Amendments to In-UseTesting 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 heavy-
                  duty 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.

                  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 measure'
                        ment 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 regenera-
                        tion 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,
United States
Environmental Protection
Office of Transportation and Air Quality
                   October 2010

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 manu-
       facturers to use oxides of nitrogen and non-methane hydrocarbon (NOx+NMHC)
       credits to show compliance,
       Amend the transitional flexibilities program for manufacturers of specialized higlvaltitude
       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

          E-mail: a'and'r'
             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

For More Information
You can access the rule and related documents on EPA's Office of Transportation and Air
Quality (OTAQ) Web site at:


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, MI48105
          Voice-mail: (734)  214-4636