[Federal Register Volume 76, Number 109 (Tuesday, June 7, 2011)]
[Proposed Rules]
[Pages 32886-32896]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-13851]



40 CFR Part 86


Control of Emissions From New Highway Vehicles and Engines; 
Guidance on EPA's Certification Requirements for Heavy-Duty Diesel 
Engines Using Selective Catalytic Reduction Technology

AGENCY: Environmental Protection Agency (EPA).

ACTION: Request for comments.


SUMMARY: EPA is requesting comment on draft guidance and related 
interpretations concerning the application of certain emission 
certification regulations to those on-highway heavy-duty diesel engines 
that are using selective catalytic reduction systems to meet Federal 
emission standards. EPA will review the comments and provide final 
guidance and interpretations in a future Federal Register document.

DATES: Any party may submit written comments by July 7, 2011.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2010-0444, by one of the following methods:
     On-line at http://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     E-mail: [email protected].
     Fax: (202) 566-1741.
     Mail: Air and Radiation Docket, Docket ID No. EPA-HQ-OAR-
2010-0444, Environmental Protection Agency, Mailcode: 6102T, 1200 
Pennsylvania Avenue, NW., Washington, DC 20460. Please include a total 
of two copies.
     Hand Delivery: EPA Docket Center, Public Reading Room, EPA 
West Building, Room 3334, 1301 Constitution Avenue, NW., Washington, DC 
20460. Such deliveries are only accepted during the Docket's normal 
hours of operation, and special arrangements should be made for 
deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2010- 0444. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through http://www.regulations.gov your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional information about EPA's public 
docket, visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm. For additional instructions on submitting 
comments, go to ``What Should I Consider as I Prepare My Comments for 
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Air and Radiation 
Docket, 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: Greg Orehowsky, Heavy-Duty and Nonroad 
Engine Group, Compliance and Innovative Strategies Division, Office of 
Transportation and Air Quality, U.S. Environmental Protection Agency; 
1200 Pennsylvania Avenue, (6405J), NW., Washington, DC 20460. Telephone 
number: 202-343-9292; Fax number: 202-343-2804; E-mail address: 
[email protected].


I. Purpose

    This Federal Register document describes and seeks public comment 
on draft guidance for complying with adjustable parameter regulations 
at 40 CFR 86.094-22 as they apply to certification of on-highway heavy-
duty diesel engines using selective catalytic reduction (SCR) 
technology to meet emission standards for oxides of nitrogen 
(NOX). This draft guidance includes EPA's interpretation of 
relevant regulatory provisions in light of available information on 
current and developing approaches for effective SCR controls. After 
considering any public comments received, EPA will issue the guidance 
and interpretations in the Federal Register, and will use them in 
reviewing any application for certification application involving SCR 
received on or after the effective date of the guidance. The draft 
guidance contained in this document reflects the fact that 
manufacturers of heavy-duty engines and operators of trucks have gained 
significant experience in the design and use of SCR systems for these 
engines, and this experience should be reflected in the certification 
process. We invite public comment on the draft guidance and 
interpretations set forth below.
    Until the effective date of the final guidance and interpretations, 
manufacturers should continue to refer to the regulations and the 
existing guidance documents noted below and to work with their 
certification representatives. We recognize that SCR technology will 
continue to mature, and we anticipate that appropriate designs

[[Page 32887]]

for heavy-duty diesel vehicles and heavy-duty diesel engines using SCR 
systems may continue to evolve as additional experience with the 
technology is gained.
    This draft document provides specific examples of how we interpret 
existing certification regulations and how we intend to apply these 
regulations to heavy-duty diesel engines using SCR systems, based on 
the information available to us. These examples are not exclusive and 
are to be considered examples. Manufacturers remain able to present 
their own unique strategies that are not the same as the examples we 
are providing, and such strategies will remain subject to our review 
and approval under the certification regulations. Manufacturers must 
still show EPA that they meet all statutory and regulatory requirements 
when they apply for certification.

II. Overview

    In promulgating the 0.20 gram per brake horsepower-hour 
NOX standard for 2010 model year heavy-duty diesel engines, 
based on a specified regulatory test procedure, EPA recognized SCR 
technology as one potential approach for achieving the required 
emission reductions. EPA identified several issues for manufacturers to 
address in developing and applying SCR technology. Those issues related 
largely to the technology's use of a chemical reducing agent to reduce 
NOX emissions. The reductant is generally in liquid form, 
which is referred to in this document as DEF (``diesel exhaust 
fluid''). DEF is stored in a tank located on the vehicle and is 
injected into the exhaust downstream of the engine. SCR technologies 
require drivers to refill DEF on a regular basis and are dependent on 
appropriately broad availability of DEF.\1\ EPA regulations governing 
certification of engines generally require manufacturers to show that 
emission control technologies are adequately designed to limit 
adjustments that may increase emissions (``adjustable parameters,'' 
discussed in detail below). SCR is unique among emission controls in 
that it requires on-going driver interaction to ensure proper operation 
of the system.

    \1\ A Class 8 truck equipped with standard dual 150-gallon fuel 
tanks can travel approximately 3,600 miles between DEF tank refills, 
assuming a 20-gallon DEF tank and representative DEF dosing rate of 
3 percent of fuel usage. DEF price varies depending on whether it is 
supplied via bulk container (commonly used by fleets and growing 
numbers of truck stops) or a 1 to 2.5-gallon jug. Current prices for 
bulk DEF at a truck stop are generally less than $3.00 per gallon 
and jug prices can be $4.00 or more per gallon.

    To comply with the NOX standard, most heavy-duty engine 
manufacturers developed SCR systems because of their high efficiency in 
reducing NOX emissions. A relatively unsophisticated SCR 
system can achieve 60 percent reduction and a robust system can achieve 
greater than 80 percent reduction. This enables engine calibrations 
that increase fuel economy. Additionally, SCR technology has a 
relatively lower cost compared to NOX adsorber technology.
    In developing SCR systems, manufacturers consulted with EPA about 
how SCR systems could be designed and what other steps would be needed 
(e.g., concerning DEF availability) to allow SCR to be used consistent 
with EPA regulations. Over a period of years, EPA has developed and 
refined guidance to address how manufacturers could effectively address 
issues related to compliance with the regulations for adjustable 
parameters. Manufacturers have addressed the adjustable parameter 
regulations by designing engines that employ warning systems for the 
driver and engine operation-related inducements for drivers to refill 
DEF tanks with proper DEF.
    Manufacturers have also worked to increase DEF availability through 
infrastructure development. DEF infrastructure and sales volume have 
continued to grow since introduction of 2010 model year trucks equipped 
with SCR systems. Initially, DEF availability was concentrated around 
major truck routes, but has since increased in areas away from these 
locations. DEF is now available for sale in every state at truck stops 
and service facilities, and is available for delivery to fleet 
locations, as well. To assist drivers in finding DEF, multiple 
Internet-based DEF locator services have also been developed. Sales 
volumes of DEF are increasing significantly and are believed to 
correlate with the increased delivery and use of SCR equipped trucks. 
Increasing demand supported by sales volume should continue to drive 
the expanding infrastructure.

III. Relevant Regulatory Provisions

    Under Section 203(a)(1) of the Clean Air Act, engines and/or 
vehicles must be certified as conforming with all applicable 
regulations before they may be introduced into commerce. Of particular 
relevance for on-highway heavy-duty diesel engines using SCR technology 
are the provisions that govern adjustable parameters at 40 CFR 86.094-
22.\2\ In particular, 40 CFR 86.094-22(e) authorizes EPA to determine 
those vehicle or engine parameters that will be subject to adjustment 
for emission testing purposes, and 40 CFR 86.094-22(e)(1) discusses how 
the Agency determines which parameters are subject to adjustment.

    \2\ The regulatory provisions governing allowable maintenance at 
40 CFR 86.004-25 and 40 CFR 86.094-25, and auxiliary emission 
control devices, or AECDs at 40 CFR 86.004-2, 40 CFR 86.082-2 and 40 
CFR 86.004-16 are also relevant to certification of engines using 
SCR technology, but are outside the scope of this document. 
Manufacturers should continue to refer to existing guidance noted 
below covering these regulatory provisions.

    It is important for manufacturers to control the emissions 
performance of an engine or vehicle over the full range of any 
adjustable parameter in order to ensure that in-use operation is as 
good as projected at the time of certification. When emission-related 
parameters can be adjusted, there is a concern that the engine or 
vehicle can be operated at settings other than the manufacturer's 
recommended setting, possibly increasing emission levels.
    If a parameter is subject to adjustment, the engine may be tested 
over any point in the range of adjustment and must meet the emissions 
standard through the range of adjustment. The Administrator determines 
the range of adjustment for emissions testing based on whether the 
means used to inhibit improper adjustment (e.g., limits, stops, seals) 
are adequate. 40 CFR 86.094-22(e)(2) sets forth how EPA determines the 
adequacy of the limits, stops, seals or other means used to inhibit 
improper adjustment. For any parameter that is not adequately limited, 
40 CFR 86.094-22(e) authorizes EPA to adjust the setting within the 
physical limits or stops during certification and other compliance 
testing. If a parameter is determined to be adequately inaccessible, 
sealed, or otherwise inhibited from adjustment, the vehicle will only 
be emission tested at the actual settings to which the parameter is 
adjusted during production. 40 CFR 86.094-22(e)(2)(i) and (ii) 
identifies certain types of parameters subject to adjustment, and 
identifies criteria related to technology, time, or expense for 
determining whether adjustment of the parameter is adequately limited. 
These provisions indicate that the technology used to limit adjustment, 
or the burden on the operator to make an adjustment (e.g., more than 
one-half hour in time or more

[[Page 32888]]

than $20.00 in cost),\3\ can be adequate to determine that the 
parameter is adequately limited and would not be treated as adjustable 
outside of the specified range for purposes of emissions testing for 
compliance with the standard. 40 CFR 86.094-22(e)(2)(iv) states that in 
determining the adequacy of a physical limit, stop, seal, or other 
means used to inhibit adjustment of an adjustable parameter, EPA will 
consider the likelihood that settings other than the manufacturer's 
recommended setting will occur during in-use operation of the vehicle 
or engine, considering such factors as, but not limited to: (1) The 
difficulty and cost of getting access to make an adjustment, (2) the 
damage to the engine/vehicle if an attempt is made, (3) the effect of 
settings beyond the limits, stops, seals, or other means on engine 
performance characteristics other than emission characteristics, and 
(4) surveillance information from similar in-use vehicles or engines.

    \3\ This cost is represented in terms of 1978 dollars. Adjusting 
for inflation, this would equate to roughly $70.00 in 2011 dollars.

    The emission control efficiency of an SCR system is highly 
dependent on the presence and quality of the reducing agent. 
Consequently, it is critical that a SCR-equipped vehicle be designed so 
that it is highly unlikely that the vehicle will be used without proper 
reducing agent. Given that most SCR system designs store the required 
DEF in a tank located on the vehicle and depend on the vehicle operator 
to refill the tank with DEF, EPA has indicated in previous guidance 
that manufacturers relying on SCR systems for emission control must 
incorporate engine design elements that make it highly unlikely the 
vehicle will operate for any substantial period without the appropriate 
DEF. In practice, this has meant designing engines or vehicles to alert 
operators of when the engine will run out of DEF, when the DEF is 
inadequate, or if the SCR system is not properly operating due to 
tampering or some malfunction. This has also meant designing engines or 
vehicles with features that motivate operators to ensure proper use of 
the SCR system, such as engine derates and vehicle speed inhibitors. 
Engine derates and vehicle speed inhibitors alter important vehicle 
performance characteristics, such as acceleration, maximum vehicle 
speed attainable, and ability to maintain speed under various loads, 
that are clearly noticeable to a driver.

IV. Prior Guidance

    On March 27, 2007, EPA issued guidance regarding the certification 
of light-duty and heavy-duty motor vehicles and heavy-duty motor 
vehicle engines using SCR systems (CISD-07-07).\4\ The purpose of the 
guidance was to discuss EPA's intended approach to certification of 
engines using SCR technologies and to facilitate manufacturer planning 
in advance of certification. EPA noted that several regulatory 
requirements are uniquely relevant to the certification and 
implementation of engines using SCR, specifically the regulatory 
provisions dealing with allowable maintenance and adjustable 
parameters. EPA suggested that an SCR system that requires the vehicle 
operator to replenish DEF periodically is potentially an adjustable 
parameter, and that unless operation of the vehicle without DEF was 
sufficiently inhibited through built-in performance deterioration or 
some similar system, vehicles using SCR could be treated as having an 
adjustable parameter range including no DEF in the tank and could not 
be certified if the vehicle would exceed emission standards without DEF 
in the tank. EPA provided guidance regarding how engines using SCR 
could be designed consistent with these regulatory provisions to allow 
for certification of such engines. EPA provided examples of possible 
sufficient inducements, including prohibiting operation if DEF is not 
present and having vehicle performance degraded in a manner that would 
be safe but onerous enough to discourage the user from operating the 
vehicle until the DEF tank was refilled. EPA also highlighted the need 
to assure that DEF would be available and accessible to operators and 
suggested places where DEF could be made available, such as dealerships 
and truck stops. We recognized that SCR technology was evolving and 
that our guidance also might need to evolve.

    \4\ U.S. Environmental Protection Agency, Dear Manufacturer 
Letter regarding ``Certification Procedure for Light-Duty and Heavy-
Duty Diesel Vehicles and Heavy-Duty Diesel Engines Using Selective 
Catalytic Reduction (SCR) Technologies,'' March 27, 2007, reference 
number CISD-07-07 (LDV/LDT/MDT/HDV/HDE), available at http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=16677&flag=1.

    On February 18, 2009, EPA issued additional guidance (CISD-09-04) 
to supplement CISD-07-07.\5\ This guidance provided additional details 
regarding certification of heavy-duty engines with SCR systems. 
Particularly, it outlined design elements that would make it highly 
likely operators would replenish DEF prior to the tank being empty and 
operators would not tamper with SCR systems. The guidance provided 
specific examples of robust driver warnings and inducements to help 
ensure operators addressed conditions such as low reductant level, 
improper reductant quality, and tampered system components. EPA 
continued to note the potential need for additional guidance or changes 
in our approach for SCR certification.

    \5\ See docket number EPA-HQ-OAR-2010-0444-0018.

    On December 30, 2009, EPA revised CISD-09-04.\6\ The intent of this 
revision was to clarify that CISD-09-04 was guidance and did not set 
forth binding requirements. EPA revised the guidance and made clear 
that manufacturers wishing to certify engines using SCR technology 
should consult the revised guidance document as well as the guidance 
provided in CISD-07-07. EPA also reminded manufacturers that they 
should work with their certification representatives to provide EPA 
adequate descriptions of the strategies that are incorporated in their 
SCR systems in order to demonstrate compliance with EPA's certification 
requirements as set forth in 40 CFR Part 86.

    \6\ U.S. Environmental Protection Agency, Dear Manufacturer 
Letter regarding ``Revised Guidance for Certification of Heavy-Duty 
Diesel Engines Using Selective Catalyst Reduction (SCR) 
Technologies,'' December 30, 2009, reference number CISD-09-04 
(HDDE), available at http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=20532&flag=1.

    EPA has continued to monitor the development of SCR technology and 
its effectiveness in achieving emission control in use. On July 20, 
2010, in conjunction with the California Air Resources Board (CARB), we 
conducted a public workshop to review existing guidance and policies 
regarding design and operation of SCR-equipped heavy-duty diesel 
engines.\7\ In particular, EPA reviewed approaches to designing SCR-
equipped engines to monitor and induce appropriate responses to 
insufficient or improper DEF, as well as strategies regarding SCR 
systems that are tampered with or defective. EPA developed a strawman 
proposal regarding future certification of heavy-duty diesel engines 
equipped with SCR technology,\8\ and opened a docket to allow public 
comment regarding these issues.\9\ As part of the strawman, EPA 
included approaches for engines

[[Page 32889]]

equipped with SCR, including designs that monitor on-board DEF supply 
and induce action to avoid low DEF supply and operation with no DEF (or 
an insufficient amount to allow proper dosing). EPA also discussed 
detection of poor quality DEF, as well as warnings and inducements if 
poor quality DEF is detected. In addition, EPA discussed designs for 
engines equipped with SCR systems to sufficiently reduce the likelihood 
that SCR system operation would be circumvented. EPA cautioned 
manufacturers to review any element of design that could be tampered 
with and prevent proper operation of the SCR system. Lastly, EPA noted 
DEF freeze protection and infrastructure requirements, and requirements 
regarding unregulated pollutants.

    \7\ See 75 FR 39251 (July 8, 2010).
    \8\ See docket number EPA-HQ-OAR-2010-0444-0016. The strawman 
proposal was not final guidance.
    \9\ See 75 FR 39251 (July 8, 2010). Public comments received in 
response to the public workshop are available in EPA's docket EPA-
HQ-OAR-2010-0444, available at http://www.regulations.gov.

V. Experience to Date

A. EPA's Certification Program

    For the 2010 and 2011 model years, EPA has certified a total of 71 
on-highway heavy-duty diesel engine families with SCR systems produced 
by 11 engine manufacturers. As part of the certification process, 
engine manufacturers are required to disclose various aspects of the 
SCR system designs, including elements of their system that may be 
adjustable parameters. To date, manufacturers' designs have employed 
driver warnings and inducements for low reductant level, poor reductant 
quality, and tampered or malfunctioning SCR systems.
    In order to ensure adequate availability of DEF for use with 
manufacturers' engines, at the time of certification EPA reviews 
manufacturers' plans for DEF availability and accessibility. EPA 
expects manufacturers to have DEF available at their dealerships, to 
encourage DEF availability at third-party locations, and to have an 
emergency backup plan in case DEF is not readily available.
    When manufacturers implement new emission controls, the engine 
technology generally evolves and the manufacturers make improvements 
over the course of initial model years as they develop and certify 
engines and vehicles for each new model year. The process of 
certification involves interaction between manufacturers and EPA 
technical staff about the nature and effectiveness of emission controls 
and often results in manufacturers modifying emission control 
strategies based on feedback from EPA. In the case of SCR technology, 
manufacturers have certified only a few model years of engines that 
incorporate SCR technology, and EPA has seen maturing approaches to 
implementing the technology. For example, from the 2010 to 2011 model 
years manufacturers improved or developed new engine/vehicle diagnostic 
software that provides more or better driver warnings and inducements 
related to the SCR system. Similarly, manufacturers are also evaluating 
various sensors that are expected to reduce the amount of time 
necessary to detect poor quality DEF in future model years. As with 
other new engine technologies, defects in the operation of SCR system 
strategies (e.g., driver inducements) are sometimes discovered in the 
field, and manufacturers initiate campaigns to fix the issues and 
incorporate these fixes in current and new model year production 

B. California Air Resources Board SCR Field Evaluation

    The California Air Resources Board (CARB) recently conducted field 
investigations within the State of California to evaluate 
implementation of SCR technology for 2010 model year vehicles.\10\ The 
investigations included: (1) A survey of DEF availability, (2) a survey 
to determine whether drivers are using DEF or have tampered with SCR 
components, (3) an evaluation of SCR driver inducements, and (4) an 
evaluation of the potential emissions impact of improper SCR operation.

    \10\ California Air Resources Board, Report regarding ``Heavy-
Duty Vehicle Selective Catalytic Reduction Technology Field 
Evaluation,'' May 2011, available at http://www.arb.ca.gov/msprog/cihd/cihd.htm.

    CARB conducted surveys of DEF availability in March 2010 and August 
2010. Both surveys indicated that DEF is readily available at major 
diesel truck stop refueling stations along major interstate highways in 
California. In the first survey DEF was determined to be available at 
85 percent of refueling stations, and in the second survey DEF was 
determined to be available at 92 percent of refueling stations. In 
addition, both surveys indicated that 30 percent of retailers that 
normally supply parts for heavy-duty vehicles have DEF available. CARB 
noted that as older engines are retired and an increasing number of 
SCR-equipped engines enter into operation, the availability of DEF 
should increase with demand. It concluded that DEF is currently being 
offered in adequate supply for the relatively limited number of 
vehicles using SCR.
    In September 2010, CARB conducted random inspections of 69 trucks 
equipped with 2010 model year engines to determine whether DEF was 
being used, whether the DEF was of appropriate quality, and whether 
driver warning indicators (i.e., warning lights, messages, or audible 
alarms) were present. CARB found that all trucks were using DEF and 
that the DEF was of appropriate quality. No DEF-related warning 
indicators were active and there was no evidence of tampering with SCR 
system components. Additionally, CARB solicited information from 
drivers about their experience with locating DEF. Sixty drivers 
indicated that they encountered no problem locating DEF, while nine 
indicated they had minor problems locating DEF in California or in 
other states. For those encountering problems, the issue was limited to 
not being able to purchase DEF at a particular refueling station and 
instead having to purchase it at a different refueling station. Sixty-
eight drivers stated that they never ran out of DEF while operating 
their vehicles and only one driver indicated that he drove for only 10 
miles with an empty DEF tank as indicated by the driver's gauge.
    In the second half of 2010, CARB conducted an evaluation of SCR 
inducements on three trucks equipped with 2010 model year engines and 
SCR systems. The trucks evaluated were a Freightliner Cascadia equipped 
with a 12.8-liter Detroit Diesel DD13 engine (Test Vehicle 1), a 
Kenworth T800 equipped with a 14.9-liter Cummins ISX engine (Test 
Vehicle 2), and a Dodge 5500 equipped with a 6.7-liter Cummins ISB 
engine (Test Vehicle 3). Each truck was operated under various test 
conditions to observe the operation of driver inducements and their 
effectiveness in compelling the driver to take a particular course of 
action. The conditions under which the trucks were operated included: 
(1) Operation until the DEF tank was depleted, (2) operation with water 
in the reductant tank instead of DEF, and (3) operation with a disabled 
DEF system. CARB staff referenced the vehicle owner's manuals and the 
February 2009 EPA guidance to ascertain the expected driver warning 
indicators and inducement strategies that were expected in each 
    On Test Vehicle 1, the warnings and inducements were implemented as 
expected. CARB deemed the warnings effective in drawing the driver's 
attention to the need for SCR-related service. The initial inducement 
incorporated in Test Vehicle 1 was a 25 percent engine torque derate 
and a 55 mph speed limitation. CARB concluded that driving the truck 
with these inducements was neither acceptable nor tolerable, especially 
when trying to accelerate or driving up-hill, and would

[[Page 32890]]

likely cause a driver to refill with DEF or correct the SCR problem as 
needed. If the initial inducement were ignored, the severe inducement 
incorporated in Test Vehicle 1 was a 5 mph speed limitation, which 
worked as designed. The only way to resume normal operation after the 
severe inducement was to have the vehicle serviced by draining the 
water out of the system, filling the reductant tank with DEF, and 
having the system reset by an authorized service technician. CARB 
determined that the inducements were effective for this vehicle because 
the constant inducement strategies and risk of costly repairs would not 
be worth the downtime and financial loss to the business when DEF could 
simply have been added to ensure proper vehicle operation.
    On Test Vehicles 2 and 3, the warnings and some inducements were 
implemented as expected, but certain inducements were not. Test Vehicle 
2 implemented the initial inducement (25 percent engine torque derate) 
in response to DEF depletion, DEF contamination, and DEF tampering 
conditions, but failed to implement the severe inducement (5 mph speed 
limitation) in response to any of these conditions. Test Vehicle 3 
incorporates an engine no-restart severe inducement after a 500-mile to 
no-restart countdown. After the 500-mile countdown reaches zero and a 
safe harbor event (key-off) is experienced, the truck should not 
restart. The inducement worked as expected in response to DEF 
contamination and DEF tampering conditions. In response to the DEF 
depletion condition, Test Vehicle 3 started the 500-mile to no-restart 
countdown as expected. However, after the countdown reached zero and 
the truck was shut off, the truck successfully started the next day and 
reset the countdown. On a subsequent restart attempt after the 
countdown reached zero, the truck successfully implemented the no-
restart condition.
    CARB contacted Cummins, the engine manufacturer for Test Vehicles 2 
and 3, about the failures. Cummins was aware of and addressing the 
issues underlying the failures. In the case of Test Vehicle 2, Cummins 
in the second quarter of 2010 had implemented a correction on their 
engine production line and in the third quarter of 2010 had begun a 
voluntary recall of the engine family to correct the problem.\11\ 
Similarly, in the case of Test Vehicle 3, Cummins was aware of a DEF 
heater malfunction that contributed to the final inducement not 
initiating as expected and was already addressing the issue. CARB 
concluded that for both Test Vehicles 2 and 3, the warnings were deemed 
effective in drawing the driver's attention to the need for SCR-related 
service. CARB also concluded that the inducements on Test Vehicle 2 
were difficult to objectively assess due to a malfunctioning throttle 
position sensor that was encountered during the testing. CARB concluded 
that the inducements on Test Vehicle 3 were effective once the DEF 
heater malfunction was corrected.

    \11\ Voluntary recalls are a typical method for manufacturers to 
remedy emission-related problems they discover. Manufacturers are 
required to report voluntary emission recalls to EPA and ARB, and 
Cummins did so in this case.

C. American Trucking Associations Survey

    In 2010, the American Trucking Associations (ATA) through its 
technical advisory group conducted a survey of 12 trucking fleets 
operating across the United States regarding their experience operating 
trucks with SCR-equipped engines.\12\ The surveyed fleets are some of 
the largest in the country and operate an approximate total of 2,000 
SCR-equipped trucks. The fleet owners indicated that they would 
probably purchase approximately 5,900 SCR-equipped trucks in 2011.

    \12\ See docket number EPA-HQ-OAR-2010-0444-0019.

    None of the surveyed fleets reported any problems locating DEF and 
none reported an engine derate, vehicle speed limitation, or no-restart 
event caused by operation with an empty DEF tank. Similarly, no fleet 
reported issues with the quality of DEF. There were six reported 
instances of an engine derate resulting from circumstances other than 
an empty DEF tank. Two of these instances were caused by malfunctioning 
sensors and four were caused by melted DEF supply hoses. None of these 
instances were associated with the behavior of the operator. Survey 
respondents also reported a total of five instances of NOX 
sensor malfunctions, none of which were related to driver 
tampering.\13\ ATA's fleet survey indicates that drivers do not favor 
inducements involving an engine power derate, especially if it occurs 
while a truck under heavy load is driving up-hill.

    \13\ When a manufacturer determines that an emission-related 
defect exists in 25 or more engines of the same class or category 
and model year, they are required to file an Emission Defect 
Information Report in accordance with 40 CFR 85.1901 et seq.

D. Cummins Survey

    In 2010, Cummins collected information from 47 different customer-
owned vehicles that were equipped with Cummins 11.9-liter and 15-liter 
engines using SCR.\14\ The vehicles were equipped with data-loggers 
that wirelessly transmit data to Cummins periodically on the operation 
of those vehicles. At the time the data was gathered, the vehicles had 
accumulated a total of more than 2.4 million miles of operation across 
the United States. For approximately 99.7 percent of the operating 
miles of the surveyed vehicles, the DEF level was above 10 percent of 
tank capacity. For the remainder of vehicle operation:

    \14\ See docket number EPA-HQ-OAR-2010-0444-0020.

     DEF level was between 5 and 10 percent of tank capacity 
for less than 0.13 percent of the operating miles (i.e., approximately 
3,000 miles).
     DEF level was between 2.5 and 5 percent of tank capacity 
for less than 0.03 percent of the operating miles (i.e., approximately 
740 miles).
     DEF level was between zero and 2.5 percent of tank 
capacity (a condition at which engines experienced derated performance) 
for less than 0.04 percent of the operating miles (i.e., approximately 
920 miles).
     DEF level was at zero percent of tank capacity (a 
condition at which engines experienced derated performance) for less 
than 0.02 percent of the operating miles (i.e., approximately 520 
    In addition, DEF quality was unacceptable (i.e., a faulted 
condition existed) for less than 0.18 percent of the operating miles 
(i.e., approximately 4,400 miles).

E. Navistar EnSIGHT Report

    In 2010, Navistar retained EnSIGHT, Inc. to test three 2010 model 
year SCR-equipped trucks to analyze inducements provided for in EPA 
certification guidance.\15\ The following three trucks were tested: (1) 
One Freightliner Cascadia with a 15-liter Detroit Diesel engine, (2) 
one Kenworth T-660 with a 15-liter Cummins ISX 15 435B engine, and (3) 
one Dodge Ram 5500 crew cab flatbed with a 6.7-liter Cummins ISB 6.7 
305 engine. As part of testing, the three trucks were operated with the 
intent of circumventing the manufacturer-designed inducements, which is 
in contravention to EPA tampering regulations.\16\

    \15\ See docket number EPA-HQ-OAR-2010-0444-0015 for the August 
2010 report. Navistar provided EPA with supplemental details on the 
August 2010 report in a follow-up October 2010 report. See docket 
number EPA-HQ-OAR-2010-0444-0022 for the October 2010 report.
    \16\ Section 203(a)(3) prohibits tampering with emission 
controls. Such actions are illegal, unless conducted as part of a 
testing program covered by an Agency-issued testing exemption.


[[Page 32891]]

    Based on their testing program, EnSIGHT reported the following:
     All trucks physically could be operated for extended 
periods under an initial inducement. Provided the driver took 
particular actions, final inducements could be avoided indefinitely. 
For example, the Freightliner Cascadia was driven over 1,000 miles on 
an empty DEF tank at a limited speed of 55 mph, which is the initial 
inducement. As long as no more than 30 percent of the fuel tank 
capacity (approximately 100 gallons) was added at any single refueling 
event, the final inducement, a 5 mph vehicle speed limitation was not 
triggered. The Kenworth T-660 was driven with an empty DEF tank and a 
25 percent engine torque derate, which is the initial inducement. As 
long as the engine was not shut off for more than a few minutes at a 
time, the 5 mph vehicle speed limitation final inducement was not 
     When DEF tanks were empty and water was added instead of 
DEF, two trucks were able to run indefinitely. When the Dodge 5500 was 
low on DEF and began its 500-mile to final inducement (i.e., no-restart 
condition) countdown, the driver was able to fill the DEF tank with 
water, start the truck, and drive normally. This action cleared the 
500-mile countdown and the driver display indicated a full DEF tank. On 
one test run, the truck displayed visual and audible warning signals 
after 73 miles of driving with water in the DEF tank and eventually 
displayed the 500-mile to no-restart countdown after 694 miles of 
driving. Upon shutting off the truck after a total of 1,278 miles of 
driving, a no-restart condition was encountered. On a subsequent test 
run with water in the DEF tank, the truck was driven over 4,000 miles 
and encountered no warning signals or inducements. The Freightliner 
Cascadia was driven over 15,000 miles with only water in its DEF tank 
and triggered no initial or final inducement.
     SCR system components could be repeatedly disconnected and 
reconnected to avoid particular inducements. On the Dodge 5500, the 
driver was able to disconnect the injector electrical connector, which 
would initiate a 500-mile to final inducement (i.e., no-restart 
condition) countdown. As the mileage countdown continued, the driver 
could reconnect the component and reset the 500-mile countdown. On the 
Freightliner Cascadia, when electrical connections to the DEF injector, 
gauge, or tank pump were unplugged, the truck was driven for over 1,000 
miles prior to triggering an inducement.
     Although the testing program was designed to intentionally 
operate the trucks until final inducements were encountered, EnSIGHT 
also provided an assessment of the impact of initial inducements on 
driver behavior. They concluded that a 25 percent engine torque derate 
would not induce a corrective response by the drivers, including when 
the truck was fully loaded. With this level of derate, EnSIGHT's 
drivers were able to operate the Freightliner Cascadia and the Kenworth 
T-660 at speeds up to 55 mph and 65 mph, respectively. Of the Kenworth 
T-660, EnSIGHT's drivers indicated that the truck could easily be 
operated and was acceptable for typical driving for long periods of 
time under derate.

F. DEF Infrastructure and DEF Quality

    The DEF infrastructure and sales volume have continued to grow 
since introduction of 2010 model year trucks equipped with SCR systems. 
Initially, DEF availability was concentrated around major truck stops 
and truck routes and 2.5-gallon jugs represented the common mode of 
supply. Although very limited, bulk DEF dispensing typically utilized 
small storage tanks located apart from the fuel islands at truck stops. 
The refilling of fuel and DEF tanks at truck stops was also more likely 
to require two separate purchase transactions.
    The continually increasing DEF infrastructure and sales volume have 
resulted in improved DEF availability along major truck routes as well 
as other locations. ``AdBlue and DEF Monitor,'' a publication of 
Integer Research, reports that DEF is available for sale in jug form in 
every state.\17\ Integer Research also reports that DEF is available 
for delivery to fleet locations in every state, as well. To assist 
drivers in finding DEF, multiple Internet-based DEF locator services 
have been developed. One of these services, DiscoverDEF.com, run by 
Integer Research, recently announced that DEF consumption in the U.S. 
reached 2.3 million gallons per month in December 2010 and that in 
August of the same year consumption volumes increased 43% compared to 
the previous month. Also, a number of suppliers reported sales volumes 
doubling in September 2010 alone. These increases in DEF consumption 
are believed to correlate with the increased delivery and use of SCR-
equipped trucks.

    \17\ See docket number EPA-HQ-OAR-2010-0444-0021.

    Increasing demand supported by sales volume helps drive the 
continuing expansion of DEF infrastructure. The same locator service 
recently reported that more than 100 truck stops in the U.S. and Canada 
now have DEF available at the pump. Additionally, this service 
maintains a list of over 3,000 locations that have packaged DEF, and a 
majority of the locations are in the U.S. As truck stops such as Travel 
Centers of America roll out on-island DEF dispensers, they usually 
incorporate technology which allows for single transaction fuel and DEF 
filling, which makes buying DEF quicker, more efficient, and customer-
friendly. On-island DEF dispensing typically requires truck stops to 
utilize a mini-bulk system with at least 800-gallon above ground 
storage tanks or even larger underground storage tanks. The transition 
to larger tanks supports bulk purchases as well as cheaper end-user 
prices for DEF. This information is consistent with the survey 
information discussed above.
    Regarding DEF quality, ISO 22241-1 sets forth generally accepted 
industry-wide quality specifications for DEF that were developed by 
vehicle manufacturers and other affected stakeholders. The American 
Petroleum Institute (API) Diesel Exhaust Fluid Certification Program 
(http://www.apidef.org) is a DEF quality licensing program intended to 
ensure that DEF of known specifications and quality is available. We 
understand that more than 20 of the largest producers of DEF are 
participating in the Certification Program and that the associated DEF 
Aftermarket Audit Program has also begun. In 2010, API tested all 
licensed products and the vast majority of those products met the ISO 
22241-1 specifications. Where deficiencies were found, API and DEF 
manufacturers are working to identify the cause and helping to ensure 
that future batches conform to the ISO specifications. Because of API's 
Audit Program and its responsiveness to failed test results, we believe 
good quality DEF is broadly and generally available. API's 
Certification and Audit Programs were developed under the SCR 
Stakeholder Group, an informal consortium of vehicle/engine 
manufacturers, urea manufacturers, DEF blenders and distributors, and 
associated technology companies. EPA has been an active participant in 
the Stakeholder Group for several years. We also understand that the 
Petroleum Equipment Institute, its members, and associated stakeholders 
have developed Recommended Practices for the Storage and Dispensing of 
Diesel Exhaust Fluid (DEF), which will provide useful advice to any 

[[Page 32892]]

who stores and dispenses DEF. Given that the vast majority of DEF 
production is accounted for in API's certification program and that the 
follow-up audit program is showing high rates of conformance to the ISO 
specifications, we believe these programs will be adequate to ensure 
DEF quality.

VI. Reasons for Revised Guidance

    Considering the developments in SCR-related technologies, DEF 
infrastructure, and the other available information described above, we 
believe it is appropriate to further refine our guidance to 
manufacturers regarding certification of SCR-equipped engines to be 
compliant with applicable regulations. As discussed in this section of 
the document, on-highway heavy-duty diesel SCR systems introduced into 
commerce to date have been highly successful in inducing operators to 
refill DEF tanks on a timely basis and to avoid interfering with SCR 
operation, with a few specific exceptions.\18\ At the same time, the 
Agency believes it is appropriate to refine its guidance, particularly 
as experience is gained with SCR in-use and as technology advances. We 
seek comment on the draft guidance and interpretations presented here 
and plan to incorporate what more we learn in the next version of the 
guidance to be issued later this year.

    \18\ It is worth noting again in this context that under Section 
203(a)(3) of the Clean Air Act, tampering with SCR systems or other 
emission controls is prohibited.

A. Current SCR Systems Are Highly Effective in Use

    As trucks equipped with SCR systems have been introduced into U.S. 
commerce, drivers have become familiar with this technology. Current 
information concerning in use operation of SCR-equipped trucks, 
including all of the studies and other information discussed above, 
indicates that warning signals work correctly and that drivers do not 
wait for SCR-related inducements to be triggered to ensure appropriate 
and continuing operation of the systems. Specifically, the overwhelming 
majority of drivers surveyed by CARB, ATA, and Cummins did not wait for 
activation of warning indicators prior to refilling their DEF tanks 
and, where warnings did occur, generally did not drive distances long 
enough to lead to activation of inducements. Further, as the 
infrastructure for making DEF available becomes even more widespread, 
drivers will have increased and more convenient access to DEF when they 
need it. As documented in part by CARB's survey, there are currently 
few availability issues and those appear to stem primarily from limited 
situations where DEF was not found at the first location at which it 
was sought. As DEF infrastructure and supply continue to expand, EPA 
also expects the price of DEF to decrease, in part because of the move 
to bulk dispensing that is already underway. In addition, EPA expects 
that the DEF quality assurance programs described above will make it 
increasingly easy for drivers to find DEF which meets the 
specifications necessary for proper operation of the SCR systems. The 
strong indication from all of this evidence is that DEF warning systems 
are working correctly, and that when warned, drivers have not continued 
to drive distances long enough to lead to inducements. Inducements 
appear to be triggered in very few cases.
    Navistar's study and CARB's field evaluation provide some evidence 
indicating that in some cases there have been issues related to SCR-
equipped engines and assurance of their proper operation. Navistar's 
study identifies specific problems associated with the design or 
manufacture of certain SCR-equipped engines, and outlines the 
intentional actions taken by drivers employed by Navistar's contractor 
in conducting the study. The study's findings are properly considered 
in the context of all the available information on SCR operation. In 
light of the investigations and surveys conducted by CARB, ATA, and 
Cummins, EPA does not believe Navistar's findings reflect the overall 
efficacy of SCR systems on heavy-duty diesel engines currently in 
operation or the way they are actually used.
    Most of Navistar's findings resulted from actions by the 
contractor's drivers to intentionally circumvent the manufacturer-
designed inducements of the three test vehicles. For example, drivers 
avoided triggering inducements associated with an empty DEF tank by 
limiting refueling quantities or keeping the truck running when it 
normally would be turned off. Both ways of circumventing the 
inducements exact their own costs on drivers in terms of time, 
convenience, and expense. To illustrate, never refilling above about 
30% of the tank leads to approximately three times as many refueling 
events, and the time and expense associated with this kind of 
disruption detract from the efficient operation of truck operators, who 
work in a competitive business. Navistar's contract drivers also 
disconnected and reconnected various SCR system components as a means 
of avoiding DEF inducements. Such intentional actions would be 
considered tampering and are illegal.\19\ While it is possible that 
drivers could intentionally take such actions to circumvent 
inducements, manner of truck operation conducted in the Navistar study 
is clearly not representative of the vast majority of truck operation, 
as indicated by the CARB and ATA surveys. We do not think that the 
marginal cost and effort involved in purchasing DEF provide sufficient 
motivation for a driver to follow such inconvenient and risky courses 
of action.

    \19\ Such actions are illegal, unless conducted as part of a 
testing program covered by an Agency-issued testing exemption.

    We also do not agree with Navistar's view that initial inducements 
are ineffective to produce corrective responses by drivers. ATA's fleet 
survey indicates that drivers do not favor inducements involving an 
engine power derate, especially if it occurs while a truck under heavy 
load is driving up-hill. Thus, drivers are likely to maintain proper 
SCR operation to avoid encountering these inducements. CARB's 
investigation shows that most inducements functioned properly during 
expected truck operating conditions and their assessment of the 
effectiveness of initial inducements was contrary to Navistar's 
findings. CARB determined that the inducements were effective because 
operating in a way that avoids the inducement strategies and raise the 
risk of costly repairs would not be worth the downtime and potential 
financial loss to business. In fact, Cummins' survey, which included 
some of the same 15-liter engines in Navistar's study, found that 
surveyed trucks operated with DEF in their tanks for greater than 99.9 
percent of their total operation. Cummins' survey also found that 
trucks operated with unacceptable DEF quality for less than 0.18 
percent of their total operation. This strongly indicates that the 
inducements have the intended effect of motivating appropriate driver 
    The report of Navistar's study found that some manufacturers' 
designs did not adequately detect water in the urea tank and thus did 
not prevent the driver from refilling the tank with something other 
than DEF. Navistar and CARB findings on DEF quality detection were not 
consistent in all cases. For example, Navistar found that initial and 
final inducements for the Freightliner Cascadia equipped with the 12.8-
liter Detroit Diesel DD13 engine were not triggered when the DEF tank 
was filled with water. During CARB's field investigation, both the 
initial and final inducements were implemented for Test

[[Page 32893]]

Vehicle 1 as expected when the DEF tank was filled with water. CARB's 
investigation discovered various production defects for Test Vehicles 2 
and 3 that prevented the systems from working fully (as designed, the 
systems appeared to have sufficient capabilities to detect and respond 
to DEF quality problems). CARB followed up with Cummins and learned 
that the manufacturer was aware of the performance problems and 
addressing them in a manner consistent with regulatory provisions 
governing defect reporting and repair.\20\ The defect reports submitted 
by Cummins corroborated that the manufacturer was appropriately 
responding to the problems. Additionally, Detroit Diesel informed EPA 
that they knew of problems with their system and had developed an 
updated software calibration to fix them as early as June 2010, prior 
to Navistar reporting the results of their study. Detroit Diesel has 
since begun addressing the problems on in use trucks consistent with 
regulatory provisions governing defect reporting and repair. As noted 
above, the problems with detecting water in the urea tank appear to be 
related to defects in production of these engines, as opposed to 
deficient designs. These production defects are being addressed in the 
same manner that problems with new technology are addressed under EPA's 

    \20\ See 40 CFR Part 85, Subpart T.

B. Regulations Should Be Applied in Light of Continuing Information and 
Process Improvements

    EPA's regulatory provisions for adjustable parameters are intended 
to ensure that manufacturers design their emissions control system in a 
way that makes it unlikely that they will be operated inappropriately. 
It appears that manufacturer's past SCR designs and EPA's guidance have 
resulted in highly effective controls to protect the operation of SCR 
systems, as evidenced by the surveys and other data which show that 
drivers are properly operating their SCR-equipped trucks. There have 
been indications of specific problems with some engines in-use, and the 
manufactures involved have been addressing them through production and 
other improvements as the problems are identified. We believe it is 
appropriate to evaluate the experience gained to date and to make 
continuing, appropriate adjustments to our certification process for 
SCR-equipped engines as technology evolves and in-use experience is 
gained. EPA recognizes that development of even more robust sensors and 
inducements does not negate past approaches implemented pursuant to 
existing regulations. Rather, continual improvement is expected given 
the mounting experience with, and the maturing of, SCR technology, and 
the greater availability of DEF. As improved strategies and 
capabilities for proper SCR operation become feasible, EPA may guide 
their application to provide even further assurance that the technology 
is operating as intended on SCR-equipped engines.

C. As SCR Technology Matures, Further Guidance Is Appropriate

    Several developments in SCR technology allow continuing refinement 
in SCR design. One area of potential improvement in design involves 
sensors that can detect poor quality DEF. Current SCR system designs 
incorporate NOX sensors to determine catalyst efficiency and 
detect catalyst malfunction. Since the sensors are part of the system 
design, they have also been used to detect poor quality DEF through 
correlation of NOX emission rates with various 
concentrations of urea. Urea quality sensors have been identified as a 
means to help improve detection capabilities for poor quality urea. 
They directly measure quality and appear likely to represent a quick 
detection method for addressing quality concerns. Manufacturers are 
currently evaluating the performance and durability of various sensor 
    Since the 2010 model year, manufacturers have also been refining 
their engine/vehicle system diagnostics software to incorporate 
additional capabilities for implementing SCR-related inducements. For 
example, many manufacturers today have developed multiple triggers for 
triggering inducements, including detection of refueling, extended 
idling, and engine shutdown events. Incorporation of additional 
inducement triggers into designs further decreases the likelihood of 
improper operation of the SCR system. Manufacturers are also improving 
their diagnostics software to ensure that SCR-related inducements 
cannot be reset or erased by diagnostic scan tools available to the 
general public or by disconnecting components in the field.
    Many manufacturers are implementing improved designs in their 2011 
model year engines/trucks that may be sold in the State of California. 
After the July 2010 public workshop, CARB and EPA began encouraging 
manufacturers to adopt the elements of design that were discussed. In 
order to avoid the need for multiple engine/vehicle production designs, 
manufacturers have often incorporated the design elements of vehicles 
sold in California into their 49-state vehicles.
    Improving sensor capabilities and inducement strategies should 
present low risk and little burden for both manufacturers and drivers. 
Manufacturers are already in the process of improving their SCR 
designs, and overwhelmingly drivers are not waiting for SCR-related 
warnings or inducements to be triggered before they refill DEF tanks 
and otherwise maintain proper operation of SCR systems. Given the 
importance of reducing NOX emissions from heavy-duty diesel 
engines for attaining and maintaining national air quality standards, 
we have developed the following draft revised guidance to reflect 
improving capabilities for designing SCR systems to ensure proper 

VII. SCR Adjustable Parameter Design Criteria

    This section discusses design criteria for on-highway heavy-duty 
diesel vehicles or engines using SCR technology. EPA believes that 
vehicles and engines that meet these design criteria would meet the 
requirements of the regulations regarding adjustable parameters. EPA 
will still review each certification application to ensure that the 
regulatory provisions are met. Likewise, in the case of design criteria 
that are not fully specified in this guidance, EPA will review the 
application to ensure that the engine design meets the regulatory 
requirements. EPA may review and revise this guidance as the technology 
continues to mature and as EPA receives more information regarding the 
use of SCR systems. In addition, manufacturers may present other 
designs for EPA consideration. All designs will remain subject to EPA 
approval under the existing certification regulations.
    As noted above, in determining the adequacy of an engine's means of 
inhibiting adjustment of a parameter, EPA considers the likelihood that 
settings other than the manufacturer's recommended setting will occur 
in use. With this in mind, EPA is providing these draft SCR adjustable 
parameter design criteria based on our view that an SCR-equipped 
vehicle that complies with these criteria will be adequately inhibited 
from use when the SCR system is not operating properly.
    EPA is asking for comments on the draft guidance discussed below. 
The design criteria are divided into four categories. The categories 
    A. Reductant tank level driver warning system.

[[Page 32894]]

    B. Reductant tank level driver inducement.
    C. Identification and correction of incorrect reducing agent.
    D. Tamper resistant design.

A. Reductant Tank Level Warning System

    The emissions performance of SCR-equipped vehicles depends on 
having an adequate supply of appropriate quality reducing agent in the 
system. SCR systems require regular user interaction to ensure that the 
system is operating properly. Therefore, it is critical that the 
operator both know when reducing agent is needed and have enough time 
to replace it before it runs out. A properly designed driver warning 
system should address these concerns.
    To achieve this design goal, under our criteria, the manufacturers 
would use a warning system including the following features:
    1. The warning system should incorporate visual and possibly 
audible alarms informing the vehicle operator that reductant level is 
low and must soon be replenished. The manufacturer should design the 
warning system to activate well in advance of the reducing agent 
running out so that the operator is expected to have one or more 
refueling opportunities to refill the reductant tank before it is 
    2. The warning alarm(s) should escalate in intensity as the 
reducing agent level approaches empty, culminating in driver 
notification that is difficult to ignore, and cannot be turned off 
without replenishment of the reducing agent.
    3. To provide adequate notice, the visual alarm should, at a 
minimum, consist of a DEF level indicator, a unique light, reducing 
agent indicator symbol or message indicating low reducing agent level. 
The warning light, symbol or message should be different from the 
``check engine'' or ``service engine soon'' lights used by the On Board 
Diagnostic (OBD) system or other indicators that maintenance is 
required. The symbol or message used as the warning indicator should 
unmistakably indicate to the vehicle operator that the reducing agent 
level is low. The reducing agent indicator symbol shown below has been 
generally accepted in the industry and EPA considers it acceptable as 
an indicator of low reducing agent level.

    4. The light, indicator symbol or message should be located on the 
dashboard or in a vehicle message center. The warning light or message 
does not initially have to be continuously activated, but as the 
reducing agent level approaches empty the illumination of the light or 
message would escalate, culminating with the light being continuously 
illuminated or the message continuously broadcast in the message 
center. Many current designs have been found acceptable and EPA does 
not anticipate requiring changes in the foreseeable future. Unique SCR 
system warning lights and message designs that deviate from previously 
approved designs or the design criteria outlined above would need to be 
approved by EPA.
    Manufacturers may also incorporate an audible component of the low 
DEF warning system. As the reducing agent level approaches empty the 
audible warning system should escalate.

B. Low Reductant Level Inducement

    The warning systems discussed above can play a critical role in 
achieving vehicle compliance. As noted, a well designed warning system 
should deter drivers from operating SCR-equipped vehicles without 
reducing agent. However, we believe an additional, stronger deterrent 
is necessary and appropriate. Therefore, at some point after the 
operator receives the initial signal warning that reductant level is 
low, it is important that the engine design incorporates measures to 
induce users to replenish the reducing agent.
    Under these design criteria, manufacturers would design their 
engines with a final inducement system that accomplishes the following 
when the reductant tank is empty or the SCR system is incapable of 
proper dosing:
    1. Maximum vehicle speed is decreased at the quickest safe rate to 
5 miles per hour while the vehicle is operating; or
    2. The maximum engine fueling and engine speed are decreased at the 
quickest safe rate while the vehicle is operating, resulting in engine 
shutdown or limiting operation capability to idle only.
    Some manufacturers prefer to trigger the above final inducement 
only when the vehicle has stopped at a safe location. Under this 
approach, a vehicle may be assumed to be in a safe location if the 
engine is purposefully shut off (key turned to the off position), has 
experienced an extended idle of 60 minutes (as indicated by zero 
vehicle speed for 60 minutes), or a refueling event has occurred 
(meaning a volume of fuel has been added equal to or greater than 15 
percent of vehicle operating fuel capacity).
    If a manufacturer chooses to implement final inducement only when 
the vehicle is stopped, we believe the engine will need to be designed 
with the following additional characteristics:
    a. Be able to trigger final inducement when the vehicle is stopped 
at a safe location. The final inducement will consist of limiting the 
vehicle speed to 5 mph, shutting the engine down, or limiting engine 
operation to idle only.
    b. Prior to triggering final inducement, be able to impose a severe 
inducement which makes prolonged operation of the vehicle unacceptable 
to the driver and compels the driver to replenish the reducing agent 
prior to the SCR system becoming incapable of proper dosing. The severe 
inducement will consist of an engine derate, a vehicle speed 
limitation, or a limitation on the number of engine restarts. For 
example, an engine torque derate of 40 percent may be utilized as a 
severe inducement for the operator of a Class 8 line-haul truck to 
replenish the reducing agent. The severe inducement should occur while 
there is enough reductant in the tank to continue to provide proper SCR 
dosing for approximately one full day of vehicle operation. For 
example, it may be appropriate to initiate severe inducement with a 10 
percent reserve of reducing agent in the reductant tank.
    c. Be able to determine when the vehicle has arrived at a safe 
location for the purpose of imposing a final inducement. Such a 
determination will be based upon the vehicle experiencing the next key-
off, refueling, or 60-minute idling event after imposing severe 
inducement. During the course of one day of vehicle operation, EPA 
believes it sufficiently likely an operator will encounter one of the 
three events triggering final inducement. In the unlikely scenario that 
one of the three events is not encountered, the severe inducement 
should still provide sufficient incentive for the operator to refill 
the reductant tank.
    The above final and severe inducements are not meant to limit the 
use of other inducements prior to severe or final inducement. EPA 
encourages the use of additional inducements which would serve to 
minimize the amount of time either severe or final inducements are 
    When developing inducement strategies for review by EPA at the time 
of certification, manufacturers should be prepared to detail the type 
and level of inducements chosen and demonstrate how they will 
sufficiently compel drivers to maintain appropriate reductant levels 
and ensure vehicle operation is limited only to periods when proper SCR 
dosing is occurring.

[[Page 32895]]

    EPA believes that an engine that is designed with warning and 
inducement strategies consistent with those above will be highly 
unlikely to be driven with an empty reductant tank, and therefore that 
such an engine would be adequately protected from operation with an 
empty tank.

C. Identification and Correction of Incorrect Reducing Agent

    Assuring that an SCR-equipped engine is unlikely to be operated 
without proper reducing agent calls for an SCR system design that is 
able to detect incorrect or poor quality reducing agent. As noted above 
in the context of maintaining an adequate level of reducing agent, the 
emissions performance of SCR-equipped vehicles is dependent on having 
reducing agent in the system and the reducing agent must be of the 
proper quality. Therefore, the system must be able to identify and 
appropriately respond to poor reductant quality such as filling the 
reductant storage tank with a fluid other than the manufacturer-
specified reducing agent, or with excessively diluted reducing agent. 
An example would be filling the tank with water rather than DEF, when 
DEF is the specified reducing agent.
    Current urea-based SCR technology uses a robust NOX 
sensor system to detect poor quality reductant. High NOX 
emissions can be correlated to poor reductant quality and 
NOX sensors are already part of the SCR system. Urea quality 
sensors directly measure DEF quality and appear likely to represent a 
quick detection method for addressing quality concerns in the future. 
Manufacturers are currently evaluating the performance and durability 
of various sensor designs.
    NOX sensor systems will take somewhat longer to detect 
poor quality reducing agent compared to urea quality sensors. Under 
ideal conditions, NOX sensors can detect poor quality in 20 
minutes, but may take as long as one hour to detect poor quality 
reductant. An advantage of urea quality sensors is that, once fully 
developed, they will provide operator notification of poor quality 
while the vehicle is still at a filling location.
    Because NOX sensors do not directly measure DEF quality, 
they do not detect variations in DEF quality as small as those detected 
by urea quality sensors. However, NOX sensors adequately 
detect water which is the most likely substitute for DEF. Therefore, 
NOX sensors are likely able to detect and prevent the 
majority of serious quality problems. Because of the ability of urea 
quality sensors to detect smaller concentration deviations in urea 
quality, we believe urea quality sensors will soon be the best 
reasonable technology to help manufacturers meet the adjustable 
parameter requirement. Urea quality sensors will also permit the 
emission control system to adjust DEF dosing based on the detected 
quality of the DEF and, in conjunction with the inducement strategies, 
help ensure that only compliant DEF is used. We expect urea quality 
sensors to be available for use in 2013 model year vehicles.
    Under these design criteria, the engine design would have the 
following features to identify and respond appropriately to poor 
quality reducing agent or incorrect fluid:
    1. Given the current technology, we believe manufacturers should be 
capable of detecting poor reductant quality within one hour. As 
improved technology becomes available, such as urea quality sensors, 
manufactures should decrease the likelihood, and increase the 
performance consequences of operation with poor quality reductant by 
incorporating the technology which best and most promptly detects poor 
reductant quality.
    2. Immediately upon detection, the operator should be notified of 
the problem with warnings similar to those discussed above for 
inadequate reductant level. EPA expects the warning light or message 
addressing incorrect reducing agent would quickly increase in intensity 
to be continuously activated.
    3. Given the current state of technology, the engine design should 
implement final inducement while the vehicle is operating and within 4 
hours of detection. Alternately, if a manufacturer chooses to implement 
final inducement when the vehicle is stopped at a safe location, the 
engine design should implement severe inducement and search for final 
inducement triggers within 4 hours of detection. For this alternate 
approach, some lesser inducement should precede severe inducement at 2 
hours after detection. While we believe it is appropriate that the 
vehicle respond in a similar manner when poor quality reducing agent is 
detected as when the vehicle runs low on reducing agent, we believe the 
inducement should not begin immediately. It is currently possible for a 
driver to receive poor quality reductant unknowingly and for a driver 
to need a certain amount of time after being alerted to the problem to 
have it remedied. Therefore, we think it currently appropriate to allow 
no more than 4 hours of operation following detection before imposing 
severe or final inducement. The 4 hours until severe or final 
inducement will allow the operator sufficient time to reach a service 
facility to remedy the problem.
    4. If poor quality reductant is detected again within 40 hours 
after putting proper reducing agent in the tank, then the operator 
should be immediately notified and the poor quality final inducement or 
the alternate severe inducement approach should begin immediately. We 
believe continuing to monitor for repeat instances of poor quality 
reductant for 40 hours is likely to capture the vast majority of 
operators intentionally trying to circumvent SCR controls.
    EPA believes design requirements that alert the operator to 
inadequate reducing agent and that institute inducements to assure 
correction of reducing agent quality are needed in order to ensure that 
the ``adjustable parameter'' of reductant quality is sufficiently 
limited. EPA believes that the warnings and inducements associated with 
poor quality reducing agent discussed above are burdensome enough that 
they ensure that introduction of poor quality reductant would not occur 
often or purposely and that in the unlikely event it occurs, proper 
actions will be taken within reasonable time limits to adequately 
minimize the operation of the vehicle/engine with poor quality 
reductant and associated excess emissions. We also believe the 4 hours 
until severe or final inducement is currently needed to allow the 
operator to locate and drive to a service facility capable of draining 
and refilling the tank.
    EPA believes that an engine that is designed with the warning and 
inducement strategies discussed above will be highly unlikely to be 
driven with inadequate reductant for any significant period, and 
therefore that such an engine would be adequately protected from 
operation with inadequate reductant.

D. Tamper Resistant Design

    SCR systems should be designed to be tamper resistant to reduce the 
likelihood that the SCR system will be circumvented or that the 
operating parameters of the system will be purposefully or 
inadvertently altered. Manufacturers should be careful to review any 
element of design that would prevent the proper operation of the SCR 
system to make tampering with that element of design impossible or 
highly unlikely. Manufacturers will have to demonstrate to EPA that 
their SCR system design is tamper resistant. 40 CFR 86.094-22(e) 
contains provisions regarding actions and criteria to ensure that 
elements of design related

[[Page 32896]]

to the adjustable parameters of DEF level and quality are adequately 
inaccessible, sealed, physically limited or stopped, or otherwise 
inhibited from adjustment.
    1. At a minimum, the following actions, if done intentionally, 
would be considered tampering and manufacturers should design their SCR 
systems to ensure that restraints on such actions, whether purposeful 
or not, are adequate and such results are unlikely:

a. Disconnected reductant level sensor
b. Blocked reductant line or dosing valve
c. Disconnected reductant dosing valve
d. Disconnected reductant pump
e. Disconnected SCR wiring harness
f. Disconnected NOX sensor (that is incorporated with the 
SCR system)
g. Disconnected reductant quality sensor
h. Disconnected exhaust temperature sensor
i. Disconnected reductant temperature sensor

    2. EPA believes that the warnings and inducements described above 
for incorrect reducing agent would also be adequate under 40 CFR Sec.  
86.094-22(e) to prevent tampering or accidental actions causing the 
above results. The engine should be able to detect tampering as soon as 
possible, but no longer than one hour after a tampering event.
    3. Immediately upon detection, the operator should be notified of 
the problem.
    4. We believe the inducement should not begin immediately. It is 
possible that a part failure that occurs in the course of normal 
operation will be recognized as a result of these diagnostics. An 
operator should not immediately receive inducement for an event which 
may not have been caused by tampering. Therefore, we think it 
appropriate to allow 4 hours of operation following detection before 
implementing final inducement while the vehicle is in operation. 
Alternately, if a manufacturer chooses to implement final inducement 
when the vehicle is stopped at a safe location, the engine design 
should implement severe inducement and search for final inducement 
triggers within 4 hours of detection. For this alternate approach, some 
lesser inducement should precede severe inducement at 2 hours after 
detection. The 4 hours until severe or final inducement will allow the 
operator sufficient time to reach a service facility to remedy the 
    5. If tampering of the same component is detected again within 40 
hours after repair, then the operator should be immediately notified 
and the tampering final inducement, or the alternate severe inducement 
approach, should begin immediately. We believe continuing to monitor 
for repeat instances of tampering for 40 hours is likely to capture the 
vast majority of operators intentionally trying to circumvent SCR 
    EPA believes that an engine that is designed with the warning and 
inducement strategies discussed above will be highly unlikely to be 
driven for any significant period under the aforementioned conditions, 
and that such an engine would be adequately protected from operation 
under such circumstances.

VIII. Conclusion

    EPA is releasing this draft document for comments. We will continue 
to work with manufacturers, other stakeholders, and the public 
regarding issues related to its existing regulatory requirements and 
SCR technology.

    Dated: May 27, 2011.
Margo Tsirigotis Oge,
Director, Office of Transportation and Air Quality, Office of Air and 
[FR Doc. 2011-13851 Filed 6-6-11; 8:45 am]