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88 FR 4487, Jan. 24, 2023, unless otherwise noted.
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(a) The provisions of this section apply for calculating NOX emission credits.
(b) For each participating family, calculate positive or negative emission credits relative to the otherwise applicable emission standard. Calculate positive emission credits for a family that has an FEL below the standard. Calculate negative emission credits for a family that has an FEL above the standard. Sum your positive and negative credits for the model year before rounding. Calculate emission credits to the nearest megagram (Mg) for each family using the following equation:
Emission credits (Mg) = (Std−FL) · CF · Volume · UL · c Eq. 1036.705-1
Where:
Std = the emission standard, in (mg NOX)/hp·hr that applies under subpart B of this part for engines not participating in the ABT program of this subpart (the “otherwise applicable standard”).
FL = the engine family's FEL, in mg/hp·hr, rounded to the same number of decimal places as the emission standard.
CF = a transient cycle conversion factor (hp·hr/mile), calculated by dividing the total (integrated) horsepower-hour over the applicable duty cycle by 6.3 miles for engines subject to spark-ignition standards and 6.5 miles for engines subject to compression-ignition standards. This represents the average work performed over the duty cycle.
Volume = the number of engines eligible to participate in the averaging, banking, and trading program within the given engine family during the model year, as described in paragraph (c) of this section.
UL = the useful life for the standard that applies for a given primary intended service class, in miles.
c = 10−9.
Example for model year 2028 Heavy HDE generating NOX credits:
Std = 35 mg/hp·hr
FEL = 20 mg/hp·hr
CF = 9.78 hp·hr/mile
Volume = 15,342
UL = 650,000 miles
c = 10−9
Emission credits = (35−20) · 9.78 · 15,342 · 650,000 · 10−9
Emission credits = 1,463 Mg
(c) Compliance with the requirements of this subpart is determined at the end of the model year by calculating emission credits based on actual production volumes, excluding the following engines:
(1) Engines that you do not certify to the standards of this part because they are permanently exempted under subpart G of this part or under 40 CFR part 1068.
(2) Exported engines.
(3) Engines not subject to the requirements of this part, such as those excluded under § 1036.5.
(4) Engines certified to state emission standards that are different than the emission standards referenced in this section, and intended for sale in a state that has adopted those emission standards.
(5) Any other engines if we indicate elsewhere in this part that they are not to be included in the calculations of this subpart.
[91 FR 7782, Feb. 18, 2026]