking This Action?

EPA is proposing to amend its regulations to facilitate engine manufacturers’ 

design and implementation of reliable and robust emission control systems with 

regeneration strategies and other features that do not interfere with the mission of 
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emergency vehicles. Through the comments and letters we have received, as well as our 

own outreach and data-gathering efforts, we have learned that some emission control 

systems on fire trucks and ambulances today, in particular, certain applications using 

diesel particulate filters, are requiring an unexpected amount of operator interventions, 

and there are currently a nontrivial number of emergency vehicles that are electronically 

programmed to cut power or speed – even while responding to an emergency - when 

certain operational parameters are exceeded in relation to the emission control system. 

As we understand it, the experiences of operators are mixed, with some not reporting any 

problems and some reporting problems that raise public safety and welfare concerns. 

EPA’s standards are performance-based, and reflect the greatest degree of 

emission reduction achievable, according to CAA sections 202(a)(3) and 213(a)(3). Our 

on-highway and nonroad PM standards do not specify the type of diesel particulate filter 

for manufacturers to use, nor do they even mandate the use of such a filter. Our analysis 

of the feasibility of the 2007 on-highway PM standard is presented in Chapter III of the 

final Regulatory Impact Analysis (RIA) for that rule.12 Our analysis of the feasibility of 

the Tier 4 nonroad compression ignition engine standards that will be phasing in through 

2015 is presented in Chapter 4 of that rule’s final RIA.13 For most nonroad engines, these

standards are similar in stringency to the 2007 on-highway heavy-duty engine and vehicle 

standards. As described below in Section VII, these two rules are providing billions of 

 

12 Final Regulatory Impact Analysis for the “2007 Heavy-Duty Highway Rule,” EPA420-R-00-026, 

December 2000. Chapter III, Emissions Standards Feasibility, is available at 

http://www.epa.gov/otaq/highway-diesel/regs/ria-iii.pdf

13 Final Regulatory Impact Analysis for “Control of Emissions from Nonroad Diesel Engines,” EPA420-R04-007, May 2004. Chapter 4, Technologies and Test Procedures for Low-Emission Engines, is available 

http://www.epa.gov/nonroad-diesel/2004fr/420r04007e.pdf
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dollars of annual health benefits by virtually eliminating harmful PM emissions from the 

regulated engines. Even so, EPA is required by sections 202(a)(4)(B) and 213(c) of the 

Act to, among other things, consider methods for reducing risk to public safety and 

welfare associated with the use of emission control devices or systems. 

Based on the information available to us, we have concluded that there is an 

indirect risk to public safety and welfare associated with some examples of emission 

control systems when they are deployed on emergency vehicles that experience extreme 

duty cycles. This indirect risk is related to the readiness of emergency vehicles and the 

risk that they may not be able to respond during emergencies with the full power, torque, 

or speed that the engine is designed to provide. While this risk is not inherent to the 

requirement to reduce emissions or to the use of diesel particulate filters on emergency

vehicles, EPA believes it is appropriate to ensure that emergency vehicles can perform 

their emergency missions without the chance of such consequences. 

EPA’s current rules already provide the opportunity for manufacturers to address 

many issues through applications for certification of new engines and new vehicles. 

There is also currently a mechanism for manufacturers to deploy field modifications to 

the in-use fleet, including those that are substantially similar to approved upgrades for 

new vehicles, as well as those that apply only to vehicles that are no longer in production. 

As manufacturers become aware of the need for upgrades or enhancements, this process 

occurs within the new and in-use fleet with various degrees of application. While that 

process is occurring today, EPA views this issue as serious enough that we would be 

remiss if we did not act to ensure that our regulations clearly offer the needed flexibilities 

for emergency vehicles.
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(1) How Does a DPF Work?

To explain more fully the issues that we are addressing with this action, and hence 

why we are taking this action, we are providing here some background information on 

diesel particulate filters and the process of DPF regeneration. DPF’s are exhaust aftertreatment devices that significantly reduce emissions from diesel-fueled vehicles and 

equipment. DPF’s physically trap PM and remove it from the exhaust stream. Figure 

IV-1 depicts a schematic of a wall-flow monolith style filter, with the black arrows 

indicating exhaust gas laden with particles, and the gray arrows indicating filtered 

exhaust gas. This style of filter is the most common in today’s heavy-duty diesel engines, 

and has very high rates of filtration, in excess of 95 percent.14 

 

14 See Final RIA Chapter III, Note 12, above.
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Figure IV-1 Illustration of air flow pattern in a wall-flow monolith style PM filter 

(Source: Corning)

To be successful, these devices generally must be able to accomplish two things: 

collect PM and clean away accumulated PM. There are two main types of PM that can 

accumulate: combustible and non-combustible, and two very different types of cleaning 

methods: regeneration and ash cleaning. Regeneration occurs relatively frequently, and 

is designed to complete the combustion (oxidation) of the trapped combustible PM 

components, releasing them to the exhaust as gas-phase compounds (mostly H2O and 

CO2). In contrast to the PM that can be oxidized and carried out the tailpipe as gases, the 

non-combustible PM such as metallic ash cannot be destroyed through regeneration and 

will always remain inside a DPF. To clean ash from a DPF, the filter unit is removed 

from the vehicle and professionally cleaned with a special machine. Fortunately, there is 

very little ash formation from modern diesels so ash cleaning and ash disposal occurs 
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very infrequently, generally with at least 150,000 mile service intervals, and the mass of 

accumulated ash is generally small (a few teaspoons).15,16 This distinction is made here 

because the ash cleaning process is not a source of concern that has given rise to this EPA 

action. The infrequent cleaning of noncombustible materials from DPF’s is not part of 

the scope of this action. 

 Regeneration, however, is a type of routine DPF cleaning that must occur 

regularly, and for which EPA does not specify a minimum interval in its regulations, in 

contrast to the ash cleaning process. At its very essence, regeneration involves burning 

off the accumulated soot. Since this burning can involve extra heat and/or oxygen or 

oxygen-containing compounds, this must be done carefully and safely to avoid 

uncontrolled burns. The discussion below in Section IV.C.(1)(b) describes the three 

types of routine DPF regeneration: passive regeneration, automatic active regeneration, 

and manual (parked) active regeneration. A more detailed discussion is provided in a 

memorandum to the docket.17 Before discussing the ways that manufacturers achieve 

regeneration, though, first we discuss the reason why it is needed at all. 

(a) Failure of a DPF

When the style of filter installed on a diesel vehicle is the wall-flow type that is 

predominant in the market today, it physically traps so much of the PM that the particles 

 

15

 EPA’s regulations at 40 CFR 86.004-25(b)(4) for heavy-duty diesel engine maintenance specify a 

minimum interval for DPF ash cleanout from 100,000 to 150,000 mi. Many manufacturers design DPF 

systems with longer maintenance intervals.

16

 See http://www.arb.ca.gov/diesel/tru/documents/ashguide.pdf

17

 See memo dated May 4, 2012, “Diesel Particulate Filter Regeneration,” Docket ID EPA-HQ-OAR2011-1032. 
Page 24 of 125

accumulate on the inside of the filter and if not burned off, this PM can over time block 

the passages through the filtering media, making it more restrictive to exhaust flow. This 

is commonly referred to as “trap plugging.” Some other styles of filter, such as flowthrough DPF’s, are less prone to plugging, but do not generally reduce the PM emission 

rate sufficiently to meet today’s stringent PM standard. Any time something gets in the 

way of free flowing air through an engine, it creates what we call “exhaust backpressure.” 

Even a clean, new DPF generates a small amount of exhaust backpressure due to the 

porous walls through which all of the exhaust flows.

Engines can tolerate a certain range of exhaust backpressure. When an increase in 

this backpressure, or resistance, is detected, engines can compensate to a point. An 

increase in exhaust backpressure from a DPF trapping more and more PM represents 

increased work demanded from the engine to force the exhaust gas through the 

increasingly restrictive DPF. However, unless the DPF is frequently cleansed of the 

trapped PM, this increased work demand can lead to reductions in engine performance

and increases in fuel consumption. This loss in performance may be noticed by the 

vehicle operator in terms of poor acceleration and generally poor drivability of the 

vehicle. 

If a DPF is not regenerated and it becomes plugged, there is a risk of two types of 

failure. The degree of this risk and which consequence may be experienced will depend 

on the engine and emission control system design. One consequence is that the lack of 

air flowing through an engine will cause an engine to shut down because it can no longer 

compensate for the extra work being demanded of it. The other is a risk of catastrophic 

DPF failure when excessive amounts of trapped PM begin to oxidize at high temperatures 
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(i.e., DPF regeneration temperatures above 1,000°C) leading to a “runaway” combustion 

of the PM within the DPF. This can cause temperatures in the filter media to increase 

beyond its physical tolerance, possibly creating high thermal stresses where the DPF 

materials could crack or melt. This is an unsafe condition, presenting physical danger to 

occupants as well as to objects and persons near the vehicle. Further, catastrophic failure 

can allow significant amounts of the diesel PM to pass through the DPF without being 

captured. That is, the DPF is destroyed and PM emission control is lost. For all these 

reasons, most manufacturers generally design their emission control systems to prevent 

uncontrolled shutdown or runaway DPF regeneration by programming the engine’s 

electronic control module (ECM) to limit maximum engine speed, torque and/or power

when excessive backpressures are detected. This mode of engine operation at reduced 

performance may allow a vehicle to “limp home” to receive service. In extreme cases the 

ECM may command the engine to shut down to prevent a catastrophic failure.

(b) Types of Regeneration

There are three types of routine DPF regeneration. Passive regeneration refers to 

methods that rely strictly on the temperatures and constituents normally available in the 

vehicle’s exhaust to oxidize PM from a DPF in a given vehicle application. Passive 

regeneration is an automatic process that occurs without the intervention of an engine’s 

on-board diagnostic and control systems, and often without any operator notice or 

knowledge. Passive regeneration is often a continuous process, because of which, it is 

sometimes referred to as continuous regeneration. In a vehicle whose normal operation 

does not generate temperatures needed for passive DPF regeneration, the system needs a 

little help to clean itself. This process is called active regeneration, and supplemental 
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heat inputs to the exhaust are provided to initiate soot oxidation. There are two types of 

active regeneration: those that may occur automatically either while the vehicle is in 

motion, while idling, or while powering an auxiliary device such as a pump or ladder 

(power take-off (PTO) mode)), and those that must be driver-initiated and occur only 

while the vehicle is stationary and out-of-service. 

Vehicles with automatic active regeneration systems require operators to be alert 

to dashboard lamps and indicators. Written instructions are provided to operators to 

explain what each lamp means (such as high temperatures or need for regeneration) and 

what action is called for (such as driving at highway speeds or initiating a manual active 

regeneration). Because EPA emissions standards are performance based; and therefore, 

do not dictate any required emission control system technologies or configurations, each 

manufacturer has the discretion to program the timing and sequence of lamps as needed 

to inform drivers of the condition of the emission control system. As noted above, it is 

not uncommon in today’s heavy-duty fleet for an engine’s ECM to limit its maximum 

speed, torque or power when a plugging DPF is detected. These engine and emission 

control system protection measures can alert drivers to the need to change driving 

conditions to facilitate automatic active regeneration or to make plans to allow for a 

manual active regeneration.

A manual active regeneration allows the engine’s ECM to increase engine speed 

and exhaust temperature to a greater extent than what is typically allowed during an 

automatic active regeneration. Because the ECM takes full control of an engine during a 

manual active regeneration, the vehicle must remain parked and not used for other 

purposes, such as pumping water in PTO mode. Some manual active regenerations may
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require towing the vehicle to a special service center, and may occur while the DPF is on 

the vehicle, or offline with the DPF removed from the vehicle. In such cases, if a spare 

DPF is not available, the vehicle could be out of service overnight. If a driver disregards 

such warnings, the risk of uncontrolled engine shutdown or a catastrophic DPF failure 

may increase. EPA encourages the design of robust systems calling for minimal driver 

interventions, while providing drivers with clear and early indicators before any 

interventions are needed. EPA also encourages accurate and thorough operator training 

to ensure that the correct remedial action is taken at the earliest available time.

Actively regenerating DPF systems typically require sufficient air flow, 

temperature and soot accumulation before an automatic active regeneration will be 

requested by the engine’s ECM. As mentioned above, this may occur either while the 

vehicle is in motion or parked, if pre-set engine operating conditions are met (such as 

speed and temperature). When the engine’s ECM signals the initiation of an automatic 

active regeneration and the extra heat is generated, an ideal DPF system accomplishes 

this as a transparent process, with no effects perceivable by the driver.

A variety of manufacturer approaches can be taken to produce the supplemental 

heat needed for active regeneration. Diesel engines of MY 2007 or newer often 

incorporate one or more of the following approaches:

 On-board electrical heaters upstream of the filter.

 Air-intake throttling in one or more of the engine cylinders. When necessary, this 

device would limit the amount of air entering the engine, raising the exhaust 

temperature and facilitating regeneration.
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 Exhaust brake activation. When necessary, this device would limit the amount of 

exhaust exiting the engine, raising the exhaust temperature and facilitating 

regeneration.

 Engine speed increases. This approach is sometimes used in combination with the 

other approaches to deliver more heat to the filter to facilitate regeneration.

 Post top-dead-center (TDC) fuel injection. Injecting small amounts of fuel in the 

cylinders of a diesel engine after pistons have reached TDC introduces a small 

amount of unburned fuel in the engine’s exhaust gases. This unburned fuel can then 

be oxidized over an oxidation catalyst upstream of the filter or oxidized over a 

catalyzed particulate filter to combust accumulated particulate matter. 

 Post injection of diesel fuel in the exhaust upstream of an oxidation catalyst and/or 

catalyzed particulate filter. This method serves to generate heat used to combust 

accumulated particulates by oxidizing fuel across a catalyst present on the filter or on 

an oxidation catalyst upstream of the filter

 On-board fuel burners upstream of the filter 18

These are presented here merely as examples, and are by no means a complete list 

of the strategies available to manufacturers when designing engines that use automatic 

active DPF regeneration, though not all may be applicable to all engines. A common 

approach that gets a lot of consumer attention is the use of fuel burners or fuel injection 

strategies. This approach is often called “dosing.” Vehicle owners may notice an 

increase in fuel consumption when driving a vehicle that relies heavily on fuel dosing for 

 

18 MECA Diesel Particulate Filter Maintenance: Current Practices and Experience (June 2005) 

http://www.meca.org/galleries/default-file/Filter_Maintenance_White_Paper_605_final.pdf
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its automatic active regenerations. In this case, when an engine’s ECM gives the signal, 

the doser injects a metered amount of diesel fuel into the exhaust flow (or cylinders), 

which reacts with the DPF catalyst to raise the temperature to a point that enables 

regeneration. EPA does not have information about which manufacturers employ this 

technique or the number or types of vehicles with engines that use fuel dosing as part of 

the active regeneration strategy. Estimates of the additional fuel use by a vehicle whose 

DPF regeneration system employs fuel dosing are described below in Section VII.B. 

This is also mentioned here because one of the possible outcomes of this EPA action is 

that some manufacturers may alter their strategies for automatic active regenerations on 

emergency vehicles, which may have a modest effect on supplemental fuel use due to 

dosing. Further discussion of this is provided below in Section VII.

(2) Why Are Emergency Vehicles Having Problems with DPF Regeneration?

At the time of promulgation of the heavy-duty highway rule, EPA and the engine 

manufacturers expected the 2007-compliant engine emission control systems would be 

integrated with advanced engine controls to ensure DPF regeneration under all vehicle 

operating conditions and environments. While this is widely true today, the experience 

of the rule implementation thus far indicates there are still some exceptions.

Although EPA is aware of a relatively small number of emergency vehicles that 

are experiencing problems with DPF regeneration, of those that are having problems, 

most of the problems can be related to the vehicle’s duty cycle, the ambient conditions, 

and/or the engine’s combustion characteristics. A vehicle’s duty cycle means how it is 

driven, including its speeds, loads, and distances, as well as time out of service and time 
Page 30 of 125

spent idling. A vehicle’s duty cycle can vary by the demographic of the service area, 

including whether the vehicle responds to emergencies in a rural or urban community, 

and whether it drives over flat or hilly terrain. Because DPF regeneration requires heat 

and oxygen (basic ingredients for combustion), the success of DPF regeneration 

strategies can also be influenced by ambient conditions such as extreme cold winter 

temperatures and whether the vehicle operates near sea level or at a high elevation. The 

engine combustion and exhaust characteristics can influence the success of a DPF 

regeneration strategy since parameters such as engine-out NOX and PM emission levels 

can influence how easily the soot can be oxidized, and how much soot needs to be 

oxidized and how often.

Both the engine’s duty cycle and the overall control strategy of the engine’s 

emission control system play a large role in the success of integrating a DPF with an 

engine to control PM emissions. In this section we provide additional discussion of how 

engine combustion characteristics and vehicle duty cycle can lead to DPF regeneration 

problems on emergency vehicles. In Section IV.E, below, we discuss our proposed 

regulatory action to address these issues. While our proposed approach specifically 

targets engine combustion characteristics and emission control system design, we 

encourage emergency vehicle owners to inquire with their dealers and manufacturers 

regarding suitable vehicle and engine options that are appropriate for their duty cycle as 

well as their demographic and geographic location.
Page 31 of 125

(a) Engine Combustion Characteristics

Engine combustion characteristics can be designed to enable continuous passive 

regeneration or to rely heavily on automatic active regeneration. As mentioned above, 

regeneration is a combustion process, burning off the accumulated PM or soot. The PM 

is created because the initial combustion process in the engine was imperfect. To 

completely convert all fuel to CO2 and water, the combustion process needs more heat 

and oxygen. Both of these things create NOX because nitrogen (N2) is naturally present 

in the air and readily oxidizes at high temperatures. Thus there is a NOX-PM trade-off of 

most diesel combustion processes (homogeneous charge compression ignition being an 

exception) where lower combustion temperatures help control NOX but create more PM, 

and higher temperatures that destroy PM (or prevent it from being created) can generate 

more NOX. 

In an engine with a DPF system, combustion settings, or calibrations that enable 

continuous passive regeneration, tend to be those with higher engine-out NOX and lower 

engine-out PM, partly because of the higher temperatures that create the NOX, partly 

because of the NOX itself that can act as an oxidizer (to burn off soot), and partly because 

of the lighter soot loading rate. In contrast, engine calibrations that may lead to a heavy 

reliance on automatic active regeneration tend to be those with lower engine-out NOX and 

higher engine-out PM, partly because of the lower temperatures, partly because of a lack 

of helpful NOX, and partly because of a heavier soot loading rate. Note that “engine-out” 

means emissions upstream of any after-treatment cleaning devices such as DPF or SCR. 

An example of a DPF system that may rely almost exclusively on active regeneration to 

maintain a clean PM filter, from an engine calibration perspective, would be an engine 
Page 32 of 125

using advanced exhaust gas recirculation, because it would have very low engine-out 

NOX and relatively high engine-out PM. An example of a DPF system that may rarely 

experience automatic active regeneration (and frequently passively regenerate), from an 

engine calibration perspective, would be an engine using SCR to control NOX, because it 

could have comparatively high engine-out NOX and relatively low engine-out PM. The 

SCR after-treatment would then reduce the high engine-out NOX to provide very low 

tailpipe NOX.

Thus it is important to note that this NOX-PM trade-off is a critical design 

parameter when developing an engine that will be successfully integrated with a DPFequipped emission control system. To date, all of the concerns expressed to EPA 

regarding emergency vehicles with DPF regeneration issues have been for vehicles that 

do not employ SCR technology, and thus may have higher engine-out PM. The 

differences in engine combustion characteristics of the MY 2007 vehicles compared to 

those of the majority of MY 2010+ vehicles support the concept that the emergency

vehicle fleet may experience fewer DPF regeneration troubles as it migrates to engines 

that use after-treatment to meet EPA’s 2010 NOX standards. Such a trend may indicate 

that some engine manufacturers may see a greater need to address in-use emergency

vehicles than new vehicles.

(b) Duty Cycles

As noted above, the duty cycle of a vehicle is one of the factors that influences 

how often the DPF regenerates passively or actively. It is important to note that all DPF 

systems with active regeneration components also have the capability to passively
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oxidize soot accumulated on the filter, though some of the above-described factors may

inhibit successful passive regeneration. Operation at highway speeds and high engine 

loads (high load means demanding more work from the engine, such as accelerating, 

driving uphill or carrying heavy cargo) typically leads to successful passive regeneration 

of a DPF. An example from a duty-cycle perspective of a vehicle that frequently

experiences automatic passive regeneration would be a long-haul tractor-trailer. There is 

also often a threshold of speed or load that is required for automatic active regeneration 

strategies as well, though not as great as for passive regeneration – often at least 5 

miles/hour or parked with a PTO engaged. In some vehicles, passive regeneration occurs 

so rarely that a DPF system relies almost exclusively on active regenerations to maintain 

a clean PM filter. An example of this from a duty-cycle perspective would be a vehicle 

that operates at idle, low speed and low load over most of its duty cycle. Many

emergency vehicles fall into this category.

It is possible to collect duty cycle data from trucks by extracting information that 

is broadcast by the engine’s ECM. ECM’s broadcast information such as engine speed, 

load, temperature, DPF backpressure, and many other parameters relevant to engine 

operation. In 2004 the Fire Apparatus Manufacturers Association conducted a datacollection project, downloading logged data from emergency vehicles in use across the 

United States, to document duty cycles and engine conditions typically experienced in the 

emergency fleet, including pumpers, aerials, and rescue vehicles in urban, suburban and 

rural communities.19 The 2004 FAMA data set includes 26 service months of data from 

51 pumper trucks, 31 service months of data from 21 aerial trucks, and 14 service months 

of data from 4 rescue vehicles. Overall, the data reveal that emergency vehicles in urban 

centers log more hours than vehicles in suburban or rural areas, with the urban and 

suburban vehicles logging over five and four times the average rural engine hours, 

respectively, on an annual basis. This demographic data could be helpful to fleet 

managers who wish to understand why they have or have not experienced certain troubles 

with their vehicles. The data also indicate that vehicles with PTO capability (pumpers 

 

19 Fire Apparatus Manufacturer’s Association, Fire Apparatus Duty Cycle White Paper, August 2004, 

available at http://www.deepriverct.us/firehousestudy/reports/Apparatus-Duty-Cycle.pdf
Page 34 of 125

and aerials) operate in PTO mode on average about 10 percent of their operating time. 

Further, the data indicate the vast majority of emergency fleet operation is at loads below 

10 percent of maximum capacity and engine speeds below 1,000 rpm. Data of this type 

could be helpful to engine manufacturers who may wish to assure that their emission 

control system designs will be successful for a given application. For the vehicles from 

which operating data were collected, FAMA determined an average engine load using the 

total horsepower, percent load, and percent time at load. Table IV-1 presents a summary

of the engine load data compiled in FAMA’s study. 

Table IV-2 presents operating data by both vehicle type and demographic, and 

Table IV-3 presents an overview of the data by vehicle type.
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Table IV-1 FAMA Engine Load Data

Apparatus Type Capacity Range in 

Study

Population Average 

Percent Running Load

Pumper 315-500 hp 18 %

Aerial 170-500 hp 30 %

Rescue 350-500 hp 20 %

Table IV-2 FAMA Duty Cycle Data by Demographic

Service 

Area

Operating Condition Pumper Aerial Rescue Service 

Area 

Average

Rural Engine Hours (Avg Annual) 301 204 301 295

PTO Hours (Avg Annual) 70 63 - -

Low Speed (% Time < 1,000 

RPM)

63 73 51 62a

Medium Speed (% Time 1,000 < 

RPM < 1,800)

27 19 42 29a

High Speed (% Time > 1,800 

RPM)

11 9 7 9

a

Low Load (% Time < 10%) 61 83 59 68a

Medium Load (% Time 10% < 

Load < 90%)

36 11 39 29a

High Load (% Time > 90%) 3 6 2 4

a

Suburban Engine Hours (Avg Annual) 1364 1133 367 1272

PTO Hours (Avg Annual) 168 123b- -

Low Speed (% Time < 1,000 

RPM)

71 68 77 72a

Medium Speed (% Time 1,000 < 

RPM < 1,800)

23 27 17 22a

High Speed (% Time > 1,800 

RPM)

6 5 7 6

a

Low Load (% Time < 10%) 54 37 78 56a

Medium Load (% Time 10% < 

Load < 90%)

44 58 22 41a

High Load (% Time > 90%) 3 5 0 3

a

Urban Engine Hours (Avg Annual) 1107 2379 1686 1681

PTO Hours (Avg Annual) 93 213b- -

Low Speed (% Time < 1,000 

RPM)

62 73 57 64a

Medium Speed (% Time 1,000 < 

RPM < 1,800)

32 22 32 29a
Page 36 of 125

High Speed (% Time > 1,800 

RPM)

5 5 11 7

a

Low Load (% Time < 10%) 73 53 44 57a

Medium Load (% Time 10% < 

Load < 90%)

24 42 51 39a

High Load (% Time > 90%) 3 5 5 4

a

Notes:

a

Straight average by EPA from summary results. Other values in this table are weighted 

averages compiled by FAMA using individual vehicle data

b

Includes both pumping and aerial operating hours

Table IV-3 FAMA Duty Cycle Data by Vehicle Type

Operating Condition Pumper Class 

Average

Aerial Class 

Average

Rescue Class 

Average

Fleet Average

Engine Hours (Avg Annual) 924a1239a785a1244

PTO Hours (Avg Annual) 117b- -

Low Speed (% Time < 1,000 

RPM) 66 71 61 67

Medium Speed (% Time 1,000 

< RPM < 1,800) 27 23 30 26

High Speed (% Time > 1,800 

RPM) 7 5 9 7

Low Load (% Time < 10%) 62 50 56 58

Medium Load (% Time 10% < 

Load < 90%) 35 45 41 38

High Load (% Time > 90%) 3 5 3 3

Notes:

a

Straight average by EPA from summary results. Other values in this table are weighted 

averages compiled by FAMA using individual vehicle data

b

Includes only pumping hours. Aerial operating hours averaged 69 hours per year.

We can see from this study that engines on emergency vehicles across the country

are commonly operated over duty cycles that offer very limited opportunities to 

regenerate DPF’s. It is also important to note that emergency vehicles do not typically 

get deployed on planned duty schedules with predictable blocks of garage time for 

servicing or maintenance. While some other types of vocational vehicles may have duty 

cycles with many characteristics similar to those shown above, emergency vehicles are 
Page 37 of 125

unique in their need to be ready to deploy at any moment for the purpose of protecting 

public safety and welfare by saving human lives that may be in immediate danger.

When trucks with an engine-driven PTO are working in a stationary PTO mode, 

some engines achieve the conditions to enable an automatic active regeneration during 

this time. While this is normally designed to be a transparent process, in practice some 

effects of this type of regeneration have been noticed by operators. EPA has received 

information from fire chiefs indicating that there have been instances where engine 

ECM’s took control from the operator during water pumping operations. When an 

automatic active regeneration is initiated during a water pumping operation, for example, 

an ECM may be programmed to alter throttle position or engine speed to achieve the 

conditions needed to complete an automatic active regeneration. Depending on the 

design of the water pumping system’s pressure regulation, this may in turn affect the 

water pressure in the fire hoses. EPA has not heard of this occurring on a widespread 

basis, and has reason to believe that affected engine and truck manufacturers have 

identified and corrected this issue on some vehicles. EPA’s current regulations already 

allow manufacturers to develop and request EPA approval for certification of engines 

with emission control strategies where the process of undergoing automatic active 

regeneration would not interfere with safely pumping fire suppressant. EPA requests 

comment on whether any EPA action should be taken to explicitly address this situation 

beyond what we are already proposing in this action.

While not addressed directly in this proposed action, there are technologies that 

could be implemented to decrease the amount of time emergency vehicles spend with 

their main engines operating at light loads and at idle. These technologies include 
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electronically programmed automatic engine start/stop systems and hybrids. Automatic 

start/stop systems automatically stop and start an engine depending upon whether or not 

it is needed to supply power to the vehicle. This technology is already being 

implemented on other heavy-duty vehicles to decrease unnecessary engine idling. Hybrid 

drivetrains also decrease engine idling with an integrated alternate power source such as a 

battery. We are currently seeing an increase in the use of hybrid technologies in heavyduty diesel vocational vehicles. Garbage trucks, utility company trucks, and other work 

trucks are using hybrid technology to power on-board hydraulic systems and cab heating 

and cooling systems. In conventional vehicles these systems are powered by a main 

engine typically operating at light load or at idle. Because automatic start/stop and 

hybrid technologies improve fuel economy and decrease greenhouse gas emissions, we 

believe that they will be used in more and more vehicles in the future. We believe there 

is potential for these technologies to be integrated into future designs of emergency

vehicles to decrease their operation at light loads and at idle. Such technologies would 

not only improve fuel economy and decrease greenhouse gas emissions from emergency

vehicles, they would also help to prevent their diesel particulate filters from becoming 

plugged due to excessive operation at light loads and at idle. While we are not proposing 

any specific action at this time related to decreasing the amount of time emergency

vehicles operate at light load or at idle, we request comment on the potential for 

application of alternate power sources and idle reduction technologies on emergency

vehicles.
Page 39 of 125

(3) What Are the Concerns for Emergency Vehicles Using SCR?

Selective Catalytic Reduction (SCR) is an exhaust after-treatment system used to 

control NOX emissions from heavy-duty engines by converting NOX into nitrogen (N2) 

and water (H2O). The technology depends on the use of a catalytic converter and a 

chemical reducing agent, which generally is in an aqueous urea solution, and is often 

referred to as diesel exhaust fluid (DEF). Some trade names for this chemical reductant 

include AdBlue, BlueDef, NOxBlue, and TerraCair.

Most engine manufacturers chose to comply with the 2010 NOX emission 

standard by adding SCR to their engine models. In general, the approach with an SCR 

system has been a sound and cost effective pathway to comply with EPA’s 2010 

emissions standards, and it is the primary path being used today. 

DEF is injected into the exhaust upstream of the SCR catalyst where it forms 

ammonia and carbon dioxide. The ammonia then reacts with NO and NO2, so that one 

molecule of urea can reduce two molecules of NO or one molecule of NO2. A robust 

SCR system can achieve about 90 percent reduction in cycle-weighted NOX emissions. 

Improvements have been made over the last several years to improve the NOX conversion 

rate and reduce the impact of lower exhaust temperatures on the conversion efficiency.

Because an SCR system is only effective when DEF is injected into the exhaust, 

we consider refilling a vehicle’s DEF tank to be a critical emission-related engine 

maintenance requirement. We are taking action elsewhere in this notice (See Section V) 

to establish this in our regulations. Therefore, manufacturers have implemented a number 

of strategies to induce a vehicle operator to refill a vehicle’s DEF tank when needed. 
Page 40 of 125

These operator inducements generally include first illuminating one or more dashboard 

lights to warn the operator that the DEF tank needs to be refilled soon. However, if such 

initial inducements are persistently ignored by the vehicle operator, eventually additional 

inducements are typically activated that decrease the maximum speed or power of the 

vehicle. These additional inducements are intended to create conditions making 

operational conditions of the vehicle increasingly unacceptable if the initial dashboard 

lamp illumination inducements are persistently ignored. Similar inducements may occur 

in cases where DEF quality does not meet system specifications, or if the SCR system is 

not functioning correctly for another reason.

While decreasing vehicle performance can be an effective inducement strategy, 

we believe it may not be appropriate in all situations for emergency vehicles because of 

their special need to be ready at any moment for the purpose of protecting public safety 

and welfare by saving human lives that may be in immediate danger. We recognized this 

during the initial implementation of our 2010 NOX standards, and we worked with the 

Fire Apparatus Manufacturers’ Association (FAMA), the Ambulance Manufacturers 

Division of the National Truck Equipment Manufacturers Association, and the 

International Association of Fire Chiefs to support the publication of a May 18, 2010 

memo that instructed emergency vehicle manufacturers and engine manufacturers to 

implement less severe inducement strategies for emergency vehicles.20 In this proposal 

we are taking additional steps so that emergency vehicle manufacturers and engine 

manufacturers have the option to further reduce the severity or eliminate altogether any 

 

20 FAMA 2010, Emergency Vehicle SCR and DEF Inducement Guidelines; 2010 Engine Emissions 

Control Requirements
Page 41 of 125

performance related inducements that are or could be implemented on emergency

vehicles and their engines during emergency situations. We believe that this additional 

flexibility will help to prevent any abnormal condition of a vehicle’s emission control 

system from adversely affecting the speed, torque, or power of an emergency vehicle 

during emergency situations.

D. What Would Occur if EPA Took No Action?

(1) The Industry Would Continue to Get Smarter

Improving the components of diesel particulate filters is the current subject of 

research and development activities within the automotive and air pollution control 

industries. Aspects that are being improved include filter ash storage capacity, filter 

pressure drop, substrate durability, catalyst activity, as well as other physical and 

chemical properties that can optimize the device for heavy-duty vehicle applications. 

Engine manufacturers have taken a systems approach, optimizing the engine with 

its after-treatment system to realize the best overall performance possible. Manufacturers 

can manage the functioning of the emission control system by adjusting parameters such 

as the thermal profile of the after-treatment system, the exhaust gas chemical 

composition, the rate of consumption of DEF, the rate of particle deposition, and the 

conditions under which DPF regenerations (soot cleaning) may occur.

In a broad and general sense, the trend is that DPF’s are slowly becoming even 

more robust without EPA intervention. Future DPF’s will need fewer total regenerations 

during the useful life of the engine and control system, more passive and fewer active 

regenerations will occur, and manual regenerations will become rarer. 
Page 42 of 125

In addition, vehicle operators and fleet managers will continue to become more 

experienced with this new generation of sophisticated electronically-controlled vehicles. 

Manufacturers across the country are providing training on actions fleet managers can 

take to decrease problems with DPF regenerations. These actions include:

 Use low-ash engine oils

 Avoid extended idling

 Maintain insulation on the exhaust pipe

 Maintain the crankcase filter

 Periodically operate a vehicle at higher speeds and loads

The Technology & Maintenance Council (TMC) of the American Trucking 

Associations conducted a survey in late 2011 to compare user experiences between EPA 

2010, EPA 2007, and EPA 2004 vintage trucks. 21 According to TMC, 72 percent of the 

survey respondents indicated that driver understanding of the 2007-vintage aftertreatment system was worse than driver understanding of the 2004-vintage aftertreatment system, and 33 percent of respondents indicated that driver understanding of 

the 2010-vintage after-treatment system was worse than driver understanding of the 

2007-vintage after-treatment system. The responses regarding driver understanding of 

fault codes and dash lamps indicated that drivers have 69 percent poorer understanding of 

2007 vs. 2004 fault codes and dash lamps, and 50 percent poorer understanding of 2010 

 

21 American Trucking Associations, Technology & Maintenance Council, S3 Engine Study Group. Survey

conducted Fall 2011, public slides dated February 2012 available at 

http://www.truckline.com/Federation/Councils/TMC/Documents/2012%20Annual%20Meeting%20and%2

0Exhibition%20Documents/TMC12A_TECH2.pdf
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vs. 2007 fault codes and dash lamps. We expect that this education component will 

gradually improve over time without EPA intervention.

(2) The Fleet Would Continue to Migrate to the 2010 Standards 

Vehicles with 2010-compliant heavy-duty diesel engines tend to place different 

demands on their DPF systems than pre-2010 vehicles. With the addition of NOX aftertreatment such as SCR, engines may be tuned to emit lower engine-out PM (recall the 

NOX-PM trade-off described above). When an SCR system is integrated, it provides the 

opportunity to run an engine at lower soot levels and elevated levels of NO2, which is a 

chemical species that efficiently oxidizes the soot in the absence of elevated 

temperatures. It is EPA’s expectation that vehicles of MY 2010 and beyond, particularly 

those using SCR, will generally experience fewer troubles with DPF’s than the earlier 

model year vehicles, due to the nature of the on-board technology as well as the many

years of experience gained by manufacturers since 2007. The 2011 TMC survey

included an assessment of relative satisfaction levels between EPA 2010, EPA 2007, and 

EPA 2004 vintage trucks. The survey results indicate that after-treatment durability is 

better with EPA 2010 trucks compared to EPA 2007 trucks, with less time out of 

service.22 As an illustration, according to a Volvo product brochure, the company’s EPA 

2010-compliant trucks eliminate the need for active DPF regeneration, reducing driver 

 

22 See ATA/TMC, Note 21.
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involvement with the emission control system, using a design that allows for the DPF 

system to reliably oxidize accumulated soot using continuous passive regeneration.23

(3) Some Trucks Would Continue to Experience Problems

Even though such trends would indicate that instances of emergency vehicles 

experiencing difficulty managing regeneration of DPF’s would decrease, in the absence 

of this EPA action, some vehicles would be likely to continue to experience some 

problems. 

EPA has learned that some engine manufacturers have disabled these engine 

protection measures on some emergency vehicles. In these cases the manufacturer has 

reasoned that an operator should be allowed to remain in control of an emergency vehicle 

even facing risk of catastrophic failure, with the consequences of that failure being less 

severe than the consequences of the vehicle prematurely losing power, torque and/or 

speed while performing emergency services.

Without a clear action from EPA to provide the regulatory flexibility needed for 

swift deployment of robust remedies throughout the emergency vehicle fleet, 

implementation of best practices could be inconsistent, insufficient, or even impossible 

due to regulatory constraints. Some vehicles would continue to experience frequent 

plugging of DPF’s, frequent forced filter regenerations, and reduced engine power, speed 

or torque that diminish the ability of first responders to save lives and property. There 

 

23 See Volvo 2010 product brochure, “Volvo’s SCR No Regen Engine,” available at 

http://www.volvotrucks.com/SiteCollectionDocuments/VTNA_Tree/ILF/Products/2010/09-

VTM075_NoRegen_SS_041609.pdf
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would also remain a heightened risk that an emergency vehicle could be taken out of 

service when it is most needed.

E. Proposed Regulatory Action

As described above in Section IV.C, many DPF-equipped vehicles include engine 

controls and driver alerts that lead to decreases in maximum speed, torque, or power 

when DPF backpressure exceeds normal levels, as protective measures for either the 

engine or the DPF, or as inducements for the operator to immediately conduct DPF 

regeneration. Similarly, vehicles equipped with selective catalytic reduction (SCR) 

systems for NOX reduction currently have engine controls and driver alerts that lead to 

eventual loss of speed, torque, or power when the SCR controls detect abnormal 

conditions (such as a malfunction, low DEF levels, etc.), as inducements to take 

immediate corrective action to allow the SCR to function normally. In most vehicles, 

these alerts and inducements may be easily avoided with normal driving and routine 

maintenance, and if activated, these inducements would not have any significant effect on 

public safety and welfare. In emergency vehicles, however, should any of these limits on 

maximum speed, torque, or power occur while a vehicle is responding to an emergency, 

it could be a matter of life or death. To address these issues that could otherwise limit the 

maximum speed, torque or power of an emergency vehicle’s engine when it is needed 

most, EPA is proposing to amend 40 CFR part 86 to revise the definition of defeat 

device; add new definitions of emergency vehicle, ambulance and fire truck; and add new 

labeling requirements for new on-highway engines with approved Auxiliary Emission 

Control Devices for emergency vehicles. EPA is also amending its regulations at 40 CFR 

part 1039 to revise the definition of defeat device, add a new definition of emergency
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equipment, and add a new labeling requirement for nonroad engines with approved 

Auxiliary Emission Control Devices for emergency equipment.

In our current regulations, engine manufacturers may request as part of an 

application for new engine or vehicle certification, and EPA may approve, Auxiliary

Emission Control Devices, if they are not determined to be “defeat devices.” Auxiliary

Emission Control Devices, or AECD’s, are any design element of an engine’s emission 

control system that senses temperature, vehicle speed, engine RPM, transmission gear, 

manifold vacuum, or any other parameter for the purpose of activating, modulating, 

delaying, or deactivating the operation of any part of the emission control system.24 

Some AECD’s can temporarily decrease the effectiveness of an emission control system. 

This type of AECD is only permitted in very limited situations, for example, when such 

excursions are deemed to be necessary in order to protect the vehicle, engine, and or 

emission control system during limited modes of operation.

A defeat device is a type of AECD that reduces the effectiveness of vehicle 

emission controls in situations when such reduction in effectiveness is not approved or 

permitted by EPA. Defeat devices are not permitted by the Clean Air Act or EPA. 

Approvals of AECD’s are made by EPA on a case-by-case basis. In applications 

for engine certification, manufacturers must include a detailed description of each AECD 

to be installed in or on any vehicle (or engine) covered by the application, as well as a 

detailed justification of each AECD that results in a reduction in effectiveness of the 

 

24 See 40 CFR 86.082-2 
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emission control system. According to 40 CFR 86.094-21(b)(1)(i)(B), EPA may

disapprove a request for an AECD based on consideration of currently available 

technology. Use of an unauthorized or disapproved AECD can be considered a violation 

of section 203 of the Act.25

In this action, EPA is proposing to revise the definition of defeat device at 40 CFR 

86.004-2, 86.1803-01, and 40 CFR 1039.115 to exclude AECD’s that apply only for 

engines on emergency vehicles, where the need for an AECD is justified in terms of 

preventing the vehicle or equipment from losing speed, torque, or power due to abnormal 

conditions of the emission control system, or in terms of preventing such abnormal 

conditions from occurring during operation related to emergency response.

In this action, EPA is proposing to define an emergency vehicle as a vehicle that is 

an ambulance or a fire truck. EPA is proposing to adopt a definition of ambulance

consistent with the current U.S. General Services Administration Star of Life 

specification.26 EPA is proposing to define fire truck as a vehicle designed to be used 

under emergency conditions to transport personnel and equipment and to support the 

suppression of fires and mitigation of other hazardous situations, consistent with the 

scope of standards for automotive fire apparatus issued by the National Fire Protection 

Association.27 We are defining emergency equipment as specialized vehicles to perform 

 

25 See 40 CFR 86.094-21 and 094-22

26 U.S. General Services Administration, Federal Specification for the Star-of-Life Ambulance, August 1, 

2007, http://www.deltaveh.com/f.pdf.

27 See National Fire Protection Association web page. Accessed April 2012 at 

http://www.nfpa.org/catalog/product.asp?title=Code-1901-2009-Automotive-FireApparatus&category%5Fname=&pid=190109&target%5Fpid=190109&src%5Fpid=&link%5Ftype=search

&icid=
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aircraft rescue and firefighting functions at airports, or wildland fire apparatus. With 

these definitions, it is EPA’s intent to include vehicles that are purpose-built and 

exclusively dedicated to firefighting, emergency/rescue medical transport, and/or 

performing other rescue or emergency personnel or equipment transport functions related 

to saving lives and reducing injuries coincident with fires and other hazardous situations. 

EPA requests comment on whether we should refine or expand our definition of 

emergency vehicle within the scope of this action to include those equipped with heavyduty diesel engines that serve other civilian rescue, law enforcement or emergency

response functions. We are especially interested in information regarding instances of 

such vehicles experiencing or risking loss of power, speed or torque due to abnormal 

conditions of the emission control system, and how that may inhibit mission-critical lifeand property-saving work. 

EPA is also proposing an associated engine labeling requirement so that engines 

with approved emergency vehicle AECD’s would be clearly identified and distinguished 

from other similar engines.

As mentioned above in Section IV.C, some engine manufacturers currently 

specify that when an engine is sold for installation in an emergency vehicle, some of the 

default power, torque or speed inducements be de-activated or set to alternate, less severe 

settings. In such applications, when the DPF system requests regeneration, the warning 

lights remain illuminated while the vehicle remains in complete control of the driver. In 

these cases the manufacturer has likely reasoned that the consequences of catastrophic 

failure would be less severe than the consequences of the vehicle prematurely losing 
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power, torque and/or speed while performing emergency services. EPA has granted 

related AECD’s in the past.

However, without the proposed optional flexibilities provided by EPA in this 

action, manufacturers could be prevented from implementing truly failsafe solutions for 

all affected vehicles. For example, while current custom solutions may allow an 

emergency vehicle to continue pumping water or transporting a person to safety, its DPF 

would continue to accumulate particles and the risk of catastrophic failure would 

increase.

In this action, EPA is proposing amendments so that manufacturers could apply

for (and EPA could approve) AECD’s that would be justified in terms of preventing the 

occurrence of abnormal conditions of the emission control systems for emergency

vehicles or in terms of preventing the engines from losing speed, torque, or power due to 

such abnormal conditions. In this context, EPA would consider abnormal conditions to 

be parameters outside normal ranges for proper operation, such as excessive exhaust 

backpressure from high soot loading on a DPF or insufficient DEF for use with an SCR 

system. 

EPA is encouraging manufacturers to apply for AECD’s that are tailored for 

engines on emergency vehicles, considering the duty cycle information presented above 

in Section IV.C(2)(b) along with any other information needed to design failsafe 

emission control systems for new emergency vehicles. EPA is also encouraging 

manufacturers to design field modifications to address these issues on in-use emergency
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vehicles, including those whose engines are no longer in production. Further discussion 

of field modifications is provided below in Section IV.F(2).

To achieve these goals, EPA understands that increased flexibility would be 

needed because EPA’s strict NOX and PM standards present many design constraints. 

Below we describe some solutions that EPA believes it could approve as part of an 

emergency vehicle AECD or field modification, as proposed. Upon adoption of these 

amendments, EPA would encourage requests by engine manufacturers for emergency

vehicle AECD’s and/or field modifications for in-use emergency vehicles for which 

service disruptions related to abnormal conditions of emission control systems may occur 

or have occurred. EPA suggests that such AECD’s or field modifications could include, 

but are not limited to, one or more of the following strategies:

(1) Liberalized Regeneration Requests

It is current practice that most modern diesel engine ECM’s are set to initiate an 

automatic active regeneration only above a designated DPF soot load, and those vehicles 

equipped with manual regeneration switches are set to not allow the option of initiating 

manual active regeneration until an even greater soot load is detected. The reason why 

manufacturers do this is related to certification of engine families and vehicle test groups. 

If manufacturers can limit the frequency of regenerations by design, then they can be 

assured that average emissions will remain below the certified average emission level. 

Excess regenerations could lead to higher average emissions, since some exhaust 

emissions increase during regeneration. Particularly for engines not equipped with SCR 

systems, NOX emissions can increase by an order of magnitude during regeneration, and 

these temporary increases in emission are accounted for in EPA’s certification process. 
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See Section VII, below, for more information about the emissions impacts of DPF 

regenerations. In addition, excess regenerations could shorten the useful life of the DPF 

system since high temperatures place stress on filter substrates. 

EPA believes that emergency vehicle AECD’s that enable more frequent 

automatic active and manual active DPF regenerations, associated with a wider range of 

soot loads could improve the reliability of DPF systems without significantly

compromising emissions reductions or durability. As explained below Section IV.F(4), 

EPA does not expect this provision to affect other aspects of certification. For 

emergency vehicles with approved AECD’s that involve changes in the frequency of 

regeneration, EPA proposes that the resulting increase in NOX emissions not be counted 

against certification levels for applicable engine families or vehicle test groups. 

Furthermore, EPA proposes that emissions certification testing be conducted with any 

approved AECD’s for emergency vehicle or equipment deactivated. According to EPA’s 

current engine certification data, engines from MYs 2008 and 2011 have an average 

maximum automatic active regeneration frequency near 20 percent, with the typical 

frequency between three and seven percent. Those with frequencies near zero rely almost

exclusively on passive regeneration.28 EPA requests comment on whether an option for 

more frequent automatic active and/or manual active DPF regenerations for emergency

vehicles would be beneficial for reliability of those DPF systems, and whether EPA 

should apply any constraints on the frequency of manual active DPF regenerations when 

approving AECD’s for emergency vehicles. 

 

28 Frequency in percent refers to the fraction of engine test cycles during which an automatic active 

regeneration occurs.
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(2) Engine Recalibration 

As mentioned above, in-cylinder combustion chemistry dictates a NOX-PM tradeoff where engines calibrated to reduce in-cylinder NOX tend to have higher PM levels. 

These factors lead to higher rates of particle accumulation and lower rates of particle 

oxidation on filters. EPA believes that AECD’s that incorporate engine calibration 

modifications could enable operation in a “low soot mode” with a reduced rate of particle 

deposition that would lead to more frequent and effective passive regenerations. Such 

calibration modifications could also extend the operating time between all types of 

regenerations, improve active regeneration effectiveness, and boost reliability of the DPF 

systems. On engines with downstream (i.e., SCR) NOX controls, SCR control could be 

modulated such that engine recalibration would not significantly affect NOX emissions. 

On engines without downstream NOX controls, EPA believes that some degree of 

increased NOX emissions during the conditions justified by the AECD would be 

approvable for emergency vehicles. As explained below in Section IV.F(4), EPA does 

not expect this provision to affect other aspects of certification. When manufacturers 

calculate the average NOX emissions during a test cycle, they incorporate data regarding 

both the frequency of regeneration and the increase in NOX emissions during 

regeneration. For emergency vehicles with approved AECD’s that involve recalibration 

to alter regeneration frequency or average NOX emissions, EPA proposes that the 

resulting increase in NOX emissions not be counted against certification levels for 

applicable engine families or vehicle test groups. Furthermore, EPA proposes that 

emissions certification testing be conducted with any approved AECD’s for emergency

vehicle or equipment deactivated. A discussion of the estimated emissions impacts of 

recalibration is found below in Section VII.B. EPA requests comments on whether an 
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upper limit of average NOX emissions - considering regeneration frequency and duration, 

peak NOX emission rate, and operating conditions under which the AECD is triggered -

should be established as part of the implementation of this AECD option, and what levels 

may be appropriate.

(3) Backpressure Relief

It is EPA’s objective that all of our clean diesel emissions standards be 

implemented with reliable technologies that require a minimum amount of driver 

intervention and do not compromise the utility of vehicles. EPA understands that 

manufacturers are motivated to seek design solutions that are cost effective and easily 

deployable. However, by focusing solely on preventive measures such as those described 

above, manufacturers may not achieve a completely failsafe DPF strategy on all 

emergency vehicles. EPA anticipates that some vehicles may benefit from an additional 

failsafe measure that relieves engine exhaust backpressure as a last resort to prevent loss 

of engine speed, torque or power. There are products on the market today that could be 

configured to temporarily relieve excessive engine exhaust backpressure when detected, 

then return the system to normal at the instant that backpressure returns to a safe level. 

Such a device may be justified as a failsafe measure, and may be included as part of an 

overall strategy that also includes preventive measures, if justified and properly limited, 

where excess PM emissions would be expected to be emitted only during a small fraction 

of vehicle operation. That is, the vast majority of DPF operating cycles would be 

expected to have continuous PM emission control, while any temporary backpressure 

relief that reduced PM control or allowed bypass of controls would be expected relatively

infrequently. EPA requests comment on whether a failsafe measure to provide engine 
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exhaust backpressure relief should be available as an approvable AECD option, and what 

constraints, if any, should be established for this option.

F. What Engines and Vehicles Would be Affected?

Today’s proposal would apply to new and in-use fire trucks and ambulances, new 

and in-use airport fire apparatus and wildland fire apparatus, and heavy-duty diesel 

engines on these emergency vehicles and equipment.

(1) Newly Certified Engines and Vehicles

Of those new diesel engines covered by EPA’s current heavy-duty diesel 

standards, only those installed in vehicles or equipment meeting the definition of 

emergency vehicle or emergency equipment would be eligible to obtain an approved 

AECD of the type discussed above in Section IV.E. Where a vehicle is chassis-certified 

and either sold as an incomplete vehicle to a truck body manufacturer or built and sold as 

a complete vehicle, only those sold and built as emergency vehicles would be eligible to 

obtain an approved AECD of the type discussed above in Section IV.E.

(2) Certified Engines and Vehicles In-Use

To address in-use engines and vehicles, EPA proposes to allow engine and 

vehicle manufacturers to submit requests for EPA approval of Emergency Vehicle Field 

Modifications (EVFMs) for on-highway emergency vehicles and Emergency Equipment 

Field Modifications (EEFMs) for nonroad emergency equipment. EVFMs and EEFMs 

would be modifications to existing hardware and software to be installed on in-use 

vehicles or equipment to prevent loss of speed, torque, or power due to abnormal 
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conditions of emission control systems, or to prevent such abnormal conditions from 

occurring, during vehicle or equipment operation related to emergency response. EPA 

proposes to use an approval process similar to the process that is currently utilized to 

submit modifications to current applications for certification, also known as “running 

changes.” The information submitted by a manufacturer to EPA as part of this request 

and approval process would be similar to the information submitted for emergency 

vehicle or equipment AECD’s.

 It is important to emphasize that this proposal would allow only those approved 

modifications to be deployed by manufacturers and their authorized dealers. 

Modifications made by end users are not generally approvable; rather the tampering 

prohibitions would generally apply to such modifications.

EPA has identified three types of field modifications that would be permitted for 

emergency vehicles and emergency equipment under the proposed regulations, based on 

the extent to which the modification is being incorporated into new production vehicles 

and equipment. The three types are: 

 Type A: Any field modification that is a change to a certified vehicle (i.e., a 

vehicle, engine or equipment covered by a certificate of conformity) that is 

identical in all respects to a running change that is approved for incorporation in 

new vehicles by the manufacturer. Where the running change was approved by

EPA for implementation only in conjunction with certain other running changes, 

the field modification may be considered to be a Type A field modification only if 

implemented under the same constraints. 
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 Type B: Any field modification that is not identical in all respects to, but provides 

for essentially the same purpose as, a running change that is being incorporated in 

new vehicles by the manufacturer or that would have been incorporated if the 

vehicle were still in production. A Type B field modification is used when it is not 

practical to incorporate the exact running change in vehicles that have left the 

assembly line, or when the vehicles are no longer in production.

 Type C: Any field modification that is made selectively only to vehicles which 

have left the assembly line and which would not have been incorporated on the 

assembly line. For example, this would apply when making a field modification 

to a vehicle that is no longer in production where there are no similar vehicles in 

production.

The amount of justification needed for the field modification differs depending on 

which type of modification is being requested.

(3) Labeling Requirements

Because the engines and vehicles eligible for the AECD’s described in this 

proposal belong to broadly certified engine families and test groups, when they are sold 

for installation in an emergency vehicle and equipped with one or more approved 

emergency vehicle AECD’s, they must be labeled as such, to distinguish them from other 

certified engines. EPA is proposing adding a labeling requirement to 40 CFR part 86 

subpart A, such that engines with one or more approved AECD’s for emergency vehicle 

applications must be labeled with the statement: “THIS ENGINE IS FOR 

INSTALLATION IN EMERGENCY VEHICLES ONLY.” EPA is also proposing 
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adding a labeling requirement to 40 CFR part 86 subpart S, such that vehicles with one or 

more approved AECD’s for emergency vehicles, include the following statement on the 

emission control information label: “THIS VEHICLE HAS A LIMITED EXEMPTION 

AS AN EMERGENCY VEHICLE.” EPA is also adding a labeling requirement to 40 

CFR part 1039, such that nonroad engines with one or more approved AECD’s for 

emergency equipment include a label with the following statement: “THIS ENGINE IS 

FOR INSTALLATION IN EMERGENCY EQUIPMENT ONLY.”

EPA requests comment on whether these labeling requirements are satisfactory to 

ensure that engines and vehicles operating with approved emergency AECD’s are 

permanently distinguished from similar certified engines. EPA also requests comment on 

whether a similar label should be required for an in-use emergency vehicle or equipment 

where a field modification is deployed that prevents the engine from losing speed, torque, 

or power due to any occurrences of abnormal conditions of the emission control system, 

or prevents such abnormal conditions from occurring.

(4) Other Regulatory Provisions

Today’s proposal would not alter the tampering prohibition in 40 CFR 

1068.101(b)(1). This provision describes a general prohibition against anyone from 

removing or rendering inoperative an engine’s emission controls before or after entering 

into service, where an exception is provided in 1068.101(b)(1)(ii) for engine 

modifications needed to respond to a temporary emergency, provided that the engine is 

restored to proper functioning as soon as possible after the emergency has passed. EPA 

encourages manufacturers to design their emergency vehicle AECD’s to be engaged only 
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to the extent necessary to prevent the engine from losing speed, torque, or power due to 

abnormal conditions of the emission control system, or to prevent such abnormal 

conditions from occurring during operation related to emergency response. EPA 

recognizes that there may be cases where an AECD may need to be engaged at times 

other than while actively responding to an emergency, in order to assure that loss of 

speed, torque or power does not occur during operation related to emergency response. 

EPA also recognizes that some AECD’s may involve electronic approaches where the 

engine’s functions would be modulated based on exhaust backpressure or other 

parameters that are not correlated with any emergency situation. EPA may even, in 

extreme cases, such as at high altitude or with certain older MY engines allow 

engagement of AECD’s at all times, if they are justified as necessary to prevent engine 

from losing speed, torque, or power during operation related to emergency response. 

We would also encourage manufacturers to design their emission control systems 

to discourage tampering. According to EPA’s tampering prohibition, a vehicle operator 

who abuses or alters an approved AECD may be guilty of tampering. For example, if an 

AECD includes enabling an operator to initiate more frequent manual active 

regenerations, engine manufacturers may choose to prevent the abuse of this function by

means such as a daily or weekly cap on the number of manual active regenerations, or a 

minimum soot loading for the function to engage. As another example, if an emergency

vehicle alerts a driver to an abnormal condition of its emission control system by

illuminating dash lamps, alarms or other warnings that do not limit vehicle performance, 
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it is the operator’s responsibility to take prompt action to remedy the problem.29 If an 

operator disregards such warnings beyond the time needed to respond to the emergency, 

this may be considered tampering. It is important to note that if an emergency vehicle is 

not equipped to ever allow an operator to initiate a manual active regeneration, this may

in practice encourage tampering by the end user.

Manufacturers of highway and nonroad engines would be required to describe any

emergency vehicle AECD in an application for certification. In this action, we are not 

proposing any revisions to the information needed to review and approve AECD’s. It is 

common practice for manufacturers, in describing AECD’s, to identify engine parameters 

such as those that would operate differently to preserve adequate engine performance

during an emergency, including information about how the engine would respond under 

different in-use operating conditions under the various sets of conditions that would 

otherwise cause the engine to operate at less than full performance levels. Other than the 

requirement for a manufacturer to describe the emergency vehicle AECD in its 

application for certification, we do not expect this provision to be relevant for other 

aspects of certification. For example, EPA proposes that emissions certification testing 

be conducted with any approved AECD’s for emergency vehicle or equipment 

deactivated. Additionally, manufacturers would not need to consider emergency vehicle 

AECD’s when developing infrequent regeneration adjustment factors (IRAFs) or when 

developing deterioration factors (DFs). Thus, EPA proposes that manufacturers could 

 

29 Although this action would not affect certification of engine families or test groups, EPA’s regulations do 

offer options to manufacturers who wish to ensure that emission-related maintenance will occur in use, 

including visible signals that are not reset until maintenance occurs. 40 CFR 86.004-25(b)(6)(ii).
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include emergency and non-emergency engines and vehicles in the same engine families 

and test groups. EPA also proposes that manufacturers may apply for emergency vehicle 

AECD’s for new, existing, and/or formerly approved emissions certificates. EPA 

requests comments on this aspect of the proposal.

V. Scheduled Maintenance and Maintenance Interval for Replacement of Diesel 

Exhaust Fluid

EPA is proposing to include new provisions in its regulations that explicitly

permit replacement of diesel exhaust fluid (DEF) as part of approved emission-related 

scheduled maintenance and set out the permitted maintenance intervals for replacement 

of DEF on diesel fueled new motor vehicles, new motor vehicle engines and new 

nonroad compression-ignition (NRCI) engines.

A. Background

EPA’s regulations define the emission-related scheduled maintenance that may be 

performed for purposes of durability testing and for inclusion in maintenance instructions 

provided to purchasers of new motor vehicles and new motor vehicle engines. See 40 

CFR 86.094-25(b); 40 CFR 86.004-25(b); 40 CFR 86.1834-01(b). The regulations 

include lists of emission-related maintenance and intervals for this maintenance. See 40 

CFR 86.004-25(b)(4); 40 CFR 86.1834-01(b)(4). For example, in general, the 

maintenance interval for the adjustment, cleaning, repair of the following items is 

100,000 miles of use, and then at 100,000 mile intervals thereafter for diesel cycle lightduty vehicles, diesel cycle light-duty trucks, and light heavy-duty diesel engines and at 

150,000 mile intervals for medium and heavy heavy-duty diesel engines: fuel injectors, 

turbochargers, electronic engine control units, particulate trap or trap-oxidizers, exhaust 
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gas recirculation systems, and catalytic converters. The regulations also include a 

procedure that allows manufacturers to request a different maintenance schedule or to 

request new scheduled maintenance, which includes maintenance that is a direct result of 

the implementation of new technology not found in production prior to the 1980 model 

year. See 40 CFR 86.094-25(b)(7); 40 CFR 86.1834-01(b)(7). 

Similarly, EPA’s regulations applicable to nonroad compression-ignition (NRCI) 

engines define the emission-related maintenance that may be performed for purposes of 

providing ultimate purchasers written instructions for properly maintaining and using the 

engine. Such emission-related maintenance and associated intervals apply to service 

accumulation on emission-data engines. See 40 CFR 1039.125. This regulation includes 

lists of emission-related maintenance and intervals for this maintenance. See 40 CFR 

1039.125(a)(2) and 1039.125(a)(3). For example, in general, the maintenance interval for 

adjustment, cleaning, repair or replacement for catalytic converters on engines below 130 

kilowatt (kW) may not occur more frequently than after 3,000 hours and 4,500 hours for 

engines at or above 130 kW. This regulation also includes a procedure that allows 

manufacturers to request a different maintenance schedule or to request new scheduled 

maintenance, which includes maintenance on emission-related components that were not 

in widespread use on NRCI engines prior to 2011.

EPA adopted new emission standards applicable to emissions of NOX from lightduty vehicles and trucks on February 10, 2000 (65 FR 6698). Similarly EPA adopted 

new standards applicable to emissions of NOX from heavy-duty highway engines and 

vehicles on January 18, 2001 (66 FR 5002). These standards have been phased in since 

model year 2004 and all were fully phased-in by 2010. Most manufacturers of affected 
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diesel engines and vehicles have chosen to use a NOX reduction technology known as 

selective catalytic reduction (SCR) in order to meet these requirements. SCR systems use 

a nitrogen-containing reducing agent that usually contains urea and is known as diesel 

exhaust fluid (DEF). The DEF is injected into the exhaust gas and requires periodic 

replenishment by refilling the DEF tank. 

In addition, EPA adopted new emission standards applicable to emissions of NOX

from NRCI engines on June 29, 2004 (69 FR 38958). These standards have begun to be 

implemented pursuant to a phase-in that began in the 2011 model year. EPA conducted a 

webinar workshop on July 26, 2011 with NRCI engine manufacturers to address the 

application of SCR emission technology. Some manufacturers are currently certifying 

their NRCI engines with the use of SCR systems and we expect that many manufacturers 

will use SCR systems to meet the final Tier IV NOX reduction requirements for their 

diesel engines. 

In a Guidance Document signed on March 27, 2007 (CISD-07-07), EPA indicated 

its belief that the requirements for critical emission-related maintenance would apply to 

replenishment of the DEF tank and that manufacturers wanting to use SCR technology

would likely have to request a change to scheduled maintenance per 40 CFR §86.1834-

01(b)(7) or §86.094-25(b)(7).
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Following the completion of the Guidance, EPA received several requests for new 

maintenance intervals for SCR-equipped motor vehicles and motor vehicle engines.30 

EPA granted these requests for model years 2009 through 2010 for light-duty vehicles 

and 2009 through 2011 for heavy-duty engines, in a notice that was published in the 

Federal Register (74 FR 57671, November 9, 2009). In granting the requests, EPA stated 

that it

believes the maintenance of performing DEF refills on SCR systems 

should be considered as ‘critical emission-related scheduled maintenance.’ 

EPA believes the existing allowable schedule maintenance mileage 

intervals applicable to catalytic converters are generally applicable to SCR 

systems which contain a catalyst, but that the DEF refills are a new type of 

maintenance uniquely associated with SCR systems. Therefore, the 

100,000-mile interval at 40 CFR §86.1834-01(b)(4)(ii) for catalytic 

converters on diesel-cycle light-duty vehicles and light-duty trucks (and 

any other chassis-certified vehicles) and the 100,000-mile interval (and 

100,000 mile intervals thereafter) for light heavy-duty diesel engines and 

the 100,000-mile interval (and 150,000 mile intervals thereafter) for 

medium and heavy heavy-duty diesel engines at 40 CFR §86.004-

25(b)(4)(iii) are generally applicable to SCR systems. As noted, the SCR 

systems are a new type of technology designed to meet the newest 

emission standards and the DEF refill intervals represent a new type of 

scheduled maintenance; therefore, EPA believes that manufacturers may

request from EPA the ability to perform the new scheduled maintenance 

of DEF refills. 

EPA approved a maintenance interval for refill of DEF tanks equal to the 

applicable vehicle’s scheduled oil change interval for light-duty vehicles and light-duty

trucks. For heavy-duty engines, EPA approved a maintenance interval equal to the range 

(in miles or hours) of the vehicle operation that is no less than the vehicle’s fuel capacity 

 

30 See letter dated March 31, 2009 from Giedrius Ambrozaitis, Alliance of Automobile Manufacturers, 

Director, Environmental Affairs to Karl Simon, EPA, Director, Compliance and Innovative Strategies 

Division; Letter dated May 8, 2009 from Jed Mandel, Engine Manufacturers Ass’n to Karl Simon, EPA, 

Director, Compliance and Innovative Strategies Division; Letters dated June 29, 2009 and October 8, 2009 

from Steven C. Berry, Director Government Relations Volvo Powertrain. 
Page 64 of 125

(i.e., a 1:1 ratio), for vocational vehicles such as dump trucks, concrete mixers, refuse 

trucks and similar typically centrally fueled applications. For all other vehicles equipped 

with a constantly viewable DEF level indicator (e.g. a gauge or other mechanism on the 

dashboard that will notify the driver of the DEF fill level and the ability to warn the 

driver of the need to refill the DEF tank before other inducements occur), EPA approved 

a DEF tank refill interval equal to no less than twice the range of vehicle’s fuel capacity 

(i.e., a 2:1 ratio). For all other vehicles that do not have a constantly viewable DEF level 

indicator, EPA approved a DEF tank refill interval equal to no less than three times the 

range of the vehicle’s fuel capacity (i.e., a 3:1 ratio).

Engine and vehicle manufacturers provided additional requests for new 

maintenance intervals for vehicles and engines in model years not covered by the 

November 9, 2009 Federal Register notice.31 On January 5, 2012 (77 FR 488), EPA 

approved new maintenance intervals for the refill of DEF tanks applicable to light-duty

vehicles and light-duty trucks, as well as for heavy-duty engines for 2011 and later model 

years. For light-duty vehicles and light-duty trucks the approved interval for DEF refill 

remains at the scheduled oil change interval. For heavy-duty engines the approved 

maintenance interval for vocational vehicles remains at 1:1 and for all other types of 

heavy-duty vehicles the approved maintenance interval is 2:1.

 

31 See letter dated July 20, 2010 from Giedrius Ambrozaitis, Alliance of Automobile Manufacturers, 

Director, Environmental Affairs to Karl Simon, EPA, Director, Compliance and Innovative Strategies 

Division; Letter dated June 13, 2011 from Timothy A. French, Engine Manufacturers Ass’n to Justin G. 

Greuel, EPA, Compliance and Innovative Strategies Division; Letter dated April 28, 2011 from Steve 

Berry, Volvo Powertrain; Letters dated August 18, 2011 and September 27, 2011 to Karl Simon, EPA, 

Director, Compliance and Innovative Strategies Division from R. Latane Montague, Hogan Lovells. 
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On July 26, 2011, EPA conducted a webinar workshop for NRCI engine 

manufacturers in order to provide EPA’s thinking, at the time, about the certification of 

SCR-equipped NRCI engines. EPA discussed the issue of maintenance intervals for the 

refill of DEF and instructed manufacturers to follow the regulatory provisions in order to 

petition EPA for what it thought were appropriate intervals. Following the workshop, 

EPA received several requests for new maintenance intervals for SCR-equipped NRCI

engines. EPA granted these requests for 2011 and later model years in a notice that was 

published in the Federal Register (77 FR 497, January 5, 2012). In granting the requests, 

EPA stated that it

believes that SCR systems are a new technology and are properly 

considered a critical emission-related component. EPA believes the 

existing allowable schedule maintenance mileage intervals applicable to 

catalytic converters are generally applicable to SCR systems which 

contain a catalyst, but that the SCR systems are a new type of technology

and that DEF refills are a new type of maintenance uniquely associated 

with SCR systems. Therefore, the 3,000 hour (engines below 130 kW)

and 4,500 hour (engines at or above 130kW) intervals are generally

applicable to SCR systems. As noted, the SCR systems are a new type of 

technology designed to meet the newest emission standards and the DEF 

refill intervals represent a new type of scheduled maintenance; therefore, 

EPA believes that manufacturers may request from EPA the ability to 

perform the new scheduled maintenance of DEF refills. 

EPA approved a maintenance interval for refill of DEF tanks that shall be no less 

than the equipment’s fuel capacity (i.e., a 1:1 ratio of DEF refill to fuel refill). 

B. Proposed Regulatory Action

EPA is today proposing to add DEF replenishment to the list of scheduled 

emission-related maintenance for diesel-fueled motor vehicles and motor vehicle engines, 
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as well as for NRCI engines that use SCR. EPA is also proposing to incorporate 

appropriate maintenance intervals for this scheduled maintenance. 

(1) Scheduled Emission-Related Maintenance

EPA is proposing to list DEF replenishment as scheduled emission-related 

maintenance in 40 CFR 86.004-25(b)(4) and 40 CFR 86.1834-01(b)(4) for diesel-fueled 

motor vehicles and motor vehicle engines, as well as 40 CFR 1039.125(a)(2) and 40 

CFR 1039.125(a)(3) for NRCI engines that use SCR.

Over the past several model years, since the implementation of the most recent 

standards for NOX, many manufacturers have chosen SCR as the technology used to meet 

these stringent NOX standards. Typically, should a manufacturer desire new maintenance 

(that it wishes to recommend to purchasers and perform during service accumulation on 

emission-data engines) not found in 40 CFR 86.004-25(b)(4) and 86.1834-01(b)(4) or at 

40 CFR 1039.125(a)(2) and 40 CFR 1039.125(a)(3), then it utilizes the provisions 

allowing manufacturers to request such maintenance. Given that SCR use is now 

common in the industry and replenishment of DEF is necessary for SCR to be effective, it 

is appropriate to add DEF replenishment to the list of scheduled emission-related 

maintenance published in the Code of Federal Regulations (CFR), rather than rely on the 

provisions of paragraph (b)(7) for motor vehicles and paragraph 1039.125(a)(5) for NRCI 

engines. 
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(2) Maintenance Intervals for On-Highway Diesel Engines

EPA is also proposing to incorporate appropriate maintenance intervals for this 

scheduled maintenance. In general, they are the same as were approved under the (b)(7) 

process. For light-duty vehicles and light-duty trucks, we are proposing an interval equal 

to the scheduled oil change interval for the vehicle. Light-duty vehicles and trucks do not 

have the carrying and storage capacity required for the quantity of DEF needed to satisfy

longer maintenance intervals such as the 100,000 mile scheduled maintenance interval 

generally applicable to catalytic converters. As EPA explained in its previous notices 

regarding this issue, automobile manufacturers have stated that it takes approximately an 

8 gallon DEF tank to assure the DEF will last for the length of a typical scheduled oil 

change interval. Assuming an oil change interval of 10,000 miles, a DEF tank size of 

approximately 80 gallons would be required to meet a 100,000 mile DEF refill 

maintenance interval. Even a 16-20 gallon DEF tank (to meet a 2 oil change interval) 

would interfere with the space that is necessary for typical light-duty vehicle design and 

transportation needs of the consumer. Interior cabin volume and cargo space are highly 

valued attributes in light-duty vehicles and trucks. Manufacturers have historically

strived to optimize these attributes, even to the point of switching a vehicle from rearwheel drive to front-wheel drive to gain the extra interior cabin space taken up by where 

the drive shaft tunnel existed, or switching the size of the spare tire from a conventional 

sized tire to a small temporary tire to gain additional trunk space. Thus any significant 

interior, cargo or trunk space used to store a DEF tank would be unacceptable to 

customers. There are also packaging concerns with placing a large DEF tank in the 

engine compartment or in the vehicle’s undercarriage. Most vehicle undercarriages are 
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already crowded with the engine, exhaust system, including catalytic converters and 

mufflers, fuel tank, etc. limiting any available space for a DEF tank.

In addition to the inherently space constrained areas on the vehicle to place both 

fuel tanks and DEF tanks (an additional 8 gallon tank represents a very significant 

demand for space) the addition of the weight associated with the DEF represents 

significant concerns (e.g. performance and efficiency) on the operation of the vehicle. 

For example, assuming a density of 9 lb/gallon, an 8 gallon DEF tank represents an 

additional 72 lbs on a vehicle already looking to optimize performance. Adding 

additional DEF tank size to even accommodate a two-oil change interval is not feasible or 

practical given these weight constraints. A requirement for a larger DEF tank may also 

have an adverse effect on the ability of a manufacturer to meet greenhouse gas emission 

standards and fuel economy standards. 

EPA notes that a DEF refill maintenance interval that is equivalent and occurring 

with the oil change interval is a fairly long interval (e.g. 7,500 to 12,500 miles) for lightduty vehicles and trucks and is not likely to result in overly frequent maintenance under 

typical vehicle driving. EPA also believes that an adequate DEF supply will be available 

to perform the DEF refills at the stated intervals. EPA believes it important to also 

consider when, where and how often vehicle owners or operators are most likely to 

perform the DEF refill maintenance. For light-duty vehicles and light-duty trucks, EPA 

believes the requested DEF refill interval’s association with the oil change interval is 

appropriate given the likelihood of DEF availability at service stations and the likelihood 

that DEF refill would occur during such service. 
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EPA also notes that heavy-duty engines that are certified as part of complete 

trucks have been treated in the same manner as light-duty trucks and thus have been 

subject to the DEF refill interval associated with the oil change. We are proposing to 

continue this treatment in the regulations. In addition, EPA is aware that several 

manufacturers are exploring whether the DEF refill interval should not be linked to the 

oil change interval since the historical oil change interval (e.g., 7,000-8,500 miles) is 

potentially increasing to higher mile intervals (e.g., 15,000 to 30,000 miles, even higher 

for synthetic oil). We invite comment on the necessity and appropriateness of “delinking” the DEF refill interval from the oil change interval, as well as comments on 

proper methods to increase the likelihood that DEF refill maintenance would occur in the 

appropriate interval (e.g., linking to vehicle fuel capacity, inducement criteria, etc.), 

should it not be linked to the oil change interval.

For heavy-duty engines, we are proposing that for vocational vehicles such as 

dump trucks, concrete mixers, refuse trucks and similar typically centrally fueled 

applications, the DEF tank refill interval should equal the range (in miles or hours) of the 

vehicle operation that is no less than the vehicle’s fuel capacity (i.e., a 1:1 ratio). For all 

other vehicles, the DEF tank refill interval must provide a range of vehicle operation that 

is no less than twice the range of vehicle’s fuel capacity (i.e., a 2:1 ratio). EPA believes it 

is reasonable to base the DEF refilling event on diesel refueling intervals given that it is 

likely that the DEF refill maintenance would be undertaken at the time of fuel refill due 

to DEF infrastructure developed at diesel refueling stations. EPA believes that these DEF 

refilling intervals are technologically necessary. EPA knows of no SCR technology for 

any heavy-duty engine application that is capable of operating without a DEF refill for 
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the high mileage levels associated with other maintenance intervals. As an example, 

assuming that 25,000 gallons of diesel fuel were consumed to reach a 150,000 mile 

interval, the amount of DEF required (assuming a 3% DEF consumption rate) would 

require 750 gallons of DEF weighing approximately 6,750 lbs. A line-haul truck is 

allowed a maximum gross vehicle weight of 85,000 lbs. of which approximately 45,000 

pounds is for cargo carrying. A DEF tank of 750 gallons would reduce the cargocarrying capacity by 15%. Another example from the line haul industry suggests that a 

DEF tank size of over 900 gallons would be needed to reach the 150,000 mile interval for 

a common highway vehicle with a diesel fuel capacity of 200 gallons and achieving 6.5 

miles per gallon fuel economy. Similarly, a medium heavy-duty engine (“chassis cabs”) 

example would require 375 gallons of DEF weighing 3,275 lbs to meet a 150,000 mile 

interval. EPA believes that such tank sizes are clearly not technologically feasible in light 

of the weight and space demands and constraints on heavy-duty trucks and the consumer 

demand to maximize cargo carrying capacity.

The Agency also believes that intervals shorter than 150,000 miles but longer than 

those we are proposing would require DEF tanks that are too large or too heavy to be 

feasibly incorporated into vehicles. Available data show that heavy-duty engines 

equipped with SCR-based systems will consume DEF at a rate that is approximately 2%-

4% of the rate of diesel fuel consumption. Because of inherent space and weight 

constraints in the configuration and efficient operation of heavy-duty vehicles, there are 

size limits on the DEF tanks. Currently, there are truck weight limits that manufacturers 

must address when making or modifying truck designs. EPA expects and believes that 

manufacturers are taking significant and appropriate steps in order to install reasonably 
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sized DEF tanks to achieve the DEF refills intervals noted. For example, manufacturers 

are taking such steps as reducing the number of battery packs on vehicles despite 

customer demands or designing space saving configurations, in some instances extending 

an already very limited frame rail distance to incorporate the DEF tanks and SCR 

systems, moving compressed air tanks inside the frame rails, redesigning fuel tank 

configurations at significant costs, and otherwise working with significant size and 

weight constraints to incorporate DEF tanks. There are several factors that support the 

good engineering judgment that underlies the recommended DEF refill intervals. The 

great majority of heavy-duty engines produced with SCR DEF tanks will provide a range 

of vehicle operation that is no less than twice the range of the vehicle’s fuel capacity; 

thus, the DEF tank size will provide at least double the vehicle’s operating range as 

provided by the fuel tank. Vehicle operators will generally refill DEF at the same time 

and location that they refill the tanks thus these vehicles will already be carrying twice as 

much DEF as the SCR system could ever consume between refills. Also, manufacturers 

have been incorporating warning signals and performance-related inducements on their 

SCR-equipped vehicles to ensure the substantial likelihood that DEF refilling will 

occur,32 and there is considerable evidence that heavy-duty vehicle operators in the 

United States have in practice been refilling their DEF tanks prior to the tanks becoming 

empty in virtually all situations.33 

 

32

 As discussed in Section IV above, we are proposing options for manufacturers of emergency vehicles 

and engines to avoid the harsh consequences of certain performance inducements. Since 2010, some 

manufacturers have been implementing guidance on alternative inducement criteria for emergency 

vehicles.

33

 See 76 FR 32886 (June 7, 2011) and the studies cited at 32889-32891.
Page 72 of 125

EPA was provided with examples of the consequences of requiring heavy-duty

vehicles to accommodate a DEF refill interval of 5:1, and the information provided to the 

Agency strongly suggested that great compromises would be required in cost, weight and 

utility. Increased tank sizes and weights on the magnitude of 150 to 325 lbs. would be 

required and in some cases diesel fuel volumes would need to be reduced. The extra 

weight associated with the DEF required to meet the 2:1 refill intervals represents a 

significant challenge to manufacturers seeking to meet both weight and size requirements 

for their vehicle designs. In addition, requiring a longer DEF refill interval may result in 

increased greenhouse gases and decreased fuel economy. EPA believes that in light of 

the existing tight space constraints and the overall desire to maximize cargo-carrying 

capacity to minimize emissions and meet consumer operational demands, and the built-in 

DEF tank size buffer to insure DEF refills, that the proposed tank DEF tank sizes are 

technologically necessary and are also reasonable and appropriate. EPA believes that 

requiring tank sizes above these ratios will cause increases in space constraints and 

weight that would not be appropriate for these vehicles. Similarly, manufacturers note 

that only a small number of applications will employ the 1:1 refilling ratio and that such 

vehicle applications have very limited vehicle space available to house surplus DEF. 

Such applications (e.g., a garbage truck, concrete mixer, beverage truck, or airport 

refueler) will also be refueled daily at central locations. At approximately 0.134 ft3per 

gallon, any extra DEF would displace significant space available to vehicle components 

and subsystems on both the vocational trucks at the 1:1 refill interval as well as the 2:1 

vehicles.
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During the previous administrative process leading to the January 5, 2012 Federal 

Register notice approving new maintenance intervals, EPA received a comment from one 

manufacturer (Navistar) suggesting that a longer DEF refill interval in the range of 

35,000 to 45,000 miles was appropriate. EPA responded to these comments in detail in 

that notice.34 As discussed in that notice, Navistar claimed that other technology is 

available that would need a maintenance interval no shorter than this. However, EPA 

found no evidence that such technology is actually available at this time. More 

importantly, the fact that other technology may be able to have a longer maintenance 

interval does not mean that a longer maintenance interval is appropriate for DEF-based 

SCR. Navistar suggested that maintenance intervals can be increased by doubling DEF 

tank size. EPA does not believe that requiring such an increase is appropriate given the 

numerous negative consequences discussed above. EPA also explained that Navistar’s 

suggestion of reducing engine-out emissions of NOX would likely lead to an increase in 

fuel consumption, and possible increases in GHG emissions, and could either require 

increases in the size of the fuel tank or more reductions in the operating range of a 

vehicle before needing to refill, which would compromise a critical design parameter of 

heavy-duty vehicles. EPA does not believe the desire to increase DEF maintenance 

intervals justifies such consequences. After reviewing these data, EPA believes that 

longer refill intervals than those proposed above would require larger and heavier DEF 

tanks. The design and engineering work performed by manufacturers thus far indicates 

that the recommended DEF refill intervals noted above approximate the maximum 

feasible maintenance intervals associated with reasonable DEF tank sizes. In any case 

 

34

 See 77 FR 488, at 495-96 (January 5, 2012).
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these refill intervals are appropriate and reasonable given the substantial negative 

consequences of longer DEF refill interval requirements. The recommended 

maintenance intervals ensure that the function and operational efficiency of such vehicles 

are not overly compromised. Based on this information we believe the proposed intervals 

are warranted. 

EPA has received comments from certain manufacturers indicating that EPA 

should set the minimum required DEF refill interval at an interval equal to the vehicle’s 

fuel capacity (i.e., a 1:1 ratio) for all heavy-duty engines.35 The commenters claim that 

this shorter maintenance interval is “necessary and appropriate to reflect current and 

anticipated changes in vehicle designs, significant changes in inducement strategies, and 

the increased availability of DEF.” The commenters note that certification practices of 

the EPA regarding inducement practices for SCR-equipped engines make it “essentially

impossible for an SCR vehicle to operate without regular DEF replenishment.” They

state that the severity of inducements related to DEF levels (e.g. severe reduction in 

engine power and/or vehicle speed) is “extraordinary and must be taken into account” 

when EPA is determining appropriate maintenance intervals. They state that “in light of 

these severe inducements, it is reasonable to expect that a driver with a 1:1 tank ratio will 

operate under a firm discipline that the DEF tank must be refilled every time the fuel 

tanks are filled, as opposed to a driver with a 2:1 or greater tank ratio who may become 

accustomed to filling the DEF tank only when necessary, and is therefore more likely to 

rely on gauge levels, warnings, and inducements to trigger refills.”

 

35 See letters dated August 18, 2011 and September 27, 2011 to Karl Simon, EPA, Director, Compliance 

and Innovative Strategies Division from R. Latane Montague and Hogan Lovells.
Page 75 of 125

The commenters also state that EPA’s promulgation of new standards regulating 

greenhouse gases increase the size and weight restraints associated with DEF tank size. 

EPA has adopted new greenhouse gas standards for heavy-duty on-highway

trucks, and manufacturers have moved to voluntarily increase the fuel efficiency of their 

vehicles in advance of the effective dates of those regulations. Within these regulations, 

EPA recognizes the impact of weight savings on fuel efficiency and GHG emissions. In 

addition, manufacturers have developed innovative new DEF dosing strategies to reduce 

CO2 emissions. These new strategies may involve increasing the DEF dosing rate. 

Increasing the DEF dosing rate also makes it more difficult to satisfy a 2:1 tank size ratio 

without increasing the size of the DEF tank above the size EPA previously considered the 

maximum reasonable size. For this reason, if the application of the 1:1 tank ratio is not 

expanded, EPA will effectively be mandating larger DEF tanks, with their accompanying 

weight increase, in order to accommodate technology advancements developed to reduce 

CO2 emissions—tanks that are larger than the tanks EPA determined to be the maximum 

reasonably required in 2009. In addition, this could inadvertently cause manufacturers to 

restrict application of the most fuel efficient engines to vehicles that have reduced range 

between fuel and DEF refills, such that they will be unattractive to the line-haul fleets 

that consume the most fuel.

The commenters elaborated that:

To meet the next round of GHG reduction requirements, some 

manufacturers expect to increase DEF dosing by as much as 100% over 

current levels. These increased levels of dosing will require a 

corresponding increase in DEF tank capacity and size to meet the existing 

2:1 tank ratio requirements. For example, increasing DEF dosing by 40% 

on average would require an increase in DEF tank size of approximately
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40% (depending on how much extra capacity was included in the tanks 

used in previous model years). The shape, size and location of DEF tanks 

on a truck frame are constrained by a number of factors including: the 

need to place the tank below the filler-neck; the need for clearance from 

other components such as fuel tanks, battery boxes, air tanks, diesel 

particulate filters, and the drive axle and wheels; the need for gravity feed; 

body installation requirements; clear-back-of-cab requirements; weight 

distribution requirements; bridge formula and related axle placement 

issues; and fuel capacity/driving range demands.

The commenters state that another consequence of the greenhouse gas regulations 

is more attention to improved aerodynamics and weight reduction, which are harmed by 

the need for a 2:1 DEF tank size requirement. They claim that EPA should allow 

manufacturers to use all available options to increase fuel efficiency and meet greenhouse 

gas standards. They claim that the possible harm of allowing shorter maintenance 

intervals are minimal, given the severe negative inducements associated with failure to 

replenish the DEF tank. 

EPA is not proposing to allow a 1:1 DEF maintenance interval across the heavyduty engine class at this time. EPA notes that manufacturers have been meeting a 2:1 

ratio for DEF tank size for the past two years and the commenters have not provided 

sufficient evidence that this ratio will be infeasible in the future. Moreover, the 

commenters have not shown that any change in the maintenance interval is necessary or 

appropriate throughout the heavy-duty engine category, rather than for particular 

applications, or that a refill interval as low as 1:1, rather than 1.8:1 or 1.5:1, is necessary

or appropriate. The feasibility of the greenhouse gas standards was not predicated on 

substantial increases in DEF dosing rate, although that was a possible method of 

compliance, and the commenters have not shown that the increase in tank size that would 

be associated with increased dosing, which need not be large, would be inconsistent with 
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space constraints. While EPA agrees that the warnings and inducements in place for 

failure to replenish DEF will restrict the ability of operators to run without DEF, and have 

made operation without DEF virtually unheard of, a DEF tank ratio of 1:1 greatly 

increases the likelihood that operators will need to make more frequent stops to replenish 

DEF, and possibly may need to stop solely to replenish DEF, which may place a greater 

burden on the operator in terms of the frequency of DEF refills. However, we request 

comment on this proposal and we do not rule out the possibility we may in the final rule 

allow a shorter maintenance interval at least in some situations beyond what we have 

proposed. In particular, we request comment on whether such an interval may be 

appropriate in the future or whether an approach that is limited to a portion of the heavyduty engine category or that uses an interval between 2:1 and 1:1 may be appropriate. 

EPA also notes that the regulations allow any manufacturer to petition EPA under 

the “paragraph (b)(7) process” for a shorter maintenance interval than that promulgated 

for DEF refills if the manufacturer can show that a shorter interval is technologically 

necessary for the particular engine or vehicle configuration being certified.

(3) Maintenance Intervals for Nonroad Compression-Ignition Engines

EPA is also proposing to incorporate appropriate maintenance intervals for the 

scheduled maintenance of DEF refills on SCR-equipped NRCI engines. We are 

proposing the same interval (i.e., 1:1 ratio) as was approved under the § 1039.125(a)(5) 

process. 

EPA believes it appropriate to evaluate the DEF refill rates by taking into 

consideration the space and weight constraints typically involved with the range of 
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nonroad compression-ignition engines using SCR systems, including safety and impacts 

of weight and dosing rates on greenhouse gas emissions and fuel economy. EPA also 

believes it appropriate to take into consideration the likelihood that the maintenance of 

DEF refills will be performed by the owner or operator.36

EPA knows of no SCR technology for NRCI engines that is yet capable of 

attaining longer operation (generally beyond one tank full of diesel) without a DEF refill. 

As noted by the requests received for a shorter interval, there are significant space and 

weight constraints associated with increasing the DEF tank size in order to accommodate 

a 2:1 refill ratio. EPA believes it appropriate to take into consideration the need for 

locating the DEF tank in close proximity to the fuel tank and the remainder of the SCR 

system, as well as the increased likelihood that the DEF tank will be refilled if it becomes 

standard operating practice to refill it at the same time as the fuel tank. EPA believes that 

such nonroad equipment is similar to centrally-fueled heavy-duty on-highway vehicles 

and that there is a sufficient basis and a reasonable expectation that DEF tank refills will 

occur on a timely basis. In addition, because this maintenance is considered critical 

emission-related maintenance, § 1039.125 requires that manufacturers ensure that it have 

a reasonable likelihood of being done at the recommended intervals on in-use engines. 

Paragraph 1039.125(a)(1) sets forth several methods by which such demonstration can be 

made, including data showing that if a lack of maintenance increases emissions, it also 

unacceptably degrades the engine’s performance. Thus, manufacturers will need to show 

compliance with this requirement to be certified. In the context of SCR systems and the 

 

36

 See 40 CFR 1039.125(a)(5). 
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potential of an empty DEF tank and an inoperable SCR system, EPA notes that 

equipment under such operating conditions are expected to shut down or idle only.

37

VI. Nonroad Engines in Temporary Emergency Service

As noted previously, EPA is proposing to adopt special provisions for engines 

used in dedicated emergency vehicles to ensure that manufacturers are able to design and 

implement reliable, robust emission control systems with regeneration strategies that do 

not interfere with the mission of emergency vehicles. However, we are not proposing to 

extend this option for other engines that are not intended for emergency vehicles. 

Nevertheless, based on information provided to us from engine manufacturers, we have 

some concern that nonroad engines not normally used for emergencies may be needed in 

unusual emergency situations that may require very limited and temporary relief so that 

emission controls do not hinder the engine’s performance in such emergency conditions. 

This section describes a flexibility that we are proposing to address this.

Our existing nonroad engine compliance regulations in 40 CFR 1068.101(b)(1)(ii) 

allow operators to temporarily disable or remove emission controls to address emergency 

situations. However, they do not necessarily allow manufacturers to design the emission 

controls to be disabled or removed. This has become a potential problem for modern 

electronically controlled engines, where many emission controls are integrated into the 

engine’s control software. There is currently no way for an operator to selectively 

disable emission control software, while maintaining engine function. The proposed 

 

37

 See 76 FR 32886 (June 7, 2011) and related inducement criteria, see also Note 32 above regarding 

inducements for emergency vehicles and engines.
Page 80 of 125

regulatory text would effectively extend the policy expressed in 40 CFR 

1068.101(b)(1)(ii) to emission control software.

A. Use of Nonroad Engines in Emergency Situations

The provisions we are proposing are intended primarily to address engines used 

for power generation or in construction equipment. However, it is important to note that 

we are not proposing to limit this flexibility to such engines. For example, portable 

diesel-powered generators are often used to provide electrical power after natural 

disasters. If the generator is providing power to a medical facility, then any interruption 

in service could risk the lives of the patients. This is just one example of how an ordinary

piece of nonroad equipment could be used in an emergency situation. Others would 

include bulldozers repairing a levee or a crane removing debris. 

The Tier 4 standards have resulted in much of this equipment being equipped with 

SCR catalysts that require a reductant. The reductant is typically supplied as a urea water 

solution known as diesel exhaust fluid (DEF). The engines in this equipment generally 

include controls that limit the function of the engines if they are operated without urea. 

Such controls are generally call “inducements”, because they induce the operator to 

supply urea to the equipment. While we are confident that DEF is now widely and easily 

available in the United States, we are concerned that in emergency circumstances there 

may be a possibility of a temporary supply shortage. We believe that in such situations, 

temporary flexibilities may be appropriate because the possibility of risk to human life 

sufficiently outweighs the temporary emissions increases that may occur if SCRequipped engines are used without DEF. As indicated below, this flexibility is very
Page 81 of 125

narrow and contains several provisions to ensure the need for the relief. We do not 

believe it can or will be used in situations where there is no critical need for such relief.

B. Proposed Regulatory Action

(1) General Requirements

We are proposing a new section 1039.665 that would specify provisions that 

allow for AECD’s that are necessary to ensure proper function of engines and equipment 

in emergency situations. AECD’s approved under this section would not be defeat 

devices. The section would include the following provisions:

 Manufacturers would be allowed to ask for approval at any time. Still, we would 

encourage manufacturers to obtain preliminary approval before submitting an 

application for certification. And in unusual circumstances, we could allow 

manufacturers to apply an approved emergency AECD to engines and equipment that 

have already been placed into service as a “field fix”.

 The manufacturer would be required to keep records to document requests for and use 

of emergency AECD’s under this section and submit a report to EPA within 60 days 

of the end of each calendar year in which it authorizes use of the AECD

 We would approve an AECD only where we determine certain criteria are met, as 

described below.

We are proposing to address such AECD’s as part of certification and would only

authorize the certifying manufacturer to activate them.
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(2) Approval Criteria

Approval of AECD’s under the proposed regulations would be based on certain 

general and specific criteria. A general criterion is that the AECD would need to be 

consistent with good engineering judgment. When used in our regulations, the phrase 

“good engineering judgment” has a specific meaning as described in 40 CFR 1068.5. By

specifying that the AECD be consistent with good engineering judgment, we address 

unforeseen technical details that may arise.

We are also proposing three specific criteria that must be met. Each of these 

criteria is intended to ensure that any adverse environmental impacts are minimized. 

These criteria are:

 The AECD must be designed so that it cannot be activated without the specific 

permission of the certificate holder. We would specify that the AECD must require 

the input of a temporary code or equivalent security feature.

 The AECD must become inactive within 24 engine hours of becoming active (or other 

period we approve in unusual circumstances).

 The manufacturer must show that the AECD deactivate emission controls (such as 

inducement strategies) only to the extent necessary to address the expected 

emergency situation. 

(3) Allowable Use of Emergency AECD’s 

This allowance is intended generally to address SCR-equipped engines operating 

in emergency situations when DEF is unavailable. In such cases, inducement strategies 
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could result in a loss of power of the engine which could effectively prevent the 

equipment from functioning. Under this provision, a manufacturer could include a 

dormant feature in the engine’s control software that could be activated to disable 

inducement strategies.

We are also proposing to allow this for other types of controls, where a 

manufacturer can clearly demonstrate that this relief could be needed. We are requesting 

comment about whether we should specifically identify such other controls or leave the 

regulatory text more open ended.

Finally, we are requesting comment about the circumstances under which we 

should allow the AECD to be activated. Should emergency situations include only those 

circumstances where human life is at stake? Should it be allowed automatically

whenever a federal disaster is declared? 

VII. Economic, Environmental, and Health Impacts of Proposed Rule

A. Economic Impacts

(1) Economic Impacts of Emergency Vehicle Proposal

EPA expects the economic effects of this proposal to be small, and to potentially

have benefits that are a natural result of easing constraints.

(a) Costs to Manufacturers

Due to the optional and voluntary nature of this proposal, there are no direct 

regulatory compliance costs to engine manufacturers. To the extent manufacturers elect 
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to develop and deploy upgrades to engines for emergency vehicles, they may voluntarily 

incur some degree of costs associated with the following:

 Design and testing to determine effectiveness of potential AECD’s

 Education & outreach to intermediate vehicle manufacturers and end users

 Deployment of AECD’s onto new and in-use emergency vehicles

 Labeling costs

EPA expects any fixed costs would be small, and any variable costs would apply

only to the engines sold for installation in emergency vehicles or emergency equipment, 

which comprise less than one percent of the heavy-duty on-road fleet, and an even 

smaller fraction of the nonroad fleet. As per standard practice, manufacturers would be 

free to set a fair market price for any approved AECD or field modification they offer, to 

offset the costs incurred in its development. 

(b) Operational Costs

Depending on the type of AECD or field modification that a manufacturer 

voluntarily elects to deploy, some operational costs could increase and some could 

decrease.

(i) Maintenance and Warranty Costs

When an emergency vehicle is experiencing frequent plugging of its DPF, this 

increases maintenance costs for owners and warranty costs for manufacturers. 

Maintenance costs can include service calls for a technician-controlled regeneration, 

towing fees where on-site regeneration cannot be achieved, and costs to deploy reserve 
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vehicles while the impaired vehicle is being serviced. These costs are expected to 

decrease with this proposal, and are discussed further below.

Manufacturers incur warranty costs when a vehicle under warranty must be 

returned for service. Because this proposed action would allow manufacturers the 

flexibility to improve the reliability of their engines, EPA expects warranty costs for 

emergency vehicles and engines in emergency vehicles would decrease as a result of this 

action.

Should an AECD be deployed that allows manual active regenerations at more 

frequent intervals, this could increase the total number of regenerations, exposing the 

DPF substrate to more frequent thermal stress and general wear & tear. However, while 

it is expected that the frequency of regenerations would increase, the duration of each 

regeneration would decrease because the total soot loading of the DPF would likely

remain unchanged or be reduced due to other control strategies within the approved 

AECD. Because manufacturers are held to strict standards related to the warranty, 

maintenance and durability of these systems, EPA expects that measures will be taken to 

ensure that any AECD that is deployed would not decrease the ash cleaning interval or 

otherwise decrease the durability of the emission control system.38

With this proposal, manufacturers would have the flexibility to design alternate 

calibrations to reduce soot loading to the DPF and extend the interval between 

regenerations. There would also be more flexibility to enable more passive and automatic 

 

38 EPA prohibits engine manufacturers from requiring repair or replacement of particulate traps on heavy 

heavy-duty diesel engines more than once every 150,000 miles. 40 CFR 86.004-25(b)(4)(iii).
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active regenerations, which both expose the DPF to less thermal stress than do manual 

active regenerations. In summary, EPA does not expect any warranty or maintenance 

costs would increase due to this proposal, and it is very likely that these would decrease. 

Furthermore, EPA believes that the potential for reduced warranty costs may help to 

offset the cost to produce and deploy any optional AECD’s. Similarly, EPA believes the 

potential for reduced maintenance and operational costs may offset the cost to owners for 

obtaining requested AECD’s.

(ii) Fuel Costs from Dosing

Where DPF systems employ fuel dosing to enable active automatic regenerations, 

it is uncertain whether liberalizing the parameters for initiating regenerations would 

affect fuel consumption. Operators have reported that vehicles burn more fuel during 

regenerations, though the quantity varies among vehicles.

Where automatic active regenerations employ fuel dosing, it is uncertain whether 

fuel consumption would increase with an increased number of regenerations during a 

given operating period. If all else were to remain the same, it is likely that the duration of 

each automatic active regeneration may be decreased. To the extent regenerations are 

enabled with other means besides fuel, or demand for regenerations is reduced through 

recalibration, then any potential increase in fuel use from dosing would be mitigated.

As an illustration, we have estimated the additional fuel use for a truck with a 

dosing strategy where its regeneration interval is decreased from 25 hours to eight hours, 

due to the increased availability of operator-commanded regenerations. In this example, 

we assume a single regeneration consumes approximately half a gallon of supplemental 
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fuel. If the vehicle has average engine operating hours of 1,200 per year, then its number 

of regeneration events would increase from about 50 per year to 150 per year, under the 

above assumptions. If the amount of supplemental fuel use remained unchanged under 

the new regime (a conservative assumption) then potentially the vehicle could consume 

an additional 50 gallons of fuel per year from the increased frequency of regenerations 

alone. Considering current costs of ultra low sulfur diesel fuel, this could translate to 

about $200 per vehicle in additional annual fuel costs.

As explained above, EPA does not believe this is a likely scenario, as the amount 

of fuel used per regeneration event would likely decrease with increasing frequency, and 

engine manufacturers would be likely to adjust combustion parameters to avoid placing 

additional thermal stress on the DPF. A more detailed analysis of fuel use and potential 

costs associated with dosing strategies is included in a memo to the docket associated 

with this rulemaking.39

(c) Societal Costs

Because this proposal eases constraints on the development of robust DPF 

systems, the economic impacts can only improve with this action. It is presumed that the 

benefits to society of enabling first responders to act quickly when needed outweigh the 

costs to society of any temporary increase in emissions from this small segment of 

vehicles.

 

39 See memo dated May 4, 2012, “Fuel Use With Dosing for DPF Regeneration,” Docket ID EPA-HQOAR-2011-1032. 
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(2) Economic impacts of SCR Maintenance Proposal

This action would codify previously published final agency actions regarding 

SCR maintenance intervals. No new regulatory burdens would be imposed. Rather, by

codifying former decisions that were based on administrative petitions and of limited 

applicability, EPA is providing regulatory certainty that will allow affected 

manufacturers to plan their product development accordingly.

(3) Economic Impacts for Nonroad Engines Used in Emergency Situations

EPA expects the economic effects of this proposal to be small, and to potentially

have benefits that are a natural result of easing constraints. Due to the optional and 

voluntary nature of this proposal, there are no direct regulatory compliance costs to 

engine manufacturers. To the extent manufacturers elect to develop and deploy upgrades 

to engines for emergency vehicles, they may voluntarily incur some degree of costs. We 

do not expect there to be any operator costs for this allowance, other than the potential 

cost associated with sending written confirmation of an emergency situation to the 

certificate holder. However, since this option would be activated rarely (or perhaps not at 

all), total costs to operators would be negligible.

B. Environmental Impacts

(1) Environmental Impacts of Emergency Vehicle Proposal

We expect any environmental impacts from this proposal would be small. By

promulgating these amendments, it is expected that the emissions from this segment of 

the heavy-duty fleet would not change significantly.
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(a) Fleet Characterization and Emission Inventory

EPA estimates that on-road emergency vehicles comprise less than one percent of 

the national heavy-duty fleet. According to the International Council on Clean 

Transportation (ICCT), less than one percent of all new heavy-duty truck registrations in 

2003 to 2007 were for emergency vehicles (includes class 8 fire trucks plus other class 3-

8 emergency vehicles).40 On average, the ICCT’s data suggest that approximately 5,700 

new emergency vehicles are sold in the U.S. each year; about 0.8 percent of the 3.4 

million new heavy-duty trucks registered between 2003 and 2007. The available 

information indicates that the emergency vehicles included in the scope of this 

rulemaking have lower annual vehicle miles traveled than average non-emergency

vehicles. Therefore, we conclude that they contribute less than 1% of the annual air 

emissions from the heavy-duty diesel truck fleet.

(b) Emission Impacts from Auxiliary Emission Control Devices on Emergency 

Vehicles

Due to the optional and voluntary nature of this action, it is difficult to estimate its 

overall emissions impact accurately. The proposed amendments offer many options to 

manufacturers, and the emissions impacts will depend on which options and strategies are 

employed, and for how many vehicles.

 

40 ICCT, May 2009, “Heavy-Duty Vehicle Market Analysis: Vehicle Characteristics & Fuel Use, 

Manufacturer Market Shares.”
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(i) NOX Emissions Impacts

During both automatic active and manual active regenerations, emission rates 

increase for some pollutants, especially NOX when post-DPF after-treatment devices are 

not present. The higher than normal combustion chamber temperatures during active 

regeneration with high rates of oxidation occurring across the catalyst can create 

conditions conducive to NOX formation. From certification data for 2008 model year 

engines, the difference between the NOX emission rate during normal operation and the 

rate during active regeneration can range from an undetectably small difference to a fivefold increase. The magnitude of the NOX increase is only part of the story, however. As 

part of their certifications, engine manufacturers may provide frequency factors that 

adjust for the average excess emissions during DPF regeneration. As used in engine 

certification, the frequency factor indicates the percent of test cycles during which DPF 

regeneration is expected to occur. From certification data for 2008 and 2011 model year 

engines, DPF regeneration frequency factors for heavy-duty engines range from near zero 

to nearly 20 percent. Overall, the certification data indicate that the higher the increase in 

NOX during a DPF regeneration event, the less often active regeneration occurs on that 

engine, especially over the transient test cycle. A summary of this information is 

presented in a memo to the docket associated with this rulemaking.41

As a result of this proposed action, it is possible that some engine manufacturers 

will submit applications for AECD’s with liberalized parameters under which automatic 

 

41 See memo dated May 4, 2012, “NOX Emissions from DPF Regeneration,” Docket ID EPA-HQ-OAR2011-1032. 
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active and/or manual active regenerations may occur, for emergency vehicles. Under 

these liberalized parameters, several outcomes are possible, depending on the engineering 

design. While the NOX emission rate during DPF regeneration could increase above the 

rate of the current certified configuration, it is also possible that the duration of each 

event could decrease. While the frequency of manual active regenerations could increase 

if the engine controls permitted operators to initiate parked regeneration at any soot 

loading, it is also possible the frequency of automatic or manual active regenerations 

could decrease with the new designs, making wider use of passive regeneration strategies. 

Given that it is difficult to estimate how popular each option may be, and what other 

actions may be taken to alter engines and/or emission control systems, EPA has provided 

examples of possible emission scenarios due to this proposal in a memo to the docket.42

(ii) PM emissions Impacts

In the comment letters EPA received urging swift action providing relief for 

emergency vehicles, it was often cited that the pollution from a structural fire is far worse 

than the tailpipe emissions of a fire truck. To provide some perspective on this, EPA is 

providing a brief discussion of PM emissions in this section. 

A rough method for estimating emissions from structural fires is obtained by

multiplying a national average factor of 2.3 fires per 1,000 residents by the national 

population, along with a PM emission factor of 10.8 lb per ton burned, and an average 

fuel loading of 1.1 tons burned per fire. Using these estimates, EPA calculates just under 

 

42

 See NOX Memo, Note 41, above.
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5,000 tons of PM is emitted in the U.S. each year from structural fires. A more detailed 

analysis of PM emissions from structural fires in relation to PM emissions from 

emergency vehicles is included in a memo to the docket associated with this 

rulemaking.43

We expect manufacturers who choose to develop optional AECD’s for emergency

vehicles to employ strategies that prevent the occurrence of abnormal conditions of the 

emission control system. Where preventive strategies alone are not demonstrated to be 

failsafe, EPA expects there may be instances where it is justified to provide engine 

exhaust backpressure relief, either mechanical or through other means. While we expect 

this will not be a widespread solution, there may be cases where a relief valve may be 

employed on a vehicle whose DPF became plugged frequently, allowing temporary

emission control bypass to occur as a last resort to prevent engine failure. An example of 

possible PM emissions changes due to this proposal is presented in a memo to the docket 

associated with this rulemaking.44

(iii) Fuel Use from Dosing

As described above in Section IV.C, only some control systems employ fuel 

dosing as a strategy to initiate active regeneration. In a memo to the docket associated 

with this rulemaking, EPA estimates the potential increase in fuel use due to more 

frequent operator-commanded regenerations with dosing at an average of about 50 

gallons per year per vehicle, if other measures to reduce the need for regenerations are 

 

43 See memo dated May 4, 2012, “PM Emissions Impacts,” Docket ID EPA-HQ-OAR-2011-1032

44 See PM memo, Note 43, above. 
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not taken.45 The emissions associated with this supplemental fuel use are discussed 

above. EPA requests comment on the impact of this proposed action on fuel 

consumption in emergency vehicles whose active regeneration strategies include fuel 

dosing.

(2) Environmental Impacts of SCR Maintenance Proposal

EPA believes that the likelihood of emissions-related maintenance occurring in 

use would remain unchanged as a result of this action. Therefore, there are no anticipated 

adverse environmental impacts.

(3) Environmental Impacts for Nonroad Engines Used in Emergency Situations

EPA does not expect any significant environmental effects as a result this 

proposal. This option would be activated rarely (or perhaps not at all) and would only

affect emissions for a very short period.

C. Health Effects

EPA’s clean diesel standards are already providing substantial benefits to public 

health and welfare and the environment through significant reductions in emissions of 

NOX, PM, nonmethane hydrocarbons (NMHC), carbon monoxide, sulfur oxides (SOX), 

and air toxics. We project that by 2030, the on-highway program alone will reduce annual 

emissions of NOX, NMHC, and PM by 2.6 million, 115,000 and 109,000 tons, 

respectively. These emission reductions will prevent 8,300 premature deaths, over 9,500 

 

45 See Fuel Dosing Memo, note 39, above.
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hospitalizations, and 1.5 million work days lost. All told, the monetized benefits of the 

on-highway rule plus the nonroad diesel Tier 4 rule total over $150 billion. A sizeable 

part of the benefits in the early years of these programs has come from large reductions in 

the amount of direct and secondary PM emitted by the existing fleet of heavy-duty 

engines and vehicles, by requiring the use of the higher quality diesel fuel in these 

vehicles. While this proposed action may slightly increase some emissions, as explained 

in the previous section, we do not expect that these small increases will significantly

diminish the health benefits of our stringent clean diesel standards.

VIII. Public Participation

We request comment by July 27, 2012 on all aspects of this proposal. This section 

describes how you can participate in this process. 

A. How Do I Submit Comments?

We are opening a formal comment period by publishing this document. We will 

accept comments through July 27, 2012. If you have an interest in the program described 

in this document, we encourage you to comment on any aspect of this rulemaking. We 

request comment on various topics throughout this proposal. 

Your comments will be most useful if you include appropriate and detailed 

supporting rationale, data, and analysis. If you disagree with parts of the proposed 

program, we encourage you to suggest and analyze alternate approaches to meeting the 

goals described in this proposal. You should send all comments, except those containing 
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proprietary information, to our Air Docket (see ADDRESSES) before the end of the 

comment period. 

If you submit proprietary information for our consideration, you should clearly 

separate it from other comments by labeling it “Confidential Business Information 

(CBI).” You should send CBI directly to the contact person listed under FOR FURTHER 

INFORMATION CONTACT instead of the public docket. This will help ensure that no 

one inadvertently places proprietary information in the docket. If you want us to use your 

confidential information as part of the basis for the final rule, you should send a nonconfidential version of the document summarizing the key data or information. We will 

disclose information covered by a claim of confidentiality only through the application of 

procedures described in 40 CFR part 2. If you do not identify information as confidential 

when we receive it, we may make it available to the public without notifying you. 

EPA is also publishing a Direct Final Rule (DFR) addressing the emergency 

vehicle provisions described in Section IV of this document. If we receive adverse 

comments on the emergency vehicle provisions in this proposal by [Insert date 30 days 

from date of publication in the Federal Register], we will publish a timely withdrawal 

in the Federal Register informing the public that the direct final rule will not take effect, 

and we will complete the process of responding to comments and issuing a final rule.

EPA is publishing the DFR to expedite the deployment of solutions that will best 

ensure the readiness of the nation’s emergency vehicles. We request that commenters 

identify in your comments any portions of the emergency vehicle proposed action 

described in Section IV above with which you agree and support as proposed, in addition 
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to any comments regarding suggestions for improvement or provisions with which you 

disagree. In the case of a comment that is otherwise unclear whether it is adverse, EPA 

would interpret relevant comments calling for more flexibility or less restrictions for 

emergency vehicles as supportive of the direct final action. In this way, the EPA will be 

able to adopt those elements of the DFR that are fully supported and most needed today, 

while considering and addressing any adverse comments received on the proposed rule, 

in the course of developing the final rule.

Note that Docket Number EPA-HQ-OAR-2011-1032 is being used for both the 

DFR and this Notice of Proposed Rulemaking (NPRM).

B. Will There Be a Public Hearing?

We will hold a public hearing at the EPA’s National Vehicle and Fuels Emission 

Laboratory, 2565 Plymouth Road in Ann Arbor, Michigan on June 27, 2012. The 

hearing will start at 10:00 am and continue until everyone has had a chance to speak. 

If you would like to present testimony at the public hearing, we ask that you 

notify the contact person listed above under FOR FURTHER INFORMATION 

CONTACT at least ten days before the hearing. You should estimate the time you will 

need for your presentation and identify any needed audio/visual equipment. We suggest 

that you bring copies of your statement or other material for the EPA panel and the 

audience. It would also be helpful if you send us a copy of your statement or other 

materials before the hearing. 
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We will make a tentative schedule for the order of testimony based on the 

notifications we receive. This schedule will be available on the morning of the hearing. In 

addition, we will reserve a block of time for anyone else in the audience who wants to 

give testimony. We will conduct the hearing informally, and technical rules of evidence 

won’t apply. We will arrange for a written transcript of the hearing and keep the official 

record of the hearing open for 30 days to allow you to submit supplementary information. 

You may make arrangements for copies of the transcript directly with the court reporter. 

IX. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive 

Order 13563: Improving Regulation and Regulatory Review

This action is not a “significant regulatory action” under the terms of Executive 

Order (EO) 12866 (58 FR 51735, October 4, 1993) and is therefore not subject to review 

under Executive Orders 12866 and 13563 (76 FR 3821, January 21, 2011).

B. Paperwork Reduction Act

This action does not impose any new information collection burden. The proposed 

regulatory relief for emergency vehicles would be voluntary and optional, and the 

proposed revisions for engine and vehicle maintenance would merely codify existing 

guidelines. However, the Office of Management and Budget (OMB) has previously

approved the information collection requirements contained in the existing regulations 

under the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and has 

assigned OMB Control Numbers 2060-0104 and 2060-0287. The OMB control numbers 

for EPA’s regulations in 40 CFR are listed in 40 CFR part 9.
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C. Regulatory Flexibility Act

The Regulatory Flexibility Act (RFA) generally requires an agency to prepare a 

regulatory flexibility analysis of any rule subject to notice and comment rulemaking 

requirements under the Administrative Procedure Act or any other statute unless the 

agency certifies that the rule will not have a significant economic impact on a substantial 

number of small entities. Small entities include small businesses, small organizations, 

and small governmental jurisdictions.

For purposes of assessing the impacts of this rule on small entities, small entity is 

defined as: (1) a small business primarily engaged in shipbuilding and repairing as 

defined by NAICS code 336611 with 1,000 or fewer employees (based on Small 

Business Administration size standards); (2) a small business that is primarily engaged in 

freight or passenger transportation on the Great Lakes as defined by NAICS codes 

483113 and 483114 with 500 or fewer employees (based on Small Business 

Administration size standards); (3) a small business primarily engaged in commercial and 

industrial machinery and equipment repair and maintenance as defined by NAICS code 

811310 with annual receipts less than $7 million (based on Small Business 

Administration size standards); (4) a small governmental jurisdiction that is a government 

of a city, county, town, school district or special district with a population of less than 

50,000; and (5) a small organization that is any not-for-profit enterprise which is 

independently owned and operated and is not dominant in its field.
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After considering the economic impacts of today’s proposed rule on small 

entities, I certify that proposed rule would not have a significant economic impact on a 

substantial number of small entities. 

In determining whether a rule has a significant economic impact on a substantial 

number of small entities, the impact of concern is any significant adverse economic 

impact on small entities, since the primary purpose of the regulatory flexibility analyses 

is to identify and address regulatory alternatives “which minimize any significant 

economic impact of the rule on small entities.” 5 U.S.C. 603 and 604. Thus, an agency

may certify that a rule will not have a significant economic impact on a substantial 

number of small entities if the rule relieves regulatory burden, or otherwise has a positive 

economic effect on all of the small entities subject to the rule. 

This proposed rule provides regulatory relief related to emergency vehicles and 

codifies existing guidelines related to engine and vehicle maintenance. As such, we 

anticipate no costs and therefore no regulatory burden associated with this rule. We have 

concluded that this rule will not increase regulatory burden for affected small entities.

D. Unfunded Mandates Reform Act

This proposal contains no Federal mandates under the regulatory provisions of 

Title II of the UMRA for State, local, or tribal governments. The proposal imposes no 

enforceable duty on any State, local or tribal governments. EPA has determined that this 

proposal contains no regulatory requirements that might significantly or uniquely affect 

small governments. The agency has determined that this proposal does not contain a 

Federal mandate that may result in expenditures of $100 million or more for the private 
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sector in any one year. Manufacturers have the flexibility and will likely choose whether 

or not to use optional AECD’s based on their strategies for complying with the applicable 

emissions standards. Similarly, manufacturers may choose to use DEF maintenance 

intervals longer than the minimums proposed in this action, and manufacturers may elect 

to use SCR strategies that consume lower amounts of DEF. Thus, today’s proposal is not 

subject to the requirements of sections 202 and 205 of the UMRA.

E. Executive Order 13132: Federalism

Executive Order 13132, entitled “Federalism” (64 FR 43255, August 10, 1999), 

requires EPA to develop an accountable process to ensure “meaningful and timely input 

by State and local officials in the development of regulatory policies that have federalism 

implications.” “Policies that have federalism implications” is defined in the Executive 

Order to include regulations that have “substantial direct effects on the States, on the 

relationship between the national government and the States, or on the distribution of 

power and responsibilities among the various levels of government.” 

This proposed action does not have federalism implications. It will not have 

substantial direct effects on the States, on the relationship between the national 

government and the States, or on the distribution of power and responsibilities among the 

various levels of government, as specified in Executive Order 13132. This proposed rule 

would apply to manufacturers of heavy-duty diesel engines and not to state or local 

governments. Thus, Executive Order 13132 does not apply to this action. 
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In the spirit of Executive Order 13132, and consistent with EPA policy to promote 

communications between the agency and State and local governments, the agency

specifically solicits comment on this proposed action from State and local officials.

F. Executive Order 13175: Consultation and Coordination with Indian Tribal 

Governments

This action does not have tribal implications, as specified in Executive Order 

13175 (65 FR 67249, November 9, 2000). This proposal will be implemented at the 

Federal level and would impose compliance costs only on affected engine manufacturers 

depending on the extent to which they take advantage of the flexibilities offered. Tribal 

governments would be affected only to the extent they purchase and use vehicles with 

regulated engines. Thus, Executive Order 13175 does not apply to this proposed rule. 

EPA specifically solicits additional comment on this proposed action from tribal officials.

G. Executive Order 13045: Protection of Children from Environmental Health 

and Safety Risks

Executive Order 13045: “Protection of Children from Environmental Health 

Risks and Safety Risks” (62 FR 19885, April 23, 1997) applies to any rule that: (1) is 

determined to be “economically significant” as defined under Executive Order 12866, 

and (2) concerns an environmental health or safety risk that EPA has reason to believe 

may have a disproportionate effect on children. If the regulatory action meets both 

criteria, the agency must evaluate the environmental health or safety effects of the 

planned rule on children, and explain why the planned regulation is preferable to other 

potentially effective and reasonably feasible alternatives considered by the agency.
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EPA interprets Executive Order 13045 as applying only to those regulatory

actions that are based on health or safety risks, such that the analysis required under 

section 5-501 of the Order has the potential to influence the regulation. This proposed 

rule is not subject to Executive Order 13045 because it does not establish an 

environmental standard intended to mitigate health or safety risks.

H. Executive Order 13211: Energy Effects

This proposed action is not subject to Executive Order 13211 (66 FR 28355 (May

22, 2001)), because it is not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer Advancement Act

Section 12(d) of the National Technology Transfer and Advancement Act of 1995 

(“NTTAA”), Public Law No. 104-113, 12(d) (15 U.S.C. 272 note) directs EPA to use 

voluntary consensus standards in its regulatory activities unless to do so would be 

inconsistent with applicable law or otherwise impractical. Voluntary consensus standards 

are technical standards (e.g., materials, specifications, test methods, sampling procedures, 

and business practices) that are developed or adopted by voluntary consensus standards 

bodies. NTTAA directs EPA to provide Congress, through OMB, explanations when the 

Agency decides not to use available and applicable voluntary consensus standards. 

This action does not involve technical standards. Therefore, EPA is not considering 

the use of any voluntary consensus standards.
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J. Executive Order 12898: Federal Actions to Address Environmental Justice in 

Minority Populations and Low-Income Populations

Executive Order 12898 (59 FR 7629 (Feb. 16, 1994)) establishes federal 

executive policy on environmental justice. Its main provision directs federal agencies, to 

the greatest extent practicable and permitted by law, to make environmental justice part 

of their mission by identifying and addressing, as appropriate, disproportionately high 

and adverse human health or environmental effects of their programs, policies, and 

activities on minority populations and low-income populations in the United States. 

EPA has determined that this proposed rule would not have disproportionately

high and adverse human health or environmental effects on minority or low-income 

populations. This action is expected to increase the level of environmental protection for 

all affected populations because this proposed rule increases the ways that manufacturers 

can demonstrate compliance with heavy-duty engine standards.

List of Subjects

40 CFR Part 85

Confidential business information, Imports, Labeling, Motor vehicle pollution, Reporting 

and recordkeeping requirements, Research, Warranties.

40 CFR Part 86

Administrative practice and procedure, Confidential business information, Motor vehicle 

pollution, Reporting and recordkeeping requirements.
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40 CFR Part 1039

Environmental Protection, Administrative practice and procedure, Air pollution control, 

Confidential business information, Imports, Labeling, Penalties, Reporting and 

recordkeeping requirements, Warranties.

Dated: May 23, 2012 Lisa P. Jackson

Administrator

For the reasons set forth in the preamble, the Environmental Protection Agency proposes 

to amend title 40, chapter I of the Code of Federal Regulations as follows:

PART 85— CONTROL OF AIR POLLUTION FROM MOBILE SOURCES

1. The authority citation for part 85 continues to read as follows:

Authority: 42 U.S.C. 7401-7671q.

Subpart R–[Amended]

2. Add §85.1716 to subpart R to read as follows:

§ 85.1716 Approval of an emergency vehicle field modification (EVFM).
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This section describes how you may implement design changes for an emergency vehicle 

that has already been placed into service to ensure that the vehicle will perform properly 

in emergency situations. This applies for any light-duty vehicle, light-duty truck, or 

heavy-duty vehicle meeting the definition of emergency vehicle in 40 CFR 86.004-2 or 

86.1803. In this section, “you” refers to the certifying manufacturer and “we” refers to 

the EPA Administrator and any authorized representatives. 

(a) You must notify us in writing of your intent to install or distribute an emergency 

vehicle field modification (EVFM). In some cases you may install or distribute an EVFM 

only with our advance approval, as specified in this section.

(b) Include in your notification a full description of the EVFM and any documentation to 

support your determination that the EVFM is necessary to prevent the vehicle from losing 

speed, torque, or power due to abnormal conditions of its emission control system, or to 

prevent such abnormal conditions from occurring during operation related to emergency

response. Examples of such abnormal conditions may include excessive exhaust 

backpressure from an overloaded particulate trap, or running out of diesel exhaust fluid 

for engines that rely on urea-based selective catalytic reduction. Your determination 

must be based on an engineering evaluation or testing or both.

(c) You may need our advance approval for your EVFM, as follows:

(1) Where the proposed EVFM is identical to an AECD we approved under this part 

for an engine family currently in production, no approval of the proposed EVFM is 

necessary.

(2) Where the proposed EVFM is for an engine family currently in production but the 

applicable demonstration is based on an AECD we approved under this part for an 
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engine family no longer in production, you must describe to us how your proposed 

EVFM differs from the approved AECD. Unless we say otherwise, your proposed 

EVFM is deemed approved 30 days after you notify us.

(3) If we have not approved an EVFM comparable to the one you are proposing, you 

must get our approval before installing or distributing it. In this case, we may request 

additional information to support your determination under paragraph (b) of this 

section, as follows:

(i) If we request additional information and you do not provide it within 30 days 

after we ask, we may deem that you have retracted your request for our approval; 

however, we may extend this deadline for submitting the additional information.

(ii) We will deny your request if we determine that the EVFM is not necessary to 

prevent the vehicle from losing speed, torque, or power due abnormal conditions 

of the emission control system, or to prevent such abnormal conditions from 

occurring, during operation related to emergency response.

(iii) Unless we say otherwise, your proposed EVFM is deemed approved 30 days 

after we acknowledge that you have provided us with all the additional 

information we have specified.

(4) If your proposed EVFM is deemed to be approved under paragraph (c)(2) or (3) of 

this section and we find later that your EVFM in fact does not meet the requirements 

of this section, we may require you to no longer install or distribute it.

PART 86--CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY 

VEHICLES AND ENGINES
Page 107 of 125

3. The authority citation for part 86 continues to read as follows:

Authority: 42 U.S.C. 7401-7671q.

Subpart A–[Amended]

4. Section 86.004-2 is amended as follows:

a. By adding a definition for “Ambulance” in alphabetical order.

b. By revising the definition for “Defeat device”.

c. By adding definitions for “Diesel exhaust fluid”, “Emergency vehicle”, and “Fire 

truck” in alphabetical order.

§ 86.004–2 Definitions.

* * * * *

Ambulance has the meaning given in §86.1803.

Defeat device means an auxiliary emission control device (AECD) that reduces the 

effectiveness of the emission control system under conditions which may reasonably be 

expected to be encountered in normal vehicle operation and use, unless:

(1) Such conditions are substantially included in the applicable Federal emission test 

procedure for heavy-duty vehicles and heavy-duty engines described in subpart N of this 

part;

(2) The need for the AECD is justified in terms of protecting the vehicle against damage 

or accident; 

(3) The AECD does not go beyond the requirements of engine starting; or

(4) The AECD applies only for engines that will be installed in emergency vehicles, and 

the need is justified in terms of preventing the engine from losing speed, torque, or power 
Page 108 of 125

due abnormal conditions of the emission control system, or in terms of preventing such 

abnormal conditions from occurring, during operation related to emergency response. 

Examples of such abnormal conditions may include excessive exhaust backpressure from 

an overloaded particulate trap, and running out of diesel exhaust fluid for engines that 

rely on urea-based selective catalytic reduction. 

Diesel exhaust fluid (DEF) has the meaning given in §86.1803.

Emergency vehicle means a vehicle that is an ambulance or a fire truck. 

Fire truck has the meaning given in §86.1803.

* * * * *

5. Section 86.004-25 is amended as follows:

a. By revising paragraph (b)(4) introductory text.

b. By adding paragraph (b)(4)(v).

c. By revising paragraph (b)(6)(i) introductory text and (b)(6)(i)(H).

d. By adding paragraph (b)(6)(i)(I).

§ 86.004-25 Maintenance.

* * * * *

(b) * * *

(4) For diesel-cycle heavy-duty engines, emission-related maintenance in addition to or 

at shorter intervals than the following specified values will not be accepted as 

technologically necessary, except as provided in paragraph (b)(7) of this section:

* * * * *
Page 109 of 125

(v) For engines that use selective catalytic reduction, the replenishment of diesel exhaust 

fluid shall occur according to the following schedule:

(A) For heavy-duty engines in vocational vehicles such as dump trucks, concrete 

mixers, refuse trucks and similar applications that are typically centrally fueled, at an 

interval, in miles or hours of vehicle operation, that is no less than the vehicle’s fuel 

capacity. 

(B) For all other heavy-duty engines, at an interval, in miles or hours of vehicle 

operation, that is no less than twice the vehicle’s fuel capacity.

* * * * *

(6)(i) The following components are defined as critical emission-related components:

* * * * *

(H) Components comprising the selective catalytic reduction system (including diesel 

exhaust fluid tank).

(I) Any other component whose primary purpose is to reduce emissions or whose failure 

would commonly increase emissions of any regulated pollutant without significantly

degrading engine performance. 

* * * * *

6. Section 86.0004-28 is amended by revising paragraph (i) introductory text to read as 

follows:

§ 86.004-28 Compliance with emission standards.

* * * * *
Page 110 of 125

(i) Emission results from heavy-duty engines equipped with exhaust aftertreatment may

need to be adjusted to account for regeneration events. This provision only applies for 

engines equipped with emission controls that are regenerated on an infrequent basis. For 

the purpose of this paragraph (i), the term “regeneration” means an event during which 

emission levels change while the aftertreatment performance is being restored by design. 

Examples of regenerations are increasing exhaust gas temperature to remove sulfur from 

an adsorber or increasing exhaust gas temperature to oxidize PM in a trap. For the 

purpose of this paragraph (i), the term “infrequent” means having an expected frequency

of less than once per transient test cycle. Calculation and use of adjustment factors are 

described in paragraphs (i)(1)–(5) of this section. If your engine family includes engines 

with one or more AECDs for emergency vehicle applications approved under paragraph 

(4) of the definition of “defeat device” in § 86.004-2, do not consider additional 

regenerations resulting from those AECDs when calculating emission factors or 

frequencies under this paragraph (i).

* * * * *

7. Section 86.095-35 is amended by revising paragraph (a)(3)(iii)(O) to read as follows:

§ 86.095-35 Labeling.

(a) * * *

(3) * * *

(iii) * * *
Page 111 of 125

(O) For engines with one or more approved AECDs for emergency vehicle applications 

under paragraph (4) of the definition of “defeat device” in § 86.004-2, the statement: 

“THIS ENGINE IS FOR INSTALLATION IN EMERGENCY VEHICLES ONLY.”

* * * * *

Subpart B–[Amended]

8. Section 86.131-00 is amended by adding paragraph (g) to read as follows:

§ 86.131-00 Vehicle preparation.

* * * * *

(g) You may disable any AECDs that have been approved solely for emergency vehicle 

applications under paragraph (4) of the definition of “defeat device” in § 86.004-2. The 

emission standards do not apply when any of these AECDs are active.

Subpart N–[Amended]

9. Section 86.1305-2010 is amended by adding paragraph (i) to read as follows:

§ 86.1305-2010 Introduction; structure of subpart.

* * * * *

(i) You may disable any AECDs that have been approved solely for emergency vehicle 

applications under paragraph (4) of the definition of “defeat device: in § 86.004-2. The 

emission standards do not apply when any of these AECDs are active.

10. Section 86.1370-2007 is amended by adding paragraph (h) to read as follows:

§ 86.1370-2007 Not-To-Exceed test procedures. 

* * * * *
Page 112 of 125

(h) Emergency vehicle AECDs. If your engine family includes engines with one or more 

approved AECDs for emergency vehicle applications under paragraph (4) of the 

definition of “defeat device” in § 86.004-2, the NTE emission limits do not apply when 

any of these AECDs are active.

Subpart S–[Amended]

11. Section 86.1803-01 is amended as follows:

a. By adding a definition for “Ambulance” in alphabetical order.

b. By revising the definition for “Defeat device”.

c. By adding definitions for “Diesel exhaust fluid”, “Emergency vehicle”, and “Fire 

truck” in alphabetical order.

§ 86.1803-01 Definitions.

* * * * *

Ambulance means a vehicle used for emergency medical care that provides all of the 

following:

(1) A driver’s compartment.

(2) A patient compartment to accommodate an emergency medical services provider and 

one patient located on the primary cot so positioned that the primary patient can be given 

intensive life-support during transit.

(3) Equipment and supplies for emergency care at the scene as well as during transport.

(4) Safety, comfort, and avoidance of aggravation of the patient’s injury or illness.

(5) Two-way radio communication.

(6) Audible and visual traffic warning devices.
Page 113 of 125

* * * * *

Defeat device means an auxiliary emission control device (AECD) that reduces the 

effectiveness of the emission control system under conditions which may reasonably be 

expected to be encountered in normal vehicle operation and use, unless:

(1) Such conditions are substantially included in the Federal emission test procedure;

(2) The need for the AECD is justified in terms of protecting the vehicle against damage 

or accident;

(3) The AECD does not go beyond the requirements of engine starting; or

(4) The AECD applies only for emergency vehicles and the need is justified in terms of 

preventing the vehicle from losing speed, torque, or power due to abnormal conditions of 

the emission control system, or in terms of preventing such abnormal conditions from 

occurring, during operation related to emergency response. Examples of such abnormal 

conditions may include excessive exhaust backpressure from an overloaded particulate 

trap, and running out of diesel exhaust fluid for engines that rely on urea-based selective 

catalytic reduction.

* * * * *

Diesel exhaust fluid (DEF) means a liquid compound used in conjunction with 

selective catalytic reduction to reduce NOX emissions. Diesel exhaust fluid is generally 

understood to conform to the specifications of ISO 22241.

* * * * *

Emergency vehicle means a vehicle that is an ambulance or a fire truck.

* * * * *
Page 114 of 125

Fire truck means a vehicle designed to be used under emergency conditions to 

transport personnel and equipment and to support the suppression of fires and mitigation 

of other hazardous situations.

* * * * *

12. Section 86.1807-01 is amended by adding paragraphs (h) and (i) to read as follows:

§ 86.1807-01 Vehicle labeling.

* * * * *

(h) Vehicles powered by model year 2007 through 2013 diesel-fueled engines must 

include permanent readily visible labels on the dashboard (or instrument panel) and near 

all fuel inlets that state “Use Ultra Low Sulfur Diesel Fuel Only” or “Ultra Low Sulfur 

Diesel Fuel Only”.

(i) For vehicles with one or more approved AECDs for emergency vehicles under 

paragraph (4) of the definition of defeat device in § 86.1803, include the following 

statement on the emission control information label: “THIS VEHICLE HAS A LIMITED 

EXEMPTION AS AN EMERGENCY VEHICLE.”

§86.1807-07 – [Removed

13. Subpart S is amended by removing §86.1807-07.

]

14. Section 86.1834-01 is amended as follows:

a. By revising paragraph the introductory text of (b)(4).
Page 115 of 125

b. By adding paragraph (b)(4)(iii).

c. By revising paragraph (b)(6)(i)(H).

d. By adding paragraph (b)(6)(i)(I).

§ 86.1834-01 Allowable maintenance.

* * * * *

(b) * * *

(4) For diesel-cycle vehicles, emission-related maintenance in addition to, or at shorter 

intervals than the following will not be accepted as technologically necessary, except as 

provided in paragraph (b)(7) of this section:

* * * * *

(iii) For vehicles that use selective catalytic reduction, the replenishment of diesel 

exhaust fluid shall occur at an interval, in miles or hours of vehicle operation, that is no 

less than the scheduled oil change interval.

* * * * *

(6) * * *

(i) * * *

(H) Components comprising the selective catalytic reduction system (including diesel 

exhaust fluid tank).

(I) Any other component whose primary purpose is to reduce emissions or whose failure 

would commonly increase emissions of any regulated pollutant without significantly

degrading engine performance.

* * * * *
Page 116 of 125

15. Section 86.1840-01 is amended by revising paragraph (c) to read as follows:

§ 86.1840-01 Special test procedures.

* * * * *

(c) Manufacturers of vehicles equipped with periodically regenerating aftertreatment 

devices must propose a procedure for testing and certifying such vehicles, including 

SFTP testing, for the review and approval of the Administrator. The manufacturer must 

submit its proposal before it begins any service accumulation or emission testing. The 

manufacturer must provide with its submittal sufficient documentation and data for the 

Administrator to fully evaluate the operation of the aftertreatment devices and the 

proposed certification and testing procedure.

* * * * *

PART 1039–CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD 

COMPRESSION-IGNITION ENGINES

16. The authority citation for part 1039 continues to read as follows:

Authority: 42 U.S.C. 7401-7671q.

Subpart B–[Amended]

17. Section 1039.115 is amended by adding paragraphs (g)(4) and (5) to read as follows:

§1039.115 What other requirements apply?

* * * * *

(g) * * *
Page 117 of 125

(4) The auxiliary emission control device applies only for engines that will be 

installed in emergency equipment and the need is justified in terms of preventing the 

equipment from losing speed or power due to abnormal conditions of the emission 

control system, or in terms of preventing such abnormal conditions from occurring, 

during operation related to emergency response. Examples of such abnormal 

conditions may include excessive exhaust backpressure from an overloaded 

particulate trap, and running out of diesel exhaust fluid for engines that rely on ureabased selective catalytic reduction. The emission standards do not apply when any 

AECDs approved under this paragraph (g)(4) are active.

(5) The auxiliary emission control device operates only in emergency situations as 

defined in §1039.665 and meets all of the requirements of that section, and you meet 

all of the requirements of that section.

18. Section 1039.125 is amended by adding paragraphs (a)(2)(iii) and (a)(3)(iii) to read

as follows:

§ 1039.125 What maintenance instructions must I give to buyers?

* * * * *

(a) * * *

(2) * * *

(iii) For SCR systems, the minimum interval for replenishing the diesel exhaust fluid is 

the number of engine operating hours necessary to consume a full tank of fuel based on 

normal usage starting from full fuel capacity for the equipment. 

(3) * * *
Page 118 of 125

(iii) For SCR systems, the minimum interval for replenishing the diesel exhaust fluid is 

the number of engine operating hours necessary to consume a full tank of fuel based on 

normal usage starting from full fuel capacity for the equipment. 

* * * * *

19. Section 1039.130 is amended by revising paragraph (b)(3) to read as follows:

§ 1039.130 What installation instructions must I give to equipment manufacturers?

* * * * *

(b) * * *

(3) Describe the instructions needed to properly install the exhaust system and any other 

components. Include instructions consistent with the requirements of §1039.205(u). Also 

describe how to properly size diesel exhaust fluid reservoirs consistent with the 

specifications in §1039.125(a) if applicable.

* * * * *

20. Section 1039.135 is amended by adding paragraph (c)(15) to read as follows:

§1039.135 How must I label and identify the engines I produce?

* * * * *

(c) * * *

(15) For engines with one or more approved auxiliary emission control devices for 

emergency equipment applications under §1039.115(g)(4), the statement: “THIS 

ENGINE IS FOR INSTALLATION IN EMERGENCY EQUIPMENT ONLY.”

* * * * *
Page 119 of 125

Subpart F–[Amended]

21. Section 1039.501 is amended by adding paragraph (g) to read as follows:

§ 1039.501 How do I run a valid emission test?

* * * * *

(g) You may disable any AECDs that have been approved solely for emergency 

equipment applications under §1039.115(g)(4). 

22. Section 1039.525 is amended by revising the introductory text to read as follows:

§ 1039.525 How do I adjust emission levels to account for infrequently 

regenerating aftertreatment devices?

This section describes how to adjust emission results from engines using aftertreatment 

technology with infrequent regeneration events. For this section, “regeneration” means an 

intended event during which emission levels change while the system restores 

aftertreatment performance. For example, exhaust gas temperatures may increase 

temporarily to remove sulfur from adsorbers or to oxidize accumulated particulate matter 

in a trap. For this section, “infrequent” refers to regeneration events that are expected to 

occur on average less than once over the applicable transient duty cycle or ramped-modal 

cycle, or on average less than once per typical mode in a discrete-mode test. If your 

engine family includes engines with one or more AECDs for emergency equipment 

applications approved under §1039.115(g)(4), do not consider additional regenerations 

resulting from those AECDs when calculating emission factors or frequencies under this 

section.
Page 120 of 125

* * * * *

Subpart G–[Amended]

23. Add §1039.665 to subpart G to read as follows:

§1039.665 Special provisions for use of engines in emergency situations.

This section specifies provisions that allow for AECDs that are necessary to ensure 

proper functioning of engines and equipment regulated under this part in emergency

situations. For purposes of this section, an emergency situation is one in which the 

functioning (or malfunctioning) of emission controls poses a significant risk to human 

life. For example, a situation in which a feature of emission controls inhibits the 

performance of an engine being used to rescue a person from a life-threatening situation 

would be an emergency situation. AECDs approved under this section are not defeat 

devices.

(a) Manufacturers may ask for approval under this section at any time; however, we 

encourage manufacturers to obtain preliminary approval before submitting an application 

for certification. We may allow manufacturers to apply an approved emergency AECD 

to engines and equipment that have already been placed into service.

(b) We will approve an AECD where we determine the following criteria are met:

(1) Activation of the AECD cannot occur without the specific permission of the 

certificate holder, and must require the input of a temporary code or equivalent 

security feature.

(2) The AECD must become inactive within 24 engine hours of becoming active.
Page 121 of 125

(3) The AECD may deactivate emission controls as necessary to address the 

emergency situation. For purposes of this paragraph (b)(3), inducement strategies 

related to operating SCR-equipped engines without reductant are considered to be 

emission controls.

(4) The AECD’s design is consistent with good engineering judgment.

(c) The certificate holder must keep records to document requests for and use of 

emergency AECDs under this section. 

(1) The operator (or other person responsible for the engine/equipment) must send a 

written request to the certificate holder prior to use, or a written confirmation of a 

verbal request within 30 days of making the request, including a description of the 

emergency situation, the reason for the use of the AECD, and a signature from an 

official acknowledging the conditions of the emergency situation (such as a county 

sheriff, fire marshal, or hospital administrator). Such requests are deemed to be 

submissions to EPA. Where written confirmation is not submitted by the operator, 

we will deem operation of the engine with an activated emergency AECD to be a 

violation of 40 CFR 1068.101(b)(1).

(2) If the operator does not submit the applicable confirmation within 30 days, the 

certificate holder must send written notification to the operator that failure to submit 

written confirmation may subject the operator to penalties under 40 CFR 1068.101. 

(3) Within 60 days of the end of each calendar year in which the certificate holder 

authorizes use of the AECD, the certificate holder must send a report to the 

Designated Compliance Officer to summarize such use, including a description of the 

emergency situation precipitating each use, and copies of the written confirmation 
Page 122 of 125

provided by operators (or statements that the operator did not provide confirmation). 

We may require more frequent reporting if we find that the certificate holder does not 

collect or attempt to collect written confirmation for each situation. 

(d) We may set other reasonable conditions to ensure that this provision is not used to 

circumvent the emission standards of this part.

24. Add §1039.670 to subpart G to read as follows:

§ 1039.670 Approval of an emergency equipment field modification (EEFM).

This section describes how you may implement design changes for emergency equipment 

that has already been placed into service to ensure that the equipment will perform 

properly in emergency situations.

(a) You must notify us in writing of your intent to install or distribute an emergency 

equipment field modification (EEFM). In some cases you may install or distribute an 

EEFM only with our advance approval, as specified in this section.

(b) Include in your notification a full description of the EEFM and any documentation to 

support your determination that the EEFM is necessary to prevent the equipment from 

losing speed, torque, or power due to abnormal conditions of its emission control system, 

or to prevent such abnormal conditions from occurring during operation related to 

emergency response. Examples of such abnormal conditions may include excessive 

exhaust backpressure from an overloaded particulate trap, or running out of diesel 

exhaust fluid (DEF) for engines that rely on urea-based selective catalytic reduction. 

Your determination must be based on an engineering evaluation or testing or both.

(c) You may need our advance approval for your EEFM, as follows:
Page 123 of 125

(1) Where the proposed EEFM is identical to an AECD we approved under this part 

for an engine family currently in production, no approval of the proposed EEFM is 

necessary.

(2) Where the proposed EEFM is for an engine family currently in production but the 

applicable demonstration is based on an AECD we approved under this part for an 

engine family no longer in production, you must describe to us how your proposed 

EEFM differs from the approved AECD. Unless we say otherwise, your proposed 

EEFM is deemed approved 30 days after you notify us.

(3) If we have not approved an EEFM comparable to the one you are proposing, you 

must get our approval before installing or distributing it. In this case, we may request 

additional information to support your determination under paragraph (b) of this 

section, as follows:

(i) If we request additional information and you do not provide it within 30 days 

after we ask, we may deem that you have retracted your request for our approval; 

however, we may extend this deadline for submitting the additional information.

(ii) We will deny your request if we determine that the EEFM is not necessary to 

prevent the equipment from losing speed, torque, or power due abnormal 

conditions of the emission control system, or to prevent such abnormal conditions 

from occurring, during operation related to emergency response.

(iii) Unless we say otherwise, your proposed EEFM is deemed approved 30 days 

after we acknowledge that you have provided us with all the additional 

information we have specified.
Page 124 of 125

(4) If your proposed EEFM is deemed to be approved under paragraph (c)(2) or (3) of 

this section and we find later that your EEFM in fact does not meet the requirements 

of this section, we may require you to no longer install or distribute it.

Subpart I–[Amended]

25. Section 1039.801 is amended by adding definitions for “Diesel exhaust fluid” and 

“Emergency equipment” in alphabetical order to read as follows:

§ 1039.801 What definitions apply to this part?

* * * * *

Diesel exhaust fluid (DEF) means a liquid compound used in conjunction with 

selective catalytic reduction to reduce NOX emissions. Diesel exhaust fluid is generally 

understood to conform to the specifications of ISO 22241.

* * * * *

Emergency equipment means either of the following types of equipment:

(1) Specialized vehicles used to perform aircraft rescue and fire-fighting functions at 

airports, with particular emphasis on saving lives and reducing injuries coincident with 

aircraft fires following impact or aircraft ground fires.

(2) Wildland fire apparatus, which includes any apparatus equipped with a slip-on firefighting module, designed primarily to support wildland fire suppression operations.

* * * * *

26. Section 1039.805 is amended by adding abbreviations for “DEF”, “EEFM”, “ISO”, 

and “SCR” in alphabetical order to read as follows:
Page 125 of 125

§ 1039.805 What symbols, acronyms, and abbreviations does this part use?

* * * * *

DEF Diesel exhaust fluid.

EEFM Emergency equipment field modification.

* * * * *

ISO International Organization for Standardization (see www.iso.org).

* * * * *

SCR Selective catalytic reduction.

* * * * *