The following restrictions apply for using emission credits:
(a) Averaging sets. Except as specified in paragraph (c) of this section, emission credits may be exchanged only within an following averaging sets There are four principal averaging sets for engines subject to this subpart:
(1) Spark-ignition engines.
(2) Compression-ignition light heavy-duty engines.
(3) Compression-ignition medium heavy-duty engines.
(4) Compression-ignition heavy heavy-duty engines.
(b) Applying credits to prior year deficits. Where your credit balance for the previous year is negative, you may apply credits to that credit deficit only after meeting your credit obligations for the current year.
(c) Credits from hybrid engines and other advanced technologies. The averaging set restrictions of paragraph (a) of this section do not apply for credits generated under Sec. 1036.615 or 40 CFR 1037.104(d)(7) or 1037.615 from hybrid power systems with regenerative braking, or from other advanced technologies. Such credits may also be used under 40 CFR part 1037.
(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 heavy-duty vehicles. This group comprises the averaging sets listed in paragraphs (a)(1) and (2) of this section and the averaging set listed in 40 CFR 1037.740(a)(1).
(ii) Medium heavy-duty compression-ignition engines and medium heavy-duty vehicles. This group comprises the averaging sets listed in paragraph (a)(3) of this section and 40 CFR 1037.740(a)(2).
(iii) Heavy heavy-duty compression-ignition engines and heavy heavy-duty vehicles. This group comprises the averaging sets listed in paragraph (a)(4) of this section and 40 CFR 1037.740(a)(3).
(2) The limit specified in paragraph (c)(1) of this section does not limit the amount of advanced technology credits that can be used within a service class group if they were generated in that same service class group.
(d) Credit life. Credits expire after five years.
(e) Other restrictions. Other sections of this part specify additional restrictions for using emission credits under certain special provisions.