40 CFR § 1037.740 - Restrictions for using emission credits.
The following restrictions apply for using emission credits:
(a) Averaging sets. Except as specified in paragraph (b) of this section, emission credits may be exchanged only within an averaging set. The following principal averaging sets apply for vehicles certified to the standards of this part involving emission credits as described in this subpart:
(1) Light HDV.
(2) Medium HDV.
(3) Heavy HDV.
(4) Long trailers.
(5) Short trailers.
(6) Note that other separate averaging sets also apply for emission credits not related to this part. For example, vehicles certified to the greenhouse gas standards of 40 CFR 86.1819 comprise a single averaging set. Separate averaging sets also apply for engines under 40 CFR part 1036, including engines used in vehicles subject to this subpart.
(b) Credits from hybrid vehicles and other advanced technologies. Credits you generate under § 1037.615 from Phase 1 vehicles may be used for any of the averaging sets identified in paragraph (a) of this section; you may also use those credits to demonstrate compliance with the CO2 emission standards in 40 CFR 86.1819 and 40 CFR part 1036. Similarly, you may use advanced-technology credits generated under 40 CFR 86.1819-14(k)(7) or 40 CFR 1036.615 to demonstrate compliance with the CO2 standards in this part. Credits generated from Phase 2 vehicles are subject to all the averaging-set restrictions that apply to other emission credits.
(1) The maximum amount of credits you may bring into the following service class groups is 60,000 Mg per model year:
(i) Spark-ignition engines, light heavy-duty compression-ignition engines, and Light HDV. This group comprises the averaging set listed in paragraphs (a)(1) of this section and the averaging set listed in 40 CFR 1036.740(a)(1) and (2).
(c) Credit life. Banked credits may be used only for five model years after the year in which they are generated. For example, credits you generate in model year 2018 may be used to demonstrate compliance with emission standards only through model year 2023.
(d) Other restrictions. Other sections of this part specify additional restrictions for using emission credits under certain special provisions.