(a) The provisions of this section apply separately for calculating emission credits for each pollutant.
(b) For each participating family, calculate positive or negative emission credits relative to the otherwise applicable emission standard based on the engine family's FCL for greenhouse gases. If your engine family is certified to both the vocational and tractor engine standards, calculate credits separately for the vocational engines and the tractor engines (as specified in paragraph (b)(3) of this section). Calculate positive emission credits for a family that has an FCL below the standard. Calculate negative emission credits for a family that has an FCL above the standard.
Sum your positive and negative credits for the model year before rounding. Round the sum of emission credits to the nearest megagram (Mg), using consistent units throughout the following equations:
(1) For vocational engines:
Emission credits (Mg) = (Std-FCL) [middot] (CF) [middot] (Volume) [middot] (UL) [middot] (10-6) Where:
Std = the emission standard, in g/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'').
FCL = the Family Certification Level for the engine family, in g/hp-hr, measured over the transient duty cycle, 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 duty cycle (average of vocational engine configurations weighted by their production volumes) by 6.3 miles for spark-ignition engines and 6.5 miles for compression-ignition engines. This represents the average work performed by vocational engines in the family over the mileage represented by operation over the duty cycle.
Volume = the number of vocational 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 given engine family, in miles.
(2) For tractor engines:
Emission credits (Mg) = (Std-FCL) [middot] (CF) [middot] (Volume) [middot] (UL) [middot] (10-6) Where:
Std = the emission standard, in g/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'').
FCL = the Family Certification Level for the engine family, in g/hp-hr, measured over the SET duty cycle 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 duty cycle (average of tractor-engine configurations weighted by their production volumes) by 6.3 miles for spark-ignition engines and 6.5 miles for compression-ignition engines. This represents the average work performed by tractor engines in the family over the mileage represented by operation over the duty cycle. Note that this calculation requires you to use the transient cycle conversion factor even for engines certified to SET-based standards. Volume = the number of tractor 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 given engine family, in miles.
(3) For engine families certified to both the vocational and tractor engine standards, we may allow you to use statistical methods to estimate the total production volumes where a small fraction of the engines cannot be tracked precisely.
(4) You may not generate emission credits for tractor engines (i.e., engines not certified to the transient cycle for CO2) installed in vocational vehicles (including vocational tractors certified pursuant to 40 CFR 1037.630 or exempted pursuant to 40 CFR 1037.631). We will waive this requirement where you demonstrate that less than five percent of the engines in your tractor family were installed in vocational vehicles. For example, if you know that 96 percent of your tractor engines were installed in non-vocational tractors, but cannot determine the vehicle type for the remaining four percent, you may generate credits for all the engines in the family.
(c) As described in Sec. 1036.730, compliance with the requirements of this subpart is determined at the end of the model year based on actual U.S.-directed production volumes. Keep appropriate records to document these production volumes. Do not include any of the following engines to calculate emission credits:
(1) Engines that you do not certify to the CO2 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 Sec. 1036.5. For example, do not include engines used in vehicles certified to the greenhouse gas standards of 40 CFR 1037.104.
(4) [Reserved]
(5) Any other engines if we indicate elsewhere in this part 1036 that they are not to be included in the calculations of this subpart.
(d) You may use CO2 emission credits to show compliance with CH4 and/or N2O FELs instead of the otherwise applicable emission standards. To do this, calculate the CH4 and/or N2O emission credits needed (negative credits) using the equation in paragraph (b) of this section, using the FEL(s) you specify for your engines during certification instead of the FCL. You must use 25 Mg of positive CO2 credits to offset 1 Mg of negative CH4 credits. You must use 298 Mg of positive CO2 credits to offset 1 Mg of negative N2O credits.