Regulatory Announcement

Amendments to In-Use Testing for 

Heavy-Duty Diesels, Measurement 

and Instrumentation, and Off-Highway 

Engine Regulations 

The U.S. Environmental Protection Agency (EPA) is publishing a 

Direct Final Rulemaking to make several amendments to EPA’s 

mobile source emission standards and test procedures. These revisions 

affect the in-use particulate matter (PM) testing program for heavyduty diesel engines, locomotives, spark-ignition (SI) marine engines, 

small SI engines, Tier 4 nonroad diesel engines, and PM measurement 

and assessment for both laboratory and field testing. 

Overview 

This Direct Final Rule makes several revisions to EPA’s mobile source emission 

standards and test procedures including the heavy-duty diesel engine in-use testing 

program. The amendments are as follows: 

•	 EPA adopted a final accuracy margin for PM for portable emission measurement systems that resulted from a comprehensive research program. This final 

PM accuracy margin will replace the interim emission measurement “accuracy” 

margin for the requisite portable emission measurement devices, 

•	 Delay enforcement of the PM in-use testing program for heavy-duty diesel 

engines until 2011, 

•	 Grant flexibilities for heavy-duty diesel engine manufacturers to complete 

testing obligations under PM pilot program, 

•	 Clarify the analytical requirements for in-use PM measurement as a result of 

lessons learned in the research program, 

•	 Clarify acceptable accounting protocols for emission control system regeneration events when calculating not-to-exceed (NTE) results, 

•	 Allow fuel rate information derived from the engine control module (ECM) 

to determine NTE mass emission rate during in-use testing, 

Office of Transportation and Air Quality 

EPA-420-F-10-042 

October 2010 
Regulatory Announcement 

 

A set of minor changes will affect categories of highway and nonroad engines. 

•	 Allow partial flow dilution sampling for transient test cycle PM measurement, 

•	 Extend interim flexibilities for locomotives, 

•	 Allow later notification deadline for small-volume manufacturers of marine SI engines to 

qualify for a delay in the new exhaust emission standards, 

•	 Revise the phase-in provisions for the Tier 4 nonroad emission standards to allow manufacturers to use oxides of nitrogen and non-methane hydrocarbon (NOx+NMHC) 

credits to show compliance, 

•	 Amend the transitional flexibilities program for manufacturers of specialized high-altitude 

equipment, 

•	 Correct former errors in the E2 Ramped Modal Cycle, 

•	 Clarify applicable exclusions for small SI engines installed in nonhandheld equipment. 

Public Participation Opportunities 

This rule is being released as a Direct Final Rule. However, comments can be submitted under 

a parallel Notice of Proposed Rulemaking (NPRM). Comments will be accepted for 30 days 

beginning when the NPRM is published in the Federal Register. All comments should be 

identified by Docket ID No. EPA-HQ-OAR-2010-0142 and submitted by one of the following 

methods: 

Internet: www.regulations.gov
 

E-mail: a-and-r-Docket@epa.gov
 

Mail:
 

Environmental Protection Agency
 

Mail Code 2822T
 

1200 Pennsylvania Avenue NW
 

Washington, DC 20460
 

Hand Delivery: 

U.S. Environmental Protection Agency
 

EPA Headquarters Library
 

EPA West Building
 

Room 3334
 

1301 Constitution Avenue NW
 

Washington, DC
 

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Regulatory Announcement 

For More Information 

You can access the rule and related documents on EPA’s Office of Transportation and Air 

Quality (OTAQ) Web site at: 

www.epa.gov/otaq/hd-hwy.htm 

For more information on this Direct Final Rule, please contact the Assessment and Standards 

Division at: 

U.S. Environmental Protection Agency
 

Assessment and Standards Division
 

Office of Transportation and Air Quality
 

2000 Traverwood Drive
 

Ann Arbor, MI 48105
 

Voice-mail: (734) 214-4636
 

E-mail: asdinfo@epa.gov
 

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